Journal of Materials Chemistry (v.22, #25)

Front cover (12391-12392).

Contents list (12393-12414).

Dye mediated charge recombination dynamics in nanocrystalline TiO2 dye sensitized solar cells by John N. Clifford; Eugenia Martínez-Ferrero; Emilio Palomares (12415-12422).
Dye-electrolyte interactions play an important role in mediating the recombination between injected electrons in the TiO2 electrode and the iodide/tri-iodide red-ox electrolyte in Dye Sensitized Solar Cells. This reaction reduces both cell voltage and efficiency and controlling it is therefore key to optimization and stability of such devices. This highlight will focus on experimental methods developed to monitor these recombination processes in functioning cell devices. Moreover, we discuss how certain dye structures seem to greatly accelerate recombination, in particular, in the case of highly conjugated sensitizers. Greater understanding of dye-interactions and ways to minimize them will help in the design of new sensitizers that show negligible recombination ultimately leading to optimization of cell efficiency.

Metal and metal oxide nanoparticles (NPs) have many uses, and the size, shape and purity of the NPs must be uniform to ensure that the particles function in a known and consistent manner. The synthesis of uniform NPs usually requires high temperatures, high pressures, and harsh chemical reagents, which is both economically and environmentally costly. In nature, biomineralisation is used to produce precise, pure NPs, using far milder reaction conditions and reagents. Recently, a bioinspired approach has been adopted to produce NPs using proteins and peptides that: occur in nature; are artificially selected from a random peptide library by biopanning; or are rationally designed to control NP formation under mild conditions. Here we highlight the recent advances in metal and metal oxide NP binding and synthesis using proteins and peptides. We then investigate bioinspired patterning of NPs onto surfaces. This is done to demonstrate the possible avenues available to develop environmentally friendly, biotemplated devices and nanotechnologies in the future.

Strategies for chemical modification of graphene and applications of chemically modified graphene by Jingquan Liu; Jianguo Tang; J. Justin Gooding (12435-12452).
Graphene's unique thermal, electric and mechanical properties originate from its structure, including being single-atom thick, two-dimensional and extensively conjugated. These structural elements endow graphene with advantageous thermal, electric and mechanical properties. However, the application of graphene is challenged by issues of production, storage and processing. Therefore, the stabilization and modification of graphene have attracted extensive interest. In this review we summarize the strategies for chemical modification of graphene, the influence of modification and the applications in various areas. Generally speaking, chemical modification can be achieved via either covalent or non-covalent interactions. Covalent modifications often destroy some of the graphene conjugation system, resulting in compromising some of its properties. Therefore, in this review we focus mainly on the non-covalent modification methodologies, e.g.π–π stacking interactions and van der Waals force, because the non-covalent modifications are believed to preserve the natural structure and properties. We also discuss the challenges associated with the production, processing and performance enhancement. Future perspectives for production of graphene in large size with fewer defects and under milder conditions are discussed along with the manipulation of graphene's electric, mechanical and other properties.

Ring-like PdO–NiO with lamellar structure for gas sensor application by Lili Wang; Zheng Lou; Rui Wang; Teng Fei; Tong Zhang (12453-12456).
A new type of ring-like architecture with a lamellar structure was prepared via a simple hydrothermal strategy in the case of PdO–NiO, which showed a low operating temperature, a high response and rapid response/recovery to CO gas.

Bacteria survival and growth in multi-layered silica thin films by Christophe Depagne; Sylvie Masse; Thorben Link; Thibaud Coradin (12457-12460).
A layer-by-layer approach was used to build up silica thin films (<500 nm) compatible with Escherichia coli bacteria immobilization and spatially confined growth.

We report a seed-mediated synthetic approach to produce hyperbranched PtRu alloy nanoparticles under mild conditions. As-synthesized PtRu particles have a high alloying degree, display high index facets, and show improved activity for electro-oxidation of methanol when compared to commercial PtRu black.

Preparation of graphene oxide by solvent-free mechanochemical oxidation of graphite by Oleg Yu. Posudievsky; Oleksandra A. Khazieieva; Vyacheslav G. Koshechko; Vitaly D. Pokhodenko (12465-12467).
Graphenes with different oxidation degrees are prepared by ultrasound assisted aqueous exfoliation of solvent-free mechanochemically treated graphite in the presence of solid oxidants, under comparatively mild conditions without using aggressive concentrated acids.

Graphene supported Pd@Co core–shell nanocatalysts with magnetically recyclability were synthesized via the in situ synthesis strategy utilizing the distinction in reduction potentials of the two precursors with appropriate reductant. The as-synthesized catalysts exerted satisfied catalytic activity (916 L mol−1 min−1) and recycle stability for hydrolytic dehydrogenation of ammonia borane.

Synthesis and photoresponse of novel Cu2CdSnS4 semiconductor nanorods by Yong Cui; Gang Wang; Daocheng Pan (12471-12473).
Novel semiconductor Cu2CdSnS4 nanorods with a wurtzite structure have been successfully synthesized and characterized in detail. The suitable band gap of 1.4 eV and photoresponse property of Cu2CdSnS4 nanorods indicate that they have a high potential application in low-cost thin film solar cells.

Detection of nitro explosives via LSPR sensitive silver clusters embedded in porous silica by Wei Zou; Wenwen Liu; Limei Luo; Shufen Zhang; Rongwen Lu; Götz Veser (12474-12478).
LSPR sensitive silver clusters embedded in porous silica, which show high LSPR sensitivity to both nitroaromatic and nitroaliphatic explosives, are prepared by a reverse microemulsion. The performance of this hybrid nanostructure is due to the combination of accumulation of nitro explosives in the porous silica and the interaction of the silver clusters with nitro explosives. This results in highly sensitive and selective sensing of nitro explosives via the changes of the LSPR extinction intensity of the embedded silver clusters, with sensitivity down to at least 1 μM concentrations.

Strength and toughness are commonly two contradictory properties in polymer materials. For polymer elastomers, the addition of stiff filler frequently results in enhanced stiffness but reduced toughness and ductility. Inspired by biomimetic studies, here we demonstrate a new method that can simultaneously improve strength and toughness while maintaining the good ductility of polyurethane elastomers. This method constructs sacrificial bonds and hidden lengths at the interface of graphene nanosheet/polyurethane (GN/PU) composites by exploiting covalently and non-covalently functionalized GNs (HO-GNs). GNs are prepared by reduction of graphene oxide with hydrazine. The residual functional groups such as hydroxyl and epoxide groups on GNs enable PU oligomer chains to be covalently bonded to GNs by sequentially reacting with diisocyanate and polyethylene glycol oligomer. Non-covalently bonded PU oligomer chains are formed by the π–π interaction between GNs and pyrene derivatives. Both Fourier transform infrared spectra and thermogravimetric results provide direct evidence for the covalent bonding in HO-GNs while fluorescence spectra and decay curves confirm the existence of non-covalent bonding. The resulting HO-GNs exhibit a good dispersion capacity in organic solvents and the PU matrix, improving the load transfer and the particle mobility in GN/PU composites. Upon loading, both rupture of the π–π interaction (sacrificial bonds) and release of the hidden length (dissociation of H-bonds between the PU oligomer and polymer chains) enable the composite to exhibit high toughness and ductility nearly identical to the neat polyurethane (strain at break >900%). This approach is expected to be helpful for developing novel strong, tough and highly ductile polymer elastomers.

Simultaneous modification of pyrolysis and densification for low-temperature solution-processed flexible oxide thin-film transistors by You Seung Rim; Woong Hee Jeong; Dong Lim Kim; Hyun Soo Lim; Kyung Min Kim; Hyun Jae Kim (12491-12497).
High-pressure annealing (HPA) affected the thermodynamics of the formation of a solution-processed oxide film through the simultaneous modification of thermal decomposition and compression, and enabled the use of lower annealing temperatures, which was favourable for device implementation. HPA also reduced the film thickness and decreased the porosity, resulting in enhanced device characteristics at low temperature. Surface and depth profile characterization using X-ray reflectivity (XRR), X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), and ellipsometry suggested that the HPA process supported the effective decomposition of commercial metal-nitrate and/or -salt precursors and strong bonding between oxygen and the metal ions, ultimately reducing the amount of organic residue. The as-optimized HPA process allowed for high-performance solution-processed flexible InZnO (IZO) TFTs on a polymeric substrate at 220 °C with low sub-threshold voltage swing (as low as 0.56 V dec−1), high on–off ratio of over 106, and field-effect mobility as high as 1.78 cm2 V−1 s−1, respectively. These results demonstrate that this is a simple and efficient promising approach for improving the performance of solution-processed electronic devices at low temperatures.

Elucidating the morphological and structural evolution of iron oxide nanoparticles formed by sodium carbonate in aqueous medium by Cristina Blanco-Andujar; Daniel Ortega; Quentin A. Pankhurst; Nguyen Thi Kim Thanh (12498-12506).
Ferrimagnetic iron oxides are the common choice for many current technologies, especially those with application in biology and medicine. Despite the comprehensive knowledge accumulated about their chemistry in the bulk state, the sequence of changes taking place during the precipitation of iron oxide nanoparticles in aqueous media is much less extensive. We show that using sodium carbonate as a co-precipitating agent for the synthesis of uncoated iron oxide nanoparticles, the reaction proceeds sufficiently slowly to enable a detailed study of both the reaction pathway and products. The effect of pH, temperature and reaction time on particle size, morphology, crystalline phase and its magnetic properties was investigated. The obtained nanoparticles showed an increase in average particle size of about 10 nm per pH unit for the magnetite phase leading to 6.9 ± 0.4 nm, 18 ± 3 nm and 28 ± 5 nm for pH 8, 9 and 10 respectively. Goethite was initially formed by an olation mechanism at room temperature, followed by a slow transformation into magnetite over a 24 h period, as tracked by X-ray diffraction. In another set of experiments where the reaction temperatures were varied, magnetite was obtained directly by the oxolation mechanism at temperatures above 45 °C. The optimization of the experimental parameters led to superparamagnetic nanoparticles with a high saturation magnetization of 82 A m2 kg−1 at 300 K when synthesized at pH 9.

Fluorescent carbazole dendrimers for the detection of nitroaliphatic taggants and accelerants by Andrew J. Clulow; Paul L. Burn; Paul Meredith; Paul E. Shaw (12507-12516).
The detection of explosive taggant 2,3-dimethyl-2,3-dinitrobutane (DMNB) and accelerant nitromethane (NM) by oxidative quenching of dendrimer fluorescence is examined. Two fluorescent dendrimers incorporating a 3,6-disubstituted-9-n-hexylcarbazole-based core and first-generation biphenyl-based dendrons linked directly or with acetylene bridges are reported. The dendrimers display good photoluminescence (PL) quantum yields in both solution and thin films and appropriate excited state energies for oxidation by the nitroaliphatic analytes. The dendrimer natural excited state lifetimes in solution of 6.8 and 7.4 ns were found to be significantly longer than previously reported fluorescent conjugated polymers and dendrimers for sensing applications. Steady-state PL quenching measurements in solution revealed the highest quenching efficiencies for the detection of nitroaliphatics reported to date of 59 ± 1 M−1 for DMNB and 78 ± 1 M−1 for NM. Furthermore, PL lifetime quenching measurements confirmed that the dendrimers were quenched by a predominantly collisional quenching mechanism. As such, the unprecedented quenching efficiencies with nitroaliphatics in solution are due to the combination of the long excited state lifetimes of the dendrimers and efficient collisional quenching. The fluorescence of dendrimer thin films was also reversibly quenched by exposure to pulses of sub-saturation concentrations of analyte vapours. However, in the thin film case the sensitivity towards DMNB was found to be greater than NM, highlighting the disparity between solution and thin film fluorescence quenching measurements.

Ink-jet printed conductive copper patterns with enhanced substrate adhesion were fabricated using a conductive copper ink containing a silane coupling agent as an adhesion promoter. The effect of the silane coupling agent on the copper complex ion ink properties, including viscosity and surface tension, was systematically investigated. The copper complex ion ink that was ink-jet printed on a polyimide film was transformed to copper films by thermal treatment at 200 °C for 2 h in H2. The phase, microstructure, resistivity and peel strength were examined by X-ray diffraction, field emission scanning electron microscopy, the four-point probe technique, the 90° peel test and the ASTM D3359 tape test. The proper amount of silane coupling agent was determined according to the electrical conductivities and adhesive strengths of the ink-jet printed copper patterns containing varied amounts of adhesion promoter. As a result, the patterns formed from copper complex ion ink containing 3 wt% silane coupling agent exhibited not only the highest peel strength (240.3 gf mm−1 and 4B) but also low resistivity (approx. 20 μΩ cm). The mechanism of adhesion promotion via the silane coupling agent was also suggested.

How the linkage positions affect the performance of bulk-heterojunction polymer solar cells by Shuang Li; Zhicai He; Jian Yu; Su'an Chen; Aoshu Zhong; Runli Tang; Hongbin Wu; Jingui Qin; Zhen Li (12523-12531).
Two new alternating copolymers. PCT-10,13-BPz (P1) and PCT-2,7-BPz (P2), which were constructed from the same monomers and only different in the connecting points, were synthesized via Suzuki coupling reaction. The UV-vis absorptions, thermal stability, energy levels, field-effect carrier mobility and photovoltaic characteristics of the two copolymers were systematically evaluated to understand the relationships between the polymer structure at the molecular level and the photovoltaic performances. Photovoltaic cells based on the two copolymers with a structure of ITO/PEDOT : PSS/Polymer : PC71BM/PFN/Al exhibited PCEs of 4.31% and 0.64%, respectively, under one sun of AM 1.5 solar simulator illumination (100 mW cm−2).

Double-shelled ZnO/CdSe/CdTe nanocable arrays for photovoltaic applications: microstructure evolution and interfacial energy alignment by Hao Wang; Tian Wang; Xina Wang; Rong Liu; Baoyuan Wang; Hanbin Wang; Yang Xu; Jun Zhang; Jinxia Duan (12532-12537).
A series of high-density double- and single-shelled ZnO/CdSe/CdTe, ZnO/CdTe/CdSe, ZnO/CdTe and ZnO/CdSe nanocable arrays were synthesized as photoanodes by an electrodeposition method using ZnO nanorod arrays as cores. For ZnO/CdSe/CdTe nanocable arrays, the uniform CdSe and CdTe nanoshells were composed of zinc-blende phase nanocrystals with a respective average size range of 10–20 nm and 7–15 nm, and formed a compact and continuous interface in between. Based on the band offset of the bulk material before contact and the interfacial Fermi level shift after contact, the energy level alignments at the CdSe/CdTe and CdTe/CdSe interface were deduced for the double-shelled nanocable arrays. The CdTe/CdSe interface of the ZnO/CdTe/CdSe nanocables has a negative band offset of −0.16 eV whilst for ZnO/CdSe/CdTe nanocables, the band edge of CdTe lies above CdSe with a conduction band offset of 0.16 eV at the CdSe/CdTe interface. Such a stepwise band alignment, together with the compact interface, fewer grain boundaries along the radial direction, and the fast transfer rate along the axial direction of the nanocables, makes the ZnO/CdSe/CdTe nanocable arrays photoanode have a saturated photocurrent of ∼14.3 mA cm−2. This is under the irradiation of AM1.5G simulated sunlight at 45 mW cm−2, which is greatly higher than ZnO/CdTe/CdSe, ZnO/CdSe or ZnO/CdTe nanocable arrays.

Single step aqueous synthesis of pure rare earth nanoparticles in biocompatible polymer matrices by Sayantani Chall; Abhijit Saha; Sampad K. Biswas; Aparna Datta; Subhash Chandra Bhattacharya (12538-12546).
The room temperature synthesis of water soluble, stable rare earth (RE) metal nanoparticles (MNPs) with controlled size is a long standing interest. In the present work, we have established a synthetic strategy for the preparation of pure europium (Eu0) metal nanoparticles (NPs) in aqueous solution employing a γ-radiolytic reduction technique. Since radiolysis is the cleanest method amongst all other chemical routes, we preferentially choose this technique for the reduction of precursor Eu3+ ions to nanoscale metals in our work. This has been possible as hydrated electrons (eaq) having a very high reduction potential (E0(H2O/eaq) = −2.87 VNHE) produced in situ can efficiently reduce Eu3+ to Eu0. Synthesized Eu0 MNPs were stabilised within the matrices of biocompatible polymers, polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP). Reduction of the metal ion has been conducted at different irradiation doses with a maximum dose of 83.88 kGy. The irradiated solution shows an absorption maximum at 266 ± 2 nm and an emission maximum at 394 ± 5 nm. Analysis of transmission electron microscopy (TEM) images shows that the average sizes of PVA and PVP encapsulated Eu0 NPs are 13 ± 0.6 nm and 17 ± 1.01 nm, respectively ([Eu3+] = 5.0 × 10−3 mol dm−3, [polymer] = 1.0%). Formation of monodisperse pure Eu0 MNPs was further characterised by dynamic light scattering (DLS), energy dispersive X-ray (EDX) as well as Fourier transformed infrared (FTIR) spectroscopy and cyclic voltammetry (CV) studies.

Two energy donor–acceptor self-assembly systems have been constructed by using π–π, lipophilic, and ionic interactions in water. π-stacked N,N′-ditridecylperylenediimide (PDI), which forms nanoribbons, has been dispersed in water in the presence of myristyltrimethylammonium bromide (MTAB) through lipophilic interactions of tridecyl groups of PDIs with long tails of MTAB molecules. Cationic heads of MTAB molecules, anchored on the bulk of the side-chains of the nanoribbons, attract water-soluble zinc tetra(4-sulfonatophenyl)porphyrin tetrapotassium salt (ZnTPPSK4) and lucifer yellow CH dipotassium salt (LY). By this design, efficient photosensitization of non-aggregated energy donors, ZnTPPSK4 and LY, has been achieved while retaining the one-dimensional order at nanoscale, resulting in the efficient excitation energy transfer to PDI nanoribbons in each system.

A facile in situ hydrophobic layer protected selective etching strategy for the synchronous synthesis/modification of hollow or rattle-type silica nanoconstructs by Kun Zhang; Hangrong Chen; Yuanyi Zheng; Yu Chen; Ming Ma; Xia Wang; Lijun Wang; Deping Zeng; Jianlin Shi (12553-12561).
A novel and general in situ hydrophobic shell-protected selective etching strategy has been developed to synchronously synthesize and modify hollow mesoporous silica nanoparticles (HMSNs) and rattle-type mesoporous silica nanoparticles (RMSNs) with well-defined morphology, effectively avoiding the drawbacks of post-modification. The key point of the strategy lies in the hydrophilicity differences between the pure silica inner core and the organic hybrid silica shell, which results in the preferential etching of the pure silica inner core. Except that amino group functionalized HMSNs (amino-HMSNs) can be synthesized via this strategy, it can be readily applied for the synthesis of HMSNs and RMSNs synchronously grafted with different kinds of functional groups by employing other silane coupling agents, directly indicating the generality of this strategy. Furthermore, adding no additional reduction agents, the amino-HMSNs can be regarded as nanoreactors, and a distinctively heterogeneous rattle-type structure, Au@HMSN/Au, with an entrapped size-tunable Au nanoparticle and some small Au nanocrystals embedded in the hollow cavity and shell of each nanoparticle, respectively, is obtained. As hybrid ultrasound contrast agents (UCAs), unlike micro-sized organic UCAs merely confined to blood pool imaging, the as-synthesized nano-sized amino-HMSNs can achieve excellent in vitro ultrasound imaging, and potentially be applied in cell-level imaging. More importantly, relying on the process merits of our strategy, such as the doping of silane coupling agents and no calcination treatment, amino-HMSNs exhibit enhanced ultrasound imaging to some certain extent compared to the calcined ones.

Cellulose-based material with amphiphobicity to inhibit bacterial adhesion by surface modification by Chengfeng Jin; Yufeng Jiang; Tao Niu; Jianguo Huang (12562-12567).
Amphiphobic cellulose-based material was prepared by functional surface modification of nanofibres of a natural cellulose substance (e.g., commercial filter paper). The filter paper was firstly etched by alkaline solution to enhance the surface roughness, and then ultrathin titania films were deposited onto the cellulose nanofibre surfaces of the etched filter paper by a facile surface sol–gel process. A 1H,1H,2H,2H-perfluorooctyl trimethoxysilane (PFOTMS) monolayer was further self-assembled onto the titania ultrathin film pre-coated cellulose nanofibres. Due to the rough morphology of the etched filter paper and the low surface energy coating with PFOTMS monolayers, the naturally hydrophilic filter paper is converted into an amphiphobic material with both superhydrophobicity and high oleophobicity, which effectively inhibits the adhesion of bacteria such as lysogenic E. coli.

In this work, an efficient approach for targeting and detecting cancer cells has been developed through the design of the assembly of fluorescent carbon nanodots and folic acid (C-dots–FA), which is endocytosible by the overexpressed folate receptor (FR) molecule. The fluorescent C-dots were prepared by a facile microwave pyrolysis method, but their surfaces were passivated with 4,7,10-trioxa-1,13-tridecanediamine, so that active amino groups could be engineered for the further conjugation with FA. The uptake of the designed C-dots–FA by HeLa cancer cells, as revealed by confocal laser scanning microscopy, is via receptor-mediated endocytosis, which is further confirmed by competition experiments as well as a comparative study with FR-negative MCF-7 cells. The proposed method shows excellent biocompatibility, and, most notably, its applicability to discriminating FR-positive cancer cells from normal cells has been successfully demonstrated by culturing and analyzing the first model cell mixture of NIH-3T3 and HeLa cells, which makes it of great potential for cancer diagnosis studies.

A new and facile approach for the surface modification of high-voltage LiNi1/3Co1/3Mn1/3O2 cathode active materials is demonstrated. This strategy is based on polyimide (PI) gel polymer electrolyte (GPE)-directed nanoscale wrapping. The PI coating layer successfully wraps a large area of the LiNi1/3Co1/3Mn1/3O2 surface via thermal imidization of (pyromellitic dianhydride/oxydianiline) polyamic acid. Salient features of the PI wrapping layer are the highly continuous surface coverage with nanometre thickness (∼10 nm) and the facile ion transport through the nanoscale layer. Based on a sound understanding of the nanoarchitectured PI wrapping layer, its influence on the cell performance and thermal stability of high-voltage LiNi1/3Co1/3Mn1/3O2 is investigated as a function of charge cut-off voltage (herein, 4.6 and 4.8 V). The anomalous PI wrapping layer substantially improves the high-voltage cycling performance and alleviates the interfacial exothermic reaction between delithiated LiNi1/3Co1/3Mn1/3O2 and liquid electrolyte. These results demonstrate that the PI wrapping layer effectively prevents the direct exposure of the LiNi1/3Co1/3Mn1/3O2 surface to liquid electrolytes that are highly vulnerable to electrochemical decomposition at high charge voltage conditions, thus behaving as a novel ion-conductive protection skin that mitigates the unwanted interfacial side reactions.

We report the first example of monometallic gold nanoparticles, functionalized with amine and encapsulated in silica nanospheres, as a high-performance catalyst for hydrogen generation from aqueous formic acid for chemical hydrogen storage. Remarkably, the presence of amine in the silica sphere can make the gold nanoparticles highly active although the unsupported or silica-supported gold NPs being inactive for this reaction. The strong metal–molecular support interaction (SMMSI) could be extended, as a general strategy, to the development of nanocatalysts which need necessary environments around the active sites for a variety of catalytic reactions.

Halogenated two-dimensional germanium: candidate materials for being of Quantum Spin Hall state by Yandong Ma; Ying Dai; Chengwang Niu; Baibiao Huang (12587-12591).
The electronic band structure of halogenated germanene in the presence of spin–orbit coupling is investigated using first-principles calculations. Our results demonstrate that, compared with pure germanene, the π and π* bands of germanene adsorbed with Cl, Br and I remain crossed at the Fermi level – despite the crossing point shifting from K to Γ points. Moreover, we find that appreciable gaps in halogenated germanene can be opened at Dirac-like points, several orders of magnitude larger than that in pure germanene due to the robust spin–orbit coupling; for example, Cl, Br and I yield a SOC-induced gap of 86 meV, 237 meV and 162 meV at Γ points, respectively. In addition, since the germanene would be unstable at ambient conditions due to the dangling unsaturated Ge bonds, the manufacture of fully halogenated germanene with a robust spin–orbit coupling effect is more feasible than that of germanene experimentally. Therefore, our work may provide a potential avenue to observe the Quantum Spin Hall Effect at room temperature.

It is widely accepted that ultraviolet (UV) light illumination of ferroelectric films can result in polarization imprint because of the accumulation of photoinduced carriers on the domain walls and/or on the electrode–film interfaces, and then the decrease of the reversible remnant polarization. In this paper, however, the enhancement of remnant polarization was exhibited in Pb(Zr0.2Ti0.8)O3 (PZT) films when irradiated by UV light. The time-dependent photocurrent and hysteresis loop of PZT films indicated that the transient behavior of photocurrent and coercive voltage offset were closely related to the polarization states, moveable defect charge (mainly oxygen vacancy) density, and aging time. Based on the observation of piezoresponse force microscopy, the mechanism behind the observed photoelectric and ferroelectric phenomena was proposed.

Fluoride-containing bioactive glasses are attracting particular interest in many fields of dentistry and orthopedics because they combine the bone-bonding ability of bioactive glasses with the anticariogenic protection provided by fluoride ions. Since the biomedical applications of these materials critically depend on the release of ionic species in the surrounding physiological environment, a deep knowledge of their environments is required. In this paper, density functional theory calculations and spin effective Hamiltonians have been employed to analyse the NMR signatures of the various environments of 19F, 29Si, 31P and 23Na atoms in fluorinated bioglasses structural models previously generated by Car–Parrinello molecular dynamics simulations. Comparison with experimental spectra expressly recorded in this work shows a good agreement and allows the enlightenment of some longstanding issues about the atomic structure of fluorinated bioglasses, such as the presence of Si–F and Si–O–P bonds. In particular, it is shown that Si–F bonds cannot be resolved by using MAS NMR experiments only, and 29Si{19F} REDOR experiments, that probes directly spatial proximities among atoms, must be employed. Our results show that F is coordinated entirely to the modifier ions Na and Ca, and that no Si–F bonds are present in the real glass structure. Thus, the addition of fluorine to the 45S5 Bioglass® increases the polymerization of the silicate network by removing modifiers from the siliceous matrix and reducing its reactivity. Finally, the computed isotropic chemical shifts of the various environments of phosphorus show that, if present, Si–O–P bonds should be clearly noticeable in the 31P static NMR experimental spectrum. Instead, the latter show that P is present as isolated orthophosphate units and does not enter into the siliceous matrix by forming Si–O–P bonds as conjectured by molecular dynamics simulations.

Two different nanostructured copper–isonicotinic acid (INA) coordination polymers, Cu(C6H4NO2)2(H2O)4 and [Cu(C6H4NO2)(OH)]H2O have been successfully synthesized under hydrothermal conditions on a large scale without the assistance of surfactants or template. Cu(C6H4NO2)2(H2O)4 has the morphology of 2-dimensional (2D) butterfly-like nanosheet structures, while [Cu(C6H4NO2)(OH)]H2O consists of one-dimensional (1D) nanorods. A possible formation mechanism of the obtained coordination polymer nanostructures is proposed with provision of the crystal structure. After heat treatment, hierarchical CuO butterfly-sheet-like nanostructures and CuO nanotubes were obtained. The photocatalytic and antibacterial studies indicate that the as-obtained CuO samples have great photocatalytic activities for the degradation of Rhodamine B and good bacteriostatic activities. In addition, the electrochemical measurements show that CuO samples exhibit high reversible discharge capacities and stable cyclic performances.

A single Alq3 submicro-wire Schottky diode and its negative differential resistance by Shih-Shou Lo; Wei-Hsiu Hsu; Shu-Hao Sie; Hoang-Jyh Leu (12618-12621).
This study fabricated high-quality tris(8-hydroxyquinoline) aluminium (Alq3) submicro-wires as well as a Schottky diode with a single Alq3 submicro-wire across Ag electrodes. Rectifying and negative differential resistance (NDR) of the fabricated diode was obtained and the turn-on voltage and breakdown voltage was 4 V and 12 V, respectively. The NDR of the diode was observed when the forward bias exceeded 4 V and the peak-to-valley ratio in the current was more than 6 : 1 at room temperature. The mechanism of NDR in the Schottky diode was discussed. These results may facilitate applying Alq3 submicro-wires for advanced organic/inorganic hybrid nanostructure devices.

Fabrication of nanostructured W–Y2O3 materials by chemical methods by Sverker Wahlberg; Mazher A. Yar; Mohammad Omar Abuelnaga; Hanadi G. Salem; Mats Johnsson; Mamoun Muhammed (12622-12628).
A novel method for the fabrication of highly uniform oxide dispersion-strengthened (ODS) materials made by chemical processing is presented. The powders are fabricated by a two-step route starting with a chemical synthesis at room temperature, producing nanocrystalline yttrium doped tungsten trioxide hydrate precursor powders. Thermogravimetric analysis with evolved gas analysis revealed the presence of ammonium nitrate in the precursors. The second step is the reduction of the precursor in a hydrogen atmosphere at 600 and 800 °C. The reduced powders, containing W-1.2%Y2O3, showed two types of tungsten particles, cube-shaped with a size less than 250 nm and finer particles (<50 nm) of both spherical and cubic shape. The powder was consolidated by spark plasma sintering at 1100 °C, producing a bulk material with a relative density of 88%. Characterization of the sintered materials by high resolution scanning electron microscopy revealed a uniform microstructure with tungsten grains of less than 300 nm and nanosized oxide particles uniformly dispersed at the tungsten grain boundaries, as well as inside the tungsten grains. Experimental determination of the elastic properties was conducted by nanoindentation tests and fracture toughness was studied by radial indentation cracking.

A simple method is described for the preparation of Fe-doped TiO2 nanoparticles (Ti1−xFexO2) that can be used as a high performance support material for a CO oxidation catalyst. The method allows one to fabricate Ti1−xFexO2 with uniform sizes and shapes. Microstructural studies using XRD, Raman spectroscopy and EPR analyses indicate that the Fe dopant is substitutionally incorporated by replacing Ti4+ cations. Electrochemical results indicate that, when a small amount of Fe molecules (less than 8 atomic%) are incorporated into a TiO2 structure, the support material has greatly improved redox characteristics. This suggests that an Fe-doped TiO2 support enhances both the release and uptake of oxygen atoms from the catalysts, thus resulting in a high catalytic activity in CO oxidation reactions. The results confirmed that a Au catalyst supported on Fe-doped TiO2 containing a 6 atom% Fe dopant showed an outstanding oxidation performance. The findings reported herein represent an innovative route to designing high performance catalysts for oxidation reactions.

New opportunities in Stöber synthesis: preparation of microporous and mesoporous carbon spheres by Jerzy Choma; Dominik Jamioła; Katarzyna Augustynek; Michal Marszewski; Min Gao; Mietek Jaroniec (12636-12642).
The recent extension of the Stöber recipe to the synthesis of carbon particles creates tremendous opportunities in the design of novel carbon spheres having micropores, mesopores, or both, as well as composite carbon spheres with incorporated inorganic nanoparticles such as silica and silver.

Low-temperature hydrothermal synthesis of WO3 nanorods and their sensing properties for NO2 by Shouli Bai; Kewei Zhang; Ruixian Luo; Dianqing Li; Aifan Chen; Chung Chiun Liu (12643-12650).
Tungsten trioxide (WO3) nanorods with an aspect ratio of ∼50 have been successfully synthesized by hydrothermal reaction at a low temperature of 100 °C. The crystal structure, morphology evolution and thermal stability of the products are characterized in detail by XRD, FESEM, FTIR, and TG/DTA techniques. The diameter evolution and distribution of WO3 nanorods strongly depend on hydrothermal temperature and time. Hydrothermal conditions of 100 °C and 24 h ensure the formation of well-defined WO3 nanorods. The transition of the crystal structure from monoclinic WO3 to hexagonal WO3 occurs after calcination at 400 °C. The appropriate calcination conditions of the WO3 nanorods are defined to be 600 °C and 4 h for gas-sensing applications. Response measurements reveal that the WO3 sensor operating at 200 °C exhibits high sensitivity to ppm-level NO2 and small cross-sensing to CO and CH4, which makes this kind of sensor a competitive candidate for NO2-sensing applications. Moreover, impedance measurements indicate that a conductivity mechanism of the sensor is mainly dependent on the grain boundaries of WO3 nanorods. A possible adsorption and reaction model is proposed to illustrate the gas-sensing mechanism.

Harnessing Hansen solubility parameters to predict organogel formation by J. Gao; S. Wu; M. A. Rogers (12651-12658).
Hansen solubility parameters predict the capacity of molecular gels to form in a vast array of organic solvents. The prediction ability for 12-hydroxystearic acid is closely associated with the hydrogen-bonding Hansen solubility parameter (δh). Solvents with a hydrogen-bonding Hansen solubility parameter less than 4.7 MPa1/2 produce clear organogels, opaque organogel formed between 4.7 < δh < 5.1 MPa1/2 and solutions remained when the hydrogen-bonding Hansen solubility parameter is greater than 5.1 MPa1/2. Furthermore, the critical gelator concentration is linearly correlated with the hydrogen-bonding Hansen solubility parameter. Solvents with the same functional group, which varied only by chain length, have correlations between the static relative permittivity, Hansen solubility parameter, dispersive HSP, polar HSP and hydrogen-bonding HSP and the critical gelator concentration.

Synthesis and properties of 3,4,5-trinitropyrazole-1-ol and its energetic salts by Yanqiang Zhang; Damon A. Parrish; Jean'ne M. Shreeve (12659-12665).
3,4,5-Trinitropyrazole-1-ol and its nitrogen-rich salts were synthesized and well characterized by 1H, 13C NMR (some with 15N NMR), and IR spectroscopy, and by elemental analysis. Additionally, the structures of the ammonium and triazolium 3,4,5-trinitropyrazole-olates were confirmed by single-crystal X-ray diffraction. With respect to measured or calculated properties, such as thermal stability (Td, 118–186 °C), density (1.72–1.90 g cm−3), detonation performance (P, 28.77–36.40 GPa; vD, 8175–8676 m s−1), and impact sensitivity (1–40 J), 3,4,5-trinitropyrazole-1-ol and its salts have the potential to be useful energetic materials.

Photocatalytic cellulosic electrospun fibers for the degradation of potent cyanobacteria toxin microcystin-LR by Nicholas M. Bedford; Miguel Pelaez; Changseok Han; Dionysios D. Dionysiou; Andrew J. Steckl (12666-12674).
Non-woven, high surface area photocatalytic cellulosic electrospun fibers were fabricated for solar-light-driven water treatment purposes and tested for photocatalytic decomposition of the potent cyanobacteria toxin microcystin-LR (MC-LR). Electrospun fibers of cellulose acetate were converted to succinylated cellulose and then loaded with titania nanoparticles using a simple solution based technique. It was found that the type of titania nanoparticle (visible light activated or UV light activated), the surface area of the fiber mat, and loading solution pH all have an effect on the distribution of titania along the fibers. The titania coverage and surface area of the fiber mats were found to correlate well with the degree of MC-LR degradation under both visible and solar light irradiation. The difference in titania coverage, determined using X-ray photoelectron microscopy (XPS), was two to three times smaller in the lower surface area samples. These photocatalytic electrospun fibers could be advantageously used for drinking water and wastewater treatment applications using solar light as a renewable source of energy.

High surface area mesoporous Co3O4 from a direct soft template route by Naween Dahal; Ilich A. Ibarra; Simon M. Humphrey (12675-12681).
Mesoporous Co3O4 with hexagonally ordered cylindrical channels has been synthesized by a single-step method using Pluronic soft micellar templates. The resulting material has been directly compared to isomorphous Co3O4 that was obtained via an established but laborious five-step nanocasting method. The soft template route employs only surfactant templates and a decane additive, which yields directly mesoporous Co3O4 by a gelling process in a carefully controlled basic (pH = 12.7) alcohol solution at 35 °C. The method is significantly faster and more economical than conventional nanocasting, and has similar overall reproducibility to the conventional multi-step route. The soft templated Co3O4 displays long-range ordered cylindrical microchannels with crystalline walls. Most importantly, it exhibits an unparalleled N2 BET surface area of 367 m2 g−1.

Nanocrystalline diamond AFM tips for chemical force spectroscopy: fabrication and photochemical functionalization by Michael E. Drew; Andrew R. Konicek; Papot Jaroenapibal; Robert W. Carpick; Yoko Yamakoshi (12682-12688).
The chemical modification of nanocrystalline diamond (NCD) atomic force microscope (AFM) tips was investigated and used for chemical force spectroscopy (CFS). In contrast to common chemical modification routes for gold or silicon AFM tips, this method creates stable C–C bonding to attach functional moieties to the NCD tip. There have been no previous studies reporting the chemical functionalization of NCD AFM tips. In this study, hydrogen-terminated NCDs (H-NCDs) were deposited on both silicon wafers and silicon AFM tips and subsequently subjected to a photochemical reaction with undecylenic acid (UA) to create UA attached to NCD surface (UA-NCD). The UA-NCD on wafers were used for surface analyses (water contact angle, attenuated total reflectance-Fourier transform infrared (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and near-edge X-ray absorption fine structure (NEXAFS) measurements) to confirm the chemical modification. The UA-NCD AFM tips were subjected to fluorescent labelling to confirm the existence of carboxylic acid on the tip and AFM adhesion measurements to assess their performance as a probe for the detection of chemical species on surfaces. These results indicate the promising ability of this method to serve as an ideal platform for CFS, which requires robust chemical functionalities on the AFM tip surfaces.

Solution processeable organic–inorganic hybrids based on pyrene functionalized mixed cubic silsesquioxanes as emitters in OLEDs by Xiao Hui Yang; Tommaso Giovenzana; Brian Feild; Ghassan E. Jabbour; Alan Sellinger (12689-12694).
Traditional materials for application in organic light emitting diodes (OLEDs) are primarily based on small molecules and polymers, with much fewer examples of intermediate molecular weight materials. Our interest lies in this intermediate molecular weight range, specifically in hybrids based on 3-dimensional silsesquioxane (SSQ) cores that represents a new class of versatile materials for application in solution processable OLEDs. We report here various SSQ based hybrids that are easily prepared in one high-yield step from the Heck coupling of commercially available 1-bromopyrene, and 1-bromo-4-heptylbenzene with octavinyl-T8-SSQ, and a mixture of octavinyl-T8-, decavinyl-T10- and dodecavinyl-T12-SSQ. The resulting materials offer numerous advantages for OLEDs including amorphous properties, high-glass-transition temperatures (Tg), low polydispersity, solubility in common solvents, and high purity via column chromatography. Solution processed OLEDs prepared from the SSQ hybrids provide sky-blue emission with external quantum efficiencies and current efficiencies of 3.64% and 9.56 cd A−1 respectively.

A ZnO/N-doped carbon nanotube nanocomposite charge transport layer for high performance optoelectronics by Ji Sun Park; Ju Min Lee; Sun Kak Hwang; Sun Hwa Lee; Hyun-Jung Lee; Bo Ram Lee; Hyung Il Park; Ji-Seon Kim; Seunghyup Yoo; Myoung Hoon Song; Sang Ouk Kim (12695-12700).
Metal oxide charge transport layers are widely used to promote the interfacial charge transport of organic optoelectronics. Nevertheless, frequently used wide-bandgap metal oxides with low electrical conductivities reveal inherent limitations in the charge transport enhancement. We present the remarkable electro-conductivity enhancement of solution processable ZnO charge transport layers upon dispersing a tiny amount (less than 0.1 wt%) of chemically doped CNTs and the corresponding device performance improvement of light-emitting diodes (OLEDs). Using various undoped or doped CNTs, whose work function was systematically tuned by substitutional doping of electron deficient B or electron rich N,N-doped CNT (N-CNT), the composite showed a lowered work function matching well with the conduction band of ZnO. Consequently, the ZnO/N-CNT nanocomposite transport layer with 0.08 wt% N-CNT showed a five-fold enhancement of electron mobility, while maintaining the intrinsic bandgap energy levels, optical transparency and solution processability of pure ZnO. The inverted OLEDs employing ZnO/N-CNT nanocomposite electron transport layers could facilitate well-balanced electron–hole injection and, thus, more than two-fold enhancement of maximum luminance (from 21 000 cd m−2 at 14.6 V to 46 100 cd m−2 at 14.0 V) and efficiency (from 6.9 cd A−1 at 13.4 V to 14.3 cd A−1 at 13.6 V). This highly effective charge mobility enhancement enabled by work function tunable, chemically doped CNTs would be beneficial for various organic and inorganic charge transport materials with different energy levels.

Enhanced photodynamic selectivity of nano-silica-attached porphyrins against breast cancer cells by Wenbing Li; Wentong Lu; Zhen Fan; Xianchun Zhu; Aisha Reed; Brandon Newton; Yazhou Zhang; Shavelle Courtney; Papireddy T. Tiyyagura; Roslyn R. Ratcliff; Shufang Li; Ebonie Butler; Hongtao Yu; Paresh C. Ray; Ruomei Gao (12701-12708).
The synthesis and characterization of bare silica (4 nm in diameter) nanoparticle-attached meso-tetra(N-methyl-4-pyridyl)porphine (SiO2–TMPyP, 6 nm in diameter) are described for pH-controllable photosensitization. Distinguished from organosilanes, SiO2 nanoparticles were functionalized as a potential quencher of triplet TMPyP and/or singlet oxygen (1O2) at alkaline pH, thereby turning off sensitizer photoactivity. In weak acidic solutions, TMPyP was released from the SiO2 surface for efficient production of 1O2. By monitoring 1O2 luminescence at 1270 nm, quantum yields of 1O2 production were found to be pH-dependent, dropping from ∼0.45 in the pH range of 3–6 to 0.08 at pH 8–9, which is consistent with the pH-dependent adsorption behavior of TMPyP on the SiO2 surface. These features make bare SiO2-attached cationic porphyrin a promising candidate for use in PDT for cancer treatment in which efficient 1O2 production at acidic pH and sensitizer deactivation at physiological pH are desirable. The enhanced therapeutic selectivity was confirmed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) tests and trypan blue exclusion tests of cell viability in breast cancer cell lines. Bimolecular quenching rate constants of 1O2 by free TMPyP, SiO2 and SiO2–TMPyP nanoparticles were also determined.

Self-alignment and high electrical conductivity of ultralarge graphene oxide–polyurethane nanocomposites by Nariman Yousefi; Mohsen Moazzami Gudarzi; Qingbin Zheng; Seyed Hamed Aboutalebi; Farhad Sharif; Jang-Kyo Kim (12709-12717).
Polyurethane (PU)-based composite films containing highly aligned graphene sheets are produced through an environmentally benign process. An aqueous liquid crystalline dispersion of graphene oxide (GO) is in situ reduced in PU, resulting in a fine dispersion and a high degree of orientation of graphene sheets. The PU particles are adsorbed onto the surface of the reduced graphene oxide (rGO), and the rGO sheets with a large aspect ratio of over 10 000 tend to self-align during the film formation when the graphene content is high enough, say more than 2 wt%. The resulting composites show excellent electrical conductivity with an extremely low percolation threshold of 0.078 vol%, which is considered one of the lowest values ever reported for polymer composites containing graphene. The electrical conductivity of the composites with high graphene contents presents significant anisotropy due to the preferential formation of conductive networks along the in-plane direction, another proof of the existence of the self-aligned, layered structure.

Single-component room-temperature discotic nematic liquid crystals formed by introducing an attraction-enhancing in-plane protrusion onto the hexa(phenylethynyl)benzene core by Hsiu-Hui Chen; Hsin-An Lin; Shih-Chieh Chien; Tsai-Hui Wang; Hsiu-Fu Hsu; Tzenge-Lien Shih; Chunhung Wu (12718-12722).
Single-component room-temperature discotic nematics have been achieved within large temperature ranges by introducing an attraction-enhancing protrusion onto hexa(phenylethynyl)benzenes. X-ray diffraction investigations revealed the nematic phases of these new discotic nematic materials to be cybotactic.

This work describes the encapsulation of conducting polypyrrole (PPy) into electrospun TiO2 nanofibers to form PPy/TiO2 nanocomposites using V2O5 as an oxidant and sacrificial template via a simple vapor phase polymerization approach. The PPy/TiO2 nanocomposites could be used as nanoreactors for loading Pd nanocatalysts towards the catalytic reduction of p-nitrophenol by sodium borohydride (NaBH4) at ambient conditions. The Pd nanocrystals synthesized through the in situ reduction by the PPy/TiO2 matrix have a small size of only about 2.0 nm. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible-near infrared spectroscopy (UV-vis-NIR) and thermo-gravimetric analysis (TGA) results demonstrated that PPy/TiO2 and PPy/TiO2/Pd composite nanofibers were successfully synthesized. Pd nanoparticles supported on the PPy/TiO2 composite nanofibers exhibited good catalytic activity when they worked as catalysts for the reduction of p-nitrophenol. The apparent kinetic rate constant (Kapp) was calculated to be about 12.2 × 10−3 s−1. The protective PPy/TiO2 composite nanofibers render the Pd nanoparticles stable against poisoning by the product of the reaction, enabling the composite nanocatalysts to be recyclable when used over multiple cycles.

Probing the growth mechanism of self-catalytic lead selenide wires by Mohammad Afzaal; Kibriya Ahmad; Paul O'Brien (12731-12735).
Highly crystalline lead capped lead selenide wires are generated by using unusual growth conditions falling between CVD and CVT, using lead dialkyldithiocarbamate, grey selenium powder and Si/SiO2 (100) substrates. Various morphologies can be obtained by modifying the source temperature. Nucleation of highly faceted lead selenide wires from bulk lead selenide crystallites is explored and the possible growth mechanisms are given. A reduction in the energy of the surface exposed on the microcrystal is one factor that governs the unique growth characteristics of the one dimensional structure that evolves.

To make Ir(iii)-based complexes potentially multifunctional materials, two new cationic Ir(iii) complexes with a 2-(5-phenyl-2-phenyl-2H-1,2,4-triazol-3-yl)pyridine (Phtz) ancillary ligand were designed and synthesized. By introducing the pendant phenyl ring into the ancillary ligand, the two complexes possess desired intramolecular π–π stacking between the pendant phenyl ring of the Phtz ligand and one of the phenyl rings of the cyclometalated ligand, which renders the complexes more stable. Density functional theory calculation indicates that the intramolecular π–π interactions in both complexes can reduce the degradation reaction in metal-centered (3MC) states to some extent, which further implies their stability. With these results in combination with their reversible oxidation and reduction processes as well as excellent photophysical properties, the stable light-emitting cells (LECs) would be expected. Furthermore, the two synthesized complexes exhibit reversible piezochromism. Their emission color can be smartly switched by grinding and heating, which is visible to the naked eye. In light of our experimental results, the present piezochromic behavior is due to interconversion between crystalline and amorphous states.

Enhanced performance of graphite anode materials by AlF3 coating for lithium-ion batteries by Fei Ding; Wu Xu; Daiwon Choi; Wei Wang; Xiaolin Li; Mark H. Engelhard; Xilin Chen; Zhenguo Yang; Ji-Guang Zhang (12745-12751).
The surface of commercial graphite powders has been successfully modified with a thin AlF3 coating via chemical precipitation for the first time. A thin (∼2 nm thick) and uniform AlF3 coating up to 2 wt% content is observed without an evident change in the bulk structure of graphite particles. An AlF3-coated graphite anode delivers a higher initial discharge capacity with much improved rate performance when compared to an uncoated graphite anode. Additionally, the AlF3-coated graphite anode demonstrates a much better cycle life than the uncoated graphite. After 300 cycles, batteries with anodes made from 1 wt% AlF3-coated graphite and uncoated graphite show capacity retentions of 92% and 81%, respectively. It is believed that a more stable and conductive solid electrode interphase layer is formed on AlF3-coated graphite particles, which enhances the performance of graphite anodes in lithium-ion batteries.

A novel strategy of adopting the reversible swelling effect of a promising scaffold—hypercrosslinked porous poly(styrene-co-divinylbenzene) resin (PSDB) to nanoconfine hydrogen storage materials is reported, in which nanoconfined ammonia–borane (AB) is endowed with high loading ratio and significantly improved hydrogen storage capabilities. To verify the importance of swelling behavior displayed by this polymeric scaffold in dehydrogenation, an ammonia-dissolving route (PSDB–AB (NH3)) that does not involve swelling, was performed to enable direct comparison with the methanol-dissolving route (PSDB–AB (CH3OH)). Moreover, solid-state 11B NMR measurements were employed to illustrate the different reaction mechanisms in these two PSDB-confined AB samples, where decomposition involving both the diammoniate of diborane (DADB) and linear dimer are observed for PSDB–AB (NH3) but only the latter route is seen for PSDB–AB (CH3OH), deeply demonstrating the difference of dehydrogenation properties in these two samples. Our findings establish a prospective approach via utilizing this class of polymers for promoting the design and construction of advanced energy materials with high performances.

Supramolecular light-emitting polymers for solution-processed optoelectronic devices by Jie Zhang; Kai Zhang; Xuelong Huang; Wanzhu Cai; Cheng Zhou; Shengjian Liu; Fei Huang; Yong Cao (12759-12766).
Supramolecular light-emitting polymers (SLEPs) based on host–guest interactions were developed for solution processed organic electronic devices. The dibenzo-24-crown-8 functionalized blue-emitting conjugated oligomer 1 and green-emitting conjugated oligomer 3 were used as the host materials, and the dibenzylammonium salt functionalized blue-emitting conjugated oligomer 2 was used as the guest material. The resulting linear SLEPs were obtained from the self-organization of the host and guest oligomers, which were confirmed by the nuclear magnetic resonance, viscosity and differential scanning calorimetry studies. Highly fluorescent SLEP nanofibers can be easily obtained by drawing or electron-spinning from the equimolar solution of the host and guest oligomers. The photophysical and electroluminescence properties of the resulting SLEPs were fully investigated. It was found that the SLEPs' emission colors can be well tuned from blue to green with significantly enhanced photoluminescent efficiencies by using 3 as the dopant, which is due to the efficient energy transfer caused by the exciton trapping on narrow band gap host oligomer 3 in the SLEPs. As a result, the designed SLEPs showed comparable electroluminescence device performances to those analogous traditional conjugated polymers. Considering the precisely defined starting monomers and catalyst-free polymerization process for the designed SLEPs, combining the good device performances, the present study provides a promising alternative route to develop solution processed semiconductors for optoelectronic applications.

Nanostructured Zn-based composite anodes for rechargeable Li-ion batteries by Yoon Hwa; Ji Hyun Sung; Bin Wang; Cheol-Min Park; Hun-Joon Sohn (12767-12773).
The mechanism of the electrochemical reaction of Zn with Li was investigated by ex situ X-ray diffraction (XRD) analysis combined with a differential capacity plot of the Zn electrode at a low current of 10 mA g−1. The pure Zn electrode showed a high reactivity with Li, with first discharge and charge capacities of 574 and 351 mA h g−1, respectively. In addition, Zn–C and Zn–Al2O3–C composites prepared by simple high-energy mechanical milling were evaluated for use as anode materials in rechargeable Li-ion batteries. The Zn–C nanocomposite was composed of nanosized Zn in an amorphous C matrix, while the Zn–Al2O3–C nanocomposite (obtained by the mechanochemical reduction of ZnO and Al) was composed of nanocrystalline Zn and amorphous Al2O3 in the amorphous C matrix. Electrochemical tests showed that the Zn–Al2O3–C nanocomposite electrode exhibited a high volumetric capacity of more than 1800 mA h cm−3 over 100 cycles.

Highly stable printed polymer field-effect transistors and inverters via polyselenophene conjugated polymers by Dongyoon Khim; Woo-Hyung Lee; Kang-Jun Baeg; Dong-Yu Kim; In-Nam Kang; Yong-Young Noh (12774-12783).
We report the use of two polyselenophene-based conjugated polymers, poly(3,3′′-didodecyl-2,2′:5,2′′-terselenophene) (P3Se) and poly(3,3′′,3′′′,3′′′′-tetradodecyl-2,5′:2′,2′′:5′′,2′′′-pentaselenophene) (P5Se), as an active layer of printed p-channel organic field-effect transistors (OFETs). Top-gate/bottom-contact (TG/BC) P5Se OFETs showed a high-saturation hole mobility of up to ∼0.1 cm2 V−1 s−1 and a high on/off ratio of ∼105 with no hysteresis. In addition, polyselenophene-based OFETs exhibited a much better bias and ambient stability when compared with poly(3-hexylthiophene)-based OFETs. The excellent air stability of those polyselenophenes enables the realization of complementary metal-oxide semiconductor (CMOS) inverters via extended periods of ink-jetting under ambient conditions. CMOS inverters were demonstrated using p-[P5Se] and n-channel [poly{[N,N′-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-s,6-diyl]-alt-5,5′-(2,2′-dithiophene)}] ([P(NDI2OD-T2)], Polyera ActivInk N2200/OFETs) by inkjet printing of conjugated polymers. Printed CMOS inverters exhibited a stable voltage transfer characteristic with negligible hysteresis, a DC voltage gain of ∼10, and a power consumption of ∼0.025 mW at VDD = −60 V.

Fabrication of porous rhodium nanotube catalysts by electroless plating by Falk Muench; Cornelia Neetzel; Sebastian Kaserer; Joachim Brötz; Jean-Christophe Jaud; Zhirong Zhao-Karger; Stefan Lauterbach; Hans-Joachim Kleebe; Christina Roth; Wolfgang Ensinger (12784-12791).
A versatile electroless plating procedure for the fabrication of rhodium nanomaterials was developed, leading to deposits consisting of loosely agglomerated metal nanoparticles. By using carbon black as the substrate, supported rhodium nanoparticle clusters were obtained. In combination with ion track etched polymer templates, the deposition protocol allowed the first direct synthesis of rhodium nanotubes. Polymer dissolution provided access to well defined, supportless and free-standing rhodium nanotubes of nearly cylindrical shape, 300 nm opening diameter, 28 μm length and 50 nm wall thickness. The characterization by SEM, TEM, EDS and XRD confirmed the purity of the deposit, displayed a small particle size of approximately 3 nm and revealed gaps in the range of a few nanometers between the rhodium particles. BET analysis verified the presence of pores of <5 nm. To evaluate the electrocatalytic potential of the rhodium nanotubes, they were applied in the amperometric detection of hydrogen peroxide. Compared to classical nanoparticle-based sensing concepts, improved performance parameters (sensitivity, detection limit, and linear range) could be achieved.

In the present work we grow anodic TiO2 nanotube layers under defined hydrodynamic conditions using a rotating Ti anode. We show that hydrodynamic control can be beneficially used to achieve two main effects. First, under conditions where tube growth is controlled by diffusion (for low concentration of fluoride ions in the electrolyte), growth can significantly be accelerated (or even be enabled) by increasing flow rates in the electrolyte. Second, ill-defined nanotube top morphologies can be avoided – this is particularly important in view of designing optimum tube geometries for the use of TiO2 nanotube layers in photoelectrochemical applications such as DSSCs.

We report here for the first time a universal method to achieve a covalent surface modification of plasticized poly(vinyl chloride) (PVC). A copper(i)-catalyzed azide–alkyne cycloaddition (‘click chemistry’) is performed on plasticized PVC containing partial azide substitutions. This surface modification is performed under mild conditions after membrane casting and is likely to be generally applicable to electrochemical and optical sensors. The concept is illustrated by attaching fluorescein and sulfonated Nile blue derivatives, as well as tetraethylene glycol to the membrane surface. Characterization by confocal microscopy, ATR-IR, QCM, UV/Vis spectroscopy and pulsed chronopotentiometry supports the surface modification procedure. As an initial example of practical utility, tetraethylene glycol modification is shown to significantly reduce surface adsorption by albumin, as evidenced by QCM and electrochemical experiments.

Magnetic and optical properties of multifunctional core–shell radioluminescence nanoparticles by Hongyu Chen; Daniel C. Colvin; Bin Qi; Thomas Moore; Jian He; O. Thompson Mefford; Frank Alexis; John C. Gore; Jeffrey N. Anker (12802-12809).
When X-rays irradiate radioluminescence nanoparticles, they generate visible and near infrared light that can penetrate through centimeters of tissue. X-ray luminescence tomography (XLT) maps the location of these radioluminescent contrast agents at high resolution by scanning a narrow X-ray beam through the tissue sample and collecting the luminescence at every position. Adding magnetic functionality to these radioluminescent particles would enable them to be guided, oriented, and heated using external magnetic fields, while their location and spectrum could be imaged with XLT and complementary magnetic resonance imaging. In this work, multifunctional monodispersed magnetic radioluminescent nanoparticles were developed as potential drug delivery carriers and radioluminescence imaging agents. The particles consisted of a spindle-shaped magnetic γ-Fe2O3 core and a radioluminescent europium-doped gadolinium oxide shell. Particles with solid iron oxide cores displayed saturation magnetizations consistent with their ∼13% core volume, however, the iron oxide quenched their luminescence. In order to increase the luminescence, we partially etched the iron oxide core in oxalic acid while preserving the radioluminescent shell. The core size was controlled by the etching time which in turn affected the particles' luminescence and magnetic properties. Particles with intermediate core sizes displayed both strong magnetophoresis and luminescence properties. They also served as MRI contrast agents with relaxivities of up to 58 mM−1 s−1 (r2) and 120 mM−1 s−1 (r2*). These particles offer promising multimodal MRI/fluorescence/X-ray luminescence contrast agents. Our core–shell synthesis technique offers a flexible method to control particle size, shape, and composition for a wide range of biological applications of magnetic/luminescent nanoparticles.

Nanoporous nitrogen doped carbon was used to modify the surfaces of graphene sheets by carbonizing a mixture of graphene oxide and phenol–melamine–formaldehyde (PMF) pre-polymer in the presence of a soft template (F127). The resulting graphene based composite sheets (G-PMFs) have a sandwich structure with one graphene layer and two nanoporous nitrogen-doped carbon layers. G-PMFs have large specific surface areas of 190 to 630 m2 g−1 and exhibited high electrocatalytic activity, good durability and high selectivity for the oxygen reduction reaction. The performance of the Zn–air fuel cell with a G-PMF anode was tested and found to be comparable to that of the Zn–air cell with a commercial Pt/C anode. Thus, these metal-free catalysts are promising for applications in practical fuel cells.

Photovoltaic and field effect transistor performance of selenophene and thiophene diketopyrrolopyrrole co-polymers with dithienothiophene by Munazza Shahid; Raja Shahid Ashraf; Zhenggang Huang; Auke J. Kronemeijer; Thomas McCarthy-Ward; Iain McCulloch; James R. Durrant; Henning Sirringhaus; Martin Heeney (12817-12823).
Here we report the synthesis of two new alternating co-polymers of thiophene and selenophene flanked diketopyrrolopyrrole with dithienothiophene. We find that the inclusion of the rigid fused dithienothiophene co-monomer affords semi-crystalline polymers, that exhibit promising ambipolar field effect transistor performance, with hole mobilities up to 0.23 cm2 V−1 s−1. The selenophene containing co-polymer exhibits a reduced band gap compared to the thiophene co-polymer, as a result of stabilisation of the polymer LUMO and destabilisation of the HOMO. The thiophene co-polymer exhibits promising solar cell performance in blends with PC71BM, with device efficiencies up to 5.1%.

Atomic layer deposition of germanium-doped zinc oxide films with tuneable ultraviolet emission by Paul R. Chalker; Paul A. Marshall; Peter J. King; Karl Dawson; Simon Romani; Paul A. Williams; John Ridealgh; Matthew J. Rosseinsky (12824-12829).
Thin films of germanium-doped zinc oxide have been deposited by atomic layer deposition. The zinc oxide matrix was grown from cyclic pulses of diethylzinc and water vapour over the temperature range of 100–350 °C substrate temperature. Tetramethoxygermanium(iv) was employed as a novel germanium-doping source, which could be incorporated up to 17 at%. At 2.1 at% germanium doping at a deposition temperature of 250 °C, the maximum carrier concentration of 2.14 × 1020 cm−3 coincides with a carrier mobility of approximately 5 cm2 V−1 s−1. No evidence for the formation of nanometre-scale germanium clustering or segregation was observed in the X-ray diffraction patterns or high-resolution transmission electron micrographs of these films. The near band edge photoluminescence shifts to higher energy with increasing germanium incorporation either by the Burstein–Moss mechanism or by alloy formation.

Ultralong one-dimension Al3CON nanostructures: synthesis, elastic deformation behavior and photoelectric properties by H. Cui; Y. Sun; S. X. Jin; X. M. Xiong; W. J. Mai; C. X. Wang (12830-12836).
The Al–O–C–N system is known as a kind of Al2O3-based ceramic material with various different chemical compositions and structures. Considering its superior physical and mechanical properties, the corresponding one-dimensional Al–O–C–N system may have huge potential applications in future nanodevices. Herein, for the first time, two types of ultralong one-dimensional Al3CON nanostructures, nanowires and bicrystalline nanobelts, were simultaneously synthesized by asimple CVD process. The products were characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy as well as energy dispersive X-ray spectrometry. Corresponding property studies were carried out to explore the potential applications of the products. The force measurement based on a single nanostructure was performed by using an atomic force microscope (AFM) and the nanostructure showed high strength with a Young's modulus of 251 GPa. Semiconductor characteristics were also observed by electrical measurement at room temperature, which may be attributed to the doping and/or native defects. In addition, the Al3CON nanostructures showed deep-ultraviolet photoconductivity, in which the conductance increases only when illuminated with 254 nm light rather than 365 nm light.

Experimental and theoretical studies of photoluminescence from Bi82+ and Bi53+ stabilized by [AlCl4] in molecular crystals by Hong-Tao Sun; Yoshio Sakka; Naoto Shirahata; Hong Gao; Tetsu Yonezawa (12837-12841).
The photophysical properties of Bi82+ and Bi53+ polycations stabilized by [AlCl4] have been studied experimentally and theoretically. The obtained product was thoroughly evaluated by powder X-ray diffraction and photoluminescence spectroscopy, making it clear that both Bi82+ and Bi53+ contribute to the observed broad near-infrared emission. Furthermore, it was revealed that the Bi82+ polycation shows emission peaking at ca. 1180 nm, while Bi53+ shows the longer-wavelength emission. The following quantum chemistry calculation on the Bi82+ polycation helps us attribute some of the observed excitation bands in the visible spectral range to specific electronic transitions of bismuth polycations. It is believed that systematic investigation of structural and luminescent properties as well as detailed quantum chemistry calculation of molecular crystals containing such kinds of bismuth units allows us to obtain a clearer picture of bismuth-related photophysical behaviors, which not only serve to solve the confusions on the luminescence origin of bismuth in other material systems such as bulk glasses, glass fibers and conventional crystals, but also is helpful to develop novel applicable broadband tunable laser mediums.

High performance all-solid-state dye-sensitized solar cells based on cyanobiphenyl-functionalized imidazolium-type ionic crystals by Huizi Cao-Cen; Jie Zhao; Lihua Qiu; Dan Xu; Qing Li; Xiaojian Chen; Feng Yan (12842-12850).
Organic ionic crystals carrying 4-cyano-4′-hydroxybiphenyl and imidazolium units were synthesized and applied as the electrolytes for dye-sensitized solar cells (DSSCs). The fabricated all-solid-state DSSCs achieved a cell efficiency of ∼5.11% at 55 °C under the simulated air mass 1.5 solar spectrum illuminations at 100 mW cm−2 because of the enhanced light harvesting capability of the electrolyte. To further improve the cell efficiency, 1-propyl-3-methylimidazolium iodine (PMII), was added into the electrolytes as a crystal growth inhibitor. These fabricated devices showed an enhanced power conversion efficiency (PCE) of ∼6.55% at 45 °C under the simulated air mass 1.5 solar spectrum illuminations at 50 mW cm−2, and a superior long-term stability. The cyanobiphenyl-functionalized ionic crystal based electrolytes have expanded our vision to explore new types of all-solid-state electrolytes for high-efficiency DSSCs.

Tunable photoluminescence from the visible to near-infrared wavelength region of non-stoichiometric AgInS2 nanoparticles by Meilin Dai; Shoji Ogawa; Tatsuya Kameyama; Ken-ichi Okazaki; Akihiko Kudo; Susumu Kuwabata; Yasuyuki Tsuboi; Tsukasa Torimoto (12851-12858).
Non-stoichiometric AgInS2 (AIS) semiconductor particles were synthesized by the thermal decomposition of single-source precursors in solutions of two kinds of primary amines (oleylamine and octylamine). The Ag content in the resulting nanoparticles was controlled by adjusting the chemical composition of the precursor used, in which the mole ratio of Ag+ to total metal ions was varied from 0.1 to 0.7, resulting in the production of non-stoichiometric AIS particles with varying amounts of Ag vacancies. The average size of AIS particles was slightly decreased from 4.3 to 3.8 nm on changing the solvent from oleylamine to octylamine in the preparation, while the particle size seemed to be constant regardless of the content of Ag. On the other hand, the optical properties of AIS particles were considerably modified depending on the Ag content in the particles. The absorption onset was blue-shifted from 750 to 580 nm with a decrease in the Ag content, due to the enlargement of the energy gap of particles. Intense photoluminescence originating from the donor–acceptor pair recombination was observed for each kind of AIS particle and then the photoluminescence peak wavelength was also blue-shifted from 830 to 650 nm, being similar to the behavior of the absorption onset. The maximum photoluminescence quantum yield was ca. 70% for octylamine-modified AIS nanoparticles having a ratio of Ag+ to total metal ions of 0.37, which probably contained the optimum amount of Ag vacancies acting as the sites of donor–acceptor pair recombination with few surface defect sites for non-radiative recombination.

In this study, highly ordered, flexible, homogeneous and reinforced microcrystalline cellulose (MCC)–graphene oxide (GO) composite films regenerated from MCC/1-butyl-3-methylimidazolium chloride ([Bmim]Cl) solutions were prepared, and their nanostructures, thermal stability and mechanical properties were investigated by Fourier-transform infrared spectra, X-ray diffraction spectra, scanning electron microscopy images, thermal gravimetric analyses and tensile strength measurements. Moreover, the effect of the dispersion state of GO in MCC/[Bmim]Cl solutions with varying GO contents was studied by rheological tests. The mechanical properties of composite films could be remarkably improved over those of pure MCC film and there is a close relationship between the dispersion state and reinforcement effect of GO. Specifically, in comparison with pure MCC film, the composite film containing 0.5 wt% of GO exhibits a 64.7% enhancement in tensile strength and an 85.1% enhancement in strain-to-failure whereas the mechanical properties of the composite films are inferior to that of pure MCC film when the GO content is higher than 1 wt%.

The two pairs of structurally related donor–acceptor polymers (P1–P4) derived from diketopyrrolopyrrole (DPP) and diazapentalene (DAP) building blocks were synthesized and compared for their optical and photovoltaic properties with potential applications in solar cells and near-infrared (NIR) photodetectors. Having the electron-rich fluorene and bis(2′-thienyl)pyrrole (TPT) units as donors, the synthesized donor–acceptor polymers have band gap levels in the range 1.22–1.79 eV. The solar cells based on the blend of P2 (DPP–TPT polymer) and PC71BM exhibited the best performance, showing a Voc of 0.61 V, Jsc of 10.38 mA cm−2, FF of 0.44 and PCE of 2.8%. The photodetector based on the NIR-absorbing P4 (DAP–TPT polymer) displayed a good photovoltaic response over a wide spectral range of 400–1100 nm and an EQE of 13% and detectivity of 2.3 × 1010 Jones at 800 nm.

LiNiO2 (LNO)-based layered materials for use as cathodes in lithium ion batteries generally take the form of agglomerates composed of small particles. Such morphologies produce low electrode densities compared with LiCoO2 (LCO). In this study, the surface energies of various LNO and LCO crystal facets were calculated, and the morphological characteristics of the materials were interpreted based on these results. Crystal models were constructed and the energy of each facet was calculated using density functional theory methods. The chemical mechanisms underlying the atomic structure at each type of facet surface were analyzed using molecular orbital methods. All facet planes yielded surface energies for LNO that were lower than those for LCO. Atoms in the LNO crystal were found to be less ionized than in LCO, which provided weaker ionic bonding and a lower surface energy. The surface energy was proposed to be the main driving force underlying the morphological differences between LNO and LCO. LNO was expected to favor a high fraction of Li atoms at the facet planes. The interpretations based on the theoretical calculations were supported by the experimental results and showed excellent agreement.

We reported the fabrication of a highly sensitive, fast, and thermally switchable humidity sensor based on a β-Ga2O3–amorphous-SnO2 core–shell microribbon, which was synthesized via a simple one-step chemical vapour deposition. The as-grown microribbons were investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) and the results indicated that the microribbon has a well-defined core–shell structure with β-Ga2O3 in the core and amorphous SnO2 in the shell. At 25 °C, the conductivity of the humidity sensor at 75% relative humidity (RH) was three orders of magnitude larger than that in dry air (5% RH). The response time and recovery time were ∼28 and ∼7 s, respectively, when RH was switched between 5 and 75%. Interestingly, by changing the temperature between 12 and 40 °C at 75% RH, the sensitivity can be tuned between ∼105 (12 °C) and ∼102 (40 °C). Typical thermally switchable properties of β-Ga2O3–amorphous-SnO2 core–shell microribbons at 75% RH were demonstrated using a heating–cooling cycle between 20 and 30 °C. The possible mechanisms have been proposed based on the novel core–shell structures and water adsorption–desorption processes. Our findings pave the way for new types of humidity sensors and thermal switches.

The primary inadequacy of chemotherapeutic drugs is their relative non-specificity and potential side effects towards healthy tissue. To overcome this, in this study a novel drug delivery system, namely, carboxymethyl chitosan capped magnetic nanoparticle intercalated montmorillonite nanocomposites (CMCS-capped-MNP/MMT) was developed and characterized by transmission electron microscopy, dynamic light scattering, Fourier transform infrared spectroscopy, X-ray diffraction, small-angle X-ray scattering, zeta potential analysis and a superconducting quantum interference device. The optimum pH value for the encapsulation of doxorubicin (DOX) into CMCS-capped-MNP/MMT was examined. The controlled release behavior of DOX was examined at 5.0 and 7.4 pH. The release rate of the loaded drug molecules was slow at pH 7.4 but increased significantly at acidic pH 5.0. The cytotoxicity of DOX-loaded-CMCS-capped-MNP/MMT towards MCF-7 cancer cells was investigated. The results showed that DOX-loaded-CMCS-capped-MNP/MMT retained significant antitumor activities. The cellular uptake of the fluorescent coumarin 6-loaded CMCS-capped-MNP/MMT on HeLa cells was analyzed with confocal laser scanning microscopy (CLSM) and flow cytometry and the results showed that MMT enhanced the cellular uptake efficiency. The effects of DOX and DOX-loaded-CMCS-capped-MNP/MMT on H9c2 cell death were investigated by using a microplate reader. The heating characteristics of the magnetic nanocomposites were investigated in a high frequency alternating magnetic gradient; a stable maximum temperature of 45 °C was successfully achieved within 40 min. The study demonstrated that CMCS-capped-MNP/MMT is not only a good delivery system for DOX but also appears to be a promising strategy for protecting against oxidative injury observed in DOX induced cardiotoxicity.

In situ diffusion growth of Fe2(MoO4)3 nanocrystals on the surface of α-MoO3 nanorods with significantly enhanced ethanol sensing properties by Yujin Chen; Fanna Meng; Chao Ma; Zhiwei Yang; Chunling Zhu; Qiuyun Ouyang; Peng Gao; Jianqi Li; Chunwen Sun (12900-12906).
In situ diffusion growth of Fe2(MoO4)3 nanocrystals on the surface of α-MoO3 nanorods was achieved through a facile method. The obtained Fe2(MoO4)3@α-MoO3 nanorods exhibit significantly enhanced ethanol sensing properties compared with those of the pristine α-MoO3 nanorods and the Fe2(MoO4)3 nanoparticles, which are attributed to the improved catalytic properties of Fe2(MoO4)3 at low temperature.

High strength composite fibres from polyester filled with nanotubes and graphene by Umar Khan; Karen Young; Arlene O'Neill; Jonathan N. Coleman (12907-12914).
We have prepared composite fibres based on the polyester, polyethylene terephthalate (PET), filled with both single walled nanotubes and graphene by a combination of solution and melt processing. On addition of ≤2 wt% filler we observe increases in both modulus and strength by factors of between ×2 and ×4 for both fillers. For the nanotube-based fibres, the mechanical properties depend strongly on fibre diameter due to a combination of defect and nanotube orientation effects. For the graphene filled fibres, the modulus is approximately invariant with diameter while the strength is defect limited, scaling weakly with diameter. Using this production method, the best fibre we prepared had modulus and strength of 42 GPa and 1.2 GPa respectively (2 wt% SWNT). We attribute this reinforcement predominately to the dispersion quality resulting from the solvent exfoliation of both nanotubes and graphene. In general, marginally better reinforcement was observed for the nanotube filled fibres. However, because of the low cost of graphite, we suggest graphene to be the superior reinforcement material for polymer fibres.

Study on formaldehyde gas-sensing of In2O3-sensitized ZnO nanoflowers under visible light irradiation at room temperature by Lina Han; Dejun Wang; Jiabao Cui; Liping Chen; Tengfei Jiang; Yanhong Lin (12915-12920).
In2O3-sensitized flowerlike ZnO with visible light photoelectric response properties were synthesized by a facile two-step process, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), EDAX, HRTEM and UV-vis diffuse reflectance spectroscopy. The results revealed that In2O3 nanoparticles have grown and eventually coalesced on the surface of the flowerlike ZnO successfully, and the samples exhibited significant response to visible light. The photoelectric gas-sensing of the In2O3-sensitized ZnO was also studied to formaldehyde (HCHO) under 460 nm light irradiation at room temperature with the help of surface photocurrent technique. It was found that ZnO sensitized with In2O3 could enhance the gas response to HCHO under the visible light illumination. This may be due to the fact that the composite structure of In2O3–ZnO extends the photo absorbing range to visible light area, inhibits the recombination of photo-generated electrons and holes, and thus increases the utilization of photo-generated carriers in photoelectric gas detection, resulting in the higher sensing response in some extent. The gas response to 5 ppm and 100 ppm formaldehyde can reach to 19% and 419% under visible light irradiation at room temperature, respectively. These results should be valuable for designing a new type of visible-light assisted gas sensor at room temperature.

Inside back cover (12921-12921).

Back cover (12922-12922).