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Applied Surface Science (v.258, #14)

A facile and efficient approach for pore-opening detection of anodic aluminum oxide membranes by Jiewu Cui; Yucheng Wu; Yan Wang; Hongmei Zheng; Guangqing Xu; Xinyi Zhang (pp. 5305-5311).

► We introduce a simple and efficient approach for removal of oxide barrier layer of AAO membranes. ► Pore diameter and morphology of AAO membranes can be precisely controlled by this novel approach. ► Shape of AAO membrane pore prepared by tradition method is truncated cone shaped. ► Pore shape of AAO membrane fabricated by novel method is cylindrical. ► Truncated cone shaped pores of AAO templates can be used to fabricate one-dimensional gradient metal nanowires.The well aligned porous anodic aluminum oxide (AAO) membrane is fabricated by a two-step anodization method. The oxide barrier layer of AAO membrane must be removed to get through-hole membrane for synthesizing nanowires and nanotubes of metals, semiconductors and conducting polymers. Removal of the barrier layer of oxide and pore-extending is of significant importance for the preparation of AAO membrane with through-hole pore morphology and desired pore diameter. The conventional method for pore opening is that AAO membrane after removing of aluminum substrate is immersed in chemical etching solution, which is completely empirical and results in catastrophic damage for AAO membrane frequently. A very simple and efficient approach based on capillary action for detecting pore opening of AAO membrane is introduced in this paper, this method can achieve the detection for pore opening visually and control the pore diameter precisely to get desired morphology and the pore diameter of AAO membrane. Two kinds of AAO membranes with different pore shape were obtained by different pore opening methods. In addition, one-dimensional gradient gold nanowires are also fabricated by electrodeposition based on AAO membranes.

Keywords: Anodic aluminum oxide membrane; Pore-opening; Pore-extending; Oxide barrier layer; Gold nanowires

A facile strategy to synthesize bimetallic Au/Ag nanocomposite film by layer-by-layer assembly technique by Li Zhang; Cong Wang; Yi Zhang (pp. 5312-5318).

► A facile strategy has been developed for the preparation of bimetallic Au/Ag nanocomposite films. ► Ag and Au nanoparticles in the films possess sphere structure with small size. ► The bimetallic film inherits the properties from both the metal Ag and Au. ► The bimetallic film is superior to the monometallic film in the applications of catalysis and SERS.A facile strategy has been developed for the preparation of bimetallic gold–silver (Au–Ag) nanocomposite films by alternating absorption of poly-(ethyleneimine)–silver ions and Au onto substrates and subsequent reduction of the silver ions. The composition, micro-structure and properties of the {PEI–Ag/Au}_n nanocomposite films were characterized by ultraviolet visible spectroscopy (UV–vis), transmisson electron microscopy (TEM), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), surface enhanced Raman scattering (SERS) and cyclic voltammetry (CV). The UV–vis characteristic absorbances of {PEI–Ag/Au}_n nanocomposite thin film increase almost linear with the number of bilayers, which indicates a process of uniform assembling. Appearance of a double plasmon bands in the visible region and the lack of apparent core–shell structures in the TEM images confirm the formation of bimetallic Au–Ag nanoparticles. The result of XPS also demonstrates the existence of Ag and Au nanoparticles in the nanocomposite films. TEM and FESEM images show that these Ag and Au nanoparticles in the films possess sphere structure with the size of 20–25nm. The resulting {PEI–Ag/Au}_n films inherit the properties from both the metal Ag and Au, which exhibits a unique performance in SERS and electrocatalytic activities to the oxidation of dopamine. As a result, the {PEI–Ag/Au}_n films are more attractive compared to {PEI–Ag/PSS}_n and {PEI/Au}_n films.

Keywords: {PEI–Ag/Au}; _n; bimetallic nanocomposite film; Layer-by-layer self-assembly; Electrocatalysis

Optical nonlinearities of nanostructured VO₂ thin films with low phase transition temperature by Boqing Wang; Sihai Chen; Zhangli Huang; Ming Fu (pp. 5319-5322).

► VO₂ thin films with phase transition temperature of 29°C have been fabricated. ► The average grain diameter of the VO₂ crystallite is between 20nm and 50nm. ► Nanostructured VO₂ thin films exhibit two-photon absorption and a negative nonlinear index of refraction. ► The optical nonlinearities are due to excitation of electronic subsystem.Vanadium dioxides (VO₂) thin films which change from a monoclinic semiconductor phase to a tetragonal metallic structure at the temperature of 29°C have been fabricated by reactive ion beam sputtering. Micrograph of scanning electron microscope (SEM) shows that the grain size of VO₂ crystallite ranges from 20nm to 50nm. Regeneratively amplified Ti:sapphire laser pulses were applied to induce the phase transition, which was accompanying with the third-order optical nonlinearities in VO₂ thin films. Open-aperture and closed-aperture measurements of Z-scan were used to study the optical absorptive and refractive nonlinearities. Nanostructured VO₂ thin films exhibit two-photon absorption and a negative nonlinear index of refraction when phase transition is induced. The optical nonlinearities are due to excitation of electronic subsystem only and without involving of the structural semiconductor-to-metal phase transition.

Keywords: VO; ₂; thin film; Low phase transition temperature; Nonlinearity; Ultrafast

Room-temperature preparation and dielectric properties of amorphous Bi_3.95Er_0.05Ti₃O₁₂ thin films on flexible polyimide substrates via pulsed laser deposition method by Zhong Mo; Guangheng Wu; Dinghua Bao (pp. 5323-5327).

► Amorphous Bi_3.95Er_0.05Ti₃O₁₂ (BErT) films were prepared on flexible polyimide. ► The flexible BErT films show excellent dielectric characteristics. ► Curved BErT films still remain superior dielectric performance. ► The BErT films show good dielectric aging effect and high optical transparency.Bi_3.95Er_0.05Ti₃O₁₂ (BErT) thin films were prepared on flexible polyimide (PI) substrates at room temperature by pulsed laser deposition. These BErT thin films deposited under low oxygen pressures are dense, uniform, and crack-free with an amorphous structure. The highly flexible thin film with a thickness of about 160nm deposited under 3Pa oxygen pressure shows excellent dielectric characteristics, such as a dielectric constant of 51 and a dielectric loss of 0.025, and a maximum capacitance density of 237nF/cm² at 1kHz. When it is curved at different curvature radii (by applying external deformation), the thin film still remains superior dielectric performance. In addition, the thin film also shows good dielectric aging characteristic (or thermal stability) and high optical transparency. BErT thin films can find applications in flexible optoelectronic devices and embedded capacitors.

Keywords: BErT thin film; Flexible substrate; Dielectric property; Pulsed laser deposition

Environment-friendly Pd free surface activation technics for ABS surface by Zengnian Shu; Xu Wang (pp. 5328-5331).

. An environment-friendly surface etching and activation technics for ABS surface metallization were investigated as a replacement for conventional chromic acid etching bath and palladium catalyst. After etching by H₂SO₄–MnO₂ colloid, the ABS surfaces became roughness; meanwhile the carboxyl and hydroxyl groups were formed on the surface. With absorption and a reduction by a dimethylamineborane solution, copper particles were deposited on the ABS surface, which serves as a catalyst replacement for SnCl₂/PdCl₂ colloid. The effects of CuSO₄ concentration, (CH₃)₂NHBH₃ concentration, reduction temperature and reduction time on the adhesion strength between the ABS surface and the electroless copper film were investigated. And the average adhesion strengths reached 1.31kNm⁻¹, which is near the values (1.19kNm⁻¹) obtained by SnCl₂/PdCl₂ colloid.► The ABS surfaces were etched by H₂SO₄–MnO₂ colloid. ► With absorption and a reduction by a dimethylamineborane solution, copper particles were deposited on the ABS surface, which serves as a catalyst replacement for SnCl₂/PdCl₂ colloid. ► The adhesion strength between the ABS surface and the electroless copper film were investigated.An environment-friendly surface etching and activation technics for acrylonitrile–butadiene–styrene (ABS) surface metallization were investigated as a replacement for conventional chromic acid etching bath and palladium catalyst. After etching by H₂SO₄–MnO₂ colloid, the ABS surfaces became roughness; meanwhile the carboxyl and hydroxyl groups were formed on the surface. With absorption and a reduction by a dimethylamineborane solution, copper particles were deposited on the ABS surface, which serves as a catalyst replacement for SnCl₂/PdCl₂ colloid. The effects of CuSO₄ concentration, (CH₃)₂NHBH₃ concentration, reduction temperature and reduction time on the adhesion strength between the ABS surface and the electroless copper film were investigated. And the average adhesion strengths reached 1.31kNm⁻¹, which is near the values (1.19kNm⁻¹) obtained by SnCl₂/PdCl₂ colloid.

Keywords: Electroless plating; Reducing agent; ABS resin material; Adhesion strength

Influence of surface charge on lysozyme adsorption to ceria nanoparticles by Binghui Wang; Peng Wu; Robert A. Yokel; Eric A. Grulke (pp. 5332-5341).

► 12nm ceria were functionalized to develop three different surface charges. ► Lysozyme (+ charge) was adsorbed to (+), neutral, and (−) ceria surfaces. ► Isotherms were compared to orientation and surface alignment limits. ► Lysozyme loadings on the negatively charged ceria exceeded the jamming limit. ► Site energy distributions may help interpret protein coronas on nanoparticles.Understanding mechanisms for forming protein coronas on nanomaterial surfaces is essential to designing drug delivery systems and designing and interpreting the results of nanomaterial toxicity tests. The study reports the adsorption behavior of a positively charged protein, lysozyme, on cerium dioxide (ceria) nanoparticles with three different surface charges. Adsorption isotherms were modeled with the Toth and Sips equations. Isotherm loading levels were compared to monolayer coverage estimate for ‘side-on’ and ‘end-on’ lysozyme orientations as well as random packing (jamming) and maximum packing limits. Evaluation of adsorption site energy distributions (generated using the model coefficients) suggested that the negatively charged ceria surface had a very broad site energy distribution and that its surface heterogeneity controls the adsorption process. By contrast, the adsorption of lysozyme on the positively charged nanoparticles appears to be influenced by lateral effects from adsorbed protein species. The results illustrate the importance of nanoparticle surface chemistry to protein adsorption. The modeling and site energy distribution evaluations may be useful for interpreting the formation of protein coronas on nanoparticles.

Keywords: Nanoparticle; Ceria; Functionalization; Protein sorption; Site energy distribution

Low dielectric loss of Mg doped Ni–Cu–Zn nano-ferrites for power applications by M. Abdullah Dar; Vivek Verma; S.P. Gairola; W.A. Siddiqui; Rakesh Kumar Singh; R.K. Kotnala (pp. 5342-5347).

► Magnesium substituted Nickel Copper Zinc nano-ferrite having general formulae Ni0.5−_xCu_0.2Zn_0.3Mg_xFe₂O₄(0.0≤ x≤0.4) has been prepared at relatively lower temperature (900°C) by sol-gel technique.► The value of permittivity is observed to increase to a maximum value of ∼8×10² for x=0.4 sample.► A remarkable decrease in power loss and loss tangent is observed with the increase in Mg concentration, which is useful for power application of ferrites.► Improvement in magnetic properties has also been observed in the magnesium substituted Nickel Copper Zinc nano-ferrite.Magnesium substituted nickel copper zinc nano-ferrite having the general formulae Ni0.5−_xCu_0.2Zn_0.3Mg_xFe₂O₄ (0.0≤ x≤0.4) were prepared at relatively lower temperature (900°C) by sol–gel technique. Thermal gravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy were used for the characterization of as-synthesized samples. It has been observed that the value of permittivity increases to a maximum value of ∼8×10² for x=0.4 sample. A remarkable decrease in power loss and loss tangent has been observed with the increase in Mg concentration. The Cole–Cole diagrams were investigated in which a single semi-circle is obtained for all the samples except for the sample with x=0.4. The presence of two semi-circles for the sample with x=0.4 indicates that the conduction is due to the grain and grain boundary, while for the rest of the samples the conduction due to the grain boundary is predominant. An improvement in magnetic properties has also observed in the magnesium substituted nickel copper zinc nano-ferrite. Also coercivity was found to decrease with Mg concentration which is useful for power applications.

Keywords: Nano-materials; Magnetization; Permittivity; Dielectric loss

A facile and efficient approach to decoration of graphene nanosheets with gold nanoparticles by Zhang-Gao Le; Zhirong Liu; Yong Qian; Chunyan Wang (pp. 5348-5353).

► We have demonstrated a simple and effective approach to the decoration of AuNPs on GNs by using PDDA as eco-friendly reducing agent and stabilizer for the first time. ► A uniform distribution of AuNPs on the surface of GNs without agglomerates can be obtained through this route. ► AuNPs@GNs exhibits excellent electrochemical activity and good electrocatalytic activity toward AA.In this study, we present a simple and effective approach to the in situ decoration of gold nanoparticles on graphene nanosheets (AuNPs@GNs), employing graphene oxide (GO) as precursor and poly(diallyldimethylammonium chloride) (PDDA) as environmentally friendly reducing agent and stabilizer. The microstructures of as-prepared GO and AuNPs@GNs were characterized in detail. The results confirmed that the high dispersion of AuNPs with mean particle size around 4.1nm on the surface of graphene nanosheets (GNs) could be easily obtained via using PDDA as reductant; moreover the AuNPs@GNs hybrids exhibited excellent electrochemical activity. This work presents a facile approach to synthesize GNs and opens up a new possibility for preparing graphene and graphene-based nanomaterials for large-scale applications.

Keywords: Graphene nanosheets; Poly(diallyldimethylammonium chloride) (PDDA); Gold nanoparticles

Effect of oxygen partial pressure on the structure and properties of Cu–Al–O thin films by Yongjian Zhang; Zhengtang Liu; Liping Feng; Duyang Zang (pp. 5354-5359).

► Cu–Al–O films have been obtained by RF magnetron sputtering method. ► CuAlO₂ phase has been obtained after annealing treatment at Ar ambience at 1000°C for 3h. ► The structures and properties of the annealed films are affected significantly by oxygen partial pressure during deposition.We have studied the electrical and optical properties of Cu–Al–O films deposited on silicon and quartz substrates by using radio frequency (RF) magnetron sputtering method under varied oxygen partial pressure P_O. The results indicate that P_O plays a critical role in the final phase constitution and microstructure of the films, and thus affects the electrical resistivity and optical transmittance significantly. The electrical resistivity increases with the increase of P_O from 2.4×10⁻⁴mbar to 7.5×10⁻⁴mbar and afterwards it decreases with further increasing P_O up to 1.7×10⁻³mbar. The optical transmittance in visible region increases with the increase of P_O and obtains the maximum of 65% when P_O is 1.7×10⁻³mbar. The corresponding direct band gap is 3.45eV.

Keywords: Cu–Al–O film; Magnetron sputtering; Oxygen partial pressure; Electrical resistivity

A spectrocolorimetric and chemical study on color modification of heat-treated wood during artificial weathering by Xianai Huang; Duygu Kocaefe; Yasar Kocaefe; Yaman Boluk; Andre Pichette (pp. 5360-5369).

► Investigate the detailed color variation caused by artificial weathering of three heat-treated regional North American species due to artificial weathering with Kubelka–Munk (K–M) spectra and CIE- L* a* b* system. ► Chemical analysis of heat-treated wood main components during weathering. ► Identify the connection between heat-treated wood discolorations and the degradation of wood components.Effect of artificial weathering on the wood surface color modifications of three North American species (jack pine, aspen, and birch) heat-treated under different temperatures was studied by spectrocolorimetric colormeter (datacolor, CHECK TM). Data was analyzed using the reflectance spectra (400–700nm) as well as the CIE- L* a* b* system and Δ E. Kubelka–Munk (K–M) spectra of samples were recorded as a function of artificial weathering time to obtain the absorption maxima of the chromophore woods formed during artificial weathering. The results were compared with those of the respective untreated (Kiln-dried) species. Analysis of chemical components shows that the lignin percent of jack pine, aspen, and birch increased after heat treatment (28.66–35.9%, 20.27–26.41%, and 19.04–22.71% respectively) which might be due to smaller influence of heat treatment on lignin content than hemicelluloses. This improves the resistance of heat-treated wood to photo-degradation. This is also supported by the smaller change observed in K–M spectra and total color parameters in CIE- L* a* b* system of heat-treated wood samples compared to those of untreated wood when weathered for72h. However, the lignin percent of heat-treated woods reduce to maximum 2.5% after artificial weathering of 1512h. This suggests that the weathering degrades most lignin matrix; consequently, both the colors of heat-treated woods and untreated woods are lighter and very similar after a long period of artificial weathering.

Keywords: Heat-treated wood; Color modifications; Artificial weathering; Chemical component degradation; Reflectance spectra; Kubelka–Munk; CIE-; L; *; a; *; b; * parameters

Oxidative decomposition of volatile organic compounds using thermally-excited activity of hydroxyapatite by Harumitsu Nishikawa; Takashi Oka; Naoki Asai; Hiroyuki Simomichi; Takashi Shirai; Masayoshi Fuji (pp. 5370-5374).

► We would like to propose that HAp has also thermally-excited activity in addition to the normal catalytic property with active site. ► The oxidation of VOCs must be caused by the activation of oxygen due to the electron trapped on vacancy in HAp from our ESR studies. ► The efficiency of the complete oxidation for VOCs on stoichiometric HAp exceeded to that on calcium-deficient HAp. ► That is, the oxidative activity of stoichiometric HAp was higher than that of calcium-deficient HAp. ► The difference of ESR signal intensity of each HAp sample would show that of the activity.Oxidative decomposition of volatile organic compounds, i.e. toluene, on hydroxyapatite (HAp) under high temperatures was studied. Gaseous toluene, ethyl acetate and iso-propanol, decomposed oxidatively and converted to CO and CO₂ effectively at 400–500°C over stoichiometric or calcium-deficient HAp. From the direct measurement of ESR spectra under high temperatures, the ESR signals ( g-value at around 2.003) for stoichiometric and calcium-deficient HAp under 300–400°C were assigned to the electron trapped on vacancy in HAp. Then, it was concluded that volatile organic compounds were decomposed by the active oxygen radical due to the electron trapped on vacancy in HAp under high temperatures. We propose that HAp has also thermally-excited activity similar to TiO_2.

Keywords: Hydroxyapatite; Volatile organic compounds; Decomposition; Thermally-excited activity; Radical formation

Preparation of porous titanium oxide films onto indium tin oxide for application in organic photovoltaic devices by Andreia G. Macedo; Luana L. Mattos; Edna R. Spada; Rafael B. Serpa; Cristiani S. Campos; Isabel R. Grova; Leni Ackcelrud; Françoise T. Reis; Maria L. Sartorelli; Lucimara S. Roman (pp. 5375-5379).

Display Omitted► Porous ordered TiO₂ films were prepared through sol gel route by using a monolayer of polystyrene spheres as template on indium-tin oxide/glass substrate. ► UV–vis absorbance spectrum show a pseudo band gap (PBG) with maxima at 460nm. ► Organic solar cell prepared with porous titania interlayer displayed higher efficiencies than devices using compact titania films as electrode.In this work, porous ordered TiO₂ films were prepared through sol gel route by using a monolayer of polystyrene spheres as template on indium-tin oxide/glass substrate. These films were characterized by SEM, AFM, Raman spectroscopy, UV–vis absorbance and XRD. The UV–vis absorbance spectrum show a pseudo band gap (PBG) with maxima at 460nm arising from the light scattering and partial or total suppression of the photon density of states, this PBG can be controlled by the size of the pore. We also propose the use of this porous film as electron acceptor electrode in organic photovoltaic cells; we show that devices prepared with porous titania displayed higher efficiencies than devices using compact titania films as electrode. Such behaviour was observed in both bilayer and bulk heterojunction devices.

Keywords: Porous titanium oxide; Organic photovoltaic

Structure and corrosion behavior of iron-based metallic glass coatings prepared by LPPS by Guang Liu; Yulong An; Zhihong Guo; Jianmin Chen; Guoliang Hou; Jie Chen (pp. 5380-5386).

► We prepared a series of iron-based metallic glass coatings by low pressure plasma spraying at different hydrogen flow rates. ► Increasing hydrogen flow rate will improve the denseness of coatings. ► Increase of hydrogen flow rate could lead to phase transformation of coatings from amorphous to partial crystallization. ► All coatings show superior corrosion resistance to cast 316L stainless steel. ► The coating with partial crystallization exhibits better corrosion resistance and higher hardness than amorphous coatings.Low pressure plasma spraying (LPPS) has been used to prepare coatings from the spraying powders of FeCrMoWSiBC at different hydrogen flow rates. X-ray diffraction (XRD), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) were used to study the microstructural characteristics of the spraying powders and as-sprayed coatings. Vickers hardness tester was used to measure the hardness of spraying powders and coatings. At the same time, the corrosion behavior of coatings was evaluated by potentiodynamic polarization test and immersion test. Along with the increase of hydrogen flow rate, the denseness of the as-sprayed coatings increases. Amorphous coatings were obtained at the hydrogen flow rates of 4 and 6Lmin⁻¹, while partial crystallized coating was obtained at hydrogen flow rate of 8Lmin⁻¹. In general, the as-sprayed coatings possess good corrosion resistance in aqueous solutions of 3.5% NaCl and 1N HCl. It is found that the denseness of coatings affects the corrosion resistance positively. Moreover, in this study, the partially crystallized coating shows better corrosion resistance than amorphous coatings. The partially crystallized coating even shows much higher hardness than amorphous coatings and spraying powders. This implies that such coating may find more promising application in engineering owing to desired corrosion resistance in association with good wear resistance.

Keywords: Low pressure plasma spraying; Metallic glass; Amorphous coating; Corrosion

Preparation and characterization of dopamine-decorated hydrophilic carbon black by Lijun Zhu; Yonglai Lu; Yiqing Wang; Liqun Zhang; Wencai Wang (pp. 5387-5393).

► Hydrophilic carbon black were prepared by the encapsulation of hydrophilic PDA for the CB. ► PDA was formed by the oxidative polymerization of dopamine under an aerobic and alkaline condition, and the polymerization was controlled by dopamine concentration and reaction time. ► The modified CB exhibited excellent hydrophilicity and dispersion stability.Inspired by the bio-adhesive proteins secreted by mussels for attachment to almost all wet substrates, a facile method involving oxidative polymerization of dopamine was proposed to prepare highly hydrophilic carbon black (CB) particles. A self-assembled polydopamine (PDA) ad-layer was formed via the oxidative polymerization of dopamine on the surface of CB simply by dipping the CB into an alkaline dopamine solution and mildly stirring at room temperature. The process is simple, controllable, and environment-friendly. The surface composition and structure of the CB were characterized by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The surface morphology of the CB was observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that the PDA ad-layer was successfully deposited on the CB surfaces. The PDA-functionalized CB (CB-PDA) gave a stable colloidal dispersion in water. Contact angle measurement results indicated that the hydrophilicity of CB was significantly improved after dopamine modification. TGA results confirmed that the modified CB maintained good heat resistance. The method provided a facile route to prepare hydrophilic CB having terminal hydroxyl groups.

Keywords: Carbon black; Dopamine; Surface; Hydrophilic

Effect of anodizing voltage on the sorption of water molecules on porous alumina by I. Vrublevsky; K. Chernyakova; A. Bund; A. Ispas; U. Schmidt (pp. 5394-5398).

► Porous alumina films were obtained by double-sided anodizing in a 0.3M oxalic acid. ► The amount of water adsorbed on surface of films is a function of anodizing voltage. ► The structure and composition of anodic alumina were studied by FTIR, SEM, TG/DTA.The amount of water adsorbed on different centers on the surface of oxalic acid alumina films is a function of the anodizing voltage. It is decreased with increasing the anodizing voltage from 20 up to 50V, came up to maximum value at 20–30V and slightly increased at voltages above 50V. Water adsorption by oxide films formed at voltages below 50V can be due to the negative surface charge that is present on the alumina surface. The negative surface charge disappears in the films formed at voltages higher than 50V, and thus, the water is adsorbed on aluminum ions in a tetrahedral and octahedral environment. The correlation between anodizing conditions of aluminum in oxalic acid and the structure and composition of anodic alumina was established by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), thermogravimetric and differential thermal analyses (TG/DTA).

Keywords: Oxalic acid alumina films; Water sorption; DTA; Adsorption centers

TiO₂ nanotube arrays deposited on Ti substrate by anodic oxidation and their potential as a long-term drug delivery system for antimicrobial agents by Claus Moseke; Felix Hage; Elke Vorndran; Uwe Gbureck (pp. 5399-5404).

► Morphological features of TiO₂ nanotube arrays are influenced by a variety of anodization parameters. ► The release kinetics of different medical agents may differ, even when applied to the same surface structure. ► The adjustment of anodization parameters can be utilized to provide for tailored release kinetics for specific medical applications.Nanotube arrays on medical titanium surfaces were fabricated by two different anodization methods and their potential for storage and release of antimicrobial substances was evaluated. The treatment of the Ti surfaces in fluoride containing electrolytes on water as well as on polyethylene glycol basis led to the formation of TiO₂ nanotubes with up to 6.54μm length and average diameters of up to 160nm. Drug release experiments with the model antibiotic vancomycin and with antibacterial silver ions showed that the increased surface area of the anodized samples enabled them to be loaded with up to 450% more active agent than the untreated Ti surfaces. Significant surface-dependent differences in the release kinetics of vancomycin were observed. In comparison to surfaces anodized in an aqueous electrolyte, the release of the antibiotic from surfaces anodized in an electrolyte based on ethylene glycol was significantly retarded, with a release of noticeable amounts over a period of more than 300 days. Loading of nanotube surfaces fabricated in aqueous electrolyte with silver ions revealed increased amounts of adsorbed silver by up to 230%, while the release kinetics showed significant differences in comparison to untreated Ti. It was concluded that nanotube arrays on favored medical implant materials have a high potential for loading with antimicrobial agents and also provide the possibility of tailored release kinetics by variation of anodization parameters.

Keywords: Nanotubes; Anodization; Self-organization

Ultraviolet photodetectors based on ZnO sheets: The effect of sheet size on photoresponse properties by Abbas Ghasempour Ardakani; Meysam Pazoki; Seyed Mohammad Mahdavi; Ali Reza Bahrampour; Nima Taghavinia (pp. 5405-5411).

► UV photodetectors were fabricated based on ZnO sheet thin film. ► The sheets were grown on a ZnO buffer layer instead of expensive conducting substrates such as FTO. ► It was shown that photodetection properties strongly depend on the size of sheets. ► Using comb-like electrode leads to faster response of the device.In this work, ultraviolet photodetectors based on electrodeposited ZnO sheet thin films were fabricated on a glass substrate. Before electrodeposition, a thin buffer layer of ZnO was deposited on the glass by pulsed laser deposition method. This layer not only acted as a nucleation site for ZnO sheet growth, but also made it possible to use cheap glass substrate instead of conventional fluorine-doped tin oxide (FTO) substrate. Our results showed that photoresponse properties of the photodetectors strongly depend on the sheet sizes. The smaller sheets exhibited enhanced photosensitivity, shortened fall times and decreased gain compared to larger ones. We showed that photodetectors based on ZnO sheets have a faster response than ones based on polycrystalline films. It was also shown that even less response time could be obtained by using comb-like electrodes instead of two-electrode.

Keywords: ZnO sheets; UV photodetector; Electrodeposition; Response time

Pinning platinum and Pt-oxide nanoparticles on graphite by Jianzhi Gao; Quanmin Guo (pp. 5412-5417).

► A thermal cracking source is used to co-deposit atomic oxygen and PtO nanoparticles on graphite. ► Atomic oxygen attached to surface carbon atoms serve as pinning site for incoming Pt and PtO. ► Highly-dispersed PtO nanoparticles are formed on the flat terraces of highly-oriented pyrolitic graphite surface.Nanoparticles of platinum oxide are deposited onto a highly oriented pyrolitic graphite (HOPG) substrate. The platinum oxide particles are formed by flowing oxygen gas through a hot (1425K) platinum capillary tube in vacuum. By controlling the temperature and the gas flow, a condition can be reached so that Pt atoms are evaporated from the inner walls of the tube and subsequently oxidised by oxygen either before or after landing on HOPG. Atomic oxygen, produced inside the tube through thermal cracking of O₂, is co-deposited onto HOPG. Atomic oxygen form strong bonds with carbon atoms on the HOPG surface and hence a significant number of pinning sites are created for the incoming platinum and platinum oxide particles.

Keywords: Pt clusters; Platinum; Graphite; Oxidation; Catalysis; Scanning tunnelling microscopy (STM); Surface defects; Adsorption

Platelet adhesion-resistance of titanium substrate with mussel-inspired adhesive polymer bearing phosphorylcholine group by Ye Yao; Kyoko Fukazawa; Wenyong Ma; Kazuhiko Ishihara; Nan Huang (pp. 5418-5423).

Display Omitted► The Ti substrate was modified by the phospholipid polymer. ► The catechol groups in the polymer made stable binding on the Ti substrate. ► The modified surface improved protein and platelet adhesion-resistance significantly. ► It is effective surface modification method on Ti substrate for medical use.To make improvement of hemocompatibility on the titanium (Ti) substrate, mussel-inspired adhesive polymer (PMDP) with both catechol groups for surface anchoring and phosphorylcholine groups for obtaining biocompatibility was synthesized. Only 10s-immersion of Ti substrate into an aqueous solution of PMDP resulted in reliable coating, because the coating was stable during one month rinsing. The PMDP-coated Ti substrate showed significant reduction of amount of proteins and number of platelets adhered on the surface compared with the non-treated Ti substrate. For this immobilization method, no chemical pretreatment of the substrates is necessary, and a stable and hemocompatible coating can be prepared by a simple, one-step procedure. Thus, we concluded that the proposed PMDP immobilization method has promising approach for improving hemocompatibility of Ti substrate for cardiovascular implant application.

Keywords: Surface modification; Catechol group; 2-Methacryloyloxyethyl phosphorylcholine polymer; Titanium substrate; Improved hemocompatibility

Enhancement of characteristics of ZnO thin film surface acoustic wave device on glass substrate by introducing an alumina film interlayer by Wen-Ching Shih; Tzyy-Long Wang; Yan-Kai Pen (pp. 5424-5428).

► We investigate effect of alumina film on SAW properties of ZnO thin film SAW devices. ► V_p and K² were increased with increasing thickness of alumina film. ► Excellent TCF of SAW device was obtained with increasing thickness of alumina film. ► The alumina film could enhance SAW properties of ZnO/glass thin film SAW device.ZnO films with c-axis (0002) orientation have been successfully grown by RF magnetron sputtering on Al₂O₃/glass substrates. The alumina films were deposited on glass substrates by electron beam evaporation. The crystalline structure and surface roughness of the films were investigated by X-ray diffraction and atomic force microscopy, respectively. The phase velocity and coupling coefficient of SAW device were apparently increased when we increased the thickness of alumina film. Besides, an excellent temperature coefficient of frequency of SAW device was obtained with increasing the thickness of alumina film. The experimental result is beneficial to improve the performance of the ZnO thin film SAW devices on cheap glass substrate with easier process and lower cost.

Keywords: ZnO film; Surface acoustic wave device; Alumina film

Facile preparation of dendritic Ag–Pd bimetallic nanostructures on the surface of Cu foil for application as a SERS-substrate by Zao Yi; Xiulan Tan; Gao Niu; Xibin Xu; Xibo Li; Xin Ye; Jiangshan Luo; Binchi Luo; Weidong Wu; Yongjian Tang; Yougen Yi (pp. 5429-5437).

Dendritic Ag–Pd bimetallic nanostructures were synthesized using a multi-stage galvanic replacement reaction method at 100°C. These dendritic Ag–Pd bimetallic nanostructures exhibit high SERS activity and may have potential applications in investigating the surface chemistry in a particular reaction using SERS, for example, “in situ” Pd catalytic reactions.Display Omitted► Dendritic Ag–Pd bimetallic nanostructures were synthesized using a multi-stage galvanic replacement reaction method. ► Dendritic Ag–Pd bimetallic nanostructures together with the Cu substrate can be directly used as SERS substrate to probe molecules. ► The dendritic Ag–Pd bimetallic nanostructures exhibit high SERS activity.Dendritic Ag–Pd bimetallic nanostructures have been synthesized on the surface of Cu foil via a multi-stage galvanic replacement reaction (MGRR) of Ag dendrites in a Na₂PdCl₄ solution. After five stages of replacement reaction, one obtained structures with protruding Ag–Pd flakes; these will mature into many porous structures with a few Ag atoms that are left over dendrites. The dendritic Ag–Pd bimetallic nanostructures were characterized by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray (EDX), selected area electron diffraction (SAED) and X-ray photoelectron spectroscopy (XPS). The morphology of the products strongly depended on the stage of galvanic replacement reaction and reaction temperature. The morphology and composition-dependent surface-enhanced Raman scattering (SERS) of the as-synthesized Ag–Pd bimetallic nanostructures were investigated. The effectiveness of these dendritic Ag–Pd bimetallic nanostructures on the surface of Cu foil as substrates toward SERS detection was evaluated by using rhodamine 6G (R6G) as a probe molecule. The results indicate that as-synthesized dendritic Ag–Pd bimetallic nanostructures are good candidates for SERS spectroscopy.

Keywords: Dendritic Ag–Pd bimetallic nanostructures; Copper foil; Surface enhanced Raman scattering; Rhodamine 6G

Prediction of surface and adhesion energies of nanoimprint lithography materials and anti-sticking layers by molecular dynamics simulation by Ji-Hoon Kang; Kwang-Seop Kim; Kyung-Woong Kim (pp. 5438-5442).

► A noble MD method is suggested to predict surface and adhesion energies. ► The MD simulation and experimental results using liquid contact angle are compared. ► The suggested MD method gives a good prediction of surface and adhesion energies. ► The relative error is about 10% for PMMA and SAM, and about 20% for amorphous SiO₂.Molecular dynamics (MD) simulations are performed to calculate the surface and adhesion energies of nanoimprint lithography materials. The proposed simulation models include an amorphous SiO₂, an amorphous poly(methylmethacrylate) film and self-assembled monolayers as anti-sticking layers. For the calculation of the surface and adhesion energies, a noble MD method is suggested to take into account the temperature effect, calculating the potential energy difference between the contacting and separate surfaces. The results of simulations are compared with the results of experiments obtained from liquid contact angle measurements and previous references. The relative error between simulations and experiments is about 10% for poly(methylmethacrylate) and self-assembled monolayers, and about 20% for amorphous SiO₂, respectively. It is concluded that the suggested MD simulation model has given a satisfactory prediction of surface and adhesion energies and could provide more accurate results with the help of improved force fields.

Keywords: Molecular dynamics simulation; Surface and adhesion energy; Anti-sticking materials

Fabrication of transparent superhydrophobic silica-based film on a glass substrate by Shing-Dar Wang; Shih-Shiang Luo (pp. 5443-5450).

Display Omitted► A film realized transmission of 90.90% and water contact angle of 154.32°. ► 1TEOS:48C₂H₅OH:4H₂O (pH 1.2) was used to hydrolyze TEOS at 70°C. ► HMDS was reacted with hydrolyzed TEOS to produce hydrophobic silica. ► Sol aged at 20°C in refrigerator for 48h yielded a transparent superhydrophobic film. ► No additional surface chemistry modification was needed.Tetraethoxysilane (TEOS) was hydrolyzed in an acidic environment and then reacted with hexamethyldisilazane (HMDS) to obtain a superhydrophobic transparent film on a glass substrate. The molar ratios of water and ethanol to TEOS, the pH value of the acidic (or basic) water that is used to hydrolyze TEOS, the heat treatment conditions and other factors were investigated systematically to optimize the transmission through, and the contact angle of water on the film. HMDS (total amount of HMDS/TEOS=2) was divided into 20 parts, which were added into the sol successively to prevent the sudden production of a large quantity of NH₃ in a small area of the sol. The optical and hydrophobic properties of the sol gel continued to change after it had been prepared. The conditions that TEOS was hydrolyzed with acidic water at pH 1.2 at 70°C and the sol gel was aged at 20°C for 48h realized transmission of 90.9% and a water contact angle of 154.3°. No additional surface chemistry modification was needed.

Keywords: Superhydrophobic; Water contact angle; Transparent; Sol gel; Hydrolyze

Porous-pyramids structured silicon surface with low reflectance over a broad band by electrochemical etching by Hongjie Lv; Honglie Shen; Ye Jiang; Chao Gao; Han Zhao; Jiren Yuan (pp. 5451-5454).

► Porous-pyramids structured silicon surface was fabricated and the PS was formed by using electrochemical etching firstly. ► Much lower reflectance of silicon wafer with this structure was obtained compared with that of single pyramid or porous silicon. ► An average reflectance of 2.7% has been achieved over a broad wavelength range (200–2000nm) and from 400 to 800nm. ► The antireflection mechanism of multilayer PS possessing gradient indices was discussed according to A.J. Fresnel formula about reflectance.Porous-pyramids structured silicon surface was prepared and its influence on the reflectance of the silicon surface was studied. The porous-pyramids structured surface was prepared by electrochemical etching in HF/C₂H₅OH solution after texturization in NaOH/IPA solution. The average reflectance of the surface in the range of 400–800nm was as low as 1.9%. The optical photographs and SEM images of the surfaces prepared under optimized condition were investigated. The porous-pyramids structured surface has a gradient-index multilayer structure (i.e., the refraction index of the structure increase from the top to the bottom). A formula that describes the relationship between the reflectance and the index of refraction was used to explain the excellent broadband antireflection of the multilayer silicon surface. The technique of this paper may be valuable in the texturization process for high-efficiency silicon solar cells.

Keywords: Porous-pyramids; Reflectance; Electrochemical etching; Silicon

Alkali-dependent synthesis of flower-like ZnO structures with enhanced photocatalytic activity via a facile hydrothermal method by Lin Sun; Rong Shao; Zhidong Chen; Lanqin Tang; Yong Dai; Jianfei Ding (pp. 5455-5461).

► Flower-like ZnO structures are prepared by a facile hydrothermal method. ► Alkaline environments are responsible for the morphological transition. ► Flower-shaped ZnO samples exhibit the highest photocatalytic activity. ► The growth mechanism and photodegradation process are proposed.Flower-like ZnO structures with high photocatalytic performance were successfully synthesized via a facile hydrothermal method. Alkaline environment played a critical role during the morphological transformation. When the molar ratio of Zn(CH₃COO)₂·2H₂O to NaOH was set as 1:8 in the presence of triethanolamine (TEA), and the molar ratio of Zn²⁺ to TEA was 1:9, the flower-like ZnO product was produced. The hexagonal sphere-like, oblate-like, and hexagonal biprism-like samples were also obtained by adjusting the molar ratio of Zn²⁺ to NaOH as 1:2, 1:5 and 1:12 with the presence of invariable amount of TEA, respectively. The prepared ZnO products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) surface area. Photodegradation experiments of the samples were carried out by choosing Methylene Blue (MB) as a model target under UV irradiation with homemade photocatalytic apparatus. Among these products, flower-shaped samples exhibited the highest photocatalytic activity.

Keywords: ZnO; Hydrothermal method; Crystal growth; Photocatalysis

Characterization and properties of amorphous carbon coatings prepared by middle frequency pulsed unbalanced magnetron sputtering at different substrate bias by H.Y. Dai; Y.Q. Wang; X.R. Cheng; C.Y. Zhan; N.K. Huang (pp. 5462-5466).

► a-C coatings were synthesized by middle frequency pulsed unbalanced magnetron sputtering technique. ► The coating deposited at 120V exhibited the optimized synthetic properties. ► The AES depth profile exhibited that the C element distributes uniformly and has penetrated into the Si substrate. ► The influences of substrate bias on the sp3 fraction can be explanted by the sub-plantation model. ► The coatings may be used as antireflection protection coatings.The amorphous carbon (a-C) coatings were synthesized at different substrate bias using a middle frequency pulsed unbalanced magnetron sputtering technique. Some properties of the coatings were characterized using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), nano-indentation tests, spectroscopic ellipsometry (SE). SEM measurement shows that the deposited a-C coatings are comparatively uniform. XPS and AES measurements show that sp³ content in a-C coatings changes with increasing substrate bias voltage. AES depth profile exhibits that the C element distributes uniformly across the coating thickness, and carbon atoms have penetrated into the Si substrate. Nano-indentation and spectroscopic ellipsometry tests indicate that the coating deposited at the substrate bias of 120V shows the optimized synthetic properties with higher nanohardness, higher elastic modus, higher refractive index and lower extinction coefficient. These results above are useful for the practical application of a-C as antireflection protection coatings. The influences of substrate bias on the sp³ fraction can be explanted by the sub-plantation model.

Keywords: Amorphous carbon coating; Substrate bias; Properties

Influence of humidity on atmospheric pressure air plasma treatment of aluminium surfaces by V. Prysiazhnyi; V. Zaporojchenko; H. Kersten; M. Černák (pp. 5467-5471).

► Uniform aluminium surface cleaning from the hydrocarbon contaminants. ► Aluminium oxide hydration effect by plasma treatment. ► Aging effect of plasma treated aluminium surfaces.Atmospheric pressure air plasma treatment of aluminium surfaces and its aging behaviour in different environments were studied. Two types of aluminium samples with different purity and surface morphology were treated using the diffuse coplanar surface barrier discharge (DCSBD). Surface free energy (SFE) and X-ray photoelectron spectroscopy (XPS) have been utilised to characterise changes induced by the plasma. A significant decrease of hydrocarbon contaminants after the plasma treatment was observed. It is concluded that besides the re-contamination by exposure to ambient air, the aging effect, i.e. decrease of the surface free energy of plasma treated surfaces, can be due by dehydration of aluminium oxide layer. Also, it was observed that the humid air plasma treatment resulted in generation ofNO_x surface groups.

Keywords: Aluminium; Humid air plasma; Surface treatment; Aging effect; Surface DBD

Coating pretreatment for Mg alloy AZ91D by H.Y. Yang; X.B. Chen; X.W. Guo; G.H. Wu; W.J. Ding; N. Birbilis (pp. 5472-5481).

► Tuning the surface chemistry on AZ91D was achieved by activation and conditioning. ► The ability to be able to tune the surface roughness by activation is apparent. ► Anodic/cathodic activity on the surface was tuned by activation and conditioning. ► The methods described are ‘green’ in that they do not advocate the use of chromate and fluoride.Coating defects and coating failure upon Mg alloy AZ91D are usually due to non-uniform coating growth, which is intrinsically caused by the microstructural heterogeneity of the Mg substrate. This is the case for both conversion coatings and electroplated (incl. electroless) coatings. In the present study, coating pretreatment for the purpose of tailoring surface chemistry on AZ91D was studied. Pretreatments to control β-phase morphology and surface homogeneity include alkaline conditioning and acid activation in four different non-toxic (F-free) acid solutions: H₃PO₄, HNO₃, HCl and C₆H₈O₇. The results show that careful pretreatment can do all of the following: modify surface roughness; remove β-phase; modify solid solution chemistry; and most importantly, tailor the anodic/cathodic character of the surface. This allows surface pretreatment to be customized to optimize the subsequent coating. The influence of different acids was shown to be marked.

Keywords: Pretreatment; AZ91D Mg alloy; Roughness; Conversion coating; Electroplating

Electromagnetic energy absorption potential and microwave heating capacity of SiC thin films in the 1–16GHz frequency range by B. Aïssa; N. Tabet; M. Nedil; D. Therriault; F. Rosei; R. Nechache (pp. 5482-5485).

EM absorption tests show that temperatures exceeding 2000K can be reached in a very short time, less than 100s exposure to microwaves, showing a promising potential for specific microwave heating applications.Display Omitted► We have PECVD grown a-SiC:H thin films on un-doped Si substrates. ► Our SiC films show deep EM absorption – up to 96% of the total EM irradiation. ► These SiC films have a high efficiency in converting EM absorption to heat. ► Temperature exceeding 2000K reached in less than 100s exposure to EM were obtained. ► Higher-quality SiC films could be obtained after their microwave heating.We report on the electromagnetic (EM) absorption potential and microwave heating capacity of amorphous hydrogenated silicon carbide thin films (a-SiC:H) in the 1–16GHz frequency domain. a-SiC:H thin films with typical thickness of 1μm were deposited by plasma enhanced chemical vapor deposition on [100] undoped silicon substrates, and exhibit a deep EM absorption – up to 96% of the total EM energy irradiation – which is systematically converted into heat. Two-wavelength pyrometer tests show that temperatures exceeding 2000K can be reached in a very short time, less than 100s exposure to microwaves, showing a promising potential for specific microwave heating applications.

Keywords: PECVD; Silicon carbide materials; EM absorption; Microwave heating

Ferromagnetic anisotropy of carbon-doped ZnO nanoneedles fabricated by ion beam technique by C.S. Wei; S.P. Lau; M. Tanemura; M. Subramanian; Y. Akaike (pp. 5486-5489).

► We report the ferromagnetic anisotropy of carbon-doped ZnO (ZnO:C) nanoneedles. ► The anisotropy of the ZnO:C was studied using the dipole–dipole interaction model. ► The ferromagnetic anisotropy with an easy axis perpendicular to the shape axis of the ZnO:C nanoneedles.Carbon-doped ZnO (ZnO:C) nanoneedles were fabricated using ion beam irradiation with a simultaneous supply of carbon at room temperature. The structure and the magnetic properties of the ZnO:C nanoneedles were investigated. Hysteresis loops and zero-field cooling (ZFC) and field cooling (FC) curves demonstrated the ferromagnetic properties of the ZnO:C nanoneedles. The Curie temperature of the ZnO:C is above 330K. The ferromagnetic anisotropy with an easy axis perpendicular to the shape axis of the ZnO:C nanoneedles was observed due to the dipole–dipole magnetic interaction amongst nanoneedles.

Keywords: PACS; 75.75.Cd; 75.50.Pp; 75.30.GwZnO:C nanoneedles; Ion beam irradiation; Ferromagnetic properties; Ferromagnetic anisotropy

Characterization of air-formed surface oxide film on a Co–Ni–Cr–Mo alloy (MP35N) and its change in Hanks’ solution by Akiko Nagai; Yusuke Tsutsumi; Yuta Suzuki; Keiichi Katayama; Takao Hanawa; Kimihiro Yamashita (pp. 5490-5498).

Display Omitted► The surface of a polished Co–Ni–Cr–Mo alloy (MP35N) consists of chromium-enriched (Cr³⁺) oxide. ► By immersion in Hanks’ solution, chromium (Cr³⁺) is more enriched in the oxide. ► During immersion in Hanks’ solution, calcium phosphate was formed. ► Nickel decreased in both the surface oxide and the substrate alloy when specimens were immersed in Hanks’ solution.The air-formed surface oxide films used for stents were characterized to determine their composition and chemical state on a Co–Ni–Cr–Mo alloy. The change of the films in Hanks’ solution was used to estimate the reconstruction of the film in the human body. Angle-resolved X-ray photoelectron spectroscopy was used to characterize the composition of the film and substrate, as well as the film's thickness. The surface oxide film on the Co–Ni–Cr–Mo alloy (when mechanically polished) consists of oxide species of cobalt, nickel, chromium, and molybdenum, contains a large amount of OH⁻, and has a thickness of approximately 2.5nm. Cations exist in the oxide as Co²⁺, Ni²⁺, Cr³⁺, Mo⁴⁺, Mo⁵⁺, and Mo⁶⁺. Chromium is enriched and cobalt and nickel are depleted in the oxide; however, nickel is enriched and cobalt is depleted in the substrate alloy just under the surface oxide film. Concentration of chromium was low and that of nickel was high at small take-off angles. This indicates that distribution of chromium is greater in the inner layer, but nickel is distributed more in the outer layer of the surface oxide film. During immersion in Hanks’ solution, cobalt and nickel dissolved, and the film composition changed to mostly chromium oxide (Cr³⁺), along with small amounts of cobalt, nickel, and molybdenum oxides, and calcium phosphate containing magnesium, potassium, and carbonate. After immersion in Hanks’ solution, the thickness of the surface layer containing calcium phosphate increased to more than 4nm, while the amount of OH⁻ increased. The amount of cobalt and nickel in the surface oxide film and in the substrate alloy just below the oxide decreased during immersion.

Keywords: Cobalt–nickel–chromium–molybdenum alloy; Surface oxide; XPS; Calcium phosphate

Pt(II) porphyrin modified TiO₂ composites as photocatalysts for efficient 4-NP degradation by Ming-yue Duan; Jun Li; Min Li; Zeng-qi Zhang; Chen Wang (pp. 5499-5504).

► Three new Pt(II) porphyrin modified TiO₂ composites as photocatalysts were investigated for the first time. ► Pt(II) porphyrins greatly enhanced the photocatalytic efficiency of bare TiO₂ in photodegrading the 4-NP. ► The distinct space tropisms of peripheral substituents in meso-sites of porphyrin ring led to different photoactivity.Three Pt(II) porphyrins 5,10,15,20-tetra-[2 or 3 or 4-(3-phenoxy)propoxy]phenyl porphyrin]platinum(II) (1–3) were synthesized and characterized spectroscopically. The corresponding Pt(II) porphyrins–TiO₂ composites were then prepared and characterized by means of FT-IR and diffused reflectance spectra, X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of Pt(II) porphyrins–TiO₂ catalyst was investigated by testing the photodegradation of 4-nitrophenol (4-NP) in aqueous solution under irradiation with Xenon lamp. The results indicated that Pt(II) porphyrins greatly enhanced the photocatalytic efficiency of bare TiO₂ in photodegrading the 4-NP, and the distinct space tropisms of peripheral substituents in meso-sites of porphyrin ring led to different results.

Keywords: Pt(II) porphyrin; Titanium dioxide; Photocatalysis; Photodegradation; 4-Nitrophenol

Influence of plasma treatment time on plasma induced vapor phase grafting modification of PBO fiber surface by B. Song; L.H. Meng; Y.D. Huang (pp. 5505-5510).

Display Omitted► Oxygen plasma induced vapor phase grafting of acrylic acid on PBO fibers. ► The interfacial adhesion between PBO fibers and epoxy resin was enhanced by plasma induced vapor phase grafting (PIVPG) method. ► The time of plasma pre-treatment has an obviously influence on the surface properties of treated PBO fibers using PIVPG method.The surface of poly- p-phenylene benzobisthiazole (PBO) fibers was treated through oxygen plasma induced vapor phase grafting (PIVPG) method under various oxygen plasma pre-treatment time conditions. The surface chemical composition, surface morphologies and surface free energy of pristine and treated PBO fibers were studied using X-ray photoelectron spectroscopy, atomic force microscopy, scanning electron microscopy, and Cahn DCAA system. The mechanics property of these fibers was evaluated by tensile strength and interfacial shear strength (IFSS). It was found that the surface characteristics of treated PBO fibers occurred significant change compare with the pristine PBO fibers. After treatment, the polar functional groups were introduced on the fiber surface. Carbon concentration decreased; oxygen concentration and elemental ratio of oxygen to carbon increased. Acrylic acid can react with the activated PBO fibers surface, which led to the fiber surface roughness increased. The surface free energy increased from 41.4mN/m to 62.8mN/m when PBO fibers were plasma pre-treated for 10min, while the IFSS of PBO fibers with epoxy resin increased from 36.6MPa to 55.8MPa. Therefore, PIVPG can be used to enhance the interfacial bond between PBO fibers and epoxy resin.

Keywords: PBO fiber; Plasma induced vapor phase grafting; Surface modification; Interfacial adhesion; XPS; SEM

Thermal stability of magnetic characteristics in Tb₄₀(FeCoV)₆₀ films by T.F. Feng; Z.Y. Chen (pp. 5511-5515).

► A minimum μ₀ H_c (⊥) and a maximum M_s are obtained at T_s=150°C before annealing. ► Stripe and island domain are obtained at T_s<250°C and at T_s=250°C respectively. ► Annealing can relax anisotropy and can turn easy direction of magnetization. ► Films show hardly relaxation of μ₀ H_c until T_A reaches the original T_s.Films with a composition of Tb₄₀(FeCoV)₆₀ were fabricated by dc magnetron cosputtering from a multiple target arrangement at different substrate temperatures. The samples before and after annealing have been investigated by magnetic force microscope, vibrating sample magnetometer and other testing means for their structure and performance. With the increase of substrate temperature ( T_s), out-of-plane coercivity decreases to a minimal value at T_s=150°C and then increases rapidly while saturation magnetization reaches their highest value at a moderate substrate temperature of 150°C. A homogenous high-contract stripe domain and a low-contrast island domain are obtained for the samples prepared at 150°C and at 250°C, respectively. High substrate temperature stabilizes the films against subsequent annealing which tends to eliminate the anisotropy. The coercivity decreases with increasing annealing temperature ( T_A), but which shows hardly relaxation until the T_A reaches the original T_s. The easy direction of magnetization can be turned from perpendicular to in-plane direction at high annealing temperatures which increase with substrate temperature.

Keywords: TbFeCoV alloy films; Substrate temperature; Annealing; Magnetic domain

Adsorption of Pb(II) from aqueous solution by a poly-elemental mesoporous adsorbent by Xiu-Wen Wu; Hong-Wen Ma; Jing Yang; Feng-Jiao Wang; Zhi-Hong Li (pp. 5516-5521).

. The mesoporous adsorbent is poly-element, was prepared from microcline, and with cetyltrimethylammonium bromide as synthesis directing agent. The Pb(II) experimental uptake of the adsorbent was about 367mgg⁻¹.Display Omitted► A poly-elemental mesoporous adsorbent was hydrothermally prepared from microcline in an alkaline condition with cetyltrimethylammonium bromide as synthesis directing agent. ► BET specific surface area was 835m²g⁻¹, and pore size distribution ranging from 1.5nm to 7.0nm. ► The Pb(II) experimental uptake was about 367mgg⁻¹, a little smaller than the theoretical one (377.17mgg⁻¹) given by Langmuir isotherm model.A poly-elemental mesoporous adsorbent was hydrothermally prepared from microcline in an alkaline condition with cetyltrimethylammonium bromide as synthesis directing agent. The properties of the mesoporous adsorbent were determined by X-ray powder diffraction, high-resolution transmission electron microscope, N₂ adsorption, and solid-state Magic Angle Spinning Nuclear Magnetic Resonance. The pore size distribution was detected by small angle X-ray scattering. The particles size was observed by Scanning electron microscope imagine. The chemical content of SiO₂ in the mesoporous adsorbent was determined by spectrometry of the silicone molybdenum and sulfosalicylic acid complexes, and Al₂O₃ determined by complexometry with ethylene diamine tetraacetic acid in the presence of KF–Zn(Ac)2 tests. The adsorption properties of the mesoporous adsorbent to Pb(II) were studied, and three main factors, the adsorption time, solution pH, and initial concentration of Pb(II), were considered in the adsorption experiments.

Keywords: Adsorption; Pb(II); Mesoporous adsorbent; Water purification

In situ X-ray photoelectron spectroscopy characterization of Al₂O₃/InSb interface evolution from atomic layer deposition by D.M. Zhernokletov; H. Dong; B. Brennan; J. Kim; R.M. Wallace (pp. 5522-5525).

An in situ half-cycle atomic layer deposition/X-ray photoelectron spectroscopy (ALD/XPS) study was conducted in order to investigate the evolution of the Al₂O₃ dielectric interface with InSb(111)A surfaces after sulfur passivation. A thick sulfide layer was observed to form on the as-treated surfaces, with sulfur bonded to both In and Sb. Upon annealing at 300°C in the ALD reactor, the level of Sb bonded to sulfur and oxygen is below the XPS detection limit, while significant concentrations of indium oxide/sulfur states are detected. The “clean-up” of the surface oxides and sulfides by the ALD process is presented.

Keywords: InSb; ALD; Half-cycle; Al; ₂; O; ₃; High-; k

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Applied Surface Science (v.258, #14)

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Applied Surface Science (v.258, #14)