Journal of Sol-Gel Science and Technology (v.68, #2)

Sol–gel synthesis, characterization and catalytic activity of γ-alumina with bimodal mesopore distribution by Vladimir V. Vinogradov; Alexander V. Vinogradov; Anton S. Kraev; Alexander V. Agafonov; Vadim G. Kessler (155-161).
In this study, boehmite sols were used for preparation of mesoporous γ-alumina with bimodal mesopore distribution. Superfine nanospheres of poly(methyl methacrylate) (PMMA) prepared by water based emulsion polymerization method were used as a template. Nitrogen sorption revealed that aluminas prepared using this approach demonstrated bimodal mesopore size distribution with maxima at 3.8 and 25.7 nm, respectively. Catalytic tests showed that bimodal mesopore distribution within γ-Al2O3 prepared with PMMA nanospheres as a template provides improved catalytic activity in the methanol dehydration reaction.
Keywords: Sol–gel synthesis; Dimethyl ether; Template; Mesopore

Preparation and characterization of crack-free sol–gel based SiO2–TiO2 hybrid nanoparticle film by Shumaila Islam; Rosly Abdul Rahman; Zulkafli Othaman; Saira Riaz; M. A. Saeed; Shahzad Naseem (162-168).
Owing to the diverse potential applications of hybrid silica–titania thin films, the synthesis and characterization of these films have been carried out with a special focus on application as a medium index layer for multilayered functional coatings. For synthesis, tetraethylorthosilicate and titanium tetraisopropoxide were chosen as precursors for the formation of silica-titania hybrid thin films/nano-composites through an in situ sol–gel process. These films were sequentially obtained on Cu substrate utilizing spin coating. The hybrids were characterized by field emission scanning electron microscope, energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction, atomic force microscopy and Fourier transform infrared spectroscopy (FTIR). Field emission scanning electron microscope morphology displayed a smooth, densified and crack- free layer of silica-titania hybrid nanoparticles in the range of 20–71 nm after calcinations at low temperature of 300ºC for 1 h. X-ray diffraction pattern confirms the phases of titania with higher crystallinity and phase transformation at low temperature. The prepared films were uniform with low 8.852 nm RMS value. The stoichiometry of films was confirmed by EDX results. The FTIR spectroscopy indicated the establishment of heterogeneous chemical bonding between the Ti and Si surfaces through oxygen.
Keywords: Sol–gel; Silica–titania hybrid; Crack-free

Synthesis of LiNi1/3Co1/3Mn1/3O2 cathode material by a modified sol–gel method for lithium-ion battery by Yaoyao Zhang; Xiaoyan Wu; Ye Lin; Dan Wang; Chunming Zhang; Dannong He (169-174).
LiNi1/3Co1/3Mn1/3O2 was prepared by a modified sol–gel method, selecting ethylene diamine tetraacetic acid and citric acid as the co-chelating agent. The mole ratios of ethylene diamine tetraacetic acid (EDTA) to metal ion (Mn+) were 0:1, 1:1 and 2:1. The obtained samples were characterized by XRD, BET and SEM. The XRD showed that LiNi1/3Co1/3Mn1/3O2 had good crystallinity and well-ordered layered structure. After calcined at 850 °C, the LiNi1/3Co1/3Mn1/3O2 particles exhibited a three-dimensional space network structure, which was greatly correlated with the ratio of EDTA to metal ion. The LiNi1/3Co1/3Mn1/3O2 obtained from a mole ratio of 1:1 (EDTA:Mn+) had the best electrochemical performance. The reversible capacities were reached 168 and 100 mAh/g at 1C and 10C discharge rate, respectively. The result of the cycling performance showed a high capacity maintenance ratio of 89.3 % at 1C and 25 °C after 50 cycles. The further electrochemical performance was evaluated by electrochemical impedance spectroscopy and cyclic voltammetry.
Keywords: LiNi1/3Co1/3Mn1/3O2 ; Sol–gel method; Co-chelating agent; Lithium-ion battery

Lead zirconate titanate (PZT) thin films with a Zr/Ti ratio of 57/43, elaborated by a derived sol–gel process, have been deposited onto bare and RuO2 coated aluminium substrate 16 μm thick. Commercial aluminium foil presents many advantages as ultra light weight (43 g m−2), conformability, conduction, can be easily cut, and is one of the cheapest substrates used for PZT thin films deposition (<0.1$ m-2). XRD measurements have shown a well crystallized PZT in the perovskite structure and ferroelectric behaviour has also been observed. By the use of a RuO2 film 100 nm thick at the PZT/aluminium interface, the coercive field and tunability values have been strongly improved despite an increase of the dielectric losses. The lead excess introduced in the precursor solution has been increased up to 65 % in order to lower the crystallization temperature of the PZT around 560 °C and tunability has been studied as a function of annealing time and temperature.
Keywords: PZT; Aluminium foil; Tunable

Vanadium doped titanium dioxide (V–TiO2) photocatalyst was synthesized by the sol–gel method using ammonium vanadate as vanadium source. The prepared samples were characterized by XRD, N2 adsorption–desorption method, UV–Vis DRS, Fourier transform infrared (FTIR), scanning electron microscope–energy dispersive X-ray and photoluminescence (PL) analysis. The results show that V5+ ions were successfully incorporated into the crystal lattice of TiO2 as a consequence, not only an obvious decrease in the band gap and a red shift of the absorption threshold into the visible light region was recorded for the V modified TiO2, but, also a decrease in photogenerated electrons and holes recombination rate was observed as demonstrated by PL analysis. FTIR study indicated that in undoped TiO2 sample the acetate group favored a bidentate bridging mode of binding with titanium atoms, whereas a bidentate chelating mode of linkage was observed in V–TiO2 powders. The crystallite size of the samples calcined at 300 and 500 °C were decreased beyond the molar ratio of 200:1 (V:Ti), this may be due to dopant presence in the grain boundaries hindering the crystal growth. The photocatalytic activities for both pure and vanadium doped TiO2 powders were tested in the discoloration of a reactive dyestuff, methylene blue, under visible light. The 100:1 (V:Ti) doped photocatalyst, calcined at 300 °C showed enhanced photocatalytic activity under visible light with a rate constant (kobs) of 5.024 × 10−3 min−1 which is nearly five times higher than that of pure TiO2, as result of low band gap value, high specific surface area and a decrease in recombination rate.
Keywords: Band gap; Doped TiO2 ; Photocatalyst; Recombination rate; Sol–gel synthesis

Structural and optical characterizations of rare earth pentaphosphates LnP5O14 (Ln = La, Gd) synthesized by the sol–gel process by Aïcha Mbarek; Geneviève Chadeyron; Daniel Avignant; Damien Boyer; Mohieddine Fourati; Daniel Zambon (193-203).
The sol–gel chemistry route has successfully been used to prepare samples of LnP5O14 (Ln = La, Gd) pentaphosphates from lanthanides chlorides and phosphorous pentoxide dissolved in isopropanol. Crystallized powders of single phase were obtained after calcination of gels at 350 °C. The structural characterizations of materials were investigated by means of X-ray diffraction as well as infrared and Raman spectroscopies, whereas their thermal behavior has been studied by differential thermal analyse and thermogravimetric analyses. Powders morphology was analyzed by means of scanning electron microscopy and laser granulometry. The photoluminescence properties of the Eu3+ ions in sol–gel derived LaP5O14 and GdP5O14 samples were investigated and compared with homologous samples synthesized by the conventional solid state reaction.
Keywords: Pentaphosphates; Sol–gel chemistry; Photoluminescence; Lanthanides

Growth, structure and optical properties of tartaric acid-templated silica nanotubes by sol–gel method by Fei Gao; Yanhua Song; Ye Sheng; Chunming Lin; Qisheng Huo; Haifeng Zou (204-212).
Photoluminescent nano material has been reported as an intriguing field during the past few decades. In this article, tartaric-templated silica nanotubes were conveniently synthesized by sol–gel method. X-ray diffraction analysis, scanning electron microscopy, transmission electron microscopy, fourier transform infrared spectra and photoluminescence spectra analysis were employed to characterize the growth, structure, morphology and optical property of the products. It is found that tartaric templates can form spindle/spherical-like aggregates composed of many sheets under static/stirring condition, which lead to the different shapes of silica nanotubes. Then the probable strategies for silica nanotubes templating with tartaric acid were described particularly. Hydrogen-bond interaction, supramolecular interaction and a competition of various effects may be the reasons of the nanotubes formation. Moreover, under ultraviolet light excitation, the silica nanotubes exhibited blue emission and luminescent intensity of the tubes prepared under the static condition is much stronger than the stirring ones, mostly because of more defect centers in the structures obtained under stirring condition.
Keywords: Tartaric acid; Template; Silica nanotubes; Sol–gel; Photoluminescence

Preparation and photocatalytic antibacterial property of nitrogen doped TiO2 nanoparticles by Pingting He; Jie Tao; Xianli Huang; Jianjun Xue (213-218).
Nitrogen doped TiO2 (N-TiO2) nanoparticles with about 30 nm in size were produced by a sol–gel method and characterized respectively by UV–vis, X-ray diffraction (XRD), Transmission electron microscopy, X-ray photoelectron spectroscopy (XPS). Their photocatalytic antibacterial properties were evaluated by the antibacterial ratio against Escherichia coli in dark and under simulated sunlight respectively. The XRD pattern showed that the doped nano-TiO2 was mainly composed of anatase phase. The XPS spectra of the N-TiO2 sample indicated that TiO2 was doped by nitrogen atom. The nitrogen doping created a new N 2p state slightly above the valence band top consists of O 2p state, and this pushes up the valence band top and decreased the band gap. Which leaded to the absorption edge was red-shifted to the visible light region of UV–vis spectra of nitrogen doped nano-TiO2 comparing with pure nano-TiO2. The antibacterial percentage of N-TiO2 against E. coli reached to 90 % under simulated sunlight for 2 h, which was much better than that in dark, also than that of pure nano-TiO2. The photo-catalytic antibacterial activity was activated under visible light. The structure and integrity of cell wall and cell membrane were destructed, and even caused the bacteria death.
Keywords: Inorganic antibacterial agent; Titanium dioxide; Doped with inorganic non-metal elements; Photocatalysis

Role of reaction atmosphere in preparation of potassium tantalate through sol–gel method by Josef Buršík; Přemysl Vaněk; Filip Mika (219-233).
Potassium tantalate (KT) thin films and powders of both K2Ta2O6 (KT pyrochlore) and KTaO3 (KT perovskite) structures were prepared by means of chemical solution deposition method using Si(111) with ZnO and MgO buffer layers as a substrate. The influence of reaction atmosphere on reaction pathway and phase composition for both KT powders, and KT thin films has been studied mainly by means of powder diffraction and infrared spectroscopy. When an oxygen flow instead of static air atmosphere has been used the process of pyrolysis in oxygen runs over much narrower temperature interval (200–300 °C), relatively to air atmosphere (200–600 °C) and almost no (in case of powders), or no (in case of thin films) pyrochlore intermediate phase has been detected in comparison with treatment in air, where the pyrochlore phase is stable at temperatures 500–600 °C (powders). KT perovskite phase starts to crystallize at temperatures 50° and 150 °C lower compared to air atmosphere in case of powders and thin films, respectively. Microstructure formed by near-columnar grains and small grains of equiaxed shape was observed in films treated in oxygen and air atmosphere, respectively.
Keywords: Potassium tantalate; Thin films; Sol–gel; Crystallization; Reaction atmosphere

Synthesis of gold nanoparticles in sol–gel glass porogens containing [bmim][BF4] ionic liquid by A. Ruivo; M. G. Ventura; M. D. R. Gomes da Silva; C. A. T. Laia (234-244).
The [bmim][BF4] ionic liquid effect on gold nanoparticles formation in silica sol–gel materials is studied in order to produce gel-derived glasses with optical properties. The characteristic red color from gold nanoparticles is observed for transparent glass monoliths obtained sintering, between 365 and 425 °C, a silica sol–gel precursor containing HAuCl4·3H2O and [bmim][BF4], under normal atmospheric conditions. The effect of sintering the ionogel at different temperatures (Tsint) or times (tsint) on the optical properties, shape, size, and distribution of gold nanoparticles is discussed. Presence of the gold particles is observed using transmission electron microscopy images followed by energy dispersive X-ray spectroscopy analysis. The thermal decomposition of [bmim][BF4] in the ionogel is investigate using calorimetric and spectroscopic techniques, and by analysis of volatile compounds released by the sol–gel material during sintering. With these results a mechanism for the formation of the gold nanoparticles is proposed, where a first ionic liquid degradation step provides the reductive environment that enables the gold nanoparticles production at the range of temperatures between 350 and 425 °C. Upon sintering the synthesized materials the ionic liquid acts as a sacrificial additive and the ionic liquid thermal decomposition products enables the formation of gold nanoparticles in the sol–gel matrix.
Keywords: Ionic liquids; Sol–gel; Gold nanoparticles; Spectroscopy; Thermal decomposition

Non-aqueous reactions of aluminum isopropoxide with 8-hydroxyquinoline (Hq = HONH6C9) in 1:1, 1:2 and 1:3 molar ratios in anhydrous benzene yield complexes of the type [qnAl(OPri)3−n] {where n = 1 (1), n = 2 (2), n = 3 (3)}. Progress of the reactions were monitored by estimating liberated 2-propanol in benzene-2-propanol azeotrope by oxidimetric method. All the products were fluorescent green powders, sparingly soluble in CHCl3. They were characterized by elemental analysis, FT-IR and (1H, 13C and 27Al) NMR studies. The ESI mass spectral studies indicate dimeric nature for (1) and (2) and monomeric nature for the compound (3). The XRD spectra of (13) showed crystalline nature with the average particle size of 45, 32 and 27 nm respectively, as evaluated from DebyeScherrer equation. The XRD spectrum of (3) also suggests the formation of β-crystalline polymorphs of Alq3. The SEM images appear to indicate granular morphology for (1) and formation of cylindrical shaped rods for (2) and (3). Sol–gel hydrolysis of (1), (2) or (3) in presence of a strong acid as well as of the precursor, Al(OPri)3,without acid or base catalyst, followed by sintering at 950 °C yielded tetragonal primitive phase of nano-sized δ-alumina in all the cases, as reflected by their powder X-ray diffraction pattern. The IR, SEM and EDX studies also support the formation of transition alumina.
Keywords: Tris (8-hydroxyquinoline) aluminium; β-Crystalline polymorphs of Alq3 ; Aluminium(III) isopropoxide derivatives; Sol–gel precursors; Nano-sized δ-alumina

Alginate scaffold has potential use in the controlled release of drugs and as a three dimensional structure for the formation of tissue matrix. This article describes the changes in the alginate scaffold when the moisture was removed from the scaffold under vacuum. Here, some scaffolds have self-aligned gas bubbles with average diameter of 500 μm, introduced through fluidic arrangement, prior to the crosslinking of the aqueous alginate film. The crosslinked gel film was dried in a vacuum oven at a constant temperature. The image of the alginate film prior to crosslinking was acquired under digital microscope, and was compared with the images of the dried scaffolds from the scanning electron microscope. The voids retained their identity at the time of drying, while the diameter was reduced to half of the initial value. The thickness of the scaffold was reduced ten folds. The presence of voids enhanced the drying rate when the drying was conducted at higher temperature. The drying primarily occurred in the falling rate period. The constant rate period was approached at lower moisture content for thin scaffolds without voids indicating the presence of surface moisture for substantial period. This feature was not observed for the scaffolds with voids. For these scaffolds, the shrinkage was insignificant except for the initial phase of drying. Based on this information, the conclusions were drawn on how the de-saturation of the various parts of the scaffold was phased.
Keywords: Alginate; Gel; Scaffold; Void; Drying

Air atmosphere sol–gel process is often applied to prepare metallic oxide materials. Here we show that metallic nickel phase can also be obtained by citric acid (CA) based air atmosphere sol–gel process in appropriate procedure. Pure fcc or hcp phases of nickel can be obtained in air atmosphere by using CA, nickel (II) acetylacetone, organic solvents and organic surfactants such as oleylamine (OAM), hexadecylamine. However, only NiO can be prepared by aqueous CA based sol–gel process. Oleic acid and OAM can also be used in organic solution mediated sol–gel process to prepare nickel nanoparticles in N2 atmosphere with pure fcc phase at appropriate calcination temperature when 1-hexyl alcohol has been used as solvent. Impurities, such as hcp Ni or Ni3N phase, do not occur in this experimental condition. Our results provide a new and facile way in preparation of metallic nanoparticles.
Keywords: Sol–gel; Fcc and hcp nickel; Nanoparticles; Air atmosphere

The effect of recrystallization time on pore size and surface area of mesoporous SBA-15 by Ephraim Vunain; Rehana Malgas-Enus; Kalala Jalama; Reinout Meijboom (270-277).
Triblock copolymer, pluronic P123 (EO20PO70EO20) was used as the structure directing agent for the simple synthesis and characterization of mesoporous SBA-15 with various porosities. Extending the sample recrystallization time, after the initial synthesis and ageing, seems to have a significant effect on the pore size. It also leads to an increase in the surface area and a narrow pore size distribution. The prepared materials could find applications in areas where the diffusion of large molecules is important, and in catalysis, where greater pore accessibility would enhance the activity and selectivity of the catalyst. A possible mechanism has been proposed to describe the effect of extended recrystallization on pore sizes.
Keywords: Mesoporous materials; SBA-15; Block copolymer; Pore size determination; Recrystallization

Long-lived emission from Eu3+:PbF2 nanocrystals distributed into sol–gel silica glass by Barbara Szpikowska-Sroka; Lidia Żur; Rozalia Czoik; Tomasz Goryczka; Andrzej S. Swinarew; Maria Żądło; Wojciech A. Pisarski (278-283).
This paper reports an optical investigation of Eu3+:PbF2 nanocrystals distributed into silica glasses fabricated by sol–gel methods. The sample microstructure was investigated using scanning transmission electron microscopy. The β-cubic PbF2 crystalline phase was identified using X-ray diffraction analysis. The observed emission bands correspond to 5D0 → 7FJ (J = 0–4) transitions of Eu3+. The spectroscopic parameters for Eu3+ ions were determined based on excitation and emission measurements as well as luminescence decay analysis. Emission originating from 5D0 state of Eu3+ ions in sample containing PbF2 nanocrystals is long-lived in comparison to precursor sol–gel silica glasses.
Keywords: Nanocrystals; Europium ions; Sol–gel method; Glass ceramics; Luminescence properties

Core–shell silica (SiO2) coated CdS nanorods (NR) and nanospheres (NS) were prepared (SiO2@CdS) by deposition of a Si–O–Si amorphous layer over the CdS surface through the hydrolysis of 3-mercaptopropyltrimethoxysilane and tetraethylorthosilicate. Nanoporous SiO2 matrix (NPSM), hollow SiO2 nanotubes (HSNT) and nanospheres (HSNS) useful for efficient adsorption and catalytic processes were prepared by chemical dissolution of CdS–NS (size: 9–10 nm) and CdS–NR (length: 116–128 nm and width: 6–11 nm) template from SiO2@CdS with 2 M HNO3. These SiO2 nanostructures were characterized by optical absorption, TEM, EDX, SAED and BET surface area analysis. TEM images revealed the fabrication of slightly distorted HSNS (size: 9–12 nm) and closed HSNT (length: 30–45 nm and diameter: 9–14 nm) of shorter dimensions than the CdS–NR template used. The BET surface area (112–134 m2 g−1) of NPSM and HSNS is found to be larger than the surface area (29–51 m2 g−1) of SiO2@CdS composites indicating hollow SiO2 morphology. Silica coated Au (SiO2@Au) composites formed by CdS dissolution from Au (2 wt%) deposited CdS–NR core-encapsulated into SiO2 shell (SiO2@Au–CdS–NR) exhibited a surface plasmon band at 550 nm and displayed high catalytic activity for 4-nitrophenol reduction by Au nanoparticle.
Keywords: Hollow SiO2 nanostructures; CdS (core)–SiO2 (shell) morphology; High surface area; CdS template; SiO2 coated Au nanocomposites

Synthesis of novel Schiff base doped sol–gel silicas by Shazia Naheed; Farzana Mehmood; Hafiz Badaruddin Ahmad; Waheed Ahmad; Ghulam Zakria (294-301).
Sulfonamide Schiff bases were doped uniformly in silica sol–gels prepared from liquid precursors by a fast and easy way at room temperature and processed to form xerogels. Schiff bases are efficient chelating agents, bioactive and catalytically active compounds. The structures of the newly synthesized Schiff base doped xerogels were elucidated by their physical (morphology, surface area, porosity), spectral (FTIR) and analytical (CHNSO/Si) data. The powder X-ray diffraction studies were carried out to confirm the formation of single phase. Characterization confirmed that Schiff base molecules are entrapped inside the pores as well as physically bound onto the silica surface. All Schiff base doped xerogels are stable mesoporous materials showing hydrophilic properties. Loadings of Schiff bases from 0.10 to 0.23 g/g of xerogel were obtained resulting amorphous materials. The doping of Schiff bases with xerogel caused change in surface area, pore volume and pore diameter of xerogel without damaging the main framework of siliceous skeleton. Morphology and colour of xerogel was also changed after doping. The entrapment of Schiff bases in xerogel caused increase in their decomposition temperatures. The final Schiff base doped xerogels show remarkable thermal stability.
Keywords: Sulfonamide Schiff bases; Sol–gel method; Blank xerogel; Schiff base doped xerogels

Preparation of single-layer antireflective SiO2 coating with broadband transmittance using PEG-modified sol–gel method by Wenwen Dou; Yuchao Niu; Xiangju Liu; Yong Xu; Zhenxing Wen; Xiaoli Wang (302-306).
Adding polyethylene glycol (PEG) with different molecular weights, a usual acid-catalyzed sol–gel was modified to prepare single-layer antireflective SiO2 coatings with high and broadband transmittance and relatively better hardness. The test results of atomic force microscope and field emission scanning electron microscope show that the addition of PEG significantly affects the porosity and surface morphology of the coating layer. Due to the addition of PEG, the surface of the coatings presents groove-like and their porosity is increased, both of which contribute to the increase in transmittance. In the case of same PEG mass, PEG4000 modified coating has higher porosity and higher transmittance than PEG1000 modified one. In the present paper, the reflectance of samples for both sides was tested by ultraviolet–visible–near-infrared spectrophotometer (LAMBDA 950). The best coating’s reflectance can be decreased below 5 % from 460 to 1,740 nm. The transmittance peak value of the substrate is 90.6 % and its average value is 90.0 %, while the peak value of the best coating can reach up to 99.4 % and its average value is 95.5 % which increased by 5.5 % from wavelength of 325 to 1,000 nm. Hardness measurements show that the coatings have relatively better hardness.
Keywords: Sol–gel; Antireflective SiO2 coating; Polyethylene glycol (PEG) modified; Transmittance

Encapsulation of complementary model drugs in spray-dried nanostructured materials by Mohamed Fatnassi; Corine Tourné-Péteilh; Pradial Peralta; Thomas Cacciaguerra; Philippe Dieudonné; Jean-Marie Devoisselle; Bruno Alonso (307-316).
Two model drugs of different physico-chemical and pharmaceutical properties (ibuprofen, acetaminophen) have been incorporated together or separately in silica-based microspheres using sol–gel and spray-drying processes. A variable amount of a neutral surfactant Brij-56© has also been added. The properties of the microspheres vary significantly depending on their composition. Three kinds of texture are identified: (1) silica containing spheroid nano-domains (formed by ibuprofen; diameters between 20 and 100 nm), (2) silica containing worm-like mesophases (formed by Brij-56© and both model drugs, typical correlation distances ~6 nm), (3) silica intimately mixed with the drug (acetaminophen) without visible phase-separation. The kinetics of drug release in simulated intestinal fluid strongly depend on these textures. The association of ibuprofen and acetaminophen in a single type of microsphere and without surfactant favours a concomitant release. Possible mechanisms of materials’ formation are discussed.
Keywords: Acetaminophen; Ibuprofen; Drug delivery systems; Self-assembly; Sol–gel materials; Spray-drying

Nanoporous alumina (γ- and α-phase) gel cast thick film for the development of trace moisture sensor by Manju Pandey; Prabhash Mishra; Debdulal Saha; K. Sengupta; Kiran Jain; S. S. Islam (317-323).
Nanoporous metal oxide thick film in two phases was fabricated by gel-cast technique to use as trace moisture sensor. High resolution was observed only at 1 kHz frequency in both the phases of alumina. The sensitivity of moisture sensors at sub/low ppm range was estimated on the basis of capacitance, which depend upon the water concentration and frequency of excitation in porous structure of alumina based moisture sensor. The sensitivity towards trace level was confirmed by impedance spectroscopy. FESEM, BET, AFM and XRD techniques were employed for the microstructural characterization. The results are highly encouraging and will be very useful for developing trace level commercial moisture sensor.
Keywords: Gel cast; Moisture sensor; Thick film; Dielectric

The low temperature perovskite-type calcium titanate (CaTiO3) thin films and powders with nanocrystalline and mesoporous structure were prepared by a straightforward particulate sol–gel route. The prepared sol had a narrow particle size distribution about 17 nm. X-ray diffraction and Fourier transform infrared spectroscopy revealed that, the synthesized powders had highly pure and crystallized CaTiO3 structure with preferable orientation growth along (1 2 1) direction at 400–800 °C. The activation energy of crystal growth was calculated 5.73 kJ/mol. Furthermore, transmission electron microscope images showed that the average crystallite size of the powders annealed at 400 °C was around 3.5 nm. Field emission scanning electron microscope analysis and atomic force microscope images revealed that, the deposited thin films had uniform, mesoporous and nanocrystalline structure with the average grain size in the range 33–39 nm depending on annealing temperature. Based on Brunauer–Emmett–Teller (BET) analysis, the synthesized powders showed mesoporous structure with BET surface area in the range 51–21 m2/g at 400–800 °C. One of the smallest crystallite size and one of the highest surface areas reported in the literature is obtained which can be used in many applications, such as photocatalysts.
Keywords: CaTiO3 ; Nanocrystalline; Particulate sol–gel process

In this paper, we reports on the structural and optical properties of Zn1−x−yBexMgyO thin films prepared by sol–gel method, which are new materials for optoelectronic and ultraviolet-light-emitting devices. The crystal structure and core level spectra of these films are studied by X-ray diffraction and X-ray photoelectron spectroscopy. Surface morphology of the films is analyzed by scanning electron microscope images and the surface is composed of spherical shaped grains. Micro-photoluminescence shows a near edge band emission and the peak values tuned from 3.26 eV for the undoped to 3.4 eV for the doped ZnO film. Near infrared emission is observed in the region 1.64–1.67 eV for pure and co-doped ZnO films. In micro-Raman spectra, multiple-order Raman bands originating from ZnO-like longitudinal optical (LO) phonons are observed. A Raman shift of about 5–18 cm−1 is observed for the first-order LO phonon. A comparative study was made on Raman band for BeZnO, MgZnO and BeMgZnO nanocrystals with the LO phonon band of bulk ZnO. The ultraviolet resonant Raman excitation at room temperature shows multi-phonon LO modes up to the fourth order. Deformation energy of all the films is calculated and BeMgZnO film has the minimum deformation energy.
Keywords: Be, Mg co-doped ZnO; Sol–gel method; Micro-Raman; Near infrared emission; X-ray photoelectron

Synthesis of monodispersed silica nanoparticles with high concentration by the Stöber process by Kiyoharu Tadanaga; Koji Morita; Keisuke Mori; Masahiro Tatsumisago (341-345).
Silica nanoparticles with high concentration were prepared by the sol–gel process based on the Stöber method using tetraethoxysilane as a starting material. It was found that silica sol with about 4 wt% in concentration and with a diameter of about 10 nm was obtained by controlling the reaction conditions in the Stöber process. By removing the solvent under a reduced pressure, the particle concentration was increased up to 15 wt% without aggregation.
Keywords: The Stöber method; Monodispersed particles; Silica

Magnetoelectric (ME) xLa0.6Ca0.4MnO3–(1 − x)Bi3.4Nd0.6Ti3O12 (LCMO–BNT) composite thin films have been prepared by a sol–gel process and spin-coating technique. The effects of LCMO content on the microstructure, leakage current density, ferroelectric properties, fatigue endurance and ME voltage coefficient of LCMO–BNT thin films derived by sol–gel method were studied. It was found that the composite thin films have better fatigue endurance properties and lower leakage current densities compared with pure BNT thin films, as well as large ME voltage coefficients.
Keywords: Multiferroic films; Electrical properties; Magnetoelectric

α-Axis oriented ZnS thin film synthesised by dip coating method by K. R. Bindu; P. V. Sreenivasan; Arturo I. Martinez; E. I. Anila (351-355).
The structural, morphological, optical and electrical properties of α-axis oriented nanostructured ZnS thin film prepared by dip coating have been studied in this article. The X-ray diffraction studies of the film shows that the ZnS was crystallized with cubic structure of particle size 27 nm with a strong orientation along (200) plane which is advantageous for optoelectronic devices. The scanning electron microscopy and TEM micrograph reveals that the film consists of nano crystalline columnar particles. From the investigation of the absorption spectra of this ZnS film, the band-gap is found to be higher (4 eV) than bulk (3.7 eV) indicating a blue shift. It is found that the film is having a transparency of >90 % in the visible-near IR region from 400 to 800 nm. From the photoconductivity measurements, it is evident that the film is photosensitive in nature. From the electrical resistivity measurements the conductivity of the film was found to be 3.4 × 10−2 Ω−1 cm−1. Hot probe method indicates that the synthesized ZnS film is n-type.
Keywords: Nanostructures (A); Semiconductors (A); X-ray diffraction (C); Electrical properties (D); Optical properties (D)

Drug release behaviors of a pH/thermo-responsive porous hydrogel from poly(N-acryloylglycinate) and sodium alginate by Xin Ma; Lirong Dong; Xiaojing Ji; Qian Li; Yubo Gou; Xueying Fan; Meng Wang; Yingying Di; Kuilin Deng (356-362).
A pH/thermo-responsive hydrogel with porous structure (HME), composed of poly(N-acryloylglycine methyl ester), poly(N-acryloylglycine ethyl ester) and sodium alginate (SA) was prepared for the controllable drug carrier. The resultants, CO2 and CaCl2 from the reaction of CaCO3 particles and HCl act as pore-forming and crosslinking of SA, respectively. The porous HME was characterized by differential scanning calorimetry, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy and surface area and porosity analysis. The sheet, porous structure was clearly observed by the SEM measurement and the specific surface area of HME was evidently increased with an increase of CaCO3 content. At pH 2.1 phosphate buffered saline (PBS), the release amount of caffeine at room temperature was only 7.2 % within 600 min, while this value approached to 65.3 % at pH 7.4 PBS. Additionally, the cumulative release at 37 °C is much higher than that at room temperature due to the thermo-sensitivity of HME. The experimental results indicated that porous HME has a potential to be used as the promising release-controlled drug carrier in the biomedical fields.
Keywords: Hydrogel; Porous structure; pH/thermo-responsive; Drug release