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2D V2O5 IO films with various pore sizes and phases are fabricated, in which small pores buffer stress-induced pulverization but fasten chemical dissolution, while introducing a small amount of V6O13+y into V2O5 improves electrochromic and electrochemical cycling stability.

A new strategy, the ‘alkaline steaming-assisted conversion route,’ has been developed to synthesize pure NiFe2O4 and CoFe2O4 nanoparticles by using ethylenediamine, together with ammonia, collectively as the alkaline steaming vapor.

Cathodic amorphous tungsten trioxide (WO3) thin films have been deposited by reactive direct current magnetron sputtering and have been studied for their colorimetric and electrochromic properties. Those studies were carried out under two different potential cycling process: (i) switching mode (the response between coloration and bleaching in increasing potential steps) and (ii) modulation mode (the stepwise modulation to coloration with increasing potential and back to bleaching). Optical measurements, performed as a function of applied potential, showed excellent transmittance contrasts (∼80%) between colored and bleached states. The color stimuli and the changes that take place upon reversible switching or modulation were recorded based on the Commisson International de l’Éclairage (CIE) system. It was found that, under various potentials, significant changes occurred in the hue and saturation for WO3, as exhibited by the CIE 1931 xy chromaticity coordinates. As WO3 was reduced (W6+ + e– → W5+), a sharp decrease in luminance was observed. Excellent reversibility is demonstrated not only by colorimetric properties, but also by the corresponding intrinsic structures of the films, as investigated by µ-Raman spectroscopy. Furthermore, the WO3 films displayed a fast response time and good long-term cycling durability, which was attributed to their amorphous nature.

Pure anatase two dimensional (2D) TiO2 inverse opal (IO) films, consisting of a highly ordered hexagonal-patterned structure, are synthesized from various sized polystyrene spheres (PS) as colloidal template simply coupled with TiOSO4 aqueous solution as TiO2 precursor using a “dynamic-hard-template infiltration” strategy. Herein, the TiOSO4 solution is directly infiltrated into the interstices of the 2D self-assembled PS opal template at an air/water interface resulting in a TiOSO4/PS opal composite film floating on the surface of water which was further deposited onto ITO or silicon substrates. Calcination of the obtained opal composite films at temperatures ranging from 300 to 550 °C resulted in 2D TiO2 IO films with various pore sizes having an inverse moth's eye structure. Based on EDS measurements, sulfur ions S6+ were detected in the IO films calcined up to 550 °C. In order to eliminate these S6+ ions and obtain pure anatase 2D TiO2 IO, aqueous immersion was performed after calcination without disturbance of the IO ordered structure. Surface morphology, crystal phase and optical transmittance of the TiO2 IO films, were concurrently investigated by SEM, Raman and UV-vis-NIR. Owing to their precisely adjustable structure, the obtained TiO2 2D IO films exhibited structural colors varying from pale purple, to blue, to polychrome as the array period increases. The films obtained on ITO substrates were successfully used as active electrodes in the fabrication of electrochromic (EC) devices.

The open-layered structure of Vanadium pentoxide (V2O5) has triggered significant interest in exploring its energy-related application as lithium (Li) intercalation cathode material. Various methods are extensively studied to improve the Li diffusion using thin films or nanoarchitecture. In this work, high-quality two-dimensional (2D) inverse opal α-V2O5 films were synthesized via a modified ‘dynamic hard template’ infiltration strategy using sacrificial polystyrene spheres (PS, a diameter of 530 nm) photonic crystal as a template. The new material exhibited an excellent porous array with featured structural colors in a large area. The electrochromic behavior was explored by combining bandgap and electrochemical characterization. On the one hand, the intercalation/deintercalation of Li+ played an important role in the bandgap (Eg), and thereafter on the visible range transmittance through changing the film’s stoichiometry and the valence of vanadium ions. On the other hand, the asymmetry of the lattice due to the disordered distribution of Li+ within the V2O5 interlayer and/or the formation of an irreversible phase explained the change in transmittance with voltage.

The open-layered structure of Vanadium pentoxide (V

Crack-free large-area two dimensional (2D) VO2 inverse opal (IO) films are fabricated by an improved “dynamic hard-template infiltration” strategy using a sacrificial PS sphere photonic crystal as the template. Instead of room temperature, the VO2 precursor (NH4VO3) was infiltrated at increased temperature, rendering higher infiltration into the accommodative interstices of the 2D PS sphere photonic crystal at the air–water interface. The obtained floating NH4VO3/PS opal composite film was deposited on quartz substrates, followed by calcination in air at 310 °C to yield 2D V2O5 IO films. Further heating of the films at 500 °C under an argon atmosphere resulted in VO2 IO films. Concurrently, the color change brought by the photonic crystal structure of the IO films successfully modified the intrinsic unpleasant brownish color of the VO2 films into a pleasant blue-green color. To the best of our knowledge, this is the first time that large area crack-free 2D VO2 IO films are reported. Laser stimuli and temperature-dependent Raman spectra of the films displayed a clear reversible semi-conductor to metal phase transition (MIT) process. The thus obtained films show high optical contrast ΔTIR (12.4% at 1100 nm), low change in visible transmittance ΔTsol (1.2 at 700 nm), a mean MIT temperature of 57.9 °C with ΔTC = 12.3 °C and good cycling properties upon exposure to temperature-dependent Raman and laser stimuli, demonstrating their prospects in various color requirement for industrial windows.

A new one step method for self-assembly of sacrificial polystyrene (PS) spheres colloidal crystal with a transition metal oxide (TMO) precursor matrix material is developed to fabricate highly ordered, crack-free two-dimensional (2D) TiO2 and 2D WO3 inverse opal (IO) films over a centimeter scale. Opal composite monolayer PS/WO3 and PS/TiO2 films have been successfully generated via simultaneous assembly of polymeric colloidal spheres floating on aqueous TiO2 and WO3 precursor solutions, thereby avoiding the infiltration step of the TMO precursor solution into a preassembled opal template. Large-area crack-free 2D WO3 and 2D TiO2 IO films were subsequently obtained after the removal of the PS opal template by chemical method. Such new strategy avoids the need for liquid infiltration into a preassembled PS opal template and minimizes the associated large cracks and inhomogeneity that often occur during the fabrication of IO films. The obtained PS/WO3 and PS/TiO2 opal composite monolayer films were also used as building blocks for the fabrication of highly ordered bilayer (3D) IO films with homo- and hetero-structure via a bottom-up, layer by layer route, through repeated operations of this new one step self-assembly method. Hence, four types of bilayer IO films were synthesized: homo-structural TiO2 and WO3, hetero-structural TiO2 (bottom layer)/WO3 (top layer) and WO3 (bottom layer)/TiO2 (top layer). The underlying mechanism of multilayer assembly that may account for the formation of large area crack-free multilayer films, is discussed. The electrochromic behavior of these 2D and 3D IO samples was investigated.

Large-area crack-free 2D and 3D WO 3 inverse opal (IO) films, using a wide range of sizes of sacrificial PS spheres as colloidal crystal template, were fabricated by “dynamic hard template infiltration strategy”. First a dynamic PS opal film was formed floating on the surface of water followed by infiltration of a preformed WO 3 sol underneath the PS opal film. The resultant PS/WO 3 opal composite film was then deposited on various types of substrates (rigid and flexible) and 2D WO 3 IO films were obtained following the removal of the PS template by chemical method. Based on this strategy, multiple layer WO 3 IOs were fabricated through a layer by layer route. The WO 3 IO films deposited on indium tin oxide coated conductive (ITO) substrates were used as active electrode in the fabrication of electrochromic devices, demonstrating their advanced properties for electrochromic application.

Pure anatase two dimensional (2D) TiO

Crack-free large-area SiO2 single-layer inverse opal (IO) films, which possess typical circular holes on their surface similar to an “inverse moth's eye” structure, were designed based on the “dynamic hard-template infiltration strategy” by using a wide range of sizes of sacrificial polystyrene (PS) sphere templates, ranging from 220 to 930 nm. According to this strategy, a dynamic opal single-layer film of PS spheres is firstly self-assembled on the surface of water, followed by the infiltration of SiO2 precursor sol from underneath into the voids of the PS opal template. The obtained floating SiO2/PS opal composite film is deposited on high alumina silicate glass substrates, followed by calcination at 680 °C to yield single-layer SiO2 IO films with various pore sizes presenting a surface configuration similar to an inverse moth's eye structure. The effects of the porous structure on transmittance in the visible region are investigated. The pore depth, pore wall thickness and pore size concurrently play important roles in transmittance. It has been found that the transmittance increases as the opal period decreases and the intersection point between the transmittance spectra of the single-layer SiO2 IO films and that of the bare substrate red shifts as the pore size increases. To our knowledge, this is the first time that the fabrication of silica single-layer IO films having an inverse moth's eye structure and the relationship between their porous structure and optical properties in the visible region have been reported.

Large area polystyrene (PS)/WO3 opal composite monolayers were successfully fabricated via a modified "dynamic-hard-template" infiltration strategy. These composite monolayers were then used as building blocks for the synthesis of three-dimensional (3D) WO3 inverse opal (IO) films in a bottom-up approach. To achieve this, a PS/WO3 opal composite monolayer serves as a support upon which another PS/WO3 opal composite monolayer is added, and so on, one over the other, rendering possible, after removal of the PS spheres template, the fabrication of large area 3D WO3 IO films. Similarly, bilayer, and trilayer WO3 IOs with large area, having the same pore sizes from layer to layer, can be obtained by repeatedly applying this strategy. This approach also allows control over hierarchical porosity and film thickness by simply changing the diameter of the sacrificial colloidal template and/or the inorganic precursor used in each layer. 3D WO3 IO films fabricated with this technique exhibit good electrochemical reversibility, cycling stability, and increased coloration efficiency (CE) as the number of WO3 IO layers is increased.

This chapter introduces new routes for fabrication of TiO2 inverse opal films, especially monolayer inverse opals and their application in intelligent devices. It starts by presenting the self-assembly of monolayer colloidal crystals template which is instrumental to subsequent fabrication of TiO2 inverse opal. It then details the various routes of fabrication of TiO2 two-dimensional inverse opals, from the synthesis of small-size films to potential large-area fabrications, followed by the introduction of some recent progresses in the fabrication of three-dimensional TiO2 inverse opals. At the end of this chapter, the main applications of TiO2 inverse opal films in photocatalysis for the removal of bacteria and harmful organic materials from water and air, as well as in various devices including solar cells, LEDs, sensors, chromic devices and so on, are explained. A full discussion on the merits of various technologies to fabricate two-dimensional TiO2 inverse opals is also presented.

Plasmonic-photonic metallo-dielectric structures have attracted recent research interests due to their novel optical properties. Au–SiO2 based photonic structures have been built and have shown promising applications for example, as SERS substrates. However, due to the lack of control over the constraints in the various stages of conventional colloidal crystal templating approach, monolayer metallo-dielectric inverse opal structures have not been widely reported. In this work, a 2D hexagonal inverse opal (IO) photonic structure of Au nanoparticles (NP) embedded in a SiO2 matrix is constructed using a new strategy. Here in, a binary Au–SiO2 sol was infiltrated into the accommodative interstices of 2D self-assembled polystyrene (PS) spheres in an air-water interface. Effective removal of the PS spheres by chemical method resulted in Au–SiO2 IO structures. Optical properties of these structures show interesting plasmonic-photonic coupling. When they are used as substrates for Raman signal enhancement of crystal violet, they show better enhancement than either Au nanoparticles aggregates or Au–SiO2 non-photonic structures. The Au–SiO2 IO structures were also used to perform Raman spectroscopy analysis of astaxanthin rich shrimp oil, a novel value-added product extracted from the water used in shrimp processing. The surface enhanced Raman spectra showed the presence of favourable esterified form of astaxanthin in shrimp oil.

In this work anodic NiO electrochromism is investigated under two potential cycling modes: i) the response between coloration and bleaching in increasing potential steps (switching); ii) the stepwise modulation to coloration with increasing potential and back to bleaching (modulation). The films’ response is investigated by optical spectroscopy, colorimetry studies, Raman spectroscopy, XRD, cyclic voltammetry and chronoamperometry. Using the CIE (Commisson International de l’Eclairage) system of colorimetry the color stimuli of the films and the changes that take place upon reversible switching/modulation are recorded under various potentials. As shown by the CIE 1931 xy chromaticity coordinates, when NiO film is oxidized, a sharp decrease in luminance is observed. Optical measurements, performed as a function of applied potential, show excellent contrast between colored and bleached states. Up to now, for NiO, the coloration mechanism was considered as a surface phenomenon. Here, for the first time we show that upon ion insertion/extraction the lattice constant of NiO changes, proving that the EC coloration mechanism involves the unit cells in the bulk material. Furthermore, the fraction ratio of Li to Ni atoms ( L i N i ) is proposed. Considering the actual film fabrication conditions, the x value in LixNiO is found to be equal to 0.0046.

Composite materials aimed at bone tissue engineering need to have suitable bioactivity in order to promote cell proliferation and adhesion. In this article, we study the potential of boronic acids to improve the bioactivity of chitosan-based composite materials. Samples were prepared using boronic acid functionalised chitosan and Bioglass 45S5. These composite materials, prepared by freeze-drying, exhibit 3D interconnected porosity. The materials were fully characterized using scanning electron microscopy (SEM), FT-IR and x-ray diffraction. Their bioactivity was assessed by immersion in simulated body fluid and cell cytotoxicity assays. Composite materials containing boronic acid show no toxicity for Mouse Sertoli (TM4), Human embryonic kidney 293 (Hek293) and Human bone marrow/stroma (HS-5) cells, as opposed to composites containing non-functionalised chitosan.

A facile and versatile polyol mediated solvo-thermal process using zinc acetate has been adopted for the synthesis of mesoporous ZnO nanomaterials having novel morphologies. Polyols used in this study, i.e. ethylene glycol (EG) and polyethylene glycols (PEG) of molecular weight 200 and 400, not only act as solvents but also as structure directing agents. The synthesis using EG leads to the formation of novel square bipyramidal zinc glycolate intermediate, which upon thermal treatment is converted into a nanocrystalline (NC) wurtzite ZnO structure, preserving the square bipyramidal morphology. Zinc glycolate upon hot water treatment (∼85 °C), results in the formation of NC wurtzite ZnO having a bicone morphology. However, when the synthesis is carried out by replacing EG with PEG-200 or 400, NC wurtzite ZnO having spherical morphologies have been directly isolated. In the case of PEG-200, the NC ZnO spheres displayed radially oriented nanorod features on the surface. A mechanism of formation of these ZnO morphologies is proposed. The synthesized ZnO materials have been used as catalysts for the photodegradation of crystal violet dye under UV-B and UV-C irradiation. The catalytic behavior of the ZnO samples is explained based on their porosity, crystallinity, and microstructure.

Recent research interests in geometrical isomers of astaxanthin (AST) are motivated by their metabolic activities in aquatic animals and human. It has been established that cis-isomers of AST are selectively absorbed in human plasma during the metabolic process; however, exact absorption mechanism is still unclear. Hence, a detailed investigation of the structural and optical properties of geometrical isomers of AST is required. Among the techniques available for the study of AST and other carotenoids, Raman spectroscopy has been much acclaimed. Raman spectra have been shown to be influenced by the electronic and mechanical confinement effects arising from the conjugated polyene chain of carotenoids. In this work, we present Raman studies of geometrical isomers of AST, along with their optical absorption characteristics. Geometrical isomers of AST were prepared by heating all trans-AST in solution form, and the isomers were separated using high performance liquid chromatography. Optical absorption spectra of cis-isomers of AST showed hypsochromic shifts in the main absorption band and formation of new bands at lower wavelengths. A detailed Raman spectral analysis performed on the cis-isomers of AST showed new modes which have not been observed and accounted for so far. In addition, we demonstrate that the electronic and mechanical confinement effects in the polyene chain of AST play an important role in the Raman spectra of geometrical isomers of AST. It is anticipated that this work will demonstrate that Raman spectroscopy is an important diagnostic tool in distinguishing and identifying the geometrical isomers of AST. Copyright © 2014 John Wiley & Sons, Ltd.

Two-dimensional (2D) inverse opal (IO) TiO2 films, synthesized by colloidal crystal templating, such as polystyrene (PS) spheres, are particularly interesting because of their potential applications in sensors, solar cells, and electrochromic devices. For these applications, high crystallinity is essential for device performance. Usually, to achieve the IO structure with high crystallinity, the PS opal template is first removed by calcination at a temperature of ∼400 °C, and subsequently to crystallize amorphous TiO2, a temperature higher than 400 °C is needed. This results in cracks and collapse of the macroporous framework. Furthermore, this route is limited to thermally stable substrates, such as glass, which is a significant drawback as the increasing development of technologies and modern electronics requires the design of inexpensive, lightweight, and efficient optoelectronic devices on flexible substrates. In order to circumvent these problems, we developed a ‘dynamic-hard-template’ infiltration strategy for the fabrication of large-area crack-free nanocrystalline (NC) anatase 2D-TiO2 IO films on rigid transparent conducting substrates and on ITO coated flexible polyethyleneterephthalate (ITO/PET) substrates, by using various sizes of PS spheres. According to this strategy, first a dynamic opal 2D film of PS spheres is self-assembled on the surface of water, followed by the infiltration of preformed anatase TiO2 nanoparticle sol from the bottom into the PS opal crystal as the guest material, thus eliminating the need for high temperature crystallization. The obtained floating PS/TiO2 opal composite film is deposited on ITO-coated glass and ITO/PET substrates. An optimized low temperature chemical method is adopted to remove the PS template to yield NC anatase 2D-TiO2 IO films. The films obtained on ITO/PET substrates were successfully used as an active electrode in the fabrication of a flexible electrochromic device.

We present our results on successful synthesis of pyrazine–MoO 3 nanorod hybrids by using pyrazine and MoO 3 nanorods. On the first stage, MoO 3 nanorods were grown hydrothermally and, on the second stage, their mixture with pyrazine was again involved in a hydrothermal reaction to produce organic–inorganic hybrids. To understand the growth mechanism of the hybrids we varied time and temperature of the hydrothermal process. Intercalation of pyrazine was confirmed through X-ray diffraction analysis, X-ray photoelectron spectroscopy, X-ray emission spectroscopy, scanning electron microscopy methods. Upon calcinations, pyrazine was deintercalated, i.e. removed from the MoO 3 hybrid system, and the MoO 3 nanorods were found to bind together resulting in formation of MoO 3 microslabs with increased surface area. Photodecomposition performance of the MoO 3 nanorods, pyrazine–MoO 3 hybrids and MoO 3 microcrystals was studied against Procion Red MX-5B textile dye. A high photodecomposition performance was found to decrease when going from MoO 3 nanorods to MoO 3 microcrystal and, further, to pyrazine–MoO 3 hybrids.

Results of a study on the application of a copolymer of fluorine as acceptor and 1H-pyrazolo[3,4-b]quinoxaline as a donor in bulk heterojunction solar cells are given. To the best of our knowledge, 1H-pyrazolo[3,4-b]quinoxaline co-polymers were not applied in organic photovoltaic devices yet. Organic photovoltaic devices as well as devices of active layers with TiO2 nanocrystals of different crystallite size were investigated. The methods of polymer and TiO2 nanocrystllites synthesis are presented and their physical properties are given. The fabricated photovoltaic structures possess high values of U oc voltage as as well as relatively high parameters of I sc currents. The maximally achieved parameters corresponded to open circuit voltage U oc = 1.13[V], and short current density Isc = 33.49[μA] under illumination 1,3 [μW cm−2], which correspond to energy conversion efficiency equal to about 0.80 %. The TiO2 nanocrystallites play a crucial role in the photovoltaics parameters.

The paper describes technology and principal results concerning the studies of hybrid photovoltaic devices possessing layers of ZnO nanocrystals with different sizes. The presented studies have shown that better photovoltaic efficiency is achieved for the ZnO nanocrystals with smaller sizes. The physical origin of the observed effects is observed.

Hierarchical porous titanium dioxide is of great interest as a potential photocatalyst material because of its enhanced mass transfer capability and light capture efficiency. Tuning of these nanostructures allows for the design of new photocatalysts with improved performance. In this study, we report the synthesis of hierarchically meso–macroporous TiO 2 materials through a template-free aqueous technique. Controlled porous textures and crystalline structures of TiO 2 were obtained by varying the pH of the starting aqueous solution and the method of crystallization. The catalytic efficiency of these materials was investigated using photodegradation of methyl orange and the results show that specific surface area, pore volume and crystallinity play a key role in the photocatalytic performance. The hierarchical titania prepared by the hydrothermal method at a pH of 2 has the highest efficiency with an apparent reaction rate of 9.10 × 10 −2 min −1 , surpassing that of Degussa P25, hence showing its promising potential in environmental remediation.

The complex studies of photoinduced absorption, second harmonic generation and third harmonic generation were performed for TiO2 films of different morphology. In particular we have studied the influence of a bicolor laser beam treatment by a 300 mW green cw laser emitting at 532 nm on changes of absorption, birefringence and third harmonic generation on TiO2 films. We have performed the corresponding measurements using as a photoinducing light a glass erbium 10 ns pulsed laser with a fundamental wavelength of about 1540 nm together with its second harmonic generation (SHG) at 770 nm using the method of bicolor laser treatment and a frequency repetition of about 10 Hz. Varying the power density ratios between the fundamental and its SHG we have established the optimal conditions to achieve maximal photoinduced changes of absorption, birefringence and third harmonic generation (THG). We have detected changes of the birefringence and of the THG immediately after the laser treatment. We study an influence of the nanoparticle's sizes on the observed changes of the optical features. Additionally we have studied the role of different chemical treatment on the structural and optical parameters.

Iron tungstate (FeWO 4 ) and cobalt tungstate (CoWO 4 ) nanostructures were prepared by the hydrothermal method using sodium tungstate (Na 2 WO 4 ·2H 2 O), ferrous ammonium sulfate [(NH 4 ) 2 Fe(SO 4 ) 2 ·6H 2 O] and cobalt chloride (CoCl 2 ·6H 2 O) solutions as precursors. The crystal structure and morphology of the as-prepared tungstates were characterized by X-ray diffraction analysis and transmission electron microscopy. The above characterizations render that the products obtained belong to the monoclinic crystal system and P2/a space group, with average sizes of nanoparticles of about 150 nm and 70 nm in the case of FeWO 4 and CoWO 4 , respectively. Electronic properties of the FeWO 4 and CoWO 4 tungstates were studied using several X-ray spectroscopy methods, mainly X-ray photoelectron spectroscopy (XPS), X-ray emission spectroscopy (XES) and X-ray absorption spectroscopy (XAS). The XPS valence-band and core-level spectra, the XAS W L III edges (unoccupied W d-like states) as well as the XES bands reflecting the energy distribution of the valence W d- and O p-like states were recorded. The present XPS and XAS results reveal that the as-prepared FeWO 4 and CoWO 4 tungstates are in a composition close to a stoichiometric one. The XES results render that the W 5d- and O 2p-like states contribute throughout the whole valence-band region of the FeWO 4 and CoWO 4 tungstates, however maximum contributions of the O 2p-like states occur in the upper, whilst the W 5d-like states in the lower portions of the valence band, respectively.

Anatase nanocrystalline TiO2 thin films were obtained by a sol–gel dip-coating method, in which the nanocrystallization is effected by a simple hot water treatment of the deposited films at temperatures below 90 °C under atmospheric pressure for 1 h. The dip-coating sol was prepared by reacting titanium tetra-n-butoxide [Ti(OnBu)4] with polyethylene glycol (PEG) in ethanol. Films obtained from a sol that do not contain PEG show no sign of crystallization, demonstrating the importance of PEG in the crystallization process. Raman studies of reaction dynamics show that PEG undergoes a nucleophilic substitution reaction replacing butoxy groups in Ti(OnBu)4. Stoichiometric reactions of Ti(OnBu)4 with PEG in polar and nonpolar solvents were performed, and they yielded different titanium–PEG hybrid polymers, which were isolated and characterized by various spectroscopic techniques such as IR, Raman, solid-state NMR and MALDI-TOF-MS. NMR studies evidenced the location and the way in which PEG is bonded with titanium atoms in the titanium–PEG hybrid polymers. On the basis of these studies, we have proposed structures for these polymers. It is demonstrated that the structure of the obtained polymers plays an important role in the formation of anatase TiO2 nanoparticles in hot water at temperatures below 90 °C under atmospheric pressure. Copyright © 2009 John Wiley & Sons, Ltd.

Domoic acid (DA) is a water-soluble marine neurotoxin produced and released by certain species of the diatom genus Pseudo-nitzschia. Present in coastal waters, it can be a threat to public health and marine life, and can result in severe economic losses to the molluscan shellfish and crustacean harvesting industries. Here we report on the efficiency of nanocrystalline (NC) titania (TiO(2)) thin films used as a photocatalyst in the ultraviolet light photodegradation of DA. Titanium dioxide thin films produced by a sol-gel dip-coating method in the presence of polyethylene glycol of different molecular weights (200, 400 and 600) were deposited on glass substrates and crystallised at 90 degrees C. The films were characterised using spectroscopic ellipsometry, Fourier transform infrared spectrometer (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy. The photocatalytic activity measurements were carried out by immersing the NC TiO(2) films in a DA solution (2500 ng ml(-1)) and then exposing them for various times at room temperature to UVA irradiation (lambda = approximately 350 nm). The degradation of DA, quantified by HPLC analysis, was not significant when using daylight or ultraviolet light irradiation alone, whereas the NC TiO(2) films prepared at low temperature proved to be a very efficient photocatalyst when used in conjunction with UVA light. The effectiveness of the photodegradation was improved by increasing molecular weight of polyethylene glycol, which increased the thickness of the film. The presence, transformation and degradation of three DA isomers were observed. The approach may eventually be practical for destroying DA in seawater used by aquaculture industry depuration facilities.

Tungsten trioxide (WO3) nanostructures were synthesized by hydrothermal method using sodium tungstate (Na2WO4·2H2O) alone as starting material, and sodium tungstate in presence of ferrous ammonium sulfate [(NH4)2Fe(SO4)2·6H2O] or cobalt chloride (CoCl2·6H2O) as structure-directing agents. Orthorhombic WO3having a rectangular slab-like morphology was obtained when Na2WO4·2H2O was used alone. When ferrous ammonium sulfate and cobalt chloride were added to sodium tungstate, hexagonal WO3nanowire clusters and hexagonal WO3nanorods were obtained, respectively. The crystal structure and orientation of the synthesized products were studied by X-ray diffraction (XRD), micro-Raman spectroscopy, and high-resolution transmission electron microscopy (HRTEM), and their chemical composition was analyzed by X-ray photoelectron spectroscopy (XPS). The optical properties of the synthesized products were verified by UV–Vis and photoluminescence studies. A photodegradation study on Procion Red MX 5B was also carried out, showing that the hexagonal WO3nanowire clusters had the highest photodegradation efficiency.

High surface area titanium glycolate microporous multi-faceted nanorods were synthesized from the reaction of titanium alkoxides (Ti(OEt)4, Ti(OiPr)4, or Ti(OnBu)4) with ethylene glycol, using a sol–gel reflux method. The specific surface area of the as-synthesized titanium glycolate nanorods obtained from Ti(OEt)4 is ~480 m2/g. A hot water treatment at 90 °C for 1 h transformed the titanium glycolate microporous nanorods into mesoporous anatase TiO2 nanorods. The shape of the nanorods was conserved after hot water treatment and the microporous to mesoporous transformation took place without significant change in the surface area (477 m2/g). Micro Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, solid state NMR, and nitrogen adsorption/desorption were used to characterize the samples. As a demonstration of potential applications, the thus formed mesoporous anatase TiO2 nanorods were tested for their photocatalytic efficiency in the degradation of crystal violet, and a photodegradation mechanism is proposed.

Domoic acid (DA) is a water-soluble marine neurotoxin produced and released by Pseudo-nitzschia species. It is remarkably pervasive in North American coastal waters, where it is a threat to public health and some marine life, and has resulted in severe economic losses in the shellfish and crustacean harvesting industry. In this paper we report on the development of nanocrystalline titania thin films that were used as photocatalyst in the UV photodegradation of DA. TiO 2 thin films produced by a sol–gel dip-coating method in the presence of polyethylene glycol (PEG) of different molecular weights (200, 400 and 600), were deposited on glass and fused quartz substrates, and crystallized at different temperatures (90, 500 and 900 °C). The films were characterized using UV–vis, FTIR, SEM, XRD, and Raman spectroscopy. For the photocatalytic activity measurements, the TiO 2 films were immersed in a DA solution (2500 ng/mL) and exposed for various times at room temperature to UV irradiation ( λ ∼ 350 nm). DA analysis was carried out by HPLC, and the photocatalytic activity was quantified as the rate of disappearance of DA. The photocatalytic activity of the TiO 2 thin films was studied as a function of their crystallization temperature, type of PEG content, and thickness. The films prepared at low temperature proved to be very efficient photocatalysts. They showed a higher photocatalytic activity than those produced at high temperature. Also, using PEG of higher molecular weight in the TiO 2 coating solutions increased the effectiveness of the degradation. When using UV irradiation alone, without photocatalyst, the degradation of DA was not significant. The presence, transformation, and degradation of various DA isomers were observed during the photodegradation process, and a photodegradation mechanism is proposed.

A hierarchically porous anatase TiO2 coated-WO3 2D inverse opal (IO) bilayer film was fabricated on ITO glass using a layer by layer route with a hierarchically porous TiO2 top layer and an ordered super-macroporous WO3 2D IO bottom layer. This novel TiO2 coated-WO3 2D IO bilayer film was evaluated for photochromic applications.

Raman studies were performed on titania thin films prepared by polyethylene glycol (PEG) assisted, low-temperature, sol–gel method. The Raman spectra of the films show a systematic blue shift in the peak position and a broadening in the full width at half-maximum (FWHM) when compared with those of the bulk anatase TiO2 powder. Several reports have appeared indicating this kind of peak shift and broadening of FWHM, which were attributed to the confinement of phonons in the anatase nanocrystallites. In this paper, we report an analysis of quantum size effect in the Raman spectra of nanocrystalline TiO2 thin films performed by utilizing the phonon dispersion relation of the anatase phase which has been obtained from a work based on density functional perturbation theory (DFPT). For comparison purposes the quantum size effect calculations have also been done utilizing the dispersion relations of the rutile phase. There is good agreement between the crystallite sizes evaluated from the equally weighted Raman line intensity of the dispersion relations obtained from the DFPT and those determined by X-ray diffraction. Copyright © 2006 John Wiley & Sons, Ltd.

Nanocrystalline titania films were prepared by a complexing agent-assisted sol-gel dip-coating process. The effect of acetylacetone, diethanolamine and polyethylene glycol on the structure of the heat-treated titania films was examined by Raman and FTIR spectroscopy and X-ray diffraction. The effect the complexing agents have on the anatase to rutile phase transition during the heat treatment process is studied. The understanding of this effect is expected to enhance our capacity to tailor the composition and morphology of films and thus their properties. The Raman and the infrared spectra of nanocrystalline titania films and the changes induced by the heat treatment were also investigated. We have also studied the size of the crystallites in TiO2 films and its dependence on the type of complexing agent used.

Recent developments in the synthesis of mesoporous nanocrystalline titanium oxide (TiO2) have opened up several new opportunities in the construction of efficient photovoltaic (PV) cells. In this chapter, we describe principles involved in the construction of organic photovoltaic cell and the influence of the main parameters for the case of PEDOT:PSS polymers. At the outset different architectures of the PEDOT:PSS photovoltaics are described and later incorporation of the TiO2 nanoparticles in their architectures is carefully considered. A special attention is given to the technique of photovoltaic cell preparation and the basic principles of their functionality. A significant emphasis has been devoted to the current–voltage characteristics of photovoltaic cells, thus constructed with and without nanocrystalline TiO2, as well as to the ways it can be further improved. We also describe the synthesis of mesoporous TiO2 nanoparticles using titanium alkoxides as precursor and polyethylene glycol (PEG) of different molecular mass as templating agent to induce mesoporosity. The interaction of PEG with titanium alkoxides in polar and nonpolar solvents was studied in detail by macro-Raman spectroscopy, solid-state NMR and MALDI-TOF-MS. The removal of PEG as well as the crystallization process was obtained by hot water treatment at low temperature (90 °C). The mesoporosity was retained after further calcination up to 500 °C. Porosity, morphology, and microstructures of the resultant products were characterized by SEM, nitrogen adsorption–desorption measurements, micro-Raman spectroscopy and XRD. The mesostructure of the TiO2 particles facilitates enhanced transport of electrons, resulting in improved photovoltaic efficiency. Influence of TiO2 nanoparticles on the photovoltaic efficiency of the ITO/PEDOT:PSS/fluorine copolymers/polythiophene:TiO2/Al architecture is analyzed. Influence of TiO2 NP on the principal parameters of different PV architecture is discussed. The analysis of the efficiency is performed using both experimental and theoretical quantum chemical approach.

Nanocrystalline titania films were prepared by a complexing agent-assisted sol-gel dip-coating process. The effect of acetylacetone, diethanolamine and polyethylene glycol on the structure and morphology of the heat-treated titania films was examined by Raman and FTIR spectroscopy, x-ray diffraction and atomic force microscopy (AFM). The effect the complexing agents have on the anatase to rutile phase transition during the heat treatment process is studied. The understanding of this effect is expected to enhance our capacity to tailor the composition and morphology of films and thus their properties. The Raman and the infrared spectra of nanocrystalline titania films and the changes induced by the heat treatment were also investigated. We have studied the size of the crystallites in TiO 2 films and its dependence on the type of complexing agent used.

A 'dynamic hard-template' infiltration strategy for crack-free large-area synthesis of 2D WO3 inverse opal (IO) films on ITO substrates using a wide range of sizes of sacrificial PS spheres is reported. Thus prepared WO3 IO films were successfully used as an active electrode in the fabrication of an electrochromic device.

Porous orthorhombic tungsten oxide (o-WO3) thin films, stabilized by nanocrystalline anatase TiO2, are obtained by a sol–gel based two stage dip coating method and subsequent annealing at 600 °C. An Organically Modified Silicate (ORMOSIL) based templating strategy is adopted to achieve porosity. An asymmetric electrochromic device is constructed based on this porous o-WO3 layer. The intercalation/deintercalation of lithium ions into/from the o-WO3 layer of the device as a function of applied coloration/bleaching voltages have been studied. XRD measurements show systematic changes in the lattice parameters associated with structural phase transitions from o-WO3 to tetragonal LixWO3 (t-LixWO3) and a tendency to form cubic LixWO3 (c-LixWO3). These phase transitions, induced by the Li ions, are reversible, and the specific phase obtained depends on the quantity of intercalated/deintercalated Li. Raman spectroscopy data show the formation of t-LixWO3 for an applied potential of 1.0 V and the tendency of the system to transform to c-LixWO3 for higher coloration potentials. Optical measurements show excellent contrasts between colored and bleached states. An alternate photochromic device was constructed by sensitizing the o-WO3 layer with a ruthenium based dye. The nanocrystalline anatase TiO2 in the o-WO3 layer has led to an enhanced photochromic optical transmittance contrast of ∼51% in the near IR region. The combination of the photochromic and electrochromic properties of the synthesised o-WO3 layer stabilized by nanocrystalline anatase TiO2 opens up new vista for its application in energysaving smart windows.

High aspect ratio molybdenum trioxide (MoO3) nanorods grown along the [100] direction were successively synthesized by a simple hydrothermal method. We used sodium molybdate and hydrochloric acid as starting materials and from their reaction we obtained MoO3 nanorods of high aspect ratio. The dimensions of the nanorods were found to be uniform in size, with well-defined boundaries. The intercalation of an organic molecule (pyrazine) into these nanorods has resulted in single-crystalline MoO3 microstructures, with a change in their length and breadth of a few orders. Pyrazine has acted as a stitching molecule and has bound the nanorods together along their length to form micron sized single crystalline MoO3. The presence of pyrazine and its intercalation was confirmed by a uniform shift in the XRD [0k0] peak positions. As the size of the pyrazine is similar to the van der Waals gap of the orthorhombic MoO3 crystal, it seemed to fit well within the gap and thereby helped to bind the nanorods along the [0k0] direction. The Raman ring deformation modes, at 714 and 996 cm−1, have also supported the intercalation of the pyrazine in the van der Waals gap. The deintercalation process was done by calcinating the sample at 400 °C and the removal of pyrazine was confirmed by TGA and XRD measurements. The influence of pyrazine in the valence band electronic density of states (DOS) of MoO3 was also analyzed by XPS and XES methods. The replacement of oxygen at the van der Waals gap by nitrogen from the intercalating pyrazine caused a shift in the valence band towards the Fermi level. A photoluminescence study was also conducted, reflecting the intercalation effect on the emission characteristics of the MoO3 nanostructures.

The author first examines the various public declarations which form the basis of the federal government's official languages policy, and then identifies the various stages in the application of this policy to the public service sector. He concludes with an examination of the current situation.