Tio2 Nanostructure

Titanium dioxide is an important metal oxide semiconductor (MOSs) used in many electronic applications, the most famous of which are gas sensor applications. This review discusses the techniques used for preparing the TiO2 thin films and the effect of the crystalline phases in which this compound forms, on the gas sensing properties. There are three phases to crystallize titanium dioxides, brookite, anatase, and rutile phase. Amongst these varied phases of crystal, the greatest steady main phase is rutile. The phase of anatase and brookite are usually more stable than the rutile phase as the surface energy of them is less than that of the rutile. Therefore, the applications of sensing by anatase TiO2 and rutile TiO2 were fully studied. TiO2 characterizations were established on surface reactions using oxidizing or reducing gases, which; therefore, influences the conductivity of the film. Titanium dioxide gas sensors have healthier steadiness and sensitivity at high temperature compared with that of the other metal oxides. Surveys on titanium dioxide thin film applied in gas sensor devices used in a varied range of applications such as sensor devices, dye-sensitized solar cells, and catalysis. The gas sensor is a function of the crystal structure, particle size, morphology, and the method of synthesis. In this work, characteristic of the titanium dioxide films investigated using various techniques, as reported by many researchers. The aim of this study was to review previous studies through which the best properties can obtained to manufacture TiO2 gas sensor thin films with high sensitivity.

TiO 2 has already established itself as one of the most attractive nanomaterials for the functionalisation of textiles due to its unique structural, physicochemical, optical and electrical properties, nontoxicity and low cost. This review paper provides a comprehensive overview of recent advances in the chemical and physical modification of textile fibres with TiO 2 nanoparticles and nano-/microstructures and summarises the most important findings on the application processes and performance of TiO 2-modified textile substrates. Photocatalytic self-cleaning, antimicrobial activity, UV protection, hydrophobicity, thermal stability, flame retardancy and electrical conductivity are highlighted as central discussion topics in the review. Insights into the mechanisms for providing functional properties are presented; the influence of various factors on functionality is shown; and the latest strategies for TiO 2 surface modification to enhance visible light photocatalytic activity, including multiphase heterojunctions, ion doping, metal doping/loading, coupling with other semiconductors and surface sensitization, are discussed. This paper presents some new ideas for producing TiO 2-functionalized textile surfaces and suggests future research perspectives and directions in this research area.

Tungsten, silver and tungsten/silver co-doped titania nanopowders were synthesised via an aqueous sol–gel method. The size distribution and zeta potential of the starting sols were determined via photon correlation spectroscopy (PCS). The dried gels were thermally treated at two different temperatures, and the occurrence of amorphous phase was assessed using the combined Rietveld–RIR X-ray powder diffraction method. A systematic study of the optical properties of the powders was made with diffuse reflectance spectroscopy (DRS), and the energy band gaps were calculated using the differential reflectance method; while their morphology was investigated using electron microscopy analysis (TEM). The photocatalytic activity of the samples was assessed in liquid–solid phase, under UVA-light and visible-light irradiation, monitoring the degradation of an organic dye. The influence of the phase composition, optical properties, dimensions, and specific surface area of the powders on the photocatalytic activity was thoroughly discussed.

Heterogeneous photocatalysis is a promising technology especially for environmental remediation. Despite more than a decade of worldwide research in developing photocatalytic efficiency improving techniques, many questions regarding the large scale application of photocatalytic reactors still remain unanswered. Recently, improving the photocatalytic efficiency has gained scientific attention because it might lead to more economical and robust photocatalytic operation for environmental remediation. In this review, fundamental and comprehensive assessments of the photocatalytic concepts and their applications for environmental remediation are reviewed. The existing challenges and strategies to improve the photocatalytic efficiency are discussed. Further, recent developments and future research prospects on photocatalytic systems for environmental applications are also addressed.

Titanium dioxide (TiO2) is well established as one of the most common photocatalysts used for many environmental, anti-pollution and antibacterial applications. However, in this work, novel photocatalytic TiO2 nanopowders were modified with additions of 1 mol% copper, zinc or copper + zinc (with various Cu: Zn ratios). These were prepared via a green sol–gel route and thermally treated at 450 ºC. For the first time, a direct comparison of the effects of these two modifying agents was performed, both as single and co-substitution. The compounds were thoroughly characterised by means of advanced X-ray diffraction (Whole Powder Pattern Modelling, WPPM) and spectroscopic methods (Raman and UV–vis). For functional properties, the photocatalytic activity in the gas-solid phase (nitrous oxides (NOx) and isopropanol degradation (VOCs)) was tested under UV and visible light, and antibacterial activity against Gram positive and Gram negative bacterial strains was also investigated. Neither copper nor zinc entered into the TiO 2 structure, but nucleated as oxides at the surface of titania nanoparticles, thus creating a nano-heterojunction between the semiconductor materials; this also retarded the anatase-to-rutile phase transition. When comparing and contrasting their functional properties, it was found that Zn modification gave greater photocatalytic activity than that with Cu. On the contrary, for antibacterial activity, copper was shown to be a better additive. Co-modification with both metals did not improve the antibacterial behaviour, but did lead to an increase in photocatalytic activity in some cases.

Highly crystalline TiO2 nanostructures were prepared through a facile inorganic acid-assisted hydrothermal treatment of hexagonal-structured assemblies of nanocrystalline titiania templated by cetyltrimethylammonium bromide (Hex-ncTiO2/CTAB Nanoskeleton) as starting materials. All samples were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The influence of hydrochloric acid concentration on the morphology, crystalline and the formation of the nanostructures were investigated. We found that the morphology and crystalline phase strongly depended on the hydrochloric acid concentrations. More importantly, crystalline phase was closely related to the morphology of TiO2 nanostructure. Nanoparticles were polycrystalline anatase phase, and aligned nanorods were single crystalline rutile phase. Possible formation mechanisms of TiO2 nanostructures with various crystalline phases and morphologies were proposed.

The first scientific opinion on the safe use of titanium dioxide as a UV-filter at a maximum 4 concentration of 25% in cosmetic products was adopted 24 October 2000 by the SCCNFP 5 (SCCNFP/0005/98). 6
However, a review of the substance in its nanoform is deemed necessary according to the 7 opinion on Safety of Nanomaterials in Cosmetic Products adopted on 18 December 2007 8 (SCCP/1147/07), where it is stated that: 9
10
"The SCCNFP opinion from 2000 (SCCNFP/0005/98) is on micro-crystalline preparations of 11 TiO2 and preparations of coarse particles. However, since this opinion, new scientific data 12 on nanosized particles including, TiO2 has become available. Therefore, the SCCP considers 13 it necessary to review the safety of nanosized TiO2 in the light of recent information. Also, a 14 safety assessment of nanosized TiO2, taking into account abnormal skin conditions and the 15 possible impact of mechanical effects on skin penetration needs to be undertaken". 16
17
Supplementary information on nanosized Titanium dioxide was submitted following a 18 meeting with stakeholders on 1 October 2008, where data requirements were agreed. 19
20
Titanium Dioxide is currently regulated - irrespectively of its form - as a UV-filter in a 21 concentration up to 25% in cosmetic products in Annex VII, entry 27 of the Cosmetics 22 Directive.

In this comprehensive study, the influence of titanium dioxide (TiO2) dopants decorated on Reduced Graphene Oxide (rGO) via spin coating technique as an efficient photoelectrode in DSSCs was investigated in detail. This study aims to determine the optimum spinning duration for decorating TiO2 onto rGO nanosheet photoanode for high DSSCs performance. The rGO nanosheet was prepared using the electrodeposition method. A dropped of 0.2 wt% of TiO2 solution was absorbed using micro-pipette (0.1 μl) and continuously applied on FTOrGO surface with the rate of 0.1 μl/5s. The spinning duration was varied from 10 to 50 s, and resultant samples were labelled as Lt, where t= 10, 20, 30, 40 and 50s, respectively. The experimental results showed that TiO2 decorated rGO nanosheet photoanode for 30s spinning duration exhibited a maximum power conversion efficiency of 9.98% than that of pure rGO nanosheet photoanode (4.74%) under 150 W of xenon irradiation, which is about 2.1 times improvement in DSSCs performance. Ti4+ ion was decorated onto rGO nanosheet leading to the highest interactions with the O-H functional group or Ti4+ could react with the epoxide or phenolic groups in rGO forming the Ti-O-C bonds.

Titanium dioxide (TiO2) nanostructures (nanorods and nanoparticles) were prepared using a low-cost microwave irradiation method from a polyol medium of glycerol. Titanium glycerolate and TiO2 powders were obtained in the glycerol medium for the first time with four different power densities (240 W, 480 W, 720 W, 960 W) of irradiation using a domestic microwave oven of 2.45 GHz, to understand the impact of power on morphology tuning. The structural and morphological features of the titanium glycerolate and TiO2 powders were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and Raman spectra analysis. The TiO2 was successfully used in the fabrication of photovoltaic devices and as a proof-of-concept binder free paste was prepared and successfully employed for photo-anode using screen printing on the fluorine-doped tin oxide substrate.

Mesoporous TiO 2 nanoparticle films are used as photoanodes for high-efficiency dye-sensitized solar cells (DSCs). In spite of excellent photovoltaic power conversion efficiencies (PCEs) displayed by titanium dioxide nanoparticle structures, the transport rate of electrons is known to be low due to low electron mobility. So the alternate oxides, including ZnO, that possesses high electron mobility are being investigated as potential candidates for photoanodes. However, the PCE with ZnO is still lower than with TiO 2 , and this is typically attributed to the low internal surface area. In this work, we attempt to make a one-to-one comparison of the photovoltaic performance and the electron transfer dynamics involved in DSCs, with ZnO and TiO 2 as photoanodes. Previously such comparative investigations were hampered due to the morphological differences (internal surface area, pore diameter, porosity) that exist between zinc oxide and titanium dioxide films. We circumvent this issue by depositing different thicknesses of these oxides, by atomic layer deposition (ALD), on an arbitrary mesoporous insulating template and subsequently using them as photoanodes. Our results reveal that at an optimal thickness ZnO exhibits photovoltaic performances similar to TiO 2 , but the internal electron transfer properties differ. The higher photogenerated electron transport rate contributed to the performances of ZnO, but in the case of TiO 2 , it is the low recombination rate, higher dye loading, and fast electron injection.

This study is carried out to study the effect of Gibberellic acid (GA3) and Titanium Dioxide Nanoparticles (Nano- TiO2) on some characteristics of medicinal plant of Ocimum basilicum Lamiaceae) under drought stress. The experiment was conducted as a factorial arrangement in randomized complete block design with four replications in which A, B, C are the three factors and factor A is related to the irrigation content as fc 100%, fc 70% and fc 40% and factor B in three levels with GA3 application with concentrations of 0 (control), 250 ppm, 500 ppm and factor C with three doses of titanium nanoparticles with concentrations of 0%, 0.01% and 0.03%. The results showed that the drought stress caused to decreasing of plant biomass and the foliar relative water content, and
the increasing of catalase and the level of anthocyanin in the medicinal plant of basil, while, the application of gibberellin and titanium nanoparticles caused to improving of the negative effects of the stress.The results of the study indicated that the drought stress causes to decreasing of quantitative and qualitative characteristics of the plant. The best treatments were recognized as follows: in 100% irrigation regime, non-application of gibberellin and application of Nano-TiO2 with concentration of 0.01%; in 70% irrigation regime, the application of gibberellin with concentration of 250 ppm and Nano-TiO2 with concentration of 0.03%; and in 40% irrigation
regime, the application of gibberellin with concentration of 500 ppm and Nano-TiO2 with concentration of 0.03%.

Abstract    Transparent semiconducting thin films of titanium oxide (TiO2) were deposited on glass substrates by the sol–gel method and spin-coating technique. The phys- ical properties of the  prepared films  were studied  as  a function of the number of spun-cast layers. The micro- structure and surface orphology of the TiO2 films were characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM), with respect to the film thickness. The XRD analysis reveals that the films are polycrystalline with an anatase crystal structure and a preferred grain orienta- tion in the (101) direction. The morphological properties were investigated by AFM, which shows a porous mor- phology structure for the films. The optical properties of the films were characterized by UV–Visible spectropho- tometry, which shows that the films are highly transparent in the visible region and their transparency is slightly influenced by the film thickness, with an average value above 80 %. The dependence of the refractive index (n), extinction coefficient (k), and absorption coefficient (a) of the films on the wavelength was
investigated. A shift in the optical band gap energy of the films from 3.75 to 3.54 eV, as a function of the film thickness, has been observed.

Tahun 2006, jumlah industri tekstil Indonesia mencapai 2.699 perusahaan, dengan total investasi Rp 135,7 triliun. Jumlah ini mengalami kenaikan dibanding tahun sebelumnya yang berjumlah 2.656 perusahaan. Peningkatan ini akan terus terjadi seiring dengan peningkatan kebutuhan kain baik dalam maupun luar negeri. Kain merupakan salah satu kebutuhan yang penting bagi kehidupan manusia. Hal ini karena fungsinya sebagai pakaian atau baju memberikan rasa nyaman dengan melindungi bagian tubuh dari benda asing di udara atau paparan sinar matahari sehingga tidak bersinggungan secara langsung dengan kulit manusia. Pada umumnya industri kain di Indonesia belum menerapkan sistem teknologi maju seperti teknologi self-cleaning untuk meningkatkan kualitas dan umur kain. Hal ini penting untuk diterapkan karena berkaitan erat dengan penggunaan pakaian di luar ruangan akan mengakibatkan penurunan kualitas dan umur kain yang disebabkan kontak kain secara langsung dengan udara bebas yang mengandung partikel debu, mikroorganisme atau partikulat mikron lainnya yang menempel pada permukaan kain dan paparan sinar matahari langsung. Benda asing yang menempel pada permukaan kain ini tidak dapat langsung dibersihkan karena penggunaan kain pada umumnya dilakukan secara berulang-ulang, sehingga akan memberikan kondisi kain yang kusam, kotor dan merusak benang kain. Kondisi ini terjadi secara terus menerus dalam jangka waktu tertentu menyebabkan kain menjadi cepat rusak dan tidak dapat dipakai kembali. Hal ini dapat ditanggulangi melalui pemanfaatan teknologi self-cleaning berbasis fotokatalis nano-TiO2. TiO2 merupakan katalis semikonduktor yang tidak beracun, harganya terjangkau, melimpah di alam, bersifat inert, pengoksidator kuat, efektif digunakan sebagai fotokatalis untuk mendegradasi polutan di udara. Nano-TiO2 yang tersubtitusi pada pori atau menempel pada permukaan kain akan aktif ketika terkena paparan sinar matahari langsung sehingga menghasilkan elektron dan hole (h+). Elektron yang dihasilkan ini dapat bereaksi dengan udara (O2) menghasilkan radial oksigen (•O2-), sedangkan hole dapat bereaksi dengan uap air (H2O) membentuk radikal hidroksil (•OH). Spesis radikal kimia ini baik •O2-, •OH dan hole akan menghancurkan polutan di udara yang menempel pada permukaan kain seperti debu atau mikroorganisme yang dapat merusak kain. Oleh karena itu, penerapan inovasi teknologi self-cleaning pada kain akan mampu meningkatkan umur dan kualitas kain sehingga meningkatkan daya saing dan kemandirian sektor industri kain Indonesia baik di dalam dan luar negeri.

The exceptional properties of localised surface plasmons (LSPs), such as local field enhancement and confinement effects, resonant behavior, make them ideal candidates to control the emission of luminescent nanoparticles. In the present work, we investigated the LSP effect on the steady-state and time-resolved emission properties of quantum dots (QDs) by organizing the dots into self-assembled dendrite structures deposited on plasmonic nanostructures. Self-assembled structures consisting of water-soluble CdTe mono-size QDs, were developed on the surface of co-sputtered TiO2 thin films doped with Au nanoparticles (NPs) annealed at different temperatures. Their steady-state fluorescence properties were probed by scanning the spatially resolved emission spectra and the energy transfer processes were investigated by the fluorescence lifetime imaging (FLIM) microscopy. Our results indicate that a resonant coupling between excitons confined in QDs and LSPs in Au NPs located beneath the self-assembled structure indeed takes place and results in (i) a shift of the ground state luminescence towards higher energies and onset of emission from excited states in QDs, and (ii) a decrease of the ground state exciton lifetime (fluorescence quenching).

TiO 2 has already established itself as one of the most attractive nanomaterials for the functionalisation of textiles due to its unique structural, physicochemical, optical and electrical properties, nontoxicity and low cost. This review paper provides a comprehensive overview of recent advances in the chemical and physical modification of textile fibres with TiO 2 nanoparticles and nano-/microstructures and summarises the most important findings on the application processes and performance of TiO 2-modified textile substrates. Photocatalytic self-cleaning, antimicrobial activity, UV protection, hydrophobicity, thermal stability, flame retardancy and electrical conductivity are highlighted as central discussion topics in the review. Insights into the mechanisms for providing functional properties are presented; the influence of various factors on functionality is shown; and the latest strategies for TiO 2 surface modification to enhance visible light photocatalytic activity, including multiphase heterojunctions, ion doping, metal doping/loading, coupling with other semiconductors and surface sensitiza-tion, are discussed. This paper presents some new ideas for producing TiO 2-functionalized textile surfaces and suggests future research perspectives and directions in this research area.

Here, a Sb-doped SnO2 (ATO) nanorod underneath an α-Fe2O3 nanorod sheathed with TiO 2 for photoelectrochemical (PEC) water splitting is reported. The experimental results, corroborated with theoretical analysis, demonstrate that the ATO nanorod underlayer effect on the α-Fe2O3 nanorod sheathed with TiO2 enhances the PEC water splitting performance. The growth of the well-defined ATO nanorods is reported as a conductive underlayer to improve α-Fe2O3 PEC water oxidation performance. The α-Fe2O3 nanorods grown on the ATO nanorods exhibit improved performance for PEC water oxidation compared to α-Fe2O3 grown on flat fluorine-doped tin oxide glass. Furthermore , a simple and facile TiCl4 chemical treatment further introduces TiO2 passivation layer formation on the α-Fe2O3 to reduce surface recombination. As a result, these unique nanostructures show dramatically improved photo-current density (139% higher than that of the pure hematite nanorods).

Sol-gel technique for the synthesis of anatase TiO2 at 420 C produces nanocrystals of 10-20 nm in size with Ti4+ in crystal volume and Ti3+ at terminal planes of the crystal. The study of Li+ co-doping effects on the structure, morphology, absorption, and luminescence of Eu3+ activated TiO2 anatase nanocrystals is presented. Pure anatase structure is achieved up to 9 at.% Li, with significant improvement in crystallinity of europium doped anatase TiO2. The Li þ co-doping reduces the unit cell volume of the crystal, induces the blue shift of the absorption edge, lengthens the lifetime of Eu3+ 5D0 excited state, and improves the Eu3+  emission intensity up to 37.5%. Judd-Ofelt analysis of Eu3+ emission showed enhancement of quantum efficiency from 66.4% to 98.7% when TiO2:Eu3+ was co-doped with 9 at.% of Li.

A novel, facile method based on a non-aqueous sol–gel solvothermal process has been developed to synthesise spherical TiO2 nanoparticles (NPs) in one pot. The reaction between titanium(IV) tert-butoxide (Ti[OC(CH3)3]4) and benzyl alcohol was a simple process, which resulted in the formation of highly crystalline titania NPs with a small size of only 6 nm, and with a correspondingly high surface area. The chemical formation mechanism of the metal oxide NPs has been proposed, and the degree of surface hydroxyls (–OH groups) has been examined. The products of the synthesis were characterised by X-ray powder diffraction (XRPD) using the advanced whole powder pattern modelling (WPPM) method, high-resolution transmission electron microscopy (HR-TEM), thermo-gravimetric analysis (TGA), UV-visible diffuse reflectance spectroscopy (DRS), Fourier transform infrared spectroscopy (FT-IR), and nuclear magnetic resonance (NMR) spectroscopy. The photocatalytic activity (PCA) was evaluated in both the liquid–solid phase, by monitoring the degradation of an organic dye (methylene blue (MB)) under UV-light irradiation, and in the gas–solid phase, by following the degradation of 2-propanol under UV-and visible-light exposures. The synthesized titania powders not only exhibited excellent photocatalysis in the liquid–solid phase (under UV irradiation), but also possessed a superior PCA in the gas–solid phase under a visible-light exposure. The effects on the PCA of the very small crystalline domain size, surface composition and the presence of organic molecules due to the synthesis process of the TiO2 NPs were shown to account for this behaviour.

A series of titania–transition metal and titania–rare earth element mixtures, with the stoichiometry Ti1−xMxO2, where M=Ce, Eu, La, Nb, W, Y, and x ranging from 0 to 0.05 atoms per formula unit, were prepared via solid-state reaction of the precursor oxides. The products of the synthesis were thermally treated in air and two maximum temperatures (900 and 1000 °C) were reached.

The addition of transition metal and rare earth ions to the TiO2 structure modified the anatase-to-rutile phase transition temperature, depending on the valence state of the ions added. Transition metals entered the titania structure, but essentially no solid solution between the rare earth elements and TiO2 was detected.

The photocatalytic activity of the powders was assessed in liquid–solid and gas–solid phases, under UVA and visible-light irradiation, monitoring the degradation of an organic dye and isopropanol, respectively. The results were explained by taking into account the relative amounts of anatase and rutile in the samples, the specific surface area of the powders, and their optical properties.

The hybrid structure of Fe2O3 nanoparti-
cles/TiO2 nanofibers (NFs), combines the merits of
large surface areas of TiO2 NFs and absorption in
ultraviolet light–visible light range. This structure can
be used for many applications such as photoelectro-
chemical water splitting and photo-catalysis. Here, a
sol-flame method is used for depositing Fe2O3 on TiO2
NFs that were prepared by hydrothermal on Ti sheets.
The obtained materials were characterized by XRD,
SEM, UV/Vis diffuse reflectance, Raman, and XPS.
The results revealed the formation of rutile and anatase
crystalline phases together with Fe2O3. This process
moves the absorption threshold of TiO2 NFs support
into visible spectrum range and enhances the photo-
current in comparison to bare TiO2 NFs, although no
hole scavenger was used. The impedance measure-
ment at low and high frequencies revealed an increase
in series resistance and a decrease in resistance of
charge transfer with sol-flame treatment time. A
mechanism for explaining the charge transfer in these
TiO2 NFs decorated with Fe2O3 nanoparticles was
proposed.

TiO 2 electrodes are deposited on FTO-glass substrates at 350 and 400 8C by aerosol-assisted chemical vapour deposition (AACVD) and the deposited TiO 2 electrodes are irradiated with microwave radiation (2.45 GHz) at various percentages (10, 25, 50, and 100%). X-ray diffraction (XRD) pattern shows that the deposited electrodes have anatase phase TiO 2 oriented in the (101) direction, and the crystallinity of these electrodes increases after microwave treatment. Field emission gun scanning electron microscopy (FEG-SEM) surface topography analysis proves the preservation of the nanostructure after exposure to various percentages of microwave radiation. The photoelectrochemical (PEC) studies prove a threefold enhancement of photocurrent density of AACVD-produced TiO 2 electrodes after 100% microwave irradiation. This improved performance of PEC properties is attributed to improvements in the crystallinity and the particle-necking properties. The results presented demonstrate that microwave processing is a promising alternative method to conventional sintering for TiO 2 photoanodes.

Mesoporous TiO 2 was prepared, inside "Taurasi" grape skins. The peel impregnation was followed by magnetic resonance imaging, to monitor the transport process in the natural template and the interaction of the solute with the templating structure. Moreover, the prepared mesoporous structure was used to support ultra-small platinum nanoparticles (USNPs), allowing high dispersion and maximizing active metals utilization. USNPs characterization was performed by means of high-resolution analytical transmission electron microscopy, CO-Diffuse Reflectance Infrared Fourier Transform spectroscopy, and X-ray photoelectron spectroscopy. Low Pt loaded TiO 2 was then tested in methanol oxidation reactions, showing an excellent behavior: negligible onset potentials (0.06 V) and very high If/Ib ratio (3.85). The results obtained in this work evidence the outstanding performances of the synthesized nano-electrocatalysts.

TiO2 is an effective and extensively employed photocatalyst, but its practical use in visible-light-mediated organic synthesis is mainly hindered by its wide band gap energy. Herein, we have discovered that Rh-photodeposited TiO2 nanoparticles selectively dehydrogenate N-heterocyclic amines with the concomitant generation of molecular hydrogen gas in an inert atmosphere under visible light (λmax = 453 nm) illumination at room temperature. Initially, a visible-light-sensitive surface complex is formed between the N-heterocycle and TiO2. The acceptorless dehydrogenation of N-heterocycles is initiated by direct electron transfer from the HOMO energy level of the amine via the conduction band of TiO2 to the Rh nanoparticle. The reaction condition was optimized by examining different photodeposited noble metals on the surface of TiO2 and solvents, finding that Rh0 is the most efficient cocatalyst, and 2-propanol is the optimal solvent. Structurally diverse N-heterocycles such as tetrahydroquinolines, tetrahydroisoquinolines, indolines, and others bearing electron-deficient as well as electron-rich substituents underwent the dehydrogenation in good to excellent yields. The amount of released hydrogen gas evinces that only the N-heterocyclic amines are oxidized rather than the dispersant. This developed method demonstrates how UV-active TiO2 can be employed in visible-light-induced synthetic dehydrogenation of amines and simultaneous hydrogen storage applications.

This paper reports the synthesis of Fe-titanate nanotubes by means of the conventional ion-exchange method with iron nitrate solutions. As the iron-rich nanotubes were found to contain the catalyst precursor intrinsically dispersed in their structures, the unprecedented possibility of using this kind of materials for building carbon nanostructures, firmly attached at the surface of the forming TiO2 nanoparticles, was verified. The catalytic decomposition of ethylene, used as a carbon source, was performed at a relatively high temperature (750 °C) when the nanotubes undergo an irreversible phase transformation to form anatase and rutile nanoparticles. Due to the different amounts of Fe ions in the nanotubes, distinct types of carbon/TiO2 hybrid interfaces were formed, ranging from amorphous (lower Fe3+ concentration) to the more crystalline graphitic domains (higher Fe3+ concentrations), as documented by the microstructure of the treated samples. The present approach is of potential interest for (photo)catalytic and energy conversion/transport applications.

This paper reports a simple, biogenic and green approach to obtain narrow band gap and visible light-active TiO 2 nanoparticles. Commercial white TiO 2 (w-TiO 2) was treated in the cathode chamber of a Microbial Fuel Cell (MFC), which produced modified light gray TiO 2 (g-TiO 2) nanoparticles. The DRS, PL, XRD, EPR, HR-TEM, and XPS were performed to understand the band gap decline of g-TiO 2. The optical study revealed a significant decrease in the band gap of the g-TiO 2 (E g = 2.80 eV) compared to the w-TiO 2 (E g = 3.10 eV). The XPS revealed variations in the surface states, composition, Ti 4+ to Ti 3+ ratio, and oxygen vacancies in the g-TiO 2. The Ti 3+ and oxygen vacancy-induced enhanced visible light photocatalytic activity of g-TiO 2 was confirmed by degrading different model dyes. The enhanced photoelectrochemical response under visible light irradiation further supported the improved performance of the g-TiO 2 owing to a decrease in the electron transfer resistance and an increase in charge transfer rate. During the TiO 2 treatment process, electricity generation in MFC was also observed, which was ~0.3979 V corresponding to a power density of 70.39 mW/m 2. This study confirms narrow band gap TiO 2 can be easily obtained and used effectively as photocatalysts and photoelectrode material.

Control of surface wetting properties is of interest in many different applications ranging from microfluidics, biomicroarrays, printing, green energy technologies to self-cleaning surfaces. We propose to program surfaces with full wetting re-versibility by micro-nano patterning of titanium dioxide (TiO2) thin films. Our TiO2 is deposited by Atomic Layer Deposition (ALD). We study the effects of surface preparation, film thickness, deposi-tion temperature and micro and nanopatterns on UV photoswitchability and recovery. We show superhy-drophilic (SHL) to hydrophobic (HB) reversible transitions by UV exposure and dark storage. With fixed TiO2 thickness, temperature variation in ALD film quality has been investigated by water contact angle (CA) measurements. We conform to control the TiO2 thin films switchability by controlling the ALD effective factors.

The harvesting of hot carriers produced by plasmon decay to generate electricity or drive a chemical reaction enables the reduction of the thermalization losses associated with supra-band gap photons in semiconductor photoelectrochemical (PEC) cells. Through the broadband harvesting of light, hot-carrier PEC devices also produce a sensitizing effect in heterojunctions with wide-band gap metal oxide semiconductors possessing good photostability and catalytic activity but poor absorption of visible wavelength photons. There are several reports of hot electrons in Au injected over the Schottky barrier into crystalline TiO 2 and subsequently utilized to drive a chemical reaction but very few reports of hot hole harvesting. In this work, we demonstrate the efficient harvesting of hot holes in Au nanoparticles (Au NPs) covered with a thin layer of amorphous TiO 2 (a-TiO 2). Under AM1.5G 1 sun illumination, photoanodes consisting of a single layer of ∼50 nm diameter Au NPs coated with a 10 nm shell of a-TiO 2 (Au@a-TiO 2) generated 2.5 mA cm −2 of photocurrent in 1 M KOH under 0.6 V external bias, rising to 3.7 mA cm −2 in the presence of a hole scavenger (methanol). The quantum yield for hot-carrier-mediated photocurrent generation was estimated to be close to unity for high-energy photons (λ < 420 nm). Au@a-TiO 2 photoelectrodes produced a small positive photocurrent of 0.1 mA cm −2 even at a bias of −0.6 V indicating extraction of hot holes even at a strong negative bias. These results together with density functional theory modeling and scanning Kelvin probe force microscope data indicate fast injection of hot holes from Au NPs into a-TiO 2 and light harvesting performed near-exclusively by Au NPs. For comparison, Au NPs coated with a 10 nm shell of Al 2 O 3 (Au@ Al 2 O 3) generated 0.02 mA cm −2 of photocurrent in 1 M KOH under 0.6 V external bias. These results underscore the critical role played by a-TiO 2 in the extraction of holes in Au@a-TiO 2 photoanodes, which is not replicated by an ordinary dielectric shell. It is also demonstrated here that an ultrathin photoanode (<100 nm in maximum thickness) can efficiently drive sunlight-driven water splitting.

Fire retardants are very important class of materials which has importance in saving the persons lives and the properties via reducing the possibility of polymer fires. In this work, High density Polyethylene (HDPE)/titanium dioxide (TiO2) nano-composite was prepared by melt extrusion to assess the efficiency of nano Titanium dioxide as fire retardant and to detect its effect on melting point of composite. Different weight percentages of nano TiO2 (0, 2%, 4%, 6%) were used. The Fire retardancy of prepared samples were tested according to standard methods [ASTM D 635, ASTM D4804].The results showed that addition of this kind of nano particles contributed in improving the fire retardancy of high density polyethylene composite for all samples which contained nano TiO2. The rate of burning and height of flame were varied according to different additions ratios. The maximum decreases in rate of burning and minimum height of flame was recorded for sample S2 (4%wt. addition) while the addition effect was very limited on melting point. The result clarified the synergic effect of nano titanium dioxide as co-fire retardant of High density polyethylene composites.

Doping semiconductor nanowires (NWs) for altering their electrical and optical properties is a critical strategy for tailoring the performance of nanodevices. ZnO NWs grown by hydrothermal method are pervasively used in optoelectronic, photovoltaic, and piezoelectric energy-harvesting devices. We synthesized in situ Cl-doped ZnO NWs with metallic conductivity that would fit seamlessly with these devices and improve their performance. Possible Cl doping mechanisms were discussed. UV–visible absorption spectroscopy confirmed the visible light transparency of Cl-doped ZnO NWs. Cl-doped ZnO NW/TiO2 core/shell-structured photoelectrochemical (PEC) anode was fabricated to demonstrate the application potential of highly conductive ZnO NWs. Higher photocurrent density and overall PEC efficiency compared with the undoped ZnO NW-based device were achieved. The successful doping and low resistivity of ZnO could unlock the potential of ZnO NWs for applications in low-cost flexible transparent electrodes.

The present studies are about surfactant free simple synthesis for titania (TiO 2) nanostructures, by which morphology and phase can be tuned through temperature variation. The formation of oval shaped nanocrystals and nanorods at different temperatures are attributed to the phase transformation between anatase and rutile by one-step chemical reaction involving titanium tetraisopropoxide and aqueous ethyl alcohol. Categorically, two different morphologies of TiO 2 were observed with respect to variation in temperature with nanorods formation at −20°C and − 10°C and oval shape formation at − 40°C and − 30°C with higher surface area. Crystalline nature and size of nano-TiO 2 were determined by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The energy gap of TiO 2 nanoparticles were determined by optical absorption measurement and found to be in the range of~2.92 to 3.02 eV with an indirect band nature.

Atomic Layer Deposition (ALD) has been used to deposit Titanium Dioxide (TiO2) and Aluminum Oxide (Al2O3) thin film on stainless steel and Si-wafer (100) substrates. For TiO2, Tetrakis (dimethylamido) titanium (TDMAT) {Ti (NMe2)4} was used. Also for Al2O3 , Trimethylaluminum (TMA) {Al (CH3)3 } was used. H2O as precursors used for two of them and at 250 °C deposition temperatures. Growth rates of thin film, thin film properties (including thickness, refractive index, and reflectivity) and surface roughness were determined using Spectroscopic Ellipsometry and Optical Profillometer. The results
showed good quality films without micro crack, good thin films properties and non-linear growth rates were observed from the results data. Al2O3 ALD film exhibited low surface roughness values, low growth rates diversion and the nearest film thickness compared with
TiO2 ALD film.

Achieving advanced multifunctional materials displaying several coexisting properties is currently one of the most exciting and innovative research topics. In this study, we report the engineering of a multifunctional material exhibiting, at the same time, tuneable photochromic behaviour and gas-sensing properties for acetone detection. The photochromic property of silver modified (1–10 mol% Ag) titanium dioxide (titania, TiO2) NPs was monitored under consecutive UVA-light exposure times, and the change in colour was thoroughly investigated with both spectroscopic and colourimetric analyses. All Ag modified samples exhibited a significant change in colour and visible spectra after only 15 seconds of exposure, and this increased with further exposure. It was shown that both the silver molar content in the Ag–TiO2 nano-heterostructure, as well as the UVA-light irradiation time, governed the tunability of the photochromic behaviour (the colour changed from pale yellow to dark blue in Ag-modified specimens, while it remained white in unmodified TiO2). The same nano-heterostructures were also tested as sensing materials for resistive metal oxide gas sensors (MOS). These Ag–TiO2 nano-heterostructures proved to be highly sensitive for the detection of acetone vapours at low concentrations (<1 ppm), superior to the best TiO2-based sensors so far reported. This is the first thorough study to qualitatively monitor, in real-time, the growth of Ag0 NPs on a TiO2 matrix, assessing both optical spectroscopy and colourimetric CIEL*a*b* analysis (e.g. what meets the eye), and to also demonstrate the superior acetone gas-sensing properties of such nano-heterostructures.

Titanium dioxide exists in a large number of polymorphs, the most common ones being, in order of abundance, rutile, anatase and brookite. Recently, there has been an increasing degree of attention on TiO2 , due to its photocatalytic and antibacterial properties. In this work, titania nanopowders synthesized via an aqueous sol–gel method were modified with silver and/or tungsten, with potential application as photocatalysts and antibacterial agents. The dried gels were thermally treated at two temperatures, and the occurrence of amorphous phase—in both dried and calcined gels—was obtained using the Rietveld method. In powders calcined at 600 °C, the crystal structure of rutile was determined with the Rietveld method on the full profile fitting of the X-ray powder diffraction patterns, while microstructural information was achieved by means of Williamson–Hall plots and line broadening analysis methods. The photochromic property of the Ag and W/Ag modified samples—when subjected to both UV-and visible-light irradiation and for different time expo-sures—was also investigated via UV–Vis spectroscopy. Powders were shown to possess a tuneable photochromism due to the surface plasmon resonance of the added silver, depending on the firing temperature, light (and time) exposure, and on whether or not tungsten was present in the nanopowders.

A layer of titanium dioxide (TiO 2 -NT) nanotubes 500 nm thick with average diameters of 60 nm is grown via anodizing. Memristive behavior typical of synthesized Ti/TiO 2 -NT/Au structures is observed in full cycles of resistive switching, and during the multiple reading of data. Impedance in the states of low (R LRS ≈ 3 Ohm) and high (R HRS ≈ 180 Ohm) resistance are estimated for the obtained memristors.

Luminescence temperature sensing with Eu3+ doped TiO2 nanoparticles was tested over a temperature range of 307-533 K. Anatase Eu 3+:TiO2 nanoparticles of 10-20 nm in diameter are prepared using the hydrolytic sol-gel route. In photoluminescence emission spectra of Eu3+:TiO2 nanoparticles two distinct spectral regions are observed: the high energy spectral region associated with the trap emission of the TiO2 host, and the low energy spectral region with well resolved emission peaks of the Eu3+ ions. The ratio between Eu3+ emission and TiO2 trap emission, and the Eu3+ emission decay shows strong temperature dependence, and are tested for temperature sensing. It is found that relative sensor sensitivity ranges from 0.17 to 2.43% K-1 and is among the highest recorded for inorganic nanosensors. Temperature resolution is better than 1 K over a wide temperature range and reaches 0.33 K for decay measurements and 0.46 K for the fluorescence intensity ratio measurements at about 400 K.

Understanding the mechanism of NO 2 interaction on semiconductor surfaces such as TiO 2 is a key step in designing the catalytic processes for conversion of NO 2 to useful products. In the present work, through density functional theory calculations and NEB simulations, we have performed a comprehensive electronic structure study and established the reaction steps for efficient conversion of NO 2 to HONO on TiO 2 surface in the presence of water vapor. We predict the dimerization of NO 2 to form a metastable N 2 O 4. The latter's dissociation to NO δ+ and NO 3 δ− complexes occurs in two pathways: (i) direct disproportionation reaction and (ii) through formation of NO 2 δ+ and NO 2 δ− intermediates followed by O transfer. The introduction of H 2 O on a NO 2 chemisorbed surface leads to the formation of nitrous acid through the interaction of NO δ+ with the water. The reaction pathways leading to formation of nitrous and nitric acids are formulated.