Properties and microstructures of epoxy resin/TiO2 and SiO2 hybrids

Epoxy resin/TiO₂ and epoxy resin/SiO₂ hybrids were prepared by different procedures, and their mechanical properties were correlated to their microstructures, as indicated by small‐angle X‐ray scattering (SAXS) measurements. Epoxy resin/TiO₂ hybrids were prepared by mixing the epoxy resin (EP828) with N‐(2‐aminoethyl)‐3‐aminopropyltrimethoxysilane (S320) in acetone, and then titanium‐n‐butoxide (TnBU) was added. In addition, epoxy/SiO₂ hybrids were prepared by mixing EP828 with a curing agent, a diamino heterocyclic compound (B002) in acetone, and an organo silica sol (silica nanoparticles dispersed in methylethylketone) was added. In the EP828/S320/TiO₂ hybrid systems, the TiO₂ component was attached to both of the chain ends of the epoxy matrix, hence leading to the formation of inorganic domains via the covalent bonds. SAXS profiles of these hybrids showed peaks at q = 2.3 nm^?1, caused by interference between the domains. The storage modulus increased with increasing TiO₂ content above the T_g, owing to the strong interactions between TiO₂ and the epoxy matrix. The tanδ peak position did not change, although the intensity decreased with increasing TiO₂ content. The SAXS profiles of the EP828/B002/SiO₂ hybrids were very different to those of the corresponding EP828/S320/TiO₂ hybrids, and indicated that SiO₂ particles with rough surfaces were randomly dispersed in the epoxy matrix. The storage moduli of the EP828/B002/SiO₂ hybrid systems increased only slightly with SiO₂ content, because of the weak interactions. These mechanical properties are well explained by the microstructures derived from the SAXS profiles. Copyright © 2004 Society of Chemical Industry     

Engineered TiO2 and SiO2‐TiO2 films on silica‐coated glass for increased thin film durability under abrasive conditions

Thin films durability is critical to retain its performance in real life applications. For automotive glass, further factors such as haze appearance developed under abrasive conditions become relevant to ensure the driver's visibility. Macroscopic abrasion resistance tests of TiO₂/SiO₂ and SiO₂–TiO₂/SiO₂ thin films on soda‐lime silica (SLS) glass were performed according to an American standard for safety grazing. The purpose of this, was to increase the top active film durability in a bilayer system by understanding how film thickness and top film composition influence abrasion performance. In order to achieve this understanding, three approaches were considered: (a) determination of the influence of TiO₂ top film thickness, (b) replacement of the TiO₂ top film by SiO₂–TiO₂ films, and (c) determination of the influence of SiO₂–TiO₂ film thickness. Results showed that thinner top TiO₂ film thickness leads to SiO₂/TiO₂ bilayers with lower haze value and improved abrasion resistance. It was also found that SiO₂ addition to TiO₂ top film composition promotes the thin film adhesion and sample durability against abrasive wear. Friction coefficient and micro‐hardness measurements support the abrasion results. Factors contributing to the improvement of the lifetime performance of TiO₂ and SiO₂–TiO₂ thin films were identified.     

Photocatalytic Activity and Electronic Structure Analysis of N‐doped Anatase TiO2: A Combined Experimental and Theoretical Study

N‐Doped TiO₂ photocatalysts were prepared by a hydrothermal method with tetra‐n‐butyl titanate (TTNB) and triethanolamine as precursors. The obtained samples were characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM), and UV‐visible diffuse reflectance spectra (DRS), respectively. Photocatalytic activities of the anatase products were investigated on the degradation of methyl orange (MO). The incorporation of nitrogen impurity in anatase TiO₂ was studied by the first‐principles calculations based on the density functional theory (DFT). The calculated electronic band structures for substitutional and interstitial N‐doped TiO₂ indicated the formation of localized states in the band gap, which lied above the valence band. Excitation from the impurity states of N 2p to the conduction band could account for the optical absorption edge shift toward the lower energies. It was consistent with the experimentally observed absorption of N‐doped samples in the visible region.     

Liquid‐phase hydrogenation of cinnamaldehyde over Cu‐Au/SiO2 catalysts

The synthesis, characterization, and application of silica‐supported Cu‐Au bimetallic catalysts in selective hydrogenation of cinnamaldehyde are described. The results showed that Cu‐Au/SiO₂ bimetallic catalysts were superior to monometallic Cu/SiO₂ and Au/SiO₂ catalysts under identical conditions. Adding a small amount of gold (6Cu‐1.4Au/SiO₂ catalyst) afforded eightfold higher catalytic reaction rate compared to Cu/SiO₂ along with the high selectivity (53%, at 55% of conversion) toward cinnamyl alcohol. Characterization techniques such as x‐ray diffraction, H₂ temperature‐programmed reduction, ultraviolet‐visible spectroscopy, transmission electron microscopy, Fourier‐transform infrared spectra of chemisorbed CO, and x‐ray photoelectron spectroscopy were employed to understand the origin of the catalytic activity. A key genesis of the high activity of the Cu‐Au/SiO₂ catalyst was ascribed to the synergistic effect of Cu and Au species: the Au sites were responsible for the dissociative activation of H₂ molecules, and Cu⁰ and Cu⁺ sites contributed to the adsorption‐activation of C?C and C?O bond, respectively. A combined tuning of particle dispersion and its surface electronic structure was shown as a consequence of the formation of Au‐Cu alloy nanoparticles, which led to the significantly enhanced synergy. A plausible reaction pathway was proposed based on our results and the literature. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3300–3311, 2014     

Preparation and characterization of a novel activated carbon‐supported N‐doped visible light response photocatalyst (TiO2−xNy/AC)

A photocatalyst, TiO_2?xN_y/AC (activated carbon (AC) supported N‐doped TiO₂), highly active in both the Vis and UV range, was prepared by calcination of the TiO₂ precursor prepared by acid‐catalyzed hydrolysis in an ammonia atmosphere. The powders were characterized by diffuse reflectance spectroscopy, scanning electron microscopy, X‐ray diffraction, N₂ adsorption, Fourier transform infrared spectroscopy and phenol degradation. The doped N in the TiO₂ crystal lattice creates an electron‐occupied intra‐band gap allowing electron‐hole pair generation under Vis irradiation (500–560 nm). The TiO_2?xN_y/AC exhibited high levels of activity and the same activity trends for phenol degradation under both Vis and UV irradiation: TiO_2?xN_y/AC calcined at 500 °C for 4 h exhibited the highest activity. The band‐gap level newly formed by doped N can act as a center for the photo‐generated holes and is beneficial for the UV activity enhancement. The performance of the prepared TiO_2?xN_y/AC photocatalyst revealed its practical potential in the field of solar photocatalytic degradation of aqueous contaminants. Copyright © 2007 Society of Chemical Industry     

Core‐shell method of synthesis,characterizations, and ac conductivity studies of polyaniline/n‐TiO2 composites

Polyaniline/nano‐titanium dioxide composites (PANI/n‐TiO₂) were prepared using α‐dextrose as surfactant and ammonium per sulfate as oxidant. The PANI/n‐TiO₂ composite is characterized by Fourier transform infrared spectra and confirmed the presence of benzenoid and qunoide ring structures and also formation of free ions. The transmission electron microscopy study reveals that the size of TiO₂ is in the order of 7 nm where as the composite size is of the order of 13 nm; further, it is observed that the TiO₂ particles are intercalated to form a core shell of PANI. The X‐ray diffraction (XRD) studies show that the monoclinic structure of the composites. ac Conductivity, permittivity, and tangent loss studies on these samples suggest that these composites may be well suited for gas sensor. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Enhanced photocatalytic performance of nanocrystalline TiO2 membrane by both slow photons and stop‐band reflection of photonic crystals

An nc‐TiO₂/SnO₂ inverse opal composite membrane was fabricated, the photo‐activity of which was significantly enhanced by utilizing both slow photons and stop‐band reflection of the photonic crystal layer. The materials of the photonic crystal layer must be transparent in the area of adsorption edge of the nc‐TiO₂, so that SnO₂, having much greater electronic band gap than TiO₂, was used for the materials of the photonic crystal layer. The photonic band‐gap of the SnO₂ photonic crystal was designed at the semiconductor band gap of TiO₂ to harvest slow photons in the interface between the SnO₂ layer and the TiO₂ layer. The two layer structure makes it possible to couple the stop‐band reflectivity of the photonic layer to the photocatalyst. Composite membranes can improve solar energy harvesting and substantially improve photocatalysts for photolysis and photochemical degradation of environmental pollutants. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Antimicrobial properties of silver nanoparticles synthesized by bioaffinity adsorption coupled with TiO2 photocatalysis

BACKGROUND: On the basis of effective bioaffinity adsorption of Ag⁺, silver nanoparticles (Ag NPs) were synthesized on the surface of chitosan‐TiO₂ adsorbent (CTA) by TiO₂ photocatalysis for crystal growth. RESULTS: Among the microstructure characterizations of the resulting silver nanoparticles‐ loaded chitosan‐TiO₂ adsorbent (Ag‐CTA), X‐ray diffraction (XRD) and scanning electron microscopy (SEM) equipped with energy dispersive X‐ray (EDX) revealed the formation of metallic Ag on the CTA, which was further confirmed by the surface plasmon resonance of Ag NPs in the UV‐visible absorption spectrum. The underlying mechanism behind the formation of Ag NPs on the CTA by TiO₂ photoreduction was studied by Fourier transform infrared (FTIR) spectroscopy. The distinctive feature of Ag‐CTA after adsorption was the highly efficient antimicrobial activity in inactivating different test strains. In the case of Escherichia coli, 1.50 mg 1.67 wt% Ag‐CTA could totally inhibit 1.0–1.2 × 10⁷ colony forming units (CFU) in 100 mL nutrient medium, which was superior to that previously reported. CONCLUSIONS: CTA effectively adsorbed the precious metal ion Ag⁺ onto active imprinting sites on the adsorbent and then exerted efficient antimicrobial effects against diverse microbes. This research will be useful for designing a novel CTA‐based wastewater treatment for multi‐functional performance. Copyright © 2010 Society of Chemical Industry     

Preparation and characterization of bipolar membranes modified using photocatalyst nano‐TiO2 and nano‐ZnO

The nano‐ZnO and nano‐TiO₂ were added into chitosan (CS) anion layer to prepare polyvinyl alcohol (PVA) ‐ sodium alginate (SA)/ TiO₂‐ZnO‐CS (here, PVA:polyvinyl alcohol; SA:sodium alginate) bipolar membrane (BPM), which was characterized using scanning electron microscopy, atomic force microscopy (AFM), thermogravimetric analysis (TG), electric universal testing machine, contact angle measurer, and so on. Experimental results showed that nano‐TiO₂‐ZnO exhibited better photocatalytic property for water splitting at the interlayer of BPM than nano‐TiO₂ or nano‐ZnO. The membrane impedance and voltage drop (IR drop) of the BPM were obviously decreased under the irradiation of high‐pressure mercury lamps. At a current density of 60 mA/cm², the cell voltage of PVA‐SA/TiO₂‐ZnO‐CS BPM‐equipped cell decreased by 1.0 V. And the cell voltages of PVA‐SA/TiO₂‐CS BPM‐equipped cell and PVA‐SA/ZnO‐CS BPM‐equipped cell were only reduced by 0.7 and 0.6 V, respectively. Furthermore, the hydrophilicity, thermal stability, and mechanical properties of the modified BPM were increased. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Counterion‐Switched Reversibly Hydrophilic and Hydrophobic TiO2‐Incorporated Layer‐By‐Layer Self‐Assembled Membrane for Nanofiltration

The manipulation of surface wettability has been regarded as an efficient strategy to improve the membrane performances. Herein, the counterion‐switched reversibly hydrophilic and hydrophobic surface of TiO₂‐loaded polyelectrolyte membrane are prepared by layer‐by‐layer assembly of poly(sodium 4‐styrene sulfonate) (PSS) and poly(diallydimethyl‐ammoniumchloride (PDDA) containing TiO₂@PDDA nanoparticles (NPs) on the hydrolyzed polyacrylonitrile (PAN) substrate membrane. The obtained polyelectrolyte multilayer (PEM) membranes [PEM‐TiO₂]_4.5⁺X^? (X^? = Cl^?, PFO^? [perfluorooctanoate] etc.) show different hydrophilicity and hydrophobicity with various counterions. The integration of TiO₂ NPs obviously improves the wettability and nanofiltration (NF) performance of PEM membrane for (non)aqueous system of dyes (crystal violet, eriochrome black T) with a high recyclability. The highly hydrophilic [PEM‐TiO₂]_4.5⁺Cl^? (water contact angle [WCA]: 13.2 ± 1.8°) and hydrophobic [PEM‐TiO₂]_4.5⁺PFO^? (WCA: 115.4 ± 2.3°) can be reversibly switched via counterion exchange between Cl^? and PFO^?, verifying the surface with a reversible hydrophilic–hydrophobic transformation. For such membranes, the morphology, wettability, and NF performance rely on the loading of TiO₂@PDDA NPs and surface counterion. Meanwhile, the motion and interaction of water or ethanol in the hydrophilic or hydrophobic membrane are revealed by low‐field nuclear magnetic resonance. This work provides a facile and rapid approach to fabricate smart and tunable wetting surface for potential utilization in (non)aqueous NF separation.     

Synthesis of conducting polyaniline/TiO2 composite nanofibres by one‐step in situ polymerization method

Conducting polyaniline (PANI)/titanium dioxide (TiO₂) composite nanofibres with an average diameter of 80–100 nm were prepared by one‐step in situ polymerization method in the presence of anatase nano‐TiO₂ particles, and were characterized via Fourier‐transform infrared spectra, UV/vis spectra, wide‐angle X‐ray diffraction, thermogravimetric analysis, and transmission electron microscopy, as well as conductivity and cyclic voltammetry. The formation mechanism of PANI/TiO₂ composite nanofibres was also discussed. This composite contained ～ 65% conducting PANI by mass, with a conductivity of 1.42 S cm^?1 at 25°C, and the conductivity of control PANI was 2.4 S cm^?1 at 25°C. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Preparation of novel nano/submicrofiber catalyst containing nano‐TiO2 particles

A novel Nano/submicrofiber catalyst was prepared via electrospinning technology from poly (vinyl pyrrolidone) (PVP) and nano‐TiO₂. First, nano‐TiO₂ particles were added into the mixture of ethanol and deionized water, the mass ratio of ethanol and deionized water was 1 : 1, the TiO₂ suspension was obtained after 1 h with ultrasonic treatment and centrifugal effect, Then PVP was added into the above‐mentioned suspension and the content of PVP in the sol was 28%. The TiO₂/PVP solution was electrospun with different voltage. The effects of the content of TiO₂ and electrospinning voltage on diameter of nano/submicrofiber were studied. The nano/submicrofiber catalyst was characterized by scanning electron microscopy, transmission electron microcopy, X‐ray diffraction, and Fourier transform infrared. The results show that the diameter of nano/submicrofiber increases with an increase of the content of nano‐TiO₂ and decreases with the increase of electrospinning voltage. The analytical result showed that the nano‐TiO₂ particles were well dispersed in the matrix of PVP, moreover, the crystal type of nano‐TiO₂ was a mixture of anatase and rutile and the diameter of nano‐TiO₂ particles in the nano/submicrofiber is in the range of 20–60 nm and the nano‐TiO₂ particle was monodisperse, and the nano‐TiO₂ particle and PVP molecule was connected by a hydrogen bonding. This nano/submicrofiber catalyst has a high efficiency on degradation on CH₂O. 56.8 percent of CH₂O was degraded under ultraviolet radiation in 80 min when the content of nano‐TiO₂ is 20% in nano/submicrofibers. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Experimental analysis and optimization of the synthesizing property of nitrogen‐modified TiO2 visible‐light photocatalysts

BACKGROUND: The aim of this study was to investigate improvement of the photocatalytic activity of visible‐light driven nitrogen‐modified TiO₂ (N‐TiO₂) powder toward methyl blue (MB) and direct blue‐86 (DB‐86) dyes. The Taguchi method with an L₉ orthogonal array was applied to plan the synthesis parameters, i.e. nitrogen sources, nitrogen source concentrations, stirring time and calcined temperatures. 95% confirmation experiments were undertaken to verify the effectiveness of the Taguchi method. RESULTS: All N‐TiO₂ photocatalysts were shifted toward the visible light region with the optical band gap (Eg). Nitrogen source concentrations were significant parameters for the photocatalytic decolorization rate constants (k values). In comparison with pure TiO₂, the photodecolorization behavior of N‐TiO₂ toward DB‐86 was superior with a reaction rate constant of 1.68 × 10^?3 min^?1, and a 4 h photodecolorization efficiency of 34%. CONCLUSION: The Taguchi method was reported to alter the surface properties of commercial Degussa P25 TiO₂, which could then be used as a visible‐light driven photocatalyst. The visible‐light‐driven photocatalyst was investigated to determine material characteristics. Greater photodecolorization of MB and DB‐86 dye pollutants using optimally‐prepared N‐TiO₂ under visible light irradiation was successfully obtained. Copyright © 2011 Society of Chemical Industry     

Sonocatalytic damage of bovine serum albumin (BSA) under ultrasonic irradiation by mixed TiO2/SiO2 powder

BACKGROUND: In order to effectively damage some biomolecules under ultrasonic irradiation, a mixed TiO₂/SiO₂ powder with high catalytic activity and selectivity was used as a sonocatalyst. RESULTS: The mixed TiO₂/SiO₂ powder heat treated at 450 °C for 30 min was adopted as a sonocatalyst and the damage to BSA molecules under ultrasonic irradiation was assessed. In addition, the effects of such variables as molar ratio of TiO₂ and SiO₂, treatment temperature and time, ultrasonic irradiation time, catalyst amount, solution acidity, ionic nature and strength, ultrasonic irradiation power and D₂O concentration on the damage to BSA molecules were studied by means of UV‐visible and fluorescence spectra. The results showed that the degree of damage was aggravated by an increase in ultrasonic irradiation time, catalyst amount, solution acidity, ultrasonic irradiation power and D₂O concentration, but was reduced by an increase in ionic strength. CONCLUSION: The results indicated that the mixed TiO₂/SiO₂ powder displayed higher activity and selectivity compared with nano‐sized TiO₂ and SiO₂ powders during the sonocatalytic damage of BSA. The extent of the damage decreased in the order TiO₂/SiO₂ > nano‐sized TiO₂ > nano‐sized SiO₂. These results are of great significance for applying sonocatalytic methods to treat tumours. Copyright © 2008 Society of Chemical Industry     

Clean synthesis of methyl N‐phenyl carbamate over ZnO‐TiO2 catalyst

BACKGROUND: Methyl N‐phenyl carbamate (MPC) is an intermediate for the preparation of methylene diphenyl diisocyanate (MDI), which is an important monomer for polyurethane synthesis. The synthesis of MPC by the reaction of aniline and dimethyl carbonate (DMC) is becoming more and more attractive. However, most of the catalysts used in MPC synthesis are homogeneous and not environment‐friendly. Therefore, it is important and necessary to develop a new kind of oxide catalyst, that is not only friendly to the environment, but also exhibits higher activity and longer service time. RESULTS: A new heterogeneous catalyst, ZnO‐TiO₂, was prepared for MPC synthesis. ZnO‐TiO₂ catalyst with a molar ratio Ti/Zn = 2 and calcined at 673 K exhibited good catalytic activity: aniline conversion was 96.9% and MPC yield 66.7%. CONCLUSION: ZnO‐TiO₂ exhibits better catalytic activity than ZnO or TiO₂ alone, which may result from the formation of ZnTiO₃ and Zn₂TiO₄. Compared with ZnTiO₃, Zn₂TiO₄ has better selectivity for MPC synthesis. Lewis acid sites with weaker acid strength favour MPC synthesis. The catalyst activity can be recovered almost completely by calcination. Copyright © 2008 Society of Chemical Industry     

CuGaO2/TiO2 heterostructure nanosheets: Synthesis,enhanced photocatalytic performance,and underlying mechanism

Effective separation and fast transport of photogenerated carriers are vital links determining the photocatalytic performance. Heterostructure constructed by two complementary semiconductors is a feasible strategy to achieve this goal. By one-pot hydrothermal method, 0D-TiO₂ nanoparticles are loaded onto 2D-CuGaO₂ nanosheets, forming a mixed dimension, closely combined heterostructure. The photocurrent density of CuGaO₂/TiO₂ heterostructure is ∼16.6 μA/cm², which is 1.24 times higher than that of pristine CuGaO₂ nanosheets (∼13.4 μA/cm²) and 15 times higher than that of TiO₂ (∼1.1 μA/cm²). In the tetracycline hydrochloride degradation experiment, the degradation efficiency of tetracycline hydrochloride by CuGaO₂/TiO₂ heterostructure reached 99% within 90 min, which was 1.2 times the degradation efficiency of CuGaO₂ nanoparticles (82%) and 20.2 times the degradation rate of TiO₂ (4.9%). A series of experimental characterizations combined with density functional theory calculations revealed that it is the built-in electric field in the CuGaO₂/TiO₂ interface region that drives the photogenerated electron–hole pairs to travel in the opposite direction, thus inhibiting their recombination. Furthermore, the energy band offset of the CuGaO₂/TiO₂ interface makes it easier for the photogenerated holes and electrons to gather onto the valence band of the CuGaO₂ nanosheets and the conduction band of the TiO₂ nanoparticles, respectively. Therefore, appropriate interface lattice matching, suitable configuration of band gap and band edge positions, and strong opposite drive of interface electric field enable CuGaO₂/TiO₂ heterostructure to achieve wide spectral response and effective separation of photogenerated electron–hole pairs at the same time.     

Construction of Au/TiO2 Heterojunction with high photocatalytic performances under UVA illumination

Anatase TiO₂ nanoparticles (NPs) were successfully prepared through a hydrothermal approach, and Au NPs at various Au (0.1–2 wt%) contents were photodeposited onto the TiO₂ NPs surface. The photocatalytic efficiency for the Au/TiO₂ NPs for resorcinol photodegradation throughout UVA illumination was assessed. The TEM images and XPS findings indicated that the Au NPs are highly distributed onto TiO₂ surface in the metallic state. The 0.1%Au/TiO₂ NPs exhibited the highest photocatalytic efficiency of about 95.34%; however, 72.36% is given by pure TiO₂ NPs. It was found that the photodegradation rate of 0.1% Au/TiO₂ NPs exhibited 1.5 times of magnitude higher than pure TiO₂ NPs. 0.1%Au/TiO₂ NPs was considered to be the outstanding photoactive due to the ultimate efficient charge-carriers separation through charge transfer between Au and TiO₂ NPs. The Au NPs sizes, its dispersity on TiO₂ surface and surface plasmon resonance (SPR) were believed the critical factors for the higher photocatalytic performance of 0.1% Au/TiO₂ NPs. The prepared photocatalysts are found to be the promising materials for toxic organic compounds remediation and solar conversion.     

An experimental and theoretical understanding of a UV photodetector based on Ag nanoparticles decorated Er-doped TiO2 thin film

Glancing angle deposition (GLAD) was employed to synthesise plasmonic Silver (Ag) nanoparticles (NPs) on the chemically prepared Erbium-doped Titanium dioxide (Er:TiO₂) thin films (TFs). The impact of using Ag NPs on the morphological, optical, and electrical aspects of Er:TiO₂ TFs were sequentially analysed. From the field emission scanning electron microscopy (FESEM) image, the Ag NPs appeared spherical and uniformly distributed on the Er:TiO₂ TFs. The size (diameter) of the maximum number of Ag NPs was ~15 nm (calculated from FESEM image). Energy dispersive X-ray (EDX) spectra assured the presence of Ag NPs on the TFs. X-ray diffraction (XRD) pattern for Ag NPs decorated Er:TiO₂ TFs closely resembled the face centred cubic crystal structure of Ag NPs and body centred tetragonal Ag–O compound. The optical spectroscopy (UV–visible diffuse reflectance and photoluminescence) elucidated that the absorption of light was significantly enhanced in the UV–visible spectral range for the TFs in which Ag NPs were sandwiched between Er:TiO₂ TF layers (Er:TiO₂/Ag NPs/Er:TiO₂). The Schottky contact-based Au/Er:TiO₂/Si photodetector (PD) and Au/Er:TiO₂/Ag NPs/Er:TiO₂/Si (plasmonic) PD were constructed. The plasmonic PD offered a better photo-responsivity of ~4.5 fold higher as compared to Er:TiO₂ TF-based PD upon 380 nm illumination under ?6 V bias. An increase in detectivity and a decrease in noise equivalent power was observed for the plasmonic device compared to Er:TiO₂ device in the UV region. A theoretical approach had been adopted to calculate the wavelength-dependent responsivity for both devices. Further, the important parameters like photoconductive gain, electron transit time and electron mobility were calculated by simulating the experimental responsivity curves of the devices. These parameters exhibited improvement in the UV regime for the plasmonic PD. The fast temporal response with short rise and decay time proves the excellent efficiency of the plasmonic UV PD.     

Synthesis and characterization of a conducting polyaniline/TiO2−SiO2 composites

Polyaniline/TiO₂?SiO₂ composites were prepared by an in situ chemical oxidation polymerization approach in the presence of hybrid TiO₂?SiO₂ fillers. The obtained polyaniline/TiO₂?SiO₂ composites were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectrometer (FTIR), X‐ray diffraction (XRD), thermogravimetry (TG), and current?voltage (I?V) measurements. SEM picture shows a variation in morphology of polyaniline (PANI) from fiber shape to relatively regular particle shape with increasing TiO₂?SiO₂ contents in the composites. The floccule‐like structures were observed by high resolution TEM, which may help improve the efficiency of conductive network. SEM, XRD, TG, and FTIR spectra all reveal that a relatively strong interaction exist between TiO₂?SiO₂ and PANI. The I?V characteristics in such composites indicate that the charge transport is mainly governed by the space charge effects, which occurs at the interface between the conducting PANI and TiO₂?SiO₂. Meanwhile, PANI/TiO₂?SiO₂ composites exhibit significant increase in conductivity than PANI/TiO₂ or PANI/SiO₂. The reasons about high conductivity of PANI/TiO₂?SiO₂ have also been discussed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2288–2295, 2013     

Production of Synthesis Gas via Dry Reforming of Methane over Co‐Based Catalysts: Effect on H2/CO Ratio and Carbon Deposition

The effect of support type on synthesis gas production using Co‐based catalysts supported over TiO₂‐P25, Al₂O₃, SiO₂, and CeO₂ was investigated. The catalysts were prepared by the incipient wet impregnation method and characterized by various techniques for comparison. Experiments were performed in a micro tubular reactor. The results revealed that all Co‐supported catalysts produced synthesis gas ratios of 1 and below and, thus, proved to be well‐suited for methanol and Fischer‐Tropsch syntheses. Co catalysts supported over TiO₂‐P25 and Al₂O₃ provided better synthesis gas ratios and stability performances. The promotion of a Co/TiO₂‐P25 catalyst with Ce had a substantial influence on its catalytic activity and the amount of carbon deposit. A Ce‐promoted catalyst diminished markedly the extent of carbon deposition and thus boosted the performance towards better activity and stability.