Showing papers on "Chemical bath deposition published in 2013"

p-n Heterojunction photoelectrodes composed of Cu2O-loaded TiO2 nanotube arrays with enhanced photoelectrochemical and photoelectrocatalytic activities

Abstract: Cu2O/TiO2 p–n heterojunction photoelectrodes were prepared by depositing different amounts of p-type Cu2O nanoparticles on n-type TiO2 nanotube arrays (i.e., forming Cu2O/TiO2 composite nanotubes) via an ultrasonication-assisted sequential chemical bath deposition. The success of deposition of Cu2O nanoparticles was corroborated by structural and composition characterizations. The enhanced absorption in the visible light region was observed in Cu2O/TiO2 composite nanotubes. The largely improved separation of photogenerated electrons and holes was revealed by photocurrent measurements. Consequently, Cu2O/TiO2 heterojunction photoelectrodes exhibited a more effective photoconversion capability than TiO2 nanotubes alone in photoelectrochemical measurements. Furthermore, Cu2O/TiO2 composite photoelectrodes also possessed superior photoelectrocatalytic activity and stability in the degradation of Rhodamine B. Intriguingly, by selecting an appropriate bias potential, a synergistic effect between electricity and visible light irradiation can be achieved.

MoS2/CdS Heterojunction with High Photoelectrochemical Activity for H2 Evolution under Visible Light: The Role of MoS2

Abstract: MoS2/CdS p-n heterojunction films with high photoelectrochemical activity for H2 evolution under visible light were successfully prepared by electrodeposition followed by chemical bath deposition. The films were characterized by X-ray diffraction, scanning electron microscopy, UV–visible absorption, X-ray photoemission spectroscopy, photoluminescence, and photoelectrochemical response. The MoS2/CdS heterostructure shows much higher visible-light photoelectrocatalytic activity and higher stability toward the water splitting than pure CdS film. The MoS2/CdS film with an optimal ratio of 0.14% exhibits the highest photocurrent of 28 mA/cm2 and the highest IPCE of ca. 28% at 420 nm at 0 V vs Ag/AgCl. The critical role of MoS2 in the MoS2/CdS film was investigated. The improved photoelectrochemical performance of the MoS2/CdS heterojunction film was attributed to the visible light absorption enhanced by MoS2 and the formation of a p-n junction between CdS and MoS2, which accelerates the effective separation of...

Band gap determination using absorption spectrum fitting procedure

Abstract: In this article, using the Tauc model, the absorption spectrum fitting method was applied to estimate the optical band gap and width of the band tail of the CdSe nanostructural films that requires only the measurement of the absorbance spectrum, and no additional information such as the film thickness or reflectance spectra is needed. Samples are prepared by chemical bath deposition method. Fabricated nanostructural thin films are thick but are composed from nanoparticles.

Chemical Solution Deposition of Functional Oxide Thin Films

Abstract: Introduction.-Solution Chemistry Simple alkoxide based precursor systems Carboxylate based precursor systems Single-source precursors Acqueos Precursor Systems Solution Synthesis Strategies.-Analytical Methods Introduction Thermal Analysis NMR Sepctroscopy EXAFS Other Methods (XRM, SEM,TEM scattering methods at nanocrystalline films) Spin-Coating Dip Coating Inkjet Printing and Other Direct Writing Methods(dip point and imprint techniques) Chemical Bath Deposition Polymer Assisted Deposition.-Processing and Crystallization Thermodynamics and Heating Processes Material Systems Dominated by Heterogeneous Nucleation Material Systems Dominated by Homogeneous Nucleation Low Temperature Processing Epitaxial Films Powder Assisted Film Fabrication UV-and E-Beam Direct Patterning of Photosensitive CSD Films Template Controlled Growth.-Functions and Applications Introduction Integrated Capacitors Base Metal Electrodes Polar Oxide Films for MEMS Applications Conducting Films and Electrodes Transparent conducting oxides Superconducting Films Porous Films for Gas Sensors Luminescent Fims.-Appendix Synthesis for Standard material Systems.

Low-temperature selective catalytic reduction of NO with NH₃ over nanoflaky MnOx on carbon nanotubes in situ prepared via a chemical bath deposition route.

Abstract: Nanoflaky MnOx on carbon nanotubes (nf-MnOx@CNTs) was in situ synthesized by a facile chemical bath deposition route for low-temperature selective catalytic reduction (SCR) of NO with NH3. This catalyst was mainly characterized by the techniques of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), N2 adsorption–desorption analysis, X-ray photoelectron spectroscopy (XPS), H2 temperature-programmed reduction (H2-TPR) and NH3 temperature-programmed desorption (NH3-TPD). The SEM, TEM, XRD results and N2 adsorption–desorption analysis indicated that the CNTs were surrounded by nanoflaky MnOx and the obtained catalyst exhibited a large surface area as well. Compared with the MnOx/CNT and MnOx/TiO2 catalysts prepared by an impregnation method, the nf-MnOx@CNTs presented better NH3-SCR activity at low temperature and a more extensive operating temperature window. The XPS results showed that a higher atomic concentration of Mn4+ and more chemisorbed oxygen species existed on the surface of CNTs for nf-MnOx@CNTs. The H2-TPR and NH3-TPD results demonstrated that the nf-MnOx@CNTs possessed stronger reducing ability, more acid sites and stronger acid strength than the other two catalysts. Based on the above mentioned favourable properties, the nf-MnOx@CNT catalyst has an excellent performance in the low-temperature SCR of NO to N2 with NH3. In addition, the nf-MnOx@CNT catalyst also presented favourable stability and H2O resistance.

Photoelectrocatalytic degradation of organic pollutants via a CdS quantum dots enhanced TiO2 nanotube array electrode under visible light irradiation

Abstract: Ultra-fine CdS quantum dots modified TiO2 nanotube arrays (TiO2-NTs) with enhanced visible-light activity are fabricated via a cathodic electro-deposition combined with ion-exchange route (CEDIE). The as-formed CdS quantum dots were highly dispersed both outside and inside the TiO2-NTs. The proposed CEDIE strategy results in the strong combination and heterojunctions between CdS and TiO2 through Cd–O bonds. The crystal phases, chemical compositions and physicochemical properties of as-obtained CdS/TiO2-NTs have been investigated based on various characterizations. Compared to CdS/TiO2-NTs prepared via a sequential chemical bath deposition method, the as-synthesized samples exhibit stronger visible-light absorption capability, higher photocurrent density, excellent stability, and greatly enhanced photoelectrocatalytic (PEC) activity toward degradation of methyl orange (MO) aqueous solutions under visible light irradiation (λ > 400 nm). Such enhanced PEC activity may be ascribed to the strong combination and heterojunctions between CdS and TiO2, favorable for visible-light response and charge separation of TiO2-NTs.

Fabrication of Ag/Ag3PO4/TiO2 heterostructure photoelectrodes for efficient decomposition of 2-chlorophenol under visible light irradiation

Abstract: TiO2 nanotube arrays were decorated with Ag/Ag3PO4 nanoparticles through a sequential chemical bath deposition and followed by partial reduction of Ag+ ions in the Ag3PO4 nanoparticles to Ag0 under UV irradiation. The structure and optical properties of the Ag/Ag3PO4/TiO2 nanotube electrode were characterized by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-Vis diffuse reflectance spectroscopy, photoluminescence (PL) spectroscopy and electrochemical techniques. The photoelectrocatalytic (PEC) activity of the composite electrode was evaluated by the decomposition of 2-chlorophenol under visible light irradiation (λ > 420 nm). Clusters of Ag/Ag3PO4 nanoparticles were successfully formed on the surface of the TiO2 nanotubes (NTs) causing no damage to the ordered structure of the nanotubes. The PL intensity of Ag/Ag3PO4/TiO2 NTs was much lower than that of TiO2 nanotubes. The p-type Ag3PO4 and Ag nanoparticles deposited on the TiO2 NTs could promote the transfer of photo-generated electrons, which inhibited the recombination of electrons and holes effectively, leading to a significant increase in the photocurrent density. Moreover, the Ag/Ag3PO4/TiO2 heterostructure photoelectrodes showed much higher PEC activity than the pure TiO2 NTs for the degradation of 2-CP aqueous solution under visible light irradiation. The enhanced PEC activity could be attributed to the visible-light photocatalytic activity of Ag3PO4 and the heterostructure between Ag3PO4 and TiO2. The electron spin resonance (ESR) spin-trap study further demonstrated that ˙OH could be generated on the Ag/Ag3PO4/TiO2 NTs under visible light irradiation.

A high-sensitivity room-temperature hydrogen gas sensor based on oblique and vertical ZnO nanorod arrays

Abstract: The high surface area to volume ratio, the networks connections of vertically and oblique nanorod arrays, and the absence of seed layer, were the key factors responsible for the high sensitivity of ZnO nanorod arrays based hydrogen sensor at room temperature. Arrays of vertical and oblique zinc oxide nanorods were grown on a c -plane sapphire substrate by microwave-assisted chemical bath deposition. Polyvinyl alcohol (PVA)–Zn(OH) 2 nanocomposites were used as a novel seed material to seed the sapphire substrate prior to the growth of the ZnO nanorods. The hydrogen sensing capabilities of the ZnO nanorod arrays, without the use of a metal catalyst, were investigated at room temperature. The rods exhibited excellent sensitivity, of 500%, in the presence of 1000 ppm of H 2 while consuming an ultralow level of power ( 2 gas. Hysteresis was noticed in the sensor for different concentrations of H 2 at different temperatures. It can be surmised that this hydrogen gas sensor has potential for use as a portable room-temperature gas sensor.

Surfactant-assisted morphological tuning of hierarchical CuO thin films for electrochemical supercapacitors

Abstract: Copper oxide (CuO) thin films are successfully synthesized using a surfactant assisted chemical bath deposition method for application in supercapacitors. The effect of organic surfactants such as Triton X-100 and polyvinyl alcohol (PVA) on structural, morphological, surface areas and electrochemical properties of CuO thin films is investigated. The films deposited using organic surfactants exhibit different surface morphologies. It is observed that the organic surfactants play important roles in modifying the morphology, surface area and pore size distribution. Electrochemical analysis confirms that the nanostructures of the electrode material play a vital role in supercapacitors. The cyclic voltammetry studies show a considerably improved high rate pseudocapacitance of CuO samples synthesized using organic surfactants. The maximum specific capacitance of 411 F g−1 at 5 mV s−1 is obtained for the CuO sample prepared using an organic surfactant (Triton X-100). Furthermore, all the CuO nanostructures exhibit high power performance, excellent rate as well as long term cycling stability. The Ragone plot ascertains better power and energy densities of CuO nanostructured samples. This is an easy and simple way to tune the morphology using surfactants which can be applied for other energy storage materials.

Conformal coating of Ni(OH)2 nanoflakes on carbon fibers by chemical bath deposition for efficient supercapacitor electrodes

Abstract: A novel supercapacitor electrode structure has been developed in which a uniform and conformal coating of nanostructured Ni(OH)2 flakes on carbon microfibers is deposited in situ by a simple chemical bath deposition process at room temperature. The microfibers conformally coated with Ni(OH)2 nanoflakes exhibit five times higher specific capacitance compared to planar (non-conformal) Ni(OH)2 nanoflake electrodes prepared by drop casting of Ni(OH)2 powder on the carbon microfibers (1416 F g−1vs. 275 F g−1). This improvement in supercapacitor performance can be ascribed to the preservation of the three-dimensional structure of the current collector, which is a fibrous carbon fabric, even after the conformal coating of Ni(OH)2 nanoflakes. The 3-D network morphology of the fibrous carbon fabric leads to more efficient electrolyte penetration into the conformal electrode, allowing the ions to have greater access to active reaction sites. Cyclic stability testing of the conformal and planar Ni(OH)2 nanoflake electrodes, respectively, reveals 34% and 62% drop in specific capacitance after 10 000 cycles. The present study demonstrates the crucial effect that electrolyte penetration plays in determining the pseudocapacitive properties of the supercapacitor electrodes.

Layer-by-layer assembly of transparent amorphous Co3O4 nanoparticles/graphene composite electrodes for sustained oxygen evolution reaction

Abstract: Amorphous Co3O4 nanoparticle/graphene composites (Co3O4/GR) were fabricated via layer-by-layer (LBL) assembly onto indium tin oxide (ITO) coated conductive glass and applied as a catalyst for efficient oxygen evolution reaction in electrolytic water splitting. A thin uniform graphene layer was deposited onto the ITO surface through electrophoretic deposition (EPD), followed by subsequent deposition of a thin layer of Co3O4 nanoparticles onto the graphene surface by chemical bath deposition (CBD) to yield a transparent Co3O4/GR bi-layer. X-ray diffraction spectroscopy (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were employed to characterise the fabricated composites. The layered Co3O4/GR composite is applied for electrocatalytic oxygen evolution reaction (OER) in 0.1 M KOH and exhibits remarkable catalytic activity with a high Faradaic efficiency (95%) and excellent long-term stability.

Fabrication and performance of polypyrrole (Ppy)/TiO2 heterojunction for room temperature operated LPG sensor

Abstract: In this paper, we report on the fabrication and performance of room temperature operated liquefied petroleum gas (LPG) sensor based on polypyrrole/TiO 2 (Ppy/TiO 2 ) heterojunction. Ppy/TiO 2 heterojunction was prepared by sequencial depositing TiO 2 film by chemical bath deposition and Ppy film by electrodeposition method. Ppy and TiO 2 films were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM), FTIR and thermo-emf techniques. The XRD study revealed amorphous and nanocrystalline natures for Ppy and TiO 2 films, respectively. The SEMs of Ppy and TiO 2 films showed cauliflower-like and densely compact morphologies respectively. Maximum gas response of 55% was observed for Ppy/TiO 2 heterojunction at 1040 ppm of LPG. Relative humidity affected the gas sensing performance of heterojunction. Good stability, fast response and recovery times indicate that Ppy/TiO 2 heterojunction is a one of the candidate for room temperature LPG detection.

Enhanced ethanol sensing performance of porous ultrathin NiO nanosheets with neck-connected networks

Abstract: Porous ultrathin NiO nanosheets have been synthesized by a simplified chemical bath deposition method with subsequent thermal decomposition of a layered precursor of nickel hydroxide (Ni(OH)2). The crystalline and morphological structures of products, which were characterized by X-ray diffraction, field-emission scanning electron microscopy and high resolution transmission electron microscopy, show that the nanopores form with a phase transition at the calcination process. The pure cubic NiO phase, with an average grain size of 4.67 nm and a thickness less than 5 nm, forms at 450 °C for 2 h in air. Moreover, the NiO nanosheets synthesized here show an enhanced response to ethanol at a low temperature of 200 °C. The unique architecture with neck-connected networks and a high specific area was applied to explain the enhancement of the ethanol sensing performance. Furthermore, the sensor exhibits an excellent selectivity to ethanol against methanol, acetone, toluene, hydrogen, and methane by a cross-response test.

CdS/CdSe Core–Shell Nanorod Arrays: Energy Level Alignment and Enhanced Photoelectrochemical Performance

Abstract: Novel CdS/CdSe core–shell nanorod arrays were fabricated by a chemical bath deposition of CdSe on hydrothermally synthesized CdS nanorods. The CdS rods were hexagonal phase faced and the top of the rod was subulate. After the chemical bath deposition approach, CdS nanorod arrays were encapsulated by a uniform CdSe layer resulting enhanced absorbance and extended absorption edges of the films. A tandem structure of the energy bands of CdS/CdSe was also formed as a result of the Fermi level alignment, which is a benefit to the efficient separation of photogenerated charges. CdS/CdSe core–shell arrays gave a maximum photocurrent of 5.3 mA/cm2, which was 4 and 11 times as large as bare CdS and CdSe, respectively.

Significantly Enhanced Open Circuit Voltage and Fill Factor of Quantum Dot Sensitized Solar Cells by Linker Seeding Chemical Bath Deposition

Abstract: We have significantly improved open circuit voltage and fill factor with a Pt counter electrode of quasi-solid state quantum dot sensitized solar cells (QDSSCs) by achieving compact coverage of QDs on a TiO2 matrix through a linker seeding chemical bath deposition process, leading to 4.23% power conversion efficiency, nearly two times that with conventionally deposited control photoanode. The distinguishing characteristic of our linker seeding synthesis is that it does not rely on surface adsorption of precursor ions directly on TiO2 (TiO2∼Cdx) but rather nucleates special ionic seeds on a compact linker layer (TiO2-COORS-Cdx), thereby resulting in a full and even coverage of QDs on the TiO2 surface in large area. We have shown that the compact coverage not only helps to suppress recombination from electrolyte but also gives rise to better charge transport through the QD layer. This linker seeding chemical bath deposition method is general and expected to reinforce the hope of quasi-solid state QDSSCs as ...

Characteristics of nanostructured CdO/Si heterojunction photodetector synthesized by CBD

Abstract: In the present work, CdO/Si heterojunction detectors were fabricated by depositing nanostructured CdO film on single crystal silicon wafer by chemical bath deposition (CBD) technique. Films deposition was carried out at different temperatures. To obtain good film stoichiometry heating of films in static air at temperature of 400 °C for 90 min was carried out. The structural properties of CdO films was characterized by X-ray diffraction and atomic force microscope (AFM), these investigations showed that the deposited CdO films have cubic structure. The surface morphology investigation revealed that CdO film is almost homogeneous and consisted of the nanowires with diameter less than 100 nm at temperature of solution 40 °C.The band gap of the films changes from 2.4 to 2.5 eV with increasing preparation temperature. The current–voltage characteristics of photodiodes under dark exhibit good rectification behavior and that ideality factor of heterojunction was found to be in the range of 1.56–3.69 depending on solution temperature. The capacitance–voltage characteristic shows a typical abrupt heterojunction and the built-in-potential was determined. CdO/Si detector has good spectral responsivity in visible and NIR and the maximum responsivity was 0.56 A/W. Rise time of the photodetectors was strongly dependent on solution temperature and the shortest rise time obtained was 45 ns at 2 V.