Liquid Phase Deposition Technique Research Articles

Metal-semiconductor-metal UVA photodetector based on TiO2 thin films synthesized via liquid phase deposition method

In this work, titanium dioxide (TiO2) thin film-based metal-semiconductor–metal (MSM) ultraviolet (UV) photodetectors (PDs) were fabricated on glass substrates via liquid phase deposition (LPD) technique at various deposition time in the range of 3–6 h. Varying deposition time significantly impacted the physical properties of the films. Increasing the deposition time revealed a mixture of clusters and hexagonal-like structures in film’s morphology. The energy band gap of the TiO2 films decreased from 3.30 to 3.09 eV upon increasing the deposition time. Photodetection characteristics were examined by exposing the MSM UV PD to 390 nm UV light with an intensity of 1.6 mW cm−2 and a bias voltage of 5 V. The fabricated PDs implied characteristics of I-V ohmic contact. The optimum photodetection characteristics were achieved for TiO2 film deposited at 6 h which exhibited 36.9 μA maximum photocurrent, 20080.3% sensitivity, 201.80 gain, 225 mA W−1 responsivity, 81.07% external quantum efficiency, 0.276 s response time, and 0.274 s recovery time. The photoelectric properties of the films were strongly affected by the increased grain size and improved crystallinity of the films due to the prolonged deposition time. The optimum film demonstrated its potential to be a promising candidate for UV PD applications.

Optimizations of Liquid Phase Deposition Processes for Enhanced Photoelectrocatalytic Activities of Tungsten Oxide Thin Films.

This study focuses on the preparation of tungsten oxide (WO3) as the photoanode for water oxidations by the liquid phase deposition (LPD) technique and its optimizations to improve the photoelectrochemical performance. The alternative precursor large stock solution process was achieved to simplify the LPD process for WO3 thin film preparation. The effect of boric acid in the precursor solutions on the physicochemical properties of the deposited WO3 thin films was investigated. As a result, we found that the optimized concentration of boric acid realized the highest photoelectrochemical performance. Through the optimizations of reaction conditions and surface analyses, we concluded that the preparations of a semiconductor film via the LPD technique had the potential to obtain high-performance photoelectrocatalytic applications.

Ultra-stable Cu-based catalyst for dimethyl oxalate hydrogenation to ethylene glycol

Dimethyl oxalate (DMO) hydrogenation is a crucial step in the coal to ethylene glycol (CTEG) process. Herein, Cu catalyst supported on fibrous mesoporous silica (Cu/FMS) was synthesized via liquid phase deposition technique and applied for the DMO hydrogenation to EG. The catalyst exhibited a remarkable EG selectivity of 96.95% and maintained its activity without deactivation for 1000 h. Fibers of FMS support and liquid phase deposition technology cooperated to give high dispersion of Cu species in the Cu/FMS catalyst, resulting in a high Cu surface area. The formation of Si—O—Cu during catalyst preparation process increased the Cu+/(Cu0 + Cu+) ratio and enhanced the thermal and valence stability of Cu species. The high Cu+ surface area and Cu stability (thermal and valence stability) of the Cu/FMS catalyst were key factors for achieving superior EG selectivity and ultra-high stability.

Improvement of the performance of dye-sensitized solar cells employing NickelPalladium alloy-reduced graphene oxide counter electrode: Influence of palladium content

In this work, NickelPalladium-reduced graphene oxide (NiPd-rGO) films have been prepared via liquid phase deposition technique and used as free-platinum (Pt) counter electrode for dye-sensitized solar cell (DSSC). The effect of Pd content in term of various Ni:Pd ratios on the properties such as structure, optical transmission, surface morphology and elemental compositions have been studied. The morphology of NiPd-rGO sample is in the form of crumpled vertical folds in layers and white strips. The influence of Pd content on photovoltaic parameters of the device has also been investigated. The performance parameters were significantly influenced by the Pd content. The device using NiPd-rGO counter electrode prepared at Ni:Pd ratio of 20:2 demonstrated the highest PCE of 3.09%. This is due to the device owns the highest charge recombination resistance (Rrec) and shortest carrier transport time (τ). The efficiency has been improved at the optimum content of Pd. The finding from this work implies that NiPd-rGO is able to substitute Pt as counter electrode in DSSC due to its efficiency is comparable to that of the device employing Pt counter electrode.

Low-Temperature Synthesis of Cu-Doped Anatase TiO2 Nanostructures via Liquid Phase Deposition Method for Enhanced Photocatalysis.

Titanium dioxide (TiO2) photocatalysis can harness the energy from sunlight, providing a solution to many green- and energy-related problems. In this study, we aimed to produce Cu doped TiO2 (Cu-TiO2) structures at a low temperature (~70 °C) under atmospheric pressure based on liquid phase deposition. The products prepared with Cu nitrate exhibited anatase-phase TiO2 with the presence of Cu, and the particles showed a waxberry-like structure. Changing the Cu nitrate concentration allowed control of the atomic concentration; we confirmed ~1.3 atm.% of Cu ions in the product when we applied 10 mM in the precursor solution. By doping Cu, the light absorption edge shifted to 440 nm (~2.9 eV), and we proved the photocatalytic reaction through action spectral measurement. We observed the decomposition of acetaldehyde into CO2 on Cu-TiO2 photocatalysts, which produced optimized improvements in photocatalytic activity at Cu dopant levels between 0.2 and 0.4 atm.%. This study demonstrates that the liquid phase deposition technique can be used for doping metallic ions into TiO2, which shows promise for preparing novel and unique nanomaterials as visible light photocatalysts.

One-step preparation of TiO2 anti-reflection coating and cover layer by liquid phase deposition for monocrystalline Si PERC solar cell

This study proposed a one-step liquid phase deposition (LPD) technique to fabricate a front-side anti-reflective coating (ARC) and rear-side cover layer for a passivated emitter and rear cell solar cell. The production process involves the deposition of TiO 2 thin film by using a (NH 4 ) 2 TiF 6 and H 3 BO 3 mixture in a liquid phase filter and cycling deposition system, in which H 3 BO 3 concentration influences the TiO 2 thin film deposition rate, the Ti x Si 1-x O y interfacial layer thickness, and thin film quality. The proposed technique is a one-step, uniform, and large-scale double-sided coating batch process viable for non-vacuum environments, thus enabling a simple manufacturing process and requiring low equipment costs. The fabricated LPD-TiO 2 thin film demonstrated ASTM 5B adhesion and 3.3% uniformity. The technique involves the use of a 0.2 M (NH 4 ) 2 TiF 6 and 0.5 M H 3 BO 3 mixture for deposition under 50 °C to deposit a 68-nm-thick LPD-TiO 2 thin film on pyramid Si wafer. The average reflectance and transmittance of the thin film at 400–800 nm wavelength was 2.7% and 96.5%, respectively. Passivated emitter and rear contact solar cells prepared using the proposed LPD-TiO 2 coating technique demonstrated the following outstanding properties: 9.8 A short-circuit current, 0.68 V open circuit voltage, 81.0% fill factor, and 21.3% photoelectric conversion efficiency (η). The proposed technique demonstrates high potential for use in the low-cost manufacturing of silicon solar cells. • Passivated emitter and rear contact (PERC) solar cells are fabricated. • Front-side anti-reflective and back-side cover layers are prepared in one step. • Low cost and batch-type of TiO 2 films are made by liquid phase deposition (LPD). • PERC solar cell with the LPD functional films shows the better characteristics. • LPD-TiO 2 functional films are favorable for high performance PERC solar cells.

Liquid-phase deposition of Al2O3 coating on quartz fiber for enhanced strength at elevated temperature

ABSTRACT In the manuscript, the liquid-phase deposition technique was used to successfully deposit an Al2O3 ceramic coating on the quartz fiber. The thickness of the coating was not uniform. The thickest part of the coating can reach to 1159 nm. The main coating formed is Al2O3, but there are still hydrous Al(OH)3. With the extension of the deposition time, the micro-morphology of the coating changed from nano-scale clusters to dense flakes. The coating had an amorphous structure. In this case, the coating effectively improved the mechanical properties of the quartz fiber at high temperatures, and the breaking load of the fiber increased with the extension of the deposition time. After high temperature annealing, the breaking load of the coated fiber deposited for 6 h was 126.1 N, compared to 50.3 N of the blank fiber. The protection mechanism of Al2O3 coating was studied from the aspect of microstructure. By observing the surface morphologies of blank fiber and coated fiber after high temperature annealing. It was found that the presence of the coating hindered the damage of the fiber surface by high temperature, and the defects on the fiber surface were reduced, so the mechanical properties were effectively improved.

Morphological Analysis of Ag Doped on TiO2/Ti Prepared via Anodizing and Thermal Oxidation Methods

In this work, we present the morphology analysis of TiO2/Ti prepared via anodizing and thermal oxidation (TO) methods and doped by Ag-TiO2 sol-gel nanocomposites through liquid phase deposition (LPD) technique. The comparative morphology of both semiconductors has been observed to inform the catalysis preparation for better morphology structures to the photocatalytic performance. Based on these results, we report that the TiO2/Ti prepared via anodizing method exhibits TiO2 nanotubes arrays (TNTAs) formed like honeycomb structures, while the TiO2/Ti TO (TTO) has diverse size structures. The neat arrangement of TNTAs has a larger surface area and pore volume than TTO structures, which can expose more adsorption and reaction sites, resulting in higher catalytic activity. Uniquely, both semiconductors, after coated by Ag-TiO2 sol-gel, show lamellar sediments covering the surface of TNTAs and TTO. We believe that the anodizing method is a good ability for photocatalysis compared with TTO in terms of small surface area and nanosize structures.

Comparison of the Physicochemical Properties of Carboxylic and Phosphonic Acid Self-Assembled Monolayers Created on a Ti-6Al-4V Substrate.

This study compared the tribological properties in nano- and millinewton load ranges of Ti‑6Al-4V surfaces that were modified using self-assembled monolayers (SAMs) of carboxylic and phosphonic acids. The effectiveness of the creation of SAMs with the use of the liquid phase deposition (LPD) technique was monitored by the contact angle measurement, the surface free energy (SFE) calculation, X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared spectroscopy (FTIR) measurements. The obtained results indicated that more stable and well-ordered layers, which were characterized by the lowest values of the coefficient of friction, adhesion, and wear rate, were obtained using phosphonic acid as a surface modifier. Based on the obtained results, it was found that the Ti-6Al-4V alloy modified by phosphonic acid would be the most advantageous for practical applications, especially in micro- and nanoelectromechanical systems (MEMS/NEMS).

Influence of annealing temperature of ZnS-coated TiO2 films on the performance of dye-sensitized solar cells

This work deals with ZnS-coated TiO2 films prepared via liquid phase deposition and immersion techniques and then applied as photoanode of dye-sensitized solar cells. The samples underwent annealing treatment at various annealing temperatures. The morphology of TiO2 is nanograss and covered by agglomerate and hexagonal ZnS layer. The anatase crystallite size, absorption peak wavelength and optical reflectance increase with annealing temperature. However, the energy gap decreases with the temperature. The device utilizing the sample annealed at 400 °C performed the highest η of 0.24 % due to this device owns the lowest leak current and the longest carrier lifetime.

Crack-free TiO2 films prepared by adjusting processing parameters via liquid phase deposition technique

TiO2 thin films with controllable morphology and grain size were prepared via a liquid phase deposition (LPD) technique. The effects of the processing parameters including the (NH4)2TiF6 concentration, solution pH, and (NH4)2TiF6:H3BO3 molar ratio on the grain size and morphology of the films were investigated. The prepared samples were characterized by X-ray diffraction, scanning electron microscopy, and ultraviolet–visible spectroscopy. The results showed that the deposition parameters significantly affected the growth and nucleation velocities of the crystalline grains, which resulted in the formation of TiO2 films with different morphologies and grain sizes. The capillary stress among the grains of the film, which resulted in the cracking of the film, depended on the size of the grains. Thus, the cracking of the LPD-derived TiO2 films could be mitigated by adjusting the deposition parameters.

Deposition of Conformal Catalyst Coatings on Porous Electrodes Using a Layer-By-Layer Surface Sol-Gel Process

The state-of-the-art cathode of solid oxide fuel cells suffers from accelerated degradation and slow reaction kinetics for the oxygen reduction reaction (ORR). Surface modification of the cathode has been widely investigated and shown to greatly improve catalytic activity and prevent the formation of insulating phases. However, there is a need to improve the quality of the surface modification coatings while reducing the cost. In this presentation, we report a novel surface modification technique, coined layer-by-layer surface sol-gel (LbL SSG), for deposition of BaO and Pr2O3 on a porous La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) cathode, greatly increasing the catalytic activity for ORR and tolerance against contaminants. This low-cost, liquid phase deposition technique produces conformal coatings with precise thickness control by utilizing alternating self-limiting reactions between chemisorbed metal alkoxides and water on hydroxyl-rich surfaces. The availability of many different metal alkoxide precursors previously proved in traditional sol-gel processes, capability to deposit at room temperature, and lack of expensive vacuum equipment make this technique extremely promising over other conformal deposition techniques such as atomic layer deposition. LbL SSG is shown to produce much more conformal coatings throughout the entire porous cathode and further reduce degradation over similar coatings produced via solution infiltration. Electrochemical impedance spectroscopy analysis shows a great reduction in polarization resistance of symmetrical cells with electrodes modified by catalyst coatings. Utilizing the precise thickness control of the layer by layer process via deposition cycle count, the optimum thickness is determined to be about 8 nm (derived from 30 cycles). Thinner films are shown to be instable, breaking down and degrading over the first 30 hours, while thicker films increase the polarization resistance due to the lower ionic conductivity of the catalyst coatings. The process also demonstrates excellent scalability and versatility by coating larger cathodes (one inch in diameter) and depositing various oxides using different metal alkoxide precursors. Figure 1. SEM images of bare and coated porous electrodes showing the conformal BaO film deposited via LbL SSG. The polarization resistance versus time for various deposition cycle counts showing greatly improved stability for coated cells. Figure 1

Impact of Perfluoro and Alkylphosphonic Self-Assembled Monolayers on Tribological and Antimicrobial Properties of Ti-DLC Coatings.

The diamond-like carbon (DLC) coatings containing 1.6%, 5.3% and 9.4 at.% of Ti deposited by the radio frequency plasma enhanced chemical vapor deposition (RF PECVD) method on the silicon substrate were modified by n-decylphosphonic acid (DP) and 1H, 1H, 2H and 2H-perfluorodecylphosphonic acid (PFDP). The presence of perfluoro and alkylphosphonic self-assembled monolayers prepared by the liquid phase deposition (LPD) technique was confirmed by Fourier transform infrared spectroscopy (FTIR). It was shown that DP and PFDP monolayers on the surface of titanium incorporated diamond-like carbon (Ti-DLC) coatings had a huge influence on their wettability, friction properties, stability under phosphate- and tris-buffered saline solutions and on antimicrobial activity. It was also found that the dispersive component of surface free energy (SFE) had a significant influence on the value of the friction coefficient and the percentage value of the growth inhibition of bacteria. The dispersive component of SFE caused a reduction in the growth of bacteria and the friction coefficient in mili- and nano-newton load range. Additionally, both self-assembled monolayers prepared on Ti-DLC coatings strongly reduced bacterial activity by up to 95% compared to the control sample.

Effect of Silver Concentration towards Formationof AgPt Nanofernfilms as SERS Substrates

This paper reports the preparation of silver-platinum (AgPt) nanofernson ITO surface using liquid phase deposition technique with various concentrations of silver nitrate in synthesis solution. The different morphologies of AgPt thin films were grown on the surface using 0.1 mM to 0.8 mM of silver concentration. This silver effect on the growth of AgPt on the surfacewas studied using FESEM and UV-Vis characterization. It was found that the optimum silver concentration in synthesis solution supplied the appropriate Ag+ion to grow the nanofernsstructure on the surface. AgPt films were then carried out to sense 1.0 M of creatinine concentration to learn their performance as surface-enhanced Raman scattering (SERS) substrate. The sensitivity of SERS substrate towards creatinine detection was studied by observing the change of Raman spectra of the creatinine on ITO surface and creatinine on AgPt films surface.

Liquid Phase Deposition of Nickel-Doped ZnO Film with Enhanced Visible Light Photoelectrocatalytic Activity

Metal element doping is an effective way to tune visible light absorption ability and improve the charge carrier separation efficiency of a semiconductor. Herein, we studied the visible light photoelectrocatalytic property of ZnO doped with nickel (Ni-ZnO). The Ni-ZnO film was prepared by using a liquid phase deposition technique. Scanning electron microscopy analysis and X-ray diffraction measurement indicated that the as-prepared Ni-ZnO film comprised of many prismatic wurtzite nanoparticles. X-ray photoelectron spectroscopy analysis indicated that Ni2+ entered the ZnO lattice. Cyclic voltammetric analysis confirmed that Ni2+ in the ZnO lattice was electroactive and a pair of Ni2+/Ni3+ redox waves were observed. UV-visible diffuse reflectance and photoluminescence spectra showed that doping of Ni in ZnO improved the visible light utilization and separation of photogenerated charge carriers. The Ni-ZnO film subsequently exhibited a higher photocurrent than the ZnO film. The photoelectrocatalytic activity of the Ni-ZnO film was evaluated by the degradation of tetracycline under visible light illumination. The degradation rate constant for tetracycline on Ni-ZnO film was found to be 1.65 times higher than that of ZnO film.

Optimum growth time in AgPt nanofern preparation for enhancement of surface-enhanced Raman scattering intensity44Report presented at 9th International Workshop on Advanced Materials Science and Nanotechnology (IWAMSN2018), 7–11 November 2018, Ninh Binh City, Vietnam.

Surface-enhanced Raman scattering (SERS) is a phenomenon where the signal of the Raman spectrum of an analyte increased due to a plasmonic effect of metal nanoparticles. This phenomenon is potentially be implemented in biosensor application to detect the presence of a molecule in blood and urine. This paper reports a study on bimetallic thin film of argentum-platinum (AgPt) nanoferns as a SERS substrate for detection of creatinine. Nanofern-shaped AgPt was prepared directly on ITO surface using liquid phase deposition technique. The growth time of the AgPt preparation was varied from 5 to 60 min to study the effect of growth time towards deposition of AgPt nanofern on the surface. This sensitivity of SERS measurement was studied by comparing the Raman spectra of creatinine on ITO surface and creatinine on AgPt surface. We observed that the sensitivity of the spectroscopy system towards creatinine molecule detection is dependent on the morphology structures of AgPt substrate.

Hydrothermal growth of a composite TiO2 hollow spheres/TiO2 nanorods powder and its application in high performance dye-sensitized solar cells

In this research a composite powder including TiO2 hollow spheres (HSs) and TiO2 nanorods (NRs) was prepared and applied as the light scattering layer in the photoanode of the dye-sensitized solar cells (DSCs). TiO2 HSs with external diameters around 450nm were synthesized using hydrothermally grown carbon spheres as the template and through a liquid phase deposition (LPD) technique. TiO2 NRs were also prepared by additional hydrothermal growth in the presence of sub-micronic HSs to form a composite mixture. The two different scattering structures i.e. the TiO2 HSs and NRs were well-mixed in the final composite powder. Besides, the number ratio of TiO2 NRs/HSs was calculated as 1.0 from the SEM images. TiO2 nanocrystals (NCs) were also grown by a hydrothermal method with dominant particle size of 25nm. Three kinds of photoelectrodes composed of TiO2 NCs, TiO2 HSs and TiO2 NRs were fabricated and applied in DSCs. The first photoanode was made of a single nanocrystalline TiO2 layer with about 8μm thickness. The next two other kinds were composed of a TiO2 NCs layer covered by a TiO2 HSs or composite TiO2 HSs/NRs scattering layers. The photovoltaic characteristics of the corresponding DSCs were investigated and explained. According to the results, the energy conversion efficiency of the DSC with composite TiO2 HSs/NRs scattering layer was measured about 9.6%. This efficiency was increased about 35% and 6% compared to those of the cells with light scattering-free and TiO2 NCs/TiO2 HSs photoelectrodes. The reason was attributed to the increased dye adsorption and light scattering of the pioneer cell.

Influence of rGO Cladding in Improving the Sensitivity and Selectivity of ZnO Nanoflowers-Based Alcohol Sensor

Development of ultra-sensitive and selective 2-propanol sensor employing hybrid structure of reduced graphene oxide (rGO) and 3-D ZnO nanoflowers (NFs) is reported in this paper. The 3-D ZnO NFs were synthesized on n-Si wafer, using liquid phase deposition technique, while a dip coating technique was adopted for the deposition of rGO, in the form of discrete claddings, on the ZnO NFs layer. The detailed morphological (field emission scanning electron microscopy) and structural (Raman and XPS) characterizations were carried out to compare the structural and morphological properties of pristine ZnO NFs and rGO-ZnO NFs hybrid structure. The sensing properties of ZnO NFs and rGO-ZnO NFs devices were investigated toward different alcohol vapors (2-propanol, ethanol, and methanol) in the concentration range of 0.5–700 ppm at 100 °C–275 °C. The rGO-ZnO NFs 3-D hybrid device offered ultra-high sensitivity (645% response magnitude at 700 ppm) toward 2-propanol at ~160 °C. In addition, the same sensor also offered excellent selectivity against interfering neighbors (i.e., ethanol, methanol, acetone, and benzene). The underlying mechanism for such experimental findings has been discussed with the properties of rGO–ZnO hybrid junction and respective band bending in air and target species.

Preparation of BiVO4/ZnO composite film with enhanced visible-light photoelectrocatalytic activity

In this work, a BiVO4/ZnO composite film was fabricated via a combination of the liquid phase deposition technique and the successive ionic layer adsorption and reaction (SILAR) process. Scanning electron microscopy and X-ray diffraction observations revealed that wurtzite ZnO and monoclinic BiVO4 were successfully formed in the composite film. UV–visible spectra indicated that the formation of the BiVO4/ZnO film resulted in improved absorption and an obvious redshift. Photoluminescence analysis revealed that the BiVO4/ZnO film exhibited superior charge-transfer properties to pure ZnO and BiVO4 films. The fabricated BiVO4/ZnO film was applied to the photoelectrocatalytic (PEC) degradation of tetracycline. The BiVO4/ZnO film showed higher visible-light PEC activity than did pure ZnO and BiVO4 films. Moreover, the tetracycline degradation efficiency achieved by the PEC process over the BiVO4/ZnO film was higher than those achieved using the photolysis, electrochemical oxidation, and photocatalysis processes. The BiVO4/ZnO film was able to effectively remove more than 90% tetracycline when the initial concentration of tetracycline was lower than 10mg/L.

Fe-doped TiO2/SiO2 nanofibrous membranes with surface molecular imprinted modification for selective photodegradation of 4-nitrophenol

In this study, Fe-doped TiO2/SiO2 (Fe@TS) nanofibrous membranes with molecular imprinted modification, were fabricated by a combination of sol-gel process, electrospinning, calcination and liquid phase deposition techniques. The precursor sol was prepared from one-pot condensation of poly(vinylpyrrolidone), ferric chloride hexahydrate, tetraethyl orthosilicate and titanium n-butoxide in the mixture solvents of N,N-dimethylformamide and ethyl alcohol. Fibrous membrane wasthen fabricated by electrospinning, followed by calcination to form the Fe@TS composite. The physicochemical properties of Fe@TS were characterized. Thereafter, 4-nitrophenol (4NP) was used as the template to deposit onto nanofibrous Fe@TS membranes, with a thin layer of molecular imprinted polymer in liquid phase. The photodegradation capabilities of 4NP and methyl orange wereexamined in both single and binary systems. The results demonstrated that molecular imprinted Fe@TS membranes exhibited excellent selectivity for photodegradation of 4NP.