Liquid Phase Deposition Process Research Articles

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.

Fabrication of Amorphous Silicon-Carbon Hybrid Films Using Single-Source Precursors.

The aim of this study was the preparation of different amorphous silicon-carbon hybrid thin-layer materials according to the liquid phase deposition (LPD) process using single-source precursors. In our study, 2-methyl-2-silyltrisilane (methylisotetrasilane; 2), 1,1,1-trimethyl-2,2-disilyltrisilane (trimethylsilylisotetrasilane; 3), 2-phenyl-2-silyltrisilane (phenylisotetrasilane; 4), and 1,1,2,2,4,4,5,5-octamethyl-3,3,6,6-tetrasilylcyclohexasilane (cyclohexasilane; 5) were utilized as precursor materials and compared with the parent compound 2,2-disilyltrisilane (neopentasilane; 1). Compounds 2-5 were successfully oligomerized at λ = 365 nm with catalytic amounts of the neopentasilane oligomer (NPO). These oligomeric mixtures (NPO and 6-9) were used for the preparation of thin-layer materials. Optimum solution and spin coating conditions were investigated, and amorphous silicon-carbon films were obtained. All thin-layer materials were characterized via UV/vis spectroscopy, light microscopy, spectroscopic ellipsometry, XPS, SEM, and SEM/EDX. Our results show that the carbon content and especially the bandgap can be easily tuned using these single-source precursors via LPD.

Fe-doped BiVO4 photocatalyst assisting SnO2 nanorod arrays for efficient visible-light-driven degradation of Basic Red 46

BackgroundDesigning and constructing heterogeneous structures is an effective approach employed to improve photocatalytic performance. This study aimed to use Fe-doped BiVO4/SnO2 nanocomposites for photocatalytic degradation of Basic Red 46 (BR46) dye under visible-light irradiation. MethodsBiVO4 nanoparticles doped with varying amounts of Fe were synthesized using the sol-gel method and interspersed on SnO2 nanorods with an average diameter of about 100 nm fabricated using the liquid phase deposition (LPD) process. FE-SEM, EDX, XRD, FT-IR, XPS, BET, DRS, and PL analysis were used to characterize the morphology and structure of the samples. Significant findingsThe 1.5 wt% Fe-doped BiVO4/SnO2 nanocomposite exhibited the highest visible-light photoactivity with excellent stability, resulting in complete degradation of BR46 within 90 min of irradiation. The boost photocatalytic activity of Fe-doped BiVO4/SnO2 nanocomposite can be attributed to the enhanced separation of photo-generated carriers derived from synergistic effects by the BiVO4/SnO2 heterostructure, Fe doping in BiVO4 lattice, and partly the extended light absorption ability. These findings show that designing a heterogeneous BiVO4/SnO2 structure with Fe-doping can be a promising strategy for the application in constructing efficient and stable photocatalysts for the degradation of dyes from industrial wastewater pollutions.

Applications of Ni-Al Layered Double Hydroxide as Oxygen Evolution Reaction Catalysts Synthesized by Liquid Phase Deposition Process

Applications of Ni-Al Layered Double Hydroxide as Oxygen Evolution Reaction Catalysts Synthesized by Liquid Phase Deposition Process

Inorganic Chemistry in Dalian University of Technology: Fundamental Science and Solution for Renewable Energy, Environment, Health, and Materials

Inorganic Chemistry in Dalian University of Technology: Fundamental Science and Solution for Renewable Energy, Environment, Health, and Materials

Silicone Nanofilament Coatings as Flexible Catalyst Supports for a Knoevenagel Condensation Reaction in Batch and Flow Systems.

In this work, silicone nanofilament (SNF) coatings were prepared via a droplet-assisted growth and shaping (DAGS) approach, where the preparation of the coatings is allowed under ambient conditions. The application of SNF coatings as catalyst supports for amino moieties from (3-aminopropyl)triethoxysilane (APTES) was investigated. With the optimized coating conditions identified, the Brunauer-Emmett-Teller surface areas of a bare glass filter substrate and bare glass beads after the coating have increased by 5-fold and 16-fold, respectively. The SNF-coated filters were readily functionalized with amino groups via a liquid-phase deposition process, and their catalytic activities for a Knoevenagel reaction were evaluated using a batch reactor and a packed bed reactor. In both reactors, the as-prepared filters demonstrated superior catalytic performance over the functionalized filters without SNF coatings. Notably, the unique flexibility of the SNF coatings allowed the facile preparation of a packed bed reactor and a scalable catalytic system. It is expected that the packed bed system established in this study will support the development and the use of various SNF-supported organocatalysts and catalytic materials.

Ni-nanoparticle-modified Cu nanowires for enhanced electrocatalytic nitrate removal

Copper (Cu)-based materials have been extensively studied for nitrate (NO3 −) removal as an inexpensive and abundant electrocatalyst for water purification through the nitrate reduction reaction (NO3RR). However, it typically suffers from nitrite (NO2 −) accumulation due to high selectivity toward nitrite formation. To address this issue, the authors herein report a strategy of modifying copper nanowires with nickel (Ni) nanoparticles to improve the NO3RR performance. The nickel nanoparticles both facilitate electron transfer from nickel to copper and enhance the conversion of nitrite, thereby improving the overall removal of nitrate with a minimal yield of nitrite. Through a facile liquid-phase deposition process, the loading amount of nickel nanoparticles can be easily tailored by simply changing the concentration of precursors, and the best copper/nickel molar ratio for nitrate removal performance is 20. At this ratio, the material simultaneously delivers a high nitrate removal rate of 92.2% and low nitrite selectivity of only 2.2% at −0.9 V against the reversible hydrogen electrode, accompanied with superior stability for a continuous NO3RR. This study thus offers an efficient, stable and low-cost copper–nickel bimetallic catalyst for NO3RR.

Black Silicon Solar Cell Passivated by Sio2 Thin Film Using Liquid Phase Deposition Process

Black Silicon Solar Cell Passivated by Sio2 Thin Film Using Liquid Phase Deposition Process

Enhanced dielectric properties and energy storage density of Mg-doped SrTiO3 nanowire films

To improve dielectric properties of SrTiO3-based materials and meet their development requirements in various scientific and technology fields, Mg-doped SrTiO3 nanowire films (with 0, 0.5, 1, 1.5 and 2mol% Mg) were fabricated by liquid phase deposition (LPD) process. The results showed that structural and dielectric properties of the prepared samples can be effectively affected by Mg doping. Thus, the SrTiO3 nanowire film doped with 1.5mol% Mg has high dielectric constant of 594.2, a low dielectric loss of 0.0167 and the highest breakdown strength of 463.1 kV/cm at 1 kHz, therefore resulting in a high energy density of 5.64 J/cm3, which is about 3.9 times higher than that of the pure SrTiO3 nanowire films (1.44 J/cm3). Based on findings in this research, it was shown that improvement of dielectric properties of SrTiO3 ceramic systems can be obtained with formation of one-dimensional structures and selecting reasonable Mg content for doping.

Facile Preparation of N/F Co-Doped Mesoporous TiO2 vis-Photocatalyst based on a Bi-Functional Template

Developing nonmetal-doped mesoporous TiO2 is highly attractive for preparing semiconductor visible photocatalyst with high activities. Here, we prepare N/F co-doped mesoporous TiO2 with high vis-photocatalytic activities by a simple liquid phase deposition process followed by annealing in air using C[Formula: see text]TAB as a bi-functional template (forming mesoporous and providing dopants). N2 adsorption isotherms, low-angle X-ray diffraction (XRD) and transmission electron microscopy (TEM) indicate the formation of wormhole-like mesoporous structure. Wide-angle XRD and high-resolution TEM demonstrate the presence of anatase TiO2 mesopore wall. XPS analyses reveal that N is doped into TiO2 lattice in the forms of substitutional and interstitial N species, and that F is doped into the TiO2 lattice in the form of interstitial F. The mesopore-forming and doping mechanisms are thoroughly discussed based on the bi-function of C[Formula: see text]TAB template. Mesoporous structure results in a high BET surface area of TiO2. High-concentration nitrogen species in anatase lattice and mesoporous structure remarkably increase the visible absorption of TiO2. As a result, the reaction rate constant of MB degradation catalyzed by N/F co-doped mesoporous TiO2 photocatalysts is about 7 times that by P25.

Photocatalytic degradation evaluation of N-Fe codoped aligned TiO2 nanorods based on the effect of annealing temperature

In this paper, a comparative study on the photocatalytic degradation of the Rhodamine B (RhB) dye as a model compound using N-Fe codoped TiO2 nanorods under UV and visible-light (λ ≥420 nm) irradiations has been performed. TiO2 photocatalysts were fabricated as aligned nanorod arrays by liquid-phase deposition process, annealed at different temperatures from 400 to 800 °C. The effects of annealing temperature on the phase structure, crystallinity, BET surface area, and resulting photocatalytic activity of N-Fe codoped TiO2 nanorods were also investigated. The degradation studies confirmed that the nanorods annealed at 600 °C composed of both anatase (79%) and rutile phases (21%) and offered the highest activity and stability among the series of nanorods, as it degraded 94.8% and 87.2% RhB in 120 min irradiation under UV and visible-light, respectively. Above 600 °C, the photocatalytic performance of nanorods decreased owning to a phase change, decreased surface area and bandgap, and growth of TiO2 crystallites induced by the annealing temperature. It is hoped that this work could provide precious information on the design of ID catalyst materials with more superior photodegradation properties especially under visible-light for the further industrial applications.

Facile design of F-doped TiO2/g-C3N4 heterojunction for enhanced visible-light photocatalytic activity

To maximize the photocatalytic performance of practical energy devices, F-doped TiO2 particles are anchored on g-C3N4 nanosheets through the liquid phase deposition (LPD) and calcination process. The photocatalytic activity of F-doped TiO2/g-C3N4 (T-CN) composite is evaluated by the degradation of Rhodamine B (RhB) solution under visible-light illumination. The T-CN-300 sample (contain 300 mg g-C3N4) degrades 97% RhB after its illumination for 20 min. The quantum yield of the T-CN-300 sample is about three times higher than that of the pristine F-TiO2 and g-C3N4 samples. Moreover, the trapping experiments of the T-CN-300 sample indicate that the superoxide radical (·O2−) is the main active species upon the photocatalytic process. The spin-trapping experiments confirm that the T-CN-300 sample can produce more·O2− species than the other samples. The reduced interfacial charge transfer resistance of the T-CN-300 sample significantly enhances the photocurrent. The results reveal that the unique heterojunction of F-TiO2 and g-C3N4 can effectively separate the photogenerated electron–hole pairs, accelerate the photocatalytic reaction, and increase the ·O2− species in the photodegradation system.

Dynamic liquid phase deposition of doped nanostructured PANI tube sensor for trace-level NH3 gas detection

We proposed a polyaniline-camphorsulfonic acid/titanium dioxide (PANI-CSA/TiO2) coated glass capillary tube sensor structure in this work. The PANI-CSA/TiO2 sensitive material was grown on the inner wall of silica glass capillary tube. A dynamic liquid phase deposition (DLPD) process was developed to fabricate the tube sensor samples. The optimum processing parameters, microstructures, morphology and gas detective performances of the PANI-CSA/TiO2 tube sensors were investigated. PANI-CSA/TiO2 capillary tube sensor samples (core size 1 mm, length 7 cm) with better properties were obtained at an optimum liquid flow rate of 0.62 mL min−1. The tube sensor shows response time of 84 s, response of 877 % and recovery time of 55 s for detecting 3 ppm NH3 gas while the plane sensor sample has response time of 152 s, response of 17.8 % and recovery time of 367 s. The capillary tube sensor exhibits convenience for detecting a small volume of gas sample. For a 1 mL, 0.1 ppm NH3 gas sample, the PANI-CSA/TiO2 capillary tube sensor exhibits 54 s response time, 454 % response while the plane-shaped sensor fails to detect.

Gas Sensor by Direct Growth and Functionalization of Metal Oxide/Metal Sulfide Core-Shell Nanowires on Flexible Substrates.

We have developed a novel fabrication method for flexible gas sensors for toxic gases based on sequential wet chemical reaction. In specific, zinc oxide (ZnO) nanowires were locally synthesized and directly integrated on a flexible polymer substrate using localized hydrothermal synthesis methods and their surfaces were selectively functionalized with palladium (Pd) nanoparticles using a liquid phase deposition process. Because the entire process is conducted at a low temperature in a mild precursor solution, it can be applied for flexible substrates. Furthermore, the surface of ZnO nanowires was sulfurized by hydrogen sulfide (H2S) gas to form zinc oxide/zinc sulfide (ZnO/ZnS) core-shell nanowires for stable sensing of H2S gas. The locally synthesized ZnO/ZnS core-shell nanowires enable an ultracompact-sized device, and Pd nanoparticles improve the sensing performance and reduce the operating temperature (200 °C). The device shows a high sensitivity [(Ggas - Gair)/Gair × 100% = 4491% to 10 ppm], fast response (response/recovery time <100 s) to hydrogen sulfide, and outstanding selectivity (>100 times) to other toxic gases (e.g., carbon monoxide, acetone, ethanol, and toluene). Moreover, vertically synthesized nanowires provide a long bending path, which reduces the mechanical stresses on the structure. The devices showed stable gas sensing performance under 9 mm positive radius of curvature and 5 mm negative radius of curvature. The mechanical robustness of the device was also verified by numerical simulations which showed dramatic decrease of maximum stress and strain to 4.2 and 5.0%, respectively.

Effect of annealing on UV‐visible absorption and photoluminescence behavior of liquid phase deposited TiO2 nanorods

AbstractIn this work, anatase and rutile TiO2 nanorods were fabricated using one‐step liquid phase deposition process, followed by heat treatment in the range 300‐800°C. The direct and indirect band gap of the TiO2 nanorods was estimated form optical absorption data which illustrated a red shift at higher temperatures owing to the different nature of excitons in anatase and rutile phases. The photoluminescence (PL) spectra revealed the presence of two main emission bands consisting of four peaks. It was found that two high‐energy peaks located at 2.95‐3.30 eV could be generated from exciton transitions from the conduction band to the valence band of TiO2 nanorods, while two low‐energy peaks located at 2.43‐2.64 eV may arise from surface state transitions. The PL intensity firstly increased with temperature and at 500°C reached a maximum value, then decreased through increasing temperature up to 800°C. These variations in the intensity of PL emission could be explained in terms of changes in phase structure, crystallinity, and amount of the oxygen vacancies, which are all dependent to the annealing temperature based on X‐ray diffractometer and X‐ray photoelectron spectrometer studies. These results indicated that annealing temperature allows to manipulate the properties of TiO2 nanorods for opto‐electronic applications.

Gas-assisted liquid phase deposition of crystalline ceria films

A modified liquid phase deposition process named “gas-assisted liquid phase deposition (G-LPD)” was developed to fabricate oxide films at a synthesis temperature below 100 °C and atmospheric pressure using readily available metal salts such as nitrates and chlorides. One of the major points of this process was that a moderately low initial pH of the aqueous metal salt solution was required. In addition, a slight increase of the hydroxide ion concentration was required to facilitate oxide deposition through an equilibrium reaction between metal ions and oxides. Gaseous ammonia generated from aqueous hexamethylenetetramine solution slightly increased the hydroxide ion concentration of the metal salt solution. This process required only one sealed vessel and two beakers, one of which contained an aqueous solution of metal salts and the other hexamethylenetetramine solution. The slow rate of the equilibrium reaction induced heterogeneous nucleation at solid–liquid interfaces, resulting in film formation. Crystalline ceria films were fabricated at 60 °C by keeping the pH almost constant in the range from 4.6 to 5.2. The thickness of ceria films fabricated on polyether sulfone substrates from aqueous 0.05 M cerium nitrate solutions after 3, 7, and 14 days were about 120, 210, and 380 nm, respectively.

Germanium-dioxide periodic nanostructure from inverse replication of butterfly wings

A photonic crystal can be used for controlling light propagation by defining a photonic stop band that is decided by both the periodic structure and material. In this study, the photonic structure in butterfly wing was inversely replicated with germanium dioxide through a facile liquid phase deposition process. Precise replicas of both micro-tile array and dispersed micro-cubes were produced by adjusting the depositing conditions. This work provides the possibility that the abundant photonic crystals in nature can be further enriched by combining the merits of both artificial tailoring and constituents.

Flexible Ultraviolet and Ambient Light Sensor Based on a Nanomaterial Network Fabricated Using Selective and Localized Wet Chemical Reactions.

We report ZnO nanowire- and TiO2 nanotube-based light sensors on flexible polymer substrates fabricated by localized hydrothermal synthesis and liquid phase deposition (LPD). This method realized simple and cost-effective in situ synthesis and integration of one-dimensional ZnO and TiO2 nanomaterials. The fabricated sensor devices with ZnO nanowires and TiO2 nanotubes show very high sensitivity and quick response to the ultraviolet (UV) and ambient light, respectively. In addition, our direct synthesis and integration method result in mechanical robustness under external loading such as static and cyclic bending because of the strong bonding between the nanomaterial and the electrode. By controlling the reaction time of the LPD process, the Ti/Zn ratio could be simply modulated and the spectral sensitivity to the light in the UV to visible range could be controlled.

Fabrication of Co-Doped ZnO Photoanode by Liquid Phase Deposition for Photoelectrocatalytic Degradation of Ofloxacin under Visible Light

A cobalt (Co)-doped ZnO film electrode was facilely fabricated via a one-step liquid phase deposition process. It was found that many rhombus-like nanoparticles with wurtzite crystal structure were uniformly deposited on the surface of electrode, and the doped Co in the film was at bivalent state. Moreover, the as-deposited film was investigated by UV-visible diffuse reflectance spectroscopy, photoluminescence, and cyclic voltammetry. Under visible light illumination, the Co-ZnO film electrode showed higher photocurrent than pure ZnO film electrode. It was explored as photoanode for visible light-driven photoelectrocatalytic (PEC) degradation of ofloxacin (OFL). The amount of Co doped in ZnO film for PEC degradation of OFL was optimized as 7.5% (at.%). Compared with other degradation methods such as direct photolysis, photocatalysis and electrochemical oxidation, PEC exhibited the highest degradation efficiency for OFL which reached 86.7% after 6-h treatment. Furthermore, the major intermediate products during the PEC process of OFL were identified by high-performance liquid chromatography-mass spectrometry; and a possible degradation mechanism for OFL on the Co-ZnO film electrode was proposed.

Ionic Conduction of Non-Aqueous Lithium Electrolyte Solution through Surface Modified Anodized Alumina Membrane Prepared By LPD Process Using Aqueous-Organic Mixed Solvent

The reduction of the internal resistance by the accelerations of Li+ transport and electron transfer promotes the high-speed charge/discharge of lithium ion batteries (LIBs). Recently, the improving charge/discharge has been attempted by exploiting model porous electrodes which have mesoporous structures such as anodic aluminum oxide (AAO) [1]. AAO is a suitable template for the preparation of the multi layered structures using its regular nanopore array. TiO2 thin films have potential application in the negative electrodes of LIBs, so we prepared the SiO2 or TiO2/AAO nanocomposite by the liquid phase deposition (LPD) procedure in this work. The LPD method involves a metal oxide and hydroxide thin films synthetic procedure using the hydrolysis equilibria reactions of metal-fluoro complexes as follows; (Hydrolysis reaction) MF x (x-2n)- + H2O → MO n + xF- + 2nH+ (F- scavenging reaction) Al3+ + 6HF → H3AlF6 + 3/2H2 Previously, TiO2 was deposited on the surface of AAO mesopores by the LPD within 250 nm, and in this study, the TiO2 thin film onto AAO mesopore wall which has the extreme small diameter, i.e., ca. 20-40 nm, was prepared by the LPD. In this research, the achievement of the LPD reaction at 0 °C or less by the use of the H2O/EtOH mixed solvent and the deposition of oxide thin film to mesopore inner wall owing to the decrease of the LPD reaction activity under low temperature were executed. Furthermore, the specific ion conductivity of the electrolyte solution in the mesopore channels in the prepared TiO2/AAO nanocomposites was evaluated. AAO membranes were prepared by two-step anodization as previous report [1,2]. AAO template whose thichness is ca. 500 m (i.e. the aspect ratio of a AAO membrane thichness to a mesopore diameter is ca. 5000) was dipped in (NH4)2SiF6 or (NH4)2TiF6 solution of various concentration for 0-60 h at -20-40 °C. Prepared SiO2 or TiO2/AAO nanocomposite was used as a separator of a four-electrode cell and an impedance measurement was carried out. LiClO4/EC:DEC = 1:1 (v/v) of 0.5 to 2.5 mol L-1was used as an electrolyte solution. The results of LPD reaction using (NH4)2TiF6 solution of 10 mol L-1 in 1 : 1 (v/v) H2O/EtOH at -20-5 °C (The LPD reaction solution was still liquid-state at -20 °C) for 10 h were shown in Fig. 1. The TiO2 thin film deposition within the deep mesopores without collapse of the mesopore structure was achieved at -13.5 °C. The AAO mesopore structure collapsed because the LPD reaction reactivity was too high at 5 °C, and the TiO2 thin film was not generated because the reactivity was too low at -20 °C. It is suggested that the moderate decrease in the LPD reaction activity by using an aqueous/organic solvent mixture was necessary to achieve oxide thin films deposition on the AAO mesopore wall, while retaining the AAO mesoporous structure. The Nyquist plots for four-electrode cells using SiO2 or TiO2/AAO nanocomposites show two semicircles for each nanocomposite. The lower frequency region of the semi-circle was assigned as ion transport resistance in the SiO2 and TiO2 modified mesopore walls, and the fitting of the semicircle in the low frequency region, the specific conductivity in the pore was calculated. For a LiClO4 solution of 0.5-2.5 mol L-1, the specific Li+ ion conductivities after SiO2 or TiO2 thin film coating by LPD in the mesopore of the AAO nanocomposites was compared with those without thin film coating (i.e. as-prepared AAO). The conductivity for the TiO2/AAO nanocomposite is 3 times that for as-prepared AAO, whereas that the conductivity for the SiO2/AAO nanocomposite is similar for as-prepared AAO. Even if the concentration was changed, the ratios of the specific Li+ ion conductivity in the SiO2 or TiO2 modified mesopore to the electrolyte solution and as-prepared AAO were almost constant. These activation energies of Li+ ion conduction in mesopores for each sample are 14.6 (as-prepared AAO), 13.8 (SiO2/AAO), 13.2 kJ mol-1 (TiO2/AAO), respectively. It is suggested that the ionic conduction are influenced by surface electric potential of oxides. This work was supported by CREST, JST. [1] T. Fukutsuka, et al., Electrochim. Acta., 199, 380 (2016) [2] H. Masuda et al., Science, 268, 1466 (1995) Figure 1