Photochemical Deposition Research Articles

Highly efficient amorphous binary cobalt-cerium metal oxides for selective oxidation of 5-hydroxymethylfurfural to 2,5-diformylfuran

This study reports for the first time the use of amorphous mixed cobalt-cerium metal oxides (Co10-aCeaOx), obtained by photochemical metal-organic deposition, for 5-hydroxymethylfurfural (HMF) oxidation. The optimized Co8Ce2Ox exhibites a good electrocatalytic activity toward HMF oxidation with a current density of 2.8 mA cm−2 at 1.60 V, which is 1.4 times higher than that of pure CoOx. Operando Raman spectra reveal that the incorporation of Ce alters the electronic structure of the composite by facilitating the formation of CoOOH/CoO2, thus promoting catalytic activity. Notably, it is found that the oxidation of HMF proceeds dominantly via the oxidation of the alcohol group, followed by its subsequent oxidation in both alkaline and neutral media. Due to the stability of the aldehyde group in neutral media, high valuable 2,5-diformylfuran (DFF) with the selectivity of 60%–92% is obtained, thus open the new route for electrocatalytic DFF production.

Grain boundary effect on the resistive switching characteristics of SrTi1-xFexO3 directly patterned via photochemical organic-metal deposition

Ionic memristors are a promising candidate for use in next-generation non-volatile memory and neuromorphic computing systems. To ensure that ionic memristors exhibit appropriate resistive switching characteristics, the precise control of oxygen vacancies is required. The ABO3 structure can accommodate various ions of different sizes in the A and B sites, and this flexibility allows for the accurate design of materials and for the oxygen defects to be controlled. This study systematically investigated the effect of Fe doping on the resistive switching characteristics of SrTi1-xFexO3 (x = 0, 0.05, 0.10, and 0.15) films fabricated using photochemical organic–metal deposition. The Fe dopant created oxygen vacancies via Schottky defects, especially at grain boundaries, with the space charge at the grain boundaries inhibiting grain growth and increased the number of defective grain boundaries. Since the defective grain boundary acts as a conducting path filament, an increase in the Fe content reduced the initial resistance of the films, and SrTi1-xFexO3 film optimized Fe content exhibited complementary resistive switching behavior without the need for a forming process. The Fe doping effects on the crystal and electronic structure were also analyzed using X-ray diffraction, valence band, O 1s X-ray absorption, and Raman spectra.

Evaluation of alkoxide β-diketonates Ce(III), Er(III), Ln(III) complexes as precursors for the photo-deposition of CeO2:Er/Ln amorphous thin films and their influence on the luminescent properties (where Ln = Pr or Yb)

We propose the use of alkoxide β-diketonates of Ce(III), Er(III), Pr(III) and Yb(III) as precursors for photochemical deposition of CeO2:Er and CeO2:Er/Ln (Ln = Pr or Yb) thin films, followed by subsequent annealing at 950 °C. The measurements of luminescent properties revealed that CeO2:Er samples under excitation at 980 nm exhibit up-conversion emissions at 540 nm and near infrared emissions centered at 1550 nm. When co-doping is performed on the CeO2 films, CeO2:Er/Pr reduces its up-conversion characteristics and the NIR emissions increase. However, the CeO2:Er/Yb samples significantly increase the up-conversion properties and inhibit NIR emissions. Different mechanisms based on energy transfer processes are proposed to explain these differences in the degree of intensity of these emissions.

Photochemical Deposition of Ag, Cu, Cu@Ag, and Ag@Cu on TiO2 Nanotubes and their Optical Properties and Photoelectrochemical Activity

Photochemical Deposition of Ag, Cu, Cu@Ag, and Ag@Cu on TiO2 Nanotubes and their Optical Properties and Photoelectrochemical Activity

Amorphous Nickel Oxide as Efficient Electrocatalyst for Urea Oxidation Reaction

Amorphous nickel oxide loaded on nickel foam (a-NiOx/NF) is synthesized via a facile photochemical metal-organic deposition (PMOD) approach and evaluated as catalyst for urea oxidation reaction (UOR). It exhibits superior activity with current density of 1 and 10 mA cm−2 at 1.240 (0.002) and 1.256 (0.001) V vs. RHE in 1.0 M KOH and 0.5 M urea solution, surpassing most of reported UOR catalysts. It also shows decent durability at 100 mA cm−2. The UOR mechanism exploration reveals that the rate-determining step is the removal of the last proton from the amino-group. This work demonstrates that amorphous materials can be efficient electrocatalysts for UOR which enables efficient H2 production.

Effectiveness of the Nanosilver/TiO2-Chitosan Antiviral Filter on the Removal of Viral Aerosols.

Background: The precaution of airborne transmission of viruses, such as influenza, SARS, MERS, and COVID-19, is essential for reducing infection. In this study, we applied a zero-valent nanosilver/titania-chitosan (nano-Ag0/TiO2-CS) filter bed, whose broad-spectrum antimicrobial efficacy has been proven previously, for the removal of viral aerosols to minimize the risk of airborne transmission. Methods: The photochemical deposition method was used to synthesize the nano-Ag0/TiO2-CS antiviral material. The surface morphology, elemental composition, and microstructure of the nano-Ag0/TiO2-CS were analyzed by a scanning electron microscopy/energy dispersive X-ray spectroscopy and a transmission electron microscopy, respectively. The MS2 bacteriophages were used as surrogate viral aerosols. The antiviral efficacy of nano-Ag0/TiO2-CS was evaluated by the MS2 plaque reduction assay (PRA) and filtration experiments. In the filtration experiments, the MS2 aerosols passed through the nano-Ag0/TiO2-CS filter, and the MS2 aerosol removal efficiency was evaluated by an optical particle counter and culture method. Results and Conclusions: In the MS2 PRA, 3 g of nano-Ag0/TiO2-CS inactivated 97% of MS2 bacteriophages in 20 mL liquid culture (2 ± 0.5 × 1016 PFU/mL) within 2 hours. The removal efficiency of nano-Ag0/TiO2-CS filter (thickness: 6 cm) for MS2 aerosols reached up to 93%. Over 95% of MS2 bacteriophages on the surface of the nano-Ag0/TiO2-CS filter were inactivated within 20 minutes. The Wells-Riley model predicted that when the nano-Ag0/TiO2-CS filter was used in the ventilation system, airborne infection probability would reduce from 99% to 34.6%. The nano-Ag0/TiO2-CS filter could remain at 50% of its original antiviral efficiency after continuous operation for 1 week, indicating its feasibility for the control of the airborne transmission.

Solution-based CdS thin film transistors with low temperature-processed Al2O3-GPTMS-PMMA as hybrid dielectric gate

Herein, we report the low-temperature fabrication process and the electrical response of n-type cadmium sulfide (CdS)-based thin-film transistors (TFTs) with an Al2O3-GPTMS-polymethylmethacrylate (PMMA) hybrid dielectric gate. The TFTs with bottom-gate structure were assembled on ITO (indium-tin-oxide)-coated glass substrates employing solution processes for the deposition of both the dielectric gate and semiconductor layers. The hybrid dielectric layers were deposited by the sol-gel process and subsequently annealed at 150 °C. The FTIR and XPS analysis of the hybrid films demonstrated a proper link between Al2O3 and PMMA through the cross-linking agent 3-glycidoxy(propyltrimethoxysilane) silane (GPTMS). The surface characteristics were obtained by contact angle and atomic force microscope studies, the results show that the surface of hybrid films displays a hydrophobic behavior with a smooth surface. The CdS active layer was deposited on the hybrid dielectric gate at room temperature by a simple photochemical bath deposition using a 313 nm UV lamp. The CdS-TFTs showed outstanding electrical performance with a low threshold voltage of 1.3 V, I ON /I OFF of 104, subthreshold swing of 440 mV dec−1, and remarkable high mobility value of 64.4 cm2 V−1 s−1. Ultimately, the feature of these completely solution-based CdS TFTs is the maximum processing temperature of 150 °C, and the findings of this study are very promising for potential low-cost solution-processed TFTs.

Photo-Chemically-Deposited and Industrial Cu/ZnO/Al2O3 Catalyst Material Surface Structures During CO2 Hydrogenation to Methanol: EXAFS, XANES and XPS Analyses of Phases After Oxidation, Reduction, and Reaction

Industrial Cu/ZnO/Al2O3 or novel rate catalysts, prepared with a photochemical deposition method, were studied under functional CH3OH synthesis conditions at the set temperature (T) range of 240–350 °C, 20 bar pressure, and stoichiometric carbon dioxide/hydrogen composition. Analytical scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray adsorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) methods were systematically utilized to investigate the interfaces, measured local geometry, and chemical state electronics around the structured active sites of commercially available Cu/ZnO/Al2O3 material or synthesized Cu/ZnO. Processed Cu K-edge EXAFS analysis suggested that various Cu atom species, clusters, metallic fcc Cu, Cu oxides (Cu2O or CuO) and the Cu0.7Zn2 alloy with hexagonal crystalline particles are contained after testing. It was proposed that in addition to the model’s Cu surface area, the amount, ratio and dispersion of the mentioned bonded Cu compounds significantly influenced activity. Additionally, XPS revealed that carbon may be deposited on the commercial Cu/ZnO/Al2O3, forming the inactive carbide coating with Cu or/and Zn, which may be the cause of basicity’s severe deactivation during reactions. The selectivity to methanol decreased with increasing T, whereas more Cu0.7Zn2 inhibited the CO formation through reverse water–gas shift (RWGS) CO2 reduction.

In situ photochemical deposition of Ag nanoparticles on polyester fiber membranes as flexible SERS substrates for sensitive detection of sodium saccharin in soft drinks

Flexible surface-enhanced Raman scattering (SERS) substrates, specifically paper-based SERS substrates, are generally employed in many practical applications. However, paper-based SERS substrate quantitation is still challenging because of the inferior uniformity originating from the irregular morphology of the paper. The present study synthesized Ag nanoparticles (NPs) via the in situ photochemical reduction of Ag+ ions on a titanium dioxide (TiO2) film at the polyester fiber membranes (PFMs) surface. This generated many “hot spots” that presented significant SERS activity with an enhancement factor of 2.1 × 109. Sodium saccharin (SS) bonded to the Ag NPs surface via the carbonyl oxygen and ring nitrogen atoms. A SERS sensor with photochemically deposited Ag NPs was prepared for the sensitive and rapid detection of SS in soft drinks with a limit of detection of 0.3 mg/L. The recovery rate ranged from 93% to 103%, indicating that this method is reliable in actual sample detection with simple pretreatment steps and can be potentially applied for the on-site detection of food additives for food safety.

Trace Amounts of Co3O4 Nano-Particles Modified TiO2 Nanorod Arrays for Boosted Photoelectrocatalytic Removal of Organic Pollutants in Water.

Trace amounts of Co3O4 modified TiO2 nanorod arrays were successfully fabricated through the photochemical deposition method without adding any nocuous reagents. The Co3O4/TiO2 nanorod arrays fabricated in acid solution had the highest photo-electrochemical activity. We elaborated on the mechanism of Co3O4-TiO2 fabricated in different pH value solutions. The Co3O4-TiO2 had a more remarkable photo-electrochemical performance than the pure TiO2 nanorod arrays owing to the heterojunction between Co3O4 and TiO2. The degradation of methylene blue and hydroquinone was selected as the model reactions to evaluate the photo-electrochemical performance of Co3O4-TiO2 nanorod arrays. The Co3O4/TiO2 nanorod arrays had great potential in waste water treatment.

Decoration of titanium dioxide nanotubes with silver nanoparticles using the photochemical deposition method and their application as an electrocatalyst to determine tinidazole.

In this study, titanium nanotube electrodes were decorated with silver nanoparticles (AgNPs/TiO2NTs) and used as an electrocatalyst for the reduction of tinidazole. AgNPs/TiO2NTs are constructed by anodization of titanium sheet metal and photochemical deposition of AgNPs on TiO2NTs. The structural and elemental analysis characteristics of the AgNPs/TiO2NT electrode have been studied by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) methods. Based on the cyclic voltammetric data, it has been confirmed that the AgNPs/TiO2NT electrode has good electrocatalytic activity to reduce tinidazole. Two liner concentration ranges of 0.2-55.0 μM and 55.0-111.2 μM were obtained by amperometric method. A detection limit of 60.9 nM was obtained for measuring tinidazole at the AgNPs/TiO2NT electrode surface. In addition, the designed sensor has been successfully used for quantitative measurement of tinidazole in pharmaceutical and human urine samples.

Photo-Assisted Sequential Assembling of Uniform Metal Clusters With Sub-Nanometers on Semiconductor Supports

Dispersing metal subnano-clusters on the oxide supports is attracting close attention in heterogeneous catalysis, but great challenges still lie in controlling the size and dispersion of subnano-clusters due to the inevitable agglomeration. Here, we propose a sequential photochemical deposition strategy named “first store, and then release” to uniformly fabricate the size-controlling noble metal subnano-clusters on semiconductor oxides. Using the typical semiconductor TiO2, the photoexcited electrons can be first stored as reduced species (e.g. Ti3+) under irradiation and the Ti3+ species can optimize both the nucleation and growth processes in dark reaction, resulting in a uniform dispersing of various noble metals (Au, Pt, Ag etc.) with size diameters of ~1 nm. The subnano-clusters catalysts exhibited superior performance in catalytic oxidation of HCHO compared with that of nanoparticles. This work brings a new and useful strategy to construct size-controlling noble metals on the oxide supports for heterogeneous catalysis and the related fields.

Synthesis of magnetic photocatalyst by photochemical deposition and co-precipitation techniques: investigation of its photocatalytic and sonophotocatalytic activity for dye removal

ABSTRACT In this study, photochemical deposition and co-precipitation methods were used to synthesise Ag/TiO2 and magnetic Ag/TiO2/Fe3O4 photocatalysts, respectively. The physical and chemical properties of the Ag/TiO2 and Ag/TiO2/Fe3O4 photocatalysts were characterised by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FT-IR) analyses. The synthesised photocatalysts were used to remove Reactive Red 195 (RR195) dye the most commonly used in the textile industry. The photocatalytic and sonophotocatalytic removal was investigated using different light types such as UV-A and visible light. In the optimum conditions (UV-A and visible light intensity 27 W, 25 mg/L initial RR195 concentration, pH 6 ve 0.1 g/L catalyst dose) of photocatalysis, the photodegradation of magnetic Ag/TiO2/Fe3O4 was found 72% at 120 min irradiation of visible light but the degradation was 65% at 30 min irradiation of UV-A light. While in case of the sonophotocatalysis, the degradation of magnetic Ag/TiO2/Fe3O4 was found 85% at 120 min irradiation of visible light but the degradation was 85% at 30 min irradiation of UV-A light.

Photochemical deposition of palladium nanoflowers on TiO2 nanotubes and their application for the electrocatalytic measurement of iodate ions

In the present study, a layer of titanium oxide nanotubes (TiO2NT) was formed by the electrochemical anodization of a titanium sheet (Ti) to produce TiO2NT/Ti. Then, palladium nanoflowers (PdNF) were deposited on the surface of a TiO2NT/Ti electrode by the photocatalytic reduction process. The characterization of TiO2NT/Ti and PdNF/TiO2NT/Ti was performed by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) techniques. The PdNF/TiO2NT/Ti electrode proved to have catalytic activity for iodate ion (IO3−) reduction. As it was observed, the peak potential of iodate ion reduction at the surface of the PdNF/TiO2NT/Ti electrode shifted toward less negative values than that at the surface of a TiO2NT/Ti electrode. Through an amperometric method, three linear calibration ranges were obtained for iodate ion determination at the modified electrode surface. The detection limit calculated through the same method was 3.4 µM. Finally, the PdNF/TiO2NT/Ti electrode was put to use to determine iodate ions in a commercial salt sample, a nourishment supplement and a drinking water sample. The results were satisfactory.

Directly-Patternable Bi2O3 Nanoparticle for Polymer Nanocomposite Capacitor

A polyvinylidene fluoride (PVDF) film incorporating size-controlled, uniformly dispersed, directly patterned Bi2O3 nanoparticles was developed to achieve a high-k polymer nanocomposite capacitor. The photochemical metal-organic deposition (PMOD) method was employed to form uniformly dispersed and directly patterned nanoparticles on the substrate. Bi nanoparticles were produced by spin coating a Bismuth 2-ethylhexanoate solution on a Pt substrate with UV irradiation for 1, 4, 7, and 10 min. The average diameter of nanoparticles and the number of nanoparticles per unit area (μm2) were about 30, 70, and 120 nm and 30, 30, and 31 particles/μm2 for UV irradiation times of 4, 7, and 10 min, respectively. In addition, the capacitance of PVDF nanocomposite film could be controlled by the Bi2O3 nanoparticle size. The PVDF nanocomposite film containing Bi2O3 nanoparticles with 1, 4, 7, and 10 min UV irradiation were able to improve capacitance by about 1.4, 2.0, 2.7, and 3.4 times compared with an as-prepared PVDF film. By using a mask aligner, directly pattered Bi nanoparticles on the substrate, which had a 5 μm line width pattern, were successfully defined and demonstrated.

The morphology and electrochemical properties of WO3 and Se-WO3 films modified with cobalt-based oxygen evolution catalyst

In this paper, we have studied morphology and electrochemical properties of novel (photo)electrocatalyst of selenium doped tungsten trioxide (Se-WO3) modified with cobalt-based oxygen evolution catalyst (Co–Pi). Se-WO3 films were electrodeposited on fluorine doped tin oxide coated glass (FTO) support. Then photochemical deposition was employed to modify the surface of produced films with Co–Pi catalyst in order to increase their performance in photo(electrochemical) water splitting. Morphological and (photo)electrochemical properties were identified using X-ray powder diffraction (XRD), Scanning electron microscopy (SEM) with Energy dispersive X-ray analysis (EDX) and Fourier-transform infrared spectroscopy (FTIR), as well as electrochemical techniques in order to determine photon-to-current efficiency (IPCE) and photoconversion efficiency. The results indicated that the presence of cobalt-based catalyst effectively changes the activity of Se-WO3 films: the incident photon-to-current efficiency and photoconversion efficiency increased nearly twice and the onset potential for O2 evolution in the dark was also shifted towards lower values.

Photochemical deposition of palladium nanoparticles on TiO2 nanoparticles and their application for electrocatalytic measurement of nitrate ions in potato, onion and cabbage using bipolar electrochemical method

A nanoparticle modified recordable digital versatile disc (DVD) blade was used as the bipolar electrode. The cathodic pole of the DVD blade was modified by TiO2 nanoparticles. Then, Pd nanoparticles were deposited at the TiO2NPs/DVD surface by photochemical method. In the proposed setup, when the required potential was applied by using a direct power supply, the nitrate ions are reduced electrocatalytic at the PdNPs/TiO2NPs cathodic pole and the oxidation reaction of the silver layer is performed at the anode pole of the bipolar electrode, simultaneously. The oxidation process led to the dissolution of the silver layer. The results show that the dissolution length of the silver layer on the surface of the anodic pole at constant interval time is proportional to the nitrate ion concentration in the analytical solution. Finally, this method was used to measure the concentration of nitrate ions in the various real samples and obtained satisfactory results.

Mechanism insight of dual synergistic effects of plasmonic Pd-SrTiO3 for enhanced solar energy photocatalysis

This study presents the integration of UV-active semiconductor with plasmonic noble metal nanoparticles for enhanced solar energy photocatalysis. Nanocubes strontium titanate (SrTiO3) is synthesized via a simple hydrothermal process. Then palladium (Pd) nanoparticles will be deposited onto the surface of SrTiO3 by simple photochemical deposition route. The deposition of plasmonic Pd nanoparticles significantly increased the light absorption, especially in visible and near-infrared region and enhanced charge separation efficiency. The photocatalytic performance of Pd-deposited SrTiO3 is assessed by photodegradation of bisphenol A (BPA) and 4-chlorophenol (4CP) under solar light. The results confirm that the existence of Pd nanoparticles in SrTiO3 has improved the photocatalysis efficiency compared to pure SrTiO3. The higher weight percentage of Pd loading achieved better photocatalytic performance compared to lower weight percentage of Pd loading. This improvement can be deduced from the dual localized surface plasmon resonance effects that led to higher photoresponse and generation of free electrons. Moreover, the existence of Pd nanoparticles further retards the recombination rate of electron and hole pairs. This leads to the excess presence of electrons that contributed to the formation of active radicals that enhanced the oxidation of BPA and 4CP. Thus, this study will provide a new mechanism insight and approach to modify visible and near-infrared light-driven photocatalysts in degrading various organic pollutants.

Resistive switching characteristics of directly patterned Y-doped CeO2 by photochemical organic-metal deposition

Resistive RAM (ReRAM), which uses the anion-based resistive switching characteristic of transition metal oxide, is one of the strong candidates for next-generation non-volatile memory. The resistance switching characteristics depend on oxygen defects and their electrochemical migration. This study systematically investigated the Y3+ doping effect in CeO2 resistive switching behavior to control oxygen vacancy. The resistive switching devices of Ce1-xYxO2-y (CYO) (x = 0, 0.05, 0.1, 0.15, and 0.2) were fabricated by the photochemical metal-organic deposition method, which could successfully obtain directly patterned CYO films. The XRD pattern and Raman spectrum confirmed that the lattice shrink and structural distortion was induced and increased gradually by increasing the oxygen vacancy concentration with yttrium content. All the CYO devices showed bipolar filament-type resistive switching, and both resistance of the pristine state and forming voltage decreased with increasing Y content from an increase in oxygen vacancy concentration. And the on/off ratio decreased with increasing Y content because of reduced HRS resistance, even after the recovered insulation oxide region by HRS switching, due to fixed defect sites with trapped electrons formed by yttrium. And with a SPEM experiment, we found that ceria loses 24% oxygen for LRS resistive switching, which induced a resistance change of about five orders of magnitude.

Ratiometric fluorescence determination of hydrogen peroxide using carbon dot-embedded Ag@EuWO4(OH) nanocomposites.

A sheet-like carbon dot-embedded Ag@EuWO4(OH) luminescent nanoprobe was successfully developed for assaying hydrogen peroxide. Firstly, the carbon dot-embedded EuWO4(OH) nanosheets were prepared in a Eu(NO3)3·6H2O-(NH4)10H2(W2O7)6·xH2O-CS(NH2)2 hydrothermal synthetic system. Subsequently, the carbon dot-embedded EuWO4(OH) was functionalized by Ag nanoparticles using an in situ photochemical deposition strategy upon ultraviolet light irradiation. Taking advantage of the dual emissions of the luminescence from carbon dots and characteristic red transitions of Eu3+ ions in the integrated system, the carbon dot-embedded Ag@EuWO4(OH) luminescent composites exhibit ratiometric fluorescence responsive activity towards hydrogen peroxide. The luminescent intensity ratio of Eu3+ (614nm) to carbon dots (389nm) shows a polynomial function with changing hydrogen peroxide concentration. The corresponding detection limit is 60 μM at a signal-to-noise ratio of 3 (S/N = 3) implying the potential use of the carbon dot-embedded Ag@EuWO4(OH) as nanoprobe. The method was applied to the quantification of H2O2 in real samples with satisfactory results. Graphical abstract A carbon dot-embedded Ag@EuWO4(OH) luminescence ratiometric probe was successfully prepared through hydrothermal method and in situ photochemical deposition strategy. The luminescence intensity ratio of Eu3+ to carbon dots shows synergistic luminescence response activity towards H2O2 with detection limit of 60 μM.