Effect of heat treatment on photoelectrochemical performance of hydrothermally synthesised Ag2S/ZnO nanorods arrays

Low temperature hydrothermal method was used to produce a large surface area ZnO NRs on conductive glass. The same method was used to fabricate a photoelectrode of Ag2S quantum dots onto the nanorod arrays. Ag2S QDs/ZnO NRAs heterostructure was employed as photoanode in a standard 3-electrodes photoelectrochemical cell. A significant enhancement in the photoelectrochemical performance was observed for the Ag2S QDs/ZnO upon heat treatment 400 °C which displayed an impressive photoconversion efficiency of 4.08% by achieving ∼10-times higher compared to bare ZnO NRAs. This enhancement was attributed to the improved morphological structure, crystallinity and optical properties of the synthesised heterostructures

Effect of hydrothermal growth time on ZnO nanorod arrays photoelectrode performance

High density and vertically aligned zinc oxide nanorod arrays (ZnO NRs) have been prepared directly on indium-doped tin oxide (ITO) substrates via two-steps preparation: sol-gel spin coating and hydrothermal process. The nanostructured ZnO was characterized for its morphology, crystalline structure and optical properties by using field emission scanning electron microscopy (FESEM), X-ray diffractometry, and ultraviolet-visible spectroscopy respectively. In addition, the photoeletrochemical (PEC) properties were investigated through photocurrent measurements. The ZnO NRs/ITO had wurtzite-structured (hexagonal) ZnO and preferred growth along (0001) direction. When the growth time was 4 h, ZnO NRs/ITO showed impressive photoresponse. The PEC analysis verified that the ZnO NRs gave better photocurrent response and photoconversion efficiency with approximately 42 times greater than seed layer

Electrochemical deposition of CdSe-sensitized TiO2 nanotube arrays with enhanced photoelectrochemical performance for solar cell application

Particular interest has been given to the self-organized titania nanotube TiO2 thin films prepared by using anodisation method followed by annealing in the air, while the CdSe layer was potentiostatically electrodeposited onto the TiO2 nanotube films at various pH. The resulting films were studied by using energy dispersive X-ray spectroscopy, X-ray diffraction, field emission scanning electron microscopy, UV–Vis spectroscopy and photoelectrochemical analysis to characterize their compositional, crystalline structure, surface morphological, optical, and photoconversion efficiency characteristics. The resulting CdSe/TiO2 nanotube exhibits significant enhancement in optical absorption, photocurrent density and photoconversion efficiency. CdSe/TiO2 nanotube prepared at pH 3 exhibited the highest photocurrent density of 2.13 mA cm−2 and photoconversion efficiency of 1.02 % which is 51 times higher than TiO2 nanotube array. This may due to the formation of CdSe nanocrystals which were well crystallized and bonded with TiO2 NTAs contributing to the enhanced photoresponse and photostability of the overall performance of CdSe/TiO2 NTAs heterostructures

Effect of Varying AgNO3 and CS(NH2)2 Concentrations on Performance of Ag2S/ZnO NRs/ITO Photoanode

This research focuses on improving the photoelectrochemical performance of binary heterostructure Ag2S/ZnO NRs/ITO by manipulating synthesis conditions, particularly the concentrations of sliver nitrate AgNO3 and thiourea CS(NH2)2. The photoelectrochemical performance of Ag2S/ZnO nanorods on indium tin oxide (ITO) nanocomposite was compared to pristine ZnO NRs/ITO photoanode. The hydrothermal technique, an eco-friendly, low-cost method, was used to successfully produce Ag2S/ZnO NRs at different concentrations of AgNO3 and CS(NH2)2. The obtained thin films were characterized using field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), ultraviolet-visible spectroscopy (UV-vis), and photoelectrochemical studies (PECs). We observed that there was an enhancement in absorbance in the visible region and effective photoelectron transfer between the Ag2S/ZnO NRs/ITO photoelectrode and the electrolyte Red-Ox when illuminated with 100 mW cm−2. Increasing the concentration of AgNO3 caused a remarkable decrease in the optical bandgap energy (Eg) values. However, we noticed that there was an unstable trend in Eg when the concentration of CS(NH2)2 was adjusted. The photoelectrochemical studies revealed that at a bias of 1.0 V, and 0.005 M of AgNO3 and 0.03 M of CS(NH2)2, the maximum photocurrent of the Ag2S/ZnO NRs/ITO photoanode was 3.97 mA/cm2, which is almost 11 times that of plain ZnO nanorods. Based on the outcomes of this investigating, the Ag2S/ZnO NRs/ITO photoanode is proposed as a viable alternative photoanode in photoelectrochemical applications

Zinc Oxide Nanoparticles and Nanorods as Antimicrobial Agents: Particle Size Influence

The aim of this study is to find out about the antibacterial activity of a variety of ZnO nanostructures, along with their derivative nanoparticles (ZnO NPs) and nanorods (ZnO NRs) against numerous clinic strains of Gram-negative Escherichia coli (E. coli), Salmonella typhi (S. typhi), Pseudomonas aeruginosa (P. aeruginosa) as well as Gram-positive Streptococcus pneumonia (Strept. pneumonia) bacteria. ZnO NPs and ZnO NRs were efficiently synthesized by using sol-gel and hydrothermal strategies, respectively. Various properties, consisting of the morphology, structure and optical, had been described by using field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) as well as ultraviolet-visible (UV-Vis) spectroscopy analysis. This check was performed in Mueller-Hinton agar. The impact of different particle sizes and morphologies of ZnO nanomaterials on the growth of bacteria was measured. In the antibacterial assay, each type of ZnO nanostructure showed effective inhibition. The findings showed that ZnO NRs exhibited more efficient antibacterial activity than that of ZnO NPs agents. This was once the case for both Gram-positive and Gram-negative bacteria. Hence, the study indicated that the antibacterial of ZnO NRs against Strept. Pneumonia was similar to those for S. typhi. However, depending on the particle size effect of ZnO nanostructure, it was found that ZnO NPs showed much less antibacterial activity towards S. typhi than ZnO NRs did

Titania Nanotubes Arrays Based-Gas Sensor: NO2-Oxidizing Gas and H2-Reducing Gas

Gas sensor based on titanium dioxide (TiO2) nanotube was manufactured and its sensitivity to hydrogen (H2) and to nitrogen dioxide (NO2) gasses was investigated using anodization method. The TiO2 NT structure was studied using X-ray diffraction (XRD). The surface morphology of prepared Titania was analysed using field-emission electron-scanning microscopy (FE-SEM). Starting with (XRD) study it confirms the tetragonal phase structure of the prepared Titania (anatase and rutile). In addition, the TiO2 anatase averaged crystallite size was 25.9 nm. The FE-SEM images revealed that the nanotube's average diameters are within 70 ± 2 nm. Gas response measurements at room temperature (27 ℃) for hydrogen and nitrogen dioxide gases at various concentrations (100, 150, 200, 250 and 300 ppm) were investigated. Our study has shown that the higher resistance of NO2 gas was 30 Ω at 300 ppm while it was equal 18.29 Ω at 150 ppm for H2 gas at room temperature

Sensitization of TiO2 nanotube arrays photoelectrode via homogeneous distribution of CdSe nanoparticles by electrodeposition techniques

CdSe has attracted interest as the absorber layer in photoelectrochemical cell applications. In this work, titania nanotubes thin film electrodes were prepared by the anodisation method of titanium foil were used due to their ability to produce a uniformly stable structure with high surface area, excellent charge transfer, low interfacial grain boundaries and effective absorption of light. Three electrochemical deposition techniques were used to deposit CdSe onto TiO2 NTAs, namely potentiostatic deposition, cyclic voltammetric deposition, and pulse electrodeposition techniques as a novel to compare between these methods. X-ray diffractometry (XRD), field emission scanning electron microscopy (FESEM) coupled with energy dispersive X-ray spectroscopy (EDX), high-resolution transmission electron microscopy (HRTEM), and UV–Visible diffuse reflectance spectroscopy were used for the characterization of CdSe/TiO2 NTAs nanostructures. The photoelectrochemical performance of the nanostructured CdSe/TiO2 NTAs was investigated in 0.01 M Na2S under visible light illumination. The use of pulse electrodeposition resulted in a greater uniformity in the distribution of CdSe loaded onto TiO2 nanotube arrays. Thus the performance of semiconductor heterostructures prepared by this technique shows a substantial improvement compared to the other two techniques

Enhancement in NO2 and H2-Sensing Performance of CuxO/TiO2 Nanotubes Arrays Sensors Prepared by Electrodeposition Synthesis

The CuxO/TiO2 nanotubes arrays are fabricated in two stages. Firstly, TiO2-NTs are grown by the Ti-foil anodization process and then annealed for 2h at 500 ℃. Subsequently, CuxO thin film was deposited with different deposition times on the nanotubes by electrochemical cathodic reaction, then heated twice, once at 200 ℃ in the air and then at 300 ℃ in the closed furnace for 2 h, respectively. Pure-TNT and CuxO/TNTs heterostructure are characterized by XRD, FE-SEM, EDX, Hall effect, and as a gas sensor. Results show that the gas sensor (CuOx=1/TiO2 for NO2 and H2 gases) prepared at the time (1 min) is higher than the pure TiO2-NTs and also higher than Cux=2O/TiO2 which were synthesized at various times 3, 5, 7, and 10 mins

Enhanced photoelectrochemical performance of Bi2S3/Ag2S/ZnO novel ternary heterostructure nanorods

The current work investigates the morphology, crystallinity and photoelectrochemical (PEC) performance of bismuth sulfide/silver sulfide/zinc oxide nanorods (Bi2S3/Ag2S/ZnO NRAs) photoelectrodes as prepared at different annealing temperature. ZnO NRAs was initially grown hydrothermally, deposited in sequence with Ag2S and Bi2S3 via successive ionic layer adsorption and reaction (SILAR) method before undergoing the annealing treatment. The optimised photoelectrode (Bi2S3/Ag2S/ZnO NRAs-400 °C) possesses an optical bandgap of 1.60 eV extending the absorption edge of ZnO to visible light spectrum. The current-voltage characterization of Bi2S3/Ag2S/ZnO NRAs photoelectrodes revealed that the photocurrent density and photoconversion efficiency were strongly dependent on the annealing temperature. The PEC study shows that the photoelectrode annealed at 400 °C achieved impressive photocurrent density of 12.95 mA/cm2 at +0.5 V (vs Ag/AgCl/saturated KCl) under 100 mW/cm2 illumination with superior photoconversion efficiency of 12.63%. This improvement is due to the cascade-designed band structure alignment of Bi2S3/Ag2S/ZnO/ITO and to the brilliant role of Ag2S as an intermediate layer that reduced random chance of electron-hole (e−-h+) pairs recombination and improved the electrons collection efficiency. This work is highly anticipated to give contribution on further utilisation of Bi2S3/Ag2S/ZnO NRAs as a promising semiconductor material in PEC related applications