Enhanced Photocatalytic Activity of ZnO–CdS Composite Nanostructures towards the Degradation of Rhodamine B under Solar Light

A simple chemical precipitation route was utilized for the synthesis of ZnO nanoparticles (NPs), CdS NPs and ZnO–CdS nanocomposites (NCs). The synthesized nanostructures were examined for the crystal structure, morphology, optical properties and photodegradation activity of rhodamine B (RhB) dye. The ZnO–CdS NCs showed a mixed phase of hexagonal wurtzite structure for both ZnO NPs and CdS NPs. Pure ZnO NPs and CdS NPs possessed bandgaps of 3.2617 and 2.5261 eV, respectively. On the other hand, the composite nanostructures displayed a more narrow bandgap of 2.9796 eV than pure ZnO NPs. When compared to bare ZnO NPs, the PL intensity of near-band-edge emission at 381 nm was practically suppressed, suggesting a lower rate of photogenerated electron–hole (e−/h+) pairs recombination, resulting in enhanced photocatalytic activity. Under solar light, the composite nanostructures displayed a photodegradation efficiency of 98.16% towards of RhB dye. After four trials, the structural stability of ZnO–CdS NCs was verified.

Study of the photoelectrochemical activity of ZnO: Ag/rGO photo-anodes synthesized by two-steps sol-gel method

This work investigate the influence of Silver Plasmon and reduced graphene oxide (rGO) on the photoelectrochemical performance (PEC) of ZnO thin films synthesized by the sol-gel method. The physicochemical properties of the obtained photo-anodes were systematically studied using several characterization techniques. The X-ray diffraction analysis showed that all samples presented hexagonal Wurtzite structure with apolycrystalline nature. Raman and EDX studies confirmed the existence of both Ag and rGO in ZnO: Ag/rGO thin films. The estimated grain size obtained from (SEM) analysis decreased with Ag doping, then increased to a maximum value after rGO addition. The UV-vis transmission spectra of the as-prepared ZnO: Ag and ZnO: Ag/rGO thin films have shown a reduction in the visible range with a redshift at the absorption edges. The bandgaps were estimated to be around 3.17, 2.7, and 2.52 eV for ZnO, ZnO: Ag, and ZnO: Ag/rGO, respectively. Moreover, the electrical measurements revealed that the charge exchange processes were enhanced at the ZnO: Ag/rGO/electrolyte interface, accompanied by an increase in the (PEC) performance compared to ZnO and ZnO: Ag photo-anodes. Consequently, the photocurrent density of ZnO: Ag/rGO (0.2 mA.cm-2) was around 4 and 2.22 times higher than photo-anodes based on undoped ZnO (0.05 mA.cm-2) and ZnO: Ag (0.09 mA.cm-2), respectively. Finally, from the flat band potential and donor density, deduced from the Mott-Schottky, it was clear that all the samples were n-type semiconductors with the highest carrier density for the ZnO: Ag/rGO photo-anode.

Chemical Route Manufactured ZnO Nanoparticles And Their Biological Accumulation

ZnO nanocrystalline powder was successfully synthesized via co-precipitation method coupled with high annealing treatment. X-ray diffraction analysis revealed that the NPs have a pure hexagonal wurtzite structure with a mean crystallite size of approximately 59 nm. FESEM observations along with EDS analysis indicated the formation of fine particles in the nanoscale regime, with hexagonal shape and high purity. Both Raman and photoluminescence characterizations confirmed the high crystalline and the optical quality of the synthesized ZnO NPs. The assessment of the impact of ZnO-based nanoparticles and their effects on body and bioaccumulative bioindicators of pollution, Helix aspersa snails was performed in order to preserve the safe development of nanotechnology.

Biosynthesis of Zinc Oxide Nanoparticles Using Leaf Extract of Prosopis juliflora as Potential Photocatalyst for the Treatment of Paper Mill Effluent

This paper reports on the manufacture of ZnO nanoparticles (ZnO NPs) from Prosopis juliflora leaf extracts. Various methods of characterization were used, including X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), and transmission electron microscope TEM. ZnO NPs has a hexagonal wurtzite structure with a preferred orientation of 101 planes, according to XRD. The functional groups found in ZnO NPs isolated from leaves are responsible for the FT-IR peaks that correspond to them. The morphology of the produced nanoparticles is a sphere-like form, as shown in the SEM pictures. TEM examination revealed ZnO NPs with a size of 50–55 nm. These ZnO NPs were used to remediate pollutants in paper mill effluents, and they were able to remove 86% of the organic pollutants from the sample at 0.05 mg/L dose and reduce 89% of the organic pollutants during a 5-h reflex time. Meanwhile, for the photocatalysis of paper mill effluents, it has been noted that COD was removed by 74.30%, 63.23%, and 57.96% for the first, second, and third cycles, respectively.

Facile synthesis of hierarchical ZnO structure for photocatalytic degradation of dimethyl phthalate

A facile co-precipitation method was employed to fabricate hierarchical ZnO structure and characterized by various analytical instruments. The images of ZnO from field-emission scanning electron microscopy exhibited spheroidal morphology which composed of numerous layers of nanosheets and formed a hierarchical structure. Energy dispersive X-ray spectrum validated the presence of Zn and O atoms and its purity. X-ray diffraction pattern of ZnO revealed the establishment of hexagonal wurtzite structure. Optical property analysis disclosed that the as-fabricated ZnO had strong absorbance of wavelength from 350-410 nm with an absorption band edge of 367 nm. In this paper, the photocatalytic activity of hierarchical ZnO structure was confirmed by degradation of endocrine disrupting chemical, namely dimethyl phthalate under UV lamp irradiation. The photodegradation of dimethyl phthalate in aqueous solution over as-fabricated ZnO reached 55.9% after 60 min irradiation. The photocatalytic degradation of DMP obeyed the pseudo first-order kinetic reaction with a rate constant of 0.0166 min−1.

Substrate Critical Effect on the Structural and H2 Gas Sensing Characteristics of Solution-Processed Zn0.075Cu0.025O Films

In this study, we report the synthesis of Zn0.075Cu0.025O films by chemical bath deposition to determine the effect of substrate (glass slide or ZnO seed layer) on the structural and H2 gas sensing properties of the produced films. The crystal phase, structural topography, surface morphology and functional groups of the as-synthesized films as well as H2 gas sensing properties were investigated. Although both films have a hexagonal wurtzite structure, ZnO seed layer-based Zn0.075Cu0.025O film is more crystalline than glass slide-based Zn0.075Cu0.025O films. ZnO seed layer-based Zn0.075Cu0.025O films exhibited much more nanorod and less nanosphere forms compared to glass slide-based Zn0.075Cu0.025O films. EDX analysis and Raman spectra of both samples confirmed the presence of defects in Cu:ZnO samples. ZnO seed layer-based sensors showed higher response (140%) and lower operating temperature (80°C) compared to glass slide-based sensors (87% response and 140°C operating temperature). The most important thing to note here is that the fabricated sensors exhibited high response at room temperature. The responses at room temperature was found as 46% and 23% for the ZnO seed layer-based and glass slide-based sensors, respectively. Sensors operating at room temperature are especially important for commercial applications.

Improvement of the UV-Sensing Performance of Ga-Doped ZnO Nanostructures via a Wet Chemical Solution at Room Temperature

In this investigation, ultraviolet (UV) photodetectors (PDs) were fabricated from zinc oxide (ZnO) and Ga-doped ZnO nanostructures on a Corning glass substrate by a simple wet chemical solution method at room temperature. The prepared devices contained two-dimensional (2-D) nanosheet (NS) structures, which could provide a large surface-area-to-volume ratio for UV-sensing. The ZnO and Ga-doped ZnO materials were respectively named ZPD and ZPD-G. All of the samples revealed a hexagonal wurtzite structure and grew preferentially along the (002) crystal plane. Compared with the photoluminescence (PL) spectrum of the ZPD NSs, the corresponding spectra of the ZPD-G NSs in the 380 nm region and green emission were clearly red-shifted and the number of oxygen vacancies slightly decreased. Under 380 nm UV illumination and a 3 V applied bias, the ZnO UV PDs doped with Ga elements exhibited much higher photoresponsivity and stability compared with the un-doped ZnO PDs, indicating good electrical performance. The ZPD-G samples possessed higher rise and recovery times compared with the ZPD samples; this finding could be attributed to the ability of the former to generate numerous electrons.

Tuning of Photoluminescence and Antibacterial Properties of ZnO Nanoparticles through Sr Doping for Biomedical Applications

Sr-doped ZnO nanoparticles have been synthesized using a soft chemical method. The doping ratio of Sr is varied in the range of 0 at.%, 3 at.%, and 5 at.% to 7 at.%. X-ray diffractograms revealed that the samples had hexagonal (wurtzite) structure without a trace of any mixed phase. The average crystallite size of the nanoparticles (NPs) ranged from 39 to 46 nm. The average crystallite size was increased for the initial doping (3 at.%) of Sr ions, and further increase in the doping ratio reduced the particle size due to some distortion produced in the lattice. The surface morphology of the samples and structure of the NPs were investigated using FESEM (Field Emission Scanning Electron Microscopy) and TEM (Transmission Electron Microscopy) pictures, respectively. EDX (energy-dispersive X-ray) spectroscopy confirmed the presence of strontium (Sr) in the host lattice. Photoluminescence and X-ray diffraction confirmed that the dopant ions replace some of the lattice zinc ions and that Sr2+ and Sr3+ ions coexist in the ZnO lattice. The Sr-doped ZnO exhibited violet and blue luminescence spectra at 408 nm and 492 nm, respectively. ZnO : Sr nanoparticles showed increased antibacterial activity against one gram-positive as well as one gram-negative bacteria.

Investigation of the optical properties of monocrystalline silicon with a deposited layer of spherical zinc sulfide nanoparticles

In the present work zinc sulfide (ZnS) nanoparticles (NPs) were synthesized on silicon wafer by femtosecond pulsed ablation processing of ZnS bulk target using an electrostatic field in argon gas atmosphere. The morphology, size distribution and structural characterization of obtained ZnS NPs were investigated using scanning electron microscope (SEM), dynamic light scattering (DLS) technique and X-ray diffraction (XRD). Dominant size of obtained NPs lies in the range 10-20 nm, NPs are in spherical shape, particles of other shape and agglomerates of particles are absent. XRD investigation of synthesized NPs identified hexagonal wurtzite structure. There is a structural phase transition from the sphalerite ZnS bulk (target) structure to the structural phase of wurtzite (obtained NPs).The optical characterization of synthesized by laser ablation ZnS NPs was carried out using a photoluminescence (PL) measurement. ZnS NPs show a strong broad PL emission spectra covering the entire visible electromagnetic spectra region (range from 380 to 800 nm) centered at 513.7 nm.

Structural, Magnetic, and Optical Properties of Mn2+ Doping in ZnO Thin Films

MnxZn1−xO thin films (x = 0%, 1%, 3%, and 5%) were grown on corning glass substrates using sol–gel technique. Single-phase hexagonal wurtzite structure was confirmed using X-ray diffraction. Raman analysis revealed the presence of Mn content with an additional vibrational mode at 570 cm−1. The surface morphology of the samples was observed by scanning electron microscopy which suggested that the grain size increases with an increase in Mn concentration. The optical bandgap increases with increasing Mn concentration due to a significant blueshift in UV–visible absorption spectra. The alteration of the bandgap was verified by the I–V measurements on ZnO and Mn-ZnO films. The various functional groups in the thin films were recorded using FTIR analysis. Magnetic measurements showed that MnxZn1−xO films are ferromagnetic, as Mn induces a fully polarised state. The effect of Mn2+ ions doping on MnxZn1−xO thin films was investigated by extracting various parameters such as lattice parameters, energy bandgap, resistivity, and magnetisation. The observed coercivity is about one-fifth of the earlier published work data which indicates the structure is soft in nature, having less dielectric/magnetic loss, and hence can be used as ultra-fast switching in spintronic devices.