Surface Of ZnO NRs Research Articles

The effects of nontoxic bio-based substances (egg white) on the performance and passivation of ZnO nanorods arrays-based light emitting devices

An innovative approach is proposed to passivate the existing defects from metal oxide semiconductors by functionalizing nontoxic bio-based substances. As a demonstration, we synthesized zinc oxide nanorods (ZnO NRs) using a hydrothermal method and incorporated chicken egg white (albumen) as a passivator to the defects. X-ray diffraction analysis of ZnO NRs shows enhanced quality and crystallinity features after incorporating albumen. XPS measurements were performed not only to introduce the chemical bonding between the albumen and the bare ZnO NRs but also specifically provide evidence of successful capping and defect passivation to the surface layer of ZnO NRs. It was observed that when the albumen was annealed, it formed sulfhydryl groups and disulfide bonds (which created disulfide bridges) from the chemical reaction in irreversible thermal denaturation. Steady-state photoluminescence of ZnO NRs showed two emission bands, i.e. near band-edge emission (NBE) and deep-level emission (DL). The NBE is significantly improved as compared to DL emission after capping and annealing the albumen, while the quenching of DL emission confirmed the reduced defects arising from the surface of ZnO NRs. The advantages and enhanced characteristics of the albumen-capped ZnO NRs led to fabricating a stable and highly efficient light-emitting device. This work opens the great potential of utilizing nontoxic and low-cost biomaterials in passivating the defects of metal oxide nanomaterials for the development of bio-inspired and stable optoelectronic devices.

Copper sulfide and zinc oxide hybrid nanocomposite for wastewater decontamination of pharmaceuticals and pesticides

In this work, hybrid nanocomposites of CuS QDs @ ZnO photocatalysts are fabricated through a facile microwave-assisted (MW) hydrothermal method as a green preparation process. The prepared photocatalysts (PCs) are employed under simulated sunlight (SL) for the degradation of ciprofloxacin, ceftriaxone, ibuprofen pharmaceuticals, methylene blue dye, and 2,4,5-trichlorophenoxyacetic acid (2,4-D) pesticide. The prepared photocatalysts are characterized in detail using several compositional, optical, and morphological techniques. The influence of the CuS (QDs) wt. % on morphological, structural, as well as photocatalytic degradation efficiency have been investigated. The small displacement between the (107) plane of CuS and the (102) plane of ZnO can confirmed the existence of lattice interaction, implying the formation of p-n heterojunctions. TEM and XRD results demonstrated that the CuS QDs are established and uniformly decorated on the surface of ZnO NRs, confirming the forming of an efficient CuS QDs @ ZnO heterojunction nanostructures. The CuS QDs @ ZnO hybrid nanocomposites showed enhancement in crystallinity, light absorption, surface area, separation of e–h pair and inhibition in their recombination at an interfacial heterojunction. In addition it is found that, 3 wt% CuS QDs @ ZnO has the foremost influence. The results showed improvement of photocatalytic activity of the 3% CuS QDs @ ZnO hybrid nanocomposite as compared to the bare ZnO nanorods. The impressive photocatalytic performance of CuS @ ZnO heterostructure nanorods may be attributed to efficient charge transfer. The prepared CuS QDs @ ZnO hybrid nanocomposites exhibited 100% removal for MB dye, after 45 min, and after 60 min for ibuprofen, ciprofloxacin pharmaceuticals, and 2.4.5 trichloro phenoxy acetic acid pesticide with the catalyst amount of 0.2 g/L. Although 100% removal of ceftriaxone pharmaceutical acheived after 90 min. In addition CuS QDs @ ZnO hybrid nanocomposites exhibited complete removal of COD for ibuprofen, ceftriaxone pharmaceuticals and 2.4.5 trichloro phenoxy acetic acid pesticide after 2 h with no selectivity. Briefly, 3% CuS QDs@ZnO hybrid nanocomposites can be considered as promising photoactive materials under simulated sunlight for wastewater decontamination.

Aminosilicate modified zinc oxide Nanorod-GO nanocomposite for DSSC photoanodes

Amine-functionalized ZnO nanorods@graphene oxide (ZnO-NR/NH2/GO) nanocomposites prepared by a facile solution route have been investigated through X-ray diffraction, diffuse reflectance spectra, Raman spectra, scanning electron microscopy and transmission electron microscopy. The amine-functionalized ZnO-NR/NH2/GO-2 nanocomposite exhibits very strong visible light absorption. Dye-sensitized solar cell (DSSC) made of ZnO-NR/NH2/GO-2 nanocomposite (with optimum 2 wt % GO) photoanode delivers a power conversion efficiency (PCE) of 3.76% which is much higher than the efficiency of unmodified ZnO-NR/GO photoanodes based DSSC (2.27%). The enhancement of PCE is primarily caused by the increased current density, attributed to the incorporation of aminosilicate and GO on the surface of ZnO-NRs which facilitates rapid transfer of electron from conduction band of ZnO to conducting surface of FTO. This diminished recombination of photogenerated electrons and holes improve the electron transfer at the photoanode/electrolyte interfaces.

Self-powered UV photodetector performance optimization based on Ag nanoparticles-encapsulated-ZnO nanorods by photo-deposition method

Simple and cost-effective hydrothermal technique combined with the photo-deposition method was successfully employed to synthesize silver nanoparticles-encapsulated-zinc oxide nanorods (Ag NPs/ZnO NRs) arrays on Silicon (Si) substrate for the fabrication of self-power metal-semiconductor-metal (MSM) Ultraviolet (UV) photodetector device. The Field Emission Scanning Electron Microscope (FESEM) results showed that there was a noticeable change in the morphological surface of ZnO NRs after the photo-deposition process, corroborating the presence of Ag NPs. For Ag NPs/ZnO NRs photodetector, the current-voltage (I-V) characteristics demonstrated that its conductivity was significantly enhanced compared to the photodetector without Ag NPs. For the MSM device fabricated with (Ag NPs/ZnO NRs), it has recorded a responsivity value of 42.79 A W−1, and external quantum efficiency (EQE) of 13,436.06% at 15 V bias voltage. Lastly, the modified device has a sensitivity of 18503% at 0 V bias voltage, making the device suitable as self-powered photodetectors.

ZnO@NiCo-LDH core-shell nanostructures grown on carbon cloth for high-performance flexible supercapacitor electrodes

ABSTRACT The ZnO@NiCo-LDH core-shell nanostructures on carbon cloth (CC) are synthesised by a combination of hydrothermal and electrochemical deposition method. The effects of deposition times on the morphology, structure and electrochemical properties of the product are studied. The results show that deposition times at 300 s NiCo-LDH sheets are anchored onto the surface of ZnO NRs, forming a three-dimensional (3D) interconnected thin-walled network structure. ZnO@NiCo-LDH300s electrode shows excellent electrochemical performance, such as areal capacitance of 667.3 mF cm−2 at 1 mA cm−2, and good cycle stability (86.78% capacitance retention after 2000 cycles), which may be attributed to the larger contact area and rich active sites between electrode provided by the NiCo-LDH grown on ZnO NRs. Furthermore, the asymmetric supercapacitor (ASC) is assembled with the ZnO@NiCo-LDH300s and active carbon (AC) as the electrodes, which exhibits an energy density of 0.044 mWh cm−2 at 1.17 mW cm−2.

Vertically aligned ZnO/In2S3 core/shell heterostructures with enhanced photoelectrochemical properties

ZnO/In2S3 core/shell heterostructures were successfully synthesized through a successive ion layer absorption and reaction (SILAR) method. The thickness of In2S3 shells were adjusted from 6.8 to 36.1 nm by adopting different SILAR cycles. Compared with pure ZnO NRs, the ZnO/In2S3 core/shell NRs presented better light absorption, higher photocurrent density and enhanced incident photon-to-current conversion efficiency (IPCE). Both the highest photocurrent density and IPCE of obtained ZnO/In2S3 core/shell heterostructures were almost three times higher than that of pristine ZnO NRs. The PL spectra, i–t curves, EIS plots, Mott–Schottky plots and ECSA curves were also recorded to investigate the influence of the In2S3 deposition on the photoelectrochemical (PEC) performance of ZnO NRs. The In2S3 nanoparticles deposited on the surface of ZnO NRs enhanced the light absorption of the heterostructures and facilitated the separation of photogenerated electron–hole pairs, eventually resulting in the enhanced PEC performance. The preparation of ZnO/In2S3 core/shell heterostructures by the simple SILAR method would increase the possibility for its practical application of photoelectrodes in the future.

Reusability of metals/metal oxide coupled zinc oxide nanorods in degradation of rhodamine B dye

Purpose This paper aims to investigate the reusability of metal/metal oxide-coupled ZnO nanorods (ZnO NRs) to degrade rhodamine B (RhB). Design/methodology/approach ZnO NRs particles were synthesized by precipitation method and used to remove various types of metal ions such as Cu2+, Ag+, Mn2+, Ni2+, Pb2+, Cd2+ and Cr2+ ions under UV illumination. The metal/metal oxide-coupled ZnO NRs were characterized by scanning electron microscope, X-ray diffraction and UV-Vis diffuse reflectance. The photodegradation of RhB dye by these metal/metal oxide-coupled ZnO NRs under UV exposure was assessed. Findings The metal/metal oxide-coupled ZnO NRs were successfully reused to remove RhB dye in which more than >90% of RhB dye was degraded under UV exposure. Furthermore, the coupling of Ag, CuO, MnO2, Cd and Ni particles onto the surface of ZnO NRs even enhanced the degradation of dye. The dominant reactive species involved in the degradation of RhB dye were •OH- and •O2−-free radicals. Research limitations/implications The coupling of metal/metal oxide onto the surface of ZnO NRs after metal ions removal could affect the photocatalytic performance of ZnO NRs in the degradation of organic pollutants in subsequent stage. Practical implications A good reusability performance of metal/metal oxide-coupled ZnO NRs make ZnO NRs become a desirable photocatalyst material for the treatment of wastewater, which consists of both heavy metal ions and organic dyes. Originality/value Metal/metal oxide coupling onto the surface of ZnO NRs particles improved subsequent UV-assisted photocatalytic degradation of RhB dye.

ZnO-SiO2 nanohybrid decorated sustainable geopolymer retaining anti-biodeterioration activity with improved durability

Geopolymer, consists of industrial by-product fly ash, and alkaline activator, possesses similar strength along with durability like conventional cement composite, is an alternative construction substantial of Portland cement in current scenario. Corrosion of the concrete materials resulted mainly from the chemical degradation. Besides chemical degradation, biogenic-deterioration is also another alarming issue especially in the sewer systems, bridge piers, several pipelines and offshore platforms and the need to act on it is long-standing. In this study, application of zinc oxide–silica nanohybrid based sustainable geopolymer (GMZnO–Si) has been investigated for the development of a sustainable, anti-biodeteriorate cementitious material having significant mechanical strength and durability. Initially, zinc oxide nano-rods (ZnO NRs) have been synthesized and spherical silica nanoparticles were decorated on the surface of ZnO NRs. The ZnO-SiO2 composite was characterized by various techniques (FTIR, XRD, FESEM, EDS, TEM, and XPS). Ambient temperature cured GMZnO–Si mortar was further explored in terms of mechanical strength, durability, mechanistic anti-microbial (E. coli, S. aureus, A. niger) influences. Mechanical properties of GMZnO–Si are found significantly higher than that of control samples. MIC, MBC, and MFC results demonstrate enhanced anti-microbial efficacy of GMZnO-Si. Inner permeability assay, reactive oxygen species generation and microscopic images of cell wall rupture and DNA damage studies supported the detailed understanding of anti-microbial activities. These experimental findings suggest that incorporation of ZnO-SiO2 hybrid in geopolymer will pave the way for biodeterioration resistant concrete with enhanced mechanical and structural behaviour.

Defect modification to improve field emission of ZnO NRs by coating ultrathin Pt films

Ultrathin platinum (Pt) films are coated on the surface of ZnO NRs grown on Fe alloy substrates and display excellent field emission performance with the turn-on field Eto as low as 0.40 V/μm and the threshold field Ethr down to 2.62 V/μm. By coating ultrathin Pt films on the surface of the ZnO NRs, this not only helps to modify the linear defects on the outer surface of ZnO NRs, but also suppresses random electron emission along the defect directions. At an external electric field, a large amount of electrons are transported to the top of ZnO NRs where a highly localized electric field is caused, which results in enhanced field emission. Besides, ZnO NRs grown on Fe alloy substrates have a low interfacial contact resistance and intend to reduce the barrier between the substrate and the ZnO. Meanwhile, metal Pt films can help to obtain emitting centers that ensure highly conductive paths for the electrons from the ZnO NRs towards the vacuum, which effectively decrease the barrier between the ZnO and the vacuum. Finally, a schottky contact of Fe-ZnO and matched Fermi levels of ZnO-Pt contribute to the enhanced current emission efficiency. This work may help the development of the practical electron sources and advanced devices based on ZnO field emitters.

Sensitive detection of hydrocarbon gases using electrochemically Pd-modified ZnO chemiresistors.

Pristine and electrochemically Pd-modified ZnO nanorods (ZnO NRs) were proposed as active sensing layers in chemiresistive gas sensors for hydrocarbon (HC) gas detection (e.g., CH4, C3H8, C4H10). The presence of Pd nanoparticles (NPs) on the surface of ZnO NRs, obtained after the thermal treatment at 550 °C, was revealed by morphological and surface chemical analyses, using scanning electron microscopy and X-ray photoelectron spectroscopy, respectively. The effect of the Pd catalyst on the performance of the ZnO-based gas sensor was evaluated by comparing the sensing results with those of pristine ZnO NRs, at an operating temperature of 300 °C and for various HC gas concentrations in the range of 30–1000 ppm. The Pd-modified ZnO NRs showed a higher selectivity and sensitivity compared to pristine ZnO NRs. The mean sensitivity of Pd-modified ZnO NRs towards the analyzed HCs gases increased with the length of the hydrocarbon chain of the target gas molecule. Finally, the evaluation of the selectivity revealed that the presence or the absence of metal nanoparticles on ZnO NRs improves the selectivity in the detection of specific HCs gaseous molecules.

Synthesis of ZnO nanorods-Au nanoparticles hybrids via in-situ plasma sputtering-assisted method for simultaneous electrochemical sensing of ascorbic acid and uric acid

In this study, ZnO nanorods-Au nanoparticles (ZnO NRs-Au NPs) hybrids were prepared using an in-situ plasma sputtering-assisted method without any template. Characterization results from scanning electron microscopy, high-resolution transmission electron microscopy, and energy dispersive X-ray spectroscopy showed that Au NPs are highly dispersed and tightly anchored on the surface of ZnO NRs. The size and surface coverage of Au NPs were well controlled by plasma sputtering time. Moreover, the hybrids exhibited excellent electrocatalytic properties towards oxidation of ascorbic acid (AA) and uric acid (UA) due to large surface area of Au NPs and ZnO NRs, and thus can be used as electrochemical sensors. Differential pulse voltammetry results showed that AA and UA could be detected simultaneously by ZnO NRs-Au NPs hybrids modified glassy carbon electrode. The linear ranges for AA and UA are 0.1 to 4 mM and 0.01 to 0.4 mM, respectively. The results suggest promising future applications in clinical diagnosis.

Investigation on visible-light photocatalytic degradation of 2,4-dichlorophenoxyacetic acid in the presence of MoO3/ZnO nanorod composites

Nanoscaled MoO3 particles loaded on ZnO nanorods (ZnO NRs) were synthesized via a hydrothermal-precipitation method. X-ray diffraction, field emission-scanning electron microscopy, high resolution transmission electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, UV–vis absorption and photoluminescence studies were used to characterize the structures, morphologies and optical properties of the composites. The results showed that pure orthorhombic phase of α-MoO3 nanoparticles with average sizes of 15–21nm were well dispersed on the surface of ZnO NRs. The MoO3/ZnO NR composites also showed high charge separation efficiency and ·OH generation ability as evidenced by their photoluminescence spectra. The photocatalytic studies revealed that the MoO3/ZnO NRs showed superior visible-light degradation rate for herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) compared with the pure ZnO NRs. Such enhancement might be attributed to the high separation efficiency of photogenerated electron–hole pairs based on the cooperative roles between bi-components of MoO3 and ZnO NRs. The photocatalytic studies also showed that various parameters such as the MoO3 content in the composite, MoO3/ZnO NRs amount, initial 2,4-D concentration and solution pH exerted their individual influence on the 2,4-D degradation. Moreover, the MoO3/ZnO NRs could be easily recovered and reused due to their one-dimensional nanostructural property.

A white-emitting ZnO–Au nanocomposite and its SERS applications

We reported a simple method to synthesize ZnO–Au nanocomposites (hybrid A) by combining hydrothermal and electric beam evaporation deposition method. It was found that Au deposition time takes an important role in the generation of Au nanoparticles. Changing Au deposition time makes the thickness of Au formed on ZnO nanorods increase from 10nm to 70nm. On the other hand, white-emitting ZnO–Au nanocomposites (hybrid B) were obtained after treating hybrid A with HCl solution. Thanks to the covering of Au film and acid etching, it induces many defects on the surface of ZnO NRs, and largely enhances the visible emission of surviving ZnO and finally generates white emission on Au mesocrystals (hybrid B). Both of the ZnO–Au hybrids (A and B) can be applied as substrates in surface-enhanced Raman scattering (SERS) measurement. A typical probe molecule, 4-ATP was used to test the SERS activity of the ZnO–Au composites and the results indicated good Raman activity on the substrates.