ZnO Nanosheets Research Articles

BiOBr/SnO2/ZnO Catalyst With Interfacial Effect Enhanced Photocatalytic Degradation of Organic Dye

ABSTRACTBiOBr nanosheets were loaded onto SnO2 quantum dots, ZnO nanosheets, and SnO2/ZnO‐2 (SZ‐2) to form different heterojunction photocatalysts by sonochemistry, respectively. The photocatalytic activity of the prepared photocatalysts was evaluated by degrading the target dye Rhodamine B (RhB). The results showed that the degradation efficiency of BiOBr/SnO2/ZnO (BSZ) for RhB reached 97.5% at 80 min. The significant increase in catalytic activity of BSZ was attributed to the synergistic and interfacial effects among the three materials. Combined with the radical trapping experiments, it can be concluded that the catalytic mechanism of BSZ as a dual Z‐type heterojunction.

Constructing 2D Porous ZnO Gas Sensors Based on Polyvinylpyrrolidone-Assisted Zn-MOF Nanosheets for NO2 Detection.

Two-dimensional (2D) ZnO nanomaterials are promising for gas sensing, because of their large surface area, abundant active sites, and rapid charge transfer. However, it is challenging to prepare 2D ZnO nanosheet gas sensors with high sensing performance, due to the tight interlayer stack and low adsorptive property of ZnO for NO2 molecules. Herein, we synthesized Zn-MOF nanosheets employing polyvinylpyrrolidone (PVP) as the structure-directing agent, further through pyrolysis of the Zn-MOF to obtain 2D ZnO nanosheet gas sensors. As anticipated, the 2D ZnO gas sensors exhibited high sensitivity and selectivity for NO2, and the optimal sample could achieve a response value of 162 at the working temperature of 160 °C, which is 10 times higher than that of pristine ZnO. Meanwhile, experimental and DFT results showed that PVP plays critical roles in the lateral lattice growth of 2D Zn-MOF nanosheets, while the existence of PVP makes the ZnO gas sensors with rich porous property and more oxygen vacancy after the pyrolysis process, which promoted the adsorption, activity, and surface reaction for NO2 molecules. It provides a new approach for the application of 2D ZnO nanosheets in the NO2 detection field.

High-Performance Supercapacitor Stability and Capacitance Enhancements Using Ultrasonic-Assisted Synthesis of Cr2O3-ZnO Nanocomposites

An extensive examination of composite electrode materials is essential for advancing supercapacitors with elevated specific capacitance and outstanding stability. This study introduces a straightforward and effective technique that utilizes ultrasonic-assisted chemical precipitation to create a nanocomposite of Cr2O3 NPs bonded to ZnO nanosheets (Cr2O3-ZnO NCs). XRD spectra indicate that Cr2O3 is consistent with JCPDS card No. 38-1479, whilst ZnO nanosheets are in agreement with JCPDS card No. 36-1451. HR-TEM analysis reveals that the Cr2O3 NPs in the Cr2O3-ZnO NCs have diameters ranging between 14.5–16.7 nm. The CV profiles within 10–200 mV/s scan rates exhibit well-defined redox pair reactions with no distortion in the integrated area. According to the studies of Trasatti and Dunn’s, 90.94% of the charge distribution is caused by capacitance, whereas 9.05% is a result of diffusion. The GCD plots demonstrate that Cr2O3-ZnO NCs exhibit a 926.6 F/g (specific capacitance) when subjected to a current density of 1 A/g. Furthermore, these NCs retain 83.3% of their initial capacitance even after undergoing 2000 charge and discharge cycles. The improved achievement is ascribed to the existence of Cr2O3 NPs which boost conductivity, promote pseudocapacitive processes, and hinder the aggregation of ZnO nanosheets by serving as spacers. The features of Cr2O3-ZnO NCs make them highly promising for use in supercapacitor applications.

Microwave-assisted CuO-modified porous ZnO nanosheet for photocatalytic degradation of organic pollutants and antibacterial inactivation

The present study investigated the development of a porous ZnO/CuO photocatalyst for photocatalytic dye degradation and antibacterial inactivation of bacteria. Porous ZnO nanosheets are prepared by calcinating inorganic-organic ZnS(en)0.5. Further, CuO was integrated on a porous ZnO nanosheet using the microwave (MW)-assisted synthesis technique. Additionally, the effect of CuO at different concentrations on the photocatalytic activity of CuO/ZnO was investigated. Under 1.5G light illumination, an optimized ZnO/CuO-5 photocatalyst exhibited higher degradation efficiencies of 99.3%, 98%, and 99% for orange II dye, methylene blue (MB), and Eosin-Y respectively. The optimized photocatalyst exhibited inactivation efficiencies of 98% and 90% towards Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria, after 3h. The enhanced photocatalytic activity was attributable to a porous structure, extended visible light responsiveness, and delayed electron-hole recombination in nanostructured CuO/ZnO photocatalysts. Moreover, radical scavenger tests confirmed that superoxide radicals (•O2−) accompanied most degradation, followed by holes (h+) as minor factors. Our work suggests a simple photocatalytic interfacial engineering technique based on porous ZnO/CuO nanostructures to decompose organic chemicals and inactivate microorganisms in wastewater sources.

Pt-functionalized ZnO nanosheets gas sensor for highly sensitive detecting of methane

Pt-functionalized ZnO nanosheets gas sensor for highly sensitive detecting of methane

Porous Lithium‐Doped ZnO Nanosheets with Abundant Oxygen Vacancies for Accelerating Li+ Transport in Solid‐State Composite Electrolyte

The flexible Li‐ion conducting solid polymer electrolyte (SPE) endows a stable long‐term cycling to Li‐metal anode to significantly improve the energy density of solid‐state lithium batteries; however, the practical application of the SPE is limited by its low ionic conductivity and small critical current density for dendrite nucleation. Herein, Li+‐doped porous ZnO (LZO) nanosheets are introduced into the poly(ethylene oxide) (PEO)‐based SPE, releasing more mobile Li ions for faster Li‐ion transport due to the enhanced interaction between abundant oxygen vacancies and anions of Li‐salt. As a result, the optimized LZO/PEO composite polymer electrolyte exhibits a high Li‐ion conductivity of 3.3 × 10−4 S cm−1 at 50 °C, 4 times higher than the pure PEO electrolyte. The solid‐state LiFePO4/Li cell shows extraordinarily long‐term stable cycling, up to 1500 cycles with a high average Coulombic efficiency of 99.8%. In addition, the cycling stability of the high‐voltage LiNi0.8Mn0.1Co0.1O2 (NMC811)/Li cell was also obviously improved compared to the nondoped pure PEO electrolyte, indicating the positive contribution of the LZO on interfacial stability.

Low-cost Ag/ZnO nanosheets arrays as sensitive and recyclable surface-enhanced Raman scattering substrates

The development of surface-enhanced Raman scattering (SERS) substrate based on metal/semiconductor nanostructured platforms has emerged as a promising technique for achieving highly sensitive and recyclable detection across various fields, including environmental monitoring, food safety, biomedical diagnostics, and the preservation of cultural heritage. However, the design and fabrication of cost-effective metal/semiconductor nanostructures suitable for SERS substrates remain a formidable challenge. In this study, a low-cost, recyclable SERS substrate based on Ag nanoparticle decorated ZnO nanosheets (Ag/ZnO NSs) arrays was developed using hydrothermal growth and photochemical reduction approaches. The optimized Ag/ZnO NSs arrays demonstrated local electric field enhancement and multi-path charge transfer, ensuring an enhancement factor of 107 and a detection limit of 10−10 mol/L for crystal violet molecules. This research not only sheds light on the economical production of metal/semiconductor SERS substrates but also paves the way for a broader spectrum of SERS-based detection applications in diverse fields.

An efficient Au/ZnO catalyst for the photocatalytic conversion of methane to formaldehyde

The photocatalytic oxidation of methane to value-added chemical products under mild conditions is crucial for resource utilization and environmental protection. However, inefficient generation of reactive oxygen species partially limits methane activation. To tackle this issue, we have developed highly dispersed Au-modified ZnO nanosheets through photo-deposition method for the photocatalytic oxidation of methane to formaldehyde. The optimized Au0.1/ZnO catalyst (0.1 wt% Au on ZnO) achieves a HCHO yield of 19.14 μmol h−1 with a selectivity of 87.94 %. Electron paramagnetic resonance, Raman, X-ray photoelectron spectroscopy and density functional theory show that Au enhances the concentration of oxygen vacancies (OVs) in ZnO. This enhancement is attributed to a strong interaction between Au and ZnO, which facilitates the transfer of electrons from the ZnO surface to Au. Under irradiation, Au and OVs function as hole and electron acceptors, respectively. This interaction promotes carrier separation, reduces charge recombination, enhances oxygen adsorption, and effectively generates reactive oxygen species, such as ·OH. Subsequently, CH4 is oxidized to ·CH3 by holes from Au. Concurrently, O2 is reduced by electron from OVs, following the pathways O2 → OOH→H2O2 → ·OH. The rapid oxidation of CH3OH by ·CH3 and ·OH results in the formation of HCHO.

Performance of different Ga-doped ZnO nanosheets ultraviolet photodetectors: experimental and theoretical studies

Performance of different Ga-doped ZnO nanosheets ultraviolet photodetectors: experimental and theoretical studies

Fabrication of Highly Sensitive and Selective Nitrite Colorimetric Sensor Based on the Enhanced Peroxidase Mimetic Activity of Using Acetic Acid Capped Zinc Oxide Nanosheets.

Nitrite ions (NO2-), as one of the leading type-A inorganic-anion, showing significant-effects in the aquatic environment and also to humans health. Whereas, the higher uptake causes detrimental threat to human health leading to various chronic diseases, thus demanding efficient, reliable and convenient method for its monitoring. For this purpose, in the present research study we have fabricated the mimetic nonozyme like catalyst based colorimetric nitrite sensor. The acetic acid capped Zinc Oxide (ZnO) nanosheets (NSs) were introduce as per-oxidase mimetic like catalyst which shows high efficiency towards the oxidative catalysis of colorless tetramethylbenzidine (TMB) to oxidized-TMB (blue color) in the presence of Hydrogen-peroxide (H2O2). The present nitrite ions will stimulate the as formed oxidized-TMB (TMBox), and will caused diazotization reaction (diazotized-TMBox), which will not only decreases the peak intensity of UV-visible peak of TMBox at 652nm but will also produces another peak at 446nm called as diazotized-TMBox peak, proving the catalytic reaction between the nitrite ions and TMBox. Further, the prepared colorimetric sensor exhibits better sensitivity with a wider range of concentration (1 × 10-3-4.50 × 10-1 µM), lowest limit of detection (LOD) of 0.22 ± 0.05 nM and small limit of quantification (LOQ) 0.78 ± 0.05 nM having R2 value of 0.998. Further, the colorimetric sensor also manifest strong selectivity towards NO2- as compared to other interference in drinking water system. Resultantly, the prepared sensor with outstanding repeatability, stability, reproducibility, re-usability and its practicability in real water samples also exploit its diverse applications in food safety supervision and environmental monitoring.

Highly Specific Aptamer-Antibody Birecognized Sandwich Module for Ultrasensitive Detection of a Low Molecular Weight Compound.

Herein, the aptamer-antibody sandwich module was first introduced to accurately recognize a low molecular weight compound (mycotoxin). Impressively, compared with the large steric hindrance of a traditional dual-antibody module, the aptamer-antibody sandwich with low Gibbs free energy and a low dissociation constant has high recognition efficiency; thus, it could reduce false positives and false negatives caused by a dual-antibody module. As a proof of concept, a sensitive electrochemiluminescence (ECL) biosensor was constructed for detecting mycotoxin zearalenone (ZEN) based on an aptamer-antibody sandwich as a biological recognition element and porous ZnO nanosheets (Zn NSs) supported Cu nanoclusters (Cu NCs) as the signal transduction element, in which the antibody was modified on the vertex of a tetrahedral DNA nanostructure (TDN) with a rigid structure to increase the kinetics of target recognition for promoting the detection sensitivity. Moreover, the Cu NCs/Zn NSs exhibited an excellent ECL response that was attributed to the aggregation-induced ECL enhancement through electrostatic interactions. The sensing platform achieved trace detection of ZEN with a low detection limit of 0.31 fg/mL, far beyond that of the enzyme-linked immunosorbent assay (ELISA, the current rapid detection method) and high-performance liquid chromatography (HPLC, the national standard detection method). The strategy has great application potential in food analysis, environmental monitoring, and clinical diagnosis.

Controllable synthesis of cross-linked 3D ZnO nanosheet toward a nitrite electrochemical sensor

A 3D cross-linked ZnO (cl-ZnO) nanosheets were prepared via a simple one-pot hydrothermal approach, and then characterized by a series of modern advanced technique including XRD, SEM, TEM and XPS. This nanomaterial was used to modify the glass carbon electrode (GCE), obtaining an electrochemical sensor (cl-ZnO/GCE) of which the electrochemical properties were studied using various electrochemical techniques such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The sensor exhibited remarkably enhanced electrocatalytic activity for nitrite ions (NO2-) in comparison to that of the commercially available ZnO-modified GCE. Two electrochemical techniques, including chronoamperometry (CA) and linear sweep voltammetry (LSV) were adopted to test the determination performance of the sensor for nitrite, it exhibited a good linear relationship within the range of 0.8 μmol·L-1 - 0.462 mmol·L-1 and 0.608 - 7.84 mmol·L-1 evaluated by CA, the limit of detection (LOD) and sensitivity for NO2- were 0.26 μmol·L-1 (S/N = 3) and 824.6 µA (mmol·L-1)-1cm-2, respectively. For LSV, the two linearity responses of 0.95 μmol·L-1- 0.515 mmol·L-1 and 0.667 mmol·L-1- 5.41 mmol·L-1, high sensitivity of 1336.1 µA (mmol·L-1)-1cm-2 with low LOD of 0.32 μmol·L-1 were gained. This sensor can be employed to detect trace amount of NO2- in ham sausage and pickled vegetables successfully, supporting an insight and strategy for more sensitive nitrite electrochemical sensor.

Machine-learning-assisted orbital angular momentum recognition using nanostructures

The recognition of orbital angular momentum (OAM) in light beams holds significant importance in optical communication. The majority of current OAM recognition techniques are highly sensitive to stringent alignment issues. The speckle-based OAM recognition method reported in J. Opt. Soc. Am. A 39, 759 (2022)JOAOD61084-752910.1364/JOSAA.446352 is alignment-free in the transverse direction of light propagation and has been shown to operate successfully in the far-field region using macrostructures. This study introduces a proof-of-concept for speckle-learned OAM recognition with nanostructures, relaxing the strict alignment requirements in both the transverse and along the direction of light propagation. When the OAM beam interacts with random inhomogeneities at micron and/or nanoscale, it generates an OAM speckle field. Initially, a comprehensive examination of the dynamic evolution of OAM speckle fields, ranging from near field to far field, has been conducted using a ground glass diffuser, featuring random phase inhomogeneities at the micron scale. Subsequently, the investigation proceeds to randomly grown ZnO nanosheets on an aluminum substrate. To achieve rapid and precise OAM recognition, a tailored three-layer CNN is trained and tested on OAM speckle fields ranging from near field to far field to attain an accuracy surpassing 92%. This research expands the technique’s applicability, enabling recognition of OAM across near-field to far-field regimes, while leveraging micro- to nanostructures.

Molecularly imprinted polymer-based extended-gate field-effect transistor chemosensors for selective determination of antiepileptic drug.

Ultrathin molecularly imprinted polymer (MIP) films were deposited on the surfaces of ZnO nanorods (ZNRs) and nanosheets (ZNSs) by electropolymerization to afford extended-gate field-effect transistor sensors for detecting phenytoin (PHT) in plasma. Molecular imprinting efficiency was optimized by controlling the contents of functional monomers and the template in the precursor solution. PHT sensing was performed in plasma solutions with various concentrations by monitoring the drain current as a function of drain voltage under an applied gate voltage of 1.5V. The reliability and reproducibility of the fabricated sensors were evaluated through a solution treatment process for complete PHT removal and PHT adsorption-removal cycling, while selectivity was examined by analyzing responses to chemicals with structures analogous to that of PHT. Compared withthe ZNS/extracted-MIP sensor and sensors with non-imprinted polymer (NIP) films, the ZNR/extracted-MIP sensor showed superior responses to PHT-containing plasma due to selective PHT adsorption, achieving an imprinting factor of 4.23, detection limit of 12.9ng/mL, quantitation limit of 53.0ng/mL, and selectivity coefficients of 3-4 (against tramadol) and ~ 5 (against diphenhydramine). Therefore, we believe that the MIP-based ZNR sensing platform is promising for the practical detection of PHT and other drugs and evaluation of their proper dosages.

Defect-Free, Few-Atomic-Layer Thin ZnO Nanosheets with Superior Excitonic Properties for Optoelectronic Devices.

Two-dimensional (2D) wide bandgap materials are gaining significant interest for next-generation optoelectronic devices. However, fabricating electronic-grade 2D nanosheets from non-van der Waals (n-vdW) oxide semiconductors poses a great challenge due to their stronger interlayer coupling compared with vdW crystals. This strong coupling typically introduces defects during exfoliation, impairing the optoelectronic properties. Herein, we report the liquid-phase exfoliation of few-atomic-layer thin, defect-free, free-standing ZnO nanosheets. These micron-sized, ultrathin ZnO structures exhibit three different orientations aligned along both the polar c-plane as well as the nonpolar a- and m-planes. The superior crystalline quality of the ZnO nanosheets is validated through comprehensive characterization techniques. This result is supported by density functional theory (DFT) calculations, which reveals that the formation of oxygen vacancies is energetically less favorable in 2D ZnO and that the c-plane loses its polarity upon exfoliation. Unlike bulk ZnO, which is typically dominated by defect-induced emission, the exfoliated nanosheets exhibit a strong, ambient-stable excitonic UV emission. We further demonstrate the utility of solution processing of ZnO nanosheets by their hybrid integration with organic components to produce stable light emitting diodes (LEDs) for display applications.

High-Rate and Selective C2H6-to-C2H4 Photodehydrogenation Enabled by Partially Oxidized Pdδ+ Species Anchored on ZnO Nanosheets under Mild Conditions.

Photocatalytic C2H6-to-C2H4 conversion is very promising, yet it remains a long-lasting challenge due to the high C-H bond dissociation energy of 420 kJ mol-1. Herein, partially oxidized Pdδ+ species anchored on ZnO nanosheets are designed to weaken the C-H bond by the electron interaction between Pdδ+ species and H atoms, with efforts to achieve high-rate and selective C2H6-to-C2H4 conversion. X-ray photoelectron spectra, Bader charge calculations, and electronic localization function demonstrate the presence of partially oxidized Pdδ+ sites, while quasi-in situ X-ray photoelectron spectra disclose the Pdδ+ sites initially adopt and then donate the photoexcited electrons for C2H6 dehydrogenation. In situ electron paramagnetic resonance spectra, in situ Fourier transform infrared spectra, and trapping agent experiments verify C2H6 initially converts to CH3CH2OH via ·OH radicals, then dehydroxylates to CH3CH2· and finally to C2H4, accompanied by H2 production. Density-functional theory calculations elucidate that loading Pd site can lengthen the C-H bond of C2H6 from 1.10 to 1.12 Å, which favors the C-H bond breakage, affirmed by a lowered energy barrier of 0.04 eV. As a result, the optimized 5.87% Pd-ZnO nanosheets achieve a high C2H4 yield of 16.32 mmol g-1 with a 94.83% selectivity as well as a H2 yield of 14.49 mmol g-1 from C2H6 dehydrogenation in 4 h, outperforming all the previously reported photocatalysts under similar conditions.

Understanding the role of ZnO nanosheet surface in photocatalytic dye degradation: The key to effective wastewater treatment

The current study proposes an introduction of interfering ions to the reaction medium as a simple way for obtaining efficient visible-light driven photocatalysts with active surface based on ZnO nanosheets. 9 samples with different morphological and structural parameters were obtained via simple and inexpensive precipitation and hydrothermal methods. XRD, SEM, FTIR, SSA, XPS, Raman, absorption spectra and DLS methods were used for ZnO nanosheet characterisation. An original approach was used to determine the amount of defects by processing Raman spectra via software specially designed for this purpose. XPS was used to estimate an overall amount of oxygen vacancies in the samples, and the DFT method was employed to model oxygen vacancies in the crystal structure. The latter were verified via absorption spectra. The most effective sample showed a dye degradation efficiency of 94 % after 60 min of irradiating by a common LED lamp available in a local store. The kinetic studies showed that the rate of adsorption and photodegradation depends on the DFT-calculated “surface-dye” interaction energy. Consequently, by regulating the ratio of ZnO nanosheet surface parameters, adsorption and photodegradation efficiency against a particular dye can be improved.

An efficient ZnO and Ag/ZnO honeycomb nanosheets for catalytic green one-pot synthesis of coumarins through Knoevenagel condensation and antibacterial activity

Abstract This study pioneers the synthesis of porous Ag/ZnO nanosheets, focusing on their role as a catalyst in Knoevenagel condensation. Notably, these nanosheets display exceptional catalytic efficacy and captivating antibacterial properties. The research delves into the Ag/ZnO catalyst’s recyclability and proposes a potential reaction mechanism, marking the first comprehensive exploration of Knoevenagel condensation on porous Ag/ZnO nanosheets. Key findings underscore the successful synthesis of coumarin derivatives using various o-hydroxy benzaldehyde and 1,3-dicarbonyl compounds, with nano-Ag/ZnO serving as a catalyst via a monomode microwave-assisted approach. X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), Transmission Electron Microscopy (TEM) and UV–Vis spectroscopy were used in conjunction with other physicochemical methods to characterize the synthesized catalytic samples. The method boasts advantages such as high product yields, brief reaction durations, and the ability to reuse the catalyst for multiple cycles. The Ag/ZnO nanosheets, functioning as an acid catalyst, activate carbonyl groups and facilitate their interaction with methylene-containing active molecules. In addition, antibacterial activity assessments demonstrate the superior effectiveness of Ag/ZnO nanocomposites compared to ZnO nanosheets against Staphylococcus aureus germs. This multifaceted study not only advances catalytic synthesis but also unveils promising biological applications of porous Ag/ZnO nanosheets.

Hydrothermal synthesis of Z-type SnO2 quantum dot-modified ZnO nanosheets with enhanced photocatalytic activity

Hydrothermal synthesis of Z-type SnO2 quantum dot-modified ZnO nanosheets with enhanced photocatalytic activity

Enhanced Photocatalytic Activity of V2C MXene-Coupled ZnO Porous Nanosheets with Increased Surface Area and Effective Charge Transfer.

Photocatalysis performs excellently when degrading organic pollutants, but the photocatalytic degradation rate is not high for most photocatalysts due to their narrow sunlight adsorption range and high recombination rate of electron hole pairs. Herein, we use V2C-MXene with a wide sunlight adsorption range to couple ZnO porous nanosheets and form ZnO/MXene hybrids using a facile electrostatic self-assembly method. The ZnO/MXene hybrids acquired demonstrated improved photochemical efficiency in breaking down methylene blue (MB) when contrasted with porous ZnO nanosheets. The degradation rate of MB reached 99.8% under UV irradiation for 120 min after the ZnO/MXene hybrid formation, while 38.6% was attained by the ZnO porous nanosheets. Moreover, photodegradation rate constants (k) were calculated as 3.05 × 10-3 and 5.42 × 10-2 min-1 for ZnO porous nanosheets and ZnO/MXene hybrids, respectively, indicating that the photodegradation performance was enhanced by 17.8 times after the modification of V2C. This was probably because the modification of V2C can increase the specific surface area to provide more sites for MB adsorption, widen the sunlight adsorption range to produce good photothermal effect, and facilitate the transfer of photogenerated carriers in ZnO to promote the reaction of more photogenerated carriers with MB. Hence, this work offers a simple approach to creating effective photocatalysts for breaking down organic contaminants.