ZnO Heterojunction Research Articles

Novel N-doped ZnO and O-doped g-C₃N₄ heterojunction: Enhanced photocatalytic degradation and robust electrochemical biosensing of ascorbic acid

Novel N-doped ZnO and O-doped g-C₃N₄ heterojunction: Enhanced photocatalytic degradation and robust electrochemical biosensing of ascorbic acid

ZnO@In2O3 Core-Shell Heterojunctions Constructed With ZIF-8 and MIL-68 (In) for Improving Photogenerated Carrier Transfer Process.

The realization of fast carrier transport can effectively enhance photocatalytic performance. A core-shell structure of ZnO and In2O3 is successfully constructed by using MIL-68 (In) and ZIF-8 as a substrate, forming a heterojunction. This MOF-derived core-shell heterojunction inherits the advantages of ZIF-8, with pores facilitating carriers transfer to the surface for reactions and a large specific surface area providing more active sites. This Z-scheme heterojunction of ZnO and In2O3 can effectively separate and improve the utilization of photogenerated carriers. The well-designed interface of the core-shell structure achieves the rapid transfer of photogenerated carriers. The photocatalytic degradation capability of ZnO@ In2O3 is enhanced by the synergistic effect of Z-scheme heterojunction and core-shell structure. This work provides insight into the investigation of constructing core-shell heterojunctions.

High Performance Self‐Powered p+‐GaN/n−‐ZnO/Au UV Heterojunction Phototransistor with 3D Interconnected ZnO Nanowire Network for Solar‐Blind Imaging and Optical Communication

AbstractHeterojunction phototransistor (HPT) is considered the most promising detector technology in weak ultraviolet (UV) signal detection due to its inherent internal gain through transistor action. However, achieving high‐performance self‐powered UV HPTs remains a significant challenge. In this study, a high‐performance self‐powered p+‐GaN/n−‐ZnO/Au UV HPT with ZnO serving as the floating base is cleverly designed. The device features a unique back‐to‐back configuration of the p+‐GaN/n−‐ZnO heterojunction and n−‐ZnO/Au Schottky junction, along with an ultrathin ZnO base layer of a 3D nanowire network structure. This design enables the fabricated p+‐GaN/n−‐ZnO/Au UV HPT to operate in a self‐powered mode with exceptional performance metrics. Under zero bias, the device exhibits outstanding characteristics including ultralow dark current of 1.7 × 10−13 A, remarkable Iphoto/Idark ratio of 106, fast response speed (tr = 150 µs / tf = 250 µs), high responsivity of 9.74 A W−1, and detectivity of 1.58 × 1014 Jones, representing the best result achieved for UV HPTs thus far at zero bias. Moreover, the fabricated UV HPT is successfully demonstrated in solar‐blind imaging and UV communication systems without the need for an external power supply. This work presents effective and practical design strategies for achieving high‐performance self‐powered UV HPTs.

High ultraviolet gain in Ga2O3/ZnO heterojunction photodetector based on MSM structure

Amorphous Ga2O3 (a-Ga2O3) has attracted extensive attention due to its simple preparation process and low cost, but the extension of photoelectron lifetime caused by the trap state inhibits the responsiveness of a-Ga2O3 photodetector (PD), and how to improve the ultraviolet (UV) gain of a-Ga2O3 based PD is still a challenge. In this study, an a-Ga2O3/ZnO heterojunction PD based on metal-semiconductor-metal (MSM) structure was designed and fabricated by radio frequency magnetron sputtering (RFMS), and a high-concentration electron transport channel was formed by using carrier multiplication and specific band structure in the high-field region of MSM structure, which achieved high optical gain and extraordinary optical detection ability. In the UVC-UVA band, the device has a peak responsivity of 1.59 A W−1 and a high light-dark ratio, EQE and D* of 1×104, 647 % and 3.6×1012 Jones under 5 V, respectively. In particular, compared to ZnO PD and a-Ga2O3 PD, the responsivity of the device is improved by a factor of 21 and 90, respectively. This study provides a new and effective method for the significant improvement of a-Ga2O3 based UV photoelectric detection performance.

Photo-rechargeable zinc-ion battery using highly ordered and vertically oriented C@VO2/ZnO microrod arrays

Development of photo-rechargeable batteries is a potential resolution for supplying off-grid solar power system in remote locations. Here, we present a photo-rechargeable zinc-ion battery (PRZIB) that can be directly recharged by the light without external photovoltaic cells and controllers. A highly ordered and vertically oriented ZnO microrod arrays (ZMRAs) were prepared using hydrothermal method in micron-scale patterned ZnO substrate defined by lithographic technology, which are used to incorporate with carbon encased vanadium oxide (C@VO2) nanocomposite to form a large specific surface area of three-dimensional network of C@VO2/ZnO heterojunction. PRZIB was assembled using C@VO2/ZMRAs structure as the photovoltaics as well as intercalation host for Zinc-ions, which demonstrates a photo-conversion efficiency of 3.3 % and gravimetric capacities of 286.0 mAh g−1 and 339.3 mAh g−1 at 500 mA g−1 in dark and light conditions. An excellent long-term cycling stability was achieved with a capacity retention of 88.79 % after 300 cycles at 1000 mA g−1 in dark condition. It is suggested that the distinctive morphologies and structure of C@VO2/ZMRAs provide effective strategies for enhancing photo-electrochemical redox reaction kinetics.

Enhanced Photodegradation of Acetaminophen Using Efficient ZnO-NiO Nanofibers

The increasing presence of pharmaceutical pollutants, such as acetaminophen, in water bodies poses a significant environmental challenge due to their persistence and potential toxicity. This study investigated the enhanced photodegradation of acetaminophen using ZnO-NiO nanofibers as superior photocatalysts. The nanofibers synthesized with varying NiO contents (designated as ZN0.5, ZN1, ZN1.5, and ZN2), were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman, FTIR, Brunauer–Emmett–Teller (BET) analysis, and diffuse reflectance spectroscopy (DRS) to elucidate their structural, morphological, and optical properties. Thermogravimetric analysis (TGA) indicated that the nanofibers exhibit high thermal stability, with major weight loss attributed to the decomposition of the polymer matrix and residual organics. The BET analysis revealed that the specific surface area remains stable after increasing the NiO content up to a certain ratio. This stability correlates with the enhanced photocatalytic performance due to increased light absorption and improved charge separation. The diffuse reflectance spectra and Kubelka–Munk plots demonstrated a reduction in bandgap energy with higher NiO content, facilitating greater visible light absorption. Photocatalytic experiments under visible light irradiation, in the presence of peroxymonosulfate (PMS), showed that the ZN1.5 nanofibers achieved the highest acetaminophen degradation rate, i.e., 92%, within 3 h. Mechanistic studies, supported by radical trapping experiments, revealed that the improved photocatalytic efficiency is due to the synergistic effects of ZnO and NiO heterojunctions, which enhance charge separation and reactive oxygen species (ROS) generation. This research highlights the potential of ZnO-NiO nanofibers as effective photocatalysts for the degradation of pharmaceutical pollutants. The findings demonstrate that optimizing the composition and structure of nanofibers can significantly improve their environmental remediation capabilities, providing a promising solution for sustainable water treatment.

Radiant synergy: Illuminating methyl orange dye removal with g-C3N4/ZnO heterojunction photocatalyst

In this study, a robust hybrid heterojunction composite of g-C3N4/ZnO was successfully synthesized using a straightforward and cost-effective coprecipitation method. The resulting composite amalgamates the properties of graphitic carbon nitride (g-C3N4) and zinc oxide nanoparticles (ZnO NPs). Thorough characterization using techniques such as XRD, FT-IR, FE-SEM, HR-TEM, UV-DRS, EIS, PL, and EDX confirmed the structural and elemental composition of the catalyst. The challenge of using photons as the sole energy source for the activation of photocatalysts under ambient conditions was addressed. The photocatalytic potential of the hybrid heterojunctions was assessed by degrading the methyl orange (MO) dye under sunlight. The 10 wt% g-C3N4/ZnO composite exhibited effective suppression of charge recombination during photocatalytic degradation. Notably, the heterojunction 10 wt% g-C3N4/ZnO composite displayed remarkable photocatalytic performance, achieving a substantial 98 % degradation of MO within 90 min of solar irradiation, outperforming other materials. Moreover, the synthesized composites exhibited favorable attributes in terms of recyclability and mechanical stability, retaining their efficacy over five cycles. This substantiates their promising role as potential candidates for future photocatalyst applications. In essence, g-C3N4/ZnO heterojunction composites offer a robust solution for efficient and sustainable photocatalytic degradation of organic pollutants.

Evaluation of Homogeneous NiO Particles on ZnO Heterojunction: Insights into Its Properties for Antifungal Applications

Evaluation of Homogeneous NiO Particles on ZnO Heterojunction: Insights into Its Properties for Antifungal Applications

Construction of novel BiOI/CuInS2/ZnO dual S-scheme charge transfer pathway for efficient antibiotic degradation

The present work explored the photocatalytic activity of BiOI–CuInS2–ZnO ternary heterojunction for the photodegradation of the tetracycline (TCl). The bare photocatalysts were prepared via hydrothermal method while the ternary heterojunction was synthesized using simple physical mixing route. The ternary heterojunction of BiOI, CuInS2 and ZnO followed the S-scheme charge transfer pathway exhibiting superior photodegradation ability compared to other synthesized photocatalysts. The attained degradation efficiency of BiOI–CuInS2–ZnO S-scheme ternary heterojunction was 96.75 % within 90 min of light illumination which was much higher than other photocatalysts. Electron spin resonance (ESR) investigations and scavenging experiment indicated that •O2−, and •OH radicals plays an important role in photodegradation of TCl. Furthermore, the structural analysis of synthesized bare photocatalysts was also done via density functional theory (DFT) calculations. The results showed that after the formation of S-scheme heterojunction, the ternary heterojunction showed lower recombination rate (validated via PL analysis) with boosted charge carriers separation rate (confirmed through EIS and TPR analysis) and light absorption ability. This had led to upgradation in photodegradation efficiency of ternary BiOI–CuInS2–ZnO photocatalyst. The reusability test of the photocatalysts confirmed excellent stability of ternary photocatalysts with 90.25 % degradation rate up to five catalytic cycles.

Self-powered poly(3-hexylthiophene)/ZnO heterojunction ultraviolet photodetectors decorated by silver nanoparticles

Self-powered poly (3-hexylthiophene)/zinc oxide (P3HT/ZnO) heterojunction ultraviolet photodetectors decorated by silver nanoparticles (Ag NPs) were fabricated by sol-gel and spin-coating techniques. The ultraviolet photoresponse performance of the P3HT/ZnO heterojunction photodetectors influenced by the position of plasmonic Ag NPs was investigated. The responsivity and detectivity of the P3HT/Ag/ZnO photodetector with placed Ag NPs at the interface of ZnO and P3HT layers enhanced to 1.92 and 1.15 times compared to the reference devices. When the Ag NPs embedded into ZnO layer, the responsivity, detectivity and external quantum efficiency were 16.42 mA/W, 5.97 × 1011 Jones, and 5.36 %, respectively, which were 5.77 times, 4.64 times and 5.77 times to that of the pristine P3HT/ZnO photodetector. The enhancement mechanism of plasmonic metallic nanoparticles to the performance of the photodetectors was discussed in details. This study presents a simple route to high performance self-powered photodetectors.

In-situ controllable preparation of ZIF-8-wrapped ZnO heterojunction nanorods array for ppb-level Cl2 detection operated at near room temperature

Real-time monitoring of chlorine gas (Cl2) with a strong irritating odor is an indispensable means of avoiding its contamination of the air and harm to the body. To achieve this purpose, a novel gas-sensitive material capable of detecting low concentrations of Cl2 at near room temperature is developed in this paper. ZIF-8 with a kinetic diameter of 3.4 Å in the designed ZnO@ZIF-8 composites is able to sieve gas molecules with different kinetic diameters, enabling effective improvement of the selectivity of the gas-sensitive materials. In addition, the porous structure of ZIF-8 can provide more reactive sites, which is conducive to improving gas adsorption capacity and providing of channels for gas diffusion. In this study, ZnO@ZIF-8 heterojunction composites are prepared by combining the advantages of ZnO and ZIF-8, which provides a new method for real-time monitoring of low concentrations of Cl2, and also has potential practical applications in fields such as environmental monitoring and industrial safety.

Twisted leaf like ZnO-flake-like BiOI@CNF grown on ITO substrate as a nanostructured pioneering platform for photoelectrochemical water splitting

Despite ZnO nanostructures garnering significant attention for photoelectrochemical (PEC) water splitting, the quest for efficient ZnO-based photoelectrodes with optimal light absorption, effective electron-hole separation, and transfer remains a challenge. The formation of ZnO heterojunctions with lower bandgap nanostructures of semiconductors has emerged as a strategy to enhance charge transfer while mitigating recombination rates. Additionally, the introduction of carbon nanofibers (CNFs) to these heterojunctions serves to further suppress recombination by electron trapping and enhances catalytic active sites, thereby elevating PEC performance. In this study, twisted leaf-like ZnO, flake-like BiOI, ZnO-BiOI nanostructure heterojunctions, and ZnO-BiOI@C composites were synthesized through a solvothermal method. Notably, the ZnO-BiOI@C photoelectrode exhibited outstanding performance, achieving a photocurrent density of 5.6 mA/cm2 through linear sweep voltammetry under light illumination. Each synthesized photoelectrode demonstrated robust photocurrent responsiveness and excellent stability under chopped conditions for up to 1150 s with a 50 s interval. This remarkable stability is attributed to the unique and stable morphological characteristics and strong crystallinity of the synthesized materials. The formed heterojunction between ZnO-BiOI was found to extend light absorption capabilities, while the incorporation of CNFs effectively trapped electrons from the heterojunction's conduction band, enhancing overall water splitting performance. The results underscore the potential of the ZnO-BiOI@C composite as a high-performing photoelectrode for PEC applications, emphasizing the importance of morphological and compositional considerations in advancing PEC technologies.

Gas-Sensitive Performance Study of Metal (Au, Pd, Pt)/ZnO Heterojunction Gas Sensors for Dissolved Gases in Transformer Oil.

An oil-immersed transformer is a critical electrical device for power delivery. Online monitoring of transformer operation is the key to ensuring the regular operation of power systems. This paper proposes Au/ZnO, Pd/ZnO, and Pt/ZnO heterojunctions as new gas-sensitive materials and investigates their gas-sensitive performance to dissolved gases (C2H4, CO, and H2) in transformer oil. Upon theoretical density functional theory (DFT) calculations, the analysis of the total density of states (TDOS), partial density of states (PDOS), molecular orbital theory, and charge deformation density reveals that Au, Pd, and Pt form heterojunctions with ZnO, which enhance the electrical conductivity of the system. Meanwhile, intrinsic ZnO is unsuitable for gas detection and adsorption, while the Au/ZnO heterojunction suits C2H4 detection. In contrast, the Pd/ZnO heterojunction is suitable for H2 detection, and the Pt/ZnO heterojunction is suitable for C2H4 and CO detection. The electrical conductivity of the adsorption models is changed to varying degrees after gas adsorption. The different change rate electrical conductivity just serves as a theoretical foundation for determining the type and concentration of dissolved gases in transformer oil. The research results act as a theoretical foundation for constructing gas sensors with a ZnO-based material.

Chemiresistive n-butanol gas sensors based on Co3O4@ZnO hollow-sphere-array thin films prepared by template-assisted magnetron sputtering

Rapid and accurate detection of n-butanol in the environment is crucial owing to its negative effects on human health. Herein, gas sensors based on Co3O4@ZnO hollow-sphere-array thin films modified using Au particles are successfully prepared via template-assisted magnetron sputtering for detecting n-butanol. The best sensor performances are achieved when the thicknesses of the sputtered ZnO and Co3O4 films are 60 and 1.2 nm, respectively, and the sputtering time of the Au particles is 10 s. Furthermore, the best sensor exhibits an exceptionally high response to an n-butanol concentration of 100 pm at 275 °C (Ra/Rg = 260), a short response/recovery time (1 s/92 s), a considerably lower limit of detection (Ra/Rg = 5.8 at n-butanol concentration = 100 ppb) as well as high selectivity and repeatability. The remarkable sensing performance of the proposed sensors can be mainly attributed to the charge transfer induced by the Co3O4–ZnO heterojunction formation and the catalytic and spillover effects of the Au particles. This study is important because it provides a simple preparation method for high-performance semiconductor gas sensors using magnetron sputtering, which would enable future large-scale and integrated preparation of high-performance gas sensors.

Fully UV Modulated Artificial Synapses with Integrated Sensing, Storage and Computation

AbstractOptical synaptic devices are considered a preferred substitute to electrical synapses for low‐energy, high‐efficiency neuromorphic computing (NC). However, most optical synapses irreversible optical response severely restricts their application scenarios. In this study, a fully photon‐modulated synaptic device constructed from Si‐doped beta‐gallium oxide (β‐Ga2O3)/ZnO heterojunction is demonstrated. The device exhibits reversible conductance changes and mimics a range of synaptic behaviors, which are modulated by two different wavelengths (255 and 370 nm) of UV light. Owing to the device's plasticity, four types of logic functions including “AND”, “OR”, “NOR” and “NAND” are implemented in the device by optical stimulation. Furthermore, an artificial neural network (ANN) is simulated based on the device's excitatory and inhibitory characteristics, and an optical programming scheme is employed to enhance the network's performance, resulting in a high recognition rate of 95.5% for handwritten digits. The fully photon‐modulated synapse development strategy and programming scheme, as presented in this work, advance the utilization of optical artificial synapses in ANN.

Synthesis of PANI@Ce-doped ZnO (PCZ) heterojunction: A UV-Driven photocatalyst for reduction of methylene blue and study of their structural, optical and electrical properties

Abstract To address the significant issue of wastewater treatment, this research focused on synthesizing PANI@Ce-doped ZnO (PCZ) nanocomposites, a heterojunction with varying dopant concentrations. This heterojunction was prepared using an ultrasonic-assisted wet impregnation technique and underwent comprehensive analysis through several techniques, including XRD, UV-DRS, Photoluminescence, FE-SEM, EDAX, and Impedance Analyzer. The XRD study was done to analyse the crystalline nature of as synthesized nanocomposites, while FESEM with EDX confirm the nanoflower morphology and presence of each element respectively. The optical band gap energy (Eg) of the samples has been estimated using UV-DRS and is found in the visible region. The synergy between the organic and inorganic frameworks resulted in an additive effect on the photocatalyst’s degradation efficiency. In the photocatalytic degradation process, reactive oxygen species (ROSs), including O2, OH, and h+, played a crucial role in breaking down MB (Methylene Blue) using the PANI@Ce-doped ZnO nanocomposites. PCZ1 exhibited significantly elevated dye degradation efficiency (86.80%) in comparison to bare PANI (40.80%). This enhancement can be attributed to the improved transfer and separation of photogenerated charge carriers in prepared heterojunction.

Piezoelectricity Enhanced Self-Powered Solar-Blind Ultraviolet Photodetectors Based on Ga2O3/ZnO Heterojunction

Piezoelectricity Enhanced Self-Powered Solar-Blind Ultraviolet Photodetectors Based on Ga₂O₃/ZnO Heterojunction

ZnO heterojunction photocatalysts prepared via facile green synthesis process attaining improved photocatalytic function for degradation of methylene blue dye

ZnO heterojunction photocatalysts prepared via facile green synthesis process attaining improved photocatalytic function for degradation of methylene blue dye

Dipole Field-Driven Organic-Inorganic Heterojunction for Highly Sensitive Ultraviolet Photodetector.

Developing high-performance organic-inorganic ultraviolet (UV) photodetectors (PDs) has attracted considerable attention. However, this development has been hindered due to poor directional charge-transfer ratios in transport layers, excessive costs, and an ambiguous underlying mechanism. To tackle these challenges, we constructed a heterojunction of economic Mg-doped ZnO (MgZnO) nanorods and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) [PEDOT:PSS (P:P)] that utilizes dipole field-driven spontaneous polarization to enhance photogenerated charge kinetics. As a result, the proposed heterojunction has an improved noise equivalent power of 3.16 × 10-11 W Hz-1/2), a normalized detection rate (D*) of 8.96 × 109 jones, and external quantum efficiency comparable to other ZnO-based devices. Notably, the prepared PDs showed a photocurrent of 4.8 × 10-3 μA under a faint UV light having an intensity of 1 × 10-5 W cm-2, exceeding the performance of the most state-of-the-art ZnO-based UV sensors. The introduction of Mg into ZnO is responsible for the high performance, as it causes a lattice mismatch and distortion of the Mg-doped ZnO unit cell. It results in improved dipole movement and the creation of a dipole field, accelerating the directional electron-transfer process. Using a dipole field to manipulate the migration and transport of photogenerated carriers represents a promising approach for achieving outstanding performance in UV PDs.

Tri-layered Si/Co3O4/ZnO heterojunction for high-performance visible photodetection

Tri-layered heterojunction devices based on oxide thin films are attracting significant attention for ultra-fast visible photodetection.