Mesoporous ZnO Research Articles

Synthesis of Mesoporous ZnO•SiO2 Nanocomposite from Rice Husk for Enhanced Degradation of Organic Substances Including Janus Green B under Visible Light

Rice husk (RH) is often mentioned as an agricultural by-product, often used in the pass as fertilizer and for raw burning. With modern science, RH have been researched and found many new potential benefits and applications. In this study, RH were used to synthesize amorphous SiO2, which was used to prepare the ZnO•SiO2 nanocomposites by a hydrothermal method. The as-synthesized materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and N2 adsorption/desorption isotherm. Their photocatalytic properties were studied by an ultraviolet-vis spectrophotometer and a fluorescence spectrophotometer. The ZnO•SiO2 nanocomposite has an excellent ability to degrade organic substances such as dyes, antibiotics, caffeine, etc. The effects of operating parameters on the photo-degradation reaction progress, including catalyst dosage, initial dye concentration, and pH of the initial dye were investigated in detail. In addition, the photodegradation rate of the dye on the ZnO•SiO2 nanocomposite was evaluated using the pseudo-first-order model. The ZnO•SiO2 nanocomposite can be used as a photocatalyst for wastewater treatment as it detaches much more easily from the solution. Copyright © 2024 by Authors, Published by BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Synthesis of Self-Assembled Mesoporous ZnO Microspheres Designed for Microwave-Assisted Photocatalytic Degradation of Tetracycline.

Microwave-assisted photocatalysis offers a novel approach for degrading antibiotics, while the mechanism of enhancement of microwave-induced photocatalysis remains poorly understood. In this study, tetracycline (TC) was degraded using the method of microwave-assisted photocatalysis with a ZnO catalyst, which was synthesized by the combination of hydrothermal and calcination methods. The self-assembled mesoporous ZnO catalyst exhibited superior catalytic activity in degrading TC. It is found that the degradation efficiency of TC by the ZnO catalysts with microwave-assisted photocatalysis is 4.27 times higher than that of photocatalysis alone. Of particular significance, we found that the optical absorption range of ZnO increased and the band gap decreased when microwave was introduced into the photocatalytic system. Semi-in situ photochemical tests demonstrated that more photogenerated electron-hole pairs were detected under microwave, thus further improving the photocatalytic activity of ZnO. The separation efficiency and charge transfer efficiency of photogenerated electron-hole pairs also improved due to the increase of oxygen vacancies in the synergistic effect. Meanwhile, h+ and ·OH were the main active species in the degradation system. The mechanism of microwave-induced photocatalysis is illustrated, and an efficient way for degrading antibiotic is provided in this work.

A three-dimensional printable conductive composite dressing for accelerating wound healing under electrical stimulation

In this study, a bioink based on poly(vinyl alcohol) (PVA) and κ-carrageenan network was prepared using conductive polymer (PEDOT:PSS) as conducting medium, and (+)-Catechin-loaded mesoporous ZnO (CmZnO) as antibacterial and anti-inflammatory active medium. 3D conductive composite dressing was further fabricated by an extrusion 3D printing technology. Our results showed that the as-obtained composite dressing had suitable conductivity, efficient blood clotting capacity, and good adhesiveness. It also showed that the as-fabricated conductive composite had 92.9 % and 95.6 % antibacterial activity against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli), respectively. Furthermore, the conductive dressing with an optimal electrical stimulation (ES) parameter showed in vivo blood clotting capacity, and it enhanced in vivo wound healing process in a full-thickness skin defect model than commercial dressings by upregulating the gene expression of growth factors including CD-31 and downregulating inflammatory factor expression of IL-6.

Fabrication of solution-processed flexible resistive gas sensors based on carbon-quantum-dots decorating mesoporous ZnO fibres for room temperature sensing

In recent years, the gas sensor technology has experimented an interesting growth due to the device improvements driven by nanostructured semiconductor films. Nanostructured sensors have enabled the possibility of reducing the operation temperature at room temperature levels, which implies a significant reduction on the power consumption, as well as the possibility to develop sensors over flexible substrates. Therefore, in this work, the fabrication of flexible gas sensors using solution-processing technologies is presented. Nanostructured ZnO mesoporous fibres decorated with Carbon-Quantum-Dots has been used as active layer, and the electrical response, measured as the ratio between the resistance at the target gas respect the resistance in air, is presented. Furthermore, interdigitated electrode configuration has been used for device fabrication with finger spacing of 0.2, 0.4 and 0.6 mm. A maximum response of 0.016 was achieved.

Redox/pH Dual-Responsive Fluorescent Nanoparticles for Intelligent Pesticide Release and Visualization in Gray Mold Disease Synergistic Control.

An intelligent delivery nanoformulation could enhance the utilization efficacy, uptake, and translocation of pesticides in plants. Herein, a redox/pH-triggered and fluorescent smart delivery nanoformulation was designed and constructed by using hollow mesoporous organosilica nanoparticles (HMONs) and ZnO quantum dots as the nanocarrier and capping agent, respectively. Boscalid was further loaded to generate Boscalid@HMONs@ZnO with a loading rate of 9.8% for controlling Botrytis cinerea (B. cinerea). The quantity of boscalid released by Boscalid@HMONs@ZnO in a glutathione environment or at pH 3.0 was 1.3-fold and 1.9-fold higher than that in a neutral condition. Boscalid@HMONs@ZnO has 1.7-fold the toxicity index of boscalid technical against B. cinerea in antifungal experiments. Pot experiments revealed that the efficacy of Boscalid@HMONs@ZnO was significantly enhanced more than 1.27-fold compared to commercially available water-dispersible granules of boscalid. Due to the fluorescence properties of Boscalid@HMONs@ZnO, pesticide transport's real-time monitoring of pesticide translocation in tomato plants could be observed by confocal laser scanning microscopy. Fluorescence images revealed that HMONs@ZnO had been effectively transported via treated leaves or roots in tomato plants. This research showed the successful application of HMONs@ZnO as a nanocarrier for controlling disease and offered an effective avenue to explore the real-time tracking of pesticide translocation in plants.

Preparation of bulk micro–mesoporous silica-supported ZnO via silicic acid as a desulfurizer

Silicic acid solution, which is prepared from water glass followed by extraction with tetrahydrofuran (THF), is focused on an environmentally friendly and inexpensive source of silica. In this study, we aimed the preparation of bulk porous silica with low environmental impact and cost, and desulfurization of its supported ZnO was investigated. Bulk porous silica was prepared by the condensation of silicic acid/THF in the presence of Pluronic P123. Suitable condition was investigated for the formation of crack-free bulk body with high surface area and reproducibility under the molar ratio of H2O/Si and Si/Pluronic P123 on 121 and 100, respectively. From nitrogen adsorption–desorption measurements, this bulk porous silica was categorized into micro–mesoporous silica. Moreover, Pluronic P123 was extracted and recycled. Bulk porous silica-supported 15 wt% ZnO was prepared by the impregnation of ZnCl2 followed by calcination in air. The desulfurization ability was 8.7 mg/g.Graphical

Synthesis and characterization of copper tin sulfide counter electrode for enhanced performance in third-generation solar cells

This paper presents the fabrication of a copper tin sulfide (CTS) counter electrode for application in third-generation solar cells. The fabrication process involved modified chemical bath deposition (M-CBD) or a successive ionic layer adsorption reaction (SILAR). Initially, a ZnO seed layer was deposited onto a fluorine-doped tin oxide (FTO) substrate via CBD. Subsequently, a mesoporous layer of ZnO was deposited onto the FTO substrate using the doctor-blade method. The mesoporous ZnO layer was sensitized with CdS nanocrystals deposited using the SILAR method. Various characterization techniques, including UV–Vis spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM), were employed to analyze the optical, structural, and morphological properties of the photoanode and CTS counter electrode. The results demonstrate the successful synthesis of a CTS counter electrode with desirable properties for solar-cell applications. The fabricated CTS counter electrode exhibited a conversion efficiency of 0.49%, which was significantly higher than that of carbon-based counter electrodes.

S-dopant and O-vacancy of mesoporous ZnO nanosheets induce high efficiency and selectivity of electrocatalytic CO2 reduction to CO

Surface engineering can adjust the electronic properties of catalysts, thereby boosting their electrocatalytic performances. Herein, S-doped and O-vacant mesoporous ZnO nanosheets (ZnO-VO-S) were synthesized through the plasma-treatment method, exhibiting highly electrocatalytic selectivity and activity in the conversion of CO2 to CO. Synchrotron X-ray absorption fine structure (XAFS) investigations were used to further clarify the valence state and local coordination structure of Zn, concretely affirming the reduced electron density of Zn in ZnO-VO-S. Specifically, at −1.1 V vs. RHE, the as-prepared ZnO-VO-S demonstrated a high Faradaic efficiency of 90%. Experiments and density functional theory (DFT) suggest that the electron deficiency of Zn caused by the introduction of S dopant and O vacancy, reduces the energy barrier of CO2 to CO by improving the adsorption behavior of the intermediate *COOH.

Mechanochemical reduction of alkyl and aryl halides using mesoporous zinc oxide.

In this study, we propose a mechanochemical approach that combines mesoporous ZnO (m-ZnO) as a mechanoredox catalyst and silane-mediated atom transfer chemistry to achieve efficient hydrodehalogenation of organic halides. The reaction can be conducted under mild conditions without the use of a large amount of organic solvent. Substrates ranging from activated alkyl halides to unactivated aryl halides were converted to the corresponding debrominated hydrogenation products in moderate to excellent isolated yields (50-95%). In addition, m-ZnO can be recycled and reused without appreciable loss of catalytic activity.

Ultrasmall Cu Nanoparticles Supported on Crystalline, Mesoporous ZnO for Selective CO2 Hydrogenation

AbstractConverting CO2 to value‐added chemicals, e. g., CH3OH, is highly desirable in terms of the carbon cycling while reducing CO2 emission from fossil fuel combustion. Cu‐based nanocatalysts are among the most efficient for selective CO2‐to‐CH3OH transformation; this conversion, however, suffers from low reactivity especially in the thermodynamically favored low temperature range. We herein report ultrasmall copper (Cu) nanocatalysts supported on crystalline, mesoporous zinc oxide nanoplate (Cu@mZnO) with notable activity and selectivity of CO2‐to‐CH3OH in the low temperature range of 200–250 °C. Cu@mZnO nanoplates are prepared based on the crystal‐crystal transition of mixed Cu and Zn basic carbonates to mesoporous metal oxides and subsequent hydrogen reduction. Under the nanoconfinement of mesopores in crystalline ZnO frameworks, ultrasmall Cu nanoparticles with an average diameter of 2.5 nm are produced. Cu@mZnO catalysts have a peak CH3OH formation rate of 1.13 mol h−1 per 1 kg under ambient pressure at 246 °C, about 25 °C lower as compared to that of the benchmark catalyst of Cu−Zn−Al oxides. Our new synthetic strategy sheds some valuable insights into the design of porous catalysts for the important conversion of CO2‐to‐CH3OH.

P–N heterojunction NiO/ZnO nanowire based electrode for asymmetric supercapacitor applications

Nickel-based oxides are selected for their inexpensive cost, well-defined redox activity, and flexibility in adjusting nanostructures via optimization of the synthesis process. This communique explores the field of energy storage for hydrothermally synthesized NiO/ZnO nanowires by analysing their capacitive behaviour. The p-type NiO was successfully built onto the well-ordered mesoporous n-type ZnO matrix, resulting in the formation of p–n heterojunction artefacts with porous nanowire architectures. NiO/ZnO nanowire-based electrodes exhibited much higher electrochemical characteristics than bare NiO nanowires. The heterojunction at the interface between the NiO and ZnO nanoparticles, their specific surface area, as well as their combined synergetic influence, are accountable for the high specific capacitance (C s) of 1135 Fg−1 at a scan rate of 5 mV s−1. NiO/ZnO nanowires show an 18% dip in initial capacitance even after 6000 cycles, indicating excellent capacitance retention and low resistance validated by electrochemical impedance spectroscopy. In addition, the specific capacitance, energy and power density of the solid state asymmetric capacitor that was manufactured by employing NiO/ZnO as the positive electrode and activated carbon as the negative electrode were found to be 87 Fg−1, 23 Whkg−1 and 614 Wkg−1, respectively. The novel electrode based on NiO/ZnO demonstrates excellent electrochemical characteristics all of which point to its promising application in supercapacitor devices.

Unraveling the Morphology‐Function Correlation of Mesoporous ZnO Films upon Water Exposure

AbstractUbiquitous moisture in synthetic conditions and ambient environments can strongly influence the conductivity of ZnO semiconductors via the chemisorption and physisorption of water molecules on the ZnO surface. Such an intrinsically water‐sensitive nature will become more evident in mesoporous ZnO films where a large surface area and active sites are created simultaneously. However, fundamental insights underlying water‐mediated ZnO surface chemistry and electrical conductivity and the factors affecting them remain ambiguous due to the complexity of ZnO surfaces and the difficulties of in situ characterizations at multi‐dimensions. Here, self‐assembling diblock copolymers are exploited as structure‐directing agents to achieve mesoporous ZnO thin films with highly tailorable structural characteristics ranging from nanomorphologies, over crystalline levels, to defect contents. As verified by theoretical calculations, the presence of oxygen vacancy will facilitate favorable water adsorption and subsequent dissociation on the polar ZnO surfaces. Upon humidity exposure with progressively increased levels, mesoporous ZnO films are revealed to follow an almost positive relationship between adsorption and electrical conductivity but show superior morphological stability. This work not only elucidates the water‐governed ZnO surface chemistry but may also promote a comprehensive understanding of the morphology‐function relationship on ZnO‐based electronics.

Au nanoparticles dispersed chitosan/ZnO ternary nanocomposite as a highly efficient and reusable visible light photocatalyst

The environmental pollution in particular contamination of surrounding and ground water are major concerns for regulation authorities and scientific community. In the current work, a novel visible light ternary photocatalytic structure based on mesoporous ZnO in combination with chitosan (CSN) and gold nanoparticles (AuNPs) was synthesized for serious water pollution issue. The Au@CSN/ZnO nanocomposite photocatalyst was developed through the sol-gel methodology followed by ultrasonication and photoreduction techniques. XRD investigation revealed the hexagonal wurtzite structure of ZnO, while XPS and FTIR measurements confirmed the formation of ternary nanocomposite among Au, CSN and ZnO. TEM analysis revealed the presence of AuNPs (5–15 nm), CSN sheets (micron size) and ZnO nanoparticles (20–120 nm) in designed ternary photocatalyst. Diffuse reflectance spectroscopy showed lowering in band gap energy from 3.1 to 2.87 eV as bare ZnO modified to Au@CSN/ZnO. The as-fabricated Au@CSN/ZnO nanocomposite was proven as a decidedly efficient photocatalyst when employed on colorless insecticide imidacloprid (IMD) and on colored methylene blue (MB) dye under visible-light illumination. Efficient photocatalytic performance with 93.21% removal of insecticide only in 20 min was achieved, representing 211% more efficient than bare mesoporous ZnO. In addition, Au@CSN/ZnO nanostructure showed rapid removal of MB with almost complete destruction of complicated structure just in 12 min under visible light. Furthermore, the current-developed photocatalyst exhibited adequate stability and recyclability, which is beneficial for the practical application in environmental remediation.

Mesoporous ZnO: In nanosheets grown on g-C3N4 for improved detection of NO2

The urgent need for real-time detection of toxic and harmful NO2 in the environment has attracted much attention, which requires to improve detection accuracy and portability at low temperature even room temperature. In this work, we reported a mesoporous ZnO:In grown on the side of two-dimensional g-C3N4 by conventional hydrothermal intercalation. At normal mode the sensor exhibits excellent sensitivity at 120 °C, with a response value of 200 for 15 ppm NO2 and a response/recovery time of 18/23 s. At UV assisted mode, the sensor shows improved response value to low concentration of NO2 at room temperature and can achieve instantaneous recovery effect. The reasons for improving the sensitivity, response value, response/recovery time, and cyclic stability of the gas sensor to NO2 are not only related to the abundant mesoporous, large specific surface area, and doping of sensitizer, but also affected by the heterojunction effect of improving the photogenic charge separation efficiency. The strategy of dual-mode operating conditions presented in this work provides an effective design idea for high-sensitivity and efficient NO2 detection devices.

Anchoring Pt Particles onto Mesoporousized ZnO Holey Cubes for Triethylamine Detection with Multifaceted Superiorities.

Designing sensing materials with integrating unique spatial structures, functional units, and surface activity is vital to achieve high-performance gas sensor toward triethylamine (TEA) detection. Herein, a simple spontaneous dissolution is used with subsequent thermal decomposition strategy to fabricate mesoporousized ZnO holey cubes. The squaric acid is crucial to coordinate Zn2+ to form a cubic shape (ZnO-0) and then tailor the inner part to open a holey cube with simultaneously mesoporousizing the left cubic body (ZnO-72). To enhance the sensing performance, the mesoporous ZnO holey cubes have been functionalized with catalytic Pt nanoparticles, which deliver superior performances including high response, low detection limit, and fast response and recovery time. Notably, the response of Pt/ZnO-72 towards 200ppm TEA is up to 535, which is much higher than those of 43 and 224 for pristine ZnO-0 and ZnO-72. A synergistic mechanism combining the intrinsic merits of ZnO, its unique mesoporous holey cubic structure, the oxygen vacancies, and the catalytic sensitization effect of Pt has been proposed for the significant enhancement in TEA sensing. Ourwork provides an effective facile approach to fabricate an advanced micro-nano architecture with manipulating its spatial structure, functional units, and active mesoporous surface for promising TEA gas sensors.

Strain induced by temperature evolution of mesoporous ZnO nanopowders and its effect on structural, optical and electrical impedance properties

The structural and optical properties of ZnO nanopowder samples prepared by a novel green hydrothermal method have been studied. The prepared ZnO nanopowder samples were annealed (200, 250, 300, 400, 500 °C) and characterised through XRD (X-ray diffraction), FE-SEM (field emission scanning electron microscopy), BET (Brunauer–Emmett–Teller), FT-IR (Fourier transform infrared spectroscopy), UV–Vis (Ultraviolet–visible) spectroscopy, PL (Photoluminescence) spectroscopy and EIS (Electrochemical Impedance spectroscopy). The XRD Study revealed that the prepared samples were crystalline with ZnO hexagonal wurtzite structures. The crystallite sizes were determined using the Debye–Scherrer and Williamson–Hall methods and found to increase from 20.5037 to 25.9157 nm and 22.3261 to 31.4388 nm respectively with an increase in annealing temperature. The FE-SEM revealed that the prepared ZnO nanopowder samples were of spherical shape which corroborated the XRD results. The BET results showed that the prepared nanopowder samples were mesoporous with the average pore size varying between 15.125 and 25.583 nm and surface area varying between 15.337 and 23.959 m2/g. The presence of functional groups and chemical bonding were confirmed by the FTIR measurements. The energy band gaps were determined using the Kubelka-Munk function applied to UV–Vis spectra and found to be decreasing from 3.243 to 3.160 eV with an increase in annealing temperature. PL results revealed a clear dependence of the emission with annealing temperature which was caused by the decrease of free carrier concentration as the annealing temperature increased. EIS measurements indicated an increase in electrical resistance with an increase in annealing temperature with the sample annealed at 300 °C having the smallest resistance.

Template-free self-assembly of mesoporous ZnO nanocluster/ polymethyl methacrylate based anisotropic nanocomposite thin films with enhanced interfacial interactions and tuneable optical properties

Nature inspired biomimetic growth of anisotropic, hierarchical nanostructures could offer insight into new and exciting crystalline properties for advanced multifunctional applications. Our study demonstrates diethanolamine-mediated mesoscopic self-assembly of semiconducting ZnO Quantum Dots (3–5 nm) into lattice-aligned, symmetrical superstructures (40–50 nm) via non-classical oriented attachment (OA) crystal growth observed in various biomineralization processes. Multifunctional nanocomposite thin films of self-assembled nanostructures and polymethyl methacrylate were spin-coated onto plasma-treated Si wafers and the surface and interfacial properties were rigorously studied. HR-TEM images depicted the OA growth process with neighboring nano-crystals having perfectly aligned lattices. Preferential orientation of the thin films along <100> direction was evident from the XRD data. Quantum confinement in ZnO QDs and surface defect originating sharp green PL emission were examined through UV–Vis absorption and Photoluminescence spectra respectively. DLS and Zeta potential studies of surface-engineered colloidal superstructures established excellent long-term physico–chemical stability with no agglomeration or transparency loss observed in ZnO mesocrystal suspension even after 6 months. Diethanolamine, due to its dual functionality radically enhanced the interaction between polar ZnO and non-polar PMMA matrix resulting in highly stable thin films (Class II hybrids) with enhanced surface and interfacial properties as evident from the extremely low surface roughness and homogenous nanofiller dispersion observed in AFM and FE-SEM studies. Chemical interactions at the interface were also established quantitatively by XPS binding energy measurements which suggested hydrogen bonds and covalent bonds between organic-inorganic phases promoted via diethanolamine surface engineering.

Antireflection and photocatalytic single layer and double layer ZnO and ZnO–TiO2 thin films

Due to climate change and the need to use renewable energy resources, solar cell modification is being considered by scientists around the world. Photocatalytic and anti-reflective coatings on solar cells can affect the efficiency and stability of solar cells. In this study, single-layer zinc oxide thin films and double-layer ZnO–TiO2 thin films were investigated to study their photocatalytic and optical properties. In fact, the effect of porosity and the application of double-layer thin films on the optical and photocatalytic properties of coated glass were studied. Mesoporous thin films thinner than 100 nm were synthesized using a sol-gel process and the ZnO thin film with 2 × 10-2 M pore-forming agent (CTAB) in the coating solution had the highest transparency and ultraviolet absorption, and the ZnO thin film with 4 × 10-2 M pore-forming agent had the best antireflection performance. The double-layer thin film consisted of dense (interlayer) and mesoporous (top layer) ZnO layers had the best anti-reflection performance. It reduced the reflection of the glass substrate by 2.05%. Investigation of the effect of the coating thickness on optical properties showed that higher film thickness can lead to a shift of the visible wavelength with the highest transparency such that the increase of withdrawal speed from 1 mm/s to 5 mm/s resulted in an increase of this wavelength from 530 nm to 590 nm. The photocatalytic studies of the ZnO double-layer coatings showed that 120 min of ultraviolet irradiation could completely recover the transparency of the samples contaminated with fatty acid.

Mesoporous ZnO nanoparticles using gelatin — Pluronic F127 as a double colloidal system for methylene blue photodegradation

Mesoporous ZnO nanoparticles using gelatin — Pluronic F127 as a double colloidal system for methylene blue photodegradation

Self-cleaning application of mesoporous ZnO, TiO2 and Fe2O3 films with the accommodation of silver nanoparticles for antibacterial activity

BackgroundThe infections spread in healthcare circumstances is a growing and persistent issue worldwide, motivated by the development of microbial durability to disinfectants and antibiotics. Self-cleaning or disinfecting is one of the most attractive and promising technologies for glass windows, buildings, operating rooms, and hospitals. MethodThe transparent films of mesoporous TiO2, ZnO and Fe2O3 with different layers were synthesized and coated with silver nanoparticles through the sol-gel technique. The contact angles of the Ag/ZnO, Ag/TiO2 or Ag/Fe2O3 films were found to be less than 10°, indicating the obtained films were superhydrophilic. These films were tested for their disinfection ability for different bacteria species under direct light illumination. Significant FindingsResults have shown that Ag/TiO2 exhibited strong anti-bactericidal performances, and the Ag/TiO2 1-layer (1L), 2-layer (2L) and 3-layer (3L) films were the best of all treatments producing consistently higher antibacterial activity with Vibrio parahaemolyticus, Aeromonas hydrophila, and Bacillus subtilis in the reducing order of efficacy. The exposure time of 3 h was sufficient to reduce the cell counts of bacterial strains. The reason behind the higher antibacterial activity of Ag/TiO2, Ag/ZnO and Ag/Fe2O3 films compared with pristine ZnO, Fe2O3 and TiO2 films might be the surface plasmon resonance of Ag nanoparticles. The small Ag clusters create sinks for electrons, thus expediting the photoinduced electron- holes separation and enhancing the antibacterial activity. Therefore, the highest antibacterial activity observed for the Ag/TiO2 films was referred to as the most effective separation of charge carriers during the fast charge transfer.