ZnO Nanoclusters Research Articles

Engineering of ceramic membranes with superhydrophobic pores for different size water droplets removal from water-in-oil emulsions

Superhydrophobic (SHB) ceramic membrane surfaces have proved their superiority in water-in-oil (W/O) emulsion separation. However, the construction of ceramic membranes with SHB pores remains challenging and the interaction between the SHB pores and water droplets is still unclear. Herein, by growing uniform ZnO nanoclusters (NCs) onto the SiC grains of a symmetric SiC ceramic membrane and then grafting with triethoxy(octyl)silane, a series of ZnO NCs@SiC membranes with SHB pores were prepared. Prior to secondary hydrothermal synthesis ZnO NCs, the small-sized ZnO nanoparticles (NPs) were grown onto the SiC grains via a sol–gel process. All the ZnO NCs@SiC membranes with SHB pores showed improved water removal performance from W/O emulsions compared with that of the pristine membrane. The optimal membrane with SHB pores displayed a pore size of 0.19 μm with a water contact angle of 163.96°. The smaller water droplets in W/O emulsions, the membrane pores are easier to be polluted. When separating a 1000 ppm W/O emulsion with a water droplet size of 500 nm at a transmembrane pressure of 0.5 bar, the water rejection reached 98.90 %, and the steady-state oil flux was 92.99 L·m−2·h−1. Based on the separation experiments, the separation mechanism was revealed. This work provides significant perceptions into constructing SHB pores of ceramic membranes, which might be useful for other possible applications.

Morphological, structural and electronic properties of zinc oxide nano structures deposited on ZnO substrate layer – A theoretical perspective

The work investigates the deposition of zinc and oxygen atoms on a Zinc terminated ZnO substrate, maintaining their stoichiometric ratio (O:Zn) at 0.8, under varying incident energies (0.5 eV and 5 eV) and temperatures (300 K and 700 K) using the ReaxFF potential in Molecular Dynamics (MD) simulation. The study explores the impact of deposition conditions on growth mechanisms, film morphology, and structural parameters such as Radial Distribution Function (RDF) and Coordination Number (CN). RDF analysis highlights disordered atomic arrangements and diverse bonding configurations within the film, with CN showing deviations from perfect crystalline ZnO, indicating non-uniform, non-crystalline, and nano behaviour. Post-heating the films to temperatures approaching the ZnO melting point results in enhanced crystallinity, as evidenced by distinct, dominant, and multiple RDF peaks. Density Functional Theory (DFT) approach of the deposited structures elucidates the formation of ZnO nanoclusters-(ZnO)3 and (ZnO)4 and investigates their electronic structure properties. DFT analysis of the post-heated films reveals the formation of ZnO monomers (ZnO), indicating an approaching crystalline behaviour, yet the films exhibit non-epitaxial and non-uniform characteristics. DFT calculations were instrumental in validating the observed structural behaviours in the deposited films. The study underscores the significance of stoichiometric ratio in film deposition and demonstrates the temperature-dependent evolution of structural properties towards crystallinity, shedding light on the intricate dynamics of ZnO film growth offering tailored control over film properties for enhanced performance in practical applications such as optoelectronics and gas sensing.

Zinc Oxide Nanoclusters Encapsulated in MFI Zeolite as a Highly Stable Adsorbent for the Ultradeep Removal of Hydrogen Sulfide.

Often, trace impurities in a feed stream will cause failures in industrial applications. The efficient removal of such a trace impurity from industrial steams, however, is a daunting challenge due to the extremely small driving force for mass transfer. The issue lies in an activity-stability dilemma, that is, an ultrafine adsorbent that offers a high exposure of active sites is favorable for capturing species of a low concentration, but free-standing adsorptive species are susceptible to rapidly aggregating in working conditions, thus losing their intrinsic high activity. Confining ultrafine adsorbents in a porous matrix is a feasible solution to address this activity-stability dilemma. We herein demonstrate a proof of concept by encapsulating ZnO nanoclusters into a pure-silica MFI zeolite (ZnO@silicalite-1) for the ultradeep removal of H2S, a critical need in the purification of hydrogen for fuel cells. The Zn species and their interaction with silicalite-1 were thoroughly investigated by a collection of characterization techniques such as HADDF-STEM, UV-visible spectroscopy, DRIFTS, and 1H MAS NMR. The results show that the zeolite offers rich silanol defects, which enable the guest nanoclusters to be highly dispersed and anchored in the silicious matrix. The nanoclusters are present in two forms, Zn(OH)+ and ZnO, depending on the varying degrees of interaction with the silanol defects. The ultrafine nanoclusters exhibit an excellent desulfurization performance in terms of the adsorption rate and utilization. Furthermore, the ZnO@silicalite-1 adsorbents are remarkably stable against sintering at high temperatures, thus maintaining a high activity in multiple adsorption-regeneration cycles. The results demonstrate that the encapsulation of active metal oxide species into zeolite is a promising strategy to develop fast responsive and highly stable adsorbents for the ultradeep removal of trace impurities.

Structure, Conductivity, and Sensor Properties of Nanosized ZnO-In2O3 Composites: Influence of Synthesis Method.

The influence of the method used for synthesizing ZnO-In2O3 composites (nanopowder mixing, impregnation, and hydrothermal method) on the structure, conductivity, and sensor properties is investigated. With the nanopowder mixing, the size of the parent nanoparticles in the composite remains practically unchanged in the range of 50-100 nm. The impregnation composites consist of 70 nm In2O3 nanoparticles with ZnO nanoclusters < 30 nm in size located on its surface. The nanoparticles in the hydrothermal composites have a narrow size distribution in the range of 10-20 nm. The specific surface of hydrothermal samples is five times higher than that of impregnated samples. The sensor response of the impregnated composite to 1100 ppm H2 is 1.3-1.5 times higher than the response of the mixed composite. Additives of 15-20 and 85 wt.% ZnO to mixed and impregnated composites lead to an increase in the response compared with pure In2O3. In the case of hydrothermal composite, up to 20 wt.% ZnO addition leads to a decrease in response, but 65 wt.% ZnO addition increases response by almost two times compared with pure In2O3. The sensor activity of a hydrothermal composite depends on the phase composition of In2O3. The maximum efficiency is reached for the composite containing cubic In2O3 and the minimum for rhombohedral In2O3. An explanation is provided for the observed effects.

Green light-activated room temperature NO2 sensor based on PTCDA-loaded ZnO nanocluster

Flower-like zinc oxide nanoclusters were successfully incorporated by different amount of PTCDA organic dye molecular, forming the hetero-structured PTCDA/ZnO composites. Remarkably, a study performed on their NO2 sensing properties reveals that the 0.5 wt% PTCDA-loaded ZnO sensor exhibits high response, excellent selectivity, quick response speed and low detection limit of 7.4 ppb towards NO2 molecules at room temperature (25 °C) under green light illumination, which possesses an apparent advantage over the ZnO sensors loaded with other PTCDA concentration as well as upon other light illumination conditions. This work makes a meaningful contribution to the development of NO2 sensor based on wide-band gap semiconductors with visible light irradiation.

Doping Engineering to Modulate Lattice and Electronic Structure for Enhanced Piezocatalytic Therapy and Ferroptosis.

Piezocatalytic therapy, which generates reactive oxygen species (ROS) under mechanical force, has garnered extensive attention for its use in cancer therapy owing to its deep tissue penetration depth and less O2 -dependence. However, the piezocatalytic therapeutic efficiency is limited owing to the poor piezoresponse, low separation of electron-hole pairs, and complicated tumor microenvironment (TME). Herein, a biodegradable, porous Mn-doped ZnO (Mn-ZnO)nanocluster with enhanced piezoelectric effect is constructed via doping engineering. Mn-doping not only induces lattice distortion to increase polarization but also creates rich oxygen vacancies (OV ) for suppressing the recombination of electron-hole pairs, leading to high-efficiency generation of ROS under ultrasound irradiation. Moreover, Mn-doped ZnO shows TME-responsive multienzyme-mimicking activityandglutathione (GSH) depletion ability owing to the mixed valence of Mn (II/III), further aggravating oxidative stress. Density functional theory calculations show that Mn-doping can improve the piezocatalytic performance and enzyme activity of Mn-ZnO due to the presence of OV . Benefiting from the boosting of ROS generation and GSH depletion ability, Mn-ZnO can significantly accelerate the accumulation of lipid peroxide and inactivate glutathione peroxidase 4 (GPX4) to induce ferroptosis. The work may provide new guidance for exploring novel piezoelectric sonosensitizers for tumor therapy.

Capillary‐Driven Self‐Assembled Microclusters for Highly Performing UV Photodetectors

AbstractSelf‐assembled nanoparticle networks have emerged as multifunctional building blocks for a new generation of highly sensitive sensing technologies that offer large surface‐to‐volume ratios and a range of associated benefits. Unfortunately, with nanoparticle networks often being held together by weak van der Waals forces, the development of useful commercial devices is slowed by the relatively low robustness and poor carrier transport characteristics. This study shows how the application of a single droplet of ethanol can induce capillary forces capability of delivering significant changes to the morphological, structural, optical, and electronic properties of ZnO nanoclusters. It demonstrates how ZnO nanocluster “dendrites” and nanoparticles are forced together to form micro‐scale islands and larger nanoparticles, and thereby improve the robustness of the layers and the quality of the junctions between the nanoparticles without significantly reducing the overall porosity of the layer or degrading the structural or optical properties in any way. The commensurate improvement in the electronic transport within the layers is found to greatly improve the photoresponse of UV detectors. It seems likely that the application of ethanol and the exploitation of capillary force can provide a technique that can greatly benefit any nanostructured, ultra‐porous device where poor charge transport currently limits performance.

Construction of Flower-like ZnO Nanoclusters on Functionalized Graphene Nanosheets for Room Temperature Formaldehyde Sensing

Background: Formaldehyde (HCHO) is one of the sources of indoor air pollution and a recognized carcinogenic gas, which sets a huge threat to human health. Therefore, it is urgent to develop a formaldehyde gas sensor with high efficiency, low consumption, and low limit of detection. Methods: With solvothermal and supramolecular assembly methods, we fabricate a nanocomposite of ZnO/5-aminonaphthalene-1-sulfonic acid (ANS)-reduced graphene oxide (rGO) through in situ assembling flower-like ZnO nanoclusters on ANS-modified graphene nanosheets for room temperature formaldehyde detection. Results: The flower-like ZnO/ANS-rGO based gas sensor exhibits high response (32%, 5 ppm), ultra-fast response/recovery times (18/23 s), high selectivity, long-term stability and a low practical limit of detection (pLOD) of 1 ppm toward HCHO at room temperature, offering significant advantages and competitiveness in chemiresistive room temperature HCHO sensors. Conclusion: The unique flower-like nanostructure of ZnO and the functionalization with ANS molecules jointly improved the HCHO sensing performance of the composite at room temperature. This work provides a new approach to designing and preparing high-performance room temperature gas sensing materials.

The effect of Cl encapsulation and hydrogenation process on the performance of ZnO nanocluster as an anode in Na-ion batteries

Density functional theory (DFT) computations are performed for probing the application of a Zn12O12 nanocage as well as its geometrically engineered forms as an anode material in Na-ion batteries (NIBs). The performance of the pure Zn12O12 nanocage was low and its cell voltage (Vcell) was approximately 1.06 V. Therefore, in order to enhance the performance, two methods were projected, namely encapsulation of an anion inside the nanocage and hydrogenation of Zn atoms of the cage. The second method was unsuccessful since it demonstrated a negative Vcell, which was due to the fact that interaction between the atomic Na and the hydrogenated nanocage was stronger than the cationic Na. However, the encapsulation of a chloride inside the Zn12O12 nanocage led to a dramatic increase in the Vcell from 1.06 to 2.96 V, which was greater than the Vcell anticipated for carbon nano-tubes and C24 fullerene.

Does Water Play a Crucial Role in the Growth of ZnO Nanoclusters in ZnO/Cu Catalyst?

The catalytically active configuration of ZnO/Cu in the commercial ZnO/Cu/Al2O3 catalyst for methanol synthesis from CO2 is still not clear. In this study, we employ density functional theory based methods to shed light on the structure and stoichiometry of ZnO clusters both free in the gas phase and also deposited on the Cu(111) surface under methanol synthesis conditions. Specifically, we investigate the structural evolution of ZnO clusters in the presence of hydrogen and water. We find that the stability of ZnO clusters increases with the concentration of water until the ratio of Zn and OH in the clusters reaches 1:2, with a morphological transition from planar to 3D configurations for clusters containing more than 4 Zn atoms. These clusters exhibit weak interaction with CO2, and water is predicted to block the active center. The Cu(111) surface plays an important role in enhancing the adsorption of CO2 on the ZnO/Cu(111) systems. We infer that ZnO nanostructures covered with OH species may be the morphology of the ZnO during the methanol synthesis from the hydrogenation of CO2 on the industrial catalyst.

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.

Self-Organization Effects of Thin ZnO Layers on the Surface of Porous Silicon by Formation of Energetically Stable Nanostructures.

The formation of complex surface morphology of a multilayer structure, the processes of which are based on quantum phenomena, is a promising domain of the research. A hierarchy of pore of various sizes was determined in the initial sample of porous silicon by the atomic force microscopy. After film deposition by spray pyrolysis, ZnO nanoclusters regularly distributed over the sample surface were formed. Using the electron paramagnetic resonance (EPR) method it was determined that the localization of paramagnetic centers occurs more efficiently as a result of the ZnO deposition. An increase in the number of deposited layers, leads to a decrease in the paramagnetic center relaxation time, which is probably connected with the formation of ZnO nanocrystals with energetically stable properties. The nucleation and formation of nanocrystals is associated with the interaction of particles with an uncompensated charge. There is no single approach to determine the mechanism of this process. By the EPR method supplemented with the signal cyclic saturation, spectral manifestations from individual centers were effectively separated. Based on electron paramagnetic resonance and photoluminescence studies it was revealed that the main transitions between energy levels are due to oxygen vacancies and excitons.

Исследование пленок оксида кремния, имплантированных цинком

This paper presents the results of studying the composition, structure, and properties of amorphous SiO x film obtained by electron beam evaporation. This film was implanted by Zn ions with energy of 40 keV and a dose of 3×10 16 /cm 2 . Then, annealing was carried out in air at temperatures from 400 to 800°C with a step of 100°C for 1 hour at each stage. It has been found that, after implantation, metal Zn nanoclusters with a size of about 10 nm are formed on the surface and in the near-surface layer of silicon oxide. During annealing, the implanted layer becomes clear, since metallic Zn gradually oxidizes to transparent phases of its oxide ZnO and silicide Zn 2 SiO 4 . After annealing at 700°C, ZnO nanoclusters and surface craters were revealed on the surface and in the subsurface layer of the SiO 2 film.

Size-dependent adsorption performance of ZnO nanoclusters for drug delivery applications.

We have investigated the size-dependent adsorption performance of ZnO nanoclusters (NCs) as drug delivery carriers for the first time. Our results show that the adsorption energy of the favipiravir drug on the ZnO NCs is predicted in the range of − 26.69 and − 34.27 kcal/mol. The adsorption energy (− 34.27 kcal/mol) between (ZnO)18 NC and the favipiravir is energetically desirable and more favorable than the other interactions. The size of ZnO NCs and the position of the favipiravir on the ZnO NCs cause a decrease in the energy gap, which makes the charge-transfer process easier. The bonds between O–Zn, N–Zn, and F–Zn atoms exhibit dual covalent and ionic natures. The non-covalent interaction analysis shows that the strongest H-bonds are observed near NH2 within the favipiravir molecule. Finally, the acquired results show that the interaction of ZnO NCs with the favipiravir anticancer drug can have the potential as drug delivery carriers.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11224-022-02063-2.

Adsorption and breaking of hazardous methyl mercury on hybrid structures of ionic liquids and ZnO nanoclusters

The detection and removal of the environmentally harmful substance methyl mercury (MeHg) have become an increasingly important issue due to its devastating effects on human tissues and organs. Hybrid systems of 1-ethyl-3-methylimidazolium tetrafluoroborate (C2mim BF4) ionic liquid (IL) and (ZnO)n nanoclusters with n = 2–12 are potential candidates for adsorbing and sensing of MeHg. We are using density functional theory (DFT) calculations to better understand this functionality by calculating the bond orders, HOMO-LUMO energy gaps (Eg), and electronic projected densities of states (PDOS). With adsorption energy of −1.84 eV, IL/(ZnO)4 reveals the strongest interaction with MeHg among IL/(ZnO)n hybrid systems owing to Hg-O polarized covalent bonding. The spontaneity/feasibility of the adsorption process is validated by the negative values of ΔH and ΔG, which also suggest that the process is exothermic and energetically favorable. The adsorption of MeHg molecules causes alterations in Eg, and PDOS, demonstrating the sensing ability of the hybrid structures. Increasing the alkyl chain length results in maximum adsorption energy of MeHg over the C10mim BF4/(ZnO)4 (-1.98 eV). Our results point the way to the implementation of multi-functional IL/(ZnO)n hybrid systems for sensing and adsorbing hazardous MeHg in the environment based on low-cost, rapid, and sensitive sensors.

Constructing 3D flower-like hierarchical ZnO/SnS2 heterojunction by decorating SnS2 nanosheets with ZnO nanoclusters as synergistic photocatalyst

Flower-like ZnO/SnS2 heterojunction was constructed as photocatalyst. The heterojunction shows hierarchical architecture structure, in which SnS2 nanosheets are uniformly decorated by ZnO nanoclusters. Compared to SnS2, the ZnO/SnS2 heterojunction displays improved photocatalytic efficiency for degradation of organic dye MB and hydrogen evolution. ZnO/SnS2 heterojunction reveals an optimal hydrogen production rate of 346.1 μmol h−1 g−1, about 2.7 times higher than SnS2. The boosting photocatalytic performance is ascribed to the special hierarchical structure and synergetic effect of ZnO/SnS2 heterojunction, which can enhance the specific surface area and promote the separation of photogenerated electron–hole pairs.

A Comparative Study of CoNi-LDH/ZnO Film for Photocathodic Protection Applications in the Marine Environment

In this study, two kinds of Co–Ni-layer double hydroxide (LDH)/ZnO films were prepared with different morphologies by a simple electrochemical method. The properties of the films were investigated by SEM, XRD, UV–Vis DRS, XPS, and electrochemical techniques. It was found that Co–Ni-LDH-modified ZnO films exhibited excellent photocathodic properties in a scavenger-free environment. This is mainly due to the absorption of visible light by LDH, the formation ofp–nheterojunction, and the depletion of photo-generated holes by the cycling process of Co (II)/Co (III). Compared with CoNi-LDH/ZnO nanorods, CoNi-LDH/ZnO nanoclusters showed better photocathodic protection performance and physical barrier effect. Under illumination conditions, the rough surface of ZnO nanoclusters and the deposition of a large amount of LDH can provide more photoelectrochemical active sites, thus improving the light absorption capacity and photocathodic protection performance of CoNi-LDH/ZnO nanoclusters. Under dark conditions, the physical barrier effect of CoNi-LDH/ZnO nanoclusters was also enhanced by the dense ZnO nanoclusters and thick CoNi-LDH layers.

Green synthesis of sorbus pohuashanensis/aronia melanocarpa extracts functionalized ZnO nanoclusters and their applications

ZnO nanoclusters (ZnO NCs) had been widely utilized in optoelectronics, sensors, dye removal, and antibacterial fields. To reduce or avoid the use of toxic, harmful, and costly chemical reagents, the Sorbus pohuashanensis and Aronia melanocarpa extracts were used to green synthesize ZnO NCs with superior adsorption ability for the organic dyes. The obtained ZnO NCs were characterized by UV–vis spectroscopy (UV–vis), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), x-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). TEM and SEM results indicated that the ZnO NCs tended to aggregate into large branching and sheet structures. EDS measurement confirmed the presence of zinc ions on the ZnO NCs. FTIR results revealed that the components of the fruits extracts were bounded on the surface of ZnO NCs. The primary application experiments demonstrated that the Sorbus pohuashanensis and Aronia melanocarpa extracts functionalized ZnO NCs possess effectively removing activity for organic dyes.

Exchange Functionals and Basis Sets for Density Functional Theory Studies of Water Splitting on Selected ZnO Nanocluster Catalysts.

In this communication, we use density functional theory (DFT) to study the structural (geometry) and electronic properties (vertical detachment energy and electron affinity) of ZnO monomers and dimers that can be used to form ZnO clusters of different sizes, with a view to adapting one or more of them as catalysts or photocatalysts, standing alone or on suitable substrates like graphene, to split water. We also investigate different pairs of exchange functionals and basis sets to optimize their choice in our DFT calculations and to compare the singlet–triplet energy gaps of small ZnO clusters of different sizes to select an optimal cluster size for water splitting. We find that the B3LYP/DGDZVP2 exchange functional/basis set is a reliable combination for use with DFT to calculate the geometry and electronic properties of small ZnO nanoclusters from among several other combinations of exchange functionals and basis sets. Comparisons of the singlet–triplet energy gaps show that the trimer (ZnO)3 has an energy gap of 58.66 k cal/mol. which is approximately equal to the energy of a visible photon at a wavelength of 500 nm, and a HOMO–LUMO gap of 4.4 eV, making it a suitable choice of photocatalyst for the oxidation of water from among six (ZnO)n nanoclusters of monomers, with n ranging from 1 to 6. We used this exchange functional/basis set to study the structural and energetic details of hydration and hydrolysis of water absorbed on the (ZnO)3 nanocatalyst and calculated the corresponding potential energy profiles to identify three sets of singlet–triplet pathways for water splitting. Detailed study of a pathway showed that oxygen is produced after hydrogen, and the rate-determining step is the formation of hydrogen.

Correction: High-performance trimethylamine gas sensors based on defect-engineering MOF-derived ZnO nanoclusters with tunable surface oxygen vacancies

Correction for ‘High-performance trimethylamine gas sensors based on defect-engineering MOF-derived ZnO nanoclusters with tunable surface oxygen vacancies’ by Shaoyuan Yu et al., J. Mater. Chem. A, 2022, https://doi.org/10.1039/D2TA07048K.