Transition metal doped ZnO nanoclusters for carbon monoxide detection: DFT studies

Theoretical Study of CO, NO, NO2, Cl2, and H2S Adsorption Interactions with PdO-Graphene Composites for Gas Sensor Applications

Gas sensors play a vital role in detecting gases in the air, converting their concentrations into electrical signals for industrial, environmental, and safety applications. This study used density functional theory methods to explore the mechanism and sensitivity of a PdO-graphene composite sensor towards various gases (CO, NO, NO2, H2S, and Cl2). All calculations, including structure, energy, and frequency optimizations, were performed using the Gaussian software with appropriate configurations and basis sets. Key parameters such as the adsorption energy, charge transfer, energy gap, density of states, and HOMO-LUMO were computed for each gas molecule on the PdO-graphene composite. The sensitivity and recovery time were also evaluated. The findings show that CO exhibited the highest adsorption energy (-6.5513 eV) and adsorbed with a noticeable tilt toward the PdO-graphene plane, indicating a strong interaction, and H2S exhibited the lowest adsorption energy, calculated as -2.0110 eV. H2S demonstrated the highest charge transfer of 0.445 e and an energy gap of 3.1321 eV, and CO exhibited the lowest charge transfer, calculated as 0.036 e, while NO2 demonstrated the lowest energy gap, determined to be 2.5004 eV. NO2 demonstrated the highest sensitivity, at 1285.2% for the PdO-graphene composite, and the lowest were Cl2 and H2S, with a sensitivity of 99.9%, while Cl2 had the shortest recovery time of 7.66 × 10-11 s, and CO had the longest recovery time of 2.55 × 10-10 s. The addition of PdO significantly enhanced the interaction strength between the adsorbed gas molecules and the graphene sheet when compared to Pd-graphene or pure graphene. This enhancement is reflected in the increased adsorption energy and band gap and low charge transfer, which significantly influenced the electrical conductivity of the PdO-graphene sheet. In conclusion, the incorporation of PdO into graphene improves the sensitivity of the gas sensor, particularly for detecting NO2, making PdO-graphene a highly suitable material for gas sensing applications.

Role of transition metals in coinage metal nanoclusters for the remediation of toxic dyes in aqueous systems

A difficult issue in chemistry and materials science is to create metal compounds with well-defined components. Metal nanoclusters, particularly those of coinage groups (Cu, Ag, and Au), have received considerable research interest in recent years owing to the availability of atomic-level precision via joint experimental and theoretical methods, thus revealing the mechanisms in diverse nano-catalysts and functional materials. The textile sector significantly contributes to wastewater containing pollutants such as dyes and chemical substances. Textile and fabric manufacturing account for about 7 × 105 tons of wastewater annually. Approximately one thousand tons of dyes used in textile processing and finishing has been recorded as being discharged into natural streams and water bodies. Owing to the widespread environmental concerns, research has been conducted to develop absorbents that are capable of removing contaminants and heavy metals from water bodies using low-cost technology. Considering this idea, we reviewed coinage metal nanoclusters for azo and cationic dye degradation. Fluorometric and colorimetric techniques are used for dye degradation using coinage metal nanoclusters. Few reports are available on dye degradation using silver nanoclusters; and some of them are discussed in detailed herein to demonstrate the synergistic effect of gold and silver in dye degradation. Mostly, the Rhodamine B dye is degraded using coinage metals. Silver nanoclusters take less time for degradation than gold and copper nanoclusters. Mostly, H2O2 is used for degradation in gold nanoclusters. Still, all coinage metal nanoclusters have been used for the degradation due to suitable HOMO-LUMO gap, and the adsorption of a dye onto the surface of the catalyst results in the exchange of electrons and holes, which leads to the oxidation and reduction of the adsorbed dye molecule. Compared to other coinage metal nanoclusters, Ag/g-C3N4 nanoclusters displayed an excellent degradation rate constant with the dye Rhodamine B (0.0332 min-1). The behavior of doping transition metals in coinage metal nanoclusters is also reviewed herein. In addition, we discuss the mechanistic grounds for degradation, the fate of metal nanoclusters, anti-bacterial activity of nanoclusters, toxicity of dyes, and sensing of dyes.

Estimating the in vitro cytotoxicity of the newly emerged zinc oxide (ZnO) doped chromium nanoparticles using the human fetal lung fibroblast cells (WI38 cells)

Advances in nanotechnology have been increased for more smart applications and getting the highest level of benefits, recently modification of the surface characters of nanoparticles is a new trend to get the optimal benefits, one of these modification is doping of zinc oxide with chromium nanoparticles (ZnO doped Cr NPs), the present study aimed to identify the surface characters of doped ZnO and their possible cytotoxic effects. The doped NPs were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), Field emission scanning electron microscope (FESEM), and Electromagnetic Data Exchange (EDX). Human fetal lung fibroblast cells (WI38 Cells) was treated with variable concentrations of pure ZnO and ZnO doped Cr (0.01 %, 0.02 %, 0.03 % and 0.04 %) for 24 hr at 37 °C followed by the MTT assay. The cells treated with the obtained half-maximal inhibitory concentration (IC50). The supernatant and cells were collected for oxidant/anti-oxidant and molecular analysis.The observed FESEM features are in line with the reported XRD analysis confirming the hexagonal crystal symmetry of all samples. The findings revealed that pure ZnO exhibited potent cytotoxic effects followed by (0.03 % and 0.04 %). All tested NPs produce lipid peroxidation significantly (0.03 % and 0.04 %). The significant up regulation of Bcl-2-associated X protein (BAX) and apoptotic Caspase (Cas-3) transcription level were reported in ZnO and 0.03 % and 0.04 % in contrast the anti apoptitic B-cell lymphoma 2 (Bcl-2) is elevated in 0.01 % and 0.02 %. Doping of ZnO with Cr causing significant morphological changes which effect on their toxicity especially with 0.03 % and 0.04 %.

CuO-decorated ZnO nanotube-based sensor for detecting CO gas: a first-principles study

Understanding the effect of copper oxide (CuO)-decorated zinc oxide nanotube on carbon monoxide (CO) adsorption is crucial for designing a high-performance CO gas sensor. In this work, CO sensing properties of copper oxide-decorated zinc oxide (CuO-ZnO) nanotube are studied theoretically by employing first-principles density functional theory for the first time. The stability, adsorption mechanism, density of states, and change in electrical conductivity are studied. The results of calculating the adsorption energy show strong chemical adsorption of CO on CuO-ZnO nanotubes. The adsorption energy of CO on CuO-ZnO nanotube is calculated as 7.5 times higher than that on ZnO nanotube. The results of the Mulliken charge analysis reveal that electron transfer occurs from CO molecules to CuO-ZnO nanotubes. Additionally, the electrical conductivity of CuO-ZnO nanotubes significantly changes after adsorption of CO at room temperature. According to these studies, CuO-ZnO nanotube sensors can be used for the detection of CO gas. The results are in excellent agreement with the reported experimental results.

Recent Advances in ZnO-Based Carbon Monoxide Sensors: Role of Doping

Monitoring and detecting carbon monoxide (CO) are critical because this gas is toxic and harmful to the ecosystem. In this respect, designing high-performance gas sensors for CO detection is necessary. Zinc oxide-based materials are promising for use as CO sensors, owing to their good sensing response, electrical performance, cost-effectiveness, long-term stability, low power consumption, ease of manufacturing, chemical stability, and non-toxicity. Nevertheless, further progress in gas sensing requires improving the selectivity and sensitivity, and lowering the operating temperature. Recently, different strategies have been implemented to improve the sensitivity and selectivity of ZnO to CO, highlighting the doping of ZnO. Many studies concluded that doped ZnO demonstrates better sensing properties than those of undoped ZnO in detecting CO. Therefore, in this review, we analyze and discuss, in detail, the recent advances in doped ZnO for CO sensing applications. First, experimental studies on ZnO doped with transition metals, boron group elements, and alkaline earth metals as CO sensors are comprehensively reviewed. We then focused on analyzing theoretical and combined experimental-theoretical studies. Finally, we present the conclusions and some perspectives for future investigations in the context of advancements in CO sensing using doped ZnO, which include room-temperature gas sensing.

Solar driven CO2 hydrogenation on transition metal doped Zn12O12 cluster

Photocatalytic hydrogenation of carbon dioxide (CO₂) to produce value-added chemicals and fuel products is a critical routine to solve environmental issues. However, developing photocatalysts composed of earth-abundant, economic, and environmental-friendly elements is desired and challenging. Metal oxide clusters of subnanometer size have prominent advantages for photocatalysis due to their natural resistance to oxidation as well as tunable electronic and optical properties. Here, we exploit 3d transition metal substitutionally doped Zn₁₂O₁₂ clusters for CO₂ hydrogenation under ultraviolet light. By comprehensive ab initio calculations, the effect of the dopant element on the catalytic behavior of Zn₁₂O₁₂ clusters is clearly revealed. The high activity for CO₂ hydrogenation originates from the distinct electronic states and charge transfer from transition metal dopants. The key parameters governing the activity and selectivity, including the d orbital center of TM dopants and the energy level of the highest occupied molecular orbital for the doped Zn₁₂O₁₂ clusters, are thoroughly analyzed to establish an explicit electronic structure-activity relationship. These results provide valuable guidelines not only for tailoring the catalytic performance of subnanometer metal oxide clusters at atomic precision but also for rationally designing non-precious metal photocatalysts for CO₂ hydrogenation.

First-Principles Exploration of Hazardous Gas Molecule Adsorption on Pure and Modified Al60N60 Nanoclusters

In this work, we use the first-principles method to study in details the characteristics of the adsorption of hazardous NO₂, NO, CO₂, CO and SO₂ gas molecules by pure and heteroatom (Ti, Si, Mn) modified Al₆₀N₆₀ nanoclusters. It is found that the pure Al₆₀N₆₀ cluster is not sensitive to CO. When NO₂, NO, CO₂, CO and SO₂ are adsorbed on Al₆₀N₆₀ cluster’stop.b, edge.a_p, edge.a_h, edge.a_p andedge.a_h sites respectively, the obtained configuration is the most stable for each gas. Ti, Si and Mn atoms prefer to stay on the top sites of Al₆₀N₆₀ cluster when these heteroatoms are used to modify the pure clusters. The adsorption characteristics of above hazardous gas molecules on these hetero-atom modified nanoclusters are also revealed. It is found that when Ti-Al₆₀N₆₀ cluster adsorbs CO and SO₂, the energy gap decreases sharply and the change rate of gap is 62% and 50%, respectively. The Ti-modified Al₆₀N₆₀ improves the adsorption sensitivity of the cluster to CO and SO₂. This theoretical work is proposed to predict and understand the basic adsorption characteristics of AlN-based nanoclusters for hazardous gases, which will help and guide researchers to design better nanomaterials for gas adsorption or detection.

A DFT study on functionalization of acrolein on Ni-doped (ZnO)6 nanocluster in dye-sensitized solar cells

In this work, the functionalization of Acrolein on the Nickel-doped Zn6O6 (A-NiZn5O6) nanocluster with different adsorption configurations (C, M1 & M2) as the π conjugated bridging in dye-sensitized solar cells (DSSC) compared with the anchoring group [6,6] - phenyl-C61-butyric acid methyl ester (PCBM) have been investigated through (DFT/TD-DFT)) calculations by Gaussian 09 program. The interaction between the NiZn5O6 and the Acrolein has been explored through three functional groups are = O Carbonyl group (C), -CH Methyl group (M1), and -CH2 Methylene group (M2) of the Acrolein. The nature of the interaction between the Acrolein and NiZn5O6 has been exhaustively studied in terms of energy gap (Eg), global reactivity descriptors, molecular geometries, adsorption energy, the density of states, Mulliken atomic charges, molecular electrostatic potential, and the UV-Vis spectra for each adsorption site. The frontier molecular orbital analysis study indicated that all dyes could give a suitable electron vaccination from the LUMO orbital of A-NiZn5O6 to the HOMO orbital of PCBM. The adsorption process significantly improved the incident photon to the current conversion potency of the A-NiZn5O6. The determination of density functional theory calculations revealed that the C site of A-NiZn5O6 material was faced with a lower chemical hardness and energy gap (Eg) as well as a higher electron accepting power and light harvesting efficiency compared to other sites.

Enhanced Carbon monoxide-sensing properties of Chromium-doped ZnO nanostructures

Low power consumption, fast response and quick recovery times are important parameters for gas sensors performance. Herein, we report the experimental and theoretical studies of ZnO and Cr doped ZnO nanostructures used in low temperature (50 °C) sensors for the detection of CO. The synthesized films were characterized by XRD, UV-Vis, FE-SEM and EDX. The XRD patterns for the ZnO and 0.5 wt% Cr/ZnO films confirm the formation of a single-phase hexagonal wurtzite structure. The reduction of the ZnO optical band gap from 3.12 eV to 2.80 eV upon 0.5 wt% Cr doping is well correlated with the simulation data. The FE-SEM images of the films show spherical morphology with the estimated particle sizes of about ~40 nm and ~ 25 nm were recorded for the ZnO and 0.5 wt% Cr/ZnO films, respectively. Enhanced gas sensing performance is achieved with Cr doping and the sensitivity of ZnO increases from 9.65% to 65.45%, and simultaneously decreasing the response and recovery times from 334.5 s to 172.3 s and from 219 s to 37.2 s, respectively. These improvements in gas sensing performance are due to the reduction in particle size and optical band gap, and an increase in specific surface area.

The reactivity of CO on bimetallic Ni3M clusters (M = Sc, Ti, V, Cr, Mn, Fe, Co, Cu, Rh, Ru, Ag, Pd and Pt) by density functional theory

Surface C and O overlap with bimetallic clusters in σ, π and δ-type bonding; for example, C is a σ-donor at −15.23 eV and a π-donor at −9.29 eV, and O is a δ-acceptor at −7.76 eV in Ni₃Fe clusters.

Recent Advances in Atomic Metal Doping of Carbon-based Nanomaterials for Energy Conversion

Nanostructured metal-contained catalysts are one of the most widely used types of catalysts applied to facilitate some of sluggish electrochemical reactions. However, the high activity of these catalysts cannot be sustained over a variety of pH ranges. In an effort to develop highly active and stable metal-contained catalysts, various approaches have been pursued with an emphasis on metal particle size reduction and doping on carbon-based supports. These techniques enhances the metal-support interactions, originating from the chemical bonding effect between the metal dopants and carbon support and the associated interface, as well as the charge transfer between the atomic metal species and carbon framework. This provides an opportunity to tune the well-defined metal active centers and optimize their activity, selectivity and stability of this type of (electro)catalyst. Herein, recent advances in synthesis strategies, characterization and catalytic performance of single atom metal dopants on carbon-based nanomaterials are highlighted with attempts to understand the electronic structure and spatial arrangement of individual atoms as well as their interaction with the supports. Applications of these new materials in a wide range of potential electrocatalytic processes in renewable energy conversion systems are also discussed with emphasis on future directions in this active field of research.