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Humidity effect on adsorption kinetics of ammonia onto electrospun SnO <sub/>2</sub> nanofibers
摘要： Tin dioxide nanofibers were successfully synthesized by electrospinning homogeneous solution of SnCl4·5H2O in polyvinyl alcohol (PVA) and the potential of SnO2 nanofibers as ammonia sensing element at room temperature were also investigated. A logarithmic dependence of sensitivity on ammonia concentration was observed. We further investigate the effect of relative humidity between 0% and 70% on ammonia sensing performance of SnO2 nanofibers based conductometric sensor for the first time. Sensing experiments showed that both the baseline sensor current and the response-recovery characteristics of the SnO2 based sensor modified by pre humidification of sensing layer' surface. To study the adsorption kinetics pseudo first order and Elovich models was used and the first order kinetic model best describes the ammonia adsorption onto the SnO2 nanofibers for low concentrations (≤80 ppm) of ammonia, irrespective of humidity level. On the other hand, the results describe the best representation of Elovich model, as evidenced by the high correlation coefficients, for high concentrations of ammonia gas.
关键词： adsorption kinetics,humidity effect,ammonia sensing,electrospinning,response time
更新于2025-09-23 15:22:29
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Integrated adsorption and photocatalytic degradation of volatile organic compounds (VOCs) using carbon-based nanocomposites: A critical review
摘要： Volatile organic compounds (VOCs) are harmful for human and surrounding ecosystem, and a great number of VOC abatement technologies have been developed during the past few decades. However, the single method has some problems such as high energy consumption, unfriendly environment, and low removal efficiency. Recently, the integration of adsorption and photocatalytic degradation of VOCs is considered as a promising one. Carbon material, with large surface area, high adsorption capacity, and fast electron transfer ability, is widely used in integrated adsorptive-photocatalytic removal of VOCs. It is thus crucial to digest and summarize recent research advances in carbon-based nanocomposites as the adsorbent-photocatalyst for VOC removal. To satisfy this need, this work provides a critical review of the related literature with focuses on: (1) the advantages and disadvantages of various carbon-based nanocomposites for the applications of VOC adsorption and photocatalytic degradation; (2) models and mechanisms of adsorptive-photocatalytic removal of VOCs according to the material properties; and (3) major factors controlling adsorption-photocatalysis processes of VOCs. The review is aimed to establish the "structure-property-application" relationships for the development of innovative carbon-supported nanocomposites and to promote future research on the integrated adsorptive and photocatalytic removal of VOCs.
关键词： Modeling,Photocatalytic degradation,VOC abatement,Carbon-based nanocomposite,Adsorption
更新于2025-09-23 15:21:21
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Density, Structure, and Stability of Citrate <sup>3–</sup> and H <sub/>2</sub> Citrate <sup>–</sup> on Bare and Coated Gold Nanoparticles
摘要： We simulate the packing of citrate3– and H2citrate– onto gold nanoparticles (AuNPs) to understand how citrate anions cap and stabilize AuNPs. We determine the molecular configurations of citrate on 4, 6, and 8 nm AuNP surfaces as a function of charge state and packing density and find that both the distribution of configurations and maximum packing density are independent of AuNP size. A combination of molecular dynamics simulations and in situ Fourier transform infrared spectroscopy (FTIR) is employed to compare the molecular configurations, stability, and density of citrate on 4 nm citrate-coated (cit-AuNPs) and within polycation-wrapped 4 nm cit-AuNPs. FTIR experiments indicate the presence of H2citrate– within polycation-wrapped cit-AuNPs with coordination between the H2citrate– layer and polycation layer in agreement with simulations. Intermolecular hydrogen bonding between terminal carboxylic-acid groups of H2citrate– stabilizes the anionic layer at the interface between cit-AuNPs and adsorbing charged molecules. The calculated total density of H2citrate– on AuNPs decreases from 3.3 × 10-10 mol/cm2 to 3.0 × 10-10 mol/cm2 upon adsorption of a polycation due to some displacement of dangling H2citrate– hydrogen bonded to the surface-bound layer. The density of the surface-bound layer is consistently 2.8 × 10-10 mol/cm2 with and without polycation adsorption. We provide all-atom level insight into the distribution and organization of experimentally derived binding modes of citrate on bare and coated cit-AuNPs. The citrate density and surface charge density are determined for all-atom and coarse-grained modeling of cit-AuNPs, their functionalization, and transformations in complex environments.
关键词： polycation adsorption,gold nanoparticles,FTIR spectroscopy,citrate,molecular dynamics simulations
更新于2025-09-23 15:21:21
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High adsorptivity and visible light assisted photocatalytic activity of silver/reduced graphene oxide (Ag/rGO) nanocomposite for wastewater treatment
摘要： The present study entails a simple chemical method for the preparation of high-quality silver / reduced graphene oxide (Ag/rGO) nanocomposite. Ag/rGO nanocomposite was characterized using UV–Visible spectroscopy, High Resolution Transmission Spectroscopy (HR-TEM), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Brunauer–Emmett–Teller (BET) analysis and X-ray Diffraction spectroscopy (XRD). SEM results showed the Silver (Ag) nanoparticles were deposited on graphene oxide (GO) nanosheets. XRD results confirmed the crystalline structure of Ag/rGO nanocomposite. The photocatalytic activity and stability of Ag/rGO nanocomposite for the degradation of methyl orange (MeO) dye was significantly increased in comparison to GO nanosheets under visible light. The adsorption capacity of Total Dissolved Solids (TDS) by Ag/rGO nanocomposite and GO nanosheets were further studied by utilizing wastewater as sample. The adsorption isothermal and kinetic studies suggest that 0.4 g/L Ag/rGO nanocomposite produce optimum separation capacity. Therefore, considering the excellent photocatalytic activity and adsorptivity nature of Ag/rGO nanocomposite, the present investigation can be effective in energy and environment related application.
关键词： Nanostructures,Adsorption,Photocatalysis,Total dissolved solids
更新于2025-09-23 15:21:21
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Adsorption of the liquid crystal molecule 5CB on graphene
摘要： We use density functional theory to explore the stable adsorption geometries of the liquid crystal molecule 5CB on a graphene sheet. First, we calculate the dependence of the polarizability of 5CB on its geometry. Our results break down the contributions of the cyano, biphenyl, and alkyl groups to the optical properties of 5CB, confirming the biphenyl group as the most influential. Second, we quantify possible adsorption structures of 5CB on graphene. We find that 5CB can stably adsorb with its biphenyl group oriented intermediate to the armchair and zigzag crystallographic directions, in addition to adsorbing with the biphenyl oriented along those directions.
关键词： 5CB,graphene,density functional theory,liquid crystal,adsorption
更新于2025-09-23 15:21:21
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Density Functional Theory Calculations of Oxygen-Vacancy Formation and Subsequent Molecular Adsorption on Oxide Surfaces
摘要： The surface oxygen vacancy formation energy (EOvac) is an important parameter in determining the catalytic activity of metal oxides. Estimating these energies can therefore lead to data-driven design of promising catalyst candidates. In the present study, we determine EOvac for various insulating and semiconducting oxides. Statistical investigations indicate that the band gap, bulk formation energy, and electron affinity are factors that strongly influence EOvac. Electrons enter defect states after O desorption, and these states can be in the valence band, mid-gap, or in the conduction band. Subsequent adsorption of O2, NO, CO, CO2, and H2 molecules on an O-deficient surface is also investigated. These molecules become preferentially adsorbed at the defect sites, and EOvac is identified as the dominant factor that determines the adsorption mode as well as a descriptor that shows good correlation with the adsorption energy.
关键词： catalytic activity,molecular adsorption,oxygen vacancy formation energy,metal oxides,density functional theory
更新于2025-09-23 15:21:21
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Efficient and selective sensing of nitrogen containing gases by Si2BN nanosheets under pristine and pre-oxidized conditions
摘要： Motivated by the promise of two-dimensional nanostructures in the field of gas sensing, we have employed van der Waals corrected density functional theory calculations to study the structural, electronic and gas sensing propensities of recently designed Si2BN monolayer. Our rigorous simulations reveal that the representative members of nitrogen containing gases (NCGs) such as NO, NO2 and NH3 binds extremely strongly on pristine Si2BN monolayer. However a strong dissociative adsorption in case of NO and NO2 would poison the Si2BN and ultimately reversibility of the monolayer would be compromised. Exploring the sensing mechanism in more realistic pre-oxidized conditions, the binding characteristics of O2@Si2BN changed dramatically, resulting into much lower adsorption in associative manner for all NO, NO2 and NH3. A visible change in work function indicates the variation in conductivity of O2@Si2BN upon the exposure of incident gases. Sustainable values of binding energies would also ensure a quick recovery time that makes O2@Si2BN an efficient nano sensor for pollutants like NCGs.
关键词： Conductivity,Adsorption,Work function,Recovery time,Monolayer
更新于2025-09-23 15:21:21
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X-ray Photoelectron Spectroscopy Analysis of the Effect of Photoresist Passivation on InGaZnO Thin-film Transistors
摘要： Bottom-gate InGaZnO (IGZO) thin-film transistors (TFTs) with EOC photoresist (PR) passivation were fabricated. Compared to the unpassivated IGZO TFT with a mobility of 6.71 cm2V-1s-1, a hysteresis of 2.42 V and a poor bias stress stability, the PR-passivated IGZO TFT showed good electrical characteristics with a higher mobility of 8.85 cm2V-1s-1, a lower hysteresis of 0.06 V and a more reliable stability (△Vth = 0.36 V) under positive gate bias stress (PBS). The effect of PR passivation on the performance of IGZO-TFT was investigated by x-ray photoelectron spectroscopy (XPS), systemically. The result of XPS spectra of the O 1s core levels indicate that PR passivation effectively suppressed the adsorption/desorption effect on IGZO surface, resulting in fewer unstable states and higher electrical stability. Furthermore, XPS depth profile experiments show that the proportion of elements on the film surface changed and the IGZO surface was In-rich after PR passivation, enhancing the mobility. The PR passivation with low temperature (100 oC) process exhibited good dielectric quality and excellent barrier ability against water and oxygen molecules. Therefore, it may be a good candidate for high-mobility and high-stability flexible TFTs in future.
关键词： XPS,InGaZnO,Photoresist,Thin film transistors,Adsorption/desorption
更新于2025-09-23 15:21:21
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CH<sub>2</sub>O Adsorption on M (M = Li, Mg and Al) Atom Deposited ZnO Nano-Cage: DFT Study
摘要： The structural and electronic properties of Li, Mg and Al deposited ZnO nano-cages and their effects on the adsorption of formaldehyde molecule have been investigated using the density functional theory (DFT) computations. To understand the behavior of the adsorbed CH2O molecule on the ZnO nano-cage, results of DFT calculations of the M-deposited nano-cages (M=Li, Mg and Al), as well as complex systems consisting of the adsorbed CH2O molecule on M-deposited ZnO nano-cage were reported. The results presented include adsorption energies, bond lengths, electronic configurations, density of states and molecular orbitals. It was found that, the most energetically stable adsorption configurations of CH2O molecule on the bare ZnO leads to 12% dilation in C=O bond length of CH2O and 14% decrease in HOMO-LUMO gap of ZnO cluster. The most energetically stable adsorption configurations of CH2O molecule on Li, Mg and Al-deposited ZnO lead to 4%, 4% and 11% dilation in C=O bond length of CH2O and -0.66, -45 and , +66% change in HOMO-LUMO gap of ZnO nano cages, respectively. The interaction between CH2O with bare ZnO and M-deposited ZnO nano-cages is attributed to charge transfer mechanism. These results may be meaningful for CH2O degradation and detection.
关键词： ZnO,Adsorption,nanomaterials,Formaldehyde,DFT
更新于2025-09-23 15:21:21
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Characterizing Molecular Adsorption on Biodegradable MnO <sub/>2</sub> Nanoscaffolds
摘要： Biodegradable MnO2 nanoscaffolds have recently been designed for advanced stem cell therapy. These nanomaterials strongly bind extracellular matrix proteins and effectively deliver therapeutic molecules, which significantly enhance stem cell survival and neuronal differentiation both in vitro and in vivo. In this work, we combine molecular dynamics simulations, density functional theory calculations and UV-Vis spectroscopy experiments to examine the selectivity and efficiency of a MnO2 nanosheet in adsorbing neurogenic drugs. To uncover the fundamental principles governing the drug loading process, we have systematically examined a series of model aromatic and alkyl compounds with characteristic functional groups and demonstrated that molecular adsorption on the MnO2 nanosheet results from an interplay of dispersion, electrostatic and charge transfer interactions. We have then proposed a metric that efficiently predicts the qualitative adsorption affinity of a guest molecule on the MnO2 nanosheet based on its structural and chemical features, which will facilitate the experimental screening of proper adsorbates for efficient molecular delivery and aid the development of MnO2-based nanoscaffolds for biomedical applications.
关键词： adsorption affinity,molecular dynamics simulations,density functional theory,MnO2 nanoscaffolds,neurogenic drugs,UV-Vis spectroscopy
更新于2025-09-23 15:21:21