A theoretical study on sensing properties of in-doped ZnO nanosheet toward acetylene

Advances in 2D Materials Based Gas Sensors for Industrial Machine Olfactory Applications

The escalating development and improvement of gas sensing ability in industrial equipment, or "machine olfactory", propels the evolution of gas sensors toward enhanced sensitivity, selectivity, stability, power efficiency, cost-effectiveness, and longevity. Two-dimensional (2D) materials, distinguished by their atomic-thin profile, expansive specific surface area, remarkable mechanical strength, and surface tunability, hold significant potential for addressing the intricate challenges in gas sensing. However, a comprehensive review of 2D materials-based gas sensors for specific industrial applications is absent. This review delves into the recent advances in this field and highlights the potential applications in industrial machine olfaction. The main content encompasses industrial scenario characteristics, fundamental classification, enhancement methods, underlying mechanisms, and diverse gas sensing applications. Additionally, the challenges associated with transitioning 2D material gas sensors from laboratory development to industrialization and commercialization are addressed, and future-looking viewpoints on the evolution of next-generation intelligent gas sensory systems in the industrial sector are prospected.

Experimental and ab initio studies of Co-doped ZnO nanophotocatalyst thin films for dye mineralization

Pristine ZnO and Co-doped ZnO photocatalyst thin films were fabricated on a ceramic substrate by spray pyrolysis. The optical, morphological and structural properties of the fabricated nanophotocatalyst thin films were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy and Fourier transform infrared (FTIR) spectroscopy. Operational parameters, including dye concentration, oxidant concentration, irradiation time and pH for dye degradation, were optimized by response surface methodology (RSM). The maximum degradation obtained was 93% under ideal conditions, such as pH 7, 3 h of direct sunlight irradiation, 30 mM concentration of oxidant and 10 ppm concentration of dye (MB). The evaluation of the extent of degradation was done using the UV/visible spectrophotometry technique. The reusability of the fabricated thin film was examined under optimized conditions. Density functional theory (DFT) with the B3LYP/LanL2DZ method was used for the theoretical modelling of the fabricated nanomaterials. The optimized structure, theoretical band gaps, IR spectra and Raman spectra of the fabricated pristine ZnO and Co:ZnO nanophotocatalysts were determined.

Deciphering the electrochemical sensing capability of novel Ga12As12 nanocluster towards chemical warfare phosgene gas: insights from DFT

The applications of 3D inorganic nanomaterials in environmental and agriculture monitoring have been exploited continuously; however, the utilization of semiconductor nanoclusters, especially for detecting warfare agents, has not been fully investigated yet. To fill this gap, the molecular modelling of novel inorganic semiconductor nanocluster Ga12As12 as a sensor for phosgene gas (highly toxic for living things and the environment) is accomplished employing benchmark DFT and TD-DFT investigations. Computational tools have been applied to explore different adsorption sites and the potential sensing capability of the Ga12As12 nanoclusters. The calculated adsorption energy (-21.34 ± 2.7 kcal mol-1) for ten selected complexes, namely, Pgn-Cl@4m-ring (MS1), Pgn-Cl@6m-ring (MS2), Pgn-Cl@XY66 (MS3), Pgn-O@4m-ring (MS4), Pgn-O@XY66 (MS5), Pgn-O@XY64 (MS6), Pgn-O@Y (MS7), Pgn-planar@Y (MS8), Pgn-planar@X (MS9), and Pgn-planar@4m-ring (MS10), manifest the remarkable and excessive adsorption response of the studied nanoclusters. The explored molecular electronic properties, such as interaction distance (3.05 ± 0.5 Å), energy gap (∼2.17 eV), softness (∼0.46 eV), hardness (1.10 ± 0.01 eV), electrophilicity index (10.27 ± 0.45 eV), electrical conductivity (∼1.98 × 109), and recovery time (∼3 × 10-12 s-1) values, ascertain the elevated reactivity and an imperishable sensitivity of the Ga12As12 nanocluster, particularly for its complex MS8. QTAIM analysis exhibits the presence of a strong electrostatic bond (positive ∇2ρ(r) values), electron delocalization (ELF < 0.5), and a strong chemical bond (because of high all-electron density values). In addition, NBO analysis explores the lone pair electron delocalization of phosgene to the nanocluster stabilized by intermolecular charge transfer (ICT) and different kinds of non-covalent interactions. Also, the green region existence expressed by NCI analysis (between the nanocluster and adsorbate) stipulate the energetic and dominant interactions. Furthermore, the UV-Vis, thermodynamic analysis, and density of state (DOS) demonstrate the maximum absorbance (562.11 nm) and least excitation energy (2.21 eV) by the complex MS8, the spontaneity of the interaction process, and the significant changes in HOMO and LUMO energies, respectively. Thus, the Ga12As12 nanocluster has proven to be a promising influential sensing material to monitor phosgene gas in the real world, and this study will emphasize the informative knowledge for experimental researchers to use Ga12As12 as a sensor for the warfare agent (phosgene).

Photocatalytic degradation of air pollutant by modified nano titanium oxide (TiO2)in a fluidized bed photoreactor: Optimizing and kinetic modeling

Volatile organic compound (VOC) removal by photocatalytic oxidation (PCO) is the practical and economical process to reduce air pollutants. Many conditions, such as temperature, initial concentration of VOC, relative humidity, gas flow rate, and light intensity, affected this process. Therefore, finding the optimal operating conditions for the PCO process can increase the efficiency of the process and also operate the process more economically. Also, it is possible to scale up the process with more confidence by the kinetics modeling of the process and finding the rate constants. In this study, the effect of gas flow rate, light intensity, and VOC inlet concentration were investigated. The results show that the flow rate of 15 lit/min is more efficient, and the effect of the pollutant input concentration and light intensity directly affects the conversion percentage. The kinetic study of acetaldehyde removal was investigated in the fluidized bed reactor, and the best kinetic model was proposed based on reactor model regression on the outlet concentration data. The best model describes a langmuir-hynshelwood type model with adsorbed acetaldehyde's inhibition effect on the catalyst's surface. The R² coefficient for the best kinetic type is 0.98.

Adsorption properties of metal functionalized fullerene (C59Au, C59Hf, C59Ag, and C59Ir) nanoclusters for application as a biosensor for hydroxyurea (HXU): insight from theoretical computation

This theoretical study was conducted to evaluate the efficiency of fullerene C60 and its metal functionalized nano clusters (C59Au, C59Hf, C59Ag and C59Ir) as a sensor for hydroxyurea (HXU). The various conclusions concerning the adsorption and sensing properties of the studied nano surfaces were achieved using density functional theory (DFT) at the M062X-D3/gen/LanL2DZ/def2svp level of theory. Among the nano clusters studied for this interaction, analysis of the HOMO–LUMO energy differences (E g) showed that HXU@C59Hg (H2) reflects the least energy gap of 3.042 eV, indicating its greater reactivity, sensitivity and conductivity. Also, the adsorption phenomenon in this current study is best described as chemisorptions owing to the negative adsorption enthalpies observed. Thus, the adsorption energy (E Ad) follows an increasing pattern of: HXU@C60 (C1) (−0.218 eV) < HXU@C59Ir (I1) (−1.361 eV) < HXU@C59Au (A1) (−1.986 eV) < HXU@C59Hf (H1) (−2.640 eV) < HXU@C59Hg (H2) (−3.347 eV). Least E g, highest E Ad and non-covalent nature of interaction attributed to C59Hg surface are sufficient to show that, among all studied surfaces, C59Hg surface emerged as the most suitable adsorbent for the adsorption of HXU. Hence, it can be used in modeling future adsorbent material for hydroxyurea.

Two-Dimensional Material-Based Electrochemical Sensors/Biosensors for Food Safety and Biomolecular Detection

Two-dimensional materials (2DMs) exhibited great potential for applications in materials science, energy storage, environmental science, biomedicine, sensors/biosensors, and others due to their unique physical, chemical, and biological properties. In this review, we present recent advances in the fabrication of 2DM-based electrochemical sensors and biosensors for applications in food safety and biomolecular detection that are related to human health. For this aim, firstly, we introduced the bottom-up and top-down synthesis methods of various 2DMs, such as graphene, transition metal oxides, transition metal dichalcogenides, MXenes, and several other graphene-like materials, and then we demonstrated the structure and surface chemistry of these 2DMs, which play a crucial role in the functionalization of 2DMs and subsequent composition with other nanoscale building blocks such as nanoparticles, biomolecules, and polymers. Then, the 2DM-based electrochemical sensors/biosensors for the detection of nitrite, heavy metal ions, antibiotics, and pesticides in foods and drinks are introduced. Meanwhile, the 2DM-based sensors for the determination and monitoring of key small molecules that are related to diseases and human health are presented and commented on. We believe that this review will be helpful for promoting 2DMs to construct novel electronic sensors and nanodevices for food safety and health monitoring.

Different metal-decorated aluminum phosphide nanotubes as hydrazine sensors for biomedical applications

B3LYP, B97D, and M06-2X density functionals are utilized for probing the effect of decorating X (X = Co, Ti, Sc, or Ca) metals on the sensing performance of an aluminum phosphide nanotube (AlPNT) in detecting the hydrazine (HZ) gas. We predict that the interaction of pristine AlPNT with HZ is physisorption, and our calculated sensing response (SR) of AlPNT is approximately 2.7. The adsorption energy of HZ changes from - 4.6 to - 21.0, - 21.9, - 22.4, and - 23.8 kcal/mol by decorating the Co, Ti, Sc, and Ca metals into the AlPNT surface, respectively. Also, Co, Ti, Sc, and Ca rise the SR to 22.5, 36.8, 50.4, and 89.0, respectively, indicating that by increasing the atomic radius of metals, the sensitivity is more increased. So, we concluded that Ca much more increases the sensitivity of AlPNT toward HZ. Our calculations demonstrate that the electrostatic interaction has the main contribution in the formation of HZ/X decorated AlPNT (X@AlPNT) complexes. The expected recovery time is 22.0 s for the HZ desorption from the Ca@AlPNT at 298 K. Finally, we found that all of the X@AlPNTs have superior sensing performance toward HZ compared to the X@carbon nanotubes.

Heteroatoms (Si, B, N, and P) doped 2D monolayer MoS2 for NH3 gas detection

2D transition metal dichalcogenide MoS₂ monolayer quantum dots (MoS₂-QD) and their doped boron (B@MoS₂-QD), nitrogen (N@MoS₂-QD), phosphorus (P@MoS₂-QD), and silicon (Si@MoS₂-QD) surfaces have been theoretically investigated using density functional theory (DFT) computation to understand their mechanistic sensing ability, such as conductivity, selectivity, and sensitivity toward NH₃ gas. The results from electronic properties showed that P@MoS₂-QD had the lowest energy gap, which indicated an increase in electrical conductivity and better adsorption behavior. By carrying out comparative adsorption studies using m062-X, ωB97XD, B3LYP, and PBE0 methods at the 6-311G++(d,p) level of theory, the most negative values were observed from ωB97XD for the P@MoS₂-QD surface, signifying the preferred chemisorption surface for NH₃ detection. The mechanistic studies provided in this study also indicate that the P@MoS₂-QD dopant is a promising sensing material for monitoring ammonia gas in the real world. We hope this research work will provide informative knowledge for experimental researchers to realize the potential of MoS₂ dopants, specifically the P@MoS₂-QD surface, as a promising candidate for sensors to detect gas.

2D transition metal dichalcogenide MoS₂ monolayer quantum dots (MoS₂-QD) and their doped boron (B@MoS₂-QD), nitrogen (N@MoS₂-QD), phosphorus (P@MoS₂-QD), and silicon (Si@MoS₂-QD) counterparts are proposed as selective sensors for NH₃ gas.