A Review of Selenium (Se) Nanoparticles: From Synthesis to Applications

Selenium is an essential trace element that plays a crucial role in various physiological activities, exerting a significant impact on human health. Selenium deficiency can lead to the development of several diseases, while excessive doses can be toxic. In recent years, there is a growing interest in elemental selenium nanoparticles (SeNPs) due to their good biocompatibility, low toxicity, and high antioxidant activity, making them suitable for numerous applications. The quest for enhancing efficacy and reducing toxicity has driven extensive research on SeNPs. This review aims to provide a comprehensive summary of the recent advancements made in the synthesis, characterization, properties, and applications of SeNPs. Moreover, the challenges associated with SeNPs research, as well as the future trends in the field, are thoroughly discussed. This review aims to provide an insight into the current state of research on SeNPs and highlight areas that require further exploration and development.     

Oxide Materials for Development of Integrated Gas Sensors—A Comprehensive Review

In the recent past a great deal of research efforts were directed toward the development of miniaturized gas-sensing devices, particularly for toxic gas detection and for pollution monitoring. Though various techniques are available for gas detection, solid state metal oxides offer a wide spectrum of materials and their sensitivities for different gaseous species, making it a better choice over other options. In this article a critical parameter analysis of different metal oxides that are known to be sensitive to various gaseous species are thoroughly examined. This includes phase of the oxide, sensing gaseous species, operating temperature range, and physical form of the material for the development of integrated gas sensors. The oxides that are covered in this study include oxides of aluminum, bismuth, cadmium, cerium, chromium, cobalt, copper, gallium, indium, iron, manganese, molybdenum, nickel, niobium, ruthenium, tantalum, tin, titanium, tungsten, vanadium, zinc, zirconium, and the mixed or multi-component metal oxides. They cover gases such as CO, CO₂, CH₄, C₂H₅OH, C₃H₈, H₂, H₂S, NH₃, NO, NO₂, O₂, O₃, SO₂, acetone, dimethylamine (DMA), humidity, liquid petroleum gas (LPG), petrol, trimethylamine (TMA), smoke, and many others. Both doped and undoped oxides are analyzed for the compatibility with silicon processing conditions and hybrid microcircuit fabrication techniques. In silicon processing conditions, they are further analyzed for the suitability for simple silicon surfaces, silicon-on-insulator (SOI) surfaces, and micromachined silicon geometries for different operating temperatures. Discussion on gas-sensing properties of each material and its applications are described in the text in alphabetical order of the elemental oxides. Further, the gas-sensing properties like sensitivity, detection limits, operating temperature, and so on are summarized in tables al ong with relevant references. The figures incorporated in the present review are primarily based on discussions and data in tables. However, these figures provide a qualitative comparison and present a pictorial view to examine suitability of a material for a particular application. From the known parameters, the present study clearly indicates the suitability of certain materials and the gases that they cover for the development of integrated micro gas sensors. A clear picture has been brought out for the development of silicon-based processing technology. Various parameters are discussed for the selection of these materials, to examine their suitability and practical problems that are being associated. Etching of these metal oxides and the reliability of devices are also discussed.     

Synthesis,Properties, and Applications of 2-D Materials: A Comprehensive Review

Recent advances in atomically thin two-dimensional (2-D) materials have led to a variety of promising future technologies for post-CMOS nanoelectronics and energy generation. This review is an attempt to thoroughly illustrate the current status and future prospects for 2-D materials other than graphene (e.g., BN nanosheets, MoS₂, NbSe₂, WS₂, etc.), which have already been contemplated for both low-end and high-end technological applications. An overview of the different synthesis techniques for 2-D materials is presented here, with an exploration of the potential for developing methods of controllable large scale synthesis. Furthermore, we summarize the underlying theories which correlate the structural and physical properties of 2-D materials with their state-of-the-art applications. Finally, we show that utilizing the unprecedented properties arising from these materials would lead to innovative devices. Such devices would significantly reduce both device dimensions and power consumption, as necessary for the creation of tomorrow's sustainable technology.     

Size,Shape, and Wavelength Effect on Photothermal Heat Elevation of Gold Nanoparticles: Absorption Coefficient Experimental Measurement

Complex-shaped nanoparticles as gold nanourchins (GNU) and nanorods (GNR) are very suitable agents in the case of photothermal therapy due to their photon-heat conversion ability in the red and near-infrared region (NIR). The quantification in heat generation of complex shaped nanostructures is an important key to predict the therapeutic effect of these nanoparticles. For that, the determination of the nanoparticles absorption cross section (σ_Abs) responsible for the heat generation is one of the important steps before any application. Although it is obvious to determine σ_Abs for spheres via Mie's theory, in the case of complex structures like GNU or GNR, this parameter is difficult to model. In this work, a new methodology is used to determine experimentally σ_Abs for both GNU and GNR. Experimental measurements of the photothermal properties of 100 nm size GNU and two different sizes of GNRs are studied regarding different parameters such as concentration, laser excitation wavelength, and exposure time. By using the heat transfer theory, the temperature elevation in the nanoparticles solutions is converted to temperature elevation at the nanoparticles surface and σ_Abs values are then calculated for both GNU and GNR in the NIR spectral region.     

Recent progress in all-inorganic metal halide nanostructured perovskites: Materials design,optical properties,and application

Low-dimensional all-inorganic metal halide perovskite (AIMHP) materials, as a new class of nanomaterials, hold great promise for various optoelectronic devices. In the past few years, tremendous progress has been achieved in the development of efficient and stable AIMHP nanomaterials for optical property studies and related applications. Here, we offer a critical overview on the unique merits and the state-of-the-art design of AIMHP using different composition strategies. Then, the effects of material compositions, dimensionality, morphologies and structures on optical properties are summarized. We also comprehensively present recent advances in the development AIMHP nanomaterials for practical applications including solar cells, light-emitting diodes, lasers and photodetectors. Lastly, the critical challenges and future opportunities in this emerging field are highlighted.     

Preparation,Properties and Applications of Chitosan-Based Biocomposites/Blend Materials: A Review

Taking inspiration from many published chitosan (Cs)-based biocomposites, this article is written to highlight the significant effect of reinforcing and/or blending Cs polymer with the different constituents to increase various properties (mechanical, hydrophilic, thermal, adsorption ability and stability) of Cs without sacrificing any of its positive properties. It is concluded that the properties of Cs biocomposites with a synthetic constituent have contributed to its rigidity since only mechanical interaction occurred at the interfacial region. Instead of physical interactions, the addition of an organic constituent also promoted the chemical interactions at the interfacial region of the Cs biocomposites. This consequently produced Cs biocomposites with synthetic constituents with relatively low strength and stiffness but high resistance to fracture, whereas the ones with an organic constituent have high strength and stiffness but are very brittle. This review also screens the current applications of Cs-based biocomposites in the field of drug delivery, tissue engineering, antibacterial, food packaging, biomedical, metal adsorption and dye removal.     

A density functional theoretic study of novel silicon-carbon fullerene-like nanostructures: Si40C20, Si60C20, Si36C24, and Si60C24

Fullerene-like silicon nanostructures with twenty and twenty-four carbon atoms on the surface of the Si₆₀ cage by substitution, as well as inside the cage at various orientations have been studied within the generalized gradient approximation to density functional theory. Full geometry optimizations have been performed without any symmetry constraints using the Gaussian 03 suite of programs and the LANL2DZ basis set. Thus, for the silicon atom, the Hay-Wadt pseudopotential with the associated basis set is used for the core electrons and the valence electrons, respectively. For the carbon atom, the Dunning/Huzinaga double zeta basis set is employed. Electronic and geometric properties of these nanostructures are presented and discussed in detail. Optimized silicon-carbon fullerene like nanostructures are found to have increased stability compared to the bare Si₆₀ cage and the stability depends on the number and the orientation of carbon atoms, as well as on the nature of silicon-carbon and carbon-carbon bonding.     

Surface Texture Manufacturing Techniques and Tribological Effect of Surface Texturing on Cutting Tool Performance: A Review

The tribological characteristics of sliding surfaces have been remarkably improved by surface texturing. Surface texturing can be beneficial in many ways; for example, it can reduce friction and wear, increase load carrying capacity, and increase fluid film stiffness. The design process for surface texturing is highly correlated to the particular functions of any application for which texturing is required. Texture quality is greatly affected by manufacturing methods, therefore, it is important to have a detailed understanding of the related parameters of any technique.

The use of surface texturing to improve the cutting performance of tools is a relatively new application. These textures improve cutting performance by enhancing lubricant availability at the contact point, reducing the tool-chip contact area, and trapping wear debris. Reductions in crater and flank wear, friction force, cutting forces, and cutting temperature are the main benefits obtained by this technique. To date, surface texturing has been successfully used in drilling, milling, and turning operations.

This article provides an overview of the techniques that have been used in industry and research platforms to manufacture micro-/nano-textures for tribological applications, and it examines the effects of surface textures on cutting tool performance.     

Chemical Vapor Generation with Slurry Sampling: A Review of Applications to Atomic and Mass Spectrometry

Abstract

A critical review of published analytical methods and techniques for chemical vapor generation (CVG) with slurry sample introduction for detection by atomic and mass spectrometry is presented. The nstrumentation used for the reaction as well as separation and transport of the species, influence of chemical and physical factors, and efficiency of the process are considered. A brief comparison of detection limits obtained with atomic absorption, emission, and fluorescence as well as mass spectrometry along with practical applications to analytical samples are summarized. The current state-of-the-art, including advantages and limitations of this approach, is discussed.     

A theoretical study on the excited states of MC3 (M = Sc, V, and Cr)

The ground state structures of MC₃ (M = Sc, V, and Cr) and their anions have been investigated, employing the first-principles DFT at the B3LYP level. The calculations predict that the equilibrium geometries of both neutral MC₃ and their anions are cyclic structures with C_2v symmetry. The Mulliken charge and spin populations of MC₃ and their anions have also been calculated, and it is found the electron charge changes mainly take place on the M atoms from anions to neutral molecules. The low-lying excited states for the clusters are calculated with time-dependent DFT to assign the features of the photoelectron spectra. Our results agree well with the available experimental and theoretical data.     

Tetrahedral coordination for Zn in hexacyanometallates: Structures of Zn3A2[M(CN)6]2·xH2O with A=K, Rb, Cs and M=Ru, Os

Zinc hexacyanoruthenate (II) and hexacyanoosmate (II) were prepared and studied from X-ray diffraction (XRD), infrared (IR), and thermogravimetric (TG) data. These compounds were found to be isomorphous with the iron analogues, crystallizing with a rhombohedral unit cell (R−3c space group), where the zinc atom has tetrahedral coordination to N ends of CN groups. For Cs, compounds with formula unit ZnCs₂[M(CN)₆] and a cubic unit cell (Fm−3m) were also obtained. The crystal structures for the eight compositions were refined from the corresponding X-ray powder diffraction patterns using the Rietveld method. Related to the tetrahedral coordination for the Zn atom, the rhombohedral phase has a porous framework with ellipsoidal cavities of about 12.5×9×8 Å, communicated by elliptical windows of ∼5 Å. Within these cavities the exchangeable alkali metal ions are found. The filling of the cavity volume is completed with water molecules. IR spectrum senses certain charge delocalization from the inner metal, through the π-back donation mechanism. For Os compounds this effect is particularly pronounced, related to a more diffuse d orbitals for this metal.