Single-walled silicon nanotube as an exceptional candidate to eliminate SARS-CoV-2: a theoretical study

In this work, computational chemistry methods were used to study a silicon nanotube (Si₁₉₂H₁₆) as possible virucidal activity against SARS-CoV-2. This virus is responsible for the COVID-19 disease. DFT calculations showed that the structural parameters of the Si₁₉₂H₁₆ nanotube are in agreement with the theoretical/experimental parameters reported in the literature. The low energy gap value (0.29 eV) shows that this nanotube is a semiconductor and exhibits high reactivity. For nanomaterials to be used as virucides, they need to have high reactivity and high inhibition constant values. Therefore, the adsorption of ³O₂ and H₂O on the surface of Si₁₉₂H₁₆ (Si₁₉₂H₁₆@O₂-H₂O) was performed. In this process, the formation and activation energies were -51.63 and 16.62 kcal/mol, respectively. Molecular docking calculations showed that the Si₁₉₂H₁₆ and Si₁₉₂H₁₆@O₂H-OH nanotubes bind favorably on the receptor-binding domain of the SARS-CoV-2 spike protein with binding energy of -11.83 (Ki = 2.13 nM) and -11.13 (Ki = 6.99 nM) kcal/mol, respectively. Overall, the results obtained herein indicate that the Si₁₉₂H₁₆ nanotube is a potential candidate to be used against COVID-19 from reactivity process and/or steric impediment in the S-protein.Communicated by Ramaswamy H. Sarma.

The Magnetic Behaviour of CoTPP Supported on Coinage Metal Surfaces in the Presence of Small Molecules: A Molecular Cluster Study of the Surface trans-Effect

Density functional theory, combined with the molecular cluster model, has been used to investigate the surface trans-effect induced by the coordination of small molecules L (L = CO, NH₃, NO, NO₂ and O₂) on the cobalt electronic structure of cobalt tetraphenylporphyrinato (CoTPP) surface-supported on coinage metal surfaces (Cu, Ag, and Au). Regardless of whether L has a closed- or an open-shell electronic structure, its coordination to Co takes out the direct interaction between Co and the substrate eventually present. The CO and NH₃ bonding to CoTPP does not influence the Co local electronic structure, while the NO (NO₂ and O₂) coordination induces a Co reduction (oxidation), generating a 3d⁸ Co^I (3d⁶ Co^III) magnetically silent closed-shell species. Theoretical outcomes herein reported demonstrate that simple and computationally inexpensive models can be used not only to rationalize but also to predict the effects of the Co–L bonding on the magnetic behaviour of CoTPP chemisorbed on coinage metals. The same model may be straightforwardly extended to other transition metals or coordinated molecules.

Recent trends in gas sensing via carbon nanomaterials: outlook and challenges

The presence of harmful and poisonous gases in the environment can have dangerous effects on human health, and therefore portable, flexible, and highly sensitive gas sensors are in high demand for environmental monitoring, pollution control, and medical diagnosis. Currently, the commercialized sensors are based on metal oxides, which generally operate at high temperatures. Additionally, the desorption of chemisorbed gas molecules is also challenging. Hence, due to the large surface area, high flexibility, and good electrical properties of carbon nanomaterials (CNMs) such as carbon nanotubes, graphene and their derivatives (graphene oxide, reduced graphene oxide, and graphene quantum dots), they are considered to be the most promising chemiresistive sensing materials, where their electrical resistance is affected by their interaction with the analyte. Further, to increase their selectivity, nanocomposites of CNMs with metal oxides, metallic nanoparticles, chalcogenides, and polymers have been studied, which exhibit better sensing capabilities even at room temperature. This review summarizes the state-of-the-art progress in research related to CNMs-based sensors. Moreover, to better understand the analyte adsorption on the surface of CNMs, various sensing mechanisms and dependent sensing parameters are discussed. Further, several existing challenges related to CNMs-based gas sensors are elucidated herein, which can pave the way for future research in this area.

Ru-Doped Single Walled Carbon Nanotubes as Sensors for SO2 and H2S Detection

Carbon nanotubes are of great interest for their ability to functionalize with atoms for adsorbing toxic gases such as CO, NO, and NO2. Here, we use density functional theory in conjunction with dispersion correction to examine the encapsulation and adsorption efficacy of SO2 and H2S molecules by a (14,0) carbon nanotube and its substitutionally doped form with Ru. Exoergic encapsulation and adsorption energies are calculated for pristine nanotubes. The interaction of molecules with pristine nanotube is non-covalent as confirmed by the negligible charge transfer. The substitutional doping of Ru does not improve the encapsulation significantly. Nevertheless, there is an important enhancement in the adsorption of molecules by Ru-doped (14,0) nanotube. Such strong adsorption is confirmed by the strong chemical interaction between the nanotube and molecules. The promising feature of Ru-doped nanotubes can be tested experimentally for SO2 and H2S gas sensing.

Computational Modeling for Biomimetic Sensors

Computational modeling has become an important tool for scientists to both predict the properties of materials and systems and to gain a better understanding of the underlying mechanisms. This chapter is a brief yet holistic introduction to computational modeling, focusing on density functional theoretical (DFT) methods. The different types of computational modeling methods, including molecular mechanics, semiempirical, and ab initio methods, as well as the different software available for computational calculations are discussed. A step-by-step guide is presented using Gaussian16 software to introduce the basics of computational modeling based on our work with biomimetic polymer beads. However, the guide presented here is not limited to this particular system; it can be applied to any computational modeling case. The computational modeling methods for the building of the structures are described, and the calculation parameters, such as basis sets and exchange-correlation functionals, are explained. The output data and results are presented and discussed. Two simulation features were the focus of this work: (1) the simulation of the Raman spectra and (2) the different solvation environments. While some researchers in the field believe that computational simulation should be performed before the lab experiments, in fact they should be done simultaneously. This is so that the output of the experimental data can be used as the input of the computational parameters, as a form of semiempirical modeling, in order to achieve more accurate results for predicting the behavior of future experiments and understanding the atomic forces and mechanisms.

First-principle study of SO2 adsorption on Fe/Co-doped vacancy defected single-walled (8, 0) carbon nanotubes in sensor applications

To explore the excellent sensor for detecting the pollution gas [Formula: see text], the adsorptions of [Formula: see text] molecule on the surfaces of Fe/Co-doped carbon nanotubes (CNTs) and single vacancy defected (8, 0) CNTs were investigated by using density functional theory (DFT). In addition, the adsorption energies, geometries, energy gaps and electronic structures were analyzed. The results showed that Fe/Co-doping and single-vacancy-defected can improve the adsorption and sensitiveness of CNTs toward [Formula: see text]. Considering the changes of energy gap before and after the [Formula: see text] molecule adsorbed on each modified CNTs and its adsorption strength, Fe-doped CNTs (Fe-CNTs) and Co-doped site-2 single-vacancy-defected CNTs performed better for detecting [Formula: see text] molecule. With the decreasing number of electrons of the doped atom (Fe, Co, Ni), the adsorption became more stable. The results of this paper are profound and meaningful for designing [Formula: see text] sensing devices.

Carbon Nanotube Chemical Sensors

Carbon nanotubes (CNTs) promise to advance a number of real-world technologies. Of these applications, they are particularly attractive for uses in chemical sensors for environmental and health monitoring. However, chemical sensors based on CNTs are often lacking in selectivity, and the elucidation of their sensing mechanisms remains challenging. This review is a comprehensive description of the parameters that give rise to the sensing capabilities of CNT-based sensors and the application of CNT-based devices in chemical sensing. This review begins with the discussion of the sensing mechanisms in CNT-based devices, the chemical methods of CNT functionalization, architectures of sensors, performance parameters, and theoretical models used to describe CNT sensors. It then discusses the expansive applications of CNT-based sensors to multiple areas including environmental monitoring, food and agriculture applications, biological sensors, and national security. The discussion of each analyte focuses on the strategies used to impart selectivity and the molecular interactions between the selector and the analyte. Finally, the review concludes with a brief outlook over future developments in the field of chemical sensors and their prospects for commercialization.

First-principles descriptors of CO chemisorption on Ni and Cu surfaces

A comprehensive analysis of low coverage CO adsorption on Ni and Cu low-index miller surfaces – (100), (110), and (111) – over all the possible adsorption sites is presented.

Unveiling CO adsorption on Cu surfaces: new insights from molecular orbital principles

A holistic analysis of adsorption energies, charge transfer, and structural changes has been employed to highlight the variations in adsorption mechanisms upon changing the surface type and the adsorption site.