Rise of silicene and its applications in gas sensing.

Reviewing a subject is done to provide an insight into theoretical and conceptual background of the study. Looking back into the history of an emerging field and summarizing it in a few pages is a herculean task. Anyway, it was imperative to write a few words about the rise of silicene, its properties, and its applications as gas sensors. Currently, silicene is a growing field of interest. It is probably one of the most studied materials nowadays and scientists and researchers are studying it because of its intriguing electronic properties and potential applications in nanoelectronics. Various experimental and theoretical investigations are going on worldwide to explore the various aspects of this field. It is essential to review the literature based on investigations by various scientists in this field.

Defective GaAs nanoribbon-based biosensor for lung cancer biomarkers: a DFT study.

Density functional theory-based first-principles investigation is performed on pristine and mono vacancy induced GaAs nanoribbons to detect the presence of three volatile organic compounds (VOCs), aniline, isoprene and o-toluidine, which will aid in sensing lung cancer. The study has shown that pristine nanoribbon senses all three analytes. For the pristine structure, we observe decent adsorbing parameters and the bandgap widens after the adsorption of analytes. However, the introduction of the carrier traps induced by defect causes deep energy wells that vary the electrical properties as indicated in the bandgap analysis of GaAs, wherein adsorption of aniline and o-toluidine reduces the bandgap to 0 eV, making the structure highly conductive in nature. The adsorption energies of defect-induced nanoribbon are more as compared with the pristine counterpart. Nonetheless, the introduction of defects has improved the sensitivity further.

Analysis of uric acid adsorption on armchair silicene nanoribbons: a DFT study.

Density functional theory based first-principles investigation study is done on armchair silicene nanoribbons (ASiNRs) for adsorption of uric acid molecule. Pristine and defect-induced variants of ASiNR are considered, and the electronic and transport properties are calculated with the adsorption. The pristine ASiNR with zero band gap is engineered with defect to create a band gap, and a significant change in the band structure of defective ASiNR after the adsorption is observed. The adsorption energy of the defective complex is calculated as - 9.21 eV which is more compared to that of the pristine counterpart, whose adsorption energy comes out to be 7.76 eV. The study shows that introduction of defect reduced the sensitivity of ASiNR toward uric acid molecule.

First principles investigation on armchair zinc oxide nanoribbons as uric acid sensors.

A study is done to check the sensing functionality of armchair zinc oxide (ZnO) nanoribbon towards uric acid. The main focus of the research is to observe the change in the electronic properties (adsorption energy, bandstructure and density of states) and transport properties (current-voltage characteristics) of nanoribbon on adsorption of uric acid. In this work, two armchair ZnO nanoribbons of width, N = 4 and 6 atoms are used, and additional variations are created in the nanoribbon by introducing defect and doping agent. Manganese is used as a dopant. The work reveals that chemisorption occurs only in the case of doping for both widths of nanoribbons, and there is an enormous increase in the conductivity of defective armchair ZnO nanoribbon with width, N = 6 as compared to others on adsorption of uric acid. All calculations are carried out using density functional theory (DFT) and non-equilibrium Green's function (NEGF). Graphical abstract.

Density-functional study of hydrogen cyanide adsorption on silicene nanoribbons.

Adsorption of toxic hydrogen cyanide gas (HCN) on armchair silicene nanoribbons (ASiNRs) is investigated by the first principles method using density functional theory (DFT) to compute geometric, electronic, and transport properties. Two variants of ASiNRs are considered: pristine ASiNR (P-ASiNR) and defective ASiNR (D-ASiNR), which is created by introducing a vacancy in P-ASiNR by removal of a Si atom. Total energy optimizations are used to find the most stable structures. The calculated results reveal that although HCN is physisorbed in both variants, sensitivity in the case of D-ASiNR is sufficiently enhanced owing to more adsorption energy and charge transfer between the ASiNR-gas complex. Also, the inspection of current-voltage characteristics demonstrates that the introduction of defect has considerably increased the conductivity of ASiNR. Hence, D-ASiNR may be used as a promising sensor for HCN gas. Graphical abstract Transmission eigenstates of (a) Pristine ASiNR (b) Defective ASiNR after HCN adsorption.

Adsorption and dissociation of sulfur-based toxic gas molecules on silicene nanoribbons: a quest for high-performance gas sensors and catalysts.

The adsorption behavior of sulfur-based toxic gases (H2S and SO2) on armchair silicene nanoribbons (ASiNRs) was investigated using first-principles density functional theory (DFT). Being a zero band gap material, application of bulk silicene is limited in nanoelectronics, despite its high carrier mobility. By restricting its dimensions into one dimension, construction of nanoribbons, and by introduction of a defect, its band gap can be tuned. Pristine armchair silicene nanoribbons (P-ASiNRs) have a very low sensitivity to gas molecules. Therefore, a defect was introduced by removal of one Si atom, leading to increased sensitivity. To deeply understand the impact of the aforementioned gases on silicene nanoribbons, electronic band structures, density of states, charge transfers, adsorption energies, electron densities, current-voltage characteristics and most stable adsorption configurations were calculated. H2S is dissociated completely into HS and H species when adsorbed onto defective armchair silicene nanoribbons (D-ASiNRs). Thus, D-ASiNR is a likely catalyst for dissociation of the H2S gas molecule. Conversely, upon SO2 adsorption, P-ASiNR acts as a suitable sensor, whereas D-ASiNR provides enhanced sensitivity compared with P-ASiNR. On the basis of these results, D-ASiNR can be expected to be a disposable sensor for SO2 detection as well as a catalyst for H2S reduction. Graphical abstract Comparison of I-V characteristics of pristine and defective armchair silicene nanoribbons with H2S and SO2 adsorbed on them.