# Comprehensive first principles study on CO and NO gas adsorption effects on the structural, electronic, and optical properties of armchair silicon-tin nanoribbons

## TL;DR

This paper studies how CO and NO gases affect the structure and properties of silicon-tin nanoribbons, finding that NO adsorption significantly changes their electronic and optical behavior.

## Contribution

The novel contribution is the first-principles study of CO and NO adsorption effects on armchair silicon-tin nanoribbons, revealing distinct electronic and optical responses.

## Key findings

- NO adsorption causes a transition from semiconducting to metallic behavior in ASiSnNRs due to strong orbital hybridization.
- CO adsorption slightly widens the band gap and enhances anisotropic optical properties in the ultraviolet region.
- ASiSnNRs show potential for selective and sensitive gas sensing, particularly for NO detection.

## Abstract

This study presents a detailed first-principles investigation of the effects of CO and NO gas adsorption on the structural, electronic and optical properties of armchair silicon-tin nanoribbons (ASiSnNRs). Cohesive and adsorption energy calculations indicated that the ASiSnNR structure was thermodynamically stable, with physisorption for CO (−0.01 eV) and chemisorption for NO (−0.68 eV). Electronic band structure analysis revealed that pristine ASiSnNRs exhibited semiconducting behaviour with a narrow band gap (approx. 0.43 eV), which slightly widened upon CO adsorption and transitioned to a metallic state upon NO adsorption because of the strong orbital hybridization and charge transfer effects. Charge density and wave function analyses confirmed this mechanism, with particular emphasis on the role of the π* orbital of the CO molecule. The dielectric function, optical absorption, reflection spectra and joint density of states show significant enhancements in anisotropic optical properties after CO adsorption, especially in the ultraviolet region. These findings suggest the strong potential of ASiSnNRs for selective and highly sensitive gas-sensing applications, particularly for the detection of NO.