# Sensing capabilities of the sawtooth penta-SiC2 nanoribbon for CO2 and CO molecules based on variations in molecular density: insights from a DFT investigation

## TL;DR

This study uses computer simulations to show how a special nanoribbon material can detect and distinguish CO2 and CO gas molecules based on their concentration.

## Contribution

The study reveals how molecular density affects the selective adsorption of CO2 and CO on a p-SiC2 nanoribbon through DFT simulations.

## Key findings

- CO2 is harder to capture than CO, requiring specific positioning and distance for adsorption.
- At low concentrations, p-SiC2-SS selectively adsorbs CO2 with strong chemisorption.
- Adsorption energy decreases with higher molecular concentration for both CO2 and CO.

## Abstract

Using Density Functional Theory (DFT) simulations, we explore the gas-sensing capabilities of the sawtooth penta-SiC2 nanoribbon (p-SiC2-SS) for CO2 and CO molecules under varying concentrations. Our findings reveal that CO2 is significantly more difficult to capture than CO. Free CO2 adsorption occurs only when its initial distance from the adsorbent is less than 1.80 Å, and the molecule should be positioned parallel to the adsorbent. Under these conditions, the material’s electric field bends CO2 to an angle of around 135°, inducing polarity and enabling adsorption. At low concentrations (one molecule per approximately 54 × 10−6 cm3), p-SiC2-SS selectively adsorbs CO2via strong chemisorption, with an adsorption energy of approximately −1.60 eV. When the molecular concentration triples, p-SiC2-SS sequentially adsorbs both CO2 and CO, with the adsorption energies decreasing to approximately −0.33 eV and −0.36 eV, respectively. Additionally, the electronic properties of p-SiC2-SS undergo distinct modifications depending on the type of adsorbed molecule. In all cases, the p orbitals of carbon and silicon atoms predominantly contribute to the energy levels near the Fermi level, with the p orbitals of carbon atoms playing a dominant role at the CBM. Our study highlights the potential of p-SiC2-SS as an effective gas sensor, capable of detecting and distinguishing CO2 and CO molecules, especially across different molecular concentrations.

The adsorption mechanism as a function of (a) total energy and (b) the angle θ of CO2vs. distance d of CO2@p-SiC2-SS.