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

Interaction of the III-As monolayer with SARS-CoV-2 biomarkers: implications for biosensor development

The emergence of SARS-CoV-2 in 2019 led to the global COVID-19 pandemic, highlighting the urgency for developing cost-effective and non-invasive methods to detect diseases at an early stage. Human breath, rich in volatile organic compounds (VOCs), is promising for cost-effective and rapid disease detection, with specific VOCs like methanol, ethanal, butanone, acetone, and ethyl butyrate linked to COVID-19. Recent advances in biomarker detection and gas sensing with 2D materials, particularly III-As monolayers like BAs, GaAs, and AlAs, offer high sensitivity at low concentrations, providing a novel avenue for exploring their potential in detecting COVID-19 biomarkers. This article aims to examine the effects of adsorption on different properties of III-Arsenide (BAs, GaAs and AlAs) monolayers, particularly in connection with SARS-CoV-2 biomarkers. In order to examine the interaction between the monolayers and biomarkers, first-principles computations within the framework of density functional theory (DFT) are utilized. The present study involves an investigation of the modifications in the band structure, density of states (DOS), work function, electron density difference, and optical properties (reflectance and absorbance) of III-As monolayers, with the aim of assessing their viability for the detection of SARS-CoV-2 biomarkers along with interfering gases such as CO2 and H2O. It is observed that VOCs induce a notable change in the work function of GaAs which serves as an indicator of the presence of these biomarkers. However, the changes in work function are not as substantial as those for AlAs and BAs. Additionally, the chemiresistive sensitivity, optical sensitivity and recovery time of III-As are investigated. The findings suggest that the pristine GaAs monolayer displays a significant level of sensitivity and selectivity towards the SARS-CoV-2 biomarkers, rendering it a material with potential for utilization in sensing applications. Furthermore, it has been observed that the recovery time of the GaAs monolayer subsequent to its exposure to the VOC biomarkers lies within an acceptable threshold. Upon exposure to UV light, the recovery time is further reduced. The outcomes of our study indicate that GaAs monolayers exhibit considerable potential as chemiresistive, work function-based and optical sensors for the precise and discerning identification of VOCs linked to the SARS-CoV-2 virus compared to the other two III-As monolayers.

Nitrogen-doped zinc oxide nanoribbons for potential resonant tunneling diode applications

Armchair ZnONRs doped with nitrogen are investigated in the current manuscript for possible applications based on negative differential resistance (NDR). To conduct the theoretical research, we use density functional theory (DFT) in conjunction with the non-equilibrium Green's function (NEGF) formalism to carry out first principles computations. Pristine ZnONR (P-ZnONRs) is a semiconductor with a wide energy bandgap (E_g) of 2.53 eV. However, one edge N-doped ZnONRs (S_N-ZnO) and both edge N-doped ZnONRs (D_N-ZnO) are metallic. Partial density of states (PDOS) reveals that the metallicity is caused by the doped nitrogen atom. The transport characteristics analysis revealed the negative differential resistance (NDR) characteristics in the N-doped ZnONRs. The peak-to-valley current ratios (PVCR) are computed and measured to be 4.58 × 10²¹ and 1.83 × 10²² for S_N-ZnO and D_N-ZnO, respectively. The obtained findings suggest the significant potential of armchair ZnONRs for NDR-based applications such as switches, rectifiers, oscillators, memory devices, etc.

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.