Understanding the NO2 sensing mechanism on CdS quantum dots via experimental and first-principles calculations
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Accepted Version
Date
2026-03-31
Authors
Zoting, Krushna
Bhoye, Laxman
Kumar, Ankit
Jadhav, Om
Krishna Sabbi, Vamshi
Ghule, Balaji
Gholap, Haribhau
Journal Title
Journal ISSN
Volume Title
Publisher
American Chemical Society
Published Version
Abstract
Nitrogen dioxide (NO2) is a highly toxic atmospheric pollutant, necessitating sensing materials that combine high efficiency, selectivity, and a rapid response. In this work, cadmium sulfide (CdS) quantum dots (QDs) were synthesized via a wet-chemical precipitation route and extensively characterized using XRD, Raman, UV–vis absorption, PL/TRPL, XPS, FESEM–EDX, BET–BJH, and HRTEM. The QDs crystallize in the cubic phase with a particle size of 4–5 nm, exhibiting strong quantum confinement and high surface activity. Time-resolved PL measurements revealed a long decay lifetime of 7.11 μs, indicative of an effective trap-assisted charge retention that favors gas sensing. Experimentally, the CdS QD sensor delivered a notable NO2 response of 78% at 125 °C (at 40 ppm), with fast response and recovery times of 6 and 24 s, along with excellent selectivity and operational stability. Density functional theory (DFT) calculations using the GGA + U method showed that adsorption is strongly site-dependent: NO2 binds most strongly at the S site (Eads = −0.88 eV, charge transfer = +2.595 e), while N-on-Cd exhibits weak physisorption (−0.14 eV, +0.040 e). Optical conductivity derived from ε2(ω) indicated enhanced σ(ω) for Cd-site adsorption, supporting rapid activation, whereas S-site chemisorption governs sensitivity. These synergistic effects highlight CdS QDs as promising candidates for high-performance NO2 sensing.
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Keywords
Adsorption , Cadmium sulphide , Electrical conducting , Quantum dots , Sensors , [Chemistry]
Citation
Zoting, K, Bhoye, L, Kumar, A, Jadhav, O, Krishna Sabbi, V, Ghule, B & Gholap, H 2026, 'Understanding the NO2 sensing mechanism on CdS quantum dots via experimental and first-principles calculations', Langmuir, vol. 42, no. 12, pp. 8756-8772. https://doi.org/10.1021/acs.langmuir.6c00008