Cadmium sulfide quantum dots-polythiophene nanocomposite for electrical ammonia sensing

Quantum dots (QDs) are zero-dimensional semiconducting nanomaterial of size ranging from 1 to 10 nm. They exhibit properties like high photostability, high quantum yield, excellent photoluminescence properties, high surface-to-volume ratio, and tunable size confinement effect. In this report, fluorescent cadmium sulfide quantum dots (CdS QDs) have been synthesized using hydrothermal method with citric acid as a capping agent. Polythiophene (PTh) was prepared by oxidative polymerization process using thiophene monomer. Nanocomposites of CdS QDs and PTh were obtained through ex situ method by mixing CdS QDs with PTh in different proportions. The as-prepared products have been characterized using different characterization techniques. The CdS QDs, PTh, and their nanocomposites were tested for electrical gas sensing. Maximum sensitivity of ~ 38% for 100 ppm and ~ 48% for 130 ppm were obtained toward ammonia for equal volume proportion-loaded CdS QDs-PTh nanocomposite. The response time observed less than 1 s and recovery time was in between 4 and 8 s. The sensor shows linear response which is useful for device fabrication.