Electrogenerated chemiluminescence from CdS hollow spheres composited with carbon nanofiber and its sensing application

Abstract

The electrogenerated chemiluminescence (ECL) from nanometre-sized CdS hollow spheres and carbon nanofiber (CdSHS-CNF) nanocomposites in aqueous solution and their sensing applications were studied by entrapping them in carbon paste. The CdSHS-CNF nanocomposites exhibited a peak at −1.02 V (vs. Ag/AgCl) in 0.1 M pH 8.0 PBS containing 20 mM H₂O₂ during the cyclic sweep between 0 and −1.2 V at 40 mV s⁻¹. Compared with CdS hollow spheres (CdSHS), carbon nanofiber (CNF) and CdS nanocrystals and carbon nanofiber (CdSNC-CNF) nanocomposites, CdSHS-CNF not only enhanced the electrochemiluminescent intensity but also decreased the ECL starting potentials. Furthermore, by immobilizing cholesterol oxidase (ChOx) on CdSHS-CNF nanocomposites modified electrode, a sensitive and selective method was developed for detection of cholesterol using oxygen as a coreactant which captured more electrons from electrochemically reduced CdSHS-CNF than H₂O₂. Under optimal conditions, the sensor could be used for the determination of cholesterol from 1 × 10⁻⁶ to 4.4 × 10⁻⁴ M with a correlation coefficient of 0.9991 and a detection limit was 8 × 10⁻⁷ M at 3σ. The unique ECL intensity and stability of CdSHS-CNF would promote the application of nanometre-sized semiconductor hollow spheres based composites in fabricating sensors for chemical and biochemical analysis.