Optical biosensor based on cadmium sulfide-silver nanoplate hybrid structure

Research on surface plasmons (SPs), one of the major field in nanophotonics, explores the properties of a confined electromagnetic field over dimensions in the order of or smaller than the working wavelength. The present work focuses on the impact of SPs on the photophysical properties of chromophore, especially in photoluminescence (PL) enhancement. In the applications of SPs in bio-labeling, the modulation of active nanoparticles with noble metallic nanoparticles is a prerequisite and has provided fundamental research interest. The modulation of cadmium (Cd) chalocogenides nanoparticles with silver (Ag) nanoparticles emerges against a number of technical issues, such as forward cationic ion exchange in mutual nanoparticles, conjugation efficiency, and occurrence of PL quenching in very close mutual distance (smaller than 5 nm). To overcome these challenges cadmium sulfide (CdS) and Ag nanoplate (CdS-Ag NP) hybrid is synthesized by a forward-reverse cation exchange. The morphology, crystallinity, and atomic composition of the CdSAg NPs have been investigated using energy dispersive X-Ray spectroscopy and high resolution transmission electron spectroscopy. The CdS-Ag NPs are Cd ²⁺-rich CdS nanoparticles covalently bonded to the surfactant of the Ag NPs. PL enhancement of measured CdS is attributed to the matching of the emission bands of CdS and the tailor-made localized surface plasmon resonance (LSPR) bands provided by the Ag NP. In addition, CdS-Ag NP in HeLa cell imaging has also been demonstrated, and no apoptosis was observed. The results provide a simple and flexible methodology for conjugating complex nanoparticles, thus offering promising practical applications in nanotechnology.