An aqueous ammonia detection by hybrid Ag-CdS quantum dots

Surface plasmons are one of the most important aspects of nano-photonics, which studies the features of incident electromagnetic light radiation with the metallic nanoparticles (NPs) when the size of NPs becomes smaller than the wavelength of the light. Organic dyes or fluorophores are generally used for the sensing purpose, but quantum dots (QDs) can also be utilized as an alternate for optical sensing. A novel detection system based on the photoluminescence (PL) enhancement of Ag-CdS QDs for the direct measurement of ammonia solution (NH₄OH). The present work focuses on the fabrication of hybrid Ag-CdS QDs solution which behaves as an optical sensor for NH₄OH. The synthesized samples were characterized by PL spectroscopy for their optical properties and transmission electron microscopy for their morphological studies. This is an effective method which exhibits the effect of concentration of NH₄OH on the emission intensity of Ag-CdS QDs. Due to the presence of Ag NPs in the prepared samples of hybrid Ag-CdS QDs, the experimental results showed an enhancement in the emission intensity by adding NH₄OH with varying concentration from 30 (0.03 M) to 870 mM (0.87 M). Strong enhancement in PL intensity is observed as we further increase the concentration of NH₄OH from 1 to 4.5 M. The results presented here provide the rapid fabrication of an ultra-low-cost, simple and reproducible ammonia sensor to minimize the exposure to diseases by continuous monitoring of water quality.