3D-printed millifluidic chip for synthesising plasmonic semiconductor nanocrystals as sensors substrate

In the past, plasmonics were always referred to as the collective oscillation of free electrons on metal surfaces such as gold (Au) and silver (Ag). This changed when plasmonic behaviour was experimentally demonstrated in semiconductors, i.e. self-doped copper sulfur, nanocrystals (Cu2−xS NCs) in 2009. In fact, Cu2−xS NC possesses different plasmonic behaviour than Au and Ag, in which the resonant condition is governed by another regime (free holes as the carriers) and its sensing capability has not yet been fully explored. In this contribution, the as-prepared (organic phase) Cu2−xS NCs were transferred in water and were tested with glycerin-water mixtures and anions. The results showed that Cu2−xS NC is very sensitive to the variation of refractive index in the surrounding environment. Furthermore, it was found that the plasmonic properties of these NCs are also very sensitive to the presence of anions. By taking the advantages of this “additional” effect, Cu2−xS NC can be used as a potential substrate for the fabrication of sensor devices with enhanced sensitivity.