Fluorescent Carbon Dots for Sensing Application

Development of effective platforms for surface enhanced Raman scattering (SERS) sensing has mostly focused on fabrication of colloidal metal surfaces and tuning of their surface morphologies, designed to create “hot spots” in which plasmonic fields yield enhanced SERS signals. We fabricated distinctive SERS active flexible films comprising polydimethylsiloxane (PDMS) embedding carbon dots (C-dots) and coated with silver nanoparticles (Ag NPs). The C-dot-Ag-NP-polymer films exhibited SERS properties upon deposition of versatile targets, both conventional SERS-active dyes as well as bacterial samples. The SERS response was correlated to the formation C-dots within the polymer film and the physical proximity between the C-dots and Ag NPs, indicating that coupling between the plasmonic fields of the Ag NPs and C-dots’ excitons constituted a prominent factor in the SERS properties.

On the other hand, A new hybrid guest–host material consisting of a Fabry–Pérot porous silicon (PSi) thin film, a nanostructured high surface-area matrix, and encapsulated fluorescent carbon quantum dots (C-dots) was synthesized by a facile in situ pyrolysis treatment of the carbonaceous precursor incorporated within the nanoscale pores of the inorganic host. The effects of nanoconfinement on the integrity of the C-dots and their optical properties are characterized. We show that the resulting hybrid allows for label-free optical detection of target molecules using two orthogonal modalities, that is, the white-light reflectivity of the PSi matrix and the fluorescence of the confined C-dots, and these two signals can be observed and collected simultaneously. The resulting hybrid system exhibits superior sensing performance in comparison with that of the individual components. Notably, we demonstrate that the confined C-dots exhibit greater sensitivity toward various analytes as well as an improved linear response, thus providing evidence of the impact of the host nanoscale porous scaffold on the optical properties of the C-dots. Moreover, we show that this orthogonal detection scheme increases the dynamic range of the sensor and minimizes false negative results.