Synthesis and characterization of a nanostructured porous silicon/carbon dot-hybrid for orthogonal molecular detection

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) is described. The hybrid is 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.