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. A hybrid material with excellent molecule-sensing abilities has been created by scientists in Israel. Nanomaterials are ideal for optically identifying biomolecules. For example, carbon quantum dots emit light in a way that is highly sensitive to their environment. In contrast, nanoarchitectures based on porous silicon oxide offer versatile biosensing platforms based on light reflectivity but lack the sensitivity of quantum dots. Now, Ester Segal from the Technion Israel Institute of Technology and co-workers have developed a simple way to combine both materials. They formed carbon dots by inserting a carbon precursor into a porous silicon oxide matrix and heating it. This allowed the team to synthesize biocompatible nanomaterials for label-free detection using two independent optical signals. They used their material to detect trypsin and adenosine triphosphate with a better performance than either of the two materials on their own. A simple and robust single-step in situ synthesis of carbon dots (C-dots) within a porous silicon oxide (PSiO2) matrix is reported. The resulting new hybrid guest–host material exhibits promising capabilities as a label-free dual-mode optical biosensor via modulation of both the optical reflectance associated with the PSiO2 matrix, as well as the C-dots’ fluorescence, and these two signals can be observed and collected simultaneously. The resulting sensing platform exhibits enhanced sensitivity, improved linear response, as well as a wider dynamic range in comparison to its single components.