Fundamental Studies of Nanocrystalline Silicon Hybrids

In this project funded by the Chemical Measurement and Imaging program of the Chemistry Division, Professor Frank V. Bright of the University at Buffalo, The State University of New York is developing reagent free optical sensors for detecting and quantifying a wide variety of molecules. To meet this challenge, new chemistries are developed to modify the surface of intrinsically photoluminescent nanocrystalline materials to impart chemical selectivity. The target molecules are selectively bound to the new surface chemistry, leading to a concentration-dependent change in the nanocrystalline material photoluminescence (intensity, color). The work is having a broad impact through the potential production of new detectors and sensors. It is having a further broad impact on the next generation of scientists through a training program that targets women and underrepresented minorities. In addition, the team is partnering with their university's Veterans Services office to encourage the participation of military personnel in the research in order to facilitate their transition into STEM-related careers. This research is focused on the use of porous silicon (pSi) and free-standing Si nanocrystals (SiNCs) as the basis for new sensors. The research simultaneously exploits the attractive aspects of surface-grafted silane, hydrosilation, and MOx chemistries (selective analyte partitioning/interaction, improved stability) and the unique photophysics of silicon nanoscale architectures (photoemission that depends on the nanocrystallite surface chemistry) to develop reagentless optical sensors for detecting and quantifying a wide variety of analytes. The research aims include: (i) establishing chemistries to create spatially unique, analyte-responsive materials at nanocrystalline silicon surfaces; (ii) elucidating the effects of surface chemistry and spatially-dependent compositional gradients to optimize analyte selectivity and analytical signals; and (iii) extending these platform technologies to a wide variety of target analytes. The primary research tools used include steady-state and time-resolved photoluminescence (PL), multispectral PL and infrared (IR) imaging, IR spectroscopy, atomic force microscopy (AFM), scanning Kelvin probe microscopy (SKPM), confocal Raman microscopy and spectroscopy, co-localized AFM/SKPM and Raman imaging, and tip enhanced Raman scattering (TERS) imaging and mapping.