Porous silicon-polyvinylidene fluoride-carbon dots based portable temperature sensor

Optical sensors are an attractive alternative to semiconductor-based sensors for temperature measurement in harsh environments. Based on Porous Silicon (PSi) Fabry-Perot interferometer, this work presents a novel way of sensing temperature with PSi hybrids using a polymeric nanocomposite of polyvinylidene fluoride (PVDF) and carbon dots (CDs). The operation is based on the temperature-induced changes in the refractive index of PVDF, which in turn changes the effective refractive index of the PSi hybrid. The dual temperature sensing was based on the simultaneous monitoring of the peak wavelength redshift of the Fabry-Perot interference fringes, and the measurement of the intensity of the reflectance spectrum at a specific wavelength. Both measurements showed excellent linear responses, with coefficients of determination greater than 0.99, revealing the highest sensitivity of 0.2 nm/degrees C for the sample with the highest content of CDs. Apart from the enhanced temperature dependence of the dielectric constant of PVDF, which improved the sensitivity of the proposed PSi/PVDF-CDs based sensors, the hybrid structure facilitates the formation of beta phase up to 91.8%. The proposed silicon-based temperature sensor being very large-scale integration (VLSI) compatible, open the way towards the possible formation of freestanding PSi/PVDF-CDs films with a possible application as biocompatible micro temperature sensors.