Concentration dependent variation of thermal diffusivity in highly fluorescent carbon dots using dual beam thermal lens technique

Thermal and optical properties of fluorescent carbon dots (CDs) prepared from citric acid anhydrous as the precursor and ethylenediamine as the passivation agent by microwave assisted synthesis technique is explored in the present study. Optical absorption and emission spectra of carbon dots reveal the presence of surface states with an absorption peak around 350 nm and emission around 450 nm. Fourier Transform Infra-Red (FT-IR) spectra also indicate the presence of surface states. Transmission electron microscopy images of these nano particles indicate an average particle size of 5.8 nm. Dual Beam thermal lens (TL) spectrometry, a highly sensitive photothermal technique, is employed to measure the thermal diffusivity of the carbon dots. Thermal diffusivity is found to decrease from 0.135 m2/sec to 0.0365 m2/sec as the weight percentage of carbon dots are increased from 0.0005 g/15 ml to 0.005/15 ml which can be attributed to the enhanced scattering of thermal waves with particle density in the medium. Studies reveal carbon dots to be promising candidates as thermal insulating materials.