LAUSR

This study introduces photopyroelectric techniques for the thermal and optical characterizations of carbon nanotubes (CNTs) while focusing on the measurement of optical absorption coefficients and thermal diffusivity of suspensions of CNTs in glycerol at different concentrations. Optical absorption coefficients were measured at selected wavelengths in the visible and infrared ranges, whereas thermal characterization was conducted by measuring the thermal diffusivity (for multiwalled CNT suspensions) with an average diameter of 140 nm and a length of 7 µm, within a concentration range of 0.001–0.01 g ml−1. A linear increase in the optical absorption coefficients with CNT concentration was obtained – a finding not achievable with absorbances measured by means of conventional UV–Vis spectroscopy. In contrast, thermal diffusivities, in the range of 0.005–0.06 g ml−1, exhibited a notable increase with concentration. The fitting of this behavior to a logistic model allowed the prediction of thermal diffusivity at “infinite” CNT concentration. This prediction is confirmed by direct measurements of the thermal properties of a CNT suspension at high concentration using a self-normalized photoacoustic methodology. The direct measurement of optical absorption coefficients provides valuable insights into the absorptivity of CNT suspensions at selected wavelengths. This methodology could be very useful for determining the optical properties of CNT suspensions in other fluids and wavelengths and their relationship with other variables of interest, such as CNT dimensions.