Photothermal techniques allow, under particular experimental conditions, the simultaneous determination of specific heat, thermal conductivity, and thermal diffusivity. A comparison has been made between measurements performed with the gas-microphone (P) configuration and the photopyroelectric (PPE) one at a liquid-crystal second-order phase transition. An increase in the sensitivity with respect to thermal parameter variation has been observed in the case of PPE.

A photopyroelectric technique has been used to simultaneously measure the critical behavior of specific heat, thermal conductivity, and thermal diffusivity of ${\mathrm{Cr}}_2$ ${\mathrm{O}}_3$ at the antiferromagnetic-paramagnetic phase transition. An Ising-like behavior has been found for ‖${\mathit{t}}_{\max }$‖≤3×${10}^{\mathrm{-}3}$ with α=0.10±0.02 and A/A’=0.48±0.03. A possible crossover between Ising and Heisenberg behaviors has been found if ‖${\mathit{t}}_{\max }$‖ is increased. Thermal diffusivity data have been fitted according to the model for a uniaxial antiferromagnet with energy conservation for ‖${\mathit{t}}_{\max }$‖≤3×${10}^{\mathrm{-}3}$ with a critical exponent b=-0.11±0.02. A correction term similar to the static correction to scaling factor has been introduced in the fitting function. No anomaly has been found in thermal conductivity.

In the present study, we successfully synthesized N-doped carbon quantum dots (N-CQDs) using a top-down approach, i.e., hydroxyl radical opening of fullerene with hydrogen peroxide, in basic ambient using ammonia for two different reaction times. The ensuing characterization via dynamic light scattering, SEM, and IR spectroscopy revealed a size control that was dependent on the reaction time, as well as a more pronounced -NH₂ functionalization. The N-CQDs were probed for metal ion detection in aqueous solutions and during bioimaging and displayed a Cr³⁺ and Cu²⁺ selectivity shift at a higher degree of -NH₂ functionalization, as well as HEK-293 cell nuclei marking.