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The thermal properties of graphene oxide (GO) nanoparticles’ colloidal suspensions prepared using the microwave-assisted hydrothermal method were determined. The mode-mismatched dual-beam thermal lens technique was employed to measure the thermal diffusivity of GO nanoparticles for different concentrations in the base fluid. By fitting the experimental data to the theoretical expression, the characteristic time constant was determined. The thermal diffusivity of the fluids seemed to be strongly dependent on the presence of the nanoparticles, increasing from 15.02 ± 0.16 × 10−4 cm2·s−1 to 27.59 ± 0.51 × 10−4 cm2·s−1 for concentrations ranging from 0.82 %V to 4.00 %V of GO/H2O. As nanofluids concentration increased, a higher value of thermal diffusivity was obtained. The optical properties, morphology and chemical structure and functional groups of the nanoparticles were characterized by UV–Vis spectroscopy, transmission electron microscopy (TEM) and Fourier Transform infrared spectroscopy (FTIR). Two main absorption peaks at 230 nm and at 303 nm in the UV–Vis spectra were observed. TEM images revealed a uniform size distribution and spherical in shape NPs with mean diameter of 7.4 nm. This novel type of nanofluids have potential applications for heat transfer fluids like solar collectors and heat exchange systems.

Nanoresins from silver nanoparticles’ colloids are used for 3D printing of parts by stereolithography. This process is based on nonradioactive relaxation after interaction with an electromagnetic field of ultraviolet light. For such an application, it is important to know the thermal conductivity. This work presents a new experimental arrangement to measure the thermal conductivity of nanoresins as a function of the concentration of the metal particle using the thermal lens (TL) technique and a modified arrangement of Michelson interferometer. The result showed a nonlinear growth of the nanoresin thermal conductivity as a function of the Ag nanoparticles (AgNPs) concentration. The AgNPs were synthetized by a green method. Their size was determined by TEM (transmission electron microscopy), and the optical characterization was done by UV–Vis spectroscopy. Classic Hamilton–Crosser (H–C), Maxwell and artificial neural network (ANN) models were proposed and used to predict the thermal conductivity of the composite resin. TL and interferometry techniques represent a good alternative for the determination of heat transport in liquid media, curing systems and 3D printed parts for applications in many fields such as materials science, medicine, transport phenomena and industry.

Green extract from Jalapeno Chili (Capsicum Annuum var Annuum), was used as a reducing agent in the synthesis of silver nanoparticles (AgNPs). The overall reduction was followed by UV–vis and Fourier-transform infrared spectroscopy (FTIR), confirming the formation and growth of AgNPs by the increase in the band intensity of the surface plasmon resonance (SPR) characteristic in silver nanoparticles around 460 nm. The characteristic infrared band of the amine at 3295 cm−1 decreased as the reaction progressed and the spectra showed slight changes indicating the consumption of the initial components of the extract as the reaction proceed. Photocurable acrylic resin and AgNPs were prepared in different concentrations to measure their thermal properties by means of photothermal techniques. Complementary analyzes for the determination of shape, size, crystal structure and composition of the AgNPs such as transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray diffraction (XRD) spectroscopy were done. This is the initial step of a research conducted to study the physical and thermal properties of nanocomposites to improve their performance for possible applications in prosthetic parts, 3D printing and tissue engineering for scaffolds.