In this article, Au nanoparticles in polyvinylpyrrolidone (PVP) solution were prepared by gamma radiation at different concentrations. The solutions were irradiated at doses of 50 kGy for making different sizes. The average sizes of particle in the prepared samples were measured using the nanophox machine. A dual-beam mode-mismatched thermal lens (TL) method was used to investigate the effect of thermal diffusivity of samples. The TL measurement was carried out using a green diode laser (wavelength 532 nm, 60 mW) and a He–Ne laser (wavelength 632.8 nm, 0.5 mW) for excitation source and probe beam, respectively. The results showed that the thermal diffusivity of samples enhances with the growth of particle size and density of solutions. This increment can be attributed to phonon scattering at interface of particles–liquid and contact between the nanoparticles and surrounded liquid.

The effects of multi-walled carbon nanotube (MWNT) concentration on the structural, optical and electrical properties of conjugated polymer-carbon nanotube composite are discussed. Multi-walled carbon nanotube-polypyrrole nanocomposites were synthesized by electrochemical polymerization of monomers in the presence of different amounts of MWNTs using sodium dodecylbenzensulfonate (SDBS) as surfactant at room temperature and normal pressure. Field emission scanning electron microscopy (FESEM) indicates that the polymer is wrapped around the nanotubes. Measurement of the nonlinear refractive indices (n₂) and the nonlinear absorption (β) of the samples with different MWNT concentrations measurements were performed by a single Z-scan method using continuous wave (CW) laser beam excitation wavelength of λ = 532 nm. The results show that both nonlinear optical parameters increased with increasing the concentration of MWNTs. The third order nonlinear susceptibilities were also calculated and found to follow the same trend as n₂ and β. In addition, the conductivity of the composite film was found to increase rapidly with the increase in the MWNT concentration.

In this report, silver and silver oxide nanocomposites are synthesized using a green method at different concentrations of silver nitrate. In this method, coelomic yellow liquid extracted from earthworms has been used as a silver nitrate reduction. The crystal structure of the obtained nanoparticles was analyzed by X-ray diffraction pattern and Rietveld method. The results show that with increasing the concentration of silver nitrate, the size and strain of silver oxide nanoparticles remained unchanged, but the size of silver nanoparticles increased and strain decreased. SEM images show uniform particle distribution, high density, and spherical geometric shape. By measuring and fitting the UV spectra of the nanocomposites, the weight percentage and the absorption peak of each component were determined. Accordingly, with increasing the concentration of silver nitrate, the absorption peak for silver nanoparticles is shifted to the higher wavelengths and for silver oxide nanoparticles is almost constant. Also, the weight percentage of silver oxide remains almost constant, and increases for silver nanoparticles. In the framework of a simple kinematic model, it is shown that its origin can be related to the different reactions speed of conversion of silver nitrate to silver and silver oxide.