Colloidal dispersions of InP@ZnS nanoparticles were prepared using a single-step heating-up method relying at low temperature. The obtained particles are highly crystalline, monodisperse and exhibit size-dependent radiative emission in the range of 329−480 nm. By simply varying the concentration of the molecular precursor, the particles size can be controlled in the range from about 1.1 to 4.5 nm. The formation of InP nanocrystals has been confirmed using the techniques TEM, HRTEM, PL and UV-Vis spectroscopy.

In this work, we evaluated the effect of variation in concentration and the successive or simultaneously addition of reactants on size, dispersion and morphology of SiO2 nanospheres. Particles with different diameters were obtained by hydrolysis and condensation of TEOS in an ammonium hydroxide and alcohol solution. Simultaneously or successive addition of TEOS to different ammonium hydroxide solutions varying in concentration produced SiO2 nanoparticles with sizes ranging between 22 and 230 nm. Bigger and mono-dispersed particles were obtained at higher concentrations of ammonium hydroxide. However, when lower concentrations of ammonium hydroxide were employed, the particle size diminished but dispersion increased. The quantity of prepared sample had not a significant effect in structural properties of particles. The subsequent addition of TEOS produced SiO2 surfaces with increased roughness. Transmission electron microscopy was used to monitor the formation, size and morphology of SiO2 nanospheres. The samples was characterized with FT-IR spectroscopy we find that the nanospheres have a composition of SiO2 regardless of the experimental conditions used growth.

En este trabajo, evaluamos el efecto en el tamaño, dispersión y en la morfología de nanoesferas de SiO2 producido por la variación en la concentración y en la adición (sucesiva o simultanea) de reactantes. Partículas con diferentes diámetros fueron preparadas por hidrólisis y condensación de TEOS en una solución de hidróxido de amonio y alcohol. Con la adición simultánea y sucesiva del TEOS con diferentes contenidos de hidróxido de amonio se obtuvieron nanopartículas de SiO2 con tamaños en el rango entre 22-320 nm. Las partículas más grandes y monodispersas se obtuvieron con las mayores concentraciones de hidróxido de amonio. Sin embargo, cuando se prepararon concentraciones más bajas, el tamaño de las partículas disminuyó pero se incrementó la dispersión. La cantidad de muestra preparada no presentó efecto significativo en las propiedades estructurales de las partículas. Superficies con mayor rugosidad de SiO2 son resultado de la adición sucesiva de TEOS. Microscopia electrónica de transmisión fue empleada para monitorear la formación, tamaño y morfología de las nanoesferas de SiO2. Las muestras fueron caracterizadas por FT-IR mostrando que la composición de las nanoesferas es de SiO2 independientemente de las condiciones experimentales de crecimiento.

R6G dye with gold nanoparticles was prepared in water solution. Using a thermal lens experimental setup, the thermal diffusivity of R6G in presence of gold nanoparticles with Au different concentration was measured. The results show that, the thermal diffusivity of R6G dye mixed with gold nanoparticles increases with the increase of particle metallic concentration, enhancing the thermal diffusivity in the solution. The thermal diffusivity of the samples was studied for a constant concentration of R6G dye 0.1 g/L. The diffusivities were obtained by using the thermal lens aberrant model with lasers arranged in the mismatched mode. The characteristic time constant of the transient thermal lens was obtained by fitting the theoretical expression, for transient thermal lens, to the experimental data. UV-Vis spectroscopy and TEM were used to characterize the R6G dye gold nanoparticles.