Multiple approaches to control and assess the size of Pd nanoparticles synthesized via water-in-oil microemulsion

Production of Pd nanoparticles in microemulsions. Effect of reaction rates on the particle size

In the synthesis of metallic nanoparticles in microemulsions, we hypothesized that the particle size is controlled by the reaction rate and not by the microemulsion size. Thus, the changes observed in the particle sizes as reaction conditions, such as concentrations, temperatures, the type of surfactant used, etc., are varied which should not be correlated directly to the modification of these conditions but indirectly to the changes they produce in the reaction rates. In this work, the microemulsions were formulated with benzene and water as continuous and dispersed phases, respectively, using n-dodecyltrimethylammonium bromide (DTAB) and n-octanol as the surfactant and cosurfactant. Using time-resolved UV-vis spectroscopy, we measured the reaction rates in the production of palladium (Pd) nanoparticles inside the microemulsions at different reactant concentrations and temperatures, keeping all the other parameters constant. The measured reaction rates were then correlated with the particle sizes measured by transmission electron microscopy (TEM). We found that the nanoparticle size increases linearly as the reaction rate increases, independently of the actual reactant concentration or temperature. We proposed a simple model for the observed kinetics where the reaction rate is controlled mainly by the diffusion of the reducing agent. With this model, we predicted that the particle size should depend indirectly, via the reaction kinetics, on the micelle radius, the water volume and the total microemulsion volume. Some of these predictions were indeed observed and reported in the literature.

Nanoparticle Size Control in Microemulsion Synthesis

Quasi-monodisperse populations of (H₃O)Y₃F₁₀·xH₂O nanocrystals of varying size are prepared in Igepal-stabilized microemulsions. Correlations between microemulsion composition, micelle hydrodynamic radius, and final nanoparticle size are established and shed light on the mechanism of particle size control. Under the conditions considered here, size control appears to be primarily governed by the number of micelles and the quantities of precursor ions. More specifically, the number of NPs formed can be successfully correlated with the number of micelles present and final NP size is, in turn, determined by the number of nuclei and the total amount of material available for nanocrystal formation. This insight into nanoparticle formation facilitates the selection of appropriate synthetic conditions for the preparation of populations of a targeted size.

Preparation of CaP/pDNA nanoparticles by reverse micro-emulsion method: Optimization of formulation variables using experimental design

In this study, the CaP/pDNA nanoparticles were prepared using Triton X-100/Butanol/Cyclohexane/Water reverse microemulsion system. Optimization of preparation conditions was based on evaluation of particle size by Box–Behnken design method. The particle sizes of the optimized CaP/pDNA nanoparticles were found to be 60.23 ± 4.72 nm, polydispersity index was 0.252 and pDNA encapsulate efficiency was more than 90%. The optimized CaP/pDNA nanoparticles have pH sensitivity and biocompatibility. Further, optimized CaP/pDNA nanoparticles showed higher transfection efficiency.