ABSTRACT
Three different fractions of nanoclay (nanomer 1.44P) were functionalised with Ag forming silver nanoclay composites (Ag/nanomer 1.44P). The optical and electrochemical properties of the functionalised nanoclay were studied. Optical, morphology, and electrochemical techniques were used for the characterisation of the synthesised Ag/nanomer 1.44P nanocly composites. The presence and the absence of functional groups observed in the FTIR spectrum of Ag/nanomer 1.44P, compared with those found in the spectra of silver and pure nanomer 1.44P prove that a reaction occurred, thus a successful functionalisation of nanomer 1.44P nanoclay with silver. The XRD data of all composites showed four diffraction peaks within the silver spectrum range, with the intensity of silver decreasing with increasing concentration of nanomer 1.44P. SEM represented well-dispersed particles of different shapes with average particle sizes of 2.5, 27.5, and 5 nm with the enhanced concentration of nanomer 1.44P nanoclay. The decrease in diffusion coefficient values from 4.26 × 10-10, 2.50 × 10-13 , 1.40 × 10-13 cm2 s-1 and electron transfer rates of 1.50 × 10-5, 3.94 × 10-7, 2.86 × 10-7 cm s-1 are respectively proportional to an increase in nanomer 1.44P concentration depicting changes in nanocomposites sizes.
ABSTRACT
The synthesis process of AgNPs has been attracting a lot of attention in the fields of biosensors/sensors, diagnostics, and therapeutic applications. An attempt to understand the effect of different concentrations of reducing agents on the synthetic design process has been made. In this paper, we gather information on voltammetry studies and relate it with UV-vis and scanning electron microscopy (SEM) analyses. Given the kinetics, localized surface plasmon absorption (LSPR) band, and narrow size distribution of these methods, it was possible to compare the obtained measurements and clearly distinguish sizes and aggregation. AgNPs measured by SEM showed a statistically significant reduction of the nanoparticle sizes from 65 to 37.5 nm as the reducing agent increased. Well-matched d-spacing data calculated from selected area electron diffraction (SAED) patterns and X-ray diffraction (XRD) were obtained for all of the samples. The UV-vis studies showed that the SPR bands shift toward the blue region as the reducing agent concentration is increased, indicating a decrease in particle sizes. It is worth emphasizing that cyclic voltammetry (CV) and differential pulse voltammetry (DPV) coincide well with SEM on the aggregation of AgNPs at higher concentrations. A 10 mM reducing agent concentration resulted in uniform outcomes for producing AgNPs with the smallest size in terms of full width at half-maximum (FWHM) in all of the methods used in this study, while UV-vis band gaps increase with increasing reducing agent concentration. In agreement with all of the methods investigated, the results suggested that the best concentration of the reducing agents is 10 mM for a target application. These findings suggest the usefulness of voltammetry as a complementary method that can be used as a qualitative guide to identify the size and aggregation of NPs.
