The reduction process may be affect

The reduction process may be affected by the polarity of the solvents, therefore, thereaction was relatively slow in less polar solvents, such asethanol and DMSO.The results in Fig. 5 show UV–visible spectra of nanopar￾ticles in different extracts with respect to reduction time. Thegrowth of nanoparticle was monitored at different time inter￾vals from 5 min to 6 h with characteristic plasmon band in arange of 410–450 nm. The spectrum displayed a peak around421, 426, and 435 nm for ethanol, aqueous, and DMSO ex￾tracts, respectively. The plasmon peak for DMSO appearsonly after 3 h of reduction time which clearly indicates a slowreaction rate. The rate of reaction was the slowest in DMSOextract due to the low aldehyde content value and thus, a slowreduction process was observed which leads to the growth ofmore agglomerated nanoparticles. Also, the shifting in posi￾tion of peak with respect to reduction time clearly indicates thechange in size and shape of the nanoparticles as the peakshifted towards higher wavelength. The intensity of the peakincreased continuously with increasing time where the sharpvariation in the absorption maxima indicated the variation inthe particle size distribution.HRTEM analysis was further carried out to monitor themorphologies in terms of shape and size of the nanoparticlesin different solvent extracts (Fig. 6). The TEM images shownoticeable difference in the appearance of nanoparticles indifferent solvents. It seems that during nanoparticle growth,the biomolecules present in the extract not only act as a reduc￾ing agent but also stabilize the growth of nanoparticles whichhelp in the balancing of electrostatic force during the forma￾tion of nanoparticles. The nanoparticles in ethanol extractwere spherical in shape with a size in the range of 2–10 nmwith narrow distribution of particles. In a recent study, thesolvent influence over the nanoparticle synthesis was investi￾gated in which solvents control the morphology of the nano￾particles [36]. In aqueous extract, the nanoparticles were ob￾served in the size range of 5–25 nm with polygonal and elon￾gated shaped particles. Whereas in DMSO extract, theparticles were spherical in shape in the size range of 10–50 nm. Moreover, the particles in ethanol and DMSO extractswere more uniformly distributed as compared to the aqueousextract. The presence of the high concentration of reducingagents in ethanol extract observed rapid bioreduction and thus,restricting the crystal growth. This is due to the presence of ahigh concentration of aldehyde content in extract which isresponsible for the fast bioreduction. Similar results were ob￾served by Kumar et al, where the particle shapes were spher￾ical and elliptical [27]. It can be concluded that the polarity ofthe solvent affects the growth of nanoparticles with simulta￾neous stabilization of the electrostatic forces which does allowthe ions to adsorb on the growing nuclei. Aqueous extractexhibits high polarity which induces hydrolytic reactionsand supports the growth of polygonal and elliptical nanopar￾ticles [24]