Results and discussionFabrication of Ag nanoparticles by the refluxingmethodIn the refluxing method, AgNs were prepared by thereduction of silver nitrate in PVA solution. Then, therefluxed solution was blended with CS solution. The formationof AgNs in PVA solution before and after blendingwith CS solution at different refluxing time was monitoredby UV–Vis spectroscopy (Fig. 1). It can be observed that allUV–Vis spectra display the peak at 430 nm correspondingto the surface plasmon resonance (SPR) absorption ofAgNs, confirming the reduction of Ag ions and subsequentformation of AgNs in the PVA solution. When the refluxingtime was increased, the intensities of SPR absorption of AgNs increased, indicating that more AgNs were producedin the polymer solution. The positions of the peak maximumdid not shift to a high wavelength with increasing refluxingtime; this implies that the average sizes of the AgNs did notincrease. Jin et al. [8] explained that PVA stabilized theAgNs through the coordination between the lone pairelectrons on the hydroxyl oxygen of PVA with Ag ionsand AgNs. Moreover, the PVA chains sterically inhibitedparticle nucleation and growth. The intensities of SPRabsorption of AgNs in the CS/PVA blend solutions wereslightly higher than those of AgNs in the PVA solution.However, the wavelength of AgN absorption did notchange. This result indicates that CS played the role of boththe stabilizing and reducing agents in the formation of
AgNs, which is consistent with the result of Wei et al. [37]
and Tran et al. [13].
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