Controlled synthesis of functional Ag, Ag-Au/Au-Ag nanoparticles and their Prussian blue nanocomposites for bioanalytical applications

In this work, we report a facile approach to synthesize processable silver nanoparticles (AgNPs), bimetallic nanoparticles (Ag-Au/Au-Ag) and a decorated Prussian blue nanocomposite (PB-AgNP). The presence of cyclohexanone/formaldehyde facilitates the formation of functional AgNPs and Ag-Au/Au-Ag from 3-aminopropyltrimethoxysilane (3-APTMS) and the respective capped noble metal ions. The use of the aforementioned reducing agents (3-APTMS and cyclohexanone) also enables the synthesis of polycrystalline Prussian blue nanoparticles (PBNPs). As synthesized PBNPs, AgNPs and Au-Ag enable the formation of nano-structured composites (PB-AgNP, PB-Au-Ag) displaying better catalytic activity than that recorded with natural enzyme. The nanomaterials have been characterized by UV-vis, FT-IR and Transmission Electron Microscopy (TEM) with the following major findings: (1) 3-APTMS capped silver ions in the presence of suitable organic reducing agents [3-glycidoxypropyltrimethoxysilane (GPTMS), cyclohexanone and formaldehyde] are converted into AgNPs under ambient conditions, (2) the time course of the synthesis and dispersibility of the nanoparticles are found to be a function of the organic reducing agents, (3) the use of formaldehyde and cyclohexanone in place of GPTMS with 3-APTMS outclasses the other two in imparting better stability to amphiphilic AgNPs with reduced silanol content, (4) an increase in 3-APTMS concentrations causes a decrease in the nanogeometry of AgNPs, (5) the simultaneous synthesis of bimetallic nanoparticles under desired ratio of silver and gold cations are recorded, (6) cyclohexanone mediated synthesis of AgNPs and Ag-Au/Au-Ag enable the formation of a homogeneous nanocomposite with PBNP as a peroxidase mimetic representing a potential substitute of peroxidase enzyme. The peroxidase mimetic ability has been found to vary as a function of the 3-APTMS concentration, revealing the potential role of functional silver nanoparticles in bioanalytical applications.