Regional selective construction of nano-Au on Fe₃O₄@SiO₂@PEI nanoparticles by photoreduction

Abstract

A magnetically separatable catalyst Fe3O4@SiO2@PEI@Au (gold) nanoparticle was successfully constructed by a novel regional selective photoreduction method. Based on the photolysis mechanism of a type II photoinitiator, through controlling the distribution of polyethylene imine (PEI), Au nanoparticles about 10 nm, which are only on the surface of the Fe3O4@SiO2@PEI nanoparticle, could be photoreduced due to the PEI acting as a coordinating agent, capping agent, and photoreducing agent simultaneously. The small size Au nanoparticles endow the catalyst with a high catalytic performance toward the reduction of 4-nitroaniline to 4-aminophenol by NaBH4. In addition, magnetic Fe3O4@SiO2@PEI@Au nanoparticles could easily be recovered and could be reused at least six times still keeping catalytic efficiency higher than 95%, which contributes to their high stability and magnetization. Furthermore, compared to another reported approach, this method showed great regional selectivity of reducing metal nanoparticles by controlling the distribution of the PEI. Taking advantage of the regional selectivity of the photoreducing method could also be used to fabricate other metal nanoparticles as catalysts for various reactions.

Photoreductive synthesis of monodispersed Au nanoparticles with citric acid as reductant and surface stabilizing reagent

“…Many of the reported photoreduction methods need both reductants and surface stabilizing reagents. [22][23][24][25][26][27][28][29] Although some systems can use single chemicals behaving as both reductant and surface stabilizing reagent such as ionic liquids, dendrimers, polyvinylpyrrolidone, and trisodium citrate, they are relatively expensive or contain Na + cation contaminant. [30][31][32][33] Yang et al 34 used citric acid for photoreductive synthesis of AuNPs.…”

Surface‐Selective Grafting of Crosslinking Layers on Hydrogel Surfaces via Two Different Mechanisms of Photopolymerization for Site‐Controllable Release

“…Amines are the final radicals initiating photopolymerization, as shown in Figure . Based on this finding, if the hydrogel contains an amine group, then modification of the hydrogel surface is easily achieved …”

“…[20] Based on this finding, if the hydrogel contains an amine group, then modification of the hydrogel surface is easily achieved. [21]…”

Photoactive Polyethylenimine-Coated Graphene Oxide Composites for Enhanced Cr(VI) Reduction and Recovery

“…Chromium treatment has traditionally been accomplished via separation from the dissolved phase through adsorption via anion exchange, precipitation, and coprecipitation reactions and through size exclusion processes (e.g., ultrafiltration). , To increase sorption and removal of Cr­(VI), in particular, net positively charged organic ligands have been applied through the surface modification of fungal biomass, aerobic granules, magnetic nanoparticles, , sludge, biochar, , and polymer films, among others. , A number of these rely on cationic organic molecules and polymers containing amine-based functional groups, which act as active binding sites, including polyethylenimine (PEI), polyaniline, ethylenediamine, chitosan, and so forth. − With respect to amine functionalization for the Cr­(VI) sorption and removal, a number of materials have been proposed and demonstrated. − Some of these reports also observe reduction of Cr­(VI) to Cr­(III), albeit relatively slow and under uncontrolled conditions with regard to light exposure. ,,,,, Interestingly, under UV irradiation, amine groups, in some cases, can be photochemically converted to amine radical cations, which can subsequently react . Such photoactivated amine radical cations have been used in various chemical redox (reduction-based) processes, , including the synthesis of gold nanoparticles, , production of hydrogen peroxide, electrochemistry, , and as part of overall synthesis pathway(s) for amine-functionalized organics. , Furthermore, while amine photochemistry has been explored, to a limited degree, for CO 2 reduction and water splitting, , there has been very little reported with regard to transformation of aqueous-based inorganic pollutants, in...…”

“…22,23,27,28,30,31 Interestingly, under UV irradiation, amine groups, in some cases, can be photochemically converted to amine radical cations, which can subsequently react. 32 cations have been used in various chemical redox (reductionbased) processes, 33,34 including the synthesis of gold nanoparticles, 35,36 production of hydrogen peroxide, 37 electrochemistry, 38,39 and as part of overall synthesis pathway(s) for amine-functionalized organics. 40,41 Furthermore, while amine photochemistry has been explored, to a limited degree, for CO 2 reduction 42 and water splitting, 43,44 there has been very little reported with regard to transformation of aqueous-based inorganic pollutants, including chromium.…”