Synthesis of Positively Charged Silver Nanoparticles via Photoreduction of AgNO₃ in Branched Polyethyleneimine/HEPES Solutions

Abstract

Branched polyethyleneimine (BPEI) and 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) were used collaboratively to reduce silver nitrate under UV irradiation for the synthesis of positively charged silver nanoparticles. The effects of molar ratio of the ingredients and the molecular weight of BPEI on the particle size and distribution were investigated. The mechanism for the reduction of Ag+ ions in the BPEI/HEPES mixtures entails oxidative cleavage of BPEI chains that results in the formation of positively charged BPEI fragments enriched with amide groups as well as in the production of formaldehyde, which serves as a reducing agent for Ag+ ions. The resultant silver nanoparticles are positively charged due to protonation of surface amino groups. Importantly, these positively charged Ag nanoparticles demonstrate superior SERS activity over negatively charged citrate reduced Ag nanoparticles for the detection of thiocyanate and perchlorate ions; therefore, they are promising candidates for sensing and detection of a variety of negatively charged analytes in aqueous solutions using surface-enhanced Raman spectroscopy (SERS).

Facile Synthesis of Silver Nanoparticles Stabilized by Cationic Polynorbornenes and Their Catalytic Activity in 4-Nitrophenol Reduction

“…For example, Song et al 29 used cationic polymer nanofibers to embed silver nanoparticles to reinforce the antimicrobial activity of the embedded silver nanoparticles. Tan and co-workers reported 12 the use of branched polyethylenimine (BPEI) and 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) together to reduce silver nitrate under UV irradiation for the synthesis of silver nanoparticles. The resultant silver nanoparticles are positively charged as the BPEI amino groups are protonated in the process.…”

Extracellular biosynthesis of silver nanoparticles from Cyanobacteria

“…Biological methods for synthesizing nanoparticles have shown better results compared to chemical and physical techniques due to time consumption, slow kinetics [1,2] low cost [3] and most importantly it is more eco-friendly compared to the chemical and physical techniques [4].…”

UV photochemical synthesis of heparin-coated gold nanoparticles

“…Some of its advantages are high spatial resolution, reaction selectivity and controllability as well as shape conversion. This method can be used with light sources like lasers [17], medium and low pressure Mercury [18], Xenon, LEDs and UV lamps [19], and even white light [20].…”