The influence of branched polyethyleneimine concentration on the spectroscopic and morphology of BPEI/AuNPs for photocatalytic reduction of 4-nitrophenol

Abstract

AbstractIn this work, gold nanoparticles (AuNPs) were synthesized and stabilized by branched polyethyleneimine (BPEI) due to their amine groups as a low-cost alternative method. The concentration of BPEI as a critical factor can be used to optimize stable AuNPs with varying sizes. To evaluate BPEI concentrations on surface plasmonic resonance (SPR), size distribution, chemical coordination, and photocatalytic activity of BPEI-AuNPs products, UV–visible, transmission electron microscope, and Fourier transform infrared spectroscopy were used. The SPR bands appeared at 524, 520, and 517 nm as the BPEI concentration increased (10–30 µL), and the band remained stable as BPEI increased. TEM images show a wide range of sizes (polydisperse) for BPEI/AuNPs were formed. According to TEM images, gold nanoparticle sizes were calculated at (18, 12, and 5 nm) for BPEI concentrations 10, 20, and 30 µL. Fourier transform infrared spectroscopy (FTIR) revealed that amine groups from BPEI play an important role in stabilizing AuNPs. For accessing the photocatalytic activity of BPEI-AuNPs, the reduction of 4-nitrophenol (4-NP) by borohydride is a widely used model reaction. As the AuNPs sizes decreased from 18 to 5 nm, the reduction rate was accelerated and the reaction time of 4-NP to 4-AP conversion decreased from 270 to 150 s.