Abstract

A facile, efficient, and eco-friendly approach for the preparation of uniform silver nanoparticles (Ag NPs) was developed. The synthesis was conducted in an aqueous medium exposed to microwave irradiation for 8 min, using laboratory-prepared, water-soluble quaternized carboxymethyl chitosan (QCMC) as a chemical reducer and stabilizer and silver nitrate as the silver source. The structure of the prepared QCMC was characterized using Fourier transform infrared (FT-IR) and 1H nuclear magnetic resonance (NMR). The formation, size distribution, and dispersion of the Ag NPs in the QCMC matrix were determined using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible (UV-Vis), transmission electron microscopy (TEM), and field emission scanning electron microscope (FESEM) analysis, and the thermal stability and antibacterial properties of the synthesized QCMC-based Ag NPs composite (QCMC-Ag) were also explored. The results revealed that (1) QCMC was successfully prepared by grafting quaternary ammonium groups onto carboxymethyl chitosan (CMC) chains under microwave irradiation in water for 90 min and this substitution appeared to have occurred at -NH2 sites on C2 position of the pyranoid ring; (2) uniform and stable spherical Ag NPs could be synthesized when QCMC was used as the reducing and stabilizing agent; (3) Ag NPs were well dispersed in the QCMC matrix with a narrow size distribiution in the range of 17–31 nm without aggregation; and (4) due to the presence of Ag NPs, the thermal stability and antibacterial activity of QCMC-Ag were dramatically improved relative to QCMC.

Highlights

  • Silver nanoparticles (Ag NPs) have recently received extensive attention from researchers and developers due to their attractive optical, electronic, and catalytic properties and excellent antimicrobial activity [1,2,3]

  • Ag NPs were synthesized in a quaternized carboxymethyl chitosan (QCMC) aqueous solution without an additional reducing and stabilizing agent, using silver nitrate as the silver source

  • The synthesis was conducted in an aqueous medium in the presence of microwave irradiation for 8 min

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Summary

Introduction

Silver nanoparticles (Ag NPs) have recently received extensive attention from researchers and developers due to their attractive optical, electronic, and catalytic properties and excellent antimicrobial activity [1,2,3]. Ag NPs exhibit strong antibacterial activity toward a broad range of microorganisms [4], but simultaneously possess a remarkably low human toxicity These properties have caused these new materials to be recognized as one of the most powerful antimicrobial agents of the 21st century, resulting in their wide use in the biomedical field, food packaging, coating, clothing, textile, and other applications [5,6]. Conventional chemical reduction methods require reducing agents including sodium borohydride (NaBH4), hydrazine hydrate (HHA), or other organic compounds in addition to stabilizing agents such as triphenylphosphine, polyvinylpyrrolidone, and sodium citrate Many of these reagents have potential environmental toxicity and biological risks [9,10]. The thermal stability and antibacterial capability of the synthesized QCMC-Ag were explored

Materials
Characterization
Thermal Stability Experiment
Thermal Stability Analysis
Findings
Conclusions

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