Green and scalable synthesis of nanosilver loaded silica microparticles by spray-drying: application as antibacterial agent, catalyst and SERS substrate
Silver nanoparticles (Ag NPs) have found wide-spread applications as antibacterial agents, catalysts and in chemical detection via surface-enhanced Raman spectroscopy (SERS). To avoid agglomeration and unwanted release to the environment, Ag NPs are usually loaded onto various substrates. However, simple procedures for large-scale synthesis of this important material are still lacking. Here, we demonstrate a facile, green and scalable synthesis of Ag NPs loaded to ceramic substrates. Environment-friendly biopolymer (gum arabic) and ceramic (silica) nanoparticles were spray-dried to obtain surface-functionalized mesoporous silica substrate. Thereafter, the silver precursor was reduced in situ to obtain Ag NPs attached to the silica substrate. Gum arabic played a crucial role in reducing and attaching Ag NPs to the substrate. The resulting composite material was characterized using X-ray diffraction, high-resolution transmission electron microscopy, field emission scanning electron microscopy and Fourier transform infrared spectroscopy. The antimicrobial efficacy of the synthesized composite was evaluated against a gram-negative bacterium, Escherichia coli and a gram-positive bacterium, Staphylococcus aureus. Complete bactericidal effect was observed for composite harboring silver concentration as low as 19 µg ml−1 and 76 µg ml−1 for Escherichia coli and Staphylococcus aureus, respectively. Furthermore, the composite was used as a catalyst in the reduction reaction of 4-nitrophenol and rhodamine B by sodium borohydride. The rate constant for 4-nitrophenol reduction was found to be 1750 s−1 g−1. The composite demonstrated its applicability as a substrate for surface-enhanced Raman spectroscopy (SERS) wherein very dilute concentration (10−9 M) of crystal violet and rhodamine 6G could be easily detected.
KeywordsSilver nanoparticle Antibacterial agent Heterogeneous catalyst SERS substrate Spray-drying Metal-ceramic composite
The authors thank Analytical Chemistry Division, BARC for atomic absorption spectroscopy measurement, Ms. Naini Bajaj and Dr. M. N. Deo of High Pressure & Synchrotron Radiation Physics Division, BARC for FTIR measurement, Dr. P. U. Sastry and Mr. Jayakrishnan of Solid State Physics Division, BARC for XRD measurement and Mr. S. V. Ingale of Applied Physics Division, BARC for spray-drying.
Compliance with ethical standards
Conflict of interest
No conflict of interest to declare.
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