Synthesis and characterization of silver nanoparticles: Application to antibacterial activity

Md. Sayem Alam^a,* A. Mohammed Siddiq,^a,b  S. Sriman Narayanan,^b,c  Sujoy K. Das,^d  Debasis Samanta,^e  and Asit Baran Mandal,^a*

Council of Scientific and Industrial Research (CSIR) — Central Leather Research Institute (CLRI), ^a Industrial Chemistry Laboratory, ^dEnvironmental Technology Division, ^e Polymer Division, Adyar, Chennai 600 020, India. ^b National Center for Nanoscience and Nanotechnology, University of Madras, Chennai- 600 025, India. ^cDepartment of Analytical Chemistry, University of Madras Guindy Campus, Chennai - 600 025, India.

E-mail: sayemalam@gmail.com, abmandal@hotmail.com

Abstract:

In the present work, we describe the synthesis, characterization and application to antibacterial activity of silver nanoparticles (AgNPs). Nonionic surfactant, poly(ethylene glycol) t-octylphenyl ether, TX-100 was employed as capping agent for the Ag(0) metallic nanoparticles (synthesized by the chemical reduction of silver nitrate, AgNO₃, with excess of sodium borohydride, NaBH₄). The morphology and the kinetics of AgNPs were studied by UV–vis absorption, transmission electron microscopy (TEM), dynamic light  scattering (DLS),  and fluorescence  probe technique.  Spherical polydisperse particles of  12 ± 4 nm mean diameter. Apart from  the stabilizing role,  the nonionic surfactant promoted the agglomeration of individual AgNPs nanoparticles in small assemblies whose plasmon band features differed from those of the individual nanoparticles. The formation of AgNPs- TX-100 complex took place after full reduction of the Ag⁺ ions and it was controlled by the TX-100 concentrations. The nanoparticle morphology and the fluorescence probe technique suggested that the excess surfactant drove indirectly the AgNPs association. Free TX-100 micelles encountered above critical micellar concentration (CMC) promoted the partial desorption of the adsorbed nonionic surfactant and subsequently weakened the stability of the individual nanoparticles. In addition we explored the application to antibacterial activity of synthesized AgNPs. The antibacterial activity of the synthesized AgNPs on Gram-negative bacteria E. coli was carried out by plate count and growth kinetics methods.

Keywords: Novel metal nanoparticles; Silver nanoparticles; TX-100; Kinetics; Antibacterial activity.

Acknowledgement: Thankful to Department of Science and Technology (DST), New Delhi, Govt. of India for the financial support.