Soft Template Synthesis Of Silver Nanomaterials And Their Properties

Nanomaterials have four basic effects, that is, surface and interface effect, small size effect, quantum size effect and macroscopic quantum tunneling effect. Thus nanomaterials have their own unique good performance compared with traditional materials, and these properties make it possible for nanomaterials to play a huge role in many areas, such as catalysis, electronics, optics, surface-enhanced Raman scattering, biomedicine, biosensor, etc. These properties and applications are both closely related to the morphology and size of nanoparticles. Hence, it is very important to achieve the morphology-controlled synthesis of nanomaterials. In recent years, although new preparation methods and techniques have been developed, controllable preparation of nanomaterials is still very difficult and is not fully perfect, it is the key and difficult point in the aspect of nanomaterials preparation currently. Therefore, finding new synthesis methods for the preparation of adjustable morphology and size of nanomaterials has great significance and broad application prospects. Besides, searching for non-toxic, environmental-friendly and renewable reagents and exploring green synthesis methods are also the research focus at present.In this paper, we chose silver nanoparticles as the research object. Based on the research development of silver nanoparticles in the world, silver nanomaterials were synthesized by using sericin and polyvinylpyrrolidone (PVP) as a soft template, respectively. Firstly, we prepared hexagonal silver nanoplates through a facile and green method. The influence factors in the reaction process were studied, the growth mechanism and antibacterial activity of the obtained hexagonal silver nanoplates were also explored; Secondly, we prepared silver nanospheres using ultrasonic wave-assisted method, the influence factors in the reaction process were studied, the possible growth methanism was proposed and the catalytic degradation activity against methylene blue was also explored.The innovation points in this paper are as follows:1. Hexagonal silver nanoplates were obtained via the chemical reduction of silver nitrate at room temperature, using sericin as the surfactant and soft template and ascorbic acid as the reducing agent. The obtained hexagonal silver nanoplates were characterized by X-ray powder diffraction (XRD), UV-visible spectroscopy (UV-vis), scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM). The result showed that the prepared hexagonal silver nanoplates had a uniform morphology with the average particle size in the range of 200-300 nm and the thickness of 30 nm. The growth mechanism of "Oriented Growth by Surfactant" of hexagonal silver nanoplates was proposed, the influence of reaction time, temperature and the amount of the surfactant on the formation of hexagonal silver nanoplates was studied, the study indicated that the reaction time, temperature and the amount of the surfactant all can alter the morphology of the obtained products. The antibacterial activities of the obtained hexagonal silver nanoplates against Escherichia coli and Staphylococcus aureus were also measured, they showed appreciable antibacterial activities against Escherichia coli (Gram negative) and Staphylococcus aureus (Gram positive).2. Silver nanospheres were prepared through an ultrasonic wave-assisted method using Tollens’ reagent as the silver source, PVP as the surfactant and soft template and ascorbic acid as the reducing agent. The obtained silver nanospheres were characterized by X-ray powder diffraction (XRD), UV-visible spectroscopy (UV-vis), scanning electron microscopy (SEM), and Energy dispersive X-ray spectroscopy (EDX). The result showed that the prepared silver nanospheres had a uniform morphology and good dispersibility with the average particle size in the range of 300-400 nm. The possible growth mechanism of silver nanospheres was proposed, the ultrasonic cavitation effect played a decisive role in the formation process of silver nanospheres. The influence of ultrasonic time, the amount of PVP and ammonium hydroxide on the formation of silver nanospheres was studied, the study indicated that the ultrasonic reaction time, the amount of PVP and ammonium hydroxide all can alter the morphology of the obtained products. The catalytic degradation activity of as-prepared silver nanospheres on methylene blue was also explored, the result suggested that the obtained silver nanospheres had an excellent catalytic degradation activity on methylene blue.