Solvothermal synthesis of Silver nanoplates and its application

Abstract

Recently, controlling the shape of metal nanostructures has become a promising strategy for tailoring physical and chemical properties for various applications in fields such as biological labeling and imaging, catalysis, electronic and information technology, sensing and surface-enhanced Raman scattering (SERS). For silver, a wealth of non-classical nanocrystals, such as rods, wires, plates, and cubes, among others, have been synthesized and characterized. Exploration of these previously unknown structures can provide new perspectives into the rational design of novel nanomaterials. Synthesis of silver nanoplates, which have novel optical properties, has attracted much attention since the photo-induced chemical reaction was first published. Other successful methods include kinetically controlled chemical reduction, thermal process and micro-emulsion-assisted synthesis; but these processes are mainly achieved by slow-reduction over a long time, or at low silver precursor concentrations. Despite these growth mechanisms proposed in the literature, few studies have actually examined or published the growth process of silver nanofilms or silver connected-plates. In this study, we used a previously reported solvothermal approach to prepare silver nanoplates with widths from several tens of nanometers to a few hundred nanometers. Since the reaction has many influencing factors (such as reaction time, concentration of reactants, and reaction temperature), a series of experiments with controlled reaction conditions enabled the observation of the various products and offered a convenient way to examine the growth process of these nanoplates. Here interesting and surprising products were found, and a somewhat different growth mechanism is given. We can expect that this method will have potential applications such as in electrode materials for the information and electronic industry. The results also offer insights into the previously speculated possible formation of silver nanobelts derived from the shape transformation of triangular nanoplates. Another interesting aspect of this work is the high concentration with controlled size and shape. Most of the literature on the synthesis of silver nanoplates discussed products that are hundreds of nanometers to tens of micrometers in width, or the relatively low silver concentrations. Few studies have successfully made nanoplates with widths of less than 100 nm and at the same time obtained a high concentration of plate colloids. Our solvothermal approach was able to produce small silver nanoplates with a controlled average width of 40 nm to 100 nm. In this study, we have extended the concentration range of this approach by using silver nitrate at concentrations ranging from 20 mM to 100 mM. With triangular nanoplates of different sizes and the connected nanofilms, their self-assembled structures are also presented along with the UV-vis absorption and SERS spectra of the nanoplates.