A review on the green and sustainable synthesis of silver nanoparticles and one-dimensional silver nanostructures.

Sina Kaabipour,Shohreh Hemmati

doi:10.3762/bjnano.12.9

Abstract

The significance of silver nanostructures has been growing considerably, thanks to their ubiquitous presence in numerous applications, including but not limited to renewable energy, electronics, biosensors, wastewater treatment, medicine, and clinical equipment. The properties of silver nanostructures, such as size, size distribution, and morphology, are strongly dependent on synthesis process conditions such as the process type, equipment type, reagent type, precursor concentration, temperature, process duration, and pH. Physical and chemical methods have been among the most common methods to synthesize silver nanostructures; however, they possess substantial disadvantages and short-comings, especially compared to green synthesis methods. On the contrary, the number of green synthesis techniques has been increasing during the last decade and they have emerged as alternative routes towards facile and effective synthesis of silver nanostructures with different morphologies. In this review, we have initially outlined the most common and popular chemical and physical methodologies and reviewed their advantages and disadvantages. Green synthesis methodologies are then discussed in detail and their advantages over chemical and physical methods have been noted. Recent studies are then reviewed in detail and the effects of essential reaction parameters, such as temperature, pH, precursor, and reagent concentration, on silver nanostructure size and morphology are discussed. Also, green synthesis techniques used for the synthesis of one-dimensional (1D) silver nanostructures have been reviewed, and the potential of alternative green reagents for their synthesis has been discussed. Furthermore, current challenges regarding the green synthesis of 1D silver nanostructures and future direction are outlined. To sum up, we aim to show the real potential of green nanotechnology towards the synthesis of silver nanostructures with various morphologies (especially 1D ones) and the possibility of altering current techniques towards more environmentally friendly, more energy-efficient, less hazardous, simpler, and cheaper procedures.

Highlights

Nanotechnology has been ubiquitously applied in almost every scientific discipline
Green synthesis processes were classified among which synthesis of Ag nanostructures using plant extracts are considered to be a promising route due to their simple utilization, aqueous nature, and non-toxic properties
Plant extracts are likely to contain certain natural compounds such as polyphenols, flavonoids, alkaloids, and different functional groups such as hydroxy groups and carboxylic acids, which can provide strong reducing and capping capability. Due to their broad scope, plant extracts are used for preparation of various Ag nanostructures with different sizes, and the literature studies on this subject have been growing during the last decade

Summary

Introduction

Nanotechnology has been ubiquitously applied in almost every scientific discipline. Nanomaterials have been utilized in innumerable applications due to their unique characteristics. The research being conducted on the synthesis of silver nanowires (AgNWs) is currently gaining a lot of attention due to their promising applications in electronics This is a result of the outstanding electrical, optical, and mechanical properties of AgNWs. 1D silver nanostructures, such as AgNWs are more advantageous compared to other silver nanostructures due to several reasons. The second category in bottom-up synthesis methods consists of a set of techniques that incorporate the use of nonchemical reagents for the synthesis of silver nanostructures. We first aim to discuss the most common AgNP synthesis methodologies and to compare them based on their cost, eco-friendliness, and energy consumption to show how green chemistry can improve the process and act as an alternative compared to physical and chemical synthesis. Novel future directions including application of in situ characterization techniques in the course of reaction, continuous green and sustainable synthesis of silver nanostructures adaptable for in situ characterization, and incorporation of artificial intelligence (AI) in green silver nanostructures synthesis are discussed

Physical and chemical synthesis methodologies of silver nanoparticles

Green synthesis of silver nanoparticles

Physical methods ball milling

One-dimensional silver nanostructures and their green synthesis

Effect of reaction parameters on the green synthesis of 1D Ag nanostructures

Conclusion