Environmental Engineering Reference
In-Depth Information
19
An EnvironmEntAlly FriEndly And GrEEn
ApproAch For SynthESiS And ApplicAtionS
oF SilvEr nAnopArticlES
Muniyandi Jeyaraj, Muralidharan Murugan, Kevin John Pulikotil Anthony,
and Sangiliyandi Gurunathan
GS Institute of Bio and Nanotechnology, Coimbatore, India
19.1
introduction
This new millennium has begun with a lot of technological advancements in every sector. As a result, basic living standards
have seen many improvements in the recent past. Many scientific discoveries have opened the way for new innovations in the
health sector, food processing, and product recovery. However, there are considerable negative consequences, and they have a
great impact on the environment. Increasing industrial activities eventually leads to environmental pollution. One of the most
promising fields that has the potential to manage our environment could be “nanotechnology.” Nanotechnology in the broadest
and the simplest sense refers to all the technological developments at the nano scale, exactly one billionth of a meter.
Nanoparticles (NPs) are the particles whose size ranges from 1 to 100 nm. Their increased surface to volume ratio makes them
more catalytic [1]. NPs of metals have different physical and chemical properties than that of bulk metals. Even though NPs
have a lot of applications, the way in which they are synthesized is a matter of concern. Chemical methods are available for NP
synthesis; this adds to pollution because of the use of toxic chemicals and the generation of hazardous by-products. Physical
methods are limited to low yield [2]. Biogenesis of NPs is a possible solution, which uses only biological agents for the
development of metal NPs. Among the biological components, bacteria are used the most as they are easy to handle and product
recovery is easy with possible genetic manipulations [3, 4].
19.2
thE Story oF SilvEr nps
The earliest usage of NPs was reported during Roman times, as they used NPs for staining glasswares [5]. Faraday's findings
for colloidal gold provided a better understanding of NPs [6]. M. C. Lea in 1889 introduced a method to synthesize
citrate-stabilized silver colloid with particle size averaging 7-9 nm [7, 8]. Silver NPs were available commercially for medical
applications even as early as 1897 under the commercial name “collargol” [9] whose mean size was later determined to be
10 nm [10, 11]. Soon after, a lot more techniques for silver NP synthesis were developed, which involved both physical and
chemical methods.
The history of biogenesis of NPs has its origin in bioremediation studies of microbes on toxic metals. Many microbes
were found to have bioremedial action over heavy metals, which eventually eliminated heavy metal contamination. Close
observations showed that these metal ions were adsorbed by the microbes as aggregates over their cell wall or even into
