Environmental Engineering Reference
In-Depth Information
18
Green MethodoloGies in the synthesis of Metal
and Metal oxide nanoparticles
Aniruddha B. Patil and Bhalchandra M. Bhanage
Department of Chemistry, Institute of Chemical Technology, Mumbai, India
18.1
introduction
As early as 1959 the renowned physicist Richard Feynman proposed that the concept of “nanotechnology,” in its traditional
sense, means building things from the bottom up, with atomic precision. The prefix “nano” is derived from Greek word
nanos
meaning “dwarf” that denotes things one billionth (10
9
m) in size. Nowadays nanotechnology research is developing as a cut-
ting-edge technology interdisciplinary with chemistry, physics, material science, biology, and medicine. In the field of material
science, a material is called a “nanoparticle” when “a particle is having one or more dimensions of the order of 100 nm or less.”
There is a note associated with this definition: “Novel properties that differentiate nanoparticles from the bulk material typically
develop at a critical length scale of under 100 nm.”
The “novel properties” stated are completely dependent on the fact that at the nanoscale, their properties are unlike the prop-
erties of the bulk material (Fig. 18.1). Nanoparticles shows distinctive chemical, physical, electrical, electronic, mechanical,
magnetic, dielectric, thermal, optical, and biological properties different than that of the bulk materials [1, 2]. The dimension of
nanoparticles has a distinct effect on the physical properties that is significantly dissimilar from those of the bulk material,
caused by their large surface atoms, large surface energy, spatial confinement, and reduced imperfections. Nanoparticles show
characteristic properties in the field of physicochemistry, optoelectronics, and electronics that mostly depend on their size,
shape, and crystallinity. Because of such wide applicability and distinct characteristic properties, nanoparticles are considered
as key in the next generation of electronics, optoelectronics, and various chemical and biochemical sensors [3, 4]. Therefore,
the recent research activities focus on the synthesis of monodispersed nanoparticles with various shapes and sizes.
Though several physical and chemical methods are comprehensively applied for the synthesis of monodispersed nanoparti-
cles, the stability and the use of toxic chemicals is the topic of predominant concern. The use of nonpolar solvents and toxic
chemicals on the surface of nanoparticles in the synthesis procedure limits their applications in the clinical field. Therefore, the
development of nontoxic, clean, biocompatible, and ecofriendly methods for nanoparticle synthesis deserves merit. In this
regard, recent research is focused on the novel protocol that links it to the green aspects. The green aspects in nanoparticle prep-
aration bypass the conventional techniques and toxic organic solvents. In the literature it has been observed that the current
research focuses on the novel, nonconventional, and green methods for metal and metal oxide nanoparticle synthesis. In addition
to the benign environmental properties, the new green protocol is inexpensive and time-saving.
This chapter deals with green techniques involving biological methods, supercritical solvents, microwave, sonochemistry, elec-
trochemistry, sonoelectrochemistry, and hydrothermal energy for the synthesis of metal and metal oxide nanoparticles. The micro-
bial synthesis of nanoparticles is one of the most promising fields of research in nanobiotechnology interconnecting biotechnology
