Nanomaterials: An Introduction
5
and hazardous byproducts. Thus, there is a need for “green chemistry” that ensures
clean, non-toxic, and environment-friendly nanoparticles production [75].
In recent years, environment-friendly approaches have been developed to fabricate
stable nanoparticles with well-defined morphology and configured constricted sizes
[76]. Additionally, owing to the high demand for precious metals (like silver and gold)
and metal oxides in electronics, catalysis, medical, and other industrial applications,
its recovery from primary and secondary sources is of considerable significance and
interest. Biological recovery of these precious metals by preparing their nanoparticle
is a green alternative to the conventional physical and chemical methods [77, 78].
Bio-inspired synthesis of nanoparticles is an advanced, cost-effective, environmentfriendly approach over chemical and physical processes, without any inclusion of
high pressure, energy, temperature, and toxic chemicals [79]. For example, the plant
leaf extract is used for the biosynthesis of silver and gold nanoparticles for pharmaceutical and biomedical applications, without employing any toxic chemicals in
the synthesis protocols [80]. An environmentally acceptable solvent system, ecofriendly reducing and capping agents are considered to be an essential element for
an ultimately “green” synthesis [81]. The green synthesis techniques are generally
utilizing relatively non-toxic chemicals to synthesize nanomaterials. The fabrication
process also includes the use of non-toxic solvents such as water, biological extracts,
biological systems, etc. In this technique, generally, microwave maintains a constant
temperature of solvent systems. The conventional extraction technique using hexane,
ethanol, and water was used to collect bioactive molecules [82]. However, they are
immensely problematic due to instability as well as environmental and health hazards
[83]. To overwhelm this problem, researchers developed a new approach, i.e., supercritical fluid (SCF) extraction technology for avoiding toxic organic solvents in green
technology. SCF possesses physical properties intermediate between CO 2 gas and a
liquid at a temperature and pressure above its critical point. Since supercritical CO 2
is non-polar, non-toxicity, non-flammability, and low critical temperature.
3 Benefits of Nanotechnology
Recently, research and development in nanotechnology have seen exponential growth
due to advantages in different fields, i.e., drug delivery, cell imaging, material
improvement, and medical devices for diagnosis and treatment. More powerful
computers are being designed using nanomaterials in a smaller size, faster in speed,
and consuming very less power, having long-life batteries. Circuits consisting of
carbon nanotubes can maintain the computer system advancement. Carbon nanotubes
are also commercially used in sports equipment, to increase their strength while
maintaining a low weight. Nanoparticles or nanofibers in fabrics improve the waterresistance, stain resistance, and flame resistance, without putting on extra weight,
stiffness, or thickness of the material. Nanoparticles are used in medical products for dermal, oral or inhalation applications, and pharmaceuticals. These are
5
and hazardous byproducts. Thus, there is a need for “green chemistry” that ensures
clean, non-toxic, and environment-friendly nanoparticles production [75].
In recent years, environment-friendly approaches have been developed to fabricate
stable nanoparticles with well-defined morphology and configured constricted sizes
[76]. Additionally, owing to the high demand for precious metals (like silver and gold)
and metal oxides in electronics, catalysis, medical, and other industrial applications,
its recovery from primary and secondary sources is of considerable significance and
interest. Biological recovery of these precious metals by preparing their nanoparticle
is a green alternative to the conventional physical and chemical methods [77, 78].
Bio-inspired synthesis of nanoparticles is an advanced, cost-effective, environmentfriendly approach over chemical and physical processes, without any inclusion of
high pressure, energy, temperature, and toxic chemicals [79]. For example, the plant
leaf extract is used for the biosynthesis of silver and gold nanoparticles for pharmaceutical and biomedical applications, without employing any toxic chemicals in
the synthesis protocols [80]. An environmentally acceptable solvent system, ecofriendly reducing and capping agents are considered to be an essential element for
an ultimately “green” synthesis [81]. The green synthesis techniques are generally
utilizing relatively non-toxic chemicals to synthesize nanomaterials. The fabrication
process also includes the use of non-toxic solvents such as water, biological extracts,
biological systems, etc. In this technique, generally, microwave maintains a constant
temperature of solvent systems. The conventional extraction technique using hexane,
ethanol, and water was used to collect bioactive molecules [82]. However, they are
immensely problematic due to instability as well as environmental and health hazards
[83]. To overwhelm this problem, researchers developed a new approach, i.e., supercritical fluid (SCF) extraction technology for avoiding toxic organic solvents in green
technology. SCF possesses physical properties intermediate between CO 2 gas and a
liquid at a temperature and pressure above its critical point. Since supercritical CO 2
is non-polar, non-toxicity, non-flammability, and low critical temperature.
3 Benefits of Nanotechnology
Recently, research and development in nanotechnology have seen exponential growth
due to advantages in different fields, i.e., drug delivery, cell imaging, material
improvement, and medical devices for diagnosis and treatment. More powerful
computers are being designed using nanomaterials in a smaller size, faster in speed,
and consuming very less power, having long-life batteries. Circuits consisting of
carbon nanotubes can maintain the computer system advancement. Carbon nanotubes
are also commercially used in sports equipment, to increase their strength while
maintaining a low weight. Nanoparticles or nanofibers in fabrics improve the waterresistance, stain resistance, and flame resistance, without putting on extra weight,
stiffness, or thickness of the material. Nanoparticles are used in medical products for dermal, oral or inhalation applications, and pharmaceuticals. These are