Metallic Nanoparticles for Biomedical Applications
73
happens in a reactor containing high-pressure pumps controlled by a pressure regulator. Precursor, along with different solvents, is injected into the reactor. As a result,
the physicochemical property of the liquid phase can be modified into the gaseous
phase, and formed products are nanomaterials. The method is suitable for synthesizing a few MNPs and a wide variety of metal oxides [142]. Ultrasound method
uses either sonochemistry or ultrasonic spray pyrolysis to prepare unusual inorganic
nanomaterials like carbonyl compounds [34].
4 Conclusions and Future Prospects
In this chapter, synthesis methods for metallic nanoparticles, which are essential for biomedical applications, are explained. The technique consists of two
approaches; top-down and bottom-up. Particles synthesized with top-down methods
are not suitable for biomedical applications due to their naked form. Important
bottom-up approaches are solvothermal, chemical reduction, and biological methods.
Solvothermal based synthesis involves the formation of nanoparticles in liquid phase
solvents such as water or organic compounds. These solvents are allowed to heat
above their boiling temperature in a pressure vessel. It uses a metallic precursor,
a reducing agent (reductant), and sometimes ligands and facet specific capping
agents. In the chemical reduction method, metallic salt is reduced with the help
of reducing agent under particular conditions. Nanoparticles can be formed either
through seeded-growth or unseeded method. With the seeded approach, desired
nanostructures can be formed by changing seed size, type, amount, and ageing. Other
tuning parameters are reaction time, temperature, solvent medium, reducing agent,
ligands, capping agent, pH, and molar ratio. The biological method uses microorganisms and plant extracts to synthesize nanoparticles and can be carried out extracellular
or intracellular. The concentration of bioproduct extracted, temperature, reaction time
and pH can influence the particle synthesis. Compared to all other methods, biological method has proven so many advantages as discussed. If we can convert this
biological method into the microfluidic platform, we can utilize the features offered
by microfluidics for precise control of nanoparticles and eco-friendly synthesis.
Further, the biomimicking materials can be used to fabricate the device, which will
be beneficial for producing nanoparticles for biomedical applications. In future, it
is expected the effective usage of biological method in microfluidics with more
advanced fabrication procedures. Microfluidic-based metallic nanoparticle synthesis
are well established. This technology is an emerging field, and more materials have
to be invented for fabricating the microfluidic device as the majority of device material shows issues such as particle agglomeration and their fabrication requires clean
room environment. Very few articles addressed these issues by simply connecting the
glass capillary microreactors for metal hybrid core-shell nanoparticles. In addition,
some researchers performed parameter tuning during synthesis, makes the overall
process simpler for biomedical applications. More research has to be carried out in
fabricating the new material, device fabrication and easy parameter scanning. The
73
happens in a reactor containing high-pressure pumps controlled by a pressure regulator. Precursor, along with different solvents, is injected into the reactor. As a result,
the physicochemical property of the liquid phase can be modified into the gaseous
phase, and formed products are nanomaterials. The method is suitable for synthesizing a few MNPs and a wide variety of metal oxides [142]. Ultrasound method
uses either sonochemistry or ultrasonic spray pyrolysis to prepare unusual inorganic
nanomaterials like carbonyl compounds [34].
4 Conclusions and Future Prospects
In this chapter, synthesis methods for metallic nanoparticles, which are essential for biomedical applications, are explained. The technique consists of two
approaches; top-down and bottom-up. Particles synthesized with top-down methods
are not suitable for biomedical applications due to their naked form. Important
bottom-up approaches are solvothermal, chemical reduction, and biological methods.
Solvothermal based synthesis involves the formation of nanoparticles in liquid phase
solvents such as water or organic compounds. These solvents are allowed to heat
above their boiling temperature in a pressure vessel. It uses a metallic precursor,
a reducing agent (reductant), and sometimes ligands and facet specific capping
agents. In the chemical reduction method, metallic salt is reduced with the help
of reducing agent under particular conditions. Nanoparticles can be formed either
through seeded-growth or unseeded method. With the seeded approach, desired
nanostructures can be formed by changing seed size, type, amount, and ageing. Other
tuning parameters are reaction time, temperature, solvent medium, reducing agent,
ligands, capping agent, pH, and molar ratio. The biological method uses microorganisms and plant extracts to synthesize nanoparticles and can be carried out extracellular
or intracellular. The concentration of bioproduct extracted, temperature, reaction time
and pH can influence the particle synthesis. Compared to all other methods, biological method has proven so many advantages as discussed. If we can convert this
biological method into the microfluidic platform, we can utilize the features offered
by microfluidics for precise control of nanoparticles and eco-friendly synthesis.
Further, the biomimicking materials can be used to fabricate the device, which will
be beneficial for producing nanoparticles for biomedical applications. In future, it
is expected the effective usage of biological method in microfluidics with more
advanced fabrication procedures. Microfluidic-based metallic nanoparticle synthesis
are well established. This technology is an emerging field, and more materials have
to be invented for fabricating the microfluidic device as the majority of device material shows issues such as particle agglomeration and their fabrication requires clean
room environment. Very few articles addressed these issues by simply connecting the
glass capillary microreactors for metal hybrid core-shell nanoparticles. In addition,
some researchers performed parameter tuning during synthesis, makes the overall
process simpler for biomedical applications. More research has to be carried out in
fabricating the new material, device fabrication and easy parameter scanning. The