Metallic Nanoparticles for Biomedical Applications
35
easily, and they serve as specific biomarkers or drug carrier respectively. Absorption and fluorescent properties of these MNPs are utilized in fluorescence imaging
and marker for the detection of proteins using surface-enhanced Raman spectroscopy
(SERS) [27]. Apart from Au and Ag NPs, palladium (Pd), platinum (Pt), Cu, rhodium
(Rh), iron (Fe), and nickel (Ni) NPs are also useful in biomedical applications [32,
33]. Pd is a major component in commercial devices and industrial processes due
to its catalytic behaviour. Further, it has a strong affinity with hydrogen; hence it is
useful for purification, detection, and storage purposes. Pt NPs are found its applications in electronic, chemical, automotive, photochemical, and pharmaceutical fields
due to its features such as corrosion-resistant, electrical and catalytic properties [34].
Cu NPs have significant application in antimicrobial systems [28].
Synthesized MNPs can be characterized using various techniques; ultravioletvisual (UV-vis) absorption spectrophotometry, transmission electron microscopy
(TEM), high-resolution transmission electron microscopy (HR-TEM), highresolution-scanning transmission electron microscopy (HR-STEM), selected area
electron diffraction, infrared (IR) spectroscopy, atomic force microscopy, energydispersive X-ray spectroscopy, fibre spectrometry, dynamic light scattering (DLS)
and scanning electron microscopy (SEM). Generally, for the size distribution, DLS,
SEM, and TEM can be used. For the detailed morphological analysis, TEM, HRTEM, and HR-STEM are the best choices. UV-Vis absorption spectrum is used to
find the plasmonic peak of synthesized particles. Apart from these details, it also
provides information about the dispersity of particle and morphology.
Varieties of synthesis method involved in fabricating MNPs. However, developing
NPs at high volumes and with specific sizes, shapes, and crystalline nature is always
challenging and requires more trials. As mentioned earlier, the synthesis of MNPs
can be divided into two based on the starting material; top-down and bottom-up
method. In the top-down method, the bulk metallic material serves as the starting
material for nanoparticle formation. In contrast, in the bottom-up method, individual
nuclei or atom forms the initial material.
2 Top-Down Methods
In this method, the bulk material is chiselled down into required nano-sized particles
through physical, chemical, or mechanical treatments. According to the type of treatment, top-down approaches can be mechanical milling, laser ablation, or sputtering
[34].
2.1 Mechanical Milling
Mechanical milling involves a reduction in particle size using high energy ball milling
or mechanochemical milling. With ball milling, the bulk metallic powder is added
35
easily, and they serve as specific biomarkers or drug carrier respectively. Absorption and fluorescent properties of these MNPs are utilized in fluorescence imaging
and marker for the detection of proteins using surface-enhanced Raman spectroscopy
(SERS) [27]. Apart from Au and Ag NPs, palladium (Pd), platinum (Pt), Cu, rhodium
(Rh), iron (Fe), and nickel (Ni) NPs are also useful in biomedical applications [32,
33]. Pd is a major component in commercial devices and industrial processes due
to its catalytic behaviour. Further, it has a strong affinity with hydrogen; hence it is
useful for purification, detection, and storage purposes. Pt NPs are found its applications in electronic, chemical, automotive, photochemical, and pharmaceutical fields
due to its features such as corrosion-resistant, electrical and catalytic properties [34].
Cu NPs have significant application in antimicrobial systems [28].
Synthesized MNPs can be characterized using various techniques; ultravioletvisual (UV-vis) absorption spectrophotometry, transmission electron microscopy
(TEM), high-resolution transmission electron microscopy (HR-TEM), highresolution-scanning transmission electron microscopy (HR-STEM), selected area
electron diffraction, infrared (IR) spectroscopy, atomic force microscopy, energydispersive X-ray spectroscopy, fibre spectrometry, dynamic light scattering (DLS)
and scanning electron microscopy (SEM). Generally, for the size distribution, DLS,
SEM, and TEM can be used. For the detailed morphological analysis, TEM, HRTEM, and HR-STEM are the best choices. UV-Vis absorption spectrum is used to
find the plasmonic peak of synthesized particles. Apart from these details, it also
provides information about the dispersity of particle and morphology.
Varieties of synthesis method involved in fabricating MNPs. However, developing
NPs at high volumes and with specific sizes, shapes, and crystalline nature is always
challenging and requires more trials. As mentioned earlier, the synthesis of MNPs
can be divided into two based on the starting material; top-down and bottom-up
method. In the top-down method, the bulk metallic material serves as the starting
material for nanoparticle formation. In contrast, in the bottom-up method, individual
nuclei or atom forms the initial material.
2 Top-Down Methods
In this method, the bulk material is chiselled down into required nano-sized particles
through physical, chemical, or mechanical treatments. According to the type of treatment, top-down approaches can be mechanical milling, laser ablation, or sputtering
[34].
2.1 Mechanical Milling
Mechanical milling involves a reduction in particle size using high energy ball milling
or mechanochemical milling. With ball milling, the bulk metallic powder is added