Methods for Characterization and Quantitation of Nanomaterials

Abstract

Various pathogenic viruses and bacteria are often needed to be studied conveniently by some of the co-existing conditions of nanomaterials. This chapter briefly discusses the basic principles of standard characterization techniques of nanomaterials with emphasis on different analysis procedures to obtain structural, microstructural, optical, dielectric, magnetic, and physicochemical properties of the nanomaterials. The X-ray based techniques like X-ray diffraction (XRD) gives information about the crystalline structure, lattice parameters, and the average crystallite size, and the X-ray absorption fine spectroscopy (XAS) will provide structural information about the local environment around an atom in nanomaterials. The scanning electron microscope (SEM) with energy dispersive X-ray spectrometer (EDX) is useful in obtaining the microstructural information like the shape, size, and elemental quantities present in a nanomaterial. The Raman Spectroscopy is a versatile technique in the characterization of nanomaterials, mostly in the field of carbon-related nanomaterials, and a tool for the detection of biomolecules via Surface-enhanced Raman Spectroscopy (SERS). The UV-Vis-NIR absorption spectroscopy and Fourier transform infrared spectroscopy (FTIR) techniques are useful in correlating the band-gap to the size of the nanoparticles and the surface characterization of nanoparticles, respectively. The dynamic light scattering (DLS) is used to measure the particle size distribution, whereas electrophoretic light scattering (ELS) is used for zeta potential measurements. Zeta potential is a crucial parameter and extensively used to get the information regarding the stability of the colloidal suspension. The magnetic nanoparticles with core-shell structures or surfactant coatings and strong magnetic responsivity characterized by magnetic property tests. The magnetic correlations are quite strong at low temperatures due to the formation of magnetic clusters. Also, the magnetic nature will be destroyed or lost above Tc due to the random thermal fluctuation of spins and weak magnetic interactions. The magnetic behavior is quantified mainly by physical property measuring system – vibrating sample magnetometer (PPMS-VSM) technique, electron spin resonance spectroscopy (ESR), and AC-susceptibility measurements. Apart from the composition of the nanomaterial and temperature, the size distribution influences the magnetic interactions, which will appear as (antiferromagnetic/ferromagnetic) AFM/FM, superparamagnetic, spin-glass, and frustrated magnetic structures. The electrical barrier in nanomaterials is very high due to the larger surface to volume ratio and influences the average conductivity, characterized by the impedance spectroscopy. The impedance spectroscopy is a powerful tool to correlate the properties by quantifying the dielectric and electrical relaxations. The physicochemical properties govern the nanomaterials interactions with the biological medium, characterized by the above techniques along with additional techniques like centrifugation and electrophoresis.