## 4 Characterization of Nanomaterials
Finally, the last method is more sensitive than DTA and DSC. DMA measures damping coefficients and dynamic modulus qualities, which are significant when crystalline structures have transitioned to the amorphous phase. One of the most indispensable features is the Tg because it describes the temperature range at which the mechanical properties of the nanomaterials change from hard and brittle to more flexible, malleable, or rubbery. While the melting temperature (Tm) and energy fluctuations provide information about the amorphous content of nanomaterials, these values are gathered in a melting endotherm utilized to determine the purity of the materials [34; 35; 36]. Electron spin resonance (ESR) spectroscopy is also called electron paramagnetic resonance (EPR). It is based on the absorption of microwave radiation by a paramagnetic sample (materials with unpaired electrons) placed in an external magnetic field. ESR spectra can reveal information on the structure and identity of trapped radicals. Consequently, splitting patterns in ESR spectra were initially designed to investigate biological molecules containing extremely reactive and short-lived superoxide (O\({}_{2}\)) and hydroxyl (HO) radicals, along with the production of proteins, lipids, and polysaccharides. Therefore, ESR measurement can be a helpful approach to comprehending cellular chemical interactions and establishing a link between the generation of free radicals, such as reactive oxygen and nitrogen species (ROS/RNS), and functional products in food systems. For example, this method could be used to estimate free radical scavenging capability and determine Cu\({}^{2+}\) chelating capacity and features of irradiated foods [37]. Nuclear magnetic resonance (NMR) and solid-state nuclear magnetic resonance (SSNMR) provide information about the structure of materials, purity, ligand density, and surface chemistry. They have the potential to provide proof of cluster and nanoparticle arrangement by the effect on spin orientation induced by an electromagnetic field [36]. Phenomena such as adsorption, the electric double-layer effect, and resistance to flocculation are a consequence of attractive or repulsive forces between particles (electrostatic, hydrophobic, etc.) in dispersion mechanisms. Dynamic light scattering (DLS) provides the hydrodynamic size, while the zeta potential determines the electrokinetic potential and the surface charge. This is significant in the adsorption of biomolecules through electrostatic interactions, which relates chemically to the functional groups on the surface [29; 36; 38; 39]. Optical absorption spectra provide information on electron density, size, and structure. Thus, UV-Vis spectroscopy is a characterization tool, since their absorption depends on the material and structure. Diffuse reflectance spectroscopy (DRS) is a technique that uses broadband light to produce reflection in the visible and near-infrared wavelength ranges. The ability to absorb the wavelengths of light is directly proportional to the electron excitation. As well, characterization by infrared spectroscopy techniques, such as Fourier-transform infrared spectroscopy (FTIR), allows for the identification of functional groups through vibrational modes. Infrared radiation is transmitted through a sample after absorbing a determined wavelength, causing vibrations and rotations in bound atoms and molecules. The gathered infrared spectrum is a molecular fingerprint of the material [36], whereas Ramman spectroscopy detects the inelastic scattering caused by a high-intensity laser light beam impacting a material with wavelengths in the visible or near-infrared ranges. The Raman spectrum provides a fingerprint of a molecule in the 500-2000 cm\({}^{-1}\) range [29]. To characterize magnetic materials, we can use the method of vibrating sample magnetometry (VSM). VSM can measure the magnetic properties of magnetically soft (low coercivity) and hard (high coercivity) materials in many forms: solids, powders, single crystals, thin films, or liquids.