Table 3.

Strengths and weakness of non-destructive methods used in current work.

Techniques	Type	Advantages	Limitations	References
FS	Spectroscopic	Good signal–noise ratio, an abundant fluorophore	Autofluorescence, limited to the samples exhibiting fluoresce	[20], [59], [60], [176], [177]
THzS	Spectroscopic	Use low energy and lower ionizing energy, Can generate frequency-domain and time-domain data from physical properties and chemical structure of the sample	Cannot penetrate in water and metals, scattering effect for irregular samples is also a weakness in THzS
NIRS	Spectroscopic	The cost-effective tool can conduct qualitative and quantitative detections	Difficult to analyze samples containing water, can generate spectral data only
HIS	Spectral imaging	provide spectral and spatial data, accurately differentiate the similar components of the sample even with similar color, can detect trace elements efficiently	Abundant redundant data, data processing needs a lot of time, adaptability of chemometric methods is another problem in HSI
RS	Spectroscopic	No interference to water, provide rich molecular Raman signatures	Weak Raman scattering cost-ineffective
SERS	Spectroscopic	An ultra-sensitive and specific tool, Direct/minor sample preparation needed, No interference to water and glass	Unstable hotspot regions in substrates, Sensitivity depends on the characteristics of employed nanoparticles

Note: FS = fluorescence spectroscopy, THzS = terahertz spectroscopy, NIRS = near infrared spectroscopy, HSI = hyper spectral imaging, RS = Raman spectroscopy, SERS = surface enhanced Raman spectroscopy.