164
D. K. Pandey et al.
of GQDs. Raman spectroscopy was most recently implemented to study its electrical
conductivity and identify GO in an aqueous environment [136, 137].
4.2.2 Chalcogenides Materials
The transition metal dichalcogenides (TMDs), described by molecular formula MX 2
(M = Mo, W; X = S, Se, Te), gained considerable attention due to their exceptional
electronic and optical properties and wide-ranging applications of devices [138–
143]. Raman Spectroscopy is used extensively for characterizing these materials
[144, 145]. Tripathi and Mishra developed an analytical tool that was based on
open-source Python modules to investigate the number of layers in two-dimensional
materials [146]. The coefficient of thermal expansion which is a fundamental property
of these 2D materials must be well defined as it is essential to the dry transfer
process and thermal management of 2D material-based devices. Hence, Zhang et al.
presented the three substrates strategy to measure the coefficient of thermal expansion
of monolayer molybdenum disulfide (MoS 2 ) using micro-Raman spectroscopy [147].
Based on the symmetry analysis, they showed that owing to the influence of thermal
mismatch and free expansion, the coefficient of thermal expansion would disturb the
point optical phonon frequency via both the temperature coefficients and in-plane
thermal stress [147]. Wang et al. studied multiple orders of Raman scattering in
monolayer transition metal chalcogenides (TMDC) based on the intrinsic excitons
coupled with different phonon modes [148]. Here, researchers concluded that multi
phonon systems demonstrate multiple order overtones at the same interval of energies
of both ωLO (longitudinal optical) and ωSO (surface optical) phonon modes [148].
Also, the overtone intensities rely on the gained Huang-Rhys factor values, which
can be modulated by the intensity of the pairing of exciton-optical phonons, the
cutoff wave vector of the optical phonon modes, and the large Bohr radius exciton
[148]. To study the hydrogen evolution photocatalytic property of these TMDs, Guo
et al. employed Operando Raman spectroscopy [149]. The spectroscopic studies
indicate that the hydrogen atoms can be adsorbed by intermediate species produced
during the photocatalytic phase to active sulfur and selenium atoms. Therefore, it can
be concluded that the developed Operando Raman spectroscopy approach provides
a new tool to elucidate catalytic reaction mechanisms in a practical and complex
environment as a fast, insightful, and general analytical method.
4.2.3 Archaeological Materials
Cultural heritage stewardship includes preserving, maintaining, and restoring
tangible artwork, archaeological objects, and collections of museums. The need to
restore and preserve important works of art is obvious and has been a focus of museum
activity for centuries. Raman spectroscopy is a significant resource in art conservators and archaeologists’ arsenals and has been extensively utilized in the study of
ceramics [150, 151], gemstones [152], wall paintings [153], complex mixtures of
D. K. Pandey et al.
of GQDs. Raman spectroscopy was most recently implemented to study its electrical
conductivity and identify GO in an aqueous environment [136, 137].
4.2.2 Chalcogenides Materials
The transition metal dichalcogenides (TMDs), described by molecular formula MX 2
(M = Mo, W; X = S, Se, Te), gained considerable attention due to their exceptional
electronic and optical properties and wide-ranging applications of devices [138–
143]. Raman Spectroscopy is used extensively for characterizing these materials
[144, 145]. Tripathi and Mishra developed an analytical tool that was based on
open-source Python modules to investigate the number of layers in two-dimensional
materials [146]. The coefficient of thermal expansion which is a fundamental property
of these 2D materials must be well defined as it is essential to the dry transfer
process and thermal management of 2D material-based devices. Hence, Zhang et al.
presented the three substrates strategy to measure the coefficient of thermal expansion
of monolayer molybdenum disulfide (MoS 2 ) using micro-Raman spectroscopy [147].
Based on the symmetry analysis, they showed that owing to the influence of thermal
mismatch and free expansion, the coefficient of thermal expansion would disturb the
point optical phonon frequency via both the temperature coefficients and in-plane
thermal stress [147]. Wang et al. studied multiple orders of Raman scattering in
monolayer transition metal chalcogenides (TMDC) based on the intrinsic excitons
coupled with different phonon modes [148]. Here, researchers concluded that multi
phonon systems demonstrate multiple order overtones at the same interval of energies
of both ωLO (longitudinal optical) and ωSO (surface optical) phonon modes [148].
Also, the overtone intensities rely on the gained Huang-Rhys factor values, which
can be modulated by the intensity of the pairing of exciton-optical phonons, the
cutoff wave vector of the optical phonon modes, and the large Bohr radius exciton
[148]. To study the hydrogen evolution photocatalytic property of these TMDs, Guo
et al. employed Operando Raman spectroscopy [149]. The spectroscopic studies
indicate that the hydrogen atoms can be adsorbed by intermediate species produced
during the photocatalytic phase to active sulfur and selenium atoms. Therefore, it can
be concluded that the developed Operando Raman spectroscopy approach provides
a new tool to elucidate catalytic reaction mechanisms in a practical and complex
environment as a fast, insightful, and general analytical method.
4.2.3 Archaeological Materials
Cultural heritage stewardship includes preserving, maintaining, and restoring
tangible artwork, archaeological objects, and collections of museums. The need to
restore and preserve important works of art is obvious and has been a focus of museum
activity for centuries. Raman spectroscopy is a significant resource in art conservators and archaeologists’ arsenals and has been extensively utilized in the study of
ceramics [150, 151], gemstones [152], wall paintings [153], complex mixtures of