Molecular Spectroscopic Techniques Research Articles

Development of Highly Sensitive Techniques of Atomic and Molecular Spectroscopy and Their Application for Cultural Heritage Studies

Development of Highly Sensitive Techniques of Atomic and Molecular Spectroscopy and Their Application for Cultural Heritage Studies

High performance SERS boosting by Fabry- Pérot cavities of silica-gold-silicon multilayers

Surface-enhanced Raman scattering (SERS), an advanced technique for molecular spectroscopy, relies heavily on the preparation of SERS active materials that can significantly enhance the Raman scattering signals for highly sensitive detection of trace molecules. Traditionally, SERS measurements are performed on silicon or silica substrates, the SERS performance is determined by the structure of SERS materials. Here, we show that the SERS signal can be amplified and modulated using Fabry-Pérot (F-P) cavities made of silica-silicon (SiO2-Si) or silica-gold-silicon (SiO2-Au-Si) multilayers as substrates. Periodic SERS signal variations as SiO2 thickness increases are observed, exhibiting optimal enhancement with the SiO2 thickness of 250 nm due to the optical interference in the cavity. Although the signal enhancement by optical interference is weaker than that by plasmonic resonance, additional signal amplification is essential for highly sensitive SERS materials. Moreover, we applied this strategy to detect thiram in bean sprout extracts, demonstrating that the detection sensitivity is two orders of magnitude higher than that using Si substrates. The utilization of the pseudo-internal standard intensity calibration method facilitates the quantitative analysis of thiram concentrations. Our results provide a promising approach for further amplification of SERS signals with great potential for practical applications.

Analyzing TVB-N in snakehead by Bayesian-optimized 1D-CNN using molecular vibrational spectroscopic techniques: Near-infrared and Raman spectroscopy

Total volatile basic nitrogen (TVB-N) is one of the key indicators for assessing fish freshness. This research employed near-infrared (NIR) and Raman spectroscopy methods to detect the TVB-N content in snakehead fillets. We extracted feature variables associated with TVB-N from NIR and Raman spectroscopy using Variable Crossover Point Arithmetic - Improved Reduced-Input Vector (VCPA-IRIV). Using these features, we established partial least squares (PLS) and One-dimensional Convolutional Neural Network (1D-CNN) models. Subsequently, data fusion strategies were employed to predict the TVB-N content. Notably, feature-level fusion in conjunction with Bayesian-optimized 1D-CNN, reached the best results, as evidenced by calibration and predictive correlation coefficients of 0.9677 and 0.9676 for TVB-N. These findings underscore the effectiveness of both NIR and Raman spectroscopy in evaluating fish freshness. The fusion of these two vibrational spectroscopy techniques enables a more rapid, efficient and comprehensive quantification of fish freshness.

Pressure control of tritiated hydrogen isotopologues in hermetically sealed vessels by non-evaporable getters for sub-Doppler-resolution spectroscopy

Small molecules serve as valuable benchmarks for testing quantum chemical theories. Ultra-high-resolution spectroscopy currently offers the capability of measuring molecular hydrogen energy levels with a relative accuracy on the order of 10-10. Expanding such investigations to encompass different isotopologues of molecular hydrogen has emerged as a promising avenue for examining mass-dependent contributions to the full description of molecular structure in the framework of relativistic quantum electrodynamics. However, the delicate nature of handling radioactive tritium in a high-resolution spectroscopy environment poses significant technological challenges, thereby limiting the extension of these studies to include T2, DT and HT isotopologues. In this work, we present the experimental setup of the very sensitive, Doppler-free technique of Noise-Immune Cavity-Enhanced Optical Heterodyne Molecular Spectroscopy (NICE-OHMS), used to measure rovibrational transitions in the HT molecule. The NICE-OHMS measurements were performed in a closed cavity system without connection to an actively pumped vacuum system. For this reason, a new method for tritium storage and pressure regulation within 0.05–1Pa based on a temperature-controlled mini-getter system is employed using less activity than the tritium exemption limit (1GBq). Non-Evaporable Getters of the type SAES St171 were used for this purpose exploiting their property that hydrogen is released upon heating, while other gases remain being pumped. Prior to the NICE-OHMS experiment, the reversible sorption properties of the getter for hydrogen isotopes were investigated. We show measurements of the equilibrium (hydrogen) pressure for all three pure isotopes and for a H2:HT:T2 mixture (with H:T = 1:1) as a function of temperature for a system of defined volume and amount of gas. For the read-out of the temperature, a method using the resistance of the getter in combination with a pyrometric calibration has been implemented. We discuss the experiences from practical use of the tritium getter and show results obtained with the NICE-OHMS setup leading to frequency calibration of near-infrared transitions in HT at an accuracy, surpassing previous studies by nearly three orders of magnitude.

Synthesis, characterisation, and in vitro antiparasitic activity of new flavanoidal tetrazinan-6′-ones and their binding study with calf thymus DNA using molecular modelling and spectroscopic techniques

With the developing resistance to traditional antiparasitic medications, the purpose of this study was to efficiently develop a series of six noble flavanoidal tetrazinane-6′-one derivatives by a one-pot reaction pathway. FT-IR, 1HNMR, 13CNMR, and Mass spectra were employed for the structural elucidation of the synthesized compounds (7–12). Clinostomum complanatum, a parasite infection model that has been well-established, demonstrated that all the synthesized compounds are potent antiparasitic agents. DNA is the main target for various medicinal compounds. As a result, thestudy of how small molecules attach to DNA has received a lot of attention. In the present study, we have performed various biophysical techniques to determine the mode of binding of synthesized compounds (7–12) with calf thymus DNA (ct-DNA). It was observed from the UV–visible absorbance and fluorescence spectra that all synthesized compounds (7–12) form complexes with the ct-DNA. The value of binding constant (Kb) was obtained to be in the range of 4.36–––24.50 × 103 M - 1 at 298 K. Competitive displacement assay with ethidium bromide (EB), CD spectral analysis, viscosity measurements, and in silico molecular docking confirmed that ligands (7–12) incorporate with ct-DNA through groove binding only. Molecular docking studies were performed for all synthesized compounds with the calf thymus DNA and it was found that all the newly synthesized compounds strongly bind with the chain B of DNA in the minor groove with the value of binding energy in the range of −8.54 to −9.04 kcal per mole and several hydrogen bonding interactions.

Interactions between organic matter and alkaline minerals in bauxite residue: implication for soil restoration.

Ecological restoration of bauxite residue has received extensive attention, and organic matter plays a crucial role in the soil formation process of bauxite residue. However, the interaction between organic matter and alkaline minerals in bauxite residue is not well understood. In this work, molecular spectroscopic techniques combined with isothermal titration calorimetry (ITC) were employed to investigate the interactions between humic acid (HA) and four representative alkaline minerals in bauxite residue (calcite, garnet, sodalite, and cancrinite). The results show that the adsorption processes of HA onto calcite and garnet were primarily governed by monolayer surface adsorption and controlled by surface reactions, which were different for sodalite and cancrinite. Both garnet and cancrinite had strong binding affinities with fluorescent HA, while cancrinite only bound with a small fraction of HA. In contrast, the bindings of calcite and sodalite with fluorescent HA were weak. The ITC results indicate distinct thermodynamic properties of different alkaline minerals in the interaction with HA. The molar enthalpy of calcite was - 45.88kJ/mol, which was much higher than those of garnet, sodalite, and cancrinite, suggesting that calcite exhibited a relatively uniform interaction mechanism with HA dominated by enthalpy change, while the others showed heterogeneous entropy-driven mechanisms. The findings contribute to a better understanding on the microscale connections between organic matter and alkaline minerals in bauxite residue.

Essential oils from fennel plants as valuable chemical products: gas chromatography–mass spectrometry, FTIR, quantum mechanical investigation, and antifungal activity

AbstractIn the present study, the biomass produced by fennel plants (Foeniculum vulgare Mill.) was converted to yield bioactive chemicals, and the hydrodistillation method was used to extract the essential oils (EOs) from both the leaves and the umbels. The antifungal activity of the EOs was tested using bioassay against the development of Fusarium oxysporum MW854649 and Alternaria solani MT279570. Molecular spectroscopic detection techniques were used to evaluate the EO products using gas chromatography–mass spectrometer (GC–MS) and Fourier transform infrared spectroscopy (FTIR). GC–MS equipped with single quadruple analyzers have been used to measure the electron ionization (EI) mass spectra of the primary constituents of fennel EOs at 70 eV. The main chemical compounds in the EO from leaves were anethole, estragole, D-limonene, trans-β-ocimene, and fenchone, with percentages of 37.94, 35.56, 17.46, 1.53, and 1.49%, respectively. The abundant compounds in the EO from umbels were estragole, anethole, D-limonene, fenchone, and γ-terpinene, with percentages of 51.18, 25.08, 12.22, 6.57, and 2.86%, respectively. EI mass spectral fragmentation of the major compounds D-limonene, estragole, anethole, and fenchone has been investigated. Umbels and leaf EOs at 5000 mg/L displayed the strongest suppression of fungal growth against A. solani, with values of 87.78% and 79.63%, respectively, compared to the positive control (94.44%). The EOs from umbels and leaves at 5000 mg/L showed the highest inhibition of fungal growth against F. oxysprium as compared to the positive control (94.44%), with values of 77.77% and 72.96%, respectively. All of the important ions—including a few distinctive fragment ions—have comprehensive fragmentation pathways defined. Based on EI, the main routes of fragmentation for the primary compounds have been identified. The existence of alkenes, aliphatic alcohols, ethers, carboxylic acids, ester compounds, alkanes, hydrogen-bonded alcohols, and phenols was demonstrated by the FTIR analysis of fennel EOs. On the other hand, the reactive behavior of the studied molecules has been investigated using two quantum mechanics method: the modified neglect of diatomic overlap (MNDO), a semi-empirical method, and the density functional theory (DFT)/B3LYP hybrid density functional method with the 6-311G (d, p) basis set in the ground state for gas phase. The optimum geometries have been obtained through the execution of computations and electrostatic potential. The obtained analytical and calculated results were then used to understand the activity of the studied EOs in further medical applications.

Myricetin and dihydromyricetin as JNK1 inhibitors protect against ROS‐mediated oxidative stress and apoptosis

AbstractReactive oxygen species (ROS)‐mediated oxidative stress and apoptosis contribute to the pathogenesis and pathological conditions of various diseases induced by food and environmental pollutants. Myricetin and dihydromyricetin, as natural flavonoids, can counteract oxidative damage, apoptosis, and associated diseases. Molecular docking analysis, ELISA, fluorescence spectroscopy, and Western blot techniques were applied to examine the potential of the two flavonoids as effective therapeutics for ROS‐mediated diseases and the mechanism(s) underlying their protective effects against ethanol/H2O2‐induced damage. In Kunming mice and HepG2 cells, myricetin and dihydromyricetin inhibited ethanol/H2O2‐induced liver damage, ROS accumulation, and oxidative stress and apoptosis. Molecular docking showed that myricetin and dihydromyricetin interacted with JNK1 via hydrophobic interactions and hydrogen bonds, thereby exerting their protective effects. The significant differences in their binding patterns to JNK1 resulted from the different bond types between C2 and C3 on their C ring. Myricetin and dihydromyricetin likely protected liver injury via counteracting ROS/JNK1‐mediated oxidative stress and apoptosis. The finding that the suppression of ROS‐mediated oxidative stress and apoptosis by flavonoids via interacting with functional proteins, such as kinase, may represent an alternative strategy for treating excessive ROS‐induced health problems.

Update on chiral recognition mechanisms in separation science.

The stereospecific analysis of chiral molecules is an important issue in many scientific fields. In separation sciences, this is achieved via the formation of transient diastereomeric complexes between a chiral selector and the selectand enantiomers driven by molecular interactions including electrostatic, ion-dipole, dipole-dipole, van der Waals or π-π interactions as well as hydrogen or halogen bonds depending on the nature of selector and selectand. Nuclear magnetic resonance spectroscopy and molecular modeling methods are currently the most frequently applied techniques to understand the selector-selectand interactions at a molecular level and to draw conclusions on the chiral separation mechanism. The present short review summarizes some of the recent achievements for the understanding of the chiral recognition of the most important chiral selectors combining separation techniques with molecular modeling and/or spectroscopic techniques dating between 2020 and early 2024. The selectors include polysaccharide derivatives, cyclodextrins, macrocyclic glycopeptides, proteins, donor-acceptor type selectors, ion-exchangers, crown ethers, and molecular micelles. The application of chiral ionic liquids and chiral deep eutectic solvents, as well as further selectors, are also briefly addressed. A compilation of all published literature on chiral selectors has not been attempted.

Surface-enhanced Raman spectroscopy (SERS) substrate based on gold nanostars–silver nanostars for imidacloprid detection

Surface-enhanced Raman spectroscopy (SERS) is a powerful molecular spectroscopy technique that combines Raman spectroscopy with nanostructured metallic surfaces to amplify the Raman signals of target molecules by more than 103. The high sensitivity of SERS poses a significant opportunity for pesticide detection in complex matrices at ultralow concentrations. In this study, we improved the SERS sensitivity for imidacloprid (IMD) by employing silver nanostars (AgNs) coated with gold nanostars (AuNs) as the SERS-active substrate. The SERS response towards IMD detection increased based on the combination of AuNs and AgNs on the substrate surface. The intensity of the SERS signal of IMD using the AuNs/AgNs substrate increased compared to using individual metal nanoparticle substrates. The excellent reproducibility of SERS intensity using the AuNs/AgNs substrate was achieved with a low relative standard derivative (RSD) of 4.87% for 20 different spots on the same sample and 5.19% for 20 different samples. This detection system can be used for multiple tests, which is crucial for the advancement of handheld sensors designed for field use, where minimal or no high-level technical support is accessible.

Raman Spectroscopy as a Research and Diagnostic Tool in Clinical Hematology and Hematooncology.

Raman spectroscopy is a molecular spectroscopic technique able to provide detailed information about the chemical structure, phase, crystallinity, and molecular interactions of virtually any analyzed sample. Although its medical applications have been studied for several decades, only recent advances in microscopy, lasers, detectors, and better understanding of the principles of the Raman effect have successfully expanded its applicability to clinical settings. The promise of a rapid, label-free diagnostic method able to evaluate the metabolic status of a cell in vivo makes Raman spectroscopy particularly attractive for hematology and oncology. Here, we review widely studied hematological applications of Raman spectroscopy such as leukocyte activation status, evaluation of treatment response, and differentiation between cancer and non-malignant cells, as well as its use in still unexplored areas in hematology. We also discuss limitations and challenges faced by Raman spectroscopy-based diagnostics as well as recent advances and modifications of the method aimed to increase its applicability to clinical hematooncology.

AuNP decorated aegle marmelos leaf as SERS substrate for trace detection of antibiotics and machine learning based classification

Surface-enhanced Raman spectroscopy (SERS) has emerged as a reliable molecular spectroscopic technique for trace detection of chemical and biological samples. Present study illustrates a new SERS platform which has been obtained through surface adsorption of gold nanoparticles (AuNP) on a microscopically roughened surface of aegle marmelos (AM) leaf. The micro-structured patterns of the AM leaves promote the generation of hotspot regions for the surface deposited AuNPs thus, aids in electromagnetic enhancement for the scattered Raman signals from the sample. For the proposed SERS platform, with rhodamine6G (R6G) as an analyte, the limit of detection (LoD) was found to be 0.88 nM. The applicability of the designed SERS was realized through detection and quantification of two commonly used antibiotics- Ceftriaxone (CEFTR) and Ceftiofur sodium (CEF-Na) residues from cow milk samples. Furthermore, a dimensionality reduction method known as principal component analysis (PCA) and an optimal machine learning-based model were built to categorize the analytes in the milk samples. The suggested machine learning model’s classification accuracy was found to be 94%.

The presence of free palmitic acid modulates the effects of lutein on structural and dynamic properties of lipid membranes

Free fatty acids, like palmitic acid (PA), and xanthophyll pigments, like lutein (LUT) are the natural membrane compounds in plants. To study the effect of PA on LUT and their organization, a model membrane of 1,2-dimyristoyl-sn-glycerol-3-phosphocholine (DMPC) enriched with 2 mol% PA and 1 mol% LUT was formed. Molecular mechanisms underlying the interaction between these two compounds were examined with application of molecular spectroscopy techniques, e.g., visible spectroscopy, electron paramagnetic resonance and Fourier transform infrared. We determined the monomeric/dimeric organization of LUT in the membrane. We proved that the presence of PA in the lipid phase facilitated and stabilized the formation of LUT structures in the membrane. Lutein with PA did not form strong molecular aggregates like H- and J-structures. We presented the simplified model membrane that could be a suitable representation of the physiological process of de-esterification of PA from LUT appearing in natural biomembranes in humans.

Evaluation of Vicia faba plant genotypes using non-destructive vibrational molecular spectroscopic technique (ATR-FT/IR): molecular structure profiles of protein in relation to nutritional characteristics

This study aimed to evaluate the impact of genotypes and tannin levels on the nutritional characteristics of faba bean seeds and their relation to protein molecular structure profiles using Fourier transform infrared spectroscopy (FTIR). Eight genotypes with low tannin (LT, n = 3) and normal tannin (NT, n = 5) levels were studied. Standard methods of analysis and NRC 2001 were used to obtain chemical and energy parameters. The protein molecular spectral study was performed using a spectrometer JASCO FT/IR–4200. Molecular features were analyzed in the mid-infrared region at ~4000–800 cm−1 and protein-related functional groups were obtained using OMNIC software. Results showed higher ( P < 0.01) soluble crude protein (SCP), rapidly degradable protein fraction (PA2), and intestinal digestibility of bypass protein (dIDP) in LT than NT. The slowly degradable protein fraction (PB2) was higher in NT ( P < 0.01) compared to LT. Higher absorbance was observed in spectral peaks related to amide I, amide II, and β-sheet in NT ( P < 0.05) compared to LT. The area ratio of amide I to amide II and the height ratio of α-helix to β-sheet were higher in LT compared to NT ( P < 0.01). This study provides a better understanding of associations between structure and nutritional characteristics in faba bean genotypes with different tannin levels.

Molecular spectroscopy as a laboratory experiment: Measurement of important parameters of sodium diatomic molecules

We present an inexpensive sodium molecular spectroscopy experiment for use in an advanced undergraduate laboratory course in physics or chemistry. The molecules were excited predominantly from the ground X1Σg+(v″ = 15) state to the B1Πu(v′ = 6) state using a commercially available 532-nm broadband diode laser. The laser-induced molecular fluorescence was measured using a miniature fiber-coupled spectrometer at a resolution of 0.5 nm. The spectral peak assignments were done by comparing the observed spectrum with the calculated Franck–Condon values. Important molecular constants such as fundamental frequency, anharmonicity, bond strength, and dissociation energy of the ground electronic state were determined by using the Birge–Sponer extrapolation method. The presence of highly visible blue glowing molecules along the green laser beam creates an engaging laboratory experience. Emphasis is placed on students developing their understanding of the molecular structure, practicing molecular spectroscopic techniques, and applying knowledge of light–matter interactions to a physical system.

Molecular Spectroscopy: Underutilized Detection for Gas Chromatography

Molecular spectroscopy techniques, most commonly ultraviolet-visible (UV-vis), are usually thought of as analyzing liquid-phase samples, with techniques such as high-performance liquid chromatography (HPLC). Although not as common as in HPLC, molecular spectroscopy can be used with gas chromatography (GC) as well. In this installment, we examine molecular spectroscopy in combination with GC. The two most common techniques used with GC today are Fourier transform infrared spectrometry (FT-IR) and vacuum ultraviolet spectroscopy (VUV). Both provide structural and quantitative information and can be used in complementary fashion with the more common GC–mass spectrometry (GC–MS) and classical detectors. We will discuss the basics of GC–FT-IR and GC–VUV, when and when not to use them, and how they compare to and complement classical detectors.

Derivatives of Sri Lankan Vein Graphite: Atomic Scale Study of Graphene Oxide and Reduced Graphene Oxide

Aims: The present study examines the atomic-scale structures of Graphene Oxide (GO) and Reduced Graphene Oxide (RGO). Background: Electron microscopic studies on Sri Lankan vein graphite are considerably less; hence, this study focuses on the atomic-scale study of Sri Lankan vein graphite, using advanced electron microscopic techniques. Objective: The purpose of this research is to utilize the data obtained to explore the multidisciplinary characteristics of graphene to the maximum prospectively. Method: We report an atomic-scale study on Sri Lankan vein graphite (purest) derivatives using advanced electron microscopic techniques, including High-Resolution Transmission Electron Microscope (HRTEM), Scanning Transmission Electron Microscope (STEM), and Electron Energy Loss Spectroscopy (EELS). The present study examines the atomic-scale structures of Graphene Oxide (GO) and Reduced Graphene Oxide (RGO). Result: The results obtained exhibited an inter-atomic layer distance of 3.54 Å for RGO. The EELS study performed with the electron dose optimization for GO and RGO distinguished the differences in the C K edge with the oxygen functionalities. The XPS study confirmed the changes in oxygen functionalities obtained with EELS. Conclusion: The advanced electron microscopic techniques and other molecular spectroscopic analysis techniques allowed us to obtain a comprehensive study on Sri Lankan vein graphene-based structural and chemical features on an atomic scale.

Influence of Ligand Environment Stoichiometry on NIR-Luminescence Efficiency of Sm3+, Pr3+ and Nd3+ Ions Coordination Compounds.

Six new complexes of the ligand HQcy (-4-(cyclohexanecarbonyl)-5-methyl-2-phenyl-2,4-dihydro-3H-pyrazol-3-one) and Ln3+ ions with emission in the near-infrared (Nd3+) or visible and near-infrared (Sm3+, Pr3+) spectral regions were synthesized and characterized using various methods, including single crystal X-ray diffraction. The study demonstrated that both tris complexes [LnQcy3(H2O)(EtOH)] and tetrakis-acids [H3O][LnQcy4] can be synthesized by varying the synthetic conditions. The photochemical properties of the complexes were investigated experimentally and theoretically using various molecular spectroscopy techniques and Judd-Ofelt theory. The objective was to quantitatively and qualitatively disclose the influence of complex stoichiometry on its luminescence properties. The study showed that the addition of an extra ligand molecule (in the tetrakis species) increased molar extinction by up to 2 times, affected the shape of photoluminescence spectra, especially of the Pr3+ complex, and increased the quantum yield of the Sm3+ complex by up to 2 times. The results obtained from this study provide insights into the luminescent properties of lanthanide coordination compounds, which are crucial for the design and development of novel photonic materials with tailored photophysical properties.

Self-calibrated NICE-OHMS based on an asymmetric signal: theoretical analysis and experimental validation.

As an ultra-sensitive detection technique, the noise-immune cavity enhanced optical heterodyne molecular spectroscopy (NICE-OHMS) technique has great potential for assessment of the concentration of trace gases. To determine gas concentrations at the ppt or lower level with high accuracy, it is desirable that the technique exhibits self-calibration (or calibration-free) capabilities. Although being sensitive, NICE-OHMS has so far not demonstrated any such ability. To remedy this, this paper provides a self-calibrated realization of NICE-OHMS that is based on a switching of the feedback target of the DeVoe-Brewer (DVB) locking procedure from the modulation frequency of the frequency modulation spectroscopy (FMS) to the cavity length, which creates an asymmetrical signal whose form and size can be used to unambiguously assess the gas concentration. A comprehensive theoretical model for self-calibrated NICE-OHMS is established by analyzing the shift of cavity modes caused by intracavity absorption, demonstrating that gas absorption information can be encoded in both the laser frequency and the NICE-OHMS signal. To experimentally verify the methodology, we measure a series of dispersion signals under different levels of absorbance using a built experimental setup. An instrument factor and the partial pressure are obtained by fitting the measured signal through theoretical expressions. Our results demonstrate that fitted values are more accurate for higher partial pressures than for lower. To improve on the accuracy at low partial pressures, it is shown that the instrument factor obtained by fitting the signal at large partial pressures (in this case, above 7.8 µTorr) can be set to a fixed value for all fits. By this, the partial pressures can be assessed with a relative error below 0.65%. This technique has the potential to enable calibration-free ultra-sensitive gas detection.

Characterization and discrimination of some gem silicate minerals adopting LIBS, FTIR, and Raman spectroscopic techniques

In this paper, characterization and discrimination of some silicate gems (gemstones and low-gem quality varieties) from ancient Egyptian mines have been performed for the first time adopting molecular and elemental spectroscopic techniques. The selected gem groups are peridot, beryl/emerald, amazonite, and amethyst. In this sense, characterization of the genuine Egyptian gems and the importance of mineralogical and chemical signatures in a historical context as well as the scope of geoheritage can be achieved for the first time. Laser induced breakdown spectroscopy (LIBS) analysis has been found to be an effective method for the discrimination among different gems groups where a characterizing element for each group in a specific spectral window has been found. Raman and Fourier transform infrared (FTIR) spectroscopy spectra have proven to be fingerprints with the ability to distinguish future alteration of the gemstone depending on the molecular vibrational spectroscopy. FTIR provides the functional group that can absorb the infrared radiation and be responsible for the coloring of the gemstones.