Journal of Raman Spectroscopy最新文献

Brillouin light scattering (BLS) is the inelastic scattering of light from elementary excitations with periodic density modulation. The characteristics of non-contact, high sensitivity, and high resolution in energy, wavevector, time, space, and phase make the BLS spectrometer widely used in investigating many intriguing physical phenomena, including the acoustic phonon confinement effects, Bose-Einstein condensation (BEC), supercurrent, and soliton formation. Generally, the quick and correct assignment of the signals in the BLS spectra is a prerequisite for further investigations. Herein, we experimentally identify the high-order spurious signals in the BLS spectra, which make the interpretation of the spectra difficult. The additional signals are demonstrated to originate from the laser and the temperature-controlled laser filter used for laser filtering. Our results would contribute to the rapid assignment of the signals from the sample after excluding the spurious signals reported here. Moreover, the series of high-order modes spaced by the free spectral range can serve as a weak broadband light source, which has great potential for investigating the optical responses of materials.

Vanadium dioxide (VO₂) undergoes a reversible first-order metal-to-insulator transition (MIT) from a high-temperature metallic phase to a low-temperature insulating phase at a critical temperature T_c of 68°C. The MIT is accompanied by a structural phase transition. In addition to the metallic high-temperature rutile phase, several insulating phases may be involved depending on doping, interfacial stress, or external stimuli. Unambiguously identifying the crystal phases involved in the phase transition is of key interest from the point of view of application as well as fundamental science. We study the impact of Ti doping of VO₂ thin films on (110) rutile TiO₂ substrates. We conduct a careful analysis of structural properties by combining results of x-ray diffraction, Raman spectroscopy, and transmission electron microscopy. The transition temperature T_c of the deposited thin films decreases with increasing Ti-content. All our thin film samples undergo a structural phase transition from the monoclinic M₁-phase to the rutile R-phase with increasing temperature without passing the intermediate monoclinic M₂-phase. A careful analysis of polarization and angle-dependent Raman data reveals that, above T_c, the unit cell of the high-temperature rutile Ti_xV_1-xO₂ phase is aligned with that of the rutile TiO₂ substrate whereas, below T_c, 180°-domains of the M₁-phase of Ti_xV_1-xO₂ are observed. The structural relationship between TiO₂ substrate and the high respective low-temperature phase of the Ti_xV_1-xO₂ determined by Raman spectroscopy is in excellent agreement with TEM results on these samples. Raman spectroscopy is a powerful tool for studying structural changes of VO₂-based samples in the vicinity of MIT.

East Asian inks are a major component of calligraphy, paintings, and prints in China, Japan, and Korea and are historically made from either pine soot or oil-lamp soot mixed with a proteinaceous binder. Although the inks from the two different soot sources have different properties in East Asian works of art, no non-destructive methods to differentiate them scientifically currently exist. Raman spectroscopy (RS) of carbonaceous materials is commonly used to extract information about their properties and has been applied here to East Asian inks. Soots used in making modern inks were collected from 10 sources in China and Japan and analyzed using RS. RS using 405-, 633-, and 785-nm excitation has been able to differentiate pine soot from oil-lamp soot, also called lampblack. In addition, principal component analysis (PCA) of only 785-nm Raman spectra has been able to discriminate between two different soots used in a 19th-century Japanese woodblock printing of Kaishien Gaden. In addition to allowing discrimination between inks on East Asian works of art, these results may be of use to other fields using carbonaceous materials.

Ecstasy tablets, a type of common street drug originally consisting of 3,4-methylenedioxymethamphetamine (MDMA), provide stimulant and hallucinogen psychoactive effects. They are frequently found in nightclubs, musical festivals or other recreational events believed to create a relaxing experience for the users. From a forensic perspective, when the drug of abuse is suspected in such scenarios, the law enforcement personnel would then require an easy-to-perform, quick and accurate method to detect the existence of such controlled substance prior to the seizure and subsequent forensic examination. In this study, we assessed the performance of a portable Raman spectroscopy as the primary aid in determining ecstasy tablets at the point of use. A total of 130 ecstasy tablet samples were analysed by Raman spectroscopy and characterised by gas chromatography–mass spectrometry (GC–MS). Active chemical substances and cutting agents detected by the two instrumentations were then compared. The performance of Raman spectroscopy was further assessed in terms of its accuracy, sensitivity and specificity, corresponding to the analysis results obtained from GC–MS analysis. Overall, portable Raman Spectroscopy used in this study shows an accuracy of 85.4% in analysing ecstasy tablets obtained from case samples, while the sensitivity and specificity were determined as 85.2% and 100%, respectively. No false positives for MDMA or other drugs were reported. Our results show that portable Raman spectroscopy is a suitable technique for targeted determination of the presence of ecstasy tablets, especially in forensic cases that require non-destructive, rapid and mass screening during on-site testing by law enforcement personnel.

Drug resistance plays a vital role in both cancer treatment and prognosis. Especially, early insights into such drug-induced resistance in acute myeloid leukemia (AML) can help to improve treatment plans, reduce costs, and bring overall positive outcomes for patients. Raman spectroscopy provides precise biomolecular information and can provide all these necessities effectively. In this study, we employed machine learning (ML) discrimination of Raman micro-spectroscopic data of myelocytic leukemia cell line HL-60 from its drug-resistant counterpart HL-60/MX2. Principal component analysis (PCA), linear discriminant analysis (LDA), and logistic regression (LR) methods were evaluated for their ability to identify and discriminate drug resistance in AML cells. Our study demonstrates the power of ML to classify drug-induced resistance in AML cells utilizing subtle variations in biomolecular information contained in molecular spectroscopic data by obtaining 94.11% and 97.05% classification accuracies by LDA and LR models, respectively. We also showed that the ML methods are discernable. Our findings depict the importance of automation and its optimal usage in cancer study and diagnosis. The results of our study are expected to take ML-assisted Raman spectroscopy one step closer to making it a generalized tool in medical diagnosis in the future.

Mn₂(C₂H₆N₆)₄(NO₃)₄·2H₂O (Mn) as one of the energetic coordination complexes was chosen for high-pressure research. In this work, Mn was analyzed by in situ Raman scattering, infrared absorption, and synchrotron angle-dispersive X-ray diffraction (ADXRD) technologies up to ~20 GPa at room temperature. The vibrational modes of Mn at ambient pressure were comprehensively resolved based on the experimental results. Detailed spectral analyses revealed that Mn underwent three pressure-induced phase transitions at 0.5, 2.5, and 5.7 GPa, respectively. ADXRD experiments confirmed the existence of these three phase transitions in Raman and infrared spectra analyses. Based on the analysis of the vibrational spectra and the changes of lattice parameters under pressure, it can be considered that the deformation of the 3-hydrazino-4-amino-1, 2, 4-triazole (HATr) ligand led to the first phase transition, and the distortion of the triazole ring induced the second phase transition, and the rearrangement of the hydrogen bonds resulted in the third phase transition. In addition, it can be inferred from Raman spectra and ADXRD data that Mn may have experienced the abnormal expansion during the first phase transition. This work may lay the foundation for further investigating the structure and properties of energetic coordination complexes under pressure.

Innovative techniques are required for the in situ investigation of the surfaces of planetary bodies when landings are planned. Raman spectroscopy turned out as an excellent tool for fast mineralogical analyses on space missions. Contribution from a photoluminescence signal is not unexpected and is likely to be even more pronounced on celestial surfaces with a dilute or absent atmosphere exposed to strong space weathering, for example, micrometeorite bombardment. Such signals were found, for example, in Raman analysis of the probes from sample-return missions. While photoluminescence is generally considered as an accompanying undesired product in the Raman spectral measurement, our studies show that some analytical information can be derived from this signal, and even more, due to the specific correlation of luminescence intensity with space weathering products. Therefore, we investigate the Raman spectra alteration of characteristic rock-forming mineral mixtures (olivine, pyroxene and plagioclase) by micrometeorite bombardment, which is simulated by nanosecond-pulse laser irradiation. The changes in the minerals are strongly dependent on the composition and structure. They range from disappearing changes in the minerals with simple chemistry and structure to complete amorphization of minerals with relatively low melting enthalpy. With Raman spectroscopy, we found out that the photoluminescence signals show resonant or anti-resonant changes to specific mineral phases and amorphization. Furthermore, ablation-induced iron nanoparticles of minerals containing Fe are detectable by Raman spectroscopy due to their alteration into iron oxides. Trapped volatiles in the matrices are analysed due to the formation of the compounds containing them. This broad spectrum of results indicating specific change phenomena due to space weathering can be effectively used for in situ Raman analysis in planetary missions.

A series of non-spherical metallic Au and bimetallic core@shell AuAg nanoparticles (NPs) have been synthesized for SERS improvements. The bimetallic core@shell AuAg NPs were obtained through a controlled overgrowth of an Ag shell onto the surface of two types of non-spherical Au NPs, used as seeds, Au nanooctaheda (Au NOc) and Au nanotriangles (Au NTs). This Ag overgrowth was able to produce bimetallic core@shell structures such as nanocubes and nanopyramids, respectively. Transmission electron microscopy (TEM) was used to determine the particle size and particle morphology for metallic and bimetallic NPs, and energy-dispersive X-ray (EDX) elemental mapping analysis confirmed the core@shell structure of the bimetallic NPs. The plasmonic absorption bands exhibited for each nanosystem were observed by UV–vis spectroscopy. The concentration of Au and Ag in the bimetallic systems was determined by inductively coupled plasma mass spectrometry (ICP-MS). After synthesis and characterization, p-aminothiophenol (PATP) was used as a model analyte to investigate the surface-enhanced Raman spectroscopy (SERS) capabilities of the synthesized metallic and bimetallic nanosystems. In PATP, a dimerization reaction to 4,4′-dimercaptoazobenzene (DMAB) is produced when it is adsorbed onto the surface of certain noble metals. This SERS analysis was performed at 10⁻⁴ M of PATP and by using two different laser wavelengths (532 and 785 nm) in all cases. In this context, we were able to detect the dimerization reaction of PATP to DMAB only for the bimetallic structures and under the 532 nm laser line. Moreover, we have found that the dimerization capacity also depends on the nanoparticle morphology.

In order to investigate the adsorption process of malachite green (MG) on gold nanoparticles, a simple gold nanoparticles-assembled film was prepared as a substrate of surface-enhanced Raman spectroscopy (SERS), and it was soaked in MG solutions of different concentrations. The kinetic adsorption process was investigated by SERS method and density functional theoretical calculations. When saturated adsorption was achieved, the relationship between the characteristic SERS band signal intensity and the logarithm of solution concentration of MG was consistent with Temkin adsorption isotherm model, where the R² value was greater than 0.995, and the linear range was 1 × 10⁻³–1 × 10⁻⁷ M. Finally, a SERS quantitative analysis model of the relationship between the adsorption properties of surface species and the bulk concentration was established. According to the electrostatic interaction and co-adsorption, we proposed the surface adsorption configurations and adsorption process of MG on the nanostructured gold films.

Coherent anti-Stokes Raman scattering microscopy probing two independently selectable vibrational frequencies across the vibrational spectrum is demonstrated. A one-box femtosecond laser source provides three synchronised 100–200 fs pulses of 77 MHz repetition rate, one at a fixed wavelength of 1025 nm from an Yb oscillator and two independently tuneable ones, over 680–960 nm and 960–1300 nm, respectively, from two optically synchronised parametric oscillators. Combined with spectral focusing, the source allows addressing the fingerprint, cell silent and C–H stretch vibrational regions simultaneously, avoiding the motion artefacts seen in sequential imaging. We demonstrate the microscopy method on water/heavy water/oil emulsions, plastic beads and deuterated lipids inside cells.