Journal of Raman Spectroscopy最新文献

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.

The Raman spectra of Ca_1-xSr_xAl₂Si₂O₈ (0 ≤ x ≤ 1) feldspars have been measured, to investigate at a short-range scale the effect of changing composition on the P $�\overline{1}$ ➔ I $�\overline{1}$ and I $�\overline{1}$ ➔ I2/c phase transitions and how phase transitions affect the mechano-luminescence found in these feldspars. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) were done on the same samples, to pinpoint the transitions, by the analysis of selected area diffraction patterns (SAED) and of the spontaneous strain. Natural anorthite (CaAl₂Si₂O₈) shows a large number of well-resolved peaks, together with sharp h + k even, l odd diffractions (c-type) in SAED patterns, indicative of a P $�\overline{1}$ symmetry. In synthetic anorthite, the Raman spectrum is similar to that of natural anorthite, but the peaks are broader, and c-type reflections are elongated. As Sr increases, the c-type reflections become more diffuse and elongated, as the Raman peaks do. At x > 0.6, new peaks appear in Raman spectra, and other peaks show a change in their wavenumber. Moreover, the c-type reflections disappear completely, and the lattice becomes I-centred. Between x ~ 0.6 and x = 0.86(3), the XRD patterns prompt for a triclinic structure, with S.G. I $�\overline{1}$. The transition to the monoclinic I2/c structure is well constrained by the ferroelastic strain, whereas the Raman spectra are more similar between the monoclinic and triclinic I $�\overline{1}$ and I2/c than between I $�\overline{1}$ and P $�\overline{1}$. The absence of mechano-luminescence in triclinic I $�\overline{1}$ compositions suggests that this property is enhanced in local P