Journal of Raman Spectroscopy

High levels of the amino acid leucine have been detected for the first time within microcolonies in an Escherichia coli biofilm by Raman imaging. This work has demonstrated that our label-free Raman imaging method provides a useful platform for directly identifying as yet unknown biomolecules produced in bacterial biofilms as well as for visualizing three-dimensional distributions of biofilm constituents in situ.

Nanotransfer printing (nTP) is implemented to integrate electron beam lithography defined nanofeatures on a variety of surface-enhanced Raman scattering (SERS)-supporting surfaces. These nTP-created metal nanoparticles strongly amplify the Raman signal and complement the selection of suitable substrates for better SERS enhancement.

Seven genomic DNAs from leaves of Arnica montana (L.), Astragalus peterfii (Jáv.), Kalanchoe x hybrida, strawberry (Fragaria x ananassa Duch.), carnation (Dianthus caryophyllus L.), apple (Malus domestica Borkh.) and Persian violet (Exacum affine Balf.) have been analyzed using surface-enhanced Raman scattering (SERS). The SERS signatures, spectroscopic band assignments and structural interpretations of these genomic DNAs are reported.

A removable SERS active film applicable to the surface of paintings is fabricated. Preliminary results concerning the optimization of the physical and chemical characteristics are presented and tested on standard red pigments and mock-painting panels.

Anomalous Raman peaks are observed when taking SERS for liquid sample stored in polypropylene centrifuge tubes for months. With mass spectroscopy we identified the contaminants as derivatives of phthalic acid. As commonly used plasticizers, the contaminants are believed to leach from plastic tube upon storage. With SERS and UV absorption spectroscopy, we confirm the identity of the contaminants and estimate the concentration as 2.1 µM. We suggest SERS and UV absorption spectroscopy as quick and simple techniques to detect the contamination by plasticware.Please provide the artwork for the Graphical abstract.

We report the observation of large surface-enhanced Raman scattering (SERS) (10⁶) for 4-tert-butylpyridine molecules adsorbed on a silver electrode surface in an electrochemical cell with electrode potential set at − 0.5 V. A decrease in electrode potential to − 0.3 V was accompanied by a decrease in relative intensities of the vibrational modes. However, there were no changes in vibrational wavenumbers.

Fast and accurate algorithms for fitting coherent anti-Stokes Raman spectroscopy (CARS) and dual-pump CARS spectra for temperature and multiple chemical species are described. The algorithm employs sparse libraries. It was demonstrated by fitting synthetic dual-pump CARS spectra containing resonant N₂, O₂, H₂, and CO₂, and by fitting experimental spectra from a H₂air flat flame produced by a Hencken burner.

Excitation profiles of the coherent resonant Raman scattering (CARS and CSRS) by impurity molecules in solids are studied at high excitation power taking into account the inhomogeneity of environment. The splitting of the profiles into two groups is caused by the contribution of two turning points of a strong coherent vibration of the CARS-active mode.

We have developed a novel method for protein concentration determination via their resonance Raman intensity decrease with increasing protein concentration. This method provides a method to determine the concentration of an unknown protein mixture with the calibration of BSA.

Transmission Raman spectroscopy was explored for the direct measurement of packed polyethylene (PE) pellets to determine their density. The correct sample representation of internally inhomogeneous PE pellets by the transmission Raman measurement eventually improved the accuracy of density determination.

Raman chemical imaging was used in the characterization of pharmaceutical tablets. Multiple chemometric techniques were used to resolve the pure component spectra from the Raman maps at several signal-to-noise ratios. The different methods were compared based on the detected number of components, the quality of the resolved spectra, the visualized concentration maps, and the estimated tablet composition.

Once the optimal w is given, the background can be eliminated by subtracting the estimated background Xw directly from y. A synthetic spectrum is shown in the figure as an example, which has three Gaussian peaks on a curved background.

A process analytical technology application of Raman spectroscopy is demonstrated to monitor the dispersion kinetics of water-insoluble active pharmaceutical ingredients (API) in a pharmaceutical aqueous suspension. The Raman spectra of the API as a function of dispersion time are represented. Principal component analysis was performed to determine the end point of the API dispersion.

Forensic analysis of pyrotechnic artefacts was carried out by Raman spec- troscopy assisted with scanning electron microscopy/energy-disper-sive X-ray spectroscopy (SEM-EDS) and Fourier transform infrared (FTIR). These substances are widely used in street riots and can be used to cause aerial disasters, severe injuries, etc. Police departments fight the illegal commerce, business and storage of such substances.

Analysis of the infrared and Raman spectra in the ν(CN) region of the Prussian blue analogues suggests an interpretation based on a ‘matrix-isolated model’ which, among all, explains the existence of infrared features identified as fingerprint for a particular bond pattern.

Changes in force constants under applied stress/strain tensor fields have been given in matrix form, and close-form solutions provided for the eigenvalues of the corundum structure of sapphire. Phonon deformation potentials for both A_1g and E_g vibrational bands were retrieved by exploting controlled uniaxial stress fields externally applied to sapphire parallelepiped bars and validated by measuring the crack-tip stress field on the R-plane of the sapphire crystal.

Analysis of the variation of the E_g(ν₆) phonon wavenumber of zirconium doped TiO₂ nanoparticles in terms of surface stress and phonon confinement reveals stabilization of the anatase structure. It is found that Zr-induced surface stress influences the wavenumber shift of the Raman E_g(ν₆) mainly through the mode-Grüneisen parameter.

Raman spectroscopy was used to study the radiation damage of fluorapatite single crystals and sinters. Evolution of the strongest PO₄³⁻ mode shows that the amorphous fraction increases with fluence and with the electronic stopping power. At high fluences, the recrystallization effect competes with the damage process; it increases with the electronic stopping power also and is more important in single crystals than in sinters. Indeed, the evolution of the damaged fraction versus fluence in sinters is in good agreement with previous XRD data.

Raman spectroscopy complemented with infrared spectroscopy has been used to study the rare-earth-based mineral decrespignyite and the spectrum was compared with those of a series of selected natural halogenated carbonates from different origins including bastnasite, parisite and northupite. The Raman spectrum of decrespignyite displays three bands at 1056, 1070 and 1088 cm⁻¹ attributed to the CO₃²⁻ symmetric stretching vibration.