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Fentanyl and its derivatives have been mainstays for the treatment of pain for many years. To accurately detect them in medical applications and customs, a rapid, sensitive, and selective method is urgently needed. In this study, we established a point-of-care-testing (POCT) differential Raman approach for the detection of fentanyl substances in liquid and solid conditions. The silver nanoparticle was prepared and characterized as SERS substrate, which can adsorb fentanyl-related molecules on the rough surface to enhance the Raman signal. Subsequently, 27 kinds of fentanyl-related substances were detected to determine that the POCT spectral resolution is better than 6 cm−1, Raman detection range is 100–3200 cm−1, and the detection limit of the fentanyl-related substances at 1002 cm−1 is 0.1–25 ppb. Furthermore, the Raman characteristic peaks of fentanyl were checked through comparison between theoretical calculations and experiments to obtain a database for rapid on-site inspection. Thus, the fast, accurate, stable POCT approach can be widely applied to monitor drugs and toxins due to its sensitivity, specificity, and abundance database. [ABSTRACT FROM AUTHOR]

Identification of the gasoline purity is important for quality control and detection of gasoline adulteration. Principal component analysis and Raman spectroscopy were used to authenticate gasoline adulterated with methyl tert-butyl ether (MTBE) and benzene. Gasoline could be clearly distinguished from gasoline adulterated with MTBE and benzene by a plot of the first principal component ( x-axis) against the second principal component ( y-axis). And the radial basis function neural network was used for quantitative prediction of the volume percentages of MTBE and benzene in gasoline based on Raman Spectra. The correlation coefficient ( r) and mean absolute percentage error between predictive values and spiked values were 0.9907 and 0.9934 and 15.73 and 8.19%, respectively. Moreover, the Raman spectra of the samples were obtained with a portable Raman spectrometer. Therefore, the method is simple, effective, fast, does not require sample pre-processing, and is promising for rapid gasoline detection. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A method of principal component analysis was employed to authenticate genuine olive oil based on Raman spectroscopy, which can reliably distinguish olive oil from other types of oils and can also accurately identify the level of adulteration in a set of olive oil samples contaminated with 5% or more of other types of oils, such as soybean oil, rapeseed oil, sunflower seed oil, and corn oil. The method is very easy, effective, time-saving, and requires minimal sample preparation. Therefore, the method is a promising technique for the rapid authentication application of olive oil. [Supplementary materials are available for this article. Go to the publisher's online edition of Analytical Letters for the following free supplemental resource(s): Additional text and table] [ABSTRACT FROM AUTHOR]

Schematic images of the experimental setup of obtaining polarized Raman spectrum an experimental investigation on polarized Raman spectra of 1L, 7 L, and 15 L ReS2 supported on SiO2/Si substrate with temperature ranging from 110 K to 590 K is reported. The polarization of incident laser is tuned parallel either to the a-axis or b-axis in ReS2 flakes. It is discovered that Raman modes of ReS2 show redshifts with an increase of temperature and first-order temperature coefficients are observed for ReS2 flakes along different crystal axis. The larger temperature coefficient along b-axis may be originated from the large group phonon velocity. In addition, the full-width at half maximum (FWHM) of Raman modes of ReS2 flakes with different thicknesses along different crystal axis are also quantitatively studied and it is found phonon decay is responsible for the broadening of phonon mode. This work will promote the understanding of anisotropic thermal properties of ReS2 flakes. The study of anisotropic thermal properties of ReS2 will lay a certain foundation for exploring the stability of ReS2 optoelectronic devices. [Display omitted] • This work will promote the understanding of anisotropic thermal properties of ReS2 flakes. • The study of anisotropic thermal properties of ReS2 will lay a certain foundation for exploring the stability of ReS2 optoelectronic devices. • This work will promote the study of thermal anisotropy in two-dimensional anisotropic materials. • This work will lay a solid foundation for the development of thermoelectric and optoelectronic applications in the future. With present in-plane anisotropic optical, electrical, and optoelectronic properties, atomically thin Two-dimensional (2D) rhenium disulfide (ReS 2) is of considerable interest for its wide-range intriguing applications in novel devices. However, although the research field related to ReS 2 has made growing progress, the axis-dependent thermal properties are still unknown. Herein, temperature-dependent polarized Raman spectroscopy is carried out to systematically investigate the anisotropic thermal properties of ReS 2 flakes with layers (L) of 1, 7, and 15 with temperature ranging from 110 K to 590 K. The polarization of the incident laser is tuned parallel to the crystal axis of the ReS 2 flakes. It is discovered that Raman modes of ReS 2 redshift with an increase of temperature and the first-order temperature coefficients are obtained along different crystal axes whose values are decreased with an increase in number of layers. The different temperature coefficients along different axis may be originated from the different group phonon velocities. In addition, the full width at half maximum (FWHM) of Raman modes of ReS 2 flakes along different axes are also quantitatively studied. It is found that the broadening of phonon modes is originated from phonon decay. This work will promote the study of thermal anisotropy in two-dimensional anisotropic materials. [ABSTRACT FROM AUTHOR]

A method for surface-enhanced Raman spectroscopy (SERS) sensing of polycyclic aromatic hydrocarbons (PAHs) is reported. Gold nanoparticles (AuNPs) decorated hydrophobic porous glycidyl methacrylate–ethylene dimethacrylate (GMA–EDMA) polymer is developed as the SERS substrate. GMA–EDMA material with porosity and permeability shows rapid and efficient adsorption of PAHs through presumed hydrophobic interaction, which brings the analytes close to the substrate. Meanwhile, the three dimensional porous morphology might benefit AuNPs distribution for high SERS enhancement. Studies on the effects of AuNPs surface coverage on the substrate and time of PAHs–substrate interaction are presented. The qualitative analysis and quantitative tendency of this method for PAHs detection are investigated with anthracene, phenanthrene and pyrene as probe molecules, showing that the characteristic fingerprint vibrational peaks of each PAH can be readily identified, and the limit of detections are 0.93 × 10 −7 , 4.5 × 10 −7 and 1.1 × 10 −7 M respectively. Moreover, the substrate exhibits high reproducibility with the relative standard deviation about 16% in spot and spot SERS intensity. Using this method for rapid screening of PAHs mixture in some water samples are performed well, which might be useful for environmental pollutions monitoring. [ABSTRACT FROM AUTHOR]