Computer deconvolution of experimental excitation and emission fluorescence bands is presented and used to generate synchronous spectra. The computer simulation successfully predicts the number of synchronous fluorescence (SF) bands, band shapes, and band maximum wavelengths for any constant wavelength difference (∆λ). To test the simulation, emission, excitation, and synchronous spectra were obtained for anthracene in n-hexane. Excellent agreement is obtained reproducing and finding the origin of the experimental SF bands for values of ∆λ between 2 and 100. The excitation, emission, and synchronous (∆λ=10) spectra of toluene, aniline, naphthalene, acenaphthene, pyrene, and anthracene are obtained. The synchronous spectrum (∆λ=10) of the same mixture is presented and assigned based on the synchronous bands of the individual compounds. The synchronous fluorescence technique and the computer simulation method are proposed to complement other techniques in the analysis of fluorescent samples from comets, as well as in missions to planets and satellites of the solar system. With our experimental set-up we will be able to obtain spectra for temperatures between 77 K and 298 K. Our laboratory is currently obtaining excitation, emission, and synchronous spectra of PAHs at temperatures that could be found on the surface of Titan and Mars.

Near Infrared spectroscopy (NIRs) is a potent tool for the analysis of several materials. It finds vast applications due its versability and finds applications in many fields such as pharmaceutical industry, food science, environmental, bio-applications and medical. In this work we report several applications in plastic additives industry. The determination of specific analytes in this kind of products is challenging without expensive instrumentations or difficult sample preparation. The NIR technique instead, with the application of chemometric approach, permits the quantitative analysis in complex matrix with simple, fast, and cheap procedures. To clarify the structure of the dataset spectra employed in the calibration curve, and so the nature of the bands involved, the calculated NIR spectrum of model compound is also reported and compared to its experimental gas phase counterpart.

Tinnevelly Senna is a herbal plant whose leaves are being applied to cure many diseases in developing countries due to containing many bioactive compounds such as sennosides, phenols, and flavonoids. The conventional methods to determine the main contents of such Senna leaves are lengthy, cost-effective, require hazardous chemical solvents and reagents. In this work an elegant technique like LIBS was applied as a qualitative and quantitative method for Senna leaves sample’s elemental analysis and their biological activities were measured by evaluating anti-cancer and anti-bacterial analysis. The quantitative analysis of Senna leaves was conducted using calibration-free LIBS) algorithm indicating the concentration of many nutrient elements, and the LIBS results were counter verified by using the standard analytical ICP-OES technique. The bactericidal efficacy of the Senna leaves was also studied against Staphylococcus aureus (S. aureus) by AWD assays and morphogenesis by scanning electron microscopy (SEM) and the anticancer activity was also investigated where different concentrations of Senna leaves extract were tested on cancer cells (HCT-116 and HeLa) and normal cells (HEK-293) using the cell metabolic activity MTT assay and Propidium iodide (PI) staining. We also estimated the inhibitory concentration (IC50) value for the various extracts’ concentrations. The bactericidal efficacy of the Senna leaves extract showed significant inhibition against Gram-positive bacterium. Both MTT and PI analysis showed that Senna leaves extract induced profound inhibition on HCT-116 growth and proliferation. Additionally, Senna leaves extract did not exert an inhibitory influence on normal (HEK-293), which is non-cancerous cells. The extract specifically targets the cancerous cells is highly beneficial for the development of future safe anticancer and antibacterial drugs using these extracts.

The discovery of chlorobenzene detected in a soil sample obtained in Mars has been controversial. The original sample was subjected to pyrolysis before the analysis with the gas chromatography-mass spectrometry (GC-MS) of the Sample Analysis at Mars (SAM) instrument on the Curiosity rover. It is believed that chlorobenzene was a product of other organic molecules reacting with chlorates of the Martian soil. In this paper, synchronous fluorescence spectroscopy is suggested for analysis of Mars samples in future missions. Synchronous fluorescence spectroscopy is a variation of the fluorescence technique where the excitation and emission scans are detected simultaneously with a predetermined wavelength difference (∆λ) between the two and multiplied. Depending on the ∆λ chosen, the resulting signal could produce a narrow single fluorescence band with a peak wavelength that is characteristic of the compound. To demonstrate the utility of this technique for Mars samples and in general for planetary and astrochemical applications, we present laboratory results with the characteristic synchronous peaks of chlorobenzene, benzene, benzoic acid, phenol, phthalic acid, and mellitic acid in solutions of n-hexane or water. Finally, we demonstrate a successful application of the technique using a mixture of chlorobenzene in the presence of the likely organic precursors that have been suggested for the Cumberland drill sample on Mars. The application of SFS for solid samples of Mars analog soils is also discussed for future experiments.

Attenuated Total Reflection (ATR) Infrared spectra(IR) of artificially-prepared gasoline blends have been recorded in the 600-4000 cm⁻¹region, using the Far-Infrared Beamline at Canadian Light Source. The observed spectra reveal rich but distinct vibrational signatures of the ethanol and gasoline blend. The analysis of C-C and CO stretch bands indicates significant vibrational shifts due to the changes of force constants as the hydrocarbon content increases. The present data provide vibrational centers useful for the characterization of ethanol in the presence of hydrocarbon matrices. The validity of ATR-IR for ethanol determination in gasoline mixture has been examined by measuring the ATR-IR signal response of artificial gasoline blend over a wide range of ethanol content(0 - 100%). The obtained linear correlations allowed the determination of recovery percentage(95-100%)and thus confirming the accuracy of ATR-IR method.

Oxolan-3-one is a cyclic, oxygenated hydrocarbon that occurs frequently in the pyrolysis of many forms of biomass and is thus an important intermediate in the production of biofuels. In order to identify thermal decomposition products of oxolan-3-one, an approximately 0.4% mixture in argon was subject to pyrolysis in a resistively heated SiC microtubular reactor at 800-1400 K. Matrix-isolation FTIR spectroscopy was used to identify pyrolysis products. The products observed include ethylene, carbon monoxide, formaldehyde, ketene, acetylene, and propyne. A comprehensive computational study of the unimolecular decomposition mechanism shows reactions consistent with these products and suggests the appearance of hydroxyketene in the mechanism. Efforts were undertaken to pyrolytically generate and characterize hydroxyketene via matrix-isolation FTIR to confirm the assignment. The experimental and computational results combined provide clues to the overall mechanism of thermal decomposition of oxolan-3-one and are important in relating the molecule’s structure to the mechanism.

Methane is an important and heavily studied molecule because of its significance in astronomy, energy, and climate change. Studies of methane as a model are also important because it is the simplest hydrocarbon. For many molecules, the fundamental vibrational modes are well understood, but overtones and combination bands are often difficult to accurately identify. At higher frequencies there is significant congestion due to combination bands and overtones overlapping, making it difficult to determine which modes are responsible for each line. We have used a newly developed technique called IR HRC2DS to investigate the overtone region of CH stretches in methane. This technique uses a broadband source with wavelengths spanning the CH overtone region (5950-7000cm-1) and a tunable source scanning the CH fundamental (2900-3100cm-1). Coupling these two modes gives doubly resonant features which could allow us to confirm several frequencies from the CH overtones of methane, and to calculate the Coriolis constants for these overtones.

Stimulated Raman Scattering (SRS) has been observed for the first time in any alkali-rare gas diatomic molecule, and the observed spectra provide a powerful tool for elucidating interatomic spectra. Specifically, laser pump-probe experiments in which the K vapor/Xe mixtures are excited with a narrowband dye laser radiation near the K D₂ line yields strong amplification of a probe pulse located 50-55 cm⁻¹ to the red of the K D₁ line, a difference that is close, but not equal to the 4²P_3/2-4²P_1/2 spin-orbit splitting of K. r0pt Figure As shown by the representative data in the figure, sweeping the pump wavelength to the red, results in the SRS gain spectra spectrum (shown by the probe amplification spectra), tracking the movement of the pump. We interpret these data in terms of a molecular SRS process in which the Raman shift is associated with the KXe B²Σ⁺_1/2, A²Π_3/2, A²Π_1/2-X²Σ⁺_1/2 difference potentials at differing values of the internuclear R. Another unique aspect of this aspect of this process is that the Raman process originates with the K-Xe collision pairs in the thermal continuum of the ground state. Consequently, B²Σ⁺_1/2, A²Π_3/2, A²Π_1/2 interatomic potentials at large R can be determined by comparing experiment with calculations of B²Σ⁺_1/2, A²Π_3/2, A²Π_1/2-X²Σ⁺_1/2 Frank-Condon integrals and quasistatic line-broadening theory.

Like Carbon Dioxide (CO₂), Nitrous Oxide (N₂O) behaves as a long-lived greenhouse gas. Increases in atmospheric concentrations of N₂O due to anthropomorphic sources have contributed to stratospheric ozone depletion and climate change. For these reasons it is imperative to formulate effective techniques for trace N₂O detection. Spectral line resolution and detection sensitivity are crucial for efficient trace gas quantification. One technique which enables the precise determination of the transition frequency between the ground and excited states of an analyte is saturated absorption spectroscopy (SAS). In SAS, counter-propagating beams of the same frequency produce Doppler-free peaks in absorption spectra. Each beam produces opposite Doppler shifts, therefore only atoms/molecules traveling with nearly zero-velocity along the axis of beam propagation couple with both beams, leading to Doppler-free spectral-hole burning. Additionally, cavity enhanced spectroscopic methods, such as the revolutionary cavity ring-down spectroscopy (CRDS), employ the use of a high finesse optical cavity, wherein light is trapped and the concentration of the analyte is determined by the rate of decay of the cavity light. Due to the high intensity of the light inside the optical cavity, this technique is remarkably sensitive, even for the detection of weakly absorbing transitions. However, the high density of one-photon transitions can often lead to spectral overlap and resolution loss. On the other hand, near-resonance two-level transitions, like those found in N₂O, result in low density spectra. Here we present a novel approach of gaseous N₂O detection by SAS and two-photon CRDS of the P(18) and Q(18) ro-vibrational transitions.

r0pt Figure Plasmonic materials have increasingly grown in interest in chemical sensing, optoelectronics, and photocatalysis. Plasmonic media interact strongly with light, focusing and enhancing electromagnetic radiation to nanoscale volumes, not seen with typical propagation of electromagnetic radiation. Although plasmonic materials have countless desirable properties, we still struggle to form a fundamental understanding of energy and charge transfer at plasmonic interfaces. We specifically desire to quantify energy transfer in plasmonic-molecular systems in this work. We utilize continuous wave, surface-enhanced anti-Stokes and Stokes Raman spectroscopy to probe the vibrational energy transfer. Further, we employ a Boltzmann distribution analysis to quantify our results, to correlate the anti-Stokes to Stokes scattering ratio of Raman-active vibrational modes to their corresponding temperatures. Specifically, we examine the temperatures of plasmonic-fluorophore systems, where molecules can undergo electronic transitions, which specifically follow an unforeseen mechanism. In comparison to room temperature population densities, we observe a 100K decrease in the temperature of various fluorophore molecules under resonant steady-state excitation. In contrast, under non-resonant excitation, we see an increase in temperature up to 200K. This resonant plasmonic cooling effect occurs regardless of vibrational mode selection and solvating environment. Our work provides new insight into plasmonic-molecular interactions and an initial investigation of this occurrence.

NMR and Infrared spectroscopies were instrumental in determining the relationships between lens and tear lipid composition, conformation and function. The major lipid of the human lens is dihydrosphingomylein, discovered by NMR spectroscopy and found in quantity only in the lens. The lens contains a cholesterol to phospholipid molar ratio as high as 10:1. Lens lipids contribute to maintaining lens clarity, and alterations in lens lipid composition due to age are likely to contribute to cataract. Lens lipid composition reflects adaptations to the unique characteristics of the lens: no turnover of lens lipids or proteins and contains almost no intracellular organelles. Long-lived species such as humans and the bowhead whale exhibits lens lipid adaptations that confer resistance to oxidation, and thereby allowing the lens to stay clear for a relatively longer time than is the case in many other species. With cataract, light scattering increases due to the increase in the lipid order of lens membranes measured using infrared spectroscopy. It is plausible that the increase in lipid-lipid interactions may contribute to myopia by causing greater compaction and overall stiffness of the lens. The TFLL is a thin, 100 nm layer of lipid on the surface of tears covering the cornea that contributes to tear film stability. NMR spectroscopy found that the major lipids of the TFLL are wax esters and cholesterol esters. The hydrocarbon chains associated with the esters are longer than those found anywhere in the body, as long as 32 carbons, and many are branched. More ordered lipid with dry eye, measured using FTIR, could inhibit the flow of meibum from the meibomian glands and contribute to the formation of a discontinuous patchy TFLL, which in turn results in deteriorated spreading, and decreased surface elasticity. One may also speculate that more ordered lipid results in the attenuated capability to restore tear film lipid layer structure between blinks.