Experimental Determination of the Vibrational Constants of FeS（X5 △） by Dispersed Fluorescence Spectroscopy

Based on previous laser-induced fluorescence excitation spectroscopy work, the vibrational constants of neutral FeS in the X5 △ electronic state were obtained by directly mapping the ground-state vibrational levels up to v＂=3 using conventional laser-induced dispersed fluorescence spectroscopy. The vibrational frequency of FeS（X5 △） （518±5 cm-1） agrees well with that reported in a recent PES measurement （520±30 cm-1） [J. Phys. Chem. A 107, 2821 （2003）] which is the only one prior experimental vibrational frequency value for the 5 △ state of FeS. Careful comparisons of our experimental results and those documented in the literature （mainly from theoretical predictions） suggest that the ground state of FeS is 5 △ state.

Investigation of ultrafast dynamics of CdTe quantum dots by femtosecond fluorescence up-conversion spectroscopy

The ultrafast carrier relaxation processes in CdTe quantum dots are investigated by femtosecond fluorescence upconversion spectroscopy.Photo-excited hole relaxing to the edge of the forbidden gap takes a maximal time of ～ 1.6 ps with exciting at 400 nm,depending on the state of the photo-excited hole.The shallow trapped states and deep trap states in the forbidden gap are confirmed for CdTe quantum dots.In addition,Auger relaxation of trapped carriers is observed to occur with a time constant of ～ 5 ps.A schematic model of photodynamics is established based on the results of the spectroscopy studies.Our work demonstrates that femtosecond fluorescence up-conversion spectroscopy is a suitable and effective tool in studying the transportation and conversion dynamics of photon energy in a nanosystem.

Study of <i>in Vitro</i>Interaction of Sildenafil Citrate with Bovine Serum Albumin by Fluorescence Spectroscopy

In vitro interaction of sildenafil citrate (SC) with bovine serum albumin (BSA) was investigated at two excitation wavelengths of BSA (280 nm and 293 nm) at two different temperatures (298 K and 308 K) by fluorescence emission spectroscopy. The study showed that quenching of BSA fluores-cence by sildenafil citrate was the result of formation BSA-SC complex with probable involvement of both tryptophan and tyrosine residues of BSA. Fluorescence quenching constant was determined from Stern-Volmer equation, and both static quenching and dynamic quenching were showed for BSA by SC at the conditions. Van’t Hoff equation was used to measure the thermodynamic parameters ΔG, ΔH, and ΔS at the temperatures which indicated that the hydrogen bond and the hydrophobic forces played major roles for BSA-SC complexation. The binding number (n) was found to be ≈1 indicating that one mole BSA bound with one mole SC. The binding affinity of SC to BSA was calculated at different temperatures. The binding constant was decreased with increasing temperatures indicating that stability of BSA-SC complex decreased with increasing temperatures.

Quantitative measurement of hydroxyl radical(OH) concentration in premixed flat flame by combining laser-induced fluorescence and direct absorption spectroscopy

An accurate and reasonable technique combining direct absorption spectroscopy and laser-induced fluorescence（LIF）methods is developed to quantitatively measure the concentrations of hydroxyl in CH;/air flat laminar flame. In our approach, particular attention is paid to the linear laser-induced fluorescence and absorption processes, and experimental details as well. Through measuring the temperature, LIF signal distribution and integrated absorption, spatially absolute OH concentrations profiles are successfully resolved. These experimental results are then compared with the numerical simulation. It is proved that the good quality of the results implies that this method is suitable for calibrating the OH-PLIF measurement in a practical combustor.

Dissolved organic matter tracers reveal contrasting characteristics across high arsenic aquifers in Cambodia:A fluorescence spectroscopy study

Organic matter in the environment is involved in many biogeochemical processes,including the mobilization of geogenic trace elements,such as arsenic,into groundwater.In this paper we present the use of fluorescence spectroscopy to characterize the dissolved organic matter (DOM) pool in heavily arsenicaffected groundwaters in Kandal Province,Cambodia.The fluorescence DOM (fDOM) characteristics between contrasting field areas of differing dominant lithologies were compared and linked to other hydrogeochemical parameters,including arsenic and dissolved methane as well as selected sedimentary characteristics.Absorbance-corrected fluorescence indices were used to characterize depth profiles and compare field areas.Groundwater fDOM was generally dominated by terrestrial humic and fulvic-like components,with relatively small contributions from microbially-derived,tryptophan-like components.Groundwater fDOM from sand-dominated sequences typically contained lower tryptophan-like,lower fulvic-like and lower humic-like components,was less bioavailable,and had higher humification index than clay-dominated sequences.Methane concentrations were strongly correlated with fDOM bioavailability as well as with tryptophan-like components,suggesting that groundwater methane in these arsenic-prone aquifers is likely of biogenic origin.A comparison of fDOM tracers with sedimentary OM tracers is consistent with the hypothesis that external,surface-derived contributions to the aqueous DOM pool are an important control on groundwater hydrogeochemistry.

Investigation on the Photodissociation of Oxygen from Oxymyoglobin by Fluorescence Spectroscopy

Photodissociation of oxygen from oxymyoglobin（oxyMb） was investigated by means of fluorescence spectroscopy. One of the most important findings of the photodissociation of oxyMb was the discovery of two processes which were affected by excitation intensity, temperature, solvent viscosity, and excitation wavelength. Process I（PI） corresponded to oxygen escaping from the binding site at ferrous heme iron atom within the porphyrin ring into the heme pocket, whereas process II（PII） was ascribed to oxygen escaping from the heme pocket into the solvent. To elucidate this interesting phenomenon, we proposed a model that oxygen encountered two barriers on its way from the binding site at the ferrous heme iron to the solvent. Reversibility and wavelength sensitivity of the photodissociation were also observed.

Preparation and Characterization of Ternary Europium ComplexDoped Thin SolGel Hybrid Film by Fluorescence Spectroscopy

Ternary europium complex with dibenzoylmethane(DBM)and 1,10phenanthroline(phen)was insitu synthesized in thin SiO2/polyvinyl butyral(PVB)hybrid films by a twostep solgel process and characterized by means of fluorescence spectroscopy.The luminescence spectra,fluorescence lifetimes and photostability were all investigated.The results showed that the hybrid films exhibited the characteristic emission bands of the central rare earth Eu3+.In addition,Eu3+presented longer fluorescence lifetime than in an ethanol solution and the complex had a higher photostability in the hybrid film than in the PVB film containing the corresponding pure complex.

Fluorescence spectroscopy characteristics of humic acid by inoculating white-rot fungus during different phases of agricultural waste composting

The white-rot fungus, Phanerochaete chrysosporium (P. chrysosporium), was inoculated during different phases of agricultural waste composting, and its effect on the fluorescence spectroscopy characteristics of humic acid (HA) was studied. The results show that the emission spectra have a sharp peak at 400 nm and a broad shoulder with the maximum centered at 460 nm. The excitation spectra have two peaks and exhibit red shift (shift to longer wavelengths) at 470 nm. The synchronous scan spectra present a number of peaks and shoulders, and the peaks at shorter wavelengths disappear gradually and form a shoulder. At the final stage of composting, the fluorescence spectra have similar shapes, but the fluorescence intensities decrease. P. chrysosporium increases the degree of aromatization and polymerization of HA when it is inoculated during the second fermentation phase, while it does not produce an obvious change on the humification degree of HA when it is inoculated during the first fermentation phase. Compared with the fluorescence spectroscopy characteristics of HA from soil, the structure of HA from compost is simpler and the activity is higher.

Elemental and proximate analysis of coal by x-ray fluorescence assisted laser-induced breakdown spectroscopy

Although laser-induced breakdown spectroscopy(LIBS),as a fast on-line analysis technology,has great potential and competitiveness in the analysis of chemical composition and proximate analysis results of coal in thermal power plants,the measurement repeatability of LIBS needs to be further improved due to the difficulty in controlling the stability of the generated plasmas at present.In this paper,we propose a novel x-ray fluorescence(XRF) assisted LIBS method for high repeatability analysis of coal quality,which not only inherits the ability of LIBS to directly analyze organic elements such as C and H in coal,but also uses XRF to make up for the lack of stability of LIBS in determining other inorganic ash-forming elements.With the combination of elemental lines in LIBS and XRF spectra,the principal component analysis and the partial least squares are used to establish the prediction model and perform multi-elemental and proximate analysis of coal.Quantitative analysis results show that the relative standard deviation(RSD) of C is 0.15%,the RSDs of other elements are less than 4%,and the standard deviations of calorific value,ash content,sulfur content and volatile matter are 0.11 MJ kg,0.17%,0.79% and 0.41%respectively,indicating that the method has good repeatability in determination of coal quality.This work is helpful to accelerate the development of LIBS in the field of rapid measurement of coal entering the power plant and on-line monitoring of coal entering the furnace.

Evaluation of the inhibitory effect of docosahexaenoic acid and arachidonic acid on the initial stage of amyloid β1-42 polymerization by fluorescence correlation spectroscopy

Amyloid β(Aβ)1-42 fibrillation is a crucial step in the development of pathological hallmarks, such as neuritic plaques and neurofibrillary tangles, of Alzheimer’s disease (AD). In this study, we evaluated the effects of free docosahexaenoic acid (DHA), an essential brain polyunsaturated fatty acid (PUFA), on the inhibition of Aβ1-42 fibrillation by fluorescence correlation spectroscopy (FCS), a technique capable of detecting molecular movements and interactions in solution. We also examined whether free arachidonic acid (AA), eicosapentaenoic acid (EPA), and metabolites of DHA, including neuroprotectin D1 (NPD1, 10S, 17S-dihydroxy-DHA), resolvin D1 (RvD1, 7S, 8R, 17S-trihydroxy-DHA), and didocosahexaenoyl glycerol (diDHA), affect Aβ1-42 polymerization. The results of the FCS study reveal that DHA and AA significantly reduced the diffusion time of TAMRA (5-carboxytetramethylrhoda-mine)-Aβ1-42 by 28% and 31%, respectively, while EPA, NPD1, RvD1, and diDHA had no effects on diffusion time. These results indicate that DHA and AA inhibited Aβ1-42 polymerization and that their inhibitory effects occurred at the initial stage of Aβ1-42 polymerization. This study will advance the research on PUFAs in preventing AD progression.

Characterization of Vegetable Oils by Fluorescence Spectroscopy

Results presented in this paper show the ability to analyze vegetable oils with very cheap and easy method based on fluorescence spectroscopy. We have recorded, with a very simple experimental set up, fluorescence spectra for several vegetable oils at excitation wavelength λex = 370 nm. After deconvolution, using a Lorentzian profile, and identification of the stripes forming the spectra, a normalization of the intensities was made with respect to the vitamin E band with λ= 525 nm taken as reference. A statistical method based on Principal Component Analysis (PCA) is used to emphasize differences between refined and unrefined oils. We also noticed a significant difference between fluorescence of the argan cosmetic oil and edible argan oil due to the heating of the second one during its preparation. Stability to thermal oxidation of high oleic sunflower oil compared to the extra virgin olive, argan cosmetic and refined corn oils is also shown.

Fast Evaluation Peanut Oil Quality by Synchronous Fluorescence Spectroscopy and Statistical Analysis

Peanut oil oxidation was to monitor and quantify combining synchronous fluorescence spectroscopy and chemometrics. Peanut oil was subjected to an accelerated oxidation testing. The spectral and related chemical indicators were caught during oxidation induce testing. Fluorescence spectra were gained for each sample with simultaneous excitation from 200 to 800 nm and the offsets (Δλ) of 10 to 180 nm during the oxidation process. The results showed the induce period (IP) of the peanut oil was 16.45 h. Parallel factor analysis (PARAFAC) was performed to select the best Δλ interval of 70 nm, which spectral data was the most suitable for interval partial least square (iPLS) and synergy interval PLS (siPLS) modeling and forecast. The study presented all interval selection methods had the better results than the global spectrum modelling. iPLS reached the best into 10 intervals with a ratio of prediction to deviation (RPD) of 2.10. siPLS that separated the whole spectrum into 15 intervals and combined the third intervals (282 to 320 nm, 362 to 400 nm, and 761 to 800 nm) had a ratio of RPD of 2.26. The results showed the optimal siPLS model performed a little better than iPLS. The established model lying on interval selection could improve the prediction accuracy. It could provide a quick, accurate method to monitor oil oxidation process.

Solvent-Induced Symmetry-Breaking Charge Transfer in an Octupolar Triphenylamine Derivative Resolved with Transient Fluorescence Spectroscopy

The excited-state symmetry-breaking charge transfer (SBCT) dynamics in quadrupolar or octupolar molecules without clear infrared markers is usually hard to be tracked directly. In this work, on the basis of the evolution of instantaneous emission dipole moment obtained by femtosecond transient fluorescence spectroscopy, we presented a real-time characterization of the solvent-induced SBCT dynamics in an octupolar triphenylamine derivative. While the emission dipole moment of the octupolar trimer in weakly polar toluene changes little during the excited-state relaxation, it exhibits a fast reduction in a few picoseconds in strongly polar tetrahydrofuran. In comparison with the uorescence dynamics of dipolar monomer, we deduced that the emitting state of the octupolar trimer in strongly polar solvent, which undergoes solvent-induced structural uctuation, changes from exciton-coupled octupolar to excitation localized dipolar symmetry. In weakly polar solvent, the octupolar symmetry of the trimer is largely preserved during the solvation stabilization.

Circular Dichroism and Fluorescence Spectroscopic Study of RNA-protein Folding Patterns in Human hnRNP A3 and Their Implications in Human Autoimmune Diseases

In human cells, the heterogeneous nuclear ribonucleoproteins (hnRNP) are represented by a group of polypeptides, with various molecular properties, comprizing the most abundant constituents of the cell nucleus. Autoantibodies to hnRNPs have been reported in patients suffering from different rheumatic dieseases since 1980s. Experimental evidence indicates that hnRNP complexes undergo substantial structural changes during mRNA formation and export. However, how this contributes to disease development still has to be elucidated. Here some preliminary physicochemical features of RNA-protein folding and stability patterns of newly characterized hnRNP A3 with further functional implications in development of systemic human autoimmune states are reported.

Characterization of Anabaena cylindrica Solution System Using Synchronous-Scan Fluorescence Spectroscopy

The characterization of the algae Anabaena cylindrical solution with Fe (III)was investigated using fluorescence emission and synchronous-scan spectroscopy. The ranges ofconcentrations of algae and Fe (III) in aqueous solutions were 5.0 X 10~7-2.5 X10^8 cell/L and 10-60mu mol/L, respectively. The effective characterization method used was synchronous-scanfluorescence spectroscopy (SFS). The wavelength difference (triangle open lambda) of 90 nm wasmaintained between excitation wavelength (lambda_(ex)) and emissionwavelength(lambda_(em)). The peakwas observed at about lambda_(ex) 236 nm / lambda_(em) 326 nm for synchronous-scan fluorescencespectroscopy. The fluorescence quenching in system of algae-Fe( III )-HA was studied usingsynchronous-scan spectroscopy forthe first time, Fe(III) was clearly the effective quencher. Therelationship between I_0/I (quenching efficiency) and c (concentration of Fe (III). added) was alinear correlation for the algae solution with Fe(III). Also, Aldrich humic acid (HA) was found tobe an effective quencher.

Structure and Orientation of 1-(Hydroxyl)-5-(dodecyloxy)-naphthalene LB Films by Polarized Fluorescence Spectroscopy

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Combination of Micro-fluidic Chip with Fluorescence Correlation Spectroscopy for Single Molecule Detection

A single molecule detection technique was developed by the combination of a single channel poly （dimethylsiloxane）/glass micro-fluidic chip and fluorescence correlation spectroscopy （FCS）. This method was successfully used to determine the proportion of two model components in the mixture containing fluorescein and the rhodamine-green succinimidyl ester.

Sorption Characteristics of Rare Earth Element Eu ^(3+) onto Silica-Water Interfaces Studied by Fluorescence Spectroscopy

The sorption of Eu species onto nano-size silica-water interfaces was investigated using fluorescence spectroscopy for pH ranges of 1-8.5 and an initial Eu concentration (C Eu) of 2×10 -4 M. The sorption rate of Eu was initially low, but significantly increased at pH>4. The sorption density of Eu species on a silica surface was ～1.58×10 -7 mol/m2 when the dissolved Eu species were completely sorbed onto silica-water interfaces at pH=～5.8. The sorbed Eu species at pH<6 is aquo Eu 3+, which is sorbed onto silica-water interfaces as an outer-sphere complex at pH<5, but may be sorbed as an inner-sphere bidentate complex at 5<pH<6, due to the decrease of N H 2O to ～6 at pH=6. At pH=6-8.5, Eu(OH)+ 2, Eu(CO 3)+ and Eu(CO 3)- 2 formed in the solutions, and Eu(CO 3)+ is dominant at pH=～7.5. These ions may be sorbed onto silica-water interfaces as inner-sphere bidentate complexes.

Study of a Model Humic Acid-type Polymer by Fluorescence Spectroscopy and Atomic Force Microscopy

A model HA-type polymer of para-benzoquinone synthetic humic acid (SHA) and its complexes with copper, iron and manganese metal ions were studied using atomic force microscopy (AFM). Natural humic acids (HA) and synthetic humic acids (SHA) were examined by fluorescence spectroscopy, which indicated similarity of SHA and HA spectra. The AFM images of SHA and its complexes revealed variable morphologies, such as small spheres, aggregates and a sponge-like structure. The SHA complexes displayed morphologies similar to those of natural HA. The presence of copper, iron and manganese ions led to the formation of aggregate-type structures in an apparent arrangement of smaller SHA particles.

Classification of Blood Species Using Fluorescence Spectroscopy Combined with Deep Learning Method

In this work, a deep belief neural network model (DBN) was developed to classify doves, chickens, mice and sheep blood samples, which have many similarities in composition causing their spectra to look almost identical by visual comparison alone. The DBN model was formulated for the feature extraction from the pretreated fluorescence spectroscopy. Then, cross-validation results showed that the application of deep learning method made it possible to classify the blood fluorescence spectroscopy in a more precise way than previous methods. Especially, the classification accuracy of whole blood with 1% of concentration was up to 97.5%.