Absorption Fluorescence Spectra Research Articles

CFSA-AGD: An accurate crosstalk fluorescence spectroscopic decomposition method for identifying and quantifying FDOMs in aquatic environments

Fluorescent substances exist in various aquatic environments and other environmental media. It is a critical task to identify the components accurately and quantify their contents precisely. Based on the Crosstalk Fluorescence Spectroscopy Analysis (CFSA) model, a fluorescence spectroscopic decomposition using the Alternating Gradient Descent (AGD) algorithm is developed. By reducing the residual error of the model through alternating iterations, the CFSA-AGD method achieves unsupervised model training and automatic spectroscopic decomposition without extra experimental operations such as dilution or absorbance measurement, exempting from tedious modeling process. The objectives of this work are to validate that the CFSA-AGD method can comprehensively address the decomposition of fluorescence spectral crosstalk. Furthermore, the novel method is applied to the spectroscopic decomposition of natural FDOMs in aquatic environments as a standard tool. The spectral data analyzing the performance of this method is verified and compared with the conventional methods through the experiment on standard samples. The results indicate that CFSA-AGD has higher spectroscopic decomposition accuracy and gives more abundant information on the characteristic spectra with less residual error than parallel factor analysis. This means that the fluorescence spectra of natural FDOMs can be decomposed into the characteristic fluorescence emission spectra of single components with higher accuracy and the characteristic fluorescence absorption spectra that cannot be obtained by the conventional methods. Meanwhile, it improves the analytical precision of the contents (from R2 ≥ 0.9778 to R2 ≥ 0.9920) and reduces the ultimate residual error by two orders of magnitude (from 1.42 × 10−1 to 4.68 × 10−3) when the method is used to estimate the measured fluorescence spectra.

Vibrationally-resolved absorption and fluorescence spectra of chemically modified 2D hexagonal boron nitride quantum dots

The vibrationally-resolved absorption and fluorescence spectra of square hexagonal boron nitride (shBN) quantum dot are studied using time dependent DFT calculations. The details of the first excited state in the UV–Vis absorption spectrum significantly clarified by the inclusion of vibronic transitions. The lowest vibronic transition in the absorption or fluorescence spectra shows that shBN has a wide optical energy gap of 4.93 eV. The absorption-fluorescence spectra indicate that doping with three C-atoms (doping percentage of 6%) decreases the optical energy gap to 0.46 eV. Doping also significantly enhances the interaction with the incident photon due to the boosted dipole strength.

Dual-mode colorimetric/fluorometric sensor for the detection of glutathione based on the peroxidase-like activity of carbon quantum dots

In the current investigation, fluorescent carbon quantum dot nanoparticles were prepared using hydrothermal method. In order to achieve green preparation, waste corncob was used as raw material. Transmission electron microscope was used to examine the urface morphology of the synthesized fluorescent carbon quantum dot nanoparticles. Optical characterization was done by analyzing the ultraviolet–visible spectroscopy and fluorescence absorption spectrum. The peroxidase activity and catalytic performance of corncob fluorescent carbon quantum dots have been researched and compared with some simulated enzymes, and corncob fluorescent carbon quantum dots with peroxisase-like activity and fluorescence characteristics were used for the detection of glutathione by dual-mode colorimetric/fluorometric sensor. Our experimental results displayed that the corncob fluorescent carbon quantum dots have nanostructures and the catalytic activity of corncob fluorescent carbon quantum dots was better than that of other nanoparticles. The detection results of glutathione show that the limit of detection was 8.0133 nmol/L for the fluorometric sensor and the limit of detection was 0.3024 μmol/L for the colorimetric sensor with good selectivity and high sensitivity, exhibiting their potential for application in nanosensors.

Spectroscopic, DNA binding ability, biological activity, DFT calculations and non linear optical properties (NLO) of novel Co(II), Cu(II), Zn(II), Cd(II) and Hg(II) complexes with ONS Schiff base

The reaction of Co(II), Cu(II), Zn(II), Cd(II) and Hg(II) with the synthesized N-(2-hydroxy-1-naphthylidene)-2-aminothiophenol Schiff base ligand (H2L) at room temperature resulted in the formation of the five complexes; [Co(HL)2]H2O, 1; [M(HL)2] (M = Cu, Zn and Cd), (2–4) and [Hg(HL)Cl], 5. The ligand and its complexes were characterized based on elemental analyses, IR, 1H NMR, magnetic measurement, molar conductance, and thermal analysis. Coats and Redfern method was used to compute the kinetic and thermodynamic parameters. Antimicrobial activities of H2L and its complexes have been studied. The binding of Co(II), Cu(II) and Zn(II) complexes to calf thymus DNA (CT-DNA) has been investigated using UV–Vis and fluorescence absorption spectra. The results indicated that the ligand and its complexes may bind to DNA by intercalation modes, with a much higher binding affinity of the complexes than that of the ligand. The equilibrium geometries of the studied complexes are investigated theoretically at the B3LYP/LANL2DZ level of theory, and it was found that these geometries are non-linear. The calculated EHOMO and ELUMO energies of the studied complexes can be used to calculate the global properties. The calculated nonlinear optical parameters (NLO); first order hyperpolarizibility (β) of the studied complexes show promising optical properties.

Separating Reflective and Fluorescent Components Using High Frequency Illumination in the Spectral Domain

Hyperspectral imaging is beneficial to many applications but most traditional methods do not consider fluorescent effects which are present in everyday items ranging from paper to even our food. Furthermore, everyday fluorescent items exhibit a mix of reflection and fluorescence so proper separation of these components is necessary for analyzing them. In recent years, effective imaging methods have been proposed but most require capturing the scene under multiple illuminants. In this paper, we demonstrate efficient separation and recovery of reflectance and fluorescence emission spectra through the use of two high frequency illuminations in the spectral domain. With the obtained fluorescence emission spectra from our high frequency illuminants, we then describe how to estimate the fluorescence absorption spectrum of a material given its emission spectrum. In addition, we provide an in depth analysis of our method and also show that filters can be used in conjunction with standard light sources to generate the required high frequency illuminants. We also test our method under ambient light and demonstrate an application of our method to synthetic relighting of real scenes.

Effect of Kolavenic Acid on the Structure of Human Serum Albumin

The effect of Kolavenic acid (KA), an active component isolated from the genus Polyalthia, on the structure of human serum albumin (HSA) was investigated by fluorescence polarization, synchronous fluorescence, three-dimensional (3D) fluorescence, and absorption spectroscopy in combination with molecular modeling techniques under physiological conditions. The synchronous and absorption fluorescence spectra confirmed that KA has an effect on the microenvironment around HSA in aqueous solution. The two-dimensional (2D) and 3D fluorescence spectra showed that KA could quench the intrinsic fluorescence of HSA and make its conformation change. Fluorescence polarization measurements provided useful information on the relaxation time and aggregation behavior of the complex formed between HSA and KA, and indicated that the presence of KA caused changes in the fluidity and microviscosity of HSA. The binding constants and thermodynamic parameters for KA-HSA systems were obtained under different temperatures (298, 308, and 318 K). Molecular docking showed that the KA moiety bound to the hydrophobic cavity of HSA, and there were three hydrogen-bonding interactions between KA and the Lys195 and Asp451 residues. Fluorescent displacement measurements confirmed that KA bound to HSA at site II. In addition, the binding mechanism of KA and HSA was revealed by the physicochemical parameters at the molecular level. The results showed that the interaction between KA and HSA was strong, indicating that KA may be stored and transferred by serum albumin.

Luminescent polymeric hybrids functionalized by β-diketone with silicon–oxygen networks and carbon chains: Assembly and characterization

2-Thenoyltrifluoroacetone (TTA) was grafted onto the coupling agent 3-(triethoxysilyl)-propyl-isocyanate to construct the precursor I (TTA–Si), and polymer precursors II (PVPD, PMAA and PVPDMAA) were synthesized through the addition polymerization reactions. Then precursors I and II have coordinated to the rare-earth ions with the carbonyl, carboxyl group or nitrogen atom, respectively, and after hydrolysis and copolycondensation sol–gel process, the three kinds of polymeric hybrids were obtained. FTIR, ultraviolet–visible diffuse reflection and fluorescence absorption spectra, electronic micrographs, room-temperature X-ray diffraction patterns and TG plots were characterized and the results reveal that the hybrid materials showed uniformity in the microstructure, efficient intramolecular energy transfer system and excellent characteristic emission of terbium ions under UV irradiation.

Effect of substituents on the spectroscopic properties of all- trans-1,6-diphenyl-1,3,5-hexatriene

An extensive spectroscopic study of two derivatives of the all- trans-1,6-diphenyl-1,3,5-hexatriene (DPH) has been conducted. The one derivative carries, at the para position of one of the phenyl rings of the parent molecule, the electron donating –N–(CH 3) 2 group, while the other carries at the same position the electron withdrawing –NO 2 substituent. The absorption–fluorescence spectra, quantum yields, lifetimes and steady state fluorescence anisotropies of these derivatives, were studied in various solvents, at different temperatures and at different viscosities. The findings are presented and discussed along with the exceptional fluorescence probing properties of these two particular derivatives. For comparative purposes, the main spectroscopic properties of the parent molecule are also included.

Correction of Self Absorption on XAS Measurements in Fluorescence Mode

Self absorption and influence of neighbouring absorption edges make it necessary to correct data of XAS measurements in fluorescence mode. To simulate the fluorescence process and to calculate the absorption coefficients from experimental data, informations about stoichiometric composition and fluoresnee yields are needed. Some examples show the necessity of correction of fluorescence spectra to get true absorption coefficients and the advantage of the method: In ZnSe the Se absorption coefficient can be calculated from the Zn L absorption spectrum. In the same system the intensity breakdown of Zn L fluorescence absorption spectra due to Se absorption above the Se L-edges can be removed.

Juvenile-hormone-binding protein from the hemolymph of Galleria mellonella (L). Isolation and characterization.

A juvenile-hormone-binding protein (JHBP) has been isolated from Galleria mellonella hemolymph by gel filtration, phosphocellulose chromatography, and by chromatofocusing. The isolated protein is homogeneous as judged by column chromatography and gel electrophoresis in the presence and absence of denaturing agent. It has a relative molecular mass of 32,000, Stokes radius 2.4 nm, sedimentation coefficient of 2.3 S, molar absorption coefficient at 280 nm epsilon = 2.34 X 10(4) M-1 cm-1, and is composed of a single polypeptide chain. Chromatofocusing analysis (pI 8.6) and isoelectric focusing (pI 8.1) indicate that the JHBP is an alkaline protein. Its amino acid composition and fluorescence absorption spectra indicate that the protein does not contain tryptophan residues. The protein exhibits one class of binding sites for juvenile hormone (JH), 0.8 per molecule, with the following dissociation constants: JH I, 8.5 X 10(-8) M; JH II, 7.2 X 10(-8) M; JH III, 47 X 10(-8) M. The JHBP binds (10R, 11S)-JH II enantiomer with 2.3-times higher affinity then (10S, 11R)-JH II enantiomer. The pH optimum of binding is 7.0.