Intense Fluorescence Band Research Articles

Effect of different thermal processing methods and thermal core temperatures on the protein structure and in vitro digestive characteristics of beef

This study aimed to investigate the effect of different thermal processing treatments on the protein digestion characteristics of beef. The beef samples were subjected to different cooking methods, namely steaming, boiling, and roasting, and different core temperatures (75 °C, 80 °C, 85 °C, and 90 °C), and were subjected to in vitro gastrointestinal digestion simulation. All the thermal processing treatments increased the protein digestibility; the samples that were steamed at 85 °C (S85), boiled at 80 °C (B80), and roasted at 80 °C (R80) showed the biggest gains. The S85 released more peptide species after gastrointestinal digestion, according to peptididomic studies. These differences were closely related to protein structure. Thermal processing treatments resulted in a higher degree of proteolysis and looser protein conformation, as evidenced by decreased intrinsic fluorescence and electrophoretic band intensity, increased surface hydrophobicity, and the change in protein secondary structure from α-helix to β-sheet and random coil. Based on the results, S85 was identified as the optimal thermal processing treatment for enhancing the digestibility of beef protein. The results provide valuable insights into the nutritional qualities and digestion of heat-processed beef protein.

(Invited) Comprehensive Analysis of Exciton Diffusion with Time-Resolved Fluorescence Spectroscopy, Anisotropy and Imaging

Excitons produced in materials play a crucial role in photo-energy conversion such as photovoltaics and electroluminescence devices. The temporal and spatial diffusion of excitons is a key factor for dominating the fundamental performance of optoelectronic materials. In this context, analysis of the exciton diffusion dynamics is an important issue for obtaining the rational design of the materials. Excitons diffusing in materials can be characterized by several parameters such as the energy level, orientation of the transition dipole moment and spatial distribution, and the detection of these properties is required for the comprehensive analysis. In the present study, we show time-resolved fluorescence methods for detecting the above relevant properties of excitons.First, time-resolved fluorescence spectroscopy is a basic technique for analyzing the exciton diffusion dynamics. Fluorescence intensity is detected as functions of observation wavelength and time, and the spectral intensity and shift of fluorescence bands provide information on the population of excitons and their energy level. For example, dynamic Stokes shift indicates downhill energy migration and excitons are trapped by the defective site in molecular aggregates. Second, fluorescence anisotropy can be a good indicator for tracking the exciton diffusion in amorphous materials. Fluorescence anisotropy is sensitive to orientation change in transition dipole moments (TDMs) between absorption and fluorescence. In systems where the relative orientation of adjacent molecules is different from each other, such as amorphous solids, the exciton diffusion is accompanied with the change in TDM. Thus, appropriate modeling of molecular alignment enables quantitative estimation of the exciton diffusion coefficient and diffusion length from the anisotropy signal. Finally, time-resolved imaging is a combination of time-resolved spectroscopy and super-resolution microscopy, and an emergent technique for visualizing real-space propagation of excitons in materials. The diffraction-limited excitation beam produces excitons in several hundreds of nanometers and the subsequent exciton diffusion is evaluated by the spatial width of the fluorescence spot. The temporal broadening of the fluorescence spot directly reflects the exciton distribution and we can intuitively obtain the diffusion coefficient and length. Unlike the conventional methods for bulk materials, the advantage of the time-resolved imaging is the applicability to materials with nano- and meso-scale heterogeneous structure and it enables site-selective evaluation of the exciton transport capability. In the conference site, we will also show the application of the above methods to supramolecular polymers and thermally activated delayed fluorescence materials. Figure 1

Study of the behavior of the 4-DASPI dye in samples of silicate hydrogel by fluorescence spectroscopy and quantum chemistry

The behavior of the 4-[4-(dimethylamino)styryl]-1-methylpyridinium iodide (4-DASPI) dye in samples of silicate hydrogel obtained from tetrakis(2-hydroxyethyl) orthosilicate with the dye added at the synthesis stage or adsorbed on a previously synthesized hydrogel substrate is studied by luminescence spectroscopy and molecular dynamics and quantum chemistry calculations. Small hypsochromic shifts of the fluorescence spectra of the dye upon its interaction with silica are observed. Energies of adsorption of 4-DASPI in the ground and excited state on two types of amorphous silica are calculated and contributions of Coulomb and dispersion interactions are estimated. A transition of the 4-DASP+ cation to the TICT state upon its excitation in water and methanol solutions is proved by TD DFT calculations. Partial twisting of the 4-DASP+ cation on silica, both in the pore and on the surface, is proposed based on the results of calculations and experimental measurements. The main difference between the samples synthesized with the introduction of 4-DASPI into the reaction mixture and by the gel synthesis followed by the adsorption of 4-DASPI seems to be capturing of the dye molecule in a pore in hydrogel with freezing molecular vibrations and rotations and, consequently, the growth of fluorescence intensity in the first case and the adsorption of the dye on the silica surface with relatively easy molecular vibrations and hindered rotations in the second case. This explains a strong difference in the intensities of fluorescence bands in the spectra of the studied samples.

Alternative boronic acids in the detection of Mycolactone A/B using the thin layer chromatography (f-TLC) method for diagnosis of Buruli ulcer

BackgroundMycobacterium ulcerans is the causative agent of Buruli ulcer. The pathology of M. ulcerans disease has been attributed to the secretion of a potent macrolide cytotoxin known as mycolactone which plays an important role in the virulence of the disease. Mycolactone is a biomarker for the diagnosis of BU that can be detected using the fluorescent-thin layer chromatography (f-TLC) technique. The technique relies on the chemical derivatization of mycolactone A/B with 2-naphthylboronic acid (BA) which acts as a fluorogenic chemosensor. However, background interferences due to co-extracted human tissue lipids, especially with clinical samples coupled with the subjectivity of the method call for an investigation to find an alternative to BA.MethodsTwenty-six commercially available arylboronic acids were initially screened as alternatives to BA using the f-TLC experiment. UV–vis measurements were also conducted to determine the absorption maximum spectra of mycolactone A/B and myco-boronic acid adducts followed by an investigation of the fluorescence-enhancing ability of the boronate ester formation between mycolactone A/B and our three most promising boronic acids (BA15, BA18, and BA21). LC–MS technique was employed to confirm the adduct formation between mycolactone and boronic acids. Furthermore, a comparative study was conducted between BA18 and BA using 6 Polymerase Chain Reaction (PCR) confirmed BU patient samples.ResultsThree of the boronic acids (BA15, BA18, and BA21) produced fluorescent band intensities superior to BA. Complexation studies conducted on thin layer chromatography (TLC) using 0.1 M solution of the three boronic acids and various volumes of 10 ng/µL of synthetic mycolactone ranging from 1 µL – 9 µL corresponding to 10 ng – 90 ng gave similar results with myco-BA18 adduct emerging with the most visibly intense fluorescence bands. UV–vis absorption maxima (λmax) for the free mycolactone A/B was observed at 362 nm, and the values for the adducts myco-BA15, myco-BA18, and myco-BA21 were at 272 nm, 270 nm, and 286 nm respectively. The comparable experimental λmax of 362 nm for mycolactone A/B to the calculated Woodward-Fieser value of 367 nm for the fatty acid side chain of mycolactone A/B demonstrate that even though 2 cyclic boronates were formed, only the boronate of the southern side chain with the chromophore was excited by irradiation at 365 nm. Fluorescence experiments have demonstrated that coupling BA18 to mycolactone A/B along the 1,3-diols remarkably enhanced the fluorescence intensity at 537 nm. High-Resolution Mass Spectrometer (HR-MS) was used to confirm the formation of the myco-BA15 adduct. Finally, f-TLC analysis of patient samples with BA18 gave improved BA18-adduct intensities compared to the original BA-adduct.ConclusionTwenty-six commercially available boronic acids were investigated as alternatives to BA, used in the f-TLC analysis for the diagnosis of BU. Three (3) of them BA15, BA18, and BA21 gave superior fluorescence band intensity profiles. They gave profiles that were easier to interpret after the myco-boronic acid adduct formation and in experiments with clinical samples from patients with BA18 the best. BA18, therefore, has been identified as a potential alternative to BA and could provide a solution to the challenge of background interference of co-extracted human tissue lipids from clinical samples currently associated with the use of BA.

Crystal growth, first-principle calculations, optical properties and laser performances toward a molybdate Er3+:KBaGd(MoO4)3 crystal

A well-shaped Er3+:KBaGd(MoO4)3 (Er3+:KBGM) crystal with the size of 48 × 38 × 15 mm3 was grown by the flux method and, its structure, morphology and optical properties were studied. The first principal calculations on the band structure and density of states of the crystal were also conducted. The important spectroscopic parameters of the Er3+:KBGM crystal were calculated and analyzed by Judd-Ofelt theory. The polarized stimulated emission spectra were investigated by F-L method. The results of up-conversion spectra analysis revealed that two intense green fluorescence bands centered at 533 nm and 554 nm and a broadened weak red fluorescence band at 665 nm were observed when excited at 981 nm. According to the spectroscopic studies, as well as the analysis of decay time of the 4I13/2 state, the specific energy transfer mechanism of Er3+ ion in this crystal was elucidated. Laser experiment aiming at 1.55 μm continuous-wave laser was conducted in a plane-plane cavity and, when the optimized transmittance of output couplers was 3%, a maximum of 1.05 W laser emission was acquired with the corresponding slope efficiency of 15.36%. With the combination of all the studies, Er3+:KBGM crystal was proved to be a prominent crystal for the 1.55 μm laser.

Nature of the Ligand-Centered Triplet State in Gd3+ β-Diketonate Complexes as Revealed by Time-Resolved EPR Spectroscopy and DFT Calculations.

A series of Gd3+ complexes (Gd1–Gd3) with the general formula GdL3(EtOH)2, where L is a β-diketone ligand with polycyclic aromatic hydrocarbon substituents of increasing size (1–3), was studied by combining time-resolved electron paramagnetic resonance (TR-EPR) spectroscopy and DFT calculations to rationalize the anomalous spectroscopic behavior of the bulkiest complex (Gd3) through the series. Its faint phosphorescence band is observed only at 80 K and it is strongly red-shifted (∼200 nm) from the intense fluorescence band. Moreover, the TR-EPR spectral analysis found that triplet levels of 3/Gd3 are effectively populated and have smaller |D| values than those of the other compounds. The combined use of zero-field splitting and spin density delocalization calculations, together with spin population analysis, allows us to explain both the large red shift and the low intensity of the phosphorescence band observed for Gd3. The large red shift is determined by the higher delocalization degree of the wavefunction, which implies a larger energy gap between the excited S1 and T1 states. The low intensity of the phosphorescence is due to the presence of C–H groups which favor non-radiative decay. These groups are present in all complexes; nevertheless, they have a relevant spin density only in Gd3. The spin population analysis on NaL models, in which Na+ is coordinated to a deprotonated ligand, mimicking the coordinative environment of the complex, confirms the outcomes on the free ligands.

A simple pyridine based fluorescent chemosensor for selective detection of copper ion

A feasibly constructed novel pyridine based receptor (S) has been reported for the selective detection of copper ion over other metal ions. The metal sensing ability of receptor with diverse metal ions were studied by colorimetry, absorption and emission spectroscopic systems in CH3CN/H2O (7:3, v/v). This receptor reveals a drastic color converts from vapid to yellow and cyan under normal light and UV light with copper ion. Further, S-Cu2+ complex exhibits new UV–Visible band at 419 nm and intense fluorescence band at 494 nm upon the excitation at 388 nm. The stoichiometric binding ratio of receptor with metal ion was confirmed with Job’s method and ESI-Mass also further supported the complexation. Besides, limits of detection of Cu2+ were calculated to be 0.25 μM. The limiting capacity of receptor with Cu2+ ion was additionally explored by quantum chemical calculation. Moreover, this receptor was effectively utilized for the measurement of Cu2+ ion in various water tests.

Electron-Deficient Heteroacenes that Contain Two Boron Atoms: Near-Infrared Fluorescence Based on a Push-Pull Effect*.

Electron-deficient heteroacenes that contain two tricoordinate boron atoms in their acene skeletons and planarized phenyl ether moieties at their periphery were synthesized via the borylation of silicon-bridged precursors. X-ray crystallographic analysis revealed quinoidal structures, which give rise to two-step reversible redox processes for both the reduction and oxidation. These compounds exhibit intense absorption and sharp fluorescence bands with vibronic structures in the near-infrared (NIR) region. These properties originate from the push-pull effect along the long axis of the molecule derived from the electron-donating ether moieties and the electron-accepting boron moieties. Of particular note is the NIR emission of the thienothiophene-centered heteroacene, which has a maximum at 952 nm with a narrow band width of 309 cm-1 in cyclohexane. A Franck-Condon analysis revealed the crucial role of the sterically less-hindered thienothiophene spacer in achieving this sharp emission band.

Electron‐Deficient Heteroacenes that Contain Two Boron Atoms: Near‐Infrared Fluorescence Based on a Push–Pull Effect**

AbstractElectron‐deficient heteroacenes that contain two tricoordinate boron atoms in their acene skeletons and planarized phenyl ether moieties at their periphery were synthesized via the borylation of silicon‐bridged precursors. X‐ray crystallographic analysis revealed quinoidal structures, which give rise to two‐step reversible redox processes for both the reduction and oxidation. These compounds exhibit intense absorption and sharp fluorescence bands with vibronic structures in the near‐infrared (NIR) region. These properties originate from the push–pull effect along the long axis of the molecule derived from the electron‐donating ether moieties and the electron‐accepting boron moieties. Of particular note is the NIR emission of the thienothiophene‐centered heteroacene, which has a maximum at 952 nm with a narrow band width of 309 cm−1 in cyclohexane. A Franck–Condon analysis revealed the crucial role of the sterically less‐hindered thienothiophene spacer in achieving this sharp emission band.

Pr3+-doped B2O3–Bi2O3–ZnO–NaF glasses comprising alkali/mixed alkali oxides for potential warm white light generation, blue laser, and E-+S-+C-optical bands amplification applications

For six 1 mol% Pr 3+ -doped B 2 O 3 –Bi 2 O 3 –ZnO–NaF glasses consisting of single and mixed alkali oxides, optical absorption and visible and near-infrared (NIR) luminescence traits including visible fluorescence decay times were investigated. Judd–Ofelt (J‒O) analysis from absorption spectra was performed to calculate J‒O parameters Ω λ ( λ = 2, 4, 6) by including and omitting 3 H 4 → 3 P 2 transition. Utilizing Ω 2 , Ω 4 , and Ω 6 values and refractive indices, radiative transition probabilities ( A R ), branching ratios ( β R ), and radiative lifetimes for all Pr 3+ ion's luminescent levels were estimated. For observed intense blue fluorescence band upon 443 nm optical pumping, various parameters considered in designing visible laser systems were evaluated. Pr 3+ : Na + K ions comprising glass possesses large spectroscopic quality factor, high A R and β R , large stimulated emission cross-section ( σ em ), high quantum efficiency, large gain bandwidth, and significant optical gain for 3 P 0 → 3 H 4 transition for a potential blue lasing action among all samples. Further, Commission Internationale de l'éclairage (CIE) coordinates, correlated color temperature (CCT), color rendering index, and luminous efficiency of radiation were derived from visible luminescence spectra and deduced CIE and CCT values represent the neutral or warm white light region. Upon 3 H 4 → 3 P 2 excitation, NIR luminescence spectra show 3 P 1 + 1 I 6 → 1 G 4 , 1 D 2 → 3 F 4 , and 1 D 2 → 1 G 4 transitions in which broadband ( 1 D 2 → 1 G 4 ) at 1.3–1.65 μm range with effective bandwidth ~157 nm was obtained for Pr 3+ : Na + K ions constituting glass with high A R (1938 s −1 ), moderate β R (26%), and large σ em (2.64 × 10 −20 cm 2 ) at 1.472 μm, and its gain profile covers the E-+S-+C-optical communication bands' range for effective broadband amplification operation.

Research on a novel molybdate Er3+:KBaY(MoO4)3 crystal as a prominent 1.55 μm laser medium

An Er3+:KBaY(MoO4)3 (denoted Er3+:KBYM) crystal with excellent optical quality was grown for the first time by the top-seeded-solution growth method (TSSG) from a flux of K2Mo2O7 and its morphology, including concentration of Er3+ ions was analyzed. The concentration of Er3+ ion and spectroscopic properties were measured and investigated. Applying the Judd-Ofelt theory, the spectroscopic parameters of Er3+:KBYM crystal, including the oscillator intensity parameters Ωt(t=2,4,6), spontaneous emission probabilities, fluorescence branching ratios, and radiative lifetimes, were calculated and analyzed. The stimulated emission cross-sections at around 1.55 μm, corresponding to the 4I13/2 → 4I15/2 transition were 1.01 × 10−20 cm2, 1.32 × 10−20 cm2 and 1.10 × 10−20 cm2 for the X-, Y- and Z-polarizations, respectively. The fluorescence lifetime of the 4I13/2 state was measured and discussed. The fluorescence decay curve for the 4I13/2 state exhibited a single exponential behavior and fluorescence lifetime was fitted to be 5.35 ms. Two intense green up-conversion fluorescence bands located at 533 nm and 554 nm and a broadened weak red fluorescence at 665 nm were observed at 984 nm excitation, and the energy transfer mechanism was discussed.

Enhanced 2.7 µm mid-infrared emission in Er3+/Ho3+ co-doped tellurite glass

Improving the mid-infrared band luminescent intensity in oxide glass system is a serious challenge. In this work, Ho3+ ions was introduced into Er3+ doped tellurite glass, and the improved effect on 2.7 µm band fluorescence of Er3+ was investigated. It was found that when 0.5 mol% of Ho2O3 was incorporated into the tellurite glass with 0.5 mol% of Er2O3, the 2.7 µm band fluorescence intensity originating from Er3+:4I11/2 → 4I13/2 transition increased by about 39% under the excitation of 808 nm laser diode (LD). This significant enhancement was attributed to the energy transfers between Er3+ and Ho3+ ions which improved the population inversion ratio of this emission transition. Analyses of the intensity variations of visible and infrared band emissions as well as the fluorescence decay behavior of Er3+ ions with Ho3+ doped concentration demonstrated the existence of energy transfers, and the energy transfer mechanism was investigated by calculating the relevant micro-parameters to better clarify the origin of fluorescence enhancement. Additionally, Judd-Ofelt theory was applied to the absorption spectrum and the potential spectroscopic properties of Er3+ were evaluated, while DSC curves revealed the good thermal stability of the studied tellurite glass. All these indicated that Er3+/Ho3+ co-doped tellurite glass with appropriate concentrations is a promising candidate applied for 2.7 µm band optoelectronic devices.

Protective effect of purple corn silk extract against ultraviolet-B-induced cell damage in human keratinocyte cells.

ABSTRACTUltraviolet-B (UVB) could lead to inflammation and cell death induction. Purple corn silk (PCS), part of female flower of corn has multiple pharmacological properties. This investigation focused on determining the preventive effects of PCS extract on human keratinocyte HaCaT cell damage induced by UVB irradiation. Cells were irradiated with 25 mJ/cm2 UVB after pre-treated with PCS extract for 1 h. Then, the cells were then placed in culture medium followed by subsequent experiments. Cell survival was determined by MTT assay. The immunofluorescence, DCFH-DA, JC-1, and Hoeshst33342 staining assays were used to determine γ-H2AX, intracellular reactive oxygen species (ROS), membrane potential of mitochondria, and nuclear condensation, respectively. Western blot analysis was used to investigate the proteins expression. The statistically significant comparison was calculated by analysis of variance at P < 0.05. The fluorescence and protein band intensity were quantified by Image J densitometer. The results indicated cell survival was increased upon PCS extract pretreatment followed by UVB exposure. PCS extract decreased γ-H2AX expression, intracellular ROS overproduction, and nuclear condensation in cells induced by UVB. Furthermore, The PCS extract pretreatment attenuated apoptosis response through stabilized mitochondrial membrane potential, decreased apoptosis mediator proteins including Bax, Bak, cleaved-caspases, and cleaved-PARP, and increased Bcl-2 and Bcl-xL expression comparing to the UVB-treated control. This finding demonstrated that the PCS extract can reduce the deleterious effects from UVB exposure through decreased intracellular ROS, DNA damage, and apoptosis induction on HaCaT cells.

Boosting the properties of a fluorescent dye by encapsulation into halloysite nanotubes

The synthesis of a new biocompatible bichromophoric system (CURBO) was developed, by connecting the skeleton of the naturally occurring curcumin to a BODIPY derivative. The system exhibited an intense fluorescence band with maximum at about 510 nm in organic solvent, while its emission spectra in aqueous solution were more complicated and slightly red-shifted, due to the effect of aggregation for the poor solubility of the dyad. To overcome these problems, the bichomophoric system has been loaded into the halloysite nanotubes (HNT). The HNT/CURBO nanocomposite, suspended in aqueous solution, showed an intensity of emission in the red region of the spectrum higher than the one exhibited by the pristine CURBO. The biocompatibility and photophysical behavior of HNT/CURBO nanocomposite were studied using ASC52Telo, h-TERT immortalized adipose-derived mesenchymal stem cells. To investigate the localization of the CURBO alone and in HNT/CURBO, fluorescence epimicroscopy was performed. The HNT/CURBO nanocomposite showed a high propensity to cross cell membranes, resulting in a massive cell uptake around the cell nucleus. Moreover, it lighted up ASC52Telo cells both with intense green and red fluorescence while excited in the blue portion of the electromagnetic spectrum, a phenomenon that could not be observed for the free CURBO. Dual-channel emissions dyes and, in particular, materials, such as the HNT/CURBO nanocomposite, emitting in the red portion of the spectrum have become, in recent decades, particularly fascinating since they can minimize the autofluorescence detection of the cell medium and allow interesting microscopy applications.

DNA-Binding and Anticancer Activity of Binuclear Gold(I) Alkynyl Complexes with a Phenanthrenyl Bridging Ligand.

3,6-Diethynyl-9,10-diethoxyphenanthrene (4) was synthesized from phenanthrene and employed in the synthesis of the binuclear gold(I) alkynyl complexes (R3P)Au(C≡C–3-[C14H6-9,10-diethoxy]-6–C≡C)Au(PR3) (R = Ph (5a), Cy (5b)). The diyne 4 and complexes 5a and 5b were characterized by NMR spectroscopy, mass spectrometry, and elemental analysis. UV-Vis spectroscopy studies of the metal complexes and precursor diyne show strong π → π* transitions in the near UV region that red shift by ca. 50 nm upon coordination at the gold centers. The emission spectrum of 4 shows an intense fluorescence band centered at 420 nm which red shifts, slightly upon coordination of 4 to gold. Binding studies of 4, 5a, and 5b against calf thymus DNA were carried out, revealing that 4, 5a, and 5b have ≥40% stronger binding affinities than the commonly used intercalating agent ethidium bromide. The molecular docking scores of 4, 5a, and 5b with B-DNA suggest a similar trend in behavior to that observed in the DNA-binding study. Unlike the ligand 4, promising anticancer properties for 5a and 5b were observed against several cell lines; the DNA binding capability of the precursor alkyne was maintained, and its anticancer efficacy enhanced by the gold centers. Such phenanthrenyl complexes could be promising candidates in certain biological applications because the two components (phenanthrenyl bridge and metal centers) can be altered independently to improve the targeting of the complex, as well as the biological and physicochemical properties.

Zn(II) Complexes with Quinoline Supported Amidate Ligands: Synthesis, Fluorescence, and Catalytic Activity

Zn(II) complexes of N-(quinolin-8-yl)picolinamide (HL1) (1) and N2,N6-di(quinolin-8-yl)pyridine-2,6-dicarboxamide (H2L2) (2) have been synthesized by deprotonation of the ligands and characterized by IR, NMR, and Single crystal X-ray crystallography. The mononuclear [Zn(L1)2] (3) and homodinuclear [Zn2(L2)2] (4) complexes are characterized by distorted octahedral geometries stabilized by hydrogen bonding and weak π···π interaction. The complexes demonstrate intense fluorescence bands in comparison with their corresponding ligands with well-distinguished intensity. The complexes act as efficient catalysts in various transesterification reactions. Among those, the best results have been achieved with complex 3 in conversion of 4-nitrophenylacetate into methyl acetate within 3 h.

Oxophosphoryl Complexes of Dipyrrin: Spectral and Aggregation Characteristics of Solutions and Thin Films

The spectral characteristics of a compound representing a new class of organic luminescent materials—dipyrrin oxophosphoryl complex (PODIPY)—in organic solvents and thin films have been investigated. The compound under study exhibits high-intensity fluorescence in solutions, which is preserved when passing to thin films obtained by layer-by-layer deposition onto a substrate using the Langmuir–Schaeffer technique. PODIPY is characterized by has bright solvatochromic fluorescence, which is related to the redistribution of the intensities of absorption and fluorescence bands and their shift. This effect originates from the specific solvation of PODIPY with partition of the oxygen atoms of oxophosphoryl group. A transition from solutions to films and an increase in the number of transfers lead to the fluorescence quenching without the formation of G aggregates in the film.

Influence of Yb2O3 on the 1.53 μm spectroscopic properties in Er3+/Ce3+ co-doped TeO2-WO3-Na2O-Nb2O5 glasses

The Yb2O3 component was introduced into the Er3+/Ce3+ co-doped tellurite glasses with the composition of TeO2-WO3-Na2O-Nb2O5 to study the effect of Yb3+ on the 1.53 μm spectroscopic properties of Er3+. The X-ray diffraction (XRD) curve and Raman spectrum were measured to investigate the structure nature of synthesized tellurite glasses. The absorption spectrum, upconversion emission spectrum and fluorescence spectrum were measured to evaluate the improved effect of Yb3+ concentration on the 1.53 μm band fluorescence of Er3+. Results of the measured 1.53 μm band fluorescence intensity show a significant improvement with the increase of Yb3+ concentration, while the total quantum efficiency reveals a similar increasing trend. The results of the present work indicate that Er3+/Ce3+/Yb3+ tri-doped tellurite glass has good prospect as a promising gain medium applied for the 1.53 μm broadband amplifier.

SYNTHESIS AND OPTICAL PROPERTIES OF MESOMORPHIC GLASSY NANOCOMPOSITES BASED ON CADMIUM CAPRYLATE WITH CdSe / ZnS HETERONANOPARTICLES

The paper presents on the synthesis and optical properties of mesomorphic composites, based on a glassy liquid-crystalline caprylate matrix, with CdSе/ZnS hetero-nanoparticles. The synthesis of complex core-shell semiconductor nanoparticles was carried out by fusing together a cadmium caprylate composite with CdSе nanoparticles and zinc caprylate composite with ZnS nanoparticles. The cadmium and zinc chalcogenide nanoparticles have been synthesized in molten cadmium caprylate and zinc caprylate respectively.&#x0D; It has been found by optical spectroscopy that the have hetero-nanoparticles a core-shell structure. The effect of the composition (molar ratio of the components) of CdSе/ZnS hetero-nanoparticles on their spectral characteristics has been studied. It has been shown that the nanocomposites with hetero-nanoparticles are characterized by a more intense exciton fluorescence band than composites with individual CdSе or ZnS nanoparticles. It has been found that by varying the hetero-nanoparticle composition, one can change the core-shell thickness ratio and adjust thereby the absorption and emission band edge. As the number of ZnS nanoparticles in CdSе/ZnS hetero-nanoparticles increases some narrowing of the long- wavelength emission region first takes plase, which may be attributed to a reduction in the recombination of the smaller number of surface trapped exciton, and then, at a large ZnS content, a broadening of the long- wavelength emission region takes plase due to the extended CdSе/ZnS surface.&#x0D; It has been found that the main contribution to the exciton fluorescence of nanocomposites with CdSе/ZnS hetero-nanoparticles is made by cadmium selenide nanoparticles, and that zinc sulfide nanoparticles enhance exciton fluorescence, also due to decrease in surface emission. It has been shown that the nanocomposites with hetero-nanoparticles are characterized by a more intense exciton fluorescence band that the nanocomposites with individual CdSе. The highest emission is observed in the case of the 35-55 % ZnS content of the shell, and at a smaller or larger amount of ZnS, emission intensity decreases.&#x0D;

Non-destructive Phenotyping of Chili Pepper Ripening Using Spectroscopic Probes: A Potential Approach for Shelf-Life Measurement

This study explores the application of spectroscopic techniques (laser induced fluorescence, Raman and attenuated total reflectance Fourier transform infrared) coupled with principal component analysis for the nondestructive, extraction free and rapid evaluation of biochemical changes associated with ripening of chili peppers at four stages (mature, pre-ripe, ripe and post-ripe). The analysis of the fluorescence spectra of the exocarp of chili pepper shows a decrease in the intensity of chlorophyll bands at 685 and 735 nm and an increase in the intensity of carotenoid fluorescence bands at 490–500 nm and 565–580 nm with progress in the ripening stages. These changes are regarded to be significant phenotypic markers for the ripening of chili peppers. The observed changes in the position of carotenoid bands in Raman spectra at 1004, 1156, 1188, and 1524 cm−1 with increase in their intensity indicating the accumulation of carotenoids and change in the carotenoid composition from β-carotene in the mature chilis to capsanthin in the ripe chilis. In addition, the infrared spectra show changes in the carbohydrates, amide II, amide I and cutin at various stages of ripening. Also, the variation in the position of pectin bands indicates change in its molecular mass with decreasing content. The determined spectral signatures can be used as biomolecular index for effective monitoring of the ripening of chili peppers. The commercial application of noninvasive spectroscopic probes will be advantageous for the phenotyping of economically important plant parts, screening, grading, shelf life estimation and quality standardization.