Variation Of Fluorescence Intensity Research Articles

Preparation of Ho3+/Tm3+ Co-doped Lanthanum Tungsten Germanium Tellurite Glass Fiber and Its Laser Performance for 2.0\u2009\u03bcm

Ho3+/Tm3+ co-doped 50TeO2-25GeO2-3WO3-5La2O3-3Nb2O5-5Li2O-9BaF2 glass fiber is prepared with the rod-tube drawing method of 15 μm core diameter and 125 μm inner cladding diameter applied in the 2.0 μm-infrared laser. The 2.0 μm luminescence properties of the core glass are researched and the fluorescence intensity variation for different Tm3+ doping concentration is systematically analyzed. The results show that the 2.0 μm luminescence of Ho3+ is greatly influenced by the doping concentration ratio of Ho3+ to Tm3+ and that the maximum fluorescence intensity of the core glass can be obtained and its emission cross section can reach 0.933 × 10−21 cm2 when the sensitized proportion of holmium to thulium is 0.3 to 0.7 (mol%). Simultaneously, the maximum phonon energy of the core glass sample is 753 cm−1, which is significantly lower than that of silicate, gallate and germanate glass and the smaller matrix phonon energy can be conductive to the increase 2.0 μm-band emission intensity. The continuous laser with the maximum laser output power of 0.993 W and 2051 nm -wavelength of 31.9%-slope efficiency is output within the 0.5 m glass fiber and the experiment adopts 1560 nm erbium-doped fiber laser(EDFL) as the pump source and the self-built all-fiber laser. Therefore, the glass fiber has excellent laser characteristics and it is suitable for the 2.0 μm-band laser.

The Possible Influences of the 2012 Modena Earthquakes on the Fluorescence Spectra of Bottled Mineral Water

Two moderate earthquakes with magnitudes of 6.0 and 5.8 occurred in active tectonic crustal structures of the Po Plain in the area of Modena City in Northern Italy. These events generated temporary and/or permanent environmental changes with much damage, leading to 27 deaths. These quakes occurred on May 20, 2012, at 02:03 UTC, and on May 29, 2012, at 07:00 UTC, at depths of 5.5 and 10.1 km, respectively. In order to investigate for effects from the earthquakes on the fluorescence spectra and ion composition of groundwater within the affected area, available mineral water bottled prior to and post the two shocks were collected. Specifically, the regular production lines at the bottling plants of the brands Lieta, Ventasso, Cerelia and Monte Cimone situated in the nearest Appennine chain, contributed to this study. These bottled waters where analyzed for their fluorescence spectra using the synchronous scanning method. Variations of fluorescence intensity a month before the first earthquake of May 20, 2012, appeared to be significant only at Monte Cimone spring, where high density water samples were available. Likewise, variations in ion compositions evidenced peaks at a month before the first earthquake and a month after the second one. pH and conductivity levels of only some springs also shown significant variations at a month before the first earthquake. These findings suggest that a realization of continuous measurement networks in areas prone to incidences by strong earthquakes could be useful for investigating any possible influence of earthquakes on water geochemistry.

Simultaneous monitoring of oxygen consumption and acidification rates of a single zebrafish embryo during embryonic development within a microfluidic device

A microfluidic device with a light modulation system was developed to simultaneously measure the oxygen consumption rate (OCR) and acid extrusion rate (AER) of a single zebrafish embryo during embryonic development. The device combines two components: an array of acrylic microwells containing two sensing layers as the dual luminescent sensor for oxygen (O2) and acid (pH) detection, and a microfluidic module with pneumatically actuated glass lids to controllably seal the microwells. The continuous blue LED and modulated UV LED lights were simultaneously used to excite the dual luminescent sensor, with the emission detected by a single photodetector. The detection signals were then split into DC and AC components to measure the time variations in fluorescence intensity and phosphorescence lifetime for pH and O2 detection, respectively. We have successfully measured the OCR and AER of a single developing zebrafish embryo inside a sealed microwell from the blastula stage (3 h post-fertilization, 3 hpf) through the hatching stage of 48 hpf. We also demonstrated the measurement of the OCR and AER of a single 48 hpf zebrafish that experienced acute hypoxia by using our device to monitor the transition between aerobic and anaerobic metabolism. We observed that the AER began to significantly increase, while the OCR rapidly decreased after 20 min of hypoxia, indicating the time point of transition where the non-mitochondrial metabolism subsequently dominated the energy production. Our proposed methodology provides the potential for studying the bioenergetic metabolism in a developing organism that relates mitochondrial physiology and disease.

Cementum structure in Beluga whale teeth.

Cementum is an important tooth tissue to which the periodontal ligaments attach and consists primarily of carbonated apatite mineral and collagen. In optical microscopy of cementum thin sections, light/dark bands are formed annually, and age at death is determined by counting these bands. We employ synchrotron X-ray diffraction and X-ray fluorescence mapping to show the bands in Beluga whale cementum result from differences in mineral content and not from differences in collagen orientation as was concluded by others. Variation in Zn fluorescent intensity was found to be very sensitive indicator of changing biomineralization and suggest that Zn plays an important role this process.

Factors affecting interactions between sulphonate-terminated dendrimers and proteins: A three case study

This work proposes a deep study on the interactions between sulphonate-terminated carbosilane dendrimers and proteins. Three different proteins with different molecular weights and isoelectric points were employed and different pHs, dendrimer concentrations and generations were tested. Variations in fluorescence intensity and emission wavelength were used as protein-dendrimer interaction probes. Interaction between dendrimers and proteins greatly depended on the protein itself and pH. Other important issues were the dendrimer concentration and generation. Protein-dendrimer interactions were favored under acidic working conditions when proteins were positively charged. Moreover, in general, high dendrimer generations promoted these interactions. Modeling of protein-dendrimer interactions allowed to understand the different behaviors observed for every protein.

Interaction of curcumin with 1,2-dioctadecanoyl-sn-glycero-3-phosphocholine liposomes: Intercalation of rhamnolipids enhances membrane fluidity, permeability and stability of drug molecule

Stability of curcumin in neutral and alkaline buffer conditions has been a serious concern for its medicinal applications. We demonstrate that the stability of curucmin can be improved in 1,2-Dioctadecanoyl-sn-glycero-3-phosphocholine (DSPC) liposomes. Curcumin strongly partition into liquid crystalline phase compared to solid gel phase of DSPC liposomes. Variation of fluorescence intensity of curcumin associated with liposomes with temperature successfully determines phase transition temperature of DSPC liposomes. However, at higher molar ratio curcumin can influence phase transition temperature by intercalating into deep hydrophobic layer of liposomes and facilitating fusion of two membrane phases. Rhamnolipids (RLs) are recently being applied for various biomedical applications. Here, we have explored new insight on intercalation of rhamnolipids with DSPC liposomes. Intercalation of rhamnolipids exceptionally increases partition of curcumin into solid gel phase of DSPC liposomes, whereas this increase is moderate in liquid crystalline phase. Fluorescence quenching study establishes that permeability and fluidity of the DSPC liposomes are enhanced in the presence of RLs. Membrane permeability and fluidity can be improved further by increasing the percentage of RLs in DSPC liposomes. The phase transition temperature of DSPC liposomes decreases with increase in percentage of RLs in DSPC liposomes by encouraging fusion between solid gel and liquid crystalline phases. Intercalation of RLs is found to further boost stability of drug, curcumin, in DSPC liposomes. Thus, mixing RLs with DSPC liposomes could potentially serve as a good candidate for drug delivery application.

Observing the Heterogeneous Electro-redox of Individual Single-Layer Graphene Sheets.

Electro-redox-induced heterogeneous fluorescence of an individual single-layer graphene sheet was observed in real time by a total internal reflection fluorescence microscope. It was found that the fluorescence intensity of an individual sheet can be tuned reversibly by applying periodic voltages to control the redox degree of graphene sheets. Accordingly, the oxidation and reduction kinetics of an individual single-layer graphene sheet was studied at different voltages. The electro-redox-induced reversible variation of fluorescence intensity of individual sheets indicates a reversible band gap tuning strategy. Furthermore, correlation analysis of redox rate constants on individual graphene sheets revealed a redox-induced spatiotemporal heterogeneity or dynamics of graphene sheets. The observed controllable redox kinetics can rationally guide the precise band gap tuning of individual graphene sheets and then help their extensive applications in optoelectronics and devices for renewable energy.

Red emission fluorescent probes for visualization of monoamine oxidase in living cells.

Here we report two novel red emission fluorescent probes for the highly sensitive and selective detection of monoamine oxidase (MAO) with large Stokes shift (227 nm). Both of the probes possess solid state fluorescence and can accomplish the identification of MAO on test papers. The probe MAO-Red-1 exhibited a detection limit down to 1.2 μg mL−1 towards MAO-B. Moreover, the cleavage product was unequivocally conformedby HPLC and LCMS and the result was in accordance with the proposed oxidative deamination mechanism. The excellent photostability of MAO-Red-1 was proved both in vitro and in vivo through fluorescent kinetic experiment and laser exposure experiment of confocal microscopy, respectively. Intracellular experiments also confirmed the low cytotoxity and exceptional cell imaging abilities of MAO-Red-1. It was validated both in HeLa and HepG2 cells that MAO-Red-1 was capable of reporting MAO activity through the variation of fluorescence intensity.

Exploring the Transition of Human α-Synuclein from Native to the Fibrillar State: Insights into the Pathogenesis of Parkinson's Disease.

The etiology of Parkinson's disease involves the interplay between the environmental and genetic factors. Here in this study human α-synuclein upon exposure to 100μM pendimethalin for 12h in vitro passes through a partially folded state which proceeds to the aggregated state and terminally ends in the fibrillar phase. Variations in the ANS fluorescence intensities led to the detection of intermediate and aggregated states at 6 and 10h respectively. Far-UV CD analysis depicted significant α-helical content for intermediate state at 6h in presence of 100μM pendimethalin. Further increasing the incubation time to 12h resulted in a predominant β-sheet content which was confirmed to be fibrillar by TEM. Turbidity, Rayleigh scattering analysis, Congo red assay and ThT measurements supported the TEM data i.e. the formation of fibrillar structure of human α-synuclein upon 12h incubation. Thus, our observation could suggest a possible underlying molecular basis for Parkinson's disease. Graphical Abstract Schematic elucidation of the factors involved in the fibrillation of α-Synuclein during Parkinson's pathogenesis.

Molecular level investigation on the interaction of pluronic F127 and human intestinal bile salts using excited state prototropism of 1-naphthol

Pluronic F127 (PF127), a surfactant polymer is used as a drug delivery system and has been introduced recently in the food research to delay lipid digestion process. In this context study the interaction of this polymer with human intestinal bile salts assumes important. The studies involving interaction of PF127 with human intestinal bile salts sodium taurocholic acid (NaTC) and sodium cholate acid (NaC) by using differential scanning calorimetry (DSC) and 1-naphthol as a fluorescent molecular probe show that the bile salts induce decrease of sol–gel phase transition temperature of the PF127 to lower temperature, from ~21°C to ~18°C. Variation of neutral form fluorescence intensity of 1-naphthol with bile salts in water confirmed efficient micellar aggregation with critical micellar concentration (CMC) values of 12.6mM for NaTC and 12.7mM for NaC. Fluorescence parameters like fluorescence intensity and fluorescence lifetime of the two excited state prototropic forms {neutral form emission (λem=370nm), anion form emission (λem=470nm)} of 1-naphthol suggested that the NaTC (below critical micellar concentration 12mM) and NaC (above critical micellar concentration 12mM) induce appreciable dehydration of the hydrophilic corona as well as core region PF127 hydrogel. The micropolarity of the hydrogel microenvironment decreases with increase in concentration of both the bile salts.

Self-Assembly and Visualization of Poly(3-hexyl-thiophene) Chain Alignment along Boron Nitride Nanotubes

Boron nitride nanotubes (BNNTs) were noncovalently functionalized with poly(3-hexyl-thiophene) (P3HT) to produce stable suspensions. The conjugated polymer and BNNTs interact via π–π stacking, and the resulting self-assembly of regiorandom P3HT on the BNNT surface is immediately evident through a color change and the appearance of a partially resolved absorption band. By employing polarized excitation fluorescence microscopy, we directly visualized the polymer-functionalized BNNTs and determined the conformation of the polymer on BNNT surfaces. Variation of fluorescence intensity with linear polarization direction showed conclusively that the P3HT chains were always aligned parallel to the BNNT long axis.

A new fluorescence index with a fluorescence excitation-emission matrix for dissolved organic matter (DOM) characterization

A series of fluorescence approaches have been employed to characterize the composition, transformation, and biogeochemical cycles of aquatic dissolved organic matter (DOM). However, there is no consensus on the protocols for elucidating DOM fluorescence spectra from protein-like (young DOM) to humic-like (old DOM) types, which are associated with the intrinsic fluorescence properties involved in the excitation/emission and detection of DOM. The central objective of this study was to evaluate the excitation–emissions matrices (EEMs)-average area of fluorescence intensity response using DOM fluorescence spectra collected on six different DOM surrogates using high-performance size-exclusion chromatography techniques. We evaluated criteria and protocols of a new Y fluorescence index (YFI) for comparison with McKnight fluorescence index (MFI), in which 280nm excitation coincides with independent inferences with response to emission wavelengths from 350 to 450 nm. Our results demonstrate that YFI had sufficient distinguishing power to evaluate the characteristics of organic matter, including protein- and humic-type substances under various solution conditions. In addition, the YFI has good selectivity by showing its distinct signatures at better resolution of fluorescence intensity and little variation in different solutions including wastewater effluent-derived surface water. Although MFI has the advantage of fulvic acid-oriented correction, it revealed with a narrow spectral overlap range of 0.84–2.14 for DOM characterization of Suwannee River Humic Acid (SRHA), neomycin trisulphate salt hydrate (NTH), and bovine serum albumin (BSA). This narrow range of FI for DOM surrogate was improved with YFI, implying that all NOM substances fluoresce with considerable proportional ranges of 0.30–6.41. Our results suggest that the YFI values of the DOM surrogate data-set of fluorescence EEMs are likely proportionally lower FI of pahokee peat HA and leonardite HA relative to elliott soil HA, SRHA, and SRFA, while those of NTH, Streptomycin sesquisulfate hydrate, L-tyrosine, L-tryptophan, and BSA are higher FI.

Polarization modulation of two-photon excited fluorescence in a V-shaped dipicolinate-triphenylamine compound.

Polarization modulation of two-photon excited fluorescence in a V-shaped dipicolinate-triphenylamine compound was investigated with 100 fs 800 nm laser pulses. The peak fluorescence intensity versus the input irradiance was measured to meet a square dependence, which offered evidence for two-photon excited fluorescence. The variations of the two-photon excited fluorescence intensity showed strong response to the different polarized incident lights and were tightly dependent on the linearly polarized component of the incident light. Furthermore, the polarization modulation efficiency of the two-photon excited fluorescence had an obvious concentration dependence when the concentration of solution was under 2.5×10(-4) mol/L. The enhancement of modulation efficiency was attributed to the concentration dependence of the two-photon absorption cross section.

Van der Waals-Induced Chromatic Shifts in Hydrogen-Bonded Two-Dimensional Porphyrin Arrays on Boron Nitride.

The fluorescence of a two-dimensional supramolecular network of 5,10,15,20-tetrakis(4-carboxylphenyl)porphyrin (TCPP) adsorbed on hexagonal boron nitride (hBN) is red-shifted due to, primarily, adsorbate-substrate van der Waals interactions. TCPP is deposited from solution on hBN and forms faceted islands with typical dimensions of 100 nm and either square or hexagonal symmetry. The molecular arrangement is stabilized by in-plane hydrogen bonding as determined by a combination of molecular-resolution atomic force microscopy performed under ambient conditions and density functional theory; a similar structure is observed on MoS2 and graphite. The fluorescence spectra of submonolayers of TCPP on hBN are red-shifted by ∼30 nm due to the distortion of the molecule arising from van der Waals interactions, in agreement with time-dependent density functional theory calculations. Fluorescence intensity variations are observed due to coherent partial reflections at the hBN interface, implying that such hybrid structures have potential in photonic applications.

High-Throughput Contact Flow Lithography.

High-throughput fabrication of graphically encoded hydrogel microparticles is achieved by combining flow contact lithography in a multichannel microfluidic device and a high capacity 25 mm LED UV source. Production rates of chemically homogeneous particles are improved by two orders of magnitude. Additionally, the custom-built contact lithography instrument provides an affordable solution for patterning complex microstructures on surfaces.

Epi‐fluorescence Microscopy as a Tool for Relative Quantification of the Anti‐Biofouling Character of Atmospheric Pressure Plasma‐Polymerized Biomaterials

This study deals with the development of an original epi‐fluorescence‐based protocol to evaluate the anti‐biofouling character of atmospheric pressure plasma‐polymerized poly(ethylene glycol) samples. In this work, fluorescence microscopy is considered as an alternative to XPS for the evaluation of protein adsorption. The full set of samples is tested before and after bovine serum albumin‐fluorescein isothiocyanate treatment. It appears that their anti‐biofouling property, expressed by the variation of fluorescence intensity, is reduced when the power of the discharge is increased. The reproducibility of the experiments and the relatively high sensitivity of the proposed method are underlined.

Fluorescence properties of Schiff base – N,N′-bis(salicylidene) – 1,2-Phenylenediamine in presence of bile acid host

Fluorescence properties of Schiff base – N,N′-bis(salicylidene) – 1,2-phenylenediamine (LH2) is used to study the micelles formed by aggregation of different important bile acids like cholic acid, deoxycholic acid, chenodeoxycholic acid and glycocholic acid by steady state and picosecond time-resolved fluorescence spectroscopy. The fluorescence band intensity was found out to increase with concomitant red shift with gradual addition of different bile acids. Binding constant of the probe with different bile acids as well as critical micelle concentration was obtained from the variation of fluorescence intensity on increasing concentration of bile acids in the medium. The increase in fluorescence quantum yields, fluorescence decay times and substantial decrease in nonradiative decay rate constants in bile acids micellar environment points to the restricted motion of the fluorophore inside the micellar subdomains.

Fluorescence and room temperature activity of Y₂O₃:(Eu³⁺,Au³⁺)/palygorskite nanocomposite.

The fluorescence and room temperature activity of a palygorskite supported Y2O3:(Eu(3+),Au(3+)) nanocomposite were investigated to design a fluorescence-indicated catalyst. The effects of Au(3+) doping on the structure and surface properties of the host material were systematically characterized. The fluorescence intensity of Y2O3:Eu(3+) was affected by Au(3+) doping, which was related to the crystallinity of Y2O3. Excess Au(3+) ions were segregated to the host surface and reduced to metallic Au. The local symmetry of Eu(3+) was reduced by Au(3+) doping, which benefited the energy transfer between Eu(3+) and Au(3+). Energy absorbed by Eu(3+) was transferred from Au(3+) to metallic Au, where electrons were produced. These electrons were absorbed by O2 to change into O2(-), which acted as the oxidant for ortho-dichlorobenzene (o-DCB). The variation of fluorescence intensity during the catalytic reaction was observed. The room temperature catalytic activity of the nanocomposite under UV irradiation was revealed. The as-synthesized nanocomposite might have potential applications in environmental fields.

Fluorescent nanothermometers based on mixed shell carbon nanodots

Nanothermometers composed of a carbon nanodot core and thermo-sensitive polymeric mixed shell are prepared. Solution temperature can be traced through monitoring the fluorescence intensity variation of carbon nanodot.

PH-sensitive carbon dots for the visualization of regulation of intracellular pH inside living pathogenic fungal cells

In this paper, the pH-sensitive carbon dots were synthesized by simple one-pot hydrothermal treatment of threonine. The fluorescence of the as-synthesized carbon dots was featured by pH dependence, with the intensity decreasing as pH increases. The carbon dots can be readily internalized into plant pathogenic fungal cells for imaging with dose dependence. Moreover, intracellular pH regulation, a kind of physiological functions of living fungal cells, was visually expressed as the variation of fluorescence intensity of the internalized carbon dots. A transient reduction of the intracellular pH tightly regulated by living fungal cells under basic external condition can be presented as a gradual increase in fluorescence intensity of the carbon dots. On the contrary, the fluorescence of the carbon dots distributed in apple tissue infected by the fungal cells was soon quenched by the basic buffer because there was no intracellular pH regulation in the dead cells.