Fluorescence Anisotropy Studies on Bodipy (Pyrromethene 546) Dye as a Novel Thermal Probe

Journal of Fluorescence - In the present work, fluorescence anisotropy studies of BODIPY (pyrromethene 546 or C14H17BF2N2) dye have been performed and found that it has a potential to be used as a...     

A composite (stacked) picture generation technique for spectral profile representation of dye laser

In this paper, a new technique for data representation format from video recording of spectral profile of tunable dye laser has been formulated. Only a part of the acquired images acquired sequentially in programmed time interval, was used to make the composite picture to measure variation of the parameters. A CCD camera based imaging system was used to confine the spectral pattern. No additional hardware other than image capturing device was used. The technique developed reduces the storage space required in the computer and also enhances the measurement speed significantly. The software algorithm developed has been used effectively to measure various parameters of tunable dye lasers and other optical sources.     

Hydrophobic Interactions in Donor-Disulphide-Acceptor (DSSA) Probes Looking Beyond Fluorescence Resonance Energy Transfer Theory

Donor –linker –acceptor (DSSA) is a concept in fluorescence chemistry with acceptor being a fluorescent compound (FRET) or quencher. The DSSA probes used to measure thiol levels in vitro and in vivo. The reduction potential of these dyes are in the range of ?0.60 V, much lower than the best thiol reductant reported in literature, the DTT (?0.33 V). DSSA disulphide having an unusually low reduction potential compared to the typical thiol reductants is a puzzle. Secondly, DSSA probes have a cyclized rhodamine ring as acceptor which does not have any spectral overlap with fluorescein, but quenches its absorbance and fluorescence. To understand the structural features of DSSA probes, we have synthesized DSSANa and DSSAOr. The calculated reduction potential of these dyes suggest that DSSA probes have an alternate mechanism from the FRET based quenching, namely hydrophobic interaction or dye to dye quenching. The standard reduction potential change with increasing complexity and steric hindrance of the molecule is small, suggesting that ultra- low Eo’ has no contribution from the disulphide linker and is based on structural interactions between fluorescein and cyclized rhodamine. Our results help to understand the DSSA probe quenching mechanism and provide ways to design fluorescent probes.     

Photophysical and Electrochemical Studies of 4-Dicyanomethylene 2,6-Dimethyl-4H-Pyran (DDP) Dye with Amides in Water

Photophysical and electrochemical studies of DDP dye with Formamide and alkyl substituted amides were carried out in water. Addition of Formamide (F), Acetamide (ACM), N,N-Dimethylformamide (DMF), Dimethylacetamide (DMAC) to DDP dye result in an isosbestic point. A fluorescence enhancement of DDP dye is observed on the addition of amides. Apart from the fluorescence enhancement, the addition of formamide result in no significant shift in the position of emission maxima of DDP dye whereas addition of ACM and DMF result in a shift towards the blue and red region respectively. DDP dye exhibits three lifetime components which are unique in lifetime and amplitude. The fluorescence lifetime and relative amplitude of DDP dye varies significantly by addition of amides in aqueous solution which are influenced by amidewater hydrogen-bonding network and hydrophobic influences of the alkyl substituted amides. The nature of interaction between dye and amide be predominantly through hydrogen-bonding wherein the carbonyl oxygen (C=O) of amides are bonded to N-H hydrogen of DDP dye through water molecule. The existence of more than one microenvironment of DDP dye in aqueous phase is elucidated by Electrochemical Impedence Spectroscopy (EIS) through Nyquist plots wherein it signifies that there exist at least three different micro environments which support the existence of different fluorescence lifetimes. Fluorescence spectral technique is used as an efficient tool to elucidate the nature of interaction of water soluble probe with hydrogen-bonding solutes is established in our studies.     

Angularly resolved coherent Raman spectroscopy (ARCS)

This new crossed beam configuration produces an angularly separated Coherent Anti-Stokes Raman spectrum, eliminating the need for a spectrometer. Since one of the driving laser beams is always linearly opposed to the dye laser, it may also be used as a dye pump and the experiment performed within the dye cavity for efficient laser energy utilization. With this arrangement, a broad bandwidth dye laser produces a several wavenumber resolution spectrum from a small volume with relatively simple alignment. The spectrum is scanned by varying the incidence angle of the probe beam or taken is a single pulse using a fan shaped probe beam.     

Effect of dye dopants in poly(methylphenyl silane) light-emitting devices

To investigate the inter-molecular energy transfer between polysilane and dye dopants, poly(methylphenylsilane)(PMPS) was used as a host material and perylene as the blue dopant. The structure of the devices is indium–tin oxide (ITO)/PEDOT:PSS(30 nm)/PMPS:perylene(dye dopant 0.1–1.0 mol%)(60 nm)/Alq₃(20 nm)/LiF(0.5 nm)/Al(100 nm). Poly(3,4-ethylenedioxythiophene) (PEDOT):poly(4-styrenesulfonate) (PSS) is used as a buffer layer, tris(8-hydroxyquinoline)aluminum (Alq₃) as hole transporting layer, LiF as hole injection layer. The device shows a luminance 810 cd/m² at current density of 28 mA/cm², luminous efficiency of 0.14 lm/W. The external quantum efficiency (EQE) is about 0.5% and EQE increased up to 0.52% by doping with single wall carbon nanotubes (SWNT) into the emissive layer. We found an efficient inter-molecular energy transfer from polysilane to dye dopants. Furthermore, using the polysilane and energy-matched dye dopants enable to fabricate the electroluminescence devices through wet processes.     

异核Na(3P)+Cs(6P)系统的碰撞能量合并

置于同一池中的钠原子和铯原子,分别被连续染料激光器和铯光谱灯激发到Na(3P),Cs(6P),Na(3P)原子密度由吸收等效宽度技术来测定。利用调制技术,分离出了由异核碰撞产生的荧光光谱。观察到了Na(3P)和Cs(6P)间的碰撞能量合并现象,并测定了其碰撞截面。 关键词：     

Determination of Poly (Diallyldimethylammonium Chloride ) via Spectrophotometric Titration with Coomassie Brilliant Blue G Dye

Poly(diallyldimethylammonium chloride) (PDDA) is used as organic coagulant in water purification and auxiliary agent in paper production. Determination of PDDA in aqueous solutions is carried out usually by means of polyelectrolyte titration using streaming current detector or o-Toluidine Blue dye for endpoint recognition. The proposed method of PDDA assay takes advantage of Coomassie Brilliant Blue G dye having strong affinity to cationic macromolecules. Titration of PDDA solution with the dye is carried out measuring absorbance at 585 nm. Inflection points of the obtained zigzag photometric curves have good repeatability provided that titration rate is low enough to attain endpoint for 1 hour or more. The method assures rectilinear calibration (R2=0.999 5) in the broad range of PDDA concentrations from 0.3 to 9.6 mg·dm-3.     

Analysis of living cells grown on different titanium surfaces by time-lapse confocal microscopy

In this study we have combined fluorescence- and reflection-confocal laser scanning microscopy for the simultaneous visualization of living cells and surface topography beneath them. To this purpose we have designed a specific flow chamber and we have tested it with osteoblasts grown on an opaque, thick support, made of smooth or sandblasted titanium. Cells were loaded with Calcein-AM or tetramethylrhodamine methyl ester (TMRM), two probes employed as indicators of cell viability/morphology and mitochondrial membrane potential, respectively. Besides the acquisition of stacks of confocal sections, the system allowed also vertical views and faithful three-dimensional reconstruction of the samples. Confocal microscope implemented with our flow chamber proved to be a promising tool for time-lapse investigation of cell-biomaterial interactions.     

Er0.1La0.9P5O14非晶的双光子上转换发光

本文研究了全浓度ＥｒＬａＰ５Ｏ１４非晶在波长λ为６４９．０ｎｍ脉冲染料激光激发下的上转换发光现象，并对其进行了简要的分析。     

Quantum-chemical study of structure and spectral properties of triphenylamine-rhodanine dye 2-(5-(4-(diphenylamine)benzylidene)-4-oxo-2-thioxothiazolidine-3-yl) acetic acid

The structure and optical properties of triphenylamine-rhodanine dye 2-(5-(4-(diphenylamine)benzylidene)-4-oxo-2-thioxothiazolidine-3-yl) acetic acid, which is used as a sensitizer for nanocrystalline TiO₂ solar cells, are studied based on the density functional theory. The nature of the absorption of this dye in the visible and near UV regions is discussed within the time-dependent density functional theory (TDDFT). The calculations of the vertical excitation energies of the dye molecule taking into account the effect of solvent reveal a strong positive solvatochromic effect compared to the calculations in the vacuum approximation. The IR absorption bands of this dye in the region of 600–1850 cm⁻¹ are completely interpreted.     

Single-Pair Fluorescence Resonance Energy Transfer (spFRET) for the High Sensitivity Analysis of Low-Abundance Proteins Using Aptamers as Molecular Recognition Elements

We have developed a strategy for the detection of single protein molecules, which uses single-pair fluorescence resonance energy transfer (spFRET) as the readout modality and provides exquisite analytical sensitivity and reduced assay turn-around-time by eliminating various sample pre-processing steps. The single-protein detection assay uses two independent aptamer recognition events to form an assembly conducive to intramolecular hybridization of oligonucleotide complements that are tethered to the aptamers. This hybridization brings a donor-acceptor pair within the Förster distance to create a fluorescence signature indicative of the presence of the protein-aptamer(s) association complex. As an example of spFRET, we demonstrate the technique for the analysis of serum thrombin. The assay requires co-association of two distinct epitope-binding aptamers, each of which is labeled with a donor or acceptor fluorescent dye (Cy3 or Cy5, respectively) to produce a FRET response. The FRET response between Cy3 and Cy5 was monitored by single-molecule photon-burst detection, which provides high analytical sensitivity when the number of single-molecule events is plotted versus the target concentration. We are able to identify thrombin with high efficiency based on photon burst events transduced in the Cy5 detection channel. We also demonstrate that the technique can discriminate thrombin molecules from its analogue prothrombin. The analytical sensitivity was >200-fold better than an ensemble measurement.     

A Study of Parameters that Influence the Accuracy of the Planar Droplet Sizing (PDS) Technique

A combined theoretical and experimental study of the parameters affecting the accuracy of Planar Droplet Sizing (PDS) measurements is presented. The principle of the PDS technique relies on the assumption that the intensity emitted by a fluorescent dye added to a liquid is proportional to the volume of a resulting droplet during atomisation and that the scattered light intensity is proportional to its surface area, allowing measurement of Sauter Mean Diameter (SMD) by taking the ratio of these intensities. A geometrical optics light scattering approach was extended to calculate the fluorescence intensity emitted by a droplet, in addition to providing the scattered light intensity integrated over the collection aperture. The theoretical approach quantified the influences of scattering angle, refractive index, droplet size and dye concentration on the PDS technique. Experiments with monodisperse droplet streams confirmed the calculations in terms of dependence of the scattered and fluorescence intensities. The limitations of the technique have been established together with an appropriate calibration procedure for application in dense sprays.     

Analysis of interaction between the organic dye methylene blue and the surface of AgCl(I) microcrystals

We have used IR spectroscopy to study the nature of interaction between molecules of the organic dye methylene blue (MB) and the surface of AgCl(I) microcrystals. We recorded the IR absorption spectra of the organic dye methylene blue in the gas phase, adsorbed on the surface of AgCl(I) microcrystals, and also in the form of crystal hydrates. The results obtained allowed us to hypothesize that unsaturated dimethylamino groups and the sulfur atom in the heterocycle of this dye are the most active in the interaction between methylene blue molecules and the surface of AgCl(I) microcrystals. With the help of IR spectra of methylene blue crystal hydrates, we confirmed the significant role of OH groups during adsorption of molecules on the surface of AgCl(I) microcrystals. We suggest the possibility of formation of hydrogen bonds between the anions of the crystal lattice and the unsaturated dimethylamino groups as well as the sulfur atoms in the heterocycle, by formation of hydrogen bonds with the OH groups. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 6, pp. 731–737, November–December, 2007.     

Thermoluminescence of the blue light-emitting system based on poly(9-vinylcarbazole) doped with a pyrazoloquinoline dye

We have investigated the charge carrier trapping and recombination mechanisms in electroluminescent systems based on poly(9-vinylcarbazole)/2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole blend, used as the matrix, and the deep blue light-emitting pyrazoloquinoline dye-1-H-pyrazolo[3,4-b]quinoline (PAQ8) dopant. The thermoluminescence studies have shown that the charge carrier trapping occurs on the dye molecules as well as on the matrix components. The traps localized on the PAQ8 molecules compete with the others available in the system, however at higher concentrations of the dye a role of these traps increases. Spectral analyses of the thermoluminescence have indicated that even at low concentration of PAQ8, the dye molecules constitute the dominating recombination centres in the system.     

Pyrocatechol as a surface capping molecule on rutile TiO2 (110)

A ‘cap and dip’ method of adsorbing ruthenium di-2,2′-bipyridyl-4,4′-dicarboxylic acid diisocyanate (N3 dye) on a rutile TiO₂ (110) surface was investigated using pyrocatechol as a capping molecule. This method involves cleaning the rutile surface in ultra-high vacuum (UHV), depositing pyrocatechol onto the surface to ‘cap’ the adsorption sites, removing from vacuum, ‘dipping’ in an N3 dye solution and returning to vacuum. Photoemission measurements following the return of the crystal to vacuum suggest that the pyrocatechol keeps the surface free from contamination on exposure to atmosphere. Photoemission spectra also indicate that the pyrocatechol capping molecules are replaced by the N3 dye in solution and that the N3 dye is adsorbed intact on the rutile TiO₂ (110) surface. This technique may allow other large molecules, which are thermally unstable to evaporation in UHV, to be easily deposited onto TiO₂ surfaces.     

同步泵浦PML飞秒激光研究

采用CW锁模YAG倍频激光器同步泵浦PML飞秒染料激光器,产生了平均脉宽约55fs、功率为15mW的光脉冲。文章在理论和实验上还研究了同步泵浦飞秒激光脉冲产生技术。     

Nonlinear refractive index measurement of tris(acetylacetonato) manganese(III) solution

We present the results from investigations of the nonlinear refractive index and nonlinear absorption coefficient of tris(acetylacetonato)manganese(III) solution, using Z-scan technique with a low-power continuous-wave laser at 514 nm. We demonstrate that the light-induced nonlinear refractive index variation leads to strong self-focusing and self-defocusing. A pump and probe technique was used to investigate the cause of nonlinearity. Furthermore, the nonlinear absorption effect was utilized to demonstrate all optical switching.     

Heteronuclear energy pooling collisions: The Na(3P) + K(4P) reaction

An experiment has been performed in which two different atomic species - sodium and potassium - have been simultaneously excited in a cell by two resonant cw dye lasers and the fluorescence spectrum has been analysed by using an intermodulation technique to isolate the contributions due to the heteronuclear processes. The energy pooling collisions between Na(3P) and K(4P) have been observed for the first time and the relative collision cross sections have been measured.     

Synthesis and multifunctionality of (CeO2-NiO) nanocomposites synthesized via sonochemical technique

CeO₂, NiO and their nanocomposite were synthesized using facile sonochemical technique. XRD assure single phase CeO₂ and NiO while the nanocomposite consists of the two phases only. CeO₂ nanoparticles possess cubic shape, NiO was formed in nanorods, and CeO₂ decorated the NiO nanorods in the nanocomposite. The magnetic behavior of the nanocomposite lies between those of the two parents with a ferromagnetic tendency. Metal oxide nanoparticles acted as catalyst in the formation of carbon nanofibers (CNFs), while the nanocomposite leads to the production of carbon nanotubes. The photocatalyst (CeO₂-NiO) achieved complete dye degradation (100%) in light for the tested dye at 50 min. The decay products were analyzed using GC mass confirming mineralization of Bb red dye.