Journal: Journal of fluorescence
The first fluorescent sensor for HF2 (-) anion, N(1), N(3)-di(naphthalene-1-yl)isophthalamide (L) has been derived from α-Napthylamine and isopthaloyl chloride. In 1:1 (v/v) DMSO:H2O, L exhibits high selectivity towards HF2 (-) anion with a 4-fold enhancement in fluorescent intensity. Very little enhancement in fluorescence intensity is observed for F(-), Cl(-), Br(-), I(-), SCN(-), PO4 (3-), SO4 (2-), and CH3COO(-) anions. The stoichiometry interaction between L and HF2 (-) is found to be 1:1 from fluorescence and UV/Visible spectral data. DFT calculation shows that binding between HF2 (-) and L is 1:1 and increases the relative planarity between the two naphthyl rings causing fluorescence enhancement. A shift of 0.080 V in oxidation potential of L is observed on interaction with HF2 (-) by cyclic voltammetry and square wave voltammetry.
As the hardware of FLIM technique becomes mature, the most important criterion for FLIM application is the correct interpretation of its data. In this research, first of all, a more orthogonal phasor approach, called as Modified Phasor Approach (MPA), is put forward. It is a way to calculate the lifetime of the complex fluorescent process, and a rule to measure how much the fluorescence process deviates from single exponential decay. Secondly, MPA is used to analysis the time-resolved fluorescence processes of the transfected CHO-K1 Cell lines expressing adenosine receptor A1R tagged by CYP and YFP, measured in the channel of the acceptor. The image of the fluorescence lifetime and the multiplication of the fluorescence lifetime and deviation from single exponential decay reveal the details of the Homo-FRET. In one word, MPA provides the physical meaning in its whole modified phasor space, and broadens the way for the application of the fluorescence lifetime imaging.
Fluorescent PET (Photoinduced Electron Transfer) has been of particular growth in recent times. A novel PET based fluorescent sensor using unmodified CdSe quantum dots (QDs) has been developed for the trace determination of Nimesulide (NIM). The sensor is based on the selective fluorescence quenching of quantum dots by NIM in presence of other NSAIDs and is found that intensity of quenching is linearly related to NIM concentration in the range 8.2 × 10(-7) - 4.01 × 10(-5) M. The mechanism of interaction is discussed. Finally, the potential application of the proposed method for the trace determination of NIM in pharmaceutical formulation is demonstrated.
Based on resonance energy transfer (FRET) from dansyl to rhodamine 101, a new fluorescent probe (compound 1) containing rhodamine 101 and a dansyl unit was synthesized for detecting Hg(2+) through ratiometric sensing in DMSO aqueous solutions. This probe shows a fast, reversible and selective response toward Hg(2+) in a wide pH range. Hg(2+) induced ring-opening reactions of the spirolactam rhodamine moiety of 1, leading to the formation of fluorescent derivatives that can serve as the FRET acceptors. Very large stokes shift (220 nm) was observed in this case. About 97-fold increase in fluorescence intensity ratio was observed upon its binding with Hg(2+).
Competitive dye displacement titration has previously been used to characterize chitosan-DNA interactions using ethidium bromide. In this work, we aim to develop a fast and reliable method using SYBR Gold as a fluorescent probe to evaluate the binding affinity between ssRNA and chitosan. The interaction of chitosan with ssRNA was investigated as a function of temperature, molecular weight and degree of acetylation of chitosan, using competitive dye displacement titrations with fluorescence quenching. Affinity constants are reported, showing the high sensitivity of the interaction to the degree of acetylation of chitosan and barely dependent on the molecular weight. We propose that the mechanism of SYBR Gold fluorescence quenching is governed by both static and dynamic quenching.
Synchronous spectrofluorimetric methods could be successfully adopted for simultaneous determination of Octinoxate (OMC), Avobenzone (AVO), Octyltriazone (OT), and Phenyl benzimidazole sulfonic acid (PBSA) in moisturizing sunscreen lotion, utilizing β-CD as fluorescence enhancer, and determination of Avobenzone (AVO), Homosalate, Tinosorb M and Phenyl benzimidazole sulfonic acid (PBSA) in presence of Octocrylene (OCR) in whitening sunscreen cream, using micellar medium of Sodium Dodecyl Sulfate (SDS) to enhance fluorescence intensity. For first product, zero order synchronous spectrofluorimetric method was used for determination of OMC and AVO, and derivative synchronous spectrofluorimetric technique was utilized for OT and PBSA in quaternary mixture. Linear calibration curves were obtained in a concentration range of 0.5-8 μg mL- 1 for OMC and AVO, and in range of 0.05-3 μg mL- 1 for OT and 0.001-5 μg mL- 1 for PBSA, by measuring the fluorescence at 370, 405, 333.2 and 340.6 nm, respectively. For second product, first derivative synchronous fluorescence method was used for each UV-filter. A linear calibration curves were obtained in a concentration range of 0.5-8 μg mL- 1 for AVO, in range of 0.1-8 μg mL- 1 for Homosalate, 2-10 μg mL- 1 for Tinosorb M and 0.001-5 μg mL- 1 for PBSA, by measuring the fluorescence at 409.8, 373, 307.2 and 316.8 nm, respectively. The detection limits are well below the maximum admissible concentration. The proposed methods were validated according to ICH guidelines and successfully applied to determine sunscreens in pure form and in Cosmeceutical formulations. All the results obtained were compared with those of published methods, where no significant difference was observed.
Eu3+ doped and Dy3+ codoped yttrium oxide (Y2O3) phosphors have been prepared using solid-state reaction technique (SSR). The prepared phosphors were characterized by X-ray diffractometer (XRD), energy dispersive X-ray (EDX) spectroscopy, scanning electron microscopy (SEM) and Fourier transforms infrared spectroscopy (FTIR) techniques. Photoluminescence (PL) and Thermoluminescence (TL) properties were studied in detail. PL emission spectra were recorded for prepared phosphors under excitation wavelength 254 nm, which show a high intense peak at 613 nm for Y2O3:Dy3+, Eu3+ (1:1.5 mol %) phosphor. The correlated color temperature (CCT) and CIE analysis have been performed for the synthesized phosphors. TL glow curves were recorded for Eu3+doped and Dy3+codoped phosphors to study the heating rate effect and dose response. The kinetic parameters were calculated using peak shape method for UV and γ exposures through computerized glow curve deconvolution (CGCD) technique. The phosphors show second order kinetics and activation energies varying from 5.823 × 10- 1 to 18.608 × 10- 1 eV.
Micelles are of increasing importance as versatile carriers for hydrophobic substances and nanoprobes for a wide range of pharmaceutical, diagnostic, medical, and therapeutic applications. A key parameter indicating the formation and stability of micelles is the critical micelle concentration (CMC). In this respect, we determined the CMC of common anionic, cationic, and non-ionic surfactants fluorometrically using different fluorescent probes and fluorescence parameters for signal detection and compared the results with conductometric and surface tension measurements. Based upon these results, requirements, advantages, and pitfalls of each method are discussed. Our study underlines the versatility of fluorometric methods that do not impose specific requirements on surfactants and are especially suited for the quantification of very low CMC values. Conductivity and surface tension measurements yield smaller uncertainties particularly for high CMC values, yet are more time- and substance consuming and not suitable for every surfactant.
In the paper, hydrothermal carbon spheres (HTCs) are functionalized by the 3-aminobenzeneboronic acid (3-APBA) as a fluorescence sensor. The modification carbon spheres (3-APBA-HTCs) have shown excellent selectivity and sensitivity for efficient determination of L-tryptophan (L-Trp). The fluorescence sensor can selectively achieve the “On-Off” switchable functionality for L-Trp at an extremely low detection limit of 0.50 × 10- 5 mol/L.
Experimental studies in the aqueous solution are crucial for the detection of metal cations in environmental and biological media. Polymer materials allow to work in aqueous media for fluorescent substances which are insoluble in water. Fluorescence sensor studies of the phenanthroimidazole imine compound (PI) synthesized previously by our group were performed in the polymer medium and the selective response to Fe (III) cation was obtained. The resulting sensor exhibited a selective fluorescence quenching effect to Fe (III). A logarithmic calibration graph was obtained in the range of 5.0 × 10- 5 and 1.0 × 10- 2 M. The interference effects of other ions besides Fe (III) have been examined and it has been observed that PI compound behaves selectively to Fe (III) ion in aqueous media. In addition, regeneration and reproducibility studies were carried out to determine the long-term usage of PI doped polymer film and reproducible results have been obtained for Fe (III) cation.