SciCombinator

Discover the most talked about and latest scientific content & concepts.

Journal: Luminescence : the journal of biological and chemical luminescence

22

Three anthracene-based Schiff base complexes, R1-R3 (R1 = (E)-N´-((anthracen-10-yl)methylene)benzohydrazide; R2 = (E)-1-((anthracen-10-yl)methylene)-4-phenylsemicarbazide; and R3 = (E)-1-((anthracen-10-yl)methylene)-4-phenylthiosemicarbazide) were synthesized from 9-anthracenecarboxaldehyde, benzohydrazide, 4-phenylsemicarbazide and 4-phenylthiosemi-carbazide respectively, and characterized by various spectral techniques. The absorption spectral characteristics of R1-R3 were bathochromically tuned to the visible region by extending the π conjugation. These target compounds were weakly fluorescent in tetrahydrofuran (THF) solution because of rapid isomerization of the C=N double bond in the excited state. However, the aqueous dispersion of R1-R3 in the THF/water mixture by the gradual addition of water up to 90% resulted in an increase in the fluorescence intensity mainly due to aggregation-induced emission enhancement (AIEE) properties. The formation of nanoaggregates of R1-R3 were confirmed by scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. The compounds R1-R3 are ideal probes for the fluorescence sensing of bovine serum albumin (BSA) and breast cancer cells by optical cell imaging.

Concepts: Electron, Cancer, Breast cancer, Optics, Light, Atom, Serum albumin, Scanning electron microscope

0

This paper discusses multi-spectroscopic and molecular docking analysis of the interaction between atenolol (ATN) and deoxyribose nucleic acid (DNA) using alizarin (ALZ) as a spectroscopic probe. ATN is a β1 -receptor antagonist belonging to the β-blocker class of molecules. Experimental findings that were based on different spectroscopic analysis, melting studies, viscometric analysis, 1 H nuclear magnetic resonance and circular dichroism studies revealed the presence of a grove-binding mode. The effect of ionic strength was also studied, and observations suggested that electrostatic interaction also played a minor role during interaction. Molecular docking analysis suggested that the dominant force for the grove-binding phenomenon was hydrogen bonding between the 24-H residue of ATN and O of the 10-G residue, and the 40-H residue of ATN and N of the 17-A base residue. Competitive binding study of the ALZ-DNA complex with ATN showed that, despite an increase in the amount of ATN in the ALZ-DNA complex, the overall absorbance remained unchanged. The decrease in fluorescence in the ALZ-DNA system may be due to new non-fluorescent ATN-DNA-ALZ complex formation.

0

The present paper describes the development and validation of a simple and sensitive micelle-enhanced high-throughput fluorometric method for the determination of niclosamide (NIC) in 96-microwell plates. The proposed method is based on the reduction of the nitro group of niclosamide to an amino group using Zn/HCl to give a highly fluorescent derivative that was developed simultaneously and measured at λem 444 nm after excitation at λex 275 nm. Tween-80 and carboxymethylcellulose (CMC) have been used as fluorescence enhancers and greatly enhanced the fluorescence by factors of 100-150%. The different experimental conditions affecting the fluorescence reaction were carefully investigated and optimized. The proposed method showed good linearity (r2 ≥ 0.9997) over the concentration ranges of 1-5 and 0.5-5 μg/ml with lower detection limits of 0.01 and 0.008 μg/ml and lower quantification limits of 0.04 and 0.03 μg/ml on using Tween-80 and or CMC, respectively. The developed high-throughput method was successfully applied for the determination of niclosamide in both tablets and spiked plasma. The capability of the method for measuring microvolume samples made it convenient for handling a very large number of samples simultaneously. In addition, it is considered an environmentally friendly method with lower consumption of chemicals and solvents.

0

Bambuterol (BAM) and terbultaline (TER) are well known and effective bronchodilators. In this article highly sensitive, green and cost-effective spectrofluorimetric methods are designed to determine low concentrations of such drugs. The proposed methods are based on an investigation of the native fluorescence properties of aqueous solutions of BAM at 298 nm after excitation at 263 nm and of TER at 313 nm after excitation at 275 nm. Under optimum conditions, the plots of the relative fluorescence intensity versus concentration were rectilinear over the range 0.1-1.2 μg/mL for BAM and 0.05-0.5 μg/mL for TER with a limit of quantitation of 0.067 μg/mL for BAM and 0.018 μg/mL for TER. The methods are simple and hence suitable for application to the quantification of BAM and TER in syrups and tablets without interference from common excipients. Furthermore, based on United States Pharmacopeia (USP) guidelines, the application was extended to determine the content uniformity of the cited drugs in low dose tablets. The developed methods were fully validated according to the guidelines of the International Conference on Harmonization (ICH).

0

In this study, a colorimetric method was developed for rapid and sensitive determination of gallic acid (GA) by using floral-like magnetic Fe3 O4 @MnO2 composite material with enhanced oxidase-like activity. Fe3 O4 @MnO2 composite material is able to oxidize 3,3',5,5'-tetramethylbenzidine (TMB) to a blue product (oxTMB) with apparent color change and absorbance at 652 nm. GA can reduce the oxTMB yielding a fading blue color. Based on these results, a technique is proposed to detect GA quantitatively and qualitatively with UV-vis spectroscopy and bare eyes. A low detection limit of 0.105 μM and a detection range of 0.01 to 15 μM were obtained with UV-vis spectroscopy. This methodology possesses high potential for application in determination of GA.

0

Trivalent europium (Eu3+ ) and terbium (Tb3+ ) ions are important activator centers used in different host lattices to produce red and green emitting materials. The current work shows the design of new clay minerals to act as host lattices for rare earth (RE) ions. Based on the hectorite structure, nano-chlorohectorites and nano-fluorohectorites were developed by replacing the OH- present in the hectorite structure with Cl- or F- , thus avoiding the luminescence quenching expected due to the OH- groups. The produced matrices were characterized through X-ray powder diffraction (XPD), transmission electron microscopy (TEM), FT-IR, 29 Si MAS (magic angle spinning) NMR, nitrogen sorption, thermogravimetry-differential scanning calorimetry (TGA-DSC) and luminescence measurements, indicating all good features expected from a host lattice for RE ions. The nano-clay materials were successfully doped with Eu3+ and/or Tb3+ to yield materials preserving the hectorite crystal structure and showing the related luminescence emissions. Thus, the present work shows that efficient RE3+ luminescence can be obtained from clays without the use of organic ‘antenna’ molecules.

0

In recent years, more and more nanomaterials-based chemiluminescence (CL) systems have appeared to improve the sensitivity and expand the scope of the analytical applications with the explosive growth and development of nanomaterials and technology. As a fascinating class of luminescent carbon nanomaterials, carbon dots (CDs) are now substantially studied in fabricating CL based assays due to their unique optical and mechanical properties. Herein, we summarize and highlight the current developments of CDs-involved weak or ultraweak CL systems, as well as the corresponding mechanisms and proper applications in some fields. CDs can take part in the CL reactions as oxidants, emitting species directly involved in redox oxidation, energy acceptors of CL energy transfer, or even catalysts involving other luminophores. In fact, they always have more than one role in many cases, owing to the formation of various excited species with short life in CL systems. Therefore, in this review article, the most recent progress of the different CDs-assisted CL systems including the mechanisms and applications are presented. Finally, the conclusions and future prospects of this field are also discussed. The significant features of the CDs-based CL systems may open up new prospects and challenges in a wider range of fields.

0

BaGd2 O4 :Eu3+ scintillating phosphors by Pr3+ -codoping were synthesized at 1300°C in air using a solid-state reaction method. The as-synthesized phosphors were characterized by X-ray diffraction (XRD), photoluminescence (PL) including excitation and emission spectra, radioluminescence (RL) spectra excited by X-ray and thermoluminescence (TL) spectra. Both the PL and RL spectra are composed of the featured trivalent europium (Eu3+ ) without any praseodymium (Pr3+ ) ions, and the PL and RL intensities as well as the lifetimes of BaGd2 O4 :Eu3+ scintillating phosphors decrease dramatically with an increasing concentration of Pr3+ ions. Finally, the TL spectra reveal the trap concentration of the existing defects decrease with an increasing concentration of Pr3+ ions, while the relative TL intensity ratio of the high temperature band to the low temperature one increases with an increasing concentration of Pr3+ ions, which results in the afterglow suppression of BaGd2 O4 :Eu3+ scintillating phosphors.

0

An important form of carbon nanoparticles that are used for a wide range of applications, are carbon dots (CDs). In this study, a very easy, in expensive and green process was described for the preparation of CDs by using hydrothermal treatment of Tragacanth Gum (TG). A rapid assay for the determination of trace amounts of an anticancer medication doxorubicin (DOX) was developed, based on the quenching of the CDs derived from their aggregation. Electrostatic interaction between CDs and DOX could lead to fluorescence quenching. The optimized biosensor showed a detection range from 1 to 400 ng mL-1 and a limit of detection of 0.4 ng mL-1 . In the following, the synthesized CDs modified the Boehmite (Boh) mesoporous surface based on hydrogen bonding. The Boh has been used as supports and ideal hosts in this method, in which the particle size distribution of CDs in the pores of Boh is limited and they have controlled pore sizes. Accordingly, the surface-to-volume ratio and the presence of high-volume pores increased the longevity and sustainability of CDs; also prevented the aggregation of the CDs and improved their photo stability. The advantages of Boh are large pore volume, high surface area, and narrow size distribution. Variable factors influencing optical sensor response in DOX measurement were evaluated and optimized. In optimal conditions, the linear range was calculated from 1 to 500 ngmL-1 and the detection limit was 0.2 ng mL-1 . The sensors were used for measuring DOX in human blood plasma.

0

The photophysical properties and photodynamics of Pyronin Y (PyY) dye compound in seven polar protic solvents (n-alcohols) were examined as a function of temperature by using UV-visible, steady-state and time-resolved fluorescence spectroscopy techniques. To understand dye-solvent interactions, photophysical parameters including Stokes' shifts, fluorescence quantum yields and fluorescence lifetimes were determined. To examine the effect of solvent polarity, the difference between the ground state dipole moment and the excited state dipole moment was determined. For this purpose, the multiple regression analysis and the Kamlet-Taft technique were used. Moreover, photodynamic parameters, rotational relaxation times and steady-state anisotropy were calculated. The result showed that the specific interactions of PyY with the solvent molecules take place through hydrogen bonding. As the hydrocarbon chain of the alcohols gets longer, photophysical parameters diminish, probably because of weaker hydrogen bonding. Furthermore, it was found out that the dipole moment of excited states (μe ) is higher than that of the ground state (μg ). In addition, Brownian motions increased with the increasing temperature that weakened the fluorescence character of PyY. It was also revealed that the rotation of PyY increased with a prolonged hydrocarbon chain of alcohol series, due to the lesser extent of hydrogen bonding.