Fourier transform infrared spectral study of N,N′-dimethylformamide-water-rhodamine 6G mixture

Infrared absorption spectra of N,N′-dimethyl formamide in the absence and presence of water, rhodamine 6G and water–rhodamine 6G mixture are reported. Assignment of observed bands has been made on the basis of density functional theory calculations and available assignments in the literature. Certain bands show changes in their positions and intensities when water is added to N,N′-dimethylformamide. This is due to hydrogen bonding interaction between these molecules. Similar changes are also observed for dimethylformamide and Rh6G mixture to a lesser extent. The presence of Rh6G in a dimethylformamide–water mixture reverses these spectral changes due to preferential solvation of Cl^? by water molecules. Solvation reduces or nullifies the hydrogen bonding between dimethylformamide and water in the mixture.     

Recognition of D-Penicillamine Using Schiff Base Centered Fluorescent Organic Nanoparticles and Application to Medicine Analysis

Schiff base centered fluorescent organic compound 1,1′-[(1E,2E)-hydrazine-1,2-diylidenedi(E)methylylidene]- dinaphthalen-2-ol (HN) was synthesized followed by spectral characterization viz., NMR, IR and Mass spectroscopy. The fluorescent nanoparticles of HN prepared using reprecipitation method shows red shifted aggregation induced enhanced emission (AIEE) with respect to HN solution in acetone. The average particle size of nanoparticles (HNNPs) is of 67.2 nm shows sphere shape morphology. The surfactant cetyltrimethyl ammonium bromide (CTAB) used to stabilize HNNPs induces positive charge surface with zeta potential of 11.6 mV. The positive charge of HNNPs responsible to adsorb oppositely charged analyte on its surface with binding interactions. The fluorescence experiments performed with and without addition of different analytes to the aqueous suspension of HNNPs shows selective fluorescence quenching of HNNPs by D-Penicillamine (D-PA). The effect of other coexisting analytes does not affect the selective sensing behavior of D-PA. The mechanism of binding between HNNPs and D-PA was discussed on the basis of electrostatic interaction and adsorption phenomenon. The results interpreted by using DLS-Zeta sizer, Fluorescence lifetime measurements, conductometric titration supports the electrostatic adsorption between HNNPs and D-PA. The method has extremely low limit of detection (LOD) value 0.021 ppm is of significant as compared to reported methods. The proposed fluorescence quenching method was effectively used for quantitative estimation of D-PA from pharmaceutical medicine.

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Graphical Abstract The fluorescence quenching based selective recognition of D-Penicillamine (D-PA) by using Schiff base centered fluorescent organic nanoparticles was developed and successfully applied to quantitative determination of D-PA from pharmaceutical samples viz. capsule and tablet.

     

Easily coupled whispering gallery plasmons in dielectric nanospheres embedded in gold films

A new self-aligned robust method for coupling to whispering gallery modes (WGMs) of submicron microspheres utilizes their periodic arrangement without relying on nanopositioned external coupling devices. The microspheres are embedded in a nanostructured gold surface supporting delocalized plasmonic crystal modes that mediate the coupling, and can be tuned by the geometry. Detailed measurements of the angle- and orientation-dependent reflectivity reveal localized plasmonic WGMs whose energies scale with sphere diameter and agree closely with Mie calculations. Coupling between these plasmonic WGMs leads to mode splitting and the formation of plasmonic minibands of a controllable bandwidth.     

Effect of the inside profile of a hollow cathode on the plasmaplume

The effect of the inside profile of a hollow cathode on the intensity of plasma plume has been studied in a low-pressure (~3-torr) argon discharge. The effectiveness of three different `inside' profiles of a hollow cathode was compared by performing emission spectroscopy on the plasma plume in each case. A conical-profile hollow cathode produced a plasma plume that was much more intense than the one in a commonly used cylindrical-profile hollow cathode     

Enhanced photocatalytic activity of ultra-high aspect ratio ZnO nanowires due to Cu induced defects

We report the synthesis of ZnO nanowires in ambient air at 650°C by a single-step vapor transport method using two different sources Zn (ZnO nanowires-I) and Zn:Cu (ZnO nanowires-II). The Zn:Cu mixed source co-vaporize Zn with a small amount of Cu at temperatures where elemental Cu source does not vaporize. This method provides us a facile route for Cu doping into ZnO. The aspect ratio of the grown ZnO nanowires-II was found to be higher by more than five times compared ZnO nanowires-I. Photocatalytic activity was measured by using a solar simulator and its ultraviolet-filtered light. The ZnO nanowires-II shows higher catalytic activity due to increased aspect ratio and higher content of surface defects because of incorporation of Cu impurities.     

Enhanced Exciplex Emission of Pyrene Thin Films Doped by Perylene: Structural,Photophysical and Morphological Investigation

The present work reports on the preparation of thin films of pyrene luminophors doped by varying amounts of perylene by spin coating technique. The structural, morphological, and photophysical properties of pyrene thin films have been investigated as a function of perylene contents. X-ray diffraction studies of doped thin films show well-defined peaks, and estimated crystallite size decreases with increasing perylene content, due to the formation of closed packed crystal structure. SEM images of pure pyrene revealed smooth, and compact and separated crystals with amounts of perylene. The result of absorption spectra showed decrease in intensity with perylene content. However, the fluorescence spectra of pyrene containing higher amounts of perylene showed broad and structureless exciplex emission at 510 nm. The emission colour of pyrene luminophors tuned from blue to green by controlling the concentration of perylene. The phenomenon of change in colour was seen due to efficient excitation energy transfer from pyrene to perylene in thin films. It also found that the intensity of exciplex emission increases with increasing concentration of perylene is of high demand in fluorescent lamp as well as green organic light emitting diodes.     

Recent developments in monitoring calcium and protein interactions in cells using fluorescence lifetime microscopy

Time-resolved fluorescence lifetime microscopy (TRFLM) allows the combination of the sensitivity of fluorescence lifetime to environmental parameters to be monitored in a spatial manner in single living cells, as well as providing more accurate, sensitive, and specific diagnosis of certain clinical diseases and chemical analyses. Here we discuss two applications of TRFLM: (1) the use of nonratiometric probes such as Calcium Crimson, for measuring Ca²⁺; and (2) quantification of protein interaction in living cells using green and blue fluorescent protein (GFP and BFP, respectively) expressing constructs in combination with fluorescence resonance energy transfer microscopy (FRET). With respect to measuring Ca²⁺ in biological samples, we demonstrate thatintensity-based measurements of Ca²⁺ with single-wavelength Ca²⁺ probes such as Calcium Crimson may falsely report the actual Ca²⁺ concentration. This is due to effects of hydrophobicity of the local environment on the emission of Calcium Crimson as well as interaction of Calcium Crimson with proteins, both of which are overcome by the use of TRFLM. The recent availability of BFP (P4-3) and GFP (S65T) (which can serve as donor and acceptor, respectively) DNA sequences which can be attached to the carboxy-or amino-terminal DNA sequence of specific proteins allows the dual expression and interaction of proteins conjugated to BFP and GFP to be monitored in individual cells using FRET. Both of these applications of TRFLM are expected to enhance substantially the information available regarding both the normal and the abnormal physiology of cells and tissues.