Efficient lasing action from Rhodamine-110 (Rh-110) impregnated sol-gel silica samples prepared by dip method

Rhodamine-110/sol-gel samples are prepared by sol-gel technique using dip method. Concentration dependent photophysical studies of these samples have indicated about the least possibility of aggregate formation. The lasing action of Rh-110 in silica samples is studied as a function of dye concentration. An efficient laser emission is observed when the samples are transversely pumped at 337.1 nm and 1.5 Hz repetition rate using a nitrogen laser (400 μJ energy/pulse and 4 ns pulse duration). The maximum of 166% laser efficiency of dye doped sol-gel samples compared to Rhodamine-6G (Rh-6G) in methanol is achieved. The photostability is also measured by using N₂ laser at 1 Hz and it is found nearly 165 pulses. The possible reasons for the photodegradation of the dye molecules are discussed in detail.     

Applications of TGA in quality control of SWCNTs

Carbon nanotubes exhibit a range of chemistries, including mixtures of different nanotube diameters, lengths, and chiralities coupled with various concentrations of metallic and non-nanotube-carbon impurities. The performance of a given material for a specific application depends on the chemistry, which is dictated in large part by the manufacturing process. Here, thermogravimetric analysis is utilized as a bulk characterization method for determining nanotube quality after manufacturing. The application of thermogravimetric analysis for quantifying basic nanotube chemistry is described (e.g., carbon-to-metal content, homogeneity). In addition, extension of the method to analyze specific nanotube properties (i.e., length and diameter) is reported. Results indicate that thermogravimetric analysis is sufficiently sensitive to enable quality control at both the macro-scale (carbon-to-metal ratio) and nano-scale (single-walled to multi-walled) and can detect subtle modifications in manufacturing processes.     

Energy levels of two interacting particles in an anharmonic potential

Energy levels of two interacting mass points in an anharmonic model potential (Morse type) have been studied. Analytic expression for the energy levels has been worked out. The model potential is shown to support bound states under certain conditions. The number of such states has been found to depend on the parameters of the potential. The potential is expected to be more realistic, particularly in presence of environments for diatomic molecules and artificial atoms. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

Identification of tyrosine in the presence of tryptophan using Cd-enriched colloidal CdS nanoparticles: A fluorescence spectroscopic study

A simpler identification method of tyrosine in the presence of tryptophan using CdS nanoparticles by conventional spectroscopic technique is proposed. Effect of both sulfide-enriched CdS as well as Cd²⁺-enriched CdS on tryptophan is investigated through absorption and emission spectroscopy. Quenching of tryptophan emission obeyed Stern-Volmer relation and was found to be independent of temperature, indicating a possible static quenching. The time-resolved fluorescence decay of tryptophan was minimally affected by sulfide-enriched CdS as well as Cd²⁺-enriched CdS nanoparticles, suggesting quenching to be static. In the presence of Cd²⁺-enriched CdS nanoparticles, the emission of tryptophan in phosphate buffer shows a typical spectral broadening along with a long wavelength increase in fluorescence emission. Additionally, spectra followed a typical isoemissive point at 440 nm when tryptophan alone was there. Similarly, isoemissive point at 340 nm was observed in the case of tyrosine. However, a further red shift of isoemissive point (470 nm) in the mixture of both tyrosine and tryptophan was observed. This observation might make Cd²⁺-enriched CdS nanoparticles useful for using as marker for tyrosine in the presence of tyrptophan.     

Synthesis of 5,7-Dihydroxy-6-methoxy-2-(2-hydroxy-4-methoxyphenyl)-4H-1-benzopyran-4-one and Reassignment of Structure of Tamaridone1

The proposed structure of a new flavone, tamaridone, isolated from Tamarix dioica Roxb is untenable on the basis of comparison with its synthetic sample. Its structure has been now revised to 5,7-dihydroxy-8-methoxy-2-(3-hydroxy-4-methoxyphenyl)-4H-1-benzopyran-4-one by careful spectral studies.     

Experimentally validated Raman Monte Carlo simulation for a cuboid object to obtain Raman spectroscopic signatures for hidden material

In conventional Raman spectroscopic measurements of liquids or surfaces the preferred geometry for detection of the Raman signal is the backscattering (or reflection) mode. For non‐transparent layered materials, sub‐surface Raman signals have been retrieved using spatially offset Raman spectroscopy (SORS), usually with light collection in the same plane as the point of excitation. However, as a result of multiple scattering in a turbid medium, Raman photons will be emitted in all directions. In this study, Monte Carlo simulations for a three‐dimensional layered sample with finite geometry have been performed to confirm the detectability of Raman signals at all angles and at all sides of the object. We considered a non‐transparent cuboid container (high density polyethylene) with explosive material (ammonium nitrate) inside. The simulation results were validated with experimental Raman intensities. Monte Carlo simulation results reveal that the ratio of sub‐surface to surface signals improves at geometries other than backscattering. In addition, we demonstrate through simulations the effects of the absorption and scattering coefficients of the layers, and that of the diameter of the excitation beam. The advantage of collecting light from all possible 4π angles, over other collection modes, is that this technique is not geometry specific and molecular identification of layers underneath non‐transparent surfaces can be obtained with minimal interference from the surface layer. To what extent all sides of the object will contribute to the total signal will depend on the absorption and scattering coefficients and the physical dimensions. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis and analysis of ZnO and CdSe nanoparticles

Zinc oxide and cadmium selenide particles in the nanometer size regime have been synthesized using chemical routes. The particles were capped using thioglycerol in case of ZnO and 2-mercaptoethanol in case of CdSe to achieve the stability and avoid the coalescence. Zinc oxide nanoparticles were doped with europium to study their optical properties. A variety of techniques like UV-Vis absorption spectroscopy, X-ray diffraction (XRD), photoluminescence (PL), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR) and transmission electron microscopy (TEM) were used to carry out structural and spectroscopic characterizations of the nanoparticles.     

Current status of equation of state of nuclear matter

The equation of state (EOS) of symmetric nuclear matter (SNM) is a very important ingredient in the study of various phenomena of interest in nuclear physics and astrophysics. Accurate assessment of the value of the SNM incompressibility coefficient, K, which is directly related to the curvature of the EOS, is needed to extend our knowledge of the EOS in the vicinity of the saturation point. We review the current status of K as determined from experimental data on compression modes in nuclei using the mean-field-based random-phase approximation. The text was submitted by the authors in English.