Pulsed Laser‐Driven Molecular Self‐assembly of Cephalexin: Aggregation‐Induced Fluorescence and Its Utility as a Mercury Ion Sensor

A fluorescent self‐assembly of cephalexin is obtained by pulsed laser irradiation process. An intense fluorescence emission is found in the self‐assembled form due to occurrence of a typical aggregation‐induced emission in cephalexin molecules. It is observed that fluorescence quenching of the self‐assembled fluorescent nanostructures occurs in the presence of extremely low Hg⁺⁺ ions concentrations (10^?7 m ) as compared to other heavy metal ions e.g. Ferrous (Fe⁺⁺), Manganese (Mn⁺⁺), Magnesium (Mg⁺⁺), Cobalt (Co⁺⁺), Nickel (Ni⁺⁺) and Zinc (Zn⁺⁺) at the same concentrations.     

Parametric dependence studies on cracking of clay

We have studied the shrinkage-crack patterns formed in the process of drying of clay/water slurries employing simple laboratory experiments. Both isotropic and directional drying was studied. The objective has been to examine the correlation between the solvent, materials parameters and the crack patterns. Attempt is made to fit the observations to specific models. The dynamics of the pattern formation process and the geometric properties of the crack patterns are found to be in conformity with the hydrodynamic model by Lee and Routh [W.P. Lee, A.F. Routh, Langmuir 20 (2004) 9887].     

Microstructural effects on the dynamic rheology of a discotic mesophase pitch

The dynamic rheology and accompanying microstructure of a synthetic mesophase pitch (AR-HP) is reported. The loss modulus (G″) was found to be higher than the storage modulus (G′) at all frequencies (∼0.1 to ∼100 rad/s) and temperatures (280–305 °C) tested. The slope of the low-frequency terminal zone for G′ was found to be approximately 0.8, much lower than a value of 2 that is observed for flexible chain polymers. Cross-polarized optical microscopy with full-wave retardation plate confirmed the presence of different textures of mesophase pitch processed under different conditions. While loss moduli remained fairly unchanged, finer textures led to significantly lower storage moduli. Consistent with this trend, coarsening of the microstructure during textural relaxation led to an increase in storage moduli. Therefore, for the discotic mesophase pitch, the viscous component was found to remain unaffected by the microstructure, but the elastic modulus was dependent on the orientation of layer-planes and size of the texture.     

Ripples on the surface of a two-component fluid

The dispersion relation of ripplons on the surface of a two-component liquid has been derived using the hydrodynamic mean-field model, in terms of the interaction pair potentials of the constituent particles. The modes for planar and spherical geometries have been derived explicitly. The formalism is applied to ripples on the surfaces of liquids in which the interparticle interaction is not Coulombic, as also on the surfaces of jellium and on electron-hole droplets.     

High temperature ferromagnetism with a giant magnetic moment in transparent co-doped SnO(2-delta)

The occurrence of room temperature ferromagnetism is demonstrated in pulsed laser deposited thin films of Sn(1-x)Co(x)O(2-delta) (x<0.3). Interestingly, films of Sn(0.95)Co(0.05)O(2-delta) grown on R-plane sapphire not only exhibit ferromagnetism with a Curie temperature close to 650 K, but also a giant magnetic moment of 7.5+/-0.5 micro(B)/Co, not yet reported in any diluted magnetic semiconductor system. The films are semiconducting and optically highly transparent.     

Pulsed laser treatment at Fe/C6H6 interface: A Mössbauer effect study

The pulsed ruby laser induced reactive-quenching process at Fe/C₆H₆ Ibenzenel has been investigated using conversion electron Mössbauer spectroscopy [CEMS]. It is shown that iron carbide phases can be synthesized when an iron foil immersed in benzene is treated with ruby Laser pulses [λ=694 nm, pulse width ～30 ns, energy density =15 J/cm²]. The results indicate the formation of ε-carbide and Fe₅C₂ phases in the as-treated sample and its transformation to Fe₃C upon thermal treatment. The result of the CEMS measurements are supported by small angle X-ray diffractometry.     

Surface plasmon dispersion relation for spherical metal particles

Using the hydrodynamical model, we have obtained the surface plasmon dispersion relation for spherical metallic particles in the following two cases: (1) a sharp surface cut off in electron density and (2) a diffused electron density at the surface. The diffused density is modelled with a step function. The diffuse nature of the electron density at surface of the metal particle is necessary to understand the experimental result for particles with small radii. Shift in the absorption frequency is estimated and found to be small.     

Thermally stimulated current spectra in nitrogen implanted fluorinated ethylene propylene

Thermally stimulated current spectra of nitrogen implanted fluorinated ethylene propylene polymer foils have been studied. Two characteristic peaks have been obtained for samples implanted with nitrogen ions with energies ranging from 20 to 60 keV. The variations in the activation energies and relaxation times of charge carriers, as a function of implantation energy, have been attributed to the corresponding changes in the carrier distribution in the polymer. The carrier mobilities and mobility life-time products have also been estimated for the two characteristic peaks.     

Photoluminescence Quenching in Self‐Assembled CsPbBr3 Quantum Dots on Few‐Layer Black Phosphorus Sheets

An ordered self‐assembly of CsPbBr₃ quantum dots (QDs) was generated on the surface of few‐layer black phosphorus (FLBP). Strong quenching of the QD fluorescence was observed, and analyzed by time‐resolved photoluminescence (TR‐PL) studies, DFT calculations, and photoconductivity measurements. Charge transfer by type I band alignment is suggested to be the cause of the observed effects.