Growth and optical absorption studies on potassium dihydrogen phosphate single crystals

Growth of bulk nonlinear optical (NLO) single crystals gained new significance with the advent of solid‐state laser sources for opto‐electronic applications. An optically transparent crystal of potassium dihydrogen phosphate (KDP) has been grown from aqueous solution along (001) plane with the aid of modified growth assembly of Sankaranarayanan‐Ramasamy (SR) Method. The evaporation rate was controlled and single crystals of 5 mm diameter and 60 mm length with a growth rate 5 mm per day have been grown successfully. The improved transparency of grown crystal was investigated using DRS UV transmittance spectral analysis and the presence of functional groups in the grown crystal is confirmed using FTIR analysis. (© 2007 WILEY ‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Probing membrane topology by high-resolution 1H-13C heteronuclear dipolar solid-state NMR spectroscopy

Membrane topology changes introduced by the association of biologically pertinent molecules with membranes were analyzed utilizing the (1)H-(13)C heteronuclear dipolar solid-state NMR spectroscopy technique (SAMMY) on magnetically aligned phospholipid bilayers (bicelles). The phospholipids (1)H-(13)C dipolar coupling profiles lipid motions at the headgroup, glycerol backbone, and the acyl chain region. The transmembrane segment of phospholamban, the antimicrobial peptide (KIGAKI)(3) and cholesterol were incorporated into the bicelles, respectively. The lipids (1)H-(13)C dipolar coupling profiles exhibit different shifts in the dipolar coupling contour positions upon the addition of these molecules, demonstrating a variety of interaction mechanisms exist between the biological molecules and the membranes. The membrane topology changes revealed by the SAMMY pulse sequence provide a complete screening method for analyzing how these biologically active molecules interact with the membrane.     

PAA-derived gold nanorods for cellular targeting and photothermal therapy

A single-step LbL procedure to functionalize CTAB-capped GNRs via electrostatic self-assembly is reported. This approach allows for consistent biomolecule/GNR coupling using standard carboxyl-amine conjugation chemistry. The focus is on cancer-targeting biomolecule/GNR conjugates and selective photothermal destruction of cancer cells by GNR-mediated hyperthermia and NIR light. GNRs were conjugated to a single-chain antibody selective for colorectal carcinoma cells and used as probes to demonstrate photothermal therapy. Selective targeting and GNR uptake in antigen-expressing SW 1222 cells were observed using fluorescence microscopy. Selective photothermal therapy is demonstrated using SW 1222 cells, where >62% cell death was observed after cells are treated with targeted A33scFv-GNRs.     

Polarized naphthalimide CH donors enhance Cl- binding within an aryl-triazole receptor

The dipolar character of 1,8-naphthalimide together with polarization of the C(4)-H and C(5)-H donors has been utilized in receptor 1 to effectively bind chloride alongside triazole and phenylene units. The Cl(-) binding strength of 1 shows that the naphthalimide provides greater anion stabilization than an unactivated phenylene, and DFT calculations show that its collinear donor array can be a "urea-like" analog for CH···anion interactions.     

Synthesis of YCrO3 nanoparticles through PAA assisted sol–gel route

We report the synthesis of nanocrystalline phase-pure YCrO₃ powders by a poly acrylic acid (PAA) assisted sol–gel process at a comparatively low calcination temperature of 600 °C. The role of PAA in the powder processing was investigated systemically using Fourier transform infrared (FTIR) spectroscopy, differential thermal and thermogravimetric analyzer (DT/TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). PAA is found to have the desirable property of forming stable complexes with the cations, Y³⁺ and Cr³⁺ at a low pH. FTIR results demonstrated that in the gel-precursor, the carboxylate groups of PAA bond to Y³⁺ and Cr³⁺ in a monodentate and a bridging bidentate configuration, respectively, owing to the properties of Cr³⁺ giving the best correlation with PAA. The obtained particles have capsule-like morphology with a mean diameter of 40 nm. It is presumed that this morphology is due to the extended-chain configuration of PAA in the aqueous solution. The method showed a good control over particle size, morphology, chemical homogeneity, stoichiometry and agglomeration of the powders.     

Growth,spectral, optical,and dielectric studies on novel semiorganic NLO single crystal: d-phenylglycine hydrochloride

Good quality novel semiorganic nonlinear optical single crystal of d-phenylglycine hydrochloride has been grown from the aqueous solution by low temperature solution growth method. X-ray diffraction reveals that the crystal crystallises into orthorhombic system with noncentrosymmetric space group P2₁2₁2₁. Experimental parameters are evaluated based on single-crystal XRD and the calculated values of the polarisability were compared with the values of polarisability using Clausius–Mossotti equation. The functional groups present in the grown crystal were confirmed by Fourier transform infrared spectral analysis. The ¹H and ¹³C FT–NMR has been recorded to elucidate the molecular structure. Ultraviolet–visible-near infra-red absorption studies on this crystal reveal that the minimum absorption region is around 228 nm. The optical band gap of the crystal was found to be 2.9 eV. The scanning electron microscope study has been carried out to determine the surface morphology of the grown crystal. Photoluminescence studies show that the material emits violet fluorescence. Thermal studies bring forth that the crystal is thermally stable up to 255 °C. Dielectric studies reveal that both the dielectric constant and dielectric loss decrease with the increase in frequency as like the typical semiorganic nonlinear optical crystals such as bisthiourea zinc chloride, bisthiourea cadmium chloride and l-arginine dihydrogen phosphate. Electrical conductivity measurements were carried out and the Arrhenius plot is used to determine the value of activation energy. The Kurtz powder analysis on the crystal confirms the existence of second harmonic generation properties. The SHG efficiency was found to be 1.15 times that of KDP crystal.     

Modulation of psoralen DNA crosslinking kinetics associated with a triplex-forming oligonucleotide

A triplex-forming oligonucleotide (TFO), HPRT3, conjugated to a psoralen derivative, was designed to target a psoralen reaction site within the HPRT gene. HPRT3 bound with high affinity to a synthetic duplex target sequence. At a uniform UVA radiation dose, the ratio of psoralen monoadducts (MA) to interstrand crosslinks decreased and inverted with increasing TFO concentration. As the TFO concentration increased from 10 nm to 10 microm, the efficiency of psoralen MA formation remained relatively constant but the efficiency of interstrand crosslink formation increased several-fold. Neither shortening the TFO to reduce its dissociation constant nor altering the DNA sequences flanking the TFO binding site altered the concentration dependence of MA and crosslink yields. The psoralen photokinetics associated with 10 nm HPRT3 converted to those associated with 10 microm HPRT3 with the addition of other unrelated TFOs at 10 microm that do not specifically interact with the HPRT3 target sequence. Glycerol at concentrations of 0.5% (vol/vol) or higher also mimicked high TFO concentrations in enhancing crosslink formation. These results demonstrate that while psoralen may be targeted to react at a particular sequence by TFOs, photoreactivity associated with triplex formation is also modulated by sequence-independent factors that may affect the local macromolecular environment.     

Binary stacks of [CuC6F5]4 with arenes

Formation of the first binary stacks of an intact organocopper aggregate with the arenes naphthalene and 2,2'-bithiophene is reported; crystallographic data suggest that the supramolecular assembly process is supported by Cu-pi, Cu-S, and perfluoroarene-arene pi-interactions.