Charge transfer interactions and nonlinear optical properties of push–pull chromophore benzaldehyde phenylhydrazone: A vibrational approach

To reveal the influence of complexing agents on crystalline perfection, tristhiourea zinc(II) sulfate (ZTS), ammonium dihydrogen phosphate (ADP) and potassium hydrogen phthalate (KHP) crystals grown by slow-evaporation solution growth technique using low concentrations (5 x 10 -3 M) of dopants like ethylenediamminetetraacetic acid (EDTA) and 1,10-phenanthroline (phen) were characterized by high-resolution X-ray diffractometry (XRD) and scanning electron microscopy (SEM). High-resolution diffraction curves (DCs) recorded for ZTS and ADP crystals doped with EDTA show that the specimen contains an epilayer, as observed by the additional peak in the DC, whereas undoped specimens do not have such additional peaks. On etching the surface layer, the additional peak due to the epilayer disappears and a very sharp DC is obtained, with full width at half-maximum (FWHM) of less than 10 arcsec, as expected from the plane wave dynamical theory of X-ray diffraction for an ideally perfect crystal. SEM micrographs also confirm the existence of an epilayer in doped specimens. The ZTS specimen has a layer with a rough surface morphology, having randomly oriented needles, whereas the ADP specimen contains a layer with dendric structure. In contrast to ADP and ZTS crystals, the DC of phen-doped KHP shows no additional peak, but it is quite broad (FWHM = 28 arcsec) with a high value of integrated intensity, p (area under the DC). The broadness of the DC and the high value of p indicate the formation of a mosaic layer on the surface of the crystal. However, similar to ADP and ZTS, the DC recorded after etching the surface layer of the KHP specimen shows a very sharp peak with an FWHM of 8 arcsec. An SEM photograph of phen-doped KHP shows deep cracks on the surface, confirming the mosaicity. After removing the surface layer, the SEM pictures reveal a smooth surface. A similar trend is observed with other complexing agents, like oxalic acid, bipy and picolinic acid. However, only typical examples are described in the present article where the effects were observed prominently. The investigations on ZTS, ADP and KHP crystals, employing high-resolution XRD and SEM studies, revealed that some organic dopants added to the solution during the growth lead to the formation of a surface layer, due to complexation of these dopants with the trace metal ion impurities present in the solution, which prevents the entry of impurities, including the solvent, into the crystal, thereby assisting crystal growth with high crystalline perfection. The influence of organic dopants on the second harmonic generation efficiency is also investigated.

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Enhancement of crystalline perfection by organic dopants in ZTS, ADP and KHP crystals as investigated by high‐resolution XRD and SEM

Growth and characterization of a new metal-organic crystal: Potassium thiourea iodide

Synthesis, crystal growth and studies on non-linear optical property of new chalcones

Experimental data on the maximum supercooling ΔTmax, a measure of metastable zone width, for solutions saturated at a temperature T0, as a function of cooling rate R are analyzed, for some solute−solvent systems chosen as examples, using Nývlt’s semiempirical approach and a new approach based on the classical theory of three-dimensional nucleation combined with the formation of n-sized embryos from monomers according to the law of mass action. Instead of a linear relation between ln(ΔTmax) and lnR of the Nývlt’s approach, the new approach predicts a linear dependence of (T0/ΔTmax)2 on lnR with slope F1 and intercept F. The quantity F1/F is independent of saturation temperature T0, characteristic of a solute−solvent and is associated with the growth of the stable three-dimensional nuclei to visible entities. The value of F1 is determined by thermodynamic and solvation processes, while that of F is governed by thermodynamic and kinetic parameters as well as processes associated with solvation of solute ions...

P Santhana Raghavan

Papers

A new nonlinear optical semi-organic material: cadmium thiourea acetate

Synthesis, crystal growth and FTIR, NMR, SHG studies of 4-methoxy benzaldehyde-N-methyl-4-stilbazolium tosylate (MBST)

Optical and microhardness studies of KDP crystals grown from aqueous solutions with organic additives

Effect of EDTA on the Metastable Zone Width of ADP

Crystal growth of two-component new novel organic NLO crystals