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  • Author or Editor: G. Madhurambal x
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Abstract  

As an asymmetric organic molecular crystal, p-N,N-dimethylaminobenzaldehyde (DAB) exhibits peculiar optical property. It was first grown by solution technique adopting slow evaporation method at room temperature using CCl4 as growth medium. The solubility of DAB increases with temperature. Good quality transparent crystals of p-N,N-dimethylaminobenzaldehyde were carefully collected and subjected various characterization studies such as UV, FTIR, 1H and 13CNMR spectral studies and thermal (TG-DTG) studies to determine the purity and application oriented properties of the grown crystals.

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Abstract  

Calcium hydrogen phosphate dihydrate (CHPD) is found quite frequently in urinary calculi (stones). The CHPD crystals were grown by the single diffusion gel growth technique in sodium metasilicate gel. The crystals were found to be having platelet and broad needle type morphologies. The crystals were analyzed by FTIR spectroscopy. The thermal properties were studied by employing the thermogravimetric analysis (TG). Various kinetic and thermodynamic parameters for dehydration were estimated from the TG curve. The selected platelet was studied by scanning electron microscope (SEM) for the growth morphologies indicating that the crystals grew in the form of leaflets having prominent (010) faces. This was in agreement with earlier reported studies.

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Abstract  

A single crystal of urea–thiourea was grown by slow evaporation of aqueous solution at room temperature. The bright and transparent crystals obtained were characterised by TG–DTA, UV and FTIR spectral analyses. A fitting decomposition pattern for the title compound was formulated on the TG curve which shows a two stage mass loss between 200 and 750 °C. DTA curve shows exothermic peaks supporting the formulated decomposition pattern in this temperature range. The UV and FTIR spectra show the characteristic absorption, vibration frequencies due to urea–thiourea zinc chloride crystals. Detailed structural analysis of the compound is under progress.

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Abstract  

A mixed crystal of urea–thiourea was grown by slow evaporation of aqueous solution at room temperature. The bright and transparent crystals obtained were characterized by thermogravimetric–differential thermal analysis (TG–DTA), UV and FTIR spectroscopic analyses. A fitting decomposition pattern for the title compound was formulated on the TG curve which shows a two stage weight loss between 200 and 750 °C. In this temperature range DTA curve shows exothermic peaks supporting the formulated decomposition pattern. The UV and FTIR spectra show the characteristic absorption, vibration frequencies due to urea–thiourea mixed crystals. Detailed structural analysis of the compound is under progress.

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Abstract  

Potassium acid phthalate (KAP) which is also known as potassium hydrogen phthalate (KC8H5O4), a semi-organic compound was grown from its aqueous solution only by slow evaporation method at room temperature. The effect of metallic salts HgCl2 and PbCl2 as dopants in the growth aspects, thermal properties and SHG efficiency of KAP were determined using UV-VIS, FTIR spectral studies, thermal (TG and DTA) analysis and NLO test. There is only one significant mass loss step on TG curve of pure and doped KAP crystal. DTA curve exhibit a higher peak temperature in case of doped KAP crystal compared to those of pure KAP crystals.

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Abstract  

The experimental results of the influence of low (1 M%) and high (10 M%) concentrations of potassium chloride (KCl) dopant on ADP crystals are presented. The dopant results in an increase in the metastable zone width leading to an enhanced crystal growth rate, at its low concentrations. In the presence of high concentrations of the dopant in the medium, the growth rate decreases appreciably. Further, low concentrations of dopant improve the crystalline quality with better transparency. The diffraction patterns reveal that there is no change in basic structure except for variation in intensity by doping. Slight broadening is observed in FTIR of ADP in the 3500–3000 cm−1 range in the presence of high [KCl]. It appears that the dopant has not altered much the optical transparency of the crystal. SEM studies of pure and doped samples reveal that structure defect centers are formed in ADP crystals by the dopant. Second harmonic generation (SHG) efficiency measurements indicate that nonlinear optical (NLO) property is enhanced appreciably by [KCl] dopant and the SHG is more pronounced at high concentrations. It seems that the molecular alignment of the crystal facilitates non-linearity in the presence of the dopant.

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Synthesis and characterization of a novel non-linear optical (NLO) material

Endo anthracene maleic anhydride – Diel’s–Alder adduct of anthracene

Journal of Thermal Analysis and Calorimetry
Authors:
G. Madhurambal
,
P. Ramasamy
,
P. Srinivasan
, and
S. Mojumdar

Abstract  

Anthracene is one of the organic molecular crystals, which exhibits peculiar optical and electronic properties. Since the 9, 10 positions are very reactive in anthracene, it undergoes the Diel’s–Alder reaction with maleic anhydride in 99% yield. The synthesis of Diel’s–Alder adduct has been carried out by adopting standard procedure. The product was subjected to various characterization studies such as FTIR, UV and 1H NMR spectroscopy, and thermal studies to check its purity and determine the applicability of adduct in various applications. The second harmonic generation (SHG) efficiency of the adduct has been observed using Nd:YAG laser.

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Abstract  

To understand the structural and thermal properties of the mixed crystals, thermogravimetric (TG) and differential thermal analysis (DTA), and FTIR and Raman spectral studies were carried out for the mixed crystals of Zna/Mgb ammonium sulfate of composition namely 'a' (fraction by mass of salt Zn[NH4]2[SO4]26H2O to the total salt (both Zn[NH4]2[SO4]26H2O, Mg[NH4]2[SO4]26H2O or it can be explained as ZnaMgb[NH4]2[SO4]26H2O, a + b =1), and a = 0.1, 0.25, 0.333, 0.5, 0.666, 0.75 and 0.9 grown by a solution technique. From the correlation and analysis of the results obtained for the various crystals, the desolvation, decomposition, crystalline transition phenomena were identified. By close comparison of the endotherms, obtained for the various crystals, it was found that isomorphous substitution takes place in the crystals. Up to 0.5, Zn2+ ion replaces isomorphous Mg2+ ions in the lattice sites of Mg[NH4]2[SO4]26H2O and above 0.5, Mg2+ ions occupies the Zn2+ ion in the lattice sites of Zn[NH4]2[SO4]26H2O. Both crystals belong to monoclinic system with P 2(1)/a symmetry. The vibrations of NH4 + ion, SO4 2- ion, the complex [Mg(OH2)6]2+ the complex [Zn(OH2)6]2+ and the three different water molecules are identified. The linear distortion of SO4 2- ion is found to be greater than its angular distortion, while the NH4 + ion has suffered more angular distortion. The possibility of free rotation of the NH4 + ion is ruled out.

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Abstract  

Benzophenone is a well-known material, which exhibits non-linear optical (NLO) property. It has been grown by solution technique adopting slow evaporation method from solvents CHCl3, CCl4 for the first time. Solubility metastable zone width and inductions periods of benzophenone in CHCl3 and CCl4 were determined. Interfacial tension values at two different temperatures for various super saturations, such as 1.10, 1.15, 1.20 and 1.25 were determined using induction period. From interfacial tension values, the nucleation parameters, such as the radius of the critical nuclei (r*), the free energy change for the formation of a critical nucleus (ΔG*) and the number of molecules in the critical nucleus were also calculated for benzophenone in CHCl3 and CCl4 at two different temperature. The effect of surface tension, viscosity, density of these solvents are correlated with interfacial tension. The metastable zone width is also correlated with interfacial tension. The solution grown crystals were carefully harvested and subjected to various characterization studies to check its purity and to determine its applicability.

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Abstract  

A single crystal of sodium and potassium cinnamates was grown by slow evaporation of methanol solution at room temperature. The effect of metals sodium and potassium on the electronic structure of cinnamic acid was studied. In this research many analytical methods such as FTIR, UV, second harmonic generation (SHG) and TG–DTA were used: The spectroscopic studies lead to conclusions containing the distribution of the electronic charge in molecule, the delocalisation of π electrons and the reactivity of metal complexes. The SHG efficiency is more pronounced in the presence of sodium and potassium dopant in the growth medium. Incorporation of sodium and potassium increase the thermal stability ensuring the suitability of material for possible non-linear optical (NLO) application up to 180 °C.

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