Computational and spectroscopic studies on some organic and semiorganic nonlinear optical single crystals

Abstract

The impact of nonlinear optics NLO on science and technologyhas been a drivingforceintherejuvenationofopticaltechnology forseveralareasofscienceand engineeringNLOmaterialsare essentialforthefabricationofelectro-optic modulators whichconvertanelectricsignaltoanopticalonefor transmissiononafiberopticcableA NLOmaterialhasmany applicationssuchasimageapplicationsusingphotorefractive crystalsfrequency multipliersandmixturesfiberopticsparametricoscillatorsandoptical switchesBecauseoftheeffectivenessingenerating newfrequenciesfromexisting lasers viaharmonicgenerationandsumanddifferencefrequency generationtherehasbeenan extensiveeffortinrecentyearstoidentifyeffectivematerialsforsuchprocessesAlong with highnonlinearity these materials must be transparentnotonly i atthelaserfrequency butalsoatthenewly generated frequency These materials should beresistanttooptical damage ii havehighmechanicalhardness iii exhibit goodthermalandchemical stability(iv) be capableof beinggrown inusefulsizeand v have the appropriate phase- matchingproperties newlineThiosemicarbazone derivatives are of special importance because of their versatile biological and pharmacological activities Thiosemicarbazone derivatives have found application in drug development for the treatment of central nervous system disorders (Kavitha et al 2014) of bacterial infection as well as analgesic and antiallergic agent Thiosemicarbazones are potent intermediates for the synthesis of pharmaceutical and bioactive materials and thus they are used extensively in the field of medicinal chemistry Moreover thiosemicarbazones have found their way into almost every branch of chemistry commercially they are used as dyes photographic films plastic and in textile industry newlineTartaric acid is a white crystalline organic acid that occurs naturally in many plants most notably in grapes Its salt potassium bitartrate commonly known as cream of tartar develops naturally in the process of winemaking It is commonly mixed with sodium bicarbonate and is sold as baking powder used as a leavening agent in food preparation The acid itself is added to foods as anantioxidant and to impart its distinctive sour taste Tartaric acid and its derivatives have a plethora of uses in the field of pharmaceuticals For example tartaric acid has been used in the production of effervescent salts in combination with citric acid in order to improve the taste of oral medications The potassium antimonyl derivative of the acid known as tartar emetic is included in small doses in cough syrup as an expectorant newlineTartaric acid also has several applications for industrial use The acid has been observed to chelate metal ions such as calcium and magnesium Therefore the acid has served in the farming and metal industries as a chelating agent for complexing micronutrients in soil fertilizer and for cleaning metal surfaces consisting of aluminium copper iron and alloys of these metals respectively Many tartrate compounds have exhibited novel properties which has led to several applications for example ferroelectric properties of calcium tartrate and rubidium hydrogen tartrate electrical and thermal studies of ammonium hydrogen tartrate and thermal expansion and phase transition in sodium potassium tartrate tetra hydrate newline In the present work attempts are made to study these biologically important organic and semiorganic single crystals In addition to computational and spectroscopic studies the optical properties of these noncentrosymmetric crystals were also studied Good quality LAsT LPT BLZC and BLCB single crystals were grown and the characterization results of the XRay diffraction FTIR optical thermal mechanical dielectric photoconductivity and nonlinear optical NLO studies of these crystals are presented in this thesis newlineThe resultsof theabove investigationshavebeenpublishedacceptedin InternationalJournalsandwerealsopresented invariousNationalInternational seminars conferences newline newline