Materials Chemistry and Physics 93 (2005) 272276

Growth and characterization of seme cras a,gayaChenna, Chenn

ruary 2

Abstract

Single cry nlineasize of 22 mm CAD4shows that th tudiesco-efficients HB crystudies of L 2005 Else

Keywords: Crystal morphology; Thermal properties; Hardness; Defects; Semiorganic crystal

1. Introduction

Compleing materiaas they tenpurely orgathermal proamino acidto the factchiral carbric space groptical secmide monooptical sing[3]. Fromthe orthorha= 7.0530[3]. The strwith that o

CorresponE-mail ad

TEP representation of the molecule with 50% probability

0254-0584/$doi:10.1016/jxes of amino acids with inorganic salts are promis-ls for optical second harmonic generation (SHG),d to combine the high optical nonlinearity of thenic amino acid with the favorable mechanical andperties of the inorganic salt. The importance ofs in nonlinear optical (NLO) applications is duethat all the amino acids except glycine contain

on atom and crystallize in the non centrosymmet-oups. Therefore, they are potential candidates forond harmonic generation [1,2]. l-Histidine bro-hydrate [LHB] is one such semiorganic nonlinearle crystal with molecular formula C6H12N3O3Br

the structural point of view LHB crystallizes inombic system, whose unit cell parameters are

A, b= 9.0409 A, c= 15.2758 A and= = = 90ucture of LHB crystal is found to be isostructuralf l-histidine hydrochloride [4]. Fig. 1 shows OR-

ding author. Tel.: +91 442 2490490; fax: +91 442 8175566.dress: psagayaraj@hotmail.com (P. Sagayaraj).

ellipsoids for non-hydrogen atoms.Recently, new semiorganic single crystals like l-histidine

tetrafluroborate (l-HFB) have been successfully grown byMarcy et al. [5] and it was found that l-HFB has higher NLOproperties than l-arginine phosphate monohydrate (LAP).The growth kinetics, linear and nonlinear properties of l-HFB was reported by Aggarwal et al. [6] and Rajendran et al.[7]. Hydrogen bonding and thermal vibrations in crystallinephosphate salts of histidine and imidazole were reported forthe first time by Blessing [8]. Roman et al. [9] reported thespectroscopic and structural study of l-histidinium perchlo-rate. Karle et al. [10] studied the reaction of l-histidine withsquaric acid (H2C2O4) and Ratajczak et al. prepared a NLOactive crystal with l-histidine, 2H3AsO4 composition [11].We reported the growth and optical properties of LHB crys-tal earlier [3]. In the present paper, we report on the mor-phology of LHB crystal. The crystals have been subjected tovarious characterization studies such as thermal analysis, mi-crohardness, and micromorphology. The photoconductivitystudies of LHB is also carried out and reported for the firsttime.

see front matter 2005 Elsevier B.V. All rights reserved..matchemphys.2005.02.034optical LHB singlReena Ittyachan a, Preema C. Thom

M. Palanichamy b, P. Saa Department of Physics, Loyola College,

b Department of Chemistry, Anna UniversityReceived 9 December 2004; received in revised form 22 Feb

stals of l-histidine bromide monohydrate (LHB), a semiorganic no 20 mm 9 mm. Morphology of the crystal was identified using

e crystal starts its decomposition at 133.9 C. The microhardness sfor different orientations. Microstructural imperfections of the L

HB reveals that it exhibits positive photoconductivity.vier B.V. All rights reserved.iorganic non-linearystalD. Prem Anand a,raj a,i 600034, Indiaai 600025, India

005; accepted 28 February 2005

r (NLO) material have been successfully grown up to a-X-ray diffractometer. Thermal analysis of LHB crystalof the crystal confirm anisotropy in the work hardeningstal have been studied by etching. Photoconductivity

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R. Ittyachan et al. / Materials Chemistry and Physics 93 (2005) 272276 273

LHB cr

2. Experim

The parequivalentequivalentfied by repedistilled homaintaininture bath, wration occudesiccator

Fi

H2Oolutiom 2Fig. 1. ORTEP representation of

ental

ent compound was synthesized by dissolving oneof l-histidine in deionised water containing one

2 gmous s

22 mof hydrogen bromide [3]. The product was puri-ated crystallization, typically thrice, from double-t water. The super saturated solution was kept

g a temperature of 305 K in a constant tempera-hich has an accuracy of 0.01 C. Slow evapo-

rs by condensation of water on a relatively coollid and the rate of solvent extraction was around

g. 2. Photograph of as-grown LHB single crystal.

3. Charac

3.1. Morph

The crysalong the lystal.

per day. LHB crystals were grown from aque-n by slow evaporation technique up to a size of0 mm 9 mm (Fig. 2).terization

ology

tal grows as a polyhedron of 16 faces, with b-axis,ength of the crystal (Fig. 3). Six faces around the

Fig. 3. Morphology of LHB crystal.

274 R. Ittyachan et al. / Materials Chemistry and Physics 93 (2005) 272276

trunk of thefaces whicIn all growThere are fibut they areof the grownot morpho

3.2. Therm

Thermoanalysis (Dfor LHB crSTA 409Cout betweeheating ratis shown inmetric anaa sharp weThis is follat 260 C aof these stadecomposigives a wetween 600is found toanalysis comain. If thetemperaturloss even bsigned to losurface.

The DT50 and 135was maintashown in t133.9, 259the decompthe crystal

Fig. 5. DTA curve of LHB.

tage of decomposition at 133.9 C. The weight loss thatrred over a wide range of temperature (6001200 C) inGA trace is also seen to give a broad endotherm in thetracee DS

itrogemin1

endoakly a

ds to t4). Afbservendo

thermions inof we

r distithermrent tes, thess interring dattice.t 135.r enviFig. 4. TGA curves of LHB.

crystal (parallel to b-axis) are the most prominenth are (0 0 1), (1 0 1) and (1 0 1) and their friedels.n crystals, this (1 0 1) is the most prominent plane.ve planes each on top and bottom of the crystal,not related through friedel symmetry. The widthn crystal in the c direction (1 0 0) and (0 1 0) arelogically developed planes.

al analysis of LHB crystal

gravimetry analysis (TGA), differential thermalTA) and differential scanning calorimetry (DSC),ystal were taken using the instrument NETSZCH. The TGA analysis of LHB crystal was carriedn 50 and 1350 C in the nitrogen atmosphere. Thee was maintained at 10 C/min. The thermogramFig. 4. The trace due to differential thermo gravi-

lysis is also shown in the same figure. There isight loss at 130.1 C due to loss of lattice water.owed by two stages of weight loss, the first onend the second at 338.7 C. The total weight losstes corresponds to 56%. Hence it is assigned to

tion stage of LHB crystal. The resulting residueight loss for a wider range of temperature be-and 1200 C. The total weight loss of this stage

first soccu

the TDTA

Ththe n5 Cbroadof wespon(Fig.was o

sharpendopositstagemajoendodiffewordmentrequithe llost amajobe 34.54%. As the total weight loss in the entirerresponds to 100%, no residue is observed to re-TGA and DTG traces are compared in the lower

e region below 100 C, the existence of weightelow 50 C could be evident. This could be as-ss of some weakly adsorbed water on the crystal

A analysis of LHB was also performed between0 C in the nitrogen atmosphere. The heating rateined at 10 C min1. The DTA trace obtained is

he Fig. 5. There are sharp endothermic peaks at.8, and 328.2 C and all of these coincide withositions shown in the TGA trace (Fig. 4). Hence,

does not have any isomorphic transition below itsabove 600 C.C analysis was done between 20 and 200 C inn atmosphere. The heating rate was maintained at. The DSC trace is shown in the Fig. 6. There is atherm between 25 and 60 C. It is assigned to lossdsorbed water. This observation very well corre-

he assumption that was made in the TGA analysister this endothermic transition no other transitioned until the temperature reaches 130 C. There arethermic peaks at 135.6, 138.7 and 148.4 C. Theses do not correspond exactly to the noted decom-

the TGA trace. The TGA trace gives only oneight loss between 100 and 200 C. Hence, the twonct endotherms at 135.1 and 138.7 C and majors at 143 and 148.4 C suggest the requirement ofmperatures for the loss of lattice water. In othere water molecules are to have different environ-acting differently with them, thus making themifferent amount of energy for their expulsion fromBut, as the major portion of the lattice water is1 and 138.7 C, it suggests existence of only tworonments for lattice water in the crystal.Fig. 6. DSC curve of LHB.

R. Ittyachan et al. / Materials Chemistry and Physics 93 (2005) 272276 275

Fig. 7. Variatorientations fo

3.3. Micro

Microhausing a LeVickers dilight microtemperaturdentations.by varying

The Viccalculatedhas been plload (P). Itof (1 0 1) plwith the incbetween lois derived fapplied loaor work hamaterial. Tfrom the sl2 for the pl

3.4. Micro

The nonpends on tregated impresults theSo it is verperfectionsThe rate odepend disreacting suing and ison the crysical attackline [13].

. (a) Mictangular stacking planes observed on (1 0 1) planes of LHB crystaltching.

e etching behavior of different crystallographic facesB crystal were carried out by using double-distilled

r as an etchant. Etching of the crystal surfaces were car-out by dipping the crystal in water for few seconds attemperature and then wiping them with dry filter paper.

patterns were observed and photographed under opticalWetzlar Metallax II microscope in reflected light.e microphotograph of (1 0 1) plane of LHB crystal be-

etching is shown in Fig. 8a. The surface is not smoothe etching. No particular pattern of growth is visible. Af-ion of Vickers hardness number with load on (1 0 1) and (1 0 1)r LHB crystal.

hardness studies

rdness measurement of LHB crystal were madeitzWetzlar microhardness tester fitted with a

amond pyramidal indentor attached to an incidentscope. The static indentations were made at roome with a constant indentation time of 15 s for all in-The indentation marks were made on the surfacesthe load from 5 to 50 g.kers microhardness number Hv of the crystal wasusing the relation Hv = 1.8544P/d2 MPa. A graphotted between hardness number (Hv) and appliedis observed from the graph that the hardness valueane and (1 0 1) plane decreases and then increasesrease of the applied load (Fig. 7). A plot obtainedg (P) against log (d) gives a straight line whichrom the Meyers law, the relation connecting thed is given by P= adn. Here n is the Meyer indexrdening co-efficient and a is a constant for a givenhe work hardening co-efficient has been calculatedope of the straight line. The value of n is less thananes of LHB.

Fig. 8(b) Reafter e

Thof LHwateriedroom

EtchLeitz

Thforebeformorphology studies

linear efficiency of the NLO material mainly de-he quality of the crystal grown because the seg-urities and dislocations occurring during growthdistortion of the optical beam to be processed.

y much essential to study the microstructural im-or crystal defects in the as-grown crystals [12].

f reaction of a solution with a solid surface cantinctly on the crystallographic orientation on therfaces. This rate dependence is the basis of etch-bought intentionally by specific chemical attacktal surface. The etch pits are the result of chem-at the strain field surrounding the dislocation

ter etchingplanes) of g

Before eto be furroAfter etchietch pits ofof periodic

3.5. Photo

PhotocoKeithley 48room tempied by connand a picoacrophotograph of (1 0 1) plane of LHB crystal before etching., nearly rectangular stacking in planes (cleavagerowth is visible (Fig. 8b).tching, the (1 0 1) plane of LHB crystal is foundwed with very few conical small pits (Fig. 9a).ng for 15 s, large number of elongated rectangularsimilar shape are seen (Fig. 9b). There is a kind

ity seen in the distribution of these pits.

conductivity studies

nductivity of the crystals were studied using5 picoammeter. The experiment was performed at

erature. Dark conductivity of the sample was stud-ecting the sample in series to a dc power supply

mmeter as described by Xavier et al. [14]. Electri-

276 R. Ittyachan et al. / Materials Chemistry and Physics 93 (2005) 272276

Fig. 9. (a) Mi(b) Elongatedafter etching.

cal contactsamples us0 to 300 Vnoted fromthe samplefocusing a

F

vex lens. The dc input was increased from 0 to 300 V in stepsand the corresponding photocurrents were measured.

The variation of photocurrent (Ip) with applied field isshown in Fig. 10. The current increased when the sample wasilluminated and it decreased suddenly when the illuminationwas stopped, and thus revealing that the LHB crystal exhibits

ive photoconductivity.

onclu

orphoplane orystalf the cficienorphoown ccrysta

owled

e sincnd Dreir heemb

nai fouctivitcrophotograph of (1 0 1) plane of LHB crystal before etching.rectangular etch pits observed on (1 0 1) plane of LHB crystal

posit

4. C

Mnentthe cies oco-efcrom

as-grLHB

Ackn

Wnai afor thulty mChenconds were made at a spacing of about 0.12 cm on theing silver paint. The dc input was increased fromin steps and the corresponding dark currents werethe electrometer. For measuring the photo current,was illuminated with a halogen lamp (100 W) byspot of light, on the sample with the help of a con-

ig. 10. Current vs. applied field for LHB crystal.

Reference

[1] M.N. B376.

[2] M.N. Bh[3] R. Ittyac[4] J. Donoh[5] H.O. M

Thomas,[6] M.D. A

Shields,[7] K.V. Ra

Ramasam[8] R.H. Ble[9] P. Roma

logr. Spe[10] I.L. Kar

(1996) 7[11] H. Rata

May, J.[12] S. Muke[13] A.S. Ha

Growth[14] F.P. Xav

nines 3sion

logy studies indicate that (1 0 1) is the most promi-f the LHB crystal. Thermal analysis confirms that

is stable up to 130.1 C. The microhardness stud-rystal indicate anisotropy in the work hardening

t and Vickers hardness values of the crystal. Mi-logical studies revealed the crystal defects in therystal. The positive photoconductivity nature ofl is confirmed by photoconductivity studies.

gements

erely thank Dr. Babu Varghese, SAIF, IIT, Chen-. P. Ramasamy, CGC, Anna University, Chennailp in the analysis. Also we are thankful to the fac-ers of Loyola Institute of Frontier Energy (LIFE),r providing the facilities to carry out the photo-y experiments.

s

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ssing, Acta Crystallogr. B 42 (1986) 613.n, J.M. Gutierrez-Zorrilla, A. Luque, A. Vegas, J. Crystal-ctrosc. Res. 17 (1987) 585.le, D. Ranganathan, V. Haridas, J. Am. Chem. Soc. 118182.jczak, J. Barycki, A. Pietraszko, J. Baran, S. Debrus, M.Venurini, J. Mol. Struct. 526 (2000) 269.rji, T. Kar, Jpn. Appl. Phys. 38 (1999) 832.ja Hameed, G. Ravi, Dhanasekaran, P. Ramasamy, J. Cryst.212 (2000) 227.ier, A.R. Inigo, G.J. Goldsmith, J. Prophyrins Phathalocya-(1999) 679.

Growth and characterization of semiorganic non-linear optical LHB single crystalIntroductionExperimentalCharacterizationMorphologyThermal analysis of LHB crystalMicrohardness studiesMicromorphology studiesPhotoconductivity studies

ConclusionAcknowledgementsReferences