Growth of N-Glycyl-L-Valine (GV) single crystal and its spectral, thermal and optical characterization

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Growth of N-Glycyl-

L

-Valine (GV) single crystal and its spectral, thermal

and optical characterization

S. Janarthanan

a

_{, R. Sugaraj Samuel}

b,⇑

_{, Y.C. Rajan}

c

_{, P. Suresh}

d

_{, K. Thangaraj}

e

a

Department of Physics, St. Peter’s College of Engineering and Technology, Avadi, Chennai, India b

Department of Physics, SRM University (City Campus), Vadapalani, Chennai, India c

Department of Material Science and Engineering, National Chiao Tung University, Taiwan d

Department of Physics, Vivekanandha College of Engineering for Women, Tiruchengode, Tamil Nadu, India e_{Department of Physics, Kongu Engineering College, Perundurai, Tamil Nadu, India}

h i g h l i g h t s

"_N-Glycyl-_L_{-Valine (GV) single}

crystals were grown by slow evaporation solution growth method.

"The FTIR and1H NMR spectral

studies conducted on the GV conﬁrms the functional groups and position of protons.

"_{The UV–Vis–NIR spectral study done}

reveals that GV crystal has a good optical transparency.

"_{The TG–DTA analyses reveals that}

GV crystal is thermally stable up to 246 °C.

"_{The Kurtz–Perry test done on the GV}

crystal reveals that the grown crystals has nonlinear optical (NLO) properties.

g r a p h i c a l

a b s t r a c t

a r t i c l e

i n f o

Article history: Received 16 July 2012

Received in revised form 23 October 2012 Accepted 25 October 2012

Available online 29 November 2012 Keywords:

Crystal growth X-ray techniques Thermal analysis

a b s t r a c t

A nonlinear optical crystal of N-Glycyl-L-Valine (GV) single crystals was grown by slow evaporation

solu-tion growth technique from an aqueous solusolu-tion. The unit cell parameters and the crystal structure were determined by single crystal X-ray diffraction study. The Fourier transform infrared (FTIR) and proton nuclear magnetic resonance (1_{H NMR) spectral studies were carried out to identify the functional groups}

of the grown crystals. The ultraviolet visible near infrared (UV–Vis–NIR) spectrum was recorded to study the optical transparency of the grown crystal. The thermogravimetric (TG) and differential thermal (DTA) analyses revealed the thermal stability of the sample. The presence of second harmonic generation (SHG) for the grown crystal was conﬁrmed by Kurtz–Perry powder technique.

Introduction

Extensive research has been conducted over the past two dec-ades on the growth of non-linear optical (NLO) crystals. The NLO

property of the materials is playing a major role in emerging photonic and optoelectronic technologies. New NLO frequency con-version materials have a signiﬁcant impact on laser technology and optical data storage[1]. The focus of the recent researchers is on developing new semiorganic NLO materials, as they have the advan-tages of being both organic and inorganic materials. The origin of NLO property in these materials is due to the presence of delocalized

http://dx.doi.org/10.1016/j.saa.2012.10.078 ⇑Corresponding author. Mobile: +91 9940186016.

E-mail address:[email protected](R. Sugaraj Samuel).

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 105 (2013) 34–37

Contents lists available atSciVerse ScienceDirect

Spectrochimica Acta Part A: Molecular and

Biomolecular Spectroscopy

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p

electrons. Many natural amino acids individually exhibit the NLO properties[2]because they have a donor NH2and an acceptor COOH

leading to the possibility for intermolecular charge transfer. Glycine is the simplest amino acid and it forms several new compounds with other organic as well as inorganic materials. Re-cently, several complexes of glycine have been reported, viz., digly-cine picrate [3], glycine sodium nitrate [4], glycine lithium sulphate[5], etc. In particular, semi-organic systems provide many interesting structure and bonding schemes for the molecular engi-neering of highly efﬁcient new NLO materials. In this article, we re-port the growth of single crystals of N-Glycyl-L-Valine a new semiorganic NLO material by slow evaporation method and its characterization by, XRD, spectral, and optical analyses. Second harmonic generation (SHG) test and the thermal studies aug-mented the capability of the crystal as potential NLO material for a commendable temperature range.

Materials and methods Crystal growth

In the present study, GV crystals were grown by low temperature solution growth using slow evaporation technique. The commer-cially available N-Glycyl-L-Valine (AR grade) was purified by re-peated crystallization process before the actual growth as the quality of single crystals depends on the purity of the used materi-als. Since, the growth process and the quality of the crystals signif-icantly depend on supersaturation, appropriate selection of solvent for the growth of the material is very important in crystal growth process. Deionized water at 35 °C was found to be the suitable sol-vent for preparing the growth solution. The super saturated solution was filtered by whatmann filter paper and allowed to evaporate slowly at room temperature over a period of three weeks, which

yielded optically good quality crystals as shown inFig. 1. A large size crystal can be obtained by taking large quantity of starting material. X-ray diffraction study

In order to conﬁrm the cell parameters of the grown GV crystals, the sample was subjected to single crystal XRD studies. The single crystal XRD study of GV single crystals was carried out using EN-RAF NONIUS CAD4-F single X-ray diffractometer with Mo k

a

(k = 0.7170 Å) radiation. Reﬂections from a ﬁnite number of planes were collected. The study revealed that grown GV crystal belongs to orthorhombic system with the following cell parameters, a = 5.452 Å, b = 26.601 Å, c = 43.872 Å and V = 6362.697 (Å)3_{. These}

values have a very close agreement with reported values[6]. FTIR spectral analysis

The functional groups of GV were conﬁrmed by recording the FTIR spectrum in the range of 400–4000 cm1 ₍_{Fig. 2}_{) using}

BRUKER IFS – 66 V spectrometer by KBr pellet technique to conﬁrm the presence of amino acid in the sample qualitatively. A sharp band at 1693 cm1_{is due to the amide carboxyl group and weak}

band at 1627 cm1_{is due to the carboxylic acid carbonyl group.}

Similarly the peaks at 1548 and 3074 cm1 _{is due to the N}_AH

stretching and bending vibration of amide and freeANH2groups.

A sharp signal at 3240 cm1_{is due to the hydroxyl group in}

car-boxyl acid and the peak at 2958 cm1_{is due to the presence of}

al-kyl stretching vibration. A signal at 2653 cm1 _{is due to the}

intermolecular hydrogen bonding present in between two carbox-ylic acid groups.

Proton NMR spectral studies

Identiﬁcation of compounds is an important task and is very much accomplished by techniques like NMR spectral analysis[7]. The proton NMR spectrum was recorded for the crystal dissolved in deuterated water (D2O) using JOEL GSX 400 NB FT NMR

spec-trometer, 400 MHz. The 1_{H NMR spectrum of GV is shown in}

Fig. 3. A sharp singlet at 0.91 ppm is due to the six protons of di-methyl group. A multiplet at 1.90 ppm corresponds to HAC, b-to ACOOH group. The sharp doublet at 4.25 ppm is assigned to CAH attached

a

-to ACOOH group. The two singlets at 8.03 and 11.0 ppm are attributed to the carboxylic acid proton ACOOH and amide proton ANHAC@OA of the GV respectively. The two sharp singlets at 1.53 and 3.54 ppm correspond to free amide pro-tonsANH2and carbonyl groupACH2attached in between to the

free amide and carbonyl group.

Fig. 1. As grown crystal GV.

Fig. 2. FTIR spectrum of GV.

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UV–Vis–NIR spectral analysis

The transparent nature of GV crystal was examined by the UV– Vis–NIR spectral analysis in the region between 200 and 1000 nm using VARIAN CARY 5E UV–Vis–NIR spectrophotometer. From the spectrum (Fig. 4), it is evident that the GV has a good transmittance as its lower cutoff wave length is below 300 nm. The large trans-mission in the entire visible region enables it to be a good candi-date for optoelectronic applications.

Thermal analysis

Thermogravimetric and differential thermal analyses give infor-mation regarding phase transition, water of crystallization and dif-ferent stages of decomposition of the crystal [8]. The thermo gravimetric analysis deals with the change in the mass of the sub-stance, which is continuously monitored as a function of tempera-ture when it is heated. The thermogravimetric analysis (TGA) and differential thermal analysis (DTA) of the crystal was done using the instrument NETZSCH STA 409 °C at a heating rate of 20 °C min1_{in the temperature range of 20–800 °C and the}

ther-mogram is shown inFig. 5. The sample is found to be thermally stable up to 246 °C. The TGA curve shows sharp melting endo-therm at 246 °C followed by a weak exoendo-therm at 380 °C, the later being clearer in the DTA curve. The DTA measurements are in close agreement with the TGA analysis in the experimental limits. The sharpness of the melting curve is an indication of purity of the sample.

Nonlinear optical test

Second harmonic generation (SHG) test for GV crystal was car-ried out using the Nd-YAG laser of wavelength of 1064 nm using Kurtz and Perry powder technique[9]. The input laser beam was passed through an IR reﬂector and was then directed on the micro-crystalline powder sample packed in a capillary tube. Photodiode detector and an oscilloscope assembly detected the light emitted by the sample. The emission of green light (532 nm) conﬁrmed the SHG of the crystal.

Conclusion

The single crystals of N-Glycyl-L-Valine (GV) were grown by slow evaporation technique. The single crystal X-ray diffraction analyses conﬁrm the lattice parameters of GV crystals which were in accordance with the literature values. FTIR and1_{H NMR spectral}

studies supported the structure and purity of GV. The UV–Vis–NIR spectrum showed that it has a good optical transmittance in the entire visible region and it is a potential candidate for optoelec-tronics. The thermogravimetric analysis showed that the grown crystal is thermally stable up to the temperature of 246 °C. The SHG property was experimentlly veriﬁed. Hence, the aforesaid re-sults make GV crystals a valid candidate for the NLO applications. Acknowledgments

The authors are thankful to Dr. S. Pandi, Professor in Physics, Pres-idency College, Chennai, India and Dr. M. Vanjinathan, Assistant Professor in Chemistry, D.G. Vaishnav College, Chennai, India for their help in the crystal studies and spectral analysis respectively. Appendix A. Supplementary material

Supplementary data associated with this article can be found, in the online version, athttp://dx.doi.org/10.1016/j.saa.2012.10.078. References

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Fig. 4. UV–Vis–NIR spectrum of GV.

Fig. 5. TG–DTA curves of GV. 36 S. Janarthanan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 105 (2013) 34–37

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