Studies on the growth, structural, optical, SHG and thermal properties of γ-glycine single crystal: An organic nonlinear optical crystal

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Studies on the growth, structural, optical, SHG and thermal properties of ␥-glycine single crystal: An organic nonlinear optical crystal S. Anbu Chudar Azhagan ∗ , S. Ganesan Department of Physics, Govt. College of Technology, Coimbatore 641013, India

a r t i c l e

i n f o

Article history: Received 26 August 2012 Accepted 10 January 2013 Keywords: Crystal growth X-ray diffraction Optical studies Thermal analysis Spectral studies Nonlinear optical crystals

a b s t r a c t Single crystals of the organic nonlinear optical material ␥-glycine have been grown in the presence of Zinc sulphate by slow evaporation technique at ambient temperature for the first time. Bulk growth of ␥-glycine single crystals was grown by Top-seeded solution growth method. The ␥-phase of glycine was confirmed by powder X-ray diffraction and the FTIR analysis. Elemental analysis CHN was performed to confirm the non-inclusion of zinc sulphate species into the solution. Inductively coupled plasma optical emission spectrometry study (ICP-OES) was employed to quantify the concentration of Zinc element in the grown ␥-glycine single crystals. The optical transmission was ascertained from UV–Vis–NIR spectrum. The optical band gap was estimated for ␥-glycine single crystal using UV–Vis–NIR study. Differential scanning calorimetry analysis was employed to explore information about thermal stability, phase transition and melting point of the grown crystal. The second harmonic generation relative efficiency was measured by Kurtz and Perry powder technique. © 2013 Elsevier GmbH. All rights reserved.

1. Introduction Nonlinear optical (NLO) materials have wide applications in the area of laser technology, optical communication, telecommunication, signal processing, optical interconnection, frequency shifting, optical modulation, optical switching, optical logic and electro optics application [1,2]. The development of photonic and optoelectronic technologies rely heavily on growth of NLO materials with the greater SHG efficiency and high light no linear responses. A NLO material need to have a large NLO coefficient, large birefringence, wide transparency range, high damage threshold, broad spectral and temperature bandwidth, good chemical and mechanical stability, ease of growth and low cost [3]. A survey of literature shows that the six distinct polymorphic forms of glycine can be formed under different solution conditions: ␣-, ␤-, and ␥-forms in ambient environment and ␦-, ␧- and ␤1 -forms under high pressure conditions. Both ␣ and ␤-glycine polymorphs crystallize in centrosymmetric space group P21 /m and hence they do not exhibit second harmonic generation, while ␥-form of glycine crystallizes in the trigonal–hexagonal system with non-centrosymmetric space group P31 structure making it a suitable candidate for piezoelectric, electro optic and nonlinear optical applications. ␣-Glycine can be formed from spontaneous nucleation of pure aqueous glycine. The least stable ␤-form can be formed using mixed solvents such as

methanol or ethanol and water. ␥-Glycine is the thermodynamically most stable form at room temperature. It is produced from acidic (pH 3.40) and basic (pH 10.10) solutions. Moreover, it can be crystallized with additives in neutral aqueous solutions. At 1.9 GPa ␥-glycine begins to undergo transition to form high pressure phase ␧-glycine. The transition from ␧-glycine to a new phase of glycine ␦-glycine begins to occur at 2.74 GPa and the ␤1 -form at 0.76 GPa. In solid state, ␥-glycine exists as a dipolar ion in which carboxylic group is present as carboxylate ion and amino group are present as ammonium ion. Due to this dipolar nature, glycine has a high melting point. In addition to this, the presence of chromophores namely amino group and carboxyl group make the ␥-glycine crystal transparent in the UV–Vis region [4–11]. In the recent past, growth and various studies of ␥-glycine crystals have been reported by several scientists and it was observed that ␥-glycine single crystals have been grown using additives such as magnesium chloride [10], ammonium nitrate [12], potassium fluoride [13], phosphoric acid [14], ammonium acetate [15], ammonium carbonate [16], potassium bromide [17], and lithium acetate [18]. In the present work, we report the growth and the characterization of ␥-glycine crystals grown in aqueous solution containing zinc sulphate for the first time. 2. Experimental procedure 2.1. Materials used

∗ Corresponding author. Tel.: +91 9842445995; fax: +91 422 2455230. E-mail addresses: [email protected], [email protected] (S.A.C. Azhagan).

Glycine (C2 H5 No2 aminoaceticacid) SD-fine AR (99.5%) M.wt: 75.07 g/mol, zinc sulphate heptahydrate (ZnSo4 ·7H2 O) SD-fine AR

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Please cite this article in press as: S.A.C. Azhagan, S. Ganesan, Studies on the growth, structural, optical, SHG and thermal properties of ␥-glycine single crystal: An organic nonlinear optical crystal, Optik - Int. J. Light Electron Opt. (2013), http://dx.doi.org/10.1016/j.ijleo.2013.02.019

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3. Results and discussion 3.1. Elemental and ICP-OES analysis

Fig. 1. Photograph of harvested ␥-glycine crystal.

(99.5%) M.wt: 287.54 g/mol and double distilled water were used for the crystal growth experiments. 2.2. Crystal growth of -glycine For growing the ␥-glycine single crystals, analytical grade chemicals of ␣-glycine and zinc sulphate heptahydrate were mixed in the stoichiometric ratio 3:1 in 100 ml double distilled water, respectively. The reaction mixture was stirred well at ambient temperature for 6 h by using Remi make magnetic stirrer to obtain a homogenous mixture. The supersaturated solution was filtered by Whatman 41 filter paper. The resulting solution was taken in a beaker and it is covered with perforated sheets and kept in dust free environment. The nucleation period  for ␥-glycine single crystal is 9 days. The nucleated crystals were allowed for further growth to get reasonable size. The photograph of the harvested ␥-glycine single crystal is shown in Fig. 1. The zinc sulphate heptahydrate salt is irritant one and it is taken with extreme care to use this material as additive to yield ␥-polymorph of glycine single crystal. 2.3. Top-seeded solution growth method The calculated amount of glycine and zinc sulphate heptahydrate salt were taken in 3:1 molar ratio in 500 ml beaker. The saturated mother solution was prepared at ambient temperature after stirring the solution for 24 h. One of the good quality seed crystals obtained from slow evaporation at room temperature was hung above the saturated mother solution such that, one portion of the seed crystal just touches the solution. The portion of the crystal which touches the solution started to grow when evaporation took place. Transparent ␥-glycine single crystals of bulk size were obtained in a period of three weeks (Fig. 2).

Carbon, Hydrogen, Nitrogen analysis of the grown ␥-glycine crystals were employed out using Elemental Vario EL III analyzer. The results of the elemental analysis shows that the grown ␥-glycine single crystal contain Carbon = 31.972% (32.000), Hydrogen = 6.778% (6.714) and N = 18.693% (18.659). It is clear that the CHN analysis of the powdered sample shows good agreement with the theoretical values given in the parenthesis and it confirms the molecular formula of the grown crystal. ICP-OES is used for qualitative and quantitative determination of metals and certain non-metals in solution. In order, to determine the concentration of Zn element present in the grown crystal, the grown crystal was crushed into pieces and finely grounded in a mortar. This powdered sample weighing about 53.35 mg was digested in 5 ml HNO3 and made up into 50 ml using HPLC grade water. The filtered solution analyzed with ICP-AES system. The detection limit is 0.01 ppm. The results from the ICP-OES analysis shows that very low concentration of zinc (i.e. 0.50 ppm) present in the grown crystal and hence it can be concluded that the zinc species may be incorporated in void space with in the crystal lattice of ␥-glycine. It is evident that zinc sulphate species inhibit the growth of ␥-phase of glycine. 3.2. Powder X-ray diffraction analysis The powder X-ray diffraction studies were employed using a ´˚ radiaBruker D8 advance diffractometer with Cu K␣ ( = 1.5406 A) tion. The powdered ␥-glycine sample was scanned in the 2 values from 5◦ to 70◦ at a scan rate of 1◦ /min. Fig. 3 shows the XRD profile of the grown ␥-glycine crystal. The positions of the peaks were found to be in good agreement with the literature data available in JCPDS file no.: 06-230 [19]. The characteristic peak at 25.3◦ (2) corresponds to ␥-glycine. This study confirms the ␥-phase of glycine. The reflection peaks corresponding to different crystal h k l planes in the recorded XRD profile were indexed and the data obtained from the XRD spectrum such as Angle 2-theta, d value, h k l, peak intensity, intensity (%) and Full width half maximum value (FWHM) of every prominent peak in the spectrum are tabulated in Table 1. The sharp and strong peaks in the XRD profile confirms the good crystallinity of the grown crystal. From the XRD data, the lattice parameters of the grown ␥-glycine crystal were calculated using Unit cell software package and are presented in Table 2 along with literature values. 3.3. FTIR spectral analysis The grown ␥-glycine crystals were subjected to FTIR analysis to analyze the presence of functional groups. The Fourier transform

(1 1 0)

35000

30000

20000

15000

(2 1 1) (3 0 0)

(1 0 2) (2 0 1)

(1 0 0)

5000

(2 0 0) (1 1 1)

10000

(2 1 0)

(1 0 1)

Counts

25000

0 0

10

20

30

40

50

60

70

80

2 Theta (deg.)

Fig. 2. Bulk size ␥-glycine crystal (Top-seeded solution growth method).

Fig. 3. XRD profile of the grown ␥-glycine crystal.

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Table 1 Powder XRD profile of Gamma glycine single crystal. hkl

Angle 2-theta (◦ )

´˚ d value (A)

FWHM (◦ )

Peak intensity (Counts)

Intensity (%)

100 101 110 200 111 201 102 210 211 300

14.592 21.978 25.369 29.371 30.382 33.839 36.089 39.196 42.718 44.627

6.065 4.041 3.508 3.038 2.940 2.647 2.487 2.296 2.115 2.029

1.305 1.834 1.418 1.550 – 1.200 1.695 1.417 1.977 1.668

44.637 385.903 1000.000 99.746 29.538 40.497 178.965 134.781 26.232 22.893

4.464 38.590 100.000 9.975 2.954 4.050 17.897 13.478 2.623 2.289

Table 2 Lattice parameters of Gamma glycine single crystal.

10

[14]

[17]

[10]

Present work

a b c

7.028 7.028 5.447

7.039 7.039 5.492

7.037 7.037 5.489

7.015 7.015 5.438

infrared (FTIR) spectrum of ␥-glycine (Fig. 4) was recorded at room temperature in the spectral range 400–4000 cm−1 by KBr pellet method using the Perkin Elmer grating Infrared spectrophotometer. The peaks observed at 505, 600 and 683 cm−1 are attributed to carboxylic groups while the peak observed at 1490 cm−1 correspond to NH3 + group. Frequencies observed at 1039 and 888 cm−1 are attributed as C C N asymmetric and C C N symmetric stretching vibration. The absorption peaks observed at 926 and 1328 cm−1 are attributed to CH2 rocking and CH2 twisting mode. The peak observed at 1123 cm−1 corresponds to NH3 + rocking. The prominent band near 2161 cm−1 may be assigned to combination bond. The other peaks around 2604 and 3108 cm−1 have been attributed to NH3 + stretching group. The presence of various functional groups of the grown crystal is in good agreement with those reported in the literature values [10,13,14,17,20]. 3.4. DSC studies DSC analysis of powdered sample of ␥-glycine crystals were carried out by employing NETZSCH DSC 200F3 instrument between 30 and 500 ◦ C. The recorded DSC thermogram is shown in Fig. 5. The DSC curve shows a small exothermic peak with no loss in mass at 185.95 ◦ C. This phase transition peak corresponds to transformation of crystal from ␥-form to ␣-form. The sharpness of this exothermic peak shows good degree of crystallinity. Narayan Bhat and Dharmaprakash [11] observed that the phase transition from ␥- to ␣-glycine at 172 ◦ C. Litaka [4–7] reported that the transition point between ␥- and ␣-glycine exists at 165 ± 5 ◦ C. But Perlovich et al. [21] concluded from their studies that the transition temperature between ␣- and ␥-polymorphs can range between 165 and 201 ◦ C. The melting point of the grown crystal is indicated by broad

8

DSC(mW/mg)

´˚ Lattice parameters (A)

6

4

2

0 500

400

350

300

250

200

150

100

50

Temperature (deg.C)

Fig. 5. DSC curve of ␥-glycine crystal.

exothermic peak at 259.5 ◦ C. Thus, in the present investigation, grown ␥-glycine crystal is structurally stable up to 185.95 ◦ C. 3.5. Optical absorption and transmission studies An optical absorption and transmission spectrum were recorded in the wavelength range 200–1100 nm using Perkin Elmer Lambda 935 UV–Vis–NIR spectrometer. The obtained absorption and transmission spectra are shown in Figs. 6 and 7. The UV spectra show a wide transparency window and there is no absorption in the region between 220 and 1100 nm. The lower UV cutoff wavelength is around 200 nm. The band gap is estimated using the formula Eg = 1240/ (nm). It is found to be 6.2 eV. The observed spectra and band gap value are in good agreement with the literature values [10,15,17]. 3.6. Nonlinear optical studies The SHG efficiency of the crystals of ␥-glycine grown in presence of the small amount of zinc was measured by using the Kurtz Powder technique [22]. The Q-switched Nd-YAG laser having input beam of 1064 nm with pulse width 8 ns repetition rate 10 Hz was made to fall normal on the crystalline powder density packed in a micro capillary tube. The ␥-glycine second harmonic signal of 12

100 90

10

Absorption(%)

80

% Transmittance

450

70 60 50 40

8 6 4

30

2

20 10 0 500

0 1000

1500

2000

2500

3000

3500

Wavenumber (Cm-1)

Fig. 4. FTIR spectrum of ␥-glycine crystal.

4000

200

400

600

800

1000

1200

Wavelength (nm)

Fig. 6. Optical absorption spectrum.

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References

100

Transmittance(%)

90 80 70 60 50 40 30 20 200

10 0

400

200

600

800

1000

1200

Wavelength(nm) Fig. 7. Optical transmittance spectrum.

145 mV was obtained, while the standard inorganic material KDP gave a signal of 45 mV for the same input laser energy incident on the powder sample. Thus, the SHG relative efficiency of ␥-glycine crystal was found to be 3.22 times higher than that of KDP. 4. Conclusion Optically transparent ␥-glycine single crystals have been grown by slow evaporation method. Bulk growth of ␥-glycine was grown by Top-seeded solution growth method. The presence of small amount of zinc species in the solution during the growth does not affect the cell parameters of the grown crystal. The lattice parameters are found by powder XRD analysis and they agree well with the reported values. The presence of functional groups was identified by Vibrational FTIR analysis. The UV–Vis–NIR absorption and transmission spectrum shows that the cutoff wavelength falls at 200 nm with an energy gap of 6.2 eV and a wide transparency window between 220 and 1100 nm making it a suitable candidate for NLO applications. DSC thermogram shows a phase transition from ␥- to ␣-glycine around 185.95 ◦ C. The powder SHG efficiency of the grown crystal is 3.22 times that of standard inorganic material KDP which is suitable for photonics and optoelectronic device applications. Acknowledgements The supports extended in the research by Sophisticated Analytical instrumental Facility (STIC), Cochin, ST. Joseph’s college, Trichy and IISC, Bangalore for SHG studies are gratefully acknowledged.

[1] R.W. Boyd, Nonlinear Optics, Academic Press Inc., San Diego, 1992. [2] B.E.A. Saleh, M.C. Teich, Fundamentals of Photonics, John Wiley & Sons Inc., New York, 1991. [3] S. Foerier, V.K. Valev, G. Koeckelberghs, I.A. Kolmychek, O.A. Aksipetrov, A spectroscopic study on the nonlinear optical susceptibilities of organic molecules, Acta Phys. Pol. A 112 (2007) 927–934. [4] Y. Litaka, The crystal structure of ␥-glycine, Acta Crystallogr. 14 (1961) 1–10. [5] Y. Litaka, New form of glycine, Proc. Jpn. Acad. 30 (1954) 109–112. [6] Y. Litaka, The crystal structure of ␥-glycine, Acta Crystallogr. 11 (1958) 225–226. [7] Y. Litaka, The crystal structure of ␤-glycine, Acta Crystallogr. 13 (1960) 35–45. [8] A. Dawson, D.R. Allan, S.A. Belmonte, S.J. Clark, W.I.F. David, P.A. Mc Gregor, S. Parsons, C.R. Pulham, L. Sawyer, Effect of high pressure on the crystal structures of polymorphs of glycine, Cryst. Growth Des. 5 (2005) 1415–1427. [9] E.V. Boldyreva, High-pressure-induced structural changes in molecular crystals preserving the space group symmetry: anisotropic distortion/isosymmetric polymorphism, Cryst. Eng. 6 (2003) 235–254. [10] G.R. Dillip, G. Bhagavannarayana, P. Raghavaiah, B. Deva Prasad Raju, Effect of magnesium chloride on growth, crystalline perfection, structural, optical, thermal and NLO behavior of ␥-glycine crystals, Mater. Chem. Phys. 134 (2012) 371–376. [11] M. Narayan Bhat, S.M. Dharmaprakash, Effect of solvents on the growth morphology and physical characteristics of nonlinear optical ␥-glycine crystals, J. Cryst. Growth 242 (2002) 245–252. [12] B. Narayana Moolya, A. Jayarama, M.R. Sureshkumar, S.M. Dharmaprakash, Hydrogen bonded nonlinear optical ␥-glycine: crystal growth and characterization, J. Cryst. Growth 280 (2005) 581–586. [13] G.R. Dillip, P. Raghavaiah, K. Mallikarjuna, C. Madhukar Reddy, G. Bhagavannarayana, V. Ramesh Kumar, B. Deva Prasad Raju, Crystal growth and characterization of ␥-glycine grown from potassium fluoride for photonic applications, Spectrochim. Acta A 79 (2011) 1123–1127. [14] R. Parimaladevi, C. Sekar, Crystal growth and spectral studies of nonlinear optical ␥-glycine single crystal grown from phosphoric acid, Spectrochim. Acta A 76 (2010) 490–495. [15] S. Anbuchudar Azhagan, S. Ganesan, Effect of ammonium acetate addition on crystal growth, spectral, thermal and optical properties of glycine single crystals, Optik 123 (2012) 993–995. [16] S. Anbuchudar Azhagan, S. Ganesan, Linear and nonlinear optical studies of ␥-glycine single crystals from ammonium carbonate for optoelectronic applications, Optik (2012). [17] Sd. Zulifiqar Ali Ahamed, G.R. Dillip, P. Raghavaiah, K. Mallikarjuna, B. Deva Prasad Raju, Spectroscopic and thermal studies of ␥-glycine crystal grown from potassium bromide for optoelectronic applications, Arab. J. Chem. (2011). [18] P.V. Dhanraj, N.P. Rajesh, Growth and characterization of nonlinear optical ␥glycine single crystal from lithium acetate as solvent, Mater. Chem. Phys. 115 (2009) 413–417. [19] Organic Index to the Powder Diffraction File, Joint committee of Powder Diffraction Standards, 2002. [20] R. Silverstein, G.C. Bassler, T.C. Morrill, Spectrometric Identification of Organic Compounds, John Wiley & Sons, 1981. [21] G.L. Perlovich, L.K. Hansen, A. Bauer-Brandl, The polymorphism of Glycine. Thermochemical and structural aspects, J. Therm. Anal. Calorim. 66 (2001) 699–715. [22] S.K. Kurtz, T.T. Perry, A powder technique for the evaluation of nonlinear optical materials, J. Appl. Phys. 39 (1968) 3798–3813.

Please cite this article in press as: S.A.C. Azhagan, S. Ganesan, Studies on the growth, structural, optical, SHG and thermal properties of ␥-glycine single crystal: An organic nonlinear optical crystal, Optik - Int. J. Light Electron Opt. (2013), http://dx.doi.org/10.1016/j.ijleo.2013.02.019