ABSTRACT Single crystals of semi-organic non-linear optical Glycine Sodium Chloride (GSC) have been successfully grown from three different pH (1.1, 6.0, and 10.8

O N Balasundaram

S Palaniswamy

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RJC  Rasayan J. Chem.                                                                                                       Vol.1, No.4 (2008),782-787 
EFFECT OF pH ON THE GROWTH AND 
CHARACTERIZATION OF GLYCINE SODIUM CHLORIDE 
(GSC) SINGLE CRYSTAL 
 
S.Palaniswamy and O.N.Balasundaram 
Department of Physics, P.S.G. College of Arts and Science, Coimbatore-641 014 
E-mail:palazhamni_5003@yahoo.com 
 
ABSTRACT 
Single crystals of semi-organic non-linear optical Glycine Sodium Chloride (GSC) have been successfully grown 
from three different pH (1.1, 6.0, and 10.8) solutions by evaporation solution growth. In this report we bring out the 
influence of pH on the optical, structural and NLO properties of the grown crystals. The grown crystals have been 
subjected to powder X-ray diffraction studies to identify the crystalline nature. Single crystal X-ray diffractometer 
was utilized to measure the cell parameters and morphology of the grown crystals. The FTIR spectra taken for the 
crystals grown at different pH values show variations in the peak intensity. The NLO property is found to be varying 
with the change in the pH values. 
Keywords: re-crystallization, seed crystals, semi-organic, nonlinear optical materials. 
 
 
INTRODUCTION 
Non-linear optical materials (NLO) have wide applications in the area of laser technology, optical 
communication and in storage technology. The high nonlinearity makes it possible for organic crystals to 
double the frequency of Ga-Al-As diode lasers for generating blue light which is an important coherent 
light source. However, the short comings of the aromatic crystals such as poor physico-chemical stability, 
low hardness and cleavage tendency hinder their device applications1-3. In order to keep the merits and 
overcome the shortcomings of organic materials some new classes of NLO crystals such as LAP, GSC, 
GSB, GSN and KDP (semi-organic complex crystals) to combine the advantages of inorganic crystals 
such as good stability, with the advantages of organic crystals such as high nonlinearity, are of special 
interest. Among the semi-organic complex NLO crystals the nonlinearity of GSC is relatively high 
(GSC). GSC belongs to the monoclinic system with the molecular formula H3NClCH2COONa. The cell 
dimensions are a = 5.1061A0, b = 11.9765A0, c = 5.4652A0 and β = 111.780 The SHG intensity of GSC is 
0.5 times that of KDP. In the present study, the effect of pH on the growth and properties, such as NLO, 
structure of crystal, and optical are studied. 
 
EXPERIMENTAL 
Preparation of GSC solution at different pH values: 
The commercial reagent of Glycine (purity 99%) procured from Merck company was purified by the 
repeated recrystallization using hot deionised water solution by slow cooling. At pH 6.0, essentially the 
glycine is in the zwitterionic form. Glycine and Sodium Chloride in the equimolar ratio 1:1 were taken in 
a beaker containing double distilled Millipore water at room temperature and the saturation solution is 
brought to pH 6.0 . The reaction takes place based on the following equation and the salt is formed. 
 
                                              Cl 
                                                               | 
H2N ⎯ CH ⎯ COOH +  Na Cl   --- -    H3N ⎯ CH2 ⎯ COONa  
             | 
             H 
The purity of the synthesized salt was further increased by successive recrystallization process. The 
saturated GSC solutions of different pH (1.1, 6.0, and 10.8) have been prepared using doubly 
EFFECT OF pH ON THE GROWTH OF GSC           S.Palaniswamy and O.N.Balasundaram 782
RJC  Rasayan J. Chem.                                                                                                       Vol.1, No.4 (2008),782-787 
recrystallised salt. The solution was filtered using a sintered glass filter of 1μ porosity. The solution is 
transferred to three Petri dishes and covered by a porous paper and kept for slow evaporation process.  
                            
Growth of crystals: 
Seed perfection and selection of solvents are very important for growing single crystals of high quality 
6,7.Defects in seed crystal could cause spurious crystallization and flaws during the crystal growth. To 
ensure good quality crystals, a seed was obtained by spontaneous nucleation in supersaturated solution of 
GSC at room temperature. Transparent and good quality seeds were selected for the growth. The grown 
crystals were harvested after a typical growth period of 30 days. 
Structure and morphology: 
In order to confirm the crystallinity of the grown crystals, powder X-ray diffraction (XRD) pattern has 
been recorded using a Rich Seifert Diffactometer (Model 2002) using Cu Kα (λ = 1.5418 Aº)radiation 
The samples were scanned over the angle range 10-50º at the rate of 0.05º /min. The changes in the unit 
cell parameters and the morphology of the grown crystals have been observed from single crystal XRD 
analysis using ENRAF NONIUS CAD4-F (FR 590) single crystal diffractometer. (Table-1). 
FTIR spectral studies (fig-1,2,3): 
The infrared spectra were taken using Brukker IFS66V FTIR specrometerby KBr pellet technique to 
confirm the presence of different organic groups along with the inorganic materials presence.(Table-2) 
XRF studies:  
The X-ray Fluorescence is taken for the samples to study the abundance of Na and Cl to be present in the 
crystals.  
NLO efficiency :      
The comprehensive analysis of second order non-linearity of GSC crystals, grown from different pH was 
performed by Kurtz powder method8. The single crystals of GSC grown from different pH values were 
irradiated by an incident radiation (1064 nm)of pulse width 8ns and pulse energy of 10-800mJ from a Q-
switched quanta RAY GCR Nd:YAG laser. KDP was used for calibrating the SHG intensity. A concave 
mirror, collimated and focused onto the monochromator slit collected the SHG emitted from the crystal 
sample. The output power of the crystal was measured using OPHIR power meter model DG with power 
head model OPHIR 30A. The error in the measured SHG was typically about 5-10%. The NLO property 
of the crystal was confirmed from the estimation of strong green radiation of the crystal. The results of 
SHG efficiency of GSC are summarized in table -4. The GSC crystals grown at different pH values 
showed very good stability under laser irradiation and no signs of decomposition; crack or fracture were 
observed even for continued irradiation with laser power of 800 mW.         
 
RESULTS AND DISCUSSION 
The growth kinetics and the quality of the crystals grown from solutions are considerably influenced by 
pH of the solution. The amino acids contain both acidic  
(-NH3) and basic (-COO) groups, they are amphoteric. The predominant form of the amino acid depends 
on the pH of the solution.  In an acidic solution, the COOH group and the molecule has an overall 
positive charge.  As the pH is lowered, the - COOH loses its proton at about pH 2.  This point is called 
pKa1), the first acid-dissociation constant.  As the pH is raised, the -NH3+ group loses its proton at about 
pH 9.6.  This point is called pKa2, the second acid - dissociation constant.  Above this pH, the molecule 
has an over all negative charge.8So, we have grown crystals of GSC at:  1. pH of 1.1 which is less than pH 
2 and 2.pH of 10.8 which is greater than pH 9.6. At pH 1.1 the GSC crystals show high intensity of SHG, 
the crystal structure is Hexagonal. At pH 6.0 the GSC crystals show very low intensity of SHG, the 
crystal structure is monoclinic. At pH 10.8 the GSC crystal shows still lower intensity of SHG and the 
crystal structure is Hexagonal.         
From the FTIR studies we find for pH = 1.1, the absorption peak at 3444 cm-1 rather than OH may 
indicate the presence of NH bond. NH stretching (amide) may be indicated by the absorption band at 
1632 cm and second peak of absorption at 1495 cm-1 may confirm the NH stretching. The C=O presence 
EFFECT OF pH ON THE GROWTH OF GSC           S.Palaniswamy and O.N.Balasundaram 783
RJC  Rasayan J. Chem.                                                                                                       Vol.1, No.4 (2008),782-787 
may be indicated by the absorption bands at 1331 cm-1 and 1254 cm-1.  The CH2 vibrations are indicated 
by the absorption bands at 887 cm-1, 672  cm-1  and 502 cm-1.9
The FTIR for pH = 10.8 shows, the presence of NH bond is indicated by the absorption peak at 3436 cm-1  
and NH stretching (amide) is indicated by the absorption at 1672 cm-1 and the second peak of absorption 
at 1481 cm-1, confirms the NH stretching.  The C=O presence is indicated by the absorption band at 1333 
cm-1. The CH2 vibrations are indicated by the absorption bands at 893 cm-1 686 cm-1 and 501 cm-1.9  
From the XRF studies we find the existence of Cl in the GSC pH = 1.1 and this enhances the NLO 
property. Further the existence of Na is more in the in the GSC, pH = 10.8 and this lowers the NLO 
property. 
ACKNOWLEDGEMENTS 
This research work is supported by University Grants commission Minor Project File No.MRP-
750/05(UGC-SERC) Link No.1750.0. 
REFERENCES 
 
1. H.O.Marcy, M.J.Roskar, L.F.Warren, P.H.Canningham, C.A.Thomas, L.A.Delnach, S.P.Velsco,  
C.A.Ebbers, T.H.Liao, M.G.Konatzidis, Opt.Lett.,20,252(1995). 
2. H.W.Zhang,  A.K.Batra,  R.B.Lal,  J.Crystal Growth 137,141(1994). 
3. C.C.Frazier,  M.P.Cockerham,  J.Opt.Soc.Am.B.4, 1899(1987). 
4. S.Palaniswamy, O.N.Balasundaram, Asian J.Chem.,21 (accepted) (2009) 
5. Viting L.M., Vetn, Mosk. Univ. Ser. II Khim., 20(4), 54 (1965). 
6. P.M.Ushashree, R.Jayavel, P.Ramasamy, Mater.Chem.Phys.61,270(1999). 
7. R.Rajasekaran, P.M.Ushashree, R.Jayavel, P.Ramasamy, J.Crystal Growth ,299, 563(2001). 
8. Kennedy, G.C ., Am J. Sci,. 248, 540 (1950). 
9. K.Nakamoto, Infrared and Raman spectra of Inorganic and coordination compounds, Wiley, New 
York, 1978. 
 
 
Table-1 
 
Compd. a b c α β γ Cell vol. 
GSC(pH = 1.1) 7.0335 7.0449 5.4761 90 90 120 235.2621 
GSC(pH = 6.0) 5.1061 11.9765 5.4652 90 111.780 90 310.3383 
GSC(pH=10.8) 7.0323 7.0338 5.4916 90 90 120 235.3147 
 
 
 
 
 
 
 
 
 
Table-2 
  
GSC at pH=10.8 
Frequency cm-1 Assignment of vibration 
3436 (s)   Cisoid secondary amide 
1627 (s)   C = O stretching 
1489 (w)   NH in plane bending 
1439 (m) CH3 bending 
1410 (s) CH3 bending 
1333 (m) C – N Stretching 
1125 (w) CH3 symmetric bending 
1040 (w) = CH2 rocking 
EFFECT OF pH ON THE GROWTH OF GSC           S.Palaniswamy and O.N.Balasundaram 784
RJC  Rasayan J. Chem.                                                                                                       Vol.1, No.4 (2008),782-787 
929  (m) - CH out of plane bending 
893  (w) - COO stretching 
686  (m) - CH out of plane bending 
GSC at pH = 6 
2923 (s) CH2 symmetry stretching 
2854 (s) CH2 symmetry stretching 
2603 (s) NH2+asymmetric stretching   
2171 (m) S-C = N stretching 
1600 (s) C=O stretching 
1500 (s)   NO2 symmetry stretching 
1436 (s) N=O symmetry stretching 
1394 (s) N=O stretching 
1323 (s) C-N stretching 
1126  (s) C-O-C symmetry stretching 
1043  (m) C-O stretchingand O-H plane bending 
929 (s) CH2 out of plane bending 
889 (s) CH2 out of plane bending 
684 (s) O-N=O bending 
GSC at pH = 1.1 
3444 (s) Cisoid secondary amide 
3238 (m) N-H stretching 
2609 (s) NH3  stretching 
1632 (s) NO2 asymmetry stretching 
1495 (m) N-H in plane bending 
1410 (m) C – O Stretching 
1331 (m) C-N stretching 
1254 (m) C-N stretching 
1125  (m) N-H stretching 
1027  (w)   C-O stretching 
887  (m)     C-O-O stretching 
672   (w) O-C-N stretching 
 
 
 
 
Table-3: Power output of SHG signal developed in the KDP and the GSC crystals  
(grown from different pH) 
 
KDP 
mW 
GSC pH = 1.1 
mW 
GSC pH = 6.0 
mW 
GSC pH = 10.8 
mW   
150 200 125 100 
290 310 240 200 
330 290 210 150 
 
 
 
             
EFFECT OF pH ON THE GROWTH OF GSC           S.Palaniswamy and O.N.Balasundaram 785
RJC  Rasayan J. Chem.                                                                                                       Vol.1, No.4 (2008),782-787 
 
 
 
Fig-1 : GSC-pH=1.1 
 
 
Fig 2: GSC-pH=10.6 
 
EFFECT OF pH ON THE GROWTH OF GSC           S.Palaniswamy and O.N.Balasundaram 786
RJC  Rasayan J. Chem.                                                                                                       Vol.1, No.4 (2008),782-787 
 
Fig 3:GSC=pH-6.0 
 
 
(Received: 31 October 2008   Accepted: 7 November 2008          RJC-271) 
 
 
 
Esoc 2009: 16th European Symposium on 
Organic Chemistry 
12-16 July 2009 
Prague, Czech Republic, Europe 
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EFFECT OF pH ON THE GROWTH OF GSC           S.Palaniswamy and O.N.Balasundaram 787


EFFECT OF pH ON THE GROWTH AND CHARACTERIZATION OF GLYCINE SODIUM CHLORIDE (GSC) SINGLE CRYSTAL

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EFFECT OF pH ON THE GROWTH AND CHARACTERIZATION OF GLYCINE SODIUM CHLORIDE (GSC) SINGLE CRYSTAL

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