20120140506027

INTERNATIONAL JOURNAL OF ADVANCED RESEARCH
International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 6, June (2014), pp. 204-211 © IAEME
IN ENGINEERING AND TECHNOLOGY (IJARET)
ISSN 0976 - 6480 (Print)
ISSN 0976 - 6499 (Online)
Volume 5, Issue 6, June (2014), pp. 204-211
© IAEME: http://www.iaeme.com/IJARET.asp
Journal Impact Factor (2014): 7.8273 (Calculated by GISI)
www.jifactor.com
204

IJARET
© I A E M E
SYNTHESIS, GROWTH AND CHARACTERIZATION OF BIS (GLYCINE)
LITHIUM CHLORIDE – A SEMI-ORGANIC NLO MATERIAL
S.R. Balajia, T. Balub*, T.R. Rajasekaranc
aPost Graduate Department of Physics, V.O.Chidambaram College, Tuticorin 628 008, India
bDepartment of Physics, Aditanar College of Arts and Science, Tiruchendur 628 216, India
cDepartment of Physics, Manonmaniam Sundaranar University, Abishekapatty,
Tirunelveli 627 012, India
ABSTRACT
Bis (glycine) lithium chloride (BGLC), a semi-organic nonlinear optical material has been
synthesized and single crystals with dimensions 13mm 9mm 4mm were grown by slow
evaporation technique. The grown crystals were subjected to powder X-ray diffraction studies in
order to calculate the lattice parameter values and identifying the diffraction planes. Functional
groups of the crystallized molecules were confirmed by FTIR analysis. Transmission range of the
crystal was determined by UV-vis-NIR spectra. Vickers microhardness test was performed on the
prominent plane (110) of the gown crystal. The BGLC crystal does not decompose before melting.
This was confirmed by thermo gravimetric analysis (TGA). The NLO property of the crystal was
confirmed by Kurtz SHG test and compared with NLO efficiency of KDP crystal.
Keywords: NLO Single Crystal; X-ray Diffraction; Slow Evaporation Method; FTIR;
SHG Efficiency; TGA.
1. INTRODUCTION
High efficient nonlinear optical (NLO) materials with good mechanical strength and chemical
stability are essentially required for opto electronic applications such as optical communications,
high speed information processing and optical data storage [1, 2]. Semi-organic nonlinear optical
materials are reputed candidates for device fabrication, owing to their large nonlinear coefficient,
high laser damage threshold and exceptional mechanical and thermal stability. Semi-organic
materials are metal-organic co-ordination complexes in which the organic ligand plays a dominant
role for the NLO effect. Recently considerable efforts have been made to combine amino acids with

interesting inorganic materials to produce outstanding material to challenge the existing prospective
material [3]. The importance of amino acids in NLO applications is due to the fact that all the amino
acids have chiral symmetry and crystalline in non-centro-symmetric space group [4]. Many number
of natural amino acids are individually exhibiting the non-linear optical properties because they are
characterized by chiral carbons, a proton-donating carboxyl (-COOH) group and the proton
accepting (-NH2) group the crystal [5].
205

Glycine is the simplest of all amino acids. Glycine and its methylated analogue complexes
with mineral acids exhibiting interesting physical properties like ferro-elastic, ferroelectric or anti-ferro
electric behavior often associated with transitions to commensurate or incommensurate phases
[6]. Some complexes of glycine with CaCl2 [7], BaCl2 [8], H2SO4 [9] and CoBr2 [10] form single
crystals but none of these are reported to have nonlinear optical property. Single crystal of glycine
sodium nitrate [11], glycine lithium sulphate [12] and benzoyl glycine [13] showed non-centro-symmetry
and their quadratic nonlinear coefficients were examined. A survey of the literature shows
that no reports on the crystal growth and characterization of BGLC are available.
The present paper reports the synthesis and growth of title compound by slow evaporation
solution growth technique and characterized by powder X-ray diffraction (PXRD), Fourier transform
infrared (FTIR) spectrum, UV analysis, microhardness test, thermal analysis and SHG efficiency.
2. EXPERIMENTAL PROCEDURE
2.1 Synthesis
Bis (glycine) lithium chloride (BGLC) growth solution was prepared by dissolved analar
grade glycine (Merck) and lithium chloride (Merck) in stoichiometric ratio 2:1 in double distilled
water and stirred well for about 3 hours using a temperature controlled magnetic stirrer to yield a
homogeneous mixture of solution. The polycrystalline starting material was synthesized by
evaporating the solution to almost dryness at the temperature of 50oC according to the following
reaction,

The purity of the synthesized salt was improved by successive recrystallization process. Care
was taken during heating the solution and temperature as low as 50oC was maintained.
2.2. Solubility
The solubility of BGLC in water was determined as a function of temperature in the
temperature range 35 – 50 oC. To determine the equilibrium concentration, the solution BGLC was
prepared using double distilled water as the solvent. The solution was maintained at a constant
temperature and continuously stirred using a magnetic stirrer to ensure homogeneous temperature
and concentration throughout the volume of the solution. On reaching the saturation, the content of
the solution was analyzed gravimetrically [14] and the process was repeated for every temperature.
The solubility curve is shown in the figure 1. The solubility increases linearly with increase of
temperature.

206

32 36 40 44 48 52
84
80
76
72
68
64
60
Concentration (g/100ml)
Temperature (0C)
Fig. 1: Solubility curve of BGLC in aqueous solution.
2.3 Crystal growth
In the present study, BGLC crystals were grown by slow evaporation technique.
Recrystallized salt of BGLC was taken as raw material. Saturated BGLC solutions were prepared at
room temperature with water as solvent. The prepared solution was filtered using Whatmann 41 filter
paper to remove the suspended impurities. The solution was taken in petri dishes and closed with
perforated covers and kept in dust free atmosphere. A well-developed crystal of size
was harvested in a growth period of 37 days and is shown in figure 2.
Fig. 2: As grown crystals of BGLC
3. CHARACTERIZATION
3.1 Powder X-ray diffraction analysis
The purified samples of the grown crystals have been crushed to a uniform fine powder and
subjected to powder X-ray diffraction using a Panalytical X’Pert Powder X’Celerator Diffractometer.
The radiations ! from a copper target were used. The specimen in the form of a
thin film was scanned in the reflection mode in the # range 10-800C with four decimal accuracy.

Figure 3 represents the powder diffractograph for the grown BGLC crystals. The peaks are indexed
using least square fit method. From the powder X-ray diffraction data, the lattice parameters and the
cell volume have been calculated and are given in (Table 1).
(202)
(210)
207
3.2 FTIR analysis

Fourier Transform Infrared (FTIR) spectrum was recorded using KBr pellet technique on a
Thermo Nicolet, Avatar 370 spectrophotometer. Figure 4 shows the FTIR spectrum recorded in the
range 400 - 4000 $% to identify the functional group present in BGLC. The spectrum shows a
broad band between 2000 and 3600 $% resulting from superimposed
' and (
) stretching
)at 3110.41 $% and
band. It includes the asymmetric and symmetric stretching modes of (
(111)
10 20 30 40 50 60 70 80
15000
12000
9000
6000
3000
0
(311)
(412)
(320)
(312)
(400)
(310)
(301)
(300)
(211)
(102)
(201)
(200)
(101) (110)
(001)
Intensity (cts)
2 Theta (Deg)
Fig. 3: Powder XRD pattern of BGLC
Table. 1: Unit cell parameter of BGLC
Parameters BGLC
a
b
c
,

V
System
7.01919!
7.01919 !
5.62648 !
900
1200
240.0722 !(
Hexagonal
2602.5$%. The absorption peak at 499.61 $% is assigned to the
'
stretching vibration [15].
The band appeared at 927.79 $% is assigned to the
' out of plane deformation. The peak at
1577.23 and 1481.4 $% are due to asymmetric and symmetric bending modes of (
). The
characterizing stretching vibration of '
group and '
wagging appeared at 1152.32 and
684.2 $% respectively. The ' stretching vibration is observed at 1124.3$%. The band at
1388.04 $% is due to the asymmetric stretching mode of

-. The bands observed at 605.95 and
556.13 $% can be attributed to ' stretch.

2165.27
2230.65
208

120
100
80
60
40
20
0
-20
499.61
556.13
605.95
684.20
885.95
927.79
1040.87
1124.30
1152.32
1319.93
1388.04
1481.40
1438.01
1577.23
1646.31
2602.50
3110.41
4000 3500 3000 2500 2000 1500 1000 500
Transmittance (%)
Wavenumbers (cm-1)
Fig. 4: FTIR spectrum of BGLC
3.3 Optical assessment
For optical application, especially for SHG, the material considered must be transparent in
the wavelength region of interest. The UV-Vis-NIR spectrum (Figure 5) was recorded using Perkin
Elmer Lambda 35 UV spectrophotometer in the wavelength range 190 – 1100 nm, which covers near
ultraviolet (200 – 400 nm), visible (400 – 800 nm) and then near-infrared (800 – 1100 nm) regions.
Optically clear single crystal of dimension 6 was used for this study. The lower
cut-off wavelength is 240 nm. The crystal has sufficient transmission in the entire visible and IR
region. The transmission window in the visible region and IR region enables good optical
transmission of the second harmonic frequencies of Nd: YAG laser.
200 400 600 800 1000 1200
34
32
30
28
26
24
22
20
18
16
14
Transmittance (%)
Wavelength (cm-1)
Fig. 5: UV – Vis – NIR spectrum of BGLC
3.4 Microhardness studies
Microhardness testing is one of the best methods of understanding the mechanical properties
of materials such as fracture behavior, yield strength, brittleness index and temperature of cracking

[16]. Vickers microhardness measurements were carried out on BGLC crystal using Shimadzu
HMV – 2 microhardness tester fitted with Vickers diamond pyramidal indenter. The hardness
measurements were made on the well-developed (110) face. The well-polished crystal was mounted
on the platform of the microhardness tester and the loads of different magnitudes (25 to 100 g) were
applied over a fixed interval of time. The indentation time was fixed as 10 s. The diagonals of the
impressions were measured using a LeitzMetallux II microscope with a calibrated ocular at
magnification 500. Vickers microhardness number was evaluated from the relation
209

* +,1-./0
where Hv is the Vickers hardness number, P is the indenteor load in kg and d is the diagonal length
of the impression in mm. Figure 6 shows that the hardness number increases with the increase of the
applied load. This behavior of increasing microhardness with the load is known as reverse
indentation size effect (RISE) [17].
0 25 50 75 100 125
90
80
70
60
50
40
Vickers Hardness (Hv (kg/mm2))
Load (g)
Fig. 6: Vickers hardness versus load for BGLC crystal
3.5 Thermal analysis
The thermo gravimetric analysis (TGA) and the differential thermal analysis (DTA) give
information regarding phase transition and different stages of decomposition of the crystal system
[18]. The TG/DTA curves for BGLC were recorded for the range of temperature from 40 to 720oC
with a simultaneous thermal analyzer Perkin Elmer STA 6000. A powdered sample weighing 2.842
mg was used for the analyses. The analyses were carried out simultaneously in air at a heating rate of
10oC min-1 and it is represented in Fig.7. From the TGA curve, it is observed that there is a single
stage of weight loss starting at 225oC but the range between 38 and 100oC no loss in weight is
recorded. This illustrates the absence of physically absorbed or lattice water in the crystal. Hence the
compound is stable up to 225oC, between 225 and 265oC, there is a conspicuous loss in weight. From
DTA curve, the sharp endothermic peak observed at 249.35oC corresponds to the decomposition of
the material. The peak of the endothermic represents the temperature at which the melting terminates
which corresponds to its melting point. There is no decomposition up to melting point; this ensures
thermal stability of material for possible applications in lasers.

210

100 200 300 400 500 600 700
3.0
2.5
2.0
1.5
1.0
0.5
Heat Flow Endo Down (mW)
Temperature (0C)
Weight (mg)
249.35 0C
Area = 2312.409 mH
Delta H = 813.7191 J/g
-150
-100
-50
0
Fig. 7: TGA/DTA trace of BGLC
3.6 Second harmonic generation efficiency measurements
SHG is a nonlinear optical process, in which photons with the same frequency interacting
with a nonlinear material are effectively combined to generate new photons with twice the energy,
and therefore twice the frequency and half the wavelength of the initial photons. The first and most
widely used technique for confirming the SHG from prospective second order NLO materials is the
Kurtz powder technique [19] to identify the materials with non-centro-symmetric crystal structures.
The generation of the second harmonic by the sample was confirmed by the emission of a strong
bright green signal. The second harmonic signal of 8.2 mJ was obtained for BGLC crystal, while the
standard KDP crystal gave a SHG signal of 8.8 mJ for the same input. The result obtained shows that
the SHG efficiency of the grown crystal (BGLC) is 0.93 times that of the standard KDP crystal. This
increase of SHG of BGLC is due to the fact that the Glycine has zwitter ion ie., NH2 and COOH
group [20]. The optically active amino group may get added in the structure and increases its non –
centrosymmetry and hence increase its SHG efficiency. Hence the BGLC crystal may be useful for
laser infusion experiment and frequency conversion application.
4. CONCLUSION
Potential semi-organic nonlinear optical bis (glycine) lithium chloride (BGLC) complex was
synthesized and its solubility was analyzed in the temperature range 35 – 50 0C. The solubility curve
indicates moderate solubility of BGLC in water with a positive solubility temperature gradient.
Single crystals of BGLC have been grown by slow evaporation technique at room temperature. The
lattice parameters were obtained from powder X-ray diffraction study. The functional groups present
in the grown crystal have been confirmed by FTIR spectral analysis. UV-Visible spectrum shows
that the crystal has a wide transmission range with a lower UV-cut-off of 238 nm. Vickers hardness
values measured on (110) plane reveal its mechanical strength. Thermo gravimetric analysis (TGA)
reveals that the grown crystal can is thermally stable up to 249.35°C. The SHG efficiency measured
by the Kurtz powder test was about 0.93 times that of KDP.

20120140506027

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