Journal of Minerals & Materials Characterization & Engineering, Vol. 10, No.1, pp.49-57, 2011 Printed in the USA. All rights reserved
Growth and Characterization of L-glutamic Acid Hydro Chloro Bromide,
A New Nonlinear Optical Material
S. Kumararamana, K. Ki r ub a v at hib, K. Selvarajuc,*
a Department of Physics, Nehru Memorial College, Puthanampatti-621 007, India
b Department of Physics, Govt. Arts College for Women, Kumbakonam-612 001, India
c Department of Physics, Govt. Arts College, Ariyalur-621 713, India
*Corresponding Author:,
The influence of mixed acids in the growth and characteristic properties of a nonlinear optical
material L-glutamic acid hydro chloro bromide abbreviated as LGAHCB was examined. Single
crystal X-ray diffraction analysis was used to calculate the lattice parameters of the crystals.
Fourier transform infrared spectroscopies were performed to study the molecular vibrations of
the grown crystal. The optical transmission spectrum shows very low absorption in the entire
visible region. The powder second harmonic generation efficiency of LGAHCB is 1.5 times
efficient as potassium dihydrogen phosphate (KDP).
Key words: Growth from solution; Single crystal X-ray diffraction; Infrared spectrum;
Nonlinear optical materials
Nonlinear optics is concerned with the interaction of electromagnetic fields with various media
to produce new electromagnetic fields altered in phase, frequency and amplitude from the
incident fields. Second harmonic generation (SHG) is an example of second order nonlinear
optical (NLO) process [1,2]. Nonlinear optical materials are capable of producing higher values
of the original frequency and hence this phenomenon can find application in optical modulation,
fiber optic communication and opto-electronics [3]. In the last decades, many researchers have
tried to find varieties of new NLO materials for laser applications [4,5] .
50 . Kumararaman, K.Kirubavathi, K. Selvaraju Vol.10, No.1
Complexes of organic material with inorganic acids and salts are promising materials for optical
second harmonic generations they tend to combine the features of organic with that of inorganic
materials. In the recent years, amino acid family crystals are of interest due to their attractive
nonlinear optical properties [6,7]. The salts of amino acids like L-arginine [8], L-histidine [9],
L-threonine [10], L-alanine [11], L-valine [12], and L-cystine [13] are some of the examples
which proved their application in the field of NLO.
In the present investigation, an attempt has been made to grow L-glutamic acid hydro chloro
bromide (LGAHCB) by solvent evaporation method at room temperature. Highly transparent
optical quality crystals were grown. The grown crystals have been subjected to structural,
spectroscopic, nonlinear optical property and mechanical characterization studies.
2.1. Synthesis
The starting material was synthesized by taking L-glutamic acid hydro chloride and L-glutamic
acid hydro bromide (Loba Chemie-AR grade) in a 1:1 stoichiometric ratio. The required amount
of starting materials for the synthesis of L-glutamic acid hydro chloro bromide (LGAHCB) salt
was calculated according to the reaction
5H10NO4Cl + C5H10NO4Br C10H20N2O8Cl Br
The calculated amount of L-glutamic acid hydro chloride was first dissolved in deionized water.
L-glutamic acid hydro bromide was then added to the solution slowly by stirring. The prepared
solution was allowed to dry at room temperature and the salts were obtained by slow evaporation
technique. The purity of the synthesized salt was further improved by successive recrystallization
2.2. Solubility
The solubility of LGAHCB in deionized water was determined as a function of temperature in
the temperature range of 30-45ºC. The beaker containing the solution was maintained at a
constant temperature and continuously stirred. The amount of LGAHCB required to saturate at
this temperature was estimated and this process repeated for various temperatures. On reaching
saturation, the equilibrium concentration of the solute was determined by gravimetric method.
The variation of solubility with temperature is shown in Fig.1.
Vol.10, No.1 Growth and Characterization of L-glutamic Acid Hydro Chloro Bromide 51
Fig. 1. Solubility of LGAHCB
2.3. Crystal growth
The saturated solution of LGAHCB was prepared at room temperature from the recrystallized
salt. The solution was then filtered twice to remove the suspended impurities and allowed to
crystalline by the slow evaporation technique at room temperature. A good optical transparent
crystal of size 18 х 10 х 6 mm3 harvested in a growth period of 30 days is shown in Fig.2.
Fig. 2. As grown LGAHCB single crystal
The single crystal X-ray diffraction analysis of LGAHCB crystal was carried out using ENRAF
NONIUS CAD4 X-ray diffractometer and its lattice parameters were determined. Fourier
transform infrared spectrum was recorded by the KBr pellet technique using a BRUKER 66V
52 . Kumararaman, K.Kirubavathi, K. Selvaraju Vol.10, No.1
FTIR spectrometer to confirm the vibrational structure of the crystalline compound with
scanning range of wavenumber 400-4000cm-1. UV-Visible spectrum was recorded in the range
of 200-1400nm using VARIAN CARY 5E spectrometer. The NLO property of LGAHCB was
tested by Kurtz powder SHG test using an Nd:YAG laser (1064nm).
4.1. Single Crystal X-ray Diffraction
The grown crystals were analyzed by single crystal X-ray diffraction method using ENRAF
NONIUS CAD4 diffractometer. The structure was refined by full matrix least squares method
using SHELX program. It is observed that the LGAHCB single crystal belongs to orthorhombic
crystal system and unit cell dimensions a = 11.121A°, b = 14.030 A°, c = 5.343 A°. The
observed data are in very good agreement with previous determination [14].
4.2. FTIR Analysis
The FTIR spectrum of LGAHCB crystal was recorded in the KBr pellet technique in the
frequency region 400-4000 cm-1 using BRUKER 66V FTIR spectrometer. The recorded FTIR
spectrum of LGAHCB crystal is shown in Fig.3. The comparison of vibration of L-glutamic
acid and LGAHCB is shown in Table 1.
The broad and strong absorption band between 2100 and 3400cm-1 are assigned to the hydrogen
bonded NH3+stretching modes. The intense sharp peaks at 2903cm-1 are due to the CH stretching
modes of vibration. The C=O stretching modes of vibration is observed at 1683 and 1724 cm-1.
The intense sharp peaks at 1503 cm-1 are due to NH3+ symmetric deformation. The less intense
sharp peak at 1417 cm-1 is due to the CH2 bending modes of vibration. The C-C-H bending
modes of vibration are observed at 1370 cm-1. There are less intense resolved bands at 1268 cm-
1 are attributed to CH2 twisting. The C-O stretching modes of vibrations and O-H in-plane
bending modes of vibration is observed at 1205 cm-1. The less intense peak observed at 1075
cm-1 is due to the NH2 rocking. The C-C stretching modes of vibration and O-H out of-plane
bending modes of vibrations are observed at 852 cm-1. The band observed at 628cm-1 is assigned
to C=O in plane bending of COOH [15-17]. The NH torsion and rocking of COO- is assigned to
the band observed at 531 and 488 cm-1. This observation confirms the protonation of L-glutamic
acid by hydro chloro bromic acid.
Vol.10, No.1 Growth and Characterization of L-glutamic Acid Hydro Chloro Bromide 53
Fig. 3. FTIR spectrum of LGAHCB crystal
30002000 1500 1000 400.0
1724 1683
54 . Kumararaman, K.Kirubavathi, K. Selvaraju Vol.10, No.1
Table 1. FTIR spectral band assignments of LGAHCB.
Wave number (cm-1)
L-glutamic acid [16] LGAHCB
422 411 COO
463 488 NH3+ torsion
538 531 COO
705 671 COO
O-H in-plane-deformation
C-C stretching
CH2 rocking
1082 1075 NH3+ rocking
1220 1205 C-COO
CH2 twisting
C-C-H in-plane-deformation
1417 1417 O-H-in-plane deformation
1525 1503 NH3+ symmetric deformation
asymmetric stretching
C=O stretching
1724 COO
2081 2118 NH3+ degenerative deformation
2940 2906 CH2 symmetric stretching
3150 3124 N-H stretching
4.3. Optical Studies
The UV-Vis analysis has been measured using VARIAN CARY 5E spectrophotometer in the
wavelength range of 200–1400 nm as shown in Fig.4. The absorbance is not registered until the
wavelength 228 nm is reached from 1400 nm. At 228 nm, a sharp fall of transmittance to zero
was observed indicating a single transition in the near UV region of LGAHCB. The material is
found to be transparent to all radiations in the wavelength range of 228-1400 nm. As there is no
change in the transmittance in the entire visible region, it is an advantage as it is the key
requirement for materials having NLO properties.
Vol.10, No.1 Growth and Characterization of L-glutamic Acid Hydro Chloro Bromide 55
Fig. 4. Optical spectrum of LGAHCB crystal
4.4. Microhardness Studies
Hardness of a material is a measure of the resistance it offers to local deformation [18]. The
polished faces of the as grown single crystals are subjected to Vicker’s microhardness studies in
order to know the mechanical behavior. Selected smooth surface of the grown crystals were
subjected to Vicker’s static indentation test at room temperature using Leitz Weitzlar hardness
tester fitted with diamond indenter. The applied loads were varied from 5 to 45 g. The
indentation time was kept constant at 10s for each applied load and the hardness was calculated
using the relation 2
v*85.1H dP=kg/mm2 where P is the applied load in kg and d is the
diagonal length of the indentation impression in micrometer and 1.85 is a constant of a
geometrical factor for the diamond pyramid. Several trials of indentation were made on the
grown crystal and the average value of the diagonal length of the indentation marks at each load
was taken. The Vicker’s hardness of L-glutamic acid hydro chloro bromide single crystals as a
function of load is depicted in Fig.5. From the graph it is found that the hardness value decreases
with the increase of load upto 45 gm, above which cracks are developed. The cracks are
developed when the load are increased above 45 gm around the indentation mark as observed,
which may due to the release of internal stress generated locally by indentation.
4.5. Second Harmonic Generation
The second harmonic generation (SHG) test on the LGAHCB crystal was performed by Kurtz
powder SHG method [19]. The powdered sample of LGAHCB crystal was illuminated using the
fundamental beam of 1064nm from Q-switched Nd:YAG laser. Pulse energy 4mJ/ pulse and
pulse width of 8ns and repetition rate of 10Hz were used. The second harmonic signal generated
in the crystalline sample was confirmed from the emission of green radiation of wavelength
56 . Kumararaman, K.Kirubavathi, K. Selvaraju Vol.10, No.1
532nm collected a monochromator after separating the 1064nm pump beam with an IR-blocking
filter. A photo multiplier tube as used as detector. It is observed that the measured SHG
efficiency of LGAHCB crystal was 1.5 times that of potassium dihydrogen phosphate (KDP).
Fig. 5. Load vs Hardness number of LGAHCB crystal
Good optical quality of L-glutamic acid hydro chloro bromide (LGAHCB) single crystals was
grown by slow evaporation solution growth technique at room temperature. From the single
crystal X-ray diffraction analysis, the LGAHCB crystal has orthorhombic system. The unit cell
parameter values were also determined. The presence of the various functional groups of
LGAHCB has been confirmed by Fourier transform infrared spectroscopy analysis. From the
optical studies, the total transparency in the entire visible region, LGAHCB will be used for
optical applications. The powder second harmonic generation efficiency measurement shows
the grown LGAHCB crystal having 1.5 times higher nonlinear optical efficiency than potassium
dihydrogen phosphate (KDP).
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