Thermal, mechanical, and optical studies of
NaBr-added l-alanine crystal
T. Jayanalina, G. Rajarajan, S. Parthiban
& S. C. Mojumdar
Journal of Thermal Analysis and
Calorimetry
An International Forum for Thermal
Studies
ISSN 1388-6150
Volume 112
Number 2
J Therm Anal Calorim (2013)
112:1025-1030
DOI 10.1007/s10973-013-3058-7
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J Therm Anal Calorim (2013) 112:1025–1030
DOI 10.1007/s10973-013-3058-7
Thermal, mechanical, and optical studies of NaBr-added
L-alanine crystal
T. Jayanalina • G. Rajarajan • S. Parthiban
S. C. Mojumdar
•
Received: 7 January 2013 / Accepted: 12 February 2013 / Published online: 13 March 2013
Ó Akadémiai Kiadó, Budapest, Hungary 2013
Abstract The 1:1 adduct of L-Alanine and sodium bromide (L-ANaBr) crystal has been grown from aqueous
solution by a slow evaporation technique. L-alanine and
sodium bromide were used in the ratio 1:1 for synthesis.
Characterizations were carried out to study the thermal,
optical, and mechanical properties of the grown crystal.
Single-crystal X- ray diffraction analysis shows that the
grown crystal belongs to the monoclinic system. The crystalline nature and its various planes of reflections were
observed by powder XRD analysis. Thermal studies reveal
that the crystal is stable up to 113.37 °C. The chemical
compositions of the grown crystal were determined by
FT-IR spectral analysis. The transmittance, absorption, and
reflection spectrum of L-ANaBr crystal studied using a
UV–Vis spectrometer indicates that the crystal has good
optical transparency. The mechanical property of the grown
crystal studied using Vickers microhardness measurement
reveals that the crystal is a soft material.
T. Jayanalina
Department of Physics, KSR College of Engineering,
Tiruchengode 637215, Tamil Nadu, India
G. Rajarajan
Department of Physics, Mahendra Engineering College,
Mallasamudaram, Namakkal, Tamil Nadu, India
S. Parthiban
Department of Chemistry, Faculty of Engineering
and Technology, Annamalai University, Annamalainagar,
Chidambaram 608 002, India
S. C. Mojumdar (&)
University of Guelph, Guelph, ON, Canada
e-mail: [email protected]
S. C. Mojumdar
Trencin University of A. Dubcek, Puchov, SR, Europe
Keywords Crystal growth Amino acid crystals Thermal studies TG–DTA FT-IR XRD
Introduction
Amino acid family crystals have been studied by many
material researchers for many years because of their nonlinear
activity and ferroelectric or anti-ferroelectric properties [1, 2].
L-alanine isomer is one of the 20 amino acids encoded by the
genetic code. A single crystal of L-alanine belongs to the
orthorhombic crystal system with a space group of p212121
[3]. Recently, noticeable research has been focused on semiorganic material, which is an organic material mixed with
inorganic materials. They have been attracting much attention
due to high nonlinearity, chemical flexibility, high mechanical
and thermal stability, and good transmittance [4–6]. Amino
acids mixed with inorganic material always give interesting
results to researchers. Semi-organic nonlinear optical crystals
are formed by amino acids with inorganic materials and
possess the advantages of high optical nonlinearity of the
organic amino acids [7]. L-Alanine is the simplest amino acid
having second harmonic generation efficiency equal to onethird of the well-known KDP. The knowledge of studying its
properties is very important since L-alanine can be considered
as the fundamental building block of more complex amino
acids [8]. The cadmium chloride-added L-alanine is a good
candidate for microelectronic applications [5]. The 2:1 ratio
addition of L-alanine and nitric acid yields L-alanine alaninium
nitrate single crystal, which exhibits good second harmonic
generation efficiency [9]. Godzisz et al., prepared and studied
the structure of a b-alanine-oxalic acid (1:1) hemihydrate
crystal. Raman scattering of L-alanine was performed at two
different GPas leading to a change in the structure from
orthorhombic to tetragonal and in turn to monoclinic [10]. In
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T. Jayanalina et al.
stirred continuously for 6 h for homogenization. The
obtained product was purified by the repeated recrystallization process. A saturated growth solution was prepared and
kept at room temperature for slow evaporation. A good
quality single crystal with regular shape and size
20 9 10 9 4 mm3 was harvested within 30 days. The
image of L-ANaBr is shown in Fig. 1.
Measurements
Fig. 1 Image of L-ANaBr crystal
the present investigation, an alkali metal halide has been
added to L-alanine in the ratio 1:1 and from the obtained
product, single crystals of L-alanine sodium bromide
(L-ANaBr) were grown. The grown crystal was subjected to
various characterization techniques. Thermal, microscopic,
X-ray, and spectral analyses are very important methods in
materials’ characterization. Therefore, many authors have
applied these techniques for various materials’ characterization [6, 11–22].
The FT-IR spectral analysis was carried out using an Alpha
Bruker FT-IR spectrometer by the KBr pellet technique in
the range 500–4,000 cm-1. The powder diffraction analysis was performed using a Philips Xpert Pro Triple-axis
X-ray diffractometer. TG–DTA curves were recorded on a
Perkin Elmer thermal analyzer. The single-crystal X-ray
studies have been carried out using an ENRAF NONIUS
FR590 diffractometer with Mo radiation of wavelength
k = 0.71073 Å. The UV–Vis spectrum analysis has been
measured using a Perkin Elmer Lambda 35 UV–Vis
spectrophotometer. Vickers microhardness was evaluated
for the well-polished grown crystal using a Reichert 4000E
Ultra microhardness Tester.
Results and discussion
Experimental
FT-IR spectral analysis
Synthesis and crystal growth
The FT-IR spectrum of the grown crystal is shown in
Fig. 2. A band at 3,086 cm-1 with medium intensity represents C–H asymmetric stretching. The band appears at
2,937 cm-1 with weak intensity, showing OH stretching.
L-Alanine and sodium bromide (E. Merck) were mixed in a
stoichiometric ratio of 1:1 in doubly distilled water and then
Fig. 2 FT-IR spectrum of
L-ANaBr crystal
100
90
80
Transmittance/%
70
60
50
40
30
20
10
0
–10
–20
4000
3500
3000
2500
2000
Wavenumbers/cm–1
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1500
1000
500
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Thermal, mechanical and optical studies of NaBr
1027
Table 1 Single-crystal XRD data of L-ANaBr and L-alanine
Crystal
a/Å
b/Å
V/Å3
c/Å
L-Alanine
sodium bromide
6.03
5.80
12.38
L-Alanine
[5]
6.032
12.343
5.78
Fig. 3 Powder XRD pattern of
L-ANaBr crystal
a = b = c/8
System
433
90
Monoclinic
429.99
90
Orthorhombic
T J N – 1B
4000
Counts
3000
2000
1000
0
20
30
40
50
60
70
2θ /°
The peak at 1,620 cm-1 with strong intensity represents
C=O stretching. The peak at 2,292 cm-1 with medium
intensity represents overtones and combination bands with
prominent peaks near 2,500 and 2,000 cm-1. The peaks at
1,014 cm-1 with a variable represent C–CHO stretching.
The peak at 1,455 cm-1 with medium intensity represents
C–H in plane bending.
Single-crystal XRD analysis
The single-crystal X-ray diffraction studies have been
carried out to confirm the crystalline nature and to determine the lattice parameters of the grown crystal. The lattice
parameter values of L-ANaBr are presented in Table 1. For
comparison, lattice parameters of pure L-alanine are also
given in the same Table. L-ANaBr is monoclinic, whereas
L-alanine is orthorhombic. These results very much suggest
that a new compound could be formed on the addition of
equimolar quantity of NaBr.
Powder X-ray diffraction analysis
The grown crystals have been characterized by a powder
X-ray diffractometer to verify the single-phase nature of
the sample. Well-defined Bragg peaks are obtained at
specific 2h angles, indicating that the crystals are ordered.
The peaks in the Fig. 3 show the crystalline nature of
L-ANaBr. The crystalline size (D) was calculated using
Scherrer’s formula from the full width half maximum (b)
using the relation
D ¼
0:945k
b cos h
The crystalline size of the grown crystal was found to be
59 nm.
Thermal analysis
The TG and DTA curves of L-ANaBr were recorded with
a heating rate of 10 °C per minute (Fig. 4). These studies
reveal that it is thermally stable up to 87.87 °C where the
mass is reduced to 0.107 mg from the initial mass taken.
Thereafter, melting and dehydration processes commence.
Another endothermic peak at about 114 °C with a
reduction in mass of 0.11 mg is observed on the DTA
curve. The final residue obtained at 933.3 °C is about
0.1 mg.
Optical transmission studies
The UV–Vis spectrum gives limited information about the
structure of the molecule because of the absorption of UV,
and Visible light involves promotion of the electron in r and
p orbital from the ground state to higher energy states. To
find the transmission, absorption, and reflection range of the
newly formed L-ANaBr, the optical transmission spectrum of
L-ANaBr for the wavelengths between 500 and 2,000 nm
was recorded. The recorded optical transmittance, absorption, and reflection spectra are shown in Fig. 5. The transmittance is found to be the maximum in the entire visible and
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T. Jayanalina et al.
0.02799
0.02
3.381
3.3
3.2
0.00
3.1
Mass/mg
–0.02
3.0
–0.04
2.9
2.8
–0.06
2.7
Derivative mass/mg min–1
Fig. 4 TG-DTA of L-ANaBr
crystal
–0.08
2.6
2.5
–0.10
113.37 °C
87.87 °C –0.111 mg/min
–0.107 mg/min
2.41
38.41 100
200
400
300
500
600
700
800
–0.1176
900 933.3
1500
2000
Temperature/°C
1.2
(a)
1.0
Abs
infrared regions. The crystal shows a good transmittance in
the entire visible regions. The lower cutoff 190 nm combined with the above attests to the usefulness of this material
for optoelectronics applications and the second harmonic
generation of the Nd:YAG laser and for the generation of the
higher harmonic of the laser diodes. A good optical transmittance is very desirable in a nonlinear optical (NLO)
crystal since the absorptions, if any, in an NLO material near
the fundamental or the second harmonic of an Nd:YAG laser
will lead to loss of conversion efficiency of the second harmonic generation (SHG). The crystal is highly transparent to
wavelengths above 190–1,500 nm [23].
0.8
0.6
0.4
0.2
500
1000
Wavelength/nm
70
(b)
60
40
30
20
10
0
500
1000
1500
2000
Wavelength/nm
(c)
70
Transmittance/%
The definition of hardness depends entirely on the method
of measurement which will determine the scale of hardness
obtained. Hardness of a material is a measure of the
resistance it offers to local deformation. An important use
of the microhardness study is the possibility of making an
indirect estimate of other mechanical characteristics of
materials having a specific correction with their hardness. It
plays a key role in device fabrication. Transparent crystals
free from cracks were selected for the microhardness
measurement. L-ANaBr crystal was subjected to a Vickers
microhardness test with the load varying from 25 to 100 g.
Hardness number of the crystal was calculated using the
following relation,
R/%
50
Microhardness measurement
60
50
40
30
20
10
Hm ¼
1:8544P
kg mm2 :
d2
The Vickers microhardness profile as a function of the
applied test loads is illustrated in Fig. 6. It is evident from
123
500
1000
1500
2000
Wavelength/nm
Fig. 5 UV–Vis spectrum of L-ANaBr a Absorbance spectrum.
b Reflectance spectrum. c Transmission spectrum
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Thermal, mechanical and optical studies of NaBr
1029
Hardness number/kg mm2
85
80
75
70
65
60
55
50
45
20
30
40
50
60
70
80
90
100
110
Load/g
Fig. 6 Variation of microhardness with load of L-ANaBr
the plot that the microhardness of the crystal with load
increases with increasing the load. For L-ANaBr, the value
of the work hardening coefficient ‘‘n’’ was found to be
0.08. According to Onitsch, the work hardening coefficient
‘‘n’’ is 1.0 B n B 1.032 for a hard material and n C 1.032
for a soft material [24]. Hence, it indicates that L-ANaBr
belongs to the soft material.
Conclusions
Single crystals of L-alanine sodium bromide (L-ANaBr)
have been grown from aqueous solution by a slow evaporation technique. The lattice parameters obtained by the
single-crystal X-ray diffraction technique reveal that the
crystal belongs to the monoclinic system. Powder XRD
reveals the crystalline nature of the crystal. The FT-IR
spectrum of the grown crystal indicates that the various
functional groups are present in the grown crystal. Thermal
studies of L-ANaBr indicate that the crystal has a low
melting point. The L-ANaBr has a wide range of transparency in UV and an entire visible region, and the cutoff
wavelength is around 190 nm. The Vickers microhardness
was calculated in order to understand the mechanical stability of the grown crystals. The work is under progress to
understand the crystal structure and the amount of incorporated sodium bromide.
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