Growth and Characterization of β-Alanine Oxalate—A New Organic Single Crystal

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Journal of Minerals and Materials Characterization and Engineering, 2012, 11, 1069-1074

Published Online November 2012 (http://www.SciRP.org/journal/jmmce)

Growth and Characterization of β-Alanine Oxalate—

A New Organic Single Crystal

S. Lincy Mary Ponmani1, P. Selvarajan2*, N. Balasundari3, D. Jencylin3

1Department of Physics, St. Mother Theresa Engineering College, Tuticorin, India

2Department of Physics, Aditanar College of Arts and Science, Tiruchendur, India

3Department of Physics, Infant Jesus College Of Engineering, Tuticorin, India

Email: *[email protected]

Received July 6, 2012; revised August 10, 2012; accepted August 17, 2012

ABSTRACT

A new organic single crystal of β-Alanine Oxalate (BAO) has been grown from solution by slow evaporation technique.

Transparent, colourless crystals of size upto 11 × 9 × 4 mm3 were obtained. Formation of the new crystal has been con-

firmed by single crystal XRD and FTIR spectra. 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 unit cell parameters

and to confirm the crystal structure. BAO belongs to monoclinic system with lattice parameters a = 22.335 Å, b = 5.697

Å, c = 13.993 Å, α = 90˚, β = 115.37˚, γ = 90˚, and volume of the unit cell, V = 1609 Å3. The functional groups are con-

firmed by FTIR vibrational analysis. Optical transmission spectra revealed the optical properties of the grown crystal.

Transmission spectrum reveals that the crystal has low UV cut-off of 205 nm and has a good transmittance in the entire

visible region enabling its use in optical applications. There is no absorption in the entire visible region. Mechanical

strength of the grown material is tested by hardness studies. The value of hardness increases when the applied load is

increased.

Keywords: Amino Acid; X-Ray Diffraction; Lattice Parameters; FTIR; Transmittance; Microhardness; Organic Crystal;

SHG

1. Introduction

Amino acids and their complexes are the organic or

semi-organic materials that have attracted great attention

due to their ability in ease of processing in the assembly

of optical devices. The complete understanding of the

optical properties of amino acid crystals, as well as other

organic crystals, still requires more attention [1-7].

3-Aminopropionic acid is commonly known as β-alanine

with molecular formula C3H7NO2 and in which the

amino group is at the β-position from the carboxylate

group [8-10]. Supplementation with β-alanine has been

shown to increase the concentration of carosine in mus-

cles, decrease in fatigue in athletes and increase total

muscular work done. β-alanine is purely a synthetic

amino acid and it is a positional isomer of L-alanine

[11,12]. It forms crystalline complexes with organic,

inorganic acids or salts. In this paper, we report for the

first time the growth and characterization of a new or-

ganic crystal viz. β-alanine oxalate and the results are

presented.

2. Experimental Procedure

2.1. Growth

β-alanine and oxalic acid were taken in the molar ratio of

1:1 and the calculated amounts of β-alanine and oxalic

acid were dissolved thoroughly in de-ionized water at

room temperature. A saturated solution was prepared and

the solution was filtered using a Whatmann filter paper.

For the growth, the filtered solution in a beaker was

allowed for slow evaporation. Good colourless, trans-

parent single crystals were obtained within a period of 15 -

20 days. The grown crystal is displayed in Figure 1. The

size of a grown crystal is observed to be 11 × 9 × 4 mm3.

Re-crystallization was carried out twice to improve the

purity of the sample.

2.2. Instrumentation

Powder X-ray diffraction measurement was taken using

an automated X-ray powder diffractometer(PANalytical)

with nickel filtered, monchromated CuKα radiation (λ =

1.5406 Å). The XRD pattern was taken after the grown

crystal was crushed into fine powder. The Fourier

Transform Infrared (FTIR) spectrum was recorded using

*Corresponding author.

S. L. M. PONMANI ET AL.

1070

Figure 1. Photograph of BAO crystal.

SHIMADZU 8400 S. The sample was prepared by pres-

sing BAO with KBr into a pellet form. The UV-Vis

spectrum of BAO crystal was recorded in the wavelength

range 190 nm - 1100 nm using Perkin Elmer Lambda 35

spectrometer.

3. Results and Discussion

3.1. Solubility

The solubility of BAO was measured in the temperature

range from room temperature to 55˚C. A volume of 50

ml of water was taken in a container and re-crystallized

salt was added. The temperature of the solution was

maintained above the chosen constant temperature and

continuously stirred using a magnetic stirrer to ensure

homogeneous temperature and concentration throughout

the entire region of the solution. Once the saturation was

reached, the equilibrium concentration of the solute was

analyzed gravimetrically [13]. The experiment was car-

ried out for various temperatures from room temperature

to 55˚C in steps of 5˚C and the solubility curve was

drawn and it is presented in the Figure 2. The solubility

curve indicates that BAO crystal has positive temperature

coefficient of solubility.

3.2. XRD Analysis

From the single crystal X-ray diffraction analysis, it is

found that the BAO crystallizes in monoclinic system

with lattice parameters a = 22.335 Å, b = 5.697 Å, c =

13.993 Å, α = 90˚, β = 115.37˚, γ = 90˚, and volume of

the unit cell, V = 1609 Å3. In order to study the crystal

structure of BAO the grown sample was subjected to

powder X-ray diffraction studies with a high resolution

PANalytical X’pert PRO diffractometer. Powder XRD

pattern of BAO sample is shown in Figure 3. All the

reflections of powder XRD pattern of this work were

indexed using the TREOR and INDEXING software pac-

kages following the procedure of Lipson and Steeple [14].

The values of 2θ, hkl values and d-values etc are pre-

sented in the Table 1.

3.3. FTIR Analysis

FTIR study is used to identify the functional groups of

the samples. In the FTIR spectrum (Figure 4), the band

at 2927 cm–1 is on the high frequency side of the broad

absorption. The deformation vibration of the water mole-

cules was found at 1525 cm–1. The broad bands due to

the in-plane bending vibrations (δ OH) of the O-H···O

bending bonds are located at 1128 cm–1. The out-of-plane

bending modes of the O-H···O hydrogen bonds (γ OH)

were found at 918 and 781 cm–1. The νa COO mode gives

rise to the absorption observed at 1627 cm–1. The strong

band 1402 cm–1 is attributed to the νs COO– mode. The

carboxylic groups scissoring modes (δ COO–) are ex-

pected in the region of 500 - 750 cm–1. Weak bonds are

visible at 648 cm–1. The complete absorption bands and

their assignments for the grown BAO sample are pro-

vided in the Table 2.

3.4. UV Visible Spectral Studies

The UV-Vis analysis was made between 190 and 1100

nm, which covers near ultraviolet (200 nm - 400 nm),

Visible (400 nm - 800 nm) and then Far-Infrared (800 -

1200 nm) regions. The plot of % of transmittance versus

30 35 40

Concentration (g/100 ml)

Temperature (

Figure 2. Solubility curve of BAO crystal.

5 1015202530354045505560657075

1000

2000

3000

4000

5000

6000

7000

8000

-425

303

312

-223 -315 -421

-503

112

-125

-522

022

120

-404

410

Counts

2 theta (degrees)

Figure 3. Powder XRD pattern of BAO crystal.

S. L. M. PONMANI ET AL. 1071

Table 1. The values of 2θ, hkl and d-values for BAO crystal.

2θ (degrees) d (cal) Å d (obs) Å hkl

13.81695 6.32176 6.40386 002

15.86843 5.58079 5.58028 –401

16.67197 5.525853 5.31310 –111

17.98822 4.96093 4.92718 210

19.90698 4.43471 4.45638 –501

21.07639 4.2145 4.21169 003

22.47157 3.92216 3.95326 112

23.09904 3.85449 3.84724 –503

23.67687 3.77703 3.75467 410

24.81665 3.60886 3.58474 –213

25.2999 3.49944 3.51735 –511

26.07443 3.41713 3.41461 –404

27.36215 3.25637 3.25676 –504

27.84415 3.19245 3.20147 312

28.62254 3.16088 3.11615 004

29.15924 3.03416 3.06000 303

29.92589 2.97881 2.98333 –314

30.71410 2.92249 3.90855 213

31.11264 2.86315 2.87219 412

31.80475 2.82054 2.81125 120

32.47677 2.74613 2.75468 –221

33.05522 2.70392 2.70770 204

34.5039 2.59704 2.59752 022

35.01030 2.53712 2.56084 –421

35.75416 2.50847 2.50925 –315

36.94224 2.43091 2.43124 –223

37.83470 2.38321 2.37591 –522

2θ (degrees) d (cal) Å d (obs) Å hkl

38.93460 2.31125 2.31129 015

39.42319 2.28173 2.28376 123

40.63857 2.20793 2.21822 –324

41.11312 2.19436 2.19371 521

41.87151 2.15957 2.15571 422

45.54444 1.99303 1.99003 –425

47.12085 1.94149 1.92707 –125

48.70484 1.86774 1.86803 –231

49.35870 1.84537 1.84481 415

50.10238 1.81872 1.81915 032

52.06304 1.75284 1.75516 –333

53.19255 1.71831 1.72052 530

54.36710 1.68578 1.68610 524

55.62736 1.65202 1.65084 –134

57.32108 1.60938 1.60602 425

58.65760 1.57055 1.57258 –335

60.39421 1.53397 1.53144 525

63.95376 1.45802 1.45452 434

67.40114 1.38826 1.38826 –342

68.25821 1.37290 1.37290 –442

4500 4000 3500 3000 2500 2000 1500 1000500

0.4

0.3

0.2

0.1

0.0

1128

1014

918 827

486

401

707

1218

1251 1332

1402

1525

1627

1716

2362

2927

3089

3280

Transmittance (AU)

Wavelength (cm

-1

)

Figure 4. FTIR spectrum for the grown crystal of BAO.

Table 2. FTIR assignments for BAO crystal.

Wave number in cm–1 Band assignments

3280

3089

2927

1716

1627

1525

1458

1429

1402

1332

1251

1218

1128

1062

1014

981

918

827

781

707

648

486

401

νa H2O

νs H2O

ν N-H···O

νa C = O (β-alanine)

νa C = O (acid)

δ H2O

δ C H2/δ N-H···O

δ C H2

νs COO-(acid)

ω C H2

ν CO-H

δ OH, ν C H2-C H2

ν C-H

ρ C H2

Ρ NH3+

Ρ NH3+ , γ OH

ν C-C

γ OH

δ COO

δ COO–

ω COO–

δ COO–

wavelength is shown in Figure 5. The absorbance is not

registered until the wavelength 205 nm is reached from

1100 nm. At 205 nm, a sharp fall of transmittance was

observed indicating a single transition in the near UV

region. The nearly sharp fall in transmittance at 205 nm

suggests nearly similar distribution of energies among all

molecules of β-alanine oxalate single crystal, which oth-

erwise will yield a gradual decrease in the transmittance

from the longer wavelength to 205 nm. The plot of % of

absorbance vs wavelength is shown in Figure 6. From

the graph, it is observed that there is no absorption in the

entire UV and visible region.

3.5. Thermal Studies

Differental Thermal (DTA)/Thermaogravimetric (TG)

S. L. M. PONMANI ET AL.

1072

200 300 400 500 600 700 800 9001000110

-10

100

110

Transmittance

wavelength (nm)

analyses were carried out on the BAO samples to look

for possible phase transitions and to determine the melt-

ing point. The thermal analysis was carried out in the

temperature between 30˚ and 1000˚C. The TG/DTA re-

sponse curve of BAO is shown in Figure 7. The DTA

curve shows a major endothermic peak observed at

around 172˚C and it may attributed to the melting of the

material. The sharp DTA peak at 545˚C is attributed to

the volatilization of the material the other endothermic or

exothermic peaks observed, coincide exactly with the

decomposition observed in the TGA curve. In the TGA

trace, there is a major weight loss of 77% starting at

about 182˚C and ending at 353˚C. It is due to the de-

composition and volatilization of the compound. The next

weight loss of about 13% occurs between 353˚C and

595˚C shows that the decomposition is almost complete.

There is one more weight loss between 595˚C and 980˚C

is due to the decomposition of the residue that is left over

after the major weight loss which corresponds to 5%.

Figure 5. UV-vis-NIR transmittance spectrum for the

grown BAO crystal.

200 300 400 500 600 700 800 90010001100

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

In order to confirm the melting and volatilization of

the compound without decomposition, DSC analysis was

carried out between 20˚C and 1000˚C. The DSC trace is

shown in Figure 8. The exotherm at 172˚C is assigned to

melting of the material and a sharp endothermic peak at

548˚C is assigned to volatilization based on the results

obtained with DTA curve.

3.6. Hardness Measurements

Hardness is the resistance offered by a material to plastic

deformation caused by scratching or by indenta tion. In

ideal circumstances, measured hardness value should be

Figure 6. Absorbance spectrum of BAO crystal

Figure 7. TGA and DTA curves of BAO sample.

S. L. M. PONMANI ET AL. 1073

Figure 8. DSC curve of BAO sample.

independent of applied load. But in practice, load de-

pendence is observed. In this work, the selected smooth

surface of a BAO crystal was used for microhardness

measurements at room temperature, using a Vickers mi-

cro hardness tester (mhp-100) attached to an incident-

light microscope (Leitz-Wetzler microscope) keeping the

indentor at right angles to the crystal plane for 10 s in all

cases. An average of 10 diagonal length of the indenta-

tion mark was measured using an optical micrometer

eyepiece at a magnification of 500:1. The Vickers micro-

hardness number was calculated using the relation Hv =

1.8544 P/d kg/mm2 where P is the applied load and d is

the diagonal length of the indentation impression [15,16].

A plot of Hv versus load is shown in Figure 9. As the

load is increased, there is an increase in the hardness.

The increase of microhardness with increasing load is in

agreement with the Indentation Size Effect (ISE) as re-

ported in the literature [17].

3.7. Second Harmonic Generation (SHG) Test

The SHG test for the grown BAO crystal was carried out

by using powder Kurtz and Perry technique [18]. The

crystal was ground into a homogenous powder and

densely packed between two transparent glass slides. A

Q-switched Nd:YAG laser beam of wavelength 1064 nm

(pulse width 6 ns) was allowed to strike the sample cell

normally. A sample of potassium dihydrogen phosphate

(KDP) also powdered and was used for the same experi-

ment as a reference material in the SHG measurement.

20 30 40 50 60 70 80 90100110

Hv ( kg/mm2)

Load P (g)

Figure 9. Plot of Hv versus load for BAO crystal.

From the experiment, it is noticed that there is no green

light (no SHG emission) emitted from the sample and

this gives the conclusion that the grown BAO crystal has

zero second order susceptibility coefficient.

4. Conclusion

β-alanine oxalate crystals were grown from aqueous so-

lution by slow evaporation technique at room tempera-

ture. The X-ray diffraction studies confirm the mono-

clinic structure of the grown crystals. The FTIR analysis

confirms the presence of various functional groups. The

near zero transmittance below the cut off wavelength and

the high degree of transparency illustrates the optical

quality of the grown samples. As seen in the spectrum,

there is no significant absorption in the range 250 nm -

S. L. M. PONMANI ET AL.

1074

1100 nm. Thermal behavior of the BAO sample was

studied by employing TGA, DTA and DSC analysis. The

hardness study reveals that BAO crystal can only with-

stand low loads and at higher loads, it can break and

damage and it proves that BAO crystal is a soft material.

The present result shows that the grown BAO crystal

does not emit green light when the light from Nd:YAG

laser is passed onto the sample.

5. Acknowledgements

The authors like to thank the staff members of RRL

(Trivandrum), CECRI (Karaikudi), Crecent Engineering

College (Chennai), St. Joseph’s College (Trichy) and M.

K. University (Madurai) for having helped us to carry out

the research work.

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