# Structural, Spectroscopic, Thermal studies of Pure and DL-Methionine Doped ADP Crystals

J H Joshi, H O Jethva, P T Bagda, K Ashish Prasad, M J Joshi

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J H Joshi, H O Jethva, P T Bagda, K Ashish Prasad, M J Joshi. Structural, Spectroscopic, Thermal studies of Pure and DL-Methionine Doped ADP Crystals. Mechanics, Materials Science & Engineering Journal, 2017, 10.2412/mmse.42.48.140. [hal-01502448](https://hal.science/hal-01502448)

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# Structural, Spectroscopic, Thermal studies of Pure and DL-Methionine Doped ADP Crystals

J.H. Joshi¹, H.O. Jethva¹, P.T. Bagda¹, K. Ashish Prasad¹, M.J. Joshi¹

1 – Department of Physics, Saurashtra University, Rajkot – 360 005, India

<figure><img src="image_2.png" /></figure>

DOI 10.2412/mmse.42.48.140 provided by [Seo4U.link](https://link.springer.com/10.2412/mmse.42.48.140)

**Keywords:** ammonium dihydrogen phosphate, powder XRD, FT-IR, TGA/DTA.

**ABSTRACT.** The growth of Nonlinear Optical crystals retains great number of attention nowadays. Ammonium Dihydrogen Phosphate (ADP) is an important NLO material used for electro-optical applications and LASER material for Nd: YAG and Nd: YLF etc. Amino acids due to their properties like molecular chirality and zwitter ionic structure attract many researchers to dope them in ADP for the improvement of its properties. The Pure and 0.1wt% DL-Methionine doped ADP crystals were grown using slow solvent evaporation technique at room temperature. The Powder XRD shows single phase nature of doped crystal with slight variation in unit cell parameters. The interaction of DL-Methionine with functional groups of ADP crystal was studied using FT-IR spectroscopy. The TGA curve of pure ADP sample indicates that it remain stable upto 200 °C and then decompose slowly, while the doped sample slowly decomposes right from beginning of the analysis. The DTA curves exhibits endothermic peaks at 209 °C and 212 °C for pure and doped sample, respectively.

**Introduction.** Ammonium dihydrogen phosphate (ADP) is important isomorphs of the Potassium dihydrogen phosphate (KDP) type crystal, which is used for several nonlinear optical applications and higher SHG efficiency of fundamental laser with large NLO coefficients [1-2]. Amino acids possess properties like molecular chirality, absence of strongly conjugated bond and Zwitter ionic nature [3] attracted researcher to dope them in KDP [4] and ADP [5,6] crystals to improve the NLO performance and other properties. DL-Methionine consists of a 4-carbon aliphatic straight chain, the distal end of which is capped by a complex guanidinium group. The conjugation between the double bond and the nitrogen lone pairs, the positive charge is de-localized, enabling the formation of multiple H-bonds. In present context, the authors have doped amino acid DL-Methionine in ADP crystals to investigate its effect on structural, spectroscopic and thermal properties.

**Experimental Technique.** The slow solvent evaporation technique was employed for the growth of crystals. ADP was added to 200ml distilled water under constant stirring to achieve saturation. After rigorous stirring for 4 hours the solution was filtered using Watmann filter paper no.1. Then the solution was subdivided into two beakers; one beaker contains 100ml pure ADP solution and in the other beaker 0.1wt% DL-Methionine was added in 100 ml solution of ADP and stirred well for 4 hours. All beakers were kept in a dust free atmosphere with a porous lid to control the evaporation. After 20 days good quality, transparent, colourless crystals were harvested. Fig. 1 show the harvested crystals of pure ADP and 0.1wt %DL-Methionine doped ADP, respectively.
<figure><img src="image_3.png" /><figcaption>Fig. 1. Grown crystal of Pure and 0.1wt% DL-Methionine doped ADP crystals.</figcaption></figure>

Powder XRD was carried on PHILIPS X'PERT MPD system and the data were analyzed by software powder-X. FTIR spectra were recorded in KBr media within the region of 400-4000 cm⁻¹ employing THERMO NICOLET 6700 spectrophotometer. The TGA/DTA/ was performed on Linseis STA PT 1600 setup from room temperature to 900°C at a heating rate of 15°C/min in air atmosphere.

## Results and Discussion:

<figure><img src="image_4.png" /><figcaption>Fig. 2. Powder XRD Pattern.</figcaption></figure>

Fig. 2 shows Powder XRD pattern of pure and 0.1wt% DL-Methionine doped ADP crystals. From the Fig. it can be seen that due to doping of DL-Methionine in ADP no additional phase was observed and both the samples retained single phase nature with characteristic diffraction peaks like (2 0 0), (1 1 2), (2 0 2), (3 0 1), (3 0 3), (2 0 4), (3 2 3) etc. But the variation in intensity is observed which indicates the presence of dopant in ADP. Both the crystals belonged to tetragonal symmetry with lattice parameter a=b=7.504 Å, c=7.552 Å for pure ADP and a=b=7.507 Å, c=7.557 Å for 0.1wt% DL-Methionine doped ADP.

To estimate the lattice strain introduced by the dopant, the Williamson-Hall method was applied to power XRD patterns [7].

$$ \beta \cos\theta = K\lambda/L + \eta\sin\theta $$

where β – full width half maximum of high intensity diffraction peaks;

L – crystallite size;
$\eta$ – strain;

$K$ – 0.9;

$\lambda$ – 1.54178 Å.

<figure><img src="image_5.png" /><figcaption>Fig. 3. (a-b). W-H plots of pure and 0.1wt% DL-Methionine doped ADP crystals.</figcaption></figure>

Fig. 3(a-b) shows Williamson – Hall plots of pure and 0.1wt% DL-Methionine doped ADP crystals respectively. The linear fitted plot of $\beta\cos\theta$ versus $\sin\theta$ gives crystallite size and strain from intercept and slope respectively.

The crystallite size is found to be 0.431 mm and 0.779 mm while the strain is found to be 0.03161 and 0.00515 for pure and 0.1wt% DL-Methionine doped ADP crystals respectively. Such plots reveal that the doping of DL-Methionine in ADP increases the crystallite size of ADP and decrease the lattice strain. These results confirmed presence of DL-Methionine in ADP.

<figure><img src="image_6.png" /><figcaption>Fig. 4. FT-IR spectra of pure and 0.1wt% DL-Methionine doped ADP crystals.</figcaption></figure>

The doping of DL-Methionine in ADP was confirmed by FT-IR spectra of Fig. 4. The FT-IR spectrum of pure ADP crystal shows the O-H stretching of water at 3229 cm⁻¹, P-O-H stretching at 1084 cm⁻¹, N-H stretching of ammonium at 2825 cm⁻¹ and PO₄³⁻ vibration at 590 cm⁻¹ and 453 cm⁻¹. The FT-IR spectrum DL-Methionine doped ADP shows the peak shifting from higher to lower wavelength due
to presence of DL-Methionine in ADP, e.g., the PO₄ vibration of pure ADP is shifted from 590 cm⁻¹ to 565 cm⁻¹ in the doped ADP crystal. The FTIR spectrum of DL-Methionine doped ADP indicates absorption occurring at 2828 cm⁻¹ and 1697 cm⁻¹ are due to C-H symmetric stretching and C=O stretching of COOH group, respectively, indicating the presence of amino acid, which is absent in pure ADP.

The relation between the absorption frequency and the force constant can be written as [8],

$$v = 1330 [F (1/M_1 + 1/M_2)]^{1/2}$$

where v – absorption frequency (cm⁻¹), 1330 = (Nₐ10)¹/²/ 2πC;

Nₐ – Avogadro’s number;

F – force constant (Nm⁻¹);

M₁ and M₂ – molecular masses of atoms (u).

Presently the force constant for O-H stretching vibration were calculated. It is found to be 558 N/m and 552 N/m for pure and 0.1wt% DL-Methionine doped ADP respectively. It can be seen that the force constant altered as the DL-Methionine interacts with the hydrogen bond of ADP.

<figure><img src="image_7.png" /><figcaption>Fig. 5. (a-b) TGA/DTA curves for pure and 0.1wt% DL-Methionine doped ADP crystals.</figcaption></figure>

Figures 5 (a-b) shows the TGA/DTA curves of pure and 0.1wt% DL-methionine doped ADP crystals, respectively. The pure ADP sample destabilizes above 200°C and starts decomposing and above 500°C it is decomposed more than 69% of the original mass by expelling various gases. From the thermogram of 0.1 weight % DL-methionine doped ADP crystal, it is found that the crystal starts decomposing very slowly right from the beginning of the analysis and at 200°C it is decomposed by 6% of the original weight, thereafter, the thermal behaviour is almost the same that of the pure ADP. The endothermic reaction peak can be assigned due to melting and decomposition of ADP, i.e. decomposition to orthophosphoric acid H₃PO₄ of the crystal [9]. It can be found that the stability of the crystals is not appreciably affected by doping of amino acid DL-methionine in ADP.
<table><caption>Table 1. Thermodynamic parameters of pure and 0.1wt% DL-Methionine doped ADP crystals.</caption><thead><tr><th>Sample</th><th>Reaction</th><th>Peak Temperature (°C)</th><th>ΔH (J/kg)</th><th>ΔC<sub>p</sub> (J/kg.K)</th><th>Amount of Heat change (Vs/kg)</th></tr></thead><tbody><tr><td>Pure ADP</td><td>Endothermic</td><td>209<sup>0</sup></td><td>-45.56 * 10<sup>-4</sup></td><td>648</td><td>-160.26</td></tr><tr><td>ADP + 0.1wt% DLM</td><td>Endothermic</td><td>212<sup>0</sup></td><td>-50.75 * 10<sup>-4</sup></td><td>1351</td><td>-160.38</td></tr></tbody></table>

**Summary.** The pure and 0.1wt% DL-Methionine doped ADP crystals were successfully grown by slow solvent evaporation technique at room temperature. The powder XRD exhibits single phase nature of doped sample with slight variation in the unit cell parameters. The shifting of absorption peaks in FT-IR and the occurrence of absorptions responsible to C-H and C=O indicated interaction of amino acids with ADP. The Thermal study shows DL-methionine marginally reduced the thermal stability of ADP.

**Acknowledgement.**

The authors are thankful to UGC for financial assistance under SAP DRS - II and DST under FIST and Prof. H.H.Joshi (Head, Department of Physics, Saurashtra University, Rajkot) for his encouragement and support

**References**

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[4] K.D.Parikh, D.J.Dave, B.B.Parekh and M.J.Joshi, Bull.Mater.Scie, 30,105-112 (2007). doi:10.1007/s12034-007-0019-4.

[5] J.H.Joshi, B.V.Jogiya, M.J.Joshi and K.D.Parikh, Int. J. Chemtch. Res., 6, 1555-1558 (2014).

[6] T.Josephine Rani, F.Loretta, P.Selvarajan, S.Ramalingom, S.Peruma, Rec.Res.Scie & Tech.,3(7),69-72,2011.

[7] G.K.Williamson, W.H.Hall, X-ray line broadening from filed aluminium and wolfram, 1(1)(1953)22-31 doi:10.1016/0001-6161(53)90006-6.

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[9] A.Abdul Kadar, A.A.Ammer, S.I.Saleh, Thermochimica Acta., 176(1991)293-304. doi:10.1016/0040-6031(91)80285-Q.

Cite the paper

J.H. Joshi, H.O. Jethva, P.T. Bagda, K. Ashish Prasad, M.J. Joshi, (2017). *Structural, Spectroscopic, Thermal studies of Pure and DL-Methionine Doped ADP Crystals*. Mechanics, Materials Science & Engineering, Vol 9. doi:10.2412/mmse.42.48.140