- Email: [email protected]
Growth, structural, spectral, optical, and thermal studies on amino acid based new NLO single crystal: l -phenylalanine-4-nitrophenol
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 108 (2013) 32–37
Contents lists available at SciVerse ScienceDirect
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa
Growth, structural, spectral, optical, and thermal studies on amino acid based new NLO single crystal: L-phenylalanine-4-nitrophenol M. Prakash a,⇑, M. Lydia Caroline b, D. Geetha c a
Department of Physics, Annai College of Engineering and Technology, Kumbakonam, India Department of Physics, Arignar Anna Government Arts College, Cheyyar 604 407, Tamil Nadu, India c Department of Physics, Annamalai University, Annamalainagar 608 002, Tamil Nadu, India b
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
" Thermal stability of the LPAPN is
165 °C. " SHG efficiency of LPAPN is 1.2 times
than that of KDP crystal. " The optical cut-off wave length for
this crystal was observed at 320 nm. " LPAPN crystal is a potential
candidate for NLO application.
a r t i c l e
i n f o
Article history: Received 1 October 2012 Received in revised form 31 January 2013 Accepted 31 January 2013 Available online 9 February 2013 Keywords: Crystal growth Nonlinear optics X-ray diffraction Nuclear magnetic resonance Slow evaporation
a b s t r a c t A new organic nonlinear optical single crystal, L-phenylalanine-4-nitrophenol (LPAPN) belonging to the amino acid group has been successfully grown by slow evaporation technique. The lattice parameters of the grown crystal have been determined by X-ray diffraction studies. FT-IR spectrum was recorded to identify the presence of functional group and molecular structure was confirmed by NMR spectrum. Thermal strength of the grown crystal has been studied using TG–DTA analyses. The grown crystals were found to be transparent in the entire visible region. The existence of second harmonic generation signals was observed using Nd:YAG laser with fundamental wavelength of 1064 nm. Ó 2013 Elsevier B.V. All rights reserved.
Introduction The field of molecular nonlinear optics has benefited from both upstream rejuvenation and downstream application oriented breakthroughs, aiding to bring the field closer to industrial developments [1]. Engineering of new nonlinear optical (NLO) materials, structures, and devices with enhanced figures of merit has developed over the last two decades as a major force to help ⇑ Corresponding author. Mobile: +91 9894944592. E-mail address: [email protected] (M. Prakash). 1386-1425/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.saa.2013.01.078
drive nonlinear optics from the laboratory to real applications. The NLO process requires materials that manipulate the amplitude, phase, polarizations and frequency of optical beam. The intellectual construction of structurally controlled supramolecular assemblies (e.g., acentric and chiral solids) remains a great challenge even though the art of chemical synthesis of discrete molecules has significantly advanced in recent decades. The relevance of organic materials in this interesting context is because the delocalized electronic structure of p-conjugated organic compound offers a number of tempting opportunities in applications as NLO materials.
M. Prakash et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 108 (2013) 32–37
33
In particular, p-conjugated systems linking a donor (D) and an acceptor (A) show a large NLO response and hence have been well studied. In addition to the advantage in synthesis organic materials have ultra fast response time, photo stability and large first hyperpolarizability (b) values. Hence, they are projected as forefront candidates for fundamental and applied investigation [2]. In our earlier communications we have reported some L-phenylalanine amino acid based single crystals exhibiting second order nonlinearity [3–5]. In continuation of our work, we report in this present investigation growth, structural, spectral, optical and thermal studies on L-phenylalanine-4-nitrophenol (LPAPN) single crystals. The crystal structure of the title compound has already been reported [6]. The NLO properties of the title compound are reported for the first time in the literature.
Fig. 1. Photograph of as grown crystal of LPAPN.
Experimental 50000 020
LPAPN
L-phenylalanine-4-nitrophenol (LPAPN) crystals were grown by a slow evaporation technique. L-phenylalanine and 4-nitrophenol were dissolved separately in water and methanol, respectively. The solutions were then mixed in a 1:1 M ratio and stirred at 323 K for 6 h using a magnetic stirrer to ensure homogenous temperature and concentration over entire volume of the solutions. The solution was filtered using Whatman filter paper. The filtered solution was transferred to crystal growth vessels followed by slow evaporation at room temperature and crystals were obtained after 2 weeks. The product was purified by successive recrystallization. The photograph of as grown crystals of LPAPN is shown in Fig. 1.
-103
115 -204
-134
10000
231
220
-114
20000
012
Intensity (counts/sec)
40000
30000
C9 H11 NO2 þ C6 H5 NO3 ðL-phenylalanineÞ ð4-nitrophenolÞ
0 0
20
Crystal growth
40
60
80
2θ (degree) Fig. 2. Powder X-ray diffraction pattern of LPAPN single crystal.
100
! C9 H11 NO2 C6 H5 NO3
ðL-phenylalanine-4-nitrophenolÞ
Characterization The grown LPAPN single crystal was subjected to various characterization techniques like powder X-ray diffraction, FT-NMR,
Fig. 3. 1H NMR spectrum of LPAPN.
34
M. Prakash et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 108 (2013) 32–37
Fig. 4.
13
C NMR spectrum of LPAPN.
Table 1 Chemical shift in 1H NMR spectrum of LPAPN. Group identification
Assignment
3.05
ACH2aA
3.21
ACH2bA
3.97
ACHA
4.70 6.68 7.232–7.35
H2O in D2O OH proton in 4-nitrophenol Two aromatic protons (L-phenylalanine and 4-nitrophenol)
Doublet of doublet Doublet of doublet Doublet of doublet Singlet Singlet Multiplet
L-phenylalanine-4-
nitrophenol chemical shift (ppm)
Table 2 Chemical shifts in
13
C NMR spectrum of LPAPN.
L-phenylalanine-4-
Group identification
nitrophenol chemical shift (ppm) 36.18 55.62 127.77–134.86 169.70 173.36
ACH2A ACHA Two aromatic carbons (L-phenylalanine and 4nitrophenol) Phenolic carbon in 4-nitrophenol Carbonyl carbon of phenylalanine
Fourier transform infrared (FTIR), UV–Vis–NIR, thermal and nonlinear optical studies.
Result and discussion Powder X-ray diffraction study X-ray powder diffraction was used for the identification of the synthesized LPAPN crystal. Efforts were made to record the powder XRD pattern of the L-phenylalanine-4-nitrophenol crystal and
index them. The indexed powder XRD pattern of the grown LPAPN crystal is shown in Fig. 2. The XRD powder pattern has been indexed using CELREF programs and the lattice parameters are evaluated as a = 5.8346 Å, b = 7.009 Å, c = 17.8673 Å and b = 94.59°. The volume of the unit cell is 728.3 Å3. It is observed that the crystal belongs to monoclinic system and space group P21. The observed lattice parameters are consistent with reported values [6]. FT-NMR studies The 1H NMR and 13C NMR spectral analysis are the two important analytical techniques used to the study the structure of organic compounds. The present investigation of the grown crystals includes the 1H (500 MHz and resolution 0.31, at 27 °C) and 13C (125 MHz and resolution 1.00, at 27 °C) NMR spectra recorded with a BRUKER AVIII 500 MHz FT-NMR spectrometer with D2O as solvent. The spectra are presented in Figs. 3 and 4 respectively and the chemical shifts are tabulated with the assignments in Tables 1 and 2. The signals at d = 3.05 ppm (doublet of doublet) and at d = 3.21 ppm (doublet of doublet) are assigned to the CH2a group and the CH2b group of the amino acid respectively. The signal at 3.97 ppm is split into a doublet of doublet owing to the influence of the adjacent CAH group. The two Aromatic group signal is split into a multiplet due to the hyperfine splitting of neighboring protons, which was confirmed from the signal of LPAPN crystal centered at d = 7.29 ppm. The singlet of the OH proton of the 4nitrophenol assigned at d = 6.68 ppm. The signal due to NAH and COOH do not show up because of fast deuterium exchange which took place in those two groups, where the D2O was used as the solvent [7]. The assignment of the signal at 4.70 ppm (singlet) due to solvent H2O in D2O. The 13C NMR spectrum is shows the signals at 36.18 ppm and 55.62 ppm are attributed to the CH2 and CH carbon of the amino acid. The presence of the signal at 127.774–134.86 ppm is attributed to the carbons of the two aromatic groups (L-phenylalanine and 4-nitrophenol). A peak with intensity at d = 173.36 ppm can
35
M. Prakash et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 108 (2013) 32–37
Fig. 5. FT-IR spectrum of LPAPN.
4.5
LPAPN
Absorbance
4.0
3.5
Table 3 Comparative SHG efficiencies of different amino acid NLO crystals relative to potassium dihydrogen phosphate (KDP) equaling 1.0. Nonlinear optical crystals
SHG efficiency
LPAPN (present work)
1.2 0.65
L-phenylalaninium
trichloroacetate Tris(L-phenylalanine) L-phenylalaninium nitrate
L-phenylalanine L-phenylalaninium
3.0
2.5
acid
0.307
L-phenylalanine-benzoic
acid
0.56
L-phenylalaninium
maleate
250
500
750
1000
1250
1500
1750
2000
Wavelength (nm) Fig. 6. Optical absorption spectrum of the LPAPN crystal.
be safely attributed to carbonyl carbon of COOH group of L-phenylalanine present in the same chemical environment. The presence of the signal at 169.70 ppm is attributed to the phenolic carbon in 4nitrophenol.
FT-IR studies The recorded FTIR spectrum is shown in Fig. 5. A broad strong absorption in the region 3300–2300 cm1 corresponds to the NHþ 3 ion of the amino acid [8]. The band that appears at 2700– 1800 cm1 signifies the overtone combinations. The peak at 1742 cm1 is assigned to C@O stretching vibration. The bands at 1587 and 1525 cm1 established the presence of NHþ 3
perchlorate
0.50 0.27 0.20
L-alanine
0
0.26
nitric acid
L-phenylalanine L-phenylalaninium
1.5
0.569 0.38
L-phenylalanine-fumaric
L-phenylalanine
2.0
malonate
L-alaninium
succinate
0.23
L-alaninium
fumarate
0.058
L-alanine
acetate
0.30
L-arginine
chloride
0.20
L-arginine
bromide
0.30
L-arginine
tetrafluroborate
0.54
L-arginine
formate
0.30
L-valinium
succinate (g)
0.56
deformations. The bands at 1497 and 1165 cm1 illustrates the presence of NHþ 3 symmetric stretching and rocking respectively. The bands at 1458 and 1110 cm1 established the presence of COO stretching. The bands at 646 and 492 cm1 signifies the presence of COO wagging and rocking respectively. The bands at 1354, 1332, 1110 and 751 cm1 established the presence of CAH deformation. The OH and CAH out of plane deformation vibrations produces sharp intense peaks at 923 and 845 cm1 respectively. The bands at 1587 and 1497 cm1 was due to the presence of NO2 symmetric stretching. The peak at 706 cm1 established the
36
M. Prakash et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 108 (2013) 32–37
Fig. 7. TG and DTA curves of LPAPN.
presence of benzene ring. The presence of CACO deformation is clearly illustrated by the peak at 530 cm1. The bands at 1079 and 806 cm1 signifies the deformation benzene ring. The CH2 wagging and CAN stretching shows the characteristic vibration at 1244 and 1035 cm1 respectively. The stretching vibrations of CANO2 and CAO presence the peak at 1165 cm1. The bands at 1110 and 1005 cm1 established the presence of CAOH out of plane deformation and CACAN bending respectively. Thus, the presence of all the functional group occurring in LPAPN was confirmed and this spectrum appears largely different from that of Lphenylalanine reported in the literature [9]. From this FTIR spectrum clear that both L-phenylalanine and 4-nitrophenol functional group present in the grown crystal. Optical absorption studies The UV–Vis–NIR analysis of LPAPN crystal was carried out between 200 and 2000 nm, covering the entire near ultra violet, visible and near infrared regions. There is no appreciable absorption of light in the entire visible range as in the case for all amino acid [10]. Fig. 6 shows the UV–Vis–NIR optical absorption spectra of LPAPN crystal. The cut-off wavelength as observed from the absorption spectrum is 320 nm, which is sufficient for SHG laser radiation of 1064 nm or other application in the blue region. Interestingly, in the entire visible region starting from 310 to 1540 nm, the crystal has almost no absorption. The wide optical transmission window is an encouraging optical property seen in LPAPN crystal and is of vital importance for NLO materials. NLO studies In order to confirm the NLO property, the grown specimen was subjected to a Kurtz powder test using a Q-switched, mode locked Nd:YAG laser of 1064 nm and a pulse width of 8 ns (spot radius of 1 mm) on the powder sample of LPAPN. The input laser beam was directed on the as-grown crystal powder to get maximum powder SHG. The emitted light passed through an IR filter was measured by means of a photomultiplier tube and oscilloscope assembly. The SHG efficiency of the LPAPN crystal was evaluated by taking the microcrystalline powder of KDP as the reference material. The SHG efficiency results show a high signal output of 45 mV with input laser power of 5.5 mJ/pulse when compared to 38 mV of KDP. SHG efficiency of LPAPN is 1.2 times than that of KDP crystal. Comparison of SHG signal efficiency of LPAPN crystals along with other
amino acid based NLO crystals with respect to KDP crystal is presented in Table 3. Thermal analysis The thermal stability of LPAPN single crystal was estimated by TGA and DTA techniques. The sample was kept in nitrogen atmosphere in the temperature range 25–800 °C with a heating rate of 27 °C min1. The TGA thermogram of the LPAPN crystal is shown in Fig. 7. It is seen from the thermogram that there is a major weight loss starting at 165 °C before the start of the decomposition, illustrates the absence of physically adsorbed or lattice water in the crystal. In the DTA curve, a sharp endothermic peak at 165 °C indicates the melting of the material. This is also confirmed by melting point apparatus. Further heating above 165 °C results in the formation of volatile substances, probably carbon dioxide, ammonia, and CH4 and CO molecule. The next stage of decomposition corresponds to the decomposition of residues. Thus from thermal analyses, it is seen that the crystal can be utilized for device applications in the field of optoelectronics and photonics up to 165 °C. Conclusion Single crystals of LPAPN, were successfully grown from amino acid family by slow evaporation technique at room temperature. X-ray diffraction analysis revealed the structure of the crystal as monoclinic system with space group P21. The presence of functional group was confirmed by FT-IR. The 1H and 13C NMR also confirm the molecular structure of the grown crystals. LPAPN were optically transparent in the entire visible region with a lower cut-off wavelength 320 nm. The TG–DTA studies established that the compound undergoes no phase transition and is stable up to its melting point (i.e.) 165 °C. The optical and SHG efficiency studies show the suitability of the crystals for NLO application. SHG efficiency of LPAPN is 1.2 times than that of KDP crystal. References [1] J. Zyss, F. Nicoud, Curr. Opin. Solid State Mater. Sci. 1 (1996) 533–546. [2] P. Srinivasan, Y. Vidyalakshi, R. Gopalakrishnan, Crystal Growth Des. 8 (2008) 2329–2334. [3] M. Prakash, D. Geetha, M. Lydia Caroline, Physica B 406 (2011) 2621–2625. [4] M. Prakash, D. Geetha, M. Lydia Caroline, Spectrochim. Acta A 81 (2011) 48–52.
M. Prakash et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 108 (2013) 32–37 [5] M. Prakash, D. Geetha, M. Lydia Caroline, Spectrochim. Acta A 83 (2011) 461– 466. [6] V.H. Rodrigues, M.M.R.R. Costa, E. de Matos Gomes, E. Nogueirab, M.S. Belslsey, Acta Cryst. E62 (2006) o699–o701. [7] C. Ramachandra Raja, A. Antony Joseph, Spectrochim. Acta A 74 (2009) 825– 828.
37
[8] P. Srinivasan, Y. Vidyalakshmi, R. Gopalakrishnan, Crystal Growth Des. 8 (2008) 2329–2334. [9] R. Mahalakshmi, S.X. Jesuraja, S. Jerome Das, Cryst. Res. Technol. 41 (2006) 780–783. [10] J.J. Rodrigues Jr, L. Misoguti, F.D. Nunes, C.R. Mendonca, S.C. Zilio, Opt. Mater. 22 (2003) 35–240.
Contents lists available at SciVerse ScienceDirect
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa
Growth, structural, spectral, optical, and thermal studies on amino acid based new NLO single crystal: L-phenylalanine-4-nitrophenol M. Prakash a,⇑, M. Lydia Caroline b, D. Geetha c a
Department of Physics, Annai College of Engineering and Technology, Kumbakonam, India Department of Physics, Arignar Anna Government Arts College, Cheyyar 604 407, Tamil Nadu, India c Department of Physics, Annamalai University, Annamalainagar 608 002, Tamil Nadu, India b
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
" Thermal stability of the LPAPN is
165 °C. " SHG efficiency of LPAPN is 1.2 times
than that of KDP crystal. " The optical cut-off wave length for
this crystal was observed at 320 nm. " LPAPN crystal is a potential
candidate for NLO application.
a r t i c l e
i n f o
Article history: Received 1 October 2012 Received in revised form 31 January 2013 Accepted 31 January 2013 Available online 9 February 2013 Keywords: Crystal growth Nonlinear optics X-ray diffraction Nuclear magnetic resonance Slow evaporation
a b s t r a c t A new organic nonlinear optical single crystal, L-phenylalanine-4-nitrophenol (LPAPN) belonging to the amino acid group has been successfully grown by slow evaporation technique. The lattice parameters of the grown crystal have been determined by X-ray diffraction studies. FT-IR spectrum was recorded to identify the presence of functional group and molecular structure was confirmed by NMR spectrum. Thermal strength of the grown crystal has been studied using TG–DTA analyses. The grown crystals were found to be transparent in the entire visible region. The existence of second harmonic generation signals was observed using Nd:YAG laser with fundamental wavelength of 1064 nm. Ó 2013 Elsevier B.V. All rights reserved.
Introduction The field of molecular nonlinear optics has benefited from both upstream rejuvenation and downstream application oriented breakthroughs, aiding to bring the field closer to industrial developments [1]. Engineering of new nonlinear optical (NLO) materials, structures, and devices with enhanced figures of merit has developed over the last two decades as a major force to help ⇑ Corresponding author. Mobile: +91 9894944592. E-mail address: [email protected] (M. Prakash). 1386-1425/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.saa.2013.01.078
drive nonlinear optics from the laboratory to real applications. The NLO process requires materials that manipulate the amplitude, phase, polarizations and frequency of optical beam. The intellectual construction of structurally controlled supramolecular assemblies (e.g., acentric and chiral solids) remains a great challenge even though the art of chemical synthesis of discrete molecules has significantly advanced in recent decades. The relevance of organic materials in this interesting context is because the delocalized electronic structure of p-conjugated organic compound offers a number of tempting opportunities in applications as NLO materials.
M. Prakash et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 108 (2013) 32–37
33
In particular, p-conjugated systems linking a donor (D) and an acceptor (A) show a large NLO response and hence have been well studied. In addition to the advantage in synthesis organic materials have ultra fast response time, photo stability and large first hyperpolarizability (b) values. Hence, they are projected as forefront candidates for fundamental and applied investigation [2]. In our earlier communications we have reported some L-phenylalanine amino acid based single crystals exhibiting second order nonlinearity [3–5]. In continuation of our work, we report in this present investigation growth, structural, spectral, optical and thermal studies on L-phenylalanine-4-nitrophenol (LPAPN) single crystals. The crystal structure of the title compound has already been reported [6]. The NLO properties of the title compound are reported for the first time in the literature.
Fig. 1. Photograph of as grown crystal of LPAPN.
Experimental 50000 020
LPAPN
L-phenylalanine-4-nitrophenol (LPAPN) crystals were grown by a slow evaporation technique. L-phenylalanine and 4-nitrophenol were dissolved separately in water and methanol, respectively. The solutions were then mixed in a 1:1 M ratio and stirred at 323 K for 6 h using a magnetic stirrer to ensure homogenous temperature and concentration over entire volume of the solutions. The solution was filtered using Whatman filter paper. The filtered solution was transferred to crystal growth vessels followed by slow evaporation at room temperature and crystals were obtained after 2 weeks. The product was purified by successive recrystallization. The photograph of as grown crystals of LPAPN is shown in Fig. 1.
-103
115 -204
-134
10000
231
220
-114
20000
012
Intensity (counts/sec)
40000
30000
C9 H11 NO2 þ C6 H5 NO3 ðL-phenylalanineÞ ð4-nitrophenolÞ
0 0
20
Crystal growth
40
60
80
2θ (degree) Fig. 2. Powder X-ray diffraction pattern of LPAPN single crystal.
100
! C9 H11 NO2 C6 H5 NO3
ðL-phenylalanine-4-nitrophenolÞ
Characterization The grown LPAPN single crystal was subjected to various characterization techniques like powder X-ray diffraction, FT-NMR,
Fig. 3. 1H NMR spectrum of LPAPN.
34
M. Prakash et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 108 (2013) 32–37
Fig. 4.
13
C NMR spectrum of LPAPN.
Table 1 Chemical shift in 1H NMR spectrum of LPAPN. Group identification
Assignment
3.05
ACH2aA
3.21
ACH2bA
3.97
ACHA
4.70 6.68 7.232–7.35
H2O in D2O OH proton in 4-nitrophenol Two aromatic protons (L-phenylalanine and 4-nitrophenol)
Doublet of doublet Doublet of doublet Doublet of doublet Singlet Singlet Multiplet
L-phenylalanine-4-
nitrophenol chemical shift (ppm)
Table 2 Chemical shifts in
13
C NMR spectrum of LPAPN.
L-phenylalanine-4-
Group identification
nitrophenol chemical shift (ppm) 36.18 55.62 127.77–134.86 169.70 173.36
ACH2A ACHA Two aromatic carbons (L-phenylalanine and 4nitrophenol) Phenolic carbon in 4-nitrophenol Carbonyl carbon of phenylalanine
Fourier transform infrared (FTIR), UV–Vis–NIR, thermal and nonlinear optical studies.
Result and discussion Powder X-ray diffraction study X-ray powder diffraction was used for the identification of the synthesized LPAPN crystal. Efforts were made to record the powder XRD pattern of the L-phenylalanine-4-nitrophenol crystal and
index them. The indexed powder XRD pattern of the grown LPAPN crystal is shown in Fig. 2. The XRD powder pattern has been indexed using CELREF programs and the lattice parameters are evaluated as a = 5.8346 Å, b = 7.009 Å, c = 17.8673 Å and b = 94.59°. The volume of the unit cell is 728.3 Å3. It is observed that the crystal belongs to monoclinic system and space group P21. The observed lattice parameters are consistent with reported values [6]. FT-NMR studies The 1H NMR and 13C NMR spectral analysis are the two important analytical techniques used to the study the structure of organic compounds. The present investigation of the grown crystals includes the 1H (500 MHz and resolution 0.31, at 27 °C) and 13C (125 MHz and resolution 1.00, at 27 °C) NMR spectra recorded with a BRUKER AVIII 500 MHz FT-NMR spectrometer with D2O as solvent. The spectra are presented in Figs. 3 and 4 respectively and the chemical shifts are tabulated with the assignments in Tables 1 and 2. The signals at d = 3.05 ppm (doublet of doublet) and at d = 3.21 ppm (doublet of doublet) are assigned to the CH2a group and the CH2b group of the amino acid respectively. The signal at 3.97 ppm is split into a doublet of doublet owing to the influence of the adjacent CAH group. The two Aromatic group signal is split into a multiplet due to the hyperfine splitting of neighboring protons, which was confirmed from the signal of LPAPN crystal centered at d = 7.29 ppm. The singlet of the OH proton of the 4nitrophenol assigned at d = 6.68 ppm. The signal due to NAH and COOH do not show up because of fast deuterium exchange which took place in those two groups, where the D2O was used as the solvent [7]. The assignment of the signal at 4.70 ppm (singlet) due to solvent H2O in D2O. The 13C NMR spectrum is shows the signals at 36.18 ppm and 55.62 ppm are attributed to the CH2 and CH carbon of the amino acid. The presence of the signal at 127.774–134.86 ppm is attributed to the carbons of the two aromatic groups (L-phenylalanine and 4-nitrophenol). A peak with intensity at d = 173.36 ppm can
35
M. Prakash et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 108 (2013) 32–37
Fig. 5. FT-IR spectrum of LPAPN.
4.5
LPAPN
Absorbance
4.0
3.5
Table 3 Comparative SHG efficiencies of different amino acid NLO crystals relative to potassium dihydrogen phosphate (KDP) equaling 1.0. Nonlinear optical crystals
SHG efficiency
LPAPN (present work)
1.2 0.65
L-phenylalaninium
trichloroacetate Tris(L-phenylalanine) L-phenylalaninium nitrate
L-phenylalanine L-phenylalaninium
3.0
2.5
acid
0.307
L-phenylalanine-benzoic
acid
0.56
L-phenylalaninium
maleate
250
500
750
1000
1250
1500
1750
2000
Wavelength (nm) Fig. 6. Optical absorption spectrum of the LPAPN crystal.
be safely attributed to carbonyl carbon of COOH group of L-phenylalanine present in the same chemical environment. The presence of the signal at 169.70 ppm is attributed to the phenolic carbon in 4nitrophenol.
FT-IR studies The recorded FTIR spectrum is shown in Fig. 5. A broad strong absorption in the region 3300–2300 cm1 corresponds to the NHþ 3 ion of the amino acid [8]. The band that appears at 2700– 1800 cm1 signifies the overtone combinations. The peak at 1742 cm1 is assigned to C@O stretching vibration. The bands at 1587 and 1525 cm1 established the presence of NHþ 3
perchlorate
0.50 0.27 0.20
L-alanine
0
0.26
nitric acid
L-phenylalanine L-phenylalaninium
1.5
0.569 0.38
L-phenylalanine-fumaric
L-phenylalanine
2.0
malonate
L-alaninium
succinate
0.23
L-alaninium
fumarate
0.058
L-alanine
acetate
0.30
L-arginine
chloride
0.20
L-arginine
bromide
0.30
L-arginine
tetrafluroborate
0.54
L-arginine
formate
0.30
L-valinium
succinate (g)
0.56
deformations. The bands at 1497 and 1165 cm1 illustrates the presence of NHþ 3 symmetric stretching and rocking respectively. The bands at 1458 and 1110 cm1 established the presence of COO stretching. The bands at 646 and 492 cm1 signifies the presence of COO wagging and rocking respectively. The bands at 1354, 1332, 1110 and 751 cm1 established the presence of CAH deformation. The OH and CAH out of plane deformation vibrations produces sharp intense peaks at 923 and 845 cm1 respectively. The bands at 1587 and 1497 cm1 was due to the presence of NO2 symmetric stretching. The peak at 706 cm1 established the
36
M. Prakash et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 108 (2013) 32–37
Fig. 7. TG and DTA curves of LPAPN.
presence of benzene ring. The presence of CACO deformation is clearly illustrated by the peak at 530 cm1. The bands at 1079 and 806 cm1 signifies the deformation benzene ring. The CH2 wagging and CAN stretching shows the characteristic vibration at 1244 and 1035 cm1 respectively. The stretching vibrations of CANO2 and CAO presence the peak at 1165 cm1. The bands at 1110 and 1005 cm1 established the presence of CAOH out of plane deformation and CACAN bending respectively. Thus, the presence of all the functional group occurring in LPAPN was confirmed and this spectrum appears largely different from that of Lphenylalanine reported in the literature [9]. From this FTIR spectrum clear that both L-phenylalanine and 4-nitrophenol functional group present in the grown crystal. Optical absorption studies The UV–Vis–NIR analysis of LPAPN crystal was carried out between 200 and 2000 nm, covering the entire near ultra violet, visible and near infrared regions. There is no appreciable absorption of light in the entire visible range as in the case for all amino acid [10]. Fig. 6 shows the UV–Vis–NIR optical absorption spectra of LPAPN crystal. The cut-off wavelength as observed from the absorption spectrum is 320 nm, which is sufficient for SHG laser radiation of 1064 nm or other application in the blue region. Interestingly, in the entire visible region starting from 310 to 1540 nm, the crystal has almost no absorption. The wide optical transmission window is an encouraging optical property seen in LPAPN crystal and is of vital importance for NLO materials. NLO studies In order to confirm the NLO property, the grown specimen was subjected to a Kurtz powder test using a Q-switched, mode locked Nd:YAG laser of 1064 nm and a pulse width of 8 ns (spot radius of 1 mm) on the powder sample of LPAPN. The input laser beam was directed on the as-grown crystal powder to get maximum powder SHG. The emitted light passed through an IR filter was measured by means of a photomultiplier tube and oscilloscope assembly. The SHG efficiency of the LPAPN crystal was evaluated by taking the microcrystalline powder of KDP as the reference material. The SHG efficiency results show a high signal output of 45 mV with input laser power of 5.5 mJ/pulse when compared to 38 mV of KDP. SHG efficiency of LPAPN is 1.2 times than that of KDP crystal. Comparison of SHG signal efficiency of LPAPN crystals along with other
amino acid based NLO crystals with respect to KDP crystal is presented in Table 3. Thermal analysis The thermal stability of LPAPN single crystal was estimated by TGA and DTA techniques. The sample was kept in nitrogen atmosphere in the temperature range 25–800 °C with a heating rate of 27 °C min1. The TGA thermogram of the LPAPN crystal is shown in Fig. 7. It is seen from the thermogram that there is a major weight loss starting at 165 °C before the start of the decomposition, illustrates the absence of physically adsorbed or lattice water in the crystal. In the DTA curve, a sharp endothermic peak at 165 °C indicates the melting of the material. This is also confirmed by melting point apparatus. Further heating above 165 °C results in the formation of volatile substances, probably carbon dioxide, ammonia, and CH4 and CO molecule. The next stage of decomposition corresponds to the decomposition of residues. Thus from thermal analyses, it is seen that the crystal can be utilized for device applications in the field of optoelectronics and photonics up to 165 °C. Conclusion Single crystals of LPAPN, were successfully grown from amino acid family by slow evaporation technique at room temperature. X-ray diffraction analysis revealed the structure of the crystal as monoclinic system with space group P21. The presence of functional group was confirmed by FT-IR. The 1H and 13C NMR also confirm the molecular structure of the grown crystals. LPAPN were optically transparent in the entire visible region with a lower cut-off wavelength 320 nm. The TG–DTA studies established that the compound undergoes no phase transition and is stable up to its melting point (i.e.) 165 °C. The optical and SHG efficiency studies show the suitability of the crystals for NLO application. SHG efficiency of LPAPN is 1.2 times than that of KDP crystal. References [1] J. Zyss, F. Nicoud, Curr. Opin. Solid State Mater. Sci. 1 (1996) 533–546. [2] P. Srinivasan, Y. Vidyalakshi, R. Gopalakrishnan, Crystal Growth Des. 8 (2008) 2329–2334. [3] M. Prakash, D. Geetha, M. Lydia Caroline, Physica B 406 (2011) 2621–2625. [4] M. Prakash, D. Geetha, M. Lydia Caroline, Spectrochim. Acta A 81 (2011) 48–52.
M. Prakash et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 108 (2013) 32–37 [5] M. Prakash, D. Geetha, M. Lydia Caroline, Spectrochim. Acta A 83 (2011) 461– 466. [6] V.H. Rodrigues, M.M.R.R. Costa, E. de Matos Gomes, E. Nogueirab, M.S. Belslsey, Acta Cryst. E62 (2006) o699–o701. [7] C. Ramachandra Raja, A. Antony Joseph, Spectrochim. Acta A 74 (2009) 825– 828.
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[8] P. Srinivasan, Y. Vidyalakshmi, R. Gopalakrishnan, Crystal Growth Des. 8 (2008) 2329–2334. [9] R. Mahalakshmi, S.X. Jesuraja, S. Jerome Das, Cryst. Res. Technol. 41 (2006) 780–783. [10] J.J. Rodrigues Jr, L. Misoguti, F.D. Nunes, C.R. Mendonca, S.C. Zilio, Opt. Mater. 22 (2003) 35–240.