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Synthesis, growth, structural, optical, thermal, dielectric and mechanical studies of piperidinium p-nitrophenolate single crystals
Accepted Manuscript Title: Synthesis, growth, structural, optical, thermal, dielectric and mechanical studies of piperidinium p-nitrophenolate single crystals Author: N. Swarna Sowmya S. Sampathkrishnan S. Sudhahar M. Krishna Kumar R. Mohan Kumar PII: DOI: Reference:
S0030-4026(15)01974-9 http://dx.doi.org/doi:10.1016/j.ijleo.2015.12.065 IJLEO 57003
To appear in: Received date: Accepted date:
28-8-2015 11-12-2015
Please cite this article as: N.S. Sowmya, S. Sampathkrishnan, S. Sudhahar, M.K. Kumar, R.M. Kumar, Synthesis, growth, structural, optical, thermal, dielectric and mechanical studies of piperidinium p-nitrophenolate single crystals, Optik - International Journal for Light and Electron Optics (2015), http://dx.doi.org/10.1016/j.ijleo.2015.12.065 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Synthesis, growth, structural, optical, thermal, dielectric and mechanical studies of piperidinium p-nitrophenolate single crystals N. Swarna Sowmyaa, R. Mohan Kumard,*
S.
Sampathkrishnana,
S.
Sudhaharb,
M.
Krishna
Kumarc,
a
cr
ip t
Department of Applied Physics, Sri Venkateswara College of Engineering, Chennai-602117, India b Department of Physics, Sriram Engineering College, Chennai-602024, India c Department of Physics, Kalasalingam University, Krishnankoil-626126, India d Department of Physics, Presidency College, Chennai-600005, India
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Abstract
A novel single crystal of piperidinium p-nitrophenolate (PPNP) was successfully grown by slow
an
evaporation solution growth technique at constant temperature (308 K) with dimension 40 x 5 x 3 mm3. The structure parameters of grown crystal were confirmed from single crystal X-
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ray diffraction studies. Infrared, Raman and NMR spectral analyses were used to elucidate the
d
functional groups present in the compound. UV–Vis spectral studies indicate that the grown
te
crystal is transparent in the entire visible region with a lower cut off wavelength of 505 nm. Photoluminescence spectral study revealed the transition mechanism of ions. Thermal analysis
Ac ce p
was carried out to study the thermal behavior of PPNP crystal. The powder second harmonic generation test confirmed the nonlinear optical behavior of grown crystal. The dielectric loss and dielectric constant as a function of frequency and temperature were measured for the grown crystal. The mechanical strength of the crystal was estimated by Vicker’s hardness test. Keywords: Crystal growth; X-ray diffraction; Optical materials; Dielectrics; NLO material *Corresponding author:
Dr. R. MOHAN KUMAR Department of Physics Presidency College Chennai-600 005, India Tel: +91-9444600670; Fax: +91-44-28510732 Email: [email protected] 1
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1. Introduction In recent years, the second order nonlinear optical (NLO) single crystals with extended nonlinearity and high molecular polarizability have gained considerable interest because of
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their numerous applications in the diverse areas, such as optical communication, optical computing, optical data storage, dynamic holography, harmonic generators, frequency
cr
conversion and optical switching [1,2]. Among different types of NLO materials, organic
us
species have motivated a great deal of studies due to their high nonlinear and electro-optic coefficients, Ultra-fast response, high laser damage threshold, low dielectric constant, ease of
an
fabrication and integration into devices, commercial importance in the fields of laser technology, high speed information and signal processing [3–5]. NLO response of these organic molecular
M
crystals is ultimately governed by the constituents of molecular chromophores. The search of
d
novel molecular NLO crystals capable of manipulating electric fields, especially photonic signals
te
is currently an intense area of research. The focus of recent research on organic molecules possessing large quadratic NLO activities contains electron donor and acceptor groups connected
Ac ce p
through polarizable π-conjugated spacer. The NLO properties of polarizable dipolar compounds are caused by intense, low-energy D(π) → A(π*) intramolecular charge-transfer transitions [6]. Most of the 4-nitrophenolate derivatives show very strong second harmonic generation (SHG) and good crystal characteristics [7,8]. The p-nitrophenol was found to be a best proton acceptor for the metallic hydroxide complexes. Parasuraman et al reported that SHG efficiency of L-arginine 4-nitrophenolate 4-nitrophenol dihydrate crystal is 9.333 times greater than that of KDP [9]. Shanmugam et al reported that the second-order harmonic generation efficiency of the piperidinium
p-hydroxybenzoate
(PDPHB)
is
19
times
than
that
of
KDP
at
1064 nm radiation [10]. In the present report, high quality single crystal of piperidinium 2
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p-nitrophenolate (PPNP) was grown by slow evaporation solution growth technique. The nonlinear optical properties of grown crystal was studied by Kurtz-Perry powder technique using Nd: YAG laser. Also we report for the first time the structure, optical, thermal, mechanical, and
second
harmonic
generation
properties
piperidinium
cr
p-nitrophenolate single crystal.
of
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dielectric
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2. Experimental 2.1 Material synthesis
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Piperidinium p-nitrophenolate was synthesised by the reaction between the piperidine and p-nitrophenol taken in the ratio 1:1. The calculated amount of p-nitrophenol was dissolved
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separately in the methanol. Then, piperidine was added dropwise into the p-nitrophenol solution
d
with continuous stirring. The homogeneous mixture of solution was achieved after continuous
te
stirring for about six hours. The synthesized salt was further purified by successive recrystallization process in methanol, and it was utilized for the crystal growth. Then, the
Ac ce p
solution was allowed for slow evaporation which yielded the spontaneously nucleated crystals. The chemical synthesis scheme of PPNP compound is presented in Fig.1.
2.2 Solubility and Crystal growth
The solubility of PPNP in methanol was determined as a function of temperature in the temperature range 30–55 oC in steps of 5 oC. To determine the equilibrium concentration, the PPNP solution was prepared using methanol solvent. The beaker containing solution was kept at a constant temperature and the solution was continuously stirred using a magnetic stirrer to ensure the homogeneity in temperature and concentration throughout the volume of the solution. 3
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On reaching the saturation, the content of the solution was analyzed gravimetrically, and the same process was repeated for other temperatures. From the solubility data (Fig.2), it was found that the solubility increases linearly with increase of temperature.
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In the present study, PPNP crystals were grown by slow evaporation technique. Recrystallized salt of PPNP was taken as raw material and growth solution was prepared at room temperature
cr
using methanol solvent. The prepared solution was filtered using Whatmann filter papers to
us
remove the suspended impurities. The beaker containing solution was closed with perforated cover and kept in dust free environment. Bright yellowish single crystals of PPNP were collected
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from mother liquor after 30 days. A well developed crystal of size 40 × 6 × 3 mm3 was harvested
M
as shown in Fig.3.
d
2.3 Characterization
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Single crystal X-ray diffraction analysis of PPNP was carried out by using ENRAF NONIUS CAD-4 diffractometer with MoKα (0.71073 Å) radiation. The crystal structure data collection
Ac ce p
was performed at 295 K and crystal structure was solved using SHELXL-97 refinement programme. FTIR and FT-Raman spectra were recorded by using the JASCO FTIR 410 and Bruker RFS 27 (100 mW laser source) spectrometers respectively. Nuclear magnetic resonance spectroscopy was employed to elucidate the molecular structure of title compound using Bruker AVANCE III 500 MHz spectrometer. UV–Vis spectrum was recorded in the range 190–900 nm using Perkin Elmer Lambda35 spectrometer. Photoluminescence excitation spectrum was recorded for the grown crystal by employing RF-5301 spectrometer. Simultaneous TG-DTA thermogram of PPNP was recorded by using SDT Q 600 V8.3 Build 101 instrument. Kurtz-Perry powder technique was employed to ensure the SHG efficiency of PPNP crystal using 1064 nm 4
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fundamental wavelength. The dielectric constant (εr) and dielectric loss (tan δ) of the grown crystal were determined by using HIOCKI97 3532-50 LCR HITESTER instrument. Microhardness measurement was carried out on the grown PPNP crystal using Leitz–Weitzler
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hardness tester fitted with a diamond indenter.
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3. Results and discussion
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3.1 Single crystal X-ray diffraction study
The collected single crystal X-ray diffraction data was solved using WINGX programme and
an
structure was refined by direct method using SHELXL-97. The refined crystal structure with ‘R’ factor 0.035 reveals that, the grown crystal belongs to orthorhombic system with space group of
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P212121. The hall symbol of crystal system is P2ac2ab and the unit cell contains four ion-pairs
d
(Z = 4). The unit cell parameters were found to be a = 6.867 (5) Å, b = 10.121 (4) Å,
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c = 16.497 (6) Å, = = γ = 90 [11]. The refinement parameters and the hydrogen-bonding
Ac ce p
scheme in the structure are presented in Tables 1 & 2 respectively.
3.2 FTIR and FT-Raman studies
FTIR and FT-Raman spectral analyses were carried out to investigate the presence of functional groups and their vibration modes in PPNP sample. KBr pellet technique was used to record infrared spectrum in the range 4000–500 cm-1 as shown in Fig.4. The FT-Raman spectrum of PPNP compound was recorded in the range 4000–500 cm-1 as shown in Fig.5. These vibrational methods can provide valuable information about the force field of the molecules and can help to understand the chemical and physical properties in solid states. In the present study, the band observed at 3143 cm-1 in FTIR and the band observed at 3069 cm-1 in FT-Raman of PPNP are 5
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assigned to N–H stretching modes of vibrations. A strong NH2+ stretching band appeared at 3435 cm-1. The bands observed at 2955 and 2857 cm-1 in the FTIR spectrum are assigned to C-H symmetric stretching and the corresponding bands observed at 2988, 2956 and 2930 cm-1 in the
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Raman spectrum. The C-H in-plane bending vibrations observed at 1110 and 981 cm-1 in FTIR spectrum and 1101 and 983 cm-1 in FT-Raman spectrum respectively. The C-H out-of-plane
cr
bending vibrations observed at 849 and 818 cm-1 in FTIR spectrum and 845 and 818 cm-1 in FT-
us
Raman spectrum respectively. The very strong bands appeared at 1578, 1492 cm-1 in FTIR spectrum and 1582, 1502 cm-1 in FT-Raman spectrum are assigned to C-NO2 stretching
an
vibrations. The C-NO2 in-plane bending modes observed at 642 cm-1 in FTIR and 640 cm-1 in FT-Raman spectra respectively. The frequency observed at 1460 cm-1 is due to aromatic C-C
M
stretching vibration in FTIR spectrum. Similarly the peak observed at 1465 cm-1 is assigned to C-C stretching in FT-Raman spectrum. The bands corresponding to these vibrations found at
te
d
1267 cm-1 in FTIR and 1266 cm-1 in FT-Raman are due to the electron withdrawing ability of the
Ac ce p
substituent. The FTIR and Raman band assignments are presented in Table 3.
3.3 NMR spectral analysis
NMR technique is used to detect the presence of particular nuclei in a compound for a given nuclear species. It is also an important tool for the identification of molecules and examination of their electronic structure. Proton NMR spectrum of PPNP was recorded by dissolving the powder sample in deuterated methanol as shown in Fig.6. It was observed that the NMR spectral peak assignments correspond to the functional groups of the compound. NMR spectrum revealed the presence of hydrogen atoms in the compound and its corresponding peaks. A multiplets noted at δ = 1.65 ppm and δ = 1.74 ppm are attributed to protons in CH group of piperidinium ring. 6
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Since there was no peak for OH in 1H NMR, it confirmed the formation of the title compound. The chemical shifts of two doublets of (C-H) appeared at 6.58 ppm and 8.01 ppm are due to the ring hydrogens of p-nitrophenolate. All the observed chemical shifts of 1H NMR spectrum
ip t
clearly confirm that, all the hydrogen atoms with respective environment are present in
cr
molecular structure of the complex.
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3.4 UV-Visible spectral studies
The optical properties of the grown crystal were studied by recording UV–visible spectrum in the
an
range 200–900 nm (Fig.7). It is very useful to identify the optical absorption or transmission window and cut-off wave-length of the crystal. The absorbance at around 505 nm led to
M
electronic excitation in this region. The lower cut-off wavelength of the crystal was found to be
d
505 nm. The absence of absorption in the region between 505 and 900 nm is an advantage and it
te
is the key requirement for materials having NLO properties. As a result, it can be used as a potential material for SHG in the visible region down to blue and violet light, which makes it
Ac ce p
suitable for laser frequency doubling and related optoelectronic application.
3.5 Photoluminescence
Photoluminescence spectroscopy is a powerful tool for investigating the levels of structural organization at medium range [12]. The high sensitivity of PL technique often highlights the features which UV–Vis absorption measurements rarely define. In particular, PL is a fundamental tool to determine a class of energy levels that are invisible at UV–Vis absorption measurements [13,14]. PL is an optical phenomena caused by diverse electronic transitions occurring in different energy levels (deep or shallow holes) within the band gap [15]. Also the 7
Page 7 of 31
deep holes are origin states for the green, yellow, orange and red PL emissions at room temperature, while the shallow holes are responsible for the violet and blue emissions [16]. The photoluminescence spectrum was recorded for the PPNP crystal at room temperature with
ip t
an excitation wavelength at 445 nm (Fig.8). The emission spectrum displays a strong band from 596 to 625 nm with a maximum at 610 nm (2.03 eV). It confirmed the possibility of using the
us
cr
material for optical applications.
3.6 Thermal analysis
an
Thermogravimetric analysis measures the change in mass of a sample on heating and useful to study the crystallization. Thermo-gravimetry (TG) and differential thermal analysis (DTA) are
M
quite useful, since they provide reliable information on the physico-chemical parameters,
d
characterizing the processes of transformation of solids or participation of solids in the processes
te
of isothermal or non-isothermal heating [17,18]. TG-DTA studies were carried out simultaneously in inert nitrogen atmosphere at a slow heating rate of 10oC/min from room
Ac ce p
temperature to 800oC. The simultaneous TG-DTA measurement was performed on 4.462 mg of PPNP powder sample and the resultant curves are shown in Fig.9. From TG curve, it is clear that there is no weight loss between room temperature and 88oC and hence it shows that the PPNP is stable up to 88oC. In the DTA curve, two prominent endothermic peaks were observed for the PPNP compound. First endothermic peak was observed at 104.3oC and second endothermic peak was noted at 246.6oC. TG curve showed a single stage complete weight loss between 88.1oC and 270oC (96.2%) which illustrates the simultaneous melting and decomposition of the piperidinium and phenolate moiety and also the removal of almost all fragments as gaseous products.
8
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3.7 SHG test The preliminary study of the powder SHG conversion efficiency was carried out by using a modified setup of Kurtz and Perry [19]. A Q-switched Nd:YAG laser beam of wavelength
ip t
1064 nm, with an input power of 1.9 mJ, and pulse width of 8 ns with a repetition rate of 10 Hz were used. The powdered crystalline sample with uniform particle size of 125–150 μm, was
cr
packed in a microcapillary of uniform bore and exposed to laser radiation. The generation of
us
second harmonics was confirmed by emission of green light. The SHG output signal voltages were found to be 276 mV, 87 mV and 156 mV for PPNP, KDP and Urea respectively. The SHG
an
conversion efficiency of PPNP was found to be about 3.17 times that of KDP reference crystal.
M
3.8 Dielectric Studies
d
The knowledge regarding the electric field distribution inside the material and the computation
te
of electro-optic coefficients is essential to realize the suitability of NLO materials for device applications [20]. The dielectric characteristics of the material are important to know the
Ac ce p
transport phenomena and the lattice dynamics in the crystal. It also gives the information about the nature of atoms, ions, bonding and their polarization mechanism in the material. The dielectric measurement was carried out on the polished PPNP sample with dimension of 6 x 4 x 1 mm3 in the frequency range 50 Hz – 5 MHz. The crystal faces were coated with silver paste in order to ensure good electrical contact between the crystal sample and sample was kept between the copper electrodes. The capacitance of the sample was measured by varying the frequency at different temperatures (313 K - 343 K). The dielectric constant (εr) and dielectric loss (tan δ) were calculated using the relations,
9
Page 9 of 31
εr = Ct/ ε0A and tan δ = εrD
ip t
where, ε0 is the permittivity of free space, t is the thickness of the sample, D is the dissipation factor and A is the area of cross-section of the sample. Figure 10 shows the plot of dielectric
cr
constant (εr) as a function of frequency. It was observed that the dielectric constant decreases
us
with increase in frequency for all temperatures. The large values of dielectric constant at low frequency enumerates the contribution from all four sources of polarizations namely electronic,
an
ionic, atomic, space charge, etc., developed in the material due to the electric field variations. The large dielectric constant at low frequency observed for PPNP crystal is due to the presence
M
of space charge polarization arising at the grain boundary interfaces [21]. The low values of
d
dielectric constant at higher frequencies revealed the good optical quality of the grown crystal
te
with less defects, which is the desirable property of the materials to be used for various optical and communication devices [22]. The characteristics of low dielectric loss in the high frequency
Ac ce p
region for a given sample suggests that the sample possesses good optical quality with lesser defects [22] and this parameter is of vital importance for nonlinear optical applications.
3.9 Mechanical studies
Mechanical properties of solids are tightly connected with their structure and other physical and chemical properties and play an important role in practical applications of materials. Among the various experimental tools for the determination of mechanical properties, hardness testing is frequently used to study the mechanical properties of solids. This technique has also become 10
Page 10 of 31
increasingly important for industries involved with micromachines, microelectronics and magnetic recording [23]. In order to evaluate the Vicker’s hardness number, PPNP crystal was subjected to static indentation test at room temperature. The microhardness studies were carried
ip t
out for PPNP crystal using Leitz microhardness tester fitted with a diamond pyramidal indenter attached to an incident light microscope. The indentations were made for different loads (10, 25,
cr
50 and 100 g) on the polished (100) face of PPNP with a constant indentation time of 10 s.
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The Vicker’s hardness number (Hv) was calculated using the relation, Hv = 1.8544 P/d2 kg/mm2
an
where P is the indentation load in kg and d is the diagonal length of the impression in mm. A graph plotted between hardness number (Hv) and applied load (P) is shown in Fig.12.
M
The reason for getting the lower value of hardness at lower loads may be due to the surface
d
reaction by surface adsorbed moisture, which may reduce the strength of surface layers.
te
There was an increase in the hardness with load without saturation, which can be attributed to the work hardening of the surface layers. Beyond the load 100 g, significant cracks were occurred,
Ac ce p
which may be due to the release of internal stress generated locally by indentation [24].
4. Conclusion
Optical quality bulk single crystal of PPNP was grown by slow evaporation solution growth technique. Single crystal and powder diffraction X-ray studies confirmed the unit cell parameters and found that PPNP crystal belongs to orthorhombic crystal structure with space group P212121. The functional groups of PPNP compound were confirmed by infrared, Raman and nuclear magnetic resonance spectral studies. Optical transmission studies show that the crystal is transparent in the visible region with the lower cut-off wavelength at 505 nm and hence it is 11
Page 11 of 31
suitable for frequency conversion applications. Photoluminescence spectral study revealed the possibility of material’s use in the derived optical range. The thermal studies revealed the thermal stability of the grown crystal. The SHG efficiency of PPNP was found to be 3.17 times
ip t
that of KDP reference crystal. The dielectric constant and dielectric loss studies of PPNP established the normal dielectric behavior. Mechanical strength of the material was evaluated
Ac ce p
te
d
M
an
us
cr
by using Vicker’s microhardness test.
12
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References [1] H.S. Nalwa, S. Miyata, “Nonlinear Optics of Organic Molecules and Polymer”, CRC Press, New York, 1997, pp.813–840.
ip t
[2] P.N. Prasad, D.J. Williams, “Introduction to Nonlinear Optical Effects in Organic Molecules and Polymer”, Wiley, New York, 1991.
cr
[3] A.V. Alex, J. Philip, S. Brahadeeswaran, H.L. Bhat, Phys. Rev. B62 (2000) 2973–2975.
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[4] X. Zhang, M. Li, Z. Shi, Z. Cui, Mater. Lett. 65 (2011) 1404–1406.
[5] Y. Takahashi, H. Adachi, T. Taniuchi, M. Takagi, Y. Hosokawa, S. Onzuka,
an
S. Brahadeeswaran, M. Yoshimura, Y. Mori, H. Masuhara, T. Sasaki, H. Nakanishi, J. Photochem. Photobiol. A: Chem. 183 (2006) 247–252.
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[6] T.M. Inerbaev, F.L. Gu, H. Mizuseki, Y. Kawazoe, Int. J. Quantum Chem. 111 (2011)
d
780–787.
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[7] R. Omegala Priakumari, S. Grace Sahaya Sheba, M. Gunasekaran, Optik, 125 (2014) 4633-4636.
Ac ce p
[8] P. Muthuraja, M. Sethuram, M. Sethu Raman, M. Dhandapani, G. Amirthaganesan, J. Mol. Struct. 1053 (2013) 5–14.
[9] K. Parasuraman, K. Sakthi Murugesan, R. Samuel Selvaraj, S. Jerome Das, R. Uthrakumar, B. Milton Boaz, Optik, 125 (2014) 3534–3539. [10] G. Shanmugam, K. Thirupugalmani, V. Kannan, S. Brahadeeswaran, Spectrochim. Acta, Part A, 106 (2013) 175–184. [11]
N.
Swarna
Sowmya,
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Sampathkrishnan,
S.
Sudhahar,
G.
Chakkaravarthi,
R. Mohan Kumar, Acta Cryst. E70 (2014) 559–561.
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[12] F. Montoncello, M.C. Carotta, B. Cavicchi, M. Ferroni, A. Giberti, V. Guidi, C. Malagu, G. Martinelli, F. Meinardi, J. Appl. Phys. 94 (2003) 1501-1505. [13] V.M. Longo, L.S. Cavalcante, A.T. de Figueiredo, L.P.S. Santos, E. Longo, J.A. Varela,
ip t
J.R. Sambrano, C.A. Paskocimas, F.S. De Vicente, Appl. Phys. Lett. 90 (2007) 091906(1)- 091906(3).
cr
[14] S.K. Rout, L.S. Cavalcante, J.C. Sczancoski, T. Badapanda, S. Panigrahi, M.S. Li,
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E. Longo, Physica, B404 (2009) 3341-3347.
[15] V.M. Longo, L.S. Cavalcante, R. Erlo, V.R. Mastelaro, A.T. de Figueiredo, J.R. Sambrano,
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S. de Lazaro, A.Z. Freitas, L. Gomes, N.D. Vieira, J.A. Varela, E. Longo, Acta Mater. 56 (2008) 2191-2202.
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[16] L.S. Cavalcante, J.C. Sczancoski, F.S. De Vicente, M.T. Frabbro, M. Siu Li, J.A. Varela,
d
E. Longo, J. Sole Gel Sci. Technol. 49 (2009) 35-46.
253–262.
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[17] L. Vlaev, N. Nedelchev, K. Gyurova, M. Zagorcheva, J. Anal. Appl. Pyrol. 81 (2008)
Ac ce p
[18] V. Georgieva, D. Zvezdova, L. Vlaev, Chem. Cent. J. 6 (2012) 81–90. [19] S.K. Kurtz, T.T. Perry, J. Appl. Phys. 39 (1968) 3798-3813. [20] P. Gunter, Electro-optical properties of KNbO3. Opt. Commun. 11 (1974) 285–290. [21] S. Ishwar Bhat, P. Mohan Rao, A.P. Ganesh Bhat, D.K. Avasthi, Surf. Coat. Technol. 158 (2002) 725–728.
[22] C. Balarew, R. Duhlew, J. Solid State Chem. 55 (1984) 1–6. [23] T. Balakrishnan, K. Ramamurthi, Mater. Lett. 62 (2008) 65-68. [24] K. Sangwal, B. Surowska, P. Blaziak, Mater. Chem. Phys. 77 (2002) 511–520.
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Figure captions
Fig.1 Synthesis scheme for PPNP compound
ip t
Fig.2 Solubility curve of PPNP in methanol solvent Fig.3 Photograph of as-grown PPNP single crystal
cr
Fig.4 FT-IR spectrum of PPNP
Fig.6 Proton NMR spectrum of PPNP
an
Fig.7 UV-Visible transmission spectrum of PPNP crystal
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Fig.5 FT-Raman spectrum of PPNP
Fig.9 TG-DTA thermogram of PPNP
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Fig.8 Photoluminescence spectrum of PPNP crystal
Fig.10 Plot of dielectric constant vs. log frequency of PPNP crystal
d
Fig.11 Plot of dielectric loss vs. log frequency of PPNP crystal
Ac ce p
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Fig.12 Plot of Hardness number (Hv) vs. load (P) of PPNP crystal
15
Page 15 of 31
Empirical Formula
C5H12N+.C6H4NO3-
Formula Weight
224.26 (g/mol)
Crystal System
Orthorhombic
Space group
P212121
Unit cell dimensions
a = 6.867 (5) Å
an
b = 10.121 (4) Å
cr
SHELXL
us
Identification code
ip t
Table 1 Crystal data and structure refinement for PPNP
c = 16.497 (6) Å
M
α = β = γ = 90
1146.6 (10) Å3
Z, D (calc) [g/cm3]
4, 1.299
Ac ce p
te
d
Volume (V)
16
Page 16 of 31
ip t cr us M
an 0.90
H···A
1.92
Ac ce p
N2—H2A···O1i
D—H
te
D—H···A
d
Table 2 Hydrogen-bond geometry (Å, o).
D···A
D—H···A
2.788(2)
161
N2—H2B···O1ii
0.90
1.80
2.6985(15)
175
C6—H6··· Cg1iii
0.93
2.75
3.428(3)
130
Symmetry codes:
(i) –x, y–1/2, –z+1/2
(ii) –x+1/2, –y+1, z+1/2 (iii) x+1/2, –y+1/2, –z.
17
Page 17 of 31
ip t cr us an M d te Ac ce p Table 3 Molecular vibrational assignments of PPNP compound
18
Page 18 of 31
Wave number (cm-1)
Assignments
FT-Raman
NH2 stretching vibration
3435
–
N-H stretching vibration
3143
ip t
FT-IR
NO2 stretching vibration
1578 1460
C-O stretching vibration
1267
2956
1582
C-N asymmetric stretching vibration
1465
1266
1163
1110
d
C-H in-plane bending vibration
M
an
C-C stretching vibration
cr
2955
us
C-H symmetric stretching vibration
3069
1163 1101
1034
1033
C-H out-of-plane bending vibration
849
845
NO2 in-plane bending vibration
642
640
Ac ce p
te
C-N symmetric stretching vibration
NO2 wagging
555
554
19
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ip t cr us O2 N
an
+
OH
NH
.
O2N
O
M
NH2
Ac ce p
te
d
Fig.1 Synthesis scheme for PPNP compound
20
Page 20 of 31
ip t cr us an M d te Ac ce p
Fig.2 Solubility curve of PPNP in methanol solvent
21
Page 21 of 31
ip t cr us an M d te Ac ce p
Fig.3 Photograph of as-grown PPNP single crystal
22
Page 22 of 31
ip t cr us an M d te Ac ce p
Fig.4 FT-IR spectrum of PPNP
23
Page 23 of 31
ip t cr us an M d te Ac ce p
Fig.5 FT-Raman spectrum of PPNP
24
Page 24 of 31
ip t cr us an M d te Ac ce p
Fig.6 Proton NMR spectrum of PPNP
25
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ip t cr us an M d te Ac ce p
Fig.7 UV-Visible transmission spectrum of PPNP crystal
26
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ip t cr us an M d te Ac ce p Fig.8 Photoluminescence spectrum of PPNP crystal
27
Page 27 of 31
ip t cr us an M d te Ac ce p Fig.9 TG-DTA thermogram of PPNP 28
Page 28 of 31
ip t cr us an M d te Ac ce p Fig.10 Plot of dielectric constant vs. log frequency of PPNP crystal 29
Page 29 of 31
30
Page 30 of 31
d
te
Ac ce p us
an
M
cr
ip t
Ac ce p
te
d
M
an
us
cr
ip t
Fig.11 Plot of dielectric loss vs. log frequency of PPNP crystal
Fig.12 Plot of Hardness number (Hv) vs. load (P) of PPNP crystal 31
Page 31 of 31
S0030-4026(15)01974-9 http://dx.doi.org/doi:10.1016/j.ijleo.2015.12.065 IJLEO 57003
To appear in: Received date: Accepted date:
28-8-2015 11-12-2015
Please cite this article as: N.S. Sowmya, S. Sampathkrishnan, S. Sudhahar, M.K. Kumar, R.M. Kumar, Synthesis, growth, structural, optical, thermal, dielectric and mechanical studies of piperidinium p-nitrophenolate single crystals, Optik - International Journal for Light and Electron Optics (2015), http://dx.doi.org/10.1016/j.ijleo.2015.12.065 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Synthesis, growth, structural, optical, thermal, dielectric and mechanical studies of piperidinium p-nitrophenolate single crystals N. Swarna Sowmyaa, R. Mohan Kumard,*
S.
Sampathkrishnana,
S.
Sudhaharb,
M.
Krishna
Kumarc,
a
cr
ip t
Department of Applied Physics, Sri Venkateswara College of Engineering, Chennai-602117, India b Department of Physics, Sriram Engineering College, Chennai-602024, India c Department of Physics, Kalasalingam University, Krishnankoil-626126, India d Department of Physics, Presidency College, Chennai-600005, India
us
Abstract
A novel single crystal of piperidinium p-nitrophenolate (PPNP) was successfully grown by slow
an
evaporation solution growth technique at constant temperature (308 K) with dimension 40 x 5 x 3 mm3. The structure parameters of grown crystal were confirmed from single crystal X-
M
ray diffraction studies. Infrared, Raman and NMR spectral analyses were used to elucidate the
d
functional groups present in the compound. UV–Vis spectral studies indicate that the grown
te
crystal is transparent in the entire visible region with a lower cut off wavelength of 505 nm. Photoluminescence spectral study revealed the transition mechanism of ions. Thermal analysis
Ac ce p
was carried out to study the thermal behavior of PPNP crystal. The powder second harmonic generation test confirmed the nonlinear optical behavior of grown crystal. The dielectric loss and dielectric constant as a function of frequency and temperature were measured for the grown crystal. The mechanical strength of the crystal was estimated by Vicker’s hardness test. Keywords: Crystal growth; X-ray diffraction; Optical materials; Dielectrics; NLO material *Corresponding author:
Dr. R. MOHAN KUMAR Department of Physics Presidency College Chennai-600 005, India Tel: +91-9444600670; Fax: +91-44-28510732 Email: [email protected] 1
Page 1 of 31
1. Introduction In recent years, the second order nonlinear optical (NLO) single crystals with extended nonlinearity and high molecular polarizability have gained considerable interest because of
ip t
their numerous applications in the diverse areas, such as optical communication, optical computing, optical data storage, dynamic holography, harmonic generators, frequency
cr
conversion and optical switching [1,2]. Among different types of NLO materials, organic
us
species have motivated a great deal of studies due to their high nonlinear and electro-optic coefficients, Ultra-fast response, high laser damage threshold, low dielectric constant, ease of
an
fabrication and integration into devices, commercial importance in the fields of laser technology, high speed information and signal processing [3–5]. NLO response of these organic molecular
M
crystals is ultimately governed by the constituents of molecular chromophores. The search of
d
novel molecular NLO crystals capable of manipulating electric fields, especially photonic signals
te
is currently an intense area of research. The focus of recent research on organic molecules possessing large quadratic NLO activities contains electron donor and acceptor groups connected
Ac ce p
through polarizable π-conjugated spacer. The NLO properties of polarizable dipolar compounds are caused by intense, low-energy D(π) → A(π*) intramolecular charge-transfer transitions [6]. Most of the 4-nitrophenolate derivatives show very strong second harmonic generation (SHG) and good crystal characteristics [7,8]. The p-nitrophenol was found to be a best proton acceptor for the metallic hydroxide complexes. Parasuraman et al reported that SHG efficiency of L-arginine 4-nitrophenolate 4-nitrophenol dihydrate crystal is 9.333 times greater than that of KDP [9]. Shanmugam et al reported that the second-order harmonic generation efficiency of the piperidinium
p-hydroxybenzoate
(PDPHB)
is
19
times
than
that
of
KDP
at
1064 nm radiation [10]. In the present report, high quality single crystal of piperidinium 2
Page 2 of 31
p-nitrophenolate (PPNP) was grown by slow evaporation solution growth technique. The nonlinear optical properties of grown crystal was studied by Kurtz-Perry powder technique using Nd: YAG laser. Also we report for the first time the structure, optical, thermal, mechanical, and
second
harmonic
generation
properties
piperidinium
cr
p-nitrophenolate single crystal.
of
ip t
dielectric
us
2. Experimental 2.1 Material synthesis
an
Piperidinium p-nitrophenolate was synthesised by the reaction between the piperidine and p-nitrophenol taken in the ratio 1:1. The calculated amount of p-nitrophenol was dissolved
M
separately in the methanol. Then, piperidine was added dropwise into the p-nitrophenol solution
d
with continuous stirring. The homogeneous mixture of solution was achieved after continuous
te
stirring for about six hours. The synthesized salt was further purified by successive recrystallization process in methanol, and it was utilized for the crystal growth. Then, the
Ac ce p
solution was allowed for slow evaporation which yielded the spontaneously nucleated crystals. The chemical synthesis scheme of PPNP compound is presented in Fig.1.
2.2 Solubility and Crystal growth
The solubility of PPNP in methanol was determined as a function of temperature in the temperature range 30–55 oC in steps of 5 oC. To determine the equilibrium concentration, the PPNP solution was prepared using methanol solvent. The beaker containing solution was kept at a constant temperature and the solution was continuously stirred using a magnetic stirrer to ensure the homogeneity in temperature and concentration throughout the volume of the solution. 3
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On reaching the saturation, the content of the solution was analyzed gravimetrically, and the same process was repeated for other temperatures. From the solubility data (Fig.2), it was found that the solubility increases linearly with increase of temperature.
ip t
In the present study, PPNP crystals were grown by slow evaporation technique. Recrystallized salt of PPNP was taken as raw material and growth solution was prepared at room temperature
cr
using methanol solvent. The prepared solution was filtered using Whatmann filter papers to
us
remove the suspended impurities. The beaker containing solution was closed with perforated cover and kept in dust free environment. Bright yellowish single crystals of PPNP were collected
an
from mother liquor after 30 days. A well developed crystal of size 40 × 6 × 3 mm3 was harvested
M
as shown in Fig.3.
d
2.3 Characterization
te
Single crystal X-ray diffraction analysis of PPNP was carried out by using ENRAF NONIUS CAD-4 diffractometer with MoKα (0.71073 Å) radiation. The crystal structure data collection
Ac ce p
was performed at 295 K and crystal structure was solved using SHELXL-97 refinement programme. FTIR and FT-Raman spectra were recorded by using the JASCO FTIR 410 and Bruker RFS 27 (100 mW laser source) spectrometers respectively. Nuclear magnetic resonance spectroscopy was employed to elucidate the molecular structure of title compound using Bruker AVANCE III 500 MHz spectrometer. UV–Vis spectrum was recorded in the range 190–900 nm using Perkin Elmer Lambda35 spectrometer. Photoluminescence excitation spectrum was recorded for the grown crystal by employing RF-5301 spectrometer. Simultaneous TG-DTA thermogram of PPNP was recorded by using SDT Q 600 V8.3 Build 101 instrument. Kurtz-Perry powder technique was employed to ensure the SHG efficiency of PPNP crystal using 1064 nm 4
Page 4 of 31
fundamental wavelength. The dielectric constant (εr) and dielectric loss (tan δ) of the grown crystal were determined by using HIOCKI97 3532-50 LCR HITESTER instrument. Microhardness measurement was carried out on the grown PPNP crystal using Leitz–Weitzler
ip t
hardness tester fitted with a diamond indenter.
cr
3. Results and discussion
us
3.1 Single crystal X-ray diffraction study
The collected single crystal X-ray diffraction data was solved using WINGX programme and
an
structure was refined by direct method using SHELXL-97. The refined crystal structure with ‘R’ factor 0.035 reveals that, the grown crystal belongs to orthorhombic system with space group of
M
P212121. The hall symbol of crystal system is P2ac2ab and the unit cell contains four ion-pairs
d
(Z = 4). The unit cell parameters were found to be a = 6.867 (5) Å, b = 10.121 (4) Å,
te
c = 16.497 (6) Å, = = γ = 90 [11]. The refinement parameters and the hydrogen-bonding
Ac ce p
scheme in the structure are presented in Tables 1 & 2 respectively.
3.2 FTIR and FT-Raman studies
FTIR and FT-Raman spectral analyses were carried out to investigate the presence of functional groups and their vibration modes in PPNP sample. KBr pellet technique was used to record infrared spectrum in the range 4000–500 cm-1 as shown in Fig.4. The FT-Raman spectrum of PPNP compound was recorded in the range 4000–500 cm-1 as shown in Fig.5. These vibrational methods can provide valuable information about the force field of the molecules and can help to understand the chemical and physical properties in solid states. In the present study, the band observed at 3143 cm-1 in FTIR and the band observed at 3069 cm-1 in FT-Raman of PPNP are 5
Page 5 of 31
assigned to N–H stretching modes of vibrations. A strong NH2+ stretching band appeared at 3435 cm-1. The bands observed at 2955 and 2857 cm-1 in the FTIR spectrum are assigned to C-H symmetric stretching and the corresponding bands observed at 2988, 2956 and 2930 cm-1 in the
ip t
Raman spectrum. The C-H in-plane bending vibrations observed at 1110 and 981 cm-1 in FTIR spectrum and 1101 and 983 cm-1 in FT-Raman spectrum respectively. The C-H out-of-plane
cr
bending vibrations observed at 849 and 818 cm-1 in FTIR spectrum and 845 and 818 cm-1 in FT-
us
Raman spectrum respectively. The very strong bands appeared at 1578, 1492 cm-1 in FTIR spectrum and 1582, 1502 cm-1 in FT-Raman spectrum are assigned to C-NO2 stretching
an
vibrations. The C-NO2 in-plane bending modes observed at 642 cm-1 in FTIR and 640 cm-1 in FT-Raman spectra respectively. The frequency observed at 1460 cm-1 is due to aromatic C-C
M
stretching vibration in FTIR spectrum. Similarly the peak observed at 1465 cm-1 is assigned to C-C stretching in FT-Raman spectrum. The bands corresponding to these vibrations found at
te
d
1267 cm-1 in FTIR and 1266 cm-1 in FT-Raman are due to the electron withdrawing ability of the
Ac ce p
substituent. The FTIR and Raman band assignments are presented in Table 3.
3.3 NMR spectral analysis
NMR technique is used to detect the presence of particular nuclei in a compound for a given nuclear species. It is also an important tool for the identification of molecules and examination of their electronic structure. Proton NMR spectrum of PPNP was recorded by dissolving the powder sample in deuterated methanol as shown in Fig.6. It was observed that the NMR spectral peak assignments correspond to the functional groups of the compound. NMR spectrum revealed the presence of hydrogen atoms in the compound and its corresponding peaks. A multiplets noted at δ = 1.65 ppm and δ = 1.74 ppm are attributed to protons in CH group of piperidinium ring. 6
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Since there was no peak for OH in 1H NMR, it confirmed the formation of the title compound. The chemical shifts of two doublets of (C-H) appeared at 6.58 ppm and 8.01 ppm are due to the ring hydrogens of p-nitrophenolate. All the observed chemical shifts of 1H NMR spectrum
ip t
clearly confirm that, all the hydrogen atoms with respective environment are present in
cr
molecular structure of the complex.
us
3.4 UV-Visible spectral studies
The optical properties of the grown crystal were studied by recording UV–visible spectrum in the
an
range 200–900 nm (Fig.7). It is very useful to identify the optical absorption or transmission window and cut-off wave-length of the crystal. The absorbance at around 505 nm led to
M
electronic excitation in this region. The lower cut-off wavelength of the crystal was found to be
d
505 nm. The absence of absorption in the region between 505 and 900 nm is an advantage and it
te
is the key requirement for materials having NLO properties. As a result, it can be used as a potential material for SHG in the visible region down to blue and violet light, which makes it
Ac ce p
suitable for laser frequency doubling and related optoelectronic application.
3.5 Photoluminescence
Photoluminescence spectroscopy is a powerful tool for investigating the levels of structural organization at medium range [12]. The high sensitivity of PL technique often highlights the features which UV–Vis absorption measurements rarely define. In particular, PL is a fundamental tool to determine a class of energy levels that are invisible at UV–Vis absorption measurements [13,14]. PL is an optical phenomena caused by diverse electronic transitions occurring in different energy levels (deep or shallow holes) within the band gap [15]. Also the 7
Page 7 of 31
deep holes are origin states for the green, yellow, orange and red PL emissions at room temperature, while the shallow holes are responsible for the violet and blue emissions [16]. The photoluminescence spectrum was recorded for the PPNP crystal at room temperature with
ip t
an excitation wavelength at 445 nm (Fig.8). The emission spectrum displays a strong band from 596 to 625 nm with a maximum at 610 nm (2.03 eV). It confirmed the possibility of using the
us
cr
material for optical applications.
3.6 Thermal analysis
an
Thermogravimetric analysis measures the change in mass of a sample on heating and useful to study the crystallization. Thermo-gravimetry (TG) and differential thermal analysis (DTA) are
M
quite useful, since they provide reliable information on the physico-chemical parameters,
d
characterizing the processes of transformation of solids or participation of solids in the processes
te
of isothermal or non-isothermal heating [17,18]. TG-DTA studies were carried out simultaneously in inert nitrogen atmosphere at a slow heating rate of 10oC/min from room
Ac ce p
temperature to 800oC. The simultaneous TG-DTA measurement was performed on 4.462 mg of PPNP powder sample and the resultant curves are shown in Fig.9. From TG curve, it is clear that there is no weight loss between room temperature and 88oC and hence it shows that the PPNP is stable up to 88oC. In the DTA curve, two prominent endothermic peaks were observed for the PPNP compound. First endothermic peak was observed at 104.3oC and second endothermic peak was noted at 246.6oC. TG curve showed a single stage complete weight loss between 88.1oC and 270oC (96.2%) which illustrates the simultaneous melting and decomposition of the piperidinium and phenolate moiety and also the removal of almost all fragments as gaseous products.
8
Page 8 of 31
3.7 SHG test The preliminary study of the powder SHG conversion efficiency was carried out by using a modified setup of Kurtz and Perry [19]. A Q-switched Nd:YAG laser beam of wavelength
ip t
1064 nm, with an input power of 1.9 mJ, and pulse width of 8 ns with a repetition rate of 10 Hz were used. The powdered crystalline sample with uniform particle size of 125–150 μm, was
cr
packed in a microcapillary of uniform bore and exposed to laser radiation. The generation of
us
second harmonics was confirmed by emission of green light. The SHG output signal voltages were found to be 276 mV, 87 mV and 156 mV for PPNP, KDP and Urea respectively. The SHG
an
conversion efficiency of PPNP was found to be about 3.17 times that of KDP reference crystal.
M
3.8 Dielectric Studies
d
The knowledge regarding the electric field distribution inside the material and the computation
te
of electro-optic coefficients is essential to realize the suitability of NLO materials for device applications [20]. The dielectric characteristics of the material are important to know the
Ac ce p
transport phenomena and the lattice dynamics in the crystal. It also gives the information about the nature of atoms, ions, bonding and their polarization mechanism in the material. The dielectric measurement was carried out on the polished PPNP sample with dimension of 6 x 4 x 1 mm3 in the frequency range 50 Hz – 5 MHz. The crystal faces were coated with silver paste in order to ensure good electrical contact between the crystal sample and sample was kept between the copper electrodes. The capacitance of the sample was measured by varying the frequency at different temperatures (313 K - 343 K). The dielectric constant (εr) and dielectric loss (tan δ) were calculated using the relations,
9
Page 9 of 31
εr = Ct/ ε0A and tan δ = εrD
ip t
where, ε0 is the permittivity of free space, t is the thickness of the sample, D is the dissipation factor and A is the area of cross-section of the sample. Figure 10 shows the plot of dielectric
cr
constant (εr) as a function of frequency. It was observed that the dielectric constant decreases
us
with increase in frequency for all temperatures. The large values of dielectric constant at low frequency enumerates the contribution from all four sources of polarizations namely electronic,
an
ionic, atomic, space charge, etc., developed in the material due to the electric field variations. The large dielectric constant at low frequency observed for PPNP crystal is due to the presence
M
of space charge polarization arising at the grain boundary interfaces [21]. The low values of
d
dielectric constant at higher frequencies revealed the good optical quality of the grown crystal
te
with less defects, which is the desirable property of the materials to be used for various optical and communication devices [22]. The characteristics of low dielectric loss in the high frequency
Ac ce p
region for a given sample suggests that the sample possesses good optical quality with lesser defects [22] and this parameter is of vital importance for nonlinear optical applications.
3.9 Mechanical studies
Mechanical properties of solids are tightly connected with their structure and other physical and chemical properties and play an important role in practical applications of materials. Among the various experimental tools for the determination of mechanical properties, hardness testing is frequently used to study the mechanical properties of solids. This technique has also become 10
Page 10 of 31
increasingly important for industries involved with micromachines, microelectronics and magnetic recording [23]. In order to evaluate the Vicker’s hardness number, PPNP crystal was subjected to static indentation test at room temperature. The microhardness studies were carried
ip t
out for PPNP crystal using Leitz microhardness tester fitted with a diamond pyramidal indenter attached to an incident light microscope. The indentations were made for different loads (10, 25,
cr
50 and 100 g) on the polished (100) face of PPNP with a constant indentation time of 10 s.
us
The Vicker’s hardness number (Hv) was calculated using the relation, Hv = 1.8544 P/d2 kg/mm2
an
where P is the indentation load in kg and d is the diagonal length of the impression in mm. A graph plotted between hardness number (Hv) and applied load (P) is shown in Fig.12.
M
The reason for getting the lower value of hardness at lower loads may be due to the surface
d
reaction by surface adsorbed moisture, which may reduce the strength of surface layers.
te
There was an increase in the hardness with load without saturation, which can be attributed to the work hardening of the surface layers. Beyond the load 100 g, significant cracks were occurred,
Ac ce p
which may be due to the release of internal stress generated locally by indentation [24].
4. Conclusion
Optical quality bulk single crystal of PPNP was grown by slow evaporation solution growth technique. Single crystal and powder diffraction X-ray studies confirmed the unit cell parameters and found that PPNP crystal belongs to orthorhombic crystal structure with space group P212121. The functional groups of PPNP compound were confirmed by infrared, Raman and nuclear magnetic resonance spectral studies. Optical transmission studies show that the crystal is transparent in the visible region with the lower cut-off wavelength at 505 nm and hence it is 11
Page 11 of 31
suitable for frequency conversion applications. Photoluminescence spectral study revealed the possibility of material’s use in the derived optical range. The thermal studies revealed the thermal stability of the grown crystal. The SHG efficiency of PPNP was found to be 3.17 times
ip t
that of KDP reference crystal. The dielectric constant and dielectric loss studies of PPNP established the normal dielectric behavior. Mechanical strength of the material was evaluated
Ac ce p
te
d
M
an
us
cr
by using Vicker’s microhardness test.
12
Page 12 of 31
References [1] H.S. Nalwa, S. Miyata, “Nonlinear Optics of Organic Molecules and Polymer”, CRC Press, New York, 1997, pp.813–840.
ip t
[2] P.N. Prasad, D.J. Williams, “Introduction to Nonlinear Optical Effects in Organic Molecules and Polymer”, Wiley, New York, 1991.
cr
[3] A.V. Alex, J. Philip, S. Brahadeeswaran, H.L. Bhat, Phys. Rev. B62 (2000) 2973–2975.
us
[4] X. Zhang, M. Li, Z. Shi, Z. Cui, Mater. Lett. 65 (2011) 1404–1406.
[5] Y. Takahashi, H. Adachi, T. Taniuchi, M. Takagi, Y. Hosokawa, S. Onzuka,
an
S. Brahadeeswaran, M. Yoshimura, Y. Mori, H. Masuhara, T. Sasaki, H. Nakanishi, J. Photochem. Photobiol. A: Chem. 183 (2006) 247–252.
M
[6] T.M. Inerbaev, F.L. Gu, H. Mizuseki, Y. Kawazoe, Int. J. Quantum Chem. 111 (2011)
d
780–787.
te
[7] R. Omegala Priakumari, S. Grace Sahaya Sheba, M. Gunasekaran, Optik, 125 (2014) 4633-4636.
Ac ce p
[8] P. Muthuraja, M. Sethuram, M. Sethu Raman, M. Dhandapani, G. Amirthaganesan, J. Mol. Struct. 1053 (2013) 5–14.
[9] K. Parasuraman, K. Sakthi Murugesan, R. Samuel Selvaraj, S. Jerome Das, R. Uthrakumar, B. Milton Boaz, Optik, 125 (2014) 3534–3539. [10] G. Shanmugam, K. Thirupugalmani, V. Kannan, S. Brahadeeswaran, Spectrochim. Acta, Part A, 106 (2013) 175–184. [11]
N.
Swarna
Sowmya,
S.
Sampathkrishnan,
S.
Sudhahar,
G.
Chakkaravarthi,
R. Mohan Kumar, Acta Cryst. E70 (2014) 559–561.
13
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[12] F. Montoncello, M.C. Carotta, B. Cavicchi, M. Ferroni, A. Giberti, V. Guidi, C. Malagu, G. Martinelli, F. Meinardi, J. Appl. Phys. 94 (2003) 1501-1505. [13] V.M. Longo, L.S. Cavalcante, A.T. de Figueiredo, L.P.S. Santos, E. Longo, J.A. Varela,
ip t
J.R. Sambrano, C.A. Paskocimas, F.S. De Vicente, Appl. Phys. Lett. 90 (2007) 091906(1)- 091906(3).
cr
[14] S.K. Rout, L.S. Cavalcante, J.C. Sczancoski, T. Badapanda, S. Panigrahi, M.S. Li,
us
E. Longo, Physica, B404 (2009) 3341-3347.
[15] V.M. Longo, L.S. Cavalcante, R. Erlo, V.R. Mastelaro, A.T. de Figueiredo, J.R. Sambrano,
an
S. de Lazaro, A.Z. Freitas, L. Gomes, N.D. Vieira, J.A. Varela, E. Longo, Acta Mater. 56 (2008) 2191-2202.
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[16] L.S. Cavalcante, J.C. Sczancoski, F.S. De Vicente, M.T. Frabbro, M. Siu Li, J.A. Varela,
d
E. Longo, J. Sole Gel Sci. Technol. 49 (2009) 35-46.
253–262.
te
[17] L. Vlaev, N. Nedelchev, K. Gyurova, M. Zagorcheva, J. Anal. Appl. Pyrol. 81 (2008)
Ac ce p
[18] V. Georgieva, D. Zvezdova, L. Vlaev, Chem. Cent. J. 6 (2012) 81–90. [19] S.K. Kurtz, T.T. Perry, J. Appl. Phys. 39 (1968) 3798-3813. [20] P. Gunter, Electro-optical properties of KNbO3. Opt. Commun. 11 (1974) 285–290. [21] S. Ishwar Bhat, P. Mohan Rao, A.P. Ganesh Bhat, D.K. Avasthi, Surf. Coat. Technol. 158 (2002) 725–728.
[22] C. Balarew, R. Duhlew, J. Solid State Chem. 55 (1984) 1–6. [23] T. Balakrishnan, K. Ramamurthi, Mater. Lett. 62 (2008) 65-68. [24] K. Sangwal, B. Surowska, P. Blaziak, Mater. Chem. Phys. 77 (2002) 511–520.
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Figure captions
Fig.1 Synthesis scheme for PPNP compound
ip t
Fig.2 Solubility curve of PPNP in methanol solvent Fig.3 Photograph of as-grown PPNP single crystal
cr
Fig.4 FT-IR spectrum of PPNP
Fig.6 Proton NMR spectrum of PPNP
an
Fig.7 UV-Visible transmission spectrum of PPNP crystal
us
Fig.5 FT-Raman spectrum of PPNP
Fig.9 TG-DTA thermogram of PPNP
M
Fig.8 Photoluminescence spectrum of PPNP crystal
Fig.10 Plot of dielectric constant vs. log frequency of PPNP crystal
d
Fig.11 Plot of dielectric loss vs. log frequency of PPNP crystal
Ac ce p
te
Fig.12 Plot of Hardness number (Hv) vs. load (P) of PPNP crystal
15
Page 15 of 31
Empirical Formula
C5H12N+.C6H4NO3-
Formula Weight
224.26 (g/mol)
Crystal System
Orthorhombic
Space group
P212121
Unit cell dimensions
a = 6.867 (5) Å
an
b = 10.121 (4) Å
cr
SHELXL
us
Identification code
ip t
Table 1 Crystal data and structure refinement for PPNP
c = 16.497 (6) Å
M
α = β = γ = 90
1146.6 (10) Å3
Z, D (calc) [g/cm3]
4, 1.299
Ac ce p
te
d
Volume (V)
16
Page 16 of 31
ip t cr us M
an 0.90
H···A
1.92
Ac ce p
N2—H2A···O1i
D—H
te
D—H···A
d
Table 2 Hydrogen-bond geometry (Å, o).
D···A
D—H···A
2.788(2)
161
N2—H2B···O1ii
0.90
1.80
2.6985(15)
175
C6—H6··· Cg1iii
0.93
2.75
3.428(3)
130
Symmetry codes:
(i) –x, y–1/2, –z+1/2
(ii) –x+1/2, –y+1, z+1/2 (iii) x+1/2, –y+1/2, –z.
17
Page 17 of 31
ip t cr us an M d te Ac ce p Table 3 Molecular vibrational assignments of PPNP compound
18
Page 18 of 31
Wave number (cm-1)
Assignments
FT-Raman
NH2 stretching vibration
3435
–
N-H stretching vibration
3143
ip t
FT-IR
NO2 stretching vibration
1578 1460
C-O stretching vibration
1267
2956
1582
C-N asymmetric stretching vibration
1465
1266
1163
1110
d
C-H in-plane bending vibration
M
an
C-C stretching vibration
cr
2955
us
C-H symmetric stretching vibration
3069
1163 1101
1034
1033
C-H out-of-plane bending vibration
849
845
NO2 in-plane bending vibration
642
640
Ac ce p
te
C-N symmetric stretching vibration
NO2 wagging
555
554
19
Page 19 of 31
ip t cr us O2 N
an
+
OH
NH
.
O2N
O
M
NH2
Ac ce p
te
d
Fig.1 Synthesis scheme for PPNP compound
20
Page 20 of 31
ip t cr us an M d te Ac ce p
Fig.2 Solubility curve of PPNP in methanol solvent
21
Page 21 of 31
ip t cr us an M d te Ac ce p
Fig.3 Photograph of as-grown PPNP single crystal
22
Page 22 of 31
ip t cr us an M d te Ac ce p
Fig.4 FT-IR spectrum of PPNP
23
Page 23 of 31
ip t cr us an M d te Ac ce p
Fig.5 FT-Raman spectrum of PPNP
24
Page 24 of 31
ip t cr us an M d te Ac ce p
Fig.6 Proton NMR spectrum of PPNP
25
Page 25 of 31
ip t cr us an M d te Ac ce p
Fig.7 UV-Visible transmission spectrum of PPNP crystal
26
Page 26 of 31
ip t cr us an M d te Ac ce p Fig.8 Photoluminescence spectrum of PPNP crystal
27
Page 27 of 31
ip t cr us an M d te Ac ce p Fig.9 TG-DTA thermogram of PPNP 28
Page 28 of 31
ip t cr us an M d te Ac ce p Fig.10 Plot of dielectric constant vs. log frequency of PPNP crystal 29
Page 29 of 31
30
Page 30 of 31
d
te
Ac ce p us
an
M
cr
ip t
Ac ce p
te
d
M
an
us
cr
ip t
Fig.11 Plot of dielectric loss vs. log frequency of PPNP crystal
Fig.12 Plot of Hardness number (Hv) vs. load (P) of PPNP crystal 31
Page 31 of 31