Single crystals of p-Toluidine p-Toluenesulfonate (PTPT), an organic nonlinear optical (NLO) material, have been grown by slow evaporation method at room temperature using ethanol as solvent. The crystal system was confirmed from the single crystal X-ray diffraction analysis. The functional groups were identified using FTIR spectroscopy. UV-Vis-NIR spectrum showed that the UV cut-off wavelength of PTPT occurs at 295 nm and it has insignificant absorption in the wavelength region of 532–800 nm. The SHG efficiency of PTPT was measured by employing Kurtz and Perry powder technique using a Q-switched mode locked Nd: YAG laser emitting 1064 nm for the first time and it was found to be 52% of standard KDP. Thermal and mechanical properties of PTPT were examined by TG/DTA and Vickers microhardness test, respectively.
Materials with large nonlinear optical susceptibilities are of current interest in the area of harmonic generation and optical modulation. In recent years, some polar organic crystals, which form a noncentrosymmetric structure which exhibit second-order nonlinear optical properties that far surpassed those of the conventional materials, have led to the synthesis and evaluation of a wide range of potentially useful solids [
The title compound was obtained by the addition of p-toluenesulfonic acid (0.02 mol) to a solution of p-Toluidine (0.02 mol) in ethanol, in the stoichiometric ratio 1 : 1. Within a week, tiny crystals were formed due to the spontaneous nucleation. Optically transparent good quality crystals were used as seeds for further growth experiments. For growth, seed crystals were just immersed into the prepared solution. Good quality crystals with characteristic shape and size of
Grown Crystal of PTPT.
Molecular Structure of PTPT.
In order to confirm the grown crystal, single crystal
Using the single crystal
The density of the crystal was determined by the floatation technique (also called the sink or swim technique). For the measurement of crystal density, carbon tetrachloride of density 1.59
The FTIR spectrum recorder for the PTPT is shown in Figure
FTIR spectral data of PTPT.
S. No. | Wave number (cm−1) | Tentative assignments |
---|---|---|
1 | 3324b |
|
2 | 2677m |
|
3 | 1694s |
|
4 | 1694s |
|
5 | 1576m |
|
6 | 1502v | Ring Str |
7 | 1448m |
|
8 | 1295m | C–H bending in plane H bond |
9 | 1192m | C–H bending |
10 | 1156s |
|
11 | 1091w | C–H in plane deformation |
12 | 936s |
C–C str/ |
13 | 856s |
|
14 | 769b & 743b | N–H deformation |
15 | 664w 621w & 575w | C–C str |
16 | 769m | N–H deformation |
17 | 700w | C–C str |
18 | 559s |
|
19 | 525m | C–C deformation |
20 | 452w | C–C deformation |
FTIR Spectrum of PTPT.
To analyze the optical properties of grown PTPT crystal, UV-Vis transmittance was recorded. For this, polished sample of 1 mm thick from the grown crystal was used. The recorded UV-Vis-NIR spectrum of PTPT is shown in Figure
UV-Vis-NIR Spectrum of PTPT.
TGA/DTA curve of PTPT is given in Figure
TGA/DTA Curve of PTPT.
Hardness is one of the important mechanical properties to determine the plastic nature and strength of a material. The well polished PTPT crystal was placed on the platform of the Vicker’s microhardness tester and the loads of different magnitudes were applied over a fixed interval of time. The hardness number was calculated using the relation
(
log
Since PTPT has crystallized in a noncentrosymmetric space group, a preliminary study of the powder SHG conversion efficiency was carried. A Q-switched Nd: YAG laser beam of 1064 nm wavelength was used with an input power of 4.4 mJ pulse−1, pulse width of 10 ns, and the repetition rate of 10 Hz. The crystals of PTPT were ground to a uniform particle size of about 125–150
Single crystals of p-Toluidine p-Toluenesulfonate (PTPT) were grown from ethanol solution by slow evaporation of the solvent at room temperature. The crystal system was confirmed from the single crystal
The authors thank Dr. P. K. Das, IISc Bangalore, for providing SHG testing facilities.