K. Senthil

Bio: K. Senthil is an academic researcher from Xi'an Jiaotong University. The author has contributed to research in topics: Crystal & Single crystal. The author has an hindex of 8, co-authored 15 publications receiving 299 citations. Previous affiliations of K. Senthil include Akita University & VIT University.

Investigation of synthesis, crystal structure and third-order NLO properties of a new stilbazolium derivative crystal: a promising material for nonlinear optical devices

Abstract: A new organic stilbazolium derivative crystal 2-[2-(3-hydroxy-4-methoxy-phenyl)-vinyl]-1-methyl-pyridinium naphthalene-2-sulfonate dehydrate (C25H23NO5S·2H2O) (VSNS) was synthesized successfully. Single crystals were grown in a mixed solvent of methanol–acetonitrile (1 : 1) using a slow evaporation method at room temperature. Solubility of the synthesized VSNS material was experimentally determined for various temperatures using a methanol–acetonitrile mixed solvent. A single crystal X-ray diffraction study confirmed the crystal structure and morphology of VSNS. The crystalline nature of the title material was analyzed by powder X-ray diffraction analysis, and the presence of expected functional groups and the molecular structure of VSNS was identified by FT-IR and 1H NMR spectroscopic studies. Optical absorption was recorded using UV-Vis-NIR spectral analysis, and linear optical constants such as the absorption coefficient, band gap, extinction coefficient, refractive index and reflectance were calculated. The luminescence property of the crystal grown showed green emission radiation. The thermal stability of the crystal was analyzed by TG–DTA studies, and the hardness, Meyer index, yield strength, and elastic stiffness constant were estimated using a Vickers microhardness tester. Layer growth pattern was observed in chemical etching studies using a Carl Zeiss optical microscope at 50× magnification. Laser damage threshold energy was measured using an Nd:YAG laser (1064 nm). Variation of the dielectric response of the grown crystal was studied at room temperature. The third-order nonlinear optical property of VSNS was investigated in detail using a Z-scan technique with He–Ne laser at 632.8 nm. The second-order molecular hyperpolarizability γ of the crystal grown was 7.986 × 10−34 esu. This encouraging result of the Z-scan studies suggests that the VSNS crystal is a candidate material for photonics devices, optical switches, and optical power limiting applications.

Bulk crystal growth and nonlinear optical characterization of a stilbazolium derivative crystal: 4-[2-(3,4-dimethoxyphenyl)ethenyl]-l methylpyridinium tetraphenylborate (DSTPB) for NLO device fabrication

Abstract: The search for organic crystals with highly efficient nonlinear optical (NLO) properties with a high surface laser damage threshold (LDT) has become more of a demand in the frontier areas of optical switching and communications applications. A single crystal of 4-[2-(3,4-dimethoxyphenyl)ethenyl]-l methylpyridinium tetraphenylborate (DSTPB), which is an organic material has been successfully synthesized in the pure phase. Bulk single crystals were grown with dimensions of 28 × 11 × 6 mm3 using a slow evaporation method and reported for the first time. The structure of the title crystal and its lattice parameter were confirmed by single-crystal X-ray diffraction studies and it was found that it crystallizes in the non-centrosymmetric space group Cc with a monoclinic crystal system. The calculated HOMO and LUMO energies show that charge transfer takes place within the molecular structure, and they also indicate the NLO activity of the title crystal. A Kurtz powder test showed large second harmonic generation (SHG) about 4.53 times that of KDP crystal and make it a suitable candidate for electro-optic applications. It also exhibits good transparency (371 nm to 1100 mm) in the visible and near infra-red spectral (NIR) ranges and its thermal stability was found to be up to 260 °C. It shows a high laser-induced damage threshold of up to 4.3 GW cm−2, which is greater than that of some known organic and inorganic NLO materials. Third-order nonlinear optical properties of the title crystal were studied by the single beam Z-scan technique at 632.8 nm using a He–Ne laser. It was found that it exhibits saturable absorption (SA) and a self-focusing nature with large second-order hyperpolarizability (γ) 3.15 × 10−33 esu, which are mainly associated with electronic processes. The results indicate that the crystals exhibit large third-order optical susceptibility compared with some reported NLO crystals. The enhanced second-order and third-order optical nonlinearity of DSTPB makes it a promising candidate in the field of nonlinear optical devices.

Investigation on the crystal growth, molecular structure and nonlinear optical susceptibilities of 2-[2-(4-Ethoxy-phenyl)-vinyl]-1-ethyl-stilbazolium iodide (EESI) by Z-scan technique using He–Ne laser for third-order nonlinear optical applications

Abstract: Organic 2-[2-(4-Ethoxy-phenyl)-vinyl]-1-ethyl-stilbazolium iodide (EESI), a derivative of the stilbazolium family single crystal was synthesized by condensation method. Nearly perfect as-gown single crystals of EESI structure was confirmed by single-crystal X-ray diffraction studies. The crystal has a triclinic system with the space group P -1, the molecule consists of one pyridinium cation, one iodide anion, and 0·5H 2 O molecules. The nature of charge transfer, molecular properties, electrostatic potential map, and HOMO-LUMO energy gap of EESI have been theoretically investigated by Sparton’10 V1.0.1 program. The optical transparency of EESI was studied by Uv–Visible spectral analysis. The growth features were observed during the etching studies using a Carl Zeiss optical microscope (50X magnification). The mechanical behavior of the crystal was estimated by Vickers microhardness test, which shows reverse indentation size effect (RISE) with good mechanical stability. Both the dielectric constant and dielectric loss increases with the increasing temperature and attain almost constant at higher frequencies, which justify the crystal quality and essential parameter for electro-optic device applications. The complex impedance analysis explains the electrical property of EESI. TGA and DTA measurements determined the thermal stability of the grown crystal. Laser-induced damage threshold energy measurements exhibit that the excellent resistance with good threshold energy up to 2.08 GW/cm 2 that was found to be more than that of some known organic and inorganic NLO crystals. Photoconductivity of EESI crystal confirms that the positive photoconductivity nature. Also, the third-order nonlinear optical (NLO) properties of EESI were investigated by using the single beam Z-scan technique under the Visible light (632.8 nm) region. The results show that EESI has effective third-order nonlinear optical property with the nonlinear refractive index n 2 =1.787×10 -11 m 2 /W, third-order nonlinear optical susceptibility χ (3) =4.229×10 -6 esu and second-order hyperpolarizability (γ) =1.468×10 –33 esu. It is found to be larger than that of some organic NLO materials. All the obtained results are making it a potential candidate as useful non-linear optical (NLO) applications.

New Heterocyclic Dithioether Ligands for Highly Selective Separation and Recovery of Pd(II) from Acidic Leach Liquors of Spent Automobile Catalyst

Abstract: The solvent extraction behavior of Pd(II) from a hydrochloric acid solution with heterocyclic dithioether ligands, namely, 1,2-bis((5-methyl-1,3,4-thiadiazol-2-yl)thio)ethane (BMDTE) and 1,2-bis((5-(methylthio)-1,3,4-thiadiazol-2-yl)thio)ethane (BMTDTE) were investigated, for the first time, as potential extractants by using chloroform as diluent. Various experimental parameters such as effects of the concentration of hydrochloric acid, extractant concentration, hydrogen ion, chloride ion, and diluents on the extraction of Pd(II) was also investigated in detail. By comparing the extraction time, BMDTE exhibits a more rapid and quantitative extraction of Pd(II) even within 5 min than BMTDTE (30 min). The loading experiments indicated that the maximum loading capacity of BMDTE and BMTDTE for Pd(II) was determined to be 124 and 118 ppm, respectively. The stoichiometry of the extracted species during extraction was confirmed by 1H NMR and Job’s method analysis. Both of the two extractants exhibit high extract...

Nonlinear Optical Materials for the Smart Filtering of Optical Radiation.

Abstract: The control of luminous radiation has extremely important implications for modern and future technologies as well as in medicine. In this Review, we detail chemical structures and their relevant photophysical features for various groups of materials, including organic dyes such as metalloporphyrins and metallophthalocyanines (and derivatives), other common organic materials, mixed metal complexes and clusters, fullerenes, dendrimeric nanocomposites, polymeric materials (organic and/or inorganic), inorganic semiconductors, and other nanoscopic materials, utilized or potentially useful for the realization of devices able to filter in a smart way an external radiation. The concept of smart is referred to the characteristic of those materials that are capable to filter the radiation in a dynamic way without the need of an ancillary system for the activation of the required transmission change. In particular, this Review gives emphasis to the nonlinear optical properties of photoactive materials for the functi...

Molecular Structures and Second-Order Nonlinear Optical Properties of Ionic Organic Crystal Materials

Abstract: In recent years, there has been extensive research and continuous development on second-order nonlinear optical (NLO) crystal materials due to their potential applications in telecommunications, THz imaging and spectroscopy, optical information processing, and optical data storage. Recent progress in second-order NLO ionic organic crystal materials is reviewed in this article. Research has shown that the second-order nonlinear optical properties of organic crystal materials are closely related to their molecular structures. The basic structures of ionic organic conjugated molecules with excellent nonlinear optical properties are summarized. The effects of molecular structure, for example, conjugated π electron systems, electronic properties of donor-acceptor groups, and different counter-anion effects on second order NLO properties and crystal packing are studied.

Biocompatible Carbon Quantum Dots Derived from Sugarcane Industrial Wastes for Effective Nonlinear Optical Behavior and Antimicrobial Activity Applications.

Abstract: In this work, the green synthesis of highly fluorescent carbon quantum dots (CQDs) with an efficient quantum yield of 17.98% using sugarcane bagasse pulp as the precursor was conducted by a hydrothermal technique. The high-resolution transmission electron microscopy analysis revealed that the CQDs were competently monodispersed with the particle size ranging between 0.75 and 2.75 nm. The structural properties of CQDs were investigated using X-ray diffraction, Fourier transform infrared, and X-ray photoelectron spectroscopy analyses. The UV-visible spectrum showed two absorption peaks due to the aromatic C=C transitions of π-π* and C=O transitions of n-π*. The fluorescence spectrum of CQDs displayed a strong blue emission. However, the first-ever of its kind, sugarcane industrial solid waste carbon quantum dots caused significant orders to obey the enhancement of the third-order nonlinearity (χ(3)) when compared with other carbon dots (CDs). The calculated nonlinear optical (NLO) parameters such as n 2, β, and χ(3) were 1.012 × 10-8 cm2/W, 2.513 × 10-4, and 3.939 × 10-7 esu, respectively. The figures of merit were evaluated to be W = 6.6661 and T = 0.0132, which greatly fulfilled the optical switching conditions. Besides, the antibacterial activities of CQDs were screened against aquatic Gram-positive (Benthesicymus cereus and Staphylococcus aureus) and Gram-negative (Pseudomonas aeruginosa, Vibrio cholerae, and Escherichia coli) microbial organisms. Our findings, however, indicate that synergistic sugarcane industrial waste CQDs are promising materials for the functioning of NLO devices, bioimaging, and pharmaceutical applications.