G. Vinitha

Bio: G. Vinitha is an academic researcher from VIT University. The author has contributed to research in topic(s): Single crystal & Crystal. The author has an hindex of 23, co-authored 251 publication(s) receiving 2106 citation(s). Previous affiliations of G. Vinitha include B. S. Abdur Rahman University & Anna University.

A review on the visible light active BiFeO3 nanostructures as suitable photocatalyst in the degradation of different textile dyes

Abstract: Different effluents from textile industries which are dumped into the water bodies have been a major concern of the modern world. The uncontrolled discharge of the synthetic textile dyes in water bodies especially have led to serious environmental problems and health hazards. Among the different existing approaches to treat water, photocatalysis is an attractive approach as it uses the inexhaustible and clean solar energy. Considering its ability to absorb in the visible light of solar spectrum, its multiferroic property and its crystal structure, researchers feel BiFeO3 can provide a breakthrough in the treatment of water. In this article, a thorough review is presented on the various attempts done so far on degradation of different synthetic textile dyes solution using BiFeO3 nanostructures.

Crystal structure and characterization of a novel organic optical crystal: 2-Aminopyridinium trichloroacetate

Abstract: 2-Aminopyridinium trichloroacetate, a novel organic optical material has been synthesized and crystals were grown from aqueous solution employing the technique of controlled evaporation. 2-Aminopyridinium trichloroacetate crystallizes in monoclinic system with space group P21/c and the lattice parameters are a = 8.598(5) A, b = 11.336(2) A, c = 11.023(2) A, β = 102.83(1)° and volume = 1047.5(3) A3. High-resolution X-ray diffraction measurements were performed to analyze the structural perfection of the grown crystals. Thermal analysis shows a sharp endothermic peak at 124 °C due to melting reaction of 2-aminopyridinium trichloroacetate. UV–vis–NIR studies reveal that 2-aminopyridinium trichloroacetate has UV cutoff wavelength at 354 nm. Dielectric studies show that dielectric constant and dielectric loss decreases with increasing frequency and finally it becomes almost a constant at higher frequencies for all temperatures. The negative nonlinear optical parameters of 2-aminopyridinium trichloroacetate were derived by the Z-scan technique.

χ(3) measurement and optical limiting properties of metal complexes of thiourea using Z-scan

Abstract: The third order NLO properties of thiourea and its metal complexes were measured using a 532 nm second harmonic of diode pumped Nd:YAG laser (1064 nm, 50 mW) by employing the Z-scan technique. The magnitude of nonlinear refractive index, nonlinear absorption coefficient and third order susceptibility was found to be in the order of 10 −8 cm 2 W −1 , 10 −3 cm W −1 and 10 −6 esu respectively. The Z-scan reflects the negative nonlinearity of the samples and hence self defocusing nature is responsible for the optical limiting behavior in the regime of interest. The response time was found to be in the order of milliseconds.

Third order nonlinear optical properties of potassium dichromate single crystals by Z-scan technique

Abstract: Single crystal of potassium dichromate (KDC) has been grown from aqueous solution by slow evaporation technique. The lattice parameters of the grown crystal were determined by X-ray diffraction analysis. The optical absorption studies reveal that the crystal has UV cut-off wavelength around 240 nm. Thermo gravimetric and differential thermal (TGA/DTA) studies revealed that the crystal thermally stable up to 397.1 °C. The mechanical strength of the grown crystal was carried out by Vickers micro hardness test. The crystal perfection was confirmed by etching studies. Third order nonlinear optical studies was performed using by single beam Z-scan technique using continuous Nd:YAG laser. Closed aperture Z-scan studies reveal the negative nonlinearity in the crystals and open aperture Z-scan reveals the saturation absorption. Also various parameters such as nonlinear refractive index n 2 , absorption co-efficient β and nonlinear optical susceptibility χ (3) were calculated for the grown crystal.

Studies on growth, crystal structure and characterization of novel organic nicotinium trifluoroacetate single crystals

Abstract: An organic material, nicotinium trifluoroacetate (NTF) was synthesized and single crystals in monoclinic system were grown from aqueous solution for the first time. Its solubility and metastable zone width were estimated. The crystal structure of NTF was analyzed to reveal the molecular arrangements and the formation of hydrogen bonds in the crystal. High-resolution X-ray diffraction rocking curve measurements were performed to analyze the structural perfection of the grown crystals. Functional groups in NTF were identified by Fourier transform infrared spectral analysis. Thermal behaviour and stability of NTF were studied by thermogravimetric and differential thermal analysis and differential scanning calorimetry. Mechanical and dielectric properties of NTF crystals were analyzed. Optical studies reveal that NTF crystals are transparent in the wavelength range 286–1100 nm. The third order nonlinear optical parameters of NTF were derived by the Z-scan technique.

Two-photon polymerization initiators for three-dimensional optical data storage and microfabrication

Abstract: Two-photon excitation provides a means of activating chemical or physical processes with high spatial resolution in three dimensions and has made possible the development of three-dimensional fluorescence imaging, optical data storage, and lithographic microfabrication. These applications take advantage of the fact that the two-photon absorption probability depends quadratically on intensity, so under tight-focusing conditions, the absorption is confined at the focus to a volume of order λ3 (where λ is the laser wavelength). Any subsequent process, such as fluorescence or a photoinduced chemical reaction, is also localized in this small volume. Although three-dimensional data storage and microfabrication have been illustrated using two-photon-initiated polymerization of resins incorporating conventional ultraviolet-absorbing initiators, such photopolymer systems exhibit low photosensitivity as the initiators have small two-photon absorption cross-sections (δ). Consequently, this approach requires high laser power, and its widespread use remains impractical. Here we report on a class of π;-conjugated compounds that exhibit large δ (as high as 1, 250 × 10−50 cm4 s per photon) and enhanced two-photon sensitivity relative to ultraviolet initiators. Two-photon excitable resins based on these new initiators have been developed and used to demonstrate a scheme for three-dimensional data storage which permits fluorescent and refractive read-out, and the fabrication of three-dimensional micro-optical and micromechanical structures, including photonic-bandgap-type structures.

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...

g-C3N4/carbon dot-based nanocomposites serve as efficacious photocatalysts for environmental purification and energy generation: A review

Abstract: Most recently, graphitic carbon nitride (g-C3N4) has emerged as one of the desirable stable organic polymers, owing to its diverse applications as a semiconducting photocatalyst in photoreduction of CO2, water splitting, and elimination of various contaminants. In these regards, a series of modifications have been made in this semiconductor using carbon dots (CDs) to increase its efficiency in these photocatalytic processes, because of its fast recombination of the photoinduced charges, low specific surface area, and poor harvesting of visible light. This review highlights the applied protocols to ameliorate the photoactivity of g-C3N4/CDs-based nanocomposites through combining with various materials. This work shows that in addition to the charge effects, textural and morphological changes in g-C3N4 are also observed by coupling with CDs to change the bulk characteristics and extend its applications. This review can provide beneficial information about profundity realizing the versatile role of CDs in boosting photocatalytic ability of g–C3N4–based systems. The ultimate goal of this review can be both a tutorial to fundamental photocatalysis and a critical comment on the most recent progress in utilization of g-C3N4/CDs-based photocatalysts in different areas.

Nonlinear optical properties of metal nanoparticles: a review

Abstract: Metal nanoparticles (MNPs) hold great technological promise because of the possibility of engineering their electronic and optical properties through material design. One of the effective methods to fabricate MNPs is ion implantation. In this review, recent results on the nonlinear optical properties of nanoparticles (including copper, silver, gold, and bismuth nanoparticles) doped in various bases have been discussed. Some specific optical nonlinear properties, such as nonlinear refraction, two-photon absorption, and optical limiting, for femtosecond, picosecond, and nanosecond laser pulses have also been covered. In addition to ion implantation, we have summarized several other methods for the preparation of composite materials, and Z-scan has been used to study the nonlinear optical properties of these materials.

Nonlinear optical properties and applications of 2D materials: theoretical and experimental aspects

Abstract: In this review, we survey the recent advances in nonlinear optics and the applications of two-dimensional (2D) materials. We briefly cover the key developments pertaining to research in the nonlinear optics of graphene, the quintessential 2D material. Subsequently, we discuss the linear and nonlinear optical properties of several other 2D layered materials, including transition metal chalcogenides, black phosphorus, hexagonal boron nitride, perovskites, and topological insulators, as well as the recent progress in hybrid nanostructures containing 2D materials, such as composites with dyes, plasmonic particles, 2D crystals, and silicon integrated structures. Finally, we highlight a few representative current applications of 2D materials to photonic and optoelectronic devices.