Silver molybdate: an excellent optical limiting material under nanoregime for photonic device application.

There is a mounting demand for nonlinear optical materials with superior optical limiting performance which has a noticeable impact on protecting the delicate optical components from laser-induced damage. Transition metal molybdates have garnered attention in the nonlinear optics field due to their outstanding optical and luminescent properties, which give rise to widespread applications in next-generation optoelectronics devices. The structural confirmation of the as prepared silver molybdate nanoparticles were made by XRD and Raman spectroscopy analysis. The linear optical properties and the band gap of the synthesized material were studied using UV-Visible and photoluminescence spectroscopy. SEM analysis revealed the pebble like morphology of the silver molybdate nanostructures. The nonlinear responses of the samples were studied using open aperture z-scan approach with Nd:YAG pulsed laser (532 nm, 9 ns, 10 Hz). The sample exhibits reverse saturable absorption pattern attributed to the two photon absorption (2PA) mechanism. The obtained OL threshold value is in the order of 1012 which is suitable for fabricating optical limiters in nano second pulsed laser regime.

Experimental and Computational studies on Intramolecular charge transfer, Terahertz and Two photon absorption of 3-[(4-Nitrophenyl Azo)]-9H-Carbazole-9-Ethanol (NPACE) from their Vibrational spectra for Optical limiting and NLO applications.

Non-linear optical (NLO) features of 3-[(4-Nitrophenyl Azo)]-9H-Carbazole-9-Ethanol (NPACE) chromophore were investigated by FT-IR, FT-Raman, and UV-visible spectra aided by Density Functional Theory (DFT) using the B3LYP/6-311++G(d,p) basis set of Gaussian 16 W package. It is observed from the DFT calculation that the slight increase in the endocyclic angle of C13 -C14 -C15 and the reduction in exocyclic angle of N40 -N39 -C14 and C15 -C14 -N39 ascertained by experimental XRD values indicating the intramolecular charge-transfer interaction between the carbazole and nitrophenyl group through the diazo bridge. The vibrational contribution to the linear electro-optic effect is 15% of the total hyperpolarizability being calculated at B3LYP/6-311++G (d, p) for the NPACE molecule. It is also observed that the 8a, 19a, and 19b modes of the carbazole ring and the 8a, 8b, and 19b modes of the phenyl ring are found to be simultaneously and intensely active in IR and Raman spectra explaining the charge transfer interactions throughout the molecule. The low value of the HOMO- LUMO energy gap (2.5843 eV) and the deviation between the measured absorption wavelength (3.36 eV) from the computed (3.87 eV), both these facts substantiate the intramolecular charge transfer. The polarizability and first-order hyperpolarizability were calculated as 6.48 × 10-24 and 3.8 × 10-29 esu, respectively. The second harmonic generation (SHG) measurement experiment of NPACE was carried out using the powder method. The SHG efficiency is measured in comparison with the urea standard. The calculated torsional mode at 20 cm-1 is in excellent quantitative agreement with the experimentally determined terahertz absorption peak. The two-photon absorption coefficient of NPACE was estimated to be 0.9 × 10-11 mW-1, which is mainly due to the D-π-A type of molecular structure, and the optical limiting threshold for NPACE was estimated to be 1.52 × 1013 Wm-2 enabling this material as a potential candidate for optical limiting applications.

Influence of yttrium doping on the nonlinear optical limiting properties of cadmium molybdate nanostructures.

The emerging demand for the production of nonlinear optical materials with high optical limiting performance has an apparent impact in the field of nonlinear optics owing to their wide application in photonic devices. In this regard, transition metal molybdates have received attention owing to their remarkable optical and luminescence characteristics, leading to their extensive use in next generation optoelectronics devices. Herein, we report the nonlinear optical response of yttrium (Y3+) doped cadmium molybdate (CdMoO4) nanostructures synthesized via a co-precipitation technique. The X-ray diffraction and Raman spectroscopy results confirm the formation of CdMoO4 nanostructures with a tetragonal structure having the I41/a space group. High resolution scanning electron microscopy (HRSEM) of the pristine CdMoO4 exposed the cubic flat edged nature of the nanostructures and that doping results in particle size reduction due to lattice contraction. X-ray photo electron spectroscopy confirmed the chemical state of the elements present in Y3+doped CdMoO4. The optical properties of the samples were studied using UV-Vis Spectroscopy and the bandgap was found to increase upon Y3+ doping. The NLO response measured using the open aperture z-scan technique with a Nd: YAG pulsed laser (532 nm, 7 ns, 10 Hz) exhibited a reverse saturable absorption arising from a two photon absorption (2PA) process. An increase in the 2PA coefficient and simultaneous decrease in the onset of the optical limiting threshold clearly suggests the great potential of the yttrium-doped CdMoO4 nanoparticles for good optical limiting applications.

Bis(benzo-15-crown-5-κ5 O)barium tetra-kis-(iso-thio-cyanato-κN)cobaltate(II).

The title compound, [Ba(C14H20O5)2][Co(NCS)4], is formed by discrete anions and cations. The molecular packing is controlled by weak C-H⋯π inter-actions.

Tunable photovoltaic performance of preferentially oriented rutile TiO2 nanorod photoanode based dye sensitized solar cells with quasi-state electrolyte.

Photoanodes made of highly oriented TiO2 nanorod (NR) arrays with different aspect ratios were synthesized via a one-step hydrothermal technique. Preferentially oriented single crystalline rutile TiO2 was confirmed by the single peak in an XRD pattern (2θ = 63°, (0 0 2)). FESEM images evidenced the growth of an array of NRss having different geometries with respect to reaction time and solution refreshment rate. The length, diameter and aspect ratio of the NRs increased with reaction time as 4 h (1.98 µm, 121 nm, 15.32), 8 h (4 µm, 185 nm, 22.70), 12 h (5.6 µm, 242 nm, 27.24) and 16 h (8 µm, 254 nm, 38.02), respectively. Unlike a conventional dye-sensitized solar cell (DSSC) with a liquid electrolyte, DSSCs were fabricated here using one-dimensional rutile TiO2 NR based photoanodes, N719 dye and a quasi-state electrolyte. The charge transport properties were investigated using current-voltage curves and fitted using the one-diode model. Interestingly the photovoltaic performance of the DSSCs increased exponentially with the length of the NR and was attributed to a higher surface to volume ratio, more dye anchoring, and channelized electron transport. The higher photovoltaic performance (Jsc = 5.99 mA cm-2, Voc = 750 mV, η = 3.08%) was observed with photoanodes (16 h) made with the longer, densely packed TiO2 NRs (8 µm, 254 nm).