Novel N-substituted-5-phenyl-1H-pyrazole-4-ethyl carboxylates as potential NLO materials

In the present investigation we have synthesized a novel series of N-substituted-5-phenyl-1H-pyrazole-4-ethyl carboxylates, which are characterized by ¹H NMR, UV–Vis and FT-IR spectroscopy methods. The optical nonlinearity of the compounds in chloroform solution has been studied at 532 nm using 5 ns laser pulses, employing the open-aperture z-scan technique. It is found that compound 3c having carboxylic acid group and ester substituent has maximum nonlinearity. From measurements we conclude that compounds 3c (4-[4-(ethoxycarbonyl)-5-phenyl-1H-pyrazol-1-yl]benzoic acid) and 3e (ethyl 1-(2-bromophenyl)-5-phenyl-1H-pyrazole-4-carboxylate) are potential candidates for optical limiting applications.     

Ultrafast optical power limiting in free-standing Pt–polyvinyl alcohol nanocomposite films synthesized in situ

Free-standing platinum–polyvinyl alcohol nanocomposite films have been prepared by a simple in situ method. By thermal annealing, Pt nanoparticles of different sizes and shapes have been obtained. Their optical nonlinearity is measured using ultrafast (100 fs) laser pulses at 404 nm, in the absorption wing region. A strong optical power limiting is found in the films. The timescale of this limiting action is ultrafast, as it happens within the incident laser pulsewidth. Experimental results and numerical simulation indicate that the sign of the nonlinearity can be controlled by varying the film composition and annealing temperature. Use of ultrashort laser pulses in the free-standing film configuration permits a direct and unambiguous determination of the electronic nonlinearity of the material, since accumulative effects occur at later times lying outside the sharp measurement window.     

Effect of plasticizer on structural and electrical properties of nanocomposite solid polymer electrolytes

The solid polymer electrolyte films based on polyethylene oxide, NaClO₄ with dodecyl amine modified montmorillonite as filler, and polyethylene glycol as plasticizer were prepared by a tape casting method. The effect of plasticization on structural, microstructural, and electrical properties of the materials has been investigated. A systematic change in the structural and microstructural properties of plasticized polymer nanocomposite electrolytes (PPNCEs) on addition of plasticizer was observed in our X-ray diffraction pattern and scanning electron microscopy micrographs. Complex impedance analysis technique was used to calculate the electrical properties of the nanocomposites. Addition of plasticizer has resulted in the lowering of the glass transition temperature, effective dissociation of the salt, and enhancement in the electrical conductivity. The maximum value of conductivity obtained was ∼4.4 × 10⁻⁶ S cm⁻¹ (on addition of ∼20% plasticizer), which is an order of magnitude higher than that of pure polymer nanocomposite electrolyte films (2.82 × 10⁻⁷ S cm⁻¹). The enhancement in conductivity on plasticization was well correlated with the change in other physical properties.     

Optical limiting characteristics of Dichloridobis(1-ethyl-2, 6-dimethylpyridinium-4-olate-κO) zinc (II)

A newly synthesized metal-organic co-ordination compound Dichloridobis (1-ethyl-2,6-dimethylpyridinium-4-olate-κO) zinc(II) (EDMPZC) is characterized by FTIR to confirm the molecular structure. It crystallizes in the monoclinic system with the centrosymmetric space group C2/c and the unit cell parameters are determined from the single crystal X-ray diffraction analysis. Optical energy band gap is found to be 3.5 eV by UV-Visible absorption studies. The third order nonlinear optical properties were investigated by open-aperture Z-scan measurements using Nd:YAG laser (532 nm, 5 ns). Two-photon absorption and reverse saturable absorption mechanisms at the excitation wavelength are found to cause the observed optical limiting behavior.