Generation of multiple focal spot and focal hole of sub wavelength scale using phase modulated LG (1,1) beam

Based on the vector diffraction theory, the effect of phase modulation on the intensity distribution on tight focusing of cylindrically polarized Laguerre–Gaussian beam in the focal region of high NA lens is investigated theoretically. It is observed that a properly designed complex phase filter can generate multiple focal spot and focal hole segments useful for the manipulation of optical traps.     

Synthesis and Characterization of Two‐Photon Active Chromophores Based on Tetrathienoacene (TTA) and Dithienothiophene (DTT)

Three new donor–π–donor (D‐π‐D) tetrathienoacene (thieno[2′,3′:4,5]thieno[3,2‐b]thieno[2,3‐d]thiophene (TTA))‐cored chromophores, end‐functionalized with electron‐donating triphenylamine (TPA) groups, were developed and characterized for their two‐photon‐related properties by using both nano‐ and femtosecond laser pulses as the probing tools. TTA‐based chromophores exhibit stronger and more widely dispersed two‐photon absorption (2PA) than those of dithienothiophene (DTT)‐based congeners. As a consequence, the bithiophene‐conjugated TTA chromophore exhibits the highest maximum 2PA cross‐section value (up to 2500 GM) with good thermal stability, and thus, it is the best performing two‐photon chromophore among the studied model compounds. The bithiophene‐conjugated DTT analogue exhibits the second highest maximum two‐photon absorptivity of 1950 GM, which is nearly 7 times larger than that of previously reported DTT‐based chromophores.     

The Effect of ζ‐Potential and Hydrodynamic Size on Nanoparticle Interactions in Hydrogels

The ζ‐potential and hydrodynamic size (d_h) of nanoparticles (NPs) are systematically controlled by capping gold NPs (AuNPs) with polymers having different charges and treating them in NaCl solutions of diverse concentrations. Interactions between AuNPs in hydrogel are caused by chemical reactions induced by 1,4‐dithiothreitol. The effect of ζ‐potential is clear, as negatively charged AuNPs can be aggregated in neutral agarose gel, but the amount of aggregation is significantly affected by the magnitude of the negative surface charge on the AuNPs. However, all positively charged AuNPs show negligible aggregation in agarose gel with slightly negative polarity. The effect of d_h on AuNP aggregation is different from that of ζ‐potential. Although AuNPs with small d_h generally show more aggregation than those with large d_h, the amount of AuNP capping layer is critical. Thus, the amount of polymer present on NP surface needs to be considered to investigate the effect of d_h on AuNP aggregation. Through extended Derjaguin, Landau, Verwey, Overbeek (XDLVO) theory, it is shown that the charges of the AuNPs and the hydrogel, as well as the d_h of the NPs, are related to electrostatic repulsion and steric hindrance, which affect AuNP aggregation in hydrogel.     

Enhancement of the electrochemical properties with the effect of alkali metal systems on PEO/PVdF-HFP complex polymer electrolytes

Polymer blend electrolytes based on poly(ethylene oxide) (PEO) and poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) were prepared by using different lithium salts LiX (X = ClO₄, BF₄, CF₃SO₃, and N [CF₃SO₂]₂) using solution casting technique. To confirm the structure and complexation of the electrolyte films, the prepared electrolytes were subjected to X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analysis. Alternating current (AC) impedance analysis was performed for all the electrolyte samples at various temperatures from 303 to 343 K. The result suggests that among the various lithium salts, LiN[CF₃SO₂]₂-based electrolytes exhibited the highest ionic conductivity at 8.20 × 10^?4 S/cm. The linear variation of the ionic conductivity of the polymer electrolytes with increasing temperature suggests the Arrhenius-type thermally activated process. Activation energies were found to decrease when doping with lithium imide salt. The dielectric behavior has been analyzed using dielectric permittivity (ε*), electric modulus (M*), and dissipation factor (tanδ) of the samples. Cyclic voltammetry has been performed for the electrolyte films to study their cyclability and reversibility. Thermogravimetric and differential thermal analysis (TG/DTA) was used to ascertain the thermal stability of the electrolytes, and the porous nature of the electrolytes was identified using scanning electron microscopy via ion hopping conduction. Surface morphology of the sample having maximum conductivity was studied by an atomic force microscope (AFM).     

ZnO nanoparticles-mediated regioselective synthesis of methyl-N-alkylated 1,2,3-triazole-4-carboxylates

The 1,2,3-triazoles are versatile synthetic intermediates of many biologically active compounds, and their N-1 substituted analogues are potential pharmaceutically important derivatives. In this study, an efficient regioselective N-alkylation reaction of methyl-1H-1,2 3-triazole-4-carboxylate 3 with alkyl halides 4 catalyzed by ZnO nanoparticles in the presence of potassium hydroxide as base and DMSO as solvent is reported which leads to methyl N ₁-alkylated 1,2,3-triazole-4-carboxylates 5 in good yields.