Fast full-field out-of-plane deformation measurement using fringe reflectometry

Full-field out-of-plane deformation measurement of specular surfaces can be implemented quickly and conveniently using fringe reflectometry. The system configuration is simple and processing is fast. With the assistance of an advanced fringe pattern processing technique, the windowed Fourier ridges method, only a single two-directional fringe pattern is necessary for determination of the deformed surface profile. Thus, the whole measurement only requires a single image with the potential for high speed or even real time measurement.     

Experimental verification of enhanced electromagnetic field intensities at the photonic stop band edge of 3D polystyrene photonic crystals using Z-Scan technique

Enhancement of nonlinear absorption of polystyrene (PS) was investigated using 3D PS photonic crystals (PCs) with Z-scan technique. The Z-scan experiment was carried out at 532 nm in the picosecond (ps) regime. The transmittance of the PC was found to get modified because of the nonlinear absorption of PS particularly when 532 nm is near the photonic stop band (PSB) edge of PC. Calculations show that the field gets enhanced by 1.4 times the input field intensity within the crystal when the 532 nm wavelength falls at the PSB edge while keeping the crystal at an angle of 35°.     

Design, synthesis and antiviral potential of 14-aryl/heteroaryl-14H-dibenzo[a,j]xanthenes using an efficient polymer-supported catalyst

Polyethyleneglycol bound sulfonic acid (PEG-OSO?H), a chlorosulphonic acid-modified polyethylene glycol was successfully used as an efficient and eco-friendly polymeric catalyst in the synthesis of 14-aryl/heteroaryl-14H-dibenzo[a,j]xanthenes obtained from the reaction of 2-naphthol and carbonyl compounds under solvent-free conditions with short reaction times and excellent yields. The biological properties of these synthesized title compounds revealed that compounds 3b, 3c, 3f and 3i showed highly significant anti-viral activity against tobacco mosaic virus.     

Structure, bonding, and lowest energy transitions in unsymmetrical squaraines: a computational study

Natural resonance theory (NRT) and natural bond orbital (NBO) analysis have been carried out on a simple symmetrical and an unsymmetrical substituted squaraine with a view of understanding the structure of the latter type of squaraines. It is found that there are some fundamental differences in the structure and bonding between these two types of squaraines particularly in the resonance weights and delocalization energies. These differences are expected to reflect in the low energy transitions and charge transfer in these squaraines. To investigate this, the nature of the lowest energy transitions occurring on excitation in unsymmetrical squaraines has been studied using high-level symmetry adapted cluster-configuration interaction method (SAC/SAC-CI) and compared with reported experimental observations. In general the agreement with the experimental data is very good. The transition dipole moment always lies on the pi-backbone and is quite large in magnitude. The ground state dipole moment in some cases does not change in the excited state upon excitation while in some other cases there is a large reduction/enhancement in the magnitude indicative of some charge rearrangement in this direction. Inclusion of the solvent using the IEFPCM model, a slightly better agreement with the experiment is found in some cases. Studies are carried out with a different basis set and it is found that the change in basis set has very little effect on the transition energies. In the case of weak side donor groups attached to the central ring the larger charge transfer to the central acceptor ring in general takes place from the O- atoms of the squarylium moiety while in the case of strong donors the charge transfer from the O- atoms to the central rings drop down. We have not observed any correlation between the charge transfer in the excited state to the central ring from the side donor groups and the lowest energy excitation in the molecules. Reduction of the HOMO-LUMO gap (an indication of increase of the diradicaloid character) always leads to a bathochromic shift.     

Behavior of density functionals with respect to basis set. 3. Basis set superposition error

The impact of basis set superposition error (BSSE) upon molecular properties determined using the density functionals B3LYP, B3PW91, B3P86, BLYP, BPW91, and BP86 in combination with the correlation consistent basis sets [cc-pVnZ, where n = D(2), T(3), Q(4), and 5] for a set of first-row closed-shell molecules has been examined. Correcting for BSSE enables the irregular convergence behavior in molecular properties such as dissociation energies with respect to increasing basis set size, noted in earlier studies, to be improved. However, for some molecules and functional combinations, BSSE correction alone does not improve the irregular convergence behavior.     

Gold nanoparticle based FRET assay for the detection of DNA cleavage

We report gold nanoparticle based FRET assay to monitor the cleavage of DNA by nucleases. Fluorescence signal enhancement is observed by a factor of 120 after the cleavage reaction in the presence of S1 nuclease. The mechanism of distant dependent fluorescence quenching has been discussed. Our experimental results on distance dependent fluorescence quenching match quite well with theoretical findings obtained from the fluorescence quenching model by Gersten and Nitzan (Surf. Sci. 1985, 158, 165). Our experimental observation paradigm for the design of optical based molecular ruler strategies at distances more than double the distances achievable using traditional dipole-dipole Columbic energy transfer based methods.     

Enhancement of titanium dioxide photocatalysis by water-soluble fullerenes

Fullerenes are known for their unique electronic properties including high electron affinity. Although use of fullerenes for scavenging photo-generated electrons from titanium dioxide particles has been demonstrated, no attempts have been made to utilize the unique properties of fullerenes to increase the efficacy of photocatalysis. The present study has demonstrated that a mixture of water-soluble polyhydroxy fullerenes (PHF) and titanium dioxide (anatase polymorph) enhances photocatalytic degradation of organic dye. The PHF molecules adsorbed to the surface of titanium dioxide due to electrostatic forces, with adsorption density being higher at lower pH values. The surface coverage of titanium dioxide nanoparticles by PHF molecules determined the extent of enhancement, with an optimum dosed weight ratio of PHF to titanium dioxide at 0.001. Hydroxylation and concomitant solubilization of fullerenes allow their unique electronic properties to be harnessed for photocatalysis.     

Adsorption of Ni(II) on clays

The present work investigates the adsorptive interactions of Ni(II) ions with kaolinite, montmorillonite, and their poly(oxo zirconium) and tetrabutylammonium derivatives in aqueous medium. Batch adsorption studies were carried out with various Ni(II) concentrations, amount of clay adsorbents, pH, agitation time and temperature. The adsorption is strongly dependent on pH of the medium with enhanced adsorption as the pH turns from acidic to alkaline side till precipitation sets in. The process was very fast initially and maximum adsorption was observed within 180 min of agitation. The kinetics of the interactions, tested with pseudo first order Lagergren equation, second order kinetics, Elovich equation, liquid film diffusion model and intra-particle diffusion mechanism, showed better agreement with second order kinetics (k2 = 1.3 x 10(-2) to 5.3 x 10(-2) g/(mg min)). The adsorption data gave good fits with Langmuir and Freundlich isotherms and yielded Langmuir monolayer capacity of 2.75 to 21.14 mg/g and Freundlich adsorption capacity of 0.70 to 3.40 mg(1-1/n) l(1/n)/g for the clay adsorbents. The adsorption process was exothermic with Delta H in the range of -24.0 to -45.1 kJ/mol accompanied by decrease in entropy (DeltaS: -118.2 to -160.5 J/(mol K)) and Gibbs energy (Delta G: -34.6 to -49.5 kJ/mol). The results have shown that montmorillonite has the largest adsorption capacity followed by ZrO-montmorillonite, TBA-montmorillonite, kaolinite, ZrO-kaolinite and TBA-kaolinite. Introduction of ZrO- and TBA- groups into the clays reduced their adsorption capacity by blocking the available adsorption sites.     

Solid state structural evidence of chloroform-benzene-chloroform adduct trapped in hexaanthryl octaaminocryptand channels

Structural aspects governing the formation and stabilization of adducts in the organic channels were examined. An unprecedented structural evidence of an inverted sandwich-type benzene/chloroform (1:2) adduct was isolated within the channel formed by close packing of an aromatic substituted aminocryptand 1 host. Interestingly, this adduct was stabilized through several short contacts with the channel wall. Crystallographic study further showed that a channel formed by self-assembly of 1 can also encapsulate chloroform as a guest. Thermal analysis confirms that the chloroform-benzene-chloroform adduct as a guest has better thermal stability than that of the chloroform guest within the channel.