Measurement of angular distributions by use of low-coherence interferometry for light-scattering spectroscopy

We present a novel interferometer for measuring angular distributions of backscattered light. The new system exploits a low-coherence source in a modified Michelson interferometer to provide depth resolution, as in optical coherence tomography, but includes an imaging system that permits the angle of the reference field to be varied in the detector plane by simple translation of an optical element. We employ this system to examine the angular distribution of light scattered by polystyrene microspheres. The measured data indicate that size information can be recovered from angular-scattering distributions and that the coherence length of the source influences the applicability of Mie theory.     

A New Strategy to Exfoliate Silicone Rubber/Clay Nanocomposites

Summary: A new strategy was developed to prepare disorderly exfoliated nanocomposites, in which a soft siloxane surfactant with a weight‐average molecular weight ( ) of 1 900 was adopted to modify the clay. The modified clay slurry was then mixed with silicone rubber by hand, and exfoliation was achieved. The proposed mechanism thereof was verified by TEM and XRD. The physical entanglement of the soft siloxane surfactant plays a vital role in the diffusion and intercalation of the matrix molecules during the compounding of the slurry‐polymer mixture. This simple method is applicable to other silicone‐based materials reinforced by clay.

TEM micrograph of silicone rubber/clay‐sil nanocomposite.     

Novel high birefringent isothiocyanates based on quaterphenyl and phenylethynyltolane molecular cores

We report the synthesis of new laterally alkyl substituted high birefringent quaterphenyl and phenylethynyltolane liquid crystals with isothiocyanate terminal group. The thermal and optical properties such as birefringence are measured and discussed based on their molecular structures. The compounds exhibit birefringence (Δn) in the range of 0.44–0.63, and are expected to be appropriate components of high birefringent nematic mixtures for various applications.     

Separation and determination of synthetic impurities of sildenafil (Viagra) by reversed-phase high-performance liquid chromatography.

A simple and rapid high-performance liquid chromatographic method for the separation and determination of process-related impurities of sildenafil was developed. The separation was achieved on a reversed-phase C18 column using acetonitrile-0.05 M potassium dihydrogen orthophosphate (70:30 v/v) as a mobile solvent at a flow rate of 1.0 ml/min and UV detection at 230 nm. The method was used not only for quality assurance, but also for monitoring the chemical reactions during the synthesis of sildenafil. It was found to be specific, precise and reliable for the determination of all process-related impurities of sildenafil in bulk drugs and formulations.     

Hydrogen switches and sensors fabricated by combining electropolymerization and Pd electrodeposition at microgap electrodes

Here we describe a simple electrochemical approach to fabricate devices which behave as hydrogen sensors and switches. Devices fabricated by the electrodeposition of Pd directly across a 5 microm gap interdigitated array (IDA) of gold electrodes behaved as "hydrogen sensors". These devices had initial currents on the 10(-3) A level at -0.3 V and exhibited fast and reversible decreases in current in the presence of H(2) concentrations in a N(2) carrier gas with an average detection limit of 400 ppm. The current decrease is due to the formation of the more resistive PdH(x) in the presence of H(2). Devices fabricated by polyphenol electropolymerization on one set of electrodes and Pd electrodeposition on the other set behaved as "hydrogen switches". These devices displayed very low baseline currents of 10-100 pA at -0.3 V due to the presence of polphenol in the Electrode1/Pd/Polyphenol/Electrode 2 junction, and the current increased a remarkable 7-8 orders of magnitude in the presence of > or = 1.0% H(2) due to volume expansion upon PdH(x) formation, which leads to a direct connection between Pd (as PdH(x)) and Electrode 2 through the porous 4-10 nm thick polyphenol insulating film. The response and recovery time for the "hydrogen sensor" ranged from 20 to 60 s while that for the "hydrogen switch" ranged from 10 to >100 s. The response and recovery time generally decreased for the "hydrogen switch" as the number of polyphenol electrochemical cycles decreased.     

Design,Synthesis, and Antimicrobial Activity of (E)-4-Phenyl-2H-chromene-3-carbaldehyde O-[(1-Phenyl-1H-1,2,3-triazol-4-yl)methyl]oxime Derivatives

Russian Journal of Organic Chemistry - A new series of 1,4-disubstituted 1,2,3-triazole derivatives tethered to a 2H-chromene scaffold have been synthesized via a click reaction. The synthesized...     

Fresnel particle tracing in three dimensions using diffraction phase microscopy

We have developed a novel experimental technique for tracking small particles in three dimensions with nanometer accuracy. The longitudinal positioning of a micrometer-sized particle is determined by using the Fresnel approximation to describe the transverse distribution of the wavefront that originated in the particle. The method utilizes the high-sensitivity quantitative phase imaging capability of diffraction phase microscopy recently developed in our laboratory. We demonstrate the principle of the technique with experiments on Brownian particles jittering in water both in bulk and in the vicinity of a boundary. The particles are localized in space within an error cube of 20 nm x 20 nm x 20 nm for a 33 Hz acquisition rate and 20s recording time.     

Tissue refractometry using Hilbert phase microscopy

We present, for the first time to our knowledge, quantitative phase images associated with unstained 5 mum thick tissue slices of mouse brain, spleen, and liver. The refractive properties of the tissue are retrieved in terms of the average refractive index and its spatial variation. We find that the average refractive index varies significantly with tissue type, such that the brain is characterized by the lowest value and the liver by the highest. The spatial power spectra of the phase images reveal power law behavior with different exponents for each tissue type. This approach opens a new possibility for stain-free characterization of tissues, where the diagnostic power is provided by the intrinsic refractive properties of the biological structure. We present results obtained for liver tissue affected by a lysosomal storage disease and show that our technique can quantify structural changes during this disease development.     

Green and ecofriendly synthesis of indole-condensed benzimidazole chalcones in water and their antimicrobial evaluations

An ecofriendly synthesis of novel benzimidazole-substituted indole derivatives catalyzed by ZnO nanoparticles has been developed from simple condensation of acetyl benzimidazole and indole-3-carbaldehyde followed by Michael addition of indoles. This ZnO Nano particles (NP)-catalyzed reaction has been carried out using both step-wise and one-pot methods, and both these methods provide excellent yield of product and less reaction time in water. All the synthesized compounds were characterized by Infrared spectroscopy (IR), Proton Nuclear Magnetic Resonance spectroscopy (Proton NMR), Carbon-13 Proton Nuclear Magnetic Resonance spectroscopy (¹³C-NMR), and mass analysis and screened for their antibacterial activity against clinical strains that include Gram-positive and Gram-negative bacteria.