LC Determination of trans-3,5,3′,4′,5′-Pentamethoxystilbene in Rat Plasma

A simple LC method has been developed and validated to determine trans-3,5,3′,4′,5′-pentamethoxystilbene (PMS) in rat plasma. Chromatographic separation was achieved through gradient delivery of acetonitrile and water (1.5 mL min^?1) at 50 °C. PMS was quantified using UV detection at 320 nm. The standard curve ranged from 15 to 1,500 ng mL^?1. The intra- and inter-day precisions, in terms of CV, were all less than 10% while the inter-day and intra-day bias ranged from ?6.8 to 8.3%. The plasma PMS levels were monitored in Sprague-Dawley rats after drug administration. This simple LC method appears to be useful in the pharmacokinetic investigation of PMS.     

SERS-based immunoassay using a gold array-embedded gradient microfluidic chip

Here we report the development of a programmable and fully automatic gold array-embedded gradient microfluidic chip that integrates a gradient microfluidic device with gold-patterned microarray wells. This device provides a convenient and reproducible surface-enhanced Raman scattering (SERS)-based immunoassay platform for cancer biomarkers. We used hollow gold nanospheres (HGNs) as SERS agents because of their highly sensitive and reproducible characteristics. The utility of this platform was demonstrated by the quantitative immunoassay of alpha-fetoprotein (AFP) model protein marker. Our proposed SERS-based immunoassay platform has many advantages over other previously reported SERS immunoassay methods. The tedious manual dilution process of repetitive pipetting and inaccurate dilution is eliminated with this process because various concentrations of biomarker are automatically generated by microfluidic gradient generators with N cascade-mixing stages. The total assay time from serial dilution to SERS detection takes less than 60 min because all of the experimental conditions for the formation and detection of immunocomplexes can be automatically controlled inside the exquisitely designed microfluidic channel. Thus, this novel SERS-based microfluidic assay technique is expected to be a powerful clinical tool for fast and sensitive cancer marker detection.     

Unimolecular ligand-initiator dual functional systems (ULIS) for low copper ATRP of vinyl monomers including acrylic/methacrylic acids

A novel approach for ATRP has been developed which enables the polymerization of vinyl monomers including those bearing carboxylic acid groups such as acrylic/methacrylic acid in the free acid form with ppm amounts of copper. The quantity of copper used in the polymerization is comparable to those left in purified polymers obtained by a conventional ATRP process.     

N-Acyliminium ion cyclizations of trimethylsilylmethylallenes

N-Acyliminium ion cyclizations were studied with allenylmethylsilanes to synthesize nitrogen heterocycles. N-Acyliminium ion cyclizations were carried out by exposure of precursors 6 and 7 to Lewis acid. The precursors 6 were converted to pyrrolizidinone derivatives 9 with an exo-allene moiety, while the precursors 7 to indolizidinone derivatives 10 with an exo-1,3-diene moiety.     

Recording and reconstruction of digital Gabor hologram

This paper looks at some as yet undisclosed observations in the recording and reconstruction of digital Gabor hologram. Small particles on the specimen plane diffract the illuminating spherical wave to form the object wave which interferes with the un-diffracted reference to form the in-line hologram. The interference is similar to that between two spherical wavefronts. It is shown that resolution enhancement can be achieved in the recording process through the use of wavefronts with different curvature. Numerical reconstruction of this hologram with a conjugate of the illuminating (reference) wave provides the in-focus real image at the object plane. It is exemplified that the proper choice of the reconstruction wavefront can optically magnify the reconstructed image enabling one to better visualize the resolution enhancement. Both theoretical analysis and experimental confirmation are provided for these observations.     

Deposition of potassium-oxygen on silicon surfaces by pulsed laser ablation of potassium superoxide: Study of work function changes

Potassium-oxygen species were deposited on pure, Si nanoparticles coated and H-terminated Si nanoparticles coated p-Si(1 0 0) surfaces by pulsed laser ablation of potassium superoxide (KO₂) target. The deposition properties, composition and the work function changes of the deposited species were investigated in situ using an X-ray photoelectron spectroscopy (XPS) and a Kelvin probe measurement. The deposited species were assigned to K₂O₂ and KO₂, and they can be selectively deposited by controlling the laser fluence: i.e., at 200 mJ/cm² and at those more than 300 mJ/cm², respectively. Experimental results showed that the work function decreased drastically with depositing of KO_x (x = 1 or 2), and the minimum work function values observed were 1.0 eV and 0.7 eV for pure p-Si(1 0 0) and Si nanoparticles coated substrates, respectively. The study demonstrates the formation of the surface species with minimum work function can be identified by XPS.     

Optical and magnetic properties of laser-deposited Co-doped ZnO thin films

We report the optical and magnetic properties of laser-deposited Zn_1−xCo_xO (x=0.06-0.3) thin films with no intentional electrical carrier doping. The analysis of the high-temperature magnetization data provides an unambiguous evidence that antiferromagnetic superexchange interaction is the dominant mechanism of the exchange coupling between Co ions in Zn_1−xCo_xO alloy, yielding the value of the effective exchange integral J₁/k_B to be about −27 K. The low-temperature magnetization data reveals a spin glass transition in Zn_1−xCo_xO alloy for the Co content x>0.15, giving the value of the spin freezing temperature T_f to be ∼8 and ∼12 K for x=0.2 and 0.25, respectively. Optical spectra analysis shows a linear increase of the band gap E_g with the increase of the Co content following E_g=3.231+1.144x eV.     

Physical Continuity and Vertical Alignment of Block Copolymer Domains by Kinetically Controlled Electrospray Deposition

The fabrication of block copolymer (BCP) thin films is reported with vertically aligned cylindrical domains using continuous electrospray deposition onto bare wafer surfaces. The out‐of‐plane orientation of hexagonally packed styrene cylinders is achieved in the “fast‐wet” deposition regime in which rapid evaporation of the solvent in deposited droplets of polymer solution drives the vertical alignment of the self‐assembled structure. Thermally activated crosslinking of the polybutadiene matrix provides kinetic control of the morphology, freezing the vertical alignment and preventing relaxation of the system to its preferred parallel orientation on the nontreated substrate. Physically continuous vertically oriented domains can be achieved over several micrometers of film thickness. The ability of electrospray deposition to fabricate well‐ordered and aligned BCP films on nontreated substrates, the low amount of material used relative to spin‐coating, and the continuous nature of the deposition may open up new opportunities for BCP thin films.

     

Modeling manganese removal in chelating polymer-assisted membrane separation systems for water treatment

The removal of manganese from groundwater, using water-soluble chelating polymers such as polyacrylic acid (PAA) in combination with ultrafiltration (UF), was investigated. The effects of the solution pH and polymer dosages on the manganese removal were evaluated, and the removal efficiency was modeled considering the relevant chemical equilibria. In the absence of polymer, manganese removal with UF membranes alone was negligible at acidic pH values, but the removal increased substantially when polyacrylic acid (PAA) was added to the feed solution. The increase can be attributed to the formation of Mn²⁺–PAA chelates which are rejected by the membranes. A mathematical model was developed to explain this phenomenon based on chemical equilibria, including complex formation and precipitation. The chelation number (i.e., the number of carboxyl groups in the PAA binding to a single metal ion) and the equilibrium constants for metal–PAA chelation reactions were obtained by fitting experimental data at acidic pH in single-divalent metal systems. The model was able to predict Mn removal in chelation/UF systems at various pH levels and polymer dosages, and to account for the competitive interactions of PAA with the target (Mn²⁺) and background species (Ca²⁺, Mg²⁺) in multi-component systems. The predicted Mn removal efficiency was most sensitive to the chelation number.