A General and Efficient Synthesis of 2-Phenylbenzothiazoles From Diphenyl Disulfides

Benzothiazoles containing a substituted-phenyl at the 2 position can be synthesized cleanly and efficiently from the corresponding bis(2-aminophenyl) disulfide. Bis(2-aminophenyl) disulfides represent a stable source of 2-aminobenzenethiols.     

Adsorption of IgG on/in a PAH/PSS multilayer film: Layer structure and cell response

The binding of immunogloblulins (IgG) (mouse monoclonal recognizing IFNγ) on precoated polystyrene or silica surfaces by the layer-by-layer technique has been investigated with QCM-D and DPI. The aim of the work was to increase the sensitivity of the conventional enzyme-linked immunosorbent spot (ELISpot) assay. The polyelectrolytes used to build the multilayers were poly(allylamine hydrochloride) (PAH)/poly(sodium 4-styrenesulfonate) (PSS) alternately adsorbed from 150mM NaCl. The multilayer build up is linear and the internal structure of the PAH/PSS multilayer is compact and rigid as observed by low relative water content (20-25%) and high layer refractive index (n～1.5) after the formation of five bilayers. Incorporation of IgG within the PAH/PSS multilayer did not give rise to overcharging and did not affect the linear build up. ELISpot test on PAH/PSS multilayer modified polystyrene wells showed that the cytokine response was significantly smaller than on the regular PVDF backed polystyrene wells. This may be due to the compact and rigid nature of the PAH/PSS multilayer, which does not allow formation of the kind of three dimensional support needed to achieve bioactive IgG binding to the surface. Immunological tests of the polyelectrolyte multilayers in the absence of IgG showed that PSS terminated PAH/PSS multilayer did not induce any cytokine response whereas PAH terminated did, which suggests that PSS totally covers the surface from the cells point of view.     

Field-based angle-resolved light-scattering study of single live cells

We perform field-based angle-resolved light-scattering measurements from single live cells. We use a laser interferometer to acquire phase and amplitude images of cells at the image plane. The angular scattering spectrum is calculated from the Fourier transform of the field transmitted through the cells. A concurrent 3D refractive index distribution of the same cells is measured using tomographic phase microscopy. By measuring transient increases in light scattering by single cells during exposure to acetic acid, we correlate the scattering properties of single cells with their refractive index distributions and show that results are in good agreement with a model based on the Born approximation.     

Confocal diffraction phase microscopy of live cells

We present a new quantitative phase microscopy technique, confocal diffraction phase microscopy, which provides quantitative phase measurements from localized sites on a sample with high sensitivity. The technique combines common-path interferometry with confocal microscopy in a transmission geometry. The capability of the technique for static imaging is demonstrated by imaging polystyrene microspheres and live HT29 cells, while dynamic imaging is demonstrated by quantifying the nanometer scale fluctuations of red blood cell membranes.     

Light-emitting diodes based on poly(2,3-diphenyl-1,4-phenylene vinylene)

In this paper we report polymer light-emitting diodes based on (2,3-diphenyl-1,4-phenylene vinylene) (DP-PPV), a novel π-conjugated polymer made by using the chlorine precursor route (CPR). Thin films of the precursor polymer were formed by spin-casting on indium-tin oxide (ITO) coated glass substrates, followed by thermal conversion to give DP-PPV thin films. Single layer DP-PPV LEDs were completed by thermally evaporating magnesium (Mg) electrodes. The electroluminescent characteristics of ITO/DP-PPV/Mg devices as well as variations between precursor polymer batches are presented. Bilayer LEDs were also made, for which tris(8-hydroxyquinoline)aluminum (Alq₃) was thermally sublimed on the fully converted DP-PPV films in vacuum, followed by Mg deposition. Both significant improvement in the quantum efficiency (up to 0.7% ph/el) and a reduction in the turn-on voltage of the device were found upon incorporation of the Alq₃ layer. These observations suggest that Alq₃ enhances the injection of electrons and also participates in the recombination process. © 1997 John Wiley & Sons, Ltd.