Interfacial differences in enhanced schottky barrier height Au/n-GaAs diodes deposited at 77 K

The use of cryogenic temperatures (∼77 K) during Au Schottky contact deposition onto n-GaAs produces an increase in barrier height from 0.73 eV for room temperature diodes to 0.82 eV. Not all Schottky metals show this enhancement—for example Pt and Ti do not show any significant change in barrier height whereas Au, Pd and Ni show increases between 7 and 18%. We used X-ray reflectivity to show that the main difference between Au deposited at 77 K and room temperature is a decreased metal roughness while the interfacial roughness between the Au and GaAs is basically the same. As the diodes are annealed to 300 °C both the difference in barrier height and interfacial roughness is lost. This is a simple method with potential for improving the performance of GaAs metal-semiconductor-field-effect-transistors (MESFETs).     

Transfection and imaging of diamond nanocrystals as scattering optical labels

We report on the first demonstration of nanodiamond (ND) as a scattering optical label in a biological environment. NDs were efficiently transfected into cells using cationic liposomes, and imaged using differential interference and Hoffman modulation ‘space’ contrast microscopy techniques. We have shown that 55 nm NDs are biologically inert and produce a bright signal compared to the cell background. ND as a scattering label presents the possibility for extended biological imaging with relatively little thermal or biochemical perturbations due to the optical transparency and biologically inert nature of diamond.     

Polymersome‐forming amphiphilic glycosylated polymers: Synthesis and characterization

Copper‐catalyzed azide‐alkyne cycloaddition (CuAAC) was used to prepare glycosylated polyethylene (PE)–poly(ethylene glycol) (PEG) amphiphilic block copolymers. The synthetic approach involves preparation of alkyne‐terminated PE‐b‐PEG followed by CuAAC reaction with different azide functionalized sugars. The alkyne‐terminated PE‐b‐PEG was prepared by etherification reaction between hydroxyl‐terminated PE‐b‐PEG (M_n ～ 875 g mol^?1) and propargyl bromide and azidoethyl glycosides were prepared by glycosylation of 2‐azidoethanol. Atmospheric pressure solids analysis probe‐mass spectrometry was used as a novel solid state characterization tool to determine the outcome of the CuAAC click reaction and end‐capping of PE‐b‐PEG by the azidoethyl glycoside group. The aqueous solution self‐assembly behavior of these amphiphilic glycosylated polymers was explored by TEM and dye solubilization studies. Carbohydrate‐bearing spherical aggregates with the ability to solubilize a hydrophobic dye were observed. The potential of these amphiphilic glycosylated polymers to self‐assemble via electro‐formation into giant carbohydrate‐bearing polymersomes was also investigated using confocal fluorescence microscopy. An initial bioactivity study of the carbohydrate‐bearing aggregates is furthermore presented. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 5184–5193     

1H AND 31P NMR Spectroscopy of Agrocinopine

The ¹H NMR data of agrocinopine in D₂O solution as extracted from standard 2D NMR experiments, along with 1D ³¹P and ¹³C NMR experiments allow to support the trisaccharide structure originally proposed on basis of comparative ¹³C NMR measurements.     

Characterization of Standard Reference Material 2942, Ce-ion-doped glass, spectral correction standard for UV fluorescence

Standard Reference Material (SRM) 2942 is a cuvette-shaped, Ce-ion-doped glass, recommended for use for relative spectral correction of emission from 320 to 430 nm and day-to-day performance verification of steady-state fluorescence spectrometers. Properties of this standard that influence its effective use or contribute to the uncertainty in its certified emission spectrum were explored here. These properties include its photostability, absorbance, dissolution rate in water, anisotropy and temperature coefficient of fluorescence intensity. The expanded uncertainties in the certified spectrum are about 9% around the peak maximum at 330 nm, using an excitation wavelength of 310 nm. The SRM also exhibits a strong resistance to photodegradation, with no measurable decrease in fluorescence intensity even after 25 h of irradiation with UV light>280 nm from a Xe lamp.     

Synthesis and Crystal Structure of an Organic-Polyoxometalate (POM) Hybrid Compound Containing a Keggin Type Mo–Si Polyanion

Abstract  

Complex (1), which is comprised of a typical Keggin type anion, four protonated 3-amino-1,2,4-triazole (AmTAZ) ligands, one nitrate anion and an area of disordered unidentifiable species was synthesized via hydrothermal methods followed by slow evaporation. The structure is held together through a web of hydrogen bonding and crystallizes in the monoclinic space group P2₁/c with unit cell dimensions of a = 13.789(3) b = 15.551(3) c = 24.401(7) ?, β = 93.898(8)°, V = 5220(2) ?³ Z = 4, D = 2.896 Mg/m³.