Temperature dependence of photoinduced electron transfer within self-associated porphyrin: guanine monophosphate complexes

In the current report, the temperature dependence of photoinduced electron transfer between tetrakis-(4-tetramethylpyridyl)porphine (T4MPyP) and guanine monophosphate (GMP) has been examined. In the presence of GMP the fluorescence lifetime analysis reveals a Lorentzian distribution of lifetimes centered at 0.7 ns with a width of 0.9 ns displaying significant temperature dependence. Fitting temperature dependent data to the Marcus equation gives a reorganizational energy (λ) for the electron transfer reaction of 0.6 eV and an electronic coupling factor (H_AB) of 3×10⁻³ eV. These results suggest conformational regulation of electron transfer within the non-covalent porphyrin:nucleotide complex.     

Announcing the Burtin graphic contest winners

The graphics contest announced in Volume 23, Issue 4, of CHANCE asked readers to create a display of a 1951 data set on antibiotic effectiveness. The three winners of the contest are Mark Nicolich, Brian Schmotzer, and Dibyojyoti Haldar. The winners’ graphs are different, yet communicate the same information—each compares the antibiotics and bacteria and succinctly summarizes the influence of the gram staining factor.     

Synthesis of crystalline Ge nanoclusters in PE-CVD-deposited SiO2 films

The synthesis of evenly distributed Ge nanoclusters in plasma-enhanced chemical-vapour-deposited (PE-CVD) SiO₂ thin films containing 8 at. % Ge is reported. This is of importance for the application of nanoclusters in semiconductor technology. The average diameter of the Ge nanoclusters can be controlled in the range of 3–6 nm by variation of the annealing parameters. Using a combination of transmission electron microscopy and Raman-scattering spectroscopy, the nanoclusters were shown to be crystalline. However, photoluminescence measurements showed no light emission that could be definitively correlated to the presence of the nanoclusters. PACS 61.82.Rx; 78.67.Bf; 81.07.Bc     

The influence of oxide/nitride surface layers on diffusion in Si and SiGe

The effect of surface capping on the super- and undersaturation of point defects in Si has been investigated by the diffusion of deep (400 nm) and shallow (200 nm) high concentration profiles of boron grown by molecular beam epitaxy (MBE). Additional information is extracted from the self-diffusion of Ge in the Si-like Si_0.50Ge_0.50-matrix. The objective is to investigate the injection of vacancies and interstitials from surface or bulk with the aim of obtaining inert diffusion conditions . PACS 61.72.Ji; 66.30.-h; 68.55.Ln; 68.35.Dv; 81.65.-b     

Use of β‐cyclodextrins to control the structure of water‐soluble copolymers with hydrophobic parts

In this article, we present the synthesis and characterization of water‐soluble polymers with hydrophobic moieties. The polymers were synthesized in aqueous solutions utilizing β‐cyclodextrins as solubility enhancers to bring the hydrophobic monomers into solution. Polymers were made with different spacing between polymer backbone and phenyl moiety by using styrene, allylbenzene, and 4‐phenyl‐1‐butene as hydrophobic moieties, respectively. The effect of the presence of CDs during synthesis as well as this difference in spacing was investigated by rebinding free β‐CDs to the polymers. The interactions between polymers and CDs were studied by ITC and this revealed some differences between the polymers. Polymers made in the presence of CDs showed a markedly stronger binding to free CDs. The same was observed with polymers with a longer spacing between backbone and phenyl moiety. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6619–6629, 2009