Bacteriorhodopsin as an electronic conduction medium for biomolecular electronics

Interfacing functional proteins with solid supports for device applications is a promising route to possible applications in bio-electronics, -sensors, and -optics. Various possible applications of bacteriorhodopsin (bR) have been explored and reviewed since the discovery of bR. This tutorial review discusses bR as a medium for biomolecular optoelectronics, emphasizing ways in which it can be interfaced, especially as a thin film, solid-state current-carrying electronic element.     

Bound donor-acceptor edge luminescence line shapes in CdS

The principal contribution to the linewidth of the bound donor-acceptor luminescence spectra is shown to be due to coupling with the 5.5 meV TO phonon, with electron-phonon strength parameter equal to that of the 38.5 meV LO phonon. By including the Coulomb pair interactions, and in addition a Lorentzian-shaped Coulomb contribution from all other charged defects, excellent agreement with the lineshapes observed in the time-resolved mode is obtained over the entire range of delay times utilized (10 micros – 100 ms) for bulk and platelet samples of various defect concentrations. This permits relating the energy of the observed luminescence line maximum to the pair Coulomb energy corresponding to that delay, resulting in an improved determination of W_o, the donor-acceptor radiative transition rate for complete donor-acceptor wavefunction overlap. The effect of a particular type of heat treatment upon W_o is also presented.     

Molecular weight phenomena at high conversions in the Ziegler–Natta polymerization of butadiene

A Comparison between two different feedstocks in the homogeneous polymerization of butadiene has been conducted. The conversion and molecular weight trends were essentially the same for both feedstock systems. Changes in polydispersity at high conversions could not be explained by a living polymerization mechanism. A reaction scheme involving reuse of active cobalt centres combined with termination has been proposed.     

Heat capacity of pure and doped V2O3 single crystals

Heat capacities have been measured for single crystals of V₂O₃, either pure or doped with 1 and 1.4 mole% Cr₂O₃ and Al₂O₃ over the temperature range 100–700°K. V₂O₃ undergoes a fairly sharp transition at low temperatures (～170°K) but fails to exhibit any thermal anomaly above 300°K. The thermal behavior of (M_xV_1?x)₂O₃, M = Cr, Al, is manifested by two transitions: one at low temperatures, 170–180°K for x = 0.01 and 180–190°K for x = 0.014, and the other at high temperatures. For x = 0.01, the high-temperature (HT) anomaly extended over the range 325–345°K (Cr-doped V₂O₃) and 345–365°K (Al-doped V₂O₃), respectively. The corresponding ranges for x = 0.014 were found to be 260–280°K and 270–290°K, respectively. Further, the HT anomaly was characterized by a large hysteresis (～50°K). The values of lattice heat capacity of pure and doped V₂O₃ were, however, found to be almost the same and could be empirically represented by the Debye (D)?Einstein (E) function $\text{D}\text{(}\text{580}\text{T}\text{) + 4}\text{E}\text{(}\text{θ}\text{T}\text{)}$ with θ values 430°K (T = 100–230°K) and 465°K (T > 230°K), respectively. Further, the enthalpy change ΔH associated with the HT anomaly in doped V₂O₃ (80 ≤ ΔH ≤ 510 J/mole) was 5–10 times smaller than the ΔH corresponding to the lower-temperature transition. The results cited here appear incompatible with the Mott transition model that has been invoked to explain the HT anomaly.     

Nonstoichiometry and defects in V2O3

The structural mechanism which accommodates nonstoichiometry in V₂O₃ was investigated by transmission electron microscopy. The existence of distinct diffuse scattering was observed as the boundary of the homogeneity range was approached. The analysis of the diffuse scattering indicates the formation of one-dimensional microdomains in the c direction having a structure similar to VO₂. Orientation relations between V₂O₃ and V₃O₅ (which is formed from V₂O₃ by heat treatment in an oxidizing atmosphere) show that V₃O₅ is formed by redistribution of vanadium ions among the octahedral interstitial sites of common close-packed sublattice consisting of oxygen ions. Possible relations between the present observations and physical properties in nonstoichiometric V₂O_3+x are discussed.