We demonstrate the use of "click" chemistry to form electrochemically and photoelectrochemically active molecular interfaces to SnO(2) nanoparticle thin films. By using photochemical grafting to link a short-chain alcohol to the surface followed by conversion to a surface azide group, we enable use of the Cu(I)-catalyzed azide-alkyne [3 + 2] cycloaddition (CuAAC) reaction, a form of "click" che...

Time-resolved optical measurements encompassing the femtoseconds to seconds time scales have been used to investigate Rhodobacter capsulatus reaction centers (RCs) in which the histidine residue at position 200 on the M polypeptide has been changed to a leucine by site-directed mutagenesis. The HisM200----Leu RC, which has a heterodimer consisting of a bacteriochlorophyll and a bacteriopheophyt...

It is generally accepted that electron transfer in bacterial photosynthesis is driven by the first singlet excited state of a special pair of bacteriochlorophylls (P*). We have examined the first steps of electron transfer in a mutant of the Rhodobacter sphaeroides reaction center in which charge separation from P* is dramatically slowed down. The results provide for the first time clear eviden...

Charge transfer mechanisms lay at the heart of chemistry and biochemistry. Proton coupled electron transfers (PCET) are central in biological processes such as photosynthesis and in the respiratory chain, where they mediate long-range charge transfers. These mechanisms are normally difficult to harness experimentally due to the intrinsic complexity of the associated biological systems. Metal-pe...

This study addresses the free energy dependence of charge recombination following photoinduced bimolecular electron transfer in three different solvents of either inert (acetonitrile and benzyl acetate) or reactive (N,N-dimethylaniline) character. Femtosecond time-resolved fluorescence and transient absorption have been used to determine the time scales for charge recombination. In pure N,N-dim...

A novel white light-promoted reaction using photoluminescent nanocrystalline silicon enables the hydrosilylation of alkenes and alkynes, providing stabilization of the porous silicon without significant loss of the photoemissive qualities of the material. Photopatterning and lithographic fabrication of isolated porous silicon structures are made possible. Experiments and observations are presen...

Photon echo, photon-echo excitation, and "hole-burning" data recorded in the 800-990 nm region of Rhodobacter sphaeroides R26 and Rhodopseudomonas viridis reaction centers are reported. The primary process in these reaction centers, following excitation, was found to occur in approximately 25 fsec; the long-wavelength band of the primary electron donor (P) was largely homogeneously broadened. I...

Ethanol concentration dependence of photoinduced charge separation between zinc tetraphenylporphyrin (ZnTPP) and duroquinone (DQ) in benzonitrile was studied by nanosecond laser flash photolysis. Acceleration of the photoinduced charge separation reaction rate by hydrogen bonding between DQ anion radical and ethanol was observed. A simple analysis in the framework of the Marcus theory indicated...

In the present work, the sensitivity to the moisture (hygroscopisity) is studied for 3,4-dinitropyrazole (DNP) as a famous energetic molecule. All of the DNP-H2O complex systems (1-3) as well as individual molecules were optimized and bond lengths, bond angles, dihedral angles, charge transfer and stability via NBO analysis, corrected interaction energies with ZPE + BSSE and hydrogen bonds anal...