Maria-Elisabeth Michel-Beyerle

Bio: Maria-Elisabeth Michel-Beyerle is an academic researcher from Technische Universität München. The author has contributed to research in topics: Electron transfer & Photosynthetic reaction centre. The author has an hindex of 44, co-authored 130 publications receiving 7360 citations. Previous affiliations of Maria-Elisabeth Michel-Beyerle include Munich University of Applied Sciences.

Charge Transfer on the Nanoscale: Current Status

Abstract: This is the report of a DOE-sponsored workshop organized to discuss the status of our understanding of charge-transfer processes on the nanoscale and to identify research and other needs for progress in nanoscience and nanotechnology. The current status of basic electron-transfer research, both theoretical and experimental, is addressed, with emphasis on the distance-dependent measurements, and we have attempted to integrate terminology and notation of solution electron-transfer kinetics with that of conductance analysis. The interface between molecules or nanoparticles and bulk metals is examined, and new research tools that advance description and understanding of the interface are presented. The present state-of-the-art in molecular electronics efforts is summarized along with future research needs. Finally, novel strategies that exploit nanoscale architectures are presented for enhancing the efficiences of energy conversion based on photochemistry, catalysis, and electrocatalysis principles.

Charge transfer and transport in DNA

Abstract: We explore charge migration in DNA, advancing two distinct mechanisms of charge separation in a donor (d)–bridge ({Bj})–acceptor (a) system, where {Bj} = B1,B2, … , BN are the N-specific adjacent bases of B-DNA: (i) two-center unistep superexchange induced charge transfer, d*{Bj}a → d∓{Bj}a±, and (ii) multistep charge transport involves charge injection from d* (or d+) to {Bj}, charge hopping within {Bj}, and charge trapping by a. For off-resonance coupling, mechanism i prevails with the charge separation rate and yield exhibiting an exponential dependence ∝ exp(−βR) on the d-a distance (R). Resonance coupling results in mechanism ii with the charge separation lifetime τ ∝ Nη and yield Y ≃ (1 + δ Nη)−1 exhibiting a weak (algebraic) N and distance dependence. The power parameter η is determined by charge hopping random walk. Energetic control of the charge migration mechanism is exerted by the energetics of the ion pair state d∓B1±B2 … BNa relative to the electronically excited donor doorway state d*B1B2 … BNa. The realization of charge separation via superexchange or hopping is determined by the base sequence within the bridge. Our energetic–dynamic relations, in conjunction with the energetic data for d*/d− and for B/B+, determine the realization of the two distinct mechanisms in different hole donor systems, establishing the conditions for “chemistry at a distance” after charge transport in DNA. The energetic control of the charge migration mechanisms attained by the sequence specificity of the bridge is universal for large molecular-scale systems, for proteins, and for DNA.

Long-range charge hopping in DNA.

Abstract: The fundamental mechanisms of charge migration in DNA are pertinent for current developments in molecular electronics and electrochemistry-based chip technology. The energetic control of hole (positive ion) multistep hopping transport in DNA proceeds via the guanine, the nucleobase with the lowest oxidation potential. Chemical yield data for the relative reactivity of the guanine cations and of charge trapping by a triple guanine unit in one of the strands quantify the hopping, trapping, and chemical kinetic parameters. The hole-hopping rate for superexchange-mediated interactions via two intervening AT base pairs is estimated to be 109 s−1 at 300 K. We infer that the maximal distance for hole hopping in the duplex with the guanine separated by a single AT base pair is 300 ± 70 A. Although we encounter constraints for hole transport in DNA emerging from the number of the mediating AT base pairs, electron transport is expected to be nearly sequence independent because of the similarity of the reduction potentials of the thymine and of the cytosine.

Correction: Corrigendum: Elucidating the role of disorder and free-carrier recombination kinetics in CH 3 NH 3 PbI 3 perovskite films

Abstract: Nature Communications 6: Article number: 8903 (2015); Published: 30 July 2015; Updated: 10 March 2016 This article contains errors in the units used for carrier mobility. In Fig. 2a–d, the units on the y axis should be ‘cm2V−1s−1’ not ‘V−1s−1cm−1’. Similarly, the second and third sentences of the second paragraph of the ‘Quantum yield calculation’ section should read ‘From Fig.

Time-resolved spectroscopy of wild-type and mutant Green Fluorescent Proteins reveals excited state deprotonation consistent with fluorophore-protein interactions

Abstract: Recently steady-state and picosecond time-resolved absorption and fluorescence spectroscopy on the Green Fluorescent Protein (GFP) have been interpreted by a mechanism where the key process is an excited state deprotonation of the chromophore (M. Chattoraij, B.A. King, G.U. Bublitz and S.G. Boxer, Proc. Natl. Acad. Sci. USA, 93 (1996) 8362–8367). Such a conclusion was borne out by the mirror image of the picosecond decay of the protonated species RH∗ in the blue and the concomitant picosecond rise of the green fluorescence of the deprotonated fluorophore R−∗ as well as the significant slowing of both kinetic features upon deuteration. We report similar experiments confirming this mechanism. The results of ultrafast spectroscopy on wild-type GFP together with two important mutants combined with the recent crystal structures are shown to shed more light on the interplay between absorption and emission phenomena in GFP. Beyond some differences with previous results pertaining, for instance, to the assignment of vibronic progressions in absorption spectra and the temperature dependence of excited state deprotonation, several new features have been identified. These concern the deprotonated ground state R− in equilibrium as well as the excited state RH∗. In particular, we have studied the distributed fluorescence kinetics in the time and frequency domain, excited state absorption features observed in femtosecond time-resolution, and the dependence of excited state proton transfer kinetics on the aggregational state of the protein.

Dye-Sensitized Solar Cells

Abstract: Dye-sensitized solar cells (DSCs) offer the possibilities to design solar cells with a large flexibility in shape, color, and transparency. DSC research groups have been established around the worl ...

The green fluorescent protein

Abstract: In just three years, the green fluorescent protein (GFP) from the jellyfish Aequorea victoria has vaulted from obscurity to become one of the most widely studied and exploited proteins in biochemistry and cell biology. Its amazing ability to generate a highly visible, efficiently emitting internal fluorophore is both intrinsically fascinating and tremendously valuable. High-resolution crystal structures of GFP offer unprecedented opportunities to understand and manipulate the relation between protein structure and spectroscopic function. GFP has become well established as a marker of gene expression and protein targeting in intact cells and organisms. Mutagenesis and engineering of GFP into chimeric proteins are opening new vistas in physiological indicators, biosensors, and photochemical memories.

Plasmonic-metal nanostructures for efficient conversion of solar to chemical energy

Abstract: Recent years have seen a renewed interest in the harvesting and conversion of solar energy. Among various technologies, the direct conversion of solar to chemical energy using photocatalysts has received significant attention. Although heterogeneous photocatalysts are almost exclusively semiconductors, it has been demonstrated recently that plasmonic nanostructures of noble metals (mainly silver and gold) also show significant promise. Here we review recent progress in using plasmonic metallic nanostructures in the field of photocatalysis. We focus on plasmon-enhanced water splitting on composite photocatalysts containing semiconductor and plasmonic-metal building blocks, and recently reported plasmon-mediated photocatalytic reactions on plasmonic nanostructures of noble metals. We also discuss the areas where major advancements are needed to move the field of plasmon-mediated photocatalysis forward.