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  1. Catechol-based materials possess diverse properties that are especially well-suitable for redox-based bioelectronics. Previous top-down, systems-level property measurements have shown that catechol-polysaccharide films ( e.g. , catechol-chitosan films) are redox-active and allow electrons to flow through the catechol/quinone moieties via thermodynamically-constrained redox reactions. Here, we report that catechol-chitosan films are also photothermally responsive and enable near infrared (NIR) radiation to be transduced into heat. When we simultaneously stimulated catechol-chitosan films with NIR and redox inputs, times-series measurements showed that the responses were reversible and largely independent. Fundamentally, these top-down measurements suggest that the flow of energy through catechol-based materials via the redox-based molecular modality and the electromagnetic-based optical modality can be independent. Practically, this work further illustrates the potential of catecholic materials for bridging bio-device communication because it enables communication through both short-range redox modalities and long-range electromagnetic modalities.
    Free, publicly-accessible full text available May 16, 2023
  2. Abstract

    Eumelanin is a brown-black biological pigment with sunscreen and radical scavenging functions important to numerous organisms. Eumelanin is also a promising redox-active material for energy conversion and storage, but the chemical structures present in this heterogeneous pigment remain unknown, limiting understanding of the properties of its light-responsive subunits. Here, we introduce an ultrafast vibrational fingerprinting approach for probing the structure and interactions of chromophores in heterogeneous materials like eumelanin. Specifically, transient vibrational spectra in the double-bond stretching region are recorded for subsets of electronic chromophores photoselected by an ultrafast excitation pulse tuned through the UV-visible spectrum. All subsets show a common vibrational fingerprint, indicating that the diverse electronic absorbers in eumelanin, regardless of transition energy, contain the same distribution of IR-active functional groups. Aggregation of chromophores diverse in oxidation state is the key structural property underlying the universal, ultrafast deactivation behavior of eumelanin in response to photoexcitation with any wavelength.

  3. The ability to characterize and control the energy and charge transfer events triggered by the photoexcitation of molecules and materials is of fundamental importance to many fields, including the sustainable capture and conversion of solar energy. This article summarizes the papers that were presented and discussed at the recent Faraday discussion meeting on ultrafast photoinduced energy and charge transfer. Ultrafast laser spectroscopy and theory were at the center of discussions on photoinduced phenomena in biological and nanoscale systems of interacting absorbers. Many of the questions that motivate this field of science have occupied scientists for many decades, as a look back to a Faraday discussion meeting that took place 60 years earlier reveals.
  4. Changing the solvent from H 2 O to D 2 O dramatically affects the branching of the initial excited electronic states in an alternating G·C DNA duplex into two distinct decay channels. The slower, multisite PCET channel that deactivates more than half of all excited states in D 2 O becomes six times weaker in H 2 O.