Aqueous photo(electro)catalysis with eumelanin thin films

Migliaccio, Ludovico; Gryszel, Maciej; Đerek, Vedran; Pezzella, Alessandro; Głowacki, Eric Daniel

doi:10.1039/c8mh00715b

Cited by 33 publications

(30 citation statements)

References 38 publications

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“…1 These demands motivated us to explore the possibility of peroxide evolution catalyzed by abundant biomaterials. The present study was guided by recent findings that organic carbonyl dyes 16 and pigments 17 as well as the structurally-related biopolymer eumelanin 18 are photocatalysts for selective reduction of oxygen to peroxide. Lignin shares critical structural features with these proven catalytic speciesnamely aromatic conjugated units with quinone/ hydroquinone redox moieties.…”

Section: Introductionmentioning

confidence: 99%

Photochemical evolution of hydrogen peroxide on lignins

2020

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Section: Introductionmentioning

confidence: 99%

Photochemical evolution of hydrogen peroxide on lignins

2020

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“…Both oxygen reduction reactions are thermodynamically more favorable than hydrogen evolution, with the two-electron peroxide reaction being 700 mV lower than H 2 production. The dominance of the oxygen reduction reaction with organic semiconductors was shown in electrochemical (Warczak et al, 2018;Mitraka et al, 2019), photoelectrochemical (Jakešová et al, 2016;Gryszel et al, 2018a), and photochemical experiments (Gryszel et al, 2018b(Gryszel et al, , 2019 for a wide range of organic semiconductors, including polythiophenes like P3HT, the biopolymer melanin (Migliaccio et al, 2018), and various carbonyl pigments (Gryszel et al, 2018a). The oxygen reduction products are considered reactive oxygen species (ROS) and have numerous physiological effects ranging from toxicity at high concentrations (Huang et al, 2013) to ion channel modulation (Gamper et al, 2006) and signaling effects (Lim et al, 2016) at low concentrations.…”

Section: Photochemical Reactionsmentioning

confidence: 98%

“…In some cases where the highest occupied molecular orbital (HOMO) is sufficiently deep, oxidation of water as the donor is possible. Unfortunately, often self-oxidation of the organic semiconductor itself will serve to complete the photochemical cycle and lead to irreversible corrosion of the organic semiconductor (Gryszel et al, 2018b;Migliaccio et al, 2018). It was experimentally found that the deeper the HOMO, the more stable the semiconductor is with respect to self-oxidation.…”

Section: Photochemical Reactionsmentioning

confidence: 99%

Untangling Photofaradaic and Photocapacitive Effects in Organic Optoelectronic Stimulation Devices

Đerek

Rand

Migliaccio

et al. 2020

Front. Bioeng. Biotechnol.

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Light, as a versatile and non-invasive means to elicit a physiological response, offers solutions to problems in basic research as well as in biomedical technologies. The complexity and limitations of optogenetic methods motivate research and development of optoelectronic alternatives. A recently growing subset of approaches relies on organic semiconductors as the active light absorber. Organic semiconductors stand out due to their high optical absorbance coefficients, mechanical flexibility, ability to operate in a wet environment, and potential biocompatibility. They could enable ultrathin and minimally invasive form factors not accessible with traditional inorganic materials. Organic semiconductors, upon photoexcitation in an aqueous medium, can transduce light into (1) photothermal heating, (2) photochemical/photocatalytic redox reactions, (3) photocapacitive charging of electrolytic double layers, and (4) photofaradaic reactions. In realistic conditions, different effects may coexist, and understanding their role in observed physiological phenomena is an area of critical interest. This article serves to evaluate the emerging picture of photofaradaic vs. photocapacitive effects in the context of our group's research efforts and that of others over the past few years. We present simple experiments which can be used to benchmark organic optoelectronic stimulation devices.

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“…We based the method on our previous work on photocatalysis with organic semiconductor films and particles, [14,22] and for each of the dyes we prepared a set of solutions of different pH and containing different sacrificial electrondonating molecules. We based the method on our previous work on photocatalysis with organic semiconductor films and particles, [14,22] and for each of the dyes we prepared a set of solutions of different pH and containing different sacrificial electrondonating molecules.…”

Section: H 2 O 2 Evolution Experiments With Different Sacrificial Elementioning

confidence: 99%

Water‐Soluble Organic Dyes as Molecular Photocatalysts for H₂O₂ Evolution

Gryszel

Rybakiewicz

Głowacki

2019

Advanced Sustainable Systems

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cousin H 2 . To its advantage, H 2 O 2 forms stable aqueous solutions, [8] and does not require compression and storage as gaseous H 2 does. Photocatalytic evolution of peroxide has proven to be more selective than CO 2 reduction, [9] giving only one product. What is more, the energy accumulated in H 2 O 2 can be utilized directly for electricity generation in a membranefree hydrogen peroxide fuel cell (theoretical V oc = 1.1 V, comparable with the 1.23 V of H 2 fuel cells), which can be made as a single-compartment device based on abundant and inexpensive components. [10,11] Taken together, hydrogen peroxide offers the promise of a carbonfree liquid fuel with high energy density, which can be directly used in fuel cells. The cornerstone in the peroxide energy cycle is photogeneration via a catalyzed reaction of solar irradiation with oxygen and water. Several promising catalytic systems for oxygen reduction to peroxide have been successfully demonstrated. Photocatalysts are used in the form of suspensions of particles varying in size from tens of micrometers to a few nanometers. This convenient strategy allows for using many different materials for this purpose, such as metal oxides, [12] carbon nitride materials, [3,13] or organic semiconductors. [14] Carbon nitrides can be tailored with different organic molecular components that modulate their H 2 O 2 generation efficiency. [3,15] Molecular organic semiconductors, in addition, can be used to produce photocathodes offering high faradaicyield peroxide-generating photoelectrochemical cells. [16][17][18] On the other hand, a fundamental obstacle in all these examples is related to the fact that only the surface of the particle, exposed to the electrolyte, can actively participate in the photo(electro) catalytic process. The part of the material making up the particle core is inactive. The larger the average particle size, the higher the resulting inefficiency of the catalyst utilization. This issue can be considered more acute for the situation of oxygen reduction in aqueous medium since the low solubility of O 2 in water enforces a strict diffusion limit on the efficiency of photochemical oxygen reduction. A thought experiment therefore is: if the photocatalytic material is broken up to into smaller units, what happens when the material is divided into molecular form and dissolved in aqueous media? This is the question central to beginning the present work. Can the constituent molecules of the organic semiconductors reported to date for catalyzing peroxide evolution be photocatalytically active? It can be hypothesized that the molecule is intrinsically Photochemical generation of hydrogen peroxide via oxygen reduction is a critical component of emerging sustainable energy conversion concepts. Light-absorbing semiconductors as well as electrodes modified with sensitizers typically catalyze oxygen photoreduction to hydrogen peroxide. Here, it is reported that, in contrast to these heterogeneous systems, a homogeneous solution of a metal-free organic dye can perfor...

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Aqueous photo(electro)catalysis with eumelanin thin films

Cited by 33 publications

References 38 publications

Photochemical evolution of hydrogen peroxide on lignins

Photochemical evolution of hydrogen peroxide on lignins

Untangling Photofaradaic and Photocapacitive Effects in Organic Optoelectronic Stimulation Devices

Water‐Soluble Organic Dyes as Molecular Photocatalysts for H₂O₂ Evolution

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Aqueous photo(electro)catalysis with eumelanin thin films

Cited by 33 publications

References 38 publications

Photochemical evolution of hydrogen peroxide on lignins

Photochemical evolution of hydrogen peroxide on lignins

Untangling Photofaradaic and Photocapacitive Effects in Organic Optoelectronic Stimulation Devices

Water‐Soluble Organic Dyes as Molecular Photocatalysts for H2O2 Evolution

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Water‐Soluble Organic Dyes as Molecular Photocatalysts for H₂O₂ Evolution