1,7,9,10-Tetrasubstituted PMIs Accessible through Decarboxylative Bromination: Synthesis, Characterization, Photophysical Studies, and Hydrogen Evolution Catalysis

In this work, we present a new synthetic strategy for fourfold-substituted perylene monoimides via tetrabrominated perylene monoanhydrides. X-ray diffraction analysis unveiled the intramolecular stacking orientation between the substituents and semicircular packing behavior. We observed the remarkable influence of the substituent on the longevity and nature of the excited state upon visible light excitation. In the presence of poly(dehydroalanine)-graft-poly(ethylene glycol) graft copolymers as solubilizing template, the chromophores are capable of sensitizing [Mo3S13]2− clusters in aqueous solution for stable visible light driven hydrogen evolution over three days. © 2020 The Authors. Chemistry - A European Journal published by Wiley-VCH Gmb

A Study in Red: The Overlooked Role of Azo‐Moieties in Polymeric Carbon Nitride Photocatalysts with Strongly Extended Optical Absorption

The unique optical and photoredox properties of heptazine-based polymeric carbon nitride (PCN) materials make them promising semiconductors for driving various productive photocatalytic conversions. However, their typical absorption onset at ca. 430–450 nm is still far from optimum for efficient sunlight harvesting. Despite many reports of successful attempts to extend the light absorption range of PCNs, the determination of the structural features responsible for the red shift of the light absorption edge beyond 450 nm has often been obstructed by the highly disordered structure of PCNs and/or low content of the moieties responsible for changes in optical and electronic properties. In this work, we implement a high-temperature (900 °C) treatment procedure for turning the conventional melamine-derived yellow PCN into a red carbon nitride. This approach preserves the typical PCN structure but incorporates a new functionality that promotes visible light absorption. A detailed characterization of the prepared material reveals that partial heptazine fragmentation accompanied by de-ammonification leads to the formation of azo-groups in the red PCN, a chromophore moiety whose role in shifting the optical absorption edge of PCNs has been overlooked so far. These azo moieties can be activated under visible-light (470 nm) for H₂ evolution even without any additional co-catalyst, but are also responsible for enhanced charge-trapping and radiative recombination, as shown by spectroscopic studies

Photochemical and electrochemical hydrogen evolution reactivity of lanthanide-functionalized polyoxotungstates

The first example of hydrogen evolution reactivity (HER) of lanthanide-functionalized Keggin-based polyoxotungstates under photochemical and electrochemical conditions is reported. The HER activity under homogeneous, visible light-driven conditions and under heterogeneous, electrochemical conditions depends on the type of lanthanide functionalization, so that a new class of model HER catalysts for systematic reactivity studies is now accessible.</p

Improving the management and treatment of diabetic foot infection: challenges and research opportunities

Diabetic foot infection (DFI) management requires complex multidisciplinary care pathways with off-loading, debridement and targeted antibiotic treatment central to positive clinical outcomes. Local administration of topical treatments and advanced wound dressings are often used for more superficial infections, and in combination with systemic antibiotics for more advanced infections. In practice, the choice of such topical approaches, whether alone or as adjuncts, is rarely evidence-based, and there does not appear to be a single market leader. There are several reasons for this, including a lack of clear evidence-based guidelines on their efficacy and a paucity of robust clinical trials. Nonetheless, with a growing number of people living with diabetes, preventing the progression of chronic foot infections to amputation is critical. Topical agents may increasingly play a role, especially as they have potential to limit the use of systemic antibiotics in an environment of increasing antibiotic resistance. While a number of advanced dressings are currently marketed for DFI, here we review the literature describing promising future-focused approaches for topical treatment of DFI that may overcome some of the current hurdles. Specifically, we focus on antibiotic-impregnated biomaterials, novel antimicrobial peptides and photodynamic therapy. </p

Polymeric Carbon Nitride Coupled with a Molecular Thiomolybdate Catalyst: Exciton and Charge Dynamics in Light-Driven Hydrogen Evolution

Solar hydrogen evolution from water is a necessary step to overcome the challenges of rising energy demand and associated environmental concerns. Low-cost photocatalytic architectures based on polymeric light absorbers coupled to highly efficient molecular catalysts might represent an attractive platform to address this issue. However, to-date, our mechanistic knowledge of these systems is still largely underdeveloped. In this study, a molecular molybdenum sulfide hydrogen evolving catalyst, [Mo3S13]2–, is loaded onto polymeric carbon nitride (CNx) photoabsorber by impregnation. The resulting composite shows enhanced photocatalytic activity for hydrogen evolution compared to pristine CNx under monochromatic visible light (l = 420 nm) irradiation in the presence of sacrificial reducing agents. The light-driven dynamics of excitons and charges involved in hydrogen evolution catalysis were studied by a combination of spectroscopic (steady-state and time-resolved photoluminescence, femtosecond time-resolved transient absorption) and photoelectrochemical (open-circuit photopotential transients) methods. We demonstrate that the molecular molybdenum sulfide catalyst, at optimum loading (10 wt% nominal), improves the charge separation in the CNx absorber by facilitating the depopulation of emissive (band-edge) or non-emissive (shallow trap) states, followed by an effectively catalyzed transfer of electrons from the charge-separated state (deep trap) to protons in the solution. The results provide important insights into the complex interplay between polymeric light absorbers and molecular redox catalysts, indicating that the electron transfer to the catalyst occurs on relatively longer (nanosecond – seconds) time scale, as the catalyst had no impact on the ultrafast (sub-nanosecond) photoinduced kinetics in the CNx. These findings are of crucial importance for further development of soft-matter based architectures for solar fuels production

Exploiting a neutral BODIPY copolymer as an effective agent for photodynamic antimicrobial inactivation.

We report the synthesis and photophysical properties of a neutral BODIPY photosensitizing copolymer (poly-8-(4-hydroxymethylphenyl)-4,4-difluoro-2,6-diethynyl-4-bora- 3a,4a-diaza-s-indacene) containing ethynylbenzene links between the BODIPY units. The copolymer absorbs further towards the red in the UV-vis spectrum compared to the BODIPY precursor. Photolysis of the polymer produces a singlet excited state which crosses to the triplet surface in less than 300 ps. This triplet state was used to form singlet oxygen with a quantum yield of 0.34. The steps leading to population of the triplet state were studied using time-resolved spectroscopic techniques spanning the pico- to nanosecond timescales. The ability of the BODIPY polymer to generate a biocidal species for bactericidal activity in both solution- and coating-based studies was assessed. When the BODIPY copolymer was dropcast onto a surface, 4 log and 6 log reductions in colony forming units/ml representative of Gram-positive and Gramnegative bacteria, respectively, under illumination at 525 nm were observed. The potent broadspectrum antimicrobial activity of a neutral metal-free copolymer when exposed to visible light conditions may have potential clinical applications in infection management