Stable and Efficient Photoinduced Charge Transfer of MnFe2O4/Polyaniline Photoelectrode in Highly Acidic Solution

Tailoring conductive polymers with inorganic photocatalysts, which provide photoinduced electron-hole generation, have significantly enhanced composites leading to excellent photoelectrodes. In this work, MnFe2O4 nanoparticles prepared by a hydrothermal method were combined with polyaniline to prepare mixed (hybrid) slurries, which were cast onto flexible FTO to prepare photoelectrodes. The resulting photoelectrodes were characterized by XRD, FESEM, HRTEM and UV-VIS. The photoelectrochemical performance was investigated by linear sweep voltammetry and chronoamperometry. The photocurrent achieved by MnFe2O4/Polyaniline was 400 μA/cm2 at 0.8 V vs. Ag/AgCl in Na2SO4 (pH = 2) at 100 mW/cm2, while polyaniline alone achieved only 25 μA/cm2 under the same conditions. The best MnFe2O4/Polyaniline displayed an incident photon-to-current conversion efficiency (IPCE) and applied bias photon-to-current efficiency (ABPE) of 60% at 405 nm wavelength, and 0.17% at 0.8 V vs. Ag/AgCl, respectively. High and stable photoelectrochemical performance was achieved for more than 900 s in an acidic environment.

Plasmon-induced hot-hole generation and extraction at nano-heterointerfaces for photocatalysis

Localized surface plasmon resonance excitation presents tremendous opportunities for light-harvesting in the field of photocatalysis. Notably, the use of plasmon-generated hot carriers to drive chemical reactions offers the opportunity to control the selectivity of the reaction, unlike temperature-driven catalysis. There has been extensive development of photocatalysts based on plasmon-induced hot electron transfer. However, the equally important hole transfer process has been largely understudied mainly because of the ultrafast dynamics and shorter lifetime of holes compared to electrons. The electron and hole transport asymmetry to the catalytic site introduces additional challenges in extracting holes as oxidants for chemical adsorbents/reactants. This review provides a fundamental overview of plasmonic catalysis, emphasizing recent hot hole extraction and catalysis advancements by exploring different nano-heterointerfaces through which energetic holes can be localized to the catalytic sites. We also highlight some of the critical parameters which must be considered to address the limitations and introduce new possibilities to the field.

Uncovering dark multichromophoric states in Peridinin–Chlorophyll–Protein

It has long been recognized that visible light harvesting in Peridinin–Chlorophyll–Protein is driven by the interplay between the bright (S 2 ) and dark (S 1 ) states of peridinin (carotenoid), along with the lowest-lying bright (Q y ) and dark (Q x ) states of chlorophyll- a . Here, we analyse a chromophore cluster in the crystal structure of Peridinin–Chlorophyll–Protein, in particular, a peridinin–peridinin and a peridinin–chlorophyll- a dimer, and present quantum chemical evidence for excited states that exist beyond the confines of single peridinin and chlorophyll chromophores. These dark multichromophoric states, emanating from the intermolecular packing native to Peridinin–Chlorophyll–Protein, include a correlated triplet pair comprising neighbouring peridinin excitations and a charge-transfer interaction between peridinin and the adjacent chlorophyll- a . We surmise that such dark multichromophoric states may explain two spectral mysteries in light-harvesting pigments: the sub-200-fs singlet fission observed in carotenoid aggregates, and the sub-200-fs chlorophyll- a hole generation in Peridinin–Chlorophyll–Protein.

Active hole generation in a liquid droplet dissolving into a binary solvent

Fluorescence micrograph of the active holes created in a droplet of an ionic liquid.