Noncovalent Liquid Phase Functionalization of 2H-WS2 with PDI: An Energy Conversion Platform with Long-Lived Charge Separation

MoSe2-Sensitized Water Splitting Assisted by C60-Dendrons on the Basal Surface

To facilitate water splitting using MoSe2 as a light absorber, we fabricated water-dispersible MoSe2/C60-dendron nanohybrids via physical modification of the basal plane of MoSe2. Upon photoirradiation, the mixed-dimension MoSe2/C60 (2D/0D) heterojunction generates a charge-separated state (MoSe2⋅+/C60⋅-) through electron extraction from the exciton in MoSe2 to C60. This process is followed by the hydrogen evolution reaction (HER) from water in the presence of a sacrificial donor (1-benzyl-1,4-dihydronicotinamide) and co-catalyst (Pt-PVP). The apparent quantum yields of the HER were estimated to be 0.06 % and 0.27 % upon photoexcitation at the A- and B-exciton absorption peaks (λmax=800 and 700 nm), respectively.

Visible Light-Sensitized CO2 Methanation along a Relaxed Heat Available Route

In photocatalysis, the resulted heat by the relaxation of most of incident light no longer acts as the industrially favorite driving force back to the target photo-reaction due to more or less the negative relation between photocatalytic efficiency and temperature. Here, we reported a visible light-sensitized protocol that completely reversed the negatively temperature-dependent efficiency in photo-driven CO2 methanation with saturated water vapor. Uniform Pt/N-TiO2/PDI self-assembly material decisively injects the excited electron of PDI sensitizer into N-TiO2 forming Ti-H hydride which is crucially temperature-dependent nucleophilic species to dominate CO2 methanation, rather than conventionally separated and trapped electrons on the conductor band. Meanwhile, the ternary composite lifts itself temperature from room temperature to 305.2 °C within 400 s only by the failure excitation upon simulated sunlight of 2.5 W/cm2, and smoothly achieves CO2 methanation with a record number of 4.98 mmol g-1 h-1 rate, compared to less than 0.02 mol g-1 h-1 at classic Pt/N-TiO2/UV photocatalysis without PDI sensitization. This approach can reuse ~53.9 % of the relaxed heat energy from the incident light thereby allow high-intensity incident light as strong as possible within a flowing photo-reactor, opening the most likely gateways to industrialization.

Strong quenching of dye fluorescence in monomeric perylene orange/TMDC hybrid structures

Hybrid structures with an interface between two different materials with properly aligned energy levels facilitate photo-induced charge separation to be exploited in optoelectronic applications. Particularly, the combination of 2D transition metal dichalcogenides (TMDCs) and dye molecules offers strong light-matter interaction, tailorable band level alignments, and high fluorescence quantum yields. In this work, we aim at the charge or energy transfer-related quenching of the fluorescence of the dye perylene orange (PO) when isolated molecules are brought onto monolayer TMDCs via thermal vapor deposition. Here, micro-photoluminescence spectroscopy revealed a strong intensity drop of the PO fluorescence. For the TMDC emission, in contrast, we observed a relative growth of the trion versus exciton contribution. In addition, fluorescence imaging lifetime microscopy quantified the intensity quenching to a factor of about 103 and demonstrated a drastic lifetime reduction from 3 ns to values much shorter than the 100 ps width of the instrument response function. From the ratio of the intensity quenching that is attributed to hole or energy transfer from dye to semiconductor, we deduce a time constant of several picoseconds at most, pointing to an efficient charge separation suitable for optoelectronic devices.

InP quantum dots: Stoichiometry regulates carrier dynamics

The optical properties of non-toxic indium phosphide (InP) quantum dots (QDs) are impinged by the existence of characteristic deep trap states. Several surface engineering strategies have been adopted to improve their optical quality, which has promoted the use of InP QDs for various technological applications. An antithetical approach involves the effective utilization of the deep trap states in InP QDs to modulate back electron transfer rates. Here, we explore the influence of the core-size of InP on their In-to-P stoichiometry and charge transfer dynamics when bound to an acceptor molecule, decyl viologen (DV2+). The mechanism of interaction of InP and DV2+ based on the quenching sphere model established the presence of (i) a 1:1 complex of DV2+ bound on InP and (ii) immobile quenchers in the quenching sphere, depending on the concentration of DV2+. While the forward electron transfer rates from photoexcited InP to bound DV2+ does not substantially vary with an increase in core size, the back electron transfer rates are found to be retarded. Findings from inductively coupled plasma-optical emission spectroscopy (ICP-OES) and X-ray photoelectron spectroscopy (XPS) reveal that the In to P ratio is higher for QDs with larger core size, which further brings about increased carrier trapping and a decreased rate of charge recombination. Furthermore, long-lived charge-separated states in DV2+ bound to InP, extending to hundreds of milliseconds, are obtained by varying the number of DV2+ in the quenching sphere of the QDs.