Donor-acceptor Coupling Research Articles

Electronic Coupling Between Perovskite Nanocrystal and Fullerene Modulates Hot Carrier Capture

AbstractThe efficient harnessing of hot carriers holds transformative potential for next‐generation optoelectronic devices. Halide perovskites, with their remarkably long carrier lifetimes exceeding 10 picoseconds, stand at the forefront of this research frontier. Yet, a fundamental paradox persists: why does efficient hot carrier capture remain elusive despite these extended lifetimes? Here, this conundrum is unraveled by constructing a donor–acceptor model system: perovskite nanocrystal and fullerene hybrids. It is demonstrated that the challenge lies not only in the carrier lifetime itself but in the nature of the coupling between donor and acceptor components. Remarkably, it is discovered that the formation of ground‐state complexes, with effective coupling across a wide energy range, not only overcomes the initially forbidden hot carrier capture within these hybrids but also dramatically enhances it, achieving a ≈76% hot carrier capture efficiency. This finding shifts the paradigm of hot carrier capture from extending carrier lifetimes to engineering donor–acceptor coupling, illuminating a path toward practical hot carrier applications.

Accelerated Electron-Hole Separation at the Organic-Inorganic Anthracene/Janus MoSSe Interface.

Organic light-absorbing materials with two-dimensional semiconductor layers as contact electrodes are promising for efficient and flexible low-cost solar cells. Considering anthracene as an absorber and a MoSSe Janus monolayer, we use non-adiabatic molecular dynamics to show that electron transfer from anthracene to MoSSe is faster on the Se side than the S side. The transfer from anthracene to MoS2 and MoSe2 monolayers takes intermediate times. As a rule, we find that a shorter adsorption distance produces a stronger donor-acceptor coupling. The smaller distance on the Se side is rationalized by the attractive force between the intrinsic dipole moment of the Janus structure and that of the molecule induced due to adsorption. Quantum coherence also affects the transfer time. The study provides detailed insights into adsorption of molecules on Janus structures and the resulting electronic and electron vibrational interactions. The results suggest that the dipole interaction plays an important role in the thermodynamic stability, alignment of electronic levels, and electron vibrational dynamics.

Synthesis, Spectral and Electrochemical Properties, and Theoretical Studies of Highly Functionalized Fused Triazole-Isoindoline Derivatives as a Donor-Acceptor System

Triazole and propargyl group functionalities are frequently utilized in the construction of efficient blue-emitting materials, serving as acceptors and donors, respectively. Leveraging the synergistic effect of donor-acceptor coupling between these moieties, three new compounds, namely CB-But-I2, Ph-But-I2, and DP-But-I2, were synthesized. Given the advantageous strategy of combining electron donors and acceptors to optimize carrier injection and transport, CB-But-I2, Ph-But-I2, and DP-But-I2 demonstrate remarkable capabilities in both hole and electron transportation. A metal-free synthesis approach was employed to produce highly functionalized 1,2,3-triazole cores incorporating electronic donor and acceptor functionalities. This synthesis method involved the “Click reaction” ring formation between acetylene and azide compounds of 2-(4-bromobutyl) isoindoline-1,3-dione, catalyzed by copper sulfate pentahydrate and assisted by ascorbic acid as a base. The process boasts several advantages, including mild reaction conditions, accessibility of precursors, metal-free synthesis, straightforward setup, and the generation of various substituted regioselective triazole compounds in satisfactory yields. All synthesized compounds were found to possess thermal stability and exhibited fluorescence within the 292–355 nm range. Moreover, a significant positive solvato-chromic behavior was noted across different solvents with varying polarities, and the theoretical values were compared against experimental data for validation.

Interfacial electronic structure modulations of Au@CuS with defective Ni-doped CoS2 facilitates the electroreduction of N2 into NH3

The nitrogen reduction reaction (NRR) offers a sustainable pathway for ammonia production. However, its effectiveness is hindered by the selective adsorption of nitrogen and the subsequent occurrence of the hydrogen evolution reaction. In this work, a novel and efficient NRR catalyst, Au@CuS heterostructured nanoparticles supported on carbon-coated Ni-doped CoS2 hollow nanocages (Au@CuS/Ni-CoS2/C), was designed and synthesized to enhance the conversion of N2 to NH3 under ambient conditions. The defective Ni-CoS2@C nanocages not only provide a larger surface area for the loading of Au@CuS nanoparticles but also improve conductivity and promote synergistic effects among different components within catalyst. Both experimental investigations and density functional theory (DFT) calculations reveal that the integration of Au and CuS leads to unique inorganic donor–acceptor couplings with electron enriched in Au nanoparticles due to the higher work function of Au compared to CuS. This electron enrichment expedites the adsorption and dissociation of N2 molecules over the electron-rich Au active sites, thereby significantly optimizing the adsorption of intermediates and catalyzing subsequent hydrogenation reduction processes. Benefiting from these synergistic advantages, the resulting Au@CuS/Ni-CoS2/C catalyst exhibited high NRR electrocatalytic activity with a maximum NH3 yield of 25.61 µg h−1 mg−1cat. and a Faraday efficiency of 14.99 % at –0.3 V (vs. reversible hydrogen electrode, RHE), surpassing those of Au@CuS, Ni-CoS2/C, and Au/Ni-CoS2/C. This work presents a new strategy for precisely adjusting the valence state of Au species, thereby facilitating the production of valuable ammonia through NRR.

A donor–acceptor coupling unit modulates the spin coupling effect of a stable diradical

This study presents the synthesis and characterization of a highly conjugated stable diradical molecule composed of a donor–acceptor coupling unit.

Molecular insights into substrate promiscuity of CotA laccase catalyzing lignin-phenol derivatives

CotA laccases are multicopper oxidases known for promiscuously oxidizing a broad range of substrates. However, studying substrate promiscuity is limited by the complexity of electron transfer (ET) between substrates and laccases. Here, a systematic analysis of factors affecting ET including electron donor acceptor coupling (ΗDA), driving force (ΔG) and reorganization energy (λ) was done. Catalysis rates of syringic acid (SA), syringaldehyde (SAD) and acetosyringone (AS) (kcat(SAD) > kcat(SA) > kcat(AS)) are not entirely dependent on the ability to form phenol radicals indicated by ΔG and λ calculated by Density Functional Theory (SA < SAD ≈ AS). In determined CotA/SA and CotA/SAD structures, SA and SAD bound at 3.9 and 3.7 Å away from T1 Cu coordinating His419 ensuring a similar ΗDA. Abilities of substrate to form phenol radicals could mainly account for difference between kcat(SAD) and kcat(SA). Furthermore, substrate pocket is solvent exposed at the para site of substrate's phenol hydroxyl, which would destabilize binding of AS in the same orientation and position resulting in low kcat. Our results indicated shallow partially covered binding site with propensity of amino acids distribution might help CotA discriminate lignin-phenol derivatives. These findings give new insights for developing specific catalysts for industrial application.

Low-crystalline FeOx on carboxylic CNTs as high-performance Fenton-like catalysts: Influence of crystallinity and carbon matrix

A facile method to prepare the ultra-dispersed low-crystalline FeOx (2–5 nm) particles anchored on the carboxylic carbon nanotubes (CCNTs) was reported in this paper. The low-crystalline FeOx/CCNTs (LC-FeOx/CCNTs) system features excellent Fenton-like performance which is 24.3 times larger than that of conventional crystalline Fe2O3/CCNTs (C–Fe2O3/CCNTs). It also exhibits outstanding stability and versatility in the catalytic degradation of different types of (cationic and anionic) compounds. Through comprehensive mechanistic investigations, it's confirmed that crystallinity of iron oxide played a vital role in catalytic performance. Specifically, singlet oxygen (1O2) was detected as the main reactive intermediate by introducing surface oxygen vacancy (SOV) and Fe2+ as “Fenton-catalytic” dual reaction center to promote H2O2 decomposition, which was distinct from the common Fenton-like reaction path with HO• as the main reactive oxygen species. Furthermore, the carboxylic groups on the surface of carbon nanotubes (CNTs) complexed with metastable FeOx can accelerate the transformation of Fe(III)/Fe(II) so as to adjust the utilization of H2O2 via donor-acceptor coupling. This work addresses an imaginative leap forward the understanding of the role of crystallinity and matrix coupling in the design of Fenton-like catalyst.

Screening Strategies for Diatom Metal-Doped β-Borophene Nanosheet Catalysts for Electrochemical Synthesis of Ammonia Using Density Functional Theory

Electrocatalysis is a promising approach for ammonia production under ambient conditions. However, practically, owing to the competing hydrogen evolution reaction (HER), the Faradaic efficiency is low, and it is difficult to activate the inert N≡N. The theoretical screening method based on density functional theory calculations is a novel technique for developing and designing nitrogen reduction reaction (NRR) diatom catalysts (DACs). We proposed an NRR new type of DAC doped on β-borophene (B-β) nanosheets exhibiting enhanced catalytic activities for the NRR through the pull–pull effect of dual-metal sites and donor–acceptor coupling. By systematically evaluating the stabilities, selectivities, and activities of 24 diatom-doped β-borophene (M2@B-β) candidates, Mo2@B-β was found to be a promising NRR electrocatalyst with a low limiting potential of −0.23 V for the NRR and a high overpotential of −0.16 V for the HER. The limiting potentials for Cr2@B-β, Mn2@B-β, and Re2@B-β were −0.52, −0.51, and −0.35 V, respectively, making them suitable electrocatalysts for the NRR. Based on the Sabatier principle, we proposed two descriptors, ΔG(*N) and d-band center, as the criteria for screening and designing catalysts with high catalytic activities to reveal the intrinsic correlation between adsorption properties and structural properties. Based on the ΔG(*N) function, a volcano plot was built to predict trends in the activities. The difference, ΔG(*N2) – ΔG(*H), was used as the selectivity descriptor, where the negative values of ΔG mean that the adsorption of N2 dominates over the adsorption of H on the surface of M2@B-β. This study thus provides a feasible strategy for designing NRR electrocatalysts and is helpful for the fast screening of efficient DACs for other electroreduction reactions.

Adenine Fine-Tunes DNA Photolyase's Repair Mechanism.

The comparative study of DNA repair by mesophilic and extremophilic photolyases helps us understand the evolution of these enzymes and their role in preserving life on our changing planet. The mechanism of repair of cyclobutane pyrimidine dimer lesions in DNA by electron transfer from the flavin adenine dinucleotide cofactor is the subject of intense interest. The role of adenine in mediating this process remains unresolved. Using microsecond molecular dynamics simulations, we find that adenine mediates the electron transfer in both mesophile and extremophile DNA photolyases through a similar mechanism. In fact, in all photolyases studied, the molecular conformations with the largest electronic couplings between the enzyme cofactor and DNA show the presence of adenine in 10-20% of the strongest-coupling tunneling pathways between the atoms of the electron donor and acceptor. Our theoretical analysis finds that adenine serves the critical role of fine-tuning rather than maximizing the donor-acceptor coupling within the range appropriate for the repair function.

The magic of biaryl linkers: the electronic coupling through them defines the propensity for excited-state symmetry breaking in quadrupolar acceptor-donor-acceptor fluorophores.

Charge transfer (CT) is key for molecular photonics, governing the optical properties of chromophores comprising electron-rich and electron-deficient components. In photoexcited dyes with an acceptor-donor-acceptor or donor-acceptor-donor architecture, CT breaks their quadrupolar symmetry and yields dipolar structures manifesting pronounced solvatochromism. Herein, we explore the effects of electronic coupling through biaryl linkers on the excited-state symmetry breaking of such hybrid dyes composed of an electron-rich core, i.e., 1,4-dihydropyrrolo[3,2-b]pyrrole (DHPP), and pyrene substituents that can act as electron acceptors. Experimental and theoretical studies reveal that strengthening the donor-acceptor electronic coupling decreases the CT rates and the propensity for symmetry breaking. We ascribe this unexpected result to effects of electronic coupling on the CT thermodynamics, which in its turn affects the CT kinetics. In cases of intermediate electronic coupling, the pyrene-DHPP conjugates produce fluorescence spectra, spreading over the whole visible range, that in addition to the broad CT emission, show bands from the radiative deactivation of the locally excited states of the donor and the acceptors. Because the radiative deactivation of the low-lying CT states is distinctly slow, fluorescence from upper locally excited states emerge leading to the observed anti-Kasha behaviour. As a result, these dyes exhibit white fluorescence. In addition to demonstrating the multifaceted nature of the effects of electronic coupling on CT dynamics, these chromophores can act as broad-band light sources with practical importance for imaging and photonics.

Effect of U on the photoluminescence of Pr and structural properties of U/Pr doped and co-doped Li2O–ZnO–SrO borophosphate glass

U/Pr doped and co-doped Li2O–ZnO–SrO borophosphate glasses were prepared using the melt quenching method. XRD, SEM-EDX, and FTIR investigations were carried out to ascertain the structural properties, morphological features and homogeneity of elemental distribution in the synthesised glass phosphors. Differential thermal analysis was used to examine the thermo-physical properties. It was observed that uranium doping improved the thermal stability and rigidity of the synthesised glass host. Intense photoluminescence (PL) emissions were observed both from uranium and praseodymium in the U/Pr doped glass. Uranium showed a broad emission spectrum with peak a maximum at 526 nm and resembles the typical emission pattern of hexavalent uranyl species (UO22+) in the amorphous environment. UO22+ emission increased linearly until the onset of concentration quenching at 1.0 mol%. Similarly, praseodymium doped glasses exhibited intense red emission from overlapped 3P0→ 3H6 and 1D2 →3H4 transitions, and centred at around 609 nm. At 0.2 mol%, the Pr emission intensity was highest, concentration quenching was prevalent beyond it. The emission decay of both uranium and praseodymium followed the bi-exponential decay model and the lifetime values decreased with increasing the dopant concentration in singly doped as well as co-doped samples. The Inokuti-Hirayama model was employed for the fitting of decay profiles to explicate the nature of non-radiative interaction of excited states. The donor-acceptor coupling parameters (Cda) were determined for U–U, Pr–Pr, and U–Pr interaction. Appreciable U–Pr energy transfer via dipole-dipole interaction was observed with Cda = 4.79 × 10−40 cm6s−1. Emission of both Pr and U get suppressed in the co-doped glass samples possibly due to the concomitant U–Pr redox interactions. The CIE color coordinates and color purity suggested that U/Pr doped Li2O–ZnO–SrO borophosphate glass can be used for solid-state lighting applications.

Electrochemical Analysis in Charge-Transfer Science: Things Are Not Always What They Seem

Charge transfer (CT) and charge transport (CTr) are essential for supporting life on Earth and for making our modern ways of living possible [Phys. Chem. Chem. Phys. 2020, 22, 21583-21629]. Electrochemical analysis, while relying on heterogeneous electron transfer (ET), is of key importance for characterizing CT systems and process [Curr. Opin. Electrochem. 2022, 31, 100862]. The huge difference between the timescales of electrochemical measurements and the picosecond CT reactions of interests places inherent demands for reliable interpretations of voltammetry analyses [J. Electrochem. Soc. 2019, 166, H3175-H3187]. Concurrently, the ubiquity of electric dipole warrants deep understanding of how they affect CT thermodynamics and kinetics [J. Am. Chem. Soc. 2014, 136, 12966-12973]. The localized dipole-generated fields affect the electrochemical potentials of donors and acceptors and, thus, the Franck-Condon contribution to the CT kinetics [Angew. Chem. Intnl. Ed. 2018, 57, 12365-12369]. In the context of our latest developments in electrochemical analysis, this presentation focuses on how molecular dipoles affect not only the potentials, but also the reorganization energy and the donor-acceptor coupling. Understanding the multifaceted nature of the effects of dipoles on charge transfer and charge transport drives the emergence of new paradigms for electronics, photonics and energy science and engineering.

Effect of Direct Coupling on Electronic Transport and Thermoelectric Properties of Single Pyrene Molecule

Electron transport characteristics through a single pyrene molecule, which connects with two metallic electrodes, are investigated by using of steady-state theoretical formalism. The transmission probability, I-V characteristics and thermoelectric properties are studied according to the influence of direct coupling between donor and acceptor. The new path between the donor and acceptor provides a direct route for the transfer of electrons between the donor and the acceptor, as well as the transfer of electrons across the molecule. We find the electronic transport properties improve by increasing donor-acceptor coupling factor.

Effects of co-doping in semiconductors: CdTe

Co-doping is an important method to improve doping properties in semiconductors, which is expected to lower the defect formation energy through the Coulomb interaction or covalent coupling between co-dopants and reduce the transition energy level through the level repulsions. However, the effectiveness of co-doping is sensitive to the type of co-dopants, and in some cases, negative effects can exist. Here, using $p$-type doping in CdTe as an example, we systematically investigate different dopant combinations based on first-principles hybrid functional calculations. We show that the complex of one donor + one double acceptor, e.g., ${\mathrm{Cl}}_{\mathrm{Te}}+{\mathrm{V}}_{\mathrm{Cd}}$, can cause a decrease in defect formation energy and a reduction in acceptor level, thus improving the dopability, especially when the Cl treatment is done at low temperature. The combination of two acceptors + one donor, e.g., ${\mathrm{Cl}}_{\mathrm{Te}}+2{\mathrm{Cu}}_{\mathrm{Cd}}$, has little or even negative effects because of the coexistence of the acceptor-acceptor and donor-acceptor coupling. More importantly, we show that the combination of one deep acceptor + one shallow acceptor, e.g., ${\mathrm{Sb}}_{\mathrm{Te}}+{\mathrm{P}}_{\mathrm{Te}}$, produces a much deeper acceptor level because the nominal deep acceptor ${\mathrm{Sb}}_{\mathrm{Te}}$ acts as a donor with respect to the shallow one, and then the deep acceptor state will be pushed even deeper due to the level repulsion. Thus, we should avoid this type of acceptor-acceptor co-doping to achieve high hole concentration. Our general understanding of the co-doping approach, therefore, provides a guideline for the future design of shallow defect complexes in CdTe and other semiconductors.

(Invited) Vibronic Effect of Donor-Acceptor Interaction Determines Fate of Mutiexciton Spins Generated By Singlet Fission

Singlet fission (SF) is expected to exceed the Shockley–Queisser theoretical limit with power conversion efficiencies (PCE) ~33 % of single junction organic solar cells (OSC) because two separated triplet excitons (T+T) can be produced from one excited singlet state (S1S0) sharing its excitation energy with a neighboring ground-state chromophore. The intramolecular SF (iSF) dynamics have widely been studied using the transient absorption spectroscopic methods together with theoretical modeling taking into account the vibronic effects in the ultrafast regimes. The correlated intermolecular triplet pair 1(TT) generated with the singlet character is known to be converted to the quintet (Q) state as 5(TT). These TT pairs separate into individual triplets as the T+T state. In the previous study, we reported the iSF dynamics and subsequent separations to T+T in the pentacene dimers (PcD) bridged by a phenylene at ortho and meta positions by a combination of the ultrafast transient absorption spectroscopy and the time-resolved electron paramagnetic resonance (TREPR) method.1 Before the spin-conversions to the 5(TT) state, the initially populated 1(TT) is strongly coupled in the four unpaired spins of the two triplet excitons, i.e. the entangled spin-state by large spin-spin exchange coupling (J) with the large orbital overlap produced at femtoseconds regions. The modulations of the J-couplings are thought to be essential for the 1(TT) -> 5(TT) conversions. In an iSF system, we interpreted that the quintet ESPs were caused by the anisotropic spin conversions due to singlet-quintet spin-relaxations to the five sublevels at m S = +2, +1, 0, -1 and -2 in accordance with the anisotropy of the ZFS coupling which is highly dependent on the relative orientation of one triplet exciton (TB) with respect to the other triplet (TA) in the TATB multiexciton.2 Internal fluctuations in the J-coupling were concluded to be crucial on the quintet generations. Moreover, we reported the treatment of the EPR transitions in the weakly coupled T+T states in the framework of the spin-correlated triplet pair (SCTP) for the very weak exchange coupling including the superpositions of the nine basis functions of 5(TT) - 3(TT) - 1(TT), as treated in the spin-correlated radical pair model. 3,4 The above pioneering interpretations of the ESP mechanisms may pave a new avenue to clarify how the molecular conformations and their motions drive the spin-conversions and the ultimate T+T generations, both of which are essential but unknown for the photon-to-energy conversion process. In particular, because the J-coupling is anticipated to be sensitive to the TATB conformations, it is expected that the specific molecular motions or phonon modes may play roles for the ultimate T+T de-coupling, as the vibronic effects. So far, details of the TATB geometries, the vibration modes and frequencies, and the electronic couplings are unresolved in the iSF systems for generating the quintet multiexcitons and the subsequent T+T dissociations.We have characterized the molecular geometries, conformation dynamics and J-couplings of the intramolecular multiexcitons after the photoinduced iSF with the proposal of the density matrix analysis of ESP observed by the TREPR method. It is concluded that the J-coupling is determined by the donor-acceptor electronic coupling in the multiexciton and that terahertz TA-TB conformation dynamics plays a significant role for generating the quintet multiexcitons and for the individual T+T states caused by the J-fluctuation in the covalently linked systems.4 Sakai, H.; Inaya, R.; Nagashima, H.; Nakamura, S.; Kobori, Y.; Tkachenko, N. V.; Hasobe, T., J. Phys. Chem. Lett. 2018, 9, 3354-3360.Matsui, Y.; Kawaoka, S.; Nagashima, H.; Nakagawa, T.; Okamura, N.; Ogaki, T.; Ohta, E.; Akimoto, S.; Sato-Tomita, A.; Yagi, S., et al., J. Phys. Chem. C 2019, 123, 18813-18823.Matsuda, S.; Oyama, S.; Kobori, Y., Chem. Sci. 2020, 11, 2934-2942.Kobori, Y.; Fuki, M.; Nakamura,; S. Hasobe, T. J. Phys. Chem. B 2020, 124, 9411–9419.

Shallow distance-dependent triplet energy migration mediated by endothermic charge-transfer

Conventional wisdom posits that spin-triplet energy transfer (TET) is only operative over short distances because Dexter-type electronic coupling for TET rapidly decreases with increasing donor acceptor separation. While coherent mechanisms such as super-exchange can enhance the magnitude of electronic coupling, they are equally attenuated with distance. Here, we report endothermic charge-transfer-mediated TET as an alternative mechanism featuring shallow distance-dependence and experimentally demonstrated it using a linked nanocrystal-polyacene donor acceptor pair. Donor-acceptor electronic coupling is quantitatively controlled through wavefunction leakage out of the core/shell semiconductor nanocrystals, while the charge/energy transfer driving force is conserved. Attenuation of the TET rate as a function of shell thickness clearly follows the trend of hole probability density on nanocrystal surfaces rather than the product of electron and hole densities, consistent with endothermic hole-transfer-mediated TET. The shallow distance-dependence afforded by this mechanism enables efficient TET across distances well beyond the nominal range of Dexter or super-exchange paradigms.

Deciphering the unusual fluorescence in weakly coupled bis-nitro-pyrrolo[3,2-b]pyrroles

Electron-deficient π-conjugated functional dyes lie at the heart of organic optoelectronics. Adding nitro groups to aromatic compounds usually quenches their fluorescence via inter-system crossing (ISC) or internal conversion (IC). While strong electronic coupling of the nitro groups with the dyes ensures the benefits from these electron-withdrawing substituents, it also leads to fluorescence quenching. Here, we demonstrate how such electronic coupling affects the photophysics of acceptor–donor–acceptor fluorescent dyes, with nitrophenyl acceptors and a pyrrolo[3,2-b]pyrrole donor. The position of the nitro groups and the donor-acceptor distance strongly affect the fluorescence properties of the bis-nitrotetraphenylpyrrolopyrroles. Concurrently, increasing solvent polarity quenches the emission that recovers upon solidifying the media. Intramolecular charge transfer (CT) and molecular dynamics, therefore, govern the fluorescence of these nitro-aromatics. While balanced donor-acceptor coupling ensures fast radiative deactivation and slow ISC essential for large fluorescence quantum yields, vibronic borrowing accounts for medium dependent IC via back CT. These mechanistic paradigms set important design principles for molecular photonics and electronics.

Photocatalytic Activity of Phosphorus and Nitrogen Co-Doped Carbon Quantum Dots/TiO2 Nanosheets

Double element co-doped carbon quantum dots (CQDs) have unique electron properties and broad prospects in photocatalysis. In this paper, the phosphorus and nitrogen co-doped CQDs (PNCQDs) were loaded on TiO2 nanosheets by in-situ synthesis method. Physical structure and chemical composition of samples were analyzed by XRD, FT-IR, XPS, SEM and TEM. UV–Vis spectra show the donor–acceptor coupling between PNCQDs and TiO2 and enhanced strong UV light absorption. Photoluminescence spectra indicate that PNCQDs effectively promote charge separation, which is different from nitrogen doped CQDs. The sample 1-PNCT with the optimal phosphorus doping amount has the highest kinetic constant for photodegradation of Methylene Blue (MB), which is 3.4 times pure TiO2. A possible Z-scheme photodegradation mechanism is proposed according to the active species scavenge experiment results in which PNCQDs can not only accept but also localize photogenerated electrons to dopant sites due to the quantum wells created by P and N doping energy barriers.

Binding Orientation of a Ruthenium-Based Water Oxidation Catalyst on a CdS QD Surface Revealed by NMR Spectroscopy.

We report on the binding of a Ru-based water oxidation catalyst (WOC) to CdS quantum dots (QDs) revealed by 1H NMR spectroscopy. Spin centers within the WOC exhibit correlated trends in chemical shift and T2 lifetime shortening upon QD binding. These effects are a highly directional function of proton position within the WOC, thus uncovering orientation information relative to the QD surface. The data suggest that the WOC interacts with the QD surface via the Ru terpyridine ligand, an unexpected orientation that has important implications for interfacial charge transfer and subsequent catalysis. This binding motif enables strong enough donor-acceptor electronic coupling for ultrafast photoinduced hole transfer while maintaining electronically distinct functional subunits.

Engineering Sensitized Photon Upconversion Efficiency via Nanocrystal Wavefunction and Molecular Geometry.

Triplet energy transfer from inorganic nanocrystals to molecular acceptors has attracted strong attention for high-efficiency photon upconversion. Here we study this problem using CsPbBr3 and CdSe nanocrystals as triplet donors and carboxylated anthracene isomers as acceptors. We find that the position of the carboxyl anchoring group on the molecule dictates the donor-acceptor coupling to be either through-bond or through-space, while the relative strength of the two coupling pathways is controlled by the wavefunction leakage of nanocrystals that can be quantitatively tuned by nanocrystal sizes or shell thicknesses. By simultaneously engineering molecular geometry and nanocrystal wavefunction, energy transfer and photon upconversion efficiencies of a nanocrystal/molecule system can be improved by orders of magnitude.