Photochemical Energy Conversion Research Articles

Triplet-Sensitized Switching of High-Energy-Density Norbornadienes for Molecular Solar Thermal Energy Storage with Visible Light.

Norbornadiene-based photoswitches have emerged as promising candidates for harnessing and storing solar energy, holding great promise as a viable solution to meet the growing energy demands. Despite their potential, the effectiveness of their direct photochemical conversion into the resulting quadricyclanes has room for improvement owing to (i) moderate quantum yields, (ii) poor overlap with the solar spectrum and (iii) photochemical back reactions. Herein, we present an approach to enhance the performance of such molecular solar thermal energy storage (MOST) systems through the triplet-sensitized conversion of aryl-substituted norbornadienes. Our study combines deep spectroscopic analyses, irradiation experiments, and quantum mechanical calculations to elucidate the energy transfer mechanism and inherent advantages of the resulting MOST systems. We demonstrate remarkable quantum yields using readily available sensitizers under both LED and solar light irradiation, significantly surpassing those achieved through direct excitation with photons of higher energy. In contrast to the conventional approach, light-induced back reactions of the high-energy products do not play any role, allowing quantitative switching within minutes. These results not only underscore the potential of triplet-sensitized MOST systems to leverage the high energy storage capabilities of multistate photoswitches but they might also stimulate the broader usage of sensitization strategies in photochemical energy conversion.

Triplet‐Sensitized Switching of High‐Energy‐Density Norbornadienes for Molecular Solar Thermal Energy Storage with Visible Light

Norbornadiene‐based photoswitches have emerged as promising candidates for harnessing and storing solar energy, holding great promise as a viable solution to meet the growing energy demands. Despite their potential, the effectiveness of their direct photochemical conversion into the resulting quadricyclanes has room for improvement owing to (i) moderate quantum yields, (ii) poor overlap with the solar spectrum and (iii) photochemical back reactions. Herein, we present an approach to enhance the performance of such molecular solar thermal energy storage (MOST) systems through the triplet‐sensitized conversion of aryl‐substituted norbornadienes. Our study combines deep spectroscopic analyses, irradiation experiments, and quantum mechanical calculations to elucidate the energy transfer mechanism and inherent advantages of the resulting MOST systems. We demonstrate remarkable quantum yields using readily available sensitizers under both LED and solar light irradiation, significantly surpassing those achieved through direct excitation with photons of higher energy. In contrast to the conventional approach, light‐induced back reactions of the high‐energy products do not play any role, allowing quantitative switching within minutes. These results not only underscore the potential of triplet‐sensitized MOST systems to leverage the high energy storage capabilities of multistate photoswitches but they might also stimulate the broader usage of sensitization strategies in photochemical energy conversion.

The usage of physiological methods in the creation of soybean varieties

The results of a study of the operation of photosystem II in the leaves of nine soybean varieties bred by the All-Russian Research Institute of Soybean are presented in order to identify genotypes with increased photosynthetic activity for inclusion in the breeding process when creating highly productive varieties of a new generation. A comparative assessment of varieties is given in terms of effective quantum yield of photosynthesis (Y) and chlorophyll fluorescence (F0), relative electron transport rate (ETR) and photochemical energy conversion depending on light saturation. The soybean varieties Gracia, Sonata and Kitrossa had the highest indicators for the studied parameters, significantly exceeding the standard variety Lydia. The effective quantum yield of photosynthesis, which shows the degree of absorption of solar energy, in the Gracia and Sonata varieties during the entire growing season was at the level of 0.80–0.83 rel. units, with this indicator exceeding for the Lydia variety by 0.09–0.13 rel. units depending on the phase of plant growth and development. The quantum yield of fluorescence (F0) in the leaves of the Lydia variety during the flowering phase exceeded the Gracia, Sonata and Kitrossa varieties by 60, 56 and 63%, respectively, which indicates a reduced activity of photosystem II in this variety. The efficiency of photochemical conversion of photosynthetic energy during the flowering phase was most stable in the leaves of the Sonata variety at light levels from 600 to 1500 µmol quanta/(m2∙s). Using the soybean variety Gratsia as the maternal form (♀) when crossed with the hybrid Am.2146, which was obtained with the inclusion of the Sonata variety in the hybridization, which also has a high degree of absorption of light quanta, the Radiant variety was create. Variety passed testing in 2021–2022, and in 2023 included in the State Register of Breeding Achievements for cultivation in the Far Eastern (12) region.

Proline priming: An efficient strategy to mitigate salinity impact at early developmental stages of the oilseed halophyte Cakile maritima

Seed germination is a vital process, yet extremely sensitive to salinity. This is particularly true for coastal halophytes like the annual oilseed species Cakile maritima, which faces the simultaneous impact of wind, salt-spray and seawater inundations in its natural biotopes. At the early developmental stages, this may jeopardize seed germination, plant establishment capacity and hence its development and persistence. Osmopriming is a pre-sowing approach aiming to improve seedling emergence and establishment in adverse environments. Here, we investigate the effect of proline (at 0, 1, 5, and 20 mM) pre-treatment on salt tolerance of C. maritima at the juvenile stage under salinity (0, 100, and 200 mM NaCl). Proline seed priming enhanced the germination rate (28% to 92%) and promoted seedling establishment of C. maritima by stimulating α-amylase activity even at the highest salinity (+55 %). Besides, after transfer of non-germinated seeds on distilled water, salt impact was fully reversible. At the seedling stage, chlorophyll fluorescence parameters showed that this osmoticum increased the maximal quantum yield of PSII photochemistry (Fv/Fm) and the quantum yield of photochemical energy conversion [Y(II)]. In contrast, the quantum yield of nonregulated nonphotochemical energy dissipation [Y(NO)] and the quantum yield of regulated nonphotochemical energy dissipation [Y(NPQ)], which might be correlated to the mitigation of the salt deleterious effects on PSII. Proline and carbohydrate concentrations also increased following priming. Overall, our data provide strong arguments for using proline at low doses (1 and 5 mM) as a successful priming agent to alleviate salinity-induced adverse effect on plants.

A Ni-O-Ag photothermal catalyst enables 103-m2 artificial photosynthesis with >17% solar-to-chemical energy conversion efficiency.

The scalable artificial photosynthesis composed of photovoltaic electrolysis and photothermal catalysis is limited by inefficient photothermal CO2 hydrogenation under weak sunlight irradiation. Herein, NiO nanosheets supported with Ag single atoms [two-dimensional (2D) Ni1Ag0.02O1] are synthesized for photothermal CO2 hydrogenation to achieve 1065 mmol g-1 hour-1 of CO production rate under 1-sun irradiation. This performance is attributed to the coupling effect of Ag-O-Ni sites to enhance the hydrogenation of CO2 and weaken the CO adsorption, resulting in 1434 mmol g-1 hour-1 of CO yield at 300°C. Furthermore, we integrate the 2D Ni1Ag0.02O1-supported photothermal reverse water-gas shift reaction with commercial photovoltaic electrolytic water splitting to construct a 103-m2 scale artificial photosynthesis system (CO2 + H2O → CO + H2 + O2), which achieves more than 22 m3/day of green syngas with an adjustable H2/CO ratio (0.4-3) and a photochemical energy conversion efficiency of >17%. This research charts a promising course for designing practical, natural sunlight-driven artificial photosynthesis systems.

Preparation of core–shell structured Bi2S3@Co1-xS nanorods with heterojunction as anode materials for lithium-ion batteries

Metal sulfides (MSs) have been extensively studied in the fields of photochemical or electrochemical energy conversion and storage. Herein, core–shell structured Bi2S3@Co1-xS nanorods with heterojunction (CSBCNs) were synthesized for the first time by a facile hydrothermal method and applied in lithium-ion batteries (LIBs). The unique nanosized core–shell structure with heterojunction enhances the surface reaction kinetics and facilitates ions and charges transfer. Moreover, it can also weaken the agglomeration of the active materials and alleviate their volume change. Compared with pure Bi2S3 nanorods, Co1-xS, and Bi2S3/Co1-xS composites, CSBCNs exhibited much better cycling performance and rate capability.

Physiological performance of brassinolide-conditioned green soybean seeds

Factors associated to biotic and abiotic stresses, such as high temperatures and prolonged droughts, can induce premature plant maturation and, thus, lead to the formation of green seeds. This is major issue for the soybean (Glycine max (L.) Merrill) production chain, due to low physiological seed quality. Although seed conditioning can improve seed germination and vigor, little is known on the use of the brassinolide (BL) phytohormone during this process in green soybean seeds. This study, therefore, aimed to elucidate BL conditioning effects on green soybean seeds. A BL stock solution was prepared and cultivar AS 3680 IPRO seeds were conditioned at 0.0, 0.2, 0.4, 0.6 and 0.8 μM BL concentrations followed by drying until reaching original water contents. Seed conditioning effects were investigated by assessing germination and accelerated aging test results, seedling shoot, and root lengths, electrical conductivity, germination speed index and dry seedling mass. Gas exchanges and chlorophyll a fluorescence parameters were determined in seedlings 15 days after sowing. Seed germination and vigor were superior when conditioned with 0.6 and 0.8 μM BL. Photosynthetic rates, effective quantum yields of PSII photochemical energy conversion and electron transport rates were improved in seeds treated with 0.4, 0.6 and 0.8 μM BL. Brassinolide-conditioned seeds exhibited histochemical reserve tissue differences and greater lipid and protein accumulation compared to the control group. These findings demonstrate that green soybean seed BL treatment can increase the quality and subsequent physiological development in soybean seedlings.

Spontaneous ligand loss by soft landed [Ni(bpy)3]2+ ions on perfluorinated self-assembled monolayer surfaces.

Transition metal (TM) complexes are widely used in catalysis, photochemical energy conversion, and sensing. Understanding factors that affect ligand loss from TM complexes at interfaces is important both for generating catalytically-active undercoordinated TM complexes and for controlling the degradation pathways of photosensitizers and photoredox catalysts. Herein, we demonstrate that well-defined TM complexes prepared on surfaces using ion soft landing undergo substantial structural rearrangements resulting in ligand loss and formation of both stable and reactive undercoordinated species. We employ nickel bipyridine (Ni-bpy) cations as a model system and explore their structural reorganization on surfaces using a combination of experimental and computational approaches. The controlled preparation of surface layers by mass-selected deposition of [Ni(bpy)3]2+ cations provides insights into the chemical reactivity of these species on surfaces. Both surface characterization using mass spectrometry and electronic structure calculations using density functional theory (DFT) indicate that [Ni(bpy)3]2+ undergoes a substantial geometry distortion on surfaces in comparison with its gas-phase structure. This distortion reduces the ligand binding energy and facilitates the formation of the undercoordinated [Ni(bpy)2]2+. Additionally, charge reduction by the soft landed [Ni(bpy)3]2+ facilitates ligand loss. We observe that ligand loss is inhibited by co-depositing [Ni(bpy)3]2+ with a stable anion such as closo-dodecaborate dianion, [B12F12]2-. The strong electrostatic interaction between [Ni(bpy)3]2+ and [B12F12]2- diminishes the distortion of the cation due to interactions with the surface. This interaction stabilizes the soft landed cation by reducing the extent of charge reduction and its structural reorganization. Overall, this study shows the intricate interplay of charge state, ion surface interactions, and stabilization by counterions on the structure and reactivity of metal complexes on surfaces. The combined experimental and computational approach used in this study offers detailed insights into factors that affect the integrity and stability of active species relevant to energy production and catalysis.

Application of olive mill waste-based biochar for improving wheat response to salt stress

The production of olive mill solid waste (OMSW) raises concerns due to its toxicity and negative environmental impact. However, by utilizing pyrolysis, OMSW can be converted into biochar, a carbon-rich material that detoxifies the waste and preserves its nutrient content. The OMSW-based biochar possesses alkaline properties (pH 9.6), low electrical conductivity (EC), high cation exchange capacity (CEC), a porous surface morphology, various surface functional groups, and high mineral content. This study assessed the influence of two concentrations (5% and 10%) of OMSW-based biochar on wheat plants' growth biomarkers and physiological characteristics subjected to salt stress conditions (150 mM NaCl). Findings of the study revealed that salt stress had deleterious effects on various parameters, including shoot height, fresh and dry weights of shoots and roots, relative water content (RWC%), membrane stability index (MSI%), photosynthetic pigments, and photosynthetic parameters such as the coefficient of the effective quantum yield of photochemical energy conversion of PSII (ØPSII), photochemical quenching (qP), and photochemical efficiency of PSII (Fo, Fm, Fv/Fo, and Fv/Fm). Furthermore, the levels of lipid peroxidation (MDA), hydrogen peroxide (H2O2), superoxide dismutase (SOD), and peroxidase (POD) activities significantly increased in stressed plants. On the other hand, applying both concentrations of OMSW-based biochar effectively improved the overall performance of wheat plants, irrespective of the presence of salinity. OMSW-based biochar is a promising strategy for promoting wheat growth in salt-stressed soil by improving various growth parameters and mitigating plant oxidative stress.

Thermal stability improvement of azobenzene for the integration of photochemical and solar thermochemical energy conversion

Azobenzene is a typical photoisomerization material that is widely used in photochemical energy conversion. However, it's generally operated below 200 °C to avoid thermal decomposition. To improve the thermal stability of azobenzene for higher temperature applications, this paper discussed an option that grafting azobenzene onto graphite-like carbon nitride sheets. The synthesis was evaluated based on the performance of micro morphology and structure, thermal stability, and photochemical energy conversion. Furthermore, the photochemical conversion performance was analyzed with diverse irradiation intensities. The results demonstrate that the synthesis has a strong thermal stability below 530 °C. In this study, the most favorable excitation wavelength for photochemical conversion was 445 nm with an irradiation intensity of 40 mW/cm2.

Construction of a novel heteropoly molybdophosphate/graphitized carbon nitride s-scheme heterostructure with enhanced photocatalytic H2O2 evolution activity

The preparation of hydrogen peroxide using a photochemical energy conversion process is a promising green pathway. Herein, a series of graphite-phase carbon nitride/Polyoxometalate (CN-HMoP) composite photocatalysts were prepared by interlayer coordination and segregation strategies. During the synthesis process, the presence of –NH2 or H ions at the CN terminus makes it display a positive charge, which is capable of attracting HMoP with a polyanionic structure. Subsequently, the N atoms on the triazine ring preferentially coordinate with the Mo ions in HMoP to form Mo-N bonds, and the HMoP nanoparticles are able to be inserted layer by layer into the CN nanosheets by interlayer coordination to make the sheet exfoliation, which contributes to the enhancement of the transmission of photogenerated carriers. Notably, the establishment of the S-Scheme heterostructure facilitates the spatial separation of electron-hole pairs and maintains the strongest redox potential. More importantly, under solar/visible light irradiation, the H2O2 generation rate of CN-HMoP reached 137.1 μmol L-1h−1 and 113.1 μmol L-1h−1, which was 17.7 and 16.8 times higher than pristine CN. Therefore, this work can provide guidance for the synthesis of semiconductor photocatalysts for more efficient and green generation of H2O2.

(Allen J. Bard Award in Electrochemical Science) Toward Electrochemical Energy Conversion Via Metal-Organic Framework Materials

Consistent with the many energy-centric interests and pioneering contributions by Prof. Bard, this presentation will touch on catalytic electrochemical and photochemical energy conversion as enabled by metal-organic framework (MOF) materials. The presentation will focus on a couple of case studies that illustrate how nominally insulating MOF films can be persuaded to transport charge, deliver photo-generated molecular excitons, and catalytically drive energy-relevant, multi-electron chemical transformations.

Photoactive Electrocatalyst with Staggered p-n Heterojunction for Rechargeable Zn-Air Batteries

Rechargeable zinc-air batteries (RZBs) demonstrate significant potential as next-generation batteries as they are non-flammable, resource-abundant, cost-efficient, feasible for ambient air operation, and have remarkable theoretical energy density (1086 Wh kg-1). However, the development of RZBs needs to address many challenges to speed up their commercialization. For example, low round-trip efficiency during cycling is caused by retarded reactivity of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) at the air cathode. An air cathode with deficient electrocatalytic kinetics creates a large voltage gap, especially when the practical charge voltage is > 2.0 V, during the charging and discharging process. Moreover, the cycle life of the RZBs is limited owing to the structural degradation of air cathodes working under high charge voltage. Therefore, it is essential to improve both the round-trip efficiency and structural durability of air cathodes to ensure further development and commercialization of RZBs. For efficient energy generation and storage, photo-enhanced RZBs that combine photochemical and electrochemical energy conversion and storage with the help of solar energy, are a promising research focus. Photo-enhanced RZBs require a photoactive OER/ORR bifunctional cathode that is not merely an electrochemical catalyst but also a photo-active catalyst.In the present study, we developed a photoactive bifunctional air-electrocatalyst with a staggered p-n heterojunction band gap structure, comprising n-type g-C3N4 and p-type copper-doped ZIF-67 (CuZIF-67) composite, to accelerate sluggish OER/ORR processes via a durable structure and stable long-cycle-life performance for photo-enhanced RZBs. g-C3N4/CuZIF-67 has a suitable band gap, which ensures wide-range light absorption in the UV–Vis–NIR region, and stimulates more electrons to participate in ORR/OER electrocatalytic activity. Besides, it has a staggered bandgap structure and a BEF at the p-n junction of the catalyst, which improves electron–hole pairs separation efficiency, lowers overpotential, promotes ORR/OER electrocatalytic activity, and eventually enhances the efficiency of RZBs (the voltage gap was significantly decreased by 14% with simulated solar light irradiation). Moreover, a high concentration of pyrrolic-N groups in the cathode material, resulting in the excellent electrochemical durability of RZBs during charge/discharge cycles. The photo-enhanced RZB based on the g-C3N4/CuZIF-67 bifunctional catalyst exhibits good round-trip efficiency of 60% (2 mA cm-2) with a significantly decreased voltage gap (from 0.92 to 0.81 V) after 1000 cycles, under simulated solar light irradiation. It can be concluded that staggered p-n heterojunction and pyrrolic nitrogen-rich groups play an important role in efficient and durable photo-enhanced Zn-air batteries.

Better Covalent Connection in a Molecular Triad Enables More Efficient Photochemical Energy Storage.

Numerous studies have explored the kinetics of light-induced charge separation and thermal charge recombination in donor-acceptor compounds, but quantum efficiencies have rarely been investigated. Here, we report on two essentially isomeric molecular triads, both comprising a π-extended tetrathiafulvalene (ExTTF) donor, a ruthenium(II)-based photosensitizer, and a naphthalene diimide (NDI) acceptor. The key difference between the two triads is how the NDI acceptor is connected. Linkage at the NDI core provides stronger electronic coupling to the other molecular components than connection via the nitrogen atoms of NDI. This change in molecular connectivity is expected to accelerate both energy-storing charge separation and energy-wasting charge recombination processes, but it is not a priori clear how this will affect the triad's ability to store photochemical energy; any gain resulting from faster charge separation could potentially be (over)compensated by losses through accelerated charge recombination. The new key insight emerging from our study is that the quantum yield for the formation of a long-lived charge-separated state increases by a factor of 5 when going from nitrogen- to core-connected NDI, providing the important proof of concept that better molecular connectivity indeed enables more efficient photochemical energy storage. The physical origin of this behavior seems to root in different orbital connectivity pathways for charge separation and charge recombination, as well as in differences in the relevant orbital interactions depending on NDI connection. Our work provides guidelines for how to discriminate between energy-storing and energy-wasting electron transfer reactions in order to improve the quantum yields for photochemical energy storage and solar energy conversion.

Effect of organic photovoltaic and red-foil transmittance on yield, growth and photosynthesis of two spinach genotypes under field and greenhouse conditions

The galloping rise in global population in recent years and the accompanying increase in food and energy demands has created land use crisis between food and energy production, and eventual loss of agricultural lands to the more lucrative photovoltaics (PV) energy production. This experiment was carried out to investigate the effect of organic photovoltaics (OPV) and red-foil (RF) transmittance on growth, yield, photosynthesis and SPAD value of spinach under greenhouse and field conditions. Three OPV levels (P0: control; P1: transmittance peak of 0.11 in blue light (BL) and 0.64 in red light (RL); P2: transmittance peak of 0.09 in BL and 0.11 in RL) and two spinach genotypes (bufflehead, eland) were combined in a 3 × 2 factorial arrangement in a completely randomized design with 4 replications in the greenhouse, while two RF levels (RF0: control; RF1: transmittance peak of 0.01 in BL and 0.89 in RL) and two spinach genotypes were combined in a 2 × 2 factorial in randomized complete block design with four replications in the field. Data were collected on growth, yield, photosynthesis and chlorophyll content. Analysis of variance (ANOVA) showed significant reduction in shoot weight and total biomass of spinach grown under very low light intensities as a function of the transmittance properties of the OPV cell used (P2). P1 competed comparably (p > 0.05) with control in most growth and yield traits measured. In addition, shoot to root distribution was higher in P1 than control. RF reduced shoot and total biomass production of spinach in the field due to its inability to transmit other spectra of light. OPV-RF transmittance did not affect plant height (PH), leaf number (LN), and SPAD value but leaf area (LA) was highest in P2. Photochemical energy conversion was higher in P1, P2 and RF1 in contrast to control due to lower levels of non-photochemical energy losses through the Y(NO) and Y(NPQ) pathways. Photo-irradiance curves showed that plants grown under reduced light (P2) did not efficiently manage excess light when exposed to high light intensities. Bufflehead genotype showed superior growth and yield traits than eland across OPV and RF levels. It is therefore recommended that OPV cells with transmittance properties greater than or equal to 11% in BL and 64% in RL be used in APV systems for improved photochemical and land use efficiency.

Cu-based high-entropy two-dimensional oxide as stable and active photothermal catalyst

Cu-based nanocatalysts are the cornerstone of various industrial catalytic processes. Synergistically strengthening the catalytic stability and activity of Cu-based nanocatalysts is an ongoing challenge. Herein, the high-entropy principle is applied to modify the structure of Cu-based nanocatalysts, and a PVP templated method is invented for generally synthesizing six-eleven dissimilar elements as high-entropy two-dimensional (2D) materials. Taking 2D Cu2Zn1Al0.5Ce5Zr0.5Ox as an example, the high-entropy structure not only enhances the sintering resistance from 400 °C to 800 °C but also improves its CO2 hydrogenation activity to a pure CO production rate of 417.2 mmol g−1 h−1 at 500 °C, 4 times higher than that of reported advanced catalysts. When 2D Cu2Zn1Al0.5Ce5Zr0.5Ox are applied to the photothermal CO2 hydrogenation, it exhibits a record photochemical energy conversion efficiency of 36.2%, with a CO generation rate of 248.5 mmol g−1 h−1 and 571 L of CO yield under ambient sunlight irradiation. The high-entropy 2D materials provide a new route to simultaneously achieve catalytic stability and activity, greatly expanding the application boundaries of photothermal catalysis.

Controlling Hot Charge Carrier Transfer in Monolithic AlSiAl Heterostructures for Plasmonic On-Chip Energy Harvesting.

The generation of hot carriers by Landau damping or chemical interface damping of plasmons is of particular interest to the fundamental aspects of extreme light-matter interactions. Hot charge carriers can be transferred to an attached acceptor for photochemical or photovoltaic energy conversion. However, these lose their excess energy and relax to thermal equilibrium within picoseconds and it is difficult to extract useful work thereof with thermodynamic efficiencies that are of interest for practical devices. Without a detailed understanding of the underlying plasmon decay processes and transfer mechanisms, proper material matching and design considerations for novel plasmonic devices are extremely challenging. Here, a multifunctional AlSiAl heterostructure device with tunable Schottky barriers is presented to control plasmon-induced hot carrier injection at an abrupt metal-semiconductor interface. Light absorption, surface plasmon generation, and separation of hot carriers arising from the non-radiative decay of surface plasmons are realized in a monolithic Schottky barrier field effect transistor. Aside from barrier modulation, a virtual p-n junction can be emulated in the semiconductor channel with the distinct merit that carrier concentration and polarity are tunable by electrostatic gating. The investigations are carried out with a view to possible use for CMOS-compatible plasmonic photovoltaics, with versatile implementations for autonomous nanosystems.

Sensitivity of the Photosynthetic Apparatus in Maize and Sorghum under Different Drought Levels.

Drought is one of the main environmental stress factors affecting plant growth and yield. The impact of different PEG concentrations on the photosynthetic performance of maize (Zea mays L. Mayflower) and sorghum (Sorghum bicolor L. Foehn) was investigated. The activity of the photosynthetic apparatus was assessed using chlorophyll fluorescence (PAM and JIP test) and photooxidation of P700. The data revealed that water deficiency decreased the photochemical quenching (qP), the ratio of photochemical to nonphotochemical processes (Fv/Fo), the effective quantum yield of the photochemical energy conversion in PSII (ΦPSII), the rate of the electron transport (ETR), and the performance indexes PItotal and PIABS, as the impact was stronger in sorghum than in maize and depended on drought level. The PSI photochemistry (P700 photooxidation) in sorghum was inhibited after the application of all studied drought levels, while in maize, it was registered only after treatment with higher PEG concentrations (30% and 40%). Enhanced regulated energy losses (ΦNPQ) and activation of the state transition under drought were also observed in maize, while in sorghum, an increase mainly in nonregulated energy losses (ΦNO). A decrease in pigment content and relative water content and an increase in membrane damage were also registered after PEG treatment. The experimental results showed better drought tolerance of maize than sorghum. This study provides new information about the role of regulated energy losses and state transition for the protection of the photosynthetic apparatus under drought and might be a practical approach to the determination of the drought tolerance of plants.

Solvent Tuning Excited State Structural Dynamics in a Novel Bianthryl

Symmetry breaking charge separation (SBCS) is central to photochemical energy conversion. The widely studied 9,9-bianthryl (9,9'BA) is the prototype, but the role of bianthryl structure is hardly investigated. Here we investigate excited state structural dynamics in a bianthryl of reduced symmetry, 1,9-bianthryl (1,9'BA), through ultrafast electronic and vibrational spectroscopy. Resonance selective Raman in polar solvents reveals a Franck-Condon state mode that disappears concomitant with the rise of ring breathing modes of radical species. Solvent-dependent dynamics show that CS is driven by solvent orientational motion, as in 9,9'BA. In nonpolar solvents the excited state undergoes multistep structural relaxation, including subpicosecond Franck-Condon state decay and biexponential diffusion-controlled structural evolution to a distorted slightly polar state. These data suggest two possible routes to SBCS; the established solvent driven pathway in rapidly relaxing polar solvents and, in slowly relaxing media, initial intramolecular reorganization to a polar structure which drives solvent orientational relaxation.

Molecular-level insights on NIR-driven photocatalytic H2 generation with ultrathin porous S-doped g-C3N4 nanosheets

Unraveling how mid-gap state energy level of graphitic carbon nitride (g-C3N4) promote near-infrared (NIR) driven photochemical energy conversion at the molecular level remains a grand challenge. Here, we report a series of S double-site-doped ultrathin g-C3N4 nanosheets (SUCN) with adjustable intermediate band gap benefits from light response over NIR region. The SUCN produced after optimizing S double-site doping can effectively generate hydrogen (H2) under NIR-light irradiation. The highest H2 generation rate achieved was respectively 9.35 and 17.46 μmol g−1 h−1 under λ = 765 and λ > 800 nm, which is firstly expended photocatalytic activity of S-doped g-C3N4 to NIR region beyond λ > 765 nm. We proposed a molecular-level method, i.e., the localized oxidation state of proton acceptor triethanolamine (TEOA) in the mid-gap state to ensure the NIR-driven H2 generating behavior.