Organic Photosynthesis Research Articles

Pyrene‐Alkyne‐Based Conjugated Porous Polymers with Skeleton Distortion‐Mediated ⋅O2− and 1O2 Generation for High‐Selectivity Organic Photosynthesis

AbstractReactive oxygen species (ROS) play a crucial role in determining photocatalytic reaction pathways, intermediate species, and product selectivity. However, research on ROS regulation in polymer photocatalysts is still in its early stages. Herein, we successfully achieved series of modulations to the skeleton of Pyrene‐alkyne‐based (Tetraethynylpyrene (TEPY)) conjugated porous polymers (CPPs) by altering the linkers (1,4‐dibromobenzene (BE), 4,4′‐dibromobiphenyl (IP), and 3,3′‐dibromobiphenyl (BP)). Experiments combined with theoretical calculations indicate that BE‐TEPY exhibits a planar structure with minimal exciton binding energy, which favors exciton dissociation followed by charge transfer with adsorbed O2 to produce ⋅O2−. Thus BE‐TEPY shows optimal photocatalytic activity for phenylboronic acid oxidation and [3+2] cycloaddition. Conversely, the skeleton of BP‐TEPY is significantly distorted. Its planar conjugation decreases, intersystem crossing (ISC) efficiency increases, which makes it more prone for resonance energy transfer to generate 1O2. Therefore, BP‐TEPY displays best photocatalytic activity in [4+2] cycloaddition and thioanisole oxidation. Both above reactant conversion and its product selectivity exceed 99 %. This work systematically reveals the intrinsic structure–activity relationship among the skeleton structure of CPPs, excitonic behavior, and selective generation of ROS, providing new insights for the rational design of highly efficient and selective CPPs photocatalysts.

Pyrene-Alkyne-Based Conjugated Porous Polymers with Skeleton Distortion-Mediated ⋅O2 - and 1O2 Generation for High-Selectivity Organic Photosynthesis.

Reactive oxygen species (ROS) play a crucial role in determining photocatalytic reaction pathways, intermediate species, and product selectivity. However, research on ROS regulation in polymer photocatalysts is still in its early stages. Herein, we successfully achieved series of modulations to the skeleton of Pyrene-alkyne-based (Tetraethynylpyrene (TEPY)) conjugated porous polymers (CPPs) by altering the linkers (1,4-dibromobenzene (BE), 4,4'-dibromobiphenyl (IP), and 3,3'-dibromobiphenyl (BP)). Experiments combined with theoretical calculations indicate that BE-TEPY exhibits a planar structure with minimal exciton binding energy, which favors exciton dissociation followed by charge transfer with adsorbed O2 to produce ⋅O2 -. Thus BE-TEPY shows optimal photocatalytic activity for phenylboronic acid oxidation and [3+2] cycloaddition. Conversely, the skeleton of BP-TEPY is significantly distorted. Its planar conjugation decreases, intersystem crossing (ISC) efficiency increases, which makes it more prone for resonance energy transfer to generate 1O2. Therefore, BP-TEPY displays best photocatalytic activity in [4+2] cycloaddition and thioanisole oxidation. Both above reactant conversion and its product selectivity exceed 99 %. This work systematically reveals the intrinsic structure-activity relationship among the skeleton structure of CPPs, excitonic behavior, and selective generation of ROS, providing new insights for the rational design of highly efficient and selective CPPs photocatalysts.

The role of various organs of the wheat plant in photosynthesis

The characteristics of CO2 assimilation were studied in photosynthesizing organs of wheat varieties with contrasting morphophysiological characteristics during ontogenesis in different irrigation regimes. The maximum values of the total amount of assimilated CO2 in both studied varieties and both variants were observed in the phase of grain formation, and the minimum values were detected in the phase of wax ripeness. In the initial phases, leaves had a greater share of CO2 assimilation. Towards the end of vegetation, the role of leaves in photosynthesis decreased, and the role of organs such as the leaf sheath, the spike base, and the spike increased. In both varieties, the total amount of CO2 assimilated by phases decreased more in the drought variant. The photosynthesis of other organs along with leaves was found to be also important in the process of grain-filling, especially under drought conditions. Keywords: Wheat, spike, assimilation of CO2, leaves, spiking, drought

ACRE, a class of AP2/ERF transcription factors, activates the expression of sweet potato ß-amylase and sporamin genes through the sugar-responsible element CMSRE-1

Sugars, synthesized by photosynthesis in source organs, are loaded and utilized as an energy source and carbon skeleton in sink organs, and also known to be important signal molecules regulating gene expression in higher plants. The expression of genes coding for sporamin and β-amylase, the two most abundant proteins in storage roots of sweet potato, is coordinately induced by sugars. We previously reported on the identification of the carbohydrate metabolic signal-responsible element-1 (CMSRE-1) essential for the sugar-responsible expression of two genes. However, transcription factors that bind to this sequence have not been identified. In this study, we performed yeast one-hybrid screening using the sugar-responsible minimal promoter region of the ß-amylase gene as bait and a library composed only transcription factor cDNAs of Arabidopsis. Two clones, named Activator protein binding to CMSRE-1 (ACRE), encoding AP2/ERF transcription factors were isolated. ACRE showed transactivation activity of the sugar-responsible minimal promoter in a CMSRE-1-dependent manner in Arabidopsis protoplasts. Electric mobility shift assay (EMSA) using recombinant proteins and transient co-expression assay in Arabidopsis protoplasts revealed that ACRE could actually act to the CMSRE-1. Among the DEHYDRATION -RESPONSIVE ELEMENT BINDING FACTOR (DREB) subfamily, almost all homologs including ACRE, could act on the DRE, while only three ACREs could act to the CMSRE-1. Moreover, ACRE-homologs of Japanese morning glory also have the same property of DNA-binding preference and transactivation activity through the CMSRE-1. These findings suggested that ACRE plays an important role in the mechanism regulating the sugar-responsible gene expression through the CMSRE-1 conserved across plant species.

Charge Separation to Facilitate The Conversion of Copper‐Phenylacetylide from Aggregation‐Induced Emission to Efficient Photocatalysis

AbstractAggregation‐induced emission (AIE) materials are considered promising photocatalyst candidates due to their robust light‐harvesting and efficient photoexcitation, if their photoexcited carriers can be separated effectively. Herein, by skillfully selecting multi‐alkynyl ligands instead of phenylacetylene to construct multi‐channel charge separation, copper‐phenylacetylide (CP‐1) with AIE properties is successfully transformed into efficient photocatalysts CP‐2P (copper‐1,4‐diethynylbenzene) and CP‐2M (copper‐1,3‐diethylnylbenzene). In these structures, the multi‐alkynyl ligands connects the copper‐ladder into multi‐dimensional metal‐organic frameworks with greatly reduced bandgap, enhances charge transfer and separation, and facilitated oxygen adsorption and activation. As a representative, CP‐2P has the best photocatalytic activity and stability for photocatalytic aerobic oxidation, such as thioanisole oxidation (conv. > 99%, methyl phenyl sulfoxide sel. ≧ 94%), benzyl alcohol oxidation (conv. > 99%, benzaldehyde sel. > 99%) and benzylamine oxidation (conv. > 99%, N‐benzylidene benzylamine sel. > 99%), which can be used for large‐scale sunlight‐driven organic photosynthesis. This work confirms the feasibility of controlled conversion of the conventional copper‐alkynyl from AIE material to efficient photocatalyst using charge separation strategy, which provides an important guidance for the rational design of new high‐efficiency photocatalyst.

Coralloid W18O49@covalent organic frameworks S-scheme heterojunction for high efficiency photocatalytic aerobic oxidation

Reasonably designing and constructing efficient artificial S-mechanism photocatalysts, expanding their application in the field of photocatalytic organic synthesis, have become a hot and challenging topic in the photocatalysis. Herein, a series of coral-like W18O49@TpPa-H (TpPa-H represents COFs generated by the reaction of 1,3,5-triformylphloroglucinol (Tp) and p-phenylenediamine (Pa-H)) composites were successfully prepared by using a simple in-situ encapsulation strategy. Given the internal electric field at the S-scheme interface, W18O49 acts as an oxidative photocatalyst with sufficient positive valence band (VB) position and TpPa-H as a reductive one with enough negative conduction band (CB) position for the efficient amines oxidative coupling to imines. The resulting W18O49@TpPa-H-0.1 hybrid material shows both optimal benzylamine to imine conversion and selectivity exceeding 99 % within 4 h under 10 W 420 nm LED light irradiation, which is 9.9 and 2.8 fold greater than that of W18O49 and TpPa-H, respectively. The photocatalytic activity is even extended to 740 nm. Furthermore, the photocatalytic mechanism research confirmed that a high efficiency S-scheme heterojunction was formed between W18O49 and TpPa-H, and multiple active species, such as ·O2–, 1O2, and h+, synergistically participated in the reaction, imparting its excellent photocatalytic performance. This work may open new avenues for the development of high-efficiency COFs-based S-scheme heterojunction for organic photosynthesis.

Bridging photosynthesis and crop yield formation with a mechanistic model of whole-plant carbon–nitrogen interaction

Abstract Crop yield is determined by potential harvest organ size, source organ photosynthesis and carbohydrate partitioning. Filling the harvest organ efficiently remains a challenge. Here, we developed a kinetic model of rice grain filling, which scales from the primary biochemical and biophysical processes of photosynthesis to whole-plant carbon and nitrogen dynamics. The model reproduces the rice yield formation process under different environmental and genetic perturbations. In silico screening identified a range of post-anthesis targets—both established and novel—that can be manipulated to enhance rice yield. Remarkably, we pinpointed the stability of grain-filling rate from flowering to harvest as a critical factor for maximizing grain yield. This finding was further validated in two independent super-high-yielding rice cultivars, each yielding approximately 21 t ha−1 of rough rice at 14% moisture content. Furthermore, we revealed that stabilizing the grain-filling rate could lead to a potential yield increase of 30–40% in an elite rice cultivar. Notably, the instantaneous grain-filling rates around 15- and 38-day post-flowering significantly influence grain yield; and we introduced an innovative in situ approach using ear respiratory rates for precise quantification of these rates. We finally derived an equation to predict the maximum dried brown rice yield (Y, t ha−1) of a cultivar based on its potential gross photosynthetic accumulation from flowering to harvest (Apc, t CO2 ha−1): Y = 0.74 × Apc + 1.9. Overall, this work establishes a framework for quantitatively dissecting crop physiology and designing high-yielding ideotypes.

Roles of Calcium Signaling in Gene Expression and Photosynthetic Acclimatization of Solanum lycopersicum Micro-Tom (MT) after Mechanical Damage.

A momentary increase in cytoplasmic Ca2+ generates an oscillation responsible for the activation of proteins, such as calmodulin and kinases, which interact with reactive oxygen species (ROS) for the transmission of a stress signal. This study investigated the influence of variations in calcium concentrations on plant defense signaling and photosynthetic acclimatization after mechanical damage. Solanum lycopersicum Micro-Tom was grown with 0, 2 and 4 mM Ca2+, with and without mechanical damage. The expression of stress genes was evaluated, along with levels of antioxidant enzymes, hydrogen peroxide, lipid peroxidation, histochemistry, photosynthesis and dry mass of organs. The ROS production generated by mechanical damage was further enhanced by calcium-free conditions due to the inactivation of the oxygen evolution complex, contributing to an increase in reactive species. The results indicated that ROS affected mechanical damage signaling because calcium-free plants exhibited high levels of H2O2 and enhanced expression of kinase and RBOH1 genes, necessary conditions for an efficient response to stress. We conclude that the plants without calcium supply recognized mechanical damage but did not survive. The highest expression of the RBOH1 gene and the accumulation of H2O2 in these plants signaled cell death. Plants grown in the presence of calcium showed higher expression of SlCaM2 and control of H2O2 concentration, thus overcoming the stress caused by mechanical damage, with photosynthetic acclimatization and without damage to dry mass production.

Tissue-specific transcriptome profiles identify functional differences key to understanding whole plant response to life in variable salinity.

ABSTRACTPlants endure environmental stressors via adaptation and phenotypic plasticity. Studying these mechanisms in seagrasses is extremely relevant as they are important primary producers and functionally significant carbon sinks. These mechanisms are not well understood at the tissue level in seagrasses. Using RNA-seq, we generated transcriptome sequences from tissue of leaf, basal leaf meristem and root organs of Posidonia australis, establishing baseline in situ transcriptomic profiles for tissues across a salinity gradient. Samples were collected from four P. australis meadows growing in Shark Bay, Western Australia. Analysis of gene expression showed significant differences between tissue types, with more variation among leaves than meristem or roots. Gene ontology enrichment analysis showed the differences were largely due to the role of photosynthesis, plant growth and nutrient absorption in leaf, meristem and root organs, respectively. Differential gene expression of leaf and meristem showed upregulation of salinity regulation processes in higher salinity meadows. Our study highlights the importance of considering leaf meristem tissue when evaluating whole-plant responses to environmental change.This article has an associated First Person interview with the first author of the paper.

Photosynthetic product allocations of Pinus massoniana seedlings inoculated with ectomycorrhizal fungi along a nitrogen addition gradient.

Quantifying the allocation of photosynthetic products among different carbon (C) pools is critical for understanding and predicting plant C turnover response to climate change. A field experiment with ectomycorrhizal fungi (EMF) and nitrogen (N) was established to investigate the effects on allocation of photosynthetic products in Pinus massoniana (Lamb.) seedlings given increased N deposition. Seedlings were subjected to N addition and symbiosis with EMF, and the short-term allocation of a 13C photosynthetic pulse into leaves, branches, stems, roots, and soil was traced. Photosynthetic rate and root respiration were measured. It was found that N addition changed the allocation pattern of photosynthetic products in various organs of P. massoniana. Furthermore, N addition, mycorrhizal symbiosis, and interaction of N and EMF, all increased the amount of C produced by photosynthesis. N application less than 60 kg N hm–1 a–1 could promote the transfer and allocation of photosynthetic products in P. massoniana organs, which peaks at 60 kg N hm–1 a–1, and the highest N treatment began to decrease at 90 kg N hm–1 a–1. EMF inoculation could expand the absorption area of plant roots to obtain more nutrients and synthesize more C and N compounds for promoting the growth of itself and the host plant, improving the net photosynthetic rate and the distribution of C produced by photosynthesis in various organs. This forms a benign C and N cycle, thereby reducing the effect of high N addition on plants. The optimal N addition concentration was 60 kg N hm–1 a–1, and the optimal EMF was Pt, which provides a theoretical basis for inoculating EMF during increasing N deposition in the future climate change scenario. This enables plants to distribute more photosynthetic products to their roots, thus affecting their own C distribution for promoting growth.

Designed polymeric conjugation motivates tunable activation of molecular oxygen in heterogeneous organic photosynthesis

Photocatalytic oxidative organic reactions are important synthetic transformations, and research on reaction selectivity by reactive oxygen species (ROS) is significant. To date, however, there has rarely been any focus on the directed generation of ROSs. Herein, we report the first identification of tunable molecular oxygen activation induced by polymeric conjugation in nonmetallic conjugated microporous polymers (CMP). The conjugation between these can be achieved by the introduction of alkynyl groups. CMP-A with an alkynyl bridge facilitates the intramolecular charge mobility while CMP-D, lacking an alkynyl group enhances the photoexcited carrier build-up on the surface from diffusion. These different processes dominate the directed ROS generation of the superoxide radical (O2−) and singlet oxygen (1O2), respectively. This theory is substantiated by the different performances of these CMPs in the aerobic oxidation of sulfides and the dehydrogenative coupling of amines, and could provide insight into the rational design of CMPs for various heterogeneous organic photosynthesis.

Biomimetic donor-acceptor motifs in carbon nitrides: Enhancing red-light photocatalytic selective oxidation by rational surface engineering

Oxidation, especially selective oxidation by a heterogeneous catalyst with molecular oxygen, is a core technology for the conversion of petrochemical feedstock to commodity chemicals and pharmaceuticals. Existing catalytic approaches for efficient aerobic oxidation normally rely on the engagement of organometallic centers or transition-metal nanoparticles. In light of the necessity to develop sustainable production methodologies, multiple approaches for the metal-free polymeric carbon nitride (PCN) photocatalytic selective oxidation have been evaluated. However, the insufficient visible light optical absorption, poor charge-carriers separation and the weak driving force towards oxidation reaction impart a serious restriction on the efficiency and selectivity of the organic photosynthesis, especially under extended wavelength solar light irradiation. Here, we report a surface engineering photochemical modification method to fabricate a donor-acceptor (D-A) functional carbon nitride photocatalyst (ECN) under ambient conditions. The well-developed d-A structure, preserved high crystallinity and enlarged π-conjugation framework of the hybrid semiconductor-molecule ECN samples favor the improvement of the optical absorption, as well as the enhanced separation and migration of the photo-generated charge carriers. As a result, the obtained ECN photocatalysts exhibited remarkable enhancement in the photocatalytic aerobic oxidation of alcohols, even under an extended light wavelength of 620 nm red-light irradiation. The photocatalytic aerobic sulfides and sp3 C–H oxidation reactions were also considerably accelerated over ECN and may serve as a direct approach for the construction of value-added sulfoxide and ketone products.

Progress in Photocatalysis of g-C3N4 and its Modified Compounds

Recently, graphitic carbon nitride (g-C3N4), a polymeric semiconductorhas been widely used as a low-cost, stable, and metal-free visible-light-active photocatalyst in the sustainable utilization of solar energy, such as water splitting, organic photosynthesis, and environmental remediation, which has attracted world wide attention from energy and environmental relative fields. Base on analysis of structure and theoretical calculation, the reasons that g-C3N4 can be used as a non-metallic catalyst were discussed in this paper. Some group's research jobs that metal-supported g-C3N4, metal-supported g-C3N4/organnic semiconductor compound and heterogeneous junction adjust the semiconductor electronic band structure have been summarized. And the mechanism, effect factors, and research developments on the reaction of organic degradation by photocatalytic and splitting water for hydrogen revolution catalyzed by above-mentioned modified g-C3N4 were emphatically analyzed. Finally, the prospects for the development of highly efficient g-C3N4 based photocatalysts are also discussed.

An in situ approach to characterizing photosynthetic gas exchange of rice panicle

BackgroundPhotosynthesis of reproductive organs in C3 cereals is generally regarded as important to crop yield. Whereas, photosynthetic characteristics of reproductive organs are much less understood as compared to leaf photosynthesis, mainly due to methodological limitations. To date, many indirect methods have been developed to study photosynthesis of reproductive organs and its contribution to grain yield, such as organ shading, application of herbicides and photosynthetic measurement of excised organs or tissues, which might be intrusive and cause biases. Thus, a robust and in situ approach needs to be developed.ResultsHere we report the development of a custom-built panicle photosynthesis chamber (P-chamber), which can be connected to standard infrared gas analyzers to study photosynthetic/respiratory rate of a rice panicle. With the P-chamber, we measured panicle photosynthetic characteristics of seven high-yielding elite japonica, japonica-indica hybrid and indica rice cultivars. Results show that, (1) rice panicle is photosynthetically active during grain filling, and there are substantial inter-cultivar variations in panicle photosynthetic and respiratory rates, no matter on a whole panicle basis, on an area basis or on a single spikelet basis; (2) among the seven testing cultivars, whole-panicle gross photosynthetic rates are 17–54 nmol s−1 5 days after heading under photon flux density (PFD) of 2000 μmol (photons) m−2 s−1, which represent some 20–38% of that of the corresponding flag leaves; (3) rice panicle photosynthesis has higher apparent CO2 compensation point, light compensation point and apparent CO2 saturation point, as compared to that of a typical leaf; (4) there is a strong and significant positive correlation between gross photosynthetic rate 5 days after heading on a single spikelet basis and grain setting rate at harvest (Pearson correlation coefficient r = 0.93, p value < 0.0001).ConclusionsRice panicle gross photosynthesis is significant, has great natural variation, and plays an underappreciated role in grain yield formation. The P-Chamber can be used as a tool to study in situ photosynthetic characteristics of irregular non-foliar plant organs, such as ears, culms, leaf sheaths, fruits and branches, which is a relatively less explored area in current cereal breeding community.

Hydrogen reduction treatment of boron carbon nitrides for photocatalytic selective oxidation of alcohols

Light-driven selective oxidation of aromatic alcohols allows a sustainable and eco-friendly manner to convert solar energy into highly valuable aromatic aldehydes. However, the low separation and transfer efficiency of photogenerated charge carriers and the sluggish reaction kinetics seriously restrict the efficiency of the organic photosynthesis of desired compounds. Herein, a facile strategy is adopted to regulate the boron carbon nitrides (BCN) semiconductors by hydrogen reduction to precisely tune the structural and surface properties. The reduced BCN materials can effectively enhance charge separation and migration as well as promote O2 activation and mass transfers. As a result, this BCN catalyst therefore displays a remarkable enhancement in photosynthesis of aromatic aldehydes from the alcohols with high conversion and selectivity compared to pristine BCN.

ZnCl2 Enabled Synthesis of Highly Crystalline and Emissive Carbon Dots with Exceptional Capability to Generate O2⋅–

Summary Highly crystalline and emissive carbon dots (CDs) are firstly synthesized via an ionothermal method in organic solvents. In contrast to well-established approaches, ZnCl2 is utilized as the pyrolysis-promoting agent to prepare emissive CDs with tunable wavelengths, directly by carbonization from different O and N precursors under a mild reaction condition at 210°C. More than 50% synthetic yield and 39% photoluminescent quantum yield (blue CD) are obtained. XAFS measurements, in conjunction with TEM, HAADF-STEM, UPS, and ESR analyses, allow us to obtain energy diagram configuration and confirm the luminescent nature of these hard-core structured CDs. Importantly, the resulting CDs exhibit excellent capability to photogenerate superoxide radical anion (O2⋅–), which can be exemplified by both photodynamic therapy and photooxidative cyclization synthesis of tetrahydroquinolines. Representative pharmaceutical mifepristone can be derivatized in 90% yield within 10 min of irradiation of the CDs in an elegant flow reactor.

Физиологические исследования древесных растений

Приведены результаты изучения водного и светового режимов, а также углеродного баланса лесов в разных лесорастительных зонах, засухоустойчивости и теневыносливости разных пород деревьев. Построена математическая модель определения углеродного баланса разных пород в различных климатических условиях. Разработана методика оценки фотосинтетической продуктивности древостоев, основанная на зависимости КПД использования солнечной радиации на фотосинтез охвоенных или облиственных побегов и поглощения пологом древостоя солнечной радиации. The Laboratory of Plant Physiology was founded at the Forest Institute in 1944 under the supervision of a member of correspondent USSR Academy of Sciences L.A. Ivanova. During this time, the laboratory studied the water, light conditions and carbon balance of the forest in different forest zones. The dependence of the number and spectral composition of PARs under the forest canopy on the throughput of the canopy of the forest stand was investigated. The physiological mechanism of drought tolerance of trees in the steppe zone has been studied. It has been shown that there are various ways of adapting tree species to drought. The joint existence of species with different types of adaptation of trees to arid conditions (for example, oak, fluffy ash and small-leaved elm) reduces the life of plantings. Artificial shading studied the effect of light deficiency on growth, leaf anatomy and carbon metabolism in seedlings of different species and revealed a physiological mechanism shade tolerance. The intensity of the processes of carbon metabolism photosynthesis and respiration of various organs of trees (leaves, branches of different ages, trunk, growth and sucking roots) and their dependence on external conditions were studied. The carbon balance of individual leaves, branches, trees and stands was calculated under different weather conditions. The crown structure of several tree species was studied, the carbon balance of branches of different ages, and their lifespan. A mathematical model of the carbon balance of different species is constructed, and on this basis the possibility of the existence of a forest depending on the climate is calculated. Ecological and physiological studies were conducted (root respiration and photosynthesis of pine and birch). A methodology has been developed for assessing photosynthetic productivity based on the dependence of the efficiency of the use of absorbed solar radiation on the photosynthesis of covered or leafy shoots and the absorption of solar radiation by the canopy. It was found that forestry and photosynthetic productivity differ only slightly in these methods. It was found that the stands of pine and birch growing in optimal forest conditions have almost the same productivity. Estimates of the effect of moisture deficiency in seedlings of tree species under the canopy of wood stand.

Participation of stem and ear photosynthesis in formation of the crop and its quality in wheat

Photosynthesis of various organs and their contribution to formation of ear caryopsis were measured using14CO2 labeled carbon in the phase of caryopsis formation of spring wheat plants (Moskovskaya-35). It turned out that inclusion of14C into amino acids is more than twice as high in photosynthesis of an ear. Among labeled low molecular weight compounds in caryopsis, during a short exposure (2 hours) after photosynthesis, the most of the labeled carbon in the14CO2 was found from the photoassimilates of the flag leaf (70.4%); from the ear (55.8%), and the least – from the stem under the flag (41.5%). The difference in inclusion of14C into the caryopsis’ total proteins was observed only with a short exposure of the photosynthesizing organ (2 hours). Water-soluble proteins, as products of photosynthesis of the flag leaf, were synthesized for the most in the caryopsis (flag – 73.9%; stem – 46.4% and ear – 44.8%), and in the synthesis of complex proteins, which are soluble in alkali and Triton X-100, most of14C was from the products of photosynthesis of non-leaf organs (10.5; 21.5; 28.4 and 4.3; 12.5; 13.4), respectively.

Synergy of dopants and defects in ultrathin 2D carbon nitride sheets to significantly boost the photocatalytic hydrogen evolution

Atomically thin 2D carbon nitride sheets (CNs) can improve the photocatalytic performance due to their high specific surface area, exposed active sites, and nano-scaled diffusion path of the charge transferred to surface. However, in practical application, 2D CNs photocatalysts always suffer the low solar absorption. Here, we present a novel approach to achieve the ultrathin 2D CNs photocatalysts with wide spectrum absorption in visible-light range. The new method, i.e. thermal annealing of atomically thin CNs in Se vapor, can dramatically extend the absorption edge of the ultrathin CNs from 418 to 574 nm. Using structural characterization and spin-polarized density functional theory, we identify the loss of the nitrogen atoms at the edges and in situ Se doping into the network of ultrathin CNs, which could change the electronic band structure of the 2D CNs. As a consequence, the ultrathin 2D CNs photocatalyst via Se vapor annealing (Se-CNs) modified by Pt cocatalyst shows a superior photocatalytic hydrogen evolution activity under visible light irradiation. More significantly, the ultrathin Se-CNs photocatalyst also exhibits an impressive photocatalytic hydrogen evolution activity under visible-light irradiation in the absence of Pt cocatalyst. We believe that our study provide a facile and environmentally friendly strategy to realize the utilization of 2D CNs photocatalyst under wide spectrum range of solar radiation to harvest solar energy efficiently, and it can be further applied in various advanced fields, including CO2 photoreduction, organic photosynthesis, and pollutant controls.

Rational Ionothermal Copolymerization of TCNQ with PCN Semiconductor for Enhanced Photocatalytic Full Water Splitting.

Photocatalytic full water splitting remains the perfect way to generate oxygen (O2) and hydrogen (H2) gases driven by sunlight to address the future environmental issues as well as energy demands. Owing to its exceptional properties, polymeric carbon nitride (PCN) has been one of the most widely investigated semiconductor photocatalysts. Nevertheless, blank PCN characteristically displays restrained photocatalytic performance due to high-density defects in its framework that may perhaps perform the part of the recombination midpoint for photoproduced electron-hole pairs. Therefore, to overcome this problem, a simple approach to introduce 7,7,8,8-tetracyanoquinodimethane (TCNQ) with an electron-withdrawing characteristic modifier into the pristine PCN framework by the ionothermal method to enhance its optical, conductive, and photocatalytic properties has been undertaken. Results show that such integration of TCNQ results in the delocalization of the π-conjugated structure; significant changes in its chemical electronic configuration, band gap, and surface area; and enhanced production of electrons under visible light. As a result of this facile integration, our best sample (CNU-TCNQ9.0) produced a hydrogen evolution rate (HER) of 164.6 μmol h-1 for H2 and an oxygen evolution rate (OER) of 14.8 μmol h-1 for O2, which were found to be 2.4- and 2.6-fold greater than those produced with pure carbon nitride (CNU) sample, respectively. Hence, this work provides a reasonable alternative method to synthesize and design novel CNU-TCNQ backbone photocatalyst for organic photosynthesis, CO2 reduction, hydrogen evolution, etc.