Regulating Chlorine and Hydrogen Atom Transfer for Selective Photoelectrochemical C─C Coupling by Cu-coordination Effect at Semiconductor/Electrolyte Interfaces.

Semiconductor-based photoelectrochemical (PEC) organic transformations usually show radical characteristics, in which the reaction selectivity is often difficult to precisely control due to the nonselectivity of radicals. Accordingly, several simple organic reactions (e.g., oxidations of alcohols, aldehydes, and other small molecules) have been widely studied, while more complicated processes like C─C coupling remain challenging. Herein, a synergistic heterogeneous/homogeneous PEC strategy is developed to achieve a controllable radical-induced C─C coupling reaction mediated by the copper-coordination effect at the semiconductor/electrolyte interfaces, which additionally exerts a significant impact on the product regioselectivity. Through experimental studies and theoretical simulations, this study reveals that the copper-chloride complex effectively regulates the formation of chloride radicals, a typical hydrogen atom transfer agent, on semiconductor surfaces and stabilizes the heterogeneous interfaces by suppressing the radical-induced surface passivation. Taking the Minisci reaction (the coupling between 2-phenylquinoline and cyclohexane) as a model, the yield of the target C─C coupling product reaches up to 90% on TiO2 photoanodes with a selectivity of 95% and long-term stability over 100 h. Moreover, such a strategy exhibits a broad scope and can be used for the functionalization of various heteroaromatic hydrocarbons.

Impact of ZnO NPs on photosynthesis in rice leaves plants grown in saline-sodic soil.

Saline-sodic stress restricts the absorption of zinc by rice, consequently impacting the photosynthesis process of rice plants. In this experiment, Landrace 9 was selected as the test material and the potting method was employed to investigate the influence of ZnO nanoparticles (ZnO NPs) on zinc absorption and chlorophyll fluorescence in rice grown in saline-sodic land. The research findings demonstrate that the application of ZnO NPs proves to be more advantageous for the growth of rice in saline-sodic soil. Notably, the application of ZnO NPs significantly decreases the levels of Na+ and MDA in rice leaves in saline-sodic soil, while increasing the levels of K+ and Zn2+. Additionally, ZnO NPs enhances the content of chloroplast pigments, specific energy flux, quantum yield, and the performance of active PSII reaction center (PIABS) in rice leaves under saline-sodic stress. Furthermore, the relative variable fluorescence (WK and VJ) and quantum energy dissipation rate (φDo) of rice are also reduced. Therefore, the addition of ZnO NPs enhances the transfer of electrons and energy within the rice photosystem when subjected to saline-sodic stress. This promotes photosynthesis in rice plants growing in saline-sodic land, increasing their resistance to saline-sodic stress and ultimately facilitating their growth and development.

Zinc regulation of chlorophyll fluorescence and carbohydrate metabolism in saline-sodic stressed rice seedlings.

Saline-sodic stress can limit the absorption of available zinc in rice, subsequently impacting the normal photosynthesis and carbohydrate metabolism of rice plants. To investigate the impact of exogenous zinc application on photosynthesis and carbohydrate metabolism in rice grown in saline-sodic soil, this study simulated saline-sodic stress conditions using two rice varieties, 'Changbai 9' and 'Tonghe 899', as experimental materials. Rice seedlings at 4 weeks of age underwent various treatments including control (CT), 2 µmol·L-1 zinc treatment alone (Z), 50 mmol·L-1 saline-sodic treatment (S), and 50 mmol·L-1 saline-sodic treatment with 2 µmol·L-1 zinc (Z + S). We utilized JIP-test to analyze the variations in excitation fluorescence and MR820 signal in rice leaves resulting from zinc supplementation under saline-sodic stress, and examined the impact of zinc supplementation on carbohydrate metabolism in both rice leaves and roots under saline-sodic stress. Research shows that zinc increased the chloroplast pigment content, specific energy flow, quantum yield, and performance of active PSII reaction centers (PIABS), as well as the oxidation (VOX) and reduction rate (Vred) of PSI in rice leaves under saline-sodic stress. Additionally, it decreased the relative variable fluorescence (WK and VJ) and quantum energy dissipation yield (φDO) of the rice. Meanwhile, zinc application can reduce the content of soluble sugars and starch in rice leaves and increasing the starch content in the roots. Therefore, the addition of zinc promotes electron and energy transfer in the rice photosystem under saline-sodic stress. It enhances rice carbohydrate metabolism, improving the rice plants' ability to withstand saline-sodic stress and ultimately promoting rice growth and development.

Bias distribution and regulation in photoelectrochemical overall water-splitting cells.

The water oxidation half-reaction at anodes is always considered the rate-limiting step of overall water splitting (OWS), but the actual bias distribution between photoanodes and cathodes of photoelectrochemical (PEC) OWS cells has not been investigated systematically. In this work, we find that, for PEC cells consisting of photoanodes (nickel-modified n-Si [Ni/n-Si] and α-Fe2O3) with low photovoltage (Vph < 1 V), a large portion of applied bias is exerted on the Pt cathode for satisfying the hydrogen evolution thermodynamics, showing a thermodynamics-controlled characteristic. In contrast, for photoanodes (TiO2 and BiVO4) with Vph > 1 V, the bias required for cathode activation can be significantly reduced, exhibiting a kinetics-controlled characteristic. Further investigations show that the bias distribution can be regulated by tuning the electrolyte pH and using alternative half-reaction couplings. Accordingly, a volcano plot is presented for the rational design of the overall reactions and unbiased PEC cells. Motivated by this, an unbiased PEC cell consisting of a simple Ni/n-Si photoanode and Pt cathode is assembled, delivering a photocurrent density of 5.3 ± 0.2 mA cm-2.

The plasmonic effect of Cu on tuning CO2 reduction activity and selectivity.

Copper (Cu) has been widely used for catalyzing the CO2 reduction reaction (CO2RR), but the plasmonic effect of Cu has rarely been explored for tuning the activity and selectivity of the CO2RR. Herein, we conducted a quantitative analysis on the plasmon-generated photopotential (Ehv) of a Cu nanowire array (NA) photocathode and found that Ehv exclusively reduced the apparent activation energy (Ea) of reducing CO2 to CO without affecting the competitive hydrogen evolution reaction (HER). As a result, the CO production rate was enhanced by 52.6% under plasmon excitation when compared with that under dark conditions. On further incorporation with a polycrystalline Si photovoltaic device, the Cu NA photocathode exhibits good stability in terms of photocurrent and syngas production (CO : H2 = 2 : 1) within 10 h. This work validates the crucial role of the plasmonic effect of Cu on modulating the activity and selectivity of the CO2RR.

Highly Selective Ammonia Oxidation on BiVO4 Photoanodes Co-catalyzed by Trace Amounts of Copper Ions.

High-efficient photoelectrocatalytic direct ammonia oxidation reaction (AOR) conducted on semiconductor photoanodes remains a substantial challenge. Herein, we develop a strategy of simply introducing ppm levels of Cu ions (0.5-10 mg/L) into NH3 solutions to significantly improve the AOR photocurrent of bare BiVO4 photoanodes from 3.4 to 6.3 mA cm-2 at 1.23 VRHE , being close to the theoretical maximum photocurrent of BiVO4 (7.5 mA cm-2 ). The surface charge-separation efficiency has reached 90 % under a low bias of 0.8 VRHE . This AOR exhibits a high Faradaic efficiency (FE) of 93.8 % with the water oxidation reaction (WOR) being greatly suppressed. N2 is the main AOR product with FEs of 71.1 % in aqueous solutions and FEs of 100 % in non-aqueous solutions. Through mechanistic studies, we find that the formation of Cu-NH3 complexes possesses preferential adsorption on BiVO4 surfaces and efficiently competes with WOR. Meanwhile, the cooperation of BiVO4 surface effect and Cu-induced coordination effect activates N-H bonds and accelerates the first rate-limiting proton-coupled electron transfer for AOR. This simple strategy is further extended to other photoanodes and electrocatalysts.

Transition from Sequential to Concerted Proton-Coupled Electron Transfer of Water Oxidation on Semiconductor Photoanodes.

Accelerating proton transfer has been demonstrated as key to boosting water oxidation on semiconductor photoanodes. Herein, we study proton-coupled electron transfer (PCET) of water oxidation on five typical photoanodes [i.e., α-Fe2O3, BiVO4, TiO2, plasmonic Au/TiO2, and nickel-iron oxyhydroxide (Ni1-xFexOOH)-modified silicon (Si)] by combining the rate law analysis of H2O molecules with the H/D kinetic isotope effect (KIE) and operando spectroscopic studies. An unexpected and universal half-order kinetics is observed for the rate law analysis of H2O, referring to a sequential proton-electron transfer pathway, which is the rate-limiting factor that causes the sluggish water oxidation performance. Surface modification of the Ni1-xFexOOH electrocatalyst is observed to break this limitation and exhibits a normal first-order kinetics accompanied by much enhanced H/D KIE values, facilitating the turnover frequency of water oxidation by 1 order of magnitude. It is the first time that Ni1-xFexOOH is found to be a PCET modulator. The rate law analysis illustrates an effective strategy for modulating PCET kinetics of water oxidation on semiconductor surfaces.

Boosting Electrochemical Styrene Transformation via Tandem Water Oxidation over a Single-Atom Cr1 /CoSe2 Catalyst.

Electrocatalytic oxidation of organics using water as the oxygen source is a prospective but challenging method to produce high-value-added chemicals; especially, the competitive oxygen evolution reaction (OER) limits its efficiency. Herein, a tandem catalysis strategy based on a single-atom catalyst with Cr atoms atomically dispersed at a CoSe2 support (Cr1 /CoSe2 ) is presented. Thereinto, Co and Cr sites are endowed with a specific function to activate water and styrene respectively, and the competition between the OER and styrene oxidation is turned into mutual benefits via cooperated active sites. Under a potential of 1.6 VAg/AgCl , excellent selectivity of 95% to benzaldehyde and a high conversion rate of styrene at 88% without any exogenous oxidizing reagent are achieved. Isotopic tracing, isotope-labeled in situ Raman spectra, and detailed theoretical calculation further reveal the tandem mechanism, showing that the transfer of *OOH intermediates from the Co to the Cr sites serves as a bridge to link the oxidation of water and styrene. This work develops a new strategy for the co-oxidation of multi-species based on tandem catalysis, providing novel insights for the design of single-atom catalysts.

Responsive-released strategy based on lead ions-dependent DNAzyme functionalized UIO-66-NH2 for tumor marker.

Signal labeling on electrode interface is an important step during the construction of immunosensor and most signal substances are directly affixed on the immunoprobe or substrate so that some problems such as flimsy labeling method and interference of insulating proteins on electrode surface have been existed to affect their readout. In order to solve above problems in electrochemical immunoassay, a lead ions-decodable autocephalous signal integrator based on UIO-66-NH2 was proposed for the detection of prostate specific antigen (PSA). Briefly, a lead ions-dependent DNAzyme functionalized UIO-66-NH2, in which methylene blue was encapsulated, was independently dispersed in solution phase to be closely associated with the lead sulfide labeled sandwich bioconjugates, and internal methylene blue molecules can be sustained released once a cationic exchange reaction was occurred between lead sulfide label and adscititious silver ions. Based on this designing, immunoassay for PSA was effectively connected with the dynamic behavior of methylene blue molecules through the cleavage of DNAzyme on MOFs surface and performed a wide linear range from 1 pg mL-1 to 10 ng mL-1 and a satisfactory detection limit with 0.34 pg mL-1. The proposed strategy was expected to offer more valuable information for the application of MOFs in early and accurate cancer diagnosis.

Conjugated π Electrons of MOFs Drive Charge Separation at Heterostructures Interface for Enhanced Photoelectrochemical Water Oxidation.

Photoanode material with high efficiency and stability is extensively desirable in photoelectrochemical (PEC) water splitting for green/renewable energy source. Herein, novel heterostructures is constructed via coating rutile TiO2 nanorods with metal organic framework (MOF) materials UiO-66 or UiO-67 (UiO-66@TiO2 and UiO-67@TiO2 ), respectively. The π electrons in the MOF linkers could increase the local electronegativity near the heterojunction interface due to the conjugation effect, thereby enhancing the internal electric field (IEF) at the heterojunction interface. The IEF could drive charge transfer following Z-scheme mechanism in the prepared heterostructures, inducing photogenerated charge separation efficiency increasing as 156% and 253% for the UiO-66@TiO2 and UiO-67@TiO2 , respectively. Correspondingly, the UiO-66@TiO2 and UiO-67@TiO2 enhanced the photocurrent density as approximate two- and threefolds compared with that of pristine TiO2 for PEC water oxidation in universal pH electrolytes. This work demonstrates an effective method of regulating the IEF of heterojunction toward further improved charge separation.

Using Smartphone APP To Determine the CN- Concentration Quantitatively in Tap Water: Synthesis of the Naked-Eye Colorimetric Chemosensor for CN- and Ni2+ Based on Benzothiazole.

A naked-eye colorimetric chemosensor DK based on benzothiazole could recognize CN- effectively. When DK interacted with CN- in the aqueous solution, the obvious color change of the solution was directly observed by the naked eye. Other anions did not cause any interference. It is interesting that DK could also discriminate Ni2+ from other cations, and the possible interaction mode between them was verified based on the Job's plot, 1H nuclear magnetic resonance titration, infrared , electrospray ionization mass spectrometry, scanning electron microscopy analysis, and density functional theory calculation methods. As a result, it is clear that the mode of action between DK and CN- was different from that between DK and Ni2+. Meanwhile, the limit of detection of DK toward CN- and Ni2+ was calculated to be 1.7 × 10-8 or 7.4 × 10-9 M, respectively. In addition, CN- was recognized qualitatively by a test paper and silica gel plates made from DK. DK was able to detect CN- in tap water quantitatively, rapidly, and on-site by the use of a smartphone APP. All results implied that DK has certain prospects for practical application to identify CN- in water.

Two novel compounds from Ardisia punctata Lindl.

To study the chemical constituents of Ardisia punctata, compounds were isolated with a combination of multi-chromatography. Their structures were determined on the basis of spectral analysis and comparison to those of the known compounds. A 1,4-benzoquinone derivative and a alkylphenol were isolated from the petroleum ether extract of the roots of Ardisia punctata. Their structures were elucidated as 2-tridecyl-3-[(2-tridecyl-4-acetoxy-6-methoxy)-phenoxyl] -6-methoxy-1,4-benzoquinone (1) and 2-methoxy-4-hydroxy-6-tridecyl-phenyl acetate (2). The two compounds are both new.

Three new belamcandaquinones from Ardisia punctata.

AIM: To study the chemical constituents of Ardisia punctata. METHODS: Compounds were separated with a combination of multi-chromatography. Their chemical structures were determined on the basis of spectral analysis and single crystal X-ray diffraction. RESULTS: Three compounds were isolated from chloroform extract of the roots of Ardisia punctata. Their structures were elucidated as 2-tridecyl-3-[(2-tridecyl-3-acetoxy-4-methoxy-6-hydroxy) -phenyl]-6-methoxy-1, 4-benzoquinone (1), 2-tridecyl-3-[(2-tridecyl-4,6-dihydroxy) -phenyl]-6-methoxy-1,4-benzoquinone (2) and 2-tridecyl-3-[(2-pentadecyl-4,6-dihydroxyl) -phenyl]-6-methoxy-,4-benzoquinone (3). CONCLUSION: The three compounds are new 1,4-benzoquinone derivatives.

[Chemical constituents from roots of Ardisia punctata].

OBJECTIVE: To study the chemical constituents from the roots of Ardisia punctata. METHOD: Compounds were isolated by chromatographic techniques on silica gel and Rp-HPLC column. Their structures were elucidated by chemical and spectroscopic methods. RESULT: Twelve compounds were identified as 3-hydroxy-5-tridecyl-methyl phenyl ether (1), 5-pentadecyl-1, 3-benzenediol (2), 2-methoxy-6-tridecyl-1, 4-benzoquinone (3), 2-methoxy-6-pentadecyl-1, 4-benzoquinone (4), glutinol (5), ardisicrenoside A (6), ardisiacrispin B (7), 24-ethyl-5a-cholesta-7, 22(E)-dien-3-one (8), 24-ethyl-5alpha-cholesta-7, 22(E)-dien-3beta-ol (9), daucosterol (10), vanillin acid (11), tetratriacontanoic acid (12). CONCLUSION: All the compounds were obtained from this plant for the first time.

[Determination of acetylharpagide in Ajuga decumbens by HPLC].

OBJECTIVE: To establish a method of the quantitative determination of acetylharpagide in Ajuga decumbens. METHOD: The chromatographic conditions were as follows: a Phenomenex Luna C18 column was used, the mobile phase was composed of acetontrile-water (15:85), the flow rate was 1.0 mL x min(-1) and the UV absorbance detection was set at 197 nm. RESULT: Linearity of acetylharpagide was in the range of 0.6-3.6 microg (r = 0.9993), and the average recovery and RSD were 99.13% and 2.48%, respectively. CONCLUSION: The contents of acetylharpagide ranged 0.40%-6.39% in A. decumbens. The method was simple, accurate and sensitive.

[Chemical constituents from roots of Ficus hirta].

OBJECTIVE: To study the chemical constituents from the roots of Ficus hirta. METHOD: Compounds were isolated by chromatographic techniques on silica gel and HP-20 resin columns. Their structures were elucidated by chemical and spectroscopic methods. RESULT: Ten compounds were identified as beta-sitosterol (1), stigmasterol (2), psoralene (3), 3beta-hydroxy-stigmast-5-en-7-one (4), 5-hydroxy-4', 6, 7, 8-tetramethoxy flavone (5), 4', 5, 6, 7, 8-pentamethoxy flavone (6), 4', 5, 7-trihydroxy-flavone (7), 3beta-acetoxy-beta-amyrin (8), 3beta-acetoxy-alpha-amyrin (9) and hesperidin (10). CONCLUSION: The compounds 4, 5, 6 were obtained from this genus for the first time, and all the compounds were obtained from this plant for the first time.