MYB transcription factors (TFs) have been shown to play a key role in plant growth and development and are in response to various types of biotic and abiotic stress. Here, we clarified the structure, expression patterns, and function of a MYB TF, SlMYB86-like (Solyc06g071690) in tomato using an inbred tomato line exhibiting high resistance to bacterial wilt (Hm 2-2 (R)) and one susceptible line (BY 1-2 (S)). The full-length cDNA sequence of this gene was 1226 bp, and the open reading frame was 966 bp, which encoded 321 amino acids; its relative molecular weight was 37.05055 kDa; its theoretical isoelectric point was 7.22; it was a hydrophilic nonsecreted protein; and it had no transmembrane structures. The protein also contains a highly conserved MYB DNA-binding domain and was predicted to be localized to the nucleus. Phylogenetic analysis revealed that SlMYB86-like is closely related to SpMYB86-like in Solanum pennellii and clustered with other members of the family Solanaceae. Quantitative real-time PCR (qRT-PCR) analysis revealed that the expression of the SlMYB86-like gene was tissue specific and could be induced by Ralstonia solanacearum, salicylic acid, and jasmonic acid. The results of virus-induced gene silencing (VIGS) revealed that SlMYB86-like silencing decreased the resistance of tomato plants to bacterial wilt, suggesting that it positively regulates the resistance of tomatoes to bacterial wilt. Overall, these findings indicate that SlMYB86-like plays a key role in regulating the resistance of tomatoes to bacterial wilt.
The existence of the oxidation/reduction interface can promote the performance of a photocatalyst, due to its effect on the separation of photogenerated carriers and the surface reactivity. However, it is difficult to construct two sets of oxidation/reduction interfaces in a single crystal and compare their separation efficiency for photogenerated carriers. Introducing a high proportion of active facets into the co-exposed facets is even more challenging. Herein, a hollow anatase TiO2 tetrakaidecahedron (HTT) with two sets of oxidation/reduction interfaces ({001}/{101} and {001}/{110}) is synthesized by directional chemical etching. Theoretical and experimental results indicate that the {001}/{110} interface is a dominant oxidation/reduction interface, showing a better promotion on the separation of photogenerated carriers than the {001}/{101} interface. In the HTT, the ratio of dominant {001}/(110) is increased and the proportion of the active {110} facet is about 40% (generally about 15%). Therefore, the HTT shows excellent catalytic activity for photocatalytic reductive (hydrogen production) and oxidative (selective oxidation of sulfides) reactions. The HTT also demonstrates favorable photocatalytic activity for the cross-dehydrogenative coupling reaction, where both photogenerated electrons and photogenerated holes are involved, further verifying its high separation efficiency of photogenerated carriers and surface reactivity. This work provides an important guideline for developing advanced structures with a predetermined interface toward desired applications.
The low separation efficiency of photogenerated electron-hole (e-h) pairs severely limits the activation of photocatalyts. One brilliant strategy is to construct a p-n type semiconductor heterojunction, which can establish an inner electric field to separate the e-h pairs with high efficiency. Here, for the first time, a cuboctahedral N-doped carbon-coated CuO/TiO2 p-n heterojunction (CuO-TiO2@N-C) was designed and fabricated successfully via direct calcination of a benzimidazole-modulated cuboctahedral HKUST-Cu with titanium-tetraisopropanolate absorbed inside concomitantly. Full structural characterizations incorporating DFT computations demonstrate that the CuO/TiO2 p-n heterostructure can greatly boost the transport and separation of photoinduced e-h pairs. The nitrogen-doped carbon coating, with its excellent conductivity, porosity, stability and surface reaction activity, plays a pivotal role in promoting the overall performance and effectiveness of the reaction. The CuO-TiO2@N-C displays significantly higher photocurrent density (0.042 µA cm-2) than the CuO@N-C (0.014 µA cm-2) and TiO2@N-C (0.03 µA cm-2) electrodes, proving that the p-n heterojunction can improve the e-h generation efficiency. This unique photocatalyst affords superior photocatalytic efficiency, cycle stability and substrate scope towards cross-dehydrogenative coupling reactions.
In this paper, a series of micro-nano reactors assembled by N doped carbon coated TiO2 heterojunction nanosheets with different thickness, named TiO2/N-C hollow framework (HF), TiO2/N-C hollow hexahedron assembled by nanosheets (HHS), and TiO2/N-C hollow hexahedron assembled by ultrathin nanosheets (HHUS), have been prepared by adjusting the alcoholysis rate of NH2-MIL-125 and then pyrolysis. Experimental and theoretical studies revealed that with the decrease of the thickness of the heterojunction nanosheet subunit, more low-coordination Ti atoms would be exposed as effective sites for photocatalytic H2 evolution, and the interaction between the carbon layer and TiO2 would also be enhanced, which provided a smooth migration path for the effective separation of photogenerated carriers. Thus, TiO2/N-C HHUS with the thinnest nanosheet subunit exhibited the best photoelectric performance and the highest photocatalytic hydrogen production activity.
Rationally designing interface structure to modulate the electronic structure of a photocatalyst is an efficient strategy to facilitate the separation and migration of photogenerated charge carriers and improve photocatalytic activity. In this work, a AgCl/Pd heterostructure encapsulated by N-doped carbon nanotubes (AgCl/Pd@N-C) with a fan-like morphology assembled hollow tubes was synthesized by pyrolysis of a AgCl/Pd@Bim precursor. The unique interface structure not only increases the number of photogenerated charge carriers, but also provides an effective channel for the separation of electrons and holes, which have been proved by density functional theory (DFT) calculations. As expected, the obtained AgCl/Pd-3@N-C exhibited greatly enhanced conversion efficiency and recyclability toward the photocatalytic oxidative coupling of amine under blue-light irradiation.
In this study, we have facilely developed a SnO2-based electrocatalyst (SnO2-VO@N-C), which can combine together the favorable structure features of oxygen vacancies, porosity, and full-coating with N-doped carbon layers (N-C). Our experimental and theoretical calculation results indicated that with the facile engineering of oxygen vacancies and the full-coating of the N-doped carbon layer, the adsorption/activation of CO2 and charge transfer can be promoted in the CO2 reduction process, making SnO2-VO@N-C the electrocatalyst with improved activity and selectivity (FEHCOOH = 84%) toward the reduction of CO2 to HCOOH.
A monodisperse CeO2@N-C ultrathin nanosheet self-assembled hierarchical structure (USHR) has been prepared by metal-organic framework template methods. The uniform coating of nitrogen-doped carbon (N-C) layers could play an important role in the adsorption and activation of benzylic alcohol. The unique 3D hierarchical structure self-assembled by ultrathin nanosheets provided enough active sites for the catalytic reaction. Therefore, the CeO2@N-C USHR can afford excellent catalytic performance for selective oxidation of benzylic alcohols in water.
Developing efficient and robust bifunctional electrocatalysts are in high demand for the production of hydrogen by water splitting. Engineering an electrocatalyst with a regulated electronic structure and abundant active sites is an effective way to enhance the electrocatalytic activity. Herein, N-doped C-encapsulated Ni nanoparticles (Ni@N-C) are synthesized through a traditional hydrothermal reaction, followed by pyrolyzing under an Ar/H2 atmosphere. The electrochemical measurements and density functional theory (DFT) calculations reveal that the electron transfer between the Ni core and the N-C shell induces the electron density redistribution on Ni@N-C, which directly promotes the adsorption and desorption of H* on the N-doped carbon (N-C) layer and thus dramatically enhances hydrogen production. Taking advantage of the porous spherical structure and the synergistic effects between Ni and N-doped carbon (N-C) layer, we obtain a Ni@N-C electrocatalyst that exhibits remarkable hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activity with low overpotentials of 117 and 325 mV, respectively. Impressively, the assembled cell using Ni@N-C as both anode and cathode exhibits excellent activity as well as stable cyclability for over 12 h.
Nonmetallic doped metal oxides can be broad in their visible-light-response range. However, the half-filled or isolated impurity state can also be the new recombination center for photogenerated electrons/holes, which seriously influence the photocatalytic activity of the catalyst in the visible-light region. Therefore, how to prolong the photogenerated carrier life of nonmetallic doping metal oxides is the difficult and challenging topic in the field of photocatalysis. In this work, the hexagonal nanosheets assembled by N-doped C (N-C)-coated N-doped In2O3 (N-In2O3) nanoparticles (N-C/N-In2O3 HS) was obtained by simply pyrolyzing the In(2,5-PDC) hexagonal sheets. The N-C/N-In2O3 HS catalyst exhibit good photocatalytic activity and cycle stability in the long-wavelength region of visible light (λ = 520 and 595 nm). The effective utilization of long-wavelength visible light for N-C/N-In2O3 HS was mainly attributed to the acceptor-donor-acceptor compensation mechanism between the oxygen vacancy (VO) and substitutional N-doping (Ns) sites, which made the N-C/N-In2O3 HS possess a continuous band structure, without the half-filled or isolated impurity state in the band gap, and extended its light absorption edge to 733 nm. The compensation mechanism of nitrogen doping on In2O3 can promote the photocatalytic activity under longer-wavelength yellow light (595 nm) irradiation. The N-C layer coated on the N-In2O3 nanoparticles acted as a good acceptor of photogenerated electrons, facilitating the effective spatial separation of photogenerated carriers and extend photogenerated carrier lifetimes. The comparative photocatalytic experiments (N-In2O3 HS and N-C/N-In2O3 HS) show that the presence of N-doped C layer can enhance the photocatalytic efficiency by nearly 10-fold. This double-doping and carbon-coating strategy provided a novel research idea to solve the problem that nonmetal atoms doped metal oxides led to the secondary combination of photogenerated electrons/holes.
The low utilization efficiency in the visible region of the sunlight spectrum and the rapid recombination of photogenerated charge carriers are two crucial drawbacks that suppress the practical usage of metal oxide semiconductors as photocatalysts. In this article, we report a rational design of In2O3-In2S3 heterojunctions encapsulated by N-doped carbon with a hollow dodecahedral structure (In2O3-In2S3/N-C HDS), which can effectively handle the two drawbacks of metal oxide semiconductors and behave active for organic transformation under the irradiation of visible light even with long wavelengths. As exemplified by the selective oxidative coupling reaction of amine to imine, the obtained In2O3-In2S3/N-C HDS as the photocatalyst has exhibited excellent activity and stability. Experimental and density functional theory studies have verified that the excellent performance of In2O3-In2S3/N-C HDS can be attributed to the synergistic effect of In2O3-In2S3 heterojunctions, the coating of N-doped carbon, and the hollow porous structure with nanosheets as subunits.
Zn-doped cuprous oxide (Cu2O) nanoparticles coated by carbon layers (Zn/Cu2O@C) have been obtained via a bimetallic MOF (Zn/Cu-MOF-199) as the sacrificial precursor. Originated from the octahedral morphology of Zn/Cu-MOF-199, the as-synthesized Zn/Cu2O@C shows a porous octahedron structure. The obtained Zn/Cu2O@C can afford the following merits. (1) The cation doping of Zn inside Cu2O can enhance the light absorption by introducing impurity energy levels and facilitate the separation of photoinduced electrons and holes. (2) The coating of a carbon layer in Zn/Cu2O@C can also efficiently enhance the separation efficiency of photoinduced charge carriers. (3) The porous structure of Zn/Cu2O@C can provide increased active sites. Therefore, these merits lead to the highly improved photocatalytic activities toward various chemical reactions. In addition, the fully coated carbon layer can facilitate the cycle stability of Zn/Cu2O@C in the photocatalytic processes.
Engineering interfaces is an effective method to create efficient photocatalysts by reducing the recombination of photogenerated carriers. Still, there is a lack of proficient strategies to construct suitable interfaces. In this work, we design and synthesize an atom-precise heterometallic CuII4TiIV5 cluster, [Ti5Cu4O6(ba)16]·2CH3CN (1, Hba = benzoic acid), which is used as a precursor for fabricating efficient photocatalytic interfaces. The cluster has a precise composition and structure with hierarchical bimetal atom distribution and favorable binding properties. The resulting Cu/TiO2@N-doped C interfaces are obtained via the thermal treatment. Combined Cu/TiO2 with N-doped C interfaces provide multiple channels for the transmission of photogenerated carriers and effectively reduce the recombination probability of photogenerated charge carriers. Consequently, the novel interface structure exhibits an excellent hydrogen evolution rate via the photocatalytic water splliting. Density functional theory calculations also support high activity of the interfaces toward hydrogen evolution. As a proof-of-concept application, we show that choosing well-defined metal clusters as precursors can offer a valuable method for engineering photocatalytically efficient interfaces.
Developing high-efficiency and cost-effective electrocatalysts for the oxygen evolution reaction (OER) is crucial for various energy conversion systems. Herein, N/S co-doped C encapsulated hollow NiCo2O4/NiO hexagonal rods (HNHR@N/S-C) as the electrocatalysts for OER have been successfully prepared with rational control of structure and composition. Experimental and theoretical results have highlighted that the NiCo2O4/NiO heterojunction in the obtained electrocatalyst can provide abundant active Ni and Co sites for the OER, leading to the highly enhanced OER performance. Moreover, attributed to the hierarchical hollow structure, which can provide a large surface area, and the improved electric conductivity with a coating of the N/S co-doped carbon layer, which can facilitate charge transport during the catalytic processes, a remarkable OER activity over HNHR@N/S-C with a low overpotential (η) of 285 mV (at j = 10 mA cm-2) and a Tafel slope of 53.0 mV decade-1 has been achieved, which is comparable to that of the noble metal catalyst IrO2. Because of the protection of the N/S doped C layer coating, HNHR@N/S-C can also maintain the current density of 10 mA cm-2 for at least 12 h in alkaline media without obvious losses of activity.
Catalysts based on metallic NPs have shown high activities in heterogeneous catalysis, due to their high fractions of surface-active atoms, which, however, will lead to the sacrifices in stability and recycle of catalysts. In order to balance well the relationship between activity, stability, and recovery, in this paper, we have constructed a 3D mesoporous sphere structure assembled by N-doped carbon coated Ni/Pd NP heterojunctions (Ni/Pd@N-C). This obtained Ni/Pd@N-C has shown high catalytic activity, durability and recyclability for the hydrolytic dehydrogenation of ammonia borane (AB). Further investigations, including experimental and theoretical results, have shown that the unique structural features, the synergistic effect between Ni and Pd, and the coating of N-doped carbon layer are responsible for the good catalytic performance of Ni/Pd@N-C mesoporous spheres.
N- and S-doped C-encapsulated CeO2 with a hinge-like nanostructure (CeO2@N,S-C HN) has been obtained by using a Ce-based metal-organic framework (Ce-MOF-808) as a precursor. Due to the synergistic effects of its special structure and N,S-doped C layer, CeO2@N,S-C HN exhibits high activity of photocatalytic hydrogen (H2) evolution. Density functional calculations are used to obtain a fundamental understanding of the high H2 production rate of CeO2@N,S-C HN.
Engineering p-n heterojunctions among metal oxide semiconductors to provide a built-in electric field is an efficient strategy to facilitate the separation of photogenerated electrons and holes and improve their photocatalytic activities. However, the inherent poor conductivity of p-n heterojunctions still limits the charge-transfer step and thus hampers their practical application in photocatalysis. In this work, a nitrogen-doped carbon-coated NiO/TiO2 p-n (NCNT) heterojunction with hierarchical mesoporous sphere morphology was synthesized by in situ pyrolytic decomposition of nickel-titanium complexes. The NiO/TiO2 p-n heterojunction in NCNT was fully characterized by several techniques, supported by theoretical calculations and Mott-Schottky plots. On coating with a thin nitrogen-doped carbon layer, the electron transfer of the obtained p-n heterojunction could be significantly enhanced. On account of the favorable structural features of the p-n heterojunction with nitrogen-doped carbon coating and hierarchical mesoporous structure, NCNT exhibited excellent photocatalytic activity toward various reaction systems, including the hydrogen evolution reaction and the visible-light-induced hydroxylation of phenylboronic acids.
Multicomponent NiTiO3 /A-TiO2 /R-TiO2 photocatalysts coated with nitrogen-doped carbon (N-C/NiTiO3 /A-TiO2 /R-TiO2 ) for efficient H2 production were fabricated by directly pyrolyzing NH2 -MIL-125(Ni/Ti) metal-organic framework microrods. Owing to the synergistic effect of the N-doped carbon coating layer and multicomponent heterojunctions, the H2 production rate of N-C/NiTiO3 /A-TiO2 /R-TiO2 was even higher than that of its Pt-containing counterpart (Pt/NiTiO3 /A-TiO2 /R-TiO2 ). N-C/NiTiO3 /A-TiO2 and N-C/NiTiO3 /R-TiO2 as control photocatalysts were also prepared by simply adjusting the calcination temperature of NH2 -MIL-125(Ni/Ti) in air atmosphere. The H2 production rate followed the order of N-C/NiTiO3 /A-TiO2 /R-TiO2 >N-C/NiTiO3 /A-TiO2 >N-C/NiTiO3 >R-TiO2 , which indicates that the multicomponent heterojunction plays a key role in photocatalytic H2 generation. The mechanism for the influence of the multicomponent heterojunction on photocatalytic activity was investigated in combination with molecular simulations, which showed that N-C/NiTiO3 /A-TiO2 /R-TiO2 has a so-called double typeâ II heterojunction providing a perfect step-by-step migration pathway for effective separation of photogenerated electrons and holes. This work presents a simple and effective method for synthesizing efficient multicomponent photocatalysts.
Excellent catalytic activity, high stability and easy recovery are three key elements for fabricating efficient photocatalysts, while developing a simple method to fabricate such photocatalysts with these three features at the same time is highly challenging. In this study, we successfully synthesized double-shelled hollow rods (DHR) assembled by nitrogen (N) and sulfur (S)-codoped carbon coated indium(III) oxide (In2O3) ultra-small nanoparticles (N,S-C/In2O3 DHR). N,S-C/In2O3 DHR exhibits remarkable photocatalytic activity, high stability and easy recovery for oxidative hydroxylation reaction of arylboronic acid substrates. The catalyst recovery and surface area were well balanced through improved light harvesting, contributed by concurrently enhancing the reflection on the outer porous shell and the diffraction in the inside double-shelled hollow structure, and increased separation rate of photogenerated carriers. Photocatalytic mechanism was investigated to identify the main reactive species in the catalytic reactions. The electron separation and transfer pathway via N,S-codoped graphite/In2O3 interface was revealed by theoretical calculations.
Achieving highly efficient hierarchical photocatalysts for hydrogen evolution is always challenging. Herein, hierarchical mesoporous NiO@N-doped carbon microspheres (HNINC) are successfully fabricated with ultrathin nanosheet subunits as high-performance photocatalysts for hydrogen evolution. The unique architecture of N-doped carbon layers and hierarchical mesoporous structures from HNINC could effectively facilitate the separation and transfer of photo-induced electron-hole pairs and afford rich active sites for photocatalytic reactions, leading to a significantly higher H2 production rate than NiO deposited with platinum. Density functional theory calculations reveal that the migration path of the photo-generated electron transfer is from Ni 3d and O 2p hybrid states of NiO to the C 2p state of graphite, while the photo-generated holes locate at Ni 4s and Ni 4p hybrid states of NiO, which is beneficial to improve the separation of photo-generated electron-hole pairs. Gibbs free energy of the intermediate state for hydrogen evolution reaction is calculated to provide a fundamental understanding of the high H2 production rate of HNINC. This research sheds light on developing novel photocatalysts for efficient hydrogen evolution.
A pair of enantiopure Au13 nanoclusters have been enantioselectively synthesized by chiral ligands with stereogenic centers at the phosphorus atoms. Their structures are determined by X-ray crystallography, which are typical models with a high symmetric core and chiral surface ligand arrangement. Correlation between the crystallographic structure, the calculation, and the circular dichroism (CD) study indicates that helical ligand arrangement inducing the core into chiral distortion accounts for the chiroptical activities in the visible region. A rare example of cocrystallization of a mixture of diastereomers has been observed for the first time for gold nanoclusters, reflecting the lack of chiral self-sorting of the ligands.
