在过渡金属催化剂上的C―C键断裂以实现生物质的升级

将当前能源生产和消费结构从过度依赖化石能源转变为高效利用可再生能源,是解决能源危机、实现碳中和的有效途径。生物质是最有前途的可再生能源之一,可以取代化石燃料以获得有价值的有机化合物。近年来,大力利用生物质能已成为一种必然趋势。用于生物质转化的传统热化学催化方法通常需要高温、高压等恶劣条件,甚至还需要外部氢或氧源。相比之下,在相对温和的条件下进行的生物质有机分子电催化转化为生产高价值化学品提供了一种绿色高效的策略。特别是,通过C―C键裂解将生物质衍生的分子转化为高价值的短链化学品至关重要。近年来,大量的研究证明过渡金属(TM)电催化剂由于其丰富的三维电子结构和独特的eg轨道增强了过渡金属-氧之间的共价键合,从而在有机物的C―C键断裂中起着至关重要的作用。此外,TM电催化剂的配位环境或电子结构会影响产物的选择性。毫无疑问,明确的反应活性位点和途径有助于深入理解催化剂结构与反应活性之间的构效关系。然而,TM电催化剂介导的生物质衍生有机分子的C―C键裂解反应用于生物质升级的研究目前尚处于起步阶段,其反应机理和催化反应过程尚不清楚。因此,有必要在原子水平上系统地了解电催化剂在C―C键裂解过程中的作用。在本综述中,我们首先依次介绍了广泛研究的TM电催化剂介导的生物质衍生有机分子(包括甘油、环己醇、木质素和糠醛)的C―C键裂解反应,并给出了一些典型的例子和相应的反应途径。然后,系统回顾了过渡金属化合物催化C―C键裂解的反应机理,揭示了界面行为,并构建了TM电催化剂的结构与裂解反应活性之间的构效关系。最后,我们简要总结了上述内容,并强调了在TM电催化剂上研究C―C键裂解的挑战和展望。我们期望这项工作可以为生物质的可控转化和合理设计C―C键裂解的TM电催化剂提供指导。

Defect engineered electrocatalysts for C-N coupling reactions toward urea synthesis

Urea is extensively used in agriculture and chemical industry,and it is produced on an industrial scale from CO_(2)and Haber-Bosch NH_(3)under relatively high temperature and high pressure conditions,which demands high energy input and generates masses of carbon footprint.The conversion of CO_(2)and N sources(such as NO_(2)^(−),NO_(3)^(−),and N_(2))through electrocatalytic reactions under ambient conditions is a promising alternative to realize efficient urea synthesis.Of note,the design of electrocatalyst is one of the key factors that can improve the efficiency and selectivity of C-N coupling reactions.Defect engineer-ing is an intriguing strategy for regulating the electronic structure and charge density of electrocatalysts,which endows electrocatalysts with excellent physicochemical properties and optimized adsorption en-ergy of the reaction intermediates to reduce the kinetic barriers.In this minireview,recent advances of defect engineered electrocatalysts in urea electrosynthesis from CO_(2)and various N reactants are firstly introduced.Mechanistic discussions of C-N coupling in these advances are presented,with the aim of directing future investigations on improving the urea yield.Finally,the prospects and challenges of de-fect engineered electrocatalysts for urea synthesis are discussed.This overview is expected to provide in-depth understanding of structure-reactivity relationship and shed light on future electrocatalytic C-N coupling reactions.

Monodisperse SiO_(2) Microspheres with Large Specific Surface Area: Preparation and Particle Size Control

Monodisperse SiO_(2) microspheres have found applications in catalysis,drug delivery,coatings,cosmetics,optical sensing and plastics.The particle size of monodisperse SiO_(2) microspheres is closely related to its application.In this paper,monodisperse SiO_(2) microspheres with tunable diameter were successfully synthesized using cetyltrimethylammonium bromide(CTAB)as template.The monodisperse SiO_(2) microspheres with diameters ranging from 200 nm to 3μm were obtained by controlling the concentration of CTAB,tetraethyl orthosilicate(TEOS),diethanolamine(DEA)and reaction temperature.The BET surface area could reach 835 m^(2)·g^(-1) and mean pore diameter was 2.3 nm.The formation mechanism of monodisperse SiO_(2) microspheres was investigated.

Natural interface-mediated self-assembly of graphene-isolatednanocrystals for plasmonic arrays construction and personalized information acquisition

As Interface mediated self-assembly of nanocrystals provide excellent strategy for sensing,catalysis or photonics,the construction of innovative interfaces and development of versatile strategies for nanocrystal synthesis are urgently needed.Herein,latent fingerprints(LFPs),the most common markers for human identity,are used as naturally accessible interface for organization of graphene isolated nanocrystals(GINs).Excitingly,the selective adsorption of GINs on lipidic ridge provides a universal approach for the in-situ construction of the plasmonic arrays.Such system with intrinsic chrominance and Raman signal enables the high resolution colorimetric and surfaced-enhanced Raman spectroscopy(SERS)dual-mode imaging,which can detail the structures of the LFPs from 1st to 3rd level even the LFPs are shielded.Furthermore,the interface can be constructed on diverse materials by a simple finger-pressing process and the densely packed arrays can serve as superior SERS substrate for label-free,non-invasive acquisition of molecule information especially residues in LFPs.The combination of chemical composition with detailed structures efficiently recognizes the human identity and could help link it to a crime scene.Overall,the LFPs can act as natural platform for interface mediated localized assembly and personalized information acquisition for forensic science or precise medicine.

Organic stoichiometric cocrystals with a subtle balance of charge-transfer degree and molecular stacking towards high-efficiency NIR photothermal conversion

Charge-transfer(CT)stoichiometric cocrystals are promising choice of organic materials for unveiling the structure-property relationship.However,due to the contradiction between large CT degree required for strong NIR absorption and flexible molecular stacking,construction of stoichiomorphism-based cocystals with near-infrared(NIR)photothermal property remains challenging.Herein,the first example of stoichiomorphism-based photothermal cocrystals were accomplished through the adaptive assembly of 3,3,5,5-tetramethylbenzidine(TMB)donor and 1,2,4,5-tetracyanobenzene(TCNB)acceptor.The selective cocrystallization could be controlled by varying the donor-acceptor stoichiometries via a surfactantassisted method,resulting in two cocrystals with 1:1(T1C1)and 1:2(T2C1)stoichiometries.The absorbance intensity of T1C1 at 808 nm was nearly twice that of T2C1,while the photothermal conversion efficiency(PCE)of the former was 60.3%±0.6%,approximately 80%of that for the latter(75.5%±2.6%),which might be caused by the different intermolecular interactions in distinct molecular stacking patterns.Notably,both excellent PCEs of stoichiometric cocrystals were attributed to the nonradiative transition process,including internal conversion and charge dissociation processes,as elucidated by femtosecond transient absorption spectroscopy measurements.Furthermore,T1C1 was used as an NIR heater for preparing agarose-based photothermal hydrogel,showing great potential for light-controlled in-situ gelation.This strategy of balancing the CT degree and molecular packing orientation not only uncovered the relationship between stoichiometric stacking and photothermal property,but also provided an opportunity to develop advanced organic optoelectronic materials.

Ultrastable graphene isolated Au Ag nanoalloy for SERS biosensing and photothermal therapy of bacterial infection

Plasmonic metal nanomaterials with intrinsic surface–enhanced Raman scattering(SERS)and photothermal properties,especially AuAg nanoalloys with both the outstanding merits of Au and Ag nanocrystals,show huge application prospects in bacterial theranostics.However,the direct exposure of AuAg nanoalloys in external conditions probably cause undesirable reactions and poisonous metal ion leakage during SERS detection and photothermal antibacterial therapy process,which severely hinder bacterial theranostics applications.Herein,we report an ultrastable graphene–isolated AuAg nanoalloy(GAA)with AuAg core confined in few–layer graphitic shell as a versatile platform for bacterial detection and therapy.The encapsulation of graphene ensures the good stability of AuAg core,that its superior SERS and photothermal properties are therefore further guaranteed.GAA is used for SERS detection of two vital bacterial biomarkers(including corrosive cyanide and pyocyanin),exhibiting good SERS quantitative and multiplexing ability.GAA is further used for photothermal antibacterial therapy application,and ultrahigh antibacterial efficacies for both Gram–negative Escherichia coli and Gram–positive Staphylococcus aureus are achieved under 808 nm laser irradiation.This work proposes a valuable method to develop robust bacterial theranostic platform.

Versatile Graphene-Isolated AuAg-Nanocrystal for Multiphase Analysis and Multimodal Cellular Raman Imaging

Surface-enhanced Raman spectroscopy(SERS)-based bioanalytical technique involves the interaction of SERS-active substrate with complex environment,which has aroused intensive research interests.Compared to the commonly used Au SERS substrates,Ag nanocrystals have larger optical absorption cross section and acceptable price,but they possess poor oxidation resistance and potential biotoxicity,and the occurrence of unnecessary chemical reactions is inevitable due to the direct contact with probe molecules.Herein,we report a graphene-isolated AuAg nanocrystal(GIAAN)with the SERS-active AuAg core confined in a nanospace of few-layer graphene shell,which possesses unique Raman peaks,high SERS activity,excellent stability,superior fluorescence quenching performance and good biocompatibility.Based on the limited solubility of GIAAN in water and organic solvents,it is able to spontaneously generate interfacial self-assembled GIAAN(ISA-GIAAN)film at immiscible two-phase interfaces without any inducer,and multiphase Raman analysis of both water-and lipid-soluble drug model molecules is further achieved.Moreover,the GIAAN is further non-covalently functionalized with polyoxyethylenestearyl ether(C18-PEG)to acquire GIAAN@PEG with good water-solubility for SERS quantitative analysis in homogeneous system and multimodal Raman imaging of MCF-7 cells.We expect the versatile GIAAN holds great potential to monitor drug metabolism and guide intended drug delivery in clinic trials.

Versatile metal graphitic nanocapsules for SERS bioanalysis

The novel graphitic nanomaterial of metal graphitic nanocapsules(MGNs) with superior stability, unique optical properties and biocompatibility possess great potential in biomedical and bioanalytical applications. The graphitic shell can quench the background fluorescence interference from external environments via a fluorescence resonance energy transfer(FRET) process and even avoid unnecessary reactions catalyzed by inner metal core. The graphitic shell with several characteristic Raman bands itself can act as Raman signal probe or internal standard(IS), especially the 2D-band within the cellular Raman-silent region helps to reduce the interference signals from external conditions. The present context attempts to give a comprehensive overview about the preparation and unique properties of MGNs as well as their applications in SERS biodetection and bioimaging.

A Magnetocatalytic Propelled Cobalt-Platinum@Graphene Navigator for Enhanced Tumor Penetration and Theranostics

Complex biological environments and multiple physiological barriers significantly impede efficient accumulation and penetration of nanomaterials within tumor tissue for therapy.In situ energy conversion of nanomotors features autonomous movements and improves cancer treatment.However,one of the key challenges is to prepare nanomotors with an adequately small size,good biocompatibility,and precise positioning.Herein,we demonstrate a simple,ultrasmall,versatile,and real-time motion guidance strategy for magnetocatalytic CoPt@graphene navigators(MCGNs)that can enable highly efficient propulsion in the presence of H_(2)O_(2) or magnetic actuation.MCGNs act as highly diffusive delivery vehicles to promote tumor tissue targeting,and the amount of drug in the tumor was three times than without navigation.By engaging movements powered through in situ energy conversion,MCGNs gain considerable propulsion to penetrate a cell’s membrane and enhance intracellular delivery.

Hydrogen-Bonding-Induced H-Aggregation of Charge-Transfer Complexes for Ultra-Efficient Second Near-Infrared Region Photothermal Conversion

Aggregation plays a critical role in modulating the photophysical process of organicmolecules.However,the rational control of the construction of a functionoriented stacking mode for efficient photothermal(PT)conversion in the second near-infrared region(NIR-II;1000-1700 nm)remains a challenge.Herein,an H-aggregation of 3,3′,5,5′-Tetramethylbenzidine(TMB)-TMB dication(TMB++)complexes in linear agarose(H-TTC/LAG)with narrowed band gap(0.96 eV)was fabricated through intermolecular hydrogenbonding interactions between the amino groups of TTC and the peripheral hydroxyl groups of LAG.Charge-transfer mechanism and H-aggregation ensured NIR-Ⅱ absorption of the complex at>1400 nm.The H-aggregation also promoted a non-radiation relaxation pathway and improved the thermal stability of TTC,which together favored the constructed H-TTC/LAG with ultra-efficient PT conversion that increased rapidly to 140℃ in 15 s under the NIR-Ⅱ laser(1064 nm,1.0 W cm^(−2))irradiation.Such a unique H-TTC/LAG with good biocompatibility was used to demonstrate a superior PT therapy via high-efficie ncy tumor growth inhibition in mouse mammary carcinoma(4T1)the BALB/c mice tumor-bearing xenografts.This is the first established H-aggregation of charge-transfer complexes in a noncovalent system,which not only provides a new strategy to develop ultra-efficient NIR-Ⅱ PT materials but also paves the way for constructing functional materials with aggregates of charge-transfer complexes.