A facile route to the hierarchical assembly of Au nanoparticles on carbon nanotubes through Cu^(2＋) coordination for surface-enhanced Raman scattering

We report the hierarchical assembly of Au nanoparticles on carboxylized carbon nanotubes（c-CNTs）through Cu^（2＋） coordination. This route is facile and green, and can easily control the loading density of Au nanoparticles. The c-CNT matrix ensures uniform distribution of Au nanoparticles, which is particularly important for the enrichment of hot spots while preventing their serious agglomeration. Moreover, the cCNT matrix also contributes to the electromagnetic enhancement due to its surface plasmon resonance,and the chemical enhancement due to the adsorption of the target molecules. The resulting Au@c-CNT nanohybrids exhibit a remarkable synergy in SERS compared to neat Au nanoparticles.

Hydrophilic bi-functional B-doped g-C_(3)N_(4) hierarchical architecture for excellent photocatalytic H_(2)O_(2) production and photoelectrochemical water splitting

Graphitic carbon nitride(g-C_(3)N_(4))has attracted great interest in photocatalysis and photoelectrocatalysis.However,their poor hydrophilicity poses a great challenge for their applications in aqueous environment.Here,we demonstrate synthesis of a hydrophilic bi-functional hierarchical architecture by the assembly of B-doped g-C_(3)N_(4)nanoplatelets.Such hierarchical B-doped g-C_(3)N_(4)material enables full utilization of their highly enhanced visible light absorption and photogenerated carrier separation in aqueous medium,leading to an excellent photocatalytic H_(2)O_(2)production rate of 4240.3μM g^(-1)h^(-1),2.84,2.64 and 2.13 times higher than that of the bulk g-C_(3)N_(4),g-C_(3)N_(4)nanoplatelets and bulk B doped g-C_(3)N_(4),respectively.Photoanodes based on these hierarchical architectures can generate an unprecedented photocurrent density of 1.72 m A cm^(-2)at 1.23 V under AM 1.5 G illumination for photoelectrochemical water splitting.This work makes a fundamental improvement towards large-scale exploitation of highly active,hydrophilic and stable metal-free g-C_(3)N_(4)photocatalysts for various practical applications.

Hierarchical lichee-like Fe_(3)O_(4) assemblies and their high heating efficiency in magnetic hyperthermia

A nontoxic and biocompatible thermoseed is developed for the magnetic hyperthermia.Two kinds of thermoseed materials:hierarchical hollow and solid lichee-like Fe_(3)O_(4) assemblies,are synthesized by a facile hydrothermal method.The crystal structure of Fe_(3)O_(4) assemblies are characterized by x-ray diffraction,scanning electron microscopy,and transmission electron microscopy.Moreover,the prepared Fe_(3)O_(4) assemblies are used as a magnetic heat treatment agent,and their heating efficiency is investigated.Compared to solid assembly,hollow lichee-like Fe_(3)O_(4) assembly exhibits a higher specific absorption rate of 116.53 W/g and a shorter heating time,which is ascribed to its higher saturation magnetization,larger initial particle size,and the unique hierarchical hollow structure.Furthermore,the magnetothermal effect is primarily attributed to Neel relaxation.Overall,we propose a facile and convenient approach to enhance the heating efficiency of magnetic nanoparticles by forming hollow hierarchical assemblies.

Hierarchical Self-assembly of Atomically Precise Au Nanoclusters with Molecular Rotor-based Ligands

The hierarchical assemblies of precise nanoparticles(NPs)have created materials with emergent properties and functionalities.However,the complex assemblies remain unclear at a precise scale.Here,we show the hierarchical self-assembly of atomically precise gold nanoclusters(Au NCs)with molecular rotor-based ligands(MRL),featuring a double-layer surface.Compared to two other types of monolayer-protected(MLP)Au NCs,the significantly reduced surface density for MRL Au NCs profoundly influences their assembly behavior within the lattice.Furthermore,the long length of rotor-based ligands and the rotational freedom of the phenyl-rings of rotor-based ligands also facilitate the assembly of NCs.Our works elucidate the hierarchical assembly on a precise scale,suggesting that the rotor-based ligand’s strategy offers promising potential for designing well-defined and more complex structures in supercrystals.

Hierarchical Self-Assembly Promoted Circularly Polarized Luminescence Enhancement and Handedness Inversion of Metal–Organic Helicate

In-depth studies of hierarchical self-assembly with chirality inversion and asymmetry amplification are indispensable for understanding the chiral transfer rule in assembly systems and construction of circularly polarized luminescence(CPL)active materials.Herein,a coordination-driven primary assembly of pyrene-based chiral ligand and Zn(OTf)2 was employed for the construction of homochiral metal–organic helicate with a triple helix structure,tunable emission color,and significant chirality amplification.More excitingly,the metal–organic helicate further assembled into well-ordered hierarchical nanoarchitectures with the aid of C–H⋯πinteraction andπ–πstacking,showing significant CPL enhancement and unexpected handedness inversion.Thus,the|glum|increased from 5.20×10^(−5) to 5.60×10^(−2),and the|gabs|rose from 3.80×10^(−4) to 1.04×10^(−2) over the entire hierarchical self-assembly process.The multiple supramolecular interactions not only endowed the resultant metal–organic helicate with efficient chirality transmission and tunable emission color but also guided the(supra)molecular building block of metal–organic helicate organizing into the hierarchically chiral nanoarchitecture in a directional manner.This work provides insight into the metal–organic helicate-mediated hierarchical self-assembly and aids the development of CPLactive materials with dynamic chirality modulation and enhanced chiroptical performance.

Hierarchical Homochiral Assembly of Polyhedral Cage-Type Nanoclusters

Hierarchical chiral self-assembly is of profound significance for biomolecules for their biological functions.Atom-precise metal nanoclusters(NCs)offer better opportunities to construct hierarchical superlattices.Nevertheless,achieving hierarchical homochiral assembly of nanocrystals protected by achiral ligands has proven to be a formidable task,with existing examples primarily limited to heterochiral assembly.Here we put forward a hierarchical assembly strategy towards precisely fabricating highly ordered homochiral superstructures.First,clusterin-nanocage type copper-hydride NCs act as synthons,of which entity is featured with a hexagonal close-packed Cu_(9)kernel embedded in a C_(3)-symmetric trigonal-prismatic metallacage,leading to a chiral core-shell primary structure with either P or M conformation.Then four homochiral NCs combined with guests through synergistic noncovalent interactions spontaneously organize into a supramolecular tetrahedral secondary structure within a unit cell.Finally,these nanoscopic supramolecular motifs pack into tertiary hierarchical superlattice of chiral cubic crystalline phase.Additionally,the crystalline material shows excellent robustness,and fascinating blueexcitable near-infrared thermally activated delayed fluorescence behavior.This work not only exhibits that nanocage-type NCs can be smart as proteins to translate chiral primary structure into tertiary chiral hierarchical complexity,but also provides new insights into structure-to-superstructure,enabling bottom-up creation of higher-level hierarchical homochiral superlattice structures.

Hierarchical assemblies of molecular frameworks—MOF-on-MOF epitaxial heterostructures

Functional,porous metal-organic frameworks(MOFs)have attracted much attention as a very flexible class of crystalline,porous materials.For more advanced applications that exploit photophysical properties,the fabrication of hierarchical assemblies,including the creation of MOF/MOF heterointerfaces,is important.For the manufacturing of superstructures with length scales well beyond that of the MOF pore size,layer-by-layer(Ibl)methods are particularly attractive.These allow the isoreticular approach to be extended to superstructures with micrometer length scales,a range that is not accessible using conventional MOF design.The Ibl approach further substantially extends the compositional diversity in MOFs.At the same time,the favorable elastic properties of MOFs allow for heteroepitaxial growth,even in the case of lattice misfits as large as 20%.While the MOF-on-MOF approach to designing multicomponent superstructures with synergistic multifunctionality can also be realized with sophisticated solvothermal synthesis schemes,the Ibl(or liquid-phase epitaxy)approach carries substantial advantages,in particular when it comes to the integration of such MOF superstructures into optical or electronic devices.While the structure vertical to the substrate can be adjusted using the Ibl method,photolithographic methods can be used for lateral structuring.In this review,we will discuss the Ibl liquid-phase epitaxy approach to growing surface-anchored MOF thins films(SURMOFs)as well as other relevant one-pot synthesis methods for constructing such hierarchically designed structures and their emerging applications.

Recent Progress of Chiral Hierarchical Assemblies from a Chinese Perspective

Self-assembly of predesigned chiral molecules to form structurally diverse functional materials has been one of the most exciting recent developments in materials science and nanotechnology over the past decade.Particularly,the rationally designed chiral supermolecules and their hierarchical assemblies result in superior microenvironments,in which they interact distinctly with molecularly asymmetric guests for enantiospecific recognition.The chemistry of chiral supermolecule-based materials(CSMs)has become a lively research topic,and thus this review seeks to shed light on a range of synthetic CSMs at differing length scales developed in the past 5 years,with emphasis on the representative work from China.This review includes cavity-containing chiral supermolecules,chiral polymers,and chiral crystalline materials,aiming to tackle important issues from their design,synthesis,and structure to cutting-edge applications.This,in turn,allows for fundamental understanding of the transfer,amplification,and functional expression of chirality from the molecular to the supramolecular to the macroscopic scale.Finally,we provide perspectives on the promises,opportunities,and key challenges for the future development of useful chiral functional materials.

Hierarchical self-assembled structure and frictional response of phthalocyanine molecules

Solid evidence is needed to demonstrate the effect of molecular orientation and structure on the frictional property of boundary lubricants.In this work,the frictional properties of phthalocyanine self-assembled monolayers(SAMs)with face-on(aromatic cores parallel to the substrate)and edge-on(aromatic cores stand on the substrate)orientations have been compared and the in situ structural variation of edge-on SAMs under frictional shear has been revealed by atomic force microscope(AFM).Face-on oriented SAMs show lower adhesion,lower friction,and stronger wear resistance,compared with edge-on oriented SAMs.Hierarchical structures of edge-on oriented SAMs have been revealed by frictional topography,which are consisted of nanoscale columns,micron-scale stripes,and centimeter-scale monolayer.The column structure deforms under increasing load force,leading to a stepwise friction force curve and a transition among three friction states(ordered friction,collapsed friction,and worn friction).The structural deformation depends on both the order degree and anisotropic stiffness of columns.Columns in phthalocyanine SAMs show a larger stiffness when shearing against molecular plane than shearing along the molecular plane.The presented study on the interfacial structure and frictional mechanism promisingly supports the designing of novel boundary lubricants and their application in engineering.

Detachable and hierarchical assemblies for recyclable and highly efficient oil-fouling removal

Large-scale use of detergents to remove oil-fouling in industry continuously generates tremendous amounts of wastewater and thus leads to both economic and environmental problems.To develop recyclable oil-fouling removal strategy is an appealing solution but a challenging task.Herein,a kind of dynamic imine-based surfactant has been constructed by 2-formylbenzenesulfonic acid sodium salt(FBSS)and linear amines(CnNH_(2),n=6,7,8,10,and 12).Owing to high interfacial activity and strong assembly ability,dynamic FBSS/C8NH_(2)system can remove oil-fouling on multiple substrates for at least 10 cycles,largely reducing the toxicity to ecosystem.At basic pH,the hierarchical assemblies(from vesicle to network and hollow sphere)are formed and boost surfactant molecule enrichment around oil-fouling,leading to highly efficient emulsification.When pH is changed to acidic condition,the surfactant molecules dissociate due to the breaking of imine bonds,and accordingly the emulsion is destroyed and the released oil droplets float to the top layer.After removing the oil-fouling and adjusting the solution back to basic pH,the surfactant assemblies are reconstructed and used for the next oil-fouling cleaning cycle.This study provides a recyclable,efficient and eco-friendly oil-fouling removal approach,satisfying the need of sustainable development.