采用磁控调整和光固化光子晶体法实现结构色印刷

大自然中的许多生物,如蝴蝶和孔雀,可显示出独特绚丽的色彩,这种依靠光与物体表面周期性纳米结构的相互作用而产生的色彩,被称为"结构色"。然而,即使是目前世界上最先进的纳米加工技术仍然存在速度慢、价格昂贵和无法扩展的问题,难以模仿自然界中结构色的纳米结构。本文基于采用无掩膜光刻系统固化的新材料实现颜色连续可调,从而能在几秒钟内制作由多重结构色构成的高清晰图案。同时,发明了一种命名为"M-油墨"的新材料,其颜色可以通过磁场改变内部纳米结构周期而得到调整,也可通过光化学固定聚合物网络中的纳米结构而达到锁色效果。此外,本文也研发出一种实现结构色印刷的光子晶体。这种简单、可控、可扩展的结构色印刷方案的提出将对大众消费品的色彩生成产生重大影响。

Engineering surface strain for site-selective island growth of Au on anisotropic Au nanostructures

Controlled growth of islands on plasmonic metal nanoparticles represents a novel strategy in creating unique morphologies that are difficult to achieve by conventional colloidal synthesis processes,where the nanoparticle morphologies are typically determined by the preferential development of certain crystal facets.This work exploits an effective surface-engineering strategy for site-selective island growth of Au on anisotropic Au nanostructures.Selective ligand modification is first employed to direct the site-selective deposition of a thin transition layer of a secondary metal,e.g.,Pd,which has a considerable lattice mismatch with Au.The selective deposition of Pd on the original seeds produces a high contrast in the surface strain that guides the subsequent site-selective growth of Au islands.This strategy proves effective in not only inducing the island growth of Au on Au nanostructures but also manipulating the location of grown islands.By taking advantage of the iodide-assisted oxidative ripening process and the surface strain profile on Au nanostructures,we further demonstrate the precise control of the islands’number,coverage,and wetting degree,allowing fine-tuning of nanoparticles’optical properties.

Emulsion‐templated synthesis of 3D evaporators for efficient solar steam generation

Interfacial solar steam generation holds great promise in water desalination thanks to its high energy efficiency by heating only the top layer of water for evaporation.While three‐dimensional(3D)evaporators have been proven to increase the evaporation rate by harnessing the energy from the surroundings,further development is still required in terms of convenient fabrication with potential scalability.Herein,we propose to overcome this challenge by using a high internal phase emulsion(HIPE)to template the synthesis of 3D hierarchically porous evaporators.The HIPE‐templated synthesis combined with a molding process can efficiently fabricate the desired 3D shape without wasting any materials and generate a hierarchically porous internal structure for continuous water supply.Engineering the overall shape and internal pores produces a 3D evaporator that can suppress conduction heat loss and efficiently collect thermal energy from its surroundings,boosting the evaporation rate to 2.82 kg/(m2 h)under 1‐sun illumination,which is significantly higher than conventional 2D evaporators.HIPE‐templating synthesis is an easy but effective way to produce various porous polymers,promising for a wide range of applications where easy production,excellent shape control,and potential scalability are critical.

Magnetically Induced Anisotropic Interaction in Colloidal Assembly

The wide accessibility to nanostructures with high uniformity and controllable sizes and morphologies provides great opportunities for creating complex superstructures with unique functionalities.Employing anisotropic nanostructures as the building blocks significantly enriches the superstructural phases,while their orientational control for obtaining long-range orders has remained a significant challenge.One solution is to introduce magnetic components into the anisotropic nanostructures to enable precise control of their orientations and positions in the superstructures by manipulating magnetic interactions.Recognizing the importance of magnetic anisotropy in colloidal assembly,we provide here an overview of magnetic field-guided self-assembly of magnetic nanoparticles with typical anisotropic shapes,including rods,cubes,plates,and peanuts.The Review starts with discussing the magnetic energy of nanoparticles,appreciating the vital roles of magneto-crystalline and shape anisotropies in determining the easy magnetization direction of the anisotropic nanostructures.It then introduces superstructures assembled from various magnetic building blocks and summarizes their unique properties and intriguing applications.It concludes with a discussion of remaining challenges and an outlook of future research opportunities that the magnetic assembly strategy may offer for colloidal assembly.

Rattle-Type Silica Colloidal Particles Prepared by a Surface- Protected Etching Process

This paper explores the capability of the“surface-protected etching”process for the creation of rattle-type SiO_(2)@void@SiO_(2) colloidal structures featuring a mesoporous silica shell and a mesoporous movable silica core.The surface-protected etching process involves stabilization of the particle surface using a polymer ligand,and then selective etching of the interior to form hollow structures.In this paper,this strategy has been extended to the formation of rattle-like structures by etching SiO_(2)@SiO_(2) core shell particles which are synthesized by a two-step sol gel process.The key is to introduce a protecting polymer of polyvinylpyrrolidone(PVP)to the surface of both core and shell in order to tailor their relative stability against chemical etching.Upon reacting with NaOH,the outer layer silica becomes a hollow shell as only the surface layer is protected by PVP and the interior is removed,while the core remains its original size thanks to the protection of PVP on its surface.This process can be carried out at room temperature without the need of additional templates or complicated heterogeneous coating procedures.The etching process also results in the rattle-type colloids having mesoscale pores with two distinct average sizes.In our demonstration of a model drug delivery process,such mesoporous structures show an interesting two-step elution profile which is believed to be related to the unique porous rattle structures.

Anisotropically Shaped Magnetic/Plasmonic Nanocomposites for Information Encryption and Magnetic-Field-Direction Sensing

Instantaneous control over the orientation of anisotropically shaped plasmonic nanostructures allows for selective excitation of plasmon modes and enables dynamic tuning of the plasmonic properties.Herein we report the synthesis of rod-shaped magnetic/plasmonic core-shell nanocomposite particles and demonstrate the active tuning of their optical property by manipulating their orientation using an external magnetic feld.We further design and construct an IR-photoelectric coupling system,which generates an output voltage depending on the extinction property of the measured nanocomposite sample.We employ the device to demonstrate that the nanocomposite particles can serve as units for information encryption when immobilized in a polymer flm and additionally when dispersed in solution can be employed as a new type of magnetic-feld-direction sensor.

Self-templated formation of cobalt-embedded hollow N-doped carbon spheres for efficient oxygen reduction

The slow kinetics at the cathode of oxygen reduction reaction(ORR)seriously limits the efficiencies of fuel cells and metal-air batteries.Pt,the state-of-the-art ORR electrocatalyst,suffers from high cost,low earth abundance,and poor stability.Here a self-templated strategy based on metal-organic frameworks(MOFs)is proposed for the fabrication of hollow nitrogen-doped carbon spheres that are embedded with cobalt nanoparticles(Co/HNC).The Co/HNC manifests better ORR activities,methanol tolerance,and stability than commercial Pt/C.The high ORR performance of Co/NHC can be attributed to the hollow structure which provides enlarged electrochemically active surface area,the formation of more Co-N species,and the introduction of defects.This work highlights the significance of rational engineering of MOFs for enhanced ORR activity and stability and offers new routes to the design and synthesis of high-performance electrocatalysts.

Thickness-dependent wrinkling of PDMS films for programmable mechanochromic responses

We report a remarkable thickness-dependent wrinkling behavior of oxygen plasma-treated polydimethylsiloxane(PDMS)flms,in which an energy barrier separates the wrinkling mechanics into two regimes.For thick films,the film wrinkles with a constant periodicity which can be precisely predicted by the classic nonlinear finite mechanics.Reducing the film thickness below 1 mm leads to nonuniform wrinkles with an increasing periodicity which gives rise to random scattering and transparency changes under mechanical strains.By tuning the flm thickness,we were able to control both the quality and size of the periodic wrinkles and further design mechanochromic devices featuring briliant structural colors and programmable colorimetric responses.This work sheds light on the fundamental understanding of the wrinkling mechanics of bilayer systems and their intriguing mechanochromic applications.

Scalable synthesis of sub-lO0 nm hollow carbon nanospheres for energy storage applications

Sub-100 nm hollow carbon nanospheres with thin shells are highly desirable anode materials for energy storage applications. However, their synthesis remains a great challenge with conventional strategies. In this work, we demonstrate that hollow carbon nanospheres of unprecedentedly small sizes （down to - 32.5 nm and with thickness of - 3.9 nm） can be produced on a large scale by a templating process in a unique reverse micelle system. Reverse micelles enable a spatially confined Stober process that produces uniform silica nanospheres with significantly reduced sizes compared with those from a conventional Stober process, and a subsequent well-controlled sol-gel coating process with a resorcinol-formaldehyde resin on these silica nanospheres as a precursor of the hollow carbon nanospheres. Owing to the short diffusion length resulting from their hollow structure, as well as their small size and microporosity, these hollow carbon nanospheres show excellent capacity and cycling stability when used as anode materials for lithium/sodium-ion batteries.

Customizable Ligand Exchange for Tailored Surface Property of Noble Metal Nanocrystals

It is highly desirable,while still challenging,to obtain noble metal nanocrystals with custom capping ligands,because their colloidal synthesis relies on specific capping ligands for the shape control while conventional ligand exchange processes suffer from“the strong replaces the weak”limitation,which greatly hinders their applications.Herein,we report a general and effective ligand exchange approach that can replace the native capping ligands of noble metal nanocrystals with virtually any type of ligands,producing flexibly tailored surface properties.The key is to use diethylamine with conveniently switchable binding affinity to the metal surface as an intermediate ligand.As a strong ligand,it in its original form can effectively remove the native ligands;while protonated,it loses its binding affinity and facilitates the adsorption of new ligands,especially weak ones,onto the metal surface.By this means,the irreversible order in the conventional ligand exchange processes could be overcome.The efficacy of the strategy is demonstrated by mutual exchange of the capping ligands among cetyltrimethylammonium,citrate,polyvinylpyrrolidone,and oleylamine.This novel strategy significantly expands our ability to manipulate the surface property of noble metal nanocrystals and extends their applicability to a wide range of fields,particularly biomedical applications.

Strong photoluminescence of Cs_4PbBr_6 crystals: a long mystery story

Halide perovskite nanocrystals(NCs)with a general composition of ABX_3(A=MA,FA or Cs;B=Pb,Sn;and X=Br,I,Cl)have been widely studied for photovoltaic applications.Recently,halide perovskites NCs based light-emitting diodes(LEDs)have also attracted significant attention because they have been regarded as the next-generation display technology[1].However,we

High-Precision Colorimetric Sensing by Dynamic Tracking of Solvent Diffusion in Hollow-Sphere Photonic Crystals

Expensive instruments and complicated data processing are often required to discriminate solvents with similar structures and properties.Colorimetric sensors with high selectivity,low cost,and good portability are highly desirable to simplify such detection tasks.Herein,we report the fabrication of a photonic crystal sensor based on the self-assembled resorcinol formaldehyde(RF)hollow spheres to realize colorimetric sensing of polar solvents,including homologs and isomers based on the saturated diffusion time.The diffusion of solvent molecules through the photonic crystal film exhibits a unique three-step diffusion profile accompanied by a dynamic color change,as determined by the physicochemical properties of the solvent molecules and their interactions with the polymer shells,making it possible to accurately identify the solvent type based on the dynamic reflection spectra or visual perception.With its superior selectivity and sensitivity,this single-component colorimetric sensor represents a straightforward tool for convenient solvent detection and identification.

Self-assembly of colloidal nanoparticles into encapsulated hollow superstructures

As a distinct type of nanocapsules,hollow superstructures of inorganic nanoparticles have attracted increasing attention due to their controllable permeability,convenient functionalization,and efficient surface utilization.Conventionally,they are produced by assembling nanoparticles against expensive sacrificial templates.Herein,a general emulsion-based method is reported to assemble colloidal nanoparticles into submicron hollow superstructures,involving first co-assembly of colloidal nanoparticles with organic additives to form clusters,then overcoating the clusters with a polymer shell,and finally removing the organic additives and re-dispersing nanoparticles by exposing to a good solvent.The key to the success of this process is the re-assembly of nanoparticles against the polymer shells as driven by the capillary force during solvent evaporation,producing hollow superstructures.Such a space-confined assembly process can be well controlled by choice of solvents and their evaporation rates.This general technique provides an open and low-cost platform for creating hollow superstructures of various inorganic nanoparticles,offering many opportunities for exploring unique applications that can take advantage of the collective properties of the constituent nanoparticles and the permeable nanoshell structures.