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1.
    
Designing broadband enhanced chirality is of strong interest to the emerging fields of chiral chemistry and sensing, or to control the spin orbital momentum of photons in recently introduced nanophotonic chiral quantum and classical optical applications. However, chiral light-matter interactions have an extremely weak nature, are difficult to control and enhance, and cannot be made tunable or broadband. In addition, planar ultrathin nanophotonic structures to achieve strong, broadband, and tunable chirality at the technologically important visible to ultraviolet spectrum still remain elusive. Here, these important problems are tackled by experimentally demonstrating and theoretically verifying spectrally tunable, extremely large, and broadband chiroptical response by nanohelical metamaterials. The reported new designs of all-dielectric and dielectric-metallic (hybrid) plasmonic metamaterials permit the largest and broadest ever measured chiral Kuhn's dissymmetry factor achieved by a large-scale nanophotonic structure. In addition, the strong circular dichroism of the presented bottom-up fabricated optical metamaterials can be tuned by varying their dimensions and proportions between their dielectric and plasmonic helical subsections. The currently demonstrated ultrathin optical metamaterials are expected to provide a substantial boost to the developing field of chiroptics leading to significantly enhanced and broadband chiral light-matter interactions at the nanoscale.  相似文献   

2.
    
A new symmetrical sugar‐based perylenediimide derivative PTCDI‐BAG is synthesized and its aggregate morphologies and formation mechanisms are studied in detail in the mixed solvent system water/N,N‐dimethylformamide (H2O/DMF) with changing volume ratios. PTCDI‐BAG molecules self‐assemble into planar ribbons in 20/80 and 40/60 H2O/DMF (v/v), but their chiralities are opposite according to recorded circular dichroism (CD) spectra. With a further increase of the water content, only left‐handed helical nanowires are obtained in 60/40 and 80/20 H2O/DMF (v/v) mixtures. By combining density functional theory (DFT) calculations with the experimental investigations, it is proposed that kinetic and thermodynamic factors play key roles in tuning PTCDI‐BAG structures and helicity. The formation of the ribbon is thermodynamically controlled in the 20/80 H2O/DMF system, but kinetically controlled nucleation followed by thermodynamically controlled self‐assembly plays the governing roles for the formation of nanoribbons in 40/60 H2O/DMF. Devices based on single nanoribbons for hydrazine sensing exhibit better performance than nanofiber bundles obtained in this study and achiral nanostructures reported in previous study. This study not only provides an elaborated route to tuning the structures and helicity of PTCDI molecules, but also provides new possibilities for the construction of high‐performance nanodevices.  相似文献   

3.
    
Recent progress in direct laser writing of three‐dimensional (3D) polymer nanostructures for photonics is reviewed. This technology has reached a level of maturity at which it can be considered as the 3D analogue of planar electron‐beam lithography. Combined with atomic‐layer deposition and/or chemical‐vapor deposition of dielectrics—the 3D analogues of planar evaporation technologies, the 3D polymer templates can be converted or inverted into 3D high‐refractive‐index‐contrast nanostructures. Examples discussed in this review include positive and inverse 3D silicon‐based woodpile photonic crystals possessing complete photonic bandgaps, novel optical resonator designs within these structures, 3D chiral photonic crystals for polarization‐state manipulation, and 3D icosahedral photonic quasicrystals. The latter represent a particularly complex 3D nanostructure.  相似文献   

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5.
    
Magnetic fields are uniquely valuable for creating colloidal nanostructured materials, not only providing a means for controlled synthesis but also guiding their self-assembly into distinct superstructures. In this study, a magnetothermal process for synthesizing hybrid nanostructures comprising ferrimagnetic magnetite nanorods coated with fluorescent perovskite nanocrystals is reported and their magnetic assembly into superstructures capable of emitting linear and circularly polarized light are demonstrated. Under UV excitation, the superstructures assembled in a liner magnetic field produce linear polarized luminescence, and those assembled in a chiral magnetic field exhibit strong circularly polarized luminescence (CPL) with a glum value up to 0.44 (±0.004). The CPL is believed to originate from the dipolar interaction between neighboring perovskite nanocrystals attached to the chiral assemblies and the chiral-selective absorption of the perovskite emission by the magnetite phase. The magnetic synthesis and assembly approaches and the resulting distinctive chiral superstructures are anticipated to open up new avenues for designing diverse functional chiroptical devices.  相似文献   

6.
    
Here a novel technique is reported to construct a three‐dimensional (3D) array of well‐defined and controllable multilayered nanostructures of proteins that is based on alternate layer‐by‐layer assembly of bacterial protein nanoparticles and DNA on a patterned array of gold dots. This is the first report on protein‐based multilayer stacking, which has the following significant advantages over conventional multilayer assemblies: 1) avoiding hazardous chemicals, the multilayer assembly is implemented in aqueous solution under mild temperature and pH conditions over a relatively short period; 2) direct multilayer growth from designated position is possible by controlling the aspect ratio; 3) multicomponent stacking can be easily performed through alternate stacking of different building blocks (in this case protein nanoparticles); and 4) a wide variety of 3D arrays can be constructed using various functionalized protein nanoparticles that are easily prepared through a simple genetic engineering approach. In this study, as a proof of concept, the developed 3D and patterned arrays of protein nanoparticle multilayers are successfully applied to the multiplexed bioassays of breast and colorectal cancer markers.  相似文献   

7.
    
An innovative nanostructure, namely the core–ring structure, is reported in this paper. It occurs in NiCo2O4 nanoplatelets, synthesized by the coprecipitation decomposition method using sodium hydroxide as the precipitant. The yield of core–ring hexagonal NiCo2O4 nanoplatelets is greater than 80% at 200 °C. A high‐resolution transmission electron microscopy and energy dispersive spectroscopy investigation reveals the typical core–ring nanostructure, which shows a strong enrichment of Co in the core with a Co content higher than 80%. A mechanism for the core–ring structure formation is proposed. The core–ring NiCo2O4 can be used as an electrocatalyst for an oxygen evolution reaction (OER) in alkaline water electrolysis. Compared with the electrodes of ordinary NiCo2O4 and Co3O4, or other NiCo2O4 electrodes prepared by alternate methods, the electrode coated by core‐ring NiCo2O4 nanoplatelets exhibits the greatest electrocatalytic properties, with an over‐potential of 0.315 V at a current density of 100 mA cm?2.  相似文献   

8.
    
Reversible photocontrol of dynamic chirality in self‐assembly systems is of great importance in exploitations of artificial nanomachines for scientific and industrious applications. Here, a new strategy is proposed for achieving optically chiral controls based on photoswitchable plasmonic nanostructures. Chiral plasmonic nanoassemblies that are responsive to optomechanical perturbations exerted by circular polarized light (CPL) in the visible (vis)/near infrared (NIR) region are designed. The reversible photoswitching between opposite chiral states is verified by circular dichroism (CD) spectral signals. Theoretical simulations reveal the key role of optical torques in driving this chiral switching. By regulating light polarization or tuning light frequency to excite different plasmonic modes of the nanostructures, such an optomechanically driven chiral switching can enable a directed mirror‐symmetry breaking and selective chiral amplification in nanoassemblies. This plasmon‐based photoswitching nanosystem can operate at the optical transparent window, showing particular advantages over most of the molecular photoswitches for applications in living systems.  相似文献   

9.
    
Monodisperse Co nanoparticles (NPs), stabilized by organic coating have been synthesized, and their immobilization on a variety of self‐assembled monolayers (SAMs) bearing different terminal groups and on SAM‐based chemical templates has been studied. The NPs had an average diameter of ～10 nm and consisted of hcp cobalt covered by a thin (～1 nm) oxide film. They exhibited pronounced ferromagnetic properties with a blocking temperature above 380 K, which is unusual for the given NP size and is presumably related to the high magnetocrystalline anisotropy associated with the crystallographic perfection of the NPs. The NPs were found to attach selectively to the SAMs bearing the thiol tail group, whereas no stable immobilization to other SAMs, over the electrostatic forces, could be achieved. Finally, based on the results for the individual SAMs, high‐contrast 2D structures of the Co NPs were fabricated on SAM‐based chemical templates on both micro‐ and nanometer length scales. The templates were prepared by irradiation‐promoted exchange reaction lithography, taking an OH‐terminated aliphatic SAMs as the primary template and thiol‐bearing aromatic molecules as the substituents.  相似文献   

10.
    
Modulation of the chirality of solid‐like nanoscale membranous structures used as selective photooxidants is an important goal of chemical and materials science. Here, the fabrication of a chiral plasmonic nanoparticle monolayer film which is a highly selective photooxidant under circularly polarized light (CPL) in the visible‐light region is reported. The chiroptical activity of the film can be controlled by altering the amount and stereochemistry of amino acids. The experiments disclose that this stable and reusable catalyst is active in the selective oxidation of glucose enantiomers and CPL of opposite polarization gives around 10.3‐fold increase in conversion rates. The results reveal that the handedness of polarized light dominates the catalytic activity of the chiral film. It is demonstrated that the specific chiral binding of the amino acid ligands and the local field enhancement in the light‐limited regime regulates the selective photocatalytic performance, as confirmed by first‐principles density functional theory and physical field simulations. With the catalyst's signature ability for chiral recognition and switching of handedness of polarized light, the discovery provides a foundation for designing and tailoring chiral inorganic photooxidants. This research also sets an example for the development of light–matter interactions and polarized optics.  相似文献   

11.
    
Supraspheres (SS) composed of hundreds to thousands of metal nanoparticles (NPs) and crosslinked by dithiol linkers are assembled into larger structures, which are subsequently converted into nanoporous metals (NMs). Conversion is achieved by heating which removes organic molecules stabilizing the NPs and allows for NP fusion. Heating of SS solutions leads to NMs of overall macroscopic dimensions; localized radiation using collimated electron beam is used to prepare metallized surface micropatterns. Depending on the composition of supraspherical precursors, nanoporous materials composed of up to three metals can be obtained. Strategies for controlling pore size and nanoscale surface roughness of these materials are discussed.  相似文献   

12.
刘武  任多敏 《电子器件》1994,17(3):143-145
对催化反应的各种中间生成物实施检测以直接确定反应的基元步骤、路径和机理，是研究表面催化反应的有效手段。探索一种检测化学中间生成物的方法是一个意义重大的课题。本文提出了用激光脉冲成象原子探针（Ｐｕｌｓｅｄ－ＬａｓｅｒＩｍａｇｉｎｇＡｔｏｍ－Ｐｒｏｂｅ，ＰＬＩＡＰ）［１］研究表面催化反应的方法，并对运用ＰＬＩＡＰ检测表面催化反应中间生成物的实验条件和实验结果的真实性进行了概括和探讨。  相似文献   

13.
    
While shapes and surface properties of nanomaterials are known to play important roles in defining their properties, it remains challenging to fine-tune the morphologies systematically and predictably. Considering the extraordinary performance, prussian blue nanoparticles (PBNPs) are selected as the proof-of-concept nanomaterials. Herein, a DNA-dependence approach to fine-control the morphology of PBNPs via electrostatic interaction-mediated self-assembly of inorganic ions and protonated DNA is developed. The regulation of different DNA on the morphology of PBNPs is systematically investigated. 30-mer Oligo-C or -T (C30/T30) mediates formation of flower-like PBNPs (PB nanoflowers), whereas cubic structure with different sizes is observed in the presence of 10-mer oligo-G or 30-mer Oligo-A (G10/A30). Detailed mechanism studies indicate that the protonation of nucleobases is the key factor for the morphological evolution. C30-dependent PB nanoflowers are superior to PB nanocubes in photothermal properties, peroxidase mimetic activity, photo-Fenton catalytic performance, and light scattering property, which present 1.2-, 3.78-, 1.58-, 1.93-fold improvement, respectively. Furthermore, PB nanoflowers mediated by the diblock DNA (sDNA; comprising C30 and complementary strands of the target DNA) unexpectedly acquire biorecognition capabilities. This study opens a new avenue for the systematic and predictable synthesis of PB nanoflowers, which broadens the repertoire of PBNPs for catalysis, biosensing, and imaging.  相似文献   

14.
    
Semiconducting quantum dots (QDs) have received huge attention for energy conversion and storage due to their unique characteristics, such as quantum size effect, multiple exciton generation effect, large surface-to-volume ratio, high density of active sites, and so on. However, the holistic and systematic understanding of the energy conversion and storage mechanism centering on QDs in specific application is still lacking. Herein, a comprehensive introduction of these extraordinary 0D materials, e.g., metal oxide, metal dichalcogenide, metal halides, multinary oxides, and nonmetal QDs, is presented. It starts with the synthetic strategies and unique properties of QDs. Highlights are focused on the rational design and development of advanced QDs-based materials for the various applications in energy-related fields, including photocatalytic H2 production, photocatalytic CO2 reduction, photocatalytic N2 reduction, electrocatalytic H2 evolution, electrocatalytic CO2 reduction, electrocatalytic N2 fixation, electrocatalytic O2 evolution, electrocatalytic O2 reduction, solar cells, metal-ion batteries, lithium–sulfur batteries, metal–air batteries, and supercapacitors. At last, challenges and perspectives of semiconducting QDs for energy conversion and storage are detailedly proposed.  相似文献   

15.
    
Here, a novel and simple route to fabricate highly dense arrays of palladium nanodots and nanowires with sub‐30 nm periodicity using nanoporous templates fabricated from supramolecular assemblies of a block copolymer, polystyrene‐block‐poly(4‐vinylpyridine) (PS‐b‐P4VP) and a low molecular weight additive, 2‐(4′‐hydroxybenzeneazo) benzoic acid (HABA) is demonstrated. The palladium nanoparticles, which are directly deposited in the nanoporous templates from an aqueous solution, selectively migrate in the pores mainly due to their preferential attraction to the P4VP block covering the pore wall. The polymer template is then removed by oxygen plasma etching or pyrolysis in air resulting in palladium nanostructures whose large scale morphology mirrors that of the original template. The method adopted in this work is general and versatile so that it could easily be extended for patterning a variety of metallic materials into dot and wire arrays.  相似文献   

16.
A novel nanopatterning method using pulsed laser deposition through an ultrathin anodic aluminium oxide (AAO) membrane mask is proposed to synthesize well‐ordered nanodot arrays of magnetic CoFe2O4 that feature a wide range of applications like sensors, drug delivery, and data storage. This technique allows the adjustment of the array dimension from ～35 to ～300 nm in diameter and ～65 to ～500 nm in inter‐dot distance. The dot density can be as high as 0.21 Terabit in.?2. The microstructure of the nanodots is characterized by SEM, TEM, and XRD and their magnetic properties are confirmed by well‐defined magnetic force microscopy contrasts and by hysteresis loops recorded by a superconducting quantum interference device. Moreover, the high stability of the AAO mask enables the epitaxial growth of nanodots at a temperature as high as 550 °C. The epitaxial dots demonstrate unique complex magnetic domains such as bubble and stripe domains, which are switchable by external magnetic fields. This patterning method creates opportunities for studying novel physics in oxide nanomagnets and may find applications in spintronic devices.  相似文献   

17.
    
Bead-chain-like ZnO nanoparticles (NPs) formed in colloidal solution from oriented attachment (OA) of spherical nanoparticles. Arc discharge in liquid is a cost-effective method for quick mass production of nanostructured materials without considerable environmental footprints. Applying voltage across two zinc rods as electrodes, which were immersed in water cause explosion of electrodes and plasma generation. Zn/ZnO nanocomposites produced by interaction of different active species in high-pressure and high-temperature plasma at the solid-liquid interface. Different sized nanoparticles with diameters of 26, 35, 40 and 60 nm at applied discharge currents of 150, 100, 50 and 20 A respectively, were fabricated in water without any chemical additives. The results showed bead-like oriented attachments appeared with increasing the applied current during synthesis. Length of aggregates increases from 114 nm to 120 nm with the applied current of the arc discharge. The mechanism of OA of ZnO NPs was investigated by calculating the attractive and repulsive forces based on Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed for characterization of particle size, shape, and investigation of bead-like aggregates. X-ray diffraction (XRD) analysis was used to study the crystal structure and phase composition of the bead-chain like nanostructures. Finally, zeta potential analysis was used to measure surface charges and study the mechanism of oriented attachment. The results provide a simple and flexible method for synthesis of Zn/ZnO bead-chain like nanostructures.  相似文献   

18.
    
This article reports for the first time a novel category of hollow organic@inorganic hybrid two‐layered nanoparticles (NPs), in which the inner layer is formed by optically active helical polyacetylene, and the outer layer by silica. Such NPs show remarkable optical activity and are successfully used for enantioselective crystallization. To prepare such NPs, n‐butyl acrylate undergoes radical polymerization to first form poly(n‐butyl acrylate) (PBA) cores two shells by catalytic polymerization of substituted acetylene and sol–gel approach of TEOS (tetraethyl orthosilicate), respectively. Removal of the PBA cores provides the expected hollow core/shell NPs. The intense dircular dichroism (CD) effects demonstrate that the hollow chiral NPs possess considerable optical activity, arising from the helical substituted polyacetylenes forming the inner layer. The hollow NPs are further used as chiral templates to induce enantioselective crystallization of racemic alanines, demonstrating the significant potential applications of the hollow chiral NPs in chiral technologies. Also of particular significance is the detailed process of the induced crystallization observed by TEM. The strategy for preparing the hollow hybrid chiral NPs should be highlighted since it combines free radical polymerization and catalytic polymerization with sol–gel process in a single system, by which numerous advanced materials will be accessible.  相似文献   

19.
    
We report here “aptatags,” which consist of aptamer‐modified silver nanoparticles (NPs) held together by an optical reporter. It is possible to use these materials to design a heterogeneous method for protein identification that takes advantage of the Raman signal enhancement by metallic nanostructures and the recognition capabilities of aptamers. Aptatags are formed by linking silver NPs with an organic dithiol molecule, followed by surface modification with thiolated single‐stranded DNA (ssDNA) corresponding to the sequence of the aptamer probe. The sensing surface involves a silver layer containing the thiolated capturing aptamer and mercaptohexadecanoic acid to minimize nonspecific binding. The overall process provides excellent selectivity and sensitivity. Detailed characterization of the sensing surface by SERS maps and atomic force microscopy was carried out to understand how structural features lead to signal generation.  相似文献   

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