铁电纳米材料和纳米结构研究的进展

铁电纳米材料和纳米结构(如纳米线、纳米管、纳米环)具有新型尺寸效应特性,在铁电基电子器件的微型化方面受到广泛关注.近年来在铁电纳米材料和纳米结构的制备和(电性能和微结构)表征及理论模拟方面取得了相当进展,本文对这方面的最新进展进行评述.首先对高质量的铁电纳米材料和纳米结构的制备方法进行了简短评述,然后介绍铁电纳米材料和纳米结构的纳尺度物性表征.随后介绍了最近发展的四种理论模型(尤其对铁电纳米管、纳米线、纳米点),以及从第一原理出发理论模拟铁电纳米结构的新现象,如铁电纳米结构的自发极化螺旋有序和自发极化涡旋结构.最后总结了铁电纳米材料和纳米结构的微结构研究进展,并讨论了有关铁电纳米结构中自发极化螺旋畴的一些基础物理问题以及实验上寻找自发极化螺旋畴的研究进展.     

二维金纳米阵列制备及其光学响应

有序贵金属纳米结构由于其本身所特有的光学响应及灵活调控能力,在微纳光电子材料与器件研究领域得到了广泛应用。在众多相关研究中,如何实现金（Au）纳米周期结构的大面积快速制备是人们关心的重要问题之一。采用纳米球自组装刻蚀方法,在大孔周期结构模板内部成功制备了新型二维Au纳米阵列,并有效避免了杂散Au纳米颗粒的产生。通过进一步的工艺优化和参量控制,实现了Au纳米颗粒尺寸的灵活调控,并探讨了其结构形成的物理机理。光学测试研究结果揭示了二维Au纳米阵列的表面等离子体吸收与散射响应,并证明其在近红外飞秒脉冲激励下具有显著的双光子吸收（饱和）效应。该研究结果在太阳能电池,光开关及材料微纳制备等领域具有潜在应用。     

Preparation,Properties, and Applications of Low-Dimensional Molecular Organic Nanomaterials

In recent years, great progress has been made in research and development of small-molecule organic materials with various low-dimensional nanostructures. This paper presents a comprehensive review of recent research progress in this field, including preparation, electronic and optoelectronic properties and applications. First, an introduction gives to the reprecipitation, soft templates methods, and progress in synthesis and morphological control of low-dimensional small-molecule organic nanomaterials. Their unique optical and electronic properties and research progress in these aspects are reviewed and discussed in detail. Applications based on low-dimensional small-molecule organic nanomaterials are briefly described. Finally, some perspectives to the future development of this field are addressed.     

Etching‐Free Epitaxial Growth of Gold on Silver Nanostructures for High Chemical Stability and Plasmonic Activity

A robust method for epitaxial deposition of Au onto the surface of Ag nanostructures is demonstrated, which allows effective conversion of Ag nano­structures of various morphologies into Ag@Au counterparts, with the anisotropic ones showing excellent plasmonic properties comparable to the original Ag nanostructures while significantly enhanced stability. Sulfite plays a determining role in the success of this epitaxial deposition as it strongly complexes with gold cations to completely prevent galvanic replacement while it also remains benign to the Ag surface to avoid any ligand‐assisted oxidative etching. By using Ag nanoplates as an example, it is shown that the corresponding Ag@Au nanoplates possess remarkable plasmonic properties that are virtually Ag‐like, in clear contrast to Ag@Au nanospheres that exhibit much lower plasmonic activities than their Ag counterparts. As a result, they display high durability and activities in surface‐enhanced Raman scattering applications. This strategy may represent a general platform for depositing a noble metal on less stable metal nanostructures, thus opening up new opportunities in rational design of functional metal nanomaterials for a broad range of applications.     

Synthesis of Au–CdS Core–Shell Hetero‐Nanorods with Efficient Exciton–Plasmon Interactions

The synthesis of large lattice mismatch metal‐semiconductor core–shell hetero‐nanostructures remains challenging, and thus the corresponding optical properties are seldom discussed. Here, we report the gold‐nanorod‐seeded growth of Au–CdS core–shell hetero‐nanorods by employing Ag₂S as an interim layer that favors CdS shell formation through a cation‐exchange process, and the subsequent CdS growth, which can form complete core–shell structures with controllable shell thickness. Exciton–plasmon interactions observed in the Au–CdS nanorods induce shell thickness‐tailored and red‐shifted longitudinal surface plasmon resonance and quenched CdS luminescence under ultraviolet light excitation. Furthermore, the Au–CdS nanorods demonstrate an enhanced and plasmon‐governed two‐photon luminescence under near‐infrared pulsed laser excitation. The approach has potential for the preparation of other metal‐semiconductor hetero‐nanomaterials with complete core–shell structures, and these Au–CdS nanorods may open up intriguing new possibilities at the interface of optics and electronics.     

Recent Progress on Metal-Based Nanomaterials: Fabrications,Optical Properties,and Applications in Ultrafast Photonics

Nanomaterials have demonstrated excellent mechanical, thermal, optical, and electrical properties in various fields, including 1D carbon nanotubes, as well as 2D materials starting from graphene. Metal-based nanomaterials, mainly divided into metal and metal oxide nanoparticles, also gradually come into the sight of ultrafast photonics applications due to the outstanding optical properties. The optical properties of metal nanoparticles can be enhanced by the interaction between conduction electrons with electric fields that is called surface plasmon resonance. As for metal oxide nanoparticles, optical properties are closely related to bandgap structures. When it comes to transition metal oxides, other phenomena also play important roles in optical absorption such as spin inversion and excitons of iron. Moreover, preparation methods of materials are also crucial for their properties and further applications. Therefore, in this review, commonly used physical and chemical fabrication methods for metal-based nanomaterials are first introduced. Then the optical properties of typical metal and metal oxide nanoparticles are discussed specifically. In addition, the applications of metal-based nanomaterials in ultrafast lasers based on mode-locked and Q-switched techniques are also summarized. Finally, a summary and outlook toward the synthesis, optical properties, and applications in ultrafast photonics of metal-based nanomaterials are presented.     

飞秒激光组装一维纳米材料及其应用

一维纳米材料具有众多优异的特性,是构建微纳米功能性器件的基石。实现一维纳米材料在二维和三维空间的高精度和高定向组装是充分发挥其应用潜力的关键,同时也是制造难点。在众多纳米材料组装技术中,飞秒激光直写诱导组装技术具有独特优势,可实现一维纳米材料在任意三维结构中的可设计、高定向及高精度的组装。首先简要介绍了一维纳米材料组装研究的背景,并总结了非激光直写组装技术的研究现状和存在的挑战,然后较详细介绍了飞秒激光直写技术在一维纳米材料组装研究中的进展,重点回顾了金属(包括Au和Ag纳米线)、半导体(包括CNTs和ZnO)一维纳米材料的飞秒激光直写组装及微纳光电子功能器件的制造。并讨论了诱导一维纳米材料定向排布的光学力和非光学力(包括剪切力、体积收缩应力和空间限制)的作用机理,理论计算和实验研究结果验证了飞秒激光诱导的非光学力作用是导致一维纳米材料定向排布的主要原因。最后探讨了目前飞秒激光组装技术面临的一些问题和未来在高精度纳米材料组装和三维功能器件集成方面的发展趋势。     

Gold Nanobipyramid‐Supported Silver Nanostructures with Narrow Plasmon Linewidths and Improved Chemical Stability

Silver nanostructures with narrow plasmon linewidths and good chemical stability are strongly desired for plasmonic applications. Herein, a facile method is discussed for the preparation of Ag nanostructures with narrow plasmon linewidths and improved chemical stability through Ag overgrowth on monodispersed Au nanobipyramids. Structural evolution from bipyramid through rice to rod is observed, indicating that Ag atoms are preferentially deposited on the side surfaces of Au nanobipyramids. The resultant (Au nanobipyramid)@Ag nanostructures possess high size and shape uniformities, and much narrower plasmon linewidths than other Ag nanostructures. The spectral evolution of the supported Ag nanostructures is ascertained by both ensemble and single‐particle characterizations, together with electrodynamic simulations. Systematic measurements of the refractive index sensing characteristics indicate that Ag nanostructures in this study possess high index sensitivities and figure of merit (sensitivity divided by linewidth) values. Moreover, Ag nanostructures in this study exhibit greatly improved chemical stability. The superior sensing capability of Ag nanostructures in this study is further demonstrated by the detection of sulfide ions at a relatively low detection limit. Taken together, results of this study show that the Au‐nano­bipyramid‐supported Ag nanostructures will be an outstanding candidate for the design of ultrasensitive plasmonic sensing devices as well as for the development of other plasmon‐enabled technological applications.     

Cathodoluminescence Modulation of ZnS Nanostructures by Morphology,Doping, and Temperature

Spatially and spectrally resolved cathodoluminescence (CL) is one of the most effective methods to explore the optical properties of a nanomaterials and reveals the spatial distribution as well as the correlation between the luminescence and the sample morphology and microstructure. Here, CL modulation of ZnS nanostructures by controlled morphologies, Fe/Mn doping, and measurement temperature is demonstrated. High quality ZnS nanobelts and nanorods are synthesized on an Au‐coated Si substrate and an Au‐coated GaAs substrate via a facile thermal evaporation route. A room‐temperature sharp ultraviolet (UV) lasing‐like peak in various ZnS is achieved. The main UV luminescence peaks appear at wavelengths between 330 and 338 nm. The low temperature (32 K) CL spectrum consists of a narrow and strong UV peak centered at 330 nm and two broad, low‐intensity peaks in the visible region (514 and 610 nm). Temperature‐dependent CL from such single‐crystalline ZnS nanobelts in the temperature range of 32 to 296 K reveals two UV peaks at 3.757 and 3.646 eV. The effects of Fe doping and Fe/Mn co‐doping on the CL property of ZnS nanobelts are further investigated. These results imply that ZnS nanostructures can be used for potential luminescent materials as well as short‐wavelength nanolaser light sources.     

纳米光子学材料漫谈

评述纳米光子学材料的制备.纳米光子学材料的种类繁多,不同的纳米形态、结构具有不同的特性,其制备方法更是成千上万种.列举20种形态的纳米光子学材料,阐明它们的制备方法、特性和应用前景.     

Self-Assembled Colloidal Nanopatterns toward Unnatural Optical Meta-Materials

2D nanoscale patterns have been extensively investigated for various applications including information storage devices, non-volatile memory devices, chemical or biological sensors. Recently, such nanostructured patterns have been gaining lots of attention because of their potential uses as meta-materials or meta-surfaces with unnatural optical properties. In particular, self-assembled colloidal monolayers of gold nanoparticles (NPs) have been demonstrated as optical meta-materials for unnaturally high refractive index (n_eff > 4) at optical frequency. Raspberry-like particles or spherical assembly of NPs are also investigated for negative or near-zero index of refraction. Thanks to the recent advance in colloidal chemistry for shaping NPs with controlling the interaction, non-close-packed, or even non-periodic colloidal nanostructures can be achieved, which may be potentially useful for optical meta-surfaces. In this article, a brief introduction of optical meta-materials is provided and recent progress for high-index and negative-index meta-materials are reviewed. In the second part, the meta-surfaces will be briefly described including fundamental principle and some of the key potential applications. Finally, the recent experimental progress of high-precision self-assembly for the meta-surface fabrication will be discussed.     

Ultrasensitive Plasmonic Response of Bimetallic Au/Pd Nanostructures to Hydrogen

Hydrogen detection is crucial for the safety of all hydrogen‐related applications. Compared to electrical hydrogen sensors, which usually suffer from possible electric sparks, optical hydrogen sensors offer advantages of remote and contact‐free readout and therefore the avoidance of spark generation. Herein, bimetallic Au/Pd nanostructure monolayers that exhibit ultrasensitive plasmonic response to hydrogen are reported. Bimetallic Au/Pd nanostructures with continuous and discontinuous Pd shells are prepared. The plasmonic response to hydrogen is monitored by measuring the extinction spectra of the ensemble Au/Pd nanostructures deposited on glass slides. Introduction of hydrogen induces red plasmon shifts, which become larger for the nanostructures with thicker Pd shells. For the nanostructures with continuous Pd shell, the plasmon shift can reach 56 nm at the hydrogen volume concentration below the explosion limit. The plasmon resonance wavelength displays an excellent linear dependence on the hydrogen volume concentration below 1%. The detection limit in the experiments reaches 0.2%. The nanostructures with discontinuous Pd shell show smaller plasmon shifts than those with continuous Pd shell. The extinction measurements on the ensemble nanostructures supported on transparent substrates and the unprecedentedly large plasmon shifts and sensitivity make the results very promising for the development of practical optical hydrogen sensors.     

Evolution of non-phosphine solvents in colloidal synthesis of I-III-VI2 and I2-II-IV-VI4 group semiconductor nanomaterials – Current status

The concepts of new synthetic ideas and their implementation in the synthesis of semiconductor nanomaterials have been a subject of interest in recent years. Influence of solvents on the properties of nanomaterials is an important area being pursued extensively and need better understanding to move ahead with new innovations. The selective role of solvents is an indispensable criteria in order to achieve semiconductor nanomaterials with excellent physical and chemical properties. By selecting a suitable solvent system, the morphology, phase, size as well as the optical properties of the resultant nanomaterials could be precisely tuned. This makes a great interest in colloidal chemistry to utilize them for the synthesis of various kinds of nanostructures. Most of the recently emerging synthesis methods of I-III-VI₂ and I₂-II-IV-VI₄ group semiconductor nanomaterials are based on thermolysis of metal precursors in non-phosphine solvents. The composition and the crystallographic phase of the nanoparticles can be varied by carefully choosing suitable non-phosphine solvents. Hence, the role of non-phosphine solvents in determining the structural and optical properties of the semiconductor nanoparticles is crucial. The present review summarizes the active role of non-phosphine solvents in the crystal structure, morphology and other properties of I-III-VI₂ and I₂-II-IV-VI₄ group semiconductor nanomaterials. The recent interesting results on the developments of this subject and fundamental background literature have been discussed elaborately.     

Syntheses,Properties, and Potential Applications of Multicomponent Magnetic Nanoparticles

Multicomponent hybrid nanostructures that contain two or more nanometer‐scale components have attracted much attention recently owing to the synergistic properties induced by interactions between these different nanometer‐scale objects. Herein, we give an overview of the efforts to synthesize multicomponent nanoparticles with at least one component being magnetic, and focus on our recent developments. The syntheses are based on heterogeneous nucleation and growth of a second and third component onto seed nanoparticles. These multicomponent nanoparticles show interesting magnetic, magneto‐optical, plasmonic, and semiconducting properties that can be modulated by interfacial interactions between different nanocomponents. This opens up a new avenue to advanced multifunctional nanomaterials for device concepts and applications.     

A Library of Late Transition Metal Alloy Dielectric Functions for Nanophotonic Applications

Accurate complex dielectric functions are critical to accelerate the development of rationally designed metal alloy systems for nanophotonic applications, and to thereby unlock the potential of alloying for tailoring nanostructure optical properties. To date, however, accurate alloy dielectric functions are widely lacking. Here, a time‐dependent density‐functional theory computational framework is employed to compute a comprehensive binary alloy dielectric function library for the late transition metals most commonly employed in plasmonics (Ag, Au, Cu, Pd, Pt). Excellent agreement is found between electrodynamic simulations based on these dielectric functions and selected alloy systems experimentally scrutinized in 10 at% composition intervals. Furthermore, it is demonstrated that the dielectric functions can vary in very non‐linear fashion with composition, which paves the way for non‐trivial optical response optimization by tailoring material composition. The presented dielectric function library is thus a key resource for the development of alloy nanomaterials for applications in nanophotonics, optical sensors, and photocatalysis.     

Emerging Mono-Elemental Bismuth Nanostructures: Controlled Synthesis and Their Versatile Applications

Bismuth (Bi), as a nontoxic and inexpensive diamagnetic heavy metal, has recently been utilized for the preparation of a variety of nanomaterials, such as nanoparticles, nanowires, nanotubes, nanosheets, etc., with a tunable bandgap, unique structure, excellent physicochemical properties, and compositional features for versatile properties, such as near-infrared absorbance, high X-ray attenuation coefficient, excellent photothermal conversion efficiency, and a long circulation half-life. These features have endowed mono-elemental Bi nanomaterials with desirable performances for electronics/optoelectronics, energy storage and conversion, catalysis, nonlinear photonics, sensors, biomedical applications, etc. This review summarizes the controlled synthesis of mono-elemental Bi nanomaterials with different shapes and sizes, highlights the state-of-the-art progress of the desired applications of mono-elemental Bi nanomaterials, and presents some personal insights on the challenges and future opportunities in this research area. It is hoped that the controllable manipulation techniques of Bi nanomaterials, along with their unique properties, can shed light on the next-generation devices based on Bi nanostructures and Bi-related nanomaterials.     

Localization of Au Nanoclusters on Layered Double Hydroxides Nanosheets: Confinement‐Induced Emission Enhancement and Temperature‐Responsive Luminescence

Gold nanoclusters (Au NCs) stand for a new type of fluorescent nanomaterials with outstanding optical properties due to their discrete electronic energy and direct electron transition. However, relative low quantum yield (QY) of Au NCs in aqueous or solid state has limited their photofunctional applications. To improve the fluorescent performances of Au NCs and find an effective approach for the fabrication of Au NCs‐based films, in this work, Au NCs are localized onto 2D layered double hydroxides (LDHs) nanosheets via a layer‐by‐layer assembly process; the as‐fabricated (Au NCs/LDH)_n ultrathin films (UTFs) show an ordered and dense immobilization of Au NCs. The localization and confinement effects imposed by LDH nanosheets induce significantly increased emissive Au(I) units as confirmed by X‐ray photoelectron spectroscopy and periodic density functional theoretical simulation, which further results in promoted QY (from 2.69% to 14.11%) and prolonged fluorescence lifetime (from 1.84 µs to 14.67 µs). Moreover, the ordered (Au NCs/LDH)_n UTFs exhibit well‐defined temperature‐dependent photoluminescence (PL) and electrochemiluminescence (ECL) responses. Therefore, this work supplies a facile strategy to achieve the immobilization of Au NCs and obtain Au NCs‐based thin films with high luminescent properties, which have potential applications in PL and ECL temperature sensors.     

Beyond Seashells: Bioinspired 2D Photonic and Photoelectronic Devices

The discovery of novel materials that possess extraordinary optical properties are of special interest, as they inspire systems for next‐generation solar energy harvesting and conversion devices. Learning from nature has inspired the development of many photonic nanomaterials with fascinating structural colors. 2D photonic nanostructures, inspired by the attractive optical properties found on the inner surfaces of seashells, are fabricated in a facile and scalable way. The shells generate shining clusters for preying on phototactic creatures through interaction with incident solar light in water. By alternately depositing graphene and 2D ultrathin TiO₂ nanosheets to form 2D–2D heterostructures and homostructures, seashell‐inspired nanomaterials with well‐controlled parameters are successfully achieved. They exhibit exceptional interlayer charge transfer properties and ultrafast in‐plane electron mobility and present fascinating nacre‐mimicking optical properties and significantly enhanced light‐response behavior when acting as photoelectrodes. A window into the fabrication of novel 2D photonic structures and devices is opened, paving the way for the design of high‐performance solar‐energy harvesting and conversion devices.     

Graphene‐Based Nanomaterials: Synthesis,Properties, and Optical and Optoelectronic Applications

Graphene, a two‐dimensional, single‐atom‐thick carbon crystal arranged in a honeycomb lattice, shows extraordinary electronic, mechanical, thermal, optical, and optoelectronic properties, and has great potential in next‐generation electronics, optics, and optoelectronics. Graphene and graphene‐based nanomaterials have witnessed a very fast development of both fundamental and practical aspects in optics and optoelectronics since 2008. In this Feature Article, the synthesis techniques and main electronic and optical properties of graphene‐based nanomaterials are introduced with a comprehensive view. Recent progress of graphene‐based nanomaterials in optical and optoelectronic applications is then reviewed, including transparent conductive electrodes, photodetectors and phototransistors, photovoltaics and light emitting devices, saturable absorbers for ultrafast lasers, and biological and photocatalytic applications. In the final section, perspectives are given and future challenges in optical and optoelectronic applications of graphene‐based nanomaterials are addressed.