A Fluorescence–Phosphorescence–Phosphorescence Triple‐Channel Emission Strategy for Full‐Color Luminescence

Organic luminogens constitute promising prototypes for various optoelectronic applications. Since gaining distinct color emissions normally requires the alternation of the conjugated backbone, big issues remain in material synthetic cost and skeleton compatibility while pursuing full‐color luminescence. Upon a facile one‐step coupling, three simple but smart perchalcogenated (O, S, and Se) arenes are synthesized. They exhibit strong luminescent tricolor primaries (i.e., blue, green, and red, respectively) in the solid state with a superior quantum yield up to >40% (5–10 times higher than that in corresponding solutions). The properties originate from a fluorescence–phosphorescence–phosphorescence triple‐channel emission effect, which is regulated by S and Se heavy atoms–dependent intersystem crossing upon molecular packing, as well as Se–Se atom interaction–caused energy splittings. Consequently, full‐color luminescence, including a typical white‐light luminescence with a Commission Internationale de I'Eclairage coordinate of (0.30, 0.35), is realized by complementarily incorporating these tricolor luminescent materials in the film. Moreover, mechanochromic luminescent color conversions are also observed to achieve the fine‐tuning of the luminescent tints. This strategy can be smart to address full‐color luminescence on the same molecular skeleton, showing better material compatibility as an alternative to the traditional multiple‐luminophore engineering.     

Solid-state reactions,dynamics in molecular crystals

The mechanism of solid-state reactions has found much interest over the years. The hypothesis of minimal atomic and molecular movements did not withstand experimental scrutiny by supermicroscopy. Rather the occurrence of far-reaching and strictly lattice-controlled molecular migrations has been proven for reactions with change of the molecular shape. The crystal packing gives now much more profound information than the mere listing of distances of reaction centers. Topotactic single crystal to single crystal reactions may occur if the molecular shape does not change. Local atomic force microscopy should secure such behaviour, as several claims of topotaxy could not be supported by local experimental techniques. The dynamics in reacting crystals (migrating molecules use ‘easy ways’) can also be triggered by mechanical stress. Most importantly, the new theory encourages the development of unforeseen benign gas–solid and solid–solid reactions which use the same solid-state mechanism as thermal and photochemical conversions. None of the stoichiometric 100% yield reactions would be possible without the long-range molecular movements in the reacting crystals.     

COLLOID-CHEMICAL ASPECTS OF MECHANICAL ACTIVATION

The crystal stucture of crystalline solids is drastically changed by intensive mechanical forces: permanent lattice defects, polymorphic tranformations, total amorphisation, possible homogeneous chemical reactions, and a definite increase of surface free energy can be observed; all these phenomena show that a high share of grinding energy can be permanently stored in the ground material. Due to this mechanical activation the solid will be capable of surface and solid-state reactions, and consequently the dispersity of the system is decreased irreversibly and both the phase composition and chemical composition are changed in the direction of increased system stability, Novel type mechanochemical “capillary” reactions are also described. Reactions and surface interactions can be modified to a certain extent by vapour adsorption. Thermal and adhesion properties of solids, exposed to intensive grinding and being in an active state or having been subjected to mechanichemical transformations, are drastically changed; this change may influence several technologies involving grinding.     

Phase dependent luminescent property of N,N-di(n-octyl)quinacridone crystals

A polymorph A and a pseudopolymorph B of N,N-di(n-octyl)quinacridone (DOQA) have been prepared by altering the crystal growth conditions and their molecular structures have been identified by single-crystal X-ray diffraction. Both polymorphs show similar characteristics of molecular structures and their molecular arrangements are characterized by the intermolecular π…π interactions and CH…O hydrogen interactions. Due to the presence of methanol molecules in the form B, it is found that in crystalline polymorphs A and B the distance and the degree of overlap of π-electron are remarkably different. Simultaneously, molecules of two forms show different hydrogen bonding patterns. The different molecular packing structures result in significantly different morphologies, namely block shape for A whereas needle shape for B, and solid-state luminescent properties of two forms. From the X-ray single-crystal analysis, the obvious different molecular packing structures of two forms, due to the presence of methanol molecules in the form B, urge us to investigate the phase-dependent emission properties of DOQA in microstructures. DOQA can be employed as building blocks to fabricate luminescent microscale wires by controlling the ratio of methanol solvent.     

Fabrication of colorless organic materials exhibiting white luminescence using normal and excited-state intramolecular proton transfer processes

Organic, white luminescent materials were fabricated using a mixture of proton-transfer and nonproton-transfer fluorophores. 2'-Methoxy and 2'-hydroxy derivatives of 2-phenylimidazo[1,2-a]pyridine (PIP) have similar UV-absorption properties; however, they exhibit mechanistically different luminescence respectively ascribable to the normal (～420 nm) and excited-state intramolecular proton transfer processes (～530 nm) in the solid state. UV-irradiation of mixed solids excites both components concurrently and results in efficient white luminescence composed of two independent emissions without involving energy transfer process. White luminescent solids are easily transformed into vapor-deposited films under mild conditions, and a colorless and transparent thin film by dissolving in PMMA.     

Cyclodextrin-threaded conjugated polyrotaxanes as insulated molecular wires with reduced interstrand interactions

Control of intermolecular interactions is crucial to the exploitation of molecular semiconductors for both organic electronics and the viable manipulation and incorporation of single molecules into nano-engineered devices. Here we explore the properties of a class of materials that are engineered at a supramolecular level by threading a conjugated macromolecule, such as poly(para-phenylene), poly(4,4'-diphenylene vinylene) or polyfluorene through alpha- or beta-cyclodextrin rings, so as to reduce intermolecular interactions and solid-state packing effects that red-shift and partially quench the luminescence. Our approach preserves the fundamental semiconducting properties of the conjugated wires, and is effective at both increasing the photoluminescence efficiency and blue-shifting the emission of the conjugated cores, in the solid state, while still allowing charge-transport. We used the polymers to prepare single-layer light-emitting diodes with Ca and Al cathodes, and observed blue and green emission. The reduced tendency for polymer chains to aggregate allows solution-processing of individual polyrotaxane wires onto substrates, as revealed by scanning force microscopy.     

Mechanical property design of molecular solids

The current emphasis of crystal engineering, which has evolved over the past three decades through crystal packing analysis and identification of crystal design strategies, has shifted from structure to properties, i.e., design of molecular solids with targeted combination of properties. Amongst the panoply of chemical, physical, and biological properties that these materials exhibit, a comprehensive understanding of the mechanical properties is perhaps the most challenging as it involves connecting molecular level structural features to macroscopic mechanical behavior. However, the adoption of the nanoindentation technique, with which it is possible to measure—both quantitatively and accurately—the mechanical response of even small single crystals, in crystal engineering, has paved the way for substantial progress in the recent past. In this review, we summarize some recent results with an emphasis as to how one can design and control properties of molecular solids such as elastic modulus and hardness. This review closes with an enumeration of the key challenges that lie ahead. Such studies show a big scope for studying mechanical properties of organic crystals as a function of crystal structure, and in turn to understand their structure-property relationship for designing future smart materials. This emerging research field has prospects and a potential to play an important role in the future development of crystal engineering.     

稀土激活发光材料的研究进展

稀土发光材料是一种很有发展前途的新型功能材料.介绍了稀土发光材料的性质和应用,详细阐述了高温固相、共沉淀、燃烧、气体反应、水热和微波等稀土发光材料的制备方法,探讨了稀土离子对发光材料的激活机理,并展望了该领域的发展前景.作者利用燃烧法制备出以SrAl2O4为基质,稀土元素铈和铽为激活剂的光致黄色荧光发光材料,显示了其优越的发光性能.     

Mesostructured Composite Materials with Electrically Tunable Upconverting Properties

A promising approach of designing mesostructured materials with novel physical behavior is to combine unique optical and electronic properties of solid nanoparticles with long‐range ordering and facile response of soft matter to weak external stimuli. Here, orientationally ordered nematic liquid crystalline dispersions of rod‐like upconversion nanoparticles are designed, practically realized, and characterized. Boundary conditions on particle surfaces, defined through surface functionalization, promote spontaneous unidirectional self‐alignment of the dispersed rod‐like nanoparticles, mechanically coupled to the molecular ordering direction of the thermotropic nematic liquid crystal host. As host is electrically switched at low voltages ≈1 V, nanorods rotate, yielding tunable upconversion and polarized luminescence properties of the composite. Spectral and polarization dependencies are characterized and explained through invoking models of electrical switching of liquid crystals and upconversion dependence on crystalline matrices of nanorods, and their potential practical uses are discussed.     

Construction of nanostructures for selective lithium ion conduction using self-assembled molecular arrays in supramolecular solids

Abstract

In the development of innovative molecule-based materials, the identification of the structural features in supramolecular solids and the understanding of the correlation between structure and function are important factors. The author investigated the development of supramolecular solid electrolytes by constructing ion conduction paths using a supramolecular hierarchical structure in molecular crystals because the ion conduction path is an attractive key structure due to its ability to generate solid-state ion diffusivity. The obtained molecular crystals exhibited selective lithium ion diffusion via conduction paths consisting of lithium bis(trifluoromethanesulfonyl)amide (LiTFSA) and small molecules such as ether or amine compounds. In the present review, the correlation between the crystal structure and ion conductivity of the obtained molecular crystals is addressed based on the systematic structural control of the ionic conduction paths through the modification of the component molecules. The relationship between the crystal structure and ion conductivity of the molecular crystals provides a guideline for the development of solid electrolytes based on supramolecular solids exhibiting rapid and selective lithium ion conduction.     

Shock-induced solid-state chemical reactivity studies using time-resolved radiation pyrometry

Time-resolved radiation pyrometry has been used to study materials which undergo solid-state chemical reactions due to shock loading. Shock-induced chemical reactivity in solids is fundamentally different than that in high explosives and other energetic materials because, if no volatiles are present, the reaction products end up in the condensed, rather than the vapor, state. Bulk property changes accompanying the solid-state reactions may therefore be too small to be observable with wave profile or shock-velocity measurements. However, some solid-state reactions, such as that between metallic nickel and aluminum, are exothermic enough to give rise to a measurable increase in temperature, so pyrometry can be used to detect the reactions. Unfortunately, these measurements are complicated by the large temperature increases generated by other sources. Possible mechanisms for generation of these high temperatures, and their effect on the chemical reaction, are suggested     

二维光子晶体微腔的制备及其对硅光学材料的光量子放大

光子晶体(PC)可以增加光物质相互作用和光发射效率,在微纳光子学、量子光学及信息光学等领域中都有着广泛的应用。近年来,二维硅基光子晶体微腔的发光增强效应研究取得了较为重大的突破。本文针对现有二维光子晶体及微腔的制备方法与发光性能的调控展开论述,详细介绍了二维光子晶体微腔的制备进程与温度、泵浦能量、微腔结构对微腔Q因子以及发光性能的影响,并进一步展望了二维光子晶体在硅材料光量子放大领域未来研究所面临的问题及应用前景。     

Crystallization‐Induced Emission Enhancement of a Deep‐Blue Luminescence Material with Tunable Mechano‐ and Thermochromism

Organic luminescent materials with the ability to reversibly switch the luminescence when subjected to external stimuli have attracted considerable interest in recent years. However, the examples of luminescent materials that exhibit multiresponsive properties are rarely reported. In this work, a new stimuli‐responsive dye P1 is designed and synthesized with two identical chromophores of naphthalimide, one at each side of an amidoamine‐based spacer. This amide‐rich molecule offers many possibilities for forming intra‐ and intermolecular hydrogen bond interactions. Particularly, P1 has an intrinsic property of cocrystallizing with methanol. Compared with the pristine P1 sample, the as‐prepared two‐component cocrystalline material displays an exceptive deep‐blue emission, which is extremely rare among naphthalimide‐based molecules in the solid state. Furthermore, the target material exhibits an obvious mechanochromic fluorescent behavior and a large spectral shift under force stimuli. On the other hand, the cocrystalline material shows an unusual “turn off” thermochromic luminescence accompanied by solvent evaporation. Moreover, using external stimuli to reversibly manipulate fluorescent quantum yields is rarely reported to date. The results demonstrate the feasibility of a new design strategy for solid‐state luminescence switching materials: the incorporation of solvents into organic compounds by cocrystallization to obtain a crystalline state luminescence system.     

TbW10-Agarose柔性自支持绿光薄膜的制备及化学响应荧光开关性能研究

基于功能互补原理, 以稀土多酸Na₉TbW₁₀O₃₆(TbW₁₀)为发光功能组分、琼脂糖为成膜基质, 通过溶胶-凝胶及Casting技术制备了稀土多酸柔性自支持绿光薄膜TbW₁₀-Agarose, 利用FT-IR、Raman光谱对薄膜的组成及结构进行表征, 利用SEM、AFM和TEM对薄膜的厚度、表面粗糙度和微结构进行研究, 考察TbW₁₀掺杂量对薄膜透光率及发光性能的影响。在HCl/NH₃刺激下, 实现了TbW₁₀-Agarose绿光薄膜可逆的化学响应荧光开关性质, 利用荧光动力学方法对绿光薄膜化学响应荧光开关的响应时间及可逆性进行研究; 并拓展了该绿光薄膜对HCl气体的荧光光谱检测, 检出限为0.2731 mmol·L ^-1。     

Effect of solid surface charge on the binding behaviour of a metal-binding peptide

Over the last decade, solid-binding peptides have been increasingly used as molecular building blocks coupling bio- and nanotechnology. Despite considerable research being invested in this field, the effects of many surface-related parameters that define the binding of peptide to solids are still unknown. In the quest to control biological molecules at solid interfaces and, thereby, tailoring the binding characteristics of the peptides, the use of surface charge of the solid surface may probably play an important role, which then can be used as a potential tuning parameter of peptide adsorption. Here, we report quantitative investigation on the viscoelastic properties and binding kinetics of an engineered gold-binding peptide, 3RGBP_1, adsorbed onto the gold surface at different surface charge densities. The experiments were performed in aqueous solutions using an electrochemical dissipative quartz crystal microbalance system. Hydrodynamic mass, hydration state and surface coverage of the adsorbed peptide films were determined as a function of surface charge density of the gold metal substrate. Under each charged condition, binding of 3rGBP₁ displayed quantitative differences in terms of adsorbed peptide amount, surface coverage ratio and hydration state. Based on the intrinsically disordered structure of the peptide, we propose a possible mechanism for binding of the peptide that can be used for tuning surface adsorption in further studies. Controlled alteration of peptide binding on solid surfaces, as shown here, may provide novel methods for surface functionalization used for bioenabled processing and fabrication of future micro- and nanodevices.     

Angular dependent luminescence behavior in one-dimensional Si-based microcavities

One-dimensional all solid-state microcavities (MCs) based on amorphous silicon-nitride films have been fabricated in plasma enhanced chemical vapor deposition system. Spectral narrowing and enhancement of room temperature photoluminescence due to the modulation effect in MCs were observed. The modulated luminescence behavior in MCs was further studied by angular dependent luminescence measurements. The distinct cavity mode energy shifting and variation of luminescence intensity with the detect angle were observed, which reflected the directionality of emission properties in the planar MCs. The deviation of the measured angular dependent energy shifting from the theory prediction was discussed as being related to the structure properties of the MCs.     

Rb5Nd(MoO4)4 a self-tunable birefringent laser crystal

In this paper we report an experimental demonstration of broadband wavelength self-tuning in Rb₅Nd(MoO₄)₄ laser crystal (RNM) together with the theoretical treatment which explains the system behaviour based on its birefringent properties. The self-frequency tuning in RNM was obtained by inserting an a-cut plate inside the laser resonator close to the Brewster's angle. At a given position of the crystal plate, when the wavelength of the oscillating mode corresponds to an integral number of full-wave retardation in the plate, the laser operates in the p polarization of the Brewster surface with no losses. The experimental self-frequency tuning of the laser emission along the free spectral range of the RNM crystal (1062.94–1067.84 nm) was obtained by rotating the birefringent gain plate in its own plane. To investigate the tuning characteristics of the spectral filter, we have used the Jones-vector formalism. The calculated wavelength-selective tuning matches the experimental observations.     

Hybrid Inorganic–Organic Mesoporous Silicates—Nanoscopic Reactors Coming of Age

This review describes methods of preparing hybrid inorganic–organic mesoporous silicates with uniform channel structures, as well as some of their applications. Both reactive and passive organic groups can be incorporated in the porous solids by grafting methods or by co‐condensation under surfactant control. Functional groups have been placed selectively on the internal or external pore surfaces or even within the walls of the mesoporous solids. Organic functionalization of these solids permits tuning of the surface properties (hydrophilicity, hydrophobicity, binding to guest molecules), alteration of the surface reactivity, protection of the surface from attack, and modification of the bulk properties (e.g., mechanical or optical properties) of the material. Recent applications of hybrid mesoporous silicates are highlighted, including catalysis, sorption of metals, anions, and organics, reactors for polymerization, fixation of biologically active species, and optical applications.     

Anisotropic organic glasses

While the last decades have seen considerable efforts to control molecular packing in organic crystals, the idea of controlling packing in organic glasses is relatively unexplored. Glasses have many advantageous properties that crystals lack, such as macroscopic homogeneity and compositional flexibility, but packing in organic glasses is generally considered to be isotropic and highly disordered. Here we review and compare four areas of recent research activity showing control over anisotropic packing in organic glasses: (1) anisotropic glasses of low molecular weight organic semiconductors prepared by physical vapor deposition, (2) the use of mesogens to produce anisotropic glasses by cooling equilibrium liquid crystal phases, (3) the preparation of highly anisotropic glassy solids by vapor-depositing low molecular weight mesogens, and (4) anisotropic films of polymeric semiconductors prepared by spin-coating or solution casting. We delineate the connections between these areas with the hope of cross-fertilizing progress in the development of anisotropic glassy materials.     

Temporal and Remote Tuning of Piezophotonic‐Effect‐Induced Luminescence and Color Gamut via Modulating Magnetic Field

Light‐emitting materials have been extensively investigated because of their widespread applications in solid‐state lighting, displays, sensors, and bioimaging. In these applications, it is highly desirable to achieve tunable luminescence in terms of luminescent intensity and wavelength. Here, a convenient physical approach of temporal and remote tuning of light‐emitting wavelength and color is demonstrated, which is greatly different from conventional methods. It is shown that by modulating the frequency of magnetic‐field excitation at room temperature, luminescence from the flexible composites of ZnS:Al, Cu phosphors induced by the piezophotonic effect can be tuned in real time and in situ. The mechanistic investigation suggests that the observed tunable piezophotonic emission is ascribed to the tilting band structure of the ZnS phosphor induced by magnetostrictive strain under a high frequency of magnetic‐field excitation. Furthermore, some proof‐of concept devices, including red–green–blue full‐color displays and tunable white‐light sources are demonstrated simply by frequency modulation. A new understanding of the fundamentals of both luminescence and magnetic–optics coupling is thus provided, while offering opportunities in magnetic–optical sensing, piezophotonics, energy harvesting, novel light sources, and displays.