Nanophotonics has received broad research interest because it may provide an alternative opportunity to overcome the fundamental limitations of electronic circuits. So far, diverse photonic functions, such as light generation, modulation, and detection, have been realized based on various nano­materials. The exact structural features of these material systems, including geometric characteristics, surface morphology, and material composition, play a key role in determining the photonic functions. Therefore, rational designs and constructions of materials on both morphological and componential levels, namely nanoarchitectonics, are indispensable for any photonic device with specific functionalities. Recently, a series of nanowire heterojunctions (NWHJs), which are usually made from two or more kinds of material compositions, were constructed for novel photonic applications based on various interactions between different materials at the junctions, for instance, energy transfer, exciton–plasmon coupling, or photon–plasmon coupling. A summary of these works is necessary to get a more comprehensive understanding of the relationship between photonic functions and architectonics of NWHJs, which will be instructive for designing novel photonic devices towards integrated circuits. Here, photonic function oriented nanoarchitectonics based on recent breakthroughs in nanophotonic devices are discussed, with emphasis on the design mechanisms, fabrication strategies, and excellent performances.

Organic nanomaterials have drawn great interest for their potential applications in high-speed miniaturized photonic integration due to their high photoluminescence quantum efficiency, structural processability, ultrafast photoresponse, and excellent property engineering. Based on the rational design on morphological and componential levels, a series of organic nanomaterials have been controllably synthesized in recent years, and their excitonic/photonic behaviors has been fine-tuned to steer the light flow for specific optical applications. This review presents a comprehensive summary of recent breakthroughs in the controlled synthesis of organic nanomaterials with specific structures and compositions, whose tunable photonic properties would provide a novel platform for multifunctional applications. First, we give a general overview of the tailored construction of novel nanostructures with various photonic properties. Then, we summarize the design and controllable synthesis of composite materials for the modulation of their functionalities. Subsequently, special emphasis is put on the fabrication of complex nanostructures towards wide applications in isolated photonic devices. We conclude with our personal viewpoints on the development directions in the novel design and controllable construction of organic nanomaterials for future applications in highly integrated photonic devices and chips.

We have demonstrated a new and facile bottom-up protocol for the effective synthesis of oval-shaped iron oxide/ethylene glycol (FeO_x/EG) mesostructured nanosheets. Deprotonated ethylene glycol molecules are intercalated into iron oxide layers to form an interlayer distance of 10.6 Å. These materials display some peculiar magnetic properties, such as the low Morin temperature T_M and ferromagnetism below this T_M value. CdSe/ZnS nanoparticles can be loaded onto these mesostructured nanosheets to produce nanocomposites that combine both magnetic and fluorescence functions. In addition, iron oxide/propanediol (or butanediol) mesostructured materials with increased interlayer distances can also be synthesized. The developed synthetic strategy may be extended toward the creation of other ultrathin mesostructured nanosheets.

Supramolecular forces govern self-assembly and further determine the final morphologies of self-assemblies. However, how they control the morphology remains hitherto largely unknown. In this paper, we have discovered that the self-assembled nanostructures of rigid organic semiconductor chromophores can be finely controlled by the secondary forces by fine-tuning the surrounding environments. In particular, we used water/methanol/hydrochloric acid to tune the environment and observed five different phases that resulted from versatile molecular self-assemblies. The representative self-assembled nanostructures were nanotapes, nanoparticles and their 1D assemblies, rigid microplates, soft nanoplates, and hollow nanospheres and their 1D assemblies, respectively. The specific nanostructure formation is governed by the water fraction, R_w, and the concentration of hydrochloric acid, [HCl]. For instance, nanotapes formed at low [HCl] and R_w values, whereas hollow nanospheres formed when either the HCl concentration is high, or the water fraction is low, or both. The significance of this paper is that it provides a useful phase diagram by using R_w and [HCl] as two variables. Such a self-assembly phase diagram maps out the fine control that the secondary forces have on the self-assembled morphology, and thus allows one to guide the formation toward a desired nanostructure self-assembled from rigid organic semiconductor chromophores by simply adjusting the two key parameters of R_w and [HCl].

Electron delocalization of new mixed-valent (MV) systems with the aid of lateral metal chelation is reported. 2,2′-Bipyridine (bpy) derivatives with one or two appended di-p-anisylamino groups on the 5,5′-positions and a coordinated [Ru(bpy)₂] (bpy=2,2′-bipyridine), [Re(CO)₃Cl], or [Ir(ppy)₂] (ppy=2-phenylpyridine) component were prepared. The single-crystal molecular structure of the bis-amine ligand without metal chelation is presented. The electronic properties of these complexes were studied and compared by electrochemical and spectroscopic techniques and DFT/TDDFT calculations. Compounds with two di-p-anisylamino groups were oxidized by a chemical or electrochemical method and monitored by near-infrared (NIR) absorption spectral changes. Marcus–Hush analysis of the resulting intervalence charge-transfer transitions indicated that electron coupling of these mixed-valent systems is enhanced by metal chelation and that the iridium complex has the largest coupling. TDDFT calculations were employed to interpret the NIR transitions of these MV systems.

Single-, double-, and triple-shelled hollow spheres assembled by Co₃O₄ nanosheets are successfully synthesized through a novel method. The possible formation mechanism of these novel structures was investigated using powder X-ray diffraction, scanning and transmission electron microscopies, Fourier transform IR, X-ray photoelectron spectroscopy, and thermogravimetric analysis. Both poly(vinylpyrrolidone) (PVP) soft templates and the formation of cobalt glycolate play key roles in the formation of these novel multishelled hollow structures. When tested as the anode material in lithium-ion batteries (LIBs), these multishelled microspheres exhibit excellent cycling performance, good rate capacity, and enhanced lithium storage capacity. This superior cyclic stability and capacity result from the synergetic effect of small diffusion lengths in the nanosheet building blocks and sufficient void space to buffer the volume expansion. This facile strategy may be extended to synthesize other transition metal oxide materials with hollow multishelled micro-/nanostrucutures, which may find application in sensors and catalysts due to their unique structural features.

Doped nanoparticles were prepared from pyrene and phenanthrene using a facile reprecipitation method. The doped nanoparticles presented unique delayed fluorescent emissions of pyrene under the unprotected condition. The ratio of the intensity of delayed fluorescence (I_DF) to that of phosphorescence (I_P) is about 4:1, which almost keeps unchanged with the decrease of pyrene content at room temperature. The intensity of the delayed fluorescence emissions is dependent on the relative content of pyrene, as well as the aggregation degree of nanoparticles. The delayed emissions are contributed to efficient triplet-triplet energy transfer from phenanthrene (donor) to pyrene (acceptor). Steady fluorescence measurement have proved that the singlet-singlet energy transfer process was also existent dominated by the radiation energy transfer mechanism.

Polyoxometalates (POMs) show promising antibacterial, antiviral (particularly anti-HIV), antitumor, and anticancer activities, but the mechanism of these potential therapeutic effects remains to be elucidated at the molecular level. The interaction between the Gd-containing tungstosilicate [Gd(β₂-SiW₁₁O₃₉)₂]^13– and human serum albumin (HSA) was studied by several techniques. Fluorescence spectroscopy showed an energy transfer between the single tryptophan residue of HSA and the POM. Circular dichroism led to the conclusion that the POM significantly altered the secondary structure of HSA. Isothermal titration calorimetry revealed an enthalpy-driven binding reaction between HSA and the POM, resulting in the formation of a 1:1 complex.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

This article presents a comprehensive review of recent progress of research dedicated to low-dimensional nanomaterials constructed from functional low-molecular-weight organic compounds, whose optoelectronic properties are fundamentally different from those of their inorganic counterparts. After introducing the development of inorganic and organic macromolecular nanomaterials, we begin with a general review of the construction strategies for achieving both zero-dimensional (0D) and one-dimensional (1D) nanostructures from small organic functional molecules. We then provide an overview of the unique optoelectronic properties induced by molecular aggregation in the nanostructures. Special emphasis is put on the luminescent properties that are different from those of the corresponding bulk materials, such as aggregation-induced enhanced emission, fluorescence narrowing, multicolor emission, and tunable and switchable emissions from doped nanostructures. We conclude with a summary and our personal view of the direction of future development of organic opto-functional nanomaterials and devices.