Controlled synthesis of organic single-crystalline nanowires via the synergy approach of the bottom-up/top-down processes

Facet engineering of a two-dimensional metal-organic framework with uniquely oriented layered-structure for electrocatalytic oxygen reduction reaction

The properties of metal-organic framework (MOF) nanocrystals are highly dependent on their sizes, morphologies, and exposed facets. Facet engineering of MOFs offers an efficient strategy to tailor the active sites and optimize the catalytic activity of both MOFs and their derivatives. In this study, we prepared 1D zeolitic imidazolate framework-nanorod (ZIF-NR) through facet engineering of the parental 2D ZIF-L. The introduction of cetyltrimethylammonium bromide (CTABr) surfactant into the synthesis solution hindered the crystal growth along the c-axis of leaf-like ZIF-L, resulting in the formation of 1D ZIF-NR. The derived Co nanoparticle encapsulated N doped carbon nanorod (denoted as Co-NCR) exhibited high activity and stability for electrocatalytic oxygen reduction reactions and Zn-air batteries. Facet engineering of a 2D MOF with a uniquely oriented layered structure demonstrates the possibility of designing novel electrocatalysts.

Dynamic Epitaxial Growth of Organic Heterostructures for Polarized Exciton Conversion

Highly spatial and angular precision in epitaxial-growth process is crucial for constructing organic low-dimensional heterostructures (OLDHs) with the desired substructures, which remains significant challenge owing to the unpredicted location of complex heterogeneous nucleation. Herein, a dynamic epitaxial-growth approach is developed along the tailored longitudinal/horizontal directions to create diverse OLDHs with hierarchical architectures. The controlled morphology evolution of seed crystals from kinetic to thermodynamic species is achieved via incrementally increasing the crystallization time from 0 to 600 s. Accordingly, the kinetic and thermodynamic seed crystals respectively present the specific lattice-matching crystal-planes of (100) and (011), which facilitates the longitudinal epitaxial-growth (LG) process for triblock heterostructures, and the horizontal epitaxial-growth (HG) process for axial-branch heterostructures. The dominant core/shell heterostructures are prepared via both LG and HG processes with a crystallization time of ≈30 s. Significantly, these prepared OLDHs realize the rationally polarized exciton conversion for optical logic gate application through the exciton conversion and photon propagation at the heterojunction. This strategy provides an avenue for the precise synthesis of OLDHs with anisotropy optical characters for integrated optoelectronics.

Low-Dimensional Organic Crystals: From Precise Synthesis to Advanced Applications

Low-dimensional organic crystals (LOCs) have attracted increasing attention recently for their potential applications in miniaturized optoelectronics and integrated photonics. Such applications are possible owing to their tunable physicochemical properties and excellent charge/photon transport features. As a result, the precise synthesis of LOCs has been examined in terms of morphology modulation, large-area pattern arrays, and complex architectures, and this has led to a series of appealing structure-dependent properties for future optoelectronic applications. This review summarizes the recent advances in the precise synthesis of LOCs in addition to discussing their structure-property relationships in the context of optoelectronic applications. It also presents the current challenges related to organic crystals with specific structures and desired performances, and the outlook regarding their use in next-generation integrated optoelectronic applications.

Conductive Materials with Elaborate Micro/Nanostructures for Bioelectronics

Bioelectronics, an emerging field with the mutual penetration of biological systems and electronic sciences, allows the quantitative analysis of complicated biosignals together with the dynamic regulation of fateful biological functions. In this area, the development of conductive materials with elaborate micro/nanostructures has been of great significance to the improvement of high-performance bioelectronic devices. Thus, here, a comprehensive and up-to-date summary of relevant research studies on the fabrication and properties of conductive materials with micro/nanostructures and their promising applications and future opportunities in bioelectronic applications is presented. In addition, a critical analysis of the current opportunities and challenges regarding the future developments of conductive materials with elaborate micro/nanostructures for bioelectronic applications is also presented.

Organic Branched Heterostructures with Optical Interconnects for Photonic Barcodes

Optical interconnects exhibit superior potential in the precise regulation of photon transmission for organic photonic circuits. However, the rational design of well-defined organic heterostructures toward active optoelectronics remains challenging. Herein, we designed organic branched heterostructures (OBHs) with accurate spatial organization for optical interconnection. Notably, the precise regulation of OBHs has been controllably achieved including the trunk morphologies and the branched microwire number. Significantly, these as-prepared OBHs inherently exhibit the multichannel coupling outputs and the excitation position-dependent waveguide characteristics, leading to various outcoupling signals with tunable intensity and emission colors. The optical interconnects are realized due to the occurrence of exciton conversion and photon propagation between branch and trunk at the heterojunction, benefiting the application possibilities of two-dimensional (2D) optical barcodes.

Controlled Shape Evolution of Pure-MOF 1D Microcrystals towards Efficient Waveguide and Laser Applications

MOF-based one-dimensional materials have received increasing attention in the nanophotonics field, but it is still difficult in the flexible shape evolution of MOF micro/nanocrystals for desired optical functionalities due to the susceptible solvothermal growth process. Herein, we report on the well-controlled shape evolution of pure-MOF microcrystals with optical waveguide and lasing performances based on a bottom-up and top-down synergistic method. The MOF microcrystals from solvothermal synthesis (bottom-up) enable the evolution from microrods via microtubes to nanowires through a chelating agent-assisted etching process (top-down). The three types of MOF 1D-microstructures with high crystallinity and smooth surfaces all exhibit efficient optical waveguide performance. Furthermore, MOF nanowire with lowest propagation loss served as low-threshold pure-MOF nanolasers with Fabry-Pérot resonance. These results advance the fundamental understanding on the controlled MOF evolution mechanism, and offer a valuable route for the development of pure-MOF-based photonic components with desired functionalities.

Energy Transfer-Assisted Whispering Gallery Mode Lasing in Conjugated Polymer/Europium Hybrid Microsphere Resonators

Lanthanide metal complexes display luminescence with narrow bandwidth. Here, we present coupling of the luminescence from europium ion (Eu³⁺ ) with whispering gallery modes (WGMs) in conjugated polymer microsphere resonators. Self-assembly of fluorene-terpyridine alternating copolymer, coordinated by Eu³⁺ (F8tpy-Eu³⁺ ), forms well-defined microspheres with an average diameter of 3.2 μm. Upon focused laser excitation, a microsphere of F8tpy copolymer displays WGM photoluminescence (PL) at a wide spectral range from 420 to 680 nm. In contrast, F8tpy-Eu³⁺ hybrid microspheres exhibit sharp WGM PL at a narrow spectral range of 615-630 nm, which is characteristic of luminescence from Eu³⁺ . The PL behavior indicates that photoinduced energy transfer from F8tpy to Eu³⁺ occurs efficiently. Furthermore, the intensity of the PL peak increases nonlinearly upon strong pumping, indicating that a lasing action appears with the threshold of 1.85 mJ cm^-2 . These results will pave the way for developing microlasers and photonic devices from soft organic materials.

In Situ Construction of One-Dimensional Component-Interchange Organic Core/Shell Microrods for Multicolor Continuous-Variable Optical Waveguide

The core/shell micro-/nanostructures with versatility, tunability, stability, dispersibility, and biocompatibility are widely applied in optics, biomedicine, catalysis, and energy. Organic micro-/nanocrystals have significant applications in miniaturized optoelectronics because of their controllable self-assembly behavior, tunable optical properties, and tailor-made molecular structure. Nevertheless, the advanced organic core/shell micro-/nanostructures, which possess multifunctionality, flexibility, and higher compatibility, are rarely demonstrated because of the dynamic nature of molecular self-assembly and the complex epitaxial relationship of material combination. Herein, we demonstrate the one-dimensional organic core/shell micro-/nanostructures with component interchange, which originates from the 4,4'-((1 E,1' E)-(2,5-dimethoxy-1,4-phenylene)bis(ethene-2,1-diyl))dipyridine (DPEpe) single-crystal microrods or the DPEpe-HCl single-crystal microrods after a reversible protonation or deprotonation process. Notably, the DPEpe/DPEpe-HCl core/shell microrods display vivid visualizations of tunable emission color via an efficient energy-transfer process during the stepwise formation of a shell layer. More significantly, these DPEpe/DPEpe-HCl and DPEpe-HCl/DPEpe core/shell microrods cooperatively demonstrate the multicolor optical waveguide properties continuously adjusted from green [CIE (0.326, 0.570)], to yellow [CIE (0.516, 0.465)], and to red [CIE (0.614, 0.374)]. Our investigation provides a new strategy to fabricate the organic core/shell micro-/nanostructures, which can eventually contribute to the advanced organic optoelectronics at the micro-/nanoscale.

Stepwise evolution of Au micro/nanocrystals from an octahedron into a truncated ditetragonal prism

Stepwise evolution of Au crystals from a micro-level octahedron to a nano-level truncated ditetragonal prism was achieved by a one pot synthesis method.