Facile Fabrication of Reactive Plasmonic Substrates for Fluorescence Enhancement via Mussel-Inspired Chemistry

Based on the fascinating properties of polydopamine (PDA), a simple strategy was developed for facilely and efficiently fabricating plasmonic substrate with nanohybrid structure (PDA/Metal NPs/PDA). Because of the good reductive ability of PDA, metal nanoparticles such as Ag, Au, or Ag/Au hybrid particles with the good control of size and distribution on plasmonic substrate could be easily achieved. Also, owing to the exceptional self-adhesive nature, the presynthesized monodisperse metal NPs can be directly adsorbed to the surface to enrich plasmon response. Moreover, by carefully tuning the dopamine immersion time, the formed nanohybrid structure PDA/metal NPs/PDA enabled the distance-dependent MEF phenomenon where the distance could be controlled with a resolution of approximately 1 nm. In particular, the covalent (Michael addition or Schiff-base reaction) binding enabled us an easy but efficient way to immobilize a large diverse fluorophores or biomolecules on plasmonic substrate. All these above properties indicated the promising PDA-based plasmonic substrate for fluorescence enhancement. As a demonstration of the good fluorescence enhancement property, thiol-based dye was used. The ca. 5-fold fluorescence intensity enhancement on the plasmonic substrate with pattern structure clearly proved that PDA-based plasmonic substrate was indeed a good reactive platform for fluorescence enhancement. With the assistance of FDTD, the electromagnetic near-field distributions and the radiative power emitted by fluorophores on the substrate were found to be significantly improved, further helpful for explaining our experimental observations. Finally, the optimal set calculations guided us that based on the careful selection of fluorophore and space distance, a better fluorescence enhancement could be achieved for further optical and biological applications. These performed experiments suggested that the PDA-based fabricating protocol is indeed a powerful strategy for creating plasmon substrate that could find a wide range of applications

Chaperone-Assisted Formation of Cucurbit[8]uril-Based Molecular Porous Materials with One-Dimensional Channel Structure

Exploiting “chaperone molecule” to navigate the successful assembly energy landscapes has been extensively used in biological systems, whereas in artifical supramolecular systems the “chaperone-assisted” assembly strategy to be used for the synthesis of materials with novel structures or the structures to be hardly prepared by “conventional” methods are still far from realizing the potential functions. In this work, we present a new example of small organic molecule acting as “chaperone molecule” in the facile formation of organic molecular porous materials. This porous material is composed of pure cucurbit[8]­uril (CB[8]) macrocycle and possesses a honeycomb-like structure with an isolated and relatively large one-dimensional (1D) nanochannel. Moreover, it has good chemical and thermal stability, and shows a good adsorption capability for large molecule loading. Importantly, with the assistance of chaperone molecules, pure CB[8] could also be recycled even from a complex aqueous solution, demonstrating a powerful purification method of CB[8] from complex systems

Pyrrole-Terminated Ionic Liquid Surfactant: One Molecule with Multiple Functions for Controlled Synthesis of Diverse Multispecies Co-Doped Porous Hollow Carbon Spheres

Rationally and efficiently controlling chemical composition, microstructure, and morphology of carbon nanomaterials plays a crucial role in significantly enhancing their functional properties and expending their applications. In this work, a novel strategy for simultaneously controlling these structural parameters was developed on the base of a multifunctional precursor approach, in which the precursor not only serves as carbon source and structure-directing agent, but also contains two heteroatom doping sites. As exemplified by using pyrrole-terminated ionic liquid surfactant as such precursor, in conjunction with sol–gel chemistry this strategy allows for efficiently producing well-defined hollow carbon spheres with controlled microstructure and chemical compositions. Remarkably, the dual-doping sites in confined silica channels provide an exciting opportunity and flexibility to access various doped carbons through simply anion exchange or altering the used oxidative polymerization agent, especially the multispecies codoped materials by combination of the two doping modes. All the results indicate that the described strategy may open up a new avenue for efficiently synthesizing functional carbon materials with highly controllable capability

Electrothermally Driven Fluorescence Switching by Liquid Crystal Elastomers Based On Dimensional Photonic Crystals

In this article, the fabrication of an active organic–inorganic one-dimensional photonic crystal structure to offer electrothermal fluorescence switching is described. The film is obtained by spin-coating of liquid crystal elastomers (LCEs) and TiO₂ nanoparticles alternatively. By utilizing the property of LCEs that can change their size and shape reversibly under external thermal stimulations, the λ_max of the photonic band gap of these films is tuned by voltage through electrothermal conversion. The shifted photonic band gap further changes the matching degree between the photonic band gap of the film and the emission spectrum of organic dye mounting on the film. With rhodamine B as an example, the enhancement factor of its fluorescence emission is controlled by varying the matching degree. Thus, the fluorescence intensity is actively switched by voltage applied on the system, in a fast, adjustable, and reversible manner. The control chain of using the electrothermal stimulus to adjust fluorescence intensity via controlling the photonic band gap is proved by a scanning electron microscope (SEM) and UV–vis reflectance. This mechanism also corresponded to the results from the finite-difference time-domain (FDTD) simulation. The comprehensive usage of photonic crystals and liquid crystal elastomers opened a new possibility for active optical devices