Wanlin Zhang

Dye@bio-MOF-1 Composite as a Dual-Emitting Platform for Enhanced Detection of a Wide Range of Explosive Molecules

By incorporating a cationic dye within a metal-organic framework (MOF) through an ion-exchange process, a responsive dye@bio-MOF-1 composite has been synthesized, serving as a dual-emitting platform for enhanced detection of different kinds of nitro-explosives, especially nitroalkanes, nitramines, and nitrate esters. The dye@bio-MOF-1 composite was constructed with free amines on their well-defined cavities, which is essential for the capture of explosives into their confined nanospace. It was observed that the encapsulation of explosives into the constructed dye@bio-MOF-1 composite could dramatically alter the luminescent properties of the dyes as well as the MOF skeletons owing to the size exclusivity and confinement-induced effect. For nitroaromatics, the dye@bio-MOF-1 composite exhibits turn-off responses via fluorescence quenching. Unexpectedly, the composite shows unique turn-on responses for aliphatic nitro-organics via confinement-induced enhancement, demonstrating enhanced ability to detecting different kinds of explosives selectively in aqueous solution. Furthermore, the dye@bio-MOF-1 film was facilely fabricated, making the chemical sensing more convenient and easier to realize the discrimination of the targeted explosives. The dual tunable responses indicate that dye@bio-MOF-1 composites are favorable materials for molecular sensing. On the basis of the host-guest properties of the constructed dye@bio-MOF-1 composite, our work can be further extended to sensing specific analytes with remarkable turn-on sensing properties, in particular those difficult to recognize with conventional methods.

Efficient Construction of Well-Defined Multicompartment Porous Systems in a Modular and Chemically Orthogonal Fashion

A microfluidic assembly approach was developed for efficiently producing hydrogel spheres with reactive multidomains that can be employed as an advantageous platform to create spherical porous networks in a facile manner with well-defined multicompartments and spatiotemporally controlled functions. This strategy allows for not only large scale fabrication of various robust hydrogel microspheres with controlled size and porosity, but also the domains embedded in hydrogel network could be introduced in a modular manner. Additionally, the number of different domains and their ratio could be widely variable on demand. More importantly, the reactive groups distributed in individual domains could be used as anchor sites to further incorporate functional units in an orthogonal fashion, leading to well-defined multicompartment systems. The strategy provides a new and efficient route to construct well-defined functional multicompartment systems with great flexibility and extendibility.

Combined use of breath figures process and microphase separation of PS- b -P4VP to produce stable porous nanomaterials

Among various templating strategies available for the preparation of porous polymer films, Breath Figures (BFs) as a fast, low-cost and versatile method has aroused extensive interest. However, the prerequisite of these porous polymer films for potential application is their stability in harsh environments. In this article, we report a new method to stabilise the porous materials prepared by BFs. Polystyrene-block-poly(4-vinylpyridine) block copolymer (PS-b-P4VP) is utilized to prepare well-organized honeycomb films with pore diameters ranging from 0.45 to 2 μm via BFs. Then ethanol is selected to swell the honeycomb porous membrane to generate a nanometer-sized microstructure by solvent induced microphase separation. After the microphase separation process by swelling in ethanol, pyridine moieties as hydrogen bond acceptor or alkaline catalyst are completely exposed, vitally important for the further improvement of film stability. On the one hand, monomers with hydrogen bond donors such as pyrrole, aniline, 3-thiopheneacetic acid can composite with the exposed pyridine groups by hydrogen bond interaction, and the subsequent chemical oxidation polymerization affords hierarchically porous conducting nanomaterials with thermal and solvent stability. On the other hand, the exposed pyridine groups can also be used as alkaline catalytic sites to hydrolyze inorganic precursor like TEOS on the skeleton of PS-b-P4VP for the final formation of silica inorganic porous films with prominently enhanced stability. All the results indicate that the combination of BF process and microphase separation is a versatile and effective method to produce various stable porous nanomaterials.

Guanidinium-Based Polymerizable Surfactant as a Multifunctional Molecule for Controlled Synthesis of Nanostructured Materials with Tunable Morphologies

Rationally and efficiently controlling the morphology of nanomaterials plays a crucial role in significantly enhancing their functional properties and expending their applications. In this work, a strategy for controlled synthesis of diverse nanostructured materials with tunable morphologies was developed using a guanidinium-based surfactant with a polymerizable pyrrole unit as a multifunctional molecule that can serve not only as a structure-directing agent for mesostucture formation but also as a monomer and carbon source. The unique self-assembly behavior of the guanidinium head group under different conditions allows the synthesized surfactants to form different aggregates and thus to produce silica nanomaterials with multiple morphologies (such as sphere, disk, fiber, and cocoon) in conjunction with sol-gel chemistry. Besides the mesostructured silicates, by further exploring the polymerization and carbonization features of pyrrole units that were densely packed in the formed silica nanochannels, diverse nanostructured materials such as mesostructured conducting polymers, carbon materials, and metal-nanoparticle (NP)-decorated forms could also be easily obtained in one-pot fashion for various applications, such as energy storage and catalysis. As a demonstration, carbon nanotubes and Pd-NP-doped hollow carbon spheres were fabricated, which exhibited good specific capacitance (101.7 F g-1) at the scan rates of 5 mV s-1 and excellent catalytic performance (100% conversion for three cycles) in the Suzuki C-C coupling reaction, respectively. All of the results indicate that our strategy may open a new avenue for efficiently accessing diverse nanostructured materials with tunable morphologies for wide applications.

Poly (ionic liquid)-Based Breath Figure Films: A New Kind of Honeycomb Porous Films with Great Extendable Capability

In this work, we reported a new method for the convenient fabrication of various functional porous films, which cannot be directly generated using breath figures (BFs). A series of polystyrene-b-poly (ionic liquid) (PS-b-PIL) block copolymers were employed for BFs process for the first time. It was found that PS-b-PIL could form well-defined BFs porous structure. Remarkably, the described PS-b-PIL copolymers are prone to form hierarchical structure, and the formed pore structure is strongly dependent on the used experimental parameters. Importantly, we found that the anion exchange could provide as an effective means, by which the porous films could be further and facilely converted into other functional films. As a demonstration, in our case, porous films with different surface (hydrophilic and hydrophobic) property, porous polydopamine films decorated with Au nanoparticles or glutathione and porous SiO2 films were prepared by using different counteranions as well as further conversion. Due to the unlimited combination of cation and anion in ionic liquid moiety, all the results indicate that the BFs films generated by using PS-PIL could serve as a platform to access various functional porous films by a simple counteranion exchange, showing a great extendable capability.