Preparation and Unique Electrical Behaviors of Monodispersed Hybrid Nanorattles of Metal Nanocores with Hairy Electroactive Polymer Shells

Magnetic Janus nanocomposites with iridium(iii) complexes for heterogeneous catalysis of logic controlled RAFT polymerization using multiplexed external switching

Photoinduced electron/energy transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization has emerged as a versatile and highly-efficient method for the polymerization of more activated monomers including N,N-dimethylacrylamide and methyl acrylate, and less activated monomers including N-vinylpyrrolidone and vinyl acetate, whilst imposing composition, sequence and spatiotemporal regulation. Although significant progress has been achieved in terms of ability to regulate PET-RAFT polymerization through the implementation of myriad environmental cues, it is still a great challenge to introduce multiple external switches within a single catalyst to accomplish logic toggling of controlled radical polymerization (CRP). Herein, we report the synthesis and characterization of Fe₃O₄@aSiO₂@PNMIr Janus nanocomposites coupled with immobilized heteroleptic iridium(iii) complexes for heterogeneous catalysis of PET-RAFT polymerization. With this catalytic nanoarchitecture, we demonstrate multi-stimuli switching of CRPs using three different external physical manipulations: light "ON"/"OFF", magnet "OUT"/"IN" and temperature "LOW"/"HIGH". In addition, these magnetic Janus nanocomposites endowed radical polymerization with various attractive characteristics such as compatibility of myriad monomer formulations including "more activated" and "less activated" monomers, unique oxygen tolerance and ppm-level catalyst dosage. Logic-controlled polymerization with Fe₃O₄@aSiO₂@PNMIr nanocomposites provides a straightforward, robust and user-friendly strategy for realizing multiplexed external switching of polymer propagation using a single nanocatalyst without the involvement of exogenous reagents.

Robust hollow nanocomposites with ruthenium-bipyridine complexes for heterogeneous catalysis of logic-controlled RAFT polymerization

Photoinduced electron/energy transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization has become a powerful and eco-friendly toolkit to create well-defined macromolecular buildups while exhibiting composition, sequence and spatiotemporal control. Although PET-RAFT polymerization is generally much more convenient than living ionic polymerization, it is still a great challenge to regulate the polymerization upon multiple external stimuli and to simplify the procedures of post-polymerization purification. In this contribution, hHPGE-PFPPNRu nanocomposites were engineered as catalyst supports to firmly accommodate ruthenium-bipyridine complexes for heterogeneous catalysis of PET-RAFT polymerization. The manipulation of reaction temperature modulated the performance of the nanocatalysts, with a pronounced acceleration of the polymerization kinetics being identified at a temperature above the lower critical solution temperature (LCST) of poly(N-isopropylacrylamide) (PNIPAM) brushes compared to that below it. Consequently, the control of RAFT polymerization can be achieved upon the dual-stimuli of light and heat. Moreover, these nanocatalysts conferred radical polymerizations with myriad attractive features such as the adaptability of diverse monomer formulations and reaction media, exquisite control over the molecular variables, oxygen tolerance, and catalyst doses in the ppm range. Owing to the robust mechanical nature of nanocomposites, the separation and reuse of the nanocatalysts were readily realized by rapid centrifugation, and they showed inappreciable catalyst leakage along with consistent catalytic performance even after multiple polymerization runs.

Metalloporphyrin-bound Janus nanocomposites with dual stimuli responsiveness for nanocatalysis in living radical polymerization

The capability to spatiotemporally regulate polymerization kinetics in response to dual external stimuli of light and magnetism offers exciting pathways to precisely manipulate polymer composition and sequence. Herein, we report a strategy that adopts snowman-shaped Fe₃O₄@aSiO₂-click-ZnPTPP Janus nanocomposites with a high magnetization value (12.9 emu g^-1) and stably confined but accessible catalytic metalloporphyrin moieties as the nanocatalysts for photo-induced electron transfer reversible addition-fragmentation chain transfer (PET-RAFT) polymerization. This method enables the synthesis of diverse polymeric structures from a large range of monomers using ultralow concentrations of nanocatalysts (less than 10 ppm) with simple modulation of light and magnetism. In addition, the nanocatalysts are found to be oxygen-tolerant, and they exhibit non-agglomeration during polymerization. Finally, repeated regeneration of the used nanocatalysts by magnetic extraction or facile centrifugation effectively reduces or even eliminates the contamination and/or decomposition on the final polymer products.

Yolk-Shell Nanocomposites of a Gold Nanocore Encapsulated in an Electroactive Polyaniline Shell for Catalytic Aerobic Oxidation

Noble metal nanoparticles (NPs) have been widely applied in nanocatalysis owing to the benefits associated with their miniature size. However, improving their stability and reusability during catalytic applications still remains a great challenge. To this end, monodispersed gold@void@polyaniline yolk-shell nanocomposites (Au@void@PANI YSNs) were synthesized using bottom-up template-assisted methods. Au@SiO2 NPs, prepared from a modified sol-gel process, were used as templates for the thiol-ene click reaction with 4-vinylaniline (VAn) to immobilize the aniline moieties, which later performed as the initiation sites for the oxidative copolymerization of aniline from the outer surface of the Au@SiO2-VAn NPs with an electroactive PANI shell (Au@SiO2@PANI NPs). The silica layer sandwiched between the Au core and PANI shell was selectively removed by aqueous hydrofluoric acid to produce Au@void@PANI YSNs with a movable Au core. The electroactive PANI shell not only serves as a physical barrier that prevents the self-association of Au cores and provides a vacant cavity where chemical transformations take place on the Au cores in a controlled manner but also improves the activity and stability of Au cores due to the electrons delocalization and transfer from the Au d orbitals of the nanocores to the π-conjugated ligands of the PANI shell, as proved by the X-ray photoelectron spectroscopy results. The as-synthesized YSNs were found to perform as flexible and reusable heterogeneous catalysts with high catalytic efficiency for the aerobic oxidation of alcohol in aqueous solution. One may find the present study to be a general and effective way to fabricate monodispersed hollow nanomaterials in a controlled and green manner.

High-efficiency bulk heterojunction memory devices fabricated using organometallic halide perovskite:poly(N-vinylcarbazole) blend active layers

The as-fabricated ITO/CH₃NH₃PbI₃:PVK/Al bulk heterojunction device exhibited a nonvolatile write-once read-many-times memory effect, with a maximum ON/OFF current ratio exceeding 10³and a turn-on voltage of −1.57 V.

Yolk/shell nanoparticles: classifications, synthesis, properties, and applications

Core/shell nanoparticles were first reported in the early 1990s with a simple spherical core and shell structure, but the area is gradually diversifying in multiple directions such as different shapes, multishells, yolk/shell etc., because of the development of different new properties of the materials, which are useful for several advanced applications. Among different sub-areas of core/shell nanoparticles, yolk/shell nanoparticles (YS NPs) have drawn significant attention in recent years because of their unique properties such as low density, large surface area, ease of interior core functionalization, a good molecular loading capacity in the void space, tunable interstitial void space, and a hollow outer shell. The YS NPs have better properties over simple core/shell or hollow NPs in various fields including biomedical, catalysis, sensors, lithium batteries, adsorbents, DSSCs, microwave absorbers etc., mainly because of the presence of free void space, porous hollow shell, and free core surface. This review presents an extensive classification of YS NPs based on their structures and types of materials, along with synthesis strategies, properties, and applications with which one would be able to draw a complete picture of this area.

Organic Electronic Memory Devices

With the rapid development of the electronics industry in recent years, information technology devices, such as personal computers, mobile phones, digital cameras and media players, have become an essential part of our daily life. From both the technological and economic points of view, the development of novel information storage materials and devices has become an emergent issue facing the electronics industry. Due to the advantages of good scalability, flexibility, low cost, ease of processing, 3D-stacking capability and high capacity for data storage, organic-based electrical memory devices have been promising alternatives or supplementary devices to conventional inorganic semiconductor-based memory technology. The basic concepts and historical development of electronic memory devices are first presented. The following section introduces the structures and switching mechanisms of organic electronic memory devices classified as transistors, capacitors and resistors. Subsequently, the progress in the field of organic-based memory materials and devices is systematically summarized and discussed. Finally, the challenges posed to the development of novel organic electronic memory devices are summarized.