Memristors have been intensively studied in recent years as potential building blocks for the construction of versatile neuromorphic architectures. The prevalent developments focus on nanoionic devices due to their ease of reversible regulation, non-volatility, scalability down to the atomic level, low-energy consumption, nanosecond response times, sufficient yield and reliability, as well as their homologous regulatory mechanisms with biological synapses. However, despite their desirable structures and excellent properties, the previously reported properties of nanoionic devices are rather diverse and dissatisfactory for the delivery of reliable analog properties, which is the precondition for the imitation of brain-like functions. Here, the general requirements of neuromorphic engineering in terms of device structure, characterization parameters, synaptic functions and device engineering are introduced. A critical overview of the proposed nanoionic mechanisms for memristive switching is given, focusing particularly on providing fundamental insights into the strategies for regulating the adaptive memristive characteristics of devices that resemble the behaviors of biological synapses, which is an element of neural networks. In addition, the research progress in active materials (e.g., oxides, polymers, small molecules, bio-macromolecules and dopants), especially regarding the correlation among materials, is elaborated and a rational approach to provide insight into new design strategies is considered, and how to understand the memristor mechanisms and further achieve excellent memristive devices is discussed. Finally, the current challenges and several possible future research directions in this area are discussed.

An efficient method for the preparation of benzoxazole and benzimidazole covalently grafted graphene and their application as high performance electrode materials for supercapacitors is reported. The synthesis of such covalently functionalized graphene materials first involves a cyclization reaction of carboxylic groups on graphene oxide with the hydroxyl and aminos groups on o-aminophenol and o-phenylenediamine, and subsequent reduction by hydrazine. Results of Fourier transformed infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and thermogravimetric analysis (TGA) have confirmed that the covalent functionalization of graphene is achieved through the formation of benzoxazole and benzimidazole on the graphene sheets. The functionalized graphene materials are revealed to consist of corrugation and scrolling morphologies with less aggregation, indicating the effectiveness of functionalization in preventing restacking/aggregation of the graphene sheets. Furthermore, when applied as supercapacitor electrodes, the functionalized graphene materials exhibit good electrochemical performances in terms of high specific capacitance (730 and 781 F g À1 for benzoxazole and benzimidazole grafted graphene, respectively, at a current density of 0.1 A g À1 ) and good cycling stability, implying their potential for energy storage applications.

Nonplane molecules with multiple large aromatic planes could be promising candidates to form various polyhedral micro/nanocrystals by manipulating the different π···π stacking, tuning the cohesive energies of crystal facets, and controlling the kinetic growth process. Spirocyclic aromatic hydrocarbons (SAHs) not only have two cross-shaped aromatic planes but also offer the feature of supramolecular steric hindrance, making it favorable for the heterogeneous kinetic growth into highly symmetric polyhedra. Herein, we report that a novel SAH compound, spiro[fluorene-9,7'-dibenzo[c,h]acridine]-5'-one (SFDBAO), can self-assemble into various monodispersed shapes such as hexahedra, octahedra, and decahedra through the variation of either different types of surfactants, such as Pluronic 123 (P123) and cetyltrimethyl ammonium bromide (CTAB), or growth parameters. In addition, the possible mechanism of crystal facet growth has been proposed according to the SEM, XRD, TEM, and SAED characterization of organic polyhedral micro/nanocrystals. The unique cruciform-shaped SAHs have been demonstrated as fascinating supramolecular synthons for various highly symmetric polyhedral assembling.

Polyfluorenes containing Ir(III) complexes in the main chain are demonstrated to have promising application in a polymer memory device. A flash‐memory device is shown whereby a polymer solution is spin‐coated as the active layer and is sandwiched between an aluminum electrode and an indium tin oxide electrode. This device exhibits very good memory performance, such as low reading, writing, and erasing voltages and a high ON/OFF current ratio of more than 105. Both ON and OFF states are stable under a constant voltage stress of −1.0 V and survive up to 108 read cycles at a read voltage of −1.0 V. Charge transfer and traps in polymers are probably responsible for the conductance‐switching behavior and the memory effect. The fluorene moieties act as an electron donor and Ir(III) complex units as the electron acceptor. Furthermore, through the modification of ligand structures of Ir(III) complex units, the resulting polymers also exhibit excellent memory behavior. Alteration of ligands can change the threshold voltage of the device. Hence, conjugated polymers containing Ir(III) complexes, which have been successfully applied in light‐emitting devices, show very promising application in polymer memory devices.