Qingfeng Xu

Synthesis, characterization, and nonvolatile ternary memory behavior of a larger heteroacene with nine linearly fused rings and two different heteroatoms.

To achieve ultrahigh density memory devices with the capacity of 3(n) or larger, organic materials with multilevel stable states are highly desirable. Here, we reported a novel larger stable heteroacene, 2,3,13,14-tetradecyloxy-5,11,16,22-tetraaza-6,10,17,21-tetrachloro-7,9,18,20-tetraoxa-8,19-dicyanoenneacene (CDPzN), which has two different types of heteroatoms (O and N) and nine linearly fused rings. The sandwich-structure memory devices based on CDPzN exhibited excellent ternary memory behaviors with high ON2/ON1/OFF current ratios of 10(6.3)/10(4.3)/1 and good stability for these three states.

A Small-Molecule-Based Ternary Data-Storage Device

High-density data storage (HDDS) is urgently required to address ongoing rapid increases in amounts of information. Here we present a prototype sandwich device that has ternary data-storage performance. Three characteristic currents can be read out using a certain constant voltage after removal of the applied voltage. Two electron pull groups and one electron push group are identified as the species responsible for electron flow. We believe that our observation will offer an interesting and useful theoretical approach for a huge increase in the memory density of potential future devices.

Tailoring of Molecular Planarity to Reduce Charge Injection Barrier for High‐Performance Small‐Molecule‐Based Ternary Memory Device with Low Threshold Voltage

By introducing a coplanar fluorenone into the center of an azo molecule, the turn-on voltages of the ternary memory devices are significantly decreased to lower than -2 V due to the improved crystallinity and the reduced charge injection barrier. The resulting low-power consumption devices will have great potential applications in high-performance chips for future portable nanoelectronic devices.

A Robust and Cost‐Effective Superhydrophobic Graphene Foam for Efficient Oil and Organic Solvent Recovery

Water pollution caused by chemical reagent leaking, industrial wastewater discharging, and crude oil spills has raised global concerns on environmental sustainability, calling for high-performance absorbent materials for effective treatments. However, low-cost materials capable of effectively separating oils and organic solvents from water with a high adsorption capacity and good recyclability are rare on the market. Here, a cost-effective method is reported to fabricate high-performance graphene modified absorbents through the facile thermal reduction of graphene oxide on the skeletons of melamine foam. By integrating the high porosity, superior elasticity, and mechanical stability of raw sponge with the chemical stability and hydrophobicity of graphene sheets, the as-fabricated graphene foam not only possesses a rough and superhydrophobic surface, but also exhibits an excellent adsorption performance and extraordinary recyclability for various oils and organic solvents. It is worth mentioning that the superhydrophobic surface also endows the graphene foam with an excellent efficiency for oil/water separation. More importantly, the cost-effective fabrication method without involving expensive raw materials and sophisticated equipment permits a scale-up of the graphene foam for pollution disposal. All these features make the graphene foam an ideal candidate for removal and collection of oils and organic solvents from water.

Synthesis, physical properties, and light-emitting diode performance of phenazine-based derivatives with three, five, and nine fused six-membered rings.

Realizing the control of emission colors of single molecules is very important in the development of full-color emitting materials. Herein, three novel phenazine derivatives (2,3,7,8-tetrakis(decyloxy)phenazine (2a), 2,3-didecyloxy-5,14-diaza-7,12-dioxo-9,10- dicyanopentacene (2b), and 2,3,13,14-tetradecyloxy-5,11,16,22-tetraaza-7,9,18,20-tetraoxo-8,19-dicyanoenneacene (2c)) have been successfully synthesized and fully characterized. Compound 2c can emit blue light in toluene solution (450 nm), green light in the powder/film state (502/562 nm), and red light in the 2c/TFA state (610 nm). The OLED with 2c emits a strong green light at a peak of 536 nm with a maximum luminance of the OLED of about 8600 cd m(-2), which indicates that 2c could be a promising fluorescent dye for OLED applications.

Modification of magnetic silica/iron oxide nanocomposites with fluorescent polymethacrylic acid for cancer targeting and drug delivery

Biocompatible and water-soluble magnetic nanoparticles with mesoporous core-shell structure were prepared and successfully modified with a fluorescent polymer chain as a labelling segment and folic acid as the cancer targeting moiety and loaded with a drug for directional release. The porous silica oxide structure and long molecular chains of polymethacrylic acid embedded the drug efficiently in the nanocomposites and did not affect the magnetic properties of the carrier. Sustained release of the loaded drug was observed over 100 h under in vitro conditions. Furthermore, the drug carrier is able to drill into the cell membranes and obtain a sustained release of the anticancer drug into the cytoplasm. The in vitro cellular uptake of the drug demonstrated that the drug-loaded nanocomposites could effectively target the tumor cells. Our model experiments indicated that this multifunctional mesoporous core-shell magnetic nanoparticle can be exploited as an anticancer drug delivery vehicle for targeting and therapy applications.

Benzo[a]phenoxazinium-Based Red-Emitting Chemosensor for Zinc Ions in Biological Media

A benzo[a]phenoxazinium-based chemosensor bearing an N,N-di(2-picolyl)ethylenediamine unit was successfully synthesized. It is a long-wave emission and fully water-soluble fluorescent sensor with good membrane permeability for the selective detection of Zn(2+).

Molecular length adjustment for organic azo-based nonvolatile ternary memory devices

Two conjugated small molecules with different molecular length, DPAPIT and DPAPPD, in which an electron donor dimethylamino moiety and an electron acceptor phthalimide core unit are bridged by another electron-accepting azobenzene block, were designed and synthesized. DPAPIT molecule with longer conjugation length stacked regularly in the solid state and formed uniform nanocrystalline film. The fabricated memory devices with DPAPIT as active material exhibited outstanding nonvolatile ternary memory effect with the current ratio of ∼1 : 101.7 : 104 for “0”, “1” and “2” states and all the switching threshold voltages lower than −3 V. In contrast, the shorter molecule DPAPPD showed amorphous microstructure and no obvious conductive switching behavior was observed in the device. The crystallinity and surface roughness of DPAPIT thin films were significantly improved as the annealing temperature increased, lowering the switching threshold voltages which are highly desirable for low-power consumption data-storage devices. It is worth noting that the tristable memory signals of DPAPIT film could also be achieved by using conductive atomic force microscopy with platinum-coated probe, which enables fabrication of nano-scale or even molecular-scale device, a significant progress for the ultra-high density data storage application. Mechanism analysis demonstrated that two charge traps with different depth in the molecular backbone were injected by charge carriers progressively as the external bias increased, resulting in the formation of three distinct conductive states (OFF, ON1 and ON2 states).

Micro–Nanocomposites in Environmental Management

Water pollution, a worldwide issue for the human society, has raised global concerns on environmental sustainability, calling for high-performance materials for effective treatments. Since the traditional techniques have inherent limitations in treatment speed and efficiency, nanotechnology is subsequently used as an environmental technology to remove pollutants through a rapid adsorption and degradation process. Therefore, here, various adsorbent and photodegradation composite materials leading to effective water remediation are summarized and predicted. Notably, recent advances in simultaneous adsorption and photodegradation micro-nanocomposites are outlined. Such materials can not only completely adsorb and remove contaminants, but the micro-nanocomposites can also be directly reused without further treatment. Finally, the future development of this unique system is discussed.

The AIEE effect and two-photon absorption (TPA) enhancement induced by polymerization: synthesis of a monomer with ICT and AIE effects and its homopolymer by ATRP and a study of their photophysical properties

A monomer including pyrazoline and l,8-naphthalimide moieties and its homopolymer were prepared by atom transfer radical polymerization (ATRP). The emission of the monomer can be tuned by choosing solvents with different polarities or aggregation-induced emission (AIE). The rotation of the fluorophore of the homopolymer was further limited by both the side chain and the flexible main chain, resulting in emission enhancement in strong polar solution and aggregation-induced emission enhancement (AIEE) characteristics. More interestingly, compared to that of the monomer, the two-photon absorption (TPA) property of the homopolymer is much more enhanced both in toluene and aggregates. This is attributed to the amplification effect of the polymer chain. This may become a new and promising method with which to prepare TPA polymers.