Our understanding of the fundamental structure and bonding of graphene oxide (GO) as well as the scope of its utility have grown tremendously over the past decade. As a result, the pace of research efforts directed toward this carbon material continues to increase. Contemporary application now intersects a variety of disciplines and includes heterogeneous catalysis, flow reactor technologies, biomedicine and biotechnology, polymer composites, energy storage, and chemical sensors. Advances in these areas have been buoyed by improvements in the methods used to synthesize and characterize GO, as well as functionalized derivatives thereof. While the diverse uses of GO have been reviewed previously, herein we provide an overview of some of the most recent and significant developments in the field. A brief overview of GO's synthesis and characterization is also provided as well as several recently proposed structural models. The inherent reactivity of GO is described in the context of catalysis, and the utilization of GO's reactive oxygen groups and carbon framework to prepare functionalized derivatives is also discussed. Finally, we provide an outlook of potential areas where GO, its derivatives, and related materials may be expected to find utility or opportunity for further growth and study.

Harnessing the chemistry of graphene oxide

This Perspective reviews the design and synthesis of RAFT agents. First, we briefly detail the basic design features that should be considered when selecting a RAFT agent or macro-RAFT agent for a given polymerization and set of reaction conditions. The RAFT agent should be chosen to have an optimal Ctr (in most circumstances higher is better) while at the same time it should exhibit minimal likelihood for retarding polymerization or undergoing side reactions. The RAFT agent should also have appropriate solubility in the reaction medium and possess the requisite end-group functionality for the intended application. In this light we critically evaluate the various methods that have been used for RAFT agent synthesis. These methods include reaction of a carbodithioate salt with an alkylating agent, various thioacylation procedures, thiation of a carboxylic acid or ester, the ketoform reaction, thiol exchange, radical substitution of a bis(thioacyl) disulfide, and radical-induced R-group exchange. We also co...

RAFT Agent Design and Synthesis

https://cyberleninka.org/article/n/409052.pdf

A review on synthesis and properties of polymer functionalized graphene

Due to the advantages of good scalability, flexibility, low cost, ease of processing, 3D-stacking capability, and large capacity for data storage, polymer-based resistive memories have been a promising alternative or supplementary devices to conventional inorganic semiconductor-based memory technology, and attracted significant scientific interest as a new and promising research field. In this review, we first introduced the general characteristics of the device structures and fabrication, memory effects, switching mechanisms, and effects of electrodes on memory properties associated with polymer-based resistive memory devices. Subsequently, the research progress concerning the use of single polymers or polymer composites as active materials for resistive memory devices has been summarized and discussed. In particular, we consider a rational approach to their design and discuss how to realize the excellent memory devices and understand the memory mechanisms. Finally, the current challenges and several possible future research directions in this field have also been discussed.

Polymer‐Based Resistive Memory Materials and Devices

Ultrathin two-dimensional (2D) nanomaterials, such as graphene and MoS2, hold great promise for electronics and optoelectronics due to their distinctive physical and electronic properties. Recent progress in high-yield, massive production of ultrathin 2D nanomaterials via various solution-based methods allows them to be easily integrated into electronic devices via solution processing techniques. Non-volatile resistive memory devices based on ultrathin 2D nanomaterials have been emerging as promising alternatives for the next-generation data storage devices due to their high flexibility, three-dimensional-stacking capability, simple structure, transparency, easy fabrication and low cost. In this tutorial review, we will summarize the recent progress in the utilization of solution-processed ultrathin 2D nanomaterials for fabrication of non-volatile resistive memory devices. Moreover, we demonstrate how to achieve excellent device performance by engineering the active layers, electrodes and/or device structure of resistive memory devices. On the basis of current status, the discussion is concluded with some personal insights into the challenges and opportunities in future research directions.

/pdf/non-volatile-resistive-memory-devices-based-on-solution-3gm7i3kuhg.pdf

Non-volatile resistive memory devices based on solution-processed ultrathin two-dimensional nanomaterials

Bistable electrical conductivity switching and non-volatile memory effects were demonstrated in Al/polymer/indium-tin oxide sandwich structure devices, constructed from two poly(N-vinylcarbazole) derivatives with pendant azobenzene chromophores and terminal electron acceptor moieties (–NO2 or –CN). Both polymers (PVK-AZO-NO2 and PVK-AZO-2CN) exhibit write-once read-many-times (WORM) type memory effects, with low switching threshold voltages below −2 V and high ON/OFF current ratios of ∼105–106. The observed electrical bistability in both polymers can be attributed to the field-induced charge transfer interaction between carbazole electron donor and terminal electron acceptor (–NO2 or –CN) moieties, and subsequent charge trapping at the intermediate azobenzene chromophores. The proposed switching mechanism is supported by the changes in the UV-visible absorption spectra of the polymer film upon transition from the OFF to the ON state.

Electrical conductivity switching and memory effects in poly(N-vinylcarbazole) derivatives with pendant azobenzene chromophores and terminal electron acceptor moieties

A new approach on usage of S-1-dodecyl-S'-(α,α'-dimethyl-α"-acetic acid)trithiocarbonate (DDAT)-covalently functionalized graphene oxide (GO) as reversible addition fragmentation chain transfer (RAFT) agent for growing of poly(N-vinylcarbazole) (PVK) directly from the surface of GO was described. The PVK polymer covalently grafted onto GO has M n of 8.05 x 10 3 , and a polydispersity of 1.43. The resulting material PVK-GO shows a good solubility in organic solvents when compared to GO, and a significant energy bandgap of ~2.49 eV. Bistable electrical switching and nonvolatile rewritable memory effect, with a turn-on voltage of about -1.7 V and an ON/OFF state current ratio in excess of 10 3 , are demonstrated in the AI/PVK-GO/ITO structure.

Growing poly(N-vinylcarbazole) from the surface of graphene oxide via RAFT polymerization

Conjugated Polymer-Grafted Reduced Graphene Oxide for Nonvolatile Rewritable Memory

A new soluble conjugated polymer, poly[{9-(4-methoxyphenyl)-9H-carbazole}(9,9-dioctylfluorene)(2,5-diphenyl-1,3,4-oxadiazole)](PCFO), was synthesized through the Suzuki coupling reaction. The absolute fluorescence quantum yield of PCFO was measured using the integrating sphere of a photoluminescence spectrofluorometer, and changed from 49.1% for a dilute tetrahydrofuran solution to 16.2% for a thin film due to the existence of a strong fluorescence quenching effect in the solid state. The HOMO–LUMO bandgap (3.07 eV) calculated from the electrochemical measurement is nearly identical to the optical bandgap (3.06 eV) estimated from the ultraviolet/visible absorption onset data. This film was attached to aluminum and indium–tin oxide contacts to fabricate a memory device with typical bistable electrical switching, nonvolatile write-once read-many-times memory performance, a turn-on voltage of ∼−2.3 V and an ON/OFF ratio of ∼105. Degradation of the current density was observed for neither the ON nor OFF states after one hundred million continuous read cycles, which indicates that both states were insensitive to read cycles. A new soluble conjugated polymer, poly[{9-(4-methoxyphenyl)-9H-carbazole}(9,9-dioctylfluorene)(2,5-diphenyl-1,3,4-oxadiazole)](PCFO), was synthesized and was sucessfully used to fabricate a PCFO-based nonvolatile memory device. This device showed typical bistable electrical switching and nonvolatile write-once read-many-times memory performance, with a turn-on voltage of about −2.3 V and an ON/OFF state current ratio of ∼105.

/pdf/synthesis-and-memory-performance-of-a-conjugated-polymer-gg9rli023l.pdf

Long-Jia Zeng

Papers

Electrical conductivity switching and memory effects in poly(N-vinylcarbazole) derivatives with pendant azobenzene chromophores and terminal electron acceptor moieties

Growing poly(N-vinylcarbazole) from the surface of graphene oxide via RAFT polymerization

Conjugated Polymer-Grafted Reduced Graphene Oxide for Nonvolatile Rewritable Memory

Synthesis and memory performance of a conjugated polymer with an integrated fluorene, carbazole and oxadiazole backbone