Water-Soluble Polythiophene-Conjugated Polyelectrolyte-Based Memristors for Transient Electronics

The key to protect sensitive information stored in electronic memory devices from disclosure is to develop transient electronic devices that are capable of being destroyed quickly in an emergency. By using a highly water-soluble polythiophene-conjugated polyelectrolyte PTT-NMI⁺Br^- as an active material, which was synthesized by the reaction of poly[thiophene-alt-4,4-bis(6-bromohexyl)-4H-cyclopenta(1,2-b:5,4-b')dithiophene] with N-methylimidazole, a flexible electronic device, Al/PTT-NMI⁺Br^-/ITO-coated PET (ITO: indium tin oxide; PET: polyethylene terephthalate), is successfully fabricated. This device shows a typical nonvolatile rewritable resistive random access memory (RRAM) effect at a sweep voltage range of ±3 V and a history-dependent memristive switching performance at a small sweep voltage range of ±1 V. Both the learning/memorizing functions and the synaptic potentiation/depression of biological systems have been emulated. The switching mechanism for the PTT-NMI⁺Br^--based electronic device may be highly associated with ion migration under bias. Once water is added to this device, it will be destructed rapidly within 20 s due to the dissolution of the active layer. This device is not only a typical transient device but can also be used for constructing conventional memristors with long-term stability after electronic packaging. Furthermore, the soluble active layer in the device can be easily recycled from its aqueous solution and reused for fabricating new transient memristors. This work offers a train of new thoughts for designing and constructing a neuromorphic computing system that can be quickly destroyed with water in the near future.

Synthesis, morphological analysis, antibacterial activity of iron oxide nanoparticles and the cytotoxic effect on lung cancer cell line

Focusing on the huge importance associated in developing functional materials, this research study describes the synthesis, characterization of morphology, bactericidal activity and cytotoxic effect of iron oxide nanoparticles (IONPs). IONPs have been successfully fabricated through thermal decomposition of a diiron(III) complex precursor. The morphology of the nanoparticle has been delineated with different spectroscopic and analytic methods. Scanning and transmission electron microscopy (FE-SEM and HR-TEM) analyses estimate the cross linked porous structure of IONPs with an average size ~97 nm. Dynamic light scattering (DLS) study of IONPs determines the hydrodynamic diameter as 104 nm. The cytotoxic behavior of IONPs has been examined against human lung cancer cell line (A549) through different fluorescence staining studies which ensure the mode of apoptosis for cell death of A549. Furthermore, measurement of reactive oxygen species suggests the destruction of mitochondrial membrane of Staphylococcus aureus, leading to effective bactericidal propensity which holds a good promise for IONPs to become a clinically approved antibacterial agent.

Resistive memory devices based on novel functionalized poly(aryl ether)s with pendant azobenzene

We designed and synthesized two novel azobenzene functionalized poly(aryl ether)s (PAEs), PAE-azo-1 and PAE-azo-2, from a new azobenzene monomer via nucleophilic aromatic substitution polycondensation. This direct polymerization approach via azobenzene monomer has the advantages of controlling the distribution and amount of the azobenzene chromophores in the polymer. Both of the polymers showed very good thermal stability and excellent solubility for future application in the electronics industry. These polymers were fabricated as films by simple spin-coating and both of them were then prepared as sandwich memory devices. PAE-azo-1 and PAE-azo-2 exhibit write-once-read-many-times-type memory behavior, which can be encoded as “0” and “1,” and possess the low operation voltage below −3.0 V. The memory mechanism was investigated through ultraviolet–visible optical absorption spectrum and the cyclic voltammetry. These obtained results indicate that the novel azobenzene functionalized PAEs are a promising candidate for low power consumption and high-performance materials for data storage.

The Effect of Random and Block Copolymerization with Pendent Carbozole Donors and Naphthalimide Acceptors on Multilevel Memory Performance

Polymeric materials have been widely used in the fabrication of data-storage devices, owing to their unique advantages and defined conduction mechanisms. To date, the most-functional polymers that have been reported for memory devices were synthesized through random copolymerization, whilst there have been no reports regarding the memory effect of block polymers. Herein, we synthesized a random copolymer (PMCz₈ -co-PMBNa₂ ) and its corresponding block copolymer (PMCz₈ -b-PMBNa₂ ) to study the effect of the method of polymerization on the memory properties of the corresponding devices. Interestingly, both devices (ITO/PMCz₈ -co-PMBNa₂ /Al and ITO/PMCz₈ -b-PMBNa₂ /Al) exhibited ternary memory performance, with threshold voltages of -1.7 V/-3.3 V and -2.7 V/-3.8 V, respectively. However, based on comprehensive measurements, the memory properties of PMCz₈ -co-PMBNa₂ and PMCz₈ -b-PMBNa₂ were found to be owing to the operation of different conduction mechanisms, which resulted from different molecular stacking in the film state. Therefore, we expect that this work will be helpful for improving our understanding of the conduction mechanisms in polymer-based data-storage devices.

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.

Adjusting the Proportion of Electron-Withdrawing Groups in a Graft Functional Polymer for Multilevel Memory Performance

A polymer containing aldehyde active groups (PVB) was synthesized by atom transfer radical polymerization (ATRP), acting as a polymer precursor to graft a functional moiety via nucleophilic addition reaction. DHI (2-(1,5-dimethyl-hexyl)-6-hydrazino-benzo[de]isoquinoline-1,3-dione) and NPH (nitrophenyl hydrazine) groups, which contain naphthalimides that act as narrow traps and nitro groups that act as deep traps, were anchored onto the PVB at different ratios. A series of graft polymers were obtained and named PVB-DHI, PVB-DHI4 -NPH, PVB-DHI-NPH4 , and PVB-NPH. The chemical composition of the polymers was analyzed by (1) H-NMR spectroscopy and X-ray photoelectron spectroscopy (XPS). Memory devices were prepared from the polymers, and I-V characteristics were measured to determine the performance. By adjusting the ratio of different electron acceptors (DHI and NPH) to 4:1, ternary memory behavior was achieved. The relationship between memory behavior of PVB-DHIx NPHy and acceptor groups as well as their conduction mechanism were studied in detail.

Synthesis of imidazole derivatives and study of the ON-based different memory performances

We report the synthesis of two imidazole-based small molecules with different planarity of terminal aromatic rings and their application in memory devices with a sandwich configuration. The optical, electric, and the on-based device performances were systematically investigated. Surprisingly, the device based on BT-PMZ exhibited volatile static random access memory (SRAM) behavior, whereas that based on BT-BMZ showed nonvolatile write-once-read-many-times (WORM) behavior. Further studies on the film morphology and the molecular electronic structure were carried out to investigate the underlying mechanism for the large difference in their performance. Moreover, the performance of the device that incorporates a LiF buffer layer (5 nm) embedded at the interface between the BT-BMZ active layer and the Al top electrode as well as that of the device with a cold-deposited top electrode of mercury droplet was further investigated. At that point a dramatic change in memory performance of the devices from the WORM to SRAM type was observed. The intrinsic volatile SRAM performance for the two molecules results from the moderate electron-withdrawing strength of the acceptor moieties and thus weak trapping of the charge carriers.