Environmentally Robust Memristor Enabled by Lead-Free Double Perovskite for High-Performance Information Storage.

Memristors are emerging as a rising star of new computing and information storage techniques. However, the practical applications are severely challenged by their instability toward harsh conditions, including high moisture, high temperatures, fire, ionizing irradiation, and mechanical bending. In this work, for the first time, lead-free double perovskite Cs2 AgBiBr6 is utilized for environmentally robust memristors, enabling highly efficient information storage. The memory performance of the typical indium-tin-oxide/Cs2 AgBiBr6 /Au sandwich-like memristors is retained after 1000 switching cycles, 105 s of reading, and 104 times of mechanical bending, comparable to other halide perovskite memristors. Most importantly, the memristive behavior remains robust in harsh environments, including humidity up to 80%, temperatures as high as 453 K, an alcohol burner flame for 10 s, and 60 Co γ-ray irradiation for a dosage of 5 × 105 rad (SI), which is not achieved by any other memristors and commercial flash memory techniques. The realization of an environmentally robust memristor from Cs2 AgBiBr6 with a high memory performance will inspire further development of robust electronics using lead-free double perovskites.

Independent Memcapacitive Switching Triggered by Bromide Ion Migration for Quaternary Information Storage.

Memcapacitors are emerging as an attractive candidate for high-density information storage due to their multilevel and adjustable capacitances and long-term retention without a power supply. However, knowledge of their memcapacitive mechanism remains unclear and accounts for the limited implementation of memcapacitors for multilevel memory technologies. Here, repeatable and reproducible quaternary memories fabricated from hybrid perovskite (CH3 NH3 SnBr3 ) memcapacitors are reported. The device can be modulated to at least four capacitive states ranging from 0 to 169 pF with retention for 104 s. Impressively, an effective device yield approaching 100% for quaternary memory switching is achieved by a batch of devices; each state has a sufficiently narrow distribution that can be distinguished from the others and is superior to most multilevel memories that have a low device yield as well as an overlapping distribution of states. The memcapacitive switching stems from the modulated p-i-n junction capacitance triggered by Br- migration, as demonstrated by in situ element mapping, X-ray photoelectron spectra, and frequency-dependent capacitance measurements; this mechanism is different from the widely reported memristive switching involving filamentary conduction. The results provide a new way to produce high-density information storage through memcapacitors.

Detection of NO2 Down to One ppb Using Ion-in-Conjugation-Inspired Polymer.

Nitrogen dioxide (NO2 ) emission has severe impact on human health and the ecological environment and effective monitoring of NO2 requires the detection limit (limit of detection) of several parts-per-billion (ppb). All organic semiconductor-based NO2 sensors fail to reach such a level. In this work, using an ion-in-conjugation inspired-polymer (poly(3,3'-diaminobenzidine-squarine, noted as PDBS) as the sensory material, NO2 can be detected as low as 1 ppb, which is the lowest among all reported organic NO2 sensors. In addition, the sensor has high sensitivity, good reversibility, and long-time stability with a period longer than 120 d. Theoretical calculations reveal that PDBS offers unreacted amine and zwitterionic groups, which can offer both the H-bonding and ion-dipole interaction to NO2 . The moderate binding energies (≈0.6 eV) offer high sensitivity, selectivity as well as good reversibility. The results demonstrate that the ion-in-conjugation can be employed to greatly improve sensitivity and selectivity in organic gas sensors by inducing both H-bonding and ion-dipole attraction.

Mussel-Inspired Polydopamine Coating for Flexible Ternary Resistive Memory.

In recent years, numerous organic molecules and polymers carrying various functional groups were synthesized and used in fabrication of wearable electronic devices. Compared to previous materials that suffer from poisonousness, stiffness and complex film fabrication, we circumvent above matters by taking advantage of mussel-inspired polydopamine as our active material to realize resistive random access memories (RRAMs). Polydopamine thin films were grown on indium tin oxide glass catalyzed by Cu2 SO4 /H2 O2 and characterized by Fourier infrared spectroscopy (FT-IR), UV/Vis spectroscopy and scanning electron microscopy. The Al/Polydopamine film/ITO devices possess ternary memory behavior with good ternary device yield with two threshold voltages around 1.50 V and 3.50 V, long data retention over 104  s of continuous reading or 104 pulse reading. The two resistance switchings are attributed to defects functioning as charge traps and the formation of conductive filaments. A flexible device based on Al/polydopamine film/ITO/polyethylene terephthalate retains its ternary memory behavior after being bent with a bending radius of 1.54 cm and bending cycles up to 5000, demonstrating good compatibility and flexibility of polydopamine.

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.

Pseudohalide-Induced 2D (CH3 NH3 )2 PbI2 (SCN)2 Perovskite for Ternary Resistive Memory with High Performance.

Recently, organic-inorganic hybrid perovskites (OIHP) are studied in memory devices, but ternary resistive memory with three states based on OIHP is not achieved yet. In this work, ternary resistive memory based on hybrid perovskite is achieved with a high device yield (75%), much higher than most organic ternary resistive memories. The pseudohalide-induced 2D (CH3 NH3 )2 PbI2 (SCN)2 perovskite thin film is prepared by using a one-step solution method and fabricated into Al/perovskite film/indium-tin oxide (glass substrate as well as flexible polyethylene terephthalate substrate) random resistive access memory (RRAM) devices. The three states have a conductivity ratio of 1:103 :107 , long retention over 10 000 s, and good endurance properties. The electrode area variation, impedance test, and current-voltage plotting show that the two resistance switches are attributable to the charge trap filling due to the effect of unscreened defect in 2D nanosheets and the formation of conductive filaments, respectively. This work paves way for stable perovskite multilevel RRAMs in ambient atmosphere.

Serotonin Transporter Gene (SLC6A4) Polymorphism May Be Associated with Chinese Globus Pharyngeus and Its Antidepressant Effects.

BACKGROUND: Although globus pharyngeus is not rare in clinical practice, little is known about its associated gene polymorphism. We investigated the association between the SLC6A4 polymorphism and globus pharyngeus and its response to treatment with antidepressants. METHODS: A total of 84 patients were diagnosed with globus pharyngeus according to Rome III, and 160 healthy controls were genotyped for the SLC6A4 polymorphism using polymerase chain reaction amplification and agarose gel electrophoresis. All patients with globus were studied using high-resolution manometry pre-therapy. Globus patients were randomized into paroxetine or amitriptyline groups for a 6-week treatment and asked to complete the following pre- and post-therapy questionnaires: the Glasgow Edinburgh Throat Scale (GETS), the Pittsburgh Sleep Quality Index, and the Hamilton Rating Scale Anxiety/Depression. Treatment response was defined as a >50% reduction in the GETS scores. RESULTS: A significant difference was observed in the globus S/S genotype with anxiety compared to that without anxiety (χ2 = 14.579, p = 0.006). The L/S genotype showed a significant difference between high upper esophageal sphincter pressure (>104 mm Hg) and non-high upper esophageal sphincter pressure patients (χ2 = 14.433, p = 0.006). A significant association between the S/S genotype and the response to antidepressant treatment was also observed, while patients with sleep disorders or depression showed no association. CONCLUSION: A significant association was observed between the S/S genotype of the SLC6A4 polymorphism and globus pharyngeus, suggesting that SLC6A4 is a potential candidate gene involved in the pathogenesis of globus pharyngeus.

Better Organic Ternary Memory Performance through Self-Assembled Alkyltrichlorosilane Monolayers on Indium Tin Oxide (ITO) Surfaces.

Recently, surface engineering of the indium tin oxide (ITO) electrode of sandwich-like organic electric memory devices was found to effectively improve their memory performances. However, there are few methods to modify the ITO substrates. In this paper, we have successfully prepared alkyltrichlorosilane self-assembled monolayers (SAMs) on ITO substrates, and resistive random access memory devices are fabricated on these surfaces. Compared to the unmodified ITO substrates, organic molecules (i.e., 2-((4-butylphenyl)amino)-4-((4-butylphenyl)iminio)-3-oxocyclobut-1-en-1-olate, SA-Bu) grown on these SAM-modified ITO substrates have rougher surface morphologies but a smaller mosaicity. The organic layer on the SAM-modified ITO further aged to eliminate the crystalline phase diversity. In consequence, the ternary memory yields are effectively improved to approximately 40-47 %. Our results suggest that the insertion of alkyltrichlorosilane self-assembled monolayers could be an efficient method to improve the performance of organic memory devices.

Poly(3,4-ethylenedioxythiophene)-Poly(styrenesulfonate) Interlayer Insertion Enables Organic Quaternary Memory.

Herein, for the first time, quaternary resistive memory based on an organic molecule is achieved via surface engineering. A layer of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) was inserted between the indium tin oxide (ITO) electrode and the organic layer (squaraine, SA-Bu) to form an ITO/PEDOT-PSS/SA-Bu/Al architecture. The modified resistive random-access memory (RRAM) devices achieve quaternary memory switching with the highest yield (∼41%) to date. Surface morphology, crystallinity, and mosaicity of the deposited organic grains are greatly improved after insertion of a PEDOT-PSS interlayer, which provides better contacts at the grain boundaries as well as the electrode/active layer interface. The PEDOT-PSS interlayer also reduces the hole injection barrier from the electrode to the active layer. Thus, the threshold voltage of each switching is greatly reduced, allowing for more quaternary switching in a certain voltage window. Our results provide a simple yet powerful strategy as an alternative to molecular design to achieve organic quaternary resistive memory.

Surface Engineering of ITO Substrates to Improve the Memory Performance of an Asymmetric Conjugated Molecule with a Side Chain.

Organic multilevel random resistive access memory (RRAM) devices with an electrode/organic layer/electrode sandwich-like structure suffer from poor reproducibility, such as low effective ternary device yields and a wide threshold voltage distribution, and improvements through organic material renovation are rather limited. In contrast, engineering of the electrode surfaces rather than molecule design has been demonstrated to boost the performance of organic electronics effectively. Herein, we introduce surface engineering into organic multilevel RRAMs to enhance their ternary memory performance. A new asymmetric conjugated molecule composed of phenothiazine and malononitrile with a side chain (PTZ-PTZO-CN) was fabricated in an indium tin oxide (ITO)/PTZ-PTZO-CN/Al sandwich-like memory device. Modification of the ITO substrate with a phosphonic acid (PA) prior to device fabrication increased the ternary device yield (the ratio of effective ternary device) and narrowed the threshold voltage distribution. The crystallinity analysis revealed that PTZ-PTZO-CN grown on untreated ITO crystallized into two phases. After the surface engineering of ITO, this crystalline ambiguity was eliminated and a sole crystal phase was obtained that was the same as in the powder state. The unified crystal structure and improved grain mosaicity resulted in a lower threshold voltage and, therefore, a higher ternary device yield. Our result demonstrated that PA modification also improved the memory performance of an asymmetric conjugated molecule with a side chain.

Surface engineering to achieve organic ternary memory with a high device yield and improved performance.

Squaraine molecules deposited on indium tin oxide (ITO) substrates modified with phosphonic acids crystalize more orderly than do those on untreated ITO. The as-fabricated electro-resistive memories show the highest ternary device yield observed to date (82%), a narrower switching voltage distribution, and better retention as well as resistance uniformity.

A Novel Bat-Shaped Dicyanomethylene-4H-pyran-Functionalized Naphthalimide for Highly Efficient Solution-Processed Multilevel Memory Devices.

Small-molecule-based multilevel memory devices have attracted increasing attention because of their advantages, such as super-high storage density, fast reading speed, light weight, low energy consumption, and shock resistance. However, the fabrication of small-molecule-based devices always requires expensive vacuum-deposition techniques or high temperatures for spin-coating. Herein, through rational tailoring of a previous molecule, DPCNCANA (4,4'-(6,6'-bis(2-octyl-1,3-dioxo-2,3-dihydro-1H-benzo[de]isoquinolin-6-yl)-9H,9'H-[3,3'-bicarbazole]-9,9'-diyl)dibenzonitrile), a novel bat-shaped A-D-A-type (A-D-A=acceptor-donor-acceptor) symmetric framework has been successfully synthesized and can be dissolved in common solvents at room temperature. Additionally, it has a low-energy bandgap and dense intramolecular stacking in the film state. The solution-processed memory devices exhibited high-performance nonvolatile multilevel data-storage properties with low switching threshold voltages of about -1.3 and -2.7 V, which is beneficial for low power consumption. Our result should prompt the study of highly efficient solution-processed multilevel memory devices in the field of organic electronics.

The effects of paroxetine and amitriptyline on the upper esophageal sphincter (UES) pressure and its natural history in globus pharyngeus.

BACKGROUND: Antidepressant agents have been shown to be an effective and safe treatment method for patients with globus. However, there are few clinical trials dedicated to studying the effects of antidepressant agents on the natural history and upper oesophageal sphincter (UES) pressure of treated globus patients. AIMS: To evaluate the effect of paroxetine and amitriptyline to prevent relapses in patients with globus, the simultaneous relationship between changes in UES pressure and improvement of globus symptoms were measured. METHODS: Globus patients were randomised into amitriptyline, paroxetine and lansoprazole groups for a 6-week treatment period, and follow-up was extended to 12 additional months. Efficacy was evaluated in terms of the Glasgow-Edinburgh Throat Scale (GETS), and UES pressure was measured by standard oesophageal manometry. RESULTS: Paroxetine therapy resulted in a higher withdrawal rate due to symptom relapse (15.9% vs 44.1%, P=0.01; 15.9% vs 64.7, P=0.001) than amitriptyline and lansoprazole. Furthermore, globus symptoms were alleviated with the decrease of UES pressure after paroxetine and amitriptyline treatment (r=0.620, P=0.02; r=0.575, P=0.03) CONCLUSIONS: This follow-up study indicates that paroxetine may alter the natural history of globus and can effectively be used for the long-term management of patients with the disease. Apart from the clinical benefits, paroxetine and amitriptyline can potentially decrease UES pressure.

Upgrading Electroresistive Memory from Binary to Ternary Through Single-Atom Substitution in the Molecular Design.

Herein, two molecules based on urea and thiourea, which differ by only a single atom, were designed, successfully synthesized, and fabricated into resistive random-access memory devices (RRAM). The urea-based molecule showed binary write-once-read-many (WORM) storage behavior, whereas the thiourea-based molecule demonstrated ternary storage behavior. Atomic-force microscopy (AFM) and X-ray diffraction (XRD) patterns show that both molecules have smooth morphology and ordered layer-by-layer lamellar packing, which is beneficial for charge transportation and, consequently, device performance. Additionally, the optical and electrochemical properties indicate that the thiourea-based molecule has a lower bandgap and may be polarized by trapped charges, thus the formation of a continuous conductive channel and electric switching occurs at lower bias voltage, which results in ternary WORM behavior. This study, together with our previous work on single-atom substitution, may be useful to tune and improve device performance in the future design of organic memory.

Ion-in-Conjugation: Squaraine as an Ultrasensitive Ammonia Sensor Material.

An organic thin-film gas sensor based on squaraine detects ammonia as low as 40 ppb with impressive reversibility and stability. The resonance-stabilized zwitterionic characteristics offer squaraines high affinity and sensitivity toward electron-rich analytes without irreversible chemical binding, while the embedded squaric ring makes SA-CH3 highly sensitive. The symmetric molecular geometry and good crystallinity also contribute to the high performance.

Comparison of paroxetine and amitriptyline in the treatment of refractory globus pharyngeus.

BACKGROUND: Clinical trials of antidepressants for treatment of globus are generally rare, let alone for refractory globus pharyngeus. AIMS: To illustrate the efficacy and side-effects of antidepressants between paroxetine and amitriptyline for refractory globus patients. METHODS: Refractory globus patients were randomized into paroxetine group; amitriptyline group and lansoprazole group for 6-week treatment. All the subjects were asked to complete the following questionnaires pre- and post-therapy: Glasgow Edinburgh Throat Scale (GETS), Pittsburgh Sleep Quality Index, Hamilton Rating Scale Anxiety/Depression and Medical outcome short-form 36. Treatment response was defined as a >50% reduction in the GETS score. RESULTS: One hundred and forty-eight patients completed the study. After 6 week treatment, 71.7% of paroxetine group (33/46) were calculated as treatment response, significantly higher than that in amitriptyline group (46.2%, 24/52) and lansoprazole group (14.0%, 7/50). Compared with lansoprazole group or amitriptyline group, a more distinct improvement of emotional well-being, quality of life and quality of sleep were observed in paroxetine group after 6-week treatment. CONCLUSION: Paroxetine therapy is more efficacious than empirical high-dose antisecretory treatment, or even the low-dose amitriptyline therapy in alleviating globus symptoms, and producing global improvements for refractory globus patients.

Ternary Flexible Electro-resistive Memory Device based on Small Molecules.

Flexible memory devices have continued to attract more attention due to the increasing requirement for miniaturization, flexibility, and portability for further electronic applications. However, all reported flexible memory devices have binary memory characteristics, which cannot meet the demand of ever-growing information explosion. Organic resistive switching random access memory (RRAM) has plenty of advantages such as simple structure, facile processing, low power consumption, high packaging density, as well as the ability to store multiple states per bit (multilevel). In this study, we report a small molecule-based flexible ternary memory device for the first time. The flexible device maintains its ternary memory behavior under different bending conditions and within 500 bending cycles. The length of the alkyl chains in the molecular backbone play a significant role in molecular stacking, thus guaranteeing satisfactory memory and mechanical properties.

Epidemiology of globus symptoms and associated psychological factors in China.

OBJECTIVE: To investigate the lifetime prevalence, epidemiological characteristics and psychological factors of globus symptoms in Guangzhou (Guangzhou Province, China). METHODS: A total of 3 360 individuals were randomly selected and participated in the study. Respondents completed questionnaires about their physical and psychological characteristics, globus symptomatology and the Glasgow-Edinburgh throat scale questionnaires and quality of sleep and life. Those who had experienced a globus sensation with no history of gastroesophageal reflux disease, dysphagia, odynophagia or alerting symptoms such as weight loss and hoarseness were diagnosed as having globus. RESULTS: A total of 3 006 respondents completed the questionnaires, giving a response rate of 89.5%. The overall lifetime prevalence of globus was 21.5%, with a peak age at disease onset of 35-54 years. The prevalence of globus was higher in participants from the urban region than those from the rural areas (26.5% vs 16.4%, P = 0.001). No sex-related difference was observed (P = 0.082). Anxiety (39.8% vs 22.3%, P = 0.001), depression (31.2% vs 18.0%, P = 0.001) and sleep disorders (23.7% vs 13.6%, P = 0.001) were significantly more common in respondents with globus than in those without. Scores on all dimensions of the 36-item short-form health survey, except physical function, were lower in respondents with globus than in those without (all P < 0.05). CONCLUSIONS: Globus symptoms are common and often accompanied by psychological and sleep disorders. The medical community should pay more attention to globus in clinical setting.

Preparing non-volatile resistive switching memories by tuning the content of Au@air@TiO2-h yolk-shell microspheres in a poly(3-hexylthiophene) layer.

Crystalline hybrid microspheres, encapsulating a Au nanocore in the hollow cavity of a hairy semiconductor TiO2 shell (Au@air@TiO2-h microspheres) were prepared using template-assisted synthesis methods. The as-prepared microspheres are dispersed into a poly(3-hexylthiophene) (P3HT) matrix and used as a memory active layer. The electrical rewritable memory effects of Al/[Au@air@TiO2-h + P3HT]/ITO sandwich devices can be effectively and exactly controlled by tuning the microsphere content in the electroactive layer. To clarify the switching mechanism, different components in the device, such as P3HT and the microspheres, have been investigated. And it was determined that the switching mechanism can be attributed to the formation and rupture of oxygen vacancy filaments. These results suggest that the Au@air@TiO2-h microspheres are potentially capable of high density data storage. In addition, this finding could provide important guidelines for the reproducibility of nanocomposite-based memory devices and is helpful to demonstrate the switching mechanism of these devices.

Multilevel conductance switching of a memory device induced by enhanced intermolecular charge transfer.

The modification of the terminal electron-donating groups induces a critical change in molecular aggregation and the intermolecular charge-transfer effect of the symmetric D-A1-A2-A1-D molecules that correlate with an addressable variation of memory performance from binary to ternary.