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In this report we perform the irradiation of argon (Ar) plasma on the surface of amorphous atomic layer deposited HfO2 thin film intentionally to modulate interface between Ti and HfO2 having influence on resistive switching as well as synaptic characteristics within the Ti/HfO2/Pt memristor structure. Due to structural change in sub-TiOx interfacial layer as well as oxygen vacancy modulation at the HfO2/Ti interface, compared to the pristine HfO2 thin film, the Ar plasma-irradiated HfO2 thin film exhibits an electro-forming free repeatable switching with digital SET and multilevel voltage-induced RESET characteristics under smaller positive and negative sweeps, respectively. The multilevel resistance states are induced by applying different stopping voltages during the process of RESET. To investigate synaptic characteristics of the Ar plasma-treated device, we carried out the transient electrical measurement by designing the input stimulation with different pulse parameters in order to achieve the symmetric and near-linear conductance change. Finally, we emulated one of the important learning rules of biological synapse called spike-time-dependent-plasticity (STDP) by applying specially designed spikes at the top and bottom electrode by adjusting the time intervals between pre- and post-spikes.

Due to increasing industrialization, soils are increasingly contaminated by polycyclic aromatics such as pyrene and need gentle treatment to keep the soil functioning. This study applied a double dielectric barrier discharge (DDBD) plasma reactor and composting reactor to remediate pyrene-contaminated soil. The effect of peak-to-peak applied voltages on the remediation efficiency of pyrene was investigated. The experimental results illustrate that pyrene remediation efficiency increased from 43% to 85% when the peak-to-peak applied voltage was increased from 28.0 to 35.8 kV. When using the combined method of DDBD and composting, 90-99% of pyrene could be removed, while a reduction of 76.5% was achieved using only composting, indicating the superiority of the combined system. Moreover, the authors could demonstrate that DDBD plasma treatment improves humification in the post-composting process as humic acid (HA) concentrations increased to 7.7 mg/g with an applied voltage of 35.8 kV; when composting was used as the sole treatment method, only 3.4 mg/g HA were produced. The microbial activity in the DDBD plasma-treated soil peaked on the 5th day and had a 2nd rise afterwards. The authors demonstrate that the combined technology of DDBD plasma and composting is a promising method for soil remediation with persistent organic pollutants. This treatment approach improves pollutant degradation efficiency and facilitates further humification, potentially restoring the function of contaminated soil. This approach could be considered a cost-effective and green strategy for soil remediation with persistent organic pollutants.

We have demonstrated the co-existence of reliable analog and digital switching characteristics with tantalum oxide based memristor by appropriate rapid thermal annealing (RTA). The device without RTA exhibits a digital SET and multilevel RESET for positive and negative sweeps, respectively. On the other hands, the device shows only analog switching characteristics such that current level increases and decreases gradually for successive positive and negative voltage sweeps, respectively, before any electroforming process with the RTA in the nitrogen ambient at the crystalline temperature of tantalum oxide which is 700 °C for 60 s. Once electroforming process is done, the device exhibits a reliable digital switching with SET at positive sweep and RESET at negative sweep voltages. In the analog state of the device we successfully emulate the synaptic characteristic of the device like spike-rate dependent plasticity (SRDP), pulse-paired facilitation (PPF) and post-tetanic potentiation (PTP). Finally, the Hermann Ebbinghaus forgetting curve is obtained from these devices. The conversion of the device from the digital SET and multilevel RESET to analogue switching is attributed to structural transition of amorphous tantalum oxide to polycrystalline tantalum oxide, different defect density and interface variation in the device.

Fugitive methane (CH4) from waste treatment facilities (landfill mining), power industries (oil and gas process plants) and coal mining etc. into atmosphere is an increasing environmental concern. In this study, CH4 conversion efficiency in double dielectric barrier discharge (DDBD) has been investigated at various operating parameters including input power, feed gas-mixture flow rate, CH4 initial concentrations, and discharge gap distance between two dielectrics. Increase in input power, decrease in the gas-mixture flow rate and discharge gap distance; results in increases of CH4 conversion efficiency. In plasma alone, maximum CH4 conversion efficiency of 76% was obtained using 3 mm plasma discharge gap distance at flow rates of 2 L/min, input power of 65.8 W and is limited by experimental conditions. In addition, CH4 conversion efficiency in plasma alone and plasma-catalytic is compared by introducing various catalysts includes Pt–Sn/Al2O3, BaTiO3 and HZSM-5 in single plasma discharge zone. Results revealed that plasma combined with Pt–Sn/Al2O3 showed higher CH4 conversion efficiency (84.93%) as compare to plasma alone (56.42%) using 6 mm plasma discharge gap distance at flow rates of 2 L/min, input power of 65.8 W. Moreover, maximum energy efficiency of CH4 conversion (limited by experimental conditions) was 27.24 × 10−12 mol/kJ at 32.6 W observed in plasma-catalyst. Analysis of the exhaust gas showed that DDBD is a promising alternative reactor not only to achieve high CH4 conversion efficiency, but also to overcome the drawbacks of formation of undesirable byproducts. Moreover, deposition of carbon residues on the surface of internal electrode is not observed, which is often occurred in single DBD reactors.

The improved resistive switching (RS) characteristics of Pt/HfO2/Ti structured RRAM are demonstrated by engineering interface with argon (Ar) plasma irradiation. The Ar plasma treatment was intentionally carried out on the surface of atomic layer deposited (ALD) HfO2 thin films to modulate the conducting filament size affecting RS behaviors. Compared to ALD HfO2 RRAM without Ar plasma treatment, the Ar plasma treatment on the surface of ALD HfO2 thin film leads to forming-free process, faster switching speed, tighter low resistance state (LRS) and high resistance state (HRS) current distribution, smaller variations of SET voltage and RESET voltage, and enhanced retention/endurance characteristics under HRS. These improvements are believed to be the generation of favorably modulated interface oxide layer between HfO2 and Ti. In addition, current conduction mechanism is dominated by ohmic behavior in LRS while ohmic, space charge limited conduction (SCLC), and trap filled SCLC are observed at HRS with different field regions. The Ar plasma irradiation can be an easy and facile way to achieve the reliable and uniform RRAM characteristics.

We report a novel sensing protocol based on ultra-short (

A high concentration of toxic heavy metal cadmium (Cd) in the paddy soils and its translocation and subsequent accumulation in the rice grain and the food chain is a global environmental issue. Mechanistic understanding of soil properties that affects the uptake and translocation of Cd in rice may help to reduce Cd uptake by rice plants and its accumulation in the grains. This review discusses the known and unknown soil and plant factors involved in the transportation of Cd from the soil through roots into rice grains. Various management practices to remediate Cd from contaminated soil are known, but only a few of these technologies are practically applicable in the field. The use of effective, ecofriendly, and natural resource-based remediation practices and understanding of their underlying mechanism is indispensable. The translocation of Cd from soil to rice roots may be reduced by controlling soil pH and redox potential through wise management of nutrients and water. The uptake and translocation of Cd and its accumulation in rice grains may be reduced by developing genotypes restricting Cd uptake. This can be achieved through breeding and identifying Cd tolerant genes followed by knocking out and/or editing these genes via CRISPR/Cas9 technique.

We introduce a novel and facile synthesis strategy to design 2D MXene (Ti3C2Tx) nanosheets (NSs) coated cellulose fibers (CLF) based 3D nanostructures (CLF@Ti3C2Tx) to overcome the drawbacks of co-ion expulsion in carbon-based, commonly used CDI electrodes and restacking of MXene NSs due to van der Waals forces in the pure MXene based electrodes. CLF extracted from facial tissue paper were used as a porous carbon core-substrate to coat shell of exfoliated two-dimensional (2D) Ti3C2Tx NSs in order to prepare unique CLF@Ti3C2Tx nanostructures composite by an improved dip-coating method. After appropriate structural and chemical characterization, the designed CLF@Ti3C2Tx material was assembled in symmetric capacitive deionization (CDI) cell as an active electrode and the electrochemical properties and desalination capacity were studied in detail. Interestingly, the CLF@Ti3C2Tx based active electrodes displayed good specific capacitance of 142 F·g−1 in 1 M sodium chloride electrolyte, and high salt adsorption capacitance of 35 mg·g−1 compared with the pure MXene and carbon-based electrodes at an applied voltage of 1.2 V, with considerable cycling stability of 10 cycles. Inspired by the conventional chemical gilding process, the proposed unique and low-cost synthesis strategy and unique design open a new way to develop MXene-carbon based composite nanostructures for CDI and energy storage applications.

The monodisperse manganese oxide nanoparticles with an average diameter of 30nm were chemically synthesized. The nanoparticles assembled as a close-packed monolayer on Pt bottom electrode by dip-coating and annealing process. The Ta/Ta2O5/MnO/Pt device was fabricated. The bipolar resistive switching behaviors could be caused by the formation and rupture of conductive filaments in the switching layers. The stable self-compliance property was demonstrated which can be attributed to the high resistance Ta/Ta2O5 interface, the Schottky barrier of Ta/Ta2O5, and the discontinuity of conduction band at Ta2O5 and MnO interface. The retention characteristics of Ta/Ta2O5/MnO/Pt device were investigated. The conduction mechanisms of Ohmic conduction, space charge limited conduction, Schottky conduction and Poole-Frenkel emission had been investigated for resistance switching mechanism. Display Omitted The resistive switching behaviors with heterostructure were demonstrated.The monodisperse oxide nanoparticles were chemically synthesized.The device showed bipolar switching and repeatable self-compliance properties.The bipolar switching was caused by the formation and rupture of conductive filaments in oxide layer.The stable self-compliance property was demonstrated.

In our study, the devices with Pt/Ti/TaOx/Pt, where x ranges from 1.34 to 1.47, Pt/Ti/HfO2/Pt and Pt/Ti/TaOy/HfO2/Pt were fabricated. The TaOx and HfO2 were the switching layers for single layer devices and for hybrid device TaOy acted as oxygen reservoir and HfO2 acted as switching layer. The single layer devices exhibited co-existence of bipolar and unipolar switching. For bipolar switching the SET process occurred when positive sweep voltage was applied and RESET process occurred for negative sweep. The transition from bipolar to unipolar was observed to be irreversible. The hybrid device exhibited the unipolar switching with two high resistance state (HRS) levels. Moreover, the conduction mechanism of ohmic conduction, space charge limited conduction (SCLC); Schottky conduction and Poole-Frenkel (P-F) conduction have been investigated. Display Omitted The resistive switching behavior of tantalum oxide, hafnium oxide and their hybrid devices are studied.The tantalum oxide and hafnium oxide monolayer devices exhibited co-existence of unipolar and bipolar switching.The transition from bipolar to unipolar switching is observed to be irreversible for the mono layer devices.The hybrid device with structure Pt/Ti/TaOx/HfO2/Pt presented only unipolar switching.The resistive switching was improved by the fabrication of hybrid device.

A cotinine sensor based on the dc resistance of a polymer composite films is presented. The composite film comprises a cotinine selective molecularly imprinted polymer and carbon nanotube particles. This polymer film is deposited over a gold interdigitated electrode array to measure its electrical resistance. The electrical resistance of the imprinted polymer changes upon its selective binding to the cotinine molecule. The electrical resistance increases with the increase in cotinine concentration, for the addition of 1000 ng/ml cotinine the resistance increases by ca. 190 kΩ. As a control experiment the response of un-imprinted polymer is also tested, which does not show any dependence on the cotinine concentration. Cotinine concentration in body fluid reflects the extent of tobacco smoking. This sensor has a potential to be used to detect active and passive smoking levels.

To successively implement synaptic memristor device in the neuromorphic computing system, it is essential to perform a variety of synaptic characteristics with low power consumption and have complementary metal-oxidesemiconductor (CMOS) compatibility. In this work, we experimentally demonstrate two types of interface and filamentary resistive switching behaviors for Ni/Ta2O5/Si device by controlling electroforming process. The typical bipolar operation with filamentary switching is observed with electroforming for non-volatile memory properties such as reliable retention (>104) and high on/off ratio (>103). To achieve the synaptic characteristics such as paired pulse facilitation (PPF), potentiation, and depression, the gradual switching with low current without electroforming is used. We evaluate pattern recognition accuracy simulation from Fashion MNIST dataset by using a 3-layer neural network (784 × 512 × 10) and synaptic weight of Ni/Ta2O5/Si device. Furthermore, density of states, isosurface charge density and electron localization function plots confirm the conductivity and charge formation of Ta2O5 structure with and without oxygen vacancies. Theoretical work results reveal that the resistive switching characteristics are due to charge accumulation/depletion near the defects sites (oxygen vacancy). All things considered, the Ni/Ta2O5/p++-Si memristor could offer the flexibility for both non-volatile memory and synaptic devices by simply controlling electroforming.

We have investigated the switching mechanism of conductive bridge random access memory (CBRAM) with Ag/SnO2/Pt, Ag/InGaZnO(IGZO)/Pt and their hybrid oxide devices with different stacking sequence (Ag/SnO2/IGZO/Pt and Ag/IGZO/SnO2/Pt). Typical bipolar resistive switching is observed in single layered devices and an Ag/SnO2/IGZO/Pt hybrid device. Interestingly, a stable and reproducible unipolar resistive switching is observed for a hybrid device with a stacking sequence of Ag/IGZO/SnO2/Pt. This result suggests that the staking sequence of dielectrics in the IGZO and SnO2 electrolyte determines unipolar or bipolar switching. The different switching types in the hybrid electrolyte are based on different migration or diffusion rates of Ag ions in the solid electrolyte and redox reaction rates at the electrodes. And as compared to single layered devices, the hybrid structured devices exhibit low operation voltages, higher ION/IOFF ratio, uniform switching cycles and better endurance and retention characteristics. The results and switching mechanisms demonstrated here in hybrid devices can be extended to other hybrid devices based on CBRAM device.

In this paper, a novel approach is reported for the electrochemical measurement of chloride ions in aqueous solution. This sensor is based on the stimulus/response principle of chronopotentiometry. A current pulse is applied at the Ag/AgCl working electrode and the potential change is measured with respect to another identical Ag/AgCl electrode in the bulk electrolyte. The potential difference is related to the Cl- ion concentration via the Nernst equation and follows an inverse logarithmic trend. By varying the applied current pulse, the sensitivity of the sensor is tunable to different concentration ranges. The potential response is also influenced by the pH of the electrolyte, this effect is pronounced at lower concentration of Cl- ions (12 pH). The advantage of this approach is the use of a bare Ag/AgCl electrode as a pseudo-reference electrode, which enables this system for long term application such as the in situ measurement of Clˉ ions in concrete