Graphene/MoS_(2-x)O_(x)/graphene photomemristor with tunable non-volatile responsivities for neuromorphic vision processing

Conventional artificial intelligence(Al)machine vision technology,based on the von Neumann architecture,uses separate sensing,computing,and storage units to process huge amounts of vision data generated in sensory terminals.The frequent movement of redundant data between sensors,processors and memory,however,results in high-power consumption and latency.A more efficient approach is to offload some of the memory and computational tasks to sensor elements that can perceive and process the optical signal simultaneously.Here,we proposed a non-volatile photomemristor,in which the reconfigurable responsivity can be modulated by the charge and/or photon flux through it and further stored in the device.The non-volatile photomemristor has a simple two-terminal architecture,in which photoexcited carriers and oxygen-related ions are coupled,leading to a displaced and pinched hysteresis in the current-voltage characteristics.For the frst time,non-volatile photomemristors implement computationally complete logic with photoresponse-stateful operations,for which the same photomemristor serves as both a logic gate and memory,using photoresponse as a physical state variable instead of light,voltage and memresistance.The polarity reversal of photomemristors shows great potential for in-memory sensing and computing with feature extraction and image recognition for neuromorphic vision.

Direct patterning of reduced graphene oxide/graphene oxide memristive heterostructures by electron-beam irradiation

Memristive heterostructures,composed of reduced graphene oxide with different degree of reduction,were demonstrated through a simple method of‘direct electron-beam writing’on graphene oxide.Irradiation with an electron beam at various doses and accelerating voltages made it possible to define highand low-conductivity graphene-oxide areas.The electron beam-reduced graphene oxide/graphene oxide heterostructure clearly exhibited a nonlinear behavior and a well-controlled resistive switching characteristic at a low operating-voltage range(<1 V).The proposed memristive heterostructures are promising for highly-efficient digital storage and information process as well as for analogous neuromorphic computations.

Fractionation and fixation of rare earth elements in soils:Effect of spiking with lanthanum,cerium,and neodymium chlorides

Industrial and agricultural activities lead to the release of rare earth elements(REEs)in wastewater and aquatic ecosystems,and their accumulation in soils.However,the behavior of REEs in soils remains somewhat unclear.In the present work the fractionation and fixation of REEs in soddy-podzolic and chernozem soils spiked with La,Ce,and Nd chlorides were studied using dynamic(continuous flow)extraction,which allows natural conditions to be mimicked and artefacts to be minimised.The eluents applied are aimed to dissolve exchangeable,specifically sorbed,bound to Mn oxides,bound to metal-organic complexes,and bound to amorphous and poorly ordered Fe/Al oxides fractions extractable by 0.05 mol/L Ca(NO_(3))2,0.43 mol/L CH_(3)COOH,0.1 mol/L NH_(2)OH·HCl,0.1 mol/L K_(4)P_(2)O_(7) at pH 11,and 0.1 mol/L(NH4)_(2)C_(2)O_(4) at pH 3.2,respectively.It is found that the fixations of added La,Ce,and Nd in the form of metal-organic complexes is predominant for both types of soils:35%-38%in soddy-podzolic soil and 50%-79%in chernozem.The fixation of added elements in the first three fractions(exchangeable,specifically sorbed,and bound to Mn oxides)is significant for soddy-podzolic soil(5%-25%).For chernozem,the relative contents of added Ce and Nd in these fractions are nearly negligible.Only the content of exchangeable La is notable,about 5%.Adding any of three elements(La,Ce,or Nd)at the level of100 mg/kg to an initial sample results in changing the fractionation and bioaccessibility of other REEs present in soil.Their contents increase in the first three fractions and decrease in fifth(oxalate extractable)fraction for both soddy-podzolic soil and chernozem.The main difference is the behavior of REEs in pyrophosphate extractable fraction.For soddy-podzolic soil,adding La,Ce,or Nd results in decreasing the contents of other REEs associated with organic matter.For chernozem,on the contrary,the contents of REEs in the form of metal-organic complexes slightly increase.These processes may be attributed to competitive binding of elements and soil properties;they must be taken into account when assessing the environmental risks of soil pollution with REEs.