Photoreduced nanocomposites of graphene oxide/N-doped carbon dots toward all-carbon memristive synapses

Abstract

An all-carbon memristive synapse is highly desirable for hardware implementation in future wearable neuromorphic computing systems. Graphene oxide (GO) can exhibit resistive switching (RS) and may be a feasible candidate to achieve this objective. However, the digital-type RS often occurring in GO-based memristors restricts the biorealistic emulation of synaptic functions. Here, an all-carbon memristive synapse with analog-type RS behavior was demonstrated through photoreduction of GO and N-doped carbon quantum dot (NCQD) nanocomposites. Ultraviolet light irradiation induced the local reduction of GO near the NCQDs, therefore forming multiple weak conductive filaments and demonstrating analog RS with a continuous conductance change. This analog RS enabled the close emulation of several essential synaptic plasticity behaviors; more importantly, the high linearity of the conductance change also facilitated the implementation of pattern recognition with high accuracy. Furthermore, the all-carbon memristive synapse can be transferred onto diverse substrates, showing good flexibility and 3D conformality. Memristive potentiation/depression was stably performed at 450 K, indicating the resistance of the synapse to high temperature. The photoreduction method provides a new path for the fabrication of all-carbon memristive synapses, which supports the development of wearable neuromorphic electronics.

Chitosan-based carbon nanoparticles as a heavy metal indicator and for wastewater treatment

“…1A) conrmed the conclusion of TEM, showing that the diameter of chi-CNPs mainly distributed in the wide range of 60-100 nm, with an average diameter size of 79.06 nm. The size of carbon nanoparticles prepared in this study are larger than the traditional carbon dots (3-10 nm), [42][43][44] which might be due to the fact that chitosan is a natural polymer and contains a variety of hydrolysates in the process of forming chi-CNPs. Besides, a polymer lm was formed on the surface of the chi-CNPs by dissolving chitosan, which increased the particle size (the particle size is 54.84 nm, the polymer lm is 5.82 nm, and the polymer lm accounts for about one-tenth of the total particle size).…”

Flexible and transparent memristive synapse based on polyvinylpyrrolidone/N-doped carbon quantum dot nanocomposites for neuromorphic computing

“…No obvious resistive switching (RS) behavior is appeared in the devices without inserting NCQDs into PVP lm beacase there are no charge trapping centers that enhance the localized electric eld to aggregate electrons. 17,36 (see Fig. S3, ESI †).…”

“…3(c) and (d) show the variation of the current read at 0.2 V with the cycle number, in which the uptrend (downtrend) is observed aer applying positive (negative) sweeps. In addition, the devices with higher concentration exhibit poor A-RS performance duo to the existence of large leakage current in composite lm, 17,39 suggesting the NCQDs concentration of 40% is the optimal condition to achieve excellent A-RS performance (see Fig. S5, ESI †).…”

“…The device conductance can be continuously adjusted by controlling the number of these multiple CPs, which is similar to a model involving modulation of the number of CPs leading to a gradual change of the device conductivity of multiple CPs. 17,42,43 Such A-RS behavior in the PVP-NCQD based memristor enabled close emulation of synaptic learning functions. The current response of the memristive device under a single spike (2 V, 1 ms) is shown in Fig.…”

“…[13][14][15] In comparison with their inorganic counterparts, organic-inorganic hybrid systems have tremendous advantages in fabrication of memristive synapses owing to their costeffective, environmentally friendly, and biocompatible properties. [16][17][18] Polymers are usually used as the active matrix, and low-dimensional inorganic materials, including nanodots, 19,20 nanotubes, 21,22 and nanosheets, 23,24 are introduced into the polymer as charge trapping centers to trigger RS. In many cases, organic-inorganic hybrid based memristors exhibit digital-type RS (D-RS) between the low-resistance state (LRS) and highresistance state (HRS) for memory storage applications.…”