MXene Quantum Dots Covalently Modified with Poly[1,4‐diethynylbenzene‐alt‐spiropyran] for Analog‐Type Optoelectronic Dual‐Response Memristor

Abstract Quantum dots stand as an outstanding choice for high‐tech applications due to their fascinating edge and quantum confinement effects and unique optoelectronic properties. By using 4‐bromobenzenediazonium‐modified MXene quantum dots as a key zero‐dimensional template, highly soluble poly[1,4‐diethynylbenzene‐alt‐spiropyran] (PBSP)‐covalently functionalized MXene quantum dots (PBSP‐MQDs), in which two structural isomers of spiropyran (i.e., ring‐opened merocyanine and ring‐closed spiropyran) can interconvert into each other rapidly under different light illumination, are synthesized in situ. The weight percentage of MQDs in PBSP‐MQDs is 10.4%. For comparison purpose, PBSP‐covalently grafted MXene nanosheets (PBSP‐MXene) and PBSP are also synthesized under the same conditions. Upon UV or blue light illumination, these two reference materials do not show any memristive effect at a sweep range of ±0.5 V. On the contrary, the as‐fabricated ITO/PBSP‐MQDs/ITO device shows outstanding history‐dependent memristive switching performance, with 32 distinguishable conductance states, under the same experimental conditions. By using the difference in current between the adjacent conductive states as the weight parameters, a simple convolutional neural network for facial recognition is successfully constructed. After 200 epochs of training, the accuracy of facial recognition reaches up to 97.23%.