Opto‐Electrochemical Synaptic Memory in Supramolecularly Engineered Janus 2D MoS$_2$

Artificial synapses combining multiple yet independent signal processingstrategies in a single device are key enabler to achieve high-density ofintegration, energy efficiency, and fast data manipulation in brain-likecomputing. By taming functional complexity, the use of hybrids comprisingmultiple materials as active components in synaptic devices represents apowerful route to encode both short-term potentiation (STP) and long-termpotentiation (LTP) in synaptic circuitries. To meet such a grand challenge,herein a novel Janus 2D material is developed by dressing asymmetrically thetwo surfaces of 2D molybdenum disulfide (MoS$_2$) with anelectrochemically-switchable ferrocene (Fc)/ ferrocenium (Fc$^+$) redox coupleand an optically-responsive photochromic azobenzene (Azo). Upon varyingthe magnitude of the electrochemical stimulus, it is possible to steer thetransition between STP and LTP, thereby either triggering electrochemicaldoping of Fc/Fc$^+$pair on MoS$_2$ or controlling an adsorption/desorptionprocess of such redox species on MoS$_2$. In addition, a lower magnitude LTP is recorded by activating the photoisomerization of azobenzene chemisorbedmolecules and therefore modulating the dipole-induced doping of the 2Dsemiconductor. ... mehrSignificantly, the interplay of electrochemical and opticalstimuli makes it possible to construct artificial synapses where LTP can beboosted to 4-bit (16 memory states) while simultaneously functioning as STP.