Constructing combinational and sequential logic devices through an intelligent electrocatalytic interface with immobilized MoS2 quantum dots and enzymes

Stable molybdenum disulfide quantum dots (MoS2 QDs) were synthesized using a simple method and embedded into chitosan (Chit) films with glucose oxidase (GOD) on the surface of a polyaniline (PANI) pre-electrodeposited ITO electrode, designated as Chit-MoS2 -GOD/PANI. At the prepared film electrode, the fluorescence property of MoS2 QDs as well as the catalytic properties of MoS2 QDs and GOD were well maintained and could be reversibly regulated by external stimuli, such as pH, potential, and the concentrations of glucose and ascorbic acid (AA) in the solution. By controlling the redox state of PANI with an externally applied voltage, the color of the film electrode switched between violet blue and nearly transparent, simultaneously quenching/dequenching the fluorescence signals from MoS2 QDs through Foster resonance energy transfer (FRET). The electrocatalytic signals toward hydrogen peroxide (H2O2), a product formed by biocatalysis between glucose and GOD, could be tuned through the catalytic capacity of MoS2 QDs in the films. Thus, an intelligent platform was built based on the film electrode with pH, potential, glucose and AA as inputs and UV-vis extinction (E), photoluminescent intensity (PL), and amperometric current (I) as outputs. Combinational logic operations such as a 4-input/5output logic network and sequential logic operations such as a keypad lock and a reprogrammable delay/data (D) flip flop was first simulated in a biocomputing system with the film-modified electrode. This work demonstrated the construction of a multiple stimulus-responsive system with dual-functional nanomaterials and provided a new approach for sequential logic operations for further applications in the information storage.

Automated summary

Stable molybdenum disulfide quantum dots were synthesized and embedded into chitosan films on an electrode. The properties of the quantum dots and glucose oxidase were maintained and controlled by external stimuli. The electrode's color and the fluorescence signals from the quantum dots could be switched through the redox state of the electrode. The modified electrode was used to simulate combinational and sequential logic operations.