Study On Non-Enzymatic Glucose Sensor Based On Co₃O₄/Laser-induced Graphene Composite Materials

Compared with traditional enzymatic glucose sensors,non-enzymatic glucose sensors have the advantages of high stability,simple preparation and low cost.However,most of these sensors have problems such as poor selectivity and low anti-interference,which hinder the large-scale application of enzyme-free glucose sensors.For this reason,in the current research on non-enzymatic glucose sensors,how to prepare suitable electrode materials has become an urgent problem to be solved.In recent years,metal oxides with functionalized nanostructures have become the focus of researchers because of their many advantages,such as low cost,large electroactive surface area,strong redox properties,and good biocompatibility.Graphene has exceptional characteristics because of its distinct two-dimensional（2D）carbon nanomaterial structure,such as large specific surface area,high mechanical strength,and good electrochemical conductivity,and can also be loaded with catalytically active nanoparticles,providing reactive sites for glucose catalysis.Therefore,the successful coupling of transition metal oxide nanomaterials with graphene yields a more catalytically active catalyst,making it the most promising candidate for future research on enzyme-free glucose sensor electrode materials.The main research work of this paper is as follows:First,a flexible electrode in which Co₃O₄ nanoparticles are uniformly embedded in three-dimensional porous laser-induced graphene（Co₃O₄ NPs-LIG）was fabricated by one-step laser direct writing carbonization.The as-prepared Co₃O₄ NPs-LIG was comprehensively characterized by material characterization techniques such as TEM,SEM and XPS,and the microstructure and elemental composition of the Co₃O₄ NPs-LIG were analyzed.The results demonstrate the successful synthesis of the target substance,and the existence of Co₃O₄ NPs is beneficial to generate the disordered structure of multilayer graphene,which plays a certain role in promoting the electrochemical catalytic properties of graphene.Due to the good conductivity of LIG and the multiple high activation sites of Co₃O₄ nanoparticles,the composite electrode exhibits a remarkable synergistic effect,which can enhance the charge transfer and thus improve the electrochemical performance of the glucose sensor.The electrochemical performance of the Co₃O₄ NPs-LIG flexible electrode was evaluated,and the sensor showed a high sensitivity of 214μA m M^–1 cm^–2,a low limit of detection（LOD）of 0.41μM,and a broad linearity from 1μM to 9 m M Detection range,and fast response time within 0.49 s.Compared with other non-enzymatic glucose electrochemical sensors reported previously,the performance indicators of our developed Co₃O₄ NPs-LIG non-enzymatic glucose sensor are more excellent.Glucose concentrations in real serum samples were actual measured by the prepared sensors and compared in detail with commercial glucose meters,showing that the Co₃O₄ NPs-LIG enzyme-free glucose sensor exhibited good accuracy.The results showed that the Co₃O₄ NPs-LIG enzyme-free glucose sensor exhibited good accuracy.The results of the contact angle experiment proved that the introduction of Co₃O₄ NPs into the LIG electrode can significantly improve the electrode wettability,thereby effectively improving the transport and diffusion of water and electrolyte,which is beneficial to the adsorption of glucose molecules on the electrode.According to the first-principles calculations,the electronic structure and density of states were studied using the QUANTUM ESPRESSO software,and the possible sensing mechanism of the glucose sensor was analyzed.Moreover,utilizing screen-printing technology,a portable enzyme-free glucose sensor based on screen-printed electrodes was created.The interaction between the screen-printed electrode material and the substrate was attenuated by preparing a hybrid ink doped with Co₃O₄ NPs-LIG.The introduction of Co₃O₄ NPs-LIG enables the sensor to possess high sensitivity(143μA m M^–1 cm^–2),relatively low LOD（0.48μM）,wide linear detection range（1μM～11 m M）,and extremely fast response time.In addition,the sensor exhibited excellent repeatability,stability,and selectivity in glucose concentration detection.The porous structure of the Co₃O₄ NPs-LIG screen-printed inks possesses superior electrochemical properties than ordinary inks and can effectively increase the electron transfer rate,opening up a new avenue for the development of low-cost portable enzyme-free glucose sensors that can be used in various bioanalyses.In summary,this study opens an innovative and facile way to develop heterogeneous constructs of metal oxide nanoparticles uniformly embedded in laser direct-written graphene,providing a feasible strategy for developing flexible,wearable and highly sensitive enzyme-free glucose sensors in the near future.