Study On The Performance Of Co₃O₄/Carbon Quantum Dots For Glucose/Dopamine Sensors

Transition metal nanomaterials have a wide range of photoelectric catalysis and biosensing applications due to their relatively low cost,earth abundance availability,easy preparation,and high yield.Among many cobalt-based materials are recognized for their strong redox driven electrochemical activity.Here,cobalt oxides,hydroxides,and the layered double hydroxides(LDH)are considered important chemical constituents for the construction of electrochemical sensor systems.Despite the strong redox couple,cobalt-based materials often suffer from particle aggregation,resulting in a sluggish electrochemical activity.Combining cobalt-based materials with carbon materials with high electrical conductivity and chemical endurance could realize faster electrochemical activity besides the omission of particle aggregation,boosting the electrochemical sensitivity of the devised sensor system.In this research,Co₃O₄ nanorods(NR)and Co₃O₄ nanoplates(NP)have been surface-coated with carbon quantum dots(CDs)to construct a highly robust electroanalytical platform for biomolecules such as glucose and dopamine.The main aspects of the carried study are as follows:(1)Co₃O₄ NR and CDs were synthesized using the hydrothermal method followed by an ultrasonic assembly approach to construct Co₃O₄ NR/CDs hybrid.The CDs with excellent photoelectric characteristics and biocompatible functions as the conductive substrate realizing improved diffusion and electron transmission pathways.At the same time,1D-0D assembly of the hybrid could effectively inhibit the aggregation of Co₃O₄ nanoparticles enabling full exposure of the surface active-sites for enhanced sensing performance.In 1D0D Co₃O₄ NR/CDs,when tested against glucose,exhibited an electrochemical sensitivity of 836.5 ?A mM-1 cm-2 with a lower detection limit of 1.4 pM calculated via chronoamperometric measurements.The detection of dopamine was carried using differential pulse voltammetry,where the hybrid exhibited electrochemical sensitivity of 423.2?A mM-1 cm-2 and a detection limit of 3.9 ?M.The hybrid exhibited high selectivity with robust anti-interference ability,besides high signal reproducibility and stability,anticipating materials candidacy for multifunctional sensor system.(2)The Co₃O₄ NP were prepared using the conventional hydrothermal approach with a size domain of tens of nanometers.Similar to NR,ultrasonic assembly was used to construct a 2D-0D cobalt-based electrochemical sensing platform.Here,CDs successfully suppressed the stacking of plate-shaped Co₃O₄.In contrast,the plates provided exposed surface-based redox sites for the enhanced electrocatalysis.The difference in the best fit ratio of CDs for NR and NP,besides morphological versatility,allowed the electrode to exhibit distinct electrochemical behaviors against similar biomolecules.In the case of glucose,the Co₃O₄ NP/CDs was highly sensitive,exhibiting long-range sensing ability with two proportional linear response ranges.The devised electrode was sensitive between 0.002-0.5 mM in the low concentration range with a sensitivity reach of 620 ?A mM-1 cm-2.The higher range linearity was observed between 0.5-1mM with a sensitivity reach of 278.8 ?A mM-1 cm-2 with a detection limit of 5.7 ?M.The differential pulse voltammetry(DPV)was used as an active mode for detecting dopamine,subsequent to the appearance of reliable anode and cathode peak,respectively.The sensitivity was measured to be 895.9 ?A mM-1 cm-2,with a detection limit of 2.6 ?M besides good anti-interference performance,reproducibility and stability.