Pretreatment strategies of titanium substrates to modulate the electrochemical properties of CVD-grown Ti-doped diamond electrodes for dopamine detection

The identification of highly sensitive materials able to combine performance stability, relatively low cost, controllable and large area fabrication process is still a major bottleneck in the scientific community. Dopamine is considered a key indicator to monitor cardio and cerebrovascular diseases and its redox activeness makes electrochemical detection the most straightforward and promising sensing approach. Here we report the realization, by a simple yet effective approach, of diamond-based electrodes with a native selectivity towards dopamine. In details, three different substrate pretreatments, i.e., lapping, electropolishing and chemical etching, are adopted to tailor the morphological, structural, and sensing features of titanium doped diamond layers. SEM, AFM, Raman spectroscopy, XRD, XPS and I-V analyses demonstrate the features' modulation of the diamond layers being crucial for electrochemical and sensing performances, as confirmed by dopamine selectivity under ascorbic and uric acid interferents' excess. Furthermore, the controlled introduction of oxygen-containing groups enhances the dopamine sensitivity, lowering the detection limit from 6000 to 600 nM. In addition to giving an important insight on the physical-chemical growth processes, these preliminary results pave the way for the exploitation of these materials in a wide range of sensing applications, thanks to the non-toxicity and high surface tunability without post-synthesis treatments.