Inkjet Printing-Manufactured Boron-Doped Diamond Chip Electrodes for Electrochemical Sensing Purposes

Abstract

Fabrication of patternedboron-doped diamond (BDD) inan inexpensiveand straightforward way is required for a variety of practical applications,including the development of BDD-based electrochemical sensors. Thiswork describes a simplified and novel bottom-up fabrication approachfor BDD-based three-electrode sensor chips utilizing direct inkjetprinting of diamond nanoparticles on silicon-based substrates. Thewhole seeding process, accomplished by a commercial research inkjetprinter with piezo-driven drop-on-demand printheads, was systematicallyexamined. Optimized and continuous inkjet-printed features were obtainedwith glycerol-based diamond ink (0.4% vol/wt), silicon substratespretreated by exposure to oxygen plasma and subsequently to air, andapplying a dot density of 750 drops (volume 9 pL) per inch. Next,the dried micropatterned substrate was subjected to a chemical vapordeposition step to grow uniform thin-film BDD, which satisfied thefunction of both working and counter electrodes. Silver was inkjet-printedto complete the sensor chip with a reference electrode. Scanning electronmicrographs showed a closed BDD layer with a typical polycrystallinestructure and sharp and well-defined edges. Very good homogeneityin diamond layer composition and a high boron content (& SIM;2 x10(21) atoms cm(-3)) was confirmed by Ramanspectroscopy. Important electrochemical characteristics, includingthe width of the potential window (2.5 V) and double-layer capacitance(27 & mu;F cm(-2)), were evaluated by cyclic voltammetry.Fast electron transfer kinetics was recognized for the [Ru(NH3)(6)](3+/2+) redox marker due to the highdoping level, while somewhat hindered kinetics was observed for thesurface-sensitive [Fe(CN)(6)](3-/4-) probe. Furthermore, the ability to electrochemically detect organiccompounds of different structural motifs, such as glucose, ascorbicacid, uric acid, tyrosine, and dopamine, was successfully verifiedand compared with commercially available screen-printed BDD electrodes.The newly developed chip-based manufacture method enables the rapidprototyping of different small-scale electrode designs and BDD microstructures,which can lead to enhanced sensor performance with capability of repeateduse.