Physical Structure and Electrochemical Response of Diamond Graphite Nanoplatelets: From CVD Synthesis to Label-Free Biosensors


Hybrid diamond-graphite nanoplatelet (DGNP) thin films are produced and applied to label-free impedimetric biosensors for the first time, using avidin detection as a proof of concept. The DGNPs are synthesized by microwave plasma chemical vapor deposition through H-2/CH4/N-2 gas mixtures in a reproducible and rapid single-step process. The material building unit consists of an inner two-dimensional-like nanodiamond with preferential vertical alignment covered by and covalently bound to nanocrystalline graphite grains, exhibiting {111}(diamond)parallel to{0002}(graphite) epitaxy. The DGNP films morphostructural aspects are of interest for electrochemical transduction, in general, and for Faradaic impedimetric biosensors, in particular, combining enhanced surface area for biorecognition element loading and facile Faradaic charge transfer. Charge transfer rate constants in phosphate buffer saline/[Fe(CN)(6)](4)- solution are shown to increase up to 5.6 x 10(-3) cm s(-1) upon N-2 addition to DGNP synthesis. For the impedimetric detection of avidin, biotin molecules are covalently bound as avidin specific recognition elements on (3-aminopropyl)triethoxysilane-functionalized DGNP surfaces. Avidin quantification is attained within the 10-1000 mu g mL(-1) range following a logarithmic dependency. The limits of detection and of quantitation are 1.3 and 6.4 mu g mL(-1) (19 and 93 nM), respectively, and 2.3 and 13.8 mu g mL(-1) (33 and 200 nM) when considering the nonspecific response of the sensors.



subject category

Science & Technology - Other Topics; Materials Science


Santos, NF; Pereira, SO; Fernandes, AJS; Vasconcelos, TL; Fung, CM; Archanjo, BS; Achete, CA; Teixeira, SR; Silva, RF; Costa, FM

our authors


N.F.S. thanks FCT for the Ph.D. grant (SFRH/BD/90017/2012) and i3N for the grant BI/UI96/5177/2018. S.O.P. thanks i3N for the BPD grant (BPD/UI96/5808/2017). The authors acknowledge financial support from FEDER funds through the COMPETE 2020 Programme and National Funds through FCT-Portuguese Foundation for Science and Technology under the project UID/CTM/50025/2013.

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