Capacitive Field-effect (bio-)chemical Sensors Based on Nanocrystalline Diamond Films
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1203-J17-31
Capacitive field-effect (bio-)chemical sensors based on nanocrystalline diamond films M. Bäcker1,2, A. Poghossian1,2, M. H. Abouzar1,2, S. Wenmackers3, S. D. Janssens3, K. Haenen3,4, P. Wagner3,4, and M. J. Schöning1,2 1 Institute of Nano- and Biotechnologies, Aachen University of Applied Sciences, Campus Jülich, Germany 2 Institute of Bio- and Nanosystems, Research Centre Jülich, Germany 3 Institute for Materials Research, Hasselt University, Diepenbeek, Belgium 4 Division IMOMEC, IMEC vzw., Diepenbeek, Belgium ABSTRACT Capacitive field-effect electrolyte-diamond-insulator-semiconductor (EDIS) structures with Oterminated nanocrystalline diamond (NCD) as sensitive gate material have been realized and investigated for the detection of pH, penicillin concentration, and layer-by-layer adsorption of polyelectrolytes. The surface oxidizing procedure of NCD thin films as well as the seeding and NCD growth process on a Si-SiO2 substrate have been improved to provide high pH-sensitive, non-porous thin films without damage of the underlying SiO2 layer and with a high coverage of O-terminated sites. The NCD surface topography, roughness, and coverage of the surface groups have been characterized by SEM, AFM and XPS methods. The EDIS sensors with O-terminated NCD film treated in oxidizing boiling mixture for 45 min show a pH sensitivity of about 50 mV/pH. The pH-sensitive properties of the NCD have been used to develop an EDIS-based penicillin biosensor with high sensitivity (65-70 mV/decade in the concentration range of 0.252.5 mM penicillin G) and low detection limit (5 µM). The results of label-free electrical detection of layer-by-layer adsorption of charged polyelectrolytes are presented, too.
INTRODUCTION Artificially grown diamond is a promising transducer material for chemical and biological sensing, as it is widely considered as biocompatible, displays outstanding electrical and electrochemical properties, and allows the direct coupling of biomolecules onto the diamond surface [1-5]. Among the various proposed concepts for the development of diamond-based chemical sensors and biosensors, the semiconductor field-effect platform is one of the most attractive approaches. Most of diamond-based field-effect (bio-)chemical sensors reported have been realized on a transistor structure by using hydrogen (H)-terminated polycrystalline or monocrystalline diamond films as an active transducer material [6-8]. Owing to the simplicity of the layout, the absence of a complicated encapsulation procedure and thus, an easier and cost-effective fabrication, capacitive field-effect structures are especially suited for (bio-)chemical sensor applications. Therefore, recently, we have introduced a capacitive field-effect electrolyte-diamond-insulator-semiconductor (EDIS) structure as a platform for (bio-)chemical sensing [9-11]. This work summarizes recent experimental results on the development of EDIS sensors for the detection of pH, penicillin concentration and layer-bylayer adsorbed charged macromolecules using an oxygen (
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