pH sensitivity of nanocrystalline diamond films

Abstract

The pH‐sensitive properties of hydrogen‐ and oxygen‐terminated nanocrystalline diamond (NCD) films have been investigated using a field‐effect‐based capacitive electrolyte‐diamond‐insulator‐semiconductor (EDIS) structure as transducer. The NCD thin films (100–500 nm) were grown on p‐Si–SiO2 substrates by microwave plasma‐enhanced chemical vapour deposition. The electrochemical characterisation of EDIS sensors with NCD films of different thicknesses has been performed in buffer solutions of pH 3 to pH 11 by means of capacitance–voltage and constant–capacitance methods. The developed EDIS sensors with O‐terminated NCD surfaces show an average pH‐sensitivity of 38 mV/pH. A slightly smaller pH‐sensitivity of 29–36 mV/pH was observed for the EDIS structure with H‐terminated NCD surfaces. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Penicillin detection with nanocrystalline‐diamond field‐effect sensor

“…%, as calculated by dividing the relevant peak areas in the recorded spectra by appropriate bulk atomic sensitivity factors. These values are comparable to those that have been reported in [16,25] . 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 Figure 2 SEM (a) and TEM (b) picture of the surface morphology of a 100 nm thick NCD film and cross-section of layer structure, respectively.…”

“…The EDIS sensors show an average pH sensitivity of 40-45 mV/pH in the range of pH 4 to pH 10. A mechanism of the pH sensitivity of O-terminated NCD surfaces has been discussed in [9,16] by using the wellknown site-binding model (see, e.g. [18]).…”

“…Recently, we have introduced a field-effect capacitive EDIS (electrolytediamond-insulator-semiconductor) structure as a platform for (bio-)chemical sensing [16]. In contrast to transistor structures, EDIS sensors are simple in layout, and easy and cost-effective in fabrication.…”

“…In addition, alternating current (AC) measurements with the EDIS structure are often more informative than static direct current (DC) measurements with the transistor structure. A feasibility of this platform has exemplarily been demonstrated by realising a pH-sensitive EDIS sensor with nanocrystalline diamond (NCD) films [16]. In addition, the possibility of label-free electrical detection of charged macromolecules with the EDIS structure has been demonstrated using layer-by-layer adsorbed polyelectrolyte multilayers as model system [17].…”

Diamond‐based DNA sensors: surface functionalization and read‐out strategies

“…EDIS sensors can be operated in 'ConCap' mode, keeping the capacitance of the sensor constant using a feedbackcircuit, while measuring the voltage change [122]. With this configuration, a pH-sensor [123] and a capacitive penicillin biosensor with high sensitivity (70 mV/decade) and low detection limit (5 µM) [124] have been realized. In principle, sandwich-structures of undoped diamond deposited on top of doped diamond would have even better properties: the field effect would arise in the underlying semiconducting diamond (instead of Si).…”