New electrochemically improved tetrahedral amorphous carbon films for biological applications

Abstract

Carbon based materials have been frequently used to detect different biomolecules. For example high sp 3 containing hydrogen free diamond-like carbon (DLC) possesses many properties that are beneficial for biosensor applications. Unfortunately, the sensitivities of the DLC electrodes are typically low. Here we demonstrate that by introducing topography on the DLC surface and by varying its layer thickness, it is possible to significantly increase the sensitivity of DLC thin film electrodes towards dopamine. The electrode structures are characterized in detail by atomic force microscopy (AFM) and conductive atomic force microscopy (C-AFM) as well as by transmission electron microscopy (TEM) combined with electron energy loss spectroscopy (EELS). With cyclic voltammetry (CV) measurements we demonstrate that the new improved DLC electrode has a very wide water window, but at the same time it also exhibits fast electron transfer rate at the electrode/solution interface. In addition, it is shown that the sensitivity towards dopamine is increased up to two orders of magnitude in comparison to the previously fabricated DLC films, which are used as benchmarks in this investigation. Finally, it is shown, based on the cyclic voltammetry measurements that dopamine exhibits highly complex behavior on top of these carbon electrodes.

Electrochemical detection of hydrogen peroxide on platinum-containing tetrahedral amorphous carbon sensors and evaluation of their biofouling properties

“…For ta-C/Pt and Pt samples it is noted that as they have been cycled up to 1.3 V vs. Ag/AgCl during the cleaning step it is likely that there were some oxide species present on the surface even though the capacitance was determined from dataset where the cycling was not extended into the oxide formation region. Thus all the values in Table 2 correspond to pseudocapacitance as they probably include also some contribution from faradaic reactions [24], [45]. Especially, for Pt sample there were most likely considerable faradaic contributions that resulted in large error for the pseudocapacitance.…”

“…The values of average roughness are in the range of 1.15±0.14, 1.08±0.28 and 0.43±0.11 nm for ta-C, ta-C/Pt and Pt samples, respectively ( Table 1). The former, larger values for ta-C and ta-C/Pt derive from the fact that ta-C follows the topography of the underlying Ti layer as shown in [24]. Ti layer is used here as an adhesion promoter for undoped and Pt-doped ta-C.…”

“…In addition, current-voltage spectroscopy (Figure 2) demonstrated that electrical conduction mechanism through both ta-C containing samples can be described in terms of space-chargelimited (SCL) currents theory [24], [37], [38] with the presence of several levels of monoenergetic traps. Thus, current-voltage curves plotted in log-log coordinates (Figure 2b) contain Ohm's law regions (slope is one) and several regions with the slope equaled to two, which relate to presence of traps.…”

“…Water window in H2SO4 and the double-layer capacitance have been previously determined for pure ta-C [24]. Pt sample exhibits typical Pt features with clear peaks for hydrogen adsorption and desorption as well as for Pt surface oxidation and reduction [44].…”

“…On the other hand, adsorption of bovine albumin serum (BSA) is suggested to be favored on ta-C when compared to other types of DLC with higher hydrogen content and lower sp 3 fraction [23]. With its large water window (3.7 V in H2SO4 and 3 V in PBS [24]) ta-C is a feasible material for electrochemical detection of various analytes in aqueous media [25]. However, in our experience pure ta-C surfaces typically perform poorly in detecting H2O2.…”