Boron-doped diamond is a promising transducer material for numerous devices which are designed for contact with electrolytes. For optimized electron transfer the surface of diamond needs to be hydrogen terminated. Up to now H-termination of diamond is done by plasma chemical vapor deposition techniques. In this paper, we show that boron-doped diamond can be H-terminated electrochemically by applying negative voltages in acidic solutions. Electrochemical H-termination generates a clean surface with virtually no carbon-oxygen bonds (x-ray photoelectron spectroscopy), a reduced electron affinity (scanning electron microscopy), a highly hydrophobic surface (water contact angle), and a fast electron exchange with Fe(CN)6(-3/-4)(cyclic voltammetry)

In this report, the fabrication of all-nanocrystalline diamond (NCD) nanoelectrode arrays (NEAs) by e-beam lithography as well as of all-diamond nanoelectrode ensembles (NEEs) using nanosphere lithography is presented. In this way, nanostructuring techniques are combined with the excellent properties of diamond that are desirable for electrochemical sensor devices. Arrays and ensembles of recessed disk electrodes with radii ranging from 150 to 250 nm and a spacing of 10 μm have been fabricated. Electrochemical impedance spectroscopy as well as cyclic voltammetry was conducted to characterize arrays and ensembles with respect to different diffusion regimes. One outstanding advantage of diamond as an electrode material is the stability of specific surface terminations influencing the electron transfer kinetics. On changing the termination from hydrogen- to oxygen-terminated diamond electrode surface, we observe a dependence of the electron transfer rate constant on the charge of the analyte molecule. Ru(NH(3))(6)(+2/+3) shows faster electron transfer on oxygen than on hydrogen-terminated surfaces, while the anion IrCl(6)(-2/-3) exhibits faster electron transfer on hydrogen-terminated surfaces correlating with the surface dipole layer. This effect cannot be observed on macroscopic planar diamond electrodes and emphasizes the sensitivity of the all-diamond NEAs and NEEs. Thus, the NEAs and NEEs in combination with the efficiency and suitability of the selective electrochemical surface termination offer a new versatile system for electrochemical sensing.

This paper presents a method to distinguish graphene from graphite in powdered samples by analysing the Raman 2D band symmetry.

Silicon carbide has been proved as a candidate for power and high-frequency devices. In this paper, we show the application of nanocrystalline 3C-SiC as an electrochemical electrode and its electrochemical functionalization for biosensing applications. SiC electrodes show a wider potential window and lower background current than glassy carbon electrodes. The surface can be electrochemically functionalized with diazonium salts, as confirmed by electrochemical techniques and X-ray photoelectron spectroscopy. The nitrophenyl film is used as linker layer to bond DNA molecule to SiC. These results show that 3C-SiC can be an interesting transducer material for applications in electro- and bioelectrochemical applications.

In atomic force microscopy (AFM), sharp and wear-resistant tips are a critical issue. Regarding scanning electrochemical microscopy (SECM), electrodes are required to be mechanically and chemically stable. Diamond is the perfect candidate for both AFM probes as well as for electrode materials if doped, due to diamond's unrivaled mechanical, chemical, and electrochemical properties. In this study, standard AFM tips were overgrown with typically 300 nm thick nanocrystalline diamond (NCD) layers and modified to obtain ultra sharp diamond nanowire-based AFM probes and probes that were used for combined AFM-SECM measurements based on integrated boron-doped conductive diamond electrodes. Analysis of the resonance properties of the diamond overgrown AFM cantilevers showed increasing resonance frequencies with increasing diamond coating thicknesses (i.e., from 160 to 260 kHz). The measured data were compared to performed simulations and show excellent correlation. A strong enhancement of the quality factor upon overgrowth was also observed (120 to 710). AFM tips with integrated diamond nanowires are shown to have apex radii as small as 5 nm and where fabricated by selectively etching diamond in a plasma etching process using self-organized metal nanomasks. These scanning tips showed superior imaging performance as compared to standard Si-tips or commercially available diamond-coated tips. The high imaging resolution and low tip wear are demonstrated using tapping and contact mode AFM measurements by imaging ultra hard substrates and DNA. Furthermore, AFM probes were coated with conductive boron-doped and insulating diamond layers to achieve bifunctional AFM-SECM probes. For this, focused ion beam (FIB) technology was used to expose the boron-doped diamond as a recessed electrode near the apex of the scanning tip. Such a modified probe was used to perform proof-of-concept AFM-SECM measurements. The results show that high-quality diamond probes can be fabricated, which are suitable for probing, manipulating, sculpting, and sensing at single digit nanoscale.