Electrostatic self-assembly of diamond nanoparticles

The mechanism behind the self-assembly of diamond nanoparticles onto silicon dioxide surfaces is explained by simple electrostatic attraction. This electrostatic attraction can be controlled by the surface functional groups of the particles and the pH of the solution. By these simple techniques the nucleation density of diamond nanoparticles on SiO2 surfaces can be controlled up to 1012 cm−2, ideal for the seeding of high performance nanocrystalline diamond. Very low nucleation densities of discrete diamond nanoparticles are also obtainable, which is of use for single photon sources

Fluoreszenzfarbstoff und Verfahren zu seiner Herstellung

DE102013222931A1 [DE] Die Erfindung betrifft ein Verfahren zur Herstellung eines Fluoreszenzfarbstoffes (1), aufweisend die folgenden Schritte: Aufbringen (52) von Nanopartikeln (10) auf ein Substrat (20), wobei die Nanopartikel (10) Diamant enthalten oder daraus bestehen und Abscheiden (53) einer Diamantschicht (11) auf den Nanopartikeln (10) mittels Niederdrucksynthese aus einem Prozessgas, wobei die Temperatur des Substrates (20) geringer als 500 degrees centigrade ist und dem Prozessgas Silicium zugefuegt wird. Weiterhin betrifft die Erfindung einen durch das Verfahren erhaeltlichen Fluoreszenzfarbstoff

Size-dependent reactivity of diamond nanoparticles

Photonic active diamond nanoparticles attract increasing attention from a wide community for applications in drug delivery and monitoring experiments as they do not bleach or blink over extended periods of time. To be utilized, the size of these diamond nanoparticles needs to be around 4 nm. Cluster formation is therefore the major problem. In this paper we introduce a new technique to modify the surface of particles with hydrogen, which prevents cluster formation in buffer solution and which is a perfect starting condition for chemical surface modifications. By annealing aggregated nanodiamond powder in hydrogen gas, the large (>100 nm) aggregates are broken down into their core (4 nm) particles. Dispersion of these particles into water via high power ultrasound and high speed centrifugation, results in a monodisperse nanodiamond colloid, with exceptional long time stability in a wide range of pH, and with high positive zeta potential (>60 mV). The large change in zeta potential resulting from this gas treatment demonstrates that nanodiamond particle surfaces are able to react with molecular hydrogen at relatively low temperatures, a phenomenon not witnessed with larger (20 nm) diamond particles or bulk diamond surface

Formation of nano-pores in nano-crystalline diamond films

Various nano-pores in nano-crystalline diamond (NCD) thin films have been fabricated and characterized. Therefore in this work two aspects of NCD thin films synthesized by microwave assisted chemical-vapour-deposition (MWCVD) have been investigated. Firstly, the influence of CVD-growth conditions on the film morphology and chemical grain boundary composition and their impact on the mechanical properties. Second, the formation of nano-pores by selective etching of the non-diamond phase. Freestanding NCD membranes were fabricated and bulged to calculate the Young’s modulus which can reach surprisingly high values (1100 GPa) close to single crystal diamond. The presence of nano-pores was verified by electrochemical experiments where ions have been used to detect the porosity

Diamond foam electrodes for electrochemical applications

Nano-structured electrodes become promising materials for a vast number of applications such as bio-chemical sensing and supercapacitors. We introduce a new concept to generate surface enlarged diamond electrodes, so-called “diamond foam”. To obtain diamond foam electrodes, SiO2 spheres were used for heavily boron-doped (1021 cm−3) nano-crystalline diamond (B-NCD) overgrowth in a microwave plasma reactor. After overgrowth with B-NCD the SiO2 spheres were etched away with HF giving rise to diamond foam consisted of B-NCD shells accumulated on the substrate. This process has the advantage that the thickness of diamond foam can increase infinitely by repeating the growth and etching processes. Structural and electrochemical characterizations show that the diamond foam electrodes show a surface enlargement of around 40 while keeping good chemical stability as well as a diamond related structural properties. Keywords: Diamond foam, Nano-crystalline diamond, Heavily boron doping, Surface enlargement, Electrod

Diamond-Modified AFM Probes: From Diamond Nanowires to Atomic Force Microscopy-Integrated Boron-Doped Diamond Electrodes

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

Diamond nanophotonics

We demonstrate the coupling of single color centers in diamond to plasmonic and dielectric photonic structures to realize novel nanophotonic devices. Nanometer spatial control in the creation of single color centers in diamond is achieved by implantation of nitrogen atoms through high-aspect-ratio channels in a mica mask. Enhanced broadband single-photon emission is demonstrated by coupling nitrogen–vacancy centers to plasmonic resonators, such as metallic nanoantennas. Improved photon-collection efficiency and directed emission is demonstrated by solid immersion lenses and micropillar cavities. Thereafter, the coupling of diamond nanocrystals to the guided modes of micropillar resonators is discussed along with experimental results. Finally, we present a gas-phase-doping approach to incorporate color centers based on nickel and tungsten, in situ into diamond using microwave-plasma-enhanced chemical vapor deposition. The fabrication of silicon–vacancy centers in nanodiamonds by microwave-plasma-enhanced chemical vapor deposition is discussed in addition