A survey for nanodiamond features in the 3 micron spectra of Herbig Ae/Be stars

We have carried out a survey of 60 Herbig Ae/Be stars in the 3 micron wavelength region in search for the rare spectral features at 3.43 and 3.53 micron. These features have been attributed to the presence of large, hot, hydrogen-terminated nanodiamonds. Only two Herbig Ae/Be stars, HD 97048 and Elias 3-1 are known to display both these features. We have obtained medium-resolution spectra (R ~2500) with the ESO near-IR instrument ISAAC in the 3.15-3.65 micron range. In our sample, no new examples of sources with prominent nanodiamond features in their 3 micron spectra were discovered (detection rate less than 4%). We report tentative 3.53 micron detections in V921 Sco (=CD-42.11721), HD 163296 and T CrA. The sources which display the nanodiamond features are not exceptional in the group of Herbig stars with respect to disk properties, stellar characteristics, or disk and stellar activity. Moreover, the nanodiamond sources are very different from each other in terms of these parameters. We do not find evidence for a recent supernova in the vicinity of any of the nanodiamond sources. We have analyzed the PAH 3.3 micron feature and the Pfund delta hydrogen emission line, two other spectral features which occur in the 3 micron wavelength range. We reinforce the conclusion of previous authors that flared-disk systems display significantly more PAH emission than self-shadowed-disk sources. The Pf delta line detection rate is higher in self-shadowed-disk sources than in the flared-disk systems. We discuss the possible origin and paucity of the (nano)diamond features in Herbig stars. Different creation mechanisms have been proposed in the literature, amongst others in-situ and supernova-induced formation. Our data set is inconclusive in proving or disproving either formation mechanism.Comment: 22 pages, 9 figures, 5 tables; accepted for publication in A&A (acceptance date 16/06/2006

Nanodiamonds-induced effects on neuronal firing of mouse hippocampal microcircuits

Fluorescent nanodiamonds (FND) are carbon-based nanomaterials that can efficiently incorporate optically active photoluminescent centers such as the nitrogen-vacancy complex, thus making them promising candidates as optical biolabels and drug-delivery agents. FNDs exhibit bright fluorescence without photobleaching combined with high uptake rate and low cytotoxicity. Focusing on FNDs interference with neuronal function, here we examined their effect on cultured hippocampal neurons, monitoring the whole network development as well as the electrophysiological properties of single neurons. We observed that FNDs drastically decreased the frequency of inhibitory (from 1.81 Hz to 0.86 Hz) and excitatory (from 1.61 Hz to 0.68 Hz) miniature postsynaptic currents, and consistently reduced action potential (AP) firing frequency (by 36%), as measured by microelectrode arrays. On the contrary, bursts synchronization was preserved, as well as the amplitude of spontaneous inhibitory and excitatory events. Current-clamp recordings revealed that the ratio of neurons responding with AP trains of high-frequency (fast-spiking) versus neurons responding with trains of low-frequency (slow-spiking) was unaltered, suggesting that FNDs exerted a comparable action on neuronal subpopulations. At the single cell level, rapid onset of the somatic AP ("kink") was drastically reduced in FND-treated neurons, suggesting a reduced contribution of axonal and dendritic components while preserving neuronal excitability.Comment: 34 pages, 9 figure

Tunable cavity coupling of the zero phonon line of a nitrogen-vacancy defect in diamond

We demonstrate the tunable enhancement of the zero phonon line of a single nitrogen-vacancy color center in diamond at cryogenic temperature. An open cavity fabricated using focused ion beam milling provides mode volumes as small as 1.24 $\mu$m$^3$. In-situ tuning of the cavity resonance is achieved with piezoelectric actuators. At optimal coupling of the full open cavity the signal from individual zero phonon line transitions is enhanced by about a factor of 10 and the overall emission rate of the NV$^-$ center is increased by 40% compared with that measured from the same center in the absence of cavity field confinement. This result is important for the realization of efficient spin-photon interfaces and scalable quantum computing using optically addressable solid state spin qubits.Comment: 11 pages Main Article + 4 pages Supplementary Info Typos fixed from v

Enhancement of the Zero Phonon Line emission from a Single NV-Center in a Nanodiamond via Coupling to a Photonic Crystal Cavity

Using a nanomanipulation technique a nanodiamond with a single nitrogen vacancy center is placed directly on the surface of a gallium phosphide photonic crystal cavity. A Purcell-enhancement of the fluorescence emission at the zero phonon line (ZPL) by a factor of 12.1 is observed. The ZPL coupling is a first crucial step towards future diamond-based integrated quantum optical devices

Strongly inhomogeneous distribution of spectral properties of silicon-vacancy color centers in nanodiamonds

The silicon-vacancy (SiV) color center in diamond is a solid-state single photon emitter and spin quantum bit suited as a component in quantum devices. Here, we show that the SiV center in nanodiamond exhibits a strongly inhomogeneous distribution with regard to the center wavelengths and linewidths of the zero-phonon-line (ZPL) emission at room temperature. We find that the SiV centers separate in two clusters: one group exhibits ZPLs with center wavelengths within a narrow range of approximatly 730 nm to 742 nm and broad linewidths between 5 nm and 17 nm, whereas the second group comprises a very broad distribution of center wavelengths between 715 nm and 835 nm, but narrow linewidths from below 1 nm up to 4 nm. Supported by ab initio Kohn-Sham density functional theory calculations we show that the ZPL shifts of the first group are consistently explained by strain in the diamond lattice. Further, we suggest, that the second group showing the strongly inhomogeneous distribution of center wavelengths might be comprised of modified SiV centers. Whereas single photon emission is demonstrated for SiV centers of both clusters, we show that emitters from different clusters show different spectroscopic features such as variations of the phonon sideband spectra and different blinking dynamics

Electron spin resonance of nitrogen-vacancy centers in optically trapped nanodiamonds

Using an optical tweezers apparatus, we demonstrate three-dimensional control of nanodiamonds in solution with simultaneous readout of ground-state electron-spin resonance (ESR) transitions in an ensemble of diamond nitrogen-vacancy (NV) color centers. Despite the motion and random orientation of NV centers suspended in the optical trap, we observe distinct peaks in the measured ESR spectra qualitatively similar to the same measurement in bulk. Accounting for the random dynamics, we model the ESR spectra observed in an externally applied magnetic field to enable d.c. magnetometry in solution. We estimate the d.c. magnetic field sensitivity based on variations in ESR line shapes to be ~50 microTesla/Hz^1/2. This technique may provide a pathway for spin-based magnetic, electric, and thermal sensing in fluidic environments and biophysical systems inaccessible to existing scanning probe techniques.Comment: 29 pages, 13 figures for manuscript and supporting informatio