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ABSTRACT: It is shown that the intensity of photoluminescence of nitrogen-vacancy (NV) centers in nanodiamond decreases 4-fold (with a wide spread among nanocrystals) when the surrounding temperature rises from 300 to 670 K. The effect is accompanied by a 2.7-fold decrease in the luminescence lifetime but negligible changes in the shape of the emission spectra. The heating-cooling circle is reversible. The effect is suggested to be practically useful for thermometry with nanometre spatial resolution but also stimulates deeper insight into the photophysics and photochemistry of NV-centers.
Physical Chemistry Chemical Physics 09/2010; 12(33):9751-6. · 3.57 Impact Factor
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Small 04/2009; 5(14):1649-53. · 8.35 Impact Factor
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Small 03/2009; 5(14):1649 - 1653. · 8.35 Impact Factor
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ABSTRACT: A general method for counting of obscure events in presence of detection noise is presented. The method combines the measurement data with additional information about the system under investigation to improve the measurement accuracy with the help of probability theory. As an example, we apply the method to the case of counting molecules in a microfluidic device and show in simulations that the accuracy is always better than for a thresholding approach. As a second example, we show how it can be used for photon counting at high count rates with an electron multiplying CCD (EMCCD) camera.
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ABSTRACT: In this work we quantify and characterise the effects of air-oxidation on nitrogen-vacancy defect luminescence in both high-temperature-high-pressure and detonation synthesized nanodiamonds using Raman and luminescence spectroscopies. We find that oxidation treatments result in an increased nitrogen-vacancy centre excited state lifetime from 13 ns to 25 ns and in 5-nm diamonds the intensity of this luminescence increases by at least 5-fold. At the same time, in 5-nm diamonds, short lived surface-defect related luminescence is reduced by 10-fold. Furthermore we find that air oxidation reduces the sp2 and disordered carbon fraction of nanodiamonds by up to 5-fold in 5-nm nanodiamonds. Based on these results, the authors suggest that the disordered-carbon and graphite shell of 5-nm nanodiamonds quenches nitrogen-vacancy luminescence, and that this quenching can be partially reduced by surface oxidation. These findings provide useful insights into the role of the graphite and disordered carbon shell in quenching luminescence, and have implications for the applicability of 5-nm nanodiamonds to bio- and quantum physics applications.
Diamond and Related Materials.
