Current Status and Future Challenges for Teacher Training for ESD

STEM micrographs of 99% ¹³C graphene imaged with electrons accelerated by a voltage of 100 kV. Each item in the fileset is a ZIP archive containing a single time series of consecutive frames recorded with a medium angle annular dark field detector until an ejection was observed

12C graphene, 95 kV

STEM micrographs of 99% ¹²C graphene imaged with electrons accelerated by a voltage of 95 kV. Each item in the fileset is a ZIP archive containing a single time series of consecutive frames recorded with a medium angle annular dark field detector until an ejection was observed.<br

12C graphene, 85 kV

STEM micrographs of 99% ¹²C graphene imaged with electrons accelerated by a voltage of 85 kV. Each item in the fileset is a ZIP archive containing a single time series of consecutive frames recorded with a medium angle annular dark field detector until an ejection was observed.<br

12C graphene, 100 kV

STEM micrographs of 99% ¹²C graphene imaged with electrons accelerated by a voltage of 100 kV. Each item in the fileset is a ZIP archive containing a single time series of consecutive frames recorded with a medium angle annular dark field detector until an ejection was observed.<br

12C graphene, 90 kV

STEM micrographs of 99% ¹²C graphene imaged with electrons accelerated by a voltage of 90 kV. Each item in the fileset is a ZIP archive containing a single time series of consecutive frames recorded with a medium angle annular dark field detector until an ejection was observed.<br

13C graphene, 90 kV

STEM micrographs of 99% ¹³C graphene imaged with electrons accelerated by a voltage of 90 kV. Each item in the fileset is a ZIP archive containing a single time series of consecutive frames recorded with a medium angle annular dark field detector until an ejection was observed

Size and Purity Control of HPHT Nanodiamonds down to 1 nm

High-pressure high-temperature (HPHT) nanodiamonds originate from grinding of diamond microcrystals obtained by HPHT synthesis. Here we report on a simple two-step approach to obtain as small as 1.1 nm HPHT nanodiamonds of excellent purity and crystallinity, which are among the smallest artificially prepared nanodiamonds ever shown and characterized. Moreover we provide experimental evidence of diamond stability down to 1 nm. Controlled annealing at 450 °C in air leads to efficient purification from the nondiamond carbon (shells and dots), as evidenced by X-ray photoelectron spectroscopy, Raman spectroscopy, photoluminescence spectroscopy, and scanning transmission electron microscopy. Annealing at 500 °C promotes, besides of purification, also size reduction of nanodiamonds down to ∼1 nm. Comparably short (1 h) centrifugation of the nanodiamonds aqueous colloidal solution ensures separation of the sub-10 nm fraction. Calculations show that an asymmetry of Raman diamond peak of sub-10 nm HPHT nanodiamonds can be well explained by modified phonon confinement model when the actual particle size distribution is taken into account. In contrast, larger Raman peak asymmetry commonly observed in Raman spectra of detonation nanodiamonds is mainly attributed to defects rather than to the phonon confinement. Thus, the obtained characteristics reflect high material quality including nanoscale effects in sub-10 nm HPHT nanodiamonds prepared by the presented method