title: Size and Purity Control of HPHT Nanodiamonds down to 1 nm.
abstract: 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.
authors.affiliation: Institute of Physics ASCR , Cukrovarnická 10, 162 00 Prague 6, Czech Republic.
authors.forename: Stepan
authors.initials: S
authors.lastname: Stehlik
authors.affiliation: Institute of Physics ASCR , Cukrovarnická 10, 162 00 Prague 6, Czech Republic.
authors.forename: Marian
authors.initials: M
authors.lastname: Varga
authors.affiliation: Institute of Physics ASCR , Cukrovarnická 10, 162 00 Prague 6, Czech Republic.
authors.forename: Martin
authors.initials: M
authors.lastname: Ledinsky
authors.affiliation: Institute of Physics ASCR , Cukrovarnická 10, 162 00 Prague 6, Czech Republic.
authors.forename: Vit
authors.initials: V
authors.lastname: Jirasek
authors.affiliation: Institute of Physics ASCR , Cukrovarnická 10, 162 00 Prague 6, Czech Republic.
authors.forename: Anna
authors.initials: A
authors.lastname: Artemenko
authors.affiliation: Institute of Physics ASCR , Cukrovarnická 10, 162 00 Prague 6, Czech Republic.
authors.forename: Halyna
authors.initials: H
authors.lastname: Kozak
authors.affiliation: Institute of Physics ASCR , Cukrovarnická 10, 162 00 Prague 6, Czech Republic.
authors.forename: Lukas
authors.initials: L
authors.lastname: Ondic
authors.affiliation: Physics of Nanostructured Materials, Faculty of Physics, University of Vienna , Boltzmanngasse 5, 1090 Vienna, Austria ; SUT Center for Nanodiagnostics , Vazovova 5, 812 43 Bratislava, Slovakia.
authors.forename: Viera
authors.initials: V
authors.lastname: Skakalova
authors.affiliation: Physics of Nanostructured Materials, Faculty of Physics, University of Vienna , Boltzmanngasse 5, 1090 Vienna, Austria.
authors.forename: Giacomo
authors.initials: G
authors.lastname: Argentero
authors.affiliation: Physics of Nanostructured Materials, Faculty of Physics, University of Vienna , Boltzmanngasse 5, 1090 Vienna, Austria.
authors.forename: Timothy
authors.initials: T
authors.lastname: Pennycook
authors.affiliation: Physics of Nanostructured Materials, Faculty of Physics, University of Vienna , Boltzmanngasse 5, 1090 Vienna, Austria.
authors.forename: Jannik C
authors.initials: JC
authors.lastname: Meyer
authors.affiliation: Institute of Physics ASCR , Cukrovarnická 10, 162 00 Prague 6, Czech Republic.
authors.forename: Antonin
authors.initials: A
authors.lastname: Fejfar
authors.affiliation: Institute of Physics ASCR , Cukrovarnická 10, 162 00 Prague 6, Czech Republic.
authors.forename: Alexander
authors.initials: A
authors.lastname: Kromka
authors.affiliation: Institute of Physics ASCR , Cukrovarnická 10, 162 00 Prague 6, Czech Republic ; Faculty of Electrical Engineering, Czech Technical University in Prague , Technická 2, 16627 Prague 6, Czech Republic.
authors.forename: Bohuslav
authors.initials: B
authors.lastname: Rezek