title: Non-injection synthesis of monodisperse Cu-Fe-S nanocrystals and their size dependent properties.
abstract: It is demonstrated that ternary Cu-Fe-S nanocrystals differing in composition (from Cu-rich to Fe-rich), structure (chalcopyrite or high bornite) and size can be obtained from a mixture of CuCl, FeCl3, thiourea and oleic acid (OA) in oleylamine (OLA) using the heating up procedure. This new preparation method yields the smallest Cu-Fe-S nanocrystals ever reported to date (1.5 nm for the high bornite structure and 2.7 nm for the chalcopyrite structure). A comparative study of nanocrystals of the same composition (Cu1.6Fe1.0S2.0) but different in size (2.7 nm and 9.3 nm) revealed a pronounced quantum confinement effect, confirmed by three different techniques: UV-vis spectroscopy, cyclic voltammetry and Mössbauer spectroscopy. The optical band gap increased from 0.60 eV in the bulk material to 0.69 eV in the nanocrystals of 9.3 nm size and to 1.39 eV in nanocrystals of 2.7 nm size. The same trend was observed in the electrochemical band gaps, derived from cyclic voltammetry studies (band gaps of 0.74 eV and 1.54 eV). The quantum effect was also manifested in Mössbauer spectroscopy by an abrupt change in the spectrum from a quadrupole doublet to a Zeeman sextet below 10 K, which could be interpreted in terms of the well defined energy states in these nanoparticles, resulting from quantum confinement. The Mössbauer spectroscopic data confirmed, in addition to the results of XPS spectroscopy, the co-existence of Fe(iii) and Fe(ii) in the synthesized nanocrystals. The organic shell composition was investigated by NMR (after dissolution of the inorganic core) and IR spectroscopy. Both methods identified oleylamine (OLA) and 1-octadecene (ODE) as surfacial ligands, the latter being formed in situ via an elimination-hydrogenation reaction occurring between OLA and the nanocrystal surface.
authors.affiliation: Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw, Poland. piotrbujakchem@poczta.onet.pl.
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Gabka
authors.affiliation: Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw, Poland. piotrbujakchem@poczta.onet.pl.
authors.forename: Piotr
authors.initials: P
authors.lastname: Bujak
authors.affiliation: Academic Centre for Materials and Nanotechnology, AGH University of Science and Technology, 30-059 Kraków, Poland.
authors.forename: Jan
authors.initials: J
authors.lastname: Żukrowski
authors.affiliation: Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw, Poland. piotrbujakchem@poczta.onet.pl.
authors.forename: Damian
authors.initials: D
authors.lastname: Zabost
authors.affiliation: Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw, Poland. piotrbujakchem@poczta.onet.pl.
authors.forename: Kamil
authors.initials: K
authors.lastname: Kotwica
authors.affiliation: Faculty of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland.
authors.forename: Karolina
authors.initials: K
authors.lastname: Malinowska
authors.affiliation: Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw, Poland. piotrbujakchem@poczta.onet.pl.
authors.forename: Andrzej
authors.initials: A
authors.lastname: Ostrowski
authors.affiliation: Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw, Poland. piotrbujakchem@poczta.onet.pl.
authors.forename: Ireneusz
authors.initials: I
authors.lastname: Wielgus
authors.affiliation: Institute of Physical Chemistry, Polish Academy of Science, Kasprzaka 44/52, 01-224 Warsaw, Poland.
authors.forename: Wojciech
authors.initials: W
authors.lastname: Lisowski
authors.affiliation: Institute of Physical Chemistry, Polish Academy of Science, Kasprzaka 44/52, 01-224 Warsaw, Poland.
authors.forename: Janusz W
authors.initials: JW
authors.lastname: Sobczak
authors.affiliation: Academic Centre for Materials and Nanotechnology, AGH University of Science and Technology, 30-059 Kraków, Poland and Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, 30-059 Kraków, Poland.
authors.forename: Marek
authors.initials: M
authors.lastname: Przybylski
authors.affiliation: Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw, Poland. piotrbujakchem@poczta.onet.pl.
authors.forename: Adam
authors.initials: A
authors.lastname: Pron