ja409754v_si_001.pdf (2.03 MB)
Copper Sulfide Nanocrystals with Tunable Composition by Reduction of Covellite Nanocrystals with Cu+ Ions
journal contribution
posted on 2013-11-20, 00:00 authored by Yi Xie, Andreas Riedinger, Mirko Prato, Alberto Casu, Alessandro Genovese, Pablo Guardia, Silvia Sottini, Claudio Sangregorio, Karol Miszta, Sandeep Ghosh, Teresa Pellegrino, Liberato MannaPlatelet-shaped
copper sulfide nanocrystals (NCs) with tunable
Cu stoichiometry were prepared from Cu-rich covellite (Cu1.1S) nanoplates through their reaction with a Cu(I) complex ([Cu(CH3CN)4]PF6) at room temperature. Starting
from a common sample, by this approach it is possible to access a
range of compositions in these NCs, varying from Cu1.1S
up to Cu2S, each characterized by a different optical response:
from the metallic covellite, with a high density of free carriers
and strong localized surface plasmon resonance (LSPR), up to Cu2S NCs with no LSPR. In all these NCs the valency of Cu in
the lattice stays always close to +1, while the average −1
valency of S in covellite gradually evolves to −2 with increasing
Cu content; i.e., sulfur is progressively reduced. The addition of
copper to the starting covellite NCs is similar to the intercalation
of metal species in layered transition metal dichalcogenides (TMDCs);
i.e., the chalcogen–chalcogen bonds holding the layers are
progressively broken to make room for the intercalated metals, while
their overall anion sublattice does not change much. However, differently
from the TMDCs, the intercalation in covellite NCs is sustained by
a change in the redox state of the anion framework. Furthermore, the
amount of Cu incorporated in the NCs upon reaction is associated with
the formation of an equimolar amount of Cu(II) species in solution.
Therefore, the reaction scheme can be written as: Cu1.1S + 2γCu(I) → Cu1.1+γS + γCu(II).