TY - JOUR
T1 - Energy landscape of self-assembled superlattices of PbSe nanocrystals
AU - Quan, Zewei
AU - Wu, Di
AU - Zhu, Jinlong
AU - Evers, Wiel H.
AU - Boncella, James M.
AU - Siebbeles, Laurens D.A.
AU - Wang, Zhongwu
AU - Navrotsky, Alexandra
AU - Xu, Hongwu
PY - 2014/6/24
Y1 - 2014/6/24
N2 - Self-assembly of nanocrystals (NCs) into superlattices is an intriguing multiscale phenomenon that may lead to materials with novel collective properties, in addition to the unique properties of individual NCs compared with their bulk counterparts. By using different dispersion solvents, we synthesized three types of PbSe NC superlattices - body-centered cubic (bcc), body-centered tetragonal (bct), and face-centered cubic (fcc) - as confirmed by synchrotron small-angle X-ray scattering. Solution calorimetric measurements in hexane show that the enthalpy of formation of the superlattice from dispersed NCs is on the order of -2 kJ/mol. The calorimetric measurements reveal that the bcc superlattice is the energetically most stable polymorph, with the bct being 0.32 and the fcc 0.55 kJ/mol higher in enthalpy. This stability sequence is consistent with the decreased packing efficiency of PbSe NCs from bcc (17.2%) to bct (16.0%) and to fcc (15.2%). The small enthalpy differences among the three polymorphs confirm a closely spaced energy landscape and explain the ease of formation of different NC superlattices at slightly different synthesis conditions.
AB - Self-assembly of nanocrystals (NCs) into superlattices is an intriguing multiscale phenomenon that may lead to materials with novel collective properties, in addition to the unique properties of individual NCs compared with their bulk counterparts. By using different dispersion solvents, we synthesized three types of PbSe NC superlattices - body-centered cubic (bcc), body-centered tetragonal (bct), and face-centered cubic (fcc) - as confirmed by synchrotron small-angle X-ray scattering. Solution calorimetric measurements in hexane show that the enthalpy of formation of the superlattice from dispersed NCs is on the order of -2 kJ/mol. The calorimetric measurements reveal that the bcc superlattice is the energetically most stable polymorph, with the bct being 0.32 and the fcc 0.55 kJ/mol higher in enthalpy. This stability sequence is consistent with the decreased packing efficiency of PbSe NCs from bcc (17.2%) to bct (16.0%) and to fcc (15.2%). The small enthalpy differences among the three polymorphs confirm a closely spaced energy landscape and explain the ease of formation of different NC superlattices at slightly different synthesis conditions.
KW - Ligand interaction
KW - PbSe nanocrystal superlattices
KW - Thermodynamics
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U2 - 10.1073/pnas.1408835111
DO - 10.1073/pnas.1408835111
M3 - Article
AN - SCOPUS:84903485503
SN - 0027-8424
VL - 111
SP - 9054
EP - 9057
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 25
ER -