Unusual molecular material formed through irreversible transformation and revealed by 4D electron microscopy
Four-dimensional (4D) electron microscopy (EM) uniquely combines the high spatial resolution to pinpoint individual nano-objects, with the high temporal resolution necessary to address the dynamics of their laser-induced transformation. Here, using 4D-EM, we demonstrate the in situ irreversible transformation of individual nanoparticles of the molecular framework Fe(pyrazine)Pt(CN)4. The newly formed material exhibits an unusually large negative thermal expansion (i.e. contraction), which is revealed by time-resolved imaging and diffraction. Negative thermal expansion is a unique property exhibited by only few materials. Here we show that the increased flexibility of the metal–cyanide framework after the removal of the bridging pyrazine ligands is responsible for the negative thermal expansion behavior of the new material. This in situ visualization of single nanostructures during reactions should be extendable to other classes of reactive systems.
Additional Information© 2013 the Owner Societies. Received 7th March 2013, Accepted 9th April 2013. First published online 19 Apr 2013. This work was supported by the National Science Foundation and the Air Force Office of Scientific Research in the Gordon and Betty Moore Center for Physical Biology at the California Institute of Technology.We thank Dr Oh-Hoon Kwon for assistance during the experiment and Dr Sang Tae Park for the helpful collaboration in the heat-transfer simulations. RMV acknowledges funding from the Swiss National Science Foundation.
Published - van_der_Veen_2013.pdf
Supplemental Material - c3cp51011e.m4v
Supplemental Material - c3cp51011e.pdf
Supplemental Material - c3cp51011e_2.m4v