SiO2-coated gold nanorods (SiO2-GNRs) are of broad of interest because they have better thermal stability than uncoated GNRs.  Thermal stability of GNRs is a key issue for photothermal heating and other applications that involve exposure of GNRs to high intensity light because uncoated GNRs will revert into spherical shapes, usually at temperatures below 250 �C, in both air and in solution.  As the GNR aspect ratio decreases, the optical properties change, and the redshift in the longitudinal surface plasmon resonance (LSPR) vanishes.  Here, we report the thermal stability of SiO2-GNRs under different environments and compare with uncoated GNRs.  When measured by in situ TEM (pressure of ~1 � 10-5 Pa), SiO2-GNRs maintain their rod shape within the SiO2 shells at temperatures up to 1200 �C, which exceeds the bulk melting temperature of Au.  To the best of our knowledge, GNRs have not previously been heated to 1200 �C while maintaining their rod shape.  Uncoated GNRs maintain their shape but sublime into the vacuum at ~900 �C.  For comparison, during heating on TEM substrates in a furnace under ambient atmosphere, SiO2-GNRs become spherical at ~700 �C, while uncoated GNRs become spherical at temperatures below 400 �C.  The environment in which the samples are heated critically affects their stability, and the origin of these differences will be discussed.

Thermal stability of silica-coated and uncoated gold nanorods in different environments

248th National Meeting (2014)

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