Tuning the plasmonic heating of gold nanorod by combining the effect of dielectric coating and aspect ratio: a theoretical study

¹ The Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology,Xi’an Jiaotong University, Xi’an 710049, P.R. China
² Non-equilibrium Condensed Matter and Quantum Engineering Laboratory, The Key Laboratory of Ministry of Education,School of Science, Xi’an Jiaotong University, Xi’an 710049, P.R. China

^a e-mail: nanoptzj@163.com

Received: 23 December 2014
Revised: 24 February 2015
Accepted: 10 March 2015
Published online: 24 April 2015

Abstract

The plasmonic heating of dielectric coated gold nanorod has been studied under steady state conditions and quasi-static approximation. Theoretical calculations indicate that the maximum local heating of gold nanorod can be tuned into infrared region by dielectric coating. At resonance wavelength, increasing the shell thickness always leads to the local temperature fade down, whereas at off-resonance wavelength, the change of the local temperature becomes non-monotonic for large dielectric constant of the shell. The dielectric coating dependent temperature increase is also strongly affected by the aspect ratio of the gold nanorod. Because of the competition between transverse and longitudinal plasmonic absorption, decreasing the incident wavelength from the longitudinal resonance to transverse resonance leads to the “hot spot” of temperature transfers from the position corresponding to the nanorod with large aspect ratio to the position with small aspect ratio. When the shell thickness is fixed, increasing the dielectric constant of the coating shell leads to the maximum local temperature fade down and left shifts to the position corresponding to the nanorod with small aspect ratio. This joint effect from multiple factors including aspect ratio, shell thickness and shell dielectric constant enriches the tunability of plasmonic heating of metallic nanostructure.