Probing electron transport in plasmonic molecular junctions with two-photon luminescence spectroscopy
Zhang Qiang,
Liu Danjun,
Ren Qun,
Panoiu Nicolae C.,
Lin Li,
Ye Jian,
Huang Yang,
Liu Shao-Ding,
Leung Chi Wah,
Lei Dangyuan
Affiliations
Zhang Qiang
Department of Physics and Optoelectronics, and Key Lab of Advanced Transducers and Intelligent Control System of Ministry of Education, Taiyuan University of Technology, Taiyuan030024, China
Liu Danjun
Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong999077, China
Ren Qun
Department of Electronic and Electrical Engineering, University College London, Torrington Place, WC1E 7JE, London, UK
Panoiu Nicolae C.
Department of Electronic and Electrical Engineering, University College London, Torrington Place, WC1E 7JE, London, UK
Lin Li
State Key Laboratory of Oncogenes and Related Genes, School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai200030, China
Ye Jian
State Key Laboratory of Oncogenes and Related Genes, School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai200030, China
Huang Yang
School of Science, Jiangsu Provincial Research Center of Light Industrial Optoelectronic Engineering and Technology, Jiangnan University, Wuxi214122, China
Liu Shao-Ding
Department of Physics and Optoelectronics, and Key Lab of Advanced Transducers and Intelligent Control System of Ministry of Education, Taiyuan University of Technology, Taiyuan030024, China
Leung Chi Wah
Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong999077, China
Lei Dangyuan
Department of Materials Science and Engineering, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong999077, China
Plasmonic core–molecule–shell (CMS) nanojunctions provide a versatile platform for studying electron transport through conductive molecules under light excitation. In general, the impact of electron transport on the near-field response of CMS nanojunctions is more prominent than on the far-field property. In this work, we use two-photon luminescence (TPL) spectroscopy to probe the effect of electron transport on the plasmonic properties of gold CMS nanojunctions. Theoretical calculations show that the TPL response of such nanojunctions is closely related to the near-field enhancement inside the metal regions, and can be strongly affected by the electron transport through the embedded molecules. TPL excitation spectroscopy results for three CMS nanojunctions (0.7, 0.9 and 1.5 nm junction widths) reveal no perceivable contribution from their low-energy plasmon modes. This observation can be well explained by a quantum-corrected model, assuming significant conductance for the molecular layers and thus efficient charge transport through the junctions. Furthermore, we explore the charge transport mechanism by investigating the junction width dependent TPL intensity under a given excitation wavelength. Our study contributes to the field of molecular electronic plasmonics through opening up a new avenue for studying quantum charge transport in molecular junctions by non-linear optical spectroscopy.
