Tuning Plasmonic Enhancement of Single Nanocrystal Upconversion Luminescence by Varying Gold Nanorod Diameter

• Published in: Small (Weinheim an der Bergstrasse, Germany) Germany), 2017-09, Vol.13 (36), p.n/a
• Main Authors: Xue, Yingxian, Ding, Chengjie, Rong, Youying, Ma, Qiang, Pan, Chengda, Wu, E, Wu, Botao, Zeng, Heping
• Format: Article
• Language: English
• Subjects: Absorption; Absorption cross sections; atomic force microscope probe manipulation; Atomic force microscopy; Erbium; Excitation; Extinction; Finite difference method; Gold; gold nanorod; lanthanide; Luminescence; Nanocrystals; Nanorods; Nanotechnology; plasmonic enhancement; Scattering; Upconversion
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.201701155

Plasmonic enhancement induced by metallic nanostructures is an effective strategy to improve the upconversion efficiency of lanthanide‐doped nanocrystals. It is demonstrated that plasmonic enhancement of the upconversion luminescence (UCL) of single NaYF4:Yb3+/Er3+/Mn2+ nanocrystal can be tuned by tailoring scattering and absorption cross sections of gold nanorods, which is synthesized wet chemically. The assembly of the single gold nanorod and single upconversion nanocrystal is achieved by the atomic force microscope probe manipulation. By selecting two kinds of gold nanorods with similar longitudinal surface plasmon resonance wavelength but different diameters (27.3 and 46.7 nm), which extinction spectra are separately dominant by the absorption and scattering, the maximum UCL enhancement by a factor of 110 is achieved with the 46.7 nm‐diameter gold nanorod, while it is 19 for the nanorod with the diameter of 27.3 nm. Such strong enhancement with the larger gold nanorod is due to stronger scattering ability and greater extent of the near‐field enhancement. The enhanced UCL shows a strong dependence on the excitation polarization relative to the nanorod long axis. Time‐resolved measurements and finite‐difference time‐domain simulations unveil that both excitation and emission processes of UCL are accelerated by the nanorod plasmonic effect. Plasmonic enhancement of upconversion luminescence in single nanocrystal–Au nanorod dimers formed by atomic force microscope probe manipulation is demonstrated. By tailoring diameters of the nanorods with the similar plasmonic resonant wavelength to make scattering dominate the nanorod extinction, 110‐fold luminescence enhancement is achieved. Experimental and theoretical analyses indicate that excitation and emission processes of upconversion are all accelerated by nanorod plasmonic effect.