Optical properties of quantum dots can be drastically changed by surface plasmons excited in neighboring metallic nanostructures. Here we investigated the photoluminescence enhancement dependence of single quantum dots on the separation distance with Au microplates by a single particle spectroscopy. The quantum dot–Au microplate hybrid structures provided a photoluminescence enhancement of up to ∼16-fold when the separation distance between the surface of Au microplate and the center of QD was 18 ± 1.9 nm. Accordingly, the lifetime of those quantum dots was shortened compared with the ones on glass plates directly. Theoretical simulation revealed that the variation of photoluminescence enhancement was closely dependent on the separation distance between the QD and the Au microplate, in good agreement with the experimental results.

We report on a novel method to fabricate single, multiple and large-area high-density ensembles of nitrogen vacancy (NV) color centers in synthetic type Ib bulk diamond by femtosecond laser illumination. Electron beams generated in propagation of intense infrared laser pulses in air sputtered on a diamond sample under high temperature aroused by the laser illumination, creating NV color centers. Typical photoluminescence (PL) spectra of NV centers could be observed on the illuminated spots. Photon streams from individual photoluminescent points exhibited anti-bunching effect by the second-order correlation measurement, evidencing single and multiple photon-emitters around the laser illuminated spots.

Lanthanide doped upconversion nanoparticles reveal enormous potential for biomedical applications. However, they are limited by low upconversion efficiency. In this paper, we demonstrate tip-enhanced upconversion luminescence (UCL) from a single Yb3+–Er3+-codoped NaYF4 nanoparticle with a maximum enhancement factor of 11 by the plasmonic effect, which is a solution for improving the conversion efficiency and will become a potential technique for the applications in sensitive imaging and detection via speeding up both the absorption and the emission processes of lanthanide doped upconversion nanoparticles. By investigating the optical properties of the tip-enhanced UCL at 550 and 660 nm separately in Yb3+–Er3+-codoped NaYF4 nanoparticles, we observe that the gold-coated tip influences the upconversion process in Yb3+–Er3+-codoped NaYF4 particles by improving the reception and the transmission of incident electromagnetic fields.

We theoretically investigate the plasmonic coupling in heterogenous Al-Ag nanorod dimer. A pronounced Fano dip is found in the extinction spectrum produced by the destructive interference between the bright dipole mode from a short Al nanorod and the dark quadrupole mode from a long Ag nanorod nearby. This Fano resonance can be widely tuned in both wavelength and amplitude by varying the rod dimensions, the separation distance and the local dielectric environment. The Al-Ag heterogeneous nanorod dimer shows a high sensitivity to the surrounding environment with a local surface plasmon resonance figure of merit of 7.0, which enables its promising applications in plasmonic sensing and detection.

The localized surface plasmon resonance properties of Al and Alcore/Al2O3shell nanosphere dimers with Al and Al core nanosphere radii of 20 nm and Al2O3 shell of 2 nm in the deep-ultraviolet region have been studied using the finite difference time domain method. The extinction spectra and the electric field distribution profiles of the two dimers for various gap distances between two individual nanospheres are compared with those of the corresponding monomers to reveal the extent of plasmon coupling. It is found that with the interparticle distance decreasing, a strong plasmon coupling between two Al or Alcore/Al2O3shell nanospheres is observed accompanied by a significant red shift in the extinction spectra at the parallel polarization direction of the incident light related to the dimer axis, while for the case of the perpendicular polarization direction, a weak plasmon coupling arises characterized by a slight blue shift in the extinction spectra. The electric field distribution profiles show that benefiting from the dielectric Al2O3 shell, the gap distance of Alcore/Al2O3shell nanosphere dimers can be tailored to < 1 nm scale and results in a very high electric field enhancement. The estimated surface-enhanced Raman scattering enhancement factors suggests that the Alcore/Al2O3shell nanosphere dimers with the gap of < 1 nm gave rise to an enhancement as high as 8.1 × 107 for interparticle gap = 0.5 nm. Our studies reveal that the Alcore/Al2O3shell nanosphere dimers may be promising substrates for surface-enhanced spectroscopy in the deep-ultraviolet region.