Sensing the Moving Direction, Position, Size, and Material Type of Nanoparticles with the Two-Photon-Induced Luminescence of a Single Gold Nanorod

Abstract

We propose a numerical method to evaluate the two-photon-induced luminescence (TPL) of single gold nanorods (GNRs). The validity of this method is confirmed by the cos4 α dependence of the TPL of single GNRs on the polarization angle α, which is in good agreement with experimental observations. As comparing with their linear optical properties such as scattering and absorption, the TPL of a single GNR is found to be more sensitive to the change of the surrounding environment. This property is exploited to detect nanoparticles (NPs) approaching the GNR from a far place. By monitoring the evolution of the TPL on the distance between the GNR and a NP, it is possible to extract various information on the NP, including the moving direction, position, size, and material type. For GNRs whose extinction is dominated by absorption, the response and sensitivity are found to depend strongly on their sizes. The detection of the nonlinear optical responses of GNRs may find potential applications in the fields of nanophotonics and biophotonics.

Numerical study of nanoparticle sensors based on the detection of the two-photon-induced luminescence of gold nanorod antennas

“…Very recently, we have established a numerical method to evaluate the TPL emitted by a single GNR [7] and the method can be easily extended to the calculation of the TPL emitted by an antenna. Basically, the TPL emitted by the system composed of an antenna and a NS can be expressed as follows [7]:…”

“…Basically, the TPL emitted by the system composed of an antenna and a NS can be expressed as follows [7]:…”

“…This unique feature has been employed to fabricate sensors of different types [7][8][9][10]. The underlying physical mechanism is the existence of strongly localized electric field near the surface of the GNR.…”

“…Very recently, we demonstrated the existence of a size-dependent competition between SHG and TPL in GNRs [17]. In addition, we proposed the use of the TPL emitted by a single GNR to sense NPs approaching the GNR from far places [7]. From the viewpoint of practical application, however, the sensitivity and feasibility of the sensor need to be improved significantly.…”

“…For the sensors based on single GNRs, the TPL of the system depends not only on the size of the NP but also on its position. Therefore, it is difficult to extract the information on the size of the NP without knowing the position of the NP [7]. In comparison, the stable trapping of NPs achieved in antennas makes it possible to estimate the sizes of NPs.…”