In the following study we investigate the dynamics of high aspect ratio nanowires held in a single gradient force optical trap in an overdamped environment. Power spectrum analysis performed on the stochastic trajectory of the optically trapped nanowires indicate that the motion of these nanowires shows characteristics of underdamped motion, where a broad resonance peak is present in the power spectrum of amplitude fluctuations under certain conditions. The resonance occurs when the nanowires are trapped at a height of 50 μm from the cover slip of the sample chamber. The emergence of a resonance peak in the power spectrum could be attributed to the non-conservative motion of nanowires being nonspherical, thus creating a bias towards cyclic motion as examined theoretically by Simpson and Hanna [12].
We present a study of the trapping properties of Au nanorods of different aspect ratios in an optical tweezers and comparison with other characterization techniques like transmission electron microscope (TEM) imaging and dynamic light scattering (DLS). This study provides information on the dynamics and orientation of Au nanorods inside an optical trap based on a time study of their localised surface plasmon resonance (LSPR) features. The results indicate that the orientation of the Au nanorods trapped in our optical tweezers varies with time and LSPR spectra can provide information on the angle of the nanorod with respect to the direction of propagation of the trapping laser.
We present a novel method for spatial mapping of the luminescent properties of single optically trapped semiconductor
nanowires by combing dynamic optical tweezers with micro-photoluminescence. The technique involves the use of a
spatial light modulator (SLM) to control the axial position of the trapping focus relative to the excitation source and
collection optics. When a nanowire is held in this arrangement, scanning the axial position of the trapping beam enables
different sections of the nanowire axis to be probed. In this context we consider the axial resolution of the luminescence
mapping and optimization of the nanowire trapping by spherical aberration correction.
We report on the dynamics of micro-photoluminescence of single InP semiconductor nanowires trapped in a gradient
force optical tweezers. Nanowires studied were of zinc blende, wurtzite or mixed phase crystal poly-types and ranged in
length from one to ten micrometers. Our results show that the band-edge emission from trapped nanowires exhibits a
quenching of the initial intensity with a characteristic time scale of a few seconds and an associated spectral red shift is
also observed in the mixed phase nanowires.
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