Spaser Based on Dark Quadrupolar Mode of a Single Metallic Nanodisk

A spaser based on dark quadrupolar mode of a single metallic nanodisk coated with a layer of gain media is studied theoretically. The absorption efficiency of the metallic structure, the gain efficiency of the gain media, and the scattering efficiency of the whole nanosystem are calculated separately. It is found that the ratio of the absorption and the scattering intensities (RAS) of the dark quadrupolar mode depends strongly on the gain coefficient, which increases from 0.8 to 4.39 with gain coefficient reaches the threshold, by contrast the bright dipolar mode keeps its RAS unchanged at 0.16. This is attributed to that the gain media mainly amplifies quadrupolar eigenmode composition of the dark quadrupolar mode, thus the scattering loss caused by dipolar eigenmode composition is under effective control, which changes the RAS and leads to super low-threshold spaser. Our works may benefit the achievement of spaser system with low scattering loss.

     

Hematopoietic stem cells: multiparameter regulation

Hematopoietic stem cells (HSCs) are capable to self-renew with multi-potency which generated much excitement in clinical therapy. However, the main obstacle of HSCs in clinical application was insufficient number of HSCs which were derived from either bone marrow, peripheral blood or umbilical cord blood. This review briefly discusses the indispensable utility of growth factors and cytokines, stromal cells, extracellular matrix, bionic scaffold and microenvironment aiming to control the hematopoiesis in all directions and provide a better and comprehensive understanding for in vitro expansion of hematopoietic stem cells.     

Fano Resonance of Nanocrescent for the Detection of Single Molecules and Single Nanoparticles

This paper reports a theoretical study on the Fano resonance of a 3D nanocrescent and its application in single molecular detection. The resonance wavelength changes with the crescent radius, gap width and thickness. The Fano resonance is attributed to the interference between the quadrupolar mode supported by the horizontal crescent and the quadrupolar mode supported by the nanotip oscillating along the height direction. The Fano resonance is highly sensitive to a nanoparticle trapped by the nanocrescent. The wavelength shift is larger than 0.5 nm when a single protein nanoparticle with radius only of 1.25 nm is trapped. For a protein with radius of 0.3 nm, the wavelength shift is still larger than 0.03 nm, over the detection limit (10^?5 nm) by 3 orders in the magnitude, which indicates that the nanocrescent can be used to detect small molecule with several atoms.