Directional surface plasmon polariton scattering by single low-index dielectric nanoparticles:simulation and experiment

Directionally scattered surface plasmon polaritons(SPPs)promote the efficiency of plasmonic devices by limiting the energy within a given spatial domain,which is one of the key issues to plasmonic devices.Benefitting from the magnetic response induced in high-index dielectric nanoparticles,unidirectionally scattered SPPs have been achieved via interference between electric and magnetic resonances excited in the particles.Yet,as the magnetic response in low-index dielectric nanoparticles is too weak,the directionally scattered SPPs are hard to detect.In this work,we demonstrate forward scattered SPPs in single low-index polystyrene(PS)nanospheres.We numerically illustrate the excitation mechanism of plasmonic induced electric and magnetic multipole modes,as well as their contributions to forward SPP scattering of single PS nanospheres.We also simulate the SPP scattering field distribution obtaining a forward-to-backward scattering intensity ratio of 50.26:1 with 1μm PS particle.Then the forward scattered SPPs are experimentally visualized by Fourier transforming the real-space plasmonic imaging to k-space imaging.The forward scattered SPPs from low-index dielectric nanoparticles pave the way for SPP direction manipulation by all types of nanomaterials.

Pore-structure regulation and heteroatom doping of activated carbon for supercapacitors with excellent rate performance and power density

Activated carbon(AC)has attracted tremendous research interest as an electrode material for supercapacitors owing to its high specific surface area,high porosity,and low cost.However,AC-based supercapacitors suffer from limited rate performance and low power density,which mainly arise from their inherently low electrical conductivity and sluggish ion dynamics in the micropores.Here,we propose a simple yet effective strategy to address the aforementioned issue by nitrogen/fluorine doping and enlarging the micropore size.During the treatment,the decomposition products of NH4F react with the carbon atoms to dope the AC with nitrogen/fluorine and simultaneously enlarge the pores by etching.The treated AC shows a higher specific surface area of 1826 m2 g^(−1)(by~15%),more micropores with a diameter around 0.93 nm(by~33%),better wettability(contact angle decreased from 120°to 45°),and excellent electrical conductivity(96 S m^(−1))compared with untreated AC(39 S m^(−1)).The as-fabricated supercapacitors demonstrate excellent specific capacitance(26 F g^(−1)at 1 A g^(−1)),significantly reduced electrical resistance(by~50%),and improved rate performance(from 46.21 to 64.39%at current densities of 1 to 20 A g^(−1)).Moreover,the treated AC-based supercapacitor achieves a maximum energy density of 25 Wh kg^(−1)at 1000 W kg^(−1)and a maximum power density of 10,875 W kg^(−1)at 15 Wh kg^(−1),which clearly outperforms pristine AC-based supercapacitors.This synergistic treatment strategy provides an effective way to improve the rate performance and power density of AC-based supercapacitors.