Silicon cuboid nanoantenna with simultaneous large Purcell factor for electric dipole,magnetic dipole and electric quadrupole emission

The Purcell effect is commonly used to increase the spontaneous emission rate by modifying the local environment of a light emitter.Here,we propose a silicon dielectric cuboid nanoantenna for simultaneously enhancing electric dipole(ED),magnetic dipole(MD)and electric quadrupole(EQ)emission.We study the scattering cross section,polarization charge distribution,and electromagnetic field distribution for electromagnetic plane wave illuminating the silicon dielectric cuboid nanoantenna,from which we have identified simultaneous existence of ED,MD and EQ resonance modes in this nanoantenna.We have calculated the Purcell factor of ED,MD and EQ emitters with different moment orientations as a function of radiation wavelength by placing these point radiation source within the nanoantenna,respectively.We find that the resonances wavelengths of the Purcell factor spectrum are matching with the resonance modes in the nanoan-tenna.Moreover,the maximum Purcell factor of these ED,MD and EQ emitters is 18,150 and 118 respectively,occur-ring at the resonance wavelength of 475,750,and 562 nm,respectively,all within the visible range.The polarization charge distribution features allow us to clarify the excitation and radiation of these resonance modes as the physical ori-gin of large Purcell factor simultaneously occurring in this silicon cuboid nanoantenna.Our theoretical results might help to deeply explore and design the dielectric nanoantenna as an ideal candidate to enhance ED,MD and EQ emission simultaneously with very small loss in the visible range,which is superior than the more popular scheme of plasmonic nanoantenna.

3D printing of plasmonic nanofocusing tip enabling high resolution,high throughput and high contrast optical near-field imaging

Scanning near-field optical microscopy(SNOM)offers a means to reach a fine spatial resolution down to~10 nm,but unfortunately suffers from low transmission efficiency of optical signal.Here we present design and 3D printing of a fiber-bound polymer-core/gold-shell spiral-grating conical tip that allows for coupling the inner incident optical signal to the outer surface plasmon polariton with high efficiency,which then adiabatically transport,squeeze,and interfere constructively at the tip apex to form a plasmonic superfocusing spot with tiny size and high brightness.Numerical simulations and optical measurements show that this specially designed and fabricated tip has 10%transmission efficiency,~5 nm spatial resolution,20 dB signal-to-noise ratio,and 7000 pixels per second fast scanning speed.This high-resolution,high throughput,and high contrast SNOM would open up a new frontier of high spatial-temporal resolution detecting,imaging,and monitoring of single-molecule physical,chemical,and biological systems,and deepen our understanding of their basic science in the single-molecule level.

Cardiomyocyte-targeted anti-inflammatory nanotherapeutics against myocardial ischemia reperfusion (IR) injury

Myocardial ischemia reperfusion(IR)injury is closely related to the overwhelming inflammation in the myocardium.Herein,cardiomyocyte-targeted nanotherapeutics were developed for the reactive oxygen species(ROS)-ultrasensitive co-delivery of dexamethasone(Dex)and RAGE small interfering RNA(siRAGE)to attenuate myocardial inflammation.PPTP,a ROSdegradable polycation based on PGE2-modified,PEGylated,ditellurium-crosslinked polyethylenimine(PEI)was developed to surface-decorate the Dex-encapsulated mesoporous silica nanoparticles(MSNs),which simultaneously condensed siRAGE and gated the MSNs to prevent the Dex pre-leakage.Upon intravenous injection to IR-injured rats,the nanotherapeutics could be efficiently transported into the inflamed cardiomyocytes via PGE2-assisted recognition of over-expressed E-series of prostaglandin(EP)receptors on the cell membranes.Intracellularly,the over-produced ROS degraded PPTP into small segments,promoting the release of siRAGE and Dex to mediate effective RAGE silencing(72%)and cooperative antiinflammatory effect.As a consequence,the nanotherapeutics notably suppressed the myocardial fibrosis and apoptosis,ultimately recovering the systolic function.Therefore,the current nanotherapeutics represent an effective example for the codelivery and on-demand release of nucleic acid and chemodrug payloads,and might find promising utilities toward the synergistic management of myocardial inflammation.