NH_(2)-MIL-53(Al)for Simultaneous Removal and Detection of Fluoride Anions

To address the limitations of the separate fluoride removal or detection in the existing materials,herein,amino-decorated metal organic frameworks NH_(2)-MIL-53(Al)have been succinctly fabricated by a sol-hydrothermal method for simultaneous removal and determination of fluoride.As a consequence,the proposed NH_(2)-MIL-53(Al)features high uptake capacity(202.5 mg/g)as well as fast adsorption rate,being capable of treating 5 ppm of fluoride solution to below the permitted threshold in drinking water within 15 min.Specifically,the specific binding between fluoride and NH_(2)-MIL-53(Al)results in the release of fluorescent ligand NH2-BDC,conducive to the determination of fluoride via a concentration-dependent fluorescence enhancement effect.As expected,the resulting NH_(2)-MIL-53(Al)sensor exhibits selective and sensitive detection(with the detection limit of 0.31μmol/L)toward fluoride accompanied with a wide response interval(0.5-100μmol/L).More importantly,the developed sensor can be utilized for fluoride detection in practical water systems with satisfying recoveries from 89.6% to 116.1%,confirming its feasibility in monitoring the practical fluoride-contaminated waters.

Antenna-assisted picosecond control of nanoscale phase transition in vanadium dioxide

Nanoscale devices in which the interaction with light can be configured using external control signals hold great interest for next-generation optoelectronic circuits.Materials exhibiting a structural or electronic phase transition offer a large modulation contrast with multi-level optical switching and memory functionalities.In addition,plasmonic nanoantennas can provide an efficient enhancement mechanism for both the optically induced excitation and the readout of materials strategically positioned in their local environment.Here,we demonstrate picosecond all-optical switching of the local phase transition in plasmonic antenna-vanadium dioxide(VO_(2))hybrids,exploiting strong resonant field enhancement and selective optical pumping in plasmonic hotspots.Polarization-and wavelength-dependent pump–probe spectroscopy of multifrequency crossed antenna arrays shows that nanoscale optical switching in plasmonic hotspots does not affect neighboring antennas placed within 100 nm of the excited antennas.The antenna-assisted pumping mechanism is confirmed by numerical model calculations of the resonant,antenna-mediated local heating on a picosecond time scale.The hybrid,nanoscale excitation mechanism results in 20 times reduced switching energies and 5 times faster recovery times than a VO_(2) film without antennas,enabling fully reversible switching at over two million cycles per second and at local switching energies in the picojoule range.The hybrid solution of antennas and VO_(2) provides a conceptual framework to merge the field localization and phase-transition response,enabling precise,nanoscale optical memory functionalities.

Hybrid photonic-plasmonic cavities based on the nanoparticle-on-a-mirror configuration

Hybrid photonic-plasmonic cavities have emerged as a new platform to increase light-matter interaction capable to enhance the Purcell factor in a singular way not attainable with either photonic or plasmonic cavities separately.In the hybrid cavities proposed so far,the plasmonic element is usually a metallic bow-tie antenna,so the plasmonic gap—defined by lithography-is limited to minimum values of several nanometers.Nanoparticle-on-a-mirror(NPoM)cavities are far superior to achieve the smallest possible mode volumes,as plasmonic gaps smaller than 1 nm can be created.Here,we design a hybrid cavity that combines an NPoM plasmonic cavity and a dielectric-nanobeam photonic crystal cavity operating at transverse-magnetic polarization.The metallic nanoparticle can be placed very close(<1 nm)to the upper surface of the dielectric cavity,which acts as a low-reflectivity mirror.We demonstrate through numerical calculations of the local density of states that this hybrid plasmonic-photonic cavity exhibits quality factors𝑄above 10^(3) and normalized mode volumes𝑉down to 10^(−3),thus resulting in high Purcell factors(F_(P)≈10^(5)),while being experimentally feasible with current technology.Our results suggest that hybrid cavities with sub-nanometer gaps should open new avenues for boosting light-matter interaction in nanophotonic systems.