Plasmonic enhancement and polarization dependence of nonlinear upconversion emissions from single gold nanorod@SiO_(2)@CaF2:Yb^(3+),Er^(3+)hybrid core–shell–satellite nanostructures

Lanthanide-doped upconversion nanocrystals(UCNCs)have recently become an attractive nonlinear fluorescence material for use in bioimaging because of their tunable spectral characteristics and exceptional photostability.Plasmonic materials are often introduced into the vicinity of UCNCs to increase their emission intensity by means of enlarging the absorption cross-section and accelerating the radiative decay rate.Moreover,plasmonic nanostructures(e.g.,gold nanorods,GNRs)can also influence the polarization state of the UC fluorescence—an effect that is of fundamental importance for fluorescence polarization-based imaging methods yet has not been discussed previously.To study this effect,we synthesized GNR@SiO_(2)@CaF2:Yb^(3+),Er^(3+)hybrid core–shell–satellite nanostructures with precise control over the thickness of the SiO_(2) shell.We evaluated the shell thicknessdependent plasmonic enhancement of the emission intensity in ensemble and studied the plasmonic modulation of the emission polarization at the single-particle level.The hybrid plasmonic UC nanostructures with an optimal shell thickness exhibit an improved bioimaging performance compared with bare UCNCs,and we observed a polarized nature of the light at both UC emission bands,which stems from the relationship between the excitation polarization and GNR orientation.We used electrodynamic simulations combined with Förster resonance energy transfer theory to fully explain the observed effect.Our results provide extensive insights into how the coherent interaction between the emission dipoles of UCNCs and the plasmonic dipoles of the GNR determines the emission polarization state in various situations and thus open the way to the accurate control of the UC emission anisotropy for a wide range of bioimaging and biosensing applications.

Phylogenetic analyses and antigenic characterization of foot-and-mouth disease virus PanAsia lineage circulating in China between 1999 and 2023

Foot-and-mouth disease(FMD)is one of the most important transboundary animal diseases caused by foot-andmouth disease virus(FMDV),leading to significant economic losses worldwide.Thefirst report of PanAsia lineage of FMDV in China was in 1999.Since 2011,18 outbreaks attributed to PanAsia lineage viruses have been reported across 7 provinces or municipality in China.Phylogenetic analysis indicated that these PanAsia strains were clustered into three distinct clades(clade 1,clade 2,and clade 3),with nucleotide homology ranging from 91.4%to 100%.The outbreaks of FMD caused by clade 1 strains occurred around 1999 when this lineage was prevalent globally.Clade 2 strains dominated from 2011 to 2013,while clade 3 strains were prevalent during 2018–2019,sharing only 93%homology with clade 2 strains and 91%with clade 1 strains.Tracing analysis showed that these outbreaks represented 3 distinct introductions of PanAsia viruses into China.Virus neutralization tests(VNT)have demonstrated that current commercial vaccines are effective to protect susceptible animals against these strains(r1>0.3).However,the growing demand for livestock has promoted animal movement and encouraged the exchange of products,services,and materials between countries,thereby heightening the risk of exotic strain incursions.Therefore,it is imperative to reinforce border controls and limit animal movements among various Asian countries continually to reduce the risk of new transboundary diseases,such as FMD incursion.Additionally,PanAsia-2 strains need to be taken seriously to prevent its incursions,and the relevant vaccines against PanAsia-2 strains need to be stockpiled in preparation for any possible incursion.

Foundry manufacturing of tight-confinement,dispersion-engineered,ultralow-loss silicon nitride photonic integrated circuits

The foundry development of integrated photonics has revolutionized today’s optical interconnect and datacenters.Over the last decade,we have witnessed the rising of silicon nitride(Si_(3)N_(4)) integrated photonics,which is currently transferring from laboratory research to foundry manufacturing.The development and transition are triggered by the ultimate need for low optical loss offered by Si_(3)N_(4),which is beyond the reach of silicon and III-V semiconductors.Combined with modest Kerr nonlinearity,tight optical confinement,and dispersion engineering,Si_(3)N_(4) has today become the leading platform for linear and Kerr nonlinear photonics,and it has enabled chip-scale lasers featuring ultralow noise on par with table-top fiber lasers.However,so far all the reported fabrication processes of tight-confinement,dispersion-engineered Si_(3)N_(4) photonic integrated circuits(PICs)with optical loss down to few dB/m have only been developed on 4-inch(100 mm diameter)or smaller wafers.Yet,to transfer these processes to established CMOS foundries that typically operate 6-inch or even larger wafers,challenges remain.In this work,we demonstrate the first foundry-standard fabrication process of Si_(3)N_(4) PICs with only 2.6 dB/m loss,thickness above 800 nm,and near 100%fabrication yield on 6-inch(150 mm diameter)wafers.Such thick and ultralow-loss Si_(3)N_(4) PIC enables low-threshold generation of soliton frequency combs.Merging with advanced heterogeneous integration,active ultralow-loss Si_(3)N_(4) integrated photonics could pave an avenue to addressing future demands in our increasingly information-driven society.