Nanoplasmonics and surface enhanced spectroscopy

Ag@SiO2 nanoparticles for plasmon enhancement of Mg2TiO4:Mn4+ red luminescence
Dolgov L.1,2, Hong J.1, Zhou L.1, Li X.1, Li J.1, Djordjevic V.3, Dramicanin M.3, Shi J.1, Wu M.1
1 MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry, Sun Yat-Sen University, Guangzhou-510275, P. R. China 
E-mail: dolgov@mail.sysu.edu.cn
2 Institute of Physics, University of Tartu, W. Ostwaldi str, 1, Tartu-50411, Estonia 
3 University of Belgrade, Vinca Institute of Nuclear Sciences, P.O. Box 522, Belgrade-11001, Serbia

When electric field of incident light resonates with collective plasmon oscillations of surface electrons in noble metal nanoparticles, nanoparticles can work as analogs of optical antennas enhancing light absorption or scattering for nearby material. It can be used in so-called plasmonic solar cells, in which semiconducting absorbing medium is better involved into light absorption process in close vicinity to noble nanoparticle. It is because cross section of resonant plasmonic light absorption is larger than nanoparticle's geometrical cross section and it can cover adjacent absorbing medium. 
On the other hand, increased plasmonic light absorption can be the reason for the enhanced light emission for phosphor material placed near noble metal nanoparticle. Unfortunately, nanoparticles can be melted, aggregated or oxidized, if they are added during traditional high temperature 800-1000C sintering of inorganic phosphor powders.
Here we propose gentler sol-gel route with final annealing of material at moderate temperature 550C. Preliminary prepared Ag@SiO2 nanoparticles are added to the sol-gel precursor allowing formation of plasmonic Mg2TiO4:Mn4+ phosphor powder with them. Up to 1.5 enhancement in Mn4+ luminescence intensity is revealed at optimal concentration of nanoparticles. Since obtained plasmonic light extinction is well-overlapped with excitation spectrum of Mn4+ ions, we judge about plasmonic enhancement in Mn4+ excitation (light absorption). 

1.	Dolgov L., Hong J., Zhou L., Li X., Li J., Djordjevic V., Dramicanin M., Shi J., Wu M. Efficient Luminescence Enhancement of Mg2TiO4:Mn4+ Red Phosphor by Incorporating Plasmonic Ag@SiO2 Nanoparticles // accepted for ACS Appl. Mater. Interfaces, DOI: 10.1021/acsami.9b05781.