Investigations on multi-photon emissions of Nd3+-sensitized core/shell nanoparticles

• Published in: Journal of rare earths Vol. 35; no. 1; pp. 1 - 6
• Main Author: 张格 董浩 王棣 孙聆东 严纯华
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 2017
• Subjects: core/shell nanoparticle; multi-photon; Nd3+ sensitizer; rare earths; upconversion emission; Nd3+ sensitizer; upconversion emission; core/shell nanoparticle; multi-photon; rare earths
• ISSN: 1002-0721; 2509-4963
• DOI: 10.1016/S1002-0721(16)60165-5

The past few years witnessed extensive emergence of short-wavelength upconversion（UC） emission stimulated photoactivation studies. However, low efficiency of multi-photon process greatly limits further applications. Here, ultraviolet（UV） upconversion emissions originated from multi-photon process of Tm3+ were studied with Nd3+-sensitized NaGdF4:Yb,Tm@NaYF4:Nd,Yb core/shell nanoparticles. Crucial factors, including the contents of sensitizers Nd3+, Yb3+ and activator Tm3+, as well as the excitation power density were investigated based on the UV emission. Spectral results showed that high contents of Nd3+ in shell region up to 50%（molar fraction hereafter） and Yb3+ of 10% were essential to mediate the energy transfer via the core/shell interface and facilitate multi-photon UV emissions. Compared with segregated activator and sensitizer, a core/shell strategy with isolated Nd3+ in the shell was important for higher UV emission. Although the upconverting process was initiated with Nd3+→Yb3+, the short-wavelength emissions were intrinsically coming from four- and five-photon process. The optimized nanoparticles were found to be able to manipulate the configuration transition of azobenzene molecules, and it could be promising for near infrared（NIR） triggered optical switches applications.