Disintegration of Hexagonal NaYF4:Yb3+,Er3+ Upconverting Nanoparticles in Aqueous Media: The Role of Fluoride in Solubility Equilibrium

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• 作者：Satu LahtinenAnnika Lyytikäinen ; Henna Päkkilä ; Emmy Hömppi ; Niina Perälä ; Mika Lastusaari ; Tero Soukka
• 刊名：Journal of Physical Chemistry C
• 出版年：2017
• 出版时间：January 12, 2017
• 年：2017
• 卷：121
• 期：1
• 页码：656-665
• 全文大小：535K
• ISSN：1932-7455

文摘

The disintegration of hexagonal NaYF₄:Yb³⁺,Er³⁺ upconverting nanoparticles (UCNP) was studied by incubating various nanoparticle concentrations in aqueous suspensions over time while monitoring the upconversion emission intensity and measuring the dissolved particle-constituting ion concentrations. The results revealed that the ions dissolved into water resulting apparently in anisotropic structural disintegration of the UCNPs as observed with transmission electron microscopy. The UCNP disintegration caused partial loss of active ions Yb³⁺ and Er³⁺ from the host matrix and therefore decrease in the upconversion luminescence intensity. The decrease, however, was strongly dependent on the UCNP concentration, and dramatic drop in the intensity was observed especially at diluted nanoparticle suspensions, where the nanoparticles disintegrated almost completely until the solubility equilibrium was achieved. At the concentrated suspensions the equilibrium was achieved already with minimal disintegration, and the change in the luminescence intensity was negligible. Further, due to the high impact of fluoride ions on the solubility equilibrium the disintegration of the UCNPs could be prevented by adding fluoride to the suspension. The reported disintegration of NaYF₄:Yb³⁺,Er³⁺ nanoparticles in diluted aqueous suspensions should be taken into consideration when the UCNPs are used at low concentrations in analytical applications and in guiding the design of improved shell-stabilized UCNPs.