Core-Shell NaHoF4@TiO2 NPs: a labeling method to trace engineered nanomaterials of ubiquitous elements in the environment

Research output: Contribution to journalArticlepeer-review


External organisations

  • Loughborough University
  • University of Nottingham


Understanding the fate and behavior of nanoparticles (NPs) in the natural environment is important to assess their potential risk. Single particle inductively coupled plasma mass spectrometry (spICP-MS) allows for the detection of NPs at extremely low concentrations, but the high natural background of the constituents of many of the most widely utilized nanoscale materials makes accurate quantification of engineered particles challenging. Chemical doping, with a less naturally abundant element, is one approach to address this; however, certain materials with high natural abundance, such as TiO2 NPs, are notoriously difficult to label and differentiate from natural NPs. Using the low abundance rare earth element Ho as a marker, Ho-bearing core -TiO2 shell (NaHoF4@TiO2) NPs were designed to enable the quantification of engineered TiO2 NPs in real environmental samples. The NaHoF4@TiO2 NPs were synthesized on a large scale (gram), at relatively low temperatures, using a sacrificial Al(OH)3 template that confines the hydrolysis of TiF4 within the space surrounding the NaHoF4 NPs. The resulting NPs consist of a 60 nm NaHoF4 core and a 5 nm anatase TiO2 shell, as determined by TEM, STEM-EDX mapping, and spICP-MS. The NPs exhibit excellent detectability by spICP-MS at extremely low concentrations (down to 1 × 10-3 ng/L) even in complex natural environments with high Ti background.


Original languageEnglish
Pages (from-to)19452-19461
Number of pages10
JournalACS Applied Materials & Interfaces
Issue number21
Early online date6 May 2019
Publication statusPublished - 29 May 2019


  • spICP-MS, core−shell nanoparticles, large-scale synthesis, exposure and risk assessment, quantification, core-shell nanoparticles

ASJC Scopus subject areas