Supporting Information 
 
Optimisation of Amphiphilic-Polymer Coatings for 
Improved Chemical Stability of NaYF4-ased Upconverting 
Nanoparticles 
 
 
Tina Černič1,2, Monika Koren3,4, Boris Majaron3,4, Maja Ponikvar-Svet5, Darja Lisjak1 
 
1 Jožef Stefan Institute, Department for Materials Synthesis, Ljubljana, Slovenia 
2 Jožef Stefan International Postgraduate School, Ljubljana, Slovenia 
3 Jožef Stefan Institute, Department of Complex Matter, Ljubljana, Slovenia 
4 Faculty of Physics and Mathematics, University of Ljubljana, Slovenia 
5 Jožef Stefan Institute, Department of Inorganic Chemistry and Technology, Ljubljana, Slovenia 
 
 
Calculations of the molar fraction of the released fluoride (XF) 
 
𝑋F =  
𝐶F 𝑀NP
40 𝐶susp 𝑀F
        (Eq. S1) 
 
Here, CF denotes the concentration of dissolved fluoride in g/ml, Csusp is the total mass 
concentration of particles in the suspension in mg/ml, and MNP, MF are the molecular mass of the 
NPs with the nominal composition, atomic mass of F, respectively. 
 
 
 
 
 
Figure S1. Size-distribution of the as-synthesized UCNPs from three different batches used in 
this study. The average sizes of the specific batch were 52 ± 2 nm, 67 ± 5 nm and 69 ± 3 nm.  
  
                                                            
 Corresponding author: darja.lisjak@ijs.si 
   
 
Figure S2. TEM images of the coated UCNPs @PB-150: individual NPs (a) with an example of 
an NPs triplet, apparently glued together with an amorphous coating (b).  
 
 
 
 
  
  
   
      
Figure S3. TEM images of the UCNPs@PB-105 from 1-month old dispersions in PBS. The 
image at the bottom presents an enlarged section from the top image.