Supplementary Information for

Ligand-Dependent Luminescence of

ultra-small Eu3+-doped NaYF4 nanoparticles

Dominika Wawrzynczyk1, Artur Bednarkiewicz2,3*, Marcin Nyk1, Wiesław Strek2 and
Marek Samoc1,*

1 Institute of Physical and Theoretical Chemistry, Wroclaw University of Technology,
Wyb. Wyspianskiego 27, 50370 Wroclaw, Poland

2 Institute of Low Temperature and Structure Research, Polish Academy of Science,
Okolna 2, 50422 Wroclaw, Poland

3Wroclaw Research Center, EIT+, Stablowicka 147, 54-066 Wroclaw, Poland

* To whom correspondence should be addressed:

,

tel: + 48 71 320-44-66,

fax: + 48 71 320-33-64,

Wroclaw University of Technology,

Institute of Physical and Theoretical Chemistry,

Wybrzeze Wyspianskiego 27, 50-370 Wroclaw, Poland

tel: + 48 71395-41-66

Department of Spectroscopy of Excited States

Institute of Low Temperature and Structure Research

Polish Academy of Sciences

ul. Okolna 2, 50-422 Wroclaw, Poland

Figure 1S. FTIR spectra of the synthesized OANPs (a), TOPONPs (b) and HDANPs (c), together with corresponding FTIR spectra for the ligands used during synthesis protocols.

In the three synthesized NaYF4:4%Eu3+samples intense IR peaks at 2921cm-1 and 2851cm-1were assigned to the asymmetric (Vas) and symmetric (Vs), respectively, stretching vibrations of methylene groups(CH2) in the long alkyl chain present in the organic molecules used as capping ligands (Chen et al. 2008).In addition, for OANPs, bands at 1562cm-1 and 1467cm-1were found in the spectrum, associated with the asymmetric (Vas) and symmetric (Vs) stretching vibrations of the carboxylic group of the bound oleic acid (Chen et al. 2008).For TOPONPs the presence of a strong IR peak at 1467cm−1 with a shoulder at ∼1450cm−1 corresponds to P=O stretching vibrational modes indicating the signatures of the capping TOPO agent(Becerra et al. 1994; Sharma et al. 2008). For HDANPs, bands at 1570cm−1 and at 1670cm−1 correspond to N-H bending vibrational modes indicating also the presence of the HDA capping agent on NPs surface(Coates 2000).

Table.1S. Asymmetry ratios for NaYF4:4%Eu3+ NPs with different surface ligands dispersed in chloroform, toluene, THF and cyclohexane.

NaYF4:4%Eu3+ / Asymmetry
ratio R
OANPs / in CHCl3 / 1.30
in Toluene / 1.27
in THF / 1.29
in Cyclohexane / 1.29
TOPONPs / in CHCl3 / 2.96
in Toluene / 2.78
in THF / -
in Cyclohexane / 2.92
HDANPs / in CHCl3 / 1.09
in Toluene / 1.11
in THF / 1.16
in Cyclohexane / 1.12

Table 2S. Luminescence lifetimes of the 5D0 excited state in Eu3+ ions embedded in NaYF4 matrix with different surface ligands dispersed in chloroform, toluene, THF and cyclohexane, and corresponding values for NPs after ligand removal and dispersing them in water.

NaYF4:4%Eu3+ / 5D0 excited state luminescence lifetime 1[s] / 5D0 excited state luminescence lifetime 2 [s]
OANPs / in CHCl3 / 0.00234± 4.3x10-5 / 0.00699 ± 1.1x10-4
in Toluene / 0.00245± 1.5x10-5 / 0.00743 ± 3.3x10-5
in THF / 0.00289± 1.4x10-5 / 0.00787 ± 4.9x10-5
in Cyclohexane / 0.00210± 1.3x10-5 / 0.0065± 3.0x10-5
TOPONPs / in CHCl3 / 0.00149± 1.1x10-5 / 0.00365 ± 1.5x10-5
in Toluene / 0.00147± 9.3x10-6 / 0.0035 ± 1.6x10-5
in THF / - / -
in Cyclohexane / 0.00117± 9.4x10-6 / 0.00337 ± 1.3x10-5
HDANPs / in CHCl3 / 0.0121± 0.00133 / 0.00596 ± 1.1x10-4
in Toluene / 0.00909± 8.7x10-4 / 0.0051 ± 1.9x10-4
in THF / 0.00956± 3.3x10-4 / 0.00451 ± 1.2x10-4
in Cyclohexane / 0.01138± 8.1x10-4 / 0.00577 ± 9.9x10-5
OANPs / in water / - / 0.000134 ± 6.6x10-6
TOPONPs / in water / - / 0.00011 ± 4.4x10-7
HDANPs / in water / - / 0.00011 ± 1.3x10-6
OANPs / Ligand free in air / - / 0.000118 ± 1.8x10-6
TOPONPs / Ligand free in air / - / 0.000117 ± 3.5x10-7
HDANPs / Ligand free in air / - / 0.000114 ± 3.3x10-6

Figure 2S. Dependence of the short component of 5D0 excited state lifetimes of Eu3+ ions embedded in NaYF4 matrix with OA (blue squares), TOPO (red) and HDA (black) ligands present on the surface, on the refractive index of the solvent.

Figure 3S. Dependence of the long component of5D0 excited state lifetimes of Eu3+ ions embedded in NaYF4 matrix with OA (blue squares), TOPO (red) and HDA (black) ligands present on the surface, on the refractive index of the solvent.

Figure 4S. Luminescence lifetimes short component of the5D0 excited state in Eu3+ ions embedded in NaYF4 matrix with different capping surface ligands vs. ligand refractive index.

Figure 5S. Luminescence lifetimes long component of the 5D0 excited state in Eu3+ ions embedded in NaYF4 matrix with different capping surface ligands vs. ligand refractive index.

References

Becerra LR, Murray CB, Griffin RG, Bawendi MG (1994) Investigation of the surface morphology of capped CdSe nanocrystallites by [sup 31]P nuclear magnetic resonance. The Journal of Chemical Physics 100 (4):3297-3300

Chen ZG, Chen HL, Hu H, Yu MX, Li FY, Zhang Q, Zhou ZG, Yi T, Huang CH (2008) Versatile synthesis strategy for carboxylic acid-functionalized upconverting nanophosphors as biological labels. Journal of the American Chemical Society 130 (10):3023-3029. doi:10.1021/ja076151k

Coates J (2000) Interpretation of Infrared Spectra, A Practical Approach. Encyclopedia of Analytical Chemistry, vol 1. John Wiley & Sons Ltd, Newtown

Sharma SN, Sharma H, Singh G, Shivaprasad SM (2008) Studies of interaction of amines with TOPO/TOP capped CdSe quantum dots: Role of crystallite size and oxidation potential. Materials Chemistry and Physics 110 (2-3):471-480. doi:10.1016/j.matchemphys.2008.02.038