Nanoparticles
of NaGdF4-doped with Eu3+ and
Ce3+ were synthesized by the citrate method.28 (link) A transparent aqueous solution containing 4
mL of 0.2 M lanthanide chlorides (Sigma Aldrich, MO) and 8 mL of 0.2
M sodium citrate (Sigma Aldrich, MO) was heated to 90 °C. Sodium
fluoride (16 mL of 1 M) (Fischer Scientific, PA) solution was added
to the solution, upon which the solution turned whitish. The nanoparticles
were heated for 2 h. The nanoparticles were centrifuged and washed
twice before further measurements were carried out. As-synthesized
particles were heated in a Teflon-lined autoclave (Cole-Parmer, IL)
at 210 °C for 1 h to obtain hexagonal phase of the nanoparticles.
The pH studies were carried out by suspending 6 mg, 2.5 mg, and 2
mg of the nanoparticles obtained from three different batches in 1
mL of phosphate buffer silane with pH values ranging from 2.5 to 7.2.
pH buffers below 7.4 were prepared by adding small amounts of 10 mM
solution of HCl was used and the pH monitored by ORION 5 STAR (Thermo
Scientific, MA) pH meter.
of NaGdF4-doped with Eu3+ and
Ce3+ were synthesized by the citrate method.28 (link) A transparent aqueous solution containing 4
mL of 0.2 M lanthanide chlorides (Sigma Aldrich, MO) and 8 mL of 0.2
M sodium citrate (Sigma Aldrich, MO) was heated to 90 °C. Sodium
fluoride (16 mL of 1 M) (Fischer Scientific, PA) solution was added
to the solution, upon which the solution turned whitish. The nanoparticles
were heated for 2 h. The nanoparticles were centrifuged and washed
twice before further measurements were carried out. As-synthesized
particles were heated in a Teflon-lined autoclave (Cole-Parmer, IL)
at 210 °C for 1 h to obtain hexagonal phase of the nanoparticles.
The pH studies were carried out by suspending 6 mg, 2.5 mg, and 2
mg of the nanoparticles obtained from three different batches in 1
mL of phosphate buffer silane with pH values ranging from 2.5 to 7.2.
pH buffers below 7.4 were prepared by adding small amounts of 10 mM
solution of HCl was used and the pH monitored by ORION 5 STAR (Thermo
Scientific, MA) pH meter.