Versatile, Fast, and Easy One‐Step Method for the Synthesis of Hydrophilic Lanthanide‐Doped Nanoparticles

Abstract

The preparation of hydrophilic lanthanide-doped nanoparticles (NPs) following a versatile one-step colloidal method at low temperature and short reaction time with different doped lanthanides, capping ligands, and fluoride sources is presented. The photoluminescence of the particles, via both downshifting (DS) and up-conversion (UC), was easily tuned from blue or green by simply changing the lanthanides used. When using the same core type of particles, the size and the photoluminescence intensity were tuned by changing the fluoride source or the capping ligand used: the size of the DSNPs varied from 9 nm (PAA) to 24 nm (PEI) when changing the capping ligand, while if PAA was used as capping ligand, the nanoparticles presented the most intense emission bands. Supramolecular host groups were introduced on the surface of the UCNPs by grafting cyclodextrin (CD) groups onto the capping ligand PiBMA prior to particle synthesis, reaching a CD surface density of 0.28 CD nm -2 . In this case, a small particle size (11.7 nm) and strong UC emission bands were observed.

Host–Guest and Electrostatic Interactions in Supramolecular Nanoparticle Clusters

“…The β‐CD‐grafted poly(isobutyl‐ alt ‐maleic acid)‐capped, Yb 3+ (15 %)/Tm 3+ (0.5 %)‐doped Sr 2 GdF 7 nanoparticles (CD‐UCNPs) were prepared and characterized as recently described . The crystallite size of the NPs was 11.7 nm as determined by powder X‐ray diffraction (XRD), and the amount of CD was estimated by thermogravimetric analysis (TGA) to be 5.6 wt.‐%, which means that a solution of CD‐UCNPs of 0.5 mg mL –1 provides a CD concentration of 15 µ m .…”

“…In order to study the effect of attractive electrostatic interactions in induction of the aggregation of CD‐UCNPs, the positively charged hyperbranched polymer PEI (MW 10 kDa) was added to the CD‐UCNPs in a stepwise fashion in phosphate buffer (1 m m , pH 7.4). In this case, in the absence of complementary guest moieties, cluster formation can be induced only through attractive electrostatic forces between the negatively charged CD‐UCNPs and the protonated polymer backbone of the PEI. The size of the clusters as a function of the concentration of PEI was monitored by DLS (Figure a).…”

“…MilliQ water with a resistivity of 18.2 MΩ cm at 25 °C was used when indicated. The CD‐UCNPs were prepared as recently reported …”

“…Recently, we have studied the preparation and characterization of supramolecular nanoparticles (SNPs), composed of soft anionic polymeric host and guest components, and the influence of electrostatic interactions on the particle formation and stability . Inorganic lanthanide‐doped UCNPs, surface‐modified with cyclodextrins (CDs), were also synthesized and characterized . Here, our aim was to study the formation of hybrid inorganic‐organic, supramolecular nanoparticle clusters (SNPCs), composed of inorganic NPs functionalized with CDs (CD‐AuNPs and CD‐UCNPs) and different types of soft polymers.…”

One-step synthesis of amino-functionalized up-converting NaYF4:Yb,Er nanoparticles forin vitrocell imaging

“…The rapid progress in development of different protocols which give rise to the synthesis of monodisperse lanthanide doped NaYF 4 UCNPs through decomposition of organometallic precursors, proposed initially by Mai et al, 8 is replaced nowadays with studies devoted to in situ obtaining of biocompatible UCNPs. 9,10 This is due to the fact that synthesis from toxic organometallic, performed in an oxygen-free environment, must be followed by SiO 2 encapsulation, ligands exchange/ oxidation or by coating with a biocompatible polymer towards achieving a demanded chemical functionality for conjugation of the targeting molecular moiety. Although well established, the reproducibility of multiple steps involved in such synthesis is not trivial, since toxicity of UCNPs produced throughout is not easily predictable.…”