In-Situ Encapsulation of Quantum Dots into Polymer Microspheres

Abstract

We have incorporated fluorescent quantum dots (QDs) into polystyrene microspheres using functionalized oligomeric phosphine (OP) ligands. We find that a uniform distribution of quantum dots is loaded inside each polymer bead. Some local close-packing of quantum dots in the beads is attributed to the self-polymerization of the functionalized ligands. The presence of quantum dots disturbs the nucleation and growth processes during the formation of polymer microspheres and results in a wider size distribution of the quantum dot-embedded polystyrene beads than for the control without dots. The change in quantum efficiency of the quantum dots before (approximately 20%) and after (12%) loading into the beads substantiates the protection of oligomeric phosphine ligands yet indicates that the properties of these quantum dots are still affected during processing.

Microgels and Nanoparticles: Where Micro and Nano Go Hand in Hand

“…The reason for this might be the frequent luminescent quenching upon small changes of the semiconductor NPs surface. There are, however, several examples of successful inclusion of quantum dots in microgels while maintaining luminescent properties [36][37][38][39][40][41], even when they are present in-situ, during the monomer polymerization [42].…”

Facile and Rapid One‐Step Mass Preparation of Quantum‐Dot Barcodes

“…Current methods to prepare QD barcodes include the "swelling" technique, [18] QD entrapment inside layer-by-layer charged polymer coatings [19] or mesoporous silica microbeads, [20] and polymerizable QD encapsulation. [21,22] Microbead "swelling" and layer-by-layer techniques result only in surface-level loading of QDs into the polymer, [18,23] which are thus exposed to pH values and environmental factors that destabilize their fluorescence intensity. [24,25] Stability of the barcode (fluorescence profile) requires that the QDs be positioned well within the polymer matrix and do not leak from the bead, and thus, techniques to encapsulate the QDs during the polymerization step were developed.…”

“…[24,25] Stability of the barcode (fluorescence profile) requires that the QDs be positioned well within the polymer matrix and do not leak from the bead, and thus, techniques to encapsulate the QDs during the polymerization step were developed. [21,22] However, this process is lengthy, requires considerable presynthetic QD surface modification, and yet results in broadly dispersed microbead sizes. Moreover, a number of these barcode systems (e.g.…”

Optical Analysis of Beads Encoded with Quantum Dots Coated with a Cationic Polymer

“…This method has recently been improved by using mesoporous beads: hydrophobic silica [8] or polystyrene; [9] or by immobilizing QDs within polystyrene beads by demixing two nonmiscible solvents. [10] For the second method, efforts have been focused on the encapsulation of QDs into polystyrene microspheres by emulsion [11][12][13] or suspension polymerization. [14,15] The phase separation between polystyrene microspheres and QDs occurring during polymerization [16] is however an important drawback.…”

“…[14,15] The phase separation between polystyrene microspheres and QDs occurring during polymerization [16] is however an important drawback. Uniform distribution of QDs has been obtained with a ligand exchange prior to polymerization, [13,14] but information such as quantum yield stability or emission intensity fluctuations from bead to bead has not been reported. The last encoding method is the immobilization of QDs onto inorganic or polymeric beads via covalent bounding [17,18] or electrostatic interaction.…”