Temperature-induced aggregation of poly(N-isopropylacrylamide)-stabilized CdS quantum dots in water
Water-soluble nanosized semiconductor CdS particles (quantum dots, QDs) were synthesized with a protective layer of covalently grafting linear thermally sensitive poly(N-isopropylacrylamide) chains. Reversible association and dissociation of these CdS particles can be induced via an alteration of th...
| Veröffentlicht in: | Langmuir : the ACS journal of surfaces and colloids. - 1992. - 24(2008), 6 vom: 18. März, Seite 2727-31 |
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| Weitere Verfasser: | , , |
| Format: | Online-Aufsatz |
| Sprache: | English |
| Veröffentlicht: |
2008
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| Zugriff auf das übergeordnete Werk: | Langmuir : the ACS journal of surfaces and colloids |
| Schlagworte: | Journal Article Research Support, Non-U.S. Gov't Acrylamides Acrylic Resins Cadmium Compounds Polymers Sulfides cadmium sulfide 057EZR4Z7Q Water mehr... |
| Zusammenfassung: | Water-soluble nanosized semiconductor CdS particles (quantum dots, QDs) were synthesized with a protective layer of covalently grafting linear thermally sensitive poly(N-isopropylacrylamide) chains. Reversible association and dissociation of these CdS particles can be induced via an alteration of the solution temperature. The formation and fragmentation of the QD aggregates of the CdS particles were systematically investigated by laser light scattering (LLS) and confirmed by transmission electron microscopy (TEM). There exists a hysteresis during one heating-and-cooling cycle. The CdS particles stabilized with shorter PNIPAM chains (Mn=15,000 g/mol) can associate to form larger and denser spherical aggregates with a much higher aggregation number than those grafted with longer PNIPAM chains (Mn=31,000 g/mol) in the heating process. The dissociation (fragmentation) in the cooling process has two stages: initially, the aggregates dissociate as the temperature decreases, and then, the fragmentation stops over a wider temperature range before complete dissociation. We attribute such a two-stage fragmentation to a balanced effect of inter- and intrachain hydrogen bonding as well as the hydrophobic interaction between PNIPAM chains and CdS particles |
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| Beschreibung: | Date Completed 14.05.2008 Date Revised 20.11.2014 published: Print-Electronic Citation Status MEDLINE |
| ISSN: | 1520-5827 |
| DOI: | 10.1021/la703018p |