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4 results on '"Oya Tagit"'

1. Influence of the length and grafting density of PNIPAM chains on the colloidal and optical properties of quantum dot/PNIPAM assemblies

Author

Aliakbar Jafarpour, Oya Tagit, Jennifer Lynn Herek, Nikodem Tomczak, G. Julius Vancso, Ming-Yong Han, Dominik Jańczewski, Biomolecular Nanotechnology, Optical Sciences, and Materials Science and Technology of Polymers

Subjects
Materials science, Luminescence, Optical Phenomena, Analytical chemistry, Acrylic Resins, Bioengineering, Fluorescence correlation spectroscopy, Lower critical solution temperature, Diffusion, Colloid, Quantum Dots, General Materials Science, Colloids, Electrical and Electronic Engineering, Aqueous solution, Mechanical Engineering, Temperature, General Chemistry, Fluorescence, 22/4 OA procedure, Spectrometry, Fluorescence, Chemical engineering, Mechanics of Materials, Quantum dot, Order of magnitude
Abstract

Structural and optical characterization of water soluble, thermo-responsive quantum dot/poly(N-isopropyl acrylamide) (QD/PNIPAM) hybrid particles using fluorescence correlation spectroscopy (FCS) and time-correlated single photon counting (TCSPC) measurements performed at temperatures below and above the lower critical solution temperature (LCST) of PNIPAM is reported. By increasing the temperature above the LCST, the signature of the PNIPAM chain collapse covering the QDs is revealed by FCS measurements. Despite the significant structural change, the TCSPC measurements show that the fluorescence lifetimes remain of the same order of magnitude at T > LCST. Such QD/PNIPAM hybrid particles with water solubility and robust thermo-responsive behavior at physiologically relevant temperatures are potentially useful for (bio)molecular sensing and separation applications.

Published
2011

2. Temperature-modulated quenching of quantum dots covalently coupled to chain ends of poly(N-isopropyl acrylamide) brushes on gold

Author

Nikodem Tomczak, G. Julius Vancso, Yanina Cesa, Oya Tagit, Edmondo M. Benetti, Christian Blum, Vinod Subramaniam, Jennifer Lynn Herek, Executive board Vrije Universiteit, Biophysics Photosynthesis/Energy, Materials Science and Technology of Polymers, Optical Sciences, Faculty of Science and Technology, Biomolecular Nanotechnology, and Nanobiophysics

Subjects
Materials science, Macromolecular Substances, Surface Properties, Radical polymerization, Acrylic Resins, Molecular Conformation, Bioengineering, Research Support, Photochemistry, Lower critical solution temperature, law.invention, IR-71158, law, METIS-258181, Materials Testing, Quantum Dots, Polymer chemistry, Journal Article, Nanotechnology, General Materials Science, SDG 7 - Affordable and Clean Energy, Particle Size, Electrical and Electronic Engineering, Crystallization, Non-U.S. Gov't, Quenching, chemistry.chemical_classification, Research Support, Non-U.S. Gov't, Mechanical Engineering, Temperature, technology, industry, and agriculture, General Chemistry, Polymer, equipment and supplies, chemistry, Mechanics of Materials, Quantum dot, Covalent bond, Luminescent Measurements, Gold, Luminescence
Abstract

A thermo-responsive polymer/quantum dot platform based on poly(N-isopropyl acrylamide) (PNIPAM) brushes 'grafted from' a gold substrate and quantum dots (QDs) covalently attached to the PNIPAM layer is presented. The PNIPAM brushes are grafted from the gold surface using an iniferter-initiated controlled radical polymerization. The PNIPAM chain ends are functionalized with amine groups for coupling to water-dispersible COOH-functionalized QDs. Upon increasing the temperature above the lower critical solution temperature (LCST) of PNIPAM the QD luminescence is quenched. The luminescence was observed to recover upon decreasing the temperature below the LCTS. The data obtained are consistent with temperature-modulated thickness changes of the PNIPAM layer and quenching of the QDs by the gold surface via nonradiative energy transfer.

Published
2009
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3. Influence of the length and grafting density of PNIPAM chains on the colloidal and optical properties of quantum dot/PNIPAM assemblies.

Author

Oya Tagit, Nikodem Tomczak, Aliakbar Jafarpour, Dominik Janczewski, Ming Yong, G Julius, Vancso and, and Jennifer L Herek

Subjects
*QUANTUM dots, *COLLOIDAL crystals, *FLUORESCENCE, *POLYMERS, *TEMPERATURE effect, *BIOMOLECULES, *ACRYLAMIDE
Abstract

Structural and optical characterization of water soluble, thermo-responsive quantum dot/poly(N-isopropyl acrylamide) (QD/PNIPAM) hybrid particles using fluorescence correlation spectroscopy (FCS) and time-correlated single photon counting (TCSPC) measurements performed at temperatures below and above the lower critical solution temperature (LCST) of PNIPAM is reported. By increasing the temperature above the LCST, the signature of the PNIPAM chain collapse covering the QDs is revealed by FCS measurements. Despite the significant structural change, the TCSPC measurements show that the fluorescence lifetimes remain of the same order of magnitude at T > LCST. Such QD/PNIPAM hybrid particles with water solubility and robust thermo-responsive behavior at physiologically relevant temperatures are potentially useful for (bio)molecular sensing and separation applications. [ABSTRACT FROM AUTHOR]

Published
2011
Full Text
View/download PDF

4. Temperature-modulated quenching of quantum dots covalently coupled to chain ends of poly(N-isopropyl acrylamide) brushes on gold.

Author

Oya Tagit, Nikodem Tomczak, Edmondo M Benetti, Yanina Cesa, Christian Blum, Vinod Subramaniam, Jennifer L Herek, and G Julius

Subjects
*QUANTUM dots, *METAL quenching, *GOLD compounds, *POLYACRYLAMIDE, *SURFACE chemistry, *POLYMERIZATION, *TEMPERATURE effect
Abstract

A thermo-responsive polymer/quantum dot platform based on poly(N-isopropyl acrylamide) (PNIPAM) brushes 'grafted from' a gold substrate and quantum dots (QDs) covalently attached to the PNIPAM layer is presented. The PNIPAM brushes are grafted from the gold surface using an iniferter-initiated controlled radical polymerization. The PNIPAM chain ends are functionalized with amine groups for coupling to water-dispersible COOH-functionalized QDs. Upon increasing the temperature above the lower critical solution temperature (LCST) of PNIPAM the QD luminescence is quenched. The luminescence was observed to recover upon decreasing the temperature below the LCTS. The data obtained are consistent with temperature-modulated thickness changes of the PNIPAM layer and quenching of the QDs by the gold surface via nonradiative energy transfer. [ABSTRACT FROM AUTHOR]

Published
2009
Full Text
View/download PDF

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