Controlling the Physical and Biological Properties of Highly Fluorescent Aqueous Quantum Dots Using Block Copolymers of Different Size and Shape

Ostermann, Johannes; Merkl, Jan-Philip; Flessau, Sandra; Wolter, Christopher; Kornowksi, Andreas; Schmidtke, Christian; Pietsch, Andrea; Kloust, Hauke; Feld, Artur; Weller, Horst

doi:10.1021/nn4037859

Cited by 50 publications

(62 citation statements)

References 56 publications

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“…9 was calculated from the integrated fluorescence intensity of the CdSe/ZnS QD alone, and the change in the fluorescence decay curve indicates evidence of the FRET process. 37 The time-resolved fluorescence intensity was fitted to a single exponential curve, and coefficients of determination (R 2 ) of the fitting functions were 0.99 for both the CdSe/ZnS QD alone and Fig. 7 The relationship of the pH to the ratio of emission intensities at 605 and 660 nm.…”

Section: Resultsmentioning

confidence: 99%

CdSe/ZnS Quantum Dots Conjugated with a Fluorescein Derivative: a FRET-based pH Sensor for Physiological Alkaline Conditions

et al. 2014

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Dual pH-dependent fluorescence peaks from a semiconductor quantum dot (QD) and a pH-dependent fluorescent dye can be measured by irradiating with a single wavelength light, and the pH can be estimated from the ratio of the fluorescent intensity of the two peaks. In this work, ratiometric pH sensing was achieved in an aqueous environment by a fluorescent CdSe/ZnS QD appended with a pH-sensitive organic dye, based on fluorescence resonance energy transfer (FRET). By functionalizing the CdSe/ZnS QD with 5-(and 6)-carboxynaphthofluorescein succinimidyl ester as a pH-dependent fluorescent dye, we succeeded in fabricating sensitive nanocomplexes with a linear response to a broad range of physiological pH levels (7.5 -9.5) when excited at 450 nm. We found that a purification process is important for increasing the high-fluorescence intensity ratio of a ratiometric fluorescence pH-sensor, and the fluorescence intensity ratio was improved up to 1.0 at pH 8.0 after the purification process to remove unreacted CdSe/ZnS QDs even though the fluorescence of the dye could not be observed without the purification process. The fluorescence intensity ratio corresponds to the fluorescence intensity of the dye, and this fluorescent dye exhibited pH-dependent fluorescence intensity changes. These facts indicate that the fluorescence intensity ratio linearly increased with increasing pH value of the buffer solution containing the QD and the dye. The FRET efficiencies changed from 0.3 (pH 7.5) to 6.2 (pH 9.5).

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Section: Resultsmentioning

confidence: 99%

CdSe/ZnS Quantum Dots Conjugated with a Fluorescein Derivative: a FRET-based pH Sensor for Physiological Alkaline Conditions

et al. 2014

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“…213 In a subsequent report they detailed the synthesis of an amphiphilic miktoarm star copolymer made of two PEO and one PI chain, (PI-b-(PEO) 2 star), with control over the arm size via changes in the precursor molecular weights. 211 One of the key features of this polymer is its ability to provide an effective hydrophobic shielding around the nanocrystal surface, which drastically reduces diffusion/permeability of copper and iron ions to the QD surface. In particular, they showed that QDs encapsulated with an azide-modified block copolymer can be used to implement copper-catalyzed click reactions with minimal loss in the PL emission, circumventing previous limitations to using such coupling strategy when smaller surface ligands are used.…”

Section: Phase Transfer Via Encapsulation Within Amphiphilic Block Comentioning

confidence: 99%

Strategies for interfacing inorganic nanocrystals with biological systems based on polymer-coating

et al. 2015

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Interfacing inorganic nanoparticles and biological systems with the aim of developing novel imaging and sensing platforms has generated great interest and much activity. However, the effectiveness of this approach hinges on the ability of the surface ligands to promote water-dispersion of the nanoparticles with long term colloidal stability in buffer media. These surface ligands protect the nanostructures from the harsh biological environment, while allowing coupling to target molecules, which can be biological in nature (e.g., proteins and peptides) or exhibit specific photo-physical characteristics (e.g., a dye or a redox-active molecule). Amphiphilic block polymers have provided researchers with versatile molecular platforms with tunable size, composition and chemical properties. Hence, several groups have developed a wide range of polymers as ligands or micelle capsules to promote the transfer of a variety of inorganic nanomaterials to buffer media (including magnetic nanoparticles and semiconductor nanocrystals) and render them biocompatible. In this review, we first summarize the established synthetic routes to grow high quality nanocrystals of semiconductors, metals and metal oxides. We then provide a critical evaluation of the recent developments in the design, optimization and use of various amphiphilic copolymers to surface functionalize the above nanocrystals, along with the strategies used to conjugate them to target biomolecules. We finally conclude by providing a summary of the most promising applications of these polymer-coated inorganic platforms in sensor design, and imaging of cells and tissues.

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“…36 Furthermore, a recent work has shown that coating of colloidal CdSe-based NCs with polymer shells with different permeability can be exploited to allow or to block cation exchange reactions. 39 In this work we demonstrate an approach for NC film patterning by locally inhibiting the cation exchange reaction via the exposure of the film to an electron beam or to an X-ray beam, as illustrated in Figure 1. NCs coated by native ligand molecules are homogeneously deposited on a substrate, as depicted in Figure 1a.…”

mentioning

confidence: 99%

Nanocrystal Film Patterning by Inhibiting Cation Exchange via Electron-Beam or X-ray Lithography

et al. 2014

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In this Letter we report patterning of colloidal nanocrystal films that combines direct e-beam (electron beam) writing with cation exchange. The e-beam irradiation causes cross-linking of the ligand molecules present at the nanocrystal surface, and the cross-linked molecules act as a mask for further processing. Consequently, in the following step of cation exchange, which is performed by directly dipping the substrate in a solution containing the new cations, the regions that have not been exposed to the electron beam are chemically transformed, while the exposed ones remain unchanged. This selective protection allows the design of patterns that are formed by chemically different nanocrystals, yet in a homogeneous nanocrystal film. Spatially resolved compositional analysis by energy-dispersive X-ray spectroscopy (EDS) corroborates that the selective exchange occurs only in the nonirradiated regions. We demonstrate the utility of this lithography approach by fabricating conductive wires and luminescent patterns in CdSe/CdS nanocrystal films by converting nonirradiated regions to Cu2-xSe/Cu2-xS. Furthermore, we show that X-ray irradiation too can lead to protection from cation exchange.

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Controlling the Physical and Biological Properties of Highly Fluorescent Aqueous Quantum Dots Using Block Copolymers of Different Size and Shape

Cited by 50 publications

References 56 publications

CdSe/ZnS Quantum Dots Conjugated with a Fluorescein Derivative: a FRET-based pH Sensor for Physiological Alkaline Conditions

CdSe/ZnS Quantum Dots Conjugated with a Fluorescein Derivative: a FRET-based pH Sensor for Physiological Alkaline Conditions

Strategies for interfacing inorganic nanocrystals with biological systems based on polymer-coating

Nanocrystal Film Patterning by Inhibiting Cation Exchange via Electron-Beam or X-ray Lithography

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