Enhancing the Stability and Biological Functionalities of Quantum Dots via Compact Multifunctional Ligands

Susumu, Kimihiro; Uyeda, H. Tetsuo; Medintz, Igor L.; Pons, Thomas; Delehanty, James B.; Mattoussi, Hedi

doi:10.1021/ja0749744

Cited by 485 publications

(436 citation statements)

References 34 publications

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“…The difference of the QYs of the two dispersions reveals that QD deterioration occurred during ligand exchange, as reported previously. 11,[24][25][26][27][28] Ligand exchange changes the chemical and physical states of atoms on the QD surface, and causes QYs to decrease. 29 The QY of InP/ZnS-MPA@TMAS was similar to that of the InP/ZnS-MPA QD dispersion, while the QY of InP/ZnS-DDT@PMMA was much lower than that of the dispersion of InP/ZnS-DDT QDs.…”

Section: Resultsmentioning

confidence: 99%

Preparation of Photostable Fluorescent InP/ZnS Quantum Dots Embedded in TMAS-Derived Silica

Watanabe

Wada

Iso

et al. 2017

ECS J. Solid State Sci. Technol.

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Cd-free fluorescent InP/ZnS quantum dots (QDs) have attracted attention for use as color converters of liquid crystal displays. To protect InP/ZnS QDs from oxygen, which degrades them by photo-oxidation during excitation, we fabricated a transparent monolithic silica composite containing the QDs using an aqueous solution of tetramethylammonium silicate (TMAS) as a silica source. The TMAS solution was basic and readily dispersed the negatively charged QDs obtained by ligand exchange of 1-dodecanethiol for 3-mercaptopropionic acid (MPA). A highly transparent monolithic TMAS-derived silica composite containing the MPA-modified QDs (InP/ZnS-MPA@TMAS) was obtained from the aqueous QD dispersion through a sol-gel process. The photoluminescence (PL) quantum yield of InP/ZnS-MPA@TMAS was 21.7%. Changes in PL intensity under continuous 400-nm excitation were measured to evaluate the photostability of the QDs in InP/ZnS-MPA@TMAS. The PL intensity of InP/ZnS-MPA@TMAS was over 90% of the initial value after 180 min, while that of a reference polymethylmethacrylate film containing hydrophobic QDs decreased to 69%. The higher photostability of InP/ZnS-MPA@TMAS than that of the reference film was explained by the TMAS-derived silica acting as a gas barrier to protect the embedded QDs from photo-oxidation by oxygen in air. A quantum dot (QD) is a semiconductor nanocrystal. As the size of a QD decreases, its bandgap widens because of the quantum size effect. The fluorescent wavelength of a QD therefore depends on its size.1 The tunable fluorescent wavelength of QDs means they are applicable to white light-emitting diodes (LEDs) 2 and bioimaging. 3 CdS and CdSe QDs have been frequently studied because their fluorescent wavelength is tunable in the visible range. 4 InP QDs have recently attracted attention because they are Cd-free with low toxicity. InP QDs have been synthesized via hot injection 5 and thermal 6 methods. Yang et al. 6 coated an InP core prepared by the latter method with a ZnS shell to passivate dangling bonds on the QD surface. The obtained InP/ZnS core/shell QDs displayed a high quantum yield (QY) of up to 60%, tunable fluorescent wavelength, and narrow emission peak. The color reproduction range of liquid crystal displays could be improved by using such InP/ZnS QDs as a color converter in the LED backlight.For practical optoelectronic applications, QDs have to retain their photoluminescence (PL) intensity during continuous excitation. However, the PL intensity of QDs decreases over time because of the photooxidation of the QD surface by oxygen.7 One method used to improve the photostability of QDs is formation of a core/shell structure. However, the PL intensity of InP/ZnS core/shell QDs deteriorated to 40% of the initial PL intensity after continuous excitation by 365-nm light for 10 h. 6 Thus, it is difficult to completely avoid PL deterioration even for QDs with a core/shell structure. 6 Incorporation of well-dispersed QDs into a matrix to protect them from oxygen is another way to avoid PL deterioration of ...

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Section: Resultsmentioning

confidence: 99%

Preparation of Photostable Fluorescent InP/ZnS Quantum Dots Embedded in TMAS-Derived Silica

Watanabe

Wada

Iso

et al. 2017

ECS J. Solid State Sci. Technol.

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“…-COOH, -OH, -NH 2 (Hoshino et al 2004;Susumu et al 2007;, or CdTe and, for instance, a mixture of MPA and aminoethylthiol (Wuister et al 2003).…”

Section: Particle Functionalization (A) Chemical Functional Groupsmentioning

confidence: 99%

Surface modification, functionalization and bioconjugation of colloidal inorganic nanoparticles

Sperling

Parak

2010

Phil. Trans. R. Soc. A.

1,409

1,092

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Inorganic colloidal nanoparticles are very small, nanoscale objects with inorganic cores that are dispersed in a solvent. Depending on the material they consist of, nanoparticles can possess a number of different properties such as high electron density and strong optical absorption (e.g. metal particles, in particular Au), photoluminescence in the form of fluorescence (semiconductor quantum dots, e.g. CdSe or CdTe) or phosphorescence (doped oxide materials, e.g. Y 2 O 3 ), or magnetic moment (e.g. iron oxide or cobalt nanoparticles). Prerequisite for every possible application is the proper surface functionalization of such nanoparticles, which determines their interaction with the environment. These interactions ultimately affect the colloidal stability of the particles, and may yield to a controlled assembly or to the delivery of nanoparticles to a target, e.g. by appropriate functional molecules on the particle surface. This work aims to review different strategies of surface modification and functionalization of inorganic colloidal nanoparticles with a special focus on the material systems gold and semiconductor nanoparticles, such as CdSe/ZnS. However, the discussed strategies are often of general nature and apply in the same way to nanoparticles of other materials.

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“…Surface oxidation and pH value during storage are two prominent factors that influence QD stability. For extended stability in basic buffers, dihydrolipoic acid (DHLA) could be attached to the QD surface via a PEG linkage [18]. The hydroxylcoated QDs prepared by Kairdolf et al showed stability under both basic and acidic conditions, with minimized nonspecific binding [19].…”

Section: Quantum Dotsmentioning

confidence: 99%

Nanomaterials in fluorescence-based biosensing

2009

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Fluorescence-based detection is the most common method utilized in biosensing because of its high sensitivity, simplicity, and diversity. In the era of nanotechnology, nanomaterials are starting to replace traditional organic dyes as detection labels because they offer superior optical properties, such as brighter fluorescence, wider selections of excitation and emission wavelengths, higher photostability, etc. Their size-or shape-controllable optical characteristics also facilitate the selection of diverse probes for higher assay throughput. Furthermore, the nanostructure can provide a solid support for sensing assays with multiple probe molecules attached to each nanostructure, simplifying assay design and increasing the labeling ratio for higher sensitivity. The current review summarizes the applications of nanomaterialsincluding quantum dots, metal nanoparticles, and silica nanoparticles-in biosensing using detection techniques such as fluorescence, fluorescence resonance energy transfer (FRET), fluorescence lifetime measurement, and multiphoton microscopy. The advantages nanomaterials bring to the field of biosensing are discussed. The review also points out the importance of analytical separations in the preparation of nanomaterials with fine optical and physical properties for biosensing. In conclusion, nanotechnology provides a great opportunity to analytical chemists to develop better sensing strategies, but also relies on modern analytical techniques to pave its way to practical applications.Keywords Nanomaterials . Quantum dots . Gold nanoparticle . Silica nanoparticle . Fluorescence . FRET . Biosensing OverviewSensitive detection of target analytes present at trace levels in biological samples often requires the labeling of reporter molecules with fluorescent dyes, because fluorescence detection is by far the dominant detection method in the field of sensing technology, due to its simplicity, the convenience of transducing the optical signal, the availability of organic dyes with diverse spectral properties, and the rapid advances made in optical imaging. However, it can be difficult to obtain a low detection limit in fluorescence detection due to the limited extinction coefficients or quantum yields of organic dyes and the low dye-toreporter molecule labeling ratio. The recent explosion of nanotechnology, leading to the development of materials with submicron-sized dimensions and unique optical properties, has opened up new horizons for fluorescence detection. Nanomaterials can be made from both inorganic and organic materials and are less than 100 nm in length

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Enhancing the Stability and Biological Functionalities of Quantum Dots via Compact Multifunctional Ligands

Cited by 485 publications

References 34 publications

Preparation of Photostable Fluorescent InP/ZnS Quantum Dots Embedded in TMAS-Derived Silica

Preparation of Photostable Fluorescent InP/ZnS Quantum Dots Embedded in TMAS-Derived Silica

Surface modification, functionalization and bioconjugation of colloidal inorganic nanoparticles

Nanomaterials in fluorescence-based biosensing

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