Background-Free In vivo Time Domain Optical Molecular Imaging Using Colloidal Quantum Dots

Ma, Guobin

doi:10.1021/am3028519

Cited by 25 publications

(23 citation statements)

References 63 publications

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“…The unique optical properties of colloidal QDs have turned them into an important class of luminescent contrast agents and probes for in vitro and in vivo biomedical imaging . In contrast to conventional organic dyes and fluorescent proteins, QDs possess very broad absorption spectra, narrow PL bands, large absorption cross sections, high PL QYs (and hence superior brightness), and long PL lifetimes, and additionally, they are highly resistant to photobleaching . Furthermore, their PL can be tuned from the green to the near‐IR biological windows (i.e.…”

Section: Ternary Copper Chalcogenidesmentioning

confidence: 99%

Prospects of Colloidal Copper Chalcogenide Nanocrystals

2016

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Over the past few years, colloidal copper chalcogenide nanocrystals (NCs) have emerged as promising alternatives to conventional Cd and Pb chalcogenide NCs. Owing to their wide size, shape, and composition tunability, Cu chalcogenide NCs hold great promise for several applications, such as photovoltaics, lighting and displays, and biomedical imaging. They also offer characteristics that are unparalleled by Cd and Pb chalcogenide NCs, such as plasmonic properties. Moreover, colloidal Cu chalcogenide NCs have low toxicity, potentially lower costs, and excellent colloidal stability. This makes them attractive materials for the large-scale deployment of inexpensive, sustainable, and environmentally benign solution-processed devices. Nevertheless, the synthesis of colloidal Cu chalcogenide NCs, especially that of ternary and quaternary compositions, has yet to reach the same level of mastery as that available for the prototypical Cd chalcogenide based NCs. This review provides a concise overview of this rapidly advancing field, sketching the state of the art and highlighting the key challenges. We discuss recent developments in the synthesis of size-, shape-, and composition-controlled NCs of Cu chalcogenides, with emphasis in strategies to circumvent the limitations arising from the need to precisely balance the reactivities of multiple precursors in synthesizing ternary and quaternary compositions. In this respect, we show that topotactic cation-exchange reactions are a promising alternative route to complex multinary Cu chalcogenide NCs and hetero-NCs, which are not attainable by conventional routes. The properties and potential applications of Cu chalcogenide NCs and hetero-NCs are also addressed.

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Section: Ternary Copper Chalcogenidesmentioning

confidence: 99%

Prospects of Colloidal Copper Chalcogenide Nanocrystals

2016

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“…Probing and exciting certain sites located deep in biological tissues requires high-QY emitters, operating in the NIR spectral region [135], which is characteristic of the Pb-chalcogenide emission spectrum. However, the emitter surface has to be properly treated to make it biocompatible.…”

Section: Future Outlookmentioning

confidence: 99%

PbSe-Based Colloidal Core/Shell Heterostructures for Optoelectronic Applications

et al. 2014

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Lead-based (IV–VI) colloidal quantum dots (QDs) are of widespread scientific and technological interest owing to their size-tunable band-gap energy in the near-infrared optical region. This article reviews the synthesis of PbSe-based heterostructures and their structural and optical investigations at various temperatures. The review focuses on the structures consisting of a PbSe core coated with a PbSexS1–x (0 ≤ x ≤ 1) or CdSe shell. The former-type shells were epitaxially grown on the PbSe core, while the latter-type shells were synthesized using partial cation-exchange. The influence of the QD composition and the ambient conditions, i.e., exposure to oxygen, on the QD optical properties, such as radiative lifetime, Stokes shift, and other temperature-dependent characteristics, was investigated. The study revealed unique properties of core/shell heterostructures of various compositions, which offer the opportunity of fine-tuning the QD electronic structure by changing their architecture. A theoretical model of the QD electronic band structure was developed and correlated with the results of the optical studies. The review also outlines the challenges related to potential applications of colloidal PbSe-based heterostructures.

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“…1-8 Ligand exchange is required to remove organic surfactants and allow charge transport in nanocrystal solids as well as to prepare water-soluble nanocrystals that target specific cellular sites. These manipulations also influence surface trap states and thereby control photoluminescence quantum yield (PLQY).…”

Section: Introductionmentioning

confidence: 99%

Ligand Exchange and the Stoichiometry of Metal Chalcogenide Nanocrystals: Spectroscopic Observation of Facile Metal-Carboxylate Displacement and Binding

et al. 2013

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We demonstrate that metal carboxylate complexes (L–M(O2CR)2, R = oleyl, tetradecyl, M = Cd, Pb) are readily displaced from carboxylate-terminated ME nanocrystals (ME = CdSe, CdS, PbSe, PbS) by various Lewis bases (L = tri-n-butylamine, tetrahydrofuran, tetradecanol, N,N-dimethyl-n-butylamine, tri-n-butylphosphine, N,N,N',N'-tetramethylbutylene-1,4-diamine, pyridine, N,N,N',N'-tetramethylethylene-1,2-diamine, n-octylamine). The relative displacement potency is measured by 1H NMR spectroscopy and depends most strongly on geometric factors like sterics and chelation, though also on the hard/soft match with the cadmium ion. The results suggest that ligands displace L–M(O2CR)2 by cooperatively complexing the displaced metal ion as well as the nanocrystal. Removal of up to 90% of surface bound Cd(O2CR)2 from CdSe and CdS nanocrystals decreases the Cd:Se ratio from 1.1 ± 0.06 to 1.0 ± 0.05, broadens the 1Se-2S3/2h absorption and decreases the photoluminescence quantum yield (PLQY) from 10% to <1% (CdSe) and 20% to <1% (CdS). These changes are partially reversed upon rebinding of M(O2CR)2 at room temperature (~60 %) and fully reversed at elevated temperature. A model is proposed where electron accepting M(O2CR)2 complexes (Z-type ligands) reversibly bind to nanocrystals leading to a range of stoichiometries for a given core size. The results demonstrate that nanocrystals lack a single chemical formula, but are instead dynamic structures with concentration-dependent compositions. The importance of these findings to the synthesis and purification of nanocrystals as well as ligand exchange reactions is discussed.

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Background-Free In vivo Time Domain Optical Molecular Imaging Using Colloidal Quantum Dots

Cited by 25 publications

References 63 publications

Prospects of Colloidal Copper Chalcogenide Nanocrystals

Prospects of Colloidal Copper Chalcogenide Nanocrystals

PbSe-Based Colloidal Core/Shell Heterostructures for Optoelectronic Applications

Ligand Exchange and the Stoichiometry of Metal Chalcogenide Nanocrystals: Spectroscopic Observation of Facile Metal-Carboxylate Displacement and Binding

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