Water-dispersed semiconductor nanoplatelets with high fluorescence brightness, chemical and colloidal stability

Halim, Henry; Simon, Johanna; Lieberwirth, Ingo; Mailänder, Volker; Koynov, Kaloian; Riedinger, Andreas

doi:10.1039/c9tb02377a

Cited by 17 publications

(35 citation statements)

References 34 publications

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“…However, a thorough photophysical characterization of the NPLs can be found elsewhere. [19] As expected, the measured fluorescence intensity increases with increasing NPL concentration. After transfer to water, the capsules were again subjected to fluorescence intensity measurements, demonstrating similar fluorescence intensities for the 10:1 and the 5:1 ratio and a low fluorescence intensity for the 1:1 ratio.…”

Section: Resultssupporting

confidence: 76%

“…The key to success of the NPL markers hinged on the protective coating on the NPLs. [ 19 ] This coating makes NPLs both easy to disperse in aqueous medium and protects the NPLs’ surface from major damage during the encapsulation process, thus leading to high fluorescence after encapsulation. The potential toxicity of CdSe nanoparticles is not an issue at this stage.…”

Section: Introductionmentioning

confidence: 99%

“…Quantum dots are the commonly used fluorescent markers for intracellular tracking, but they are not as bright as NPLs for both one photon and two photon excitation. [19] Moreover, due to their small size and spherical shape it can be challenging to identify quantum dots-but also the larger, rectangular NPLs-in a cellular environment by TEM. [14,15] This might involve additional elemental analysis (e.g., energy dispersive x-ray spectroscopy [EDS] or electron energy loss spectroscopy [EELS]) to confirm the identity of the quantum dots to ultimately locate the nanocarrier.…”

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confidence: 99%

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Nanocarriers Made of Proteins: Intracellular Visualization of a Smart Biodegradable Drug Delivery System

Frey

Han

Halim

et al. 2022

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be observed by electron microscopy (EM). Correlative light and electron microscopy (CLEM) combine the strengths of both techniques and contribute to a precise localization of the nanocarriers in the cell. Using fluorescent nanodiamonds, for example, can serve as a fluorescent marker [11,12] These markers have the advantage of being biocompatible and can be easily modified to achieve a certain surface functionalization. [13] CLEM preparation ideally features a fluorophore with a stable inherent fluorescence suitable for confocal laser scanning microscopy (cLSM) which, in combination, has a contrasting component suitable for transmission electron microscopy (TEM). Another approach is using inorganic, fluorescent nanoparticles. Quantum dots are the commonly used fluorescent markers for intracellular tracking, but they are not as bright as NPLs for both one photon and two photon excitation. [19] Moreover, due to their small size and spherical shape it can be challenging to identify quantum dots-but also the larger, rectangular NPLs-in a cellular environment by TEM. [14,15] This might involve additional elemental analysis (e.g., energy dispersive x-ray spectroscopy [EDS] or electron energy loss spectroscopy [EELS]) to confirm the identity of the quantum dots to ultimately locate the nanocarrier. [16][17][18] Here, we develop a model system consisting of an organic nanocapsule (NC) labeled with a fluorescent labeling system. As fluorescent marker we utilize large (20-50 nm), rectangular CdSe-CdZnS nanoplatelets (NPLs). We encapsulated these NPLs into biocompatible NCs by a polyaddition reaction at the droplet interface in an inverse miniemulsion. We used NCs made of bovine serum albumin (BSA), crosslinked at the interface with toluene diisocyanate (TDI), forming a dense polymeric shell. [6,7] The NPLs were added to the aqueous dispersed phase during the miniemulsion process, leading to the encapsulation of the NPLs into the NCs. The key to success of the NPL markers hinged on the protective coating on the NPLs. [19] This coating makes NPLs both easy to disperse in aqueous medium and protects the NPLs' surface from major damage during the encapsulation process, thus leading to high fluorescence after encapsulation. The potential toxicity of CdSe nanoparticles is not an issue at this stage. The fluorescent marker can either be easily replaced or even omitted completely.To follow the intracellular pathway of the protein NCs, RAW264.7 macrophages were incubated with these NCs followed by different techniques like flow cytometry, cLSM, and This work analyzes the intracellular fate of protein-based nanocarriers along their endolysosomal pathway by means of correlative light and electron microscopy methods. To unambiguously identify the nanocarriers and their degradation remnants in the cellular environment, they are labeled with fluorescent, inorganic nanoplatelets. This allows tracking the nanocarriers on their intracellular pathway by means of electron microscopy imaging. From the present data, it is possible to identify d...

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Section: Resultssupporting

confidence: 76%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Nanocarriers Made of Proteins: Intracellular Visualization of a Smart Biodegradable Drug Delivery System

Frey

Han

Halim

et al. 2022

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“…(d) Sizing curves for the 3.5 ML (blue line) and 4.5 ML (green line) NPLs. For both thicknesses, filled circles represent our experimental data, while the empty squares refer to literature reports. ,,,,,,− …”

Section: Results and Discussionmentioning

confidence: 99%

Colloidal Synthesis of Laterally Confined Blue-Emitting 3.5 Monolayer CdSe Nanoplatelets

et al. 2020

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The typical synthesis protocol for blue-emitting CdSe nanoplatelets (NPLs) yields particles with extended lateral dimensions and large surface areas, resulting in NPLs with poor photoluminescence quantum efficiency. We have developed a synthesis protocol that achieves an improved control over the lateral size, by exploiting a series of long-chained carboxylate precursors that vary from cadmium octanoate (C8) to cadmium stearate (C18). The length of this metallic precursor is key to tune the width and aspect ratio of the final NPLs, and for the shorter chain lengths, the synthesis yield is improved. NPLs prepared with our procedure possess significantly enhanced photoluminescence quantum efficiencies, up to 30%. This is likely due to their reduced lateral dimensions, which also grant them good colloidal stability. As the NPL width can be tuned below the bulk exciton Bohr radius, the band edge blue-shifts, and we constructed a sizing curve relating the NPL absorption position and width. Further adjusting the synthesis protocol, we were able to obtain even thinner NPLs, emitting in the near-UV region, with a band-edge quantum efficiency of up to 11%. Results pave the way to stable and efficient light sources for applications such as blue and UV light-emitting devices and lasers.

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“…[19,20] The salient feature of these quasi-2D quantum wells is the presence of strong anisotropy in their physical dimensions. [21,22] These NPLs are a few monolayers thick with control over their vertical thickness possible in atomic precision. [23][24][25] Their typical lateral dimensions are larger than the excitonic Bohr radius.…”

Section: Introductionmentioning

confidence: 99%

Near‐Field Energy Transfer into Silicon Inversely Proportional to Distance Using Quasi‐2D Colloidal Quantum Well Donors

Humayun

Hernández‐Martínez

Gheshlaghi

et al. 2021

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Silicon is the most prevalent material system for light‐harvesting applications; however, its inherent indirect bandgap and consequent weak absorption limits its potential in optoelectronics. This paper proposes to address this limitation by combining the sensitization of silicon with extraordinarily large absorption cross sections of quasi‐2D colloidal quantum well nanoplatelets (NPLs) and to demonstrate excitation transfer from these NPLs to bulk silicon. Here, the distance dependency, d, of the resulting Förster resonant energy transfer from the NPL monolayer into a silicon substrate is systematically studied by tuning the thickness of a spacer layer (of Al2O3) in between them (varied from 1 to 50 nm in thickness). A slowly varying distance dependence of d−1 with 25% efficiency at a donor–acceptor distance of 20 nm is observed. These results are corroborated with full electromagnetic solutions, which show that the inverse distance relationship emanates from the delocalized electric field intensity across both the NPL layer and the silicon because of the excitation of strong in‐plane dipoles in the NPL monolayer. These findings pave the way for using colloidal NPLs as strong light‐harvesting donors in combination with crystalline silicon as an acceptor medium for application in photovoltaic devices and other optoelectronic platforms.

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Water-dispersed semiconductor nanoplatelets with high fluorescence brightness, chemical and colloidal stability

Abstract: Water-dispersed quasi-two dimensional core/shell semiconductor nanoplatelets exhibit high fluorescence brightness, making them promising for various applications including bioimaging.

Cited by 17 publications

References 34 publications

Nanocarriers Made of Proteins: Intracellular Visualization of a Smart Biodegradable Drug Delivery System

Nanocarriers Made of Proteins: Intracellular Visualization of a Smart Biodegradable Drug Delivery System

Colloidal Synthesis of Laterally Confined Blue-Emitting 3.5 Monolayer CdSe Nanoplatelets

Near‐Field Energy Transfer into Silicon Inversely Proportional to Distance Using Quasi‐2D Colloidal Quantum Well Donors

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