Interface formation during silica encapsulation of colloidal CdSe/CdS quantum dots observed by in situ Raman spectroscopy

Quantum Dot Patterning and Encapsulation by Maskless Lithography for Display Technologies

For their unique optical properties, quantum dots (QDs) have been extensively used as light emitters in a number of photonic and optoelectronic applications. They even met commercialization success through their implementation in high-end displays with unmatched brightness and color rendering. For such applications, however, QDs must be shielded from oxygen and water vapor, which are known to degrade their optical properties over time. Even with highly qualitative QDs, this can only be achieved through their encapsulation between barrier layers. With the emergence of mini- and microLED for higher contrast and miniaturized displays, new strategies must be found for the concomitant patterning and encapsulation of QDs, with sub-millimeter resolution. To this end, we developed a new approach for the direct patterning of QDs through maskless lithography. By combining QDs in photopolymerizable resins with digital light processing (DLP) projectors, we developed a versatile and massively parallel fabrication process for the additive manufacturing of functional structures that we refer to as QD pockets. These 3D heterostructures are designed to provide isotropic encapsulation of the QDs, and hence prevent edge ingress from the lateral sides of QD films, which remains a shortcoming of the current technologies.

Silanized Luminescent Quantum Dots for the Simultaneous Multicolor Lateral Flow Immunoassay of Two Mycotoxins

A critical point for the successful development of a fluorescent quantum dot (QD)-based immunoassay is maintaining the high fluorescence quantum yield of QDs during hydrophilization and bioconjugation. In this paper, we carefully designed CdSe/CdS and CdSe/CdS/ZnS core-shell heterostructures and extended them with silica coating of different surface composition allowing preservation of fluorescence quantum yield as high as 70% in aqueous media. The silanized QDs containing epoxy and carboxy surface groups were bioconjugated with monoclonal antibodies. The synthesized fluorescent conjugates were used in a multicolor lateral flow immunoassay for simultaneous determination of two mycotoxins. Zearalenone and deoxynivalenol were chosen as a proof of concept. Cutoff levels for the zearalenone and deoxynivalenol detection were adjusted to be at 40 and 400 μg kg^-1, respectively, complying with the European Commission regulation. Validation of the developed test was performed by analysis of 34 naturally contaminated maize and wheat samples; as a confirmatory method, LC-MS/MS was used.

Efficient Endocytosis of Inorganic Nanoparticles with Zwitterionic Surface Functionalization

PEGylation, which has traditionally been the method of choice to enhance the colloidal stability of nanostructures designed for biological applications and to prevent nonspecific protein adsorption, is now being challenged by short zwitterionic ligands. Inspired by the zwitterionic nature of cell membranes, these ligands have the potential to push forward the field of nanoparticles for nanomedicine. In this work, we report a thorough analysis of the surface chemistry of silica-coated luminescent CdSe/CdS quantum dots functionalized with either PEG-silane or zwitterionic sulfobetaine-silane by quantitative nuclear magnetic resonance spectroscopy. We demonstrate the differences in the cellular uptake propensity between particles with these two ligands. Although both ligands offer good colloidal stability in a crowded cell culture medium, the zwitterionic-functionalized nanoparticles with an optimized ligand density showed to be more easily endocytosed by HeLa cells. This approach can readily be transferred to other nanoparticle systems offering a wealth of unique properties, with great potential for intracellular bioapplications.

Two-Step-Enhanced Stability of Quantum Dots via Silica and Siloxane Encapsulation for the Long-Term Operation of Light-Emitting Diodes

Despite innovative optical properties of quantum dots (QDs) for QDs-converted light-emitting diodes (QD-LEDs), the vulnerability of the QDs, against heat and moisture, has been a critical issue for commercialization and long-term use. To overcome the instabilities, we fabricated a thermally and photostable QDs-embedded silica/siloxane (S-QD/siloxane) film by embedding QDs in silica and siloxane encapsulation through a two-step sol-gel reaction. S-QDs were stably dispersed in the oligo-siloxane resin with even a QD concentration of 5 wt % without aggregation. The two-step physical barriers of silica and siloxane acted to decrease the toxicity of QDs and improve the stability against heat and moisture [85 °C/5% relative humidity (RH), 85 °C/85% RH, and 120 °C/5% RH], light (50 and 100 mA), and chemicals (ethanol, HCl, and NaOH). Our S-QD/siloxane film was applied as a color-conversion material on a blue LED chip without additional solidification and encapsulation processes for red and white QD-LEDs, exhibiting a wider color gamut (107% in CIE 1931) compared to NTSC. These enhancements indicate that our S-QD/siloxane film is a suitable material for long-term operation of QD-enhanced films and QD-LEDs in next-generation displays.

Functional Mesoporous Silica Nanocomposites: Biomedical applications and Biosafety

The rise and development of nanotechnology has enabled the creation of a wide number of systems with new and advantageous features to treat cancer. However, in many cases, the lone application of these new nanotherapeutics has proven not to be enough to achieve acceptable therapeutic efficacies. Hence, to avoid these limitations, the scientific community has embarked on the development of single formulations capable of combining functionalities. Among all possible components, silica-either solid or mesoporous-has become of importance as connecting and coating material for these new-generation therapeutic nanodevices. In the present review, the most recent examples of fully inorganic silica-based functional composites are visited, paying particular attention to those with potential biomedical applicability. Additionally, some highlights will be given with respect to their possible biosafety issues based on their chemical composition.