Hybrid Silica Cage-Type Nanostructures Made from Triply Hydrophilic Block Copolymers Single Micelles.

Controlling the structure and functionality of porous silica nanoparticles has been a continuous source of innovation with important potential for advanced biomedical applications. Their synthesis, however, usually involves passive surfactants or amphiphilic copolymers that do not add value to the material after synthesis. In contrast, polyion complex (PIC) micelles based on hydrophilic block copolymers allow for the direct synthesis of intrinsically functional hybrid materials.

Overcoming Barriers Associated with Oral Delivery of Differently Sized Fluorescent Core-Shell Silica Nanoparticles.

Oral delivery, while a highly desirable form of nanoparticle-drug administration, is limited by challenges associated with overcoming several biological barriers. Here, the authors study how fluorescent and poly(ethylene glycol)-coated (PEGylated) core-shell silica nanoparticles sized 5 to 50 nm interact with major barriers including intestinal mucus, intestinal epithelium, and stomach acid. From imaging fluorescence correlation spectroscopy studies using quasi-total internal reflection fluorescence microscopy, diffusion of nanoparticles through highly scattering mucus is progressively hindered above a critical hydrodynamic size around 20 nm.

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.

A Comparative Study of the Band-Edge Exciton Fine Structure in Zinc Blende and Wurtzite CdSe Nanocrystals.

In this paper, we studied the role of the crystal structure in spheroidal CdSe nanocrystals on the band-edge exciton fine structure. Ensembles of zinc blende and wurtzite CdSe nanocrystals are investigated experimentally by two optical techniques: fluorescence line narrowing (FLN) and time-resolved photoluminescence. We argue that the zero-phonon line evaluated by the FLN technique gives the ensemble-averaged energy splitting between the lowest bright and dark exciton states, while the activation energy from the temperature-dependent photoluminescence decay is smaller and corresponds to the energy of an acoustic phonon.

Quantum dot lasing from a waterproof and stretchable polymer film.

Colloidal quantum dots (QDs) are excellent optical gain materials that combine high material gain, a strong absorption of pump light, stability under strong light exposure and a suitability for solution-based processing. The integration of QDs in laser cavities that fully exploit the potential of these emerging optical materials remains, however, a challenge. In this work, we report on a vertical cavity surface emitting laser, which consists of a thin film of QDs embedded between two layers of polymerized chiral liquid crystal.

General Expression for the Size-Dependent Optical Properties of Quantum Dots.

While initial theories on quantum confinement in colloidal quantum dots (QDs) led to analytical band gap/size relations or sizing functions, numerical methods describe size quantization more accurately. However, because of the lack of reliable sizing functions, researchers fit experimental band gap/size data sets using models with redundant, physically meaningless parameters that break down upon extrapolation. Here, we propose a new sizing function based on a proportional correction for nonparabolic bands.

Porous cage-derived nanomaterial inks for direct and internal three-dimensional printing.

The convergence of 3D printing techniques and nanomaterials is generating a compelling opportunity space to create advanced materials with multiscale structural control and hierarchical functionalities. While most nanoparticles consist of a dense material, less attention has been payed to 3D printing of nanoparticles with intrinsic porosity. Here, we combine ultrasmall (about 10 nm) silica nanocages with digital light processing technique for the direct 3D printing of hierarchically porous parts with arbitrary shapes, as well as tunable internal structures and high surface area.

Two-Dimensional Superstructures of Silica Cages.

Despite extensive studies on mesoporous silica since the early 1990s, the synthesis of two-dimensional (2D) silica nanostructures remains challenging. Here, mesoporous silica is synthesized at an interface between two immiscible solvents under conditions leading to the formation of 2D superstructures of silica cages, the thinnest mesoporous silica films synthesized to date. Orientational correlations between cage units increase with increasing layer number controlled via pH, while swelling with oil and mixed surfactants increase micelle size dispersity, leading to complex clathrate type structures in multilayer superstructures.

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.

Early Formation Pathways of Surfactant Micelle Directed Ultrasmall Silica Ring and Cage Structures.

By combining a surfactant, an organic pore expander, a silane, and poly(ethylene glycol) (PEG), we have observed the formation of a previously unknown set of ultrasmall silica structures in aqueous solutions. At appropriate concentrations of reagents, ∼2 nm primary silica clusters arrange around surfactant micelles to form ultrasmall silica rings, which can further evolve into cage-like structures. With increasing concentration, these rings line up into segmented worm-like one-dimensional (1D) structures, an effect that can be dramatically enhanced by PEG addition.

The Impact of Core/Shell Sizes on the Optical Gain Characteristics of CdSe/CdS Quantum Dots.

Colloidal quantum dots (QDs) are highly attractive as the active material for optical amplifiers and lasers. Here, we address the relation between the structure of CdSe/CdS core/shell QDs, the material gain they can deliver, and the threshold needed to attain net stimulated emission by optical pumping. On the basis of an initial gain model, we predict that reducing the thickness of the CdS shell grown around a given CdSe core will increase the maximal material gain, while increasing the shell thickness will lower the gain threshold.

Publisher Correction: Self-assembly of highly symmetrical, ultrasmall inorganic cages directed by surfactant micelles.

Change history: In Fig. 3b of this Letter, the labels for the outer (11.8 nm) and inner (7.

Self-assembly of highly symmetrical, ultrasmall inorganic cages directed by surfactant micelles.

Nanometre-sized objects with highly symmetrical, cage-like polyhedral shapes, often with icosahedral symmetry, have recently been assembled from DNA, RNA or proteins for applications in biology and medicine. These achievements relied on advances in the development of programmable self-assembling biological materials, and on rapidly developing techniques for generating three-dimensional (3D) reconstructions from cryo-electron microscopy images of single particles, which provide high-resolution structural characterization of biological complexes. Such single-particle 3D reconstruction approaches have not yet been successfully applied to the identification of synthetic inorganic nanomaterials with highly symmetrical cage-like shapes.

Fluorescent Silica Nanoparticles with Well-Separated Intensity Distributions from Batch Reactions.

Silica chemistry provides pathways to uniquely tunable nanoparticle platforms for biological imaging. It has been a long-standing problem to synthesize fluorescent silica nanoparticles (SNPs) in batch reactions with high and low fluorescence intensity levels for reliable use as an intensity barcode, which would greatly increase the number of molecular species that could be tagged intracellularly and simultaneously observed in conventional fluorescence microscopy. Here, employing an amino-acid catalyzed growth, highly fluorescent SNP probes were synthesized with sizes <40 nm and well-separated intensity distributions, as mapped by single-particle imaging techniques.

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

We investigate the encapsulation of CdSe/CdS quantum dots (QDs) in a silica shell by in situ Raman spectroscopy and find a distinct shift of the CdS Raman signal during the first hours of the synthesis. This shift does not depend on the final silica shell thickness but on the properties of the initial core-shell QD. We find a correlation between the Raman shift rate and the speed of the silica formation and attribute this to the changing configuration of the outermost layers of the QD shell, where an interface to the newly formed silica is created.

Magnetic polaron on dangling-bond spins in CdSe colloidal nanocrystals.

Non-magnetic colloidal nanostructures can demonstrate magnetic properties typical for diluted magnetic semiconductors because the spins of dangling bonds at their surface can act as the localized spins of magnetic ions. Here we report the observation of dangling-bond magnetic polarons (DBMPs) in 2.8-nm diameter CdSe colloidal nanocrystals (NCs).

On-Chip Integrated Quantum-Dot-Silicon-Nitride Microdisk Lasers.

Hybrid silicon nitride (SiN)-quantum-dot (QD) microlasers coupled to a passive SiN output waveguide with a 7 µm diameter and a record-low threshold density of 27 µJ cm are demonstrated. A new design and processing scheme offers long-term stability and facilitates in-depth QD material and device characterization, thereby opening new paths for optical communication, sensing, and on-chip cavity quantum optics based on colloidal QDs.

Sensitive QD@SiO2-based immunoassay for triplex determination of cereal-borne mycotoxins.

A sensitive tool for simultaneous quantitative determination of three analytes in one single well of a microtiter plate is shown for the first time. The developed technique is based on use of colloidal quantum dot enrobed into a silica shell (QD@SiO2) derivatives as a highly responsive label. Silica-coated quantum dots were prepared and subsequently modified via the co-hydrolysis with tetraethylorthosilicate (TEOS) and various organosilane reagents.

Fabrication and characterization of on-chip silicon nitride microdisk integrated with colloidal quantum dots.

We designed and fabricated free-standing, waveguide-coupled silicon nitride microdisks hybridly integrated with embedded colloidal quantum dots. An efficient coupling of quantum dot emission to resonant disk modes and eventually to the access waveguides is demonstrated. The amount of light coupled out to the access waveguide can be tuned by controlling its dimensions and offset with the disk edge.

Synthesis, modification, bioconjugation of silica coated fluorescent quantum dots and their application for mycotoxin detection.

To create bright and stable fluorescent biolabels for immunoassay detection of mycotoxin deoxynivalenol in food and feed, CdSe/CdS/ZnS core-shell quantum dots (QDs) were encapsulated in silica nanoparticles through a water-in-oil reverse microemulsion process. The optical properties and stability of the obtained silica coated QDs (QD@SiO2), modified with amino, carboxyl and epoxy groups and stabilized with polyethylene glycol fragments, were characterized in order to assess their bioapplicability. The developed co-condensation techniques allowed maintaining 80% of the initial fluorescent properties and yielded stable fluorescent labels that could be easily activated and bioconjugated.

Nanoscale and Single-Dot Patterning of Colloidal Quantum Dots.

Using an optimized lift-off process we develop a technique for both nanoscale and single-dot patterning of colloidal quantum dot films, demonstrating feature sizes down to ~30 nm for uniform films and a yield of 40% for single-dot positioning, which is in good agreement with a newly developed theoretical model. While first of all presenting a unique tool for studying physics of single quantum dots, the process also provides a pathway toward practical quantum dot-based optoelectronic devices.

The Effect of Intracellular Degradation on Cytotoxicity and Cell Labeling Efficacy of Inorganic Ligand-Stabilized Colloidal CdSe/CdS Quantum Dots.

Quantum dots (QDots) are explored in biomedicine as highly fluorescent, photostable nanomaterials, but their use is impeded by their hydrophobic nature. In the present work, we evaluate the potential biomedical use of QDots that have been transferred into the aqueous phase by means of inorganic ligands. CdSe/CdS QDots were prepared and transferred to water upon ligand exchange to S(2-) ions.

Low-loss silicon nitride waveguide hybridly integrated with colloidal quantum dots.

Silicon nitride waveguides with a monolayer of colloidal quantum dots embedded inside were fabricated using a low-temperature deposition process and an optimized dry etching step for the composite layers. We experimentally demonstrated the luminescence of the embedded quantum dots is preserved and the loss of these hybrid waveguide wires is as low as 2.69dB/cm at 900nm wavelength.

Active liquid crystal tuning of metallic nanoantenna enhanced light emission from colloidal quantum dots.

A system comprising an aluminum nanoantenna array on top of a luminescent colloidal quantum dot waveguide and covered by a thermotropic liquid crystal (LC) is introduced. By heating the LC above its critical temperature, we demonstrate that the concomitant refractive index change modifies the hybrid plasmonic-photonic resonances in the system. This enables active control of the spectrum and directionality of the narrow-band (∼6 nm) enhancement of quantum dot photoluminescence by the metallic nanoantennas.

Bright and stable CdSe/CdS@SiO₂ nanoparticles suitable for long-term cell labeling.

We report on the synthesis of luminescent CdSe/CdS@SiO2 nanoparticles and their application to cell labeling. The main novelty of these nanoparticles is the use of newly developed "flash" CdSe/CdS quantum dots (QDs), which are obtained through a new fast and efficient synthesis method recently reported. These core-shell QDs are encapsulated in silica nanoparticles through a water-in-oil microemulsion process, resulting in CdSe/CdS@SiO2 nanoparticles with good morphology and controlled architecture.