Nanocrystal Core Research Articles

Structural design of zein-cellulose nanocrystals core–shell microparticles for delivery of curcumin

The novel core–shell microparticles were fabricated to deliver curcumin by using hydrophobic zein microparticles as the core and hydrophilic cellulose nanocrystals (CNCs) as the shell. Different concentrations (0.10–1.50%, w/v) of CNCs were utilized to regulate the microstructure, physicochemical stability, and in vitro digestion of the core–shell microparticles. The size of the microparticles ranged from 1017.3 to 3663.7 nm. Electrostatic attraction and hydrophobic interactions were responsible for the assembly of zein-CNCs core–shell microparticles. The microstructure of the microparticles was dependent on the CNCs level. The retention rate of curcumin in the core–shell microparticles was increased by 76.41% after UV radiation. Furthermore, the rise of CNCs level delayed the release of curcumin from the microparticles in gastrointestinal tract and reduced its bioaccessibility. The potential of utilizing hydrophilic nanoparticles was explored to stabilize hydrophobic microparticles through interparticle interactions, which was useful to develop the novel core–shell microparticles for the application in functional foods.

Glyconanofluorides as Immunotracers with a Tunable Core Composition for Sensitive Hotspot Magnetic Resonance Imaging of Inflammatory Activity.

Nature-inspired nanosized formulations based on an imageable, small-sized inorganic core scaffold, on which biomolecules are assembled to form nanobiomimetics, hold great promise for both early diagnostics and developed therapeutics. Nevertheless, the fabrication of nanobiomimetics that allow noninvasive background-free mapping of pathological events with improved sensitivity, enhanced specificity, and multiplexed capabilities remains a major challenge. Here, we introduce paramagnetic glyconanofluorides as small-sized (<10 nm) glycomimetics for immunotargeting and sensitive noninvasive in vivo19F magnetic resonance imaging (MRI) mapping of inflammation. A very short T1 relaxation time (70 ms) of the fluorides was achieved by doping the nanofluorides’ solid crystal core with paramagnetic Sm3+, resulting in a significant 8-fold enhancement in their 19F MRI sensitivity, allowing faster acquisition and improved detectability levels. The fabricated nanosized glycomimetics exhibit significantly enhanced uptake within activated immune cells, providing background-free in vivo mapping of inflammatory activity, demonstrated in both locally induced inflammation and clinically related neuropathology animal models. Fabricating two types of nanofluorides, each with a distinct chemical shift, allowed us to exploit the color-like features of 19F MRI to map, in real time, immune specificity and preferred targetability of the paramagnetic glyconanofluorides, demonstrating the approach’s potential extension to noninvasive multitarget imaging scenarios that are not yet applicable for nanobiomimetics based on other nanocrystal cores.

Repulsive, Densely Packed Ligand-Shells Mediate Interactions between PbS Nanocrystals in Solution

The surface capping ligands on nanocrystals (NCs) impart colloidal stability and determine the organization into ordered solids when cast from solution. Here, we use small-angle neutron scattering (SANS) to measure the solution structure factor in dispersions of fully passivated, oleate-capped PbS NCs up to concentrations of 16 v/v%. Fitting the data by assuming an attractive square well interaction potential between NCs yields a repulsive core diameter larger than the physical NC core diameter. This repulsive core stems from a densely packed region of the ligand-shell near the NC surface. The spatial extent of the repulsive core increases with temperature as ligand motion increases, becoming repulsive farther out in the ligand-shell, while the portion of ligand-shell outside of the repulsive region remains attractive with a strength of ∼1 kBT. SANS provides a molecular interpretation of the fundamental interparticle interactions in colloidal nanocrystal suspensions, ultimately relevant to understanding the self-organization of nanoscale materials.

Engineering carbon-shells of M@NC bifunctional oxygen electrocatalyst towards stable aqueous rechargeable Zn-air batteries

Non-precious transition-metal based materials have attracted increasing attention as an efficient oxygen electrocatalysts for Zn-air battery although their unsatisfactory durability in harsh charging/discharging cycling condition makes their practical application still challenging. Herein, we report a facile strategy for the synthesis of high-density and well-dispersed FeCo nanocrystals encapsulated in tunable N-doped carbon shells ([email protected]) on porous carbon support. The morphology and structure of the carbon shells are intentionally engineered to achieve two types of catalysts, one with complete and well-graphitized carbon shells ([email protected]) and the other with disordered and defect-rich carbon shells ([email protected]), to investigate their influences on battery performance. Systematic experiments suggest that although two catalysts hold similar physiochemical features including nanoparticle size and loading, surface area, N-doping content as well as ORR or OER activity in half-cell measurements etc., they exhibit distinct stability during ORR/OER cycling. The complete and graphitized carbon shells were found to be able to keep FeCo nanocrystal core unchanged and maintain its ORR activity thus the battery performance during cycling. However, the disordered and defect-rich carbon shells cannot prevent the nanoparticles from conversion into hydroxide or oxyhydroxide, leading to the irreversible sharp decay of ORR activity and battery performance. As a result, the Zn-air battery with [email protected] as air catalysts demonstrates superior charging/discharging durability with much higher power density of 190.2 mW cm−2 compared with that with [email protected] These findings might inspire the strategies for the construction of efficient and durable non-precious metal based bifunctional electrocatalysts for advanced metal-air batteries and other energy devices.

Triskelion Structured Colloidal Quantum Dots.

We show, using density functional theory and ab initio molecular dynamics, that certain small colloidal quantum dots with a mixed nanocrystal core capped with achiral surface ligands spontaneously form a triskelion (from the Greek, three-legged) structure with (approximate) C3 symmetry that can be dynamically stable at room temperature when additionally capped with small amine ligands. Furthermore, the nanocrystal core also forms a triskelion structure. The focus of our study is a colloidal quantum dot with a Cd16Se7Te3 core (and a charge of +12) capped with negatively charged surface ligands to achieve charge neutrality-in the simplest instance, 12 Cl--to form the colloidal quantum dot Cd16Se7Te3Cl12. The small size of the core (for which almost all atoms are surface atoms), the high positive charge that destabilizes the core, the mixed (Cd/Te) composition that creates mechanical strain in the core, and the inclusion of precisely three Te atoms in the predominantly Se core all play critical roles in the spontaneous formation of the triskelion structure.

Suppression of temperature quenching in perovskite nanocrystals for efficient and thermally stable light-emitting diodes

The thermal quenching of light emission is a critical bottleneck that hampers the real-world application of lead halide perovskite nanocrystals in both electroluminescent and down-conversion light-emitting diodes. Here, we report CsPbBr3 perovskite nanocrystals with a temperature-independent emission efficiency of near unity and constant decay kinetics up to a temperature of 373 K. This unprecedented regime is obtained by a fluoride post-synthesis treatment that produces fluorine-rich surfaces with a wider energy gap than the inner nanocrystal core, yielding suppressed carrier trapping, improved thermal stability and efficient charge injection. Light-emitting diodes incorporating these fluoride-treated perovskite nanocrystals show a low turn-on voltage and spectrally pure green electroluminescence with an external quantum efficiency as high as 19.3% at 350 cd m−2. Importantly, nearly 80% of the room-temperature external quantum efficiency is preserved at 343 K, in contrast to the dramatic drop commonly observed for standard CsPbBr3 perovskite nanocrystal light-emitting diodes. These results provide a promising pathway for high-performance, practical light-emitting diodes based on perovskite nanostructures. Fluoride-treated CsPbBr3 nanocrystals emit light with near unity efficiency at temperatures of up to 373 K.

Nanocrystal-loaded liposome for targeted delivery of poorly water-soluble antitumor drugs with high drug loading and stability towards efficient cancer therapy

Nanocrystals (NCs) enable the delivery of poorly water-soluble drugs with improved dissolution and bioavailability. However, their uncontrolled release and instability make targeted delivery challenging. Herein, a nano-in-nano delivery system composed of a drug nanocrystal core and liposome shell (NC@Lipo) is presented, which merges the advantages of drug nanocrystals (high drug loading) and liposomes (easy surface functionalization and high stability) for targeted delivery of hydrophobic drugs to tumors. CHMFL-ABL-053 (053), a hydrophobic drug candidate discovered by our group, was employed as a model drug to demonstrate the performance of NC@Lipo delivery system. Surface PEGylated (053-NC@PEG-Lipo) and folic acid-functionalized (053-NC@FA-Lipo) formulations were fabricated by wet ball milling combined with probe sonication. 053-NC@Lipo enabled high drug loading (up to 19.51%), considerably better colloidal stability, and longer circulation in vivo than 053-NC. Compared with free 053, 053-NC@PEG-Lipo and 053-NC@FA-Lipo exhibited higher tumor accumulation and considerably better in vivo antitumor efficacy in K562 xenograft mice with tumor growth inhibition rate (TGI) of up to 98%. Additionally, more effective tumor cell targeting in vitro and higher TGI in vivo were achieved with 053-NC@FA-Lipo. The NC@Lipo strategy may contribute to the targeted delivery of poorly water-soluble drugs with high drug loading, high stability, and tailorable surface, and has potential for the development of more efficient nanocrystal- and liposome-based formulations for commercial and clinical applications. It may also provide new opportunities for potential clinical application of candidate 053.

Uncovering the Role of Countercations in Ligand Exchange of WSe2: Tuning the d-Band Center toward Improved Hydrogen Desorption

The role of countercations that do not bind to core nanocrystals (NCs) but rather ensure charge balance on ligand-exchanged NC surfaces has been rarely studied and even neglected. Such a scenario is unfortunate, as an understanding of surface chemistry has emerged as a key factor in overcoming colloidal NC limitations as catalysts. In this work, we report on the unprecedented role of countercations in ligand exchange for a colloidal transition metal dichalcogenide (TMD), WSe2, to tune the d-band center toward the Fermi level for enhanced hydrogen desorption. Conventional long-chain organic ligands, oleylamine, of WSe2 NCs are exchanged with short atomic S2- ligands having countercations to preserve the charge balance (WSe2/S2-/M+, M = Li, Na, K). Upon exchange with S2- ligands, the charge-balancing countercations are intercalated between WSe2 layers, thereby serving a unique function as an electrochemical hydrogen evolution reaction (HER) catalyst. The HER activity of ligand-exchanged colloidal WSe2 NCs shows a decrease in overpotential by down-shift of d-band center to induce more electron-filling in antibonding orbital and an increase in the electrochemical active surface area (ECSA). Exchanging surface functionalities with S2- anionic ligands enhances HER kinetics, while the existence of intercalated countercations improves charge transfer with the electrolyte. The obtained results suggest that both anionic ligands and countercationic species in ligand exchange must be considered to enhance the overall catalytic activity of colloidal TMDs.

Anion Constructor for Atomic‐Scale Engineering of Antiperovskite Crystals for Electrochemical Reactions

AbstractAmong the Pt group metals, Pd has been considered the most efficient for application in electrocatalysts as an alternative to Pt. Despite the comparable electrochemical activities of Pd and Pd‐metal alloys, they are vulnerable to liquid acidic electrolytes, leading to degradation of catalytic activity. Pd–Ni alloys have been used to enhance catalytic activity because the electronic structure of Pd can be easily changed by adding Ni. In other studies, N atoms have been introduced for more stable M–Ni catalysts by inducing the formation of Ni4N species; however, the structural analysis and the role of nitrogen have not been fully understood yet. Herein, the Pd–Ni alloy nitride with a unique crystal structure shows a promising catalytic activity for oxygen reduction reaction (ORR). The nitride PdNi nanoparticles have a novel monolithic antiperovskite structure of chemical formula (PdxNi1−x)NNi3. The unique antiperovskite crystal (PdxNi1−x)NNi3 possesses superior ORR activity and stability, originating from the downshifted d‐band center of the monolayer Pd/antiperovskite surface and the lower formation energy of the antiperovskite core nanocrystal. Consequently, (PdxNi1−x)NNi3, as a Pt‐free Pd‐based electrocatalyst, overcomes the stability issue of Pd under acidic conditions by achieving 99‐times higher mass activity than commercial Pd/C, as shown by the durability test.

Brain-targeting delivery of MMB4 DMS using carrier-free nanomedicine CRT-MMB4@MDZ

Brain-targeting delivery of 1,1′-methylenebis[4-[(hydroxyimino)methyl]-pyridinium] dimethanesulfonate (MMB4 DMS) is limited by its hydrophilic property and chemical instability. In order to solve this problem, herein, we develop a facile protocol through combining antisolvent precipitation and emulsion-solvent evaporation method to synthesize midazolam (MDZ) coated MMB4 DMS (MMB4@MDZ) nanoparticles. The as-prepared MMB4@MDZ had a MMB4 DMS nanocrystal (MMB4-NC) core and a MDZ shell. The MDZ shell prevented the MMB4-NC core from contacting the aqueous environment, and thus, guaranteed the chemical stability of MMB4 DMS. Most charmingly, the iron mimic cyclic peptide CRTIGPSVC (CRT) was modified on MMB4@MDZ surfaces to produce CRT-MMB4@MDZ which was endowed with ability to absorb transferrin (Tf)-abundant corona. Taking advantages of the Tf-abundant corona, CRT-MMB4@MDZ achieved transferrin receptor (TfR)-mediated brain-targeting delivery. With the fascinating chemical stability and brain-targeting delivery effect, CRT-MMB4@MDZ showed great clinical transform prospect as a brand-new nanomedicine. Of particular importance, this work promised not only a core–shell carrier-free nanomedicine platform for effective delivery of unstable water-soluble drug, but also a protein corona-manipulating strategy for targeting delivery.

Technology progress on quantum dot light-emitting diodes for next-generation displays.

Quantum dot light-emitting diodes (QD-LEDs) are widely recognised as great alternatives to organic light-emitting diodes (OLEDs) due to their enhanced performances. This focus article surveys the current progress on the state-of-the-art QD-LED technology including material synthesis, device optimization and innovative fabrication processes. A discussion on the material synthesis of core nanocrystals, shell layers and surface-binding ligands is presented for high photoluminescence quantum yield (PLQY) quantum dots (QDs) using heavy-metal free materials. The operational principles of several types of QD-LED device architectures are also covered, and the recent evolution of device engineering technologies is investigated. By exploring the fabrication process for pixel-patterning of QD-LEDs on an active-matrix backplane for full-colour display applications, we anticipate further improvement in device performance for the commercialisation of next-generation displays.

Triggered Release from Cellulose Microparticles Inspired by Wood Degradation by Fungi

Triggered compound release has attracted considerable attention in recent years. However, the concepts and carriers reported for triggered release are often complex while nonapproved ingredients are mostly used to make the carriers. In this study, a bioinspired reactive oxygen species (ROS)-mediated delivery system, triggered by light, is introduced. We took inspiration from the well-known ROS mediated degradation of wood (cellulose) by brown-rot fungi and designed microparticles which consist of a core of cellulose nanocrystals, loaded with a drug, surrounded by a light sensitive shell. Incorporating indocyanine green, an FDA-approved photosensitizer, in the shell of the microparticles generates ROS upon NIR laser irradiation, which degrades the cellulose nanocrystals in the microparticles. It was revealed that doxorubicin, encapsulated in the cellulose core and used as a model compound in our study, becomes specifically released upon NIR irradiation of the microparticles. Attractive as well is that the microparticles are prepared by a simple one-step gas-shearing process and fully consist of compounds generally regarded as safe (GRAS).

Molecular Origin of Electrical Conductivity in Gold-Polythiophene Hybrid Particle Films.

Hybrid electronic materials combine inorganic metals and semiconductors with π-conjugated polymers. The orientation of the polymer molecules in relation to the inorganic components is crucial for electrical material properties and device performance, but little is known of the configuration of π-conjugated polymers that bind to inorganic surfaces. Highly curved surfaces are common when using nanoscale components, for example, metal nanocrystal cores covered with conductive polymers. It is important to understand their effect on molecular arrangement. Here, we compare the molecular structures and electrical conductivities of well-defined nanoscale gold spheres and rods with shells of the covalently bound polythiophene PTEBS (poly[2-(3-thienyl)-ethyloxy-4-butylsulfonate]). We prepared aqueous sinter-free inks from the particles and printed them. The particles formed highly conductive films immediately after drying. Films with spherical metal cores consistently had 40% lower conductivities than films based on nanorods. Raman and X-ray photoelectron spectroscopy revealed differences in the gold-sulfur bonds of PTEBS on rods and spheres. The fractions of bond sulfur groups implied differences in the alignment of PTEBS with the surface. More polymer molecules were bound in an edge-on configuration on spheres than on rods, where almost all polymers aligned "face-on" with the metal surface. This leads to different interface resistances: gold-polythiophene-gold interfaces between rods with π-π-tacked face-on PTEBS apparently foster electron transport along the surface-normal direction, while edge-on PTEBS does not. Molecular confinement thus increases the conductivity of hybrid inks based on highly curved nanostructures.

Ligand structure and adsorption free energy of nanocrystals on solid substrates.

We present an investigation on the absorption of alkylthiolated nanocrystals on a solid substrate. We calculate adsorption free energies and report a number of effects induced by the substrate. Nearest neighbor distances and bonding free energies are significantly different than for a free floating case, there is a weakening of bonding free energies among nanocrystals, and the adsorption is manifestly anisotropic, i.e., stronger along certain directions of the nanocrystal core. We contend that this last result accounts for the Bain transition (fcc → bcc) observed in experimental results. We report the presence of vortices induced by the substrate, which explain the increased nearest neighbor distance among nanocrystals, which is in excellent quantitative agreement with experimental results and with the predictions of the Orbifold Topological Model. Implications for the assembly of nanostructures and future experiments are also discussed.

Phase-Controlled Growth of CuInS2 Shells to Realize Colloidal CuInSe2/CuInS2 Core/Shell Nanostructures.

Synthetic routes to deposit CuInS2 (CIS) shells with either a cubic chalcopyrite (CP) or a hexagonal wurtzite (WZ) phase on trigonal pyramidal-shaped CuInSe2 (CISe) core nanocrystals (NCs) with a cubic CP crystal structure have been developed and governed by tuning the amount of the sulfur precursor tert-dodecanethiol. During the synthesis of CP-CIS/CP-CISe core/shell NCs, the CP-CIS shell initially starts to grow epitaxially in a uniform way, while the further addition of the CIS precursor induces islandlike growth, and finally a branched CIS shell is formed. In a stark contrast, when a WZ-CIS shell is deposited, it initially grows on a portion of each of the facets of the trigonal pyramidal-shaped CISe cores to form a monolayer, which then continues to increase in thickness and forms a multilayered WZ-CIS shell. Both CP-CISe/CP-CIS core/shell NCs and CP-CISe/WZ-CISe core/shell NCs exhibit rather low photoluminescence quantum yields (<10%), even with a smaller-sized CISe core, which calls for further refinements of the shell growth methods. Synthetic methods for the growth of CIS shells as described here allow for direct deposition of cadmium-free ternary compounds as shell materials and provide important insights into the different modes of growth of heterostructured NCs, ranging from epitaxial to island- and branched-like, as well to the facet-specific multilayer deposition.

Silicate Nanocrystals: PEDOT Encapsulated and Mechanochemically Engineered Silicate Nanocrystals for High Energy Density Cathodes (Adv. Mater. Interfaces 13/2020)

In article number 2000226 Majid Rasool, George P. Demopoulos, and co-workers report the fabrication of a robust core-shell lithium iron silicate (Li2FeSiO4, LFS) cathode architecture, where nanocrystal's core is prepared via mechanochemical annealing and shell via PEDOT polymerization. As a result of the devised mechanochemical/interphasial engineering of the [email protected] nanocrystals, their Li-ion storage capacity is augmented to >1 Li, namely 200 mAh g−1 after 50 cycles or 1.2 Li+ units-the highest capacity reported for the Pmn21 LFS cathode.

Cu-In-S/ZnS@carboxymethylcellulose supramolecular structures: Fluorescent nanoarchitectures for targeted-theranostics of cancer cells

Although the field of oncology nanomedicine has shown indisputable progress in recent years, cancer remains one of the most lethal diseases, where the early diagnosis plays a pivotal role in the patient's prognosis and therapy. Herein, we report for the first time, the synthesis of biocompatible nanostructures composed of Cu-In-S and Cu-In-S/ZnS nanoparticles functionalized with carboxymethylcellulose biopolymer produced by a green aqueous process. These inorganic-organic colloidal nanohybrids developed supramolecular architectures stabilized by chemical functional groups of the polysaccharide shell with the fluorescent semiconductor nanocrystal core, which were extensively characterized by several morphological and spectroscopical techniques. Moreover, these nanoconjugates were covalently bonded with folic acid via amide bonds and electrostatically conjugated with the anticancer drug, producing functionalized supramolecular nanostructures. They demonstrated nanotheranostics properties for bioimaging and drug delivery vectorization effective for killing breast cancer cells in vitro. These hybrids offer a new nanoplatform using fluorescent polysaccharide-drug conjugates for cancer theranostics applications.

Thermal-responsive multicolor emission of single NaGdF4:Yb/Ce/Ho upconversion nanocrystals for anticounterfeiting application

Abstract This study presents a novel and high-level anticounterfeiting strategy based on Ce/Yb/Ho triply-doped NaGdF4 nanocrystals with temperature-responsive multicolor emission. A critical factor leading to the multicolor emission is confirmed by comparing the luminescence thermal behaviors of nanocrystals in various atmospheres. Through analyzing the temperature-dependent lifetimes of Yb3+ ions in air, we demonstrate that thermally-induced multicolor emission mainly originates from the gradually-attenuated H2O quenching effect. Because the cross-relaxations between Ce3+ and Ho3+ ions and the nonradiative transitions of Yb3+ ions create plenty of phonon heat, the multicolor emission of nanocrystals can be achieved under 975 nm excitation at a relatively low power density. This recognition method is efficient and convenient for security authentication. The as-synthesized core nanocrystals can be directly used to fabricate anticounterfeiting ink without further processing (e.g. core/shell or hybrid). Therefore, the small-sized β-NaGdF4:Yb/Ce/Ho nanocrystals are promising candidate for security application.

High numerical aperture photonic crystal fiber with silicon nanocrystals core for optical coherence tomography

A simple photonic crystal fiber (PCF) structure with silicon nanocrystals (Si-nc) embedded in core is proposed. The influence of geometric parameters is numerically investigated and three high numerical aperture PCFs for optical coherence tomography are designed. The zero dispersion wavelengths are at 0.83 μm, 1.06 μm and 1.31 μm wavelengths which are used for ophthalmology, dermatology and dentistry, respectively. By introducing a circular rod composed of Si-nc in the center of core region, the numerical apertures are greatly improved, which are 0.61 at 0.83 μm wavelength, 0.65 at 1.06 μm wavelength and 0.66 at 1.31 μm wavelength, respectively. The transverse resolutions as high as 0.463 μm, 0.563 μm and 0.682 μm are obtained correspondingly. Moreover, the confinement losses are as low as 4.5 × 10−8 dB/km at 0.83 μm wavelength for PCF1, 3.8 × 10−7 dB/km at 1.06 μm wavelength for PCF2, 2.2 × 10−6 dB/km at 1.31 μm wavelength for PCF3, respectively.

Development and solidification of multifunction stabilizers formulated self-assembled core-shell Deacetyl mycoepoxydience nanosuspensions

In this study, a novel core-shell structure Deacetyl mycoepoxydience nanosuspensions (CS-DM-NSs) delivery system was successfully designed by self-assembly method and the solidification technology was also investigated. The Deacetyl mycoepoxydience (DM) nanocrystals core was prepared by anti-solvent precipitation with folate modified distearoylphosphatidyl ethanolamine-polyethylene glycol (DSPE-PEG2000-FA) and D-α-tocopheryl polyethylene glycol succinate (TPGS) as functional stabilizers. Then the DM nanocrystals core was completely wrapped by the polyethylene glycol-hyaluronic acid (PEG-HA) as shell. To improve the stability, the CS-DM-NSs were solidified by spray-drying and freeze-drying, respectively. The influence of the solidification approach on the solidified powders was demonstrated by TEM and SEM. Compared with the freeze dried CS-DM-NSs, the spray dried powder presented spherical in shape with smooth surface. The dissolution velocity of the two powders was higher than to the raw drug (3.5-fold and 4.5-fold, respectively). The solidified CS-DM-NSs presented dose- and time- dependent cytotoxicity to cancer cells (MCF-7) and significantly higher cytotoxicity than the free DM. In addition, there was no significant difference between the spray-drying and the freeze-drying solidified CS-DM-NSs. Overall, the CS-DM-NSs showed promising potential as a drug carrier for cancer therapy and the spray drying could be confidently used for the CS-DM-NSs solidification with higher stability, smaller particle size, and faster dissolution rate.