One‐Step Fabrication of Multifunctional Core‐Shell Fibres by Co‐Electrospinning

In the present study, multifunctional core‐shell fibre mats were designed by co‐electrospinning. These core‐shell fibre mats have three different functionalities: 1) they are magnetic, 2) they change their optical properties with the pH of the media, and 3) they are sensitive to O₂. The shell is formed by a fluorescent pH‐sensitive co‐polymer which was previously synthesised and characterized by our research group. The core is a suspension formed by magnetic nanoparticles in a solution made up by a lipophilic indicator dye (oxygen indicator; PtOEP) and, poly‐methyl methacrylate, in THF. The magnetic nanoparticles were prepared by encapsulation of magnetite within a cross‐linked polymeric matrix (MMA‐co‐EDMA). To our knowledge, this is the first time that three functionalities (magnetic properties, sensitivity to pH, and response to O₂ concentration) were successful conjugated on the same micro‐ or nano‐material via a facile one‐step process with high yield and cost effectiveness. The morphology of the well‐organized core‐shell fibres were characterized by high resolution scanning electron microcopy (HRSEM), transmission electron microcopy (TEM), and confocal laser microscopy. The luminescent properties of core‐shell fibre mats were analysed and successfully used for simultaneously monitoring pH (from 6 to 8) and O₂, showing complete reversibility, high sensitivity (i.e., K_sv = 7.07 bar^?1 for determining O₂ in aqueous media), high magnetic susceptibility, and short response times.     

PbS/CdS/ZnS Quantum Dots: A Multifunctional Platform for In Vivo Near‐Infrared Low‐Dose Fluorescence Imaging

Over the past decade, near‐infrared (NIR)‐emitting nanoparticles have increasingly been investigated in biomedical research for use as fluorescent imaging probes. Here, high‐quality water‐dispersible core/shell/shell PbS/CdS/ZnS quantum dots (hereafter QDs) as NIR imaging probes fabricated through a rapid, cost‐effective microwave‐assisted cation exchange procedure are reported. These QDs have proven to be water dispersible, stable, and are expected to be nontoxic, resulting from the growth of an outer ZnS shell and the simultaneous surface functionalization with mercaptopropionic acid ligands. Care is taken to design the emission wavelength of the QDs probe lying within the second biological window (1000–1350 nm), which leads to higher penetration depths because of the low extinction coefficient of biological tissues in this spectral range. Furthermore, their intense fluorescence emission enables to follow the real‐time evolution of QD biodistribution among different organs of living mice, after low‐dose intravenous administration. In this paper, QD platform has proven to be capable (ex vivo and in vitro) of high‐resolution thermal sensing in the physiological temperature range. The investigation, together with the lack of noticeable toxicity from these PbS/CdS/ZnS QDs after preliminary studies, paves the way for their use as outstanding multifunctional probes both for in vitro and in vivo applications in biomedicine.     

Addressing Particle Compositional Heterogeneities in Super-Resolution-Enhanced Live-Cell Ratiometric pH Sensing with Ultrasmall Fluorescent Core–Shell Aluminosilicate Nanoparticles

The interrogation of metabolic parameters like pH in live-cell experiments using optical super-resolution microscopy (SRM) remains challenging. This is due to a paucity of appropriate metabolic probes enabling live-cell SRM-based sensing. Here, ultrasmall fluorescent core–shell aluminosilicate nanoparticle sensors (FAM–ATTO647N aC′ dots) that covalently encapsulate a reference dye (ATTO647N) in the core and a pH-sensing moiety (FAM) in the shell are introduced. Only the reference dye exhibits optical blinking enabling live-cell stochastic optical reconstruction microscopy (STORM). Using data from cells incubated for 60 min with FAM–ATTO647N aC′ dots, pixelated information from total internal reflection fluorescence (TIRF) microscopy-based ratiometric sensing can be combined with that from STORM-based localizations via the blinking reference dye in order to enhance the resolution of ratiometric pH sensor maps beyond the optical diffraction limit. A nearest-neighbor interpolation methodology is developed to quantitatively address particle compositional heterogeneity as determined by separate single-particle fluorescence imaging methods. When combined with STORM-based estimates of the number of particles per vesicle, vesicle size, and vesicular motion as a whole, this analysis provides detailed live-cell spatial and functional information, paving the way to a comprehensive mapping and understanding of the spatiotemporal evolution of nanoparticle processing by cells important, e.g., for applications in nanomedicine.     

Self‐Organization and/or Nanocrystallinity of Co Nanocrystals Effects on the Oxidation Process Using High‐Energy Electron Beam

The enhanced stability of Co nanocrystals (NCs) when they are highly ordered at both nanometer and micrometer scales is reported. For the first time, it is shown that both the crystalline structure of Co nanoparticles (NPs) and their 2D hexagonal organization have a significant impact on the oxidation process rate enabling to produce various types of nanostructures including core‐shell NPs. The Co core can be either polycrystalline or hexagonal close‐packed (hcp) single‐crystalline, whereas the oxide shell is composed either of CoO or of the spinel structrure Co₃O₄. The present results are evidenced through a careful high‐resolution transmission electron microscopy (HRTEM) study and are highly reproducible.     

Ag/Ag2S Nanocrystals for High Sensitivity Near‐Infrared Luminescence Nanothermometry

Temperature sensing in biological media (cells, tissues, and living organisms) has become essential in the development of the last generation of diagnostics and therapeutic strategies. Thermometry can be used for early detection of different diseases, such as cancer, stroke, or inflammation processes, one of whose incipient symptoms is the appearance of localized temperature singularities. Luminescence nanothermometry, as a tool to accurately provide temperature sensing in biological media, requires the rational design and development of nanothermometers operating in the second biological window. In this work, this is achieved using Ag/Ag₂S nanocrystals as multiparametric thermal sensing probes. Temperature sensing with remarkably high sensitivity (4% °C^?1) is possible through intensity‐based measurements, as their infrared emission is strongly quenched by small temperature variations within the biological range (15–50 °C). Heating also results in a remarkable redshift of the emission band, which allows for concentration‐independent temperature sensing based on infrared ratiometric measurements, with thermal sensitivity close to 2% °C^?1. These results make Ag/Ag₂S nanocrystals the most sensitive among all noncomposite nanothermometers operating in the second biological window reported so far, allowing for deep‐tissue temperature measurements with low uncertainty (0.2 °C).     

Carbon‐Based Composite as an Efficient and Stable Metal‐Free Electrocatalyst

Silicon carbide (SiC) encapsulated with graphitized nanodiamond (GD) sheaths (SiC‐GD) as a core–shell nanocrystal (NC) is synthesized with atomic H post‐treatment of vertically aligned carbon nanotubes, which are unzipped and converted into graphene nanoribbons (GNRs) and preserve their vertically aligned integrity. The SiC‐GD core–shell NCs anchor on the GNRs framework and form SiC‐GD@GNRs composite. The nucleation and growth mechanisms for single crystal nanodiamond without diamond seed are discussed. The SiC‐GD@GNRs composite as a metal‐free electrocatalyst exhibits a high activity in the hydrogen evolution reaction, with a small onset overpotential of 8 mV, Tafel slope of 54 mV dec^?1, and exchange current density @ 200 mV of 77.4 mV, as well as long term stability in acid medium. The superior electrocatalytic performances of SiC‐GD@GNRs are ascribed to a high dispersion of SiC‐GD NCs on the GNRs support and a high stability of the GD and GNRs in acid solution.     

Chitosan–Alginate Microcapsules Provide Gastric Protection and Intestinal Release of ICAM‐1‐Targeting Nanocarriers,Enabling GI Targeting In Vivo

When administered intravenously, active targeting of drug nanocarriers (NCs) improves biodistribution and endocytosis. Targeting may also improve NC oral delivery to treat gastrointestinal (GI) pathologies or for systemic absorption. However, GI instability of targeting moieties compromises this strategy. This study explores whether encapsulation of antibody‐coated NCs in microcapsules would protect against gastric degradation, providing NC release and targeting in intestinal conditions. Nanoparticles coated with antibodies against intercellular adhesion molecule‐1 (anti‐ICAM) or nonspecific immunoglobulin G (IgG) are encapsulated in chitosan (shell) ‐ alginate (core) microcapsules. Encapsulation efficiency is >95% and NC relase from microcapsules in storage is <10%. There is minimal NC release at gastric pH (<10%) and burst release at intestinal pH (75%–85%). Encapsulated NCs afford increased protection against degradation (threefold to fourfold) and increased cell targeting (8–20‐fold) after release versus the nonencapsulated NCs. Mouse oral gavage shows that microencapsulation provides 38%–65% greater protection of anti‐ICAM NCs in the GI tract, 40% lower gastric retention, and fourfold to ninefold enhanced intestinal biodistribution versus nonencapsulated NCs. Therefore, microencapsulation of antibody‐targeted NCs may enable active targeting strategies to be effective in the context of oral drug delivery.     

A Hydrogen‐Bonded‐Supramolecular‐Polymer‐Based Nanoprobe for Ratiometric Oxygen Sensing in Living Cells

The first example of a ratiometric optical oxygen nanoprobe based on a hydrogen‐bonded supramolecular polymer has been reported. The supramolecular polymer based nanoprobe (SPNP) is prepared from the co‐assembly of a bis‐ureidopyrimidinone (bis‐UPy)‐containing phosphorescent indicator (Por(Pd)‐bisUPy), fluorescent reference dye (BF₂‐bisUPy), and skeleton unit (DPA‐bisUPy) through quadruple hydrogen bonds by a mini‐emulsion method. The water‐dispersible SPNP is highly sensitive to oxygen (Q = 95%), with full reversibility, excellent storage stability and photostability, and good cell‐penetrating ability, and exhibits low cytotoxicity toward living cells. The preparation of the SPNP is straightforward and its function is easily tuned by changing the monomeric structure. This work is expected to lead to the design of other SPNPs for other important analytes in biological systems.     

Cover Picture: An Epoxy Photoresist Modified by Luminescent Nanocrystals for the Fabrication of 3D High‐Aspect‐Ratio Microstructures (Adv. Funct. Mater. 13/2007)

M. Lucia Curri and co‐workers report on p. 2009 an epoxy‐based negative tone photoresist that can be functionalized with red emitting CdSe@ZnS core/shell type nanocrystals and patterned by UV lithography. The 3D high aspect ratio of the microfabricated structures proves that lithographic properties of the functional nanocomposite are retained and the nanocrystals properties conveyed into the resist. The emitting nanocomposite represents a convenient model for material functionalization expandable to nanocrystals with different properties. An epoxy‐based negative‐tone photoresist, which is known as a suitable material for high‐aspect‐ratio surface micromachining, is functionalized with red‐light‐emitting CdSe@ZnS nanocrystals (NCs). The proper selection of a common solvent for the NCs and the resist is found to be critical for the efficient incorporation of the NCs in the epoxy matrix. The NC‐modified resist can be patterned by standard UV lithography down to micrometer‐scale resolution, and high‐aspect‐ratio structures have been successfully fabricated on a 100 mm scaled wafer. The “as‐fabricated”, 3D, epoxy‐based surface microstructures show the characteristic luminescent properties of the embedded NCs, as verified by fluorescence microscopy. This issue demonstrates that the NC emission properties can be conveniently conveyed into the polymer matrix without deteriorating the lithographic performance of the latter. The dimensions, the resolution, and the surface morphology of the NC‐modified‐epoxy microstructures exhibit only minor deviations with respect to that of the unmodified reference material, as examined by means of microscopic and metrologic investigations. The proposed approach of the incorporation of emitting and non‐bleachable NCs into a photoresist opens novel routes for surface patterning of integrated microsystems with inherent photonic functionality at the micro‐ and nanometer‐scale for light sensing and emitting applications.     

In Vivo Subcutaneous Thermal Video Recording by Supersensitive Infrared Nanothermometers

Some of the old and unrealizable dreams of biomedicine have become possible thanks to the appearance of novel advanced materials such as luminescent nanothermometers, nanoparticles capable of providing a contactless thermal reading through their light emission properties. Luminescent nanothermometers have already been demonstrated to be capable of in vivo subcutaneous punctual thermal reading but their real application as diagnosis tools still requires demonstrating their actual capacity for the acquisition of in vivo, time‐resolved subcutaneous thermal images. The transfer from 1D to 2D subcutaneous thermal sensing is blocked in the last years mainly due to the lack of high sensitivity luminescent nanothermometers operating in the infrared biological windows. This work demonstrates how core/shell engineering, in combination with selective rare earth doping, can be used to develop supersensitive infrared luminescent nanothermometers. Erbium, thulium, and ytterbium core–shell LaF₃ nanoparticles, operating within the biological windows, provide thermal sensitivities as large as 5% °C^?1. This “record” sensitivity has allowed for the final acquisition of subcutaneous thermal videos of a living animal. Subsequent analysis of thermal videos allows for an unequivocal determination of intrinsic properties of subcutaneous tissues, opening the venue to the development of novel thermal imaging‐based diagnosis tools.     

PbSe/PbS and PbSe/PbSexS1–x Core/Shell Nanocrystals

The synthesis of PbSe/PbS and PbSe/PbSe_xS_1–x core/shell nanocrystals (NCs) with luminescence quantum efficiencies of 45–55 % is reported. PbSe/PbS NCs are prepared via a two‐stage process, while the PbSe/PbSe_xS_1–x NCs are formed in a single‐stage procedure. The core/shell NCs exhibit an energy tuning of the exciton transitions, with respect to that of the core NC, that is dependent on the core diameter, shell thickness, and composition.     

Chloride and Indium‐Chloride‐Complex Inorganic Ligands for Efficient Stabilization of Nanocrystals in Solution and Doping of Nanocrystal Solids

Here, the surface functionalization of CdSe and CdSe/CdS core/shell nanocrystals (NCs) with compact chloride and indium‐chloride‐complex ligands is reported. The ligands provide not only short interparticle distances but additionally control doping and passivation of surface trap states, leading to enhanced electronic coupling in NC‐based arrays. The solids based on these NCs show an excellent electronic transport behavior after heat treatment at the relatively low temperature of 190 °C. Indeed, the indium‐chlorido‐capped 4.5 nm CdSe NC based thin‐film field‐effect transistor reaches a saturation mobility of μ = 4.1 cm² (V s)^?1 accompanied by a low hysteresis, while retaining the typical features of strongly quantum confined semiconductor NCs. The capping with chloride ions preserves the high photoluminescence quantum yield ( ≈ 66%) of CdSe/CdS core/shell NCs even when the CdS shell is relatively thin (six monolayers). The simplicity of the chemical incorporation of chlorine and indium species via solution ligand exchange, the efficient electronic passivation of the NC surface, as well as their high stability as dispersions make these materials especially attractive for wide‐area solution‐processable fabrication of NC‐based devices.     

Platelet‐in‐Box Colloidal Quantum Wells: CdSe/CdS@CdS Core/Crown@Shell Heteronanoplatelets

Here, the CdSe/CdS@CdS core/crown@shell heterostructured nanoplatelets (NPLs) resembling a platelet‐in‐box structure are developed and successfully synthesized. It is found that the core/crown@shell NPLs exhibit consistently substantially improved photoluminescence quantum yield compared to the core@shell NPLs regardless of their CdSe‐core size, CdS‐crown size, and CdS‐shell thickness. This enhancement in quantum yield is attributed to the passivation of trap sites resulting from the critical peripheral growth with laterally extending CdS‐crown layer before the vertical shell growth. This is also verified with the disappearance of the fast nonradiative decay component in the core/crown NPLs from the time‐resolved fluorescence spectroscopy. When compared to the core@shell NPLs, the core/crown@shell NPLs exhibit relatively symmetric emission behavior, accompanied with suppressed lifetime broadening at cryogenic temperatures, further suggesting the suppression of trap sites. Moreover, constructing both the CdS‐crown and CdS‐shell regions, significantly enhanced absorption cross‐section is achieved. This, together with the suppressed Auger recombination, enables the achievement of the lowest threshold amplified spontaneous emission (≈20 μJ cm^?2) from the core/crown@shell NPLs among all different architectures of NPLs. These findings indicate that carefully heterostructured NPLs will play a critical role in building high‐performance colloidal optoelectronic devices, which may even possibly challenge their traditional epitaxially grown thin‐film based counterparts.     

Designing Squaraine Dyes with Bright Deep-Red Aggregation-Induced Emission for Specific and Ratiometric Fluorescent Detection of Hypochlorite

Development of ratiometric fluorescent hypochlorite probes with strong long wavelength fluorescence in aqueous medium, high resistance to photobleaching, high sensitivity and selectivity, and low biological toxicity remains a challenge. In this work, a molecular design strategy is proposed that can transform the traditional squaraine dyes (SQs) with aggregation-caused quenching character into aggregation-induced emission (AIE)-active luminogens by functionalizing the end-groups with tetraphenylethylene units and further introducing hydrophilic sulfonate group as the side chains. The resulting TPE-SQ5 not only emits strong deep-red fluorescence with a high quantum yield of 11.0% and high photostability, but more encouragingly can serve as a ratiometric fluorescent hypochlorite probe with high selectivity and sensitivity (detection limit: 5.6 nm ), which indeed is the first report for SQs. The detailed sensing mechanism study demonstrates that the oxindole product with sulfonate substitution is responsible for the ratiometric fluorescent response. Furthermore, TPE-SQ5 nanoparticles with high biocompatibility and low cytotoxicity are successfully used for ratiometrically imaging exogenous and endogenous hypochlorite in living cells.     

Development of a Unique Class of Spiro‐Type Two‐Photon Functional Fluorescent Dyes and Their Applications for Sensing and Bioimaging

Spiro compounds with rigid structures have attracted significant attention in the recent years due to their useful applications in diverse fields such as asymmetric catalysis and organic optoelectronic materials. However, spiro cores have not yet been employed as the spiro‐type two‐photon fluorescent dyes in the aspects of sensing and bioimaging. Therefore, the spiro‐type two‐photon fluorescent dyes with excellent two‐photon properties are highly sought after. Here, a unique class of spiro‐type two‐photon fluorescent dyes ( STP ) is engineered and applied in sensing and bioimaging. The studies indicate that the novel STP fluorescent dyes have favorable two‐photon properties from the point view of spiro compounds. By exploiting the superior two‐photon optical properties of the STP dyes, the first two‐photon ratiometric HOCl fluorescent probe STP‐HClO for sensing and imaging HOCl in the living cells and living tissues is constructed, demonstrating the profound value of the new STP dyes for the unprecedented development of the sprio‐type fluorescent sensing and imaging agents. It is believed that the innovative STP dyes may pave the way for designing more efficient spiro‐type two‐photon fluorescent probes and organic optoelectronic materials as well.     

Au@pNIPAM Thermosensitive Nanostructures: Control over Shell Cross‐linking,Overall Dimensions,and Core Growth

Thermoresponsive nanocomposites comprising a gold nanoparticle core and a poly(N‐isopropylacrylamide) (pNIPAM) shell are synthesized by grafting the gold nanoparticle surface with polystyrene, which allows the coating of an inorganic core with an organic shell. Through careful control of the experimental conditions, the pNIPAM shell cross‐linking density can be varied, and in turn its porosity and stiffness, as well as shell thickness from a few to a few hundred nanometers is tuned. The characterization of these core–shell systems is carried out by photon‐correlation spectroscopy, transmission electron microscopy, and atomic force microscopy. Additionally, the porous pNIPAM shells are found to modulate the catalytic activity, which is demonstrated through the seeded growth of gold cores, either retaining the initial spherical shape or developing a branched morphology. The nanocomposites also present thermally modulated optical properties because of temperature‐induced local changes of the refractive index surrounding the gold cores.     

Plasmonic Self‐Propelled Nanomotors for Explosives Detection via Solution‐Based Surface Enhanced Raman Scattering

Nanomotors represent a class of artificial machines that span the chasm between molecular motors and bigger micromotors. Their importance lies in the fact that to effectively navigate and perform tasks in a biological environment without alerting the action of the immune system, the maximal size of the object has to be well below 200 nm. Fully nanosized gold/silver core/shell plasmonic nanomotors using the seeded growth wet chemical approach, which allows high scalability of synthesis of the nanomotors compared to planar substrate‐based methods, is presented. Using the nanoparticle tracking analysis, the catalysis driven enhanced diffusion of the plasmonic nanomotors in the presence of low concentrations of fuel is presented and shown that the prepared nanomotors are good candidates for a solution‐based surface‐enhanced Raman spectroscopy detection of picric acid, a typical explosive. In addition to the mentioned effects, ligand‐exchange is performed on the nanomotors to replace the surfactant with its thiolated analog, a combination which is already proven in literature to be stealthy to the immune response of the living organism.     

Photo‐ and pH‐Triggered Release of Anticancer Drugs from Mesoporous Silica‐Coated Pd@Ag Nanoparticles

A smart drug delivery system integrating both photothermal therapy and chemotherapy for killing cancer cells is reported. The delivery system is based on a mesoporous silica‐coated Pd@Ag nanoplates composite. The Pd@Ag nanoplate core can effectively absorb and convert near infrared (NIR) light into heat. The mesoporous silica shell is provided as the host for loading anticancer drug, doxorubicin (DOX). The mesoporous shell consists of large pores, ～10 nm in diameter, and allows the DOX loading as high as 49% in weight. DOX loaded core–shell nanoparticles exhibit a higher efficiency in killing cancer cells than free DOX. More importantly, DOX molecules are loaded in the mesopores shell through coordination bonds that are responsive to pH and heat. The release of DOX from the core‐shell delivery vehicles into cancer cells can be therefore triggered by the pH drop caused by endocytosis and also NIR irradiation. A synergistic effect of combining chemotherapy and photothermal therapy is observed in our core‐shell drug delivery system. The cell‐killing efficacy by DOX‐loaded core–shell particles under NIR irradiation is higher than the sum of chemotherapy by DOX‐loaded particles and photothermal therapy by core–shell particles without DOX.     

Very Long SiC‐Based Coaxial Nanocables with Tunable Chemical Composition

We present a simple process for the fabrication of very long SiC‐based coaxial nanocables (NCs). The versatility of this technique is confirmed by the ability to change the chemical composition of the NC outer layers from silica to carbon and boron nitride. The NCs consist of a SiC core approximately 30 nm in diameter with lengths up to several hundred of nanometers. The thickness of the coating is in the range 2–10 nm. The morphology and structural characterization of the NCs is investigated by scanning electron microscopy (SEM) and high‐resolution transmission electron microscopy (HRTEM), respectively, and their chemical composition is probed by electron energy loss spectroscopy (EELS). A vapor–solid growth mechanism is proposed to explain the growth of SiC‐based NCs of various chemical compositions, depending on the chemical nature of the vapor phase. Because of the large quantity of very long and interlaced NCs produced during the synthesis, the macroscopic aspect of the as‐grown material is like a self‐supported felt.     

ph‐Dependent Synthesis of Pepsin‐Mediated Gold Nanoclusters with Blue Green and Red Fluorescent Emission

This report demonstrates the first pH‐dependent synthesis of pepsin‐mediated gold nanoclusters (AuNCs) with blue‐, green‐, and red‐fluorescent emission from Au₅ (Au₈), Au₁₃, and Au₂₅, respectively. Pepsin is a gastric aspartic proteinase (molecular weight, 34 550 g/mol) that plays an integral role in the digestive process of vertebrates. It was found that the pH of the reaction solution was critical in determining the size of Au NCs (i.e., the number of gold atoms of AuNCs). Interestingly, enzyme function of pepsin contributes to the formation of these AuNCs. The photo‐stability of the Au₂₅ (or Au₁₃) NCs is much higher than that of Au₅NCs (i.e., Au₂₅ ～ Au₁₃ > > Au₅). The pepsin‐mediated Au₂₅NCs were also found to be useful as fluorescent sensors for the detection of Pb²⁺ ions by enhanced fluorescence and the detection of Hg²⁺ ions by fluorescence quenching. Although the detailed formation mechanisms of these AuNCs require further analysis, the synthetic route using proteinase demonstrated here is promising for preparing new types of fluorescent metal nanoclusters for application in catalysis, optics, biological labeling, and sensing.