Thin Silica Layer Research Articles

Plasmonic Coupling for High‐Sensitivity Detection of Low Molecular Weight Molecules

This article presents a novel plasmonic sensing platform designed for the detection of low molecular weight molecules, offering significant advancements in diagnostic applications. The platform features a periodic array of gold nanodisks on a 20 nm thin silica layer, supported by a 100 nm thick gold substrate. By leveraging the coupling between localized and propagating surface plasmon resonances, this design significantly enhances the sensitivity and specificity of molecular detection. Finite element method simulations are conducted to characterize the optical properties and reflectance response of the nanodisks array in the visible to near‐infrared range. Ellipsometric analysis is performed to measure the reflectance of the sample at various angles. Additionally, scanning near‐field optical microscopy in reflectance mode validates the design by revealing well‐defined plasmonic hot spots and interference patterns consistent with the simulated results. The findings demonstrate the platform's effectiveness in amplifying optical signals, achieving a limit of detection of 50 μM for molecules with a molecular weight of less than 1 KDa. This high sensitivity and specificity highlight the potential of the proposed plasmonic platform to advance the development of highly sensitive sensors for low molecular weight molecules, making it a valuable tool for diagnostics and precise molecular detection.

Coating of expanded polystyrene spheres by TiO2 and SiO2–TiO2 thin films

Expanded polystyrene spheres (EPS) were coated by SiO2–TiO2 or TiO2 for application as a fluidized bed in the photocatalytic reactor. Silica coating was realized by the sol–gel process carried out in a vacuum evaporator at 60–70 °C. The most uniform and thin layer of silica coating was obtained by the Stöber method based on the hydrolysis of tetraethyl orthosilicate (TEOS) catalysed by an ammonia solution. Effective TiO2 coating was obtained by the immersion of EPS in the titania aqueous suspension and evaporation of water in a vacuum evaporator. Heating of EPS spheres coated by SiO2, TiO2 or SiO2–TiO2 at the temperatures of 120–140 °C resulted in a shrinkage of their volume. For the thick layer coating, a strong corrugation of EPS surface was observed. The photocatalytic tests showed, that highly corrugated surface of coated EPS slowed down ethylene decomposition, whereas a thin layer coating of both, SiO2 and TiO2 was advantageous.Graphical abstract

Structural Effects on ORR Performances of Carbon-Free Connected Platinum–Cobalt Catalysts with Chemically Ordered Superlattice Structures

Polymer electrolyte fuel cells (PEFCs) have been considered as the promising next-generation energy-conversion technology, owing to their high energy efficiency and clean emissions. However, a sluggish oxygen reduction reaction (ORR) rate and the low durability of conventional catalysts in PEFCs limit the wider commercialization. To address these issues, our group has developed a carbon-free, connected Pt1–Fe1 catalyst with a porous hollow capsule structure. This catalyst comprises the nano-sized network formed by the connection of Pt1–Fe1 nanoparticles and exhibits an enhanced ORR specific activity (9 times higher than a commercial Pt/C) as well as excellent durability against start-stop operations due to the carbon-free structure.[1,2] However, during the load cycle operation, iron is dissolved from the catalyst, leading to the loss of ORR activity and the degradation of polymer electrolytes caused by the Fenton reaction.In this work, carbon-free and iron-free connected Ptx-Co1 catalysts with chemically ordered superlattice structures have been developed for the first time, as shown in Fig. 1(a). In addition, the metal compositions and chemically ordered (superlattice) degrees in the catalysts were controlled to investigate the structural effects on ORR activity and durability of the connected Ptx-Co1 catalysts.Herein, we employed the silica-coating method for the catalyst synthesis, which involves the combination of silica coating and high-temperature annealing. As shown in Fig. 1(b), the surface of the Ptx-Co1 nanoparticles/SiO2 sample was coated with thin silica layers to prevent the detachment of Ptx–Co1 nanoparticles from the SiO2 template as well as the large catalyst agglomeration and coalescence during the annealing process. We controlled the chemically ordered degrees of the connected Pt1–Co1 and Pt3–Co1 catalysts by using different annealing temperatures. The XRD patterns of the catalysts showed the peaks corresponding to L10 type and L12 type chemically ordered structures for the connected Pt1–Co1 and Pt3–Co1 catalysts annealed at 600°C, respectively. These two catalysts possessed ordered degrees (S) of ca. 50–60%. The TEM images of the connected Ptx–Co1 catalysts showed the formation of connected Ptx–Co1 nanonetwork and porous hollow capsule structures.The electrochemical measurements of ORR activity and durability were conducted in a 0.1 M HClO4 electrolyte solution. The connected Pt1–Co1 and Pt3–Co1 catalysts achieved 6- and 10-times higher ORR specific activities than that of Pt/C, respectively. Subsequently, the ORR activity and load cycle durability (0.6 V for 3 s Û 1.0 V for 3 s at 60 °C) of the connected Pt3–Co1 catalyst with different ordered degrees (S = 0%, 28%, and 58%) were evaluated. As the ordered degrees in the connected Pt3–Co1 catalysts were higher, the ORR specific activity was increased. Also, the retention of the specific activity of the ordered catalyst (S = 58%) was higher than that of the disordered catalyst (S = 0%) after 10,000 load cycles. The STEM-EDX line mapping results showed that 83% of the alloyed Co retained in the catalyst with a higher ordered degree even after 10000 load cycles, whereas the disordered and lower ordered catalysts retained lower Co ratios after the test, indicating the suppression effect of an ordered structure on metal dissolution. In addition, the L12 ordered Pt3–Co1 structure remained in the connected catalyst (S = 58%) after load cycle test, confirmed by the TEM diffraction analysis.In summary, we successfully developed the connected Ptx-Co1 catalysts with chemically ordered superlattice structures. In addition, we clarified the structural effects of metal composition and ordered degree in connected Ptx-Co1 catalysts on ORR activity and load cycle durability. These results provide useful guidelines for the design of advanced ORR catalysts towards high-performance PEFCs. Acknowledgement The part of this presentation is based on results obtained from a project, JPNP20003, commissioned by the New Energy and Industrial Technology Development Organization (NEDO).

Design and fabrication of ordered silicon micro/nano-hybrid hierarchical structures decorated by silica thin layer for superantiwetting surface

The wetting properties of micro/nano-hybrid hierarchical structures offers important applications in many fields. However, the fabrication of hierarchical micro-nanostructures still suffers the limitations of complicated fabrication process, high cost and small area. Here, we develop a novel strategy for the fabrication of uniform micro/nano-hybrid hierarchical silicon structures by combining the photolithography, thermal de-wetting and metal-assisted chemical etching (MACE). The outstanding advantage of this technique is the ability to achieve nano-patterning at the full 4″ or 6″ wafer scale in a very facile and affordable manner, regardless of the substrate surface topography. Moreover, nanostructures generated by this technique can be customized independently at a specific level with very high feature control. By oxidizing the structure and modifying it with specific functional groups or molecules, the wettability of the surface can be transformed from the underwater superoleophobic state with an oil contact angle (OCA) of ∼169° to underwater superoleophilic state (an OCA of ∼8.4°). The transition from superhydrophobic state with a water contact angle (WCA) of ∼175.5° to quasi-superhydrophilic state (a WCA of ∼10.5°) can also be achieved, which is highly desirable for optoelectronics, environment, and biomedicine fields.

An integrated cooling mechanism for photovoltaic systems

Photovoltaic (PV) panels, despite their potential as a renewable energy source, suffer from performance degradation due to temperature rise. This research proposes an integrated passive cooling system that combines finned convective and radiative cooling with graphite-infused phase change material (PCM) in a cascade configuration. The cascade arrangement creates temperature stratification, delaying and restricting temperature increases. Graphite-infused PCM enhances thermal conductivity, facilitating efficient heat dissipation. Additionally, a finned heat sink augments convective heat transfer between PCM and the ambient environment, increasing the heat transfer area. A thin silica layer with pyramid lattices is incorporated to improve radiative heat transfer, particularly beneficial in hot climates with a significant temperature difference between the PV cell and the sky. A mathematical model is developed and validated against experimental data to assess the system’s performance. The model simulates PV cell temperature variations for six different scenarios to identify the most effective cooling mechanism. The study demonstrates a remarkable 27 °C reduction in peak PV cell temperature, translating to a substantial up to 100% increase in overall PV cell efficiency. This research contributes to the evolving landscape of PV cooling technologies and provides valuable insights for optimizing PV panel performance.

Multifunctional Nanoparticles with Superparamagnetic Mn(II) Ferrite and Luminescent Gold Nanoclusters for Multimodal Imaging.

Gold nanoclusters (AuNCs) with fluorescence in the Near Infrared (NIR) by both one- and two-photon electronic excitation were incorporated in mesoporous silica nanoparticles (MSNs) using a novel one-pot synthesis procedure where the condensation polymerization of alkoxysilane monomers in the presence of the AuNCs and a surfactant produced hybrid MSNs of 49 nm diameter. This method was further developed to prepare 30 nm diameter nanocomposite particles with simultaneous NIR fluorescence and superparamagnetic properties, with a core composed of superparamagnetic manganese (II) ferrite nanoparticles (MnFe2O4) coated with a thin silica layer, and a shell of mesoporous silica decorated with AuNCs. The nanocomposite particles feature NIR-photoluminescence with 0.6% quantum yield and large Stokes shift (290 nm), and superparamagnetic response at 300 K, with a saturation magnetization of 13.4 emu g-1. The conjugation of NIR photoluminescence and superparamagnetic properties in the biocompatible nanocomposite has high potential for application in multimodal bioimaging.

A Composite of Polyether Ether Ketone and Silica‐Coated Copper Particles for Creating Tailored Conductive Tracks via Laser Printing

AbstractConventional substrates for optoelectronic systems include inorganic or organic carrier materials; however, these systems are typically subjected to environmentally harmful multistep processes to prepare printed circuit boards. To mitigate these issues, the present article reports a polyether ether ketone (PEEK)‐based composite densely filled with copper microparticles, prepared using a simple, cost‐effective, and sustainable synthesis method. The material exhibits high thermal conductivity but is electrically nonconductive prior to undergoing laser treatment. To prevent the composite from exhibiting electrical conductivity, the copper particles are coated with a thin silica layer through a sol–gel reaction. The thermal stability of PEEK and the Cu–PEEK composites with Cu contents of up to 70 vol%, which are prepared via heat melding, is investigated by thermogravimetric analysis, differential scanning calorimetry, and Fourier‐transform infrared spectroscopy to clarify the manner in which copper affects the chemical structure of the polymer. The developed composite exhibits a significantly higher thermal conductivity than that of the unfilled PEEK polymer. This paper also describes the effects of laser treatment on the surface morphology. Overall, this study suggests that conductive tracks with low electrical resistance can be created on electrically insulating substrates with high thermal conductivity.

Radiolabeled iron oxide nanoparticles functionalized with PSMA/BN ligands for dual-targeting of prostate cancer.

Prostate cancer (PCa) is the second most frequent cancer diagnosis in men and the fifth leading cause of death worldwide. Prostate Specific Membrane Antigen (PSMA) and Gastrin Releasing Peptide (GRP) receptors are overexpressed in PCa. In this study, we have developed iron oxide nanoparticles (IONs) functionalized with the Prostate Specific Membrane Antigen (PSMA) and Gastrin Releasing Peptide (GRP) ligands for dual targeting of Prostate cancer. IONs were developed with a thin silica layer on their surface with MPTES (carrying -SH groups, IONs-SH), and they were coupled either with a pharmacophore targeting PSMA (IONs-PSMA) or with bombesin peptide (IONs-BN), targeting GRP receptors, or with both (IONs-PSMA/BN). The functionalized IONs were characterized for their size, zeta potential, and efficiency of functionalization using dynamic light scattering (DLS) and Fourier-Transform Infrared Spectroscopy (FT-IR). All the aforementioned types of IONs were radiolabeled directly with Technetium-99m (99mTc) and evaluated for their radiolabeling efficiency, stability, and binding ability on two different PCa cell lines (PC3 and LNCaP). The MTT assay demonstrated low toxicity of the IONs against PC3 and LNCaP cells, while the performed wound-healing assay further proved that these nanostructures did not affect cellular growth mechanisms. The observed hemolysis ratio after co-incubation with red blood cells was extremely low. Furthermore, the 99mTc-radiolabeled IONs showed good stability in human serum, DTPA, and histidine, and high specific binding rates in cancer cells, supporting their future utilization as potential diagnostic tools for PCa with Single Photon Emission Computed Tomography (SPECT) imaging.

Facile In-Situ photocatalytic reduction of AuNPs on multilayer Core-Shell Fe3O4@SiO2@PDA magnetic nanostructures and their SERS application

Surface-enhanced Raman scattering (SERS) is a promising analytical technique for the rapid, sensitive, and repeatable detection in various SERS application fields. Herein, a new type of potential magnetically recyclable SERS substrate was designed and rapidly synthesized via a facile three-step template method. First, the magnetic ferroferric oxide (Fe3O4) cores were prepared by a convenient solvothermal approach, and coated with a thin layer of silica by a sol–gel process in order to improve their stability in complicated environments. Next, the negatively charged polydopamine (PDA)/K6[SiW11VIVO40]·7H2O (PDA/SiW11V) outer shell was assembled upon the magnetic Fe3O4@SiO2 core–shell nanoparticles via a layer-by-layer sequential adsorption process using the stickiness of PDA. The SiW11V multilayer shell can be used as the subsequent photocatalytic reduction precursors for the in-situ loading of high-density gold nanoparticles (AuNPs), without any other organic additives. The AuNPs decorated multilayer core–shell Fe3O4@SiO2@PDA magnetic nanostructures were employed as a potential magnetically recyclable SERS substrate, and showed excellent SERS performance. Using crystal violet (CV) as a model target, the as-fabricated AuNPs modified multilayer core–shell Fe3O4@SiO2@PDA magnetic nanostructures SERS substrates exhibited significant enhancement, and pushed the detection limit down to 10-12 M. Aside from the ultrahigh sensitivity, these SERS substrates also possess an excellent reproducibility (relative standard deviation (RSD) ∼ 8.3%), long-term stability (75 days), and unique chemical stability capability in different organic solvents and different environments with pH ≤ 10. Furthermore, a real-life application is also performed by the detection of melamine in spiked milk solution using the as-prepared magnetic nanostructures SERS-active substrates (limit of detection (LOD), 10-8 M). These results highlight that the rational design and controllable synthesis of multifunctional magnetic SERS substrates is a promising strategy in many different application fields such as biosensing, photoelectrocatalysis, and medical diagnosis.

Tunable Interfacial Electronic Pd-Si Interaction Boosts Catalysis via Accelerating O2 and H2O Activation.

Engineering the interfacial structure between noble metals and oxides, particularly on the surface of non-reducible oxides, is a challenging yet promising approach to enhancing the performance of heterogeneous catalysts. The interface site can alter the electronic and d-band structure of the metal sites, facilitating the transition of energy levels between the reacting molecules and promoting the reaction to proceed in a favorable direction. Herein, we created an active Pd-Si interface with tunable electronic metal-support interaction (EMSI) by growing a thin permeable silica layer on a non-reducible oxide ZSM-5 surface (termed Pd@SiO2/ZSM-5). Our experimental results, combined with density functional theory calculations, revealed that the Pd-Si active interface enhanced the charge transfer from deposited Si to Pd, generating an electron-enriched Pd surface, which significantly lowered the activation barriers for O2 and H2O. The resulting reactive oxygen species, including O2 -, O2 2-, and -OH, synergistically facilitated formaldehyde oxidation. Additionally, moderate electronic metal-support interaction can promote the catalytic cycle of Pd0 ⇆ Pd2+, which is favorable for the adsorption and activation of reactants. This study provides a promising strategy for the design of high-performance noble metal catalysts for practical applications.

Dissolution behavior of radiocesium-bearing microparticles as a function of solution compositions

More than a decade has passed since the Fukushima nuclear accident in 2011 and contamination around the nuclear power plant is primarily caused by 137Cs. One of the materials retaining radiocesium in the environment is radiocesium-bearing silicate glass microparticles (CsMPs), which have not been reported in previous nuclear accidents. Although the prediction of environmental fates of CsMPs is of interest because of their extremely high specific radioactivity, knowledge about their physicochemical properties is still limited. Here we show that the dissolution behavior of CsMPs is comparable to that of silica-rich glass and significantly depends on the surrounding environment. CsMP dissolution experiments were conducted in solutions with various solute components and pH levels at 60 °C. In neutral and basic solutions, the estimated dissolution rate was accelerated by alkali ions such as Na+, which is known to play a catalytic role for the dissolution of silica. In contrast, the dissolution in acid was slow even in the presence of alkali ions. The dissolution under acid conditions was possibly retarded by a thin amorphous silica layer formed on the CsMP surfaces. Such characteristics of the dissolution are consistent with that of silica-rich glass. To infer the dissolution behavior of CsMPs in the human body, the dissolution rate in Ringer’s solution at 37 °C was estimated as 1.00 ± 0.37 μm/year.

Understanding FRET in Upconversion Nanoparticle Nucleic Acid Biosensors.

Upconversion nanoparticles (UCNPs) have been frequently applied in Förster resonance energy transfer (FRET) bioanalysis. However, the understanding of how surface coatings, bioconjugation, and dye-surface distance influence FRET biosensing performance has not significantly advanced. Here, we investigated UCNP-to-dye FRET DNA-hybridization assays in H2O and D2O using ∼24 nm large NaYF4:Yb3+,Er3+ UCNPs coated with thin layers of silica (SiO2) or poly(acrylic acid) (PAA). FRET resulted in strong distance-dependent PL intensity changes. However, the PL decay times were not significantly altered because of continuous Yb3+-to-Er3+ energy migration during Er3+-to-dye FRET. Direct bioconjugation of DNA to the thin PAA coating combined with the closest possible dye-surface distance resulted in optimal FRET performance with minor influence from competitive quenching by H2O. The better comprehension of UCNP-to-dye FRET was successfully translated into a microRNA (miR-20a) FRET assay with a limit of detection of 100 fmol in a 80 μL sample volume.

Photothermal therapeutic ability of copper open-shell nanostructures that are effective in the second biological transparency window based on symmetry breaking-induced plasmonic properties.

In this study, a photothermal therapy agent that works efficiently in the second biological transparency window was developed based on the localized surface plasmon (LSP) resonance of symmetry-broken open-shell nanostructures of low-cost Cu (CuOSNs). The strong LSP resonance and superior photothermal conversion ability in the second biological transparency window were achieved by generating the dipolar bonding mode due to the plasmon hybridization between the nanoshell dipole and the nanohole dipole at the opening edge in CuOSNs derived from the symmetry breaking of a Cu nanoshell. Oxidative dissolution of CuOSNs in water was significantly suppressed by successive coating with the self-assembled monolayer of 16-mercaptohexadecanoic acid and a thin silica layer. Furthermore, the stability in phosphate buffered saline, which models the biological environment, was attained by further coating the nanoparticles with polyethylene glycol. It was demonstrated from in vitro cell tests using HeLa cells that the cytotoxicity of CuOSNs was effectively suppressed by the surface protection. The viability of HeLa cells incubated with CuOSNs was decreased under the irradiation of low intensity 1060 nm laser with increasing number of CuOSNs. These results demonstrate that low-cost symmetry-broken Cu-based nanostructures can act as an excellent photothermal therapy agent in the second biological transparency window.

Identification and Authentication of Milk Using Digital Colormetry of Indicator Test Systems, Smartphone, and Chemometric Analysis

A simple and an available method is proposed for the identification and authentication of milk using a test device, a smartphone, and chemometric analysis. For the identification by the region of origin and the species of milk (cow, goat, sheep, etc.) and authentication (authenticity, falsification of milk), acid-base indicator papers and test papers are used to determine the total hardness and total alkalinity of water and chloride and sulfate ions. Two indicator systems are proposed. In the first test system, 16 indicator zones are used, of which 12 zones are acid-base indicators with a color change in the pH range of 3–9, and 4 are indicator zones, the color change of which depends on the concentration of calcium ions and chloride, sulfate, carbonate, and hydrocarbonate ions. The second test system uses fluorescent indicators, as well as the intrinsic fluorescence of milk on cellulose paper and a thin silica layer. In this case, the indicator zones of the matrix are irradiated with monochromatic ultraviolet light (365 nm) after applying milk samples to them. A device and a method for measuring the colorimetric characteristics of test systems using a smartphone are proposed. The data array (the sum of the RGB channel values) is processed using the XLSTAT software. The use of chemometric analysis made it possible to establish the authenticity of milk, identify it by the region of origin, and reveal facts of milk falsification by dilution with water, the use of vegetable fats, and emulsification with surfactants. The manufacturers of pasteurized milk were identified and a possibility of determining its fat content by the data array of RGB colorimetric parameters is proved

Silica-coated gold nanorods biofunctionalization for localized surface plasmon resonance (LSPR) biosensing

We introduce here the engineering of nanobiosensors designed from gold nanorods coated with an ultrathin layer of silica (AuNR@SiO2) and biofunctionalized with antibodies for the Localized Surface Plasmon Resonance (LSPR) biosensing of proteins. Despite the outstanding properties of AuNRs, their use for LSPR biosensing is limited due to the presence of the surfactant cetyltrimethylammonium bromide (CTAB) – mandatory for their synthesis - which forms a strongly-bounded and positively-charged bilayer at their surface and significantly complicates their bio-functionalization. When coated with a thin layer of silica, these nanomaterials exhibit an improved sensitivity to refractive index change which augurs for better analytical performances. Here, we undertook an in-depth investigation of the biofunctionalization of AuNR@SiO2via three different routes to design and test a label-free LSPR biosensor operating in solution. In the first route, we took advantage of the negatively charged external silica shell to immobilize anti-rabbit IgG antibody by electrostatic physisorption. In the second and third routes, the silica surface was reacted with thiol or aldehyde terminated silanes, subsequently utilized to covalently attach anti-rabbit IgG antibody to the surface. The resulting nanoprobes were characterized by a wide range of physical methods (TEM, XPS, DLS, ELS and UV-Visible spectroscopy) then tested for the biosensing of rabbit-IgG. The three nanobiosensors maintain an excellent colloidal stability after analyte recognition and exhibit extremely high analytical performances in terms of specificity and dynamic range, with an LoD down to 12 ng/mL.

Color-selective labyrinth-like quantum dot nanobeads enable point-of-care dual assay of Mycotoxins

Complex nanoparticles with hybrid forms of quantum dots and nano-scale templates are highly interesting due to various functionalities and broad applications in point-of-care testing (POCT). High sensitivity and throughput are significant for POCT in clinical applications and food safety, especially for determining multiple targets in complex matrices. Here, we developed the labyrinth-like quantum dot nanobeads (LQDBs) with controlled size, enhanced loading capacity and an intelligent mobile detection format. We reported a smartphone readout using color-selective LQDBs as fluorescent labels for POCT of dual targets in paper-test format. The labyrinth-like nanobeads assembled with QDs provided high colloidal stability, facile functionalization, and a rough surface for more binding sites to monoclonal antibodies enabled by a thin silica layer coating. Using LQDB, the POCT of dual targets was developed assisted with an in-house application on a smartphone. This assay detected aflatoxin B1 (AFB1) and zearalenone (ZEN) within 10 min using a competitive immunoassay. The LODs for urine and agricultural products were recorded as 0.002 and 0.02 ng/mL for AFB1 and ZEN, respectively. Reasonable specificity, repeatability, reproducibility, and validation results were recorded in real samples. This biosensing platform can be widely suitable in clinical healthcare and food safety applications.

Environmentally-stable eco-friendly pectin-silica bio-hybrid foams for soil remediation

Here we present a new class of hybrid material composed of a polysaccharide macroporous core surrounded by a thin silica layer as new adsorption platforms for the retention of organic pollutants in soil media. The core-shell hybrid foams were fabricated by ice-templating to create highly anisotropic pectin foams, followed by vapor phase silica deposition. The structural stability of the hybrid foams was tested in compression, reaching a Young's Modulus up to 5 MPa, but also, and more importantly, in direct contact with wet soils over more than one month. Hybrid foams showed a sorption capacity for a toxic dye nearly two orders of magnitude higher than the surrounding soils. Altogether, these hybrid foams combine all chemical, structural and functional properties required to be effective materials for soil depollution and, thanks to their easy-recovery, should compete with common particulate sorbents.

Construction of magnetic nanochains to achieve magnetic energy coupling in scaffold

BackgroundFe3O4 nanoparticles are highly desired for constructing endogenous magnetic microenvironment in scaffold to accelerate bone regeneration due to their superior magnetism. However, their random arrangement easily leads to mutual consumption of magnetic poles, thereby weakening the magnetic stimulation effect.MethodsIn this study, magnetic nanochains are synthesized by magnetic-field-guided interface co-assembly of Fe3O4 nanoparticles. In detail, multiple Fe3O4 nanoparticles are aligned along the direction of magnetic force lines and are connected in series to form nanochain structures under an external magnetic field. Subsequently, the nanochain structures are covered and fixed by depositing a thin layer of silica (SiO2), and consequently forming linear magnetic nanochains (Fe3O4@SiO2). The Fe3O4@SiO2 nanochains are then incorporated into poly l-lactic acid (PLLA) scaffold prepared by selective laser sintering technology.ResultsThe results show that the Fe3O4@SiO2 nanochains with unique core–shell structure are successfully constructed. Meanwhile, the orderly assembly of nanoparticles in the Fe3O4@SiO2 nanochains enable to form magnetic energy coupling and obtain a highly magnetic micro-field. The in vitro tests indicate that the PLLA/Fe3O4@SiO2 scaffolds exhibit superior capacity in enhancing cell activity, improving osteogenesis-related gene expressions, and inducing cell mineralization compared with PLLA and PLLA/Fe3O4 scaffolds.ConclusionIn short, the Fe3O4@SiO2 nanochains endow scaffolds with good magnetism and cytocompatibility, which have great potential in accelerating bone repair.

Does the Encapsulation Strategy of Pt Nanoparticles with Carbon Layers Really Ensure Both Highly Active and Durable Electrocatalysis in Fuel Cells?

Platinum is a key component of commercialized proton exchange membrane fuel cells (PEMFCs) to lower the energy cost of the sluggish oxygen reduction reaction (ORR) at the cathode. Beyond the significant advances in improving its initial activity, securing catalytic durability is the next challenge for the successful implementation of PEMFCs. Encapsulation of Pt nanoparticles (NPs) with thin carbon or silica layers has recently been highlighted as a promising strategy for alleviating Pt degradation. However, unexpectedly similar or occasionally even better catalytic activity on site-blocked Pt NPs has raised fundamental interest about the nature of their catalytic sites and the origin of the prolonged durability. Herein, to answer these questions, we investigate the ORR and methanol oxidation reaction activities of carbon-encapsulated Pt NP (C@Pt/C) catalysts. By controlling the robustness of the carbon shells synthetically and electrochemically, directly exposed Pt sites, at which facile transport of reactant/product molecules occurs via the loosely packed or highly defective carbon layers, are identified as the main catalytic sites. Interestingly, online differential electrochemical mass spectroscopy and inductively coupled plasma-mass spectrometry coupled to electrochemical flow cells verify a trade-off relationship between the activity and stability of the catalysts. In addition to their role as a physical barrier for prohibiting the dissolution and agglomeration of the Pt NPs, the carbon shell acts as a sacrificial agent, questioning the practical legitimacy of the strategy for achieving both high activity and durability.

Fe Single‐atom Sites in Two‐Dimensional Nitrogen‐doped Porous Carbon for Electrocatalytic Oxygen Reduction

AbstractThe development of electrocatalysts for oxygen reduction reaction (ORR) is important for energy conversion devices, such as fuel cells, and metal‐air batteries. Here, we have developed a confined space strategy to prepare a two‐dimensional (2D) leaf‐like nitrogen (N)‐containing porous carbon as a single‐atom catalyst substrate. ZIF−L materials have been confined in a thin silica layer to regulate the pyrolysis. The obtained Fe single atoms doped N‐containing porous carbons (Fe SAs/N−C) maintain the 2D morphology and have Fe single‐atom active sites. Correspondingly, Fe SAs/N−C exhibits excellent ORR performance (E1/2 of 0.907 V), which is more positive than those of commercially available Pt/C (0.874 V) and most reported non‐noble metal catalysts. The durability test shows that Fe SAs/N−C exhibits good stability during electrocatalytic process. This rational design shows a new strategy to prepare 2D catalyst supports with single‐atom active sites.