The precise control of the size, morphology, surface chemistry, and assembly process of each component is important to construction of integrated functional nanocomposites. We report here the fabrication of multifunctional microspheres which possess a core of nonporous silica-protected magnetite particles, transition layer of active gold nanoparticles, and an outer shell of ordered mesoporous silica with perpendicularly aligned pore channels. The well-designed microspheres have high magnetization (18.6 emu/g), large surface area (236 m(2)/g), highly open mesopores (approximately 2.2 nm), and stably confined but accessible Au nanoparticles and, as a result, show high performance in catalytic reduction of 4-nitrophenol (with conversion of 95% in 12 min), styrene epoxidation with high conversion (72%) and selectivity (80%), especially convenient magnetic separability, long life and good reusability. The unique nanostructure makes the microsphere to be a novel stable and approachable catalyst system for various catalytic industry processes.

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Producing electrolytes with high ionic conductivity has been a critical challenge in the progressive development of solid oxide fuel cells (SOFCs) for practical applications. The conventional methodology uses the ion doping method to develop electrolyte materials, e.g., samarium-doped ceria (SDC) and yttrium-stabilized zirconia (YSZ), but challenges remain. In the present work, we introduce a logical design of non-stoichiometric CeO 2-δ based on non-doped ceria with a focus on the surface properties of the particles. The CeO 2−δ reached an ionic conductivity of 0.1 S/cm and was used as the electrolyte in a fuel cell, resulting in a remarkable power output of 660 mW/cm 2 at 550°C. Scanning transmission electron microscopy (STEM) combined with electron energy-loss spectroscopy (EELS) clearly clarified that a surface buried layer on the order of a few nanometers was composed of Ce 3+ on ceria particles to form a CeO 2−δ @CeO 2 core-shell heterostructure. The oxygen deficient layer on the surface provided ionic transport pathways. Simultaneously, band energy alignment is proposed to address the short circuiting issue. This work provides a simple and feasible methodology beyond common structural (bulk) doping to produce sufficient ionic conductivity. This work also demonstrates a new approach to progress from material fundamentals to an advanced lowtemperature SOFC technology.

Organophosphorus pesticides (OPs) can inhibit the activity of acetylcholinesterase (AChE) to induce neurological diseases. It is significant to exploit a rapid and sensitive strategy to monitor OPs. Here, a metal–organic framework (MOF) acted as a carrier to encapsulate AuNCs, which can limit the molecular motion of AuNCs, trigger the aggregation-induced emission (AIE) effect, and exhibit a strong fluorescence with a fluorescence lifetime and quantum yield of 6.83 μs and 4.63%, respectively. Then, the marriage of fluorescence and colorimetric signals was realized on the basis of the dual function of the enzymolysis product from AChE and choline oxidase (CHO) on AuNCs@ZIF-8. First, it can decompose ZIF-8 to weaken the restraint on AuNCs, and thus the fluorescence receded. Second, it can be used as a substrate for the peroxidase mimics of the released AuNCs to oxidize 3,3′,5,5′-tetramethylbenzidine (TMB) and a visible blue appeared. Thus, on the basis of the inhibition of AChE activity by OPs, a fluorescence–colorimetric dual-signal biosensor was established. In addition, colorimetric paper strips were exploited to realize a visual semiquantitative detection, and a smartphone APP was developed to make the visualization results more precise and realize real-time supervision of pesticide contamination.

We present an electrical sensor that uses rolling circle amplification (RCA) of DNA to stretch across the gap between two electrodes, interact with metal nanoparticle seeds to generate an electrically conductive nanowire, and produce electrical signals upon detection of specific target DNA sequences. RCA is a highly specific molecular detection mechanism based on DNA probe circularization. With this technique, long single-stranded DNA with simple repetitive sequences are produced. Here we show that stretched RCA products can be metalized using silver or gold solutions to form metal wires. Upon metallization, the resistance drops from TΩ to kΩ for silver and to Ω for gold. Metallization is seeded by gold nanoparticles aligned along the single-stranded DNA product through hybridization of functionalized oligonucleotides. We show that combining RCA with electrical DNA detection produces results in readout with very high signal-to-noise ratio, an essential feature for sensitive and specific detection assays. Finally, we demonstrate detection of 10 ng of Escherichia coli genomic DNA using the sensor concept.