Jason

Hierarchical SnO₂ hollow spheres self-assembled from nanosheets were prepared with and without carbon coating. The combination of nanosized architecture, hollow structure, and a conductive carbon layer endows the SnO₂-based anode with improved specific capacity and cycling stability, making it more promising for use in lithium ion batteries.

The legend of SnO₂ hollow: Combining the advantages of the low-dimensional nanosized building blocks, hollow structure, and elastic carbon buffering layer, the prepared carbon-coated hierarchical SnO₂/C hollow spheres show superior reversible capacity, rate stability, and cycle life as an anode for lithium ion batteries.

Platinum–copper nanoframes were produced from copper nanoparticles by a one-pot synthesis method. The growth mechanism was thoroughly studied by experiment and theoretical calculations. Owing to the unique structure, Pt-Cu nanoframes exhibited significantly enhanced catalytic activity toward the electro-oxidation of methanol compared to commercial Pt black.

Pt-Cu nanoframes were produced from copper nanoparticles by a one-pot synthesis. The growth mechanism was thoroughly studied by experiment and theoretical calculations. Owing to the unique structure, Pt-Cu nanoframes exhibited significantly enhanced catalytic activity toward the electro-oxidation of methanol compared to commercial Pt black.

By controlling the surface structure and composition at the atomic level, the catalytic properties of bimetallic alloy catalysts can be precisely and effectively tuned, and their activity and durability can be enhanced. Here, a class of highly active and durable PdAg bimetallic alloy nano-electrocatalysts is demonstrated by tuning the surface composition through a simple electrochemical treatment process in acid medium. Transmission electron microscopy, X-ray photoelectron spectroscopy, and cyclic voltammogram measurements clearly show the well-defined core–shell structure that consists of a PdAg alloy core and a few atomic layers of Pd as the shell (PdAg@Pd). Compared to pure Pd and Ag catalysts, the prepared PdAg@Pd/C exhibits enhanced electrocatalytic activity and durability for the oxygen reduction reaction in alkaline media. According to the theoretical and experimental results, the enhanced electrocatalytic activity can be attributed to the synergistic effects between the Pd and the Ag, while the durability is ascribed to the unique alloy core–ultrathin-Pd-shell structure of the PdAg@Pd/C catalyst. This study not only proposes a simple and straightforward approach for preparing highly monodisperse PdAg alloy nanoparticles and designing advanced electrocatalysts for fuel cells, but also demonstrates the crucial effect of electrochemical treatment on the electrocatalytic properties of catalysts.

A well-defined carbon-supported core–shell structure consisting of PdAg alloy core and a shell of a few atomic Pd layers (PdAg@Pd/C) is obtained by a simple electrochemical process. Due to the synergistic effect between the Pd and the Ag and their unique core–shell structure, the PdAg@Pd/C hybrids exhibit enhanced electrocatalytic activity and durability toward the oxygen reduction reaction in alkaline medium.

Gd-encapsulated carbonaceous dots (Gd@C-dots) hold great potential in clinical applications as a novel type of T₁ contrast agent for magnetic resonance imaging (MRI). However, current synthetic methods require multiple purification steps due to poor size control, making them unsuitable for high throughput. Herein, a novel, mesoporous silica nanoparticle (MSN)-templated method for the size-controlled synthesis of Gd@C-dots is reported. Briefly, MSNs nanoreactors of different pore sizes are loaded with Gd precursors. Upon calcination, carbon layers are grown around the Gd cations. The spatial restraint of the silica cavity facilitates size control of the produced Gd@C-dots. Specifically, using 3, 7, and 11 nm MSNs as templates allows the synthesis of 3.0, 7.4, and 9.6 nm Gd@C-dots, respectively. A significant size impact on the magnetic and optical properties of the nanoparticles is shown, with the smallest Gd@C-dots showing the highest r₁ relaxivity (10 mM⁻¹ s⁻¹) and fluorescence quantum yield (30.2%). The 3.0-nm Gd@C-dots were then conjugated with a tumor-targeting ligand, c(RGDyK), and injected into U87MG xenograft tumor models. Good tumor targeting was observed in T₁-weighted MRI images; whereby the unbound nanoparticles were efficiently excreted through renal clearance, avoiding long-term toxicity to the host.

Mesoporous silica nanoparticles serve as nanoreactors for the synthesis of Gd-Encapsulated carbon dots (Gd@C-dots) from Gd-complexes by calcination. Since the dimension of the silica cavity limits growth, the size distribution of the Gd@C-dots is narrow. The Gd@C-dots are successfully appied in MRI imaging.

The reduction of 4-nitrophenol (Nip) into 4-aminophenol (Amp) by NaBH₄, which is catalyzed by both binary and ternary yolk–shell noble-metal/SnO₂ heterostructures, is reported. The binary heterostructures contain individual Au or Ag nanoparticles (NPs) and the ternary heterostructures contain both Au and Ag NPs. The Au@SnO₂ yolk–shell NPs are synthesized via a silica seeds-mediated hydrothermal method. Subsequently, the Au@SnO₂@Ag and Au@SnO₂@Au yolk–shell–shell (YSS) NPs are synthesized, whereby SnO₂ is located between the Au and Ag NPs. The morphology, composition, and optical properties of the as-prepared samples are analyzed. For the binary heterostructures, the rate of the reduction reaction increases with decreasing particle size. The catalytic results demonstrate the synergistic effect of Au and Ag in the ternary metal–semiconductor heterostructures, which is beneficial to the catalytic reduction of Nip into Amp. Both the binary and ternary heterostructures exhibit significantly better catalytic performances than the corresponding bare Au and Ag NPs. It is envisaged that the current synthesized strategy will promote further interest in the field of bimetal NP-based catalysis.

Noble-metal-(Au and Ag)-coated Au@SnO₂ yolk–shell ternary and binary nanoparticles are prepared and their catalytic performance for the reduction of 4-nitrophenol into 4-aminophenol by NaBH₄ is elaborated. The ternary structures have a much higher catalytic activity than the binary heterostructures, and possible mechanisms behind this difference are investigated.

Manganese oxides are considered to be very promising materials for water oxidation catalysis (WOC), but the structural parameters influencing their catalytic activity have so far not been clearly identified. For this study, a dozen manganese oxides (MnO_x) with various solid-state structures were synthesised and carefully characterised by various physical and chemical methods. WOC by the different MnO_x was then investigated with Ce⁴⁺ as chemical oxidant. Oxides with layered structures (birnessites) and those containing large tunnels (todorokites) clearly gave the best results with reaction rates exceeding 1250   h⁻¹ or about 50 μmol_O2 m⁻² h⁻¹. In comparison, catalytic rates per mole of Mn of oxides characterised by well-defined 3D networks were rather low (e.g., ca. 90   h⁻¹ for bixbyite, Mn₂O₃), but impressive if normalised per unit surface area (>100  m⁻² h⁻¹ for marokite, CaMn₂O₄). Thus, two groups of MnO_x emerge from this screening as hot candidates for manganese-based WOC materials: 1) amorphous oxides with tunnelled structures and the well-established layered oxides; 2) crystalline Mn^III oxides. However, synthetic methods to increase surface areas must be developed for the latter to obtain good catalysis rates per mole of Mn or per unit catalyst mass.

WOC this way: A detailed, comparative study on twelve synthetic manganese oxides revealed that water oxidation catalysis is greatly influenced by oxide structure (see figure). Layered oxides and those featuring large tunnels performed best, whereas crystalline 3D-network materials showed little activity.