Controlled Formation of Metal@Al₂O₃ Yolk–Shell Nanostructures with Improved Thermal Stability

Yolk–shell structured nanomaterials have shown interesting potential in different areas due to their unique structural configurations. A successful construction of such a hybrid structure relies not only on the preparation of the core materials, but also on the capability to manipulate the outside wall. Typically, for Al₂O₃, it has been a tough issue in preparing it into a uniform nanoshell, making the use of Al₂O₃-based yolk–shell structures a challenging but long-awaited task. Here, in benefit of our success in the controlled formation of Al₂O₃ nanoshell, we demonstrated that yolk–shell structures with metal confined inside a hollow Al₂O₃ nanosphere could be successfully achieved. Different metals including Au, Pt, Pd have been demonstrated, forming a typical core@void@shell structure. We showed that the key parameters of the yolk–shell structure such as the shell thickness and the cavity size could be readily tuned. Due to the protection of a surrounding Al₂O₃ shell, the thermal stability of the interior metal nanoparticles could be substantially improved, resulting in promising performance for the catalytic CO oxidation as revealed by our preliminary test on Au@Al₂O₃

3D Copper Tetrathiafulvalene Redox-Active Network with 8‑Fold Interpenetrating Diamond-like Topology

A tetrathiafulvalene derivative has been incorporated into a diamond-like structure for the first time. The coordination network shows highly unusual 8-fold interpenetration with redox-active and photoelectric properties

Role of the Coordination Center in Photocurrent Behavior of a Tetrathiafulvalene and Metal Complex Dyad

Small organic molecule-based compounds are considered to be promising materials in photoelectronics and high-performance optoelectronic devices. However, photoelectron conversion research based on functional organic molecule and metal complex dyads is very scarce. We design and prepare a series of compounds containing a tetrathiafulvalene (TTF) moiety substituted with pyridylmethylamide groups of formulas [Ni­(acac)₂L]·2CH₃OH (<b>1</b>), [Cu₂I₂L₂]·THF·2CH₃CN (<b>2</b>), and [MnCl₂L₂]_<i>n</i>·2<i>n</i>CH₃CH₂OH (<b>3</b>) (L = 4,5-bis­(3-pyridylmethylamide)-4′,5′-bimethylthio-tetrathiafulvalene, acac = acetylacetone) to study the role of the coordination center in photocurrent behavior. Complex <b>1</b> is a mononuclear species, and complex <b>2</b> is a dimeric species. Complex <b>3</b> is a two-dimensional (2-D) coordination polymer. Spectroscopic and electrochemical properties of these complexes indicate that they are electrochemically active materials. The tetrathiafulvalene ligand L is a photoelectron donor in the presence of electron acceptor methylviologen. The effect of metal coordination centers on photocurrent response behavior is examined. The redox-active metal coordination centers should play an important role in improvement of the photocurrent response property. The different morphologies of the electrode films reflect the dimensions in molecular structures of the coordination compounds

Effect of Metal Coordination on Photocurrent Response Properties of a Tetrathiafulvalene Organogel Film

Organic low molecular weight gelators with a tetrathiafulvalene (TTF) unit have received considerable attention because the formed gels usually exhibit redox active response and conducting or semiconducting properties. However, to our knowledge, metal coordination systems have not been reported for TTF-derived gels up to date. We have designed and synthesized a series of TTF derivatives with a diamide-diamino moiety that can coordinate to specific metal ions with square coordination geometry. Gelation properties and morphologies of the films prepared by the gelators in different hydrophobic solvents are characterized. The TTF derivative with a dodecyl group shows effective gelation properties, and electrodes with the organogel films are prepared. The effect of the Ni­(II) and Cu­(II) coordination on the photocurrent response property of the electrodes is examined. The metal square coordination significantly increases the photocurrent response. This gel system is the first metal coordination related TTF-gel-based photoelectric material. The mechanism of the metal coordination-improved photocurrent response property is discussed based on the crystal structural analysis and theoretical calculations

Engineering Hollow Carbon Architecture for High-Performance K‑Ion Battery Anode

K-ion batteries (KIBs) are now drawing increasing research interest as an inexpensive alternative to Li-ion batteries (LIBs). However, due to the large size of K⁺, stable electrode materials capable of sustaining the repeated K⁺ intercalation/deintercalation cycles are extremely deficient especially if a satisfactory reversible capacity is expected. Herein, we demonstrated that the structural engineering of carbon into a hollow interconnected architecture, a shape similar to the neuron-cell network, promised high conceptual and technological potential for a high-performance KIB anode. Using melamine-formaldehyde resin as the starting material, we identify an interesting glass blowing effect of this polymeric precursor during its carbonization, which features a skeleton-softening process followed by its spontaneous hollowing. When used as a KIB anode, the carbon scaffold with interconnected hollow channels can ensure a resilient structure for a stable potassiation/depotassiation process and deliver an extraordinary capacity (340 mAh g^–1 at 0.1 C) together with a superior cycling stability (no obvious fading over 150 cycles at 0.5 C)

Engineering Hollow Carbon Architecture for High-Performance K‑Ion Battery Anode

K-ion batteries (KIBs) are now drawing increasing research interest as an inexpensive alternative to Li-ion batteries (LIBs). However, due to the large size of K⁺, stable electrode materials capable of sustaining the repeated K⁺ intercalation/deintercalation cycles are extremely deficient especially if a satisfactory reversible capacity is expected. Herein, we demonstrated that the structural engineering of carbon into a hollow interconnected architecture, a shape similar to the neuron-cell network, promised high conceptual and technological potential for a high-performance KIB anode. Using melamine-formaldehyde resin as the starting material, we identify an interesting glass blowing effect of this polymeric precursor during its carbonization, which features a skeleton-softening process followed by its spontaneous hollowing. When used as a KIB anode, the carbon scaffold with interconnected hollow channels can ensure a resilient structure for a stable potassiation/depotassiation process and deliver an extraordinary capacity (340 mAh g^–1 at 0.1 C) together with a superior cycling stability (no obvious fading over 150 cycles at 0.5 C)

Engineering Hollow Carbon Architecture for High-Performance K‑Ion Battery Anode

K-ion batteries (KIBs) are now drawing increasing research interest as an inexpensive alternative to Li-ion batteries (LIBs). However, due to the large size of K⁺, stable electrode materials capable of sustaining the repeated K⁺ intercalation/deintercalation cycles are extremely deficient especially if a satisfactory reversible capacity is expected. Herein, we demonstrated that the structural engineering of carbon into a hollow interconnected architecture, a shape similar to the neuron-cell network, promised high conceptual and technological potential for a high-performance KIB anode. Using melamine-formaldehyde resin as the starting material, we identify an interesting glass blowing effect of this polymeric precursor during its carbonization, which features a skeleton-softening process followed by its spontaneous hollowing. When used as a KIB anode, the carbon scaffold with interconnected hollow channels can ensure a resilient structure for a stable potassiation/depotassiation process and deliver an extraordinary capacity (340 mAh g^–1 at 0.1 C) together with a superior cycling stability (no obvious fading over 150 cycles at 0.5 C)

Controlling the Reaction of Nanoparticles for Hollow Metal Oxide Nanostructures

Hollow nanostructures of metal oxides have found broad applications in different fields. Here, we reported a facile and versatile synthetic protocol to prepare hollow metal oxide nanospheres by modulating the chemical properties in solid nanoparticles. Our synthesis design starts with the precipitation of urea-containing metal oxalate, which is soluble in water but exists as solid nanospheres in ethanol. A controlled particle hydrolysis is achieved through the heating-induced urea decomposition, which transforms the particle composition in an outside-to-inside style: The reaction starts from the surface and then proceeds inward to gradually form a water-insoluble shell of basic metal oxalate. Such a reaction-induced solubility difference inside nanospheres becomes highly efficient to create a hollow structure through a simple water wash process. A following high temperature treatment forms hollow nanospheres of different metal oxides with structural features suited to their applications. For example, a high performance anode for Li-ion intercalation pseudocapacitor was demonstrated with the hollow and mesoporous Nb₂O₅ nanospheres