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To enhance the catalytic activity of gold nanoparticles (AuNPs) for the hydrogenation of nitro-aromatic chemicals, Pt was introduced into AuNPs to form "bare" PtAu alloy NPs using a physical approach, pulsed laser ablation in liquid (PLAL), on single metal-mixture targets. These PLAL-NPs are deemed to favor catalysis due to the absence of any surfactant molecules on their unique "bare and clean" surface. The PLAL-NPs were facilely assembled onto CeO2 nanotubes (NTs) by simply mixing them without conducting any surface functionalization, representing another advantage of these NPs. Their catalytic activity was assessed in 4-nitrophenol (4-NP) hydrogenation. The reaction catalyzed by alloy-NP/CeO2-NT catalysts demonstrates a remarkably higher reaction rate in comparison with that catalyzed by pure Au and Pt NPs, and other similar Au and Pt containing catalysts reported recently. A "volcano-like" catalytic activity dependence of the alloy NPs on their chemical composition suggests a strong synergistic effect between Au and Pt in the 4-NP reduction, far beyond the simple sum of their individual contributions. It leads to the significantly enhanced catalytic activity of Pt30Au70 and Pt50Au50 alloy NPs, outperforming not only each single constituent, but also their physical mixtures and most recently reported AuNP based nanocatalysts. The favorable d-band center shift of Pt after alloying, and co-operative actions between Pt clusters and nearby Au (or mixed PtAu) sites were proposed as possible mechanisms to explain such a strong synergistic effect on catalysis.

We report the synthesis and characterization of new Ni(x)Ru(1-x) (x = 0.56-0.74) alloy nanoparticles (NPs) and their catalytic activity for hydrogen release in the ammonia borane hydrolysis process. The alloy NPs were obtained by wet-chemistry method using a rapid lithium triethylborohydride reduction of Ni(2+) and Ru(3+) precursors in oleylamine. The nature of each alloy sample was fully characterized by TEM, XRD, energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). We found that the as-prepared Ni-Ru alloy NPs exhibited exceptional catalytic activity for the ammonia borane hydrolysis reaction for hydrogen release. All Ni-Ru alloy NPs, and in particular the Ni(0.74)Ru(0.26) sample, outperform the activity of similar size monometallic Ni and Ru NPs, and even of Ni@Ru core-shell NPs. The hydrolysis activation energy for the Ni(0.74)Ru(0.26) alloy catalyst was measured to be approximately 37 kJ mol(-1). This value is considerably lower than the values measured for monometallic Ni (≈70 kJ mol(-1)) and Ru NPs (≈49 kJ mol(-1)), and for Ni@Ru (≈44 kJ mol(-1)), and is also lower than the values of most noble-metal-containing bimetallic NPs reported in the literature. Thus, a remarkable improvement of catalytic activity of Ru in the dehydrogenation of ammonia borane was obtained by alloying Ru with a Ni, which is a relatively cheap metal.

Interfacial oxidation–reduction reaction is herein developed to prepare hollow binary oxide nanostructures. Ce–Mn nanotubes are fabricated by treating Ce(OH)CO3 templates with KMnO4 aqueous solution, where MnO4− is reduced to manganese oxide and the Ce3+ in Ce(OH)CO3 is simultaneously oxidized to form cerium oxide, followed by selective wash with HNO3. The resulting Ce–Mn binary oxide nanotubes exhibit high catalytic activity towards CO oxidation and show significant adsorption capacity of Congo red. Moreover, guided by the same interfacial‐reaction principle, binary oxide hollow nanostructures with different shapes and compositions are synthesized. Specifically, hollow Ce–Mn binary oxide cubes, and Co‐Mn and Ce‐Fe binary oxide hollow nanostructures are achieved by changing the shape of the Ce(OH)CO3 templates from rods to cubes, by changing the tempates from Ce(OH)CO3 nanorods to Co(CO3)0.35Cl0.20(OH)1.10 nanowires, and by replacing the oxidant of KMnO4 with another strong one, K2FeO4, respectively. This work is expected to open a new, simple avenue for the general synthesis of hollow binary oxide nanostructures.

BackgroundCelastrol is an active ingredient of the traditional Chinese medicinal plant Tripterygium Wilfordii, which exhibits significant antitumor activity in different cancer models in vitro and in vivo; however, the lack of information on the target and mechanism of action of this compound have impeded its clinical application. In this study, we sought to determine the mode of action of celastrol by focusing on the processes that mediate its anticancer activity.MethodsThe downregulation of heat shock protein 90 (HSP90) client proteins, phosphorylation of c-Jun NH2-terminal kinase (JNK), and cleavage of PARP, caspase 9 and caspase 3 were detected by western blotting. The accumulation of reactive oxygen species (ROS) was analyzed by flow cytometry and fluorescence microscopy. Cell cycle progression, mitochondrial membrane potential (MMP) and apoptosis were determined by flow cytometry. Absorption spectroscopy was used to determine the activity of mitochondrial respiratory chain (MRC) complexes.ResultsCelastrol induced ROS accumulation, G2-M phase blockage, apoptosis and necrosis in H1299 and HepG2 cells in a dose-dependent manner. N-acetylcysteine (NAC), an antioxidative agent, inhibited celastrol-induced ROS accumulation and cytotoxicity. JNK phosphorylation induced by celastrol was suppressed by NAC and JNK inhibitor SP600125 (SP). Moreover, SP significantly inhibited celastrol-induced loss of MMP, cleavage of PARP, caspase 9 and caspase 3, mitochondrial translocation of Bad, cytoplasmic release of cytochrome c, and cell death. However, SP did not inhibit celastrol-induced ROS accumulation. Celastrol downregulated HSP90 client proteins but did not disrupt the interaction between HSP90 and cdc37. NAC completely inhibited celastrol-induced decrease of HSP90 client proteins, catalase and thioredoxin. The activity of MRC complex I was completely inhibited in H1299 cells treated with 6 μM celastrol in the absence and presence of NAC. Moreover, the inhibition of MRC complex I activity preceded ROS accumulation in H1299 cells after celastrol treatment.ConclusionWe identified ROS as the key intermediate for celastrol-induced cytotoxicity. JNK was activated by celastrol-induced ROS accumulation and then initiated mitochondrial-mediated apoptosis. Celastrol induced the downregulation of HSP90 client proteins through ROS accumulation and facilitated ROS accumulation by inhibiting MRC complex I activity. These results identify a novel target for celastrol-induced anticancer activity and define its mode of action.

CeO(2) nanotubes have been synthesized with a simple solid-liquid interface reaction route in the absence of any surfactants. Although the basic reaction principles are similar, two kinds of nanotubes with completely different morphologies and structures can be generated by slightly tuning the postprocessing conditions. The first formation involves employing Ce(OH)CO(3) nanorods as both the physical and chemical templates, and the other requires layered Ce(OH)3 as an anisotropic intermediate species. During this process, NaOH and reaction temperature were demonstrated as the key factors responsible for the formation of Ce(OH)(3) intermediate and final CeO(2) nanotubes with well-defined structures. The structural details were provided by a combination of XRD, SEM, TEM, and HRTEM investigations. Catalytic measurement shows that both nanotubes are very active for CO oxidation, and at 250 degrees C, the conversion rates of CeO(2) nanotubes are 3 times higher than that of the bulk counterpart.

The introduction of heteroatoms is one of the most important ways to modulate the intrinsic electronic structure of electrocatalysts to improve their catalytic activity. However, for transition metal chalcogenides with highly symmetric crystal structure (HS‐TMC), the introduction of heteroatoms, especially those with large atomic radius, often induces large lattice distortion and vacancy defects, which may lead to structural phase transition of doped materials or structural phase reconstruction during the catalytic reaction. Such unpredictable situations will make it difficult to explore the connection between the intrinsic electronic structure of doped catalysts and catalytic activity. Herein, taking thermodynamically stable cubic CoSe2 phase as an example, we demonstrate that nitrogen incorporation can effectively regulate the intrinsic electronic structure of HS‐TMC with structural phase stability and thus promote its electrocatalytic activity for the hydrogen evolution activity (HER). In contrast, the introduction of phosphorus can lead to structural phase transition from cubic CoSe2 to orthorhombic phase, and the structural phase of phosphorus‐doped CoSe2 is unstable for HER.

Core-shell structured Ni@Ru bimetallic nanoparticles are demonstrated as a bifunctional nanoplatform system for the hydrolysis reaction of ammonia-borane and also for magnetic separation.