Design and Preparation of MnO₂/CeO₂–MnO₂ Double-Shelled Binary Oxide Hollow Spheres and Their Application in CO Oxidation

Herein, we designed an extremely facile method to prepare well-defined MnO₂@CeO₂–MnO₂ ball-in-ball binary oxide hollow spheres by employing carbon spheres (CSs) as sacrificial templates. The synthesis process involves a novel self-assembled approach to prepare core–shell CSs@CeO₂ precursor, which would directly react with KMnO₄ aqueous solution to form yolk–shell CSs@MnO₂/CeO₂–MnO₂ precursor in the following step. Well-dispersed Ce–Mn binary oxide with double-shelled hollow sphere structure could be achieved after annealing the precursor in air. The evolution process and formation mechanism of this novel structure were thoroughly studied in this paper. Especially the as-prepared double-shell MnO₂/CeO₂–MnO₂ hollow spheres exhibited enhanced catalytic activity for CO oxidation compared with the pure MnO₂ hollow spheres and pure CeO₂ hollow spheres. We believe the high surface area, hierarchical porous structures, and strong synergistic interaction between CeO₂ and MnO₂ contribute to the excellent catalytic activity. Most importantly, this method could be extended to prepare other transition metal oxides. As an example, triple-shelled Co–Mn composite hollow spheres assembled by ultrathin nanoplates were successfully prepared

Pt/Zeolite Catalysts for Soot Oxidation: Influence of Hydrothermal Aging

Developments in diesel engines and gasoline direct injection (GDI) engines have spawned the requirement of soot oxidation catalysts that work well in both NO + O₂ and O₂. In this study, we found that supporting Pt on zeolites such as H-ZSM5 and USY may receive better soot oxidizers than commercial Pt/Al₂O₃ catalyst. Durability tests indicate that, even after the hydrothermal aging at 800 °C, the aged Pt/H-ZSM5 is still a better soot oxidizer than Pt/Al₂O₃ in NO + O₂, and the aged Pt/USY exhibits the best activity in O₂. Further explorations reveal that the NO₂ preferential adsorption on soot is dependent on acid sites both inside and outside micropores of zeolites, while the decomposition of surface oxygenated complexes (SOCs) can be promoted by strong acid sites on the external surface. These two factors contribute mainly to the high activity of the Pt/zeolite catalysts in NO + O₂ and O₂, respectively. Considering a relatively high external surface area is always essential to inhibiting the severe sintering of Pt, it is important to choose a zeolite support with a relatively large external surface area and a certain amount of acid sites after the hydrothermal aging

Roles of Acid Sites on Pt/H-ZSM5 Catalyst in Catalytic Oxidation of Diesel soot

Pt/H-ZSM5 and Pt/Al₂O₃ with similar surface Pt particle sizes and chemical states were prepared by incipient wetness impregnation as catalysts for soot oxidation. Pt/H-ZSM5 exhibits obviously higher activities in both O₂ and NO + O₂ than Pt/Al₂O₃. On the basis of the results obtained with in situ DRIFT and other structural and surface property characterizations, the high catalytic activity of Pt/H-ZSM5 is currently attributed to two main factors. First, the acidic H-ZSM5 support inhibits NO₂ adsorption on the catalyst, leading to a preferential adsorption of NO₂ on the surface of soot and providing more chances for NO₂–soot reactions. Second, the strong acid sites on the surface of Pt/H-ZSM5 can participate in the catalytic formation and decomposition of surface oxygenated complexes. Consequently, a high catalytic efficiency for soot oxidation is achieved on the Pt/H-ZSM5 catalyst

Pt/Zeolite Catalysts for Soot Oxidation: Influence of Hydrothermal Aging

Developments in diesel engines and gasoline direct injection (GDI) engines have spawned the requirement of soot oxidation catalysts that work well in both NO + O₂ and O₂. In this study, we found that supporting Pt on zeolites such as H-ZSM5 and USY may receive better soot oxidizers than commercial Pt/Al₂O₃ catalyst. Durability tests indicate that, even after the hydrothermal aging at 800 °C, the aged Pt/H-ZSM5 is still a better soot oxidizer than Pt/Al₂O₃ in NO + O₂, and the aged Pt/USY exhibits the best activity in O₂. Further explorations reveal that the NO₂ preferential adsorption on soot is dependent on acid sites both inside and outside micropores of zeolites, while the decomposition of surface oxygenated complexes (SOCs) can be promoted by strong acid sites on the external surface. These two factors contribute mainly to the high activity of the Pt/zeolite catalysts in NO + O₂ and O₂, respectively. Considering a relatively high external surface area is always essential to inhibiting the severe sintering of Pt, it is important to choose a zeolite support with a relatively large external surface area and a certain amount of acid sites after the hydrothermal aging

Localized Surface Plasmon Resonance Assisted Photothermal Catalysis of CO and Toluene Oxidation over Pd–CeO₂ Catalyst under Visible Light Irradiation

The extinction peak of Pd particles generally locates at the ultraviolet light region, suggesting that only 4% of solar light can be absorbed. Furthermore, the efficiency of LSPR hot electrons converted to chemical energy of reaction is very low due to the fast relaxation of carriers. It is extremely valuable to design Pd-based catalysts which have strong response to the visible light irradiation and high efficiency in photon to chemical energy. The Pd–CeO₂ catalyst was synthesized via the hexadecyl­trimethyl­ammonium bromide (CTAB) assisted liquid-phase reduction method to generate more active interfaces. The significant extinction of Pd–CeO₂ in the visible to near-infrared region indicates the strong electron interaction between Pd and CeO₂. LSPR hot electrons, transferring from the Pd metal particles to the conduction band of ceria, promote the dissociation of adsorbed oxygen. Therefore, the reaction temperature of CO and toluene oxidation can be significantly lowered by visible light irradiation. The maximum light efficiencies of Pd–CeO₂ catalyst for toluene oxidation and CO oxidation are obtained as 0.42% and 1%, which benefit from the effective Pd–O–Ce interfaces

Development of an anti-microbial peptide-mediated liposomal delivery system: a novel approach towards pH-responsive anti-microbial peptides

<div><p></p><p>On one hand, the application of anti-microbial peptides (AMPs) in the construction of AMPs-mediated drug delivery system has not yet been fully exploited; on the other hand, its non-selectivity <i>in vivo</i> has also limited its clinical application. In this work, we chose one pH-responsive peptide, [D]-H₆L₉, and functionalized it onto the surface of liposomes (D-Lip). The protonation of histidines in the sequence of [D]-H₆L₉ under pH 6.3 could switch the surface charge of D-Lip from negative (under pH 7.4) to positive (under pH 6.3), and the cellular uptake and tumor spheroids uptake were increased accordingly. Lysosome co-localization assay suggested that there was only little overlap of D-Lip with lysosomes in 12 h, which indicated that D-Lip could escape lysosomes effectively. <i>In vivo</i> biodistribution assay on C26 tumor-bearing BALB/C mice showed that DiR-labeled D-Lip could reach tumors as much as PEG-Lip, and both tumor slices and quantitative measurement of dispersed cells of <i>in vivo</i> tumors by flow cytometry demonstrated that D-Lip could be taken up by tumors more efficiently. Therefore, we have established an anti-microbial peptide-mediated liposomal delivery system for tumor delivery.</p></div

Co-delivery of doxorubicin and P-gp inhibitor by a reduction-sensitive liposome to overcome multidrug resistance, enhance anti-tumor efficiency and reduce toxicity

<p>To overcome multidrug resistance (MDR) in cancer chemotherapy with high efficiency and safety, a reduction-sensitive liposome (CL-R8-LP), which was co-modified with reduction-sensitive cleavable PEG and octaarginine (R8) to increase the tumor accumulation, cellular uptake and lysosome escape, was applied to co-encapsulate doxorubicin (DOX) and a P-glycoprotein (P-gp) inhibitor of verapamil (VER) in this study. The encapsulation efficiency (EE) of DOX and VER in the binary-drug loaded CL-R8-LP (DOX + VER) was about 95 and 70% (w/w), respectively. The uptake efficiencies, the cytotoxicity, and the apoptosis and necrosis-inducing efficiency of CL-R8-LP (DOX + VER) were much higher than those of DOX and the other control liposomes in MCF-7/ADR cells or tumor spheroids. Besides, CL-R8-LP (DOX + VER) was proven to be uptaken into MCF-7/ADR cells by clathrin-mediated and macropinocytosis-mediated endocytosis, followed by efficient lysosomal escape. <i>In vivo</i>, CL-R8-LP (DOX + VER) effectively inhibited the growth of MCF-7/ADR tumor and reduce the toxicity of DOX and VER, which could be ascribed to increased accumulation of drugs in drug-resistant tumor cells and reduced distribution in normal tissues. In summary, the co-delivery of chemotherapeutics and P-gp inhibitors by our reduction-sensitive liposome was a promising approach to overcome MDR, improve anti-tumor effect and reduce the toxicity of chemotherapy.</p

Simple Strategy Generating Hydrothermally Stable Core–Shell Platinum Catalysts with Tunable Distribution of Acid Sites

There are critical needs for platinum catalysts with high hydrothermal stability and tunable Pt–acid site proximity, which could not be achieved via traditional methods. Here, we describe a simple strategy (SiO₂ alumination combined with controlled removal of the capping agent) through which Pt-based core–shell catalysts that tolerant both high-temperature steam and boiling water can be obtained. More importantly, this strategy allows precise control of the distance between acid sites and Pt; thus, the interfacial electronic interaction can be cut off without prohibiting the spillover of adsorbed species. This tunable structure not only helps to unravel the mechanism of C₃H₈ oxidation over acidic Pt catalyst but also increases the N₂ selectivity for NO_<i>x</i> selective catalytic reduction. Given that the component of both the “core” and “shell” can be changed easily, this strategy should have wide application in mechanism exploration as well as the development of catalysts for various reactions