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Optimising surface d charge of AuPd nanoalloy catalysts for enhanced catalytic activity.

ABSTRACT: Understanding the catalytic mechanism of bimetallic nanocatalysts remains challenging. Here, we adopt an adsorbate mediated thermal reduction approach to yield monodispersed AuPd catalysts with continuous change of the Pd-Au coordination numbers embedded in a mesoporous carbonaceous matrix. The structure of nanoalloys is well-defined, allowing for a direct determination of the structure-property relationship. The results show that the Pd single atom and dimer are the active sites for the base-free oxidation of primary alcohols. Remarkably, the d-orbital charge on the surface of Pd serves as a descriptor to the adsorbate states and hence the catalytic performance. The maximum d-charge gain occurred in a composition with 33-50 at% Pd corresponds to up to 9 times enhancement in the reaction rate compared to the neat Pd. The findings not only open an avenue towards the rational design of catalysts but also enable the identification of key steps involved in the catalytic reactions.

SUBMITTER: Zhu X

PROVIDER: S-EPMC6441046 | biostudies-literature | 2019 Mar

REPOSITORIES: biostudies-literature

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Optimising surface d charge of AuPd nanoalloy catalysts for enhanced catalytic activity.

Zhu Xiaojuan X Guo Qishui Q Sun Yafei Y Chen Shangjun S Wang Jian-Qiang JQ Wu Mengmeng M Fu Wenzhao W Tang Yanqiang Y Duan Xuezhi X Chen De Wan Ying Y

Nature communications 20190329 1

Understanding the catalytic mechanism of bimetallic nanocatalysts remains challenging. Here, we adopt an adsorbate mediated thermal reduction approach to yield monodispersed AuPd catalysts with continuous change of the Pd-Au coordination numbers embedded in a mesoporous carbonaceous matrix. The structure of nanoalloys is well-defined, allowing for a direct determination of the structure-property relationship. The results show that the Pd single atom and dimer are the active sites for the base-fr ...[more]

PMID: 30926804

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Project description:BackgroundBiofilm formation is one of the main reasons for persistent bacterial infections. Recently, pH-sensitive copolymers have fascinated incredible attention to tackle biofilm-related infections. However, the proper incorporation of pH-sensitive segments in the polymer chains, which could significantly affect the biofilms targeting ability, has not been particularly investigated. Herein, we synthesized three types of pH-sensitive copolymers based on poly (β-amino ester) (PAE), poly (lactic-co-glycolic acid) (PLA) and polyethylene glycol (PEG), PAE-PLA-mPEG (A-L-E), PLA-PAE-mPEG (L-A-E) and PLA-PEG-PAE (L-E-A) to address this issue.ResultsThe three copolymers could self-assemble into micelles (MA-L-E, ML-A-E and ML-E-A) in aqueous medium. Compared with MA-L-E and ML-A-E, placing the PAE at the distal PEG end of PLA-PEG to yield PLA-PEG-PAE (ML-E-A) was characterized with proper triggering pH, fully biofilm penetration, and high cell membrane binding affinity. Further loaded with Triclosan (TCS), ML-E-A/TCS could efficiently kill the bacteria either in planktonic or biofilm mode. We reasoned that PAE segments would be preferentially placed near the surface and distant from the hydrophobic PLA segments. This would increase the magnitude of surface charge-switching capability, as the cationic PAE+ would easily disassociate from the inner core without conquering the additional hydrophobic force arising from covalent linkage with PLA segments, and rapidly rise to the outermost layer of the micellar surface due to the relative hydrophilicity. This was significant in that it could enable the micelles immediately change its surface charge where localized acidity occurred, and efficiently bind themselves to the bacterial surface where they became hydrolyzed by bacterial lipases to stimulate release of encapsulated TCS even a relatively short residence time to prevent rapid wash-out. In vivo therapeutic performance of ML-E-A/TCS was evaluated on a classical biofilm infection model, implant-related biofilm infection. The result suggested that ML-E-A/TCS was effective for the treatment of implant-related biofilm infection, which was proved by the efficient clearance of biofilm-contaminated catheters and the recovery of surrounding infected tissues.ConclusionsIn summary, elaboration on the architecture of pH-sensitive copolymers was the first step to target biofilm. The ML-E-A structure may represent an interesting future direction in the treatment of biofilm-relevant infections associated with acidity.

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Optimising surface d charge of AuPd nanoalloy catalysts for enhanced catalytic activity.

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Optimising surface d charge of AuPd nanoalloy catalysts for enhanced catalytic activity.

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