Facile Fabrication of Highly Dispersed Pd@Ag Core–Shell Nanoparticles Embedded in Spirulina platensis by Electroless Deposition and Their Catalytic Properties

Abstract

Microorganisms are widely used as the biotemplates for producing micro/ nanomaterials owing to their unique features, such as exquisite morphology, renewable, and environmentally friendly. However, mass intracellular synthesis of uniformly dispersed nanoparticles (NPs) inside microorganisms is still challenging, especially in a predictable and controllable manner. Here, a facile and efficiency strategy is proposed to controllably produce highly dispersed and surfactant-free Pd@Ag core-shell NPs within the Spirulina platensis (Sp.) cells. In this approach, the Sp. cells' permeability is enhanced by the hydrochloric acid treatment first, which enables the Pd NPs penetrate the cell envelope and distribute uniformly inside the cells, and then they can work as the catalytic seeds for the following electroless silver deposition, resulting in the intracellular fabrication of Pd@Ag core-shell NPs with no agglomeration. The Pd@Ag NPs show excellent catalytic activity (turnover frequency is up to 2893 h −1 for the 6.32 nm Pd@Ag NPs), good stability, and recyclability toward the 4-nitrophenol reductions. The excellent properties are attributed to the asymmetrical core-shell structure, small size, and good dispersion of Pd@Ag NPs. Due to its facility, cost-effectiveness, and versatility, this method can be expanded to other microorganisms, so it opens tremendous opportunities for various metallic nanoparticles intracellular synthesis as well as the practical application.

Sub‐10 nm Ag Nanoparticles/Graphene Oxide: Controllable Synthesis, Size‐Dependent and Extremely Ultrahigh Catalytic Activity

“…Our 4.3‐AgNPs/GO nanocomposites exhibit extremely high catalytic reactivity with a TOF m of as high as 2.2 × 10 5 h −1 (Figure E). This value is substantially higher than that of numerous state‐of‐the‐art Ag‐, Au‐, Pd‐, and Pt‐based catalysts previously developed by others, indicating the potential application of our 4.3‐AgNPs/GO as highly efficient catalysts. However, it should be noted that the TOF m value is practically affected by the experimental conditions, such as the ratio between 4‐NP and NaBH 4 , their respective concentrations, and the total volume of the reaction systems.…”

“…The process of the catalytic reaction is recorded by in situ video (Video S1, Supporting Information; for captured images of the initial and final stages of the reaction, see Figure A). It can be seen that the yellow color of the initial reaction system fades within no more than 2 s immediately upon the introduction of 4.3‐AgNPs/GO, although the 4‐NP concentration in this reaction system (≈0.23 × 10 −3 m ) is much higher than ≈0.1 × 10 −3 m , which is among the most frequently employed 4‐NP concentrations in the literatures . These observations fundamentally imply that our 4.3‐AgNPs/GO might be catalysts with ultrahigh catalytic activity.…”

“…Accordingly, it is not scientifically rational to conclude their ultrahigh catalytic performances simply using the TOF m value obtained under our specific experimental conditions. To make a reasonable comparison, the catalytic performances of our 4.3‐AgNPs/GO were investigated by using exactly the same experimental conditions reported by others (these literature reports are referenced since enough experimental details to permit us to conduct the reaction under absolutely the same experimental conditions have been provided) . As summarized in Table 1 , the TOF m values of our 4.3‐AgNPs/GO are substantially higher than those of the Ag‐, Au‐, Pd‐, and Pt‐based catalysts reported by others.…”

“…A histogram for the comparison of the TOF m values of our 4.3‐AgNPs/GO with those of state‐of‐the‐art Ag‐, Au, Pt‐, and Pd‐based catalysts developed by others. Our reactions are carried out under exactly the same experimental conditions as those in the referenced literature reports . These studies are referenced since enough experimental details to allow us to carry out the experiments under absolutely the same experimental conditions have been provided in the respective papers.…”

“…For these state‐of‐the‐art catalysts reported by others, they either are accommodated in 3D porous frameworks or layered scaffolds or are capped by stabilizers . In some cases, the catalyst size is larger than 10 nm .…”