Direct evidence of plasmonic enhancement on catalytic reduction of 4-nitrophenol over silver nanoparticles supported on flexible fibrous networks

• Size-controlled Ag nanoparticles are uniformly loaded onto the surface of flexible PAN electrospun fibers-network.
• Ag/PAN composite fibrous networks exhibit good catalytic activities and stability for the reduction of 4-NP to 4-AP.
• SPR-excitation of Ag nanoparticles on the electrospun network greatly promotes the catalytic activity for 4-NP reduction.
• Photothermal effect driven by the plasmon-excitation of Ag is responsible for the enhanced catalytic activity.

Direct evidence of plasmon-enhanced 4-nitrophenol (4-NP) reduction is observed in a photo-assisted catalytic process with the NaBH4 as the electron donator by using the Ag nanoparticles (AgNPs) supported onto a flexible and processable polyacrylonitrile (PAN) microfibrous network. The Ag/PAN composite fibrous networks exhibit certain activity for 4-NP reduction in general condition. Significantly, when the beam irradiation is introduced to excite the surface plasmon resonance (SPR) of AgNPs, we observed an enhanced catalytic activity for 4-NP reduction (1 ∼ 3 times). Meanwhile, the enhancement factors for the catalytic kinetic constants are directly correlated with the SPR absorption spectra of AgNPs. Further in-depth studies by adjusting the experiment conditions reveal that the SPR-induced ultrafast thermal effect of AgNPs is responsible for the enhanced catalytic activity that can not be nevertheless initiated or magnified by the hot plasmonic electrons from Ag. By combining with the theoretical analyses, we propose that this plasmon enhancement is ascribed to the promoted diffusion rate of reactants in the solution driven by increasing the local temperature around the AgNPs on the basis of SPR-enhanced electric field. Our present work provides a new sight to understand the plasmonic enhancement of metal-related catalytic reactions, and would also create more opportunities to guide the design and fabrication of high-performance plasmonic catalysts with excellent recycling property.

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