Novel Organic/Noble Metal Hybrid Nanomaterials:Preparation And Their Applications In Plasmon-Enhanced Spectra

The unique local surface plasmonic resonance（LSPR） properties of noble metal nanoparticles have been extensively applied in many fields such as biomedical technology, plasmonic-enhanced spectroscopies, catalysis, optical and optoelectronic devices. Electrospinning is the only technology for fabricating continuous nanofibers and has attracted increasing attentions in many fields such as filtration, catalysis, sensor, optoelectronic devices and energy due to their high surface-to-volume ratio. Herein, we prepared a series of electrospun polymer/noble metal hybrid nanofibrious mats, and then investigated their applications in plasmon enhanced fluorescence（PEF）, surface-enhanced Raman scattering（SERS） and in-situ Raman morniting catalytic reactions, summarized as follows: 1. Electrospun polymer/noble metal hybrid nanofibers have developed rapidly as SERSactive substrates over the last few years. However, polymer/noble metal nanofibers with plasmon-enhanced fluorescence（PEF） activity have received no attention to date. Herein, we show a general and facile approach for the preparation of polyacrylonitrile（PAN）/noble metal/SiO₂ nanofibrous mats with PEF activity for the first time by combining electrospinning and controlled silica coatings. These PEF-active nanofibrous mats can selectively improve the fluorescence intensity of conjugated polyelectrolytes（CPEs）. Importantly, the CPE solution in the presence of a PAN/noble metal/SiO₂ nanofibrous mat showed dramatic fluorescence quenching towards picomolar（pM） amounts of heavy metal ions, while the fluorescence of the CPE solution without the nanofibrous mat had no apparent quenching towards micromolar（μM） amounts of metal ions. The combination of the distance-dependent fluorescence enhancement performance of metal NPs and the ionic characteristics of the CPE solution makes the polymer/noble metal nanofibers promising substrates for greatly improving the detection sensitivity towards metal ions. We believe that this work provides a general strategy for preparing plasmon bandtuned PEF-active substrates with advantages including good selectivity, remarkable sensitivity and recyclability, which make them a preferable choice for practical sensing applications. 2. The detection of molecules in highly diluted solution with low concentration is still highly desired to date. Previous reports have demonstrated that the detection sensitivity could be improved by combining surhydrophobic surfaces and nanoplasmonic structures. Here we reported a general approach for preparing superhydrophobic polymer nanofibers decorated with gold nanoparticles for improved detection sensitivity. Superhydrophobicity of polymer nanofibers were fabricated by the combination of improved surface roughness and lowsurface-energy modification, which drived and concentrated molecules over the sensing micro-area where plasmonic electric-field hot spots are used to carry out molecule detection. The limit of detection for R6 G molecules was as low as 10-13 M. 3. Most as-reported nanostructures through galvanic replacement reactions are still symmetric hollow structures, until now. Asymmetric structures fabricated through a galvanic replacement reaction have been rarely reported. However, asymmetric heterostructures can generally lead to new intriguing properties through asymmetric synergistic coupling. Here, we report a simple synthesis of an asymmetric one ended AgPd bimetal on Au nanorods（AuNRs） by combining a galvanic replacement reaction with an Ostwald ripening process. The morphological evolution from a nanodumbbell to a dandelion structure is thoroughly investigated. The unique asymmetric AgPd–AuNR heterostructures possess the required plasmonic performance and avoid strong damping caused by the poor plasmonic metal Pd, resulting in a superior photothermal heating performance and enhanced SERS sensitivity for in situ monitoring of a catalytic reaction compared with the symmetric counterparts.