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Zhao Y.,CAS Hefei Key Laboratory of Materials for Energy Conversion | Li X.,Hefei University of Technology | Du Y.,CAS Hefei Key Laboratory of Materials for Energy Conversion | Chen G.,CAS Hefei Key Laboratory of Materials for Energy Conversion | And 4 more authors.
Nanoscale | Year: 2014

The interactions between visible light and sub-nanometer gaps were investigated by sandwiching graphene between two layers of vertically stacked Au nanoparticles. The optical properties of such a hybrid film have been effectively tuned by embedding a monolayer graphene, enabling a suppressed transmission of ∼16% accompanied by a red-shift of the resonant wavelength. Finite element simulations have shown that the strong coupling between two layers of plasmonic Au nanoparticles leads to an electric field enhancement of up to 88 times in graphene defined vertical gaps, in contrast to that of 14 times in the horizontal gaps between Au nanoparticles formed in the fabrication process. In addition, the size of gaps and thus the field enhancement can be readily tuned by the number of graphene layers sandwiched between Au nanoparticles. When being used as surface-enhanced Raman scattering (SERS) substrates, the Au nanoparticle/graphene/Au nanoparticle structures have demonstrated high Raman enhancement factors of up to 1.6 × 108for RhB and 2.5 × 108for R6G, and a detection limit of as low as 0.1 nM for Sudan III and methylene blue molecules. This journal is © the Partner Organisations 2014. Source


Du Y.,CAS Hefei Key Laboratory of Materials for Energy Conversion | Zhao Y.,CAS Hefei Key Laboratory of Materials for Energy Conversion | Qu Y.,Graphene Technologies | Qu Y.,Jiangnan Graphene Research Institute | And 4 more authors.
Journal of Materials Chemistry C | Year: 2014

By simply coating graphene films on Au nanoparticles, the optical properties of the hybrid films are investigated. It is found that the coverage of a monolayer graphene film leads to a decreased transmittance of up to 15.8% in the visible range, much higher than the 2.3% transmittance loss for intrinsic graphene. At the same time, the plasmonic resonance of the hybrid films experiences a red-shift in resonance frequency and a broadening in the transmission dip. By means of finite element simulations, these observations are attributed to strong light-matter interaction at the interface between graphene and Au nanoparticles, as indicated by the increased absorption cross section and higher electric field intensity. The electron transfer between graphene and Au nanoparticles is confirmed by high resolution X-ray photoelectron spectroscopy studies. Furthermore, the enhanced electromagnetic hot spots at the interface between graphene and Au nanoparticles make such graphene-Au nanoparticle hybrid films cost-effective and high-performance surface-enhanced Raman scattering substrates for detecting organic molecules such as rhodamine-6G, for which an enhancement factor of ∼107 is achieved. © 2014 the Partner Organisations. Source


Zhu C.,Nanjing Southeast University | Min H.,Nanjing Southeast University | Xu F.,Nanjing Southeast University | Xu F.,Brookhaven National Laboratory | And 5 more authors.
RSC Advances | Year: 2015

Utilizing inexpensive, high-efficiency counter electrodes (CEs) to replace the traditional platinum counterparts in dye-sensitized solar cells (DSSCs) is worthwhile. In this paper, we detail how we synchronously prepared composite CEs of CoS nanosheet arrays and reduced graphene oxide (rGO) layers for the first time via a low temperature, ultrafast one-step electrochemical strategy. With this approach, the whole fabrication process of the composite CEs was only a small percentage of the average time (∼15 hours) using other methods. The DSSC assembled with the rGO-CoS composite CE achieved an enhanced power conversion efficiency (PCE) of 8.34%, which is dramatically higher than 6.27% of pure CoS CE-based DSSC and even exceeds 7.50% of Pt CE-based DSSC. The outstanding PCE breakthrough is undoubtedly attributed to the enhancement in electrocatalytic ability of the rGO-CoS composite CE due to the incorporation of highly conducting rGO layers and the GO layers-induced growth of CoS nanosheet arrays with higher density and larger surface area. Therefore, lower charge-transfer resistance and higher exchange current density can be achieved as corroborated by the electrochemical impedance spectra (EIS) and Tafel polarization curves (TPCs). Further experiments also proved that the electrochemical strategy exhibited its universality of fabricating other graphene-enhanced chalcogenide functional composite films. © The Royal Society of Chemistry 2015. Source


Qin Y.,Changzhou University | Kong Y.,Changzhou University | Xu Y.,Changzhou University | Chu F.,Jiangnan Graphene Research Institute | And 2 more authors.
Journal of Materials Chemistry | Year: 2012

Highly loaded and ultrafine Pd nanoparticles were supported on graphene oxide (PdNPs-GO) via an in situ, simple and clean strategy on the basis of the direct redox reaction between Pd(OAc)2 and GO. A highly sensitive biosensor was developed for the detection of glucose based on the electrode modified with PdNPs-electrochemically reduced GO (PdNPs-ERGO). The glucose biosensor shows a wide linear range, low detection limit, good reproducibility and acceptable stability, providing a biocompatible platform for biosensing and biocatalysis. © The Royal Society of Chemistry 2012. Source


Zhao Y.,CAS Hefei Key Laboratory of Materials for Energy Conversion | Chen G.,CAS Hefei Key Laboratory of Materials for Energy Conversion | Du Y.,CAS Hefei Key Laboratory of Materials for Energy Conversion | Xu J.,CAS Hefei Key Laboratory of Materials for Energy Conversion | And 4 more authors.
Nanoscale | Year: 2014

We detail a facile method for enhancing the Raman signals of as-grown graphene on Cu foils by depositing gold nanoislands (Au Nis) onto the surface of graphene. It is found that an enhancement of up to 49 fold in the graphene Raman signal has been achieved by depositing a 4 nm thick Au film. The enhancement is considered to be related to the coupling between graphene and the plasmon modes of Au Nis, as confirmed by the finite element simulations. The plasmonic effect of the Au/graphene/Cu hybrid platform leads to a strong absorption at the resonant wavelength whose position shifts from visible light (640 nm) to near-infrared (1085 nm) when the thickness of Au films is increased from 2 nm to 18 nm. Finally, we demonstrate that hybrid substrates are reliable surface-enhanced Raman scattering (SERS) systems, showing an enhancement factor of ∼106 for dye molecules Rhodamine B and Rhodamine 6G with uniform and stable response and a detection limit of as low as 0.1 nM for Sudan III and Sudan IV. This journal is © The Royal Society of Chemistry. Source

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