Synthesis of ultrathin and compact Au@MnO2 nanoparticles for shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS)

• Published in: Journal of Raman spectroscopy Vol. 43; no. 1; pp. 40 - 45
• Main Authors: Lin, Xiao-Dong, Uzayisenga, Viviane, Li, Jian-Feng, Fang, Ping-Ping, Wu, De-Yin, Ren, Bin, Tian, Zhong-Qun
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.01.2012; Wiley Subscription Services, Inc
• Subjects: Au@MnO2 NPs; core-shell heterostructures; SERS; SHINERS
• ISSN: 0377-0486; 1097-4555
• DOI: 10.1002/jrs.3007

Shell‐isolated nanoparticle‐enhanced Raman spectroscopy (SHINERS) based on Au@SiO2 or Au@Al2O3 nanoparticles (NPs) shows great potential to break the long‐standing limitations of substrate and surface generality of surface‐enhanced Raman scattering (SERS). However, the shell of SiO2 or Al2O3 can easily be dissolved in alkaline media, which limits the applications of SHINERS in alkaline systems. Besides that, the synthesis of Au@SiO2 NPs can be further simplified and Au@Al2O3 NPs be replaced by other NPs that are more amenable for mass production. In an attempt to make SHINERS NPs available in any systems practically, we report the synthesis of ultrathin and compact Au@MnO2 NPs. The shell thickness of MnO2 can be controlled down to about 1.2 nm without any pinhole. SHINERS based on such Au@MnO2 NPs exhibits much higher Raman enhancement effect than Au@SiO2 NPs and can be applied in alkaline systems in which Au@SiO2 or Au@Al2O3 NPs cannot be applied. Copyright © 2011 John Wiley & Sons, Ltd. The peak intensity from 55 nm Au@1.2 nm MnO2 NPs is about 10 times of that from 55 nm Au@4 nm SiO2 NPs. In SHINERS, the distance of the SERS‐active core and the substrate is controlled by the thickness of the shell. Considering a much thinner shell thickness of MnO2 than that of SiO2, higher signal intensity obtained in the former system is reasonable. The improved signal intensity of Au@MnO2 SHINERS NPs has a strong advantage in increasing the sensitivity and decreasing the detection limit.