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Surface-enhanced Raman spectroscopy (SERS) can provide a fingerprint of molecules with ultrahigh sensitivity, down to the single-molecule level. However, accurate quantitative detection in practical samples using SERS is still a great challenge. Herein, a highly uniform shell-isolated Ag@SiO2 nanoparticle (Ag SHIN) monolayer film was prepared and employed as a substrate for the quantitative determination of melamine in milk samples through shell-isolated nanoparticle-enhanced Raman spectroscopy. The Ag SHIN film exhibits excellent reproducibility, high stability, as well as ultrahigh sensitivity with a limit of detection of 0.03 ppm. A linear relationship between the Raman intensity and the melamine concentration in a wide range (1 ppb to 5 ppm) was obtained. These results demonstrate that the Ag SHIN monolayer film is a promising and reliable substrate for the quantitative SERS analysis of practical samples. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) as a new member of Raman technique garnered great atten- tion among scientific community. In this work, we used an improved experimental setup to float the bare silver nanoparticles in air with the help of extraneous airflow, and used atomic layer deposition (ALD) method to coat ultra-thin inert shell without pinholes. Under optimal conditions, we successfully prepared three kinds of SHINERS NPs (Ag@Al2O3, Ag@SiO2 and Ag@TiO2) in large quantity without pinholes. The ultra-thin inert shell maintains the SERS activity of silver nanoparticles for long period of time. Transmission electron microscopy (TEM) images confirm the uniform coating of shell material on silver nanoparticles. Finally, the as-prepared SHINs have been applied to detect various samples to demonstrate the applications. The presented ALD method offers a unique way to coat ultrathin shell (1-10 nm) on metal nanoparticles in large quantity (1-10 g) for practical applications. [ABSTRACT FROM AUTHOR]