A simple and highly efficient route to the synthesis of NaLnF4–Ag hybrid nanorice with excellent SERS performances

Abstract

This paper reports the synthesis of a new class of NaLnF₄–Ag (Ln = Nd, Sm, Eu, Tb, Ho) hybrid nanorice and its application as a surface-enhanced Raman scattering (SERS) substrate in chemical analyses. Rice-shaped NaLnF₄ nanoparticles as templates are prepared by a modified hydrothermal method. Then, the NaLnF₄ nanorice particles are decorated with Ag nanoparticles by magnetron sputtering method to form NaLnF₄–Ag hybrid nanostructures. The high-density Ag nanogaps on NaLnF₄ can be obtained by the prolonging sputtering times or increasing the sputtering powers. These nanogaps can serve as Raman ‘hot spots’, leading to dramatic enhancement of the Raman signal. The NaLnF₄–Ag hybrid nanorice is found to be robust and is an efficient SERS substrate for the vibrational spectroscopic characterization of molecular adsorbates; the Raman enhancement factor of Rhodamine 6G (R6G) absorbed on NaLnF₄–Ag nanorice is estimated to be about 10¹³. Since the produced NaLnF₄–Ag hybrid nanorice particles are firmly fastened on a silicon wafer, they can serve as universal SERS substrates to detect target analytes. We also evaluate their SERS performances using 4-mercaptopyridine (Mpy), and 4-mercaptobenzoic acid (MBA) molecules, and the detection limit for Mpy and MBA is as low as 10⁻¹² M and 10⁻¹⁰ M, respectively, which meets the requirements of the ultratrace detection of analytes. This simple and highly efficient approach to the large-scale synthesis of NaLnF₄–Ag nanorice with high SERS activity and sensitivity makes it a perfect choice for practical SERS detection applications.