title: Detection of melamine on fractals of unmodified gold nanoparticles by surface-enhanced Raman scattering.
abstract: A simple way of detecting melamine in raw milk is demonstrated via surface-enhanced Raman spectroscopy (SERS) using fractals of bare and nonfunctionalized ~30 nm gold nanoparticles (AuNP) distributed on a solid support. The technique demonstrates the formation of AuNP fractals, from a random distribution, upon exposure to melamine, that enhance the Raman scattering cross-section to enable detection by SERS. The agglomeration, which is pronounced at higher melamine concentrations, is demonstrated directly through imaging, and the red-shift of the plasmon absorption peak of the AuNP fractal away from 530 nm by finite difference time domain (FDTD) calculations. The agglomeration results in a strong plasmon field, shown by FDTD, over the interparticle sites that enhances the Raman scattering cross-section of melamine and ensures unambiguous detection. Limit of detection of 100 ppb could be achieved reproducibly.
authors.affiliation: National Yang-Ming University, Institute of Biophotonics, Taipei 112, Taiwan.
authors.forename: Pradip Kumar
authors.initials: PK
authors.lastname: Roy
authors.forename: Yi-Fan
authors.initials: YF
authors.lastname: Huang
authors.forename: Surojit
authors.initials: S
authors.lastname: Chattopadhyay
mesh_terms: D000818:Animals; D003198:Computer Simulation; D017709:Fractals; D006046:Gold / Q000737:chemistry*; D057230:Limit of Detection; D053768:Metal Nanoparticles / Q000737:chemistry*; D008892:Milk / Q000737:chemistry; D013059:Spectrum Analysis, Raman / Q000379:methods*; D014227:Triazines / Q000032:analysis*
chemical_list: D014227:Triazines; D006046:Gold; C011907:melamine