The present invention is directed to self-assembled nanoparticle arrays, methods of making the nanoparticle arrays, and methods of using the nanoparticle arrays in spectroscopic methods for detecting targets of interest. The present invention is also directed to a fabrication method for surface-enhanced Raman scattering (SERS) substrates that possess a unique combination of three highly desirable attributes: (a) the SERS substrates can be tuned to match the laser wavelength of operation and maximize the enhancement factor for the particular Raman instrument and analyte in use; (b) the SERS substrates have a highly reproducible enhancement factor over macroscopic sampling areas; and (c) the fabrication method is achieved without resorting to expensive, slow nano-lithography tools.