A spectroscopic assay is provided. The assay comprises: a motive particle configured to move within a solution, the motive particle comprising a first analyte binding reagent for selectively binding to a target analyte; and a spectroscopic reporter particle configured to provide a predetermined spectroscopic signal in response to being interrogated by a spectrometer, the spectroscopic reporter particle comprising a second analyte binding reagent for selectively binding to the target analyte, wherein the motive particle and the spectroscopic reporter particle are configured to provide a sandwich assay in the presence of the target analyte via the first and second analyte binding reagents.