Optical Quantification of Metal Ions Using Plasmonic Nanostructured Microbeads Coated with Metal–Organic Frameworks and Ion-Selective Dyes

[Image: see text] Herein, we designed and synthesized a hybrid material comprising polystyrene submicrobeads coated with silver nanospheres. This material provides a dense collection of electromagnetic hot spots upon illumination with visible light. The subsequent coating with a metal-framework and the adsorption of bathocuproine on it yield an optical sensor for SERS that can specifically detect Cu(II) in a variety of aqueous samples at the ultratrace level. Detection limits with this method are superior to those of induced coupled plasma or atomic absorption and comparable with those obtained with induced coupled plasma coupled with a mass detector.