It is of very significance to stric

It is of very significance to strictly and precisely detect trace inorganic arsenic ions (As3+), which may increase the risks of cancer in the skin, lungs, bladder, and diabetes diseases. Here, we report a simple and ultrasensitive method for dual-mode detection of arsenic by colorimetric and surface-enhanced Raman spectroscopy (SERS) based on glutathione functionalized gold nanoparticles (GSH/AuNPs). When As3+ ion are present in GSH/AuNPs solution, the binding of As3+ ion with GSH ligand induces the aggregation of AuNPs. The aggregation of GSH/AuNPs not only serves as indicator of As3+ ion for the perceptible color change from wine-red to blue, but also a highly efficient on-site SERS detection of As3+ ion due to the abundant hot spots. More importantly, the sensing system exhibits superior selectivity for As3+ ion detection compared with other common metal ions (Pb2+, Hg2+, Cu+, K+, Cr3+, Co2+ and Fe3+). Meanwhile, the limit of detection (LOD) of colorimetric and SERS are estimated to be 0.11 ppb and 0.14 ppb, respectively, which is lower than the WHO defined limit (10 ppb). Our study would provide a novel method for detection of As3+ion in drinking water and marine environmental monitoring, as well as offers a strategy for developing multi-mode sensing system for different applications.