 noble 
 metals , especially gold , have been widely used in plasmon 
 resonance applications . 
 although silver has a larger optical cross 
 section and lower cost than gold , it has attracted much less attention 
 because of its easy corrosion , thereby degrading plasmonic signals 
 and limiting its applications . to circumvent this problem , 
 we report 
 the facile synthesis of superstable agcu@graphene ( acg ) nanoparticles 
 ( nps ) . 
 the growth of several layers of graphene onto the surface of 
 agcu alloy nps effectively protects the ag surface from contamination , 
 even in the presence of hydrogen peroxide , hydrogen sulfide , and nitric 
 acid . 
 the acg nps have been utilized to enhance the unique raman signals 
 from the graphitic shell , making acg an ideal candidate for cell labeling , 
 rapid raman imaging , and sers detection . 
 acg is further functionalized 
 with alkyne - polyethylene glycol , which has strong raman vibrations 
 in the raman - silent region of the cell , leading to more accurate colocalization 
 inside cells . in sum 
 , this work provides a simple approach to fabricate 
 corrosion - resistant , water - soluble , and graphene - protected agcu nps 
 having a strong surface plasmon resonance effect suitable for sensing 
 and imaging . 
Supplementary Material