Several reports show that amines with electron-rich nitrogen are easy to attach onto the electron-deficient surface of metal nanoparticles through the coordinating interactions [24–37]. In fact, the nitrogen atom of amines has strong affinity to AuNPs, and the N Au bond energy is comparable to that of the S Au bond[38]. Accordingly, OPD, as a typical aromatic amine with two sp2nitrogen atoms, can strongly bind onto the electron-deficient sur-face of AuNPs [37,39].