Tryptophan non-covalent modification of reduced graphene oxide for sensitive detection of Cu²⁺

An electrochemical sensor had been successfully designed using tryptophan non-covalently modified reduced graphene oxide via the strong π-π interaction between reduced graphene oxide (RGO) and tryptophan (Trp). Trp-RGO nanocomposite modified by glassy carbon electrode (GCE) can be used as an electrochemical sensing platform for detecting of trace Cu²⁺ and amplifying the electrochemical signal, which was characterized by fourier transform infrared (FTIR) spectroscopy and ultraviolet–visible spectroscopy, electrochemical measurement and scanning electron microscopy. Under the optimum conditions, a linear dependence was obtained from 0.24 to 48 μmol/L with a detection limit of 0.064 μmol/L (S/N = 3) (i_pc(μA) = 0.8081c(μmol/L) + 5.9128). The Trp-RGO/GCE showed excellent reproducibility via repetitive differential pulse voltammetry and the relative standard deviation is 2.13%. In addition, the influence of other experimental factors, such as pH, deposition potentials and deposition times on the detection effect of Cu²⁺ was also explored in regards to the influence on detection of Cu²⁺.