A simple

facile and reproducible approach is used for fabrication of DNA biosensors based on reduced graphene oxide（ r GO）. The graphene oxide（ GO） nanosheets are assembled onto cysteamine-modified gold electrodes via electrostatic interaction between the positively charged amino group of cysteamine and the negatively charged groups present in GO

followed by electro-reduction through linear sweep voltammetry（ LSV） and functionalization with ferrocene-labeled DNA probe. The stepwise assembly of the DNA（ Fc-DNA） biosensor is characterized with cyclic voltammetry and Raman spectroscopy. The target DNA can be quantitatively detected based on the variati

on of square wave voltammetry（ SWV） signal of the biosensor before and after hybridization with target DNA. The peak current variation has a linear relationship with the target DNA concentration in the range of 1. 0 × 10

-13

～ 1. 0 × 10

-6

M

with linearly dependent coefficient of 0. 981 and the detection limit（ LOD）is 2. 0 × 10

-13

mol/L（ S/N = 3）.