Development of ultrasensitive new sensors based on thio-functionalized heterogeneous layers of gold/graphene/copper for glucose detection

In this work, we report for the first time a new electro-chemical sensors based on (4-Nitrothiophenol) 4-NTP functionalized heterogeneous layers of gold/graphene/Cu for highly sensitive detection of glucose. 4-NTP molecules were immobilized into the surface of gold nanostructures. Surface enhanced Raman scattering was performed in order to assure of the 4-NTP bonding and the optical enhancement of gold nanostructures. SERS intensities generated by the new sensors confirm the presence of active catalytic sites rich with charges. The electrochemical measurement performed for glucose using cyclic voltammetry showed an increasing of sensitivity 3 times faster in the case of functionalized sensors than the standard ones. Nyquist plot proved a decrease in the impedance for glucose with the presence of 4-NTP into the surface. Due to the 4-NTP molecules attached to their surface, the new sensors were proved to be higher sensitive for the detection of glucose. The sensitivity obtained by cyclic voltametric techniques was 179.6 & mu;A/mM.cm2 and 420.8 & mu;A/mM.cm2 for electrode 1 and 2 respectively. The dynamic range is 2.0-19.6 mM (36.0--353.2 mg/dL) of glucose for electrode 1 while it is 2.0-29.1 mM (36.0-524.9 mg/dL) of glucose for electrode 2. The lower detection limit is thus 0.5 mM (9.0 mg/ dL) the same for both electrodes. The electrode was also tested as glucose sensor using electrochemical impedance spectroscopy (EIS) techniques.