Fig 1.
FESEM images of (a) MRGO, (b) MRGO/AuNPs, (c) MRGO/PtNPs, and (d) MRGO/PtAuNPs, for 2.5 mM precursor solution; (e) MRGO/PtAuNPs for 5 mM precursor solution; (f) MRGO/PtAuNPs for 7.5 mM precursor solution; corresponding EDX spectra of MRGO/PtAuNPs for (g) 2.5 mM loading nanoparticles, and (h) 5 mM loading nanoparticles; and (i) FESEM images of MRGO/PtAuNPs/Ch-GOx.
Fig 2.
FTIR spectra of (a) chemically modified graphite oxide (CGO), and (b) reduced graphene oxide (RGO) powder.
Fig 3.
XPS spectra of (a) CGO, and (b) MRGO; and (c) Raman spectra of RGO platelets (solid line), and MRGO sheet (dotted line).
Fig 4.
(a) Cyclic voltammograms (CVs) of fabricated MRGO modified electrodes (i) in PBS solution, (ii) in 2 mM hydrogen peroxide solution; and MRGO/PtAuNPs modified hybrid electrode (iii) in PBS, and (iv) in 2 mM hydrogen peroxide solution (PBS solution pH 7. 4, 50 mM), scan rate: 50 mV/s. (b) Amperometric response of (i) MRGO, and (ii) MRGO/PtAuNPs modified hybrid electrodes in PBS, to the consecutive addition of the concentration of H2O2 in 0.5 mM at 0.6 V, with inset calibration plots.
Fig 5.
(a) CVs of fabricated hybrid MRGO/Ch-GOx/PDDA electrodes (i) in PBS solution, and (ii) in 2 mM glucose; and MRGO/PtAuNPs/Ch-GOx/PDDA (iii) in PBS, and (iv) in 2 mM glucose, (close up views of MRGO/Ch-GOx/PDDA modified electrode in PBS and PBS with glucose solution). (b) Amperometric response of (i) MRGO/Ch-GOx/PDDA and (ii) MRGO/PtAuNPs/Ch-GOx/PDDA modified electrode in PBS (pH, 7.4, 50 mM) to consecutive drops of concentration of glucose in 0.5 mM at 0.6 V, with inset calibration plots. (c) Amperometric response of MRGO/PtAuNPs/Ch-GOx/PDDA modified hybrid electrode in PBS to consecutive drops of different concentration (a-e) 10 μM, (f-h) 50 μM, and (i-p) 0.5 mM of glucose at 0.6 V; inset shows low detection limit of glucose.
Table 1.
Performance of different glucose-sensing hybrid electrodes.
Fig 6.
(a) The current response of interference species on the MRGO/PtAuNPs/Ch-GOx/PDDA hybrid electrode upon addition of 1.5 mM glucose, then 0.3 mM UA, 0.1 mM AP, 0.1 mM AA, and further drops of 1 mM glucose in PBS solution at 0.6 V. (b) Current—time recordings for recovery characteristic of MRGO/PtAuNPs/Ch-GOx/PDDA modified electrode in step-change of glucose concentration. (c) Amperometric responses of MRGO/PtAuNPs/Ch-GOx/PDDA biosensor in PBS solution for consecutive addition of glucose in human blood plasma.