Tannic Acid-Reduced Graphene Oxide Deposited with Pt Nanoparticles for Switchable Bioelectronics and Biosensors Based on Direct Electrochemistry

Abstract

In this study, we reported a novel biosensor based on direct electrochemistry of glucose oxidase (GOx) on a tannic acid-reduced graphene oxide nanocomposite modified glassy carbon electrode deposited with Pt nanoparticles. Tannic acid (TA) was utilized for the simultaneous green reduction of Pt 4+ and graphene oxide (GO), along with modifying the reduced GO for the GOx immobilization, thus constructing a switchable surface with pH and temperature alterations. Upon the electrochemically oxidation of TA to quinone, enhanced electron transfer was obtained, and a third generation biosensor was fabricated using π−π interaction between GO and TA and Schiff-base assisted hydrogen bonds between GOx and TA interactions. The redox peaks were observed at a formal potential of −0.462 V with a peak separation (ΔE p ) of 56 mV, which reveals the fast electron transfer. The linear response to glucose oxidation was in the range of 2−10 mM with a limit of detection of 1.21 μM and a sensitivity of 27.51 μA mM −1 cm −2 . Upon the deposition of poly(Nisopropylacrylamide) (PNIPAAm) onto the constructed biosensor via hydrogen bonds, an on−off biosensor was fabricated with zipperlike interfacial properties upon the formation of the shrunken and compact globule PNIPAAm structure and varying surface charge. Therefore, this study confirmed the versatile aspects of natural TA without using complicated methods.

Reduced Graphene Oxide/Pt Nanoparticles/Zn‐MOF‐74 Nanomaterial for a Glucose Biosensor Construction

“…With the addition of MOF and enzyme, mass loss increased by 26 % owing to the decomposition of organic substances. In Figure B, XRD patterns showed the formation of rGO/Pt NPs and rGO/Pt NPs@Zn‐MOF‐74 with their characteristic peaks . In the spectrum of rGO/Pt NPs, the peak at 2θ=26° corresponds to rGO and the peaks at 2θ=42.9, 46.4, 67.9, 81.8, and 86.2 ° can be indexed to (111), (200), (220), (311) and (222) planes of face‐centered cubic Pt .…”

“…In the spectrum of rGO, the peaks at 1066 cm −1 and 1311 cm −1 correspond to the aromatic C−H deformation vibrations and hydroxyl bending, respectively. Also, the peak at 1411 cm −1 stems from symmetric stretching vibration of carbonyl moieties . In the spectrum of the Zn‐MOF‐74, the peak at 1558 cm −1 is related to aromatic C=C bonds, while the peak at 1421 cm −1 originates from symmetric stretching vibration of carbonyl groups .…”

“…In Figure D, rGO shows two characteristic absorption bands. A strong absorption band at 224 nm is associated with π−π* transition and a shoulder peak at 310 nm attributed to the n‐π* transition of the C=O bond . The π−π* transition and n−π* transition of rGO were appeared at 270 nm and 310 nm, respectively.…”

“… The three dimensional structure of the rGO/Pt NPs@Zn‐MOF‐74 favor improved enzyme immobilization and rapid mass transport owing to the large interlayer distance of regular structure. GOx immobilization on Zn‐MOF‐74 can lead to better catalytic activities compared to the free counterparts owing to the prevention of enzyme self‐aggregation, which generally leads to slow conversion rates . The substantial prevention of enzyme denaturation owing to the biocompatibility of the nanomaterial improves the enzyme activity after immobilization. Pt NPs can catalyze the decomposition of H 2 O 2 leading to synergistic effect on the oxidation current . The conductivity of Pt NPs and rGO appeared to favor electron transfer. Also Pt NPs, rGO and Zn‐MOF‐74 enlarge the surface area, and the linkage between rGO and Pt NPs facilitates the electron transfer from GOx to the electrode . …”

“…Pt NPs can catalyze the decomposition of H 2 O 2 leading to synergistic effect on the oxidation current .…”