SnO₂Quantum Dots-Reduced Graphene Oxide Composite for Enzyme-Free Ultrasensitive Electrochemical Detection of Urea

Abstract

Most of the urea sensors are biosensors and utilize urease, which limit their use in harsh environments. Recently, because of their exceptional ability to endorse faster electron transfer, carbonaceous material composites and quantum dots are being used for fabrication of a sensitive transducer surface for urea biosensors. We demonstrate an enzyme free ultrasensitive urea sensor fabricated using a SnO2 quantum dots (QDs)/reduced graphene oxide (RGO) composite. Due to the synergistic effect of the constituents, the SnO2 QDs/RGO (SRGO) composite proved to be an excellent probe for electrochemical sensing. The morphology and structure of the composite was characterized by various techniques, and it was observed that SnO2 QDs are decorated on RGO layers. Electrochemical studies were performed to evaluate the characteristics of the sensor toward detection of urea. Amperometry studies show that the SRGO/GCE electrode is sensitive to urea in the concentration range of 1.6 × 10(-14)-3.9 × 10(-12) M, with a detection limit of as low as 11.7 fM. However, this is an indirect measurement for urea wherein the analytical signal is recorded as a decrease in the amperommetric and/or voltammetric current from the solution redox species ferrocyanide. The porous structure of the SRGO matrix offers a very low transport barrier and thus promotes rapid diffusion of the ionic species from the solution to the electrode, leading to a rapid response time (∼5 s) and ultrahigh sensitivity (1.38 μA/fM). Good analytical performance in the presence of interfering agents, low cost, and easy synthesis methodology suggest that SRGO can be quite promising as an electroactive material for effective urea sensing.

Electrochemical Synthesis of Polypyrrole, Reduced Graphene Oxide, and Gold Nanoparticles Composite and Its Application to Hydrogen Peroxide Biosensor

“…Although the concentration of H 2 O 2 was two times less than interfering species, the PPy–RGO–nanoAu/GCE current response of H 2 O 2 at −0.62 V vs. SCE was far higher than interfering current. Additionally, the concentrations of the interfering species used in this study are much greater than their normal physiological values [9,44,45]. The results clearly demonstrate that PPy–RGO–nanoAu/GCE has a good selectivity towards H 2 O 2 at the negative potential, where possible interfering reactions are minimized.…”

“…Most notably, nanocomposites combining two or several different components are expected to further improve the deficient characteristics of each component, a concept which has led to the development of various electrochemical sensors [8,9]. In this context, to date, several studies have been carried out in the area of PPy, RGO and nanoAu composites.…”

Facile Synthesis of 3D Graphene Flowers for Ultrasensitive and Highly Reversible Gas Sensing

“…The less transparent regions are attributed to the overlap and folding of a single‐layered sheet or multiple‐layered sheets . The Braunauer–Emmett–Teller surface area of the porous GF was measured to be 221 m 2 g −1 , which is comparable to that of 3D Gr synthesized by other methods (Figure S1, Supporting Information) . The high surface area is attributed to a large number of nanoscale pores in Gr with an average pore radius of 3.8 nm.…”

Three-Dimensional Mesoporous Graphene Aerogel-Supported SnO2 Nanocrystals for High-Performance NO2 Gas Sensing at Low Temperature

“…From the high-resolution C 1s spectrum of the SnO 2 /rGO-4 shown in Figure 2c, the three peaks at 284.6, 286.4, and 288.7 eV could be attributed to the C−C, C−O, and CO bonds in graphene-based composites. 14 Figure 2d shows the Sn 3d spectrum of the SnO 2 /rGO-4, in which the two strong bands at 486. 8 Figure 3a and d, the 3D aerogel samples exhibit macroporous structure with well-defined interconnected pores at micrometer order.…”