SnO2QDs Deposited on GO/PPy-Modified Glassy Carbon Electrode for Efficient Electrochemical Hydrogen Peroxide Sensor

In this present work, we demonstrate an efficient electrochemical sensor for the detection of hydrogen peroxide (H₂O₂) using a glassy carbon electrode (GCE) modified with a ternary nanocomposite of tin oxide QDs/GO/PPy (SGP2). An in situ chemical oxidative polymerization method was used to create the SGP2 nanocomposite. FTIR, XRD, HR TEM, CV, DPV, and impedance analysis were used to characterize the nanocomposite. The SGP2 nanocomposite modified GCE can be used to create an effective H₂O₂ electrochemical sensor with high sensitivity and a low detection limit (LOD). With SGP2 modified GCE, the electrochemical detection test for H₂O₂ was carried out using cyclic voltammetry (CV) and amperometric methods. The SGP2 modified GCE shows improved sensing capabilities, resulting in considerable sensitivity of 11.69 µA mM cm^-2 and a very low limit of detection (LOD) of 0.758 µM for a broad linear range of H₂O₂ concentration from 0.1 mM to 0.8 mM with a correlation coefficient R² = 0.9886. Additionally, the performance of the SGP2-modified GCE electrode is on par with or nonetheless superior to that of the other functional materials that have been reported for H₂O₂. As a result, our findings suggest that combining conductive polymer with metal oxide may be a useful method for producing sophisticated and affordable electrochemical sensors.

Graphene Oxide Membrane Immobilized Aptamer as a Highly Selective Hormone Removal

Three-dimensional (3D) reduced graphene oxide (rGO) modified by polyethyleneimine (PEI) was prepared and functionalized by fluorophore-labeled dexamethasone-aptamer (Flu-DEX-apt) via π-π stacking interaction. The rGO/PEI/Flu-DEX-apt was used as a selective membrane for dexamethasone hormone removal from water. The prepared rGO/PEI/Flu-DEX-apt membranes were stable, insoluble, and easily removable from liquid media. The membrane was characterized by Raman spectroscopy, scanning electron spectroscopy, and FTIR spectroscopy. The rGO/PEI/Flu-DEX-apt membrane showed high sensitivity and specificity toward the dexamethasone hormone in the presence of other steroid hormone analogs, such as progesterone, estrone, estradiol, and 19-norethindrone. The fluorescence and UV-visible spectroscopy were used to confirm the membranes performance and the quantification of hormones removal. The resulting data clearly show that the graphene oxide concentration influence the aptamers and analytes interaction (π-π stacking interaction). It was found that by varying the graphene oxide concentration yields to different porosities of rGO/PEI/Flu-DEX-apt membranes affects the adsorption recovery rate, as well as the specificity and selectivity toward the dexamethasone hormone.

Facile Construction of Functionalized GO Nanocomposites with Enhanced Antibacterial Activity

The development of antimicrobial materials with sustained drug release performance is of great importance. Graphene oxide (GO) is considered to be an ideal drug carrier. In this study, tetracycline hydrochloride (TC) was loaded onto polyethyleneimine-functionalized GO (PG) to fabricate TC/PG nanocomposites. The success of the fabrication was confirmed by zeta potential, TEM, FTIR, and Raman analyses. The TC/PG nanocomposites showed a controlled and sustained drug release behavior, and a pseudo second order kinetic model was employed to illustrate the release mechanism. The antibacterial activity was studied using the disk diffusion method against Escherichia coli and Staphylococcus aureus. The TC/PG nanocomposites exhibited great bacterial inhibition performance. The results indicate that the fabricated TC/PG nanocomposites with effective antibacterial activity have great potential in antibacterial applications.

Sensitive determination of baicalein based on functionalized graphene loaded RuO2 nanoparticles modified glassy carbon electrode

The nanocomposite of ruthenium oxide (RuO₂) loaded on Poly-(dimethyldiallylammonium chloride) (PDDA) functionalized reduced graphene oxide (RuO₂-PDDA-rGO) was synthesized based on a one-step method. Based on the RuO₂-PDDA-rGO modified glassy carbon electrode (GCE), a new electrochemical sensor (RuO₂-PDDA-rGO/GCE) was fabricated and used in detection of baicalein for the first time. Compared with other reported electrochemical sensors for the detection of baicalein, the prepared RuO₂-PDDA-rGO/GCE had a wider linear range (2-400 nM) and lower detection limit (0.6 nM, S/N = 3). The other advantages were the excellent repeatability of proposed method and good stability of prepared sensor.

Graphene blended with SnO2 and Pd-Pt nanocages for sensitive non-enzymatic electrochemical detection of H2O2 released from living cells

This paper described a novel, facile and nonenzymatic electrochemical biosensor to detect hydrogen peroxide (H₂O₂). The sensor was fabricated based on Pd-Pt nanocages and SnO₂/graphene nanosheets modified electrode (PdPt NCs@SGN/GCE). The electrochemical behavior of PdPt NCs@SGN/GCE exhibited excellent catalytic activity toward H₂O₂ with fast response, high selectivity, superior sensitivity, low detection limit of 0.3 μM and large linear range from 1 μM to 300 μM. Under these obvious advantages, the constructed biosensor provided to be reliable for determination of H₂O₂ secreted from human cervical cancer cells (Hela cells). Hence, the proposed biosensor is a promising candidate for detection of H₂O₂ in situ released from living cells in clinical diagnostics.