Graphene deposited with silver nanoparticles (AgNPs-β-CD-Gr) has been synthesized by thermal reduction of graphene oxide and silver nitrate via β-cyclodextrin (β-CD). It offers a simple, green, and efficient procedure to yield nanocomposites with silver nanoparticles anchored on graphene support, uniformly and stably. Guanine and adenine were simultaneously detected on the modified electrode (AgNPs-β-CD-Gr/GCE) by differential pulse voltammograms. The AgNPs-β-CD-Gr/GCE obviously improved the voltammetric response of guanine and adenine demonstrating that the synergistic effect of silver nanoparticles and graphene can significantly enhance the detecting sensitivity of guanine and adenine. The electrochemical biosensor based on AgNPs-β-CD-Gr exhibits wide linear ranges of 0.3-200 and 0.5-250 μM with detection limits of 0.09 and 0.15 μM for guanine and adenine, respectively. The proposed method was also applied for the measurement of trace-level of these purine bases in herring sperm DNA (dsDNA). The results suggest that the nanocomposite has a potential application for electrocatalytic biosensing.
A novel type of glucose biosensor was designed based on dual-path electron transfer mechanism. Ferrocenecarboxylic acid (FcCA), the indirect mediator, transfers the electrons of enzymatic reaction from embedded redox active center via redox process. Reduced graphene oxide (rGO) and silver nanoparticles (AgNPs) both are conductive materials, providing fast direct electron transfer path. In this system, β-cyclodextrin (β-CD) is of key importance for not only reducing rGO and AgNPs, but providing biocompatible microenvironment for the enzyme as well. At the same time, carboxymethyl-β-cyclodextrin (CM-β-CD) formed inclusion complex with FcCA and then covalently bound with the enzyme to immobilize FcCA and GOD. The structure and morphology of modified film were characterized by FTIR, TEM, AFM, XRD, Raman and UV-vis. The rate constant (k s ) of modified electrode is calculated to be 4.648 s −1 , indicating the fast electron transfer rate on electrode. The glucose biosensor exhibited a wide linear response range from 0.105 to 11.805 mM with a low detection limit of 0.035 mM.
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