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Synthesized reduced graphene oxide–poly(methyl methacrylate) (RGO–PMMA) nanocomposites were characterized by differential scanning calorimetry, thermogravimetric analysis, and probed for volatile organic compounds (VOC) sensing. A molecular dynamics simulation is performed to investigate the interaction between PMMA and a graphene surface. The condensed-phase optimized molecular potentials for atomistic simulation studies (COMPASS), polymer consistent force-field (PCFF) and consistent valence force-field (CVFF) are used to describe the interaction of the graphene–PMMA. None of the three simulated force fields COMPASS, PCFF, and CVFF exhibits a distinctive behaviour of interaction between graphene and PMMA, but CVFF predicts a higher interaction energy in comparison with the simulated force fields COMPASS and PCFF. Experimentally, the selective response for different VOC has been analysed and the highest response together with the fastest recovery is obtained for tetrahydrofuran. A model is introduced explaining observed features.

A sensitive and disposable amperometric immunosensor for Saccharomyces cerevisiae was constructed by using carbon screen-printed electrodes modified with propionic acid-functionalized graphene oxide as transduction element. The affinity-based biosensing interface was assembled by covalent immobilization of a specific polyclonal antibody on the carboxylate-enriched electrode surface via a water-soluble carbodiimide/N-hydroxysuccinimide coupling approach. A concanavalin A-peroxidase conjugate was further used as signaling element. The immunosensor allowed the amperometric detection of the yeast in buffer solution and white wine samples in the range of 10–107 CFU/mL. This electroanalytical device also exhibited low detection limit and high selectivity, reproducibility, and storage stability. The immunosensor was successfully validated in spiked white wine samples.

The assembly of a novel disposable amperometric immunosensor for the detection of the red wine spoilage yeast Brettanomyces bruxellensis is reported. The nanostructured sensing interface was prepared by first coating carbon screen printed electrodes with a gold nanoparticles-reduced graphene oxide hybrid nanomaterial, which was then modified with 3-mercaptopropionic acid to further immobilize specific antibodies for B. bruxellensis via a carbodiimide-coupling reaction. The functionalized electrode allowed the amperometric detection of B. bruxellensis in buffered solutions and red wine samples in the range of 10–106 CFU/mL and 102–106 CFU/mL, with low detection limits of 8 CFU/mL and 56 CFU/mL, respectively. The electrochemical immunosensor also exhibited high reproducibility, selectivity, and storage stability.

Au nanoparticles modified with 4-mercaptopyridine and 6-mercapto-1-hexanol were used as coordination agents to prepare a novel hybrid nanomaterial with Ag:4,4'-bipyridine nanobelts. This nanohybrid was employed to modify glassy carbon electrodes and to construct a horseradish peroxidase-based mediatorless amperometric biosensor for H2O2. The electrode, poised at -100mV, exhibited a rapid response within 4s and a linear calibration range from 90pM to 6.5nM H2O2. The biosensor showed a high sensitivity of 283A/Mcm(2) and a very low detection limit of 45pM at a signal-to-noise ratio of 3. The enzyme biosensor showed high stability when stored at 4°C under dry conditions, retaining over 96% and 78% of its initial activity after 15 and 30days of storage at 4°C, respectively.

Gold–mesoporous silica Janus nanoparticles were prepared through a masking strategy and further employed as building blocks for the preparation of bienzyme biosensors through toposelective immobilization of the corresponding enzymes. The system was evaluated by immobilizing glucose oxidase and horseradish peroxidase on the Au and mesoporous silica faces, respectively. The anisotropic nanoparticles were deposited on glassy carbon electrodes coated with single-walled carbon nanotubes in order to construct an amperometric biosensor for glucose detection. The enzymatic electrode showed excellent electroanalytical performance with a fast response in about 6 s, a linear range of 490 nM–600 μM, a high sensitivity of 4.3 mA M−1 , and a low detection limit of 360 nM for glucose. This biosensor was successfully employed to determine the content of this monosaccharide in commercial soft drink samples.

CTQ2015-71936-REDT; CTQ2014-58989-P; MSI, Ministry of Science and Innovation, New Zealand; UCM, Universidad Complutense de Madrid; Ministry of Science, Technology and Space; FC-15-GRUPIN14-073; TEC2016-80700-R, FEDER, Federacion Espanola de Enfermedades Raras; DPI2013-046541-R, FEDER, Federacion Espanola de Enfermedades Raras; TIN2014-56967-R, FEDER, Federacion Espanola de Enfermedades Raras

Gold nanoparticles-decorated silver-bipyridine coordination polymers with intrinsic peroxidase-like activity are reported. Both morphology and mimetic enzyme activity can be tuned by rational manipulation of the nanohybrid composition. The nanomaterial was used for the electrochemical determination of H2O2 and glucose.

A novel strategy was employed to prepare a water-soluble graphene derivative by using dextran-based polymer brushes as solubilizing agents. Graphene oxide was grafted with (3-mercaptopropyl) trimethoxysilane and further decorated with Au nanoparticles. This hybrid nanomaterial was then reduced and anchored with polysaccharide-based polymer brushes by chemisorption of an end-group thiolated dextran derivative on the Au nanoparticles. The resulting hybrid nonmaterial allowed highly stable aqueous dispersions to be obtained, which were used to coat glassy carbon electrodes for the preparation of a model tyrosinase electrochemical biosensor for catechol. The enzyme electrode showed excellent electroanalytical performance with fast response in about 5 s, a linear range of 100 pM–120 nM, a very high sensitivity of 45.9 A M−1 and a very low detection limit of 40 pM for catechol.