The combination of nanomaterials and conducting polymers attracted remarkable attention for development of new immobilization matrices for enzymes. Hereby, an efficient surface design was investigated by modifying the graphite rod electrode surfaces with one-step electrospun nylon 6,6 nanofibers or 4% (w/w) multiwalled carbon nanotubes (MWCNTs) incorporating nylon 6,6 nanofibers (nylon 6,6/4MWCNT). High-resolution transmission electron microscopy study confirmed the successful incorporation of the MWCNTs into the nanofiber matrix for nylon 6,6/4MWCNT sample. Then, these nanofibrous surfaces were coated with a conducting polymer, (poly-4-(4,7-di(thiophen-2-yl)-1H-benzo[d]imidazol-2-yl)benzaldehyde) (PBIBA) to obtain a high electroactive surface area as new functional immobilization matrices. Due to the free aldehyde groups of the polymeric structures, a model enzyme, glucose oxidase was efficiently immobilized to the modified surfaces via covalent binding. Scanning electron microscope images confirmed that the nanofibrous structures were protected after the electrodeposition step of PBIBA and a high amount of protein attachment was successfully achieved by the help of high surface to volume ratio of electroactive nanofiber matrices. The biosensors were characterized in terms of their operational and storage stabilities and kinetic parameters (K(m)(app) and Imax). The resulting novel glucose biosensors revealed good stability and promising Imax values (10.03 and 16.67 μA for nylon 6,6/PBIBA and nylon 6,6/4MWCNT/PBIBA modified biosensors, respectively) and long shelf life (32 and 44 days for nylon 6,6/PBIBA and nylon 6,6/4MWCNT/PBIBA modified biosensors, respectively). Finally, the biosensor was tested on beverages for glucose detection.

Material modification is one of the hot topics recently. Hereby a novel functional monomer, 2-(4nitrophenyl)-4,7-di(thiophen-2-yl)-1H-benzo[d]imidazole (BIPN), was synthesized for matrix generation through electrochemical polymerization. Its conducting polymer was successfully used for the biolayer construction in the biosensor preparation. The electrochemical and morphological properties were improved by the introduction of carboxylic acid functionalized multiwall carbon nanotubes (f-MWCNTs).Carboxylic acid functionalization of MWCNTs was carried out via acid treatment. The electrode surface was modified with the polymer and f-MWCNTs during electropolymerization to achieve a perfect immobilization matrix for alcohol oxidase. In order to prepare a new alcohol biosensor, alcohol oxidase (AOx) was immobilized onto the modified electrode. The modified electrode was characterized by scanning electron microscopy (SEM), X-ray photoelectron microscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy techniques. Electrochemical responses of the enzyme electrodes were monitored at À0.7 V vs. Ag reference electrode by monitoring oxygen consumption in the presence of ethanol. Kinetic parameters, operational and storage stabilities were investigated. K app M , I max , LOD and sensitivity were calculated as 16.946 mM, 3.31 mA, 0.806 mM and 476 mA mM À1 cm À2 , respectively. Finally, this biosensor was applied to estimate the alcohol content in various beverages successfully.

We report on the graphene-assisted growth, crystallization, and phase transition of zinc phthalocyanine (ZnPc) vertically oriented single crystal nanopillars. Postcrystallization thermal annealing of the nanostructures results in a molecular packing change while maintaining the vertical orientation of the single crystals orthogonal to the underlying substrate. Grazing incidence X-ray diffraction and high-resolution TEM studies characterized this phase transition from a metastable crystal phase to the more stable β-phase commonly observed in bulk crystals. These vertical arrays of crystalline nanopillars exhibit a high-surface-to-volume ratio, which is advantageous for applications such as gas sensors. We fabricated chemiresistor sensors with ZnPc nanopillars grown on graphene and demonstrated its selectivity for ammonia vapors, and improvement in sensitivity in the β-phase crystal packing pillars due to their molecular orientation increasing the exposure of the Zn ion to the ammonia analyte. This work highlights the first morphology-retentive phase transition in organic single crystal nanopillars through simple postprocessing thermal annealing. This study opens up the possibility of molecular packing control without large variations in morphology, a necessity for high-performance devices and establishing structure-property relations.

Fabrication of detection elements with ultrahigh surface area is essential for improving the sensitivity of analyte detection. Here, we report a direct patterning technique to fabricate three-dimensional CeO 2 nanoelectrode arrays for biosensor application over relatively large areas. The fabrication approach, which employs nanoimprint lithography and a CeO 2 nanoparticle-based ink, enables the direct, high-throughput patterning of nanostructures and is scalable, integrable, and of low cost. With the convenience of sequential imprinting, multilayered woodpile nanostructures with prescribed numbers of layers were achieved in a "stacked-up" architecture and were successfully fabricated over large areas. To demonstrate application as a biosensor, an enzymatic glucose sensor was developed. The sensitivity of glucose sensors can be enhanced simply by increasing the number of layers, which multiplies surface area while maintaining a constant footprint. The four-layer woodpile nanostructure of CeO 2 glucose sensor exhibited enhanced sensitivity (42.8 μA mM −1 cm −2 ) and good selectivity. This direct imprinting strategy for three-dimensional sensing architectures is potentially extendable to other electroactive materials and other sensing applications.

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