Nanofiber Ion-Selective Membrane-Coated Carbon Paper All-Solid-State Sensors: One Stone, Two Birds.

Potentiometric sensors with nanostructural ion-selective membranes were prepared and tested. Electrospun nanofiber mats were applied in novel all-solid-state sensors, using carbon paper as an electronically conducting support. For the sake of simplicity, application of a solid contact layer was avoided, and redox-active impurities naturally present in the carbon paper have proven to be effective as ion-to-electron transducers. Application of a nanostructural ion-selective membrane requires an innovative approach to combine the receptor layer with the support. The nanofiber mat portion was fused with carbon paper in a hot-melt process. Applying temperature close to 120 °C for a short time (3 s) allowed binding the nanostructural ion-selective membrane with carbon paper, without significant changes in the nanofiber structure. This process was conveniently performed together with the lamination of the carbon paper support. The thus obtained, potentially disposable sensors were characterized as exhibiting highly reproducible potential readings in time as well as between sensors belonging to the same batch. The benefits of the application of nanostructural ion-selective membranes include shorter equilibration time, lower detection limit, and significantly lower material consumption. However, the nanostructural membrane is characterized by a higher electrical resistance, which is attributed to higher porosity.

Nanofiber-Supported Palladium Nanocubes-Toward Highly Active and Reusable Catalyst.

Electrospun nanofibers were used to support palladium nanocubes, resulting in a highly active, stable, and reusable catalyst. The system proposed herein offers significant advantages compared to catalysts in the form of nanoparticles suspension. The porous, solvent permeable structure of the nanofiber mat ensures uniform and stable time distribution of palladium nanoparticles; preventing coalescence and allowing multiple use of the catalyst. The proposed cross-linked poly(vinyl alcohol) nanofiber mat loaded with Pd nanocubes during the nanofiber preparation step is a macroscopic structure of intrinsically nanostructural character of the catalyst that can be easily transferred between different solutions without compromising its effectiveness in consecutive cycles. Thus, obtained system was characterized with high catalytic activity as tested on a model example of 4-nitrophenol (4-NP) reduction by NaBH4 to 4-aminophenol (4-AP). It is shown that loading nanofibers with Pd nanocubes during electrospinning resulted in a significantly more stable system compared to surface modification of obtained nanofibers with nanocube suspension.