Eric Formo

Functionalization of Electrospun TiO2 Nanofibers with Pt Nanoparticles and Nanowires for Catalytic Applications

This paper reports a simple procedure for derivatizing the surface of anatase TiO2 nanofibers with Pt nanoparticles and then Pt nanowires. The nanofibers were prepared in the form of a nonwoven mat by electrospinning with a solution containing both poly(vinyl pyrrolidone) and titanium tetraisopropoxide, followed by calcination in air at 510 degrees C. The fiber mat was then immersed in a polyol reduction bath to coat the surface of anatase fibers with Pt nanoparticles of 2-5 nm in size with controllable density of coverage. Furthermore, the coated fibers could serve as a three-dimensional scaffold upon which Pt nanowires of roughly 7 nm in diameter could be grown at a high density and with a length up to 125 nm. The fiber membranes functionalized with Pt nanoparticles and nanowires are interesting for a number of catalytic applications. It was found to show excellent catalytic activity for the hydrogenation of azo bonds in methyl red, which could be operated in a continuous mode by passing the dye solution through the membrane at a flow rate of 0.5 mL/s.

Functionalization of electrospun ceramic nanofibre membranes with noble-metal nanostructures for catalytic applications

This article reports a simple method for functionalizing the surface of TiO2 (both anatase and rutile) and ZrO2nanofibre membranes with Pt, Pd, and Rh nanoparticles. The TiO2membranes were prepared in the form of nonwoven mats by electrospinning with a solution containing both poly(vinyl pyrrolidone) and titanium tetraisopropoxide, followed by calcination in air to generate anatase (at 510 °C) or rutile (at 800 °C). The ZrO2membranes were fabricated with a solution of poly(vinyl pyrrolidone) and zirconium acetylacetonate, followed by calcination in air at 550 °C to yield the tetragonal phase. The fibre mats were then immersed in a polyol reduction bath to coat the surface of the nanofibres with Pt, Pd, or Rh nanoparticles of 2–5 nm in size. In addition, the ceramic fibres decorated with Pt nanoparticles could serve as a substrate to grow Pt nanowires ∼7 nm in diameter with lengths up to 125 nm. We subsequently demonstrated the use of Pd-coated anatase fibre membranes as a catalytic system for cross-coupling reactions in a continuous flow reactor. Contrary to the conventional setup for an organic synthesis, a continuous flow system has advantages such as short reaction time and no need for separation. The membrane-based catalytic system can also be fully regenerated for reuse.

Coaxial electrospinning of microfibres with liquid crystal in the core

Liquid crystal containing composite fibres were produced via coaxial electrospinning, demonstrating that this technique can be used for producing new functional fibres and/or to study the impact of extreme confinement on liquid crystal phases.

Adding new functions to organic semiconductor nanowires by assembling metal nanoparticles onto their surfaces

We report a new class of organic–inorganic hybrid nanostructures prepared by decorating small-molecule single-crystal organic nanowires with gold, platinum, and palladium nanoparticles. We demonstrate that field-effect transistors can be fabricated from the hybrid nanostructures with a mobility and current on/off ratio of 0.01 cm2V−1 s−1 and ∼103, respectively. To further illustrate the applicability of the hybrid nanowires, we carried out simple hydrogenation reactions to demonstrate their catalytic properties. Combined, our results open the possibility of utilizing the hybrid nanomaterials for a multitude of applications in areas such as bio- and chemical sensing, catalysis, and nanoelectronics.

Utilizing AgCl:Ag and AgCl mesostructures as solid precursors in the formation of highly textured silver nanomaterials via electron-beam induced decomposition

Herein, we report on the facile synthesis of AgCl:Ag and AgCl mesocubes with edge lengths up to 500 nm. When these mesostructures were placed under an electron beam, localized heating resulted in the decomposition of the AgCl regions of the respective materials leading to the formation of highly textured silver nanostructures. Furthermore, we utilized the AgCl:Ag and AgCl mesocubes along with their respective silver analogs for use in surface enhanced Raman spectroscopy (SERS) applications.

Surface‐Functionalized Electrospun Titania Nanofibers for the Scavenging and Recycling of Precious Metal Ions

Precious metals are widely used as catalysts in industry. It is of critical importance to keep the precious metal ions leached from catalysts at a level below one part per million (ppm) in the final products and to recycle the expensive precious metals. Here we demonstrate a simple and effective method for scavenging precious metal ions from an aqueous solution and thereby reduce their concentrations down to the parts per billion (ppb) level. The key component is a filtration membrane comprised of titania (TiO2 ) nanofibers whose surface has been functionalized with a silane bearing amino or thiol group. When operated under continuous flow at a rate of 1 mL min-1 and at room temperature, up to 99.95 % of the Pd2+ ions could be removed from a stock solution with an initial concentration of 100 ppm. This work offers a viable strategy not only for the removal of precious metal ions but also for recovering and further recycling them for use as catalysts. For example, the captured Pd2+ ions could be converted to nanoparticles and used as catalysts for organic reactions such as Suzuki coupling in a continuous flow reactor. This system can be potentially applied to pharmaceutical industry and waste stream treatment.

(Invited) Development of in situ Electrochemical Small-Angle Neutron Scattering (eSANS) for Simultaneous Structure and Redox Characterization of Nanoparticles

An in situ electrochemical small-angle neutron scattering (eSANS) method was developed to measure simultaneously the redox properties and size, shape and interactions of solution-dispersed nanomaterials. By combining multi-step potentials and chronocoulometry readout with SANS, the structure and redox properties of engineered nanomaterials are followed in one experiment. Specifically, ZnO nanoparticles were examined as dilute dispersions in pH buffered deuterium oxide solutions under negative electrode potentials. The ZnO disk-shaped nanoparticles undergo an irreversible size transformation upon reduction at the vitreous carbon electrode. The decrease in average nanoparticle size near a current maximum shows the reduction reaction from ZnO to Zn occurs. The eSANS method provides nanometer scale sensitivity to nanoparticle size and shape changes due to an electrochemical reaction that is crucial to understand in energy, healthcare, and other applications.