Ulrich Buttner

Semi-micro solid phase extraction with electrospun polystyrene fiber disks

A technique is described for performing solid phase extraction (SPE) at a semi-microscale. 10 mg of electrospun polystyrene fibers (average diameter 2.7 µm) were packed into a SPE barrel to form a disk (5 mm × 1 mm). The device was employed to evaluate the extraction of four steroids: prednisone, hydrocortisone, cortisone acetate and 19-nortestosterone from water and plasma matrices. The analytes were desorbed from the fibers with 100 µl methanol and monitored by high performance liquid chromatography with a diode array detector (HPLC-DAD). The semi-micro SPE method provided extraction recoveries of 51.14–80.13% in plasma and 66.07–93.43% in water. The breakthrough volumes at 500 ng ml−1 ranged from 200–400 µl for all analytes. At optimal conditions, the four analytes followed an excellent linear relationship in the range 12.5–400 ng ml−1 with coefficients of determination (r2) greater than 0.99 and the limits of detection ranged from 0.75 to 1.29 ng ml−1. Due to its simplicity, it is anticipated that the method will greatly simplify disk solid phase extraction.

A novel method to measure the generated voltage of a ZnO nanogenerator

A novel method to measure the output voltage of a zinc oxide nanowire nanogenerator is proposed. Various tests are performed to verify that the output voltage does indeed originate from the nanogenerator and not from environmental noise. Although noise does influence the output voltage measurements, the output voltage is easily distinguishable from the measured noise. It is also shown that the method can be used to determine the internal resistance of the nanogenerator by measuring the output voltage over different output resistors.

Fabrication of submicron YBCO Josephson junctions by a sample mosaic navigation assisted laser etching process

Taking advantage of a New Wave 213 nm laser system, equipped with high-precision submicron resolution sample mosaic navigation, we are able to laser-etch and fabricate planar submicron-size Josephson junctions on YBa2Cu3O7−x thin films successfully. The entire process of laser etching and sample navigation is software controlled. The widths were measured by atomic force microscopy (AFM), and they range from 0.7 to 1.4 µm. We report on the observed I–V characteristics and Shapiro steps, which confirm the Josephson effect in these junctions. The measured critical current dependence on temperature shows a linear relationship for micron-size constrictions. In the case of submicron constrictions, the dependence is an exponential decay type, consistent with diffusive long S–N–S junction behaviour. It is believed that the observed behaviour can be ascribed to laser heating of the constriction material, changing the superconducting phase to the normal one.

3 – Continuous yarns from electrospun nanofibers

Publisher Summary This chapter discusses the manufacture of continuous yarns from electrospun fibers. Yarn is a generic term for a continuous strand of textile fibers or filaments in a form suitable for knitting, weaving or otherwise intertwining to form a fabric. The chapter provides a brief overview of the potential applications of electrospun fiber yarns and some important textile terms related to this field. The three inherent properties of nanofibrous materials that make them very attractive for numerous applications are their high specific surface area (surface area/unit mass), high aspect ratio (length/diameter), and their biomimicking potential. These properties lead to the potential application of electrospun fibers in such diverse fields as high-performance filters, absorbent textiles, fiber-reinforced composites, etc. Therefore, the alignment or controlled orientation of the electrospun fibers is of great importance and large-scale commercialization of products will become viable only when sufficient control over fiber orientation can be obtained at high production rates. There is currently no commercially available continuous nanofiber yarn produced through electrospinning. However, it is likely to change in the very near future and will lead to rapid worldwide evaluation of the product for numerous potential applications.

The output voltage of a zinc oxide nanogenerator grown by various methods

The output voltage of a zinc oxide (ZnO) nanogenerator is investigated. Different growth methods are used to synthesis the ZnO nanowires that are used to manufacture the nanogenerator. The influence of various growth parameters on the output voltage of the nanogenerator is also investigated. It was found that the aqueous solution method yields a slightly larger voltage when compared to the VLS. The initial pressure at which the nanowires are grown via the VLS method and the concentration of the source materials in the aqueous solution method has a large influence on the output voltage of the nanogenerator.

The enhancement of superconducting YBa2Cu30 7-x thin films by electric field application during deposition

The effect of applying a high electric field in-situ during the deposition and growth of YBa2Cu3O7-x (YBCO) thin films is investigated. The YBCO films are deposited from a stoichiometric YBCO target by pulsed laser deposition (PLD) on (100) MgO single crystal substrates at 726degC, in an oxygen atmosphere. The electric field is generated by applying an electric potential to a metal electrode placed in close proximity to the surface of the substrate. The substrate and deposition chamber are grounded. Proper insulation of the electrode is extremely important in order to avoid arc discharge in the deposition chamber. The quality of the YBCO thin films grown was enhanced by the application of the electric field. These thin films showed higher superconducting transition temperatures and narrower transition widths. This technique can therefore prove useful for producing high quality thin films needed for junctions and multilayer devices.

The Enhancement of Superconducting

The effect of applying a high electric field in-situ during the deposition and growth of YBa2Cu3O7-x (YBCO) thin films is investigated. The YBCO films are deposited from a stoichiometric YBCO target by pulsed laser deposition (PLD) on (100) MgO single crystal substrates at 726degC, in an oxygen atmosphere. The electric field is generated by applying an electric potential to a metal electrode placed in close proximity to the surface of the substrate. The substrate and deposition chamber are grounded. Proper insulation of the electrode is extremely important in order to avoid arc discharge in the deposition chamber. The quality of the YBCO thin films grown was enhanced by the application of the electric field. These thin films showed higher superconducting transition temperatures and narrower transition widths. This technique can therefore prove useful for producing high quality thin films needed for junctions and multilayer devices.

{\rm YBa}_{2}{\rm Cu}_{3}{\rm O}_{7-{\rm x}}

The effect of applying a high electric field in-situ during the deposition and growth of YBa2Cu3O7-x (YBCO) thin films is investigated. The YBCO films are deposited from a stoichiometric YBCO target by pulsed laser deposition (PLD) on (100) MgO single crystal substrates at 726degC, in an oxygen atmosphere. The electric field is generated by applying an electric potential to a metal electrode placed in close proximity to the surface of the substrate. The substrate and deposition chamber are grounded. Proper insulation of the electrode is extremely important in order to avoid arc discharge in the deposition chamber. The quality of the YBCO thin films grown was enhanced by the application of the electric field. These thin films showed higher superconducting transition temperatures and narrower transition widths. This technique can therefore prove useful for producing high quality thin films needed for junctions and multilayer devices.