Youngmi Lee

A technique that combines scanning electrochemical microscopy (SECM) and scanning optical microscopy (OM) was developed. Simultaneous scanning electrochemical/optical microscopy (SECM/OM) was performed by a special probe tip, which consists of an optical fiber core for light passage, surrounded by a gold ring electrode, and an outermost electrophoretic insulating sheath, with the tip attached to a tuning fork. To regulate the tip-substrate distance, either the shear force or the SECM tip current

An improved miniature amperometric nitric oxide sensor design with a planar sensing tip (ranging from 150 microm to 2 mm in diameter) is reported. The sensor is fabricated using a platinized platinum anode and a Ag/AgCl cathode housed behind a microporous poly(tetrafluoroethylene) (PTFE; Gore-tex) gas-permeable membrane. Platinization of the working platinum electrode surface dramatically improves the analytical performance of the sensor by providing approximately 10-fold higher sensitivity (0.8

A planar-type amperometric dual microsensor for simultaneous detection of nitric oxide and carbon monoxide is presented. The sensor consists of a dual platinum microdisk-based working electrode (WE) and a Ag/AgCl counter/reference electrode covered with an expanded poly(tetrafluoroethylene) (Tetra-tex) gas-permeable membrane. The dual WE possesses two different platinized platinum disks (WE1 and WE2, 250 and 25 microm in diameter, respectively). The larger WE1 is further modified with electroche

An amperometric dual NO/CO microsensor was developed on the basis of a working electrode incorporating dual Pt microdisks (each diameter, 76 μm) and a Ag/AgCl reference electrode covered with a gas permeable membrane. One of the Pt disks was sequentially electrodeposited with Pt and Sn; the other Pt disk was deposited with Pt-Fe(III) oxide nanocomposites. The first showed activity for the oxidation of both NO and CO; the second showed activity only for NO oxidation. In the copresence of NO and C

This paper reports the simple synthesis and characterization of carbon-supported Pd layer-coated Au nanoparticles (AuPd/C). A series of AuPd/C with various Pd/Au weight percentage ratios were prepared by the spontaneous deposition of a Pd shell on a Au nanoparticle core using different Pd precursor concentrations (0.5, 5, 10, 20 mM PdCl 2 ). Au nanospheres encapsulated by the porous Pd shells are confirmed by transmission electron microscopy (TEM), UV–vis absorption spectroscopy, and scanning TE

The electrocatalytic activity of bulk Au and Au nanoparticles (AuNPs) toward the oxygen reduction reaction (ORR), before and after the electrochemical pretreatment, was investigated in a 0.05 M phosphate buffer solution (pH = 7.4). Both the Au and AuNPs were pretreated by repetitive potential cycling between −0.2 and +1.0 V (vs SCE). Rotating disk electrode (RDE) voltammetric studies showed that a more favorable ORR occurred at the AuNPs than at the Au. Interestingly, increased number of electro

A technique that combines scanning electrochemical microscopy (SECM) and optical microscopy (OM) was implemented with a new probe tip. The tip for scanning electrochemicaVoptical microscopy (SECM/OM) was constructed by insulating a typical gold-coated near-field scanning optical microscopy tip using electrophoretic anodic paint. Once fabricated, the tip was characterized by steady-state cyclic voltammetry, as well as optical and electrochemical approach experiments. This tip generated a stable s

Here, we report the unique transformation of one-dimensional tubular mixed oxide nanocomposites of iridium (Ir) and cobalt (Co) denoted as Ir x Co 1– x O y, where x is the relative Ir atomic content to the overall metal content. The formation of a variety of Ir x Co 1– x O y (0 ≤ x ≤ 1) crystalline tubular nanocomposites was readily achieved by electrospinning and subsequent calcination process. Structural characterization clearly confirmed that Ir x Co 1– x O y polycrystalline nanocomposites ha