Twin boundaries have been proved to be effective flux pinning centers in YBa 2 Cu 3 O 7 (YBCO). Increases in twin density yield higher values of critical current density. Twin spacings in melt-textured grown (MTG) YBCO with different amounts of yttria nanoparticles were investigated with a new x-ray method. Twin spacings from the x-ray method were compared with those from transmission electron microscopy to show applicability. From investigation, MTG-YBCO with 11.9 weight percent yttria and oxygenation temperature at 680 C showed a colony size of 3.65 microns. This particular sample had a small twin spacing of 33 nm with a corresponding high value of critical current density ( ) of 1.2 10 4 A/cm 2 .

The PbO nanoparticles-based electrochemical sensor can be integrated into a smartphone for on-site field testing of paraquat with high sensitivity and selectivity.

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