High piezo-photocatalytic efficiency of degrading organic pollutants has been realized from CuS/ZnO nanowires using both solar and mechanical energy. CuS/ZnO heterostructured nanowire arrays are compactly/vertically aligned on stainless steel mesh by a simple two-step wet-chemical method. The mesh-supported nanocomposites can facilitate an efficient light harvesting due to the large surface area and can also be easily removed from the treated solution. Under both solar and ultrasonic irradiation, CuS/ZnO nanowires can rapidly degrade methylene blue (MB) in aqueous solution, and the recyclability is investigated. In this process, the ultrasonic assistance can greatly enhance the photocatalytic activity. Such a performance can be attributed to the coupling of the built-in electric field of heterostructures and the piezoelectric field of ZnO nanowires. The built-in electric field of the heterostructure can effectively separate the photogenerated electrons/holes and facilitate the carrier transportation. The CuS component can improve the visible light utilization. The piezoelectric field created by ZnO nanowires can further separate the photogenerated electrons/holes through driving them to migrate along opposite directions. The present results demonstrate a new water-pollution solution in green technologies for the environmental remediation at the industrial level.

No abstract

Scattering-type scanning near-field optical microscopy (s-SNOM) allows for the characterization of optical properties of samples at the nanoscale, well below the diffraction limit of the interrogating wavelength. Typically, it relies on a model for the probe-sample interaction to extract complex optical constants of the sample. Here, we propose an s-SNOM calibration method that allows for the extraction of these constants without prior knowledge of the probe geometry nor the details of the probe-sample interactions. We illustrate the technique using terahertz time-domain spectroscopy-based s-SNOM to extract the optical properties of several organic and inorganic materials and differently doped regions of a standard silicon random access memory sample. The accuracy of the technique is comparable to that of conventional far-field techniques while additionally providing spatial distribution of optical constants at the nanoscale. The source-independent nature of the proposed technique makes it directly applicable for s-SNOM measurements in other spectral ranges.

No abstract