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Ag-based compounds are excellent co-catalyst that can enhance harvesting visible light and increase photogenerated charge carrier separation owing to its surface plasmon resonance (SPR) effect in photoelectrochemical (PEC) applications. However, the PEC performance of a ZnO/Ag/Ag 2 WO 4 heterostructure with SPR behavior has not been fully studied so far. Here we report the preparation of a ZnO/Ag/Ag 2 WO 4 photo-electrode with SPR behavior by a low temperature hydrothermal chemical growth method followed by a successive ionic layer adsorption and reaction (SILAR) method. The properties of the prepared samples were investigated by different characterization techniques, which confirm that Ag/Ag 2 WO 4 was deposited on the ZnO NRs. The Ag 2 WO 4 /Ag/ZnO photo-electrode showed an enhancement in PEC performance compared to bare ZnO NRs. The observed enhancement is attributed to the red shift of the optical absorption spectrum of the Ag 2 WO 4 /Ag/ZnO to the visible region (>400 nm) and to the SPR effect of surface metallic silver (Ag 0 ) particles from the Ag/Ag 2 WO 4 that could generate electron-hole pairs under illumination of low energy visible sun light. Finally, we proposed the PEC mechanism of the Ag 2 WO 4 /Ag/ZnO photo-electrode with an energy band structure and possible electronhole separation and transportation in the ZnO/Ag/Ag 2 WO 4 heterostructure with SPR effect for water oxidation.

A passive probe antenna for cw near-field microscopy at millimeter and submillimeter wavelengths is defined. It is based on the coupling between a free-space linearly polarized propagating beam to a wire mode. This is obtained efficiently owing to a discontinuous phase plate. This passive "optical" structure allows either the generation of a subwavelength confinement of the longitudinal electric field ͑polarized along the wire antenna͒ or, due to reciprocity, the collection of the longitudinal component of the electric field ͑along the wire antenna͒ with subwavelength resolution. The emission and collection properties of the proposed antenna have been demonstrated experimentally using a preliminary realization designed to work at 0.1 THz. Experimental results are well supported by calculations.