Tailoring the Hydrothermal Synthesis of Stainless Steel Wire Sieve-Supported Ag-Doped ZnO Nanowires to Optimize Their Photo-catalytic Activity

Regulation of the Volume Flow Rate of Aqueous Methyl Blue Solution and the Wettability of CuO/ZnO Nanorods to Improve the Photodegradation Performance of Related Microfluidic Reactors

“…A cleaned planar glass 70 mm long and 40 mm wide was immersed in the ZnO seed solution for 1 min and then taken out and annealed at 120 °C for 10 min. Thus, the ZnO seeds were deposited on the planar glass (Figure d) . Then via standard lithography a rectangular ZnO seed pattern 25 mm long and 15 mm wide on the planar glass was formed (Figure e) .…”

“…Zinc nitrate (Zn­(NO 3 ) 2 ·6H 2 O), hexamethylenetetramine (C 6 H 12 N 4 ) and DI water were mixed up to produce the growth solution of Zn 2+ concentration 75 mM in a beaker, in which the planar glass with the rectangular ZnO seed pattern was immersed. The beaker was placed into the water bath at 90 °C for 2.5 h; hence, patterned ZnONRs were hydrothermally synthesized upon the planar glass (Figure f) . Furthermore, in the presence of UV irradiation of wavelength 365 nm with irradiance intensity 6 mW/cm 2 , the ZnONR-deposited planar glass was placed in an aqueous Cu­(NO 3 ) 2 solution to synthesize nanostructured CuO upon the as-prepared ZnONRs (Figure g), and the UV irradiation was set to be 0.5, 1.0, 1.5, 2.0, 3.0, and 4.0 h .…”

“…Thus, the ZnO seeds were deposited on the planar glass (Figure 1d). 22 Then via standard lithography a rectangular ZnO seed pattern 25 mm long and 15 mm wide on the planar glass was formed (Figure 1e). 30 Zinc nitrate (Zn(NO 3 ) 2 •6H 2 O), hexamethylenetetramine (C 6 H 12 N 4 ) and DI water were mixed up to produce the growth solution of Zn 2+ concentration 75 mM in a beaker, in which the planar glass with the rectangular ZnO seed pattern was immersed.…”

“…Due to their excellent advantages like complete mineralization of pollutants, no requirement for the disposal of sludge, and low energy consumption, several photocatalytic degradation techniques with dispersive nanostructured catalyst or substrate-supported nanostructured catalyst or catalyst-coated macroscale channel, or nanostructured catalyst-based microfluidic reactor have been put forward to carbonize relevant organic species in wastewater. Of all these photocatalytic degradation techniques, the nanostructured catalyst-based microfluidic reactor has been more often used thanks to its large surface-to-volume ratio, short diffusion distance and rapid mass transport process of molecules from an aqueous solution to catalysts, high illumination homogeneity, and accurate irradiation on nanostructured catalysts, no need of postseparation and recovery which are common for suspended catalysts, and 2 orders of magnitude higher photocatalytic efficiency. − The nanostructured catalysts mainly include metal oxide or sulfide semiconductors (that is, BiVO 4 , ZnO, , TiO 2 , , ZnS, and WO 3 ), noble metal-doped metal oxide semiconductors − (for instance, Ag/ZnO, Ga/ZnO, and Au/ZnO), and surface-sensitized metal oxide semiconductors (namely, C 60 /ZnO, Graphene/ZnO, and CuO/ZnO). Owing to the unique structure of the p-n heterojunction and the effectual inhibition of the combination of photogenerated electrons and holes, the nanostructured CuO/ZnONRs have excellent photodegradation performance and thus have been widely employed to construct various microfluidic reactors. − In regard to the evaluation of the photodegradation performance of these nanostructured catalyst-based microfluidic reactors, the experimental and numerical routes and eq have been invariably used in the literature, − where K A (min –1 ) is initial rate constant, K a (min –1 ) is kinetic adsorption rate constant, and K Lev (min –1 ) is mass transport-controlled constant.…”

“…Of all these photocatalytic degradation techniques, the nanostructured catalyst-based microfluidic reactor has been more often used thanks to its large surface-to-volume ratio, short diffusion distance and rapid mass transport process of molecules from an aqueous solution to catalysts, high illumination homogeneity, and accurate irradiation on nanostructured catalysts, no need of postseparation and recovery which are common for suspended catalysts, and 2 orders of magnitude higher photocatalytic efficiency. 8−13 The nano-structured catalysts mainly include metal oxide or sulfide semiconductors (that is, BiVO 4 , 10 ZnO, 14,15 TiO 2 , 16,17 ZnS, 18 and WO 3 19 ), noble metal-doped metal oxide semiconductors 20−24 (for instance, Ag/ZnO, 22 Ga/ZnO, 23 and Au/ ZnO 24 ), and surface-sensitized metal oxide semiconductors (namely, C 60 /ZnO, 25 Graphene/ZnO, 26 and CuO/ZnO 27 ). Owing to the unique structure of the p-n heterojunction and the effectual inhibition of the combination of photogenerated electrons and holes, the nanostructured CuO/ZnONRs have excellent photodegradation performance and thus have been widely employed to construct various microfluidic reactors.…”