Synthesis of ZnO@Ag dumbbells for highly efficient visible-light photocatalysts

Abstract

The photocatalytic activity (PCA) of ZnO@Ag nanocomposites for different concentrations of Ag is reported. Dumbbells shaped zinc oxide (ZnO) nanostructures with silver (Ag) nanoparticles were synthesized by a simple chemical colloidal method. The as synthesized nanocomposites (without any heat treatment) were used for optical and photocatalytic studies. The FESEM analysis shows that the composite catalysts are composed of ZnO dumbbells coated with spherical Ag nanoparticles. UV-visible spectrum of ZnO@Ag photocatalysts shows a strong absorption band of ZnO at 380 nm with a plasmonic peak of Ag at 440 nm. The PL emission intensity of the composites varies with Ag concentration and has a minimum for the catalyst containing 13.7% of Ag. A possible growth mechanism of ZnO nanostructures with hexagonal cross-section has been proposed. Photocatalytic property of the as synthesized ZnO and ZnO@Ag catalysts was studied by investigating the degradation of methylene blue (MB) dye on exposure to UV-visible radiation. A relatively faster degradation of the dye was observed for ZnO@Ag composites as compared to pure ZnO, showing an improved photocatalytic behavior in the visible region. We proposed a possible mechanism for the enhancement in photocatalytic activity of Ag coated ZnO photocatalysts.

Ag-decorated ZnO-based nanocomposites for visible light-driven photocatalytic degradation: basic understanding and outlook

“…Precisely, whether successful synthesis of a good photocatalyst is manifested is primarily down to its essential attributes such as phase composition, macro and micro structure as well as surface chemical state, and whether they deliver excellent physical (optical, electrical, magnetic) and chemical (surface reactivity) properties for a high photocatalytic performance. To help get our heads around this, ZnO/Ag photocatalysts with diverse nanostructures including zero-dimensional (0D, nanoparticles), one-dimensional (1D, nanorods (NRs), nanowires, nanofibers, etc), 2D (nanosheets, nanofilms, etc), and threedimensional (3D, microflowers, porous microspheres, porous blocks, NR array films, other nanostructured assemblies, etc) (figure 2) have been synthesized by numerous synthesis methods comprising of chemical precipitation [55,[83][84][85][86][87][88][89][90], sol-gel [91][92][93][94][95], electrospinning [96], hydrothermal [71,73,[97][98][99][100][101][102][103][104][105][106][107][108][109][110][111], solvothermal [52,83,[112][113][114][115], solution/gel combustion [116,…”

“…To help get our heads around this, ZnO/Ag photocatalysts with diverse nanostructures including zero-dimensional (0D, nanoparticles), one-dimensional (1D, nanorods (NRs), nanowires, nanofibers, etc), 2D (nanosheets, nanofilms, etc), and threedimensional (3D, microflowers, porous microspheres, porous blocks, NR array films, other nanostructured assemblies, etc) (figure 2) have been synthesized by numerous synthesis methods comprising of chemical precipitation [55,[83][84][85][86][87][88][89][90], sol-gel [91][92][93][94][95], electrospinning [96], hydrothermal [71,73,[97][98][99][100][101][102][103][104][105][106][107][108][109][110][111], solvothermal [52,83,[112][113][114][115], solution/gel combustion [116,117], polymer-network gel [77,118], thermal decomposition [119], pulsed laser ablation in liquid…”

“…For example, Rasaki et al employed a liquid precipitation citrate reduction (LPCR) process (with KOH as the precipitation agent) to synthesize robust and recyclable ZnO/Ag NR photocatalysts with high catalytic activity for the degradation of 4-NP [86]. With changes of synthetic procedures and the chemical reagent, high active Ag@ZnO core-shell nanowire [84] and ZnO/Ag dumbbell-like NR [89] photocatalysts have been synthesized and applied to degrade RhB and MB dyes under solar light irradiation, respectively. Recently, Liu et al successfully synthesized spindle-like ZnO/Ag nanophotocatalysts by an ultrasonic-microwave co-assisted precipitation process [88].…”

Photo generated charge transport studies of defects-induced shuttlecock-shaped ZnO/Ag hybrid nanostructures

“…Zinc oxide (ZnO) has been widely reported for its extensive applications in numerous areas such as dye-sensitized solar cells (DSSC) [1][2][3], light-emitting diodes [4], surfaceenhanced resonance spectroscopy (SERS) [5], water purification [6], gas detection [7][8][9] and photocatalytic applications [10][11][12][13]. Its unique inherent properties like direct wide bandgap, high electrical and environmental stability, high exciton binding energy and high absorption in the UV region make it very useful for above applications [7,14,15].…”

“…Its unique inherent properties like direct wide bandgap, high electrical and environmental stability, high exciton binding energy and high absorption in the UV region make it very useful for above applications [7,14,15]. In recent decades, various approaches such as surface modification [7,16], the formation of hybrid metals/non-metals nanostructures [10,[17][18][19] and rareearth doping [20,21] have been employed to fine-tune the properties of ZnO to develop devices with desired functionality. Huang et al successfully synthesized the ZnO nanorods, nanowires and studied their electronic-optoelectronic properties under UV lasing action [22,23].…”