Novel Green Biomimetic Approach for Preparation of Highly Stable Au-ZnO Heterojunctions with Enhanced Photocatalytic Activity

Abstract

A simple, ecofriendly, and biomimetic approach using cumin seeds extract (CSE) was developed for the formation of Au-ZnO Schottky contact without employing any chemical capping agents or stabilizers. The various unique phytoconstituents available in cumin seeds extract synergistically convert Au3+ ions into Au0 on the surface of ZnO, as each phytoconstituent is unique in context to its molecular structure and properties. The as-prepared biogenic Au-ZnO hybrid composites were examined using various spectroscopic and microscopic techniques. The TEM investigation and XRD patterns clearly depict the well dispersed AuNPs with the size range 10–15 nm and face centered cubic lattice on wurtzite ZnO nanostructures. The optical study of the nanocomposites showed two absorption bands: one intense band around 390 nm, which corresponds to ZnO, and a second broad band approximately around 540 nm, which corresponds to Au. The photocatalytic efficacy of Au-ZnO nanocatalysts was investigated by observing the mineralization of an aqueous solution of methylene blue (MB) dye under a 200 W tungsten filament lamp as visible light source. The apparent rate constants were also calculated for degradation processes, and it has been observed that 1 and 3 wt % Au-ZnO nanocomposites respectively have 2.27 and 3.2 times higher photoactivity, compared to pure ZnO. This enhanced photoactivity of biogenic Au-ZnO composite materials was resultant from formation of stable and effective Schottky contact between Au metal and ZnO surfaces.

Green biomimetic preparation of efficient Ag–ZnO heterojunctions with excellent photocatalytic performance under solar light irradiation: a novel biogenic-deposition-precipitation approach

“…Recent advancement in the preparation of hybrid materials has drawn signicant attention to green, eco-friendly methods for fabrication of metal-metal oxide nanocomposites with efficient Schottky junctions for effective transport of charge carriers. 10,18 In the present study, an attempt has been made for cleaner production of Ag-ZnO hybrid composites using fennel seeds.…”

“…7,18 Moreover, the photocatalytic efficiency might have constructive linkage with the degree of radical formation, i.e., more rapid frequency of active radical formation causes higher photocatalytic activity of catalyst. 10,28 Overall, the experimental investigations indicate that AgNPs anchored on ZnO surfaces assist in producing highly oxidative radical species and thus accelerate efficient degradation of wastewater pollutants.…”

“…8,9 These injected e À s in CB of semiconductor and h + s in MNPs are responsible for reduction and oxidation processes, respectively, at their sites. 10 This unique mechanism widens the horizons for the advancement of efficient and active photocatalysts possessing excellent visible-light activity.…”

Rational design of magnetically separable core/shell Fe3O4/ZnO heterostructures for enhanced visible-light photodegradation performance

“…12 To overcome these limitations, recent efforts have been focused on modifying the electronic band structure of ZnO by doping transition/noble metals or combining ZnO with other materials to form a hybrid photocatalyst system such as low bandgap semiconductors and magnetic nanomaterials. [13][14][15] Currently, the synthesis of heterogeneous structures between ZnO and magnetic nanomaterials has gained some interest in the eld. [16][17][18] The combination of ZnO and several spinel ferrite nanomaterials has created a new hybrid material that is capable to enhance the visible light photocatalytic efficiency and advantageous in recovery and reusability.…”

Biomimetic Catalysts Based on Au@ZnO–Graphene Composites for the Generation of Hydrogen by Water Splitting

“…Multiple pathways to incorporate gold nanoparticles (Au NPs) can be found in the literature. Methods such as coprecipitation [ 21 ], chemical reduction [ 22 ], phytochemical reduction [ 23 ], and the hydrothermal approach [ 24 ] have been successfully implemented over the years. All these synthesis procedures take into account parameters such as the preparation procedure, gold loading (percentage of gold weight on the material), particle size, dispersion (percentage of support surface covered by gold), and shape of the particles.…”