Facile Synthesis of Mesoporous Ag₂O–ZnO Heterojunctions for Efficient Promotion of Visible Light Photodegradation of Tetracycline

Abstract

Fabrication of 3D mesoporous Ag 2 O−ZnO heterojunctions at varying Ag 2 O contents has been achieved through poly(ethylene glycol)-block-poly(propylene glycol)-block-poly-(ethylene glycol) (Pluronic F-108) as the structure-directing agent for the first time. The mesoporous Ag 2 O−ZnO nanocomposites exhibited a mesoporous structure, which revealed a large pore volume and high surface area. The photocatalytic efficiency over mesoporous Ag 2 O−ZnO nanocomposites for tetracycline (TC) compared with that over commercial P-25 and pristine ZnO NPs through the visible light exposure was studied. Mesoporous 1.5% Ag 2 O−ZnO nanocomposites indicated the highest degradation efficiency of 100% of TC during 120 min of the visible light exposure compared with 5% and 10% for pristine ZnO NPs and commercial P-25, respectively. The TC degradation rate took place much rapidly over 1.5% Ag 2 O−ZnO nanocomposites (0.798 μmol L −1 min −1 ) as compared to either commercial P-25 (0.097 μmol L −1 min −1 ) or ZnO NPs (0.035 μmol L −1 min −1 ). The mesoporous 1.5% Ag 2 O−ZnO nanocomposite revealed the highest degradation rate among all synthesized samples, and it was 23 and 8 orders of magnitudes greater than those of pristine ZnO NPs and P-25, respectively. The photoluminescence and transient photocurrent intensity behaviors have been discussed to explore photocatalysis mechanisms. It is anticipated that the present work will contribute some suggestions for understanding other heterojunctions with outstanding behaviors.

Enhanced Visible-Light-Driven Photocatalysis of Ag/Ag2O/ZnO Nanocomposite Heterostructures

“…The Ag 3d peaks were deconvoluted four peaks as shown in Figure 3 c. The two binding energy positions at 367.3 and 373.3 eV with a binding energy separation of 6 eV belonging to Ag 3d 5/2 and Ag 3d 3/2 of the metallic silver, respectively, are in agreement with the previous report [ 22 ]. The other two binding energy positions at 374.2 and 368.2 eV are attributed to Ag 3d 5/2 and Ag 3d 3/2 components of silver in the form of Ag–O, respectively, which are in agreement with the reported Ag 2 O phase [ 23 , 24 ]. In addition to the XRD results, the XPS studies proved that the 5% Ag-ZnO consists of Ag-Ag 2 O-ZnO heterostructures.…”

A New Approach for the Green Biosynthesis of Silver Oxide Nanoparticles Ag2O, Characterization and Catalytic Application

“…where α is the absorption coefficient, hν is the incident photon energy, K is a constant, Eg is the optical band gap in electron volts (eV) and n is an exponent that can take two values depending on the nature of the electronic transition, i.e. n = 2 for a direct transition, and n = 1/2 for an indirect transition as shown in Figure 2 and Figure 3 [31,32].…”

Two-Step Visible Light Photocatalytic Dye Degradation Phenomena in Ag2O-Impregnated ZnO Nanorods via Growth of Metallic Ag and Formation of ZnO/Ag0/Ag2O Heterojunction Structures

“…In the ultimate photocatalytic performance of the ZnO/Ag 2 O hybrid nanostructures, the method of synthesis and the specific morphology of the individual components are separately important. In some earlier studies, ZnO nanorods were synthesized via sol–gel methods, the photochemical process using irradiations from high-pressure mercury lamps (λ = 365 nm, 250 W) followed by vacuum drying, , the solid-state method by calcination of Zn­(C 2 H 3 O 2 ) 2 at 300 °C, or by the ultrasonic-assisted precipitation method . Enriched surface defect states in the ZnO nanorods, formed via reduction of Zn 2+ to metallic Zn, usually at higher calcination temperature, enhance the light absorption.…”

“…Therefore, the mesoporous ZnO/ Ag 2 O nanocomposites could promote the absorption of the longer wavelength part (visible light) of the solar radiation and provide better opportunities for the enhanced photogeneration of excitons useful for improved PC activities. 29…”