Effect of Silver on Plasmonic, Photocatalytic, and Cytotoxicity of Gold in AuAgZnO Nanocomposites

Abstract

Four different nanocomposites of AuAgZnO with differing compositions of silver and gold were made by solution combustion method where the EDAX analysis gave the exact composition. Nanocomposites were formed as nanospheres. The composites contained bimetallic AuAg particles on the surface of ZnO semiconductor, the interface being silver. The deconvoluted UV–DRS spectra revealed the presence of two plasmons due to Au and Ag. The amount of gold dominates the AuAg indicating the presence of only a thin layer of silver below gold causing a blue-shifted gold plasmon band and red-shifted silver plasmon band in comparison to their pure entity. The intensity of the former gets increased due to interparticle interaction with silver. Presence of excess gold in one sample of the starting materials tends to form amorphous Au2O3 as proved by both EDAX and XPS. The number of oxygen vacancies in ZnO as seen in EPR depends on AuAg metal content effects the photocatalytic degradation of Rhodamine-B and the photocatalytic production of hydrogen. The interparticle interaction of Ag with Au and ZnO also plays a major role in photocatalytic process. An in vitro cytotoxicity study of AuAgZnO nanocomposites on MCF-7 cell lines is compared with the effect of gold alone in AuZnO. The current study revealed that the presence of silver in the bimetallic system suppresses the efficacy of Au and even ZnO. Gold by itself is a powerful cytotoxic nanoagent even with small amount of ZnO, the latter being known for its nontoxicity. It is interesting to note that Ag has a negative role in cytotoxicity but it contributes positively to photocatalysis.

A Quantitative Bacteria Monitoring and Killing Platform Based on Electron Transfer from Bacteria to a Semiconductor

“…[ 14b ] The snatched electrons can enter the Ti substrate and react with the medium by the following reaction: 2 e − + 2H + → H 2 . [ 22 ] A steady electron loss is fatal to the bacteria leading to electron‐light region [ 14b ] and OH may adhere to the membrane to reach electrical equilibrium. The Ti substrate serves as a conductor and is not influenced by ET as verified by the same XRD pattern after reacting with bacteria (Figure S8, Supporting Information).…”

Highly Efficient Photocatalyst Based on a CdS Quantum Dots/ZnO Nanosheets 0D/2D Heterojunction for Hydrogen Evolution from Water Splitting

“…26,30−32 For example, Zhao et al synthesized a CdS/ ZnO heterostructure that exhibited about 9.2 and 34.5 times higher hydrogen evolution rate than those of single ZnO and CdS, respectively. 21 ZnO nanocomposite that exhibited excellent photocatalytic properties because of the driving force of the Z-scheme chargetransfer mechanism between ZnO and CdS. 30 However, up to now, the hydrogen evolution rate over a CdS/ZnO heterostructure is still far below the level of practical application, mainly because of the rapid recombination of photogenerated electrons and holes in the inner parts of bulk ZnO and bulk CdS.…”

“…Hydrogen generation from photocatalytic water splitting has been widely explored as a promising technology to solve the global energy crisis and environmental pollution. − Many semiconductor materials have been utilized as photocatalysts to convert solar energy to hydrogen energy by water splitting, such as TiO 2 , − transition-metal sulfide, − carbon nitride, − ZnO, , and composite materials of these semiconductors. Among them, ZnO with a direct band gap of 3.2 eV is one of the most attractive semiconductor photocatalysts because of its high photosensitivity, nontoxic nature, low cost, and environmental sustainability. − However, the photocatalytic efficiency of ZnO is limited by several factors, such as restrictive light absorption [only ultraviolet (UV) light can be absorbed because of its wide band gap] and fast recombination of charge carriers. , Several strategies have been explored to improve these shortcomings for enhanced photocatalytic efficiency, such as ion doping, noble-metal deposition, and the construction of a heterojunction structure. − Among these strategies, coupling ZnO with other visible-light-responsive semiconductors to form a heterojunction structure has been proven to be highly effective. CdS is a visible-light-responsive photocatalyst with a narrow band gap (2.4 eV) .…”

Facile strategy for the fabrication of noble metal/ZnS composites with enhanced photocatalytic activities

“…At the same time, with the formation of Ag/ZnS composites, a new absorption band appeared in the range of 450–800 nm, which is caused by the SPR effect of Ag, further indicating the presence of Ag. 39 As the amount of Ag increases, the absorption capacity increases continuously, indicating that the composites will exhibit improved photocatalytic activity.…”