A Facile One-Pot Synthesis of Au/Cu2O Nanocomposites for Nonenzymatic Detection of Hydrogen Peroxide

Cytotoxicity of AuCu-Cu2S Nanocomposites: Implications for Biological Evaluation of the Nanocomposite Effect on Bombyx mori Silkworms and Cell Lines

AuCu-Cu2S nanocomposites are unique materials with exceptional properties that have recently received a lot of interest. However, little is known about their potential toxicity in terrestrial organisms and their subsequent effects on the environment. Therefore, it is essential to develop effective methodologies for evaluating AuCu-Cu2S nanocomposites in biological systems. This study reports the biological evaluation of the AuCu-Cu2S nanocomposite from animal and cell entity levels. The Bombyx mori silkworm was used as a model organism to study the effects of different concentrations of AuCu-Cu2S on silkworm development. Transcriptome analysis was also carried out to examine the genetic modulation exerted by the treatment. Moreover, biocompatibility and cytotoxicity of AuCu-Cu2S were evaluated in human bronchial epithelial cells 16HBE, human lung adenocarcinoma, and the insect Spodoptera frugiperda cell sf9 cell lines. The results showed that although AuCu-Cu2S at ≤400 ppm can prolong the eating habit of silkworms and promote the weight of the cocoon layer, there was an increase in silkworm mortality and a decrease in moth formation at a concentration of ≥800 ppm. The genetic regulation by AuCu-Cu2S treatment showed varying effects in the silkworm, primarily related to functions such as transport and catabolism, metabolism of cofactors and vitamins, xenobiotic biodegradation, amino acid, and carbohydrate. 16HBE, PC-9, and sf9 treated with 300 ppm of AuCu-Cu2S showed viability percentages of 60, 20, and 90%, respectively. Thus, AuCu-Cu2S at low concentrations serves as a safe and biocompatible material for the sf9 cell lines but is lethal to 16HBE and PC-9. This research could aid in understanding the biological effects and biocompatibility of AuCu-Cu2S nanocomposites, particularly in the field of biochemistry; however, the mechanisms involved need further exploration.

Engineering Active Sites of Gold-Cuprous Oxide Catalysts for Electrocatalytic Oxygen Reduction Reaction

Understanding how the catalyst morphology influences surface sites is crucial for designing active and stable catalysts and electrocatalysts. We here report a new approach to this understanding by decorating gold (Au) nanoparticles on the surface of cuprous oxides (Cu₂O) with three different shape morphologies (spheres, cubes, and petals). The Au-Cu₂O particles are dispersed onto carbon nanotube (CNT) matrix with high surface area, stability, and conductivity for oxygen reduction reaction. A clear morphology-dependent enhancement of the electrocatalytic activity is revealed. Oxygenated gold species (AuO^-) are found to coexist with Au⁰ on the cube and petal catalysts, whereas only Au⁰ species are present on the sphere catalyst. The AuO^- species function effectively as active sites, resulting in the improved catalytic performance by changing the reaction mechanism. The enhanced catalytic performance of the petal-shaped catalyst in terms of onset potential, half-wave potential, diffusion-limited current density, and stability is closely associated with the presence of the most abundant AuO^- species on its surface. Highly active AuO^- species are identified on the surface of the catalysts as a result of the unique structural characteristics, which is attributed to the structural origin of high activity and stability. This insight constitutes the basis for assessing the detailed correlation between the morphology and the electrocatalytic properties of the nanocomposite catalysts, which has implications for the design of surface-active sites on metal/metal oxide electrocatalysts.

Seeded Growth of Au@CuxO Core-Shell Mesoporous Nanospheres and Their Photocatalytic Properties

We report a facile synthesis of Au@CuxO core-shell mesoporous nanospheres with tunable size in the aqueous phase via seeded growth. The success of the current work relies on the use of a halide-free copper (Cu) precursor and n-oleyl-1,3-propanediamine as a capping agent to facilitate the formation of a copperish oxide shell with a mesoporous structure and the presence of mixed oxidation states of Cu. By varying the amount of spherical Au seeds while keeping other parameters unchanged, their diameters could be readily tuned without noticeable change in morphology. As compared with commercial Cu2O, the as-prepared Au@CuxO core-shell mesoporous nanospheres exhibit the higher adsorption ability, enhanced activity, and excellent stability toward photocatalytic degradation of methyl orange (MO) under visible light irradiation, indicating their potential applications in water treatment.

Efficient Multifunctional Catalytic and Sensing Properties of Synthesized Ruthenium Oxide Nanoparticles

Ruthenium oxide is one of the most active electrocatalyst for oxygen evolution (OER) and oxygen reduction reaction (ORR). Herein, we report simple wet chemical route to synthesize RuO2 nanoparticles at controlled temperature. The structural, morphological and surface area studies of the synthesized nanoparticles were conducted with X-ray diffraction, electron microscopy and BETsurface area studies. The bifunctional electrocatalytic performance of RuO2 nanoparticles was studied under different atmospheric conditions for OER and ORR, respectively, versus reversible hydrogen electrode (RHE) in alkaline medium. Low Tafel slopes of RuO2 nanoparticles were found to be ~47 and ~49 mV/dec for OER and ORR, respectively, in oxygen saturated 0.5 M KOH system. Moreover, the catalytic activity of RuO2 nanoparticles was examined against the Horseradish peroxidase enzyme (HRP) at high temperature, and the nanoparticles were applied as a sensor for the detection of H2O2 in the solution.

Synthesis of Ag-Au/Reduced Graphene Oxide/TiO2 Nanocomposites: Application as a Non-enzymatic Amperometric H2O2 Sensor

Background:

Owing to the strong oxidizing and reducing properties of hydrogen peroxide (H2O2), it has been widely used in many fields. In particular, H2O2 is widely used in the aseptic packaging of drinks and milk. The residue of H2O2 in food is harmful to human health. Therefore, the quantitative detection of H2O2 is of great practical significance.

Methods:

The Ag-Au/RGO/TiO2 nanocomposites were facilely synthesized by photo-reduction approach. Transmission electron microscopy, X-ray photoelectron spectroscopy and Raman spectroscopy were used to characterize the synthesized Ag-Au/RGO/TiO2 nanocomposites. Cyclic voltammetry was used to analyze the electrochemical behavior of H2O2 on the Ag-Au/RGO/TiO2/GCE. Amperometry was applied for quantitative determination of the concentration of H2O2.

Results:

A novel Ag-Au/RGO/TiO2/GCE was prepared. The Ag-Au/RGO/TiO2/GCE displayed high electrocatalytic activity towards H2O2 reduction. An electrochemical reduction peak of H2O2 was achieved on the Ag-Au/RGO/TiO2/GCE. The current responses were linear with the concentrations of H2O2 in the range of 0.01-30 mM with the detection limit of 3.0 μM (S/N = 3).

Conclusion:

An amperometric sensor has been prepared for H2O2 detection using Ag- Au/RGO/TiO2/GCE. The Ag-Au/RGO/TiO2/GCE shows good performance for the determination of H2O2. The proposed sensor exhibits good selectivity and stability.

A Facile One-Step Synthesis of Cuprous Oxide/Silver Nanocomposites as Efficient Electrode-Modifying Materials for Nonenzyme Hydrogen Peroxide Sensor

Cuprous oxide/silver (Cu₂O/Ag) nanocomposites were prepared via a facile one-step method and used to construct an electrochemical sensor for hydrogen peroxide (H₂O₂) detection. In this method, AgNO₃ and Cu(NO₃)₂ were reduced to Cu₂O/Ag nanocomposites by glucose in the presence of hexadecyl trimethyl ammonium bromide (CTAB) at a low temperature. The optimum condition was the molar ratio of silver nitrate and copper nitrate of 1:10, the temperature of 50 °C. Under this condition, Cu₂O/Ag nanocomposites were obtained with uniformly distributed and tightly combined Cu₂O and Ag nanoparticles. The size of Cu₂O particles was less than 100 nm and that of Ag particles was less than 20 nm. Electrochemical experiments indicate that the Cu₂O/Ag nanocomposites-based sensor possesses an excellent performance toward H₂O₂, showing a linear range of 0.2 to 4000 μM, a high sensitivity of 87.0 μA mM⁻¹ cm⁻², and a low detection limit of 0.2 μM. The anti-interference capability experiments indicate this sensor has good selectivity toward H₂O₂. Additionally, the H₂O₂ recovery tests of the sensor in diluted milk solution signify its potential application in routine H₂O₂ analysis.

Surfactant-free synthesis of Cu2O yolk–shell cubes decorated with Pt nanoparticles for enhanced H2O2 detection

Novel Cu₂O yolk–shell cubes decorated with Pt nanoparticles show excellent performance for the nonenzymatic detection of H₂O₂.