Morphology-dependent activation of hydrogen peroxide with Cu2O for tetracycline hydrochloride degradation in bicarbonate aqueous solution

The design of efficient heterogeneous catalysts in bicarbonate-activated hydrogen peroxide systems (BAP) is a hot topic in wastewater treatment. In this work, Cu2O nanoparticles with different morphologies including cubic shape (c-Cu2O), octahedron shape (o-Cu2O) and spherical shape (s-Cu2O), were applied in BAP for the first time to degrade tetracycline hydrochloride (TC). Compared with Cu2+ ions and CuO, TC degradation was boosted in the presence of Cu2O in the BAP system, with the degradation rate following the order c-Cu2O > o-Cu2O > s-Cu2O. The morphology-dependent effects could be linearly correlated with the ratio of surface oxygen species (OS), but not with the surface area or Cu(I) ratio. The c-Cu2O catalyst with exposure of (100) facets contained 76.6% OS as the active site for H2O2 adsorption and activation, while the value was much lower for o-Cu2O and s-Cu2O with dominant (111) facets. The presence of HCO3- enhanced the interactions among Cu2O, H2O2 and TC, leading to facile oxidation of Cu(I) to Cu(II) by H2O2, and the formation of various reactive species such as hydroxyl radicals and Cu(III) contributed to TC degradation. This work provides a new method for enhancing H2O2 activation with heterogeneous catalysts by crystal facet engineering.

The Effect of a Dodecahedron-Shaped Structure on the Properties of an Enzyme

In this research, the influence of a dodecahedron-shaped structure on the adsorption behavior of a horseradish peroxidase (HRP) enzyme glycoprotein onto mica substrates was studied. In the experiments, samples of an aqueous HRP solution were incubated at various distances (0.03 m, 2 m, 5 m, and control at 20 m) from the dodecahedron surface. After the incubation, the direct adsorption of HRP onto mica substrates immersed in the solutions was performed, and the mica-adsorbed HRP particles were visualized via atomic force microscopy (AFM). The effect of the increased HRP aggregation was only observed after the incubation of the enzyme solution at the 2 m distance from the dodecahedron. In addition, with respect to the control sample, spectrophotometric measurements revealed no change in the HRP enzymatic activity after the incubation at any of the distances studied. The results reported herein can be of use in the modeling of the possible influences of various spatial structures on biological objects in the development of biosensors and other electronic equipment.

Ultrasensitive electrochemical detection of neuron-specific enolase based on spiny core-shell Au/CuxO@CeO2 nanocubes

As a specific biomarker, neuron-specific enolase (NSE) is an essential clinical indicator for diagnosing small cell lung cancer. In this paper, a sandwich-type electrochemical immunosensor was designed for the quantitative detection of NSE. AuPt nanoblock spherical nanoarchitectonics (AuPt NSNs), a bimetallic nanoparticle with a rugged morphology, were utilized as the substrate, which could enhance the electronic conduction and increase the immobilization capacity of the primary antibody (Ab₁). Moreover, through a simple hydrothermal method, Au/Cu_xO@CeO₂ was prepared as a spiny core-shell nanocube with cerium dioxide (CeO₂) and gold nanoparticles (Au NPs) loading. The combination of Cu₂O, CuO, and CeO₂ showed favorable catalytic activity toward hydrogen peroxide (H₂O₂). Furthermore, the deposition of Au NPs on the spiny surface structure enhanced the specific surface area and biocompatibility, thereby rendering it more effective for loading the second antibody (Ab₂). As the label material, the Au/Cu_xO@CeO₂ achieved signal amplification and sensitive detection with the immunosensor. Under optimal conditions, the designed immunosensor possessed a broad linear range of 50 fg mL^-1 to 100 ng mL^-1 and a limit of detection of 31.3 fg mL^-1, along with satisfactory performance in sensitivity, 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.

Surface-Controlled Photocatalysis and Chemical Sensing of TiO2, α-Fe2O3, and Cu2O Nanocrystals

A relatively new approach to the design of photocatalytic and gas sensing materials is to use the shape-controlled nanocrystals with well-defined facets exposed to light or gas molecules. An abrupt increase in a number of papers on the synthesis and characterization of metal oxide semiconductors such as a TiO2, α-Fe2O3, Cu2O of low-dimensionality, applied to surface-controlled photocatalysis and gas sensing, has been recently observed. The aim of this paper is to review the work performed in this field of research. Here, the focus is on the mechanism and processes that affect the growth of nanocrystals, their morphological, electrical, and optical properties and finally their photocatalytic as well as gas sensing performance.

Novel synthesis of a Cu2O–graphene nanoplatelet composite through a two-step electrodeposition method for selective detection of hydrogen peroxide

Optimized electrodeposition technique for the synthesis of Cu₂O–graphene composite for H₂O₂sensing.

Facile Synthesis of Gold Nanoparticles with Alginate and Its Catalytic Activity for Reduction of 4-Nitrophenol and H₂O₂ Detection

Gold nanoparticles (AuNPs) were synthesized using a facile solvothermal method with alginate sodium as both reductant and stabilizer. Formation of AuNPs was confirmed by UV-vis spectroscopic analysis. The synthesized AuNPs showed a localized surface plasmon resonance at approximately 520-560 nm. The AuNPs were characterized using transmission electron microscopy, X-ray diffraction and dynamic light scattering. Transmission electron microscopy revealed that the AuNPs were mostly nanometer-sized spherical particles. Powder X-ray diffraction analysis proved the formation of face-centered cubic structure of Au. Catalytic reduction of 4-nitrophenol was monitored via spectrophotometry using AuNPs as catalyst, and further a non-enzymatic sensor was fabricated. The results demonstrated that AuNPs presented excellent catalytic activity and provided a sensitive response to H₂O₂ detection.

Zinc ion mediated synthesis of cuprous oxide crystals for non-enzymatic glucose detection

Zn²⁺ was used to mediate the fabrication of Cu₂O crystals with different glucose sensing performances depending on their structures.

Synthesis and size-dependent electrochemical nonenzymatic H2O2 sensing of cuprous oxide nanocubes

The smaller size Cu₂O nanocubes can effectively increase the electrocatalytic active areas and subsequently promote electron transfer in the reduction of H₂O₂.