Cu₂O Nanoparticles Anchored on Amine-Functionalized Graphite Nanosheet: A Potential Reusable Catalyst

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.

Anodic SnO2 Nanoporous Structure Decorated with Cu2O Nanoparticles for Sensitive Detection of Creatinine: Experimental and DFT Study

Advanced anodic SnO₂ nanoporous structures decorated with Cu₂O nanoparticles (NPs) were employed for creatinine detection. Anodization of electropolished Sn sheets in 0.3 M aqueous oxalic acid electrolyte under continuous stirring produced complete open top, crack-free, and smooth SnO₂ nanoporous structures. Structural analyses confirm the high purity of rutile SnO₂ with successful functionalization of Cu₂O NPs. Morphological studies revealed the formation of self-organized and highly-ordered SnO₂ nanopores, homogeneously decorated with Cu₂O NPs. The average diameter of nanopores is ∼35 nm, while the average Cu₂O particle size is ∼23 nm. Density functional theory results showed that SnO₂@Cu₂O hybrid nanostructures are energetically favorable for creatinine detection. The hybrid nanostructure electrode exhibited an ultra-high sensitivity of around 24343 μA mM^-1 cm^-2 with an extremely lower detection limit of ∼0.0023 μM, a fast response time (less than 2 s), and wide linear detection ranges of 2.5-45 μM and 100 μM to 15 mM toward creatinine. This is ascribed to the creation of highly active surface sites as a result of Cu₂O NP functionalization, SnO₂ band gap diminution, and the formation of heterojunction and Cu(1)/Cu(ll)-creatinine complexes through secondary amines which occur in the creatinine structure. The real-time analysis of creatinine in blood serum by the fabricated electrode evinces the practicability and accuracy of the biosensor with reference to the commercially existing creatinine sensor. The proposed biosensor demonstrated excellent stability, reproducibility, and selectivity, which reflects that the SnO₂@Cu₂O nanostructure is a promising candidate for the non-enzymatic detection of creatinine.

Copper(II)-Bis-Cyclen Intercalated Graphene Oxide as an Efficient Two-Dimensional Nanocomposite Material for Copper-Catalyzed Azide–Alkyne Cycloaddition Reaction

We report stable and heterogeneous graphene oxide (GO)–intercalated copper as an efficient catalyst for the organic transformations in green solvents. The GO-intercalated copper(II) complex of bis(1,4,7,10-tetraazacyclododecane) [Cu(II)-bis-cyclen] was prepared by a facile synthetic approach with a high dilution technique. The as-prepared GO-Cu(II)-bis-cyclen nanocomposite was used as a click catalyst for the 1,3 dipolar Huisgen cycloaddition reaction of terminal alkyne and azide substrates. On directing a great deal of attention toward the feasibility of the rapid electron transfer rate of the catalyst in proliferating the yield of 1,2,3-triazole products, the click catalyst GO-Cu(II)-bis-cyclen nanocomposite was designed and synthesized via non-covalent functionalization. The presence of a higher coordination site in an efficient 2D nanocomposite promotes the stabilization of Cu(I) L-acetylide intermediate during the catalytic cycle initiated by the addition of reductants. From the XRD analysis, the enhancement in the d-interlayer spacing of 1.04 nm was observed due to the intercalation of the Cu(II)-bis-cyclen complex in between the GO basal planes. It was also characterized by XPS, FT-IR, RAMAN, UV, SEM, AFM, and TGA techniques. The recyclability of the heterogeneous catalyst [GO-Cu(II)-cyclen] with the solvent effect has also been studied. This class of GO-Cu(II)-bis-cyclen nanocomposite paves the way for bioconjugation of macromolecules through the click chemistry approach.

Synthesis of Cu2O-Modified Reduced Graphene Oxide for NO2 Sensors

Nowadays, metal oxide semiconductors (MOS)-reduced graphene oxide (rGO) nanocomposites have attracted significant research attention for gas sensing applications. Herein, a novel composite material is synthesized by combining two p-type semiconductors, i.e., Cu₂O and rGO, and a p-p-type gas sensor is assembled for NO₂ detection. Briefly, polypyrrole-coated cuprous oxide nanowires (PPy/Cu₂O) are prepared via hydrothermal method and combined with graphene oxide (GO). Then, the nanocomposite (rGO/PPy/Cu₂O) is obtained by using high-temperature thermal reduction under Ar atmosphere. The results reveal that the as-prepared rGO/PPy/Cu₂O nanocomposite exhibits a maximum NO₂ response of 42.5% and is capable of detecting NO₂ at a low concentration of 200 ppb. Overall, the as-prepared rGO/PPy/Cu₂O nanocomposite demonstrates excellent sensitivity, reversibility, repeatability, and selectivity for NO₂ sensing applications.

Gram-scale synthesis of ultra-fine Cu2O for highly efficient ozone decomposition

Dozens of grams of ultra-fine Cu₂O with efficient ozone decomposition was prepared by a facile liquid phase reduction method at room temperature.

Ultrafine AuPd nanoparticles supported on amine functionalized monochlorotriazinyl β-cyclodextrin as highly active catalysts for hydrogen evolution from formic acid dehydrogenation

Au_0.3Pd_0.7/A-M-β-CD exhibits remarkable catalytic activity for hydrogen evolution from formic acid, which is attributed to strong metal–support interaction.

A Robust Nonprecious CuFe Composite as a Highly Efficient Bifunctional Catalyst for Overall Electrochemical Water Splitting

To generate hydrogen, which is a clean energy carrier, a combination of electrolysis and renewable energy sources is desirable. In particular, for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in electrolysis, it is necessary to develop nonprecious, efficient, and durable catalysts. A robust nonprecious copper-iron (CuFe) bimetallic composite is reported that can be used as a highly efficient bifunctional catalyst for overall water splitting in an alkaline medium. The catalyst exhibits outstanding OER and HER activity, and very low OER and HER overpotentials (218 and 158 mV, respectively) are necessary to attain a current density of 10 mA cm^-2 . When used in a two-electrode water electrolyzer system for overall water splitting, it not only achieves high durability (even at a very high current density of 100 mA cm^-2 ) but also reduces the potential required to split water into oxygen and hydrogen at 10 mA cm^-2 to 1.64 V for 100 h of continuous operation.

Donor/Acceptor-Induced Ratiometric Photoelectrochemical Paper Analytical Device with a Hollow Double-Hydrophilic-Walls Channel for microRNA Quantification

Integrating ratiometric photoelectrochemical (PEC) techniques with paper microfluidics to construct a ratiometric PEC paper analytical device for practical application is often restricted by the grave dependence of ratiometric assay on photoactive materials and low mass-transfer rates of the paper channel. Herein, a universal donor/acceptor-induced ratiometric PEC paper analytical device with a hollow double-hydrophilic-walls channel (HDHC) was fabricated for high-performance microRNA-141 (miRNA-141) quantification. Concretely, a photoanode and photocathode were integrated on the paper-based sensing platform in which the photocathode served as a biosensing site for the pursuit of higher selectivity. For formulation of a cascading signal amplification strategy, a unique duplex-specific nuclease-induced target recycling reaction was engineered for the output of a double amount of all useful DNA linkers instead of conventional output of only one available DNA product, which could guarantee the output of abundant DNA linkers with the initiation of a cascade of hybridization chain reaction on both the trunk and branch in the presence of miRNA-141. Then the formed dendriform polymeric DNA duplex structures were further decorated with glucose oxidase (GOx)-mimicking gold nanoparticles by the electrostatic interaction to form a branchy gold tree (BGT). Profiting from the perfect GOx-mimicking activity of BGT and high mass-transfer rates of HDHC, the cathodic photocurrent from Ag₂S/Cu₂O hybrid structure was in a "signal off" state while the anodic photocurrent from graphene quantum dots (GQDs) and Ag₂Se QDs cosensitized ZnO nanosheets was in a "signal on" state because BGT-catalyzed glucose oxidation reaction evoked the consumption of dissolved O₂ as an electron acceptor and the generation of H₂O₂ as an electron donor. With calculation of the ratio of two photocurrent intensities, the quantitative detection of miRNA-141 was achieved with high sensitivity, accuracy, and reliability.

Formation of Copper(I) Oxide- and Copper(I) Cyanide-Polyacetonitrile Nanocomposites through Strong-Field Laser Processing of Acetonitrile Solutions of Copper(II) Acetate Dimer

Irradiation studies of acetonitrile solutions of copper(II) acetate dimer ([Cu(OAc)₂]₂) using high energy, simultaneously spatially and temporally focused (SSTF) ultrashort laser pulses are reported. Under ambient conditions, irradiation for relatively short periods of time (10-20 s) selectively produces relatively small, narrowly size-dispersed (3.5 ± 0.7 nm) copper(I) oxide nanoparticles (Cu₂O NPs) embedded in CuCN-polyacetonitrile polymers generated in situ by the laser. The Cu₂O NPs become embedded in a CuCN-polyacetonitrile network as they form, stabilizing them and protecting the air-sensitive material from oxygen. Laser irradiation of acetonitrile causes fragmentation into transient radicals that initiate and terminate polymerization of acetonitrile. Control and mechanistic investigations reveal that HCN formed during laser irradiation reacts rapidly to reduce the Cu(II) centers in [Cu(OAc)₂]₂, leading to the formation of CuCN or, in the presence of water, Cu₂O nanoparticles that bind and cross-link CuCN-polyacetonitrile chains. The acetate-bridged Cu(II) dimer unit is a required structural feature that functions to preorganize and direct the Cu(II) reduction and selective formation of CuCN and Cu₂O nanoparticles. This study illustrates how rapid deposition of energy using shaped, ultrashort laser pulses can initiate multiple photolytic and thermal processes that lead to the selective formation of composite nanoparticle/polymer materials for applications in electronics and catalysis.

Oxygen-deficient photostable Cu2O for enhanced visible light photocatalytic activity

Oxygen vacancies in inorganic semiconductors play an important role in reducing electron-hole recombination, which may have important implications in photocatalysis. Cuprous oxide (Cu2O), a visible light active p-type semiconductor, is a promising photocatalyst. However, the synthesis of photostable Cu2O enriched with oxygen defects remains a challenge. We report a simple method for the gram-scale synthesis of highly photostable Cu2O nanoparticles by the hydrolysis of a Cu(i)-triethylamine [Cu(i)-TEA] complex at low temperature. The oxygen vacancies in these Cu2O nanoparticles led to a significant increase in the lifetimes of photogenerated charge carriers upon excitation with visible light. This, in combination with a suitable energy band structure, allowed Cu2O nanoparticles to exhibit outstanding photoactivity in visible light through the generation of electron-mediated hydroxyl (OH˙) radicals. This study highlights the significance of oxygen defects in enhancing the photocatalytic performance of promising semiconductor photocatalysts.

Anchoring and Upgrading Ultrafine NiPd on Room-Temperature-Synthesized Bifunctional NH2 -N-rGO toward Low-Cost and Highly Efficient Catalysts for Selective Formic Acid Dehydrogenation

Hydrogen is widely considered to be a sustainable and clean energy alternative to the use of fossil fuels in the future. Its high hydrogen content, nontoxicity, and liquid state at room temperature make formic acid a promising hydrogen carrier. Designing highly efficient and low-cost heterogeneous catalysts is a major challenge for realizing the practical application of formic acid in the fuel-cell-based hydrogen economy. Herein, a simple but effective and rapid strategy is proposed, which demonstrates the synthesis of NiPd bimetallic ultrafine particles (UPs) supported on NH₂ -functionalized and N-doped reduced graphene oxide (NH₂ -N-rGO) at room temperature. The introduction of the NH₂ N group to rGO is the key reason for the formation of the ultrafine and well-dispersed Ni_0.4 Pd_0.6 UPs (1.8 nm) with relatively large surface area and more active sites. Surprisingly, the as-prepared low-cost NiPd/NH₂ -N-rGO dsiplays excellent hydrophilicity, 100% H₂ selectivity, 100% conversion, and remarkable catalytic activity (up to 954.3 mol H₂ (mol catalyst)^-1 h^-1 ) for FA decomposition at room temperature even with no additive, which is much higher than that of the best catalysts so far reported.

Fe3O4@Resorcinol-Formaldehyde Resin/Cu2O Composite Microstructures: Solution-Phase Construction, Magnetic Performance, and Applications in Antibacterial and Catalytic Fields

Multifunctional Fe₃O₄@resorcinol-formaldehyde resin/Cu₂O composite microstructures (denoted as Fe₃O₄@RF/Cu₂O microstructures) were successfully constructed via a simple wet chemical route that has not been reported so far in the literature. The as-obtained Fe₃O₄@RF/Cu₂O microstructures were characterized using field-emission scanning electron microscopy, (high-resolution) transmission electron microscopy, selected-area electron diffraction, X-ray diffraction, and X-ray energy dispersive spectroscopy. The investigations showed that the as-obtained microstructures presented not only excellent antibacterial activity to Staphylococcus aureus (Gram-positive bacteria) and Escherichia coli (Gram-negative bacteria) but also highly efficient catalytic ability for the reduction of 4-nitrophenol (4-NP) in a solution with excess NaBH₄. Owing to the presence of Fe₃O₄, the antibacterial reagent and the catalyst could be readily collected from the mixed systems under the assistance of an external magnetic field. It was found that the as-obtained microstructures displayed good cycling stability in antibacterial and catalytic applications. Fe₃O₄@RF/Cu₂O microstructures still retained more than 87% of the antibacterial efficiency after 5 cycles and 89% of the catalytic efficiency after 10 cycles.

Triethylenetetramine Synergizes with Pharmacologic Ascorbic Acid in Hydrogen Peroxide Mediated Selective Toxicity to Breast Cancer Cell

Breast cancer is characterized by overexpression of superoxide dismutase (SOD) and downregulation of catalase and more resistance to hydrogen peroxide (H₂O₂) than normal cells. Thus, relatively high H₂O₂ promotes breast cancer cell growth and proliferation. However, excessive intracellular H₂O₂ leads to death of breast cancer cells. In cancer cells, high level ascorbic acid (Asc) is able to be autoxidized and thus provides an electron to oxygen to generate H₂O₂. In the present study, we demonstrated that triethylenetetramine (TETA) enhances Asc autoxidation and thus elevates H₂O₂ production in MCF-7 cells. Furthermore, Asc/TETA combination significantly impaired cancer cell viability, while having much milder effects on normal cells, indicating Asc/TETA could be a promising therapy for breast cancer. Moreover, SOD1 and N-acetyl-L-cysteine failed to improve MCF-7 cells viability in the presence of Asc/TETA, while catalase significantly inhibited the cytotoxicity of Asc/TETA to breast cancer cells, strongly suggesting that the selective cytotoxicity of Asc/TETA to cancer cells is H₂O₂-dependent. In addition, Asc/TETA induces RAS/ERK downregulation in breast cancer cells. Animal studies confirmed that Asc/TETA effectively suppressed tumor growth in vivo. In conclusion, TETA synergizes pharmacologic Asc autoxidation and H₂O₂ overproduction in breast cancer cells, which suppresses RAS/ERK pathway and results in apoptosis.

Cu2O/g-C3N4 nanocomposites: an insight into the band structure tuning and catalytic efficiencies

We demonstrate an easy and scalable room-temperature synthesis of Cu₂O nanoparticle incorporated graphitic carbon nitride composites without the aid of any inert atmosphere. First principles calculations based upon density functional theory, in addition to the experimental validations, have been employed to investigate the electronic and optical properties of the nanocomposites. An insight into the band structure tunability, phase stabilisation and the dependancy of the catalytic properties of the nanocomposites upon the amount of Cu loading, in the form of Cu oxides, have been provided in this work.

Selective Cu4Pd alloy nanoparticles anchoring on amine functionalized graphite nanosheets and their use as reusable catalysts for a C–C coupling reaction with the sacrificial role of Cu for Pd-regeneration

Cu₄Pd nanoparticles have been anchored on amine functionalized graphite nanosheets and the composite has been used in C–C coupling with a sacrificial role of Cu for regeneration of metallic Pd.

Precious metal-like oxide-free copper nanoparticles: high oxidation resistance and geometric structure

Precious metal-like oxide-free copper nanoparticles, which are desired for alternatives as precious metal nanoparticles, were synthesized by environmental-friendly photoreduction method.

Facile synthesis and characterization of beta lactoglobulin–copper nanocomposites having antibacterial applications

The synthesis of Cu⁰ nanoparticles and Cu–protein nanocomposites is a great challenge.

MnO2 nanowires anchored on amine functionalized graphite nanosheets: highly active and reusable catalyst for organic oxidation reactions

MnO₂ nanowires were synthesized on amine functionalized graphite nanosheet and excellent catalytic efficiency of as-prepared composite towards organic oxidation reactions was demonstrated.