Synergistic antibacterial effect and mechanism between Cu2O nanoparticles and quaternary ammonium salt in moisture-curable acrylic coatings

Combining with various antibacterial mechanisms is the preferred strategy to fabricate coatings with effective antibacterial performance. Herein, Cu2O nanoparticles and dimethyloctadecyl [3-(trimethoxysilyl) propyl] ammonium chloride, a kind of quaternary ammonium salt (QAS), were simultaneously incorporated into a moisture-curable acrylic resin in order to achieve both contact-killing and release-killing abilities for antibacterial coatings. The surface morphology, surface composition and basic properties of the coatings were thoroughly characterized. The antibacterial performance of the coatings was determined by in-vitro bacteriostatic test. Under the constant total mass fraction of antibacterial agents, both Cu2O and QAS content possessed the highest value on the coating surface at Cu2O/QAS mass ratio of 1:1, and correspondingly, the coatings reached sterilizing rate above 99 % against both E. coli and S. loihica, indicating the existence of synergistic effect between Cu2O and QAS. The synergistic antibacterial mechanism of the coatings involved two aspects. Firstly, the combination of contact-killing and release-killing biocides resulted in high bactericidal and antibiofilm activity against different bacteria. Further, the grafting of QAS molecules on the surface of Cu2O particles brought about the spontaneous migration of nanoparticles to the coating surface. The interaction between Cu2O and QAS also inhibited the phase separation of QAS and prolonged the release of Cu2+ at the same time. The coatings, therefore, exhibited stable antibacterial performance at varied service conditions.

Modulating band structure through introducing Cu0/CuxO composites for the improved visible light driven ammonia synthesis

The photocatalytic performance of ceria-based materials can be tuned by adjusting the surface structures with decorating the transition-metal, which are considered as the important active sites. Herein, cuprous oxide-metallic copper composite-doped ceria nanorods were assembled through a simple hydrothermal reduction method. The photocatalytic ammonia synthesis rates exhibit an inverted "V-shaped" trend with increasing Cu0/CuxO mole ratio. The best ammonia production rate, approximately 900 or 521 µmol·gcal-1·h-1 under full-spectra or visible light, can be achieved when the Cu0/CuxO ratio is approximately 0.16, and this value is 8 times greater than that of the original sample. The absorption edge of the as-prepared samples shifted towards visible wavelengths, and they also had appropriate ammonia synthesis levels. This research provides a strategy for designing noble metal-free photocatalysts through introducing the metal/metallic oxide compositesto the catalysts.

Liquid- liquid (Cyclohexanone: Cyclohexanol) separation using augmented tight nanofiltration membrane: A sustainable approach

Organic solvent nanofiltration (OSN) is an incipient technology in the field of organic liquid-liquid separation. The incomplete separations and complexity involved in these, forces many organic liquids to be released as effluents and the adverse effects of these on environment is enormous and irreparable. The work prominences on the complete separation of industrially significant cyclohexanone: cyclohexanol (keto-alcohol oil) and heptane: toluene mixtures. The separations of these above-mentioned organic liquid mixtures were carried out using the fabricated Lewis acid modified graphitic carbon nitride (Cu2O@g-C3N4) incorporated polyvinylidene difluoride (PVDF) composite membranes. These fabricated membranes showed a separation factor of 18.16 and flux of 1.62 Lm-2h-1 for cyclohexanone: cyclohexanol mixture and separation of heptane and toluene mixture (with heptane flux of 1.52 Lm-2h-1) showed a separation factor of 9.9. The selectivity and productivity are based on the polarity and size of the organic liquids. The role of Cu2O@g-C3N4 is influencing the pore size distribution, increased divergence from solubility parameters, polarity, solvent uptake and porosity of the composite membranes. The developed composite membranes are thus envisioned to be apt for a wide range of liquid-liquid separations due to its implicit nature.

Facile route for preparation of cuprous oxide/copper/cupric oxide nanoparticles by using simultaneous electrochemical and reduction reaction

Cuprous oxide/copper/cupric oxide nanoparticles were synthesized through a hybrid process involving anodic dissolution and a controlled redox reaction between NaOH and glucose in the solution. The study demonstrates the structural manipulation of the material by varying the reaction components within the solution. Morphology, structural analyses using SEM (Scanning Electron Microscope), EDX (Energy-dispersive X-ray spectroscopy), TEM (Transmission Electron Microscope), FTIR (Fourier Transform Infrared Spectroscopy), XRD (X-ray diffraction), and XPS (X-ray photoelectron spectroscopy) unveiled the tunability of the material's structure based on the reaction components. Nitrogen adsorption analysis employing the Brunauer-Emmett-Teller (BET) equation confirmed the material's porosity, while Dynamic Light Scattering (DLS) measurements provided insights into the materials' hydrodynamic size and zeta potential. The results demonstrated that by increasing the glucose/NaOH ratio during the reaction, the different structures and morphologies of the distinct products were obtained from the clustering of small nanoparticles to cubic shape and flower-like structure. Antibacterial activity tests conducted on various bacterial strains showed a correlation between the morphology and structure of the material and its antibacterial properties. The highest substantial antibacterial efficacy against all tested bacterial strains at a dosage of 100 μg/L was obtained for the samples with clustering morphology, whereas the remaining materials showed no discernible antibacterial effect against one of the studied bacteria. The results also demonstrated that the sample with a clustering structure exhibited superior antibacterial properties when dispersed in water containing dimethylsulfoxide.

Biocidal activity of multifunctional cuprite-doped anion exchanger - Influence of bacteria type and medium composition

The study presents unconventional, bifunctional, heterogeneous antimicrobial agents - Cu2O-loaded anion exchangers. The synergetic effect of a cuprous oxide deposit and polymeric support with trimethyl ammonium groups was studied against the reference strains of Enterococcus faecalis ATCC 29212 and Pseudomonas aeruginosa ATCC 27853. Biological testing (minimum bactericidal concentration, MBC), time- and dose-dependent bactericidal effect (under different conditions - medium composition and static/dynamic culture) demonstrated promising antimicrobial activity and confirmed its multimode character. The standard values of MBC, for all studied hybrid polymers and bacteria, were similar (64-128 mg/mL). However, depending on the medium conditions, due to the copper release into the bulk solution, bacteria were actively killed even at much lower doses of the hybrid polymer (25 mg/mL) and low Cu(II) concentrations in solution (0.01 mg/L). Simultaneously, confocal microscopic studies confirmed the effective inhibition of bacterial adhesion and biofilm formation on their surface. The studies conducted under different conditions showed also the influence of the structure and physical properties of studied materials on the biocidal efficacy and an antimicrobial action mechanism was proposed that could be significantly affected by electrostatic interactions and copper release to the solution. Although the antibacterial activity was also dependent on various strategies of bacterial cell resistance to heavy metals present in the aqueous medium, the studied hybrid polymers are versatile and efficient biocidal agents against bacteria of both types, Gram-positive and Gram-negative. Therefore, they can be a convenient alternative for point-of-use water disinfection systems providing water quality in medical devices such as dental units, spa equipment, and aesthetic devices used in the cosmetic sector.

Photocatalytic degradation and electrochemical energy storage properties of CuO/SnO2 nanocomposites via the wet-chemical method

Integrating semiconducting functional materials is a way to enlarge the photoexcitation, energy range, and charge separation, greatly elongating the photocatalytic efficiency to enhance the chemical and physical properties of the materials. This work depicts and investigates the impact of cuprous oxide (CuO) and tin dioxide (SnO₂)-based catalysts with various CuO concentrations on photocatalytic and supercapacitor applications. Moreover, three distinct composites were made with varied ratios of CuO (5, 10, and 15% wt. Are designated as AT-1, AT-2, and AT-3) with SnO₂ to get an optimized performance. The photocatalytic properties indicate that the CuO/SnO₂ nanocomposite outperformed its bulk equivalents in photocatalysis using Methyl blue (MB) dye in a photoreactor. The results were monitored using a UV-visible spectrometer. The AT-1 ratio nanocomposite displayed 96% photocatalytic degradation compared to pure SnO₂ and CuO. CV analysis reveals a pseudocapacitive charge storage mechanism from 0.0 to 0.7 V in a potential window in an aqueous medium. The capacitive performance was also investigated for all electrodes, and we observed that a high capacitance of 260/155 F/g at 1/10 A/g was attained for the AT-1 electrode compared to others, specifying good rate performance.

Photocatalytically-assisted oxidative adsorption of As(III) using sustainable multifunctional composite material - Cu2O doped anion exchanger

The purpose of the presented study was to explore the photocatalytic activity of Cu₂O-supported anion exchangers and to explain the mechanism of their action in water purification processes. The functionality of this type of material was studied in the process of As(III) removal from water. As a result of the reactivity of cuprous oxide and functional groups of the polymer, the obtained composite exhibited complex activity towards arsenic(III) species. The adsorption studies were conducted under various conditions: dark, UV-VIS irradiation, VIS irradiation, under aerobic and anoxic conditions. The results from chemical analyses were supported by instrumental analyses - X-ray photoelectron spectroscopy, and FTIR and Raman spectroscopy. These studies showed that the mechanism of As(III) oxidative adsorption is based on the coupling of several reaction pathways: 1) photocatalytic oxidation involving Cu₂O as a photocatalyst, and photogenerated holes and ROS as oxidative agents, 2) chemical oxidation on the surface of CuO (being a result of the ageing process) with a re-oxidation of the produced Cu₂O to CuO by ROS and oxygen present in water, and 3) photochemical oxidation of As(III) in solution under UV light irradiation and subsequent adsorption of arsenates in the functional groups of the polymer.

Self-redox reaction driven in situ formation of Cu2O/Ti3C2Tx nanosheets boost the photocatalytic eradication of multi-drug resistant bacteria from infected wound

BACKGROUND

MXenes with interesting optical and electrical properties have been attractive in biomedical applications such as antibacterial and anticancer agents, but their low photogeneration efficiency of reactive oxygen species (ROS) and poor stability are major concerns against microbial resistance.

METHODS

Water-dispersible single layer Ti₃C₂T_x-based MXene through etching tightly stacked MAX phase precursor using a minimally intensive layer delamination method. After addition of Cu(II) ions, the adsorbed Cu(II) ions underwent self-redox reactions with the surface oxygenated moieties of MXene, leading to in situ formation of Cu₂O species to yield Cu₂O/Ti₃C₂T_x nanosheets (heterostructures).

RESULTS

Under NIR irradiation, the Cu₂O enhanced generation of electron-hole pairs, which boosted the photocatalytic production of superoxide and subsequent transformation into hydrogen peroxide. Broad-spectrum antimicrobial performance of Cu₂O/Ti₃C₂T_x nanosheets with sharp edges is attributed to the direct contact-induced membrane disruption, localized photothermal therapy, and in situ generated cytotoxic free radicals. The minimum inhibitory concentration of Cu₂O/Ti₃C₂T_x nanosheets reduced at least tenfold upon NIR laser irradiation compared to pristine Cu₂O/Ti₃C₂T_x nanosheets. The Cu₂O/Ti₃C₂T_x nanosheets were topically administrated on the methicillin-resistant Staphylococcus aureus (MRSA) infected wounds on diabetic mice.

CONCLUSION

Upon NIR illumination, Cu₂O/Ti₃C₂T_x nanosheets eradicated MRSA and their associated biofilm to promote wound healing. The Cu₂O/Ti₃C₂T_x nanosheets with superior catalytic and photothermal properties have a great scope as an effective antimicrobial modality for the treatment of infected wounds.

Molecularly imprinted ratiometric electrochemical sensor based on carbon nanotubes/cuprous oxide nanoparticles/titanium carbide MXene composite for diethylstilbestrol detection

Conventional molecularly imprinted polymers (MIP)-based electrochemical sensors are generally susceptible to the changes of personal operation, electrode surface, and solution conditions. Herein, a ratiometric strategy was employed through introducing Cu₂O nanoparticles (NPs) as inner reference probe to realize the reliable detection of diethylstilbestrol (DES). MIP film was prepared by electropolymerization of 1H-pyrrole-3-carboxylicacid in the presence of DES on carbon nanotubes/cuprous oxide/titanium carbide (CNT/Cu₂O NPs/Ti₃C₂T_x) modified electrodes. The Ti₃C₂T_x with accordion-like structure not only possessed good electrical conductivity, but also facilitated the immobilization of Cu₂O NPs, which contributed to stabilizing the signal. CNT was introduced to further improve the sensitivity of the sensor. Under optimum conditions, the MIP/CNT/Cu₂O NPs/Ti₃C₂T_x electrochemical sensors showed a broad linear response range of 0.01 to 70 μM, and a low detection limit of 6 nM (S/N = 3). Moreover, the sensor was applied to detect DES in real samples including lake water, milk, and pork, and the recoveries for spiked standard were 88-112%. Thus, this work provides a new way for reliable DES detection.

Enhanced photocatalytic activity of Cu2O for visible light-driven dye degradation by carbon quantum dots

Cuprous oxide (Cu₂O), a p-type semiconductor material, plays an important role in photocatalysis, which has narrower band gap (~2.1 eV), abundant availability, and low toxicity. However, the applications of Cu₂O are mainly restricted by its high recombination rate and low charge collection. Hence, it is of great significance to find an efficient method to improve the photocatalytic activity of Cu₂O. In this work, the CQDs-loaded Cu₂O nanocomposites (CQDs/Cu₂O) were successfully obtained via hydrothermal method. It was worth noting that the CQDs/Cu₂O nanocomposite displayed improved photocatalytic activity compared to that of pure Cu₂O with a lower dosage (25 mg) under visible light, which could completely degrade the methylene blue in 8 min. The recycling experiments also showed that the photocatalytic activity still remained up to 90% after 8 cycles. In addition to the photodegradation of methylene blue, the CQDs/Cu₂O nanocomposite also had an excellent antibacterial activity against Escherichia coli (100%, 30 min). These results demonstrated that introducing CQDs to Cu₂O was a feasible method to improve the photocatalytic performance of Cu₂O.

LED-driven photocatalysis of toluene, trichloroethylene and formaldehyde by cuprous oxide modified titanate nanotube arrays

In this study, cuprous oxide modified titanate nanotube arrays photocatalyst (Cu₂O/TNAs), a p-n type hetero-structure, was successfully synthesized by square wave voltammetry electrodeposition method (SWVE) with copper (II) acetate monohydrate as precursor. Cu₂O/TNAs photocatalysts were characterized by SEM, XRD, XPS, and UV-vis DRS to investigate the physical and chemical properties such as surface structure, light absorption, and element composition. Results of characterization indicated that the Cu₂O nanoparticles (Cu₂O NPs) were firmly deposited on the surface of TNAs without significant morphological change. The enhanced photocatalytic (PC) performance of as-synthesized materials was exemplified by the test of photocurrent, which revealing that the average photocurrent density of Cu₂O/TNAs (0.95 μA cm^-2) was 1.38 times higher than TNAs (0.69 μA cm^-2) under 24.2 mW cm^-2 LED irradiation. Three VOCs (volatile organic compounds), namely, Toluene, Formaldehyde and Trichloroethylene can be completely removed in the Cu₂O/TNAs PC process with rate constants (k_obs) of 2.08 × 10^-2, 3.11 × 10^-2, and 6.58 × 10^-2 min^-1, respectively, with the effort of the synergism of the photo-generated holes and hydroxyl radicals. Detail mechanism of hetero-junction Cu₂O/TNAs composite PC system was proposed to clarify the redox reaction.

Cu2 O-Catalyzed Conversion of Benzyl Alcohols Into Aromatic Nitriles via the Complete Cleavage of the C≡N Triple Bond in the Cyanide Anion

Nitrogen transfer from cyanide anion to an aldehyde is emerging as a promising method for the synthesis of aromatic nitriles. However, this method still suffers from a disadvantage that a use of stoichiometric Cu(II) or Cu(I) salts is required to enable the reaction. As we report herein, we overcame this drawback and developed a catalytic method for nitrogen transfer from cyanide anion to an alcohol via the complete cleavage of the C≡N triple bond using phen/Cu₂ O as the catalyst. The present condition allowed a series of benzyl alcohols to be smoothly converted into aromatic nitriles in moderate to high yields. In addition, the present method could be extended to the conversion of cinnamic alcohol to 3-phenylacrylonitrile.

Point-of-care testing of butyrylcholinesterase activity through modulating the photothermal effect of cuprous oxide nanoparticles

Butyrylcholinesterase (BChE) is an important indicator for clinical diagnosis of liver dysfunction, organophosphate toxicity, and poststroke dementia. Point-of-care testing (POCT) of BChE activity is still a challenge, which is a critical requirement for the modern clinical diagnose. A portable photothermal BChE assay is proposed through modulating the photothermal effects of Cu₂O nanoparticles. BChE can catalyze the decomposition of butyrylcholine, producing thiocholine, which further reduce and coordinate with CuO on surface of Cu₂O nanoparticle. This leads to higher efficiency of formation of Cu₉S₈ nanoparticles, through the reaction between Cu₂O nanoparticle and NaHS, together with the promotion of photothermal conversion efficiency from 3.1 to 59.0%, under the excitation of 1064 nm laser radiation. An excellent linear relationship between the temperature change and the logarithm of BChE concentration is obtained in the range 1.0 to 7.5 U/mL, with a limit of detection of 0.076 U/mL. In addition, the portable photothermal assay shows strong detection robustness, which endows the accurate detection of BChE in human serum, together with the screening and quantification of organophosphorus pesticides. Such a simple, sensitive, and robust assay shows great potential for the applications to clinical BChE detection and brings a new horizon for the development of temperature based POCT.

Imaging adsorption of iodide on single Cu2O microparticles reveals the acid activation mechanism

Imaging an adsorption reaction taking place at the single-particle level is a promising avenue for fundamentally understanding the adsorption mechanism. Here, we employ a dark-field microscopy (DFM) method for in situ imaging the adsorption process of I^- on single Cu₂O microparticles to reveal the acid activation mechanism. Using the time-lapsed DMF imaging, we find that a relatively strong acid is indispensable to trigger the adsorption reaction of I^- on single Cu₂O microparticle. A hollow microparticle with the increase in size is obtained after the adsorption reaction, causing the enhancement of the scattering intensity. Correlating the change of the scattering light intensity or particle size with adsorption capacity of I^-, we quantitatively analyze the selective uptake, slightly heterogeneous adsorption behavior, pH/temperature-dependent adsorption capacity, and adsorption kinetics as well as isotherms of individual Cu₂O microparticles for I^-. Our observations demonstrate that the acid-initiated Kirkendall effect is responsible for the high-reaction activity of single Cu₂O microparticles for adsorption of I^- in the acidic environment, through breaking the unfavorable lattice energy between Cu₂O and CuI as well as generating high-active hollow intermediate microparticle.

Hollow Cu2O nanospheres loaded with MoS2/reduced graphene oxide nanosheets for ppb-level NO2 detection at room temperature

Low energy consumption, high sensing response and high selectivity are the important indexes of metal oxide semiconductor (MOS) gas sensors applied in many application fields. However, the high working temperature and poor selectivity of MOS sensors severely restrict their scope of application in the Internet of Things (IoT). Herein, ternary MoS₂-rGO-Cu₂O (MG-Cu) composites with boosting ppb-level NO₂ sensing characteristics are synthesized by combining hydrothermal method and soft-template method. The optimal proportion of MoS₂, rGO and Cu₂O is systematically explored. The SEM and TEM analyses confirm the hollow Cu₂O is anchored on the surface of MG. The gas sensing tests illustrate that optimum composite sensor exhibits highest response to 500 ppb NO₂ at room temperature, which is 11 and 5 times higher compared to pure MoS₂ and binary MG15, respectively. Besides, it displays excellent selectivity and superior stability. The synergy of shell-structure with abundant mesoporous, heterojunction construction and enhanced conductivity lead to the enhanced sensing performance of ternary sensor.

In-situ growth of Cu(2-methylimidazole imidazole)2 on Cu2O polyhedrons for high-performance potassium-ion batteries

In this work, Cu₂O/Cu(2-MeIm)₂ core-shell structure was designed and used as an anode for potassium-ion batteries. The Cu₂O core not only ensured a high energy density through surface redox reactions, but also served as a copper-ion reservoir to keep the stability of skeleton structure of Cu(2-MeIm)₂ shell during electrochemical process. The Cu(2-MeIm)₂ shell, in turn, not only provided high power through rapid K⁺ adsorption/desorption, but also acted as an artificial solid electrolyte interphase layer and accommodated volumetric change during K⁺ intercalation/de-intercalation. The as-designed composite material was studied by X-ray diffraction, thermo gravimetric, Fourier transform infrared, nitrogen adsorption-desorption, X-ray photoelectron spectroscopic and electron microscopic characterizations. As an anode for potassium-ion batteries, it was galvanostatically discharged and charged to study its electrochemical properties, such as Coulombic efficiency, capacity retention and rate performance, and cyclic voltammetry curves were also tested to reveal its K-storage mechanism.

Infection microenvironment-activated nanoparticles for NIR-II photoacoustic imaging-guided photothermal/chemodynamic synergistic anti-infective therapy

Subcutaneous abscesses caused by drug-resistant bacteria pose huge challenges to human health. The design of infection microenvironment-activated biomaterials has an advantage for the diagnosis and treatment of infective diseases due to its high specificity and efficiency. Herein, a novel theranostic platform based on Cu₂O nanoparticles (NPs) is successfully constructed via a simple, fast and low-cost approach. The Cu₂O NPs exhibit high sensitivity to overexpressed H₂S and H₂O₂ in the bacterial infection microenvironment. After in situ injection, the Cu₂O NPs will rapidly react with the endogenous H₂S to generate Cu₉S₈ NPs, which exhibits high absorbance in the second near-infrared (NIR-II) biowindow. The Cu₉S₈ NPs serving as NIR-II photoacoustic contrast agents can exactly distinguish between inflammatory and normal tissues. With the guidance of NIR-II photoacoustic imaging (PAI), H₂S-activated photothermal antibacterial therapy (PTAT) can realize excellent antibacterial performance under 1060 nm laser irradiation. Meanwhile, the Cu₂O NPs can effectively catalyze H₂O₂ at the site of inflammation to produce hydroxyl radicals with strong antibacterial property via Fenton-like reaction, resulting in the damage of bacterial cell membrane. Furthermore, the application of Cu₂O NPs can enhance epidermic migration and facilitate the re-epithelialization of the infected skin. In vivo experiment shows that 97.9% methicillin-resistant Staphylococcus aureus are eliminated by the synergistic PTAT and chemodynamic antibacterial therapy.

Cotton decorated with Cu2O-Ag and Cu2O-Ag-AgBr NPs via an in-situ sacrificial template approach and their antibacterial efficiency

Cotton fabrics decorated with Cu₂O-Ag and Cu₂O-Ag-AgBr NPs have been prepared using chemically immobilized Cu₂O NPs as sacrificial templates. The objective is to prepare Cu₂O-Ag heterostructures with Ag being intimately in contact with Cu₂O NPs by galvanic replacement reactions without addition of any external reducing agent. Field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analysis were used to study the morphology and the chemical composition of the nanocomposites formed on the fabrics. The morphology of the ensuing nanostructures was shown to be dependent on the Ag precursor, AgNO₃, concentration. The antimicrobial activity of the treated fabrics was evaluated against Staphylococcus aureus and Escherichia coli as model strains of gram-negative and gram-positive, respectively. The results showed that the fabrics loaded with Cu₂O-Ag and Cu₂O-Ag-AgBr nanocomposites exhibited enhanced sterilization activity compared to the Cu₂O treated fabric.

Unveiling the Synergistic Effect between Graphitic Carbon Nitride and Cu2 O toward CO2 Electroreduction to C2 H4

Electrochemically reducing carbon dioxide (CO₂ RR) to ethylene is one of the most promising strategies to reduce carbon dioxide emissions and simultaneously produce high value-added chemicals. However, the lack of catalysts with excellent activity and stability limits the large-scale application of this technology. In this work, a graphitic carbon nitride (g-C₃ N₄ )-supported Cu₂ O composite was fabricated, which exhibited a 32.2 % faradaic efficiency of C₂ H₄ with a partial current density of -4.3 mA cm^-2 at -1.1 V vs. reversible hydrogen electrode in 0.1 m KHCO₃ electrolyte. The introduction of g-C₃ N₄ support not only enhanced the uniform dispersion of Cu₂ O nanocubes, but also stabilized the important *CO intermediates. Moreover, the g-C₃ N₄ itself had a good activity of reducing CO₂ to form *CO, which enriched the key intermediates of C-C coupling around cuprous oxide. The findings highlight the importance of the g-C₃ N₄ support, a unique two-dimensional material, including not only the strong CO₂ adsorption and activation capacity but also its synergistic effect with the cuprous oxide in CO₂ RR selectivity.

In-situ synthesis of Cu2O on cotton fibers with antibacterial properties and reusable photocatalytic degradation of dyes

In this study, the cotton fabrics/cuprous oxide-nanocellulose (Cu₂O-NC) flexible and recyclable composite material (COCO) with highly efficient photocatalytic degradation of dyes and antibacterial properties was fabricated. Using flexible cotton fabrics as substrates, Cu₂O were in-situ synthesized to make Cu₂O uniformly grew on cotton fibers and were wrapped with NC. The photocatalytic degradation ability of COCO-5 was verified by use methylene blue (MB), the degradation rate was as high as 98.32%. The mechanism of COCO-5 photocatalysis and the process of dye degradation were analyzed by using electron paramagnetic resonance (EPR) spectrum, transient photocurrent response (TPR) spectrum, Fourier transform infrared (FTIR) spectroscopy and ion chromatography (IC). This study analyzed the complete path from electron excitation to dye degradation to harmless small molecules. Qualitative and quantitative experiments demonstrate that COCO-5 has high antibacterial activity against S. aureus and E. coli, the highest antibacterial rate can reach 93.25%. Finally, the stability of COCO-5 was verified by recycling and mechanical performance tests. The textile-based Cu₂O functionalized material has photocatalytic degradation and antibacterial properties, and the preparation process is simple and convenient for repeated use, so it has great potential in wastewater treatment containing dyes and bacteria.

Electrochemical removal of anodic aluminium oxide templates for the production of phase-pure cuprous oxide nanorods for antimicrobial surfaces

Antimicrobial surfaces are ones that incapacitate or kill pathogens landing on them, which could allow for self-sanitising surfaces for hospitals or implants, ensuring healthier stays and procedures. Cuprous compounds such as Cu₂O are especially effective at incapacitating both viruses and bacteria, and nanorod arrays have been shown to prevent the adhesion of pathogens and mechanically deform bacteria to the point that their cell walls rupture. A Cu₂O nanorod array should therefore allow for the exploitation of both of these effects. In the present work, an electrochemical method is introduced, where Cu₂O nanorods formed in a substrate-supported anodic aluminium oxide (AAO) template are held at a stable electrochemical potential throughout the removal of the AAO template. This avoids the partial reduction of the nanorods from Cu₂O to Cu that was observed during chemical removal of the template, which was attributed to the presence of residual aluminium from the template fabrication process that reacts with the etchant and lowers the electrochemical potential of the nanorods to a value that favours reduction. Using the electrochemical removal method, the reliable production of phase-pure, free-standing, crystalline Cu₂O nanorod arrays on ITO/glass substrates is demonstrated. This simple method is compatible with nanorod arrays of any size.

Controlled self-template synthesis of manganese-based cuprous oxide nanoplates towards improved fire safety properties of epoxy composites

To date epoxy resins have been extensively used in the field of chemical engineering, aerospace and building materials. Nevertheless, the utilization of flammable epoxy resins has posed a huge threat to lives and properties, which restricted their applications. In this work, manganese-based cuprous oxides two-dimensional nanosheets (Mn@Cu₂O-M) are rationally designed and successfully prepared to improve the toxic effluent elimination of epoxy resin. The fire safety properties of the prepared Mn@Cu₂O-M based nanocomposites improved the heat release rate (<35 %) and total heat release (<40 %) compared to the control epoxy. Moreover, the production of smoke and toxic volatiles of the composites with Mn@Cu₂O-M nanosheets is significantly reduced. The mechanism investigations indicate that the improved flame retardancy and toxic effluent elimination of epoxy composites are attributed to the physical barrier effect and catalytic carbonization awarded by Mn@Cu₂O-M nanosheets during burning. This work provides a promising strategy to develop eco-friendly, efficient and fire-safe polymers by both physical barrier effect and catalytic carbonization.

Structure-dependent catalysis of cuprous oxides in peroxymonosulfate activation via nonradical pathway with a high oxidation capacity

Research interests have been recently thrust into the nonradical reactions in persulfate-based advanced oxidation processes (AOPs), whilst the underlying mechanism of the nonradical pathway remains ambiguous especially in metal-based AOPs systems. In this study, we investigated the reactivity of cuprous oxide (Cu₂O) for activating peroxymonosulfate (PMS) to decompose diverse organic contaminants. Cu₂O exhibited a strong catalytic dependence on the crystal morphology, and cubic Cu₂O was more reactive than the octahedral and rhombic dodecahedral structures for catalytic degradation of bisphenol A with PMS. Chemical quenching tests, electron paramagnetic resonance (EPR), solvent exchange and selective oxidation experiment were corporately conducted to illustrate that Cu₂O-catalyzed PMS did not produce free radicals or singlet oxygen. In contrast, a surface-confined metastable intermediate would be formed via outer-sphere interactions between PMS and Cu₂O, which directly attacked the organic substrate. Such a reaction pathway is intrinsically distinct from the electron-shuttling regime in carbon (or noble metal)/persulfate systems via the conductive surface of the catalyst, and the outer-sphere interactions let the activated PMS demonstrate a higher oxidizing capacity toward organic contaminants. Therefore, this study dedicates to providing new insights into the copper-catalyzed AOPs and vital supplementary to the ongoing dialogue of the nonradical catalysis in persulfate-based oxidation.

Facile Preparation of Carbon Nanotube-Cu2O Nanocomposites as New Catalyst Materials for Reduction of P-Nitrophenol

The effective synthesis and self-assembly of nanocomposites were of key importance for a broad range of nanomaterial applications. In this work, new carbon nanotube (CNT)-Cu2O nanocomposites were successfully synthesized via a facile approach. CNT was selected as the anchoring substrate to load Cu2O nanoparticles to prepare composite catalysts with well stability and good reusability. It is discovered that the prepared CNT-Cu2O nanocomposite materials could be effectively controlled via regulating preparation temperature and time without the use of any stabilizing agents. The nanostructures of synthesized composites were well characterized by many techniques, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). And the prepared CNT-Cu2O nanocomposites with optimized preparation conditions as new catalyst displayed excellent catalytic performance on the reduction reaction of p-nitrophenol, demonstrating potential applications for environmental governance and composite materials.

Electrochemical Reduction of CO2 on Hollow Cubic Cu2O@Au Nanocomposites

Surfactant-free and low Au loading Cu₂O@Au and Au hollow cubes, based on electrodeposited Cu₂O cubes as sacrificed templates, were prepared by means of a galvanic replacement reaction (GRR). The electrocatalytical performance of the as-prepared catalysts towards carbon dioxide (CO₂) electrochemical reduction was evaluated. The experimental results show that Cu₂O@Au catalyst can convert CO₂ to carbon monoxide (CO) with a maximum Faradaic efficiency (FE) of ~ 30.1% at the potential of - 1.0 V (vs. RHE) and is about twice the FE of the other catalysts at the same potential. By comparison, such electrocatalytical enhancement is attributed to the metal-oxide interface in Cu₂O@Au.

Growth of Cuprous Oxide Particles in Liquid-Phase Synthesis Investigated by X-ray Laser Diffraction

Cuprous oxide (Cu₂O) particles obtained by surfactant-assisted liquid-phase synthesis have cuboid shapes but the internal structures are difficult to be visualized by electron microscopy. Herein, we investigated the internal structures of numerous individual Cu₂O particles with submicrometer dimensions by X-ray diffraction imaging (XDI) using X-ray free-electron laser (XFEL) pulses. The reconstructed two-dimensional electron density maps, which displayed inhomogeneous internal structures, were divided into five classes characterized by the positions and shapes of high and low electron density areas. Further analysis of the maps in each class by a manifold learning algorithm revealed that the internal structures of Cu₂O particles varied in correlation with total electron density while retaining the characteristics within each class. On the basis of the analyses, we proposed a growth mechanism to yield the inhomogeneity in the internal structures of Cu₂O particles in surfactant-mediated liquid-phase synthesis.

Effect of cuprous oxide with different sizes on thermal and combustion behaviors of unsaturated polyester resin

Cuprous oxide (Cu₂O) as an effective catalyst has been applied to enhance the fire safety of unsaturated polyester resin (UPR), but the particle size influence on combustion behaviors has not been previously reported. Herein, the UPR/Cu₂O composites (metal oxide particles with average particle-size of 10, 100, and 200nm) were successfully synthesized by thermosetting process. The effects of Cu₂O with different sizes on thermostability and combustion behaviors of UPR were characterized by TGA, MCC, TG-IR, FTIR, and SSTF. The results revel that the addition of Cu₂O contributes to sufficient decomposition of oxygen-containing compounds, which is beneficial to the release of nontoxic compounds. The smallest-sized Cu₂O performs the excellent catalytic decomposition effect and promotes the complete combustion of UPR, which benefits the enhancement of fire safety. While the other additives retard pyrolysis process and yield more char residue, and thus the flame retardancy of UPR composites was improved. Therefore, catalysis plays a major role for smaller-sized particles during thermal decomposition of matrix, while flame retarded effect became gradual distinctly for the larger-sized additives.

Flower-like MoS2 decorated with Cu2O nanoparticles for non-enzymatic amperometric sensing of glucose

In this study, a novel nanohybrid consisting of flower-like MoS₂ decorated with Cu₂O nanoparticles has been successfully synthesized for non-enzymatic amperometric sensing of glucose. Structural characterizations revealed that Cu₂O nanoparticles were highly dispersed on MoS₂ nanosheets. Electrochemical performances were investigated by cyclic voltammetry (CV) and chronoamperometry. Compared to single Cu₂O component, the-synthesized Cu₂O/MoS₂ nanohybrid showed superior electrocatalysis to the oxidation of glucose. The fabricated non-enzymatic amperometric glucose sensor exhibited a wide linear range from 0.01 to 4.0mM with a low detection limit of 1.0µM (S/N =3) and a high sensitivity of 3108.87μAmM^-1cm^-2. Meanwhile, the non-enzymatic sensor also possesses satisfactory stability, good reproducibility and high selectivity to interfering components of uric acid, dopamine and ascorbic acid. The excellent analytical performances are resulted from the synergistic effect provided by the Cu₂O nanoparticals and MoS₂ nanosheets.

In situ loading ultra-small Cu2O nanoparticles on 2D hierarchical TiO2-graphene oxide dual-nanosheets: Towards reducing fire hazards of unsaturated polyester resin

Fire hazards have seriously hindered the commercial application of unsaturated polyester resin (UPR), and polymer inorganic nanosheet nanocomposites hold great promise in improving their flame-retardant properties. Herein, the hierarchical structured Cu₂OTiO₂GO nanosheets were synthesized and characterized by XRD, Raman, TEM and XPS. Then Cu₂OTiO₂GO nanosheets were incorporated into UPR matrix to obtain flame-retardant UPR nanocomposite. Incorporation of 2wt% Cu₂OTiO₂GO nanosheets into UPR matrix resulted in an obvious reduction in PHRR and THR by 29.7 and 19.1%. TG-IR-MS results revealed that toxic pyrolysis gas such as benzene, CO and aromatic compounds greatly were decreased. In addition, RIIR spectra demonstrated the limited influence of Cu₂OTiO₂GO nanosheets on thermal degradation of UPR matrix, and SEM images of char residues showed that Cu₂OTiO₂GO nanosheets could improve their compactness. Based on the analysis of gaseous and condensed phase, a plausible flame-retardant mechanism was hypothesized to elaborate how Cu₂OTiO₂GO nanosheets work inside the flaming UPR nanocomposite. This innovative idea may be expanded to other polymer system and open a new door to develop polymeric nanocomposites with high performance.

N-type Cu2O doped activated carbon as catalyst for improving power generation of air cathode microbial fuel cells

A novel n-type Cu2O doped activated carbon (AC) air cathode (Cu/AC) was developed as an alternative to Pt electrode for oxygen reduction in microbial fuel cells (MFCs). The maximum power density of MFCs using this novel air cathode was as high as 1390±76mWm(-2), almost 59% higher than the bare AC air cathode. Specifically, the resistance including total resistance and charge transfer resistance significantly decreased comparing to the control. Tafel curve also showed the faster electro-transfer kinetics of Cu/AC with exchange current density of 1.03×10(-3)Acm(-2), which was 69% higher than the control. Ribbon-like Cu2O was deposited on the surface of AC with the mesopore surface area increasing. Cubic Cu2O crystals exclusively expose (111) planes with the interplanar crystal spacing of 2.48Å, which was the dominate active sites for oxygen reduction reaction (ORR). N-type Cu2O with oxygen vacancies played crucial roles in electrochemical catalytic activity.

Surfactant-free synthesis of Cu2O hollow spheres and their wavelength-dependent visible photocatalytic activities using LED lamps as cold light sources

A facile synthesis route of cuprous oxide (Cu2O) hollow spheres under different temperatures without the aid of a surfactant was introduced. Morphology and structure varied as functions of reaction temperature and duration. A bubble template-mediated formation mechanism was proposed, which explained the reason of morphology changing with reaction temperature. The obtained Cu2O hollow spheres were active photocatalyst for the degradation of methyl orange under visible light. A self-designed equipment of light emitting diode (LED) cold light sources with the wavelength of 450, 550, and 700 nm, respectively, was used for the first time in the photocatalysis experiment with no extra heat introduced. The most suitable wavelength for Cu2O to photocatalytic degradation is 550 nm, because the light energy (2.25 eV) is closest to the band gap of Cu2O (2.17 eV). These surfactant-free synthesized Cu2O hollow spheres would be highly attractive for practical applications in water pollutant removal and environmental remediation.