Shape control mechanism of cuprous oxide nanoparticles in aqueous colloidal solutions

Electrochemiluminescence quenching effect of Cu2O towards flower-like ferric ion-doped g-C3N4 and its application for Cyfra21-1 immunosensing

In this article, ferric ion-doped floral graphite carbon nitride (Fe-CN-3, energy donor) was used to construct the substrate of the immunosensor and copper oxide nanocubes (Cu2O, energy acceptor) were taken as an efficient ECL quenching probe. A sandwich quench electrochemiluminescence (ECL) immunosensor for soluble cytokeratin 19 fragment (Cyfra21-1) detection was preliminarily developed based on a novel resonant energy transfer donor-acceptor pair. Fe-CN-3, a carbon nitride that combines the advantages of metal ion doping as well as morphology modulation, is used in ECL luminophores to provide more excellent ECL performance, which makes a significant contribution to the application and development of carbon nitride in the field of ECL biosensors. The regular shape, high specific surface area and excellent biocompatibility of the quencher Cu2O nanocubes facilitate the labeling of secondary antibodies and the construction of sensors. Meanwhile, as an energy acceptor, the UV absorption spectrum of Cu2O can overlap efficiently with the energy donor's ECL emission spectrum, making it prone to the occurrence of ECL-RET and thus obtaining an excellent quenching effect. These merits of the donor-acceptor pair enable the sensor to have a wide detection range of 0.00005-100 ng/mL and a low detection limit of 17.4 fg/mL (S/N = 3), which provides a new approach and theoretical basis for the clinical detection of lung cancer.

Anionic Coordination Control in Building Cu-Based Electrocatalytic Materials for CO2 Reduction Reaction

Renewable energy-driven conversion of CO2 to value-added fuels and chemicals via electrochemical CO2 reduction reaction (CO2RR) technology is regarded as a promising strategy with substantial environmental and economic benefits to achieve carbon neutrality. Because of its sluggish kinetics and complex reaction paths, developing robust catalytic materials with exceptional selectivity to the targeted products is one of the core issues, especially for extensively concerned Cu-based materials. Manipulating Cu species by anionic coordination is identified as an effective way to improve electrocatalytic performance, in terms of modulating active sites and regulating structural reconstruction. This review elaborates on recent discoveries and progress of Cu-based CO2RR catalytic materials enhanced by anionic coordination control, regarding reaction paths, functional mechanisms, and roles of different non-metallic anions in catalysis. Finally, the review concludes with some personal insights and provides challenges and perspectives on the utilization of this strategy to build desirable electrocatalysts.

Shape-controlled synthesis of micro-/nanosized Cu particles with spherical and polyhedral shapes using the polyol process

This study reports the synthesis of Cu micro-/nanosized particles through the polyol process. Cu particles were synthesized by reducing copper(ii) chloride in ethylene glycol (EG), polyvinylpyrrolidone (PVP), and potassium bromide (KBr) at low temperatures with or without the use of sodium borohydride (NaBH4).

Antimicrobial Activity of Morphology-Controlled Cu2O Nanoparticles: Oxidation Stability under Humid and Thermal Conditions

Metal oxides can be used as antimicrobial agents, especially since they can be fabricated into various forms such as films, masks, and filters. In particular, the durability of antimicrobial agents and the duration of their antimicrobial activity are important factors that determine their suitability for a specific purpose. These factors are related to the morphology and size of particles. The metal oxide Cu2O is often oxidized to CuO in various conditions, which reduces its antimicrobial activity. This study focused on the oxidation of nanoparticles of Cu2O with three morphologies, namely, spherical, octahedral, and cubic morphologies, in excessively humid and excessive-thermal environments for a specific duration and the antimicrobial activity of the NPs. Cu2O nanoparticles were prepared using the chemical reduction method, and their morphology could be varied by adjusting the molar ratio of OH- to Cu2+ and changing the reducing agent. It was found that cubic Cu2O was the most stable against oxidation and had the smallest reduction in antimicrobial activity. This study examined the antimicrobial activity and the oxidation stability of Cu2O NPs with different morphologies but similar particle sizes.

Nanoparticles with cubic symmetry: classification of polyhedral shapes

Structural studies of polyhedral bodies can help to analyze geometric details of observed crystalline nanoparticles (NP) where we consider compact polyhedra of cubic point symmetry as simple models. Their surfaces are described by facets with normal vectors along selected Cartesian directions (a, b, c) together with their symmetry equivalents forming a direction family {abc}. Here we focus on polyhedra with facets of families {100}, {110}, and {111}, suggested for metal and oxide NPs with cubic lattices. Resulting generic polyhedra, cubic, rhombohedral, octahedral, and tetrahexahedral, have been observed as NP shapes by electron microscopy. They can serve for a complete description of non-generic polyhedra as intersections of corresponding generic species, not studied by experiment so far. Their structural properties are shown to be fully determined by only three parameters, facet distancesR100,R110, andR111of the three facet types. This provides a novel phase diagram to systematically classify all corresponding polyhedra. Their structural properties, such as shape, size, and facet geometry, are discussed in analytical and numerical detail with visualization of typical examples. The results may be used for respective NP simulations but also as a repository stimulating the structural interpretation of new NP shapes to be observed by experiment.

Gemini ionic liquid-based surfactants: efficient synthesis, surface activity, and use as inducers for the fabrication of Cu2O nanoparticles

Discovery of green and novel synthetic routes for nanoparticles (NPs) has drawn a lot of interest due to the distinct nano size and unusual features as well as applications of such particles. Ionic liquid-based surfactants (ILBSs) and gemini ionic liquid-based surfactants (GILBSs) have become some of the best choices to be used as inducers or dispersing agents for the fabrication of nanoparticles. This work involves the synthesis, spectroscopic characterization, and surface property evaluation of three novel GILBSs (4a-c), which incorporate the imidazolium cation as the polar head with an ethylene spacer. The simple synthetic route includes, first, alkylating imidazole-N1 with the as-prepared fatty alkyl chloroacetates followed by quaternization of two equivalents of imidazole-N2 with ethylene dibromide. Investigations into the compounds' surface characteristics and thermodynamic parameters were carried out. The prepared GILBSs, 4a-c, were then used as inducers at various concentrations for the preparation of cuprous oxide nanoparticles. The size and shape of the produced NPs were examined by X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis in each case to study the effect of concentration on the NP morphology and to determine the best concentration for the NPs fabrication. The XRD patterns of the produced Cu2O NPs contain distinguishable peaks, which refer to crystalline Cu2O. Also, TEM images show that the obtained Cu2O is present in form of well dispersed nanorod particles with sizes about 55 and 23 nm at concentrations of 60 and 200 ppm, respectively.

Synthesis of Cu2O Nanoparticles by Ellipse Curve Micromixer

Micromixers offer the advantage of rapid and homogeneous mixing compared with conventional macroscale reaction systems, and thus they show great potential for the synthesis of nanoparticles. An ellipse curve serpentine micromixer, which had been proposed in our prior works was employed to synthesize Cu2O nanoparticles. Cu2O are excellent photocatalysts that have been widely utilized in the degradation of organic dyes. Owing to the excellent mixing performance, the reduction of Cu(OH)2 in micromixing synthesis was more sufficient than that in conventional stirring synthesis. The Cu2O nanoparticles synthesized by micromixing had smaller size and narrower size distribution compared with those synthesized by stirring in a beaker. The smallest Cu2O nanoparticles were obtained by micromixing with Re = 100 at T = 60 °C, while the most uniform Cu2O nanoparticles were obtained at T = 80 °C owing to Ostwald ripening. Through the photocatalytic degradation experiments of Rhodamine B, the Cu2O nanoparticles synthesized by micromixing were found to have better photocatalysis than those synthesized by stirring. The research results showed that the micromixing synthesis was a more suitable choice to produce Cu2O nanoparticles with excellent photocatalysis. The ellipse curve micromixer with a simple structure and high mixing performance can be applied in the synthesis of various nanoparticles.

A Review on Cu2O-Based Composites in Photocatalysis: Synthesis, Modification, and Applications

Photocatalysis technology has the advantages of being green, clean, and environmentally friendly, and has been widely used in CO₂ reduction, hydrolytic hydrogen production, and the degradation of pollutants in water. Cu₂O has the advantages of abundant reserves, a low cost, and environmental friendliness. Based on the narrow bandgap and strong visible light absorption ability of Cu₂O, Cu₂O-based composite materials show infinite development potential in photocatalysis. However, in practical large-scale applications, Cu₂O-based composites still pose some urgent problems that need to be solved, such as the high composite rate of photogenerated carriers, and poor photocatalytic activity. This paper introduces a series of Cu₂O-based composites, based on recent reports, including pure Cu₂O and Cu₂O hybrid materials. The modification strategies of photocatalysts, critical physical and chemical parameters of photocatalytic reactions, and the mechanism for the synergistic improvement of photocatalytic performance are investigated and explored. In addition, the application and photocatalytic performance of Cu₂O-based photocatalysts in CO₂ photoreduction, hydrogen production, and water pollution treatment are discussed and evaluated. Finally, the current challenges and development prospects are pointed out, to provide guidance in applying Cu₂O-based catalysts in renewable energy utilization and environmental protection.

Structural Reconstruction of Cu2 O Superparticles toward Electrocatalytic CO2 Reduction with High C2+ Products Selectivity

Structural reconstruction is a process commonly observed for Cu-based catalysts in electrochemical CO₂ reduction. The Cu-based precatalysts with structural complexity often undergo sophisticated structural reconstruction processes, which may offer opportunities for enhancing the electrosynthesis of multicarbon products (C₂₊ products) but remain largely uncertain due to various new structural features possibly arising during the processes. In this work, the Cu₂ O superparticles with an assembly structure are demonstrated to undergo complicated structure evolution under electrochemical reduction condition, enabling highly selective CO₂ -to-C₂₊ products conversion in electrocatalysis. As revealed by electron microscopic characterization together with in situ X-ray absorption spectroscopy and Raman spectroscopy, the building blocks inside the superparticle fuse to generate numerous grain boundaries while those in the outer shell detach to form nanogap structures that can efficiently confine OH^- to induce high local pH. Such a combination of unique structural features with local reaction environment offers two important factors for facilitating C-C coupling. Consequently, the Cu₂ O superparticle-derived catalyst achieves high faradaic efficiencies of 53.2% for C₂ H₄ and 74.2% for C₂₊ products, surpassing the performance of geometrically simpler Cu₂ O cube-derived catalyst and most reported Cu electrocatalysts under comparable conditions. This work provides insights for rationally designing highly selective CO₂ reduction electrocatalysts by controlling structural reconstruction.

Copper Oxide-Based Photocatalysts and Photocathodes: Fundamentals and Recent Advances

This work aims at reviewing the most impactful results obtained on the development of Cu-based photocathodes. The need of a sustainable exploitation of renewable energy sources and the parallel request of reducing pollutant emissions in airborne streams and in waters call for new technologies based on the use of efficient, abundant, low-toxicity and low-cost materials. Photoelectrochemical devices that adopts abundant element-based photoelectrodes might respond to these requests being an enabling technology for the direct use of sunlight to the production of energy fuels form water electrolysis (H2) and CO2 reduction (to alcohols, light hydrocarbons), as well as for the degradation of pollutants. This review analyses the physical chemical properties of Cu2O (and CuO) and the possible strategies to tune them (doping, lattice strain). Combining Cu with other elements in multinary oxides or in composite photoelectrodes is also discussed in detail. Finally, a short overview on the possible applications of these materials is presented.

Effect of the Concentration and the Type of Dispersant on the Synthesis of Copper Oxide Nanoparticles and Their Potential Antimicrobial Applications

The bactericidal properties of copper oxide nanoparticles have growing interest due to potential application in the medical area. The present research investigates the influence of sodium dodecyl sulfate (SDS) and poly(vinylpyrrolidone) (PVP) on the production of copper oxide nanoparticles prepared from copper sulfate (CuSO₄) and sodium borohydride (NaBH₄) solutions. Different analytical techniques were used to determine the crystal nature, mean size diameter, and surface morphology of the copper oxide nanoparticles. The X-ray diffraction (XRD) patterns showed formation of nanoparticles of cuprite (Cu₂O) and tenorite (CuO) when PVP and SDS were added at the beginning of the reaction. In fact, when the Cu/PVP ratio was 1.62, Cu₂O nanoparticles were obtained. In addition, nanoparticles of CuO were synthesized when the Cu/PVP ratios were 0.54 and 0.81. On the other hand, a mixture of copper oxides (CuO and Cu₂O) and cuprite (Cu₂O) was obtained when PVP (Cu/PVP = 0.81 and 1.62) and SDS (Cu/SDS = 0.90) were added 30 min after the beginning of the reaction. Transmission electron microscopy (TEM) images show agglomerated nanoparticles with a size distribution ranging from 2 to 60 nm, while individual particles have sizes between 4.1 ± 1.9 and 41.6 ± 12.8 nm. The Kirby-Bauer method for the determination of antibacterial activity shows that small CuO (4.1 ± 1.9 nm) and Cu₂O (8.5 ± 5.3 nm) nanoparticles inhibit the growth of Escherichia coli, Staphylococcus aureus MRSA, S. aureus and Pseudomonas aeruginosa bacteria. The antibacterial test of cotton fabric impregnated with nanoparticles shows positive results. The determination of the optimal ratio of copper oxide nanoparticles per cm² of fabric that are able to exhibit a good antibacterial activity is ongoing.

Biogenic-Mediated Synthesis of Mesoporous Cu2O/CuO Nano-Architectures of Superior Catalytic Reductive towards Nitroaromatics

Cu₂O/CuO nano-architectures were prepared by biogenic-mediated synthesis using pomegranate seeds extract as the reducing/stabilizing mediator during an aqueous solution combustion process of the Cu²⁺ precursor. The fabricated Cu₂O/CuO nanocomposite were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM) and nitrogen sorption. Nitrobenzene (NB) was applied a probe to test the catalytic activities of the fabricated Cu₂O/CuO nanocomposite. The results indicated that pomegranate seeds extract (PSE) manifest Cu₂O/CuO NPs of tiny particle size, larger pore volume and greater surface area compared to the bulky CuO synthesized in the absence of PSE. The surface area and total pore volume of Cu₂O/CuO NPs were 20.1 m² g⁻¹ and 0.0362 cm³ g⁻¹, respectively. The FESEM image shows the formation of broccoli-like architecture. The fabricated Cu₂O/CuO nanocomposite possesses surprising activity towards the reduction of nitro compounds in the presence of NaBH₄ into amino compounds with high conversion (94%). The reduction process was performed in water as a green solvent. Over four consecutive cycles the resulting nanocomposite also exhibits outstanding stability. In addition, the resulting Cu₂O/CuO nanocomposite suggested herein may encourage scientists to start preparing more cost-effective catalysts for marketing instead of complicated catalysts.

Aqueous-phase synthesis of nanoparticles of copper/copper oxides and their antifungal effect against Fusarium oxysporum

Different copper based-materials have been used for controlling some fungal and bacterial pathogens. However, the antifungal activity of the copper-based materials depends on different parameters, such as the crystal phase, synthesis route, and size of the particles. Herein a facile route synthesis method of Cu/Cu_xO-NPs was achieved through the aqueous phase. The influence of NaBH₄ concentration on the phase composition was studied. The synthesized Cu/Cu_xO-NPs were characterized by X-Ray diffraction (XRD), Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and dynamic light scattering. Five Cu/Cu_xO-NPs with different phase composition and nanoparticle size were obtained. The antifungal activity of the synthesized Cu/Cu_xO-NPs was studied in vitro against Fusarium oxysporum. The results indicate that a high percent of inhibition of radial growth (IGR) was obtained with NPs, which have a higher proportion of Cu₂O phase and relatively smaller size particles. Furthermore, hypha morphology, membrane damage and production of reactive oxygen species (ROS) was evaluated with SEM and confocal microscopy.

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.

Oriented Attachment Is a Major Control Mechanism To Form Nail-like Mn-Doped ZnO Nanocrystals

Here, we present a controlled synthesis of Mn-doped ZnO nanoparticles (NPs) with predominantly nail-like shapes, whose formation occurs via tip-to-base-oriented attachment of initially formed nanopyramids, followed by leveling of sharp edges that lead to smooth single-crystalline "nails". This shape is prevalent in noncoordinating solvents such as octadecene and octadecane. Yet, the double bond in the former promotes oriented attachment. By contrast, Mn-doped ZnO NP synthesis in a weakly coordinating solvent, benzyl ether, results in dendritic structures because of random attachment of initial NPs. Mn-doped ZnO NPs possess a hexagonal wurtzite structure, and in the majority of cases, the NP surface is enriched with Mn, indicating a migration of Mn²⁺ ions to the NP surface during the NP formation. When the NP formation is carried out without the addition of octadecyl alcohol, which serves as a surfactant and a reaction initiator, large, concave pyramid dimers are formed whose attachment takes place via basal planes. UV-vis and photoluminescence spectra of these NPs confirm the utility of controlling the NP shape to tune electro-optical properties.

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.

Synthesis and Evaluation of Some Phenol-Based Anionic Gemini Amphiphiles: Studying Their Influence in the Preparation of Cu2O nanoparticles

A series of phenol-based anionic gemini amphiphiles called α,ω-bis (m-dodecanoyl benzene sulfonate) with different spacers (C12-En-C12) where n = 1, 2, 3 has been synthesized via three steps of reaction: (1) acylation of phenol by dodecanoic acid using trifluromethane sulfonic acid as a catalyst, (2) tosylation of mono, di and triethylene glycol, then (3) coupling of tosylated ethylene glycols with acylated phenol, followed by sulphonation of the prepared compounds. The chemical structures of the prepared surfactants were confirmed using elementary analysis and different spectroscopic techniques including FTIR and 1H-NMR spectra. Also an evaluation of surface activity for the synthesized compounds has been determined including: surface and interfacial tension, foaming height, emulsification power, critical micelle concentration (CMC), effectiveness and efficiency. The prepared surfactants were used in the synthesis of cuprous oxide nanoparticles. The crystal structure, average particle size and morphology were investigated by X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM).

Synthesis of CuO and Cu2O nano/microparticles from a single precursor: effect of temperature on CuO/Cu2O formation and morphology dependent nitroarene reduction

CuO and Cu₂O micro/nanoparticles have been synthesized from same precursor in hydrothermal method by controlling temperature and morphology dependent nitroarenes reduction was studied with CuO nano/microparticles.

Colloidal Moderate-Refractive-Index Cu₂O Nanospheres as Visible-Region Nanoantennas with Electromagnetic Resonance and Directional Light-Scattering Properties

Moderate-refractive-index dielectric nano-spheres are found to possess strong electric and magnetic dipole resonances in the visible region. Owing to the overlap of the electric and magnetic dipole resonances, moderate-refractive-index dielectric nanospheres exhibit directional forward scattering at the strongest scattering peak. Such directional scattering is experimentally observed on colloidal Cu2O nanospheres, which are readily prepared through wet-chemistry methods.

Polymer directed aggregation and dispersion of anisotropic nanoparticles

The aggregation and dispersion of two anisotropic nanoparticles (NPs), cubes and tetrahedrons, in a polymer matrix are studied in this work using coarse-grained molecular dynamics simulations. We present the phase diagrams of NP-polymer composites, depicting microscopically phase-separated, dispersed, and bridged cubes and tetrahedrons in a polymer matrix, which depend on the interaction between the NPs and polymer (εnp), along with the NPs' volume fraction (ϕ). The microscopic phase separation occurs at very low εnp, where NPs self-organize into multidimensional structures, depending on ϕ. In particular, for tetrahedrons, a cross-over from an ordered spherical aggregate to a disordered sheet-like aggregate is observed with increasing ϕ. In the case of cubes, a transition from cubic array → square column → square array (sheet) is identified with increasing ϕ. The clusters of NPs are characterized by their asphericity and principal radii of gyration. The free energy profile for a structured assembly is estimated, which clearly shows that the successful assembly of NPs is energetically favorable at a lower temperature. However, there exists an energy barrier for the successful assembly of all the NPs in the system. At intermediate εnp, a transition from a clustered state to a state comprising dispersed cubes and tetrahedrons in a polymer matrix is observed. At higher εnp, a further transition takes place, where gas-like dispersed NPs form a liquid-like aggregate via polymer layers. Therefore, the findings in this work illustrate that the effective interaction between anisotropic NPs in a polymer matrix is very diverse, which can generate multidimensional structured assemblies, with the disordered clustering, dispersion, and bridging-induced aggregation of NPs.

Room temperature light-induced recrystallization of Cu2O cubes to CuO nanostructures in water

Visible light irradiation induces recrystallization of Cu₂O cubes to [010] growth-directed CuO nanoribbons in water due to the creation of active ˙OH and ˙O₂⁻ species and outward Cu diffusion along unstable {010} facets.

Phase diagram and structural diversity of a family of truncated cubes: degenerate close-packed structures and vacancy-rich states

Using Monte Carlo simulations and free-energy calculations, we determine the phase diagram of a family of truncated hard cubes, where the shape evolves smoothly from a cube via a cuboctahedron to an octahedron. A remarkable diversity in crystal phases and close-packed structures is found, including a fully degenerate crystal structure, several plastic crystals, as well as vacancy-stabilized crystal phases, all depending sensitively on the precise particle shape. Our results illustrate the intricate relation between phase behavior and building-block shape, and can guide future experimental studies on polyhedral-shaped nanoparticles.