Cu2O Crystals Research Articles

Full Spectrum Visible LED Light Activated Antibacterial System Realized by Optimized Cu2O Crystals.

Assisted by three-dimensional printing technology, we proposed and demonstrated a full spectrum visible light activated antibacterial system by using a combination of 500 nm sized Cu2O crystals and light-emitting diode (LED) lamps. Further improved antibacterial ratios were achieved, for the first time, with pure Cu2O for both Gram-positive bacteria and Gram-negative bacteria among all of the six different color LED lamps. For practical antibacterial applications, we revealed that the nonwoven fabric could act as excellent carrier for Cu2O crystals and provide impressive antibacterial performance. Furthermore, integrated with our self-developed app, the poly(ethylene terephthalate) film loaded with Cu2O crystals also showed significant antibacterial property, thus making it possible to be applied in field of touch screen. The present research not only provided a healthier alternative to traditional ultraviolet-based sterilization but also opened an auto-response manner to decrease the rate of microbial contamination on billions of touch screen devices.

Nonlinear optical properties of cubic cuprous oxide with different sizes

Cubic cuprous oxide (Cu2O) crystals with various sizes are successfully synthesized under room temperature by a simple solution-phase route. The surface morphology, structure properties and optical absorption spectrum of Cu2O crystals are characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and UV–visible absorption spectroscopy. The optical limiting (OL) properties of Cu2O crystals are investigated using a nanosecond laser at 532nm. The experimental results show that the OL properties of Cu2O crystals do not only come from nonlinear scattering, but also might be due to nonlinear absorption.

Oxidation Behavior of Copper at a Temperature below 300 °C and the Methodology for Passivation

In this study, we investigate the oxidation behavior of copper at temperatures below 300 °C and its mechanism. A methodology to slow down the oxidation rate is then proposed based on the observed mechanism. The oxides formed after oxidation at low temperatures have fine crystal sizes; the rate constants reach 2×10-15 m2/s and 6×10-14 m2/s at 200 °C and 300 °C, respectively. A passivation treatment at 600 °C in nitrogen produces a thin oxide layer composed of relatively large Cu2O crystals. The presence of such a layer slows down the oxidation rate constants by an order of magnitude. This study demonstrates that the oxidation of copper at low temperatures is controlled by the grain boundary diffusion. Increasing the crystal size in the surface oxide reduces the oxidation rate significantly.

Preparation of High quality Cu2O crystal and its opto-electronic properties

The growth condition, including annealing temperature, annealing time and cooling ambient on the crystal structure and opto-electronic properties of thermally oxidized polycrystalline Cu2O plate are systematically investigated. High vacuum cooling is efficient to eliminate the CuO impurity to improve the bulk mobility. Both high temperature and longtime annealing lead to preferential grow of (311) surface. Orientation dependent conductivity in a single grain is observed. Surface potential measurement reveals that the dependence is originated from the facet-dependent work function. The facet-dependent work function is also suggested to induce an energy barrier of tens of meV between grains, which explain the positive dependence of mobility on the grain size.

CuO Surfaces and CO2 Activation: A Dispersion-Corrected DFT+U Study

We have used computational methodology based on the density functional theory to describe both copper(I) and copper(II) oxides, followed by the investigation of a number of different low index CuO surfaces. Different magnetic orderings of all the surfaces were studied, and reconstructions of the polar surfaces are proposed. A detailed discussion on stabilities, electronic structure, and magnetic properties is presented. CuO(111) and CuO(111) were found to have the lowest surface energies, and their planes dominate in the calculated Wulff morphology of the CuO crystal. We next investigated the adsorption of CO2 on the three most exposed CuO surfaces, viz., (111), (111), and (011), by exploring various adsorption sites and configurations. We show that the CO2 molecule is activated on the CuO surfaces, with an adsorption energy of −93 kJ/mol on the (011) surface, showing exothermic adsorption, while (111) and (111) surfaces show comparatively weak adsorption. The activation of the CO2 molecule is characterized by large structural transformations and significant charge transfer, i.e., forming a negatively charged bent CO2–δ species with elongated C–O bonds, which is further confirmed by vibrational analyses showing considerable red shift in the frequencies as a result of the activation.

Influence of calcination temperature on CuO–CeO2/SiC catalysts for SO3 decomposition in the sulfur–iodine cycle for hydrogen production

The copper-cerium composite oxides supported on silicon carbide (SiC) catalysts (CuO–CeO2/SiC) for sulfuric acid decomposition were studied in sulfur-iodine (SI or IS) cycle. The influence of calcination temperatures (800 °C–1000 °C) of CuO–CeO2/SiC catalysts on their activities and morphology were investigated in this study. The activity of CuO–CeO2/SiC was prominently higher than that of CuO–CeO2 composite oxides catalyst. The SO3 conversion ratio of CuO–CeO2/SiC catalyst increased with calcination temperature from 800 °C to 900 °C, while decreased with calcination temperature at 900 °C–1000 °C. XRD pattern, TEM (HRTEM) images and Energy Dispersive X-ray (EDX) spectra revealed that copper–cerium composite oxides were well dispersed and immobilized on the surface of SiC grains. XRD pattern showed that the accelerated transformation of SiC crystals to amorphous SiO2 and the rapid expansion of CeO2 sub-grains at the calcination temperature of 900 °C–1000 °C, as well as the accelerated amorphization of CuO crystals at 800 °C–900 °C. The agglomeration of catalysts with sintering temperature was also proven by the BET test. At a higher calcination temperature, X-ray photoelectron spectroscopy (XPS) of Cu2p spectra revealed the reduction of more Cu2+ in the process of SiC oxidation. According to TEM (HRTEM), XPS, and infrared radiation, the amorphous SiO2 was produced by the oxidation of superficial SiC particles, and the thickness of the SiO2 layers on SiC grains increased with the calcination temperature. A simple mechanism depicted the oxidation of CuO–CeO2/SiC was created.

Copper Ion from Cu2O Crystal Induces AMPK-Mediated Autophagy via Superoxide in Endothelial Cells.

Copper is an essential element required for a variety of functions exerted by cuproproteins. An alteration of the copper level is associated with multiple pathological conditions including chronic ischemia, atherosclerosis and cancers. Therefore, copper homeostasis, maintained by a combination of two copper ions (Cu+ and Cu2+), is critical for health. However, less is known about which of the two copper ions is more toxic or functional in endothelial cells. Cubic-shaped Cu2O and CuO crystals were prepared to test the role of the two different ions, Cu+ and Cu2+, respectively. The Cu2O crystal was found to have an effect on cell death in endothelial cells whereas CuO had no effect. The Cu2O crystals appeared to induce p62 degradation, LC3 processing and an elevation of LC3 puncta, important processes for autophagy, but had no effect on apoptosis and necrosis. Cu2O crystals promote endothelial cell death via autophagy, elevate the level of reactive oxygen species such as superoxide and nitric oxide, and subsequently activate AMP-activated protein kinase (AMPK) through superoxide rather than nitric oxide. Consistently, the AMPK inhibitor Compound C was found to inhibit Cu2O-induced AMPK activation, p62 degradation, and LC3 processing. This study provides insight on the pathophysiologic function of Cu+ ions in the vascular system, where Cu+ induces autophagy while Cu2+ has no detected effect.

Shape Evolution of Cu2O Crystals Prepared by Surfactant-Free Electrodeposition

The preparation and characterization of Cu2O crystals by a simple surfactant-free electrodeposition are presented. The shape evolution of Cu2O crystals owing to the change of reaction time and PH is investigated. The shape and size of Cu2O crystals can be controlled simply by reaction time and PH without any surfactant in the electrodeposition. The Cu2O crystals obtained by the electrodeposition can be used in the organic/inorganic hybrid detectors and the films obtained can be used in organic/inorganic hybrid solar cells.

Polyhedron Cu2O@Ag composite microstructures: synthesis, mechanism analysis and structure-dependent SERS properties

The morphological evolution of polyhedral Cu2O crystals and the LSPR and SERS characteristics of the as-synthesized polyhedral Cu2O@Ag CMs with different structures.

The accelerating effect of silver ion on the degradation of methyl orange in Cu2O system

In this paper we reported an interesting phenomenon that additive Ag+ ion can rapidly and continuously capture the activated electrons which accumulated on the surface of as-prepared Cu2O catalyst, resulting in residual holes directly and rapidly reacting with methyl orange (MO) to be degraded. When 10−2M Ag+ was added rapidly into the suspension containing 800mg/L MO, the decolorizing rate immediately reached 38%, and rapidly increased to 88% in 30min. This accelerating effect of Ag+ ion on MO degradation was first observed in Cu2O system. Although the as-prepared Cu2O shows a very large particle size (∼2.2μm), it possesses loose crystal structure with rough multiple surfaces and various defect levels in the interior and on the surface to promote the massive accumulation and fast migration of electron and hole. As a result, when Ag+ ion was added into the suspension, it immediately reacted with the accumulated electron to turn into metallic Ag and deposited on the surface of Cu2O to form a core-shell structured catalyst Cu2O@Ag, resulting in fast degradation of MO via directly reacting with residual hole. The Schottky barriers which generate at the junctions of Cu2O and metallic Ag crystals can speed up the directional migration of electron and hole, resulting in effective separation of electron–hole pair. In addition, Cu2O@Ag catalyst shows strong light absorption in UV, vis and NIR region. These results indicate that the as-prepared Cu2O catalyst exhibits a very high photocatalytic activity in the case of adding high concentration Ag+ ion.

Structure-dependent activities of Cu2O cubes in thermal decomposition of ammonium perchlorate

Catalytic activity of three kinds of Cu2O cubes with different structures for thermal decomposition of ammonium perchlorate (AP) has been investigated in this paper. Cu2O crystals in the form of cubic aggregate, mono-dispersed cube and {100} planes etched cube have been synthesized through a microwave-assisted solvothermal method by adjusting the composition of solvent. The decomposition of AP in the presence or absence of Cu2O cubes has been investigated non-isothermally through thermogravimetry and differential scanning calorimetry (DSC). The data obtained from DSC have been applied for the calculation and comparison of the kinetic parameters of AP decomposition process through a model-free approach. The obtained kinetic parameters have been used to predict the reaction rate and progress of AP with Cu2O cubes under isothermal conditions or at temperature mode corresponding to real climate changes.

Comparative study of CuO crystals on the cellulose substrate by the microwave-assisted hydrothermal method and hydrothermal method

The purposes of this article were to investigate the influences of synthetic strategy on the CuO crystals using cellulose as substrate. Exploring the influences of different synthesis methods is of great importance for the understanding of the growth mechanism of CuO crystals. In this article, the products were characterized by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential thermal analysis (DTA), and cell cytotoxicity. Experimental results demonstrated the obvious differences in the CuO crystals between microwave-assisted hydrothermal and hydrothermal methods in the existence of cellulose. These researches do a favor for the understanding of growth mechanism of CuO crystals with different synthesis methods.

Control of CuO nanocrystal morphology from ultrathin “willow-leaf” to “flower-shaped” for increased hydrazine oxidation activity

Three CuO nanocrystal morphologies (willow-leaf, spiny, and flower-shaped) with different exposed crystal facets are prepared through a two-step liquid-phase procedure. The CuO crystals have high hydrazine oxidation reaction (HOR) activity and good stability. Flower-shaped CuO has the highest HOR activity and stability of the three forms, with a positive onset-potential of −0.14 V and a high oxidation peak current density of 5.23 mA cm−2. HOR activity of the CuO crystals correlates to the type of exposed crystalline facet.

ChemInform Abstract: Synthesis and Crystal Structure of Bi6 (Bi0.5Cu0.5)V2O15+y.

AbstractPolycrystalline Bi6 (Bi0.5Cu0.5)V2O15+y is prepared by heating a 3:1:1 molar mixture of Bi2O3, CuO, and V2O5 (750 °C, 12 h), and single crystals are grown from the polycrystalline product (Pt crucible, 1000 °C; cooling to 850 °C °C with a rate of 2 °C/h and to 750 °C with a rate of 5 °C/h).

Synthesis of cuprous oxide with morphological evolution from truncated octahedral to spherical structures and their size and shape-dependent photocatalytic activities

In this study, a facile room-temperature solution-chemical route has been developed to synthesize Cu2O crystals with various sizes and morphologies. Adjustment of feeding speed of the aqueous mixture of polyvinyl pyrrolidone (PVP) and ascorbic acid (AA) enables the Cu2O crystal morphology and size evolution. It is also interesting to find that, simple alteration of the feeding speed of AA aqueous solution enables the size of Cu2O crystals evolved, while the morphology of Cu2O crystals keep unchanged. These Cu2O crystals samples were used as photocatalysts for the decomposition of methyl orange (MO) under visible light irradiation. The results show that Cu2O spiny spheres with hierarchical structure exhibited superior photocatalytic activity compared with truncated octahedrons and spheres. In addition, the photocatalytic activity of truncated octahedral Cu2O can be greatly improved by decreasing the size of Cu2O particles. The work demonstrated a novel strategy for the shape and size-controlled synthesis of Cu2O crystals with superior photocatalytic activities.

Epoxidation of propylene to propylene oxide with molecular oxygen over Sb2O3–CuO–NaCl/SiO2 catalysts

Co-impregnated Sb2O3–CuO–NaCl/SiO2 catalysts were investigated for the direct gas-phase synthesis of propylene oxide (PO) from propylene and molecular oxygen at atmospheric pressure. The trimetallic system was optimized for PO formation by varying the Sb:Cu:Na ratios, total metal loadings and calcination temperatures. At a reaction temperature of 250°C and propylene/oxygen molar ratio=1:4, the highest performing catalyst achieved 40–45% PO selectivity with 0.4–0.7% propylene conversion without a co-feeding gas. The coexistence of Sb2O3 and CuO crystals was determined to play a vital role in propylene epoxidation, while NaCl helped to suppress combustion.

Hierarchical Shape Evolution of Cuprous Oxide Micro- and Nanocrystals by Surfactant-Assisted Electrochemical Deposition

Cu2O microcrystals (MCs) and nanocrystals (NCs) of various shapes were potentiostatically deposited on Ti substrates by exploiting the capping effects of differently charged surfactants on certain surfaces. Positively charged hexamethylenetetramine was adsorbed onto the {111} and {100} planes of the Cu2O crystals (copper- and oxygen-terminated surface) while negatively charged poly(vinylpyrrolidone) was adsorbed onto the {111} planes (Cu-terminated surface due to Coulombic interaction). The difference in the adsorption behaviors of the two surfactants resulted in the synthesis of differently shaped Cu2O MCs. We were also able to systematically control the shape evolution of Cu2O NCs synthesized as cubes, truncated cubes, truncated octahedrons, and stepped octahedrons into perfect octahedrons by adding or removing surfactants successively during the electrochemical deposition process. This method is a simple, flexible, and cost-effective one and should aid in the elucidation of the shape-transformation phe...

Electrical properties and temperature sensitivity of B-substituted CuO-based ceramics for negative temperature coefficient thermistors

The ceramics of B-substituted Cu0.992Y0.008O (BYCO) with weight percentages of 0.25, 0.5, 0.75, 1.0 and 1.5 % of H3BO3 were prepared by a wet-chemical synthesis method, and the related phase component and electrical properties were investigated. All the ceramics have a monoclinic structure as that of CuO crystal. The BYCO ceramics have a typical characteristic of negative temperature coefficient (NTC) of resistivity over the temperature range from 25 to 300 °C, and the NTC materials constant (B 25/85) can be adjusted from 1112 to 4376 K by changing the H3BO3 content in BYCO ceramics. Investigations of complex impedance spectra revealed that the resistivities of the BYCO ceramics mainly result from the bulk effect, and both the bulk effect and grain boundary effect contribute to the NTC feature. Both the band conduction and electron-hopping models are proposed for the conduction mechanisms in the B-substituted CuO-based ceramics.

Peculiarities of the Band Structure Formation in the Cu2O and Ag2O Crystals with a Cuprite Structure

Band structure, total and partial densities of states, charges at the lattice sites are calculated for the Cu2O and Ag2O crystals with the cuprite structure within the framework of the density functional theory in the pseudopotential and full-electron versions. Both variants of the calculation give similar band spectra and are in good agreement with the available experimental and theoretical data. The full-electron calculation results give a better agreement between the calculated and experimental band gaps. The genesis of the band spectra of crystals from the states of theirs sublattices is established. It is shown that the topological peculiarities of the crystal spectra of the degeneration and quasi-degeneration types are caused by the convolution of the sublattice spectra in the Brillouin zone of the crystal. The underestimated widths of the allowed sublattice valence bands relative to the crystal ones are caused by the significant hybridization interaction of sublattices.

Efficient visible-light photocatalytic hydrogen evolution and enhanced photostability of core@shell Cu2O@g-C3N4 octahedra

The creation of photocatalysts with controlled facets has become an important approach to enhance their activity. Cu2O octahedra formed entirely with {111} surfaces are more efficient for photocatalysis reactions than nanosphere. Core@shell structured Cu2O@g-C3N4 octahedra photocatalyst was prepared by a combined solvothermal and chemisorption method. Moreover, the Cu2O@g-C3N4 composites exhibit superior activity for H2 production to pure Cu2O crystals and g-C3N4 nanosheets. The enhanced photocatalytic activity can be mainly attributed to a synergistic effect at the interface of the Cu2O octahedra and g-C3N4 including large contact area, energy band structure and enhanced charge separation properties. Interestingly, the hybrid core@shell octahedra possess high photostability. Our results provide a new approach for the rational design and development of graphitic carbon nitride composites and open the way to a range of important applications of crystal-facet-dependent materials.