Hydrothermal fabrication of p-Cu2O−n-ZnO films and their properties for photodegradation and ultraviolet sensors

This article reports spin coating and hydrothermal approaches to the synthesis of Cu₂O seed layer−ZnO and Cu₂O film−ZnO heterojunction films on fluorine-doped tin oxide substrates. Cu₂O seed layers and an ethylene glycol (EG) reducing agent were employed to obtain pure, uniform, and adhesive Cu₂O films on the substrate. Transmission electron microscopy validated the heterojunctions with clear interfaces between each component on the p-Cu₂O film−n-ZnO (with EG) sample, the conductive types of which were determined through Mott−Schottky measurements. Constructed energy band diagrams supported the Mott−Schottky result, manifesting favorable conduction band positions for the generation of •O₂⁻ radicals for all constituent materials and indicating smooth charge carrier transport for the p-Cu₂O film−n-ZnO (with EG) sample. Furthermore, abundant p−n junction interfaces synergistically enabled the sample to exhibit the most satisfactory photodegradation capability (rate constant ≈ 8.9 × 10⁻³ min⁻¹), which was attributable to the predominance of •OH radicals. The sample's rectifying (diode) behavior with a ratio of the current density (J) at +3 V (forward bias) to that at −3 V (reverse bias) of approximately 27 was observed without ultraviolet illumination. Moreover, the J at −3 V is under illumination approximately 80 times that without illumination, implying the suitability of the sample for UV detectability.     

Structure and magnetism of a trinuclear CuII–GdIII–CuII complex derived from one-pot reaction with 2,6-di(acetoacetyl)pyridine

A unique 3d–4f mixed metal trinuclear compound, [Cu₂Gd(L)₂(NO₃)₂]NO₃ (1; H₂L=2,6-di(acetoacetyl)pyridine), is derived from a ‘one-pot’ reaction with H₂L,Cu(NO₃)₂·3H₂O and Gd(NO₃)₃·5H₂O. Two L²⁻ providing one central 2,6-diacylpyridine site and two terminal 1,3-diketonate sites hold two Cu^II ions and Gd^III ion and form a linear Cu–Gd–Cu trinuclear core. This compound shows ferromagnetic interaction between Cu^II and Gd^III.     

Thermal conversion synthesis of Cu2O photocathode and the promoting effects of carbon coating

Simplifying the synthesis of cuprous oxide (Cu₂O) photocathode has turned out to be critical for scalable application. Herein, we present a novel thermal conversion approach to synthesize a shell/core structured Cu₂O/Cu photocathode. In this method a shell comprising a mixture of CuO and Cu₂O is obtained by heating Cu mesh at 500 °C in air beforehand, and subsequent annealing in N₂ atmosphere converts the unwanted CuO into Cu₂O gradually, which results in the desired Cu₂O/Cu structure. A slightly viscous starch sol coats the Cu₂O shell as carbon source, after carbonizing under N₂ atmosphere, the Cu₂O/Cu is covered with compact carbon films, i.e. C/Cu₂O/Cu. Photoelectrochemical experiments reveal that the introduction of carbon layers on Cu₂O enhances the photocurrent density from − 1.5 to − 2.75 mA·cm^− 2 at 0 V vs. reversible hydrogen electrode (RHE). Moreover, the deposition of carbon films on Cu₂O in this work has little effect on improving the stability.     

Cu3P and Ni2P co-modified g-C3N4 nanosheet with excellent photocatalytic H2 evolution activities

Copper-nickel phosphides/ graphite-like phase carbon nitride (Cu₃P-Ni₂P/g-C₃N₄) composites were obtained through a facile one-pot in situ solvothermal approach. The coexistence of Cu₃P and Ni₂P plays an important role in enhancing the catalytic activity of g-C₃N₄. The 7 wt% Cu₃P-Ni₂P/g-C₃N₄ bimetallic phosphide photocatalyst demonstrates the best photocatalytic hydrogen (H₂) evolution rate of 6529.8 μmol g⁻¹ h⁻¹, which is 80.7-fold higher than that of g-C₃N₄. The apparent quantum yield (AQE) was determined to be 18.5% at 400 nm over the 7% Cu₃P-Ni₂P/g-C₃N₄. This in situ growth strategy produced intimate contact interfaces, leading to a significantly promoted separation of charge carriers, and hence strengthened the photocatalytic H₂ production. Moreover, the coexistence of Cu₃P and Ni₂P reduced the overpotential of H₂ during the evolution process, further benefiting H₂ production. Finally, the photocatalytic enhancement mechanism was proposed and verified by fluorescence and electrochemical analysis. This work provides a low-cost strategy to synthesize nonprecious bimetallic phosphides/carbon nitride photocatalyst with outstanding H₂ production activity. © 2020 Society of Chemical Industry     

Advanced oxidation of raw and biotreated textile industry wastewater with O3, H2O2 /UV‐C and their sequential application

The advanced chemical oxidation of raw and biologically pretreated textile wastewater by (1) ozonation, (2) H₂O₂ /UV − C oxidation and (3) sequential application of ozonation followed by H₂O₂ /UV − C oxidation was investigated at the natural pH values (8 and 11) of the textile effluents for 1 h. Analysis of the reduction in the pollution load was followed by total environmental parameters such as TOC, COD, UV–VIS absorption kinetics and the biodegradability factor, f_B. The successive treatment combination, where a preliminary ozonation step was carried out prior to H₂O₂ /UV − C oxidation without changing the total treatment time, enhanced the COD and TOC removal efficiency of the H₂O₂ /UV − C oxidation by a factor of 13 and 4, respectively, for the raw wastewater. In the case of biotreated textile effluent, a preliminary ozonation step increased COD removal of the H₂O₂ /UV − C treatment system from 15% to 62%, and TOC removal from 0% to 34%. However, the sequential process did not appear to be more effective than applying a single ozonation step in terms of TOC abatement rates. Enhancement of the biodegradability factor (f_B) was more pronounced for the biologically pretreated wastewater with an almost two‐fold increase for the optimized Advanced Oxidation Technologies (AOTs). For H₂O₂ /UV − C oxidation of raw textile wastewater, apparent zero order COD removal rate constants (k_app), and the second order OH· formation rates (r_i) have been calculated. © 2001 Society of Chemical Industry     

Direct reduction of diluted CO2 gas to C2 products by copper hydroxyphosphate microrods

Electrochemical reduction of CO₂ is widely researched in recent years. However, direct electro-reduction of diluted CO₂ to C₂ products is seldomly studied. In this work, electrocatalytic reduction of CO₂ with different concentrations were conducted on Cu₂(PO₄)(OH) catalysts. The catalytic performance in diluted CO₂ is comparable with that in pure CO₂ by using Cu₂(PO₄)(OH) as catalyst. Besides, the selectivity of C₂ product is still as high as 64.6% in 50%CO₂ concentration. The normalized C₂ current density of Cu₂(PO₄)(OH) was over 6.8 times higher than that of commonly used Cu₂O–Cu catalyst with similar size. In situ Raman spectroscopy proved that Cu⁺ is the main active site at higher potentials. More importantly, a higher local pH is realized under diluted CO₂ test conditions which is favorable for promoting C–C coupling. Finally, in situ ATR-FTIR spectroscopy was performed to further monitor and identify the adsorbed intermediates and help reveal the mechanism for the catalysts.     

Monitoring Photosynthetic Activity in Microalgal Cells by Raman Spectroscopy with Deuterium Oxide as a Tracking Probe

Microalgae offer great potential for the production of biofuel, but high photosynthetic activity is demanded for the practical realisation of microalgal biofuels. To this end, it is essential to evaluate the photosynthetic activity of single microalgal cells in a heterogeneous population. In this study, we present a method to monitor the photosynthetic activity of microalgae (in particular Euglena gracilis, a microalgal species of unicellular, photosynthetic, flagellate protists as our model organism) at single-cell resolution by Raman spectroscopy with deuterium from deuterium oxide (D₂O) as a tracking probe. Specifically, we replaced H₂O in culture media with D₂O up to a concentration of 20 % without disturbing the growth rate of E. gracilis cells and evaluated C−D bond formation as a consequence of photosynthetic reactions by Raman spectroscopy. We used the probe to monitor the kinetics of the C−D bond formation in E. gracilis cells by incubating them in D₂O media under light irradiation. Furthermore, we demonstrated Raman microscopy imaging of each single E. gracilis cell to discriminate deuterated cells from normal cells. Our results hold great promise for Raman-based screening of E. gracilis and potentially other microalgae with high photosynthetic activity by using D₂O as a tracking probe.     

CuII Pyrazolyl-Benzimidazole Dinuclear Complexes with Remarkable Antioxidant Activity

Three dinuclear coordination complexes generated from 1-n-butyl-2-((5-methyl-1H-pyrazole-3-yl)methyl)-1H-benzimidazole ( L ), have been synthesized and characterized spectroscopically and structurally by single crystal X-ray diffraction analysis. Reaction with iron(II) chloride and then copper(II) nitrate led to a co-crystal containing 78 % of [Cu(NO₃)(μ-Cl)( L’ )]₂ ( C₁ ) and 22 % of [Cu(NO₃)(μ-NO₃)( L’ )]₂ ( C₂ ), where L was oxidized to a new ligand L^’ . A mechanism is provided. Reaction with copper chloride led to the dinuclear complex [Cu(Cl)(μ-Cl)( L) ]₂ ( C₃ ). The presence of N−H⋅⋅⋅O and C−H⋅⋅⋅O intermolecular interactions in the crystal structure of C₁ and C₂ , and C−H⋅⋅⋅N and C−H⋅⋅⋅Cl hydrogen bonding in the crystal structure of C₃ led to supramolecular structures that were confirmed by Hirshfeld surface analysis. The ligands and their complexes were tested for free radical scavenging activity and ferric reducing antioxidant power. The complex C₁ / C₂ shows remarkable antioxidant activities as compared to the ligand L and reference compounds.     

Formation mechanism of Cu2O particles using layered CaSi2 as a reduction/oxidation mediator

We demonstrate that Cu₂O particles can be produced along with siloxene formation by simply dispersing layered CaSi₂ into an aqueous solution of CuCl₂ and HCl at room temperature. The Cl⁻ ions induce oxidative extraction of Ca from CaSi₂ to form siloxene and trigger the reductive deposition of Cu particles. All particles are then gradually oxidized to form Cu₂O particles under optimized conditions as follows. A trace amount of residual CaSi₂ is dissolved in the solution, which provides OH⁻ ions, and a portion of the formed Cu particles are dissolved as [Cu(OH)₄]²⁻ ions. Accordingly, Cu₂O particles would be formed through the comproportionation reaction between Cu and [Cu(OH)₄]²⁻ ions in the solution. However, under conditions with an excess amount of Cl⁻ ions results in further oxidation of Cu to also form Cu₂Cl(OH)₃. Thus, CaSi₂ acts as an effective reduction and/or oxidation mediator to tune the number of Cl⁻ and OH⁻ ions and control the oxidation state of Cu.     

One-pot syntheses,structures and properties of two novel 1-D copper complexes: [CuII2(Hbpdc)2Cl2]2·2H2O and CuI(H2bpdc)Cl (H2bpdc = 2,2′-bipyridyl-5,5′-dicarboxylic acid)

Two novel 1-D copper complexes {[Cu^II₂(Hbpdc)₂]Cl₂}₂·2H₂O (1) and Cu^I(H₂bpdc)Cl (2) (H₂bpdc = 2,2′- bipyridyl-5,5′-dicarboxylic acid) have been one-pot hydrothermally synthesized by reaction of H₂bpdc, CuCl₂·2H₂O, PrCl₃ and glacial acetic acid and structurally characterized by IR spectroscopy, X-ray photoelectron spectroscopy and single-crystal X-ray diffraction. Single-crystal structural analyses show that 1 is a novel 1-D stair-like chain constructed from centric tetra-copper clusters {[Cu^II₂(Hbpdc)₂]Cl₂}₂ by means of Cu–O weak coordination interactions whereas 2 displays a 1-D comb-like chain built by [Cu^I(H₂bpdc)Cl] units through Cl^? bridges. More interestingly, 1 and 2 were one-pot hydrothermally synthesized, which is very rare in synthetic chemistry. The photofluorescence properties of 1 and 2 have been investigated.     

High-performance Cu2O-based photocatalysts enabled by self-curling nanocelluloses via a freeze-drying route

Enhancing the photocatalytic stability of Cu₂O in the degradation of tetracycline is a great challenge in combating environmental water pollution because it is prone to deactivation by photocorrosion in aqueous environment. In this study, Cu₂O/cellulose microfiber aerogel is synthesized through freeze-drying, utilizing the self-curling effect of cellulose and then calcined to produce Cu₂O/C composite aerogel. The derived Cu₂O/C composite aerogel features hollow carbon microfibers anchored with Cu₂O nanocubes. Due to the curling structure and conductivity of the carbon microfibers, the photodegradation efficiency of the obtained Cu₂O/C composite aerogel for tetracycline is drastically improved to 97.3% under 120 min of visible-light irradiation, and remains a cycling photodegradation rate of 84.3% after 10 cycles. The Cu₂O/C composite aerogel shows remarkable strategies for designing and constructing Cu₂O-based photocatalyst in the practical photodegradation of tetracycline under visible-light exposure.     

Reduction of CuO in H2: In Situ Time-Resolved XRD Studies

CuO is used as a catalyst or catalyst precursor in many chemical reactions that involve hydrogen as a reactant or product. A systematic study of the reaction of H₂ with pure powders and films of CuO was carried out using in situ time-resolved X-ray diffraction (XRD) and surface science techniques. Oxide reduction was observed at atmospheric H₂ pressures and elevated temperatures (150-300 °C), but only after an induction period. High temperature or H₂ pressure and a large concentration of defects in the oxide substrate lead to a decrease in the magnitude of the induction time. Under normal process conditions, in situ time-resolved XRD shows that Cu¹⁺ is not a stable intermediate in the reduction of CuO. Instead of a sequential reduction (CuO Cu₄O₃ Cu₂O Cu), a direct CuO Cu transformation occurs. To facilitate the generation of Cu¹⁺ in a catalytic process one can limit the supply of H₂ or mix this molecule with molecules that can act as oxidant agents (O₂, H₂O). The behavior of CuO-based catalysts in the synthesis of methanol and methanol steam reforming is discussed in the light of these results.     

Template-free synthesis of Cu2O hollow nanospheres and their conversion into Cu hollow nanospheres

In this paper, Cu₂O hollow nanospheres were first generated through a template free process, and then Cu hollow nanospheres were prepared using Cu₂O hollow nanospheres as precursor and H₂ as reductant. Phase identification and morphology observation of the products were carried out by X-ray diffraction(XRD), Transmission electron microscopy (TEM) and Field scanning electron microscopy (FSEM). The results show that Cu₂O nanospheres generated at reflux are porous and hollow both in absolute alcohol and tert-butyl alcohol. It is feasible to fabricate well-dispersed Cu hollow nanospheres from Cu₂O hollow nanospheres at 170 °C. Moreover, a remarkable blue shift effect was found in the ultraviolet-visible light (UV-visible) absorption spectra for both Cu₂O and Cu hollow nanospheres.     

Enhancement of C2H6 Oxidation by O2 in the Presence of N2O over Fe Ion-Exchanged BEA Zeolite Catalyst

Selective catalytic reduction (SCR) of N₂O with C₂H₆ took place effectively over Fe ion-exchanged BEA zeolite catalyst (Fe-BEA) even in the presence of excess oxygen. The mechanism in the SCR of N₂O with C₂H₆ over Fe-BEA catalyst was studied by a transient response experiment and an in situ DRIFT spectroscopy. No oxidation of C₂H₆ by O₂ took place below 350 °C (in C₂H₆/O₂). In the N₂O/C₂H₆/O₂ system, however, it was found that the reaction of C₂H₆ with O₂ was drastically enhanced by the presence of N₂O even at low temperatures (200-300 °C). Therefore, it was concluded that N₂O played an important role in the oxidation of C₂H₆ (i.e., activation of C₂H₆ at an initial step). On the basis of these findings, the mechanism in the SCR of N₂O with C₂H₆ is discussed.     

Phase behavior measurements of CO2-SO2-brine mixtures

Phase behavior and physical property measurements were carried out on mixtures of SO₂-H₂O; CO₂-H₂O, 5, 10, and 20 weight percent NaCl brines; and ternary CO₂-SO₂-H₂O mixtures. The temperature was kept constant at 45°C, while saturation pressures were varied up to about 15 MPa. Binary measurements demonstrated that, at the same temperature and pressure, the mutual solubilities of SO₂ and H₂O are higher than those of CO₂ and H₂O. A three-phase region has been identified in the termary CO₂-SO₂-H₂O phase diagram at 7.24 MPa, but no such region was found at higher pressures.     

A novel one-pot synthesized CuCe-SAPO-34 catalyst with high NH3-SCR activity and H2O resistance

CuCe-SAPO-34 catalysts based on the one-pot hydrothermal synthesis method were prepared for the first time. The addition of Ce suppressed the formation of CuO and increased the amount of active Cu^2 +, resulting in better NH₃-SCR activity than Cu-SAPO-34. Ce greatly improved the H₂O resistance during the SCR process by stabilizing the zeolite structure and obstructing the transformation of active Cu^2 + into inactive forms.     

Enhanced electrical properties in W/Cu co-doped CaBi2Nb2O9 high-temperature piezoelectric ceramics

CaBi₂Nb₂O₉ (CBN)-based high-temperature piezoelectric ceramics with the formula of CaBi₂Nb_2−x(W_3/4Cu_1/4)_xO₉ were prepared via the traditional solid-state reaction method. Both the bulk microstructure and the electrical performance of the W/Cu co-doped CBN-based ceramics were systematically investigated. The results indicated that the W/Cu incorporation into the Nb-site altered the crystal structure, which enhanced the piezoelectricity and resistivity. The ceramic with the composition CaBi₂Nb_1.96(W_3/4Cu_1/4)_0.04O₉ exhibited good performance with a high d₃₃ (~14 pC/N) and T_C (~939℃). Moreover, the ceramic exhibited a good electrical resistivity (ρ) of 4.91 × 10⁵ Ω·cm and a low dielectric loss (tanδ) of 0.1 at 600℃. Furthermore, the ceramic that was annealed at 900℃ for 2 h presented a d₃₃ value of 13 pC/N, thus indicating good thermal stability of the piezoelectric properties. All these results confirm that the CaBi₂Nb_1.96(W_3/4Cu_1/4)_0.04O₉ ceramic may act as a potential promising candidate for piezoelectric device applications in high-temperature environments.     

Solvothermal synthesis of a novel mixed valence Cu(I)/Cu(II) complex containing sulphate, malate and 4,4-bipyridine, [CuCu2(mal)(SO4)(bpy)2 · H2O]n. Unique binding mode of the malate anion

The reaction of CuSO₄ · 5H₂O with 4,4^′-bipyridine and malic acid at 140 °C under solvothermal conditions afforded a mixed valence three-dimensional coordination polymer [Cu^ICu^II₂(mal)(SO₄)(bpy)₂ · H₂O]_n, (1). The building unit consists of a Cu²⁺-dimer in which copper centers are bridged by malate and sulphate anions. SO₄²⁻ anion further connects dimeric unit with the Cu¹⁺ center. Building units are linked by 4,4^′-bipyridine ligands to form double chains, that are interconnected into 3D network through additional sulphate bridge.     

Metal-organic framework Cu3 (BTC)2(H2O)3 catalyzed Aldol synthesis of pyrimidine-chalcone hybrids

A typical metal organic framework, [Cu₃ (BTC)₂(H₂O)₃, BTC = 1,3,5-benzene tricarboxylate] has been used for the synthesis of pyrimidine-chalcones. We have explored a green synthesis of pyrimidine chalcones under Cu₃(BTC)₂ catalysis by Aldol condensation. Easy isolation of product, excellent yield, and recyclable catalyst makes this reaction eco-friendly. The technology was demonstrated to be applicable to the synthesis of a host of chemical hybrids.     

Creating dual charge transfer channels to collaborative enhance the photocatalytic bacteriostatic efficiency and photocorrosion resistance of Cu2O based nanocomposites

Cuprous oxide (Cu₂O), as one of the traditional photocatalytic antifouling agents, has its own defects for practical applications such as rapid recombination of carriers, serious photocorrosion (Cu₂O changing into CuO) and explosive release of cuprous ions. Herein, a novel ternary interfacial heterojunction (Cu₂O/C/CCN) was prepared by carbon doping of g-C₃N₄ followed by in-situ carbon film covering and Cu₂O loading. Compared with pure Cu₂O and Cu₂O/g-C₃N₄, Cu₂O/C/CCN presented more powerful broad-spectrum and long-term photocatalytic antibacterial properties against S. aureus and P. aeruginosa, and the antibacterial rate remained at approximately 94.28% and 90.54%, respectively, even after storage 30 days. The high antibacterial rate of the Cu₂O/C/CCN can be attributed to the high photocatalytic performance and stable and continuous release of cuprous ions. The carbon doping of g-C₃N₄ could adjust its band gap and promote more efficient photoexcited carrier generation and transfer by the formation of delocalized large π bonds like “electron bridge” as the first charge transfer channel. The existence of carbon film between g-C₃N₄ and Cu₂O can build the second highly efficient charge transfer channel for the separation of photoexcited carriers by forming a Z-scheme interfacial heterojunction. DFT calculation and fluorescence spectrum results showed that more active electrons on CCN tend to transfer to Cu₂O through the two nonradiative decay pathways. The highly efficient carrier transport and separation can also greatly reduce the 15.3% generation of CuO compared to Cu₂O/g-C₃N₄. The more negative reduction potential further promoted the ROS generation for sterilization. In addition, the loading of Cu₂O on 2D C/CCN can reduce the contact area between Cu₂O and solution and then slow the release rate of cuprous ions by 75% compared to Cu₂O. Therefore, Cu₂O/C/CCN has great potential for practical antifouling applications.