Fabrication and photocatalytic property of ZnO nanorod arrays on Cu2O thin film

ZnO nanorod arrays were fabricated on Cu₂O thin film by a simple low-temperature liquid-phase-deposition method. The samples were characterized by X-ray powder diffraction (XRD) and field emission scanning electron microscopy (FESEM). The UV-Vis spectroscopy showed that the obtained sample was able to absorb a large part of visible light (up to 650 nm). Their photocatalytic activities were investigated by degradation of dye methylene blue (MB) under UV-Vis and visible light irradiation. It was found that the photocatalytic activity of the ZnO/Cu₂O NRs was higher than the ZnO/ZnO NRs under UV-Vis light. In a word, Cu₂O played an important role in enhancing the photocatalytic activity of the ZnO/Cu₂O NRs.     

Solvent-free synthesis of Cu-Cu2O nanocomposites via green thermal decomposition route using novel precursor and investigation of its photocatalytic activity

In the present study, Cu-Cu₂O binary nanocomposites were successfully synthesized through a one-pot, cost-effective and green thermal decomposition route using PMP-Cu(II), extracted from pomegranate marc peels (PMP) by Cu(II), as a novel starting reagent for the first time. The morphology, crystalline structure, and composition of as-prepared Cu-Cu₂O nanocomposites were extensively characterized by SEM, XRD, EDS and HRTEM. Effect of reaction parameters such as time, temperature and precursor type on product composition and morphology was evaluated. Moreover, methylene blue (MB) was used as a model of organic dye pollutant and photodegradation experiments were conducted by UV-vis spectrophotometry. The as-synthesized Cu-Cu₂O binary nanocomposites demonstrated their potential as an excellent photocatalyst for degradation of MB under visible-light irradiation and Cu-Cu₂O photocatalyst with higher content of Cu₂O (prepared in air) exhibits the highest photocatalytic efficiency (～99% degradation of MB in <150 min).     

Synthesis and Characterization of CuNi Magnetic Nanoparticles by Mechano-Thermal Route

In the present investigation, Cu_0.5Ni_0.5 nanoparticles were synthesized using high energy ball milling of a mixture of Cu₂O, NiO, and graphite powders. The mixture of powders was milled up to 50 h. The 30 h milled sample was heat treated at various temperatures for 1 h in a vacuum tube furnace. The effects of milling time and heat treatment temperature on the powder particle characteristics were studied employing X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), differential thermal analysis (DTA), and vibrating sample magnetometer (VSM) techniques. XRD results indicated incomplete formation of Cu_0.5Ni_0.5 after 30 h of milling. Further heat treatment at 500 ^°C led to the formation of a single phase Cu_0.5Ni_0.5 powder. FESEM and TEM images of the heat treated sample showed spherical Cu_0.5Ni_0.5 nanoparticles with a mean particle size of 15 nm. Magnetic properties data measured by VSM of the above sample are correlated well with the XRD results. Coercivity and saturation magnetization have been approximately achieved at 25 Oe and 18 emu/g, respectively.     

Refining of copper powder by a novel micro-abrasive milling method conducted in the air

The pure copper powder was milled by conventional high-energy ball milling (CM) and micro-abrasive milling (MAM) methods in the air or vacuum. The refining behavior of copper powder milled using these different methods has been studied, and the morphologies, microstructures, compositions, and properties of the milled powders have been thoroughly investigated. The results show that, as compared to CM, the MAMed copper powder had a better refinement behavior and contained a smaller number of agglomerates. After milling in the air for 30 h by MAM, whole copper powder was converted into Cu₂₊₁O. In addition, under the synergistic effects of micro-abrasion and exposure to oxygen, the Cu₂₊₁O powder was soft-agglomerated and had a specific surface area of 15.1031 m²/g and an average size of 375.4 nm. During the dispersion process, Cu₂₊₁O was partly converted into CuO and the microstructural evolution characteristics were disclosed. The dispersed powder had an average particle size of 179.5 nm. The refining mechanism of the copper powder prepared by the micro-abrasive milling method was also discussed.     

CNTs-copper oxide nanocomposite photocatalyst with high visible light degradation efficiency

Cu_xO (x = 1 or 2)/Carbon nanotubes (CNTs) nanocomposite was prepared through a two-step process including copper electroless deposition on CNTs followed by chemical-thermal oxidation. The effect of electroless deposition time and hence copper oxide content on the photocatalytic activity was studied, and 30 min of deposition was optimal. X-ray diffraction (XRD) and Raman results confirm the formation of both crystalline CuO and Cu₂O phases. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) images showed the dispersion of copper oxide nanoparticles onto the surface of CNTs. The diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) results showed that decreasing the copper oxide content decreases the bandgap and the electron-hole pairs recombination rate. The photocatalytic activity was investigated for the degradation of methyl orange (MO) and methylene blue (MB) under visible light irradiation. Relatively complete methylene blue (MB) degradation was obtained after 120 min for a 2 mg/L solution, while about 70% of methyl orange (MO) was degraded. The stability of the sample was also investigated, and the sample was able to maintain its performance after three cycles.     

Architecture of Cu2O@TiO2 core–shell heterojunction and photodegradation for 4-nitrophenol under simulated sunlight irradiation

A Cu₂O@TiO₂ core–shell heterojunction photocatalyst was prepared by an in situ hydrolysis and crystallization method. The as-prepared catalyst was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), UV–vis diffuse reflectance spectroscopy and photoluminescence (PL) spectroscopy. Under simulated sunlight irradiation, it exhibited high photocatalytic activity and stability for 4-nitrophenol (4-NP) degradation. Compared with neat Cu₂O and Cu₂O/TiO_2(PM) prepared by physical mixing, the heightened photocatalytic activity of Cu₂O@TiO₂ was attributed to the improvement of charge separation since large close interface was formed between the two semiconductors. The in situ method may generally be applied to develop other core–shell heterojunction photocatalysts.     

Photocatalytic degradation of methylene blue by C<Subscript>3</Subscript>N<Subscript>4</Subscript>/ZnO: the effect of the melamine/ZnO ratios

The C₃N₄/ZnO composite photocatalysts were synthesized by mechanical milling combined with a calcination process. Various ratios of melamine and ZnO powders were milled by a planetary ball mill for 10 h. After heating at 540^°C for 3 h in air, melamine was converted to C₃N₄ but the formation of C₃N₄ depended on the ratios of the melamine and ZnO (M/Z) powders. From the experimental results, the conversion of melamine to C₃N₄ could be inhibited by ZnO particles; as there was no detectable C₃N₄ in the sample at low M/Z values or high ZnO contents. The photocatalytic activities of prepared samples were investigated under the illumination of blacklight and fluorescent lamps as the low wattage light source. The C₃N₄ /ZnO showed a better photocatalytic activity than ZnO to degrade a methylene blue (MB) dye solution using blacklight lamps, but there is no significant difference in photocatalytic activities between ZnO and prepared C₃N₄/ZnO under visible light by the fluorescent lamps. However, the prepared C₃N₄/ZnO can well function under illumination by Xe lamp as the high power light source. Ecotoxicities of MB solutions before and after photocatalytic process were also studied through growth inhibition of the alga Chlorella vulgaris.     

Thermal evolution of morphological,optical, and photocatalytic properties of Au–Cu2O–CuO nanocomposite thin film

Plasmonic nanocomposite thin films find exciting applications in environmental remediation and photovoltaics. We report on thermal annealing driven development of morphology, structure and photocatalytic performance of Au–Cu₂O–CuO nanocomposite thin film. Nanocomposite thin film coatings of Au–Cu₂O–CuO, prepared by radio frequency (RF) magnetron co-sputtering, were annealed at different temperatures. Thermal annealing driven evolution of morphology of Au–Cu₂O–CuO nanocomposite was studied by field emission scanning electron microscopy (FESEM), which revealed significant growth in size of nanostructures from 10 nm to 69 nm upon annealing. X-ray diffraction (XRD) together with Raman studies confirmed the nanocomposite nature of Au–Cu₂O–CuO film. UV-visible diffuse reflectance spectroscopy (UV-vis-DRS) studies showed band gap variation from 2.44 eV to 1.8 eV upon annealing at 250 °C. Nanocomposite thin film annealed at 250 °C exhibited superior photocatalytic activity for organic pollutants [methylene blue (MB) and methyl orange (MO)] decomposition. The origins of thermal transformation of morphological, optical and photocatalytic behaviour of the Au–Cu₂O–CuO nanocomposite coating are discussed.

     

Promoting Photocatalytic Performance of ZnO Particles by Photochemically Reducing Ag+ on the Particle Surfaces

Dispersive Ag nanoparticles were formed on the surface of crystalline ZnO particles, using a photochemical reduction technique, to produce the Ag/ZnO with high photocatalytic performance. The prepared Ag/ZnO particles, as well as the ZnO particles without Ag attachments, were characterized using x-ray diffractometer, transmission electron microscope, and surface area analyzer. The abilities of the ZnO and the Ag/ZnO particles to photocatalytically decompose methylene blue under 365-nm ultraviolet light irradiation were evaluated by determining the corresponding specific reaction rate constant, k′_MB,m (based on the mass of the photocatalyst used). While the ZnO crystalline particles (k′_MB,m > 0.43 m³/(kg min)) already possessed better photocatalytic performance than the commercial photocatalyst P25 (k′_MB,m = 0.39 m³/(kg min)), the Ag/ZnO particles exhibited much better photocatalytic performance than the ZnO particles. The highest k′_MB,m for the Ag/ZnO particles was 1.93 m³/(kg min), which was about five times that of the P25.     

Utilization of ZnO nanocones for the photocatalytic degradation of acridine orange

A facile aqueous solution process was used to synthesize well-crystalline ZnO nanocones at 60 degrees C by using zinc nitrate hexahydrate and sodium hydroxide. The morphological, structural and optical properties of the synthesized ZnO nanocones were investigated by using field emission scanning electron microscopy (FESEM) attached with energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM) equipped with high-resolution (HRTEM), X-ray diffraction (XRD) pattern, Fourier transform infrared (FTIR) spectroscopy and UV-Vis. spectroscopy measurements. The structural and optical properties of the as-synthesized nanocones confirmed a pure and well crystalline product possessing wurtzite hexagonal phase. The as-synthesized ZnO nanocones were used as photocatalyst for the efficient photocatalytic degradation of acridine orange. The acridine orange was almost completely degraded within 105 minutes. This research demonstrates that the simply synthesized ZnO nanostructures could be efficient photocatalyst for the photocatalytic degradation of various organic dyes and chemicals.     

Preparation and characterization of Cu2O-TiO2: Efficient photocatalytic degradation of methylene blue

A series of copper-deposited titania were prepared by photoreduction method under irradiation with a 125-W high-pressure mercury lamp. From XPS and AES results, the deposited-copper formed Ti-O-Cu bond on the surface of TiO₂, and the Cu species on the surface of copper-deposited TiO₂ can be identified as Cu(I). The photocatalytic degradation activity of methylene blue for the Cu₂O-TiO₂ series increased with increasing Cu₂O-deposited content, and then decreased. The highest photocatalytic degradation activity of methylene blue was obtained for 0.16% Cu₂O-TiO₂. When copper-deposited content reached to 0.32%, the photocatalytic activity was lower than that of pure TiO₂. It is shown that Cu₂O on the surface of TiO₂ can trap electrons from the TiO₂ conduction band, and the electrons trapped on the Cu₂O-TiO₂ site are subsequently transferred to the surrounding adsorbed O₂, thereby avoiding electron-hole recombination, and enhancing the photocatalytic activity. Excess copper loading may screen the photocatalyst from the UV source, so the photocatalytic activity diminishes with increasing Cu₂O.     

Preparation of a high-activity ZnO/TiO2 photocatalyst via homogeneous hydrolysis method with low temperature crystallization

The nano-scale ZnO/TiO₂ coupled oxide photocatalyst was successfully synthesized by a two-step method, the homogeneous hydrolysis and low temperature crystallization. The resultant photocatalyst was characterized by ultraviolet-visible absorption spectroscopy (UV-vis), X-ray diffraction (XRD), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) techniques. The photocatalytic activity of coupled oxides was also evaluated by the degradation of methyl orange (MO) as a model compound. The experimental results showed that the prepared ZnO/TiO₂ at low hydrothermal crystallization temperature exhibited higher photocatalytic activity for the decomposition of MO than either pure phase ZnO or anatase TiO₂, and even higher than that of the Degussa P25 TiO₂.     

Dielectric properties investigation of Cu2O/ZnO heterojunction thin films by electrodeposition

Structures and morphologies of the Cu₂O/ZnO heterojunction electrodeposited on indium tin oxide (ITO) flexible substrate (polyethylene terephthalate-PET) were investigated by X-ray diffraction (XRD), scanning electronic microscopy (SEM), high resolution transmission electron microscopy (HRTEM), respectively. The dielectric response of bottom-up self-assembly Cu₂O/ZnO heterojunction was investigated. The low frequency dielectric dispersion (LFDD) was observed. The universal dielectric response (UDR) was used to investigate the frequency dependence of dielectric response for Cu₂O/ZnO heterojunction, which was attributed to the long range and the short range hopping charge carriers at the low frequency and the high frequency region, respectively.     

Highly efficient degradation of 2-chlorophenol and methylene blue with Rb0.27WO3/NiFe-CLDH composites under visible light irradiation

Novel magnetically composites photocatalyst Rb_0.27WO₃/NiFe-CLDH (RWCLDH) was fabricated via a simple method. The as-prepared catalysts were characterized using XRD, XPS, SEM, TEM, HRTEM, BET, UV–Vis DRS spectra and PL analysis. The RWCLDH-700 composites exhibit a two-fold enhancement in photocatalytic activity toward degradation of 2-chlorophenol (2-CP) and methylene blue (MB) under visible light irradiation compared to that of Rb_0.27WO₃ and NiFe-CLDH. The photocatalytic efficiency of the Rb_0.27WO₃ and NiFe-CLDH is 39%, 45% and 42%, 34%, respectively, whereas for RWCLDH-700 composites are 91% and 93%. This enhancement in photocatalytic activity is attributed to the effective separation of electron-hole pairs. Moreover, the catalyst exhibited higher photocatalytic stability and retained its degradation efficiency up to 81% after four cycles. Finally, a possible decomposition mechanism was also discussed.     

A simple method for fabricating p–n junction photocatalyst CuFe2O4/Bi4Ti3O12 and its photocatalytic activity

The synthesis of Bi₄Ti₃O₁₂ and CuFe₂O₄ powders was achieved using a conventional solid-state reaction and the Sol–Gel method, respectively. A novel p–n heterojunction photocatalyst CuFe₂O₄/Bi₄Ti₃O₁₂ was subsequently prepared through ball milling. The structures, morphologies, and optical properties of the photocatalysts were comprehensively characterized. The transmission electron microscopy (TEM) images showed a clear interface between CuFe₂O₄ and Bi₄Ti₃O₁₂, indicating that a heterojunction between CuFe₂O₄ and Bi₄Ti₃O₁₂ was formed during ball milling. In addition, the photocatalytic activity was evaluated based on the photocatalytic degradation of methyl orange (MO). The results indicated that the photocatalytic activity of the p–n heterojunction photocatalyst CuFe₂O₄/Bi₄Ti₃O₁₂ was higher than that of Bi₄Ti₃O₁₂ alone. The enhanced photocatalytic activity could be attributed to the formation of a heterojunction between CuFe₂O₄ and Bi₄Ti₃O₁₂, which suppressed the recombination of photogenerated electron–hole pairs. We also investigated the effects of procedure time and dispersant (H₂O) during ball milling on the photocatalytic activity. The mechanisms underlying the observed photocatalytic activity were also described based on the semiconductor energy band theory and p–n junction principle. Moreover, the analysis of the radical scavengers confirmed that •O₂⁻ and h⁺ were the primary reactive species to cause the degradation of the MO.     

Facile synthesis of binary metal substituted copper oxide as a solar light driven photocatalyst and antibacterial substitute

This work presents the synthesis of Cu_0.95Mn_0.05O (CMO), Cu_0.95Ag_0.05O (CAO), and Cu_0.9Mn_0.05Ag_0.05O (CMAO) samples via wet chemical route for photocatalytic and antibacterial applications. The phase, morphology, chemical composition, and absorption range of the transition metal substituted CuO samples were investigated using various techniques such as PXRD, FESEM, EDX, and UV/Visible spectroscopy . The photocatalytic and antibacterial aptitude of all the synthesized samples was tested using methylene blue (MB) and bacterial strains. The results of application studies showed that the CMAO sample has a greater potential for dye degradation and bacterial strain destruction because of its long-lived photo-generated reactive species. More precisely, among all the synthesized samples, the CMAO sample showed excellent photocatalytic activity and degraded 83.9% dye at a higher rate constant value (0.0127 min^?1). Moreover, the CMAO sample also showed better bactericidal activity against Gram-positive (S. aureus) and Gram-negative bacterial strains (E. coli). Actually, components of the bacterial cell membrane are also organic like organic dyes, so they are likely to degrade by photo-generated species. The results revealed that binary metal substituted CuO (CMAO) has an excellent ability to kill bacteria and eliminate toxic dyes from industrial effluents.     

A facile route to synthesize ternary Cu2O quantum dot/graphene-TiO2 nanocomposites with an improved photocatalytic effect

A Cu₂O quantum dot/graphene-TiO₂ composite, a novel material, was successfully synthesized using a facile hydrothermal method. The hydrothermal reaction was used to load the Cu₂O and TiO₂ particles onto graphene sheets, and the resulting photocatalysts were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM), Raman spectroscopy, and ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy (DRS). UV spectrophotometry was employed to measure the decrease in the concentration of rhodamine B (RhB), methylene blue trihydrate (MB), and reactive black B (RBB) dyes in an aqueous solution after degradation with the photocatalysts under irradiation with visible light. The results indicate that the quantum dot-sized Cu₂O is a promising material that contributes to the photocatalytic activity of Cu₂O quantum dot/graphene-TiO₂ composites.     

Synthesis of Cu2O/T-ZnOW nanocompound and characterization of its photocatalytic activity and stability property under UV irradiation

Cu₂O/tetrapod-like ZnO whisker (T-ZnO_W) nanocompound was synthesized by a simple hydrothermal chemical method. The chemical composition, morphology, band gap and photocatalytic property of the Cu₂O/T-ZnO_W nanocompound were studied in detail. It was observed that the Cu₂O particles deposited on T-ZnO_W surface had a cubic structure and the crystallinity of T-ZnO_W did not change with the increase of Cu₂O crystals. The morphology and content of Cu₂O in the Cu₂O/T-ZnO_W nanocompound played an important role on the photocatalytic activity. In addition, the coexistence of Cu₂O and T-ZnO_W nanoparticles was propitious to the high photocatalytic activity owing to their hetero-junction effect. The Cu₂O/T-ZnO_W nanocompound prepared by 7.2% Cu/Zn MR exhibited the best photocatalytic activity on the degradation of MO solution under UV light irradiation. At the first 100 min of irradiation, the photodegradation efficiency of MO solution reached up to 99.16%, which still retained its high photocatalytic activity about 89.10% even at the end of the fourth cycle. Little change was found in their phase compositions after the photocatalytic reaction process, except partial oxidation of particles’ surface. The mechanism for UV light driven photocatalytic activity enhancement over Cu₂O/T-ZnO_W nanocompound was discussed.     

An analysis of temperature dependent current-voltage characteristics of Cu2O-ZnO heterojunction solar cells

Carrier transport and recombination mechanisms in Cu₂O-ZnO heterojunction thin film solar cells were investigated through an analysis of their current-voltage characteristics in the dark and under various illumination intensities, as a function of temperature between 100 K and 295 K. The Cu₂O-ZnO heterojunction solar cells were prepared by metal organic chemical vapor deposition of Cu₂O on ZnO films sputtered on transparent conducting oxide coated glass substrates. Activation energies extracted from the temperature dependence of the J-V characteristics reveals that interface recombination is the dominant carrier transport mechanism. Tunneling across an interfacial barrier also plays an important role in current flow and a thin TiO₂ buffer layer reduces tunneling. A high open circuit voltage at low temperature (~ 0.9 V at around 100 K) indicates that Cu₂O-ZnO heterojunction solar cells have high potential as solar cells if the recombination and tunneling at the interface can be suppressed at room temperature.     

Photocatalytic degradation of dodecyl-benzenesulfonate over TiO2–Cu2O under visible irradiation

A series of TiO₂–Cu₂O mixed oxides were prepared by the hydrolysis of titanium butoxide and reduction of copper acetate with hydrazine. These composite oxides were characterized by X-ray diffraction (XRD), inductively coupled plasma spectrometry (ICP), high-resolution transmission electron microscopy (HRTEM), N₂ adsorption and UV–vis techniques. Photocatalytic degradation of dodecyl-benzenesulfonate (DBS) under visible irradiation was performed, and effects of composition of catalysts and reaction conditions were studied. It was observed that TiO₂–Cu₂O composite oxides exhibited better photocatalytic activity than Cu₂O or TiO₂ alone. Among these composite oxides, the 5%TiO₂–Cu₂O displayed the highest activity, and the degradation percentage of DBS and COD reached 97.3% and 65%, respectively. In addition, it was found that the decomposition of DBS followed the first-order kinetics and the adsorption of DBS followed the Langmuir model. Oxygen in solution played a vital role in the elimination of COD.