Copper Oxide Nanomaterials Research Articles

Novel fabrication of cellulose sprinkled crystalline nanocomposites using economical fibrous sources: High performance, compatible catalytic and electrochemical properties

We report an innovative green synthesis of cellulose based copper oxide nanomaterials by simple sol-gel derived solvo-thermal method. The physio-chemical properties of nanocomposite has enhanced by dissolving filter paper, cotton (Gossypium) and kapok cotton (Ceiba pendantra) as natural cellulose materials in cuprammonium hydroxide (Schweizer's reagent). Hybrid of polysaccharide-copper oxide nanocomposite has exhibited versatility. The composites were characterized by XRD, FESEM-EDAX, HRTEM, FT-IR, UV–Vis, CV, GCD and EIS studies. The sharp XRD peaks have confirmed the crystalline monoclinic phase of CuO as well as crystalline cellulosic materials with crystalline size of 55.7 nm. The observed FT-IR peaks at 523.19 and 1118 cm−1 has proved the Cu–O stretching as well as C–O linkage in cellulose material respectively. The UV–Vis study of nanocomposites has confirmed the specific absorption property of synthesized nanomaterials. The redox peaks in CV and GCD curve have confirmed that the synthesized nanocomposites are the very good energy storage material with the specific capacitance value of 120 F g-1 at the current density of 1 A g-1. They have showed an effective antimicrobial activity against gram positive as well as gram negative bacterial strains and also exhibited good catalytic activity as heterogeneous catalyst in esterification of biodiesel production for industrial applications.

Gas Sensors Based on Copper Oxide Nanomaterials: A Review

Metal oxide semiconductors have found widespread applications in chemical sensors based on electrical transduction principles, in particular for the detection of a large variety of gaseous analytes, including environmental pollutants and hazardous gases. This review recapitulates the progress in copper oxide nanomaterial-based devices, while discussing decisive factors influencing gas sensing properties and performance. Literature reports on the highly sensitive detection of several target molecules, including volatile organic compounds, hydrogen sulfide, carbon monoxide, carbon dioxide, hydrogen and nitrogen oxide from parts-per-million down to parts-per-billion concentrations are compared. Physico-chemical mechanisms for sensing and transduction are summarized and prospects for future developments are outlined.

Dietary exposure to copper sulphate compared to a copper oxide nanomaterial in rainbow trout: bioaccumulation with minimal physiological effects

The dietary bioaccumulation potential of engineered nanomaterials (ENMs) remains poorly understood.

Melting process of nanoparticle enhanced PCM through storage cylinder incorporating fins

This paper discusses how the arrangement of fins can affect the charging process. Mixture of paraffin and copper oxide nanomaterial has been utilized. Several configurations of fins with various position, thickness and length were discussed. Volume fraction of NEPCM in domain is constant, thus reducing melting time is criterion for good efficiency. Outputs reveal that with incorporating fins in both sides, melting process becomes more uniform. Lower melting time with using longer fins is a result of more effective buoyancy forces by dividing the whole domain into smaller blocks. Using fins over both inner and outer pipes shorten the melting time. The main purpose of current modeling is finding the optimized style of fins to gain the highest performance. Nice accommodation of outputs with empirical previous data indicates the verification of code.

(Invited) Elucidation of Activity of Copper and Copper Oxide Nanomaterials for Electrocatalytic and Photoelectrochemical Reduction of Carbon Dioxide

Copper and copper oxide based materials are, in principle, promising components (supports, reactive sites, and visible-light absorbing semiconductors) of electrocatalysts and photocathodes for reduction of carbon dioxide. Electrochemical and photoelectrochemical approaches are generally suitable for the low-temperature CO2-conversion to carbon-based simple organic fuels or utility chemicals.Different concepts of utilization, including nanostructuring, doping, admixing, preconditioning, modification or functionalization of various copper and copper oxide based systems for catalytic electroreduction and photoelectrochemical reduction of CO2 will be elucidated, as well as important strategies to enhance the systems’ overall activity and stability will be discussed. Our recent developments in the area of electrochemical and photoelectrochemical CO2R in aqueous electrolytes at copper-based catalysts and copper oxide-based p-type semiconductors (e.g., Cu2O and related mixed oxides) are focused on the preparation of stable efficient systems exhibiting possibly high activity and selectivity toward a single specific product. Obviously the binding strength (chemisorption) of CO2 and the CO-type reaction intermediates would be different at Cu and Cu-oxo species what translates to differences in activity and selectivity. We have also concentrated on intentional modification of copper and copper oxide electrodes by the addition of other metals, metal oxides, coordination compounds or even organic species to alter reaction pathways, stabilize certain reaction intermediates, and to enhance reactivity. For effective heterogeneous photoelectrochemical CO2R at copper oxide semiconductors, the improvement in stability through formation of the p-n junction and/or the interfacial modifications, e.g. by fabrication of robust, not-inhibiting over-layers having also the capability of controlling the adsorption energy and possible activation steps, is crucial. The potential gain coming from the photoelectrochemical approach concerns the ability of driving the CO2R at less negative potentials relative to what can be achieved in conventional electrocatalysis. For example, careful comparison of the data obtained during electrocatalytic and photoelectrochemical reduction of carbon dioxide at hierarchical bilayered films of copper(I) oxide decorated with tungsten(VI) oxide nanowires clearly implies that upon illumination with visible light the electroreduction of CO2 starts at ca. 0.3 V (vs. RHE) whereas under conventional electrochemical conditions, the reaction is driven below -0.2 V. Although methanol have been postulated as dominating product, the mechanisms of operation of both systems are different: while the reduced, mostly Cu0 sites, are catalytically active during electrochemical CO2R, the photoelectrochemical approach utilizes Cu2O semiconductor and long-lived charge carriers (electrons) photogenerated at the interface. The role of the WO3 over-layer can be summarized as follows: the heterojunction formed by p-type (Cu2O) and n-type (WO3) semiconductors improves the system’s overall stability, suppresses competitive hydrogen evolution, and it seems to minimize charge recombination effects. The advantage of driving CO2R at less negative potentials could be fundamentally useful for construction of water-splitting type electrolyzers for conversion of carbon dioxide. In such electrochemical reactor, the oxygen evolution (water oxidation) reaction proceeds at anode, whereas CO2 is supplied in the cathode compartment where it is electrochemically (rarely photoelectrochemically) reduced.

Effective/comparative investigation on green mediated nano copper oxide: Fabrication, characterization and environmental applications

Nanomaterials are the leading edge for the rapid development of fascinating nanotechnology. The present work deals with the synthesis, structural and optical properties of Randia Dumetorum, sandalwood leaf extracts mediated copper oxide nanoparticles successfully. The synthesized nanomaterials were characterized by XRD for crystallite size and phase; SEM for morphology and particle size; UV–Vis for absorbance of the green synthesized copper oxide nanomaterials respectively. The crystallite size of the Randia Dumetorum and sandalwood mediated copper oxide nanomaterials were found to be 59.25 and 50.25 nm respectively. The synthesized nanomaterials have showed the morphology of spherical and clusters for Randia Dumetorum and sandalwood mediated copper oxide nanomaterials respectively. The copper oxide nanoparticle has acted as efficient catalyst for the oxidation of benzaldehyde. The benzoic acid obtained from chemical and green mediated catalyst was observed to be 3.89 and 4.25 g respectively.

Influence of wavy enclosure and nanoparticles on heat release rate of PCM considering numerical study

The main goal of this attempt is achieving higher rate of solidification with employing two passive techniques. Mixing the based PCM with nanoparticles and considering the wavy shape for walls were two techniques were incorporated. Copper oxide nanomaterial was dispersed in to water with concentration of 0.04 which let us employing homogeneous model. Based on this fact, empirical formulations were utilized for predicting features of NEPCM and various shapes of nano sized particles were considered in thermal conductivity formula. Due to inherent of solidification phenomena, buoyancy can be ignored and pure conduction mechanism with involving the transient source term of solid faction was solved by means of FEM. During the process, the configurations of grids change and the regions around the solid front have finer grid. This opportunity offers outputs with greater accuracy. As shape factor rises, the greater conduction mode can be obtained and similar behavior can be achieved with considering greater amplitude of wavy walls. The best case in term of discharging time is that of m = 5.7 and A = 0.5 in which 156.17 s required to finish the process. Greater amount of shape factor can decrease the time about 5.91% and 5.89% when A = 0.5 and 0.1, respectively. Also, with growth of A, time reduces about 22.66% which indicate better solidification rate. Inclusion of nanoparticles can improve the discharging rate about 17.9%.

Rapid sensing response for phenol with CuO nanoparticles

The human beings are directly or indirectly affected with the environmental pollution, excreted from the industries in the form of liquids such as inorganic and organic hazardous material. As compared to the inorganic chemicals, the organic aromatic compounds are more toxic for the nature. The phenol (PhOH), which is one the largest applied organic compounds in industries and hose hold chemical, which affect to the human health. Due to the wide applicability of copper oxide (CuO) nanomaterial in numerous areas such as optoelectronics, photocatalysis, solar cells, and energy evolution etc; easy to process and provide enhanced and rapid detectible responses against phenol is utilized in this study. The CuO-NPs were synthesized at low refluxing (at 65°C, 90 min) temperature and were well characterize via XRD (X-ray diffraction pattern), FESEM (Field emission scanning electron microscopy), TEM (Transmission electron microscopy) and FTIR (Fourier transform infrared spectroscopy), revels the spherical shaped morphology (∼10 nm). The NPs were pasted on a glassy carbon electrode (GCE) to ascertain their sensing efficiency against PhOH via three electrode system. The efficiency of modified electrode was evaluated under different parameters,concentration effect of PhOH (very low, mid and high) (1, 10 and 31 μL/100 mL of PBS) tested and discloses that the sensor efficiency is very high and concentration dependent at all detectable limits. The formed sensor was also tested with different potentials from 1, 5, 10, 20, 50 and 100 mV/s and it’s sequential to the potential. The chronoamperometry (CuO-NPs/GCE) was investigated in absence and presence and of PhOH at four different voltages +0.05 to +1.2 V from 0 to 1500s to observe the effect of time, which is time reliant. The reproducibility and stability were also tested in terms of cyclic response for seven days (RSD 2.13%), which further displayed that the processed sensor is much reliable for a longer period. To understand well, furthermore, a possible mechanism was also presented, based on obtained results.

Energy storage analysis for discharging of nanoparticle enhanced phase change material within a triplex-tube thermal storage

Abstract In current transient modeling, discharging of PCM based on FEM has been scrutinized. Due to importance of phenomenon near the solid front, time linked mesh has been employed and to reduce the thermal irreversibility, copper oxide nanomaterial was dispersed into H2O. Outputs indicate that using wavy wall and dispersing Platelet copper oxide are capable for expedition of discharging. Obtaining the completed solidification in minimum time is main criteria for designing a storage unit. Changing shape of nanoparticle from spherical to Platelet can reduce the solidification duration about 5.96%. Utilizing greater amplitude of sinusoidal wall can reduce the discharging time by about 7.58% which is related to stronger conduction mechanism. Inclusion of nanoparticles, not only improve the phase change rate but also decline the irreversibility due to lower temperature of domain. Needed time declines about 22.7% with disperse of platelet CuO. As shape of powder changes from platelet to sphere, required time alters from 337.41 s to 358.8 s. The solidification rate for A = 0.3 is 1.06 times greater than that of A = 0.1.

Polypeptide and copper oxide nanocomposite hydrogel for toxicity elimination of wastewater

In this experimental study, a novel bionanocomposite of gelatin as a polypeptide hydrogel consisting of copper (II) oxide nanomaterial (GL–CuO) was prepared. After dispersing the synthesized CuO nanoparticles (NPs) within the GL aqueous solution, they were cross-linked by the addition of a formaldehyde solution. The resulting GL–CuO nanocomposite hydrogels were further characterized by FESEM, EDX, XRD, XPS, and FTIR. The FESEM micrographs confirmed the uniform distribution of CuO NPs in the hydrogel matrix, with dimensions ranging from 60 to 80 nm. The XRD patterns confirmed the presence of the monoclinic crystalline form of CuO NPs embedded in the GL hydrogel. The GL–CuO catalyst was tested in the reduction of two azo dyes. All the reactions were carried out in the presence of a strong reducing agent, NaBH4, with the catalyst demonstrating high activities toward methyl orange and congo red with reaction rate constants of 9.91 × 10−1 min−1 and 5.8 × 10−1 min−1, respectively. The reduction of these dyes was followed by UV–visible spectroscopy that confirmed complete reduction of the dye.

Synthesis of Copper and Copper Oxide Nanomaterials by Pulsed Electric Field in Water with Various Electrical Conductivities.

Nanomaterial synthesis is a hot research subject that has been extensively studied in the last two decades. Recently, plasmas in liquid systems have been proposed as an efficient means of synthesizing various types of nanomaterials. The formation processes implicate many physical and chemical phenomena that take place at the electrode surface, as well as in the plasma volume, which renders it difficult to fully understand the underlying mechanisms. In this study, we assess the effect of electric field on nanomaterial synthesis in a system composed of two copper electrodes immersed in water, in the absence of an electrical discharge. The obtained results indicate that various nanostructures, including copper nanoparticles, copper oxide nanowires, and/or hollow nanoparticles, may be produced, depending on the electrical conductivity of the solution (adjusted by adding highly diluted HCl to deionized water). The materials synthesized herein are collected and characterized, and a formation mechanism is proposed. Overall, our results provide insight into the physical and chemical phenomena underlying nanomaterial synthesis in plasmas in liquid.

Optimization of kraft black liquor treatment using ultrasonically synthesized mesoporous tenorite nanomaterials assisted by Taguchi design

This study explored the removal of total organic carbon (TOC) from the highly polluted pulp and paper industry black liquor effluents by utilizing the mesoporous tenorite (copper oxide) nanomaterials (NMs) prepared by ultrasonic irradiation. The catalyst prepared was fully characterized in terms of chemical, structural, microstructural, and surface characteristics. The optimization of the TOC removal was performed using the Taguchi methodology and by manipulating the operational parameters such as reaction time, initial pH, temperature, sonication time, the dosage of NMs as well as the effect of solar irradiation on the activation of tenorite NMs (30–35 nm and BET surface area = 35 m2/g). TOC removal of 84% of the black liquor was achieved under mild conditions of room temperature and pressure of 5 g/L of the catalyst in 24 h of treatment, including 12 h of solar irradiation which is the first report in the literature on treatment of black liquor Kraft mill effluents using tenorite NMs under the solar irradiation by employing the Taguchi methodology.

Elucidation of activity of copper and copper oxide nanomaterials for electrocatalytic and photoelectrochemical reduction of carbon dioxide

Copper- and copper oxide–based materials are, in principle, promising components (supports, reactive sites, and visible light–absorbing semiconductors) of electrocatalysts and photocathodes for reduction of carbon dioxide. Electrochemical and photoelectrochemical approaches are generally suitable for the low-temperature CO 2 -conversion to carbon-based simple organic fuels or utility chemicals. Different concepts of utilization, including nanostructuring, doping, admixing, preconditioning, modification, or functionalization of various copper- and copper oxide–based systems for catalytic electroreduction and photoelectrochemical reduction of CO 2 are elucidated, as well as important strategies to enhance the systems' overall activity and stability are discussed. • Copper catalysts can induce reduction of CO 2 to different organic molecules including carbon oxygenates and hydrocarbons. • Morphology of copper centers as well as their sizes and shapes influence the intrinsic activity and selectivity. • Higher activity and selectivity can be achieved through application of Cu-based bimetallic and hybrid catalysts. • Copper oxides, particularly Cu 2 O, are capable of harnessing visible light to drive photoelectrochemically CO 2 reduction. • Surface structure, interfacial modification present challenges in maintaining stable and active Cu 2 O-based photocathodes.

Green Synthesis, Characterization and Antimicrobial Activity of Copper Oxide Nanomaterial Derived from Momordica charantia.

BackgroundIn the emerging field of nanotechnology, copper oxide (CuO) nanomaterials are considered to be one of the most important transition metal oxides owing to its fascinating properties. Its synthesis from green chemistry principles is gaining importance as next-generation antibiotics due to its simplicity, eco-friendliness, and cost-effectiveness. In the present study, CuO nanorods (CuO NRs) were synthesized from the aqueous fruit extract of Momordica charantia and characterized using different analytical techniques. Further, the biomedical therapeutic potential was evaluated against multi-drug resistant microbial strains.Materials and MethodsTo synthesize CuO NRs, 0.1M of CuSO4.5H2O solution was added to aqueous extract of Momordica charantia in a 1:3 (v/v) ratio (pH=11) and heated at 50°C followed by washing and drying. The synthesized CuO NRs were subjected to characterization using different analytical techniques such as UV visible spectroscopy, zeta sizer equipped with zeta potential, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM). Further, the application as a biomedical therapeutic potential was evaluated in vitro using well diffusion method against eleven multidrug-resistant clinical bacterial strains, a fungus- Trichophyton rubrum and in ovo against the R2B virus using haemagglutination (HA) test.ResultsCharacterization was preliminarily done by the spectral study that confirms the absorbance band at 245nm. FTIR analysis at 628 cm−1 peak identified copper oxide vibration. SEM analysis revealed agglomerated particle clusters. However, with TEM clear nanorods of average diameter of 61.48 ± 2 nm were observed. EDAX confirmed CuO formation while XRD showed a typical monoclinic structure with 6 nm crystallite size. Biological screening of CuO NRs showed significant results against both in vitro and in ovo methods. Significant inhibitory activity (p<0.0001) was noted against most of the resistant human pathogenic strains including both Gram-positive and Gram-negative bacteria. The highest efficacy was observed against Bacillus cereus with a 31.66 mm zone of inhibition. Besides, the therapeutic potential of CuO NRs against Corynebacterium xerosis, Streptococcus viridians and R2B strain of Newcastle disease is reported for the first time.ConclusionBased on the present results, it could be expected that green synthesized CuO NRs would find potential applications in the field of nanomedicine.

Thermal radiation and surface roughness effects on the thermo-magneto-hydrodynamic stability of alumina–copper oxide hybrid nanofluids utilizing the generalized Buongiorno’s nanofluid model

Sequel to the fact that hybrid nanofluidic systems (e.g. scalable micro-/nanofluidic device) exhibit greater thermal resistance with increasing nanoparticle concentration, little is known on the significance of thermal radiation, surface roughness and linear stability of water conveying alumina and copper oxide nanoparticles. This study presents the effects of thermal radiation and surface roughness on the complex dynamics of water conveying alumina and copper oxide nanoparticles, in the case where the thermophysical properties of the resulting mixture vary meaningfully with the volume fraction of solid nanomaterials, as well as with the Brownian motion and thermophoresis microscopic phenomena. Based on the linear stability theory and normal mode analysis method, the basic partial differential equations governing the transport phenomenon were non-dimensionalized to obtain the simplified stability equations. The optimum values of the critical thermal Rayleigh number depicting the onset of thermo-magneto-hydrodynamic instabilities were obtained using the power series method and the Chock–Schechter numerical integration. The increase in the strength of Lorentz forces, thermal radiation and surface roughness has a stronger stabilizing impact on the appearance of convection cells. On the contrary, the stability diminishes with the increasing values of the volumetric fraction and diameter of nanomaterials. The partial substitution of the alumina nanoparticles by the copper oxide nanomaterials in the mixture stabilizes importantly the hybrid nanofluidic medium.

Synthesis of copper and copper oxide nanomaterials by electrical discharges in water with various electrical conductivities

In the present study, Cu-based nanomaterials are synthesized by initiating spark discharges between two copper electrodes immersed in de-ionized water. The electrical conductivity of water is varied by adding HCl at very low concentrations. The discharge and water properties are determined by measuring the current-voltage waveforms and monitoring water acidity and conductivity, respectively. Scanning electron and transmission electron microscopy analyses of the produced nanoparticles show that increasing water conductivity, by adding HCl, promotes the synthesis of Cu-based nanomaterials. Depending on the initial water conductivity, various nanostructures are observed, including nanoflakes of cuprite (Cu2O), dendrites with high Cu content, and unordered micrometric aggregates with a mixed Cu/Cu2O content. The initial water conductivity also affects the chemical structure, mainly the relative Cu/Cu2O crystalline content.

Importance of Surface Coating to Accumulation Dynamics and Acute Toxicity of Copper Nanomaterials and Dissolved Copper in Daphnia magna.

We evaluated the effect of copper oxide nanomaterials (CuO NMs), uncoated and with 3 different surface coatings (carboxylated, pegylated, and ammonia groups), on acute toxicity and accumulation dynamics in Daphnia magna. With the use of biodynamic modelling, biosorption and elimination rate constants were determined for D. magna following waterborne exposure to dissolved Cu and CuO NMs. The relationship between modeled parameters and acute toxicity endpoints was evaluated to investigate whether accumulation dynamics parameters could be used as a predictor of acute toxicity. The Langmuir equation was used to characterize the biosorption dynamics of Cu NMs and Cu chloride, used as dissolved Cu control. Uptake rates showed the following NM rankings: pristine-CuO > NH3 -CuO > aqueous Cu > polyethylene glycol (PEG)-CuO > COOH-CuO. To determine Cu elimination by D. magna, a one-compartment model was used. Different elimination rate constants were estimated for each chemical substance tested. Those that were easily biosorbed were also easily removed from organisms. Biosorption and depuration properties of NMs were correlated with zeta potential values and diameters of NM agglomerates in the suspensions. No link was found between biosorption and toxicity. Waterborne exposures to more difficult-to-biosorb CuO NMs were more likely to induce adverse effects than those that biosorbed easily. It is proposed that some physicochemical properties of NMs in media, including zeta potential and agglomerate diameter, can lead to higher biosorption but do not necessarily affect toxicity. The mode of interaction of the NMs with the organism seems to be complex and to depend on chemical speciation and physicochemical properties of the NMs inside an organism. Moreover, our findings highlight that coating type affects the biosorption dynamics, depuration kinetics, and dissolution rate of NMs in media. Environ Toxicol Chem 2020;39:287-299. © 2019 SETAC.

Epigenetic effects of (nano)materials in environmental species – Cu case study in Enchytraeus crypticus

Chemical stressors can induce epigenomic changes, i.e., changes that are transferred to the next generation, even when the stressor is removed. Literature on chemical induced epigenetic effects in environmental species is scarce. We here provide the first results on epigenetic effects caused by nanomaterials with an environmental OECD standard soil model species Enchytraeus crypticus species. We assessed the epigenetic potential in terms of global DNA methylation, gene-specific methylation via bisulfite sequencing and MS-HRM (Methylation Sensitive - High Resolution Melting), and gene expression qPCR for genes involved in DNA methylation, histone modifications, non-coding RNA and stress response mechanisms).We have exposed E. crypticus in a multigenerational (MG) test design to Cu (copper oxide nanomaterials (CuO NMs) and copper salt (CuCl2)). To link possible epigenetic effects to population changes, we used exposure concentrations (ECx) that caused a 10% and 50% reduction in the reproductive output (10% and 50% are the standards for regulatory Risk Assessment), the organisms were exposed for five consecutive generations (F1–F5) plus two generations after transferring to clean media (F5–F7), 7 generations in a total of 224 days. Results showed that MG exposure to Cu increased global DNA methylation and corresponded with phenotypic effects (reproduction). Gene expression analyses showed changes in the epigenetic, stress and detoxification gene targets, depending on the generation and Cu form, also occurring in post-exposure generations, hence indicative of transgenerational effects. There were in general clear differences between organisms exposed to different Cu-forms, hence indicate nanoparticulate-specific effects.

Comparison of the dietary bioavailability of copper sulphate and copper oxide nanomaterials inex vivogut sacs of rainbow trout: effects of low pH and amino acids in the lumen

Diet is an important exposure pathway of engineered nanomaterials (ENMs) in fish, but the long duration ofin vivotoxicity tests is a barrier to hazard assessment.

Toxicities of copper oxide nanomaterial and copper sulphate in early life stage zebrafish: Effects of pH and intermittent pulse exposure.

Effort has been made to standardise regulatory ecotoxicity tests for engineered nanomaterials (ENMs), but the environmental realism of altered water quality and/or pulse exposure to these pollutants should be considered. This study aimed to investigate the relative toxicity to early life-stage zebrafish of CuO ENMs at acid pH and then under pulse exposure conditions, all compared to CuSO4. At all pH values, CuSO4 was more toxic to zebrafish than CuO ENMs. Additions of H+ were protective of CuSO4 toxicity, with median lethal concentrations LC50 (with 95% confidence intervals) of: 0.36 (0.33-0.40), 0.22 (0.20-0.24) and 0.27 (0.25-0.29) mg L-1 at pH 5, pH 6 and pH 7, respectively. In contrast, the toxicity of CuO ENMs increased with acidity; LC50 values were: 6.6 (4.5-8.5), 19.4 (11.6-27.2) and >100mgL-1 at pH 5, pH 6 and pH 7, respectively. The increased toxicity of the CuO ENMs in acid water corresponded with greater dissolution of dissolved Cu from the particles at low pH, suggesting free Cu2+ ion delivery to the zebrafish was responsible for the pH-effect. In continuous 96h exposures to the substances at the LC10 values and at pH 6, both CuSO4 and CuO ENMs caused Cu accumulation, inhibition of Na+/K+-ATPase and depletion of total glutathione in zebrafish. However, two 24h pulses of CuSO4 or CuO ENMs at the same peak concentration caused similar effects to the continuous 96h exposure, despite the shorter exposure durations of the former; suggesting that the pulses were more hazardous than the continuous exposure. In conclusion, the current water quality correction for pH with respect to Cu toxicity to freshwater fish should not be applied to the nano form. Crucially, CuO ENMs are more toxic in pulse than continuous exposure and new corrections for both water pH and the Cu exposure profile are needed for environmental risk assessment.