Presence Of CuO Nanoparticles Research Articles

Structural and optical properties of polyvinyl alcohol/copper oxide (PVA/CuO) nanocomposites

In the present investigation, pristine polyvinyl alcohol (PVA) and copper oxide (CuO) incorporated nanocomposite films have been fabricated via simple solution cast technique. The structural and optical properties of the prepared films were studied in detail. Various concentrations of CuO NPs (0.1–0.4 wt %) incorporated in the PVA film were prepared. The X-ray diffraction (XRD) profiles indicate the presence of CuO nanoparticles (NPs) in PVA film. XRD results indicate that, the CuO NPs were successfully incorporated into the PVA host matrix with no additional impurity peaks. The obtained CuO NPs belong to the monoclinic phase as confirmed by the XRD results. The peak observed at 2θ = 19.4° evident for the formation of semi crystalline PVA polymer. The average crystallite size of the prepared NPs was observed to be ∼0.52 nm. The vibrational bands present in the prepared films were confirmed by the Fourier transform infra-red spectroscopy (FTIR) plots. The presence of the NPs in the films was further investigated with the help of Raman spectra. UV–visible optical absorption spectra was recorded to evaluate the band gap values of the prepared films. The band gap value for pristine PVA was found to be 5.35 eV and it decreases with increase of CuO NPs concnetration owing to the change in the electronic structure of the pure PVA. The dielectric properties were also evaluated and it was found that, with increase in the CuO NPs concentration the dielectric constant also increases owing to the increase in density of states leading to the formation of polarization. The optical conductivity of the prepared nanocomposites increases with increase in the NPs concentration due to the formation of the charge transfer complex. The obtained results reveal that, the addition of CuO NPs reduces the optical band gap of the PVA polymer films.

Synthesis of visible light-responsive cuprous oxide/sunflower stem pith hybrid materials for detoxification of methylene blue.

The detoxification of dye-contaminated water by photocatalysis has become a research priority. Here, a novel hybrid material, cuprous oxide/sunflower stem pith (Cu2O/SSP), was successfully synthesized in situ, using copper hydroxide gel, prepared by ion exchange, as the precursor to Cu2O. The presence of Cu2O nanoparticles on the SSP was confirmed by scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction analyses. Using methylene blue (MB) as the target pollutant, Cu2O/SSP delivered excellent adsorption-photocatalytic degradation and was readily photoregenerated. Cu2O/SSP removed 72.7% of MB after 60 min under visible light irradiation, an increase of 15.6 % compared with unmodified SSP. SSP plays three roles in the removal of MB: it acts as an adsorbent for the MB, a carrier for the Cu2O nanoparticles and it also inhibits photocorrosion of Cu2O. The mechanism of adsorption-photocatalysis by Cu2O/SSP was investigated and a description of the mechanism is provided. This study paves the way for the detoxification of dye-containing wastewater using hybrid biomass materials.

Photo-Fenton Catalyzed by Cu2O/Al2O3: Bisphenol (BPA) Mineralization Driven by UV and Visible Light

This work aimed to demonstrate Cu2O/Al2O3 as a catalyst of the photo-Fenton process in the UV and visible spectra. Cu2O nanoparticles were synthesized by laser ablation in liquid and supported on Al2O3. The catalytic activity of the resulting solid was assessed in the mineralization of bisphenol A (BPA). The studied variables were type of Al2O3α and γ, Cu content (0.5 and 1%), and H2O2 concentration (1, 5, and 10 times the stoichiometric amount). The response variables were BPA concentration and total organic carbon (TOC) removal percentage. The presence of Cu2O nanoparticles (11 nm) with an irregular sphere-like shape was confirmed by transmission electron microscopy (TEM) and their dispersion over the catalytic surface was verified by energy-dispersed spectroscopy (EDS). These particles improve ·OH radical production, and thus a 100% removal of BPA is achieved along with ca. 91% mineralization in 60 min. The BPA oxidation rate is increased one order of magnitude compared to photolysis and doubles that for H2O2 + UV. An increase of 40% in the initial oxidation rate of BPA was observed when switching from α-Al2O3 to γ-Al2O3. 4-hydroxybenzaldehyde, 4-hydroxybenzoic acid, acetaldehyde, and acetic acid are the BPA oxidation by-products identified using LC/MS and based on this a reaction pathway was proposed. Finally, it was also concluded that the synthesized catalyst exhibits catalytic activity not only in the UV spectrum but also in the visible one under circumneutral pH. Therefore, Cu2O/Al2O3 can be recommended to conduct a solar photo-Fenton reaction that can degrade other types of molecules.

Ethylene accelerates copper oxide nanoparticle-induced toxicity at physiological, biochemical, and ultrastructural levels in rice seedlings.

The enormous use of metal-based nanoparticles (NPs) in different sectors may result in enhanced accumulation in agricultural soil, which could impose negative effects on crop productivity. Hence, strategies are needed to explore the mechanisms of copper oxide nanoparticle (CuO NP)-induced toxicity in crops. The present study aimed to investigate the involvement of ethylene in CuO NP-induced toxicity in rice seedlings. Here, our results indicate that 450mg L-1 of CuO NPs induced toxic effects in rice seedlings. Thus, it was evidenced by the reduced plant biomass accumulation, enhanced oxidative stress indicators, and cellular ultrastructural damages. More importantly, the exogenous supply of ethylene biosynthesis and signaling antagonists cobalt (Co) and silver (Ag) respectively provided tolerance and improved the defense system of rice seedlings against CuO NP toxicity. The ethylene antagonists could significantly reduce the extent of ultrastructural and stomatal damage by controlling the ROS accumulation in rice seedlings under CuO NP stress. Furthermore, Co and Ag augmented the antioxidant defense system against CuO NP-induced toxicity. Contrary to that, all oxidative damage attributes were further enhanced exogenous application of ethylene biosynthesis precursor [1-aminocyclopropane-1-carboxylic acid (ACC)] in the presence of CuO NPs. In addition, ACC could increase the CuO NP-induced stomatal and ultrastructural damages by reducing the ROS-scavenging ability in rice seedlings. Taken together, these results indicate the involvement of ethylene in CuO NP-induced toxicity in rice seedlings.

Copper-Nanoparticle-Coated Fabrics for Rapid and Sustained Antibacterial Activity Applications

The scientific community has recognized that copper can kill bacteria; however, the effect of the particle size, concentration, and oxidation state on antibacterial activity remains unclear for copper and its nanoparticles (NPs), in particular. In this study, copper NP coatings with extremely fast and sustained antibacterial activity are reported. It is found that coating with cuprous oxide (Cu2O) NPs (∼150 nm) and coating with metallic copper NPs (∼50 nm) on commonly used fabrics for cleaning and masks can kill bacteria within 45 s. Our bacterial study was conducted using Staphylococcus aureus as a Gram-positive bacterium and Klebsiella pneumoniae and Pseudomonas aeruginosa as Gram-negative bacteria. Scanning electron micrographs suggest bacterial damage, and bacterial DNA harvested after interaction with copper-coated fabrics indicates DNA fragmentation. On top of this, significantly higher levels of 8-hydroxy-2′-deoxyguanosine are also detected in DNA after interaction with coated fabrics, signifying that both copper and Cu2O NPs rapidly induce oxidative stress. Furthermore, cumulative inoculations with K. pneumoniae for 144 h show excellent sustained bacterial killing in the presence of Cu2O NPs. Using a combination of detailed physical and chemical analysis of the NPs and a study of how bacteria interact with the coated substrate, it is possible to establish the parameters that resulted in speedy and robust antibacterial properties in Cu2O-coated fabrics. This study offers a rational strategy on how to slow down or even halt the transmission of infectious pathogens.

Fabrication and performance evaluation of CuO, NiO, and Co3O4-embedded electrospun electrolytes: Suitable for lithium polymer solvent-free batteries

Electrospun fibrous materials are promising electrolytic candidates suitable for all-solid-state lithium batteries (ASSLBs), owning to high ionic conductivity and energy density. However, the limited conductivity is yet to overcome and exploring chemistries for decorating them using electro-active filler of dopants is suggested by experts. In this direction, copper oxide (CuO), nickel oxide (NiO), and cobalt oxide (Co3O4) have also gained considerable attention due to their intriguing properties in various electrochemical devices. Herein, nano CuO, NiO, and Co3O4 were synthesized and used as the filler in the polyethylene oxide-based electrospun fibers to approach a proper electrochemical behavior. The obtained electrolytes were fully characterized using appropriate analytical systems. Based on the careful analysis of the results, incorporating 0.21 wt% nano CuO into the membrane led to approaching the most desirable characteristics by showing a higher concentration of free Li+ ions, greater amorphous domains, and lower Tg. Therefore, the highest ionic conductivity of 0.32 mS cm−1 was achieved at 25 °C. In addition, the CuO-filled fibers resulted in the activation energy drop from 53 to 19 kJ mol−1. The observed trends were confirmed through the estimation of dielectric and electrical properties. In a Li|LiCoO2 half-cell, reversible CV curves after 25 cycles as well as a stable structure up to 5.00 V were attained for the filled electrospun fibers. More significantly, the presence of CuO nanoparticles caused the discharge capacity increment from 68 to 120 mA h g−1 at 0.5 C for up to 100 cycles. Overall, the upgraded designing of the electrospun fibers through embedding the filler particles opens an influential way toward high-performance ASSLBs with appropriate safety.

Investigation on the effect of CuO nanoparticles on the IFT and wettability alteration at the presence of [C12mim][Cl] during enhanced oil recovery processes

In the current study, the effect of CuO nanoparticles (CuO-NPs) at the presence of dodecyl-3-methylimidazolium chloride ([C12mim][Cl]) is investigated on the interfacial tension (IFT) reduction, wettability alteration, and even tertiary oil recovery. Since the prepared solutions with CuO-NPs are completely dark and it is impossible to measure the IFT of these solutions in the presence of crude oil using the pendant drop method (since one of the phases must be transparent for IFT measurement using the pendant drop method), n-heptane (representative of saturates) and toluene (representative of aromatics) are used only for IFT measurement of solutions prepared by CuO-NPs, while rest of the experiments are performed using crude oil. The obtained results reveal that CuO-NPs are not stable in the aqueous solution in the absence of surfactant which means fast precipitation of CuO-NPs and a high risk of pore plugging. In this way, the stability of CuO-NPs is investigated at the presence of dodecyl-3-methyl imidazolium chloride ([C12mim][Cl]) as an effective surfactant for stabilizing the CuO-NPs in the aqueous solution (more than 1 month without precipitation using 1000 ppm of IL). Further measurements reveal that although the presence of IL in the aqueous solution can reduce the IFT of oil/aqueous solution system, especially for the aqueous solutions prepared by formation brine (0.65 mN.m−1), the presence of CuO-NPs has no considerable effect on the IFT. On the other hand, not only the contact angle (CA) measurements reveal the considerable effect of IL on the wettability alteration toward water-wet condition (68.3° for IL concentration of 1000 ppm) but also the addition of CuO-NPs can significantly boost the wettability alteration toward strongly water-wet condition (23.4° for the concentration of 1000 ppm of CuO-NPs). Finally, several core flooding experiments are performed using different combinations of chemicals to find the effect of these chemicals on the tertiary oil recovery factor. The results reveal that the presence of CuO-NPs can enhance the oil recovery of injected chemical slug (aqueous solution prepared by dissolution of IL with an oil recovery factor of 10.1% based on Original oil in place (OOIP)) to 13.8, %, 16.9%, and 21.2% based on OOIP if 500, 1000, 2000 ppm of CuO-NPs existed in the solution concomitant with 1000 ppm of [C12mim][Cl].

Interface engineered Co, Ni, Fe, Cu oxide hybrids with biphasic structures for water splitting with enhanced activity

Developing high-performance catalysts for water splitting via renewable electricity is of great significance for the clean production of hydrogen. This work reports rational design and controllable fabrication of metal oxide hybrid catalyst CoNiFe2O5·2CuO with unique biphasic microstructures for electrochemical water splitting. Benefited from the presence of CuO nanoparticles as the second phase, more defects and active sites were formed around the interfaces of CoNiFe2O5 and CuO, which led to excellent performances for electrocatalytic water splitting. In particular, the catalyst exhibited outstanding activity for hydrogen evolution reaction with a small overpotential of 30 mV to reach a current density of 10 mA cm−2 and showed a higher turnover frequency (0.3 s−1) than commercial catalyst Pt/C (0.1 s−1) under an overpotential of 50 mV. Moreover, it also displayed good activity for oxygen evolution reaction with an overpotential of 264 mV at 10 mA cm−2. Using CoNiFe2O5·2CuO as the catalyst for electrode pair to construct a cell, a very low cell voltage of 1.53 V is enough to achieve overall water splitting at 10 mA cm−2 in 1 M KOH electrolyte, and the cell could maintain the stable performance at 10 mA cm−2 within 100 h. The as-prepared metal oxide hybrids with biphasic microstructures may have promising application potentials in water splitting.

Lignin-mediated in-situ synthesis of CuO nanoparticles on cellulose nanofibers: A potential wound dressing material

Herein we present our research on the synthesis of CuO nanoparticles on the surface of electrospun cellulose (CE) nanofibers using alkali lignin as a reducing agent. Fascinatingly, CA nanofibers were deacetalized during alkali lignin treatment, which was verified by FTIR-ATR spectra. The morphology of the produced nanofibers was observed with SEM and TEM. The presence of CuO nanoparticles was verified by EDX, XRD, and XPS. The Cu/CE nanofibers showed low thermal stability. MVTR values of 2100–1900 g/m2/day are adequate for the transport of air and moisture from the wound surface. The Cu/CE showed faster release (80%) of copper ions to aqueous environment within 24 h and seemed to advance towards plateau for the next five days. The Cu/CE nanofibrous mats exhibited excellent antibacterial efficacy against both gram-negative Escherichia coli (E. coli) and gram-positive Staphylococcus aureus (S. aureus) bacteria. NIH3T3 fibroblast cells have excellent migrating and proliferating ability on our prepared nanofibrous mats. The presence of bound alkali lignin on the surface of nanofibers added a benefit of antioxidant activity. These findings revealed that such type of nanofibrous mats could be used as a potential wound dressing material.

Biothermodynamic, antiproliferative and antimicrobial properties of synthesized copper oxide nanoparticles

Nanoparticles (NPs) have been widely used as anticancer and antibacterial agents. However, before their use in biomedical applications, some in vitro assays should be carried out to investigate their interaction with biological systems. The copper oxide NPs (CuO NPs) were synthesized by hydrothermal method and their interaction with human serum albumin (HSA), leukemia K562 cells and three strains of bacteria was explored by spectroscopic, docking, cellular, and antibacterial investigations. The TEM, DLS, XRD, FTIR, Raman, and UV–visible techniques revealed that synthesized CuO NPs provide a crystalline structure corresponding to CuO nanoclusters with good colloidal stability. Biothermodynamic studies showed that CuO NPs formed a static complex with HSA molecules through hydrogen bonds which was further confirmed by docking analysis. UV–Vis spectroscopy results exhibited that the melting temperature (Tm) of HSA was slightly changed in the presence of CuO NPs. Cellular studies displayed that CuO NPs selectively resulted in the mortality of K562 cells through cell membrane leakage, caspase-9 and -3 activation, and apoptosis. Finally, antibacterial assays depicted that CuO NPs can induce an inhibitory effect in the case of both Gram-negative and Gram-positive bacteria. In conclusion, this study may provide useful data regarding the protein binding and biomedical applications of NPs.

ZnO/CuO hybrid films synthesized by sequential application of electrochemical and spin coating technique

The synthesis of ZnO/CuO films on ITO substrate was realized in two steps, first ZnO was deposited electrochemically and then CuO nanoparticles were precipitated with help of spin coating technique. ZnO nanorods were obtained in aqueous Zn(NO3)2 solution, in presence of KCl as capping agent. Spin coating technique yielded CuO nanoparticles on these nanorods, particle size was employed by copper (II) acetate and ethanolamine in 2-methoxyethanol. In addition, field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy studies were also realized for understanding the structure. UV–Visible spectrophotometer study results revealed that the bandgap value of bilayered structure was governed by presence of CuO nanoparticles. Mott–Schottky analysis was realized for characterization of prepared semiconductor materials, which indicated to + 0.571 for ZnO/CuO(3), while these values were + 0.532 V and − 0.360 V for CuO and ZnO, respectively. Electrochemical measurements were realized with help of solar simulator, for testing photocatalytic activity of ZnO/CuO as photocathode material, in aqueous solution.

CuO and ZnO Nanoparticle Application in Synthetic Soil Modulates Morphology, Nutritional Contents, and Metal Analysis of Brassica nigra.

Black mustard (Brassica nigra) was grown in pots amended with 41 nm ZnO (200–600 mg/kg soil) and 47 nm CuO (12.5–50 mg/kg soil) nanoparticles (NPs) to analyze growth response and yield characteristics. B. nigra seed germination was not affected by CuO NPs, but significant toxicity was observed by ZnO NP treatment. Both NPs significantly increased the growth profile of B. nigra, i.e., the stem height, number of leaves, average leaf area, number of branches, and number of nodes per plant. Application of ZnO and CuO NPs brought a significant dose-dependent decrease in primary root length; however, the number of secondary roots increased in the presence of CuO NPs. The average number of flowers and pods per plant significantly increased in the presence of CuO NPs. The seed yield, average seed weight per plant, and seed diameter parameters were observed to be better in the presence of CuO NPs as compared with ZnO NPs. Total protein contents and glucosinolates increased in the seeds grown in the NP-amended soil, while total oil contents decreased. Oil analysis depicted that oleic acid and linolenic acid percentage decreased while erucic acid percentage increased in seeds in the presence of both NPs in the soil. An atomic absorption spectrophotometer showed accumulation of Cu and Zn in B. nigra in the following order: root > stem > leaves > seeds. The study concludes that CuO and ZnO NPs have detrimental effect on the B. nigra plant and yield. The release of NPs and type of metal in NPs might also have a positive effect on the plant; however, their concentration in the soil also matters.

Hybrid Nanocomposites of Multi-walled Carbon Nanotubes (MWCNTs) and CuO as Electrode Materials for Energy Storage Devices

The search for electrode materials as a potential candidate for Li-ion based batteries is important to achieve high-performance devices. This work constitutes the experimental and theoretical investigation of structural stability and electrochemical behavior of cupric oxide and multi-walled carbon nanotubes (CuO/MWNNTs) nanocomposites. The electrochemical performance of nanocomposites was gauged employing charge/discharge and cyclic voltammetry studies. It is shown that electrochemical properties of pure materials, due to the synergistic effect, are considerably enhanced in CuO/MWNNTs composites. As a result, high rate capability and better cycling stability is observed in CuO-5%MWCNTs samples. In addition, this composite possesses better specific capacity 810 mAh g−1 and a high columbic efficiency of 80.86%. The DFT calculations also confirmed the improved electrochemical properties of MWCNTs in the presence of CuO nanoparticles.

Cu2O nanoparticles for adsorption and photocatalytic degradation of methylene blue dye from aqueous medium

In order to treat the organic pollutants like dyes in water bodies, the environmentally benign nanoparticles are used extensively. The nanoparticles preparation by green chemistry approach is advantageous for this purpose. The Cu2O nanoparticles (NPs) were synthesized here by using Cu(NO3)2 and T. arjuna bark extract (as reducing and capping agent) under microwave irradiation. They were characterized by X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), BET surface area and UV–vis spectra. The adsorption of methylene blue (MB) on Cu2O NPs in light and dark condition was found to be about 63% and 55%, respectively. The adsorption followed Langmuir isotherm, Freundlich isotherm and pseudo second order kinetics. The photo induced degradation of MB dye in presence of Cu2O NPs was also studied using photocatalytic reactor having UV lamp (250 W). Up to 97% degradation of MB occurred as monitored from UV–vis spectra. The degradation of MB was confirmed by HPLC and LC–MS analysis.

Augmentation of ferromagnetism in CuO–Al2O3 nanocomposite synthesized via solution combustion method

The finite size effect of CuO nanoparticles and their effect on the magnetic behavior of a CuO–Al2O3 nanocomposite synthesized via a solution combustion method are discussed here. It is observed that the introduction of CuO nanoparticles of ∼20 nm in size on the surfaces of Al2O3 nanosheets strongly influences the magnetic moment of the nanocomposite. The X-ray diffraction pattern reveals the presence of a CuO phase in the CuO–Al2O3 nanocomposite. Electron microscopy imaging shows the presence of CuO nanoparticles distributed over the surfaces of Al2O3 nanosheets. Magnetic measurements performed at 5 and 300 K revealed a strong enhancement in the saturation magnetization of the CuO–Al2O3 nanocomposite at both temperatures. This increase is due to the formation of CuO nanoparticles on the surfaces of the Al2O3 nanosheets. These CuO nanoparticles show a ferromagnetic nature due to the uncompensated surface Cu2+ spins of the copper ions. The presence of the Cu2+ state in the CuO nanoparticles in the CuO–Al2O3 nanocomposite was confirmed by X-ray photoelectron spectroscopy (XPS) measurements.

Anticancer Activity of Copper Oxide Nanoparticles Synthesized from Brassia actinophylla Flower Extract

There are many methods to synthesize metal and metal oxide nanoparticles. In this paper, copper oxide nanoparticles have been synthesized by solution combustion method using Brassia actinophylla i.e. Schefflera actinophylla flower extract belongs to Araliaceae family. The importance of solution combustion is one of the easy and simplest methods for the synthesis of metal oxide nanoparticle. The CuO nanoparticles were synthesized at various temperatures and the characterization has been carried out by UV, FTIR, PXRD, SEM, TEM and EDAX analysis. At lower temperature, the peak was not observed but at 400 ºC, the UV peak was observed at 340 nm. The FTIR peaks observed at 1000-500 cm-1 confirms again the presence of CuO nanoparticles. The monoclinic phase and crystalline structure of nanoparticles were revealed by PXRD pattern, by Scherrer′s method the average crystalline sizes were found to be in the range of 15 to 24 nm. The size and the shape of nanoparticles were confirmed by SEM and TEM reports. The SEM images of nanoparticles show spherical in shape and free from agglomeration. TEM analysis reports the nanoparticle sizes ranging from 2 to 20 nm. The percentage of copper (52 %) and oxygen (26 %) elements were recorded in the EDAX analysis. The study of size and stability of nanoparticles were done by zeta potential values. The antibacterial activity of CuO nanoparticles were carried out against Staphylococcus aureus and Escherichia coli bacteria's by agar well diffusion method. The MTT assay was performed in order to check the anticancer activity of CuO nanoparticles against HT-29 colon cancer cells.

Polyvinyl alcohol/CuO nanocomposite hydrogels: facile synthesis and long-term stability

Within this study, Polyvinyl alcohol/CuO nanocomposite hydrogels were synthesized through dispersing CuO nanoparticles in a PVA solution, using the freeze-thawing procedure in order for physically crosslinking. The average particle size of CuO nanoparticles which was added to the hydrogel was determined as 3.51 nm according to the XRD analysis after the ball milling process. The presence of CuO nanoparticles in nanocomposite hydrogels was determined by UV-vis spectroscopy, FESEM, EDS, and FTIR analysis. Also, the rheological properties of neat hydrogel and PVA/CuO nanocomposite hydrogels were examined. The addition of CuO nanoparticles to the polymer structure develops rheological features of PVA hydrogels. The Effect of CuO content of nanocomposite hydrogels on the swelling behavior and long term stability was investigated. These nanocomposite hydrogels demonstrated unique properties for biomedical applications due to their high swellability at pH 2.1 as the pH values of the stomach and long term stability. According to these results, the addition of CuO to the hydrogel structure improved the swelling characteristics of neat PVA hydrogel.

Response of Cupriavidus basilensis B-8 to CuO nanoparticles enhances Cr(VI) reduction

CuO nanoparticles (NPs) released into aqueous environments induce metal toxicity, which generally exerts negative effects on various organisms and leads to great challenge for wastewater biotreatment. In this study, a promotion effect of CuO NPs on biological process was first found. Cr(VI) reduction by Cupriavidus basilensis B-8 (hereafter B-8) was enhanced in the presence of CuO NPs. The efficiency of Cr(VI) bioreduction was much higher with B-8 and CuO NPs (approximately 100%) than with B-8 (approximately 37.6%) and CuO NPs (39.9–44.7%) alone, indicating a stimulatory effect of CuO NPs on Cr(VI) reduction by B-8. Our material analyses revealed different response mechanisms of B-8 to Cr(VI), with and without CuO NPs. The addition of CuO NPs influenced the interaction of Cr(VI) with the N-, P-, S-, and C-related functional groups of B-8. Transcriptomic analysis indicated that multiple mechanisms, including Cr(VI) uptake and reactive oxygen species detoxification, were induced by Cr(VI). Many genes involved in various metabolic processes were significantly upregulated by the addition of CuO NPs. To a certain extent, the pressure of DNA repairment by B-8 induced by Cr(VI) was also alleviated by the presence of CuO NPs. They contributed to facilitate B-8 growth and enhance Cr(VI) reduction, even with 50 mg/L Cr(VI). This study not only elaborated the mechanisms of bacterial Cr(VI) reduction when enhanced by CuO NPs, but also provided a novel perspective for wastewater biotreatment.

Stimulating effect of nanoparticles and salts on thermo and halo-tolerant cell-bonded laccase synthesis in Acinetobacter sp. UIETPU

Abstract Laccase synthesizing Acinetobacter sp. UIETPU was isolated from the rhizosphere of the paddy plant. Enzyme was firmly cell attached and no extracellular laccase activity was detected up to 96h, 37○C, and 150 rpm. Nanoparticles (NPs) of Cu and CuO (100 μM) increased the cell-bonded laccase synthesis by 2.1 and 2.3 fold respectively, but potent laccase inducer CuSO4 enhanced the enzyme production by 1.5 fold at the same concentration. There was no adverse effect of NaCl (0.5–5.0%) on laccase synthesis when added to the production media. Enzyme oxidizes the syringaldazine and 2, 6-dimethoxyphenol (specific substrates of laccase) and inhibited by the dithiothreitol (DTT), sodium azide and cystein by 98, 65 and 52% respectively. Cell-bonded laccase showed the 100% activity up to 2h and t 1 2 of the bonded enzyme was 4h at 80○C. Field emission scanning electron microscopy (FESEM) revealed that there was no lysis of Acinetobacter sp. UIETPU cells in the presence of CuO NPs.

Insights into the role of CuO in the CO2 photoreduction process

The CO2 photoreduction process to produce light hydrocarbons is known to be influenced by the presence of CuO nanoparticles, but the actual role of this material, whether as a catalyst or a reactant, has not yet been revealed. In this work, we investigate the role of CuO nanoparticles produced by a solvothermal method as a catalyst in CO2-saturated water reaction media under UV light, considering the effects of different electrolytes (Na2C2O4, KBrO3, and NaOH) and temperatures on nanoparticle phase and activity. The electrolyte strongly influenced product selectivity (NaOH led to evolution of CH4, Na2C2O4 to CO, and KBrO3 to O2) and induced CuO phase change. A long-term analysis of these processes indicated that during the initial steps, CuO acted as a reactant, rather than as a catalyst, and was converted to CuCO3.Cu(OH)2, while the as-converted material acted as a catalyst in CO2 photoreduction, with conversion values comparable to those reported in the literature.