We have synthesized ternary Ni-Co-Cr nanoclusters using one step method by simultaneous sputtering of metallic targets through inert gas condensation (IGC) deposition process. The difference in surface energy between the component atoms creates a preferential surface phase leading to the formation of multi core/shell structures. Surface structure and composition analysis reveal metallic and oxide phases characterized by extraordinary 1.43 mu m periodicity strong magnetic stripe domains with weak magnetic force microscopy signal attenuation up to a lift height value of 2.5 mu m. In addition, the ternary nanoclusters exhibit strong ferromagnetic behavior below the blocking temperature of 139 K with coercivity of 700 Oe at 4 K. The enhanced magnetic properties are attributed to Volmer-Weber growth mechanism and pave a facile way for preparing ternary core/ shell magnetic structures needed for applications which require strong magnetic anisotropy along their growth direction.
We report on the surface, sub-surface (top few nanometers) and bulk properties of hydrothermally grown zinc oxide (ZnO) nanorods (NRs) prior to and after hydrogen treatment. Upon treating with atomic hydrogen (H*), upward and downward band bending is observed depending on the availability of molecular H2O within the structure of the NRs. In the absence of H2O, the H* treatment demonstrated a cleaning effect of the nanorods, leading to a 0.51 eV upward band bending. In addition, enhancement in the intensity of room temperature photoluminescence (PL) signals due to the creation of new surface defects could be observed. The defects enhanced the visible light activity of the ZnO NRs which were subsequently used to photocatalytically degrade aqueous phenol under simulated sunlight. On the contrary, in the presence of H2O, H* treatment created an electronic accumulation layer inducing downward band bending of 0.45 eV (similar to 1/7th of the bulk ZnO band gap) along with the weakening of the defect signals as observed from room temperature photoluminescence spectra. The results suggest a plausible way of tailoring the band bending and defects of the ZnO NRs through control of H2O/H* species.
A device (10) for capacitive deionization of an aqueous media containing dissolved ion species, said device comprising a cell with a first primary electrode (2) and a second primary electrode (3) arranged opposite the first primary electrode (2) and preferably separated by at least one non-conductive spacer (4, 4'). A third electrode (7) is arranged between the first and the second electrode. The third electrode (7) is grounded whereas the first and the second electrodes are polarized versus the grounded third electrode.
The present disclosure relates to a device 10 for capacitive deionization of an aqueous media containing dissolved ion species. The device comprises a cell comprising a first primary electrode 2 and a second primary electrode 3 arranged opposite the first primary electrode 2 and preferably separated by at least one non-conductive spacer 4, 4'. A third electrode 7 is interposed between the first and the second electrode. The third electrode 7 is grounded whereas the first and the second electrodes are polarized versus the grounded third electrode.
A wooden stick coated with a novel graphene-based nanocomposite (Graphene oxide/polyethylene glycol (GO/PEG)) is introduced and investigated for its efficacy in solid phase microextraction techniques. The GO/PEG-stick was prepared and subsequently applied for the extraction of beta -blockers, acebutolol, and metoprolol in human oral fluid samples, which were subsequently detected by liquid chromatography tandem mass spectrometry (LC-MS/MS). Experimental parameters affecting the extraction protocol including sample pH, extraction time, desorption time, appropriate desorption solvent, and salt addition were optimized. Method validation for the detection from oral fluid samples was performed following FDA (Food and Drug Administration) guidelines on bioanalytical method validation. Calibration curves ranging from 5.0 to 2000 nmol L-1 for acebutolol and 25.0 to 2000 nmol L-1 for metoprolol were used. The values for the coefficient of determination (R-2) were found to be 0.998 and 0.996 (n = 3) for acebutolol and metoprolol, respectively. The recovery of analytes during extraction was 80.0% for acebutolol and 62.0% for metoprolol, respectively. The limit of detections (LODs) were 1.25, 8.00 nmol L-1 for acebutolol and metoprolol and the lower limit of quantifications (LLOQ) were 5.00 nmol L-1 for acebutolol and 25.0 nmol L-1 for metoprolol. Validation experiments conducted with quality control (QC) samples demonstrated method accuracy between 80.0% to 97.0% for acebutolol and from 95.0% to 109.0% for metoprolol. The inter-day precision for QC samples ranged from 3.6% to 12.9% for acebutolol and 9.5% to 11.3% for metoprolol. Additionally, the GO/PEG-stick was demonstrated to be reusable, with the same stick observed to be viable for more than 10 extractions from oral fluid samples.
The performance of a capacitive deionization (CDI) device is governed by complex relations between the electrode material properties, fluid velocity and fluid distribution within the device. In order to maximize fluid (water) interaction with the electrodes, the relationships between fluid flow and electrode material properties are explored here to develop novel CDI architectures which reduce the pressure drop, improve surface utilization factor and improve the electrode salt adsorption capacity. Using activated carbon cloth (ACC) as the electrode material, the pressure drop across the CDI device is quantified with respect to flow scheme (flow-between and flow-through CDI modes) used. Computational fluid dynamic (CFD) models are developed to study and optimize the fluid velocity and distribution in order to minimize the device fluid pressure losses. The model predictions are verified by constructing the conceptualized CDI devices and correlating the theoretical and experimentally obtained pressure drops, salt adsorption capacities and fluid flow parameters. The results indicate that up to 60% reduction in pressure drop and similar to 35% increase in specific salt adsorption capacity can be achieved by simple changes to the input-output port architecture of the CDI units. The results describe a method to considerably lower energy consumption in commercial CDI devices.
The magnitude and distribution of the electric field between two conducting electrodes of a capacitive deionization (CDI) device plays an important role in governing the desalting capacity. A dielectric coating on these electrodes can polarize under an applied potential to modulate the net electric field and hence the salt adsorption capacity of the device. Using finite element models, we show the extent and nature of electric field modulation, associated with changes in the size, thickness, and permittivity of commonly used nanostructured dielectric coatings such as zinc oxide (ZnO) and titanium dioxide (TiO2). Experimental data pertaining to the simulation are obtained by coating activated carbon cloth (ACC) with nanoparticles of ZnO and TiO2 and using them as electrodes in a CDI device. The dielectric-coated electrodes displayed faster desalting kinetics of 1.7 and 1.55 mg g(-1) min(-1) and higher unsaturated specific salt adsorption capacities of 5.72 and 5.3 mg g(-1) for ZnO and TiO2, respectively. In contrast, uncoated ACC had a salt adsorption rate and capacity of 1.05 mg g(-1) min(-1) and 3.95 mg g(-1), respectively. The desalting data is analyzed with respect to the electrical parameters of the electrodes extracted from cyclic voltammetry and impedance measurements. Additionally, the obtained results are correlated with the simulation data to ascertain the governing principles for the changes observed and advances that can be achieved through dielectric-based electrode modifications for enhancing the CDI device performance.
Clean water is one of the primary UN sustainable development goals for 2,030 and sustainable water deionization and disinfection is the backbone of that goal. Capacitive deionization (CDI) is an upcoming technique for water deionization and has shown substantial promise for large scale commercialization. In this study, activated carbon cloth (ACC) electrode based CDI devices are used to study the removal of ionic contaminants in water and the effect of ion concentrations on the electrosorption and disinfection functions of the CDI device for mixed microbial communities in groundwater and a model bacterial strainEscherichia coli. Up to 75 % of microbial cells could be removed in a single pass through the CDI unit for both synthetic and groundwater, while maintaining the salt removal activity. Mortality of the microbial cells were also observed during the CDI cell regeneration and correlated with the chloride ion concentrations. The power consumption and salt removal capacity in the presence and absence of salt were mapped and shown to be as low as 0.1 kWh m(-3)and 9.5 mg g(-1), respectively. The results indicate that CDI could be a viable option for single step deionization and microbial disinfection of brackish water.
Photocatalysis is a green technology which typically utilizes either supported or colloidal catalysts for the mineralization of aqueous organic contaminants. Catalyst surface area and surface energy are the primary factors determining its efficiency, but correlation between the two is still unclear. This work explores their relation and hierarchy in a photocatalytic process involving both supported and colloidal catalysts. In order to do this the active surface areas of supported zinc oxide nanorods (ZnO NR's) and colloidal zinc oxide nanoparticles (having different surface energies) were equalized and their phenol oxidation mechanism and capacity was analyzed. It was observed that while surface energy had subtle effects on the oxidation rate of the catalysts, the degradation efficiency was primarily a function of the surface area; which makes it a better parameter for comparison when studying different catalyst forms of the same material. Thus we build a case for the use of supported catalysts, wherein their catalytic efficiency was tested to be unaltered over several days under both natural and artificial light, suggesting their viability for practical applications.
Capacitive deionization is an emerging method of desalinating brackish water that has been presented as an alternative to the widely applied technologies such as reverse osmosis. However, for the technology to find more widespread use, it is important not only to improve its efficiency but also to make its modeling more accessible for researchers. In this work, a program has been developed and provided as an open-source with which a user can simulate the performance of a capacitive deionization system by simply entering the basic experimental conditions. The usefulness of this program was demonstrated by predicting how the effluent concentration in a continuous-mode constant-voltage operation varies with time, as well as how it depends on the flow rate, applied voltage, and inlet ion concentration. Finally, the generality of the program has been demonstrated using data from reports in the literature wherein various electrode materials, cell structures, and operational modes were used. Thus, we conclude that the model, termed the dynamic Langmuir model, could be an effective and simple tool for modeling the dynamics of capacitive deionization.
Aquaculture is a billion dollar industry and biofouling of aquaculture installations has heavy economic penalties. The natural antifouling (AF) defence mechanism of some seaweed that inhibits biofouling by production of reactive oxygen species (ROS) inspired us to mimic this process by fabricating ZnO photocatalytic nanocoating. AF activity of fishing nets modified with ZnO nanocoating was compared with uncoated nets (control) and nets painted with copper-based AF paint. One month experiment in tropical waters showed that nanocoatings reduce abundances of microfouling organisms by 3-fold compared to the control and had higher antifouling performance over AF paint. Metagenomic analysis of prokaryotic and eukaryotic fouling organisms using next generation sequencing platform proved that nanocoatings compared to AF paint were not selectively enriching communities with the resistant and pathogenic species. The proposed bio-inspired nanocoating is an important contribution towards environmentally friendly AF technologies for aquaculture.
Capacitive deionization (CDI) is an upcoming technique that can replace existing processes for removing and recuperating metal ions from dilute industrial waste waters. CDI removes ions via electrosorption on to its electrode surfaces, the efficiency of which is a function of CDI electrode properties that progressively change during continued operation. As such a need exists to develop a model to predict CDI performance over elongated periods which is independent of electrode properties and has negligible error values. By applying a first order non-linear dynamic model (FONDM) with inputs independent of the electrode characteristics, we propose a universal model that can predict CDI ion adsorption capacity with changes in applied potential, flow rate and electrolyte temperature to within 5% of the experimentally obtained results. The model was verified using activated carbon cloth (ACC) as a test electrode and aqueous sodium chloride solution as electrolyte, with a good prediction for ion electrosorption efficiency and time dependent electrosorption dynamics. The simplicity of the model makes it easy to adapt for various applications and in the development of intelligent control systems for CDI units in practical settings.
Microplastics are persistent anthropogenic pollutants which have become a global concern owing to their widespread existence and unfamiliar threats to the environment and living organisms. This study demonstrates the degradation of fragmented microplastics particularly low-density polyethylene (LDPE) film in water, through visible light-induced plasmonic photocatalysts comprising of platinum nanoparticles deposited on zinc oxide (ZnO) nanorods (ZnO-Pt). The ZnO-Pt nanocomposite photocatalysts were observed to have better degradation kinetics for a model organic dye (methylene blue) compared to bare ZnO nanorods, attributed to the plasmonic effects leading to better interfacial exciton separation and improved hydroxyl radical activity along with a 78% increase in visible light absorption. These demonstrations of the plasmonically enhanced photocatalyst enabled it to effectively degrade microplastic fragments as confirmed following the changes in carbonyl and vinyl indices in infrared absorption. In addition, visual proof of physical surface damage of the LDPE film establishes the efficacy of using plasmonically enhanced nanocomposite photocatalytic materials to tackle the microplastic menace using just sunlight for a clean and green approach towards mitigation of microplastics in the ecosystem.
Microplastics have recently become a major environmental issue due to their ubiquitous distribution, uncontrolled environmental occurrences, small sizes and long lifetimes. Actual remediation methods include filtration, incineration and advanced oxidation processes such as ozonation, but those methods require high energy or generate unwanted by-products. Here we tested the degradation of fragmented, low-density polyethylene (LDPE) microplastic residues, by visible light-induced heterogeneous photocatalysis activated by zinc oxide nanorods. The reaction was monitored using Fourier-transform infrared spectroscopy, dynamic mechanical analyser and optical imaging. Results show a 30% increase of the carbonyl index of residues, and an increase of brittleness accompanied by a large number of wrinkles, cracks and cavities on the surface. The degree of oxidation was directly proportional to the catalyst surface area. A mechanism for polyethylene degradation is proposed.
Capacitive deionization (CDI) is an emerging technology as a sustainable low energy process for desalination of brackish water. Activated carbon electrodes are often used in the CDI devices. Electrosorption capacity was found to be improved on asymmetric electrode configuration using activated carbon cloth doped with fluorine due to redistribution of electric potential. This led to improvement in desalination performance up to 12.4 mg/g for a desalination cycle of 6 min employing an asymmetric fluorinated electrode as cathode (ACC//F-ACC). A relatively high charge efficiency of 77 % was obtained representing 92 % charge efficiency neglecting the leakage currents. Furthermore, the ion adsorption rate was found to improve substantially due to an increased surface conductivity of the fluorinated electrode confirmed by Mott-Schottky analysis. Energy consumption during desalination of 1000 ppm sodium chloride solution of 0.71kWh/m(3) for symmetric electrode configuration was found to reduce by 36 % upon employing asymmetric configuration. This study shows some of the benefits of asymmetric configuration to achieve an optimal operation of CDI device, as well as improvements related to energy consumption.
Nanocomposite functionalized membranes were synthesized using surface functionalized mesoporous silica nanoparticles (MCM-NH2 or MCM-PEI) cross-linked to a modified polyacrylonitrile (mPAN) nanofibrous substrate for the removal of 1 mg L-1 of As(V); a concentration much higher than what has been reported for underground water in Argentina. Adsorption studies were carried out in batch mode at pH 8 with nanoparticles in colloidal form, as well as the nanoparticles supported on the modified PAN membranes (mPAN/MCM-NH2 and mPAN/MCM-PEI). Results indicate a twenty-fold improvement in As(V) adsorption with supported nanoparticles (nanocomposite membranes) as opposed to their colloidal form. The adsorption efficiency could be further enhanced by modifying the nanocomposite membrane surface with Fe3+ (mPAN/MCM-NH2-Fe3+ and mPAN/MCM-PEI-Fe3+) which resulted in more than 95% arsenic being removed within the first 15 minutes and a specific arsenic adsorption capacity of 4.61 mg g(-1) and 5.89 mg g(-1) for mPAN/MCM-NH2-Fe3+ and mPAN/MCM-PEI-Fe3+ nanocomposite membranes, respectively. The adsorption characteristics were observed to follow a pseudo-first order behavior. The results suggest that the synthesized materials are excellent for quick and efficient reduction of As(V) concentrations below the WHO guidelines and show promise for future applications.
In this work, graphene oxide–based tablets (GO-Tabs) were prepared by applying a thin layer of functionalized GO on a polyethylene substrate. The GO was functionalized with amine groups (–NH2) by poly(ethylene glycol)bis(3-aminopropyl) terminated (GO-NH2-PEG-NH2). The functionalized GO-Tabs were used for the extraction of ritonavir (RTV) in human saliva samples. RTV in plasma and saliva samples was analyzed using LC–MS/MS. Gradient LC system with MS/MS in the positive-ion mode [electrospray ionization (ESI+)] was used. The transitions m/z 721 → 269.0 and m/z 614 → 421 were used for RTV and the internal standard indinavir, respectively. This study determined the human immunodeficiency virus protease inhibitor RTV in human saliva samples using functionalized GO-Tab and LC–MS/MS, and the method was validated. The standard calibration curve for plasma and saliva samples was constructed from 5.0 to 2000 nmol L−1. The limit of detection was 0.1 nmol L−1, and the limit of quantification was 5.0 nmol L−1 in both plasma and saliva matrices. The intra- and inter-assay precision values were found to be between 1.5 and 5.8%, and the accuracy values ranged from 88.0 to 108% utilizing saliva and plasma samples. The extraction recovery was more than 80%, and the presented functionalized GO-Tabs could be reused for more than 10 extractions without deterioration in recovery.