Acid-functionalized carbon nanofibers for high stability, thermoelectrical and electrochemical properties of nanofluids

Self-assembled Au-CQDs nanofluids with excellent solar absorption and medium-high temperature stability for solar energy harvesting

Nanofluids-based direct absorption solar collectors are promising candidates for medium-high-temperature solar energy harvesting. However, nanofluids' complicated preparation process and undesirable high-temperature stability have hindered their practical applications. Herein, we propose a facile method for synthesizing gold/carbon quantum dots (Au-CQDs) nanofluids by directly carbonizing the base fluid and spontaneously assembling with Au nanoparticles (AuNPs) triggered by high temperatures. The results indicate that the self-assembled Au-CQDs nanofluids can maintain high stability at 110 °C for 100 h without precipitation and keep excellent photothermal conversion performance under 10 sun irradiation. The concentration and particle size of AuNPs are crucial factors affecting the self-assembly process. By modulating the microscopic morphologies of the self-assembled nanoparticles, the extinction coefficient of the prepared nanofluids is up to 88.7 % at a low loading of 30 ppm. The nanofluids can reach an equilibrium temperature of 50 °C under 1 sun irradiation, 10.4 °C higher than the base fluid due to the enhanced plasmonic effects and stability resulting from the CQDs dotted AuNPs. This work offers a new strategy to fabricate highly stable nanofluids with excellent light absorption properties for efficient solar thermal applications.

In silico studies and development of a protein-based electrochemical sensor for selective and sensitive detection of aflatoxin B1

Proteins from different species have been docked with aflatoxin B1 (AFB1) and identified 3 proteins (prostaglandin-E(2)9-reductase from Oryctolagus uniculus, proto-oncogene serine/threonine-protein kinase Pim-1 and human immunoglobulin G (hIgG)) as potential candidates to develop an electrochemical sensor. Fluorescence spectroscopy experiments have confirmed the interaction of hIgG with AFB1 with an affinity constant of 4.6 × 105 M-1. As a proof-of-concept, hIgG was immobilized on carbon nanocomposite (carbon nanotube-nanofiber, CNT-F)-coated glassy carbon electrode (GCE). FT-IR spectra, HR-TEM and BCA assay have confirmed successful immobilization of hIgG on the electrode (hIgG@CNT-F/GCE). The preparation of this protein electrochemical sensor requires only 1 h 36 min, which is fast as compared with preparing an electro immunosensor. hIgG@CNT-F/GCE has displayed an excellent AFB1 limit of detection (0.1 ng/mL), commendable selectivity in the presence of two other mycotoxins (ochratoxin A and patulin) and the detection of  AFB1 in spiked peanuts and corn samples.

Investigation into the Dissolution Kinetics of Different MgO Desulfurizers in Flue Gas Desulfurization

The paper introduced hydrophilic functional groups on the surface of the MgO desulfurizer to improve its dispersion and hydrophilicity on the basis of reducing the particle size of the MgO desulfurizer to the nanometer level. Mechanical grinding technology was used to improve the traditional two-step method to lay the foundation for its large-scale production. The stability test showed that the ζ potential of the 5 wt % modified MgO desulfurizer was greater than 50 mV with 30 days of storage, and the sedimentation rate was not more than 7%. The dissolution reactivity and kinetics experiments showed that the decrease of particle size and the increase of hydrophilicity and dispersion were conducive to accelerating the dissolution rate of the MgO desulfurizer and reducing the apparent activation energy. Meanwhile, the good dissolution rate of the modified MgO nanofluids prepared by the improved method could reduce the liquid film mass transfer resistance and prolonged the penetration time.

Enhancing Heat Transfer Behaviour of Ethylene Glycol by the Introduction of Silicon Carbide Nanoparticles: An Experimental and Molecular Dynamics Simulation Study

As the critical component of automotive engine coolant, ethylene glycol (E.G.) significantly matters in heat dissipation. In this study, the key aim is to investigate the heat transfer behaviour of E.G. as nano-additives base fluid. The heat transfer capability of E.G./SiC nanofluid (N.F.) was experimentally and theoretically evaluated via transient hot wire methods and equilibrium molecular dynamics (EMD) simulation, respectively. M.D. simulation exhibited a great ability to accurately forecast the thermal conductivity of N.F. compared with the experiment results. The results confirmed that the thermal stability of N.F. is relatively greater than that of E.G. base fluids. An improvement mechanism of thermal conductivity and thermal stability under an atomic scale via the analysis of mean square displacement (MSD) and radial distribution function (RDF) calculation was elaborately presented. Ultimately, the results indicated that the diffusion effect and the increasing transition rate of liquid atoms are responsible for thermal conductivity enhancement.

Nickel Hydroxide Nanofluid Cathodes with High Solid Loadings and Low Viscosity for Energy Storage Applications

Nanofluid electrodes with high loading of active solid materials have significant potential as high energy density flow battery electrolytes; however, two key criteria need to be met: they must have a manageable viscosity for pumping and simultaneously exhibit good electrochemical activity. A typical dispersion of nickel hydroxide nanoparticles (~100 nm) is limited to 5–10 wt.% of solids, above which it has a paste-like consistency, incompatible with flow applications. We report on the successful formulation of stable dispersions of a nano-scale nickel hydroxide cathode (β-Ni(OH)2) with up to 60 wt.% of solids and low viscosity (32 cP at 25 °C), utilizing a surface graft of small organic molecules. The fraction of grafting moiety is less than 3 wt.% of the nanoparticle weight, and its presence is crucial for the colloidal stability and low viscosity of suspensions. Electrochemical testing of the pristine and modified β-Ni(OH)2 nanoparticles in the form of solid casted electrodes were found to be comparable with the latter exhibiting a maximum discharge capacity of ~237 mAh/g over 50 consecutive charge–discharge cycles, close to the theoretical capacity of 289 mAh/g.

Analytical investigation of magnetized 2D hybrid nanofluid (GO + ZnO + blood) flow through a perforated capillary

The hydrothermal features of unsteady, incompressible, and laminar hybrid nanofluid motion through a porous capillary are analytically studied in the magnetic field presence. The hybrid nanofluid (GO + ZnO + Blood) is synthesized by blending nanomaterials of graphene oxide and zinc oxide with blood acting as the host fluid. The mathematical model of the flow comprises of a coupled nonlinear set of partial differential equations (PDEs) satisfying appropriate boundary conditions. These equations are reduced to ordinary differential equations (ODEs) by using similarity transformations and then solved with homotopy analysis method (HAM). The impacts of various pertinent physical parameters over the hybrid nanofluid state functions are examined by displaying 2 D graphs. It has been observed that the fluid velocity mitigates with the varying strength of M, A₀, N₀, and N₁. The enhancing buoyancy parameter ϵ augments the fluid velocity. The increasing Prandtl number causes to reduce, while the enhancing A₀, B, and N₂ augment the hybrid nanofluid temperature. The fluid concentration mitigates with the higher Schmidt number values and A₀, and augments with the increasing Soret number strength. The augmenting magnetic field strength causes to enhance the fluid friction, whereas the convective heat transfer increases with the Prandtl number rising values. The rising Sherwood number drops the mass transfer rate of the fluid. The achieved results are validated due to the agreement with the published results. The results of this computation will find applications in biomedicine, nanotechnology, and fluid dynamics.

Ultrasonic and Thermophysical Studies of Ethylene Glycol Nanofluids Containing Titania Nanoparticles and Their Heat Transfer Enhancements : Next-generation heat transfer nanofluids for industrial applications

In the present investigation, TiO2 nanostructures were synthesised via a simple sol-gel technique and characterised with X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray analysis (SEM-EDX), high-resolution transmission electron microscopy (HR-TEM) and ultraviolet-visible (UV-vis) spectroscopy. The temperature and concentration dependence of thermal conductivity enhancement (TCE) and ultrasonic velocity have been explored in ethylene glycol-based TiO2 nanofluids. The obtained results showed 24% enhancement in thermal conductivity at higher temperature (80°C) of the base fluid ethylene glycol by adding 1.0 wt% of TiO2 nanoparticles. The behaviour of TCE and ultrasonic velocity with temperature in prepared nanofluids has been explained with the help of existing phenomena. The increase in ultrasonic velocity in ethylene glycol with TiO2 nanoparticles shows that a strong cohesive interaction force arises among the nanoparticles and base fluid. These results divulge that TiO2 nanoparticles can be considered for applications in next-generation heat transfer in nanofluids.

Selim M, Ikramullah, Kumam P. Numerical modeling on hybrid nanofluid (Fe3O4+MWCNT/H2O) migration considering MHD effect over a porous cylinder

The free convective hybrid nanofluid (Fe3O4+MWCNT/H2O) magnetized non-Darcy flow over a porous cylinder is examined by considering the effects constant heat source and uniform ambient magnetic field. The developed coupled PDEs (partial differential equations) are numerically solved using the innovative computational technique of control volume finite element method (CVFEM). The impact of increasing strength of medium porousness and Lorentz forces on the hybrid nanofluid flow are presented through contour plots. The variation of the average Nusselt number (Nuave) with the growing medium porosity, buoyancy forces, radiation parameter, and the magnetic field strength is presented through 3-D plots. It is concluded that the enhancing medium porosity, buoyancy forces and radiation parameter augmented the free convective thermal energy flow. The rising magnetic field rises the temperature of the inner wall more drastically at a smaller Darcy number. An analytical expression for Nusselt number (Nuave) is obtained which shows its functional dependence on the pertinent physical parameters. The augmenting Lorentz forces due to the higher estimations of Hartmann retard the hybrid nanoliquid flow and hence enhance the conduction.

Multilayered graphene/boron nitride/thermoplastic polyurethane composite films with high thermal conductivity, stretchability, and washability for adjustable-cooling smart clothes

Polymers having high filler loading levels are not able to meet the increasing requirements of thermal interface materials by themselves; therefore, fillers and structures with unique advantages have been developed. In this study, mechanical mixing was used to disperse graphene nanoplatelets (GNPs) and boron nitride (BN) fillers inside thermoplastic polyurethane (TPU)-based films, which were then compounded into a multilayered structure. The multilayered BN-GNP/TPU composite film created during this study exhibited a high thermal conductivity of 6.86 W m^-1 K^-1 at a low filler loading of 20 wt% BN with 20 wt% GNP, which was significantly higher (2844%) than that of the neat TPU film. The composite film also had good durability to flexural fatigue and laundering. This was exhibited by maintaining thermal conductivity values of 6.25 W m^-1 K^-1 after 5000 cycles of the flexural fatigue test, and 6.85 W m^-1 K^-1 after 10 cycles of laundering, respectively. Furthermore, enhanced thermal stability, cooling, and hydrophobic properties of the multilayered BN-GNP/TPU composite films were also observed with the resulting composite film. Overall, such a system provides a facile approach that is applicable for the fabrication of multifunctional materials as thermal interface materials within smart cooling garments.

Low-cost disposable Poly(ethyleneimine)-Functionalized Carbon Nanofibers Coated Cellulose Paper as efficient solid phase extraction sorbent material for the extraction of Parahydroxybenzoates from environmental waters

Parahydroxybenzoates (parabens) are considered as emerging environmental contaminants because of their extensive usage in our daily life products, causing parabens contamination into environmental water systems and lead to toxic effects on environmental health. This study describes a greener extraction method using a new cationic polymer poly (ethyleneimine) functionalized acid-treated carbon nanofibers (PEI-CNFs) coated cellulose paper (CP) as solid-phase extraction (SPE) sorbent material for the extraction of parabens from environmental water samples. The fabrication of PEI-CNFs modified CP was confirmed using field-emission scanning electron microscope, transmission electron microscopy, and fourier-transformer infrared spectroscopy techniques. Various factors affecting the adsorption and desorption of parabens on PEI-CNFs@CP and its extraction efficiencies were studied using HPLC-UV analysis. Under the optimal experimental conditions, maximum extraction efficiencies were achieved for four target parabens, and PEI-CNFs@CP/HPLC-UV method exhibited excellent linearities ranged from 0.5-50 ng mL^-1 with regression coefficient values were between 0.9952-0.9970. The presented method showed good sensitivity with quantification limits between 0.5-0.75 ng mL^-1 and detection limits between 0.1-0.25 ng mL^-1. The developed technique was applied for the real sample analysis (river, lake, domestic sewage water, and drinking tap water). The spiked recovery revealed good recoveries between 86.8-116.0% with RSD less than 8.8% for all the water samples. These results proved that it a simple, fast, efficient, low-cost, and eco-friendly method for the extraction and determination of parabens in environmental water samples and can be applied as a routine analytical tool in environmental monitoring and quality control laboratories.

Development of electrically conductive porous silk fibroin/carbon nanofiber scaffolds

Tissue engineering applications typically require three-dimensional scaffolds which provide the requisite surface area for cellular functions, while allowing transport of nutrients, waste and oxygen to and from the surrounding tissues. Scaffolds need to ensure sufficient mechanical properties to provide mechanically stable frameworks under physiologically relevant stress levels. Meanwhile, electrically conductive platforms are also desirable for the regeneration of specific tissues, where electrical impulses are transmitted throughout the tissue for proper physiological functioning. Towards this goal, carbon nanofibers (CNFs) were incorporated into silk fibroin (SF) scaffolds whose pore size and porosity were controlled during a salt leaching process. In our methodology, CNFs were dispersed in SF due to the hydrogen bond-forming ability of hexafluoro-2-propanol, a fluoroalcohol used as a solvent for SF. Results showed enhanced electrical conductivity and mechanical properties upon the incorporation of CNFs into the SF scaffolds, while the metabolic activities of cells cultured on SF/CNF nanocomposite scaffolds were significantly improved by optimizing the CNF content, porosity and pore size range of the scaffolds. Specifically, SF/CNF nanocomposite scaffolds with electrical conductivities as high as 0.023 S cm^-1, tangent modulus values of 260 ± 30 kPa, a porosity as high as 78% and a pore size of 376 ± 53 µm were fabricated for the first time in the literature. Furthermore, an increase of about 34% in the wettability of SF was achieved by the incorporation of 10% CNF, which provided enhanced fibroblast spreading on scaffold surfaces.

Experimental Investigation on Stability, Viscosity, and Electrical Conductivity of Water-Based Hybrid Nanofluid of MWCNT-Fe2O3

The superiority of nanofluid over conventional working fluid has been well researched and proven. Newest on the horizon is the hybrid nanofluid currently being examined due to its improved thermal properties. This paper examined the viscosity and electrical conductivity of deionized water (DIW)-based multiwalled carbon nanotube (MWCNT)-Fe₂O₃ (20:80) nanofluids at temperatures and volume concentrations ranging from 15 °C to 55 °C and 0.1–1.5%, respectively. The morphology of the suspended hybrid nanofluids was characterized using a transmission electron microscope, and the stability was monitored using visual inspection, UV–visible, and viscosity-checking techniques. With the aid of a viscometer and electrical conductivity meter, the viscosity and electrical conductivity of the hybrid nanofluids were determined, respectively. The MWCNT-Fe₂O₃/DIW nanofluids were found to be stable and well suspended. Both the electrical conductivity and viscosity of the hybrid nanofluids were augmented with respect to increasing volume concentration. In contrast, the temperature rise was noticed to diminish the viscosity of the nanofluids, but it enhanced electrical conductivity. Maximum increments of 35.7% and 1676.4% were obtained for the viscosity and electrical conductivity of the hybrid nanofluids, respectively, when compared with the base fluid. The obtained results were observed to agree with previous studies in the literature. After fitting the obtained experimental data, high accuracy was achieved with the formulated correlations for estimating the electrical conductivity and viscosity. The examined hybrid nanofluid was noticed to possess a lesser viscosity in comparison with the mono-particle nanofluid of Fe₂O₃/water, which was good for engineering applications as the pumping power would be reduced.

Recent progress in environmentally friendly bio-electrochemical devices for simultaneous water desalination and wastewater treatment

Bio-electrochemical systems (BESs) use electroactive micro-organisms for degrading organic materials in wastes for energy and/or chemical production. Microbial based desalination system is a cost-effective and environmentally friendly technique that can be used for water desalination with simultaneous wastewater treatment and energy harvesting. These systems can be used as a standalone technology for water desalination such as microbial desalination cell, microbial electrolysis desalination cell, or a hybrid with other desalination technology. This review summarized the recent progress in using BESs for water desalination, including microbial fuel cell-based desalination (MDC) and microbial electrolysis cell-based desalination (MEDC). The different scaling up trials to commercialize this technology, including the controlling parameters, are discussed. Moreover, the different hybrid desalination systems based on BES are summarized. Finally, the challenges facing the commercialization of the MDC systems were summarized.

Modeling of entropy optimization for hybrid nanofluid MHD flow through a porous annulus involving variation of Bejan number

We numerically investigate the non-Darcy magnetohydrodynamic hybrid nanoparticle migration through a permeable tank using control volume finite element method through entropy generation. The roles of various amounts of Permeability, Lorentz and Rayleigh (Ra) number are investigated upon the various aspects of the hybrid nanofluid flow through contour and 3-D plots. Through curve fitting technique, analytical expressions for Nuave and Bejan number as functions of Ra, Ha and Da are obtained. It is found that the strength of the vortexes decline and temperature of the inner wall augments with the higher magnetic field, while temperature drops with increasing buoyancy forces and medium permeability. The irreversibility terms associated with the generation of the thermal energy and applied magnetic field (Sgen,th, Sgen,M) enhance while the other terms (Sgen,f, Sgen,p) drop with the rising values of the magnetic field strength. These quantities show exactly opposite behavior with augmenting Da. The Bejan number drops while Nuave augments with the rising buoyancy forces. The agreement with the previous published results confirms the accuracy of the employed computational model.