Diameter Of Nanoparticles Research Articles

Nephrotoxicity induced by different diameters of sphere gold nanoparticles with special emphasis on the nephroprotective role of quercetin.

Although, gold nanoparticles (GNPs) are attracting more and more attention due to their ease of synthesis, modification, and great potential value in biomedical applications, exhibited harmful effects on human health and other living species. Quercetin (Qur) clarifies diverse pharmacological effects, especially anti-inflammatory, antiapoptotic, and antioxidant ones. This study aimed to evaluate the probable nephrotoxicity induced by different diameters of sphere GNPs, as well as the nephroprotective role of Qur. A total of 54 healthy mature male albino rats were grouped and treated with or without sphere GNPs; 10, 20, and 50 nm and Qur (200 mg/kg b.wt.). The effects of GNPs and Qur were estimated through the collection of blood and kidney samples from euthanized rats and performed biochemical, histopathological, and immunohistochemical investigations. In comparison between different diameters of GNPs, the 10 nm GNPs revealed more significant elevations in all renal function parameters: creatinine, urea, blood urea nitrogen, and uric acid followed by 20 nm then 50 nm. Pre-cotreatment with Qur decreased all renal functional values. Histopathologically, 10 nm revealed the most potent renal pathological changes represented in the renal cortex with cloudy swelling of renal tubules, hypercellularity of some glomeruli, severe congestion of renal blood vessels, focal inter tubular edema, and vascular endotheliosis (degeneration of endothelium). In addition, the renal medulla revealed perivascular inflammatory cellular infiltration, perivascular fibrosis, intra tubular glycogen deposition, and casts deposition of mainly cellular casts. On the other hand, the Qur treatment ameliorated most of these pathological changes. The size of GNPs is pivotal in their pathological effect on renal tissues where the small-sized GNPs; 10 nm have more potent cytotoxic, inflammatory, and apoptotic effects rather than the larger ones. Otherwise, Qur clarified a significant mitigating role against the nephrotoxicity of the GNPs.

An optical nanofibre-enabled on-chip single-nanoparticle sensor.

Single-nanoparticle detection has received tremendous interest due to its significance in fundamental physics and biological applications. Here, we demonstrate an optical nanofibre-enabled microfluidic sensor for the detection and sizing of nanoparticles. Benefitting from the strong evanescent field outside the nanofibre, a nanoparticle close to the nanofibre can scatter a portion of the field energy to the environment, resulting in a decrease in the transmitted intensity of the nanofibre. On the other hand, the narrow and shallow microfluidic channel provides a femtoliter-scale detection region, making nanoparticles flow through the detection region one by one. By real-time monitoring of the transmitted intensity of the nanofibre, the detection of a single polystyrene (PS) nanoparticle as small as 100 nm in diameter and exosomes in solution is realised. Based on a statistical analysis, the mean scattering signal is related to the size of the nanoparticle. Experimentally, a mixture of nanoparticles of different diameters (200, 500, and 1000 nm) in solution is identified. To demonstrate its potential in biological applications, high-throughput counting of yeasts using a pair of microchannels and dual-wavelength detection of fluorescently labelled nanoparticles are realised. We believe that the developed nanoparticle sensor holds great potential for the multiplexed and rapid sensing of diverse viruses.

Thermal analysis of rectangular channel having Al2O3 nanofluid medium

Augmentation of the heat transfer in a rectangular channel demands a prominent technique in order to keep the pressure drop penalty at the minimum. The present work focuses on the theme of utilizing the heat transfer enhancement technique using the small height roughness. The rectangular channel, with nanofluid flow inside the duct aids in further enhancing the thermal performance of the system. The effect of geometric parameters of the roughness on heat transfer is analyzed using computational method. The geometric parameters selected for analysis are the Relative rib-groove width ratio (WP/WRG) and the Ratio of rib-groove height (eRG/Dh) along with the Al2O3/H2O nanofluid. The numerical analysis of the heat exchanger tube is carried out for Reynolds number in the range of 4000-21000. The highest increment in the Nusselt number (Nu) is found to be 276 for parameter values of WP/WRG of 3 and eRG/Dh of 0.133 along with the 4 vol% and nanoparticle diameter of 20nm, which fetches the friction factor of 0.113.

NUMERICAL SOLUTION ON MIXED CONVECTION FLOW OF NANOFLUID AROUND A FINNED ANGULAR SECTOR OF HEAT SINK

The aim of this study is to investigate mixed convection flow of nanofluid around a three-dimensional (3D) finned angular sector of heat sink by means of numerical simulations. The finite-volume method is used to solve the governing equations of mass, momentum, and energy conservation. The Brownian motion of the nanoparticles in the base fluid is explicitly taken into account in the thermal conductivity model (Patel model). A parametric study is carried out to examine the effects of several key parameters on the rate of heat transfer; the angular sector apex angle, the volume fraction of suspended nanoparticles (0 ≤ φ ≤ 0.09), the Richardson number (<i>Ri</i> = <i>Gr/Re</i><sup>2</sup>), and the size of the nanoparticles diameter (5, 20, 60, and 100 nm). It is shown that for a fixed low Richardson number <i>Ri</i>, the rate of heat transfer increases with the volume fraction of the nanoparticles, as forced convection mechanism is dominated. The heat-transfer enhancement is obtained for the nanofluid water/TiO<sub>2</sub> rather than the water/Cu at higher nanoparticles volume concentration and highest Richardson number. Moreover, the Maxwell thermal conductivity model resulted in a maximum enhancement in the case of nanofluid water/TiO<sub>2</sub> than that of water/Cu, whereas the nanofluid water/ Cu gives better heat-transfer enhancement at small particles than that of water/TiO<sub>2</sub>. It is observed too that the nanoparticles' diameter does not have a significant effect on the temperature field.

INFLUENCE OF SILVER NANOPARTICLES ON TOTAL ABSORPTION FLUXES OF METHYL AMMONIUM LEAD TRI-IODIDE PHOTOCELL

Plasmonic nanoparticles exhibit a great ability to dramatically improve photon harvesting in solar cells. They provide an exceptionally very innovative way of transforming the solar cell and photovoltaic cell industries. In photovoltaic cell research, nano-plasmonics especially noble metal nanoparticles have emerged as a new frontier runner plasmons to be incorporated in photovoltaic structures. These nano plasmons concentrate photons and channel them inside a perovskite layer. However, challenges on its effectiveness have emerged and need to be addressed. These challenges includes the loss in absorption fluxes, increased light trapping band, developing inexpensive fabrication techniques, scaling plasmonics into manufacturing levels and integrating them into perovskite active nanostructures. In this paper, we address the challenge posed by low total absorption fluxes and decreased total enhancement across the whole solar spectrum using silver nanoplasmonics to improve its total absorption fluxes. We therefore document a numerical analysis of total absorption enhancements of a model CH3NH3PbI3 perovskite photocell whose active absorber layer is embedded with spherical plasmonic silver nanoparticles of different diameters at different array spacing. It is still unknown to what extent the organic cation (framework) affects the optical and electronic properties of CH3NH3PbI3 perovskites. Further, there a number of questions that have been raised in relation to the inorganic framework or lattice though computational has suggested that CH3NH3PbI3 is influenced by different geometric parameters related to CH3NH3+ on its nitrogen K-edge (or the nitrogen 1s-orbital electrons). Therefore, new ways in which the organic cation can interact with the inorganic Pb–I lattice is believed to affect its XA spectrum and therefore its electronic structure. It has been suggested that hybridized CH3NH3+ levels in the (lead-and-iodide dominated) valence band appear to dominate in CH3NH3PbI3 crystals and the band gap in CH3NH3PbI3 can change due to the rotation of the CH3NH3+ cation, mostly by affecting the conduction band. The influence of particle size, array spacing and location is analyzed numerically and discussed in a realistic system. Results revealed that when silver nanoparticles are integrated into a CH3NH3PbI3 perovskite layer, total solar absorption enhancement increases by 8% in the infrared (IR) and by 48 % in the far-infrared (far-IR) spectra in layers of 135 nm thicknesses at minimum array spacing and maximum diameter. It was concluded that the total absorption enhancement can be improved by reinforcement from a plasmonic near-field influenced by its total cross sectional scattering effects. In this process absorption in the IR and far IR spectra is influenced in the CH3NH3PbI3 perovskite layer.

Effect of the shell thickness on the mechanical properties of arrays composed of hybrid core-shell Si/SiC nanoparticles with overlapped shells

Atomistic simulations of quasi-static compression and tension of linear arrays consisting of hybrid spherical nanoparticles (NPs) with Si cores and 6H-SiC partially overlapped shells are performed to reveal the effect of the shell thickness on the deformation mechanism and mechanical properties of such NP arrays. The overlapped shells are considered as a model of a continuous coating that promotes the mechanical integrity of a nano-powder and transforms it into a porous composite material. At compression, the transition from ductile to brittle deformation behavior with increasing shell thickness is observed. The compression of a NP array with thick shells induces the formation of a quasi-conical slip surface. The fracture of a NP array at compression involves the fracture of both shell and core materials and can induce the formation of a new β-Sn phase in the Si core. At tension, the deformation process is characterized by a relatively large proportional limit, and the fracture occurs in the weak cross sections at the necks between NPs, so that the NP cores remain intact after fracture. Before fracture, the largest microscopic stresses are observed in the shell material near the core-shell interface. The simulations predict a strong increase of modulus and strength at tension and compression with an increase in the relative shell thickness, the ratio of the shell thickness to the NP diameter, while the effect of the NP size on mechanical properties is relatively weak. This suggests that the relative shell thickness is the major similarity parameter that dominates the mechanical properties of the NP arrays. Interestingly, the simulations predict a larger modulus for NPs with thick shells compared to single-material SiC NPs. This points at a non-trivial role of the core-shell interface and the degree of the shell overlap in the load transfer in the arrays of NPs with overlapped shells.

MRT LBM Simulation on Friction Reduction by Lubrication Nanoadditives

Using Tungsten disulfide WS2 nanoparticles as a nanolubricant additive could improve the lubrication performance. The main objective of the present work is to numerically study the effect of nanoparticle diameters on the friction reduction on two sliding surfaces in a lubrication system. The studied nanofluid is 5W-30 engine oil based on WS2 nanoparticles. In this study, the flow of confined nanofluid by two moving surfaces is simulated by the Lattice Boltzmann method with multiple relaxation times. The results show that the greatest friction reduction is always obtained for large diameter nanoparticles.

Enhancement of Light Absorption in the Active Layer of Organic Solar Cells using Ag:SiO2 Core-Shell Nanoparticles

Organic solar cells still suffer from relatively low conversion efficiency despite significant progress. An Ag:SiO2 core-shell nanoparticle embedded inside the active layer of an organic solar cell is expected to enhance light absorption. Light absorption within the active layer consisting of 70 nm thickness PEDOT: PSS and P3HT: PCBM was calculated using the finite element method for a variable diameter of the silver core, the thickness of the SiO2 shell, and the relative position of nanoparticle inside the active layer. The diameter of the Ag nanoparticle varies from 20 to 50 nm, the thickness of SiO2 varies from 1 to 4 nm, and the position was shifted vertically to 70 nm. The maximum light absorption in the active layer is obtained for silver nanoparticles with a diameter of 40 nm and a SiO2 thickness of 1 nm. The optimum position of the core-shell nanoparticle was found to be not at the interface between the PEDOT: PSS and P3HT: PCBM layers but a little bit shifted down into P3HT: PCBM layer. The highest increase of light absorption, compared to without Ag:SiO2, is 210%, much higher than reported in the literature. Increasing absorption is related to the excitation of surface plasmon resonance of Ag:SiO2 nanoparticles leading to the local field and scattering enhancement in the active layer of the organic solar cell

Multi-dimensional modeling of nanoparticles transportation from capillary bed into the tumor microenvironment

In this study, we examined the extravasation of pharmaceutical inorganic nanoparticles (NPs) with a new approach from the leaky endothelium of tumor microvasculature (TMV) into the tumor microenvironment (TME) multi-dimensionally. We proposed a combination of prevailing macroscopic and microscopic methods and addressed the effect of interstitial fluid (IF) retention in solid tumor as an imperative parameter in drug delivery modeling. The Navier-Stokes equations and Darcy's law were utilized for blood flow and porous media, and the Starling's law was brought in for coupling effect. The blood flow was simulated as a non-Newtonian fluid alongside the Newtonian IF. We applied the Galerkin finite element method for the simulations. Our parametric study includes examining the effect of IF retention and TMV pressure on the distribution of tumor interstitial fluid pressure (TIFP), NPs concentration, and diameter on the penetration process, together with the time effect, on two-dimensional (2D) delivery of NPs. Our findings indicate that the IF retention in tumor cells increases TIFP depending on the amount of TMV pressure and IF retained. In addition to doubling pressure in the tumor necrotic region rather than the rest of TME, it enhances the TIFP which is an important parameter in drug delivery to solid tumors. By decreasing pressure drop within the TMV, pressure distribution within the TME becomes more uniform, creating a better condition for homogeneous penetration of NPs. Increasing both inlet pressure and NPs concentration leads to a nonlinear increase in the average concentration of tumor. Decreasing the diameter of NPs increases the penetration of NPs with a higher ratio in the TME.

Anisotropic slip impact on nanofluid flow over a biaxial exponentially stretching sheet with Hall current: Corcione's correlation

This study introduces the Corcione correlation that accentuates the role of fluid temperature, particle volume fraction, and sizes in the increment of the nanofluid heat transfer rate and thermal conductivity. Here, the flow of nanofluid comprising Al2O3/H2O over a biaxial exponentially stretching sheet is considered. The analysis is performed for nanoparticles’ sizes 28, 30, and 45 nm and volume concentrations up to 7%. The mathematical model is strengthened by the anisotropic slip and convective boundary conditions. The momentum and heat equations are enriched with the inclusion of the Hall current and the non-uniform heat generation/absorption terms respectively. The nonlinear, coupled momentum and heat nondimensionalized ordinary differential equations (ODEs) are formulated with appropriate transformations and are solved numerically. The effects of many relevant factors are depicted using graphs. It is scrutinized that by enhancing the diameter of nanoparticles (Al2O3), the skin friction coefficient enhances and the heat transfer rate in the case of different nanoparticle sizes boosts for gradually growing estimations of the volume fraction. It is also deduced that surface slip increases pumping power and the insertion of the nanoparticles into the working fluid enhances heat transmission. To support the thesis, the presented model's validation is also provided.

Role of surface hydrophilicity on MR relaxivity of PEG coated- gadolinium oxide nanoparticles

The magnetic resonance (MR) contrast enhancement capabilities of gadolinium oxide nanoparticles (GONPs) have high dependency on its surface chemistry- as the solution properties such as colloidal stability and hydrodynamic diameter of nanoparticles which are prime regulatory parameter for MR relaxivity, are all governed by grafting density of surface material. However, the purification of synthesized surface coated nanoparticles, without compromising the surface properties, remains a major challenge. Among the various cleaning methods, dialysis is often used to remove the unwanted by-products produced during synthesis. However, the effect of dialysis time may significantly impact the surface properties and hence, the MR contrast properties of such nano-formulations. The aim of the present study is to evaluate the effect of dialysis time on surface chemistry and MR contrast enhancement properties of GONPs by comparing the proton relaxivity data. Ultra-small polyethylene glycol (PEG)-coated GONPs with an average particle diameter of 17 nm were synthesized using polyol method. The impact of dialysis time has been investigated systematically on the size distribution, hydrophilicity, magnetic properties, polymer grafting density and relaxometric properties of the as synthesized GONPs. A significant impact of dialysis time was observed on surface chemistry and hence, on the MR relaxivity of synthesized NPs. We evidenced a dramatic decrease in the proton relaxivities of GONPs with increase in dialysis time, which correlated well with the observed decrease in the grafting density of surface polymer. The results clearly indicate that the proton relaxivity of GONPs of similar size and same coating material depends on the surface coating thickness and hydrophilicity of the coating polymer. Overall, it is essential to optimize the accurate time duration of dialysis treatment as the prolonged dialysis may have negative effect on the relaxation times and hence on MR contrast enhancement properties of GONPs. This study is a strategic pathway to fine-tune the dialysis treatment of as-synthesized surface-capped GONPs for pre-eminent MR contrast imaging.

Preparation of transparent photoluminescence plastic concrete integrated with lanthanide aluminate

A simple strategy was presented for potential industrial preparation of persistent afterglow lightweight plastic concrete toward smart hard surfaces. Rare-earth activated aluminate (REA) pigment nanoparticles (NPs) were integrated into plastic bar. The transparency of the prepared plastic bar can be achieved by consistent distribution of REA NPs in the plastic fluid. Unsaturated polyester resin (bulk material) was mixed with silica nanoparticles (filler) and REA NPs (luminescent agent) using methyl ethyl ketone peroxide as hardener. The curing process was accomplished for a few minutes at room temperature. The diameters of REA NPs were reported in the range of 6–11 nm. The phosphor-concrete composite can be industrially applied onto a variety of hard surfaces. The photoluminescent plastic concrete showed an emission band at 515 nm upon excitation at 372 nm. Persistent photoluminescence was detected for pigment concentrations higher than 1%, whereas fluorescence emission was monitored for pigment concentrations equal to 1%. Photochromism was observed for the prepared plastic concrete as different colors were detected under different light conditions, including colorless under daytime light, green underneath UV rays, and greenish-yellow under darkness as proved by luminescence spectra and CIE Lab parameters. The static contact angle measurements proved good superhydrophobic activity. An improved UV protection and photostability were detected. The photoluminescent hard composite concrete displayed highly durability and reversible persistent afterglow emission. The morphology, elemental composition and hardness features of the prepared plastic concrete were investigated.

Pore-scale analysis of two-phase nanofluid flow and heat transfer in open-cell metal foams considering Brownian motion

Simultaneous use of porous media and nanofluids will increase the convective heat transfer multiple times compared to non-porous and pure fluid conditions. Heat transfer and flow transport of nanofluids inside porous media are usually simulated in large-scale with average properties, which are typically highly uncertain. Pore-scale simulation as an alternative approach can capture the characteristics of flow and heat transfer more accurately. Only few studies have been conducted to study nanofluid flow through porous media in pore-scale, and most of them employed single-phase approach without focus on different affective forces. This paper uses a pore-scale approach to investigate the flow characteristics and convective heat transfer of two-phase nanofluid flow in open-cell metal foams (OCMFs). Simulation of fluid flow and heat transfer is achieved by Buongiorno’s model. Therefore, a computational code through the OpenFOAM library that operates by a direct numerical simulation (DNS) approach and the finite volume method (FVM) is used. The momentum, energy, continuity, and nanoparticle distribution equations are discretized, and the SIMPLE algorithm is utilized for pressure and velocity coupling. In the present study, three OCMFs with a constant porosity (0.86) and various pore densities are investigated. Also, variations of pressure gradient, Nusselt number, and Darcy velocity are investigated as a function of pore density (as a geometric parameter), nanoparticle diameter, concentration, and Brownian motion force. The results indicate that the Brownian force enhances the heat transfer in OCMFs from 2% by up to 14% for the nanofluid flowing with 3% nanoparticle concentration. Also, increasing the diameter of nanoparticles reduces the Darcy velocity and heat transfer by up to 4%. On the other hand, increasing particle concentration from 3% to 5%, increases heat transfer by up to 10% and reduces the Darcy velocity by up to 9%. Finally, doubling the pore density demonstrates the complex behavior of the flow patterns, in which the heat transfer increases by up to 30% and permeability and velocity are reduced by up to 70%.

Methods and Technical Means for Ensuring Uniformity of Nanoparticle Size Measurements

The paper proposes a set of technical tools for solving the problem of ensuring the uniformity of measurements of micro- and nanoparticles. To do this, it is necessary to ensure the traceabilityof particle size measurements to a unit of length – a meter, as well as equivalent diameters used in measurements in various dispersed media (aerosols and suspensions). To ensure traceability of particle diameter measurements to the meter, it is proposed to use a nanomeasuring machine with an atomic force microscope as a probing system. The paper presents a diagram of the measuring system, describes the principle of operation of the machine and the method for measuring particle sizes. The main alleged sources of errors in particle measurement by this method are also identified. To ensure the traceability of measurements of the hydrodynamic diameter of nanoparticles, which characterizes particles in a liquid (suspension), it is proposed to use a nanoparticle size analyzer that implements the method of dynamic light scattering. The scheme of the analyzer with a description of the principle of measuring the size of nanoparticles by the method of dynamic light scattering is presented in the paper. The scheme of the column of the analyzer of the differential electrical mobility of particles is presented to ensure the traceability of measurements of their diameter, which is equivalent in electrical mobility. Diameter is usually used to characterize particles in the aerosol state. A diagram of an analyzer for the differential electric mobility of particles is given with a description of the operating principle, a formula for calculating the particle diameter is derived.

Size Control of Iron Oxide Nanoparticles Synthesized by Thermal Decomposition Methods

The controlled synthesis of superparamagnetic iron oxide nanoparticles is crucial for a variety of biomedical applications. Among different synthesis routes, thermal precursor decomposition methods are the most versatile, yielding monodisperse nanoparticles on the multigram scale. Recent in situ kinetic studies of the nucleation and growth processes during thermal decomposition routes revealed nonclassical nucleation and growth paths involving amorphous precursor phases and aggregative growth steps. With the knowledge of this kinetic mechanism, we systematically examined a range of different iron oxide heat-up synthesis routes to understand and conclude which methods allow good and reproducible size control over a range of relevant nanoparticle diameters. Using transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) for the characterization of the nanoparticle size distribution, we find that a set of solvents (1-octadecene, trioctylamine, docosane) provides access to a temperature range between 300 and 370 °C, allowing us to synthesize monodisperse nanoparticles in a size range of 6–24 nm on a large scale. We confirm that a thermal pretreatment of the iron oxide precursor is essential to achieve reproducible size control. We find that each solvent provides access to a certain temperature range, within which the variation of temperature, heating rate, or precursor concentration allows us to reproducibly control the nanoparticle size.

Highly efficient and recyclable novel spindles Fe2O3@SiO2/In2O3 nanomagnetic catalyst designed for green synthesis of azomethine compounds

A novel and reusable nanomagnetic catalyst, Fe2O3@SiO2/In2O3, was synthesized by a facile chemical approach in three successive steps. The nanocatalyst was characterized by FT-IR, XRD, SEM, EDX, TEM, and VSM. The XRD pattern displays the characteristic peaks of Fe2O3 and SiO2, accompanied by new peaks assigned to different planes of In2O3 that confirm the formation of In2O3 on the surface of Fe2O3@SiO2 core/shell spindles. The TEM micrographs show spindle-like particles of Fe2O3 covered with SiO2 shell, and the In2O3 nanoparticles in an average diameter of 20 nm are hung on the surface of the Fe2O3@SiO2. The nanomagnetic catalyst Fe2O3@SiO2/In2O3 was used for the transformation of the (4-nitrophenyl)-1-phenyl-1H-pyrazole-5-amine, and chalcones derivatives, into valuable azomethine compounds of 3-(substituted)-1-(pyridine-2-yl)allylidene)-3-(4-nitrophenyl)-1-phenyl-1H-pyrazole-5-amine with high rate and efficient catalyst recovery. The yield obtained through the catalytic route reached 90–95% in shorter reaction times compared with uncatalyzed reaction method.Graphical abstract

Numerical Analysis of Forced Convection of Nanofluid under Turbulent Flow between Two Parallel Plates

As research shows, in new and renewable energy systems, including solar energy, the study of turbulent flow is of great importance due to its high efficiency in heat transfer. It is also used in petrochemical and oil industries and cooling systems. Therefore, this paper focuses on the turbulent heat transfer of nanofluid between two parallel plates and the effect of the volume fraction of nanoparticles on turbulent heat transfer is investigated. The nanofluid applied in the study was alumina-water. The beginning and the end of the walls were insulated, and the middle part was considered as the heat source. The two-equation κ - ɛ model was used to model viscosity of turbulent flow. The governing equations were solved simultaneously using the control volume method based on SIMPLER algorithm. In this study, the effects of the Reynolds’ number in the range of 104 to 5 ∗ 10 4 , volume fraction of 0.01 to 0.04, and nanoparticle diameter of 20 nm to 100 nm on field flow and rate of heat transfer were examined. The influence of Brownian movement on heat performance was considered. Evaluation showed that increasing the Reynolds’ number decreased the thickness of the laminar sublayer in turbulent flow and increased temperature and velocity differences. These greater temperature and velocity differences resulted in increased heat transfer and decreased skin friction. The findings imply that heat performance improves when nanoparticles are added to basic fluid. With increasing volume fraction of nanoparticles, shear stress of the channel wall increases, and consequently, skin friction increases too. In addition, the effect of nanoparticle diameter on thermal and hydraulic performance was studied. It was found that heat transfer and skin fraction decreased in the presence of the larger nanoparticles.

Synthesis and Characterization of Ligand-Stabilized Silver Nanoparticles and Comparative Antibacterial Activity against E. coli.

Silver is a well-established antimicrobial agent. Conjugation of organic ligands with silver nanoparticles has been shown to create antimicrobial nanoparticles with improved pharmacodynamic properties and reduced toxicity. Twelve novel organic ligand functionalized silver nanoparticles (AgNPs) were prepared via a light-controlled reaction with derivatives of benzothiazole, benzoxazine, quinazolinone, 2-butyne-1,4-diol, 3-butyne-1-ol, and heptane-1,7-dioic. UV-vis, Fourier-transform infrared (FTIR) spectroscopy, and energy-dispersive X-ray (EDAX) analysis were used to confirm the successful formation of ligand-functionalized nanoparticles. Dynamic light scattering (DLS) revealed mean nanoparticle diameters between 25 and 278 nm. Spherical and nanotube-like morphologies were observed using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Seven of the twelve nanoparticles exhibited strong antimicrobial activity and five of the twelve demonstrated significant antibacterial capabilities against E. coli in a zone-of-inhibition assay. The synthesis of functionalized silver nanoparticles such as the twelve presented is critical for the further development of silver-nanoconjugated antibacterial agents.

Second Law Analysis of MHD Forced Convective Nanoliquid Flow Through a Two-Dimensional Channel

Abstract The present study deals with fluid flow, heat transfer and entropy generation in a two-dimensional channel filled with Cu–water nanoliquid and containing a hot block. The nanoliquid flow is driven along the channel by a constant velocity and a cold temperature at the inlet, and the partially heated horizontal walls. The aim of this work is to study the influence of the most important parameters such as nanoparticle volume fraction (0%≤ϕ≤4%), nanoparticle diameter (5 nm≤dp≤55 nm), Reynolds number (50≤Re≤200), Hartmann number (0≤Ha≤90), magnetic field inclination angle (0≤γ≤π) and Brownian motion on the hydrodynamic and thermal characteristics and entropy generation. We used the lattice Boltzmann method (LBM: SRT-BGK model) to solve the continuity, momentum and energy equations. The obtained results show that the maximum value of the average Nusselt number is found for case (3) when the hot block is placed between the two hot walls. The minimum value is calculated for case (2) when the hot block is placed between the two insulated walls. The increase in Reynolds and Hartmann numbers enhances the heat transfer and the total entropy generation. In addition, the nanoparticle diameter increase reduces the heat transfer and the irreversibility, the impact of the magnetic field inclination angle on the heat transfer and the total entropy generation is investigated, and the Brownian motion enhances the heat transfer and the total entropy generation.

NUMERICAL INVESTIGATION OF THE NANOFLUID NATURAL CONVECTION FLOW IN A CPU HEAT SINK USING BUONGIORNO TOW-PHASE MODEL

In this paper, a numerical investigation using the finite element method on the cooling capacity of an electronic heat sink has been presented. This heat sink is intended for cooling applications of micro-computer CPUs. It deals with a parallelepipedal block with rectangular fins, filled with a nanofluid and crossed by four cylindrical pipes in which a cooling gas flows and dissipates the heat generated by the processor. Indeed, the cooling occurs by three transfers: the first one evacuates the heat from the processor towards the gas, the second one transfers this heat towards the nanofluid and the last one is cooled from the ambient air by means of the fins laterally arranged on the block. From this work, it has been planned to contribute to the study of the behavior of a nanofluid in the heat sink in the presence of a uniform magnetic field in order to enhance the operating and cooling performances. The effects of some control parameters have been highlighted on the hydrodynamic, thermal, and mass behavior of the nanofluid, namely: the Rayleigh number (103 ≤ Ra ≤ 105), the Hartmann number (0 ≤ Ha ≤ 100), the angle of inclination of the magnetic field (0 ≤ γ ≤ 90°) and the nanoparticles diameter (1 nm ≤ dp ≤ 10 nm). On the other hand, a new fin design has been proposed in this study allowing the enhancement of the heat exchange rate with ambient medium. The studied phenomenon is governed by the equations of the two-phase nanofluid model proposed by Buongiorno and which describe the following balances: mass, momentum, energy and nanoparticles. The system of partial differential equations with initial-boundary conditions has been solved by the finite element method. After performing a mesh independence check and validating with previous papers, the results of the investigation were presented. They showed that the application of a magnetic field significantly reduces the rate of heat exchange. However, increasing the angle of inclination of this field promotes convective heat transfer. Moreover, the use of zigzag fins improves the cooling rate by about 4% for amplitude of 0.05 compared to the standard configuration.