High Nanoparticle Concentrations Research Articles

Strain softening of natural rubber composites filled with carbon black and aramid fiber

Engineered rubber vulcanizates may contain a low content of short fibers and a high content of nanoparticles while the effects of the different fillers on the softening behavior are not yet explored. Herein, influences of carbon black (CB) and short aramid fiber (AF) on the Payne and Mullins effects of natural rubber composites are investigated for the first time by creating master curves of dynamic modulus or dissipation energy with respect to the straining responses of the matrix. It is revealed that the composite vulcanizates demonstrate the Payne effect characterized by decay of storage modulus, weak overshoot of loss modulus, and very weak high-order harmonics; this effect is mainly dominated by the rubber matrix experiencing microscopic strain amplitude enlarged by the filler. The composite vulcanizates exhibit the Mullins effect that becomes increasingly marked with increasing filler loading and is partially recovered by thermal annealing at relatively high temperatures. The energy dissipation during cyclic tensions is rooted in the viscoelastic deformation of the matrix and the filler-rubber interfacial debonding. The former is marked at room temperature where the rubber phase undergoes a crystallization-melting process during loading-unloading. The latter being marked in the presence of a small content of AF causes yieldinglike deformation for the virgin composites at low tensile strains, and its contribution to the softening is not recoverable during thermal annealing. The results show that the viscoelastic matrix is of importance in controlling the softening of the composite vulcanizates, which will be of guiding significance to conduct research studies on high-performance rubber composites products.

Investigation of Hybrid Nanoparticle-Acid Fluids (HNAFs): Influence of Wettability and Interfacial Tension Mechanisms in Harsh Carbonate Reservoirs for Improved Oil Recovery.

Over the past few years, there has been significant interest in the potential of hybrid nanoparticle-acid fluid (HNAFs) for improved oil recovery. This comprehensive study investigates the effects of nanoparticles and acid on interfacial tension (IFT) to establish a relationship between brine properties and the oil/brine IFT. This investigation is one of the first regional studies conducted utilizing candidate field data from the Middle East. Based on the literature review and screening studies conducted, a seawater (SW)-based HNAF was formulated with nanoparticles (SiO2, Al2O3, and ZnO) and HCl to measure their effect on IFT. A total of 48 formulations of HNAFs, nanofluids with and without acid, were analyzed with crude oil from a candidate field. IFT measurements were subsequently conducted using the pendant drop method under ambient conditions and in a high-pressure, high-temperature reservoir environment. Results showcased that IFT reduction was observed by increasing the acid concentration with SiO2 and Al2O3, although a reverse trend was observed with ZnO. Moreover, it was observed that IFT varied with increasing concentrations of nanoparticles, and at certain acid concentrations, IFT reduced significantly with higher nanoparticle concentrations. From the Amott studies, a clear signature was achieved, with ZnO exhibiting a total of 31.4% oil recovery, followed by SiO2 (27.3%) and Al2O3 (23.7%). The results of this study may assist in defining a screening criterion for future displacement (oil recovery) studies involving the presented nanoparticles. The results also reveal further the mechanisms involved in IFT reduction by hybrid nano-acid fluids and their potential for significant applications in the Middle East.

Shear induced fractionalized dispersion during Magnetic Drug Targeting in a permeable microvessel

Solute dispersion is a significant phenomenon during drug targeting to estimate the accumulation of drug particles at the tumour region with the capture efficiency. In this present study, we aim to predict the effective dispersion and saturated concentration of drug carriers during magnetic drug targeting in a microvessel with a time fractional derivative based dispersion model. The magnetic nanoparticles are bound with the non-magnetic materials/microgels with the therapeutic agents to prepare the drug carriers. A magnetic field is created outside the body to control and accelerate the trajectories of the drug carriers. The nature of the blood flow into the vessel is considered as Casson fluid. The velocity of the drug carriers is solved analytically, while the fractional-order dispersion equation is computed numerically using the finite difference technique with the forward time and central space discretization. The influence of fractional-order parameter and model biological parameters such as rheological parameter, permeability parameter related to hydraulic conductivity, magnetization, volume fraction of nanoparticles, tumour-magnet distance, nanoparticle radius, drug elimination, and source term on the relative effective dispersion are discussed. The outcomes showed that both rheological parameters and volume fraction increase drug carrier particle concentration, and that saturating occurs at a later time as they increase. Higher magnetization, permeability parameter related to the hydraulic conductivity, and source term are associated with faster transportation of drug carriers to the tumour site. In addition, we note that by using small particle sizes, a high concentration of the drug-coated nanoparticles will be expected in the tumour area, and this slows the rate at which it reaches the saturation point.

Phytoremediation of nanoparticle-contaminated soil using the halophyte plant species Suaeda glauca

Although concerns about the exposure of natural ecosystems to nanomaterials are increasing, research on how to remove toxic substances from the ecosystem is lacking. In this study, we investigated the phytoremediation ability of Suaeda glauca , a salt marsh plant, to remove nanomaterials introduced into the coastal ecosystem through the sewage system. TiO 2 nanoparticles (NPs) and ZnO NPs, which are commonly used in agriculture, cosmetics and industry are used for test materials. In comparison with the land plant Brassica campestris , which has been extensively used for heavy metal remediation, S. glauca was more resistant to nanomaterials and showed higher nanoparticle uptake. The Zn content of S. glauca plants was significantly higher than that of B. campestris plants in the 100 mg/kg ZnO NP treatment, and only S. glauca has survived 1000 mg/kg ZnO NP treatment. Furthermore, Ti contents of S. glauca plants was significantly higher than that of B. campestris plants in the 100 mg/kg TiO 2 NP treatment. Additionally, S. glauca showed higher dry weight than B. campestris in every treatments after exposure to nanomaterials, indicating better total remediation capacity. Our results suggest that S. glauca , and potentially other salt marsh plants, can be effectively used to remove nanoparticles from coastal ecosystems. • S. glauca showed strong resistance to the high concentration of NPs. • S. glauca showed higher NP absorption than the terrestrial plant B. campestris. • The excellent soil purification ability of individual halophytes for NPs was confirmed. • NPs can be effectively removed through phytoremediation using halophytes.

Tuning the Packing Density of Gold Nanoparticles in Peptoid Nanosheets Prepared at the Oil-Water Interface.

Two-dimensional (2D) arrays of gold nanoparticles that can freely float in water are promising materials for solution-based plasmonic applications like sensing. To be effective sensors, it is critical to control the interparticle gap distance and thus the plasmonic properties of the 2D arrays. Here, we demonstrate excellent control over the interparticle gap distance in a family of freely floating gold nanoparticle-embedded peptoid nanosheets. Nanosheets are made via monolayer assembly and collapse at the oil-water interface, allowing for fine control over the solution nanoparticle concentration during assembly. We used surface pressure measurements to monitor the assembly of the peptoid, nanoparticle, and combined system at the oil-water interface to determine a workable range of nanosheet assembly conditions suitable for controlling the interparticle gap distances within the nanosheets. These measurements revealed that the extent of nanoparticle adsorption to the peptoid monolayer can be tuned by varying the bulk nanoparticle concentration, but the ability for the monolayer to collapse into nanosheets is compromised at high nanoparticle concentrations. Peptoid nanosheets were synthesized with varying bulk nanoparticle concentrations and analyzed using light microscopy and UV-visible spectroscopy. Based on the spectral shift of the localized surface plasmon resonance peaks for the nanoparticles in the nanosheets relative to those well dispersed in toluene, we estimate that we can access interparticle gap distances within the nanosheet interior between 2.9 ± 0.5 and 9 ± 2 nm. Our results suggest that the minimum interparticle distance achievable by this method is limited by the nanoparticle ligand length, and so has the potential to be further tuned by varying the ligand chemical structure. The ability to quantitatively control and monitor the assembly conditions by this method provide an opportunity to readily tune the optoelectronic properties of this new class of 2D nanomaterial, making it a promising platform for plasmonic-based sensing applications.

Dosimetric Impact on the Flattening Filter and Addition of Gold Nanoparticles in Radiotherapy: A Monte Carlo Study on Depth Dose Using the 6 and 10 MV FFF Photon Beams.

Purpose: This phantom study investigated through Monte Carlo simulation how the dose enhancement varied with depth, when gold nanoparticles (NPs) were added using the flattening filter-free (FFF) photon beams in gold NP-enhanced radiotherapy. Method: A phantom with materials varying from pure water to a mixture of water and gold NPs at different concentrations (3–40 mg/mL) were irradiated by the 6 and 10 MV flattening filter (FF) and FFF photon beams. Monte Carlo simulations were carried out to determine the depth doses along the central beam axis of the phantom up to a depth of 40 cm. The dose enhancement ratio (DER) and FFF enhancement ratio (FFFER) were calculated based on the Monte Carlo results. Results: The DER values were found decreased with an increase of depth and increase of NP concentration in the phantom. For the maximum NP concentration of 40 mg/mL, the DER values decreased 6.9, 12, 4.6 and 7.2% at a phantom depth from 2 to 40 cm, using the 6 MV FF, 6 MV FFF, 10 MV FF and 10 MV FFF photon beams, respectively. The maximum DER values for the 6 MV beams were 1.08 (FF) and 1.14 (FFF), while those for the 10 MV beams were 1.04 (FF) and 1.07 (FFF). When the FF was removed from the linear accelerator head, the FFFER showed a more significant increase of dose enhancement for the 6 MV beams (1.057) than the 10 MV (1.031). Conclusion: From the DER and FFFER values based on the Monte Carlo results, it is concluded that the dose enhancement with depth was dependent on the NP and beam variables, namely, NP concentration, presence of FF in the beam and beam energy. Dose enhancement was more significant when using the lower photon beam energy (i.e., 6 MV), FFF photon beam and higher NP concentration in the study.

Development of Slurry Formulations for Molybdenum-Chemical Mechanical Planarization (Mo-CMP)

As integrated circuit (IC) technology continues to advance, the challenge to extend Moore’s law without sacrificing power density and energy efficiency is critical. One method of achieving these goals is through the utilization of Chemical Mechanical Planarization (CMP) to achieve surface planarity down to angstrom level uniformity. Current IC architecture relies on the integration of Cu wiring into Si (i.e., TEOS) substrates to provide effective power transfer. However, this traditional design is limited in efficiency for smaller, high-powered devices which require increased insulating properties. To combat these limitations, low resistivity metals (i.e., Ta, TaN, Mo, etc.) are incorporated for their inherent resistance to electromigration. More specifically, Mo has become increasing attractive due to the metal’s thermal stability and compatibility with Cu to serve as an efficient diffusive barrier. These ideal characteristics ultimately lead to the challenge of increased hardness resulting from inherent inert properties leading to the inhibition of effective CMP processes. To overcome this challenge, Mo-CMP involves the use of harsh polishing conditions consisting of high pressure-velocity coupled with complex slurry dispersions containing aggressive redox chemistry (i.e., KMnO4, KIO3, APS, etc.) and high abrasive nanoparticle content (i.e., Al2O3, SiO2, etc.). More specifically, the utilization of harsh oxidizers and alkaline conditions results in a metal oxide film ideal for effective material removal rate (MRR). However, it is with the implementation of these conditions that ultimately results in the generation of surface defects (i.e. scratching, pitting, etching, organic residues, galvanic corrosion, etc.) which are detrimental to the performance (i.e., power efficiency, operating frequency, etc.) for next generation IC devices. This work will focus on the investigation into conditions leading to effective MRR in Mo-CMP. More specifically, this work will utilize a suite of dynamic analytical techniques (i.e. atomic force microscopy, scanning electron microscopy, quartz crystal microbalance, contact angle, electrochemical analysis, etc.) to evaluate interfacial reaction mechanisms that lead to the productive modification for the reduction of shear force during polishing. It has been shown that the incorporation of tailored chemistries and the addition of “softer” passivating agents (i.e., polyamines) can result in the formation of surface-active complexes that trigger rapid interfacial redox reactions in H2O2 environments at a more amenable pH. Increasing the chemistry’s surface activity to Mo will result in a decreased Ea limiting the effects of nanoparticle adsorption to reduce CMP induced defectivity without the expense of corrosion events necessary for MRR. Furthermore, the implementation of “softer” passivating agents can reduce the galvanic corrosion effects with Cu which significantly reduce secondary defectivity.

Gradient alloy [formula omitted] core-shell nanoplatelets with tunable and large Stokes-shifted emission

Colloidal semiconductor nanoparticles possess unique size, shape and composition dependent optical properties, which make them appealing candidates for light-emitting devices (LEDs). However, due to enhanced reabsorption and energy transfer associated losses at high nanoparticle concentrations, which are required for LEDs, photoluminescence quantum yield of the nanoparticles significantly decreases, limiting external quantum efficiency of the LEDs. Therefore, Stokes shift engineered nanoparticles that allow for the suppression of the reabsorption and energy transfer losses are of great practical interest. Here, we report on gradient alloy CdSe1−xSx/CdS core-shell nanoplatelets, which provide tunable and large Stokes-shifted narrow emission. We demonstrate that the spectrally separation of absorption and emission peaks of CdSe1−xSx/CdS core-shell nanoplatelets is due to their gradient composition. Gradient alloy CdSe1−xSx/CdS core-shell nanoplatelets reveal an order of magnitude larger Stokes shift (310 – 422 meV) compared to that of conventional CdSe/CdS core-shell nanoplatelets. Moreover, unlike CdSe/CdS core-shell nanoplatelets, emission wavelength of gradient alloy CdSe1−xSx/CdS core-shell nanoplatelets can be finely controlled within the range of 500 – 600 nm via changing the composition of the core and thickness of the shell. We believe that the developed here gradient alloy CdSe1−xSx/CdS core-shell nanoplatelets, which provide tunable and large Stokes-shifted emission will be of interest for the development of high-efficiency LEDs with controllable optical properties.

Математична модель тепломасообміну в каналі з нанорідиною при його нерівномірному нагріві концентрованим тепловим потоком

This work is aimed at determining the expediency of using a nanofliud (a special suspension with nanoparticles) as a heat transfer agent for a parabolic trough solar plant. Adding nanoparticles to a base heat transfer agent intensifies convective heat exchange inside the channel, thus increasing the total heat efficiency of the receiver system. A refined nonlinear 3D mathematical model was developed to study heat-and-mass transfer in the receiver system of a parabolic trough solar plant that consist of a concentrator and a tube heat receiver with a nanofluid. In the mathematical model, the values of the nonuniform heat flux on the tube heat receiver surface are found by approximating numerical data obtained by the Monte Carlo method. This simplifies the classical coupled deterministic-statistical mathematical model and allows one to obtain a purely deterministic model solved by the finite volume method. The model also accounts for the thermal conductivity of the heat receiver wall, the actual ambient conditions, and the heat loss from the heat receiver surface. A numerical algorithm was developed to conduct numerical parametric studies on determining the temperature fields of Syltherm800/Al2O3 nanofluid heat transfer agent. This nanofluid is prepared from the traditional heat transfer agent of parabolic trough solar plants – Syltherm800 silicone oil – by adding aluminum oxide nanoparticles thereto. The numerical studies were conducted both for pure Syltherm800 oil and for Syltherm800/Al2O3 nanofluid with an Al2O3 nanoparticle concentration of 3, 5, and 8 per cent. This study is the first to find that the use of a nanofluid as a heat transfer agent for a parabolic trough solar plant produces a positive effect only in the case of the laminar flow of a nanofluid heat transfer agent with a high nanoparticle concentration. A verification of the obtained numerical data showed that they are in satisfactory agreement with experimental ones.

Applying negative ions to reduce surgical smoke in operation room

Long-term exposure to surgical smoke generated from electrocautery can increase health risks for medical personnel. Surgical smoke contains high concentrations of nanoparticles (NP, diameter ≤200 nm) and particulate matters with diameter less than 2.5 μm (PM 2.5 ), which can cause respiratory illnesses in medical personnel. Currently, local exhaust ventilation (LEV) is often used to reduce particles levels. However, LEV generates extra noise and can be easily blocked by blood clots formed during surgery. In this study, we added an ionizer to an electrosurgical pencil to help increase NP removal efficiency and compared the removal efficiency with that of a smoke evacuation pencil. The experiments were performed in an animal surgical facility in which air change rate, relative humidity, and temperature were controlled. We measured the PM 2.5 and NP concentrations near the source and in the breathing zone. The ionizer alone, wall suction, smoke evacuation pencil, and wall suction plus ionizer reduce NP number concentrations by 80.1%, 84.5%, 90.3%, and 92.4%, respectively in the breathing zone. The respective reductions in PM 2.5 were 86.5%, 92.9%, 93.0%, and 97.2%. Similar PM 2.5 and NP removal efficiency was seen near the source. Wall suction plus ionizer shows the highest removal efficiency for NP and PM 2.5 , but the removal efficiency is not significantly higher ( p > 0.05) than the commercial smoke evacuation pencil and wall suction. Moreover, excess lifetime carcinogenic risk also decreased by 79.1%, 90.7%, 93.0%, and 95.6% for the negative ions (NI), wall suction, smoke evacuation pencil, and NI + wall suction, respectively. The newly developed surgical smoke removal devices help reduce particle concentrations and thus can help protect the health of medical personnel. • Negative ions can help reduce surgical smoke concentrations without generating additional noise. • Adding negative ions to wall suction proves to be the most efficient method for reducing the particle number and mass concentrations in surgical smoke. • Negative ions can be used in clinical practice or other workplaces that requires silence and efficient removal rates of nanoparticles.

Echinochloa frumentacea grains extract mediated synthesis and characterization of iron oxide nanoparticles: A greener nano drug for potential biomedical applications

Iron oxide nanoparticles have been used in diverse fields due to their significant applications. The synthesis of iron oxide nanoparticles using plant material extract is a simple, inexpensive and eco-friendly approach. The present study demonstrates the effective bio-synthesis of iron oxide nanoparticles using grains extract of Echinochloa frumentacea. GC-MS analysis report revealed the information about the phytochemicals in aqueous grains extract. The formation of iron oxide nanoparticles was confirmed using UV–visible, XRD, FTIR, HRTEM, EDX, and mapping analyses. The UV–visible spectrum of iron oxide nanoparticles showed the SPR band at 289 nm. The XRD studies confirmed the formation of high crystalline iron oxide nanoparticles. HRTEM analysis showed that the formed nanoparticles were rectangular and triangular in shape and the size ranged between 20 and 40 nm. The iron oxide nanoparticles revealed significant antibacterial activity against the microbes such as Staphylococcus aureus and Salmonella typhi at 150 μg/mL and morphological changes were observed. The high concentration of nanoparticles exhibited 24 and 27 mm zone of inhibition on S. typhi and S. aureus, respectively. We observed the role of biological activities such as antioxidant, anti-inflammatory, and anti-diabetic properties of nanoparticles, and they showed excellent bioactive properties even at a low IC50 value. The antioxidant, anti-inflammatory and anti-diabetic analyses showed high activity at 95.10, 92.10 and 91.68% for 80 μg/mL concentration, respectively. Moreover, the iron oxide nanoparticles exhibited high cytotoxicity (94.36%) against A549 cancer cells and no toxicity against HEK293 normal cells which showed the biocompatibility of nanoparticles. The larvicidal and insecticidal activities of nanoparticles showed the maximum mortality at 48 h in 100 ppm and 72 h in 75, 100 μg/kg, respectively. The morphological and structural changes in larvae and insects validated the effective biological activities of iron oxide nanoparticles. The plant growth study results recommended that the lower concentration of nanoparticles at 60 ppm was helpful for the germination of seeds and growth of root and stem in the Vigna unguiculata plant. Finally, the study results suggested that the synthesized iron oxide nanoparticles can potentially be useful in pharmaceutical, agricultural, targeted drug delivery and biomedical applications.

Evaluation of Dosimetric Effect of Bone Scatter on Nanoparticle-Enhanced Orthovoltage Radiotherapy: A Monte Carlo Phantom Study.

In nanoparticle (NP)-enhanced orthovoltage radiotherapy, bone scatter affected dose enhancement at the skin lesion in areas such as the forehead, chest wall, and knee. Since each of these treatment sites have a bone, such as the frontal bone, rib, or patella, underneath the skin lesion and this bone is not considered in dose delivery calculations, uncertainty arises in the evaluation of dose enhancement with the addition of NPs in radiotherapy. To investigate the impact of neglecting the effect of bone scatter, Monte Carlo simulations based on heterogeneous phantoms were carried out to determine and compare the dose enhancement ratio (DER), when a bone was and was not present underneath the skin lesion. For skin lesions with added NPs, Monte Carlo simulations were used to calculate the DER values using different elemental NPs (gold, platinum, silver, iodine, as well as iron oxide), in varying NP concentrations (3–40 mg/mL), at two different photon beam energies (105 and 220 kVp). It was found that DER values at the skin lesion increased with the presence of bone when there was a higher atomic number of NPs, a higher NP concentration, and a lower photon beam energy. When comparing DER values with and without bone, using the same NP elements, NP concentration, and beam energy, differences were found in the range 0.04–3.55%, and a higher difference was found when the NP concentration increased. By considering the uncertainty in the DER calculation, the effect of bone scatter became significant to the dose enhancement (>2%) when the NP concentration was higher than 18 mg/mL. This resulted in an underestimation of dose enhancement at the skin lesion, when the bone underneath the tumour was neglected during orthovoltage radiotherapy.

Effects of short-term soil exposure of different doses of ZnO nanoparticles on the soil environment and the growth and nitrogen fixation of alfalfa

The extensive application of nanomaterials has increased their levels in soil environments. Therefore, clarifying the process of environmental migration is important for environmental safety and human health. In this study, alfalfa was used to determine the effects of different doses of ZnO nanoparticles (NPs) on the growth of alfalfa and the soil environment. Results showed that the alfalfa biomass was inversely proportional to the exposure concentration of ZnO NPs. The Zn concentration in the alfalfa tissue and the exposure dose presented a significant positive correlation. A high concentration of ZnO NPs decreased the nitrogen-fixing area of root nodules while the number of bacteroids and root nodules, which in turn affected the nitrogen-fixing ability of alfalfa. At the same time, it caused different degrees of damage to the root nodules and root tip cells of alfalfa. A high dose of ZnO NPs decreased the relative abundance and diversity of the soil microorganisms. Therefore, short-term and high-dose exposure of ZnO NPs causes multiple toxicities in plants and soil environments.

Optimization approach for the dilute magnetic polymer-dispersed liquid crystal

A method was investigated to improve the capacitance and electro-optical response of the dilute magnetic polymer-dispersed liquid crystals (PDLC). The proposed magnetic separation treatment further decreased the ion concentration of the liquid crystal colloid while preparing the diluted magnetic PDLC. The microstructure of the optimized diluted magnetic PDLC, including the shape, size, and distribution of the LC droplets, has not changed, but the capacitance and the electro-optical response of the PDLC have been further improved. Usually, increasing the concentration of the magnetic nanoparticles may reduce the ion concentration more, but the performance of PDLC has been a disadvantage. Our presented work shows an additional decrease in the ion concentration by doping the relatively high concentration of the magnetic nanoparticles and the magnetic separation treatment. However, the performance of the diluted magnetic PDLC has improved even more.

Stability Analysis of Fe3O4-OA-MWCNT Nanocomposite-Based Nanofluid

The aim of this project is to fabricate a highly stable Fe3O4-OA-MWCNT composite and its colloidal suspension in polyalphaolefin (PAO) base fluid for heat transfer applications. The nanocomposite was produced in three mass ratios (0.5 : 1, 1 : 1, and 1.5 : 1) to explore the concentration effects on the stability of the nanocomposite. XRD analysis and FTIR spectroscopy were conducted to inspect the phase and composition of the synthesized nanocomposite. The crystallite sizes (3.75 nm, 7.74 nm, and 7.52 nm) and dislocation densities of each composite were calculated, and it was revealed that the samples with high concentration of iron oxide nanoparticles showed small defects in their lattices. Dispersion stability of ferrofluids was also examined by natural deposition method for 365 days. The ferrofluids displayed high stability for more than one year with no sign of sedimentation. Thermal conductivity of the nanofluid was also measured via. A transient plane source method and a linear trend with slight deviation were observed.

Effect of alumina nanofluids on bubble dynamics and heat transfer under quiescent conditions

Thermal management of high heat loads is a relevant problem in various industrial applications. Nanofluids used in pool boiling based cooling systems are pointed as an attractive solution, but controversial results reported in the literature preclude a wider use of such cooling solutions. On the other hand, high costs are often reported to the fabrication of small quantities of nanoparticles, so cost-effective solutions are needed. Despite of the extensive research performed on pool boiling heat transfer of nanofluids, detailed studies on bubble dynamics and on their relation with pool boiling heat transfer is still scarcely reported in the literature. Hence, the present work addresses the effect of a cost-effective nanoparticle (alumina, Al2O3) in pool boiling heat transfer of water based nanofluids. The analysis performed here combines high-speed visualization with time and space resolved thermography to relate bubble dynamics and heat transfer. Results show that although alumina particles do not significantly affect single bubble dynamics, they result in a significant heat transfer enhancement. Hence, concentrations of 3wt% of Al2O3 lead to 38% in surface temperature reduction compared to that observed with water and an increase of 61% in the heat transfer coefficient. However, additional studies must be performed to infer if the use of such high nanoparticle concentrations is effectively beneficial, given the resulting issues (e.g. stability problems).

Effect of ferrofluid magnetization on transformer temperature rise

In electrical engineering, the heat transfer can be enhanced by changing the thermophysical properties of insulating oils. In this paper, a single-phase power transformer with a nominal power of 5 kVA is subjected to a temperature rise test with three different transformer liquids. The first test is carried out with a novel gas-to-liquid transformer oil applied as a cooling and insulating medium. The other tests are conducted with ferrofluids based on this oil and MnZn ferrite nanoparticles of a low and a high nanoparticle concentration. The ferrofluids are characterized by magnetization curves, magnetic susceptibility and temperature-dependent magnetization measurements. The nanoparticle size distribution is determined from dynamic light scattering and the magnetization data. From the temperature rise profiles of the transformer at various inner locations, it has been found that the low-concentrated ferrofluid significantly reduces the transformer temperature rise. The enhanced cooling performance is ascribed to the thermomagnetic and natural convection, and increased thermal conductivity. The application of the ferrofluid with the high nanoparticle concentration resulted in a remarkable increase of the transformer temperature rise. The deteriorative cooling effect is attributed to the hindered natural and thermomagnetic convection due to the high ferrofluid magnetization and strong magnetic interaction of the ferrofluid with the magnetic field near the transformer core.

Remedial Aspect of Zinc Oxide Nanoparticles Against Serratia Marcescens and Enterococcus Faecalis.

Zinc oxide nanoparticles (ZnO NPs) have been widely used in biomedical applications due to their high biocompatibility and low toxicity to humans. The present work aimed to investigate the antibacterial effects of different concentrations of ZnO NPs on two opportunistic pathogens, Serratia marcescens and Enterococcus faecalis. The surface interaction between nanoparticles and bacterial cell wall, and the subsequent morphological alterations on the bacterial surface, were examined through Fourier transform infrared spectroscopy and scanning electron microscope. The energy dispersive X-ray analysis was used to confirm the elemental composition of ZnO NPs and the cellular accumulation of ZnO NPs in bacteria. The growth-inhibitory test demonstrated a dose-dependent growth inhibitory effect of ZnO NPs against both the test bacteria, as the higher concentration of nanoparticles caused the higher bacterial growth inhibition. The results showed that ZnO NPs caused a higher growth inhibition (63.50 ± 2.50%) on the Gram-positive bacterium E. faecalis compared to the Gram-negative bacterium S. marcescens (51.27 ± 4.56%). Fourier transform infrared spectrum revealed the possible involvement of hydroxyl, carboxyl, amides, methylene, and phosphate groups from the biomolecules of bacterial cell wall such as proteins, carbohydrates, lipids, and phospholipids in the interaction of ZnO NPs on bacterial cell surface. Energy dispersive X-ray analysis showed the higher accumulation of ZnO NPs in E. faecalis than S. marcescens analogous to the bacterial growth inhibition. Scanning electron microscopy images confirmed the antibacterial properties of ZnO NPs, showing the loss of integrity of cell membrane and distortion of bacterial cells. Hence, the potential of ZnO NP as an antibacterial agent against S. marcescens and E. faecalis has been confirmed.

Effects of polyallylamine-coated nanoparticles on the optical and photochemical properties of rose bengal.

Inasmuch as optical and photochemical properties of a photosensitizer can be modified upon association with the nanoparticle (NP), we wondered whether the effectiveness of phototherapeutic rose bengal (RB) was affected upon tethering to the sodium lanthanide fluoride NP with an outer polyallylamine (PAH) coat. RB molecules were electrostatically bound to the NaYF 4 :Gd 3+ :Nd 3+ NPs with inner silica and outer PAH coats. The products were analyzed for their size, shape and zeta potential using transmission electron microscopy and dynamic light scattering instrument. Ultraviolet-visible absorption spectrometry and fluorescence spectrometry were used to examine the spectral properties. Photodynamic effect in terms of singlet oxygen generation was quantitatively determined using the indicator 1,3-diphenylisobenzofuran (DPBF). Photocytotoxicity mediated by NP-bound RB was tested using A549 cells (Student's t test was used for statistical evaluation). NP-bound RB had the major absorbance peak at 561 nm, in comparison with 549 nm for free RB, accompanied with a significant decrease in absorptivity. The molar extinction coefficient becomes 36 000 M -1 cm -1 , only ~35% of that for free RB. Fluorescence spectral analyses showed a paradoxical decrease in the emission with higher NP concentrations even at very low dilutions. Most importantly, the association of RB with these NPs drastically increased its singlet oxygen production upon irradiation. The interaction of RB with PAH coat could partly account for this enhancement, given our finding that PAH in solution also caused a drastic rise in DPBF reactivity by free RB. These NPs exhibited strong photocytotoxic effects, and their promise in photodynamic therapy was addressed. Our findings provide evidence that the PAH coat plays a key role in enhanced biological activities of RB delivered via NPs, including the increase in singlet oxygen production and photocytotoxic effects.

One-step fabrication of superhydrophobic nanocomposite with superior anticorrosion performance

Superhydrophobic coatings having a self-cleaning ability and anticorrosion performance are desired in many industrial contexts; however, high costs and complex fabrication methods limit their application. In this study, thin anticorrosive superhydrophobic coatings were prepared by a scalable, simple, and inexpensive spraying method to protect AA2024-T3 surfaces. The two-component coatings were designed using fluoropolyurethane and varying concentrations of surface modified silica nanoparticles. Surface characterization was performed using contact angle and contact angle hysteresis measurements, field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectrum (EDS), and atomic force microscopy (AFM) techniques. Corrosion protection, water uptake, and adhesion strength of the coatings were evaluated by electrochemical impedance spectroscopy (EIS) and cross-cut tests, respectively. Increased silica nanoparticle concentrations up to 10 wt% led to increased contact angles from 92° to 167°. The lowest contact angle hysteresis was obtained for the coating containing 4 wt% nanoparticles. FE-SEM images showed that high concentrations of nanoparticles (more than 4 wt%) led to cracks in the coating surface. The best performance of a coating was observed when the coating contained 4 wt% nanosilica particles, resulting in a 164° water contact angle, almost 60 days of surface protection, an impedance value of 2.2 × 109 Ω·cm2, 0.9% water uptake, and marked adhesion strength. The impedance value of the coating with 4 wt% nanosilica particles was about 25× that of the blank sample.