High Nanoparticle Concentrations Research Articles

Effect of ZnO nanoparticles addition to PEO coatings on AZ31B Mg alloy: antibacterial effect and corrosion behavior of coatings in Ringer’s physiological solution

ABSTRACT In this paper, the plasma electrolyte oxidation (PEO) technique was applied to modify the AZ31B Mg alloy surface. Effects of various concentrations of ZnO nanoparticles into an electrolyte with nanoparticles of hydroxyapatite (HAp) on the antibacterial and corrosion behavior of coatings were studied. Potentiodynamic polarization tests were done in Ringer’s electrolyte to study the coatings corrosion behavior. Results of XRD indicated that the provided PEO films mostly have phases of HAp, MgO, and Mg3(PO4)2 and ZnO. The results indicated that increasing the concentration of ZnO nanoparticles raised the thickness, roughness, and wetting angle and also enhanced the coatings antibacterial activity. The inhibition percentage of bacterial growth for the specimen with the highest concentration of nanoparticles (4 g/L) after 6 h against E. coli and S. aureus was 23.5% and 45.5%, respectively. The concentration of nanoparticles had no major effect on the porosity size of the ceramic coating. Moreover, adding ZnO nanoparticles declined the corrosion current density and raised the corrosion potential with regard to the metal substrate. The formed coating in the solution containing 1 g/L ZnO nanoparticles had the highest corrosion behavior among all of specimens that led to a 970 multiplication corrosion resistance of AZ31B Mg alloy.

Light- and Melanin Nanoparticle-Induced Cytotoxicity in Metastatic Cancer Cells.

Melanin nanoparticles are known to be biologically benign to human cells for a wide range of concentrations in a high glucose culture nutrition. Here, we show cytotoxic behavior at high nanoparticle and low glucose concentrations, as well as at low nanoparticle concentration under exposure to (nonionizing) visible radiation. To study these effects in detail, we developed highly monodispersed melanin nanoparticles (both uncoated and glucose-coated). In order to study the effect of significant cellular uptake of these nanoparticles, we employed three cancer cell lines: VM-M3, A375 (derived from melanoma), and HeLa, all known to exhibit strong macrophagic character, i.e., strong nanoparticle uptake through phagocytic ingestion. Our main observations are: (i) metastatic VM-M3 cancer cells massively ingest melanin nanoparticles (mNPs); (ii) the observed ingestion is enhanced by coating mNPs with glucose; (iii) after a certain level of mNP ingestion, the metastatic cancer cells studied here are observed to die—glucose coating appears to slow that process; (iv) cells that accumulate mNPs are much more susceptible to killing by laser illumination than cells that do not accumulate mNPs; and (v) non-metastatic VM-NM1 cancer cells also studied in this work do not ingest the mNPs, and remain unaffected after receiving identical optical energy levels and doses. Results of this study could lead to the development of a therapy for control of metastatic stages of cancer.

Numerical analysis of porous flat plate solar collector under thermal radiation and hybrid nanoparticles using two-phase model

Solar collectors will play a very important role in absorbing solar renewable energy for use in various industries in the future of the world. This study looks at the resulting combination of using porous medium and hybrid nanofluids, in the presence of thermal radiation, on the thermo-hydrodynamic features, heat transfer, supply temperature, and hybrid nanoparticles’ distribution within a horizontal flat plate solar collector. The two-phase approach is considered for modelling. The migration of Ag-Al2O3 hybrid nanoparticles due to the Brownian motion and thermophoresis effects was also taken into account. The set of governing equation was numerically solved employing the finite element method. The investigation is performed by reporting the roles of hybrid nanofluid concentration, porosity coefficient, Darcy number, Reynolds number, porous media to hybrid nanofluid thermal conductivity ratio, Brownian motion parameter, thermophoretic parameter, radiation parameter, and Schmidt number. The results indicate that The high values of porosity coefficient, radiation parameter, conductivity ratio, and thermophoretic parameter ameliorate thermophoresis effects, and therefore, a high concentration of nanoparticles was observed near the bottom part of the collector, especially at low Reynolds. Also, Employing hybrid nanofluid lead to a decrease in the heat transfer rate and slightly raised the supply temperature at low Re.

Estimation of Dose Enhancement for Inhomogeneous Distribution of Nanoparticles: A Monte Carlo Study

High atomic number nanoparticles are of increasing interest in radiotherapy due to their significant positive impact on the local dose applied to the treatment site. In this work, three types of metal nanoparticles were utilized to investigate their dose enhancement based on the GATE Monte Carlo simulation tool. Gold, gadolinium, and silver were implanted at three different concentrations to a 1 cm radius sphere to mimic a cancerous tumor inside a 10 × 10 × 30 cm3 water phantom. The innermost layer of the tumor represents a necrotic region, where the metal nanoparticles uptake is assumed to be zero, arising from hypoxic conditions. The nanoparticles were defined using the mixture technique, where nanoparticles are added to the chemical composition of the tumor. A directional 2 × 2 cm2 monoenergetic photon beam was used with several energies ranging from 50 keV to 4000 keV. The dose enhancement factor (DEF) was measured for all three metal nanoparticles under all beam energies. The maximum DEF was ~7 for silver nanoparticles with the 50 keV beam energy at the highest nanoparticle concentration of 30 mg/g of water. Gold followed the same trend as it registered the highest DEF at the 50 keV beam energy with the highest concentration of nanoparticles at 30 mg/g, while gadolinium registered the highest at 100 keV.

Using perceptron feed-forward Artificial Neural Network (ANN) for predicting the thermal conductivity of graphene oxide-Al2O3/water-ethylene glycol hybrid nanofluid

In this paper, Artificial Neural Network (ANN) was used to investigate the influence of temperature and volume fraction of nanoparticles on the thermal conductivity of Graphene oxide-Al2O3/Water-Ethylene glycol hybrid nanofluid. Nanofluids were prepared with the volume fraction of nanoparticles 0.1, 0.2, 0.4, 0.8, and 1.6% in the temperature range of 25–55 °C. The nanofluid's thermal conductivity results were extracted from six different volume fractions of nanoparticles and seven different temperatures. Then, to generalize the data and obtain a function, the Perceptron feed-forward ANN was used, simulating the output parameter. The outcomes show that the ANN is well trained using the trainbr algorithm and has an average of 1.67e-6 for MSE and a correlation coefficient of 0.999 for thermal conductivity. Finally, we conclude that the effect of increasing the temperature of nanofluid is less against the volume fraction of nanoparticles, especially in low concentrations. This effect is negligible and in the absence of nanoparticles, increasing the temperature from 20 °C to 55 °C leads to an enhance in thermal conductivity of about 6%. However, at high concentrations of nanoparticles, increasing the temperature leads to further thermal conductivity. At volume fraction nanoparticles 1.6%, increasing the temperature from 20 °C to 55 °C increases the thermal conductivity from 0.45 to 0.54 W/m.K.

Printable PICN Composite Mechanically Compatible with Human Teeth

Polymer-infiltrated ceramic network (PICN) composites are mechanically compatible with human enamel, and are therefore promising dental restorative materials. Fabrication technology for PICN composites used in tooth restorative material has been established through computer-aided design/computer-aided manufacturing (CAD/CAM) milling, however, to date, has not been successfully developed using 3-dimensional (3D) printing. This study aimed to develop a 3D-printable PICN composite as a restorative material. The PICN composite was fabricated using a specific method based on 3D printing. A 3D-printable precursor slurry containing a high concentration of silica nanoparticles was produced and 3D-printed using stereolithography (SLA). The 3D-printed object was sintered to obtain a nano-porous object, and subsequently infiltrated and polymerized with resin monomer. Three different fabrication condition combinations were used to produce the 3D-printed PICN composites, which were characterized based on microstructure, mechanical properties, inorganic content, physicochemical properties, and overall shrinkage. The 3D-printed PICN composites were also compared to 2 commercially available CAD/CAM composite blocks, namely a PICN composite and a dispersed-filler composite. The 3D-printed PICN composites exhibited a nano-sized dual-network structure comprising a silica skeleton with infiltrated resin. The 3D-printed PICN composite exhibited a similar Vickers hardness to enamel, and a similar elastic modulus to dentin. The 3D-printed PICN composite exhibited comparable flexural strength (>100 MPa) to the CAD/CAM block, and acceptable water sorption and solubility for practical use. Further, the 3D-printed model-crown underwent isotropic shrinkage during sintering without fatal deformation. Overall, the potential of this 3D-printable PICN composite as a restorative material with similar mechanical properties to human teeth was successfully demonstrated.

The Use of Silica Microparticles to Improve the Efficiency of Optical Hyperthermia (OH).

Although optical hyperthermia could be a promising anticancer therapy, the need for high concentrations of light-absorbing metal nanoparticles and high-intensity lasers, or large exposure times, could discourage its use due to the toxicity that they could imply. In this article, we explore a possible role of silica microparticles that have high biocompatibility and that scatter light, when used in combination with conventional nanoparticles, to reduce those high concentrations of particles and/or those intense laser beams, in order to improve the biocompatibility of the overall procedure. Our underlying hypothesis is that the scattering of light caused by the microparticles would increase the optical density of the irradiated volume due to the production of multiple reflections of the incident light: the nanoparticles present in the same volume would absorb more energy from the laser than without the presence of silica particles, resulting either in higher heat production or in the need for less laser power or absorbing particles for the same required temperature rise. Testing this new optical hyperthermia procedure, based on the use of a mixture of silica and metallic particles, we have measured cell mortality in vitro experiments with murine glioma (CT-2A) and mouse osteoblastic (MC3T3-E1) cell lines. We have used gold nanorods (GNRs) that absorb light with a wavelength of 808 nm, which are conventional in optical hyperthermia, and silica microparticles spheres (hereinafter referred to as SMSs) with a diameter size to scatter the light of this wavelength. The obtained results confirm our initial hypothesis, because a high mortality rate is achieved with reduced concentrations of GNR. We found a difference in mortality between CT2A cancer cells and cells considered non-cancer MC3T3, maintaining the same conditions, which gives indications that this technique possibly improves the efficiency in the cell survival. This might be related with differences in the proliferation rate. Since the experiments were carried out in the 2D dimensions of the Petri dishes, due to sedimentation of the silica particles at the bottom, whilst light scattering is a 3D phenomenon, a large amount of the energy provided by the laser escapes outside the medium. Therefore, better results might be expected when applying this methodology in tissues, which are 3D structures, where the multiple reflections of light we believe will produce higher optical density in comparison to the conventional case of no using scattering particles. Accordingly, further studies deserve to be carried out in this line of work in order to improve the optical hyperthermia technique.

Nejayote biopolyelectrolytes multifunctionality (glucurono ferulauted arabinoxylans) in the separation of hazardous metal ions from industrial wastewater

The scarcity and contamination of water by suspended nanoparticles and hazardous metal ions demand more performant technologies to reduce space, time and cost of wastewater treatment. For example, it is desirable to find eco-friendly chemicals that warranty simultaneous separation of colloidal particles and hazardous metallic contaminants for a more sustainable recovery of water quality.As the second part of a series of physicochemical studies about multifunctional biopolyelectrolytes (BPEs), in this paper, we present three of the main features of the glucurono ferulauted arabinoxylans (GFAXs) from nejayote: simple extraction, physicochemical characterization and multifunctional performance when used in a wastewater treatment unit. The polyelectrolytic and macrochelating properties of the GFAXs were studied through zeta potential measurements to predict and understand the multifunctional performance of GFAXs in a conventional coagulation-flocculation unitary operation. Two real cases were approached: the wastewater from silicon wafer cutting process (SWCP) and the wastewater from electroplating baths (EPB). Nejayote GFAXs showed high coagulant, flocculant and macrochelating activity in the simultaneous separation of Si4+, Al3+, Cr3+, Ni2+, Mg2+, Ca2+, Ni2+, Cd2+, Pb2+, Cu2+, Zn2+ and Fe2+. The water treatment tests demonstrate the high performance of the GFAXs in the coagulation-flocculation of the wastewater according to the following parameters: EPB wastewater at pH = 5.0 (optimal dose = 55–65 mg GFAXs/L, clarification = 380 T%/h and sedimentation kinetics = 110.4 mm/h); SWCP wastewater at pH = 5.5 (optimal dose = 30.0–32.5 mg GFAXs/L, clarification = 295 T%/h and sedimentation kinetics = 89.4 mm/h). With these results, nejayote GFAXs showed to be a sustainable solution for the wastewater treatment from semiconductor and metal finishing industry with high content of hazardous metal ions and SiO2 nanoparticles.

Metal based nanoparticles trigger the differential expression of key regulatory genes which regulate iron and zinc homeostasis mechanism in finger millet

Since green revolution, the food systems in most of the countries have dramatically changed but undernourishment still remains an inflammable problem. This alarming condition is even increasing due to the marginal supply of nutri-enriched food to eat. Under such chronically undernourished condition, dietary deficiencies of iron and zinc lead to compromised planetary health and economic losses. Given the micronutrient deficiency, there is an urgent call to devise or innovative a strategy for providing the requisite amount of iron and zinc in their daily intake to counter this issue. Thus being a high iron and zinc accumulating crop, finger millet can be efficiently used as an intricate model system to explore the prospects of genetic and molecular mechanisms which are responsible for nutrient enrichment in grains. We report here a promising role of nanotechnology in terms of their iron and zinc biofortification potentials in the finger millet. Comparative in vitro evaluation using lower concentration of Fe3O4 (100 ppm) and ZnO (5 ppm) nanoparticles (NPs) display a significant promotory effect on both mineral assimilation and growth parameters whereas higher concentrations of NPs, FeSO4.7H2O and ZnSO4.7H2O bulk salts marked inhibitory effects. The molecular modelling and docking interaction analysis infers that these nano-minerals may bind to significantly influence the modulation of regulatory genes. The result was further validated using real time PCR profiling. The differential expression profiling resulted in higher transcriptional modulation of iron and zinc transporters particularly EcFER1, EcIRT2, EcYSL2, EcZIP1 and EcZTP29 in nano-primed genotypes compared to controls. Thus in conclusion, being a nutrient by default and stress-resilient crop, nanoparticle formulations in finger millet triggers the epigenetic regulation of potential key regulatory genes involved in iron and zinc homeostasis. The study also indicates innovative role of nano-seed priming for biofortification which triggers differential modulation of iron and zinc acquisition and enrichment in grains despite nutrient limiting conditions.

Study on the improvement of supercooling and thermal properties of erythritol-based phase change energy storage materials

Ultrasound and nanoparticles are used to control the supercooling degree of the erythritol-based phase change material. The effects of particle type, ultrasonic power and initial ultrasonic temperature on the crystallization supercooling degree (SD), crystallization progress and supercooling instability of nanofluids are investigated. Meanwhile, the preparation scheme of nanofluids that satisfy both high-quality thermal performance and economic value is explored. The results show that when the particle concentrations are 0.05%, 0.1%, 0.2% and 0.3%, respectively, the SD of the nanofluids added with C decreased by 27.34%, 27.16%, 22.52% and 12.90% (24.39%, 19.91%, 5.49% and 1.22%), respectively, compared with those added with Cu (ZnO) at the same concentration. High-quality nanofluids can be obtained when the addition amounts of C, Cu, and ZnO are 0.1%, 0.3%, and 0.2%, respectively. A nanofluid with good crystallization effect can be obtained when high (low) concentration of nanoparticles is introduced and high (low) power of ultrasound is input. At the initial ultrasonic temperatures of 130 °C, 120 °C, 110 °C and 100 °C, the crystallization effect of the fluid would be worse after adding nanoparticles. With the ultrasonic power of 150W, ultrasonic time of 30 min and particle concentration of 0.5%, ET nanofluids with the best thermal property and optimal sample in economy can be produced.

Revealing the effects of cerium dioxide nanoparticles through the analysis of morphological changes in Chironomus riparius

Due to their many practical applications, engineered cerium dioxide (CeO2) nanoparticles (NPs) are commonly used today, although there are justified concerns about the environmental risks of their usage. Studies to date have shown that CeO2 NPs do not pose a lethal hazard to hydrobiocenoses at environmentally relevant concentrations, but that they induce significant negative sublethal effects. Therefore, intensive work is being done on the adaptation of standard ecotoxicological tests with the development of new, sublethal biomarkers. The present study aims to examine the sublethal effects of prolonged exposure to CeO2 NPs (2.5; 25; 250 and 2500 mg of CeO2 NPs per 1 kg of sediment) on the morphological features of the non-biting aquatic midge Chironomus riparius. Morphological variation was examined by means of two approaches: (1) Deformity rate analysis (analysis of visible morphological malformations) and (2) Geometric morphometric analysis (analysis of differences in the size and shape of the larval mandibles and mentums, as well as adult male and female wings). Changes in all the morphological structures examined were observed using a geometric morphometric approach at low and very high concentrations of CeO2 NPs (2.5 and 2500 mg of CeO2 NPs per 1 kg of sediment). The potential reduction of sexual dimorphism resulting from downsizing of the wings in females was observed. These results indicate that the sublethal changes observed in chironomids exposed to CeO2 NPs are significant and may potentially lead to further changes in metabolism, diet and behavior, which may lead to repercussions of as yet unexamined proportions. Considering our findings, and the advantages of geometric morphometrics (precision, uniformity, accurate qualification, quantification, and visualization of fine morphological changes), this approach is proven to be an exceptional assessment tool, with great applicative potential in the ecotoxicological testing of nanoparticles.

Physicochemical and microbiological characteristics of urban aerosols in Krakow (Poland) and their potential health impact

Eight aerosol samples were collected in Krakow using a low-volume sampler in February and March 2019 during variable meteorological conditions and times of the day, to study their single particles’ properties (size, morphology and chemical composition analyzed using a scanning electron microscope fitted with an energy-dispersive spectrometer) and microbiological characteristics. The content of particles of different chemical compositions larger than 2.5 μm was low. Considering the number of the particles, submicron particles strongly dominated with a high content of ultrafine particles (nanoparticles). Tar ball-type particles were relatively common in the studied samples, while soot was the dominant component. Soot was present as small agglomerates composed of few particles, but also as bigger agglomerates. Metal-containing particles of various chemical characteristics were abundant, with transition metals commonly occurring in these particles. The physicochemical characteristics of aerosols indicate that despite a relatively low mass concentration, their adverse health impact could be very strong because of the high content of nanoparticles, the abundance of soot and other fuel combustion-related particles, and the high incidence of transition metal-rich particles. Microbiological analysis was based on cultures on both solid and liquid agar. The MALDI-TOF method was used for species identification—for bacteria and fungi. Twelve different species of bacteria were isolated from the collected samples of aerosols. The most frequently isolated species was Gram-positive sporulating Bacillus licheniformis. The isolated mold fungi were of the genus Aspergillus.

Synergistic Photothermal-Chemotherapy Based on the Use of Biomimetic Magnetic Nanoparticles.

MamC-mediated biomimetic magnetic nanoparticles (BMNPs) have emerged as one of the most promising nanomaterials due to their magnetic features (superparamagnetic character and large magnetic moment per particle), their novel surface properties determined by MamC, their biocompatibility and their ability as magnetic hyperthermia agents. However, the current clinical application of magnetic hyperthermia is limited due to the fact that, in order to be able to reach an effective temperature at the target site, relatively high nanoparticle concentration, as well as high magnetic field strength and/or AC frequency are needed. In the present study, the potential of BMNPs to increase the temperature upon irradiation of a laser beam in the near infrared, at a wavelength at which tissues become partially transparent, is explored. Moreover, our results also demonstrate the synergy between photothermia and chemotherapy in terms of drug release and cytotoxicity, by using BMNPs functionalized with doxorubicin, and the effectiveness of this combination therapy against tumor cells in in vitro experiments. Therefore, the findings of the present study open the possibility of a novel, alternative approach to fight localized tumors.

Asphaltene stability during heptane injection in a glass micromodel in the presence of Co3O4 nanoparticles

Severe challenges and difficulties in oil production may arise from asphaltene precipitation and deposition in porous media and upstream facilities. The investigation for a proper solution for such detrimental damages is indispensable for the oil industry. Nanoparticles, due to their unique properties of high degree of dispersibility and high adsorption affinity, may potentially be useful for hampering the asphaltene related problems to some extent. In this study, by the use of glass micromodels, the utilization of Co 3 O 4 nanoparticles to stem asphaltene precipitation has been investigated. These nanoparticles were dispersed in synthetic solutions comprising of toluene, n-heptane and asphaltenes as well as crude oil. The prepared solutions were then subjected to n-heptane injection as asphaltene precipitator. The amount and extent of asphaltene precipitation and deposition in micromodels was then measured and analyzed. The results showed that Co 3 O 4 nanoparticles positively affect asphaltene stability in both crude oil and synthetic solutions. However, it was found that once these nanoparticles adhere to glass surface, then intense asphaltene precipitation and deposition would take place. The impacts of nanoparticle concentration were also discerned through experiments for 0.01, 0.05 and 0.1 wt% concentrations of nanoparticles. It was obtained that generally, higher concentration of nanoparticles would reduce asphaltene precipitation intensity. However, due to very little difference between the efficiency of solutions containing 0.05 and 0.1 wt% in terms of increasing asphaltene stability, 0.05 wt% of dispersed nanoparticles was found to be the optimum concentration for preventing asphaltene precipitation and deposition. This study, for the first time, provides a micro visual study in order to observe the impacts of nanoparticles on the stability of asphaltene in crude oil and synthetic oil samples in a uniformly patterned glass micromodel. • Co 3 O 4 nanoparticles reduced the intensity of asphaltene precipitation and deposition. • 0.05 wt% of Co 3 O 4 was the optimum concentration for improving asphaltene stability. • The creation of asphaltene nucleus in the presence of nanoparticles was visualized. • In some spots, Co 3 O 4 nanoparticles increased asphaltene deposition intensity.

A Review of Sintering-Bonding Technology Using Ag Nanoparticles for Electronic Packaging.

Metal nanoparticles (NPs) have attracted growing attention in recent years for electronic packaging applications. Ag NPs have emerged as a promising low-temperature bonding material owing to their unique characteristics. In this study, we mainly review our research progress on the interconnection of using polyol-based Ag NPs for electronic packaging. The synthesis, sintering-bonding process, bonding mechanism, and high-temperature joint properties of Ag NP pastes are investigated. The paste containing a high concentration of Ag NPs was prepared based on the polyol method and concentration. A nanoscale layer of organic components coated on the NPs prevents the coalescence of Ag NPs. The effects of organic components on the bondability of the Ag NP paste were studied. Compared to the aqueous-based Ag NP paste, the polyol-based Ag NP with the reduction of organic component can improve the bondability, and the coffee ring effect was successfully depressed due to the increased Marangoni flow. The sintering behaviors of Ag NPs during the bonding process were investigated using the classical sphere-to-sphere approach. The mechanical property of joints using this Ag paste was better than that using Pb95Sn5 solders after storage at high temperatures. The sintering–bonding technology using polyol-based Ag NPs was helpful to the low-temperature interconnection for electronic packaging applications.

Promoting the separation and antifouling properties of polyethersulfone-based nanofiltration membrane by incorporating of cobalt ferrite/activated carbon composite nanoparticles

In this study, a mixed matrix polyethersulfone-based nanofiltration membrane was prepared by incorporation of (cobalt ferrite/activated carbon) composite nanoparticles. The composite nanoparticles were also synthesized using the chemical precipitation technique. The FTIR, XRD and FESEM were used to characterize the synthesized nanoparticles. The fabricated membranes were also studied using SEM, 3D surface image, and water contact angle, mean pore size and porosity measurements. The water flux, salt rejection and antifouling ability of membranes were investigated. The blended membranes showed a more hydrophilic and smoother surface compared to the pristine membrane. The membrane PWF was declined initially using 0.05wt. % (CoFe2O4/AC) nanoparticles into membrane body and then enhanced by a further increase of nanoparticles’ concentration up to 0.1wt. % in membrane matrix; PWF was reduced again for the blended membranes at higher concentration of nanoparticles. The NaCl and Na2SO4 rejections were enhanced from (42% to 85%) and (55% to 95%) by the use of (CoFe2O4/AC) nanoparticles into the membrane body. The blended membranes also exhibited appropriate anti-fouling property and more stable flux compared to the pristine membrane. The highest Pb2+, Ni2+, and Cu2+ rejections were found 86%, 90%, and 97%, respectively, for the blended membrane containing of 1wt. % (CoFe2O4/AC) compared to others.

An insight into the binding behavior of graphene oxide and noble metal nanoparticles

The binding behavior of graphene oxide and metal nanoparticles (Au, Pt, and Pd) was observed by UV–Vis spectroscopy, fluorescence spectroscopy, dynamic light scattering, and zeta potential. Hybrids with a fixed concentration of graphene oxide (GO) were prepared with increasing concentration of metal nanoparticles to observe the effect of binding on their spectroscopic properties, size, and zeta potential. An increase in the absorption spectra of GO after binding with nanoparticles and a gradual decrease in fluorescence emission intensity with increasing concentration of nanoparticles was observed, representing their effective binding. Stern–Volmer plots differentiated the quenching constants of these nanoparticles, where Au shows the lowest and Pd shows the highest quenching among these nanoparticles. The initial hybrids showed more size change as compared to hybrids with a higher concentration of nanoparticles, whereas initial hybrids have charge similar to that of GO and gradual increase in the concentration of nanoparticles bring the charge near to the respective charge of nanoparticles. To the best of our understanding, this is the first report of its kind to study the binding interactions of two different moieties by studying changes occurred in the hydrodynamic radius and zeta potential of hybrids by titration experiments, having applications in surface treatment, drug delivery, and as sensors for environmental pollutants or other classes of organic molecules, etc.

Size effects of carboxylated magnetite nanoparticles on the membrane dehumidification performance

This study aims to understand the effects of different nanoparticle sizes on the dehumidification performance of thin-film nanocomposite membranes (TFN). Carboxylated magnetite (C-Fe3O4) nanoparticles of different sizes (5–30 nm) were embedded in a polyamide layer (PA) over the polysulfone (PSf) substrate. The structural and morphological characteristics of the nanoparticles and coated membranes were explored using various analytical techniques such as FT-IR, SEM, DLS, the zeta-potential, EDS, AFM, and the water contact angle. Mixed-gas permeation tests showed that there were performance peak points at specific nanoparticle concentrations. These performance peaks shifted toward a high concentration of nanoparticles with a decrease in the magnetite size. The M5(0.3) membrane with 0.3 w/w% of 5 nm magnetite particles showed the highest water vapor permeance of 1886 GPU and the highest water vapor/nitrogen gas selectivity of 688 at 30 °C and 70% relative humidity (RH). These results are in good agreement with data pertaining to the hydrophilicity of the TFN membrane. The amounts of C-Fe3O4 nanoparticles deposited on the surfaces of the M5(0.3), M15(0.3) and M25(0.3) membranes were found to be 6.95, 6.27 and 5.44 µg/cm2, respectively. The impact of the pressure, RH% and temperature on the water vapor permeation were also studied and discussed.

Understanding the abnormal thermal behavior of nanofluids through infrared thermography and thermo-physical characterization

Nanofluids (NFs) are colloidal suspensions of nanoparticles (NPs) within a base fluid. Unlike conventional mixtures, NFs exhibit dramatically enhanced properties, such as an abnormal increase in heat capacity at low concentration of NPs (e.g., Cp values 30% higher than the base material value). Understanding the thermo-physical behavior of NFs is essential for their application as thermal energy storage systems. In this study, we analyze a sodium nitrate ionic system containing 1 wt%, 3 wt% and 7 wt% of SiO2 NPs with different techniques like infrared thermography, infrared spectroscopy and differential scanning calorimetry (DSC) in order to shed light on the mechanism behind the increase of Cp. The themographies reveal the presence of a colder layer on top of the NF with 1 wt% of NPs whereas this layer does not appear at higher concentrations of NPs. The IR spectrum of this foamy top layer evidences the high amount of SiO2 bonds suggesting the clustering of the NPs into this layer linked by the nitrate ions. The linking is enhanced by the presence of hydroxyls in the NPs’ surface (i.e., hydroxilated NPs) that once mixed in the NF suffer ionic exchange between OH− and NO3− species, leading to O2–Si–O–NO2 species at the interface where a thermal boundary resistance or Kapitza resistance appears (RT = 2.2 m2 K kW−1). Moreover, the presence of an exothermic reactive processes in the calorimetry of the mixture with 1 wt% of NPs evidences a reactive process (ionic exchange). These factors contribute to the heat capacity increase and thus, they explain the anomalous behavior of the heat capacity in nanofluids.

Importance of mass and enthalpy conservation in the modelling of titania nanoparticles flame synthesis

In most simulations of fine particles in reacting flows, including sooting flames, enthalpy exchanges between gas and particle phases and differential diffusion between the two phases can be neglected, since the particle mass fraction is generally very small. However, when the nanoparticles mass fraction is very large representing up to 50% of the mixture mass, the conservation of the total enthalpy and/or the total mass becomes critical. In the present paper, we investigate the impact of mass and enthalpy conservation in the modelling of titania nanoparticles synthesis in flames, classically characterised by a high conversation rate and consequently a high nanoparticles concentration. It is shown that when the nanoparticles concentration is high, neglecting the enthalpy of the particle phase may lead to almost 70% relative error on the temperature profile and to relative errors on the main titania species mass fractions and combustion products ranging from 20% to 100%. It is also established that neglecting the differential diffusion of the gas phase with respect to the particle phase is also significant, with almost 15% relative error on the TiO mole fraction, although the effect on combustion products is minor.