Dispersion Of Nanomaterials Research Articles

Toward high-performance lubricants: Rational design and construction of supramolecular oil gels by amphiphilic telechelic polymers to stabilize two-dimensional nanomaterials in base oils

Two-dimensional (2D) nanomaterials have long been promised as environment-friendly lubricant additives. However, their agglomeration in base oils have largely limited their practical applications. Here, we report the supramolecular oil gels constructed by amphiphilic telechelic polymers poly(2-hydroxyethyl methacrylate)-block-poly(stearyl methacrylate)-block-poly(2-hydroxyethyl methacrylate) in base oils. 2D nanomaterials GO, h-BN, and g-C3N4 can be homogeneously stabilized in the oil gels over one year, which are the most stable oil dispersions of the 2D nanomaterials reported to date. The oil gels demonstrate excellent lubricating performance, which could be attributed to the 60 − 90 nm thick tribofilms formed on the worn areas. These supramolecular oil gels not only represent an efficient and versatile platform for stabilizing 2D nanomaterials, but also a universal strategy to explore high-performance lubricants.

Fewer Dimensions for Higher Thermal Performance: A Review on 2D Nanofluids

The current work aims to offer a specific overview of the homogeneous dispersions of 2D nanomaterials in heat transfer base fluids—so-called 2D nanofluids. This data compilation emerged from the critical overview of the findings of the published scientific articles regarding 2D nanofluids. The applicability of such fluids as promising alternatives to the conventional heat transfer and thermal energy storage fluids is comprehensively investigated. These are fluids that simultaneously possess superior thermophysical properties and can be processed according to innovative environmentally friendly methods and techniques. Furthermore, their very reduced dimensions are suitable for the decrease in the size of thermal management systems, and the devices have attracted a lot of attention from researchers in different fields. Some examples of 2D nanofluids are those which incorporate graphene, graphene oxide, hexagonal boron nitride, molybdenum disulfide nanoparticles, and hybrid formulations. Although the published results are not always consistent, it was found that this type of nanofluid can improve the thermal conductivity of traditional base fluids by more than 150%, achieving values of approximately 6500 W·m−1·K−1 and interface thermal conductance above 50 MW·m−2·K−1. Such beneficial features permit the attainment of increments above 60% in the overall efficiency of photovoltaic/thermal solar systems, a 70% reduction in the entropy generation in parabolic trough collectors and increases of approximately 200% in the convective heat transfer coefficient in heat exchangers and heat pipes. These findings identify those fluids as suitable heat transfer and thermal storage media. The current work intends to partially suppress the literature gap by gathering detailed information on 2D nanofluids in a single study. The thermophysical properties of 2D nanofluids and not of their traditional counterparts, as it is usually encountered in the literature, and the extended detailed sections dedicated to the potential applications of 2D nanofluids are features that may set this research apart from previously published works. Additionally, a major part of the included literature references consider exclusively 2D nanomaterials and the corresponding nanofluids, which also constitutes a major gathering of specific data regarding these types of materials. Upon its conclusion, this work will provide a general overview of 2D nanofluids.

Study on the Dispersion and Lubrication Properties of LDH in Lubricating Oil

The dispersion of nanomaterials in lubricating oil plays an important role in the lubrication and wear-resistance properties. In this work, supramolecular layered double hydroxides (LDHs) were prepared and added to lubricating oil with different dispersants. The content of key elements in the samples was measured by an oil element analyzer, and the dispersion properties of different samples were studied. The friction coefficient of the samples was measured by high-frequency linear vibration (SRV), and the morphology and composition were characterized by SEM to study the antiwear performance and action mechanism of LDH. The oxidation induction time of the samples was measured by RBOT to study the antioxygenic properties of LDH in lubricating oil. The results show that LDH can be well-dispersed in lubricating oil with the action of specific dispersants. After adding LDH, the antiwear performance of lubricating oil was improved, as a uniform and dense protective film was formed on the friction surface.

Assembling a Photoactive 2D Puzzle: From Bulk Powder to Large-Area Films of Semiconducting Transition-Metal Dichalcogenide Nanosheets

ConspectusTwo-dimensional (2D) semiconducting materials are poised to revolutionize ultrathin, high-performance optoelectronic devices. In particular, transition-metal dichalcogenides (TMDs) are well-suited for applications requiring robust and stable materials such as electrocatalytic, photocatalytic, and photo-electrochemical devices. One of the most compelling assets of these materials is the ability to produce and process 2D TMDs in the nanosheet form using solution-based (SB) exfoliation methods. Compared to other methods, SB techniques are typically inexpensive, efficient, and more suitable for scale-up and industrial implementation. In acknowledgment of the importance of this area, much work has been done to develop various SB methods starting from the exfoliation of bulk crystalline TMD materials to the chemical modification of final devices consisting of thin films of semiconducting 2D TMD nanosheets. However, not all SB methods are equally compatible or interchangeable, and they result in very diverse material and device properties. Therefore, the aim of this Account is to provide an overview of the developed SB techniques that can serve as a guide for assembling high-performance thin films of 2D TMDs. We start by introducing the most popular methods for producing 2D TMDs using liquid-phase exfoliation (LPE), discussing their working mechanisms as well as their advantages and disadvantages. Notably we highlight a recently developed LPE technique using electro-intercalation that draws on the advantages of previously presented methods. Next, we discuss processing the as-produced 2D TMD nanosheets via SB separating techniques designed for size and morphology selection while also presenting the ongoing challenges in this area. We then examine SB methods for processing the selected 2D nanomaterial dispersions into semiconducting thin films. Various methods are compared and contrasted, and special attention is paid to a recently developed method that carefully deposits 2D TMD nanoflakes with preferential alignment and has been shown scalable to the meter-squared size range. Finally, we explore strategies for increasing the optoelectronic performance of the TMD films via device engineering and defect management. We scrutinize these post-treatments based on the final device application, which are explicitly discussed. In all of the discussed processes we present the most promising SB techniques giving critical analysis and insight from experience. While we provide our own “best practices”, we stress the use of adaptability and critical thinking when designing specifically tailored procedures. By providing examples of different uses and measured improvements in one comprehensive guide, we hope to simplify process-development and aid researchers in making their own unique photoactive 2D “puzzles”.

Couple stress ternary hybrid nanofluid flow in a contraction channel by means of drug delivery function

The rheological perception of blood circulation with the dispersion of metal or non-metal nanomaterials via a squeezing channel is gaining more attention because of implementations in the blood filtration system, nano-pharmacology, obstructed hemodynamics, nano-hemodynamics, care of hemodynamic diseases, and some other areas. Inspired by the innovative importance and study in such a domain a computational hemodynamically framework is developed to simulate the hemodynamic properties of blood steam under the composition of nanomaterials through a squeezing channel. CuO, TiO2, and Al2O3 nanoparticles are dissolved in the blood to generate a tri-hybrid nano-blood emulsion (CuO+TiO2+Al2O3/blood). The blood flow is commonly described using the couple stress, fluid model. The concept of nonlinear radiation is also utilized in the equation of heat for the viability of drug delivery. The effects of MHD and the heat source are also considered. According to the existing research, the interaction of TiO2 nanoparticles with any other metal nanoparticle can kill more cancer cells than TiO2 alone. The mathematical framework of a squeezing channel is formulated for motion and energy and then solved the model problem by using the HAM technique. The numerical outputs were presented in the form of graphs for a random interval of model factors included for thermal and velocity distributions additionally to this, Cf and Nu are also deliberated through charts. Furthermore, the percentage-wise enhancement in Nul and Nuu is also displayed. The thermal profile improves as the values of M,ϕ,Rd and λ>0 grow, but it declines as λ<0 increases. The conclusions of the current model could be pertinent to regulating blood circulation and drug delivery systems.

Towards harmonisation of testing of nanomaterials for EU regulatory requirements on chemical safety – A proposal for further actions

Over the recent years, EU chemicals legislation, guidance and test guidelines have been developed or adapted for nanomaterials to facilitate safe use of nanomaterials. This paper provides an overview of the information requirements across different EU regulatory areas. For each information requirement, a group of 22 experts identified potential needs for further action to accommodate guidance and test guidelines to nanomaterials. Eleven different needs for action were identified, capturing twenty-two information requirements that are specific to nanomaterials and relevant to multiple regulatory areas. These were further reduced to three overarching issues: 1) resolve issues around nanomaterial dispersion stability and dosing in toxicity testing, in particular for human health endpoints, 2) further develop tests or guidance on degradation and transformation of organic nanomaterials or nanomaterials with organic components, and 3) further develop tests and guidance to measure (a)cellular reactivity of nanomaterials. Efforts towards addressing these issues will result in better fit-for-purpose test methods for (EU) regulatory compliance. Moreover, it secures validity of hazard and risk assessments of nanomaterials. The results of the study accentuate the need for a structural process of identification of information needs and knowledge generation, preferably as part of risk governance and closely connected to technological innovation policy.

Effect of molding on the structure and properties of poly(butylene adipate-co-terephthalate)/poly(propylene carbonate)/organically modified montmorillonite nanocomposites

As an environmentally friendly biodegradable material, poly(butylene adipate-co-terephthalate) (PBAT) has been commercialized as a shopping bag, but its high gas permeability weaken its practicability in mulch, cling film and other fields. Two kinds of barrier materials, poly(propylene carbonate) (PPC) and organically modified montmorillonite (OMt), are used to prepare PBAT/PPC/OMt composites, and the mechanical properties are improved by chain extender (Joncryl® ADR 4468). The dispersion and arrangement of nanomaterials in blends are studied with different molding methods and their effects on the gas barrier and mechanical properties are studied as well. Dissipative particle dynamics are used to simulate the rate at which O2 molecules pass through the modified PBAT films. The results show that 1 wt% of chain extender can increase the tensile stress and tear strength by about 10% and 15%, respectively. The OMt is preferentially distributed in the PBAT matrix and has a more uniform degree of orientation in the blown film, which is beneficial to the improvement of gas barrier properties. Eventually, the mechanical properties and gas permeability of PBAT films can be regulated through the adjustment of processing methods and the synergistic effect of PPC and OMt, providing a new way for high-performance packaging or agricultural mulching film materials.

Physical Processes Occurring in Dispersed Media with Carbon Nanomaterials under the Influence of Ultrasonification

The up-to-date carbon nanoparticle application in materials science and composites is mostly represented by controlling of different methods of structure formation including incorporation of nanomaterials or nano-modifiers. The efficiency of such methods depends on disagglomeration and the distribution degree of the carbon nanoparticle within a dispersion medium, which are critical parameters to produce a composite with improved performance. At the same time, common approaches such as a surface activation or using surfactants do not guarantee a homogeneous dispersion of carbon nanoparticles. This research reports on a theoretical analysis of physical processes which take place during the ultrasonic treatment which is a widely used method for dispersion of nanomaterials. The experimental data demonstrate an efficiency of the proposed method and prove the theoretical assumptions. The theoretical analysis performed in this study can be applied to implement and scale-up the process using sonicators. It was established that ultrasonic treatment has a more intensive effect in an organic hydrocarbon medium. So, in industrial oil, the heating rate from ultrasonification is 20 °C/min, in residual selective purification extract, it is 33 °C/min. For aqueous systems, the heating rate from ultrasonification is significantly lower and amounts to 2 °C /min for suspensions with Sulfanol and 11 °C/min for suspensions with ViscoCrete 2100. It was established that in the studied dispersed systems (aqueous solutions with surfactants and organic medium), there is no directly proportional dependence of the amount of heating of suspensions on the duration of ultrasound dispersion (USD), which is caused by ultrasonic dispersion not under adiabatic conditions, as well as the dependence of absorption coefficient of ultrasonic energy for dispersed systems on parameters of system structure.

Chemical-physical criticality and toxicological potential of lipid nanomaterials contained in a COVID-19 mRNA vaccine

The medicinal preparation called Comirnaty by Pfizer-BioNTech is an aqueous dispersion of lipid nanomaterials, intended to constitute, after thawing and dilution, the finished product for intramuscular injection. In the present study, we examine some evident chemical-physical criticalities of the preparation, regarding the manifest instability of its qualitative-quantitative composition, as well as its consequent toxicological potential, in this case related to the possible formation of ROS (reactive oxygen species), after intramuscular inoculation, in different biological sites, such as, potentially, kidneys, liver, heart, brain, etc., causing dysfunctions and alterations thereof.&#x0D; Of particular concern is the presence in the formulation of the two functional excipients, ALC-0315 and ALC-0159, never used before in a medicinal product, nor registered in the European Pharmacopoeia, nor in the European C&amp;L inventory. The current Safety Data Sheets of the manufacturer are omissive and non-compliant, especially with regard to the provisions of current European regulations on the registration, evaluation, authorization and restriction of nanomaterials.&#x0D; The presence of electrolytes in the preparation and the subsequent dilution phase after thawing and before inoculation raise well-founded concerns about the precarious stability of the resulting suspension and the Polydispersity index of the nanomaterials contained in it, factors that can be hypothesized as the root causes of numerous post-vaccination adverse effects recorded at statistical-epidemiological level. Further immediate studies and verifications are recommended, taking into consideration, if necessary and for purely precautionary purposes, the immediate suspension of vaccinations with the Pfizer-BioNTech Comirnaty preparation.

Dispersion and Tunable Alignment of Colloidal Silver Nanowires in a Nematic Liquid Crystal for Applications in Electric–Optic Devices

The dispersion and tunable alignment of colloidal nanomaterials is desirable for practical applications in electric-optic (E-O) devices; however, it remains challenging for large one-dimensional nanomaterials with a large aspect ratio. Here, we demonstrate a large-scale, simple, multi-microdomain, and noncontact photoalignment technology to align colloidal silver nanowires (AgNWs, length ∼4.5 μm, diameter ∼70.6 nm) in a liquid crystal (LC) with a high two-dimensional order parameter (about 0.9). The AgNWs are precisely self-assembled via photomasks with twisted nematic and planar alignment models in microdomain regions. The AgNW orientation is tuned with an electric field, through the rotation of an LC director n, which allows three-dimensional (3D) tunable orientation combined with photoalignment. The colloidal dispersions of AgNWs in the LC cell influenced the ion transfer, elastic constant, dielectric anisotropy, and near LC alignment, changing the E-O properties of the LC devices. The 3D tunable orientation of an AgNW by photoalignment and an electric field could provide a new way to assemble large colloidal nanomaterials and fabricate functional E-O devices.

Strain-Sensing Composite Nanofiber Filament and Regulation Mechanism of Shoulder Peaks Based on Carbon Nanomaterial Dispersion.

Conductive polymer composite-based strain sensors are essential components of flexible wearable devices. However, nonmonotonic responses with shoulder peaks limit their practical application. Herein, we innovatively optimized the shoulder-peak phenomenon in a strain-sensing composite nanofiber filament by regulating carbon nanomaterial dispersion. Further, the preparation methods, characteristics, and performances of the filament strain sensors were systematically introduced. On this basis, transmission electron microscopy, finite element analysis, and mathematic and structural evolution models were used to explore the origin of shoulder peaks and explain the sensing mechanism of conductive networks. Results confirmed that the beacon tower-shaped conductive network designed by constructing nanofiller agglomerates could cause strain concentration and resist the Poisson transverse contraction of nanofibers, considerably improving the monotonicity and sensitivity of the sensor. The strain-sensing performance was optimal when the nanofillers were dispersed using 2.5 wt % of an anionic dispersant. The sensor exhibited a maximum detective strain of 120%, an ultralow detection limit of 0.01%, and high sensitivity and linearity of 9.66 and 0.996 within 20% strain, respectively. Moreover, it showed the advantages of a fast response time (120 ms), excellent durability (3000 cycles), anti-interference, washability, and antibacterial capability. Finally, a smart Kinesio tape was developed for protecting/treating the human body and detecting joint/muscle movement via simple sewing.

The positive correlation between the dispersion and catalytic performance of Fe2O3 nanoparticles in nano-Fe2O3-ultrafine AP energetic composites supported by solid UV-vis spectroscopy.

Recently, the widespread use of nanocatalytic materials has contributed to an enormous improvement in the performance of energetic materials, especially, highly dispersed nanomaterials. However, the lack of quantitative methods for analyzing the dispersion of nanomaterials limits their further widespread use. Although various techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), etc. are used to analyze the relative dispersion of nanomaterials, it is not possible to quantitatively analyze their dispersion. Therefore, there has been an effort to develop new methods for the quantitative analysis of nanocatalytic materials. Fortunately, we were able to analyze the dispersion of nanocatalytic materials using the difference in their UV absorbance. More importantly, we established the corresponding difference equation to quantify the dispersion of nanocatalytic materials, which is capable of quantifying the dispersion of nano-Fe2O3 in nano-Fe2O3-ultrafine AP composites. The accuracy of the difference equation was verified using a variety of techniques and the desired results were obtained. Based on the above conclusions, the quantitative analysis method for the dispersion of nanomaterials that we established is expected to be widely used and promote the development of energetic materials.

Influence of innovative technologies on the physical and mechanical properties of building materials in the construction industry

A multifunctional additive based on a gel-like dispersion of taunitic carbon nanomaterial (CNM) is considered. The influence of its quantitative composition on the physical and mechanical properties of fine-grained concrete is studied. The results of a study of the frost resistance of fine-grained concrete enriched with a gel-like dispersion of CNM "Taunit" are presented.The main hypotheses describing the formation of the porous structure of concrete under the action of alternate freezing and thawing are considered, and the influence features of the structure of nanomodified concrete on its frost resistance and density. Nano-modified fine-grained concrete was tested by scanning microscopy, which shows that the process of forming changes in its structure occurs not only as a result of reinforcement, but also as a result of growth crystalline hydrates, the centers of which are particles of CNM "Taunit".

Investigation of multi-walled carbon nanotubes aqueous dispersions via electrical impedance spectroscopy

The present article aims to set up the bases to implement a nanocomposite mortar applied in the Monuments of Cultural Heritage. The aqueous dispersion of carbon-based nanomaterials that will be inserted in the restoration binder was investigated in laboratory scale. Four different concentrations (ranging from 0.05 to 0.20 wt%) of commercially available multi-walled carbon nanotubes (ΜWCNTs) were investigated to produce their aqueous dispersions. The aqueous solutions were dispersed with the help of an ultrasonic probe and at the same time, their electrical properties were measured through Electrical Impedance Spectroscopy (EIS). It was shown that the concentration of MWCNTs approximate to 0.15 wt% of the binder exhibited the lowest impedance values and it is recommended to be ultrasonicated at approximately 40 to 60 kJ as more than 30 % decrease in the impedance values were recorded.

Ultrasonic interfacial crosslinking of TiO2-based nanocomposite hydrogels through thiol-norbornene reactions for sonodynamic antibacterial treatment.

Nanocomposite (NC) hydrogels used for sonodynamic therapy (SDT) face challenges such as lacking interfacial interactions between the polymers and nanomaterials as well as presenting uneven dispersion of nanomaterials in the hydrogel network, reducing their mechanical properties and treatment efficiency. Here, we demonstrate a promising approach of co-engineering nanomaterials and interfacial crosslinking to expand the materials construction and biomedical applications of NC hydrogels in SDT. In this work, mesoporous silica-coated titanium dioxide nanoparticles with thiolated surface functionalization (TiO2@MS-SH) are utilized as crosslinkers to react with norbornene-functionalized dextran (Nor-Dex) through ultrasound-triggered thiol-norbornene reactions, forming TiO2@MS-SH/Nor-Dex NC hydrogels. The TiO2@MS-SH nanoparticles act not only as multivalent crosslinkers to improve the mechanical properties of hydrogels under ultrasound irradiation but also as reactive oxygen species (ROS) generators to allow the use of TiO2@MS-SH/Nor-Dex NC hydrogels in SDT applications. Particularly, the TiO2@MS-SH/Nor-Dex NC hydrogels present tailorable microstructures, properties, and sonodynamic killing of bacteria through the modulation of the ultrasound frequency. Taken together, a versatile TiO2-based NC hydrogel platform prepared under ultrasonic interfacial crosslinking reactions is developed for advancing the applications in SDT.

Sonicação de superplastificante à base de policarboxilato para aplicação em matrizes cimentícias

Abstract Sonication is widely used for nanomaterials dispersion in cementitious matrices. Polycarboxylate-based superplasticizer (SP) admixtures are usually incorporated in the aqueous nanomaterials suspension before sonication to improve the dispersion of these materials. Nevertheless, the effect of sonicating SP on its molecular structure or dispersing performance has not been fully investigated. This work assessed the effect of sonicating a commercial SP at 20 kHz, 750 W power, 50 or 80% amplitude, during 15 and 30 min. Initially, the sonication effect was evaluated in aqueous suspension by determining the SP size distribution (through dynamic light scattering – DLS) and zeta potential. Subsequently, the aqueous SP suspensions were used for Portland cement paste production. Rheological tests up to 120 minutes and compressive strength at 14 and 28 days were conducted. DLS and zeta potential results suggested that sonication reduce the size of SP chains. As a result, SP sonication increased the initial dynamic yield stress, viscosity, and hysteresis area of cement pastes. In contrast, SP sonication improved its time-dependent dispersing performance, resulting in pastes with reduced viscosity from 80 minutes onwards. Finally, SP sonication did not affect the compressive strength of cement pastes at 14 and 28 days of hydration. Overall, when SP is sonicated together with nanoparticles for application in cementitious matrices, the effect of sonicating the chemical admixture must be considered when the fresh-state properties of the composite are evaluated.

Multifunctional hexagonal boron nitride dispersions based in xanthan gum for use in drilling fluids

The development of efficient drilling fluids through nanotechnology has the goal to improve the extraction processes in the oil industry. This work aims to study the thermal and the rheological behavior of oxidized hexagonal boron nitride (h-BN-Oxi) bidimensional (2D) nanostructures dispersed directly in xanthan gum. Morphological and structural characterization of the h-BN-Oxi nanostructures have shown the successful oxidation of the h-BN, which have enhanced the exfoliation and dispersion of the 2D nanomaterials with high surface area in the polymer matrix. Therefore, different concentrations, ranging from 0 to 60 mg mL−1 of h-BN-Oxi were obtained by the liquid exfoliation method. The thermal conductivity of the h-BN-Oxi suspensions was evaluated and have shown an increase for all concentrations. The rheological properties were investigated, and the results revealed that the increase of h-BN-Oxi concentration led to the increase of viscosity with the concentration of h-BN-Oxi nanomaterials. Moreover, it was observed a transition from pseudoplastic behavior for concentration up to 15 mg mL−1, to a yield stress nanofluid above, well described by the Herschel-Bulkley model. This behavior was ascribed to the complex network obtained by the h-BN-Oxi nanostructures with the xanthan gum. Thus, exploitation of h-BN-Oxi dispersions based in xanthan gum as an additive for drilling fluid can have advantageous due to its multifunctional properties like enhanced thermal conductivity and enhanced viscosity for use in deeper offshore.

Sustainable Upcycling of Spent Electric Vehicle Anodes into Solution-Processable Graphene Nanomaterials.

A major transition to electric vehicles (EVs) is underway globally, as countries target reductions in greenhouse gas emissions from the transport sector. As this rapid growth continues, significant challenges remain around how to sustainably manage the accompanying large volumes of waste from end-of-life lithium-ion batteries that contain valuable rare earth and critical materials. Here, we show that high-shear exfoliation in aqueous surfactants can upcycle spent graphite anodes recovered from an EV into few-layer graphene dispersions. For the same hydrodynamic conditions, we report a process yield that is 37.5% higher when using spent graphite anodes as the precursor material over high-purity graphite flakes. When the surfactant concentration is increased, the average atomic layer number reduces in a similar way to that of high-purity precursors. We find that the electrical conductance of few-layer graphene produced using the graphite flake precursor is superior and identify the limitations when using aqueous surfactant solutions as the exfoliation medium for spent graphite anode material. Using these nontoxic solution-processable nanomaterial dispersions, functional paper-based electronic circuit boards were fabricated, illustrating the potential for end-to-end, environmentally sustainable upcycling of spent EV anodes into new technologies.

Easy regulation of chitosan-based hydrogel microstructure with citric acid as an efficient buffer

Being an important soft material, the chitosan-based hydrogel exhibits colorful features and widespread applications stemmed mainly from its intrinsic microstructure. In particular, the design of hydrogels with oriented channel structures is of significance importance. In this paper, polyvinyl alcohol (PVA)/chitosan (CS)/MXene-CA hydrogels with directional channel structure were obtained by simple freezing and thawing method with citric acid (CA) as a buffer. The introduction of CS increased the tensile strength of PVA hydrogel from 5.38 kPa to 29.22 kPa. The uniform distribution of MXene was efficiently enhanced within the constructed channel microstructure, and conductivity was increased to 1.91 S/m. The response time of the flexible sensor based on the hydrogel was 200 ms. It can sensitively detect large-scale deformation (blending of joints), small-scale activity (frowning), and electrocardiogram. Therefore, the paper provided an efficient way to regulate the microstructure in hydrogel network and enhance the uniform dispersion of functional nanomaterials.

Thermal performance of nanofluids based on tungsten disulphide nanosheets as heat transfer fluids in parabolic trough solar collectors

Nanofluids are considered as a new generation of heat transfer fluids since they exhibit thermophysical properties improvements compared with conventional heat transfer fluids. The high thermal conductivity of nanofluids and even the isobaric specific heat enhancements over conventional liquids make these colloidal suspensions very attractive in many research areas, including solar energy. In this work, nanofluids based on tungsten disulphide (WS 2 ) nanosheets have been prepared from the thermal oil currently used as heat transfer fluid in Concentrating Solar Power (CSP) plants. The high aspect ratio of WS 2 bidimensional nanostructures provides high long-term colloidal stability to the nanofluids and facilitates heat transport. Cetyltrimethylammonium bromide and polyethylene glycol have been used as surfactants to improve the exfoliation process and enhance the colloidal stability of the nanomaterial dispersions. Some properties such as density and viscosity of the base fluid have not been significantly altered by the presence of WS 2 nanosheets in the base fluid. However, studies on the thermal properties of nanofluids have shown promising results with increases in thermal conductivity of up to 33% and heat transfer coefficient by 21% over the base fluid. Furthermore, it has been estimated that the overall efficiency of the CSP system could be improved by 31% by replacing the conventional thermal fluid with 2D-WS 2 -based nanofluids. • The efficiency of PTC solar collectors is increased by 31% by using WS 2 nanofluids. • Nanofluids improved the heat transfer coefficient of the base fluid by 21%. • Thermal conductivity was enhanced by 33% in WS 2 -based nanofluids. • WS 2 nanofluids favours the elimination of selective coatings on the absorber tube.