WSe2 nanosheets synthesized by a solvothermal process as advanced nanofluids for thermal solar energy

Nanofluids are colloidal systems based on the suspension of nanoparticles in a fluid. Their thermal properties mean that they are promising heat transfer fluids with possible applications in different fields, concentrating solar energy being one of particular interest. Thus, this study presents the preparation of nanofluids based on WSe2 nanoparticles suspended in the eutectic mixture of biphenyl and diphenyl oxide, which is a heat transfer fluid widely used in concentrating solar power plants. To this end, solvothermal synthesis was used to prepare WSe2 nanosheets, which were characterized by means of scanning transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy. The physical and chemical stability of the nanofluids was analyzed, observing that they became more stable when Triton X-100 was used as the surfactant. The presence of WSe2 nanosheets did not result in a significant increase in density or viscosity, but, by contrast, improvements were obtained in their isobaric specific heat and thermal conductivity, up to 4.7 and 64%, respectively. Spectral optical properties were investigated as well, showing a significant effect of the WSe2 nanosheet addition to the extinction coefficient of the base fluid in the wavelength range of the solar spectrum, promising for direct absorption solar collectors. Finally, the efficiency of the nanofluids was analyzed in a solar collector considering the Ur parameter, obtaining a remarkable increase in the efficiency of up to 34% with respect to the pure heat transfer fluid. This proves the possibility to obtain a sustainable production of energy from the sun using these WSe2-based nanofluids

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 nano -fluids 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 (WS2) 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 WS2 bidimensional nanostructures provides high long-term colloidal stability to the nanofluids and facilitates heat transport. Cetyl-trimethylammonium 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 WS2 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-WS2-based nanofluids

Colloidal suspensions of totally inorganic perovskites nanoparticles: A new photoluminescent emission in the near-IR

Luminescent materials have attracted great attention due to the amazing applications. In this sense, perovskite halide materials have shown promising luminescent properties which allows them to be useful in various applications such as LEDs, sensors. In this work, colloidal suspensions of CsPbI3 and Pd-doped CsPbI3 perovskite nanoparticles were prepared at different temperatures, and their structure and luminescence properties were characterized to analyse the effect of the synthesis temperature and the Pd-doping. With the increase of temperature, the main photoluminescence band of perovskite nanoparticles are slightly red-shifted. But the most amazing result is that the Pd-doped CsPbI3 shows a new emission band at 877 nm under excitation at 785 nm. Therefore, this compound may be used as a highly sensitive luminescent sensor in several applications, such as in biosystems due to their emission in the first biological window under NIR excitatio

Surface States of (100) O-Terminated Diamond: Towards Other 1 × 1:O Reconstruction Models

Diamond surface properties show a strong dependence on its chemical termination. Hydrogen-terminated and oxygen-terminated diamonds are the most studied terminations with many applications in the electronic and bioelectronic device field. One of the main techniques for the characterization of diamond surface terminations is X-ray photoelectron spectroscopy (XPS). In this sense, the use of angle-resolved XPS (ARXPS) experiments allows obtaining depth-dependent information used here to evidence (100)-O-terminated diamond surface atomic configuration when fabricated by acid treatment. The results were used to compare the chemistry changes occurring during the oxidation process using a sublayer XPS intensity model. The formation of non-diamond carbon phases at the subsurface and higher oxygen contents were shown to result from the oxygenation treatment. A new (100) 1 x 1:O surface reconstruction model is proposed to explain the XPS quantification results of O-terminated diamond

MoS2-based nanofluids as heat transfer fluid in parabolic trough collector technology

Concentrating solar power is becoming one of options for producing energy to replace conventional polluting energy sources. However, improving the efficiency and reducing the cost of technologies based on this type of energy to make it more competitive is still a work in progress. This study proposes replacing the thermal oil used as the heat transfer fluid in the absorber tubes of parabolic trough solar collectors (PTCs) with nanofluids based on spherical molybdenum disulphide nanoparticles with the aim of improving the thermal efficiency of concentrating solar power plants. The colloidal stability of the nanofluids was verified by UltravioleteVisible spectroscopy, Zeta potential and Dynamic Light Scattering monitoring. The presence of spherical MoS2 nanoparticles resulted in an increase of up to 13% in specific isobaric heat and 6% in thermal conductivity compared to thermal oil. Finally, the efficiency of parabolic trough solar collectors was estimated to increase by 5%, which also favours the decrease of pumping power and the elimination of selective coatings on the absorber tube. To our knowledge, this is the first time that MoS2-based nanofluids are tested as heat transfer fluids in PTCs analysing its implementation in the solar energy application. © 2022 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).We acknowledge Ministerio de Ciencia, Innovaci?n y Universidades del Gobierno de Espa?a for funding under Grant No. RTI2018-096393-B-I00 and for financial support related to measurements of thermal properties, which were performed using devices acquired under Grant No. UNCA15-CE-2945. Also, this research was funded by 2014?2020 ERDF Operational Programme and by the Department of Economy, Knowledge, Business and University of the Regional Government of Andalusia, grant number FEDER-UCA18-107510

Synthesis and characterization of metal oxide-based microcapsules including phase change materials for energy storage applications

In this study, microcapsules based on Cu2O containing different phase change materials (PCM) were prepared and characterized. The elemental, structural and electronic properties of the Cu2O-based microcapsules were characterized using several techniques such as X-ray diffraction, X-ray photoelectron spectroscopy, scanning and transmission electron microscopy and Fourier-transform infrared spectroscopy. In addition, the thermal properties of the microcapsules prepared were characterized in order to analyse their possible application as a thermal energy storage medium. Heating/cooling cycles using a differential scanning calorimetry technique were performed, and the phase change temperature and enthalpy were estimated. We observed good stability after the cycles. Furthermore, the encapsulation efficiency was estimated from melting and crystallization enthalpy values, reaching a value of 14.8% for the paraffin wax-based microcapsules. Finally, isobaric specific heat was measured to evaluate the storage capability of the encapsulated PCMs with regard to pure Cu2O to evaluate their possible application as a thermal storage system. An increase of around 140% was found in the isobaric specific heat for the microcapsules based on paraffin wax with regard to pure Cu2O. © 2023, The Author(s)

Stability and Thermal Properties Study of Metal Chalcogenide-Based Nanofluids for Concentrating Solar Power

Nanofluids are colloidal suspensions of nanomaterials in a fluid which exhibit enhanced thermophysical properties compared to conventional fluids. The addition of nanomaterials to a fluid can increase the thermal conductivity, isobaric-specific heat, diffusivity, and the convective heat transfer coefficient of the original fluid. For this reason, nanofluids have been studied over the last decades in many fields such as biomedicine, industrial cooling, nuclear reactors, and also in solar thermal applications. In this paper, we report the preparation and characterization of nanofluids based on one-dimensional MoS2 and WS2 nanosheets to improve the thermal properties of the heat transfer fluid currently used in concentrating solar plants (CSP). A comparative study of both types of nanofluids was performed for explaining the influence of nanostructure morphologies on nanofluid stability and thermal properties. The nanofluids prepared in this work present a high stability over time and thermal conductivity enhancements of up to 46% for MoS2-based nanofluid and up to 35% for WS2-based nanofluid. These results led to an increase in the efficiency of the solar collectors of 21.3% and 16.8% when the nanofluids based on MoS2 nanowires or WS2 nanosheets were used instead of the typical thermal oil

Emission properties of Pd-doped CsPbBr3 perovskite nanocrystal: Infrared emission due to the Pd-doping

Perovskite-type materials have attracted great attention in recent times due to their interesting characteristics, such as their luminescent properties. The good photoluminescence quantum yields as well as the possibility of tuning the emission wavelength has allowed the study of these materials in several applications, such as sensors or LEDs. As sensors, making nanocrystals of these perovskites emitting in the near infrared (NIR) would open the possibility of using these materials in biomedical applications. In the present work, Pd-doped CsPbBr3 perovskite nanocrystals (NCs) were synthesized and characterized. We show here Pd-doped NCs synthesized emit in NIR, at about 875 nm, using a laser emitting at 785 nm as the excitation source. This result is really new and promising, because it opens the possibility of using these nanocrystals in many applications as sensor in the field of nanobiomedicine in the futur

Nanofluidos basados en nanomateriales 2D.

Resumen del proyecto de líneas prioritarias "Nanofluidos basados en nanomateriales 2D" del IMEYMAT

The Role of the Interactions at the Tungsten Disulphide Surface in the Stability and Enhanced Thermal Properties of Nanofluids with Application in Solar Thermal Energy

Transition metal dichalcogenides (TMCs) exhibit unique properties that make them of interest for catalysis, sensing or energy storage applications. However, few studies have been performed into nanofluids based on TMCs for heat transfer applications. In this study, nanofluids based on 2D-WS2 are prepared by liquid phase exfoliation to analyze their potential usage in concentrating solar power plants. Periodic-Density Functional Theory (DFT) calculations were performed to rationalize the success of the exfoliation process. The hydrogen bond interaction between the hydroxyl group from PEG, which acts as a surfactant, and the S atoms of the WS2 surface stabilizes the nanosheets in the fluid. Electron localization function (ELF) analysis is indicative of the stability of the S-H interaction from WS2 with the molecules of surfactant due to the tendency to interact through weak intermolecular forces of van der Waals solids. Moreover, improvements in thermal properties were also found. Isobaric specific heat increased by up to 10% and thermal conductivity improved by up to 37.3%. The high stability of the nanofluids and the thermal improvements were associated with the high surface area of WS2 nanosheets. These results suggest that these nanofluids could be a promising heat transfer fluid in concentrating solar power plants