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[Display omitted] • Metal-organic framework (MOF) dispersion based fluids showed high potential for solar-thermal energy conversion (STEC). • Three different MOF dispersions (CuBTC, FeBTC, ZIF8 in ethylene glycol) were systematically explored for STEC application. • FeBTC showed the highest STEC efficiency with long-term dispersion stability, making it most promising for practical use. • This report marks a significant milestone in introducing the potential of MOF dispersion-based fluids for STEC application. • This research will pave the way for future explorations on various MOF dispersions in this field. This paper discusses the potential use of metal–organic framework (MOF) dispersion based fluids for solar-to-thermal energy conversion (STEC). For this, the optical and thermal characteristics of MOF dispersion were investigated, with MOFs dispersed in ethylene glycol (EG). This study is focused on three different MOF dispersions, namely ZIF8/EG, CuBTC/EG, and FeBTC/EG, each with varying concentrations of MOF particles. The results showed that FeBTC/EG at a concentration of 0.3 wt% is the optimal fluid for STEC, exhibiting the highest absorption and STEC efficiency compared to the other two fluids. The study also highlights the trade-off between STEC efficiency and cost, as increasing the concentration of MOF particles decreases the specific absorption rate (SAR). Additionally, the paper evaluates the dispersion stability of FeBTC/EG over time, which is critical for practical STEC applications. The novelty of the paper lies in the use of MOF dispersion based fluids for STEC application, which has not been extensively studied before. This study provides valuable insights into the potential use of MOF/EG for STEC and highlights the importance of optimizing the concentration of MOF particles for efficient and cost-effective performance. This study also introduces the novel application of MOF dispersion based fluids for enhanced STEC performance, showcasing FeBTC/EG as a standout for its high efficiency and stability. It marks a significant stride in utilizing MOF materials for sustainable energy, emphasizing practical considerations of dispersion stability and cost-effectiveness in STEC systems. [ABSTRACT FROM AUTHOR]

Alkali‐activated functionalized carbon nanotubes (AFCNTs) and 2D nanostructured MoS2 are investigated as a novel hybrid material for energy‐storage applications. The nanoflower‐like 2D MoS2 is grown on the surface of AFCNT using the controlled one‐step hydrothermal technique. The activation of functionalized carbon nanotubes results in greater performance due to the improved surface area. The Brunauer–Emmett–Teller (BET) surface area of the AFCNTs is found to be 594.7 m2 g−1 which is almost 30 times of the as‐prepared carbon nanotubes (CNTs). The improved surface area with attached hydroxyl and carboxylic functional groups helps in the attachment of MoS2 nanoflowers onto the AFCNT, thus reducing the interfacial resistance and providing an easy path for electron transfer. The electrochemical analysis shows a high specific capacitance of 516 F g−1 at 0.5 A g−1 with a corresponding energy density of 71.76 Wh kg−1, which is an encouraging reported value from AFCNT and MoS2 hybrid material. To the best of our knowledge, herein, the first report on AFCNTs and 2D MoS2 nanostructured hybrid electrode material for supercapacitor applications is provided, and promising results in terms of specific capacitance, energy density, and power density by boosting the properties of individual material are explained. [ABSTRACT FROM AUTHOR]

Nanofluid has emerged as a promising heat transfer fluid (HTF) due to their significant thermophysical, and optical characteristics enhancement over base fluids. Hybrid nanofluids with multiple nanomaterials have the advantage of synergistic properties in comparison to monocomponent nanofluids. The present study proposes an energy-efficient and cleaner synthesis method for developing carbon quantum dot (C-dot), MXene, and a hybrid MXene/C-dot hybrid nanofluids, for heat transfer application. In-situ microwave pyrolysis technique and two-step method were adopted for nanomaterial and nanofluid synthesis. The morphological, phase structural, chemical, and elemental compositional analysis of the nanomaterials was performed. The material characterization confirms the hybridization of C-dot on MXene nanosheets. The thermal conductivity and volumetric heat capacity of the nanofluids were measured using the transient plane source (TPS) method. Thermal conductivity was observed to increase with nanofluid concentration and temperature. Results indicate that MXene has the highest thermal conductivity enhancement (50 %) over water, followed by hybrid (42.2 %) and C-dot nanofluid (33.2 %). The volumetric heat capacity of nanofluids decreased with concentration and temperature. A semi-empirical correlation, as a function of nanofluid concentration and temperature, was coined for predicting thermal conductivity and volumetric heat capacity. Optical property characterization study shows that C-dot nanofluid exhibited considerable absorption along the UV range, while MXene nanofluid showed absorption in the visible and near-infrared (NIR) region. Hybrid nanofluids demonstrated complementary absorption properties of C-dot and MXene nanofluids. [Display omitted] • Novel MXene/C-dot hybrid nanofluid was synthesized for heat transfer applications. • Study reveals the material and thermal-optical properties of C-dot, MXene and hybrid nanofluids. • Semi-empirical correlation were coined to predict thermal properties of nanofluids. • Highest thermal conductivity enhancement was exhibited by 0.2 wt% MXene nanofluid. • Hybrid nanofluid showed complementary absorption property of component nanofluids. [ABSTRACT FROM AUTHOR]

A statistical study of the thermospheric gravity waves has been carried out using multiwavelength daytime oxygen airglow emission intensity and equatorial electrojet (EEJ) strength data, which originate from four different altitude regions of the thermosphere. The thermospheric daytime oxygen airglow emission intensities at wavelengths 557.7, 630.0, and 777.4 nm, obtained during the January to March period in the three years 2011–2013, have been used. The percentage number of days in which waves with spectral periods in the gravity wave range have occurred are found to be greater for the relatively higher solar activity duration (in 2013) compared to that of low solar activity (in 2011). This observation is explained to be due to the altering background atmospheric density and temperature (that vary with solar activity), which, in turn, influences the propagation and dissipation of waves. Moreover, the higher frequency gravity waves (of periods Brunt–Väisälä to 30 min) have been found to be present in greater numbers in the thermosphere compared to that of low-and-moderate frequency gravity waves (of periods 30–60 min). This behavior in the frequency selection by ambient conditions at thermospheric altitude is in accordance with earlier theoretical and simulation works. The ratios of high- to low-frequency occurrences have also been found to be greater in higher solar activity period of 2013 compared to that of the relatively low solar activity period of 2011. These results thus provide experimental evidence to the earlier simulation works suggesting similar behavior, as found here, for thermospheric gravity waves. [ABSTRACT FROM AUTHOR]

We describe a multichannel camera operating in the visible to near-infrared wavelengths (450 to 900 nm) with an etendue of 0.08 cm2 sr that can be used to image extended sources across multiple optical bands, capable of 3σ detection of 20 Rayleigh signal in 120 s. It has an angular resolution of 0.1 deg and a 35 deg × 25 deg field of view, employing a charge-coupled device detector in a compact 1U CubeSat compatible form factor (10 × 10 × 8 cm3). The design uses commercial off-the-shelf components while offering versatility using a mosaic of bandpass filters to select different spectral channels to address a wide range of remote sensing needs. The specific implementation described here covers the application of the instrument to explore the neutral sodium and potassium atom density distribution in the atmospheres of the Earth or the Moon. [ABSTRACT FROM AUTHOR]

A high-spectral resolution multiwavelength imaging slit spectrograph using echelle grating (MISE) that is capable of measuring daytime optical emissions at multiple wavelengths simultaneously over a large (140°) field-of-view is presented. Optical emissions during daytime (either dayglow or daytime aurora) are buried in the strong daytime solar scattered background continuum and therefore very high spectral resolution measurements are required to obtain their contributions. MISE measures the emission intensities of OI 557.7nm, OI 630.0nm, and OI 777.4nm that originate in the upper atmosphere. The dispersion achieved by the spectrograph at these three spectral regions, respectively, is 0.004, 0.0049, and 0.0059nmpixel−1. By using an echelle grating as the dispersing element, multiple spectral regions of aeronomic interest are made to fall in the same diffraction angle range so that rotation of grating is avoided. This instrument is immune to ambient temperature fluctuations and vibrations and is suitable for long and continuous field operations. The spectral and intensity calibration of this instrument along with the data analysis methodology are discussed. Sample data of emission intensities from all the three wavelengths mentioned above for a couple of days obtained from Hyderabad (17°N, 80°E; 8.7°N Mag. Lat.) are presented which show a good similarity when compared with those of empirical and photochemical model results. The OI 557.7nm daytime emissions are measured sparsely from ground-based techniques and ground-based OI 777.4nm daytime emissions from ground are presented for the first time, to the best of our knowledge. The variability is highlighted and the potential of such measurements to derive information on vertical coupling of atmospheric regions and wave dynamics during daytime are discussed. [ABSTRACT FROM AUTHOR]

Abstract: Wurtzite GaN nanowires and nanoribbons were produced directly from Ga metal by an Au catalyst assisted thermal evaporation process in a flowing ammonia atmosphere. We have investigated the effect of different experimental parameters on the morphology of the nanoforms. The diameters of the nanowires were varied between 20 and 40nm while the widths of the nanoribbons were within 100–250nm. Microstructural studies by TEM reveals the role of vapor–liquid–solid process in the nucleation of GaN nanoforms. The evolution of the ribbon like morphology was attributed to the vapor–solid process. Photoluminescence study showed UV–blue emission from the GaN nanostructures. Field emission studies indicated the possibility of these materials to be used as the cathode materials in field emission based devices. [Copyright &y& Elsevier]

Daytime oxygen airglow emission rate variability provides us with a means of remote investigations of the upper atmospheric behavior. Dayglow emission rates typically show a diurnal pattern with a peak at around noon, especially during geomagnetic quiet conditions. The photochemical and empirical models show that the emission rates typically vary as a function of solar zenith angle (SZA) and solar flux. Thus, both, larger solar flux magnitudes and smaller solar zenith angles, contribute to larger dayglow emission rates as the yield of excited oxygen atoms is expected to be greater in those conditions. However, variability in the annual dayglow emission rates obtained from measurements at low-latitudes (Hyderabad, India; 170 N, 800 E; 8.70 N Mag. Lat.) and mid-latitudes (Boston, USA; 42.20 N, 710 W; 48.30 N Mag. Lat.) show different behavior with regard to solar flux variation. The variability in the low-latitude emission rate is primarily dependent on that of the solar flux. However, such primary dependence on the solar flux is not reflected on the emission rate variability seen over mid-latitudes. This discrepancy is understood to be due to the relative effects of solar flux and the globally changing compositional variability, characterized by the oxygen to molecular density ratios (O/N 2), that show varying behavior from mid- to low-latitudes. Seasonal compositional variation due to transport processes is attributed to be the cause for the observed discrepancy which is also confirmed by independent satellite measurements. We also present an empirical model of O/N 2 as a function of day of the year and latitude obtained using satellite based ultraviolet measurements to quantify the compositional variation. • Annual OI 630.0 nm dayglow emission rate variations over low- and mid-latitudes are presented. • The dayglow emission variability at low- and equatorial-latitudes primarily depends on solar zenith angle and solar flux. • Mid-latitude dayglow emission variability depends strongly on the variability of oxygen to molecular nitrogen ratio. • O/N 2 values are empirically simulated as a function of day of the year and latitude to assess the compositional variations. [ABSTRACT FROM AUTHOR]

This study provides a systematic and comprehensive investigation of the transformation process of copper-based metal-organic frameworks (Cu-BTC MOFs) into nanoporous copper oxides (P-CuO x ) through controlled calcination. While calcination is a well-established method for producing MOF-derived oxides, previous studies have primarily focused on their applications. Most of them often lack detailed exploration of the transformation process and decomposition mechanisms though it is crucial for achieving tunability in MOF-derived structures. Our study addresses this gap by offering valuable insights that can guide the production of various MOF-derived oxides with tunable structural and functional properties. In this report, we have meticulously analysed the combined effects of calcination parameters, including temperature (250-500 °C), heating rate (0.5-10 °C min -1 ), and duration (1 and 2 hours) on the phase transformation, morphological features, and optical properties of Cu-BTC during its transformation to P-CuO x . Results revealed that fine adjustments to these calcination parameters allow precise control over phase purity, surface area, and porosity, achieving a high surface area of 113 m 2 g -1 for derived P-CuO. Furthermore, the P-CuO x materials exhibited strong visible-light absorption, highlighting their potential for solar energy harvesting applications. This approach opens opportunities for designing advanced materials with customized performance characteristics. The findings have broad applicability and enable the research community to fully exploit MOF-derived oxides for designing advanced materials with customized properties for diverse applications, including energy, sensing, and biomedical.

Due to their facile tunability, metal-organic frameworks (MOFs) are employed as precursors and templates to construct advanced functional materials with unique and desired chemical, physical, mechanical, and morphological properties. By tuning MOF precursor composition and manipulating conversion processes, various MOF-derived materials commonly known as MOF derivatives can be constructed. The possibility of controlled and predictable properties makes MOF derivatives a preferred choice for numerous advanced technological applications. The innovative synthetic designs besides the plethora of interdisciplinary characterization approaches applicable to MOF derivatives provide the opportunity to perform a myriad of experiments to explore the performance and offer key insight to develop the next generation of advanced materials. Though there are many published works of literature describing various synthesis and characterization techniques of MOF derivatives, it is still not clear how the synthesis mechanism works and what are the best techniques to characterize these materials to probe their properties accurately. In this review, the recent development in synthesis techniques and mechanisms for a variety of MOF derivates such as MOF-derived metal oxides, porous carbon, composites/hybrids, and sulfides is summarized. Furthermore, the details of characterization techniques and fundamental working principles are summarized to probe the structural, mechanical, physiochemical, electrochemical, and electronic properties of MOF and MOF derivatives. The future trends and some remaining challenges in the synthesis and characterization of MOF derivatives are also discussed., (© 2024 The Authors. Small published by Wiley‐VCH GmbH.)

A numerical investigation was carried out in ANSYS Fluent ® on a photovoltaic/thermal (PV/T) system with MXene/water nanofluid as heat transfer fluid (HTF). The interaction of different operating parameters (nanofluid mass fraction, mass flow rate, inlet temperature and incident radiation) on the output response of the system (thermal efficiency, electrical efficiency, thermal exergy efficiency, and electrical exergy efficiency) was studied using a predictive model generated using response surface methodology (RSM). The analysis of variance (ANOVA) method was used to evaluate the significance of input parameters affecting the energy and exergy efficiencies of the nanofluid-based PV/T system. The nanofluid mass flow rate was discovered to be having an impact on the thermal efficiency of the system. Electrical efficiency, thermal exergy efficiency, and electrical exergy efficiency were found to be greatly influenced by incident solar radiation. The percentage contribution of each factor on the output response was calculated. Input variables were optimized using the desirability function to maximize energy and exergy efficiency. The developed statistical model generated an optimum value for the mass flow rate (71.84 kgh -1 ), the mass fraction (0.2 wt%), incident radiation (581 Wm -2 ), and inlet temperature (20 °C). The highest overall energy and exergy efficiency predicted by the model were 81.67% and 18.6%, respectively.

Progress in electrochemical water-splitting devices as future renewable and clean energy systems requires the development of electrodes composed of efficient and earth-abundant bifunctional electrocatalysts. This study reveals a novel flexible and bifunctional electrode ( NiO@CNTR ) by hybridizing macroscopically assembled carbon nanotube ribbons ( CNTRs ) and atmospheric plasma-synthesized NiO quantum dots (QDs) with varied loadings to demonstrate bifunctional electrocatalytic activity for stable and efficient overall water-splitting (OWS) applications. Comparative studies on the effect of different electrolytes, e.g., acid and alkaline, reveal a strong preference for alkaline electrolytes for the developed NiO@CNTR electrode, suggesting its bifunctionality for both HER and OER activities. Our proposed NiO@CNTR electrode demonstrates significantly enhanced overall catalytic performance in a two-electrode alkaline electrolyzer cell configuration by assembling the same electrode materials as both the anode and the cathode, with a remarkable long-standing stability retaining ∼100% of the initial current after a 100 h long OWS run, which is attributed to the "synergistic coupling" between NiO QD catalysts and the CNTR matrix. Interestingly, the developed electrode exhibits a cell potential ( E 10 ) of only 1.81 V with significantly low NiO QD loading (83 μg/cm 2 ) compared to other catalyst loading values reported in the literature. This study demonstrates a potential class of carbon-based electrodes with single-metal-based bifunctional catalysts that opens up a cost-effective and large-scale pathway for further development of catalysts and their loading engineering suitable for alkaline-based OWS applications and green hydrogen generation.

An atmospheric-pressure plasma system is developed and is used to treat carbon nanotube assemblies, producing a hybrid carbon-zinc structure. This system is integrated into a floating-catalyst chemical vapor deposition furnace used for the synthesis of macroscopic assemblies of carbon nanotubes to allow for the in-line, continuous, and single-step production of nano-composite materials. Material is deposited from a sacrificial zinc wire in the form of nanoparticles and can coat the surface of the individual carbon nanotubes as they form. Additionally, it is found that the deposited materials penetrate further into the carbon nanotube matrix than a comparable post-synthesis deposition, improving the uniformity of the material through the thickness. Thus, a single-step metal-based coating and carbon nanotube synthesis process which can form the basis of production scale manufacturing of metal-carbon nanotube composite materials with an atmospheric-pressure plasma system are demonstrated., (© 2023 The Authors. Small Methods published by Wiley-VCH GmbH.)

Sensitive localized surface plasmon resonance (LSPR) sensing is achieved using nanostructured geometries of noble metals which typically have dimensions less than 100 nm. Among the plethora of geometries and materials, the spherical geometries of gold (Au) are widely used to develop sensitive bio/chemical sensors due to ease of manufacturing and biofunctionlization. One major limitation of spherical-shaped geometries of Au, used for LSPR sensing, is their low refractive index (RI) sensitivity which is commonly addressed by adding another material to the Au nanostructures. However, the process of addition of new material on Au nanostructures, while retaining the LSPR of Au, often comes with a trade-off which is associated with the instability of the developed composite, especially in harsh chemical environments. Addressing this challenge, we develop a Au-graphene-layered hybrid (Au-G) with high stability (studied up to 2 weeks here) and enhanced RI sensitivity (a maximum of 180.1 nm/RIU) for generic LSPR sensing applications using spherical Au nanostructures in harsh chemical environments, involving organic solvents. Additionally, by virtue of principal component analysis, we correlate stability and sensitivity of the developed system. The relationship suggests that the shelf life of the material is proportional to its sensitivity, while the stability of the sensor during the measurement in liquid environment decreases when the sensitivity of the material is increased. Though we uncover this relationship for the LSPR sensor, it remains evasive to explore similar relationships within other optical and electrochemical transduction techniques. Therefore, our work serves as a benchmark report in understanding/establishing new correlations between sensing parameters., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

We report on a one-step hybrid atmospheric pressure plasma-liquid synthesis of ultra-small NiO nanocrystals (2 nm mean diameter), which exhibit strong quantum confinement. We show the versatility of the synthesis process and present the superior material characteristics of the nanocrystals (NCs). The band diagram of the NiO NCs, obtained experimentally, highlights ideal features for their implementation as a hole transport layer in a wide range of photovoltaic (PV) device architectures. As a proof of concept, we demonstrate the NiO NCs as a hole transport layer for three different PV device test architectures, which incorporate silicon quantum dots (Si-QDs), nitrogen-doped carbon quantum dots (N-CQDs) and perovskite as absorber layers. Our results clearly show ideal band alignment which could lead to improved carrier extraction into the metal contacts for all three solar cells. In addition, in the case of perovskite solar cells, the NiO NC hole transport layer acted as a protective layer preventing the degradation of halide perovskites from ambient moisture with a stable performance for >70 days. Our results also show unique characteristics that are highly suitable for future developments in all-inorganic 3 rd generation solar cells ( e.g. based on quantum dots) where quantum confinement can be used effectively to tune the band diagram to fit the energy level alignment requirements of different solar cell architectures., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Anisotropic growth of ZnO nanorod arrays on ZnO thin films was achieved at a temperature of 90 degrees C by a surfactant-assisted soft chemical approach with control over size and orientation. ZnO thin films with c-axis preferred orientation had been achieved by the sol-gel technique. Lengths, diameters, and the degree of alignment of the ZnO nanorods were controlled by changing the experimental parameters. It was observed that the surfactant was essential to restrict the lateral growth of the nanorods, whereas the pH level of the reaction medium controlled the length of the nanorods. On the other hand, the orientation of the nanorods depended on the crystalline orientation of the film as well as the pH of the reaction medium. Room-temperature photoluminescence studies revealed that the ZnO nanorods with the best alignment exhibited the best emission property. The ZnO nanorods exhibited a strong UV emission peak at approximately 3.22 eV, ascribed to the band-edge emission. The field emission studies of the well-aligned nanorod arrays exhibited a low turn-on field of 1.7 V/microm to get an emission current density of 0.1 microA/cm(2).