Nano

Thermal energy and its storage systems play an extensive role in day-to-day life. They store renewable energy and are capable of recovering generated heat from different systems. Storage of thermal energy can be classified into three types: sensible, latent and sorption heat storages. Thermal heat storages use different types of materials based on their capacity of heat storage, stability of duration and thermal conductivity. Various phase change materials (PCMs) that are suitable for thermal storage are reported. Low conversion ability limits their effectiveness. We reviewed some of the traditional materials synthesized recently that are used for thermal energy storage (TES). Recently developed TES materials exhibit high thermal conductivity, reduced super cooling and multiple phase change temperatures. Nano-enhanced PCMs produced an increase in thermal conductivity up to 32% with a reduction in latent heat by 32%. At this juncture, MXenes with high performance and extraordinary properties (thermal, mechanical, etc.) are of special significance. MXenes displayed an increased thermal conductivity up to 16% and 94% efficiency. In view of their structure and adaptability to be used in thermal storage systems, an attempt was made to review their role also in thermal storage applications. It is observed that MXenes highly impact storage and efficiency. Apart from MXenes, various types of PCMs along with their thermal characteristics are presented.

In this study, modified couple stress theory-dependent stability analysis of functionally graded porous nano/microbeams under deformable support conditions, for the first time, is carried out via a solution method based on the Fourier series and Stokes’ transform. The modified couple stress theory is used as a size-dependent elasticity theory including the small-scale effect. The functionally graded material formulation is based on the power-law distribution found in the literature. The governing equation of the problem and especially the force boundary conditions are determined and the appropriate solution technique is selected. Fourier sine series is chosen as the lateral displacement function of functionally graded porous nano/microbeam under axial loads. Accordingly, the Fourier coefficients are found by substituting this function in the governing equation. Then, these coefficients and the Stokes’ transformation are applied to the force boundary conditions to construct general eigenvalue problems for the stability analysis. The results are compared with the rigid boundary conditions and it is shown that an excellent agreement is achieved. Then, several examples are solved for the functionally graded porous nanobeams and the effects of different parameters are analyzed and presented in a series of graphs and tables.

CuO:Cu₂O/Si heterojunctions have been prepared with different concentrations of Cu₂O nanoparticles using the thermal evaporation technique. The X-ray diffraction (XRD) results show that the prepared films are polycrystalline with orthorhombic structure and preferential orientation (110) direction along the $c$ axis at $2𝜃=32.82^{\circ }$, which corresponds to the pure CuO with crystallite size 18nm, while the particle size ranged from 14nm to 34 nm (resulted from SEM test). The optical properties were studied by recording the absorbance spectra using the UV–visible spectrophotometer. The absorbance increased with Cu₂O doping. The high values of the energy gap refer to the quantization effect. The electrical properties including the Hall effect were studied. CuO:Cu₂O/Si heterojunctions have been prepared at different concentrations. $I$–$V$ characteristics show that the Cu₂O doping increases the energy conversion efficiency by retarding the electron–hole recombination and the improved device performance is caused by the high short-circuit current ($I_{\mathrm{\text{sc}}})$ and open circuit voltage ($V_{\mathrm{\text{oc}}})$ and found that the highest efficiency ($\eta )$ at doping 0.006 Cu₂O 3.471% with $V_{\mathrm{\text{oc}}}$ of 2.20V, $I_{\mathrm{\text{sc}}}$ of 0.0170mA cm${}^{-2}$ and F.F of 0.6497 at $P=100$mW/cm².

miRNA-21 (miR-21) is a potential biomarker for the monitoring of diseases through its expression levels. Simple, portable and sensitive miR-21 detection of is advantageous for health monitoring in Point of Care Testing (POCT). Gold nanoparticles (AuNP) as excellent colorimetric sensors are widely used in the POCT. However, their low sensitivity is a limitation of their clinical use. Herein, we developed an AuNPs-based miR-21 assay with enzyme-assisted amplification reaction to construct the colorimetric platform capable of detecting as low as 0.1nM. In this platform, template ssDNA as a signal molecule could hybridize with ssDNA-modified AuNPs to generate the color reaction. The target miR-21 specifically hybridized to the template ssDNA, which was then cleaved by exonuclease III (Exo III) to release the target miR-21. As a trigger, miR-21 catalyzed the degradation of the template ssDNA to amplify the signal by Exo III. By hybridizing miR-21 and template ssDNA in the presence of Exo III, R-21 induced a significant decrease in the level of template ssDNA to reduce the aggregation of AuNPs. There is a clear color difference in the presence/absence of miR-21 in the assay. In this assay, the optimal concentration of templated ssDNA and Exo III were 100nM and 0.06U/$\mu$L in a 100$\mu$L detection system. The LoD for UV–Vis spectrum and colorimetric reaction were 0.1nM and 0.5nM, respectively. The detection system has good selectivity and can be used to detect miR-21 in the simulated saliva. It has great potential for application in biomedical research as well as in clinical diagnostics.

Nanosized Cu–Mn composite oxide catalysts were prepared from potassium permanganate, copper nitrate, n-butanol, and cetyltrimethylammonium bromide as a manganese source, copper source, reducing agent, and surfactant, respectively. The Cu${}_{0.2}$–Mn sample possessed a small particle size (10–40nm) and a relatively high specific surface area ($46.24{\mathrm{\text{m}}}^2\cdot {\mathrm{\text{g}}}^{-1}$); its main components were Cu${}_{1.5}$Mn${}_{1.5}$O₄ and Mn₃O₄. As a consequence, the Cu${}_{0.2}$–Mn catalyst exhibited good catalytic activity in the oxidation of toluene. At a toluene concentration of 1000ppm and a space velocity of $60,000\mathrm{\text{mL}}\cdot {\mathrm{\text{g}}}^{-1}\cdot {\mathrm{\text{h}}}^{-1}$, the $T_{50}$ and $T_{90}$ of the Cu${}_{0.2}$–Mn catalyst toward toluene were 239${}^{\circ }$C and 250${}^{\circ }$C, respectively. Furthermore, even after 30h of operation at 275${}^{\circ }$C, the conversion of toluene was 99% (at the space velocity of $60,000\mathrm{\text{mL}}\cdot {\mathrm{\text{g}}}^{-1}\cdot {\mathrm{\text{h}}}^{-1}$).

Purpose: A key step in the propagation of microparticles across temperature gradients, thermophoresis deposition of particles is important for electrical and aerosol technologies. Thus, the impact of thermophoresis deposition of particles is encountered in a mixed convective flow of Williamson hybrid nanofluids (HNFs) across a stretching/shrinking sheet to monitor the fluctuation of mass deposition.

Design/methodology/approach: The transformation is used to transmute the PDEs into ODEs and then the bvp4c approach is applied to solve the modified governing equations of the problem. Graphs are used to illustrate the key variables that influence the heat, mass and flow profiles.

Findings: The results suggest that the mass transfer rate (MTR) decreases for both solutions due to the higher consequences of the thermophoretic parameter. In addition, the developed impact of the radiation parameter and the posited hybrid nanoparticles markedly raise the heat transfer rate (HTR) for both solutions. Hybrid nanoparticles are effective for generating maximum energy. They play a crucial role in providing a high rate of acceleration in the flow.

Practical implications: The stable outcomes of this examination could be very helpful in improving the energy efficiency of thermal systems.

Originality/value: The double-diffusive non-Newtonian Williamson fluid by incorporating nanofluids across a vertical stretching/shrinking sheet with thermal radiation has not been considered yet. The obtained numerical results have been validated with the published work to validate the numerical method.