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The perovskite film prepared by the two-step spin coating method is widely used in photovoltaic devices due to its good film morphology and great reproducibility. However, there usually exists excessive lead iodide (PbI2) in the perovskite film for this method, which is believed to passivate the grain boundaries (GBs) to increase the efficiency of the perovskite solar cells. Nevertheless, the excessive PbI2at the GBs of perovskite is believed to induce the decomposition of the perovskite film and undermine the long-term stability of devices. In this study, we utilize precursor engineering to realize the preparation of perovskite solar cells with high efficiency and stability. The concentration of organic salts (AX: A = MA+, FA+; X = I-, Cl-) in the precursor solution for the second step of the two-step spin coating method is adjusted to optimize the perovskite light-absorbing layer so that the excessive PbI2is converted into perovskite to obtain a smooth and pinhole-free perovskite film with high performance. Our results indicate that by adjusting the concentration of AX in the precursor solution, PbI2in the film could be completely converted into perovskite without excessive AX residue. Both the efficiency and stability of the perovskite solar cells without excessive PbI2have been significantly improved. A planar perovskite solar cell with the highest power conversion efficiency (PCE) of 21.26% was achieved, maintaining about 90% of the initial PCE after 300 h of storage in a dry air environment and in the dark, about 76% of the initial PCE after 300 h of continuous illumination of 1 Sun.
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The anisotropic heat transfer properties of two-dimensional materials play an important role in controlled heat transfer and intelligent heat management. At present, there are many references on anisotropic heat transfer of two-dimensional materials, but less systematic review of their development status, problems, and future directions. In this paper, intrinsic anisotropic heat transfer of two-dimensional materials, influencing factors and control means are introduced. The preparation methods of thin film with two-dimensional material and the influence factors of macroscopic anisotropic thermal properties are summarized. The technology of two-dimensional material oriented arrangement in matrix and the influence factors of macroscopic anisotropic thermal properties of the composite are outlined.
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BACKGROUND: In order to detect anti-HPV16E7 antibody in serum, a highly sensitive and rapid detection method based on chemiluminescence immunoassay and immunomagnetic separation was introduced. The technique that was developed is a novel, sensitive chemiluminescence (CL) immunoassay for HPV16E7 antibody detection. METHODS: Balb/C mice were immunized with HPV16E7 fusion protein to prepare monoclonal antibody against HPV16E7. The biotinylated antigen was prepared as immunomagnetic beads and its stability was tested (IMBs). The protocol used horseradish peroxidase (HRP) labeled HPV16E7 antigen and immunomagnetic beads (IMBs). The antibody induced the formation of IMBs-mAbs HPV16E7-HRP labeled antibody structures. IMBs were applied to capture CEA and immobilize CEA through the external magnetic field. Oxidized luminescence substrate can be catalyzed by HRP on antibody surface to generate optical signals which were detected by luminometer. RESULTS: HPV16E7 monoclonal antibody was prepared and validated. The HPV16E7 antigen can efficiently bind to the bead with a conjugation rate of 72%. The biological activity of IMBs did not decrease significantly when stored in the dark at 4â for 2 months. The sensitivity and stability of this proposed method were excellent and showed a good linear relationship (Y = 1.3203 X + 0.7, R2 = 0.9952). CONCLUSIONS: This proposed technique showed excellent performance in quantitative measurement of HPV6E7 and was expected to be used in clinical detection.
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Anticorpos Antivirais/isolamento & purificação , Separação Imunomagnética , Medições Luminescentes , Animais , Anticorpos Monoclonais , Peroxidase do Rábano Silvestre , Imunoensaio , Luminescência , Camundongos , PapillomaviridaeRESUMO
Recently, miniaturized power supplies have become essential components of micro-electromechanical systems (MEMS) and portable microdevices due to their high-power density, moderate specific energy, and superior long-term cyclability. In this study, microsupercapacitors with ZIF-8-derived carbons as active materials were successfully fabricate by electrophoretic deposition method. The carbon materials on microsupercapacitors, which are directly deposited or obtained by pyrolyzing predeposited ZIF-8 particles, play a crucial role in achieving outstanding electrochemical performances. The microsupercapacitor of 16 interdigital finger electrodes, prepared by electrophoretic deposition of ZIF-8 particles and subsequent pyrolysis, shows maximum specific power 687.6â mW cm-3 , specific energy 2.87â mWh cm-3 , and 97.8 % capacitance retention rate after 10 000 cycles. The simple and facile process of electrophoretic deposition and subsequent pyrolysis of ZIF-8 particles generates a film of densely populated microporous carbon particles on microsupercapacitor, leading to superior capacitive performances.
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Confronting the global challenge of energy efficiency in the backdrop of environmental concerns, the innovation of a flexible thermoelectric electrode marks a significant stride forward, especially in the realm of low-temperature heat recovery. This investigation unveils a pioneering electrode material, a nitrogen-doped SWCNT/MXene bilayer thin film, which was meticulously engineered for thermoelectric systems. Surpassing the conventional Pt electrode with inherent inflexibility and prohibitive cost, our proposed electrode showcases excellent ductility alongside commendable thermoelectric properties. Our electrodes demonstrate significant advancement, achieving a thermopower output of 14.11 µW·cm-2 with the Seebeck coefficient escalating to 1.61 mV·K-1 even at a modest temperature differential of 40 °C. The results mark a substantial 32% enhancement in thermoelectric performance compared to the power output at 10.69 µW·cm-2 for a Pt electrode under similar conditions. This remarkable improvement underscores the superior efficiency and potential of our electrodes for practical thermoelectric application, offering a viable and cost-effective alternative to traditional Pt-based solutions. This innovation not only positions itself as a formidable contender to Pt electrodes but also signals a new dawn for efficient thermoelectric energy harvesting, underscored by the material's scalability and ready availability.
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Composite films of graphene and polyaniline nanofibers are prepared by in situ polymerization of aniline monomer in graphene suspension. The morphology and microstructure of samples are examined by scanning electron microscopy (SEM), transition electron microscopy (TEM), and X-ray diffraction (XRD). Electrochemical performances are characterized by cyclic voltammetry (CV) and galvanostatic charge/discharge measurements. Graphene is homogeneously coated by polyaniline nanofibers with diameter of 40 nm. Supercapacitors based on the graphene/polyaniline conductive composite films exhibit large electrochemical capacitance (994 F/g) at a discharge rate of 2.0 A/g in 1 M H2SO4 solution, which is much higher than the graphene (320 F/g) and polyaniline electrode (210 F/g). The excellent performance is not only due to the graphene which can provide more active sites for nucleation of polyaniline, but also associated with a good redox activity of ordered polyaniline nanofibers. Moreover, the composite films exhibit excellent long cycle life during charge/discharge processes. After 1000 cycles, the specific capacitance decreases 11% of initial capacitance compared to 28% for polyaniline nanofibers. The resulting composite is a promising electrode material for high-performance electrical energy storage devices.
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We propose to enhance photothermal conversion via doping titanium carbide (Ti3C2) MXene nanosheets on the surfaces of phase-change microcapsules consisted of the n-Octadecane core and styrene divinylbenzene copolymer shell. Detected by scanning electron microscopy, the microcapsules showed a usually circular form with an appropriate dispersion. The thermal properties of the microcapsules were characterized using the differential scanning calorimetry and thermal conductivity instruments, realizing an excellent phase-change enthalpy of around 140 J/g, high encapsulation ratio of over 64 %, good heat transfer of 0.294 ± 0.003 W/(m·K), and great thermal reliability. More importantly, the microcapsules doped with Ti3C2 MXene nanosheets reach a solar-to-heat conversion efficiency of 85 ± 7 %, a substantial enhancement by 240 % in comparison with non-doping sample. The Ti3C2 MXene-doped microcapsules with excellent heat storage and solar-to-heat conversion capabilities offer great potential for high-efficiency solar energy utilization and can be applied to thermal energy storage systems and direct absorption solar collectors.
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High supercooling and single functionalization are the main barriers to the large-scale application of microencapsulated phase-change materials (PCMs) in the construction industry. To address these issues, we propose a new inorganic microencapsulated PCM, PW@CaWO4, which was synthesized via the in situ polymerization method using inorganic CaWO4 as shell and phase-change paraffin wax (PW) as core. We investigated the effects of different emulsifiers and core-to-shell ratios on microcapsule properties and found that the PW@CaWO4 microcapsules have regular spherical topography and good uniformity in particle size. During the synthesis process, the CaWO4 shell provides convenient conditions for heterogeneous nucleation of PW and effectively reduces the supercooling degree. The minimum supercooling degree of the PW@CaWO4 microcapsules is only 1.00 ± 0.08 °C, which is 3.41 °C lower than that of PW. Moreover, the PW@CaWO4 microcapsules can absorb ultraviolet radiation and exhibit fluorescence, which originates from the peculiar WO42- structure in the CaWO4 shell, eliminating the need for doping other light-activating ions into the shell. The newly prepared microcapsules possess several advantages, including suitable particle size, low supercooling, good heat storage, high thermal conductivity, good short-wave ultraviolet absorption, peculiar fluorescence, excellent proof of leakage, and so on. The microcapsules can be applied to fluorescent architectural energy-saving coatings.
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Organic-inorganic composite phase change materials (PCMs) are promising in the fields of solar energy storage and building thermal management. However, combining inorganic with organic PCMs meets a great challenge. In the current work, a shape-stable hybrid emulsion gel (EGel/GO) is developed via Pickering emulsion polymerization, which seamlessly combines sodium acetate trihydrate (SAT) in the water phase with paraffin wax (PW) in the oil phase. The polymer dual-phase cross-linking in EGel/GO forms a supporting framework that effectively enhances the material's shape stability, slows the loss of crystalline water in hydrates, and reduces supercooling. The addition of graphene oxide (GO) enhances EGel/GO-0.5's optical absorption properties, resulting in photothermal conversion efficiency as high as 89.1%. Furthermore, EGel/GO not only has high latent heat of 225.08 J/g but also has almost no leakage and no phase separation. The Pickering emulsion polymerization method paves a broad avenue for combining organic with inorganic PCMs, which is an ideal choice for the effective utilization of solar energy and building energy storage.
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Modern highly integrated microelectronic devices are unable to dissipate heat over time, which greatly affects the operating efficiency and service life of electronic equipment. Constructing high-thermal-conductivity composites with 3D network structures is a hot research topic. In this article, carbon fiber felt (CFF) was prepared by airflow netting forming technology and needle punching combined with stepped heat treatment. Then, carbon-coated carbon fiber felt (C@CFF) with a three-dimensional network structure was constructed in situ by high-temperature chemical vapor deposition (CVD). Finally, high-temperature treatment was used to improve the degree of crystallinity of C@CFF and further enhance its graphitization. The epoxy (EP) composites were prepared by simple vacuum infiltration-molding curing. The test results showed that the in-plane thermal conductivity (Kâ¥) and through-plane thermal conductivity (Kâ¥) of EP/C@CFF-2300 °C could reach up to 13.08 and 2.78 W/mK, respectively, where the deposited carbon content was 11.76 vol %. The in-plane thermal conductivity enhancement (TCE) of EP/C@CFF-2300 °C was improved by 6440 and 808% compared to those of pure EP and EP/CFF, respectively. The high-temperature treatment greatly provides an improvement in thermal conductivity for the in-plane and the through-plane. Infrared imaging showed excellent thermal management properties of the prepared epoxy composites. EP/C@CFF-2300 °C owned an in-plane AC conductivity of up to 0.035 S/cm at 10 kHz, and Lorentz-Drude-type negative permittivity behaviors were observed at the tested frequency region. The CFF thermally conductive composites prepared by the above method have a broad application prospect in the field of advanced thermal management and electromagnetics.
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There has been an explosion of research into the physical and chemical properties of carbon-based nanomaterials, since the discovery of carbon nanotubes (CNTs) by Iijima in 1991. Carbon nanomaterials offer unique advantages in several areas, like high surface-volume ratio, high electrical conductivity, chemical stability and strong mechanical strength, and are thus frequently being incorporated into sensing elements. Carbon nanomaterial-based sensors generally have higher sensitivities and a lower detection limit than conventional ones. In this review, a brief history of glucose biosensors is firstly presented. The carbon nanotube and grapheme-based biosensors, are introduced in Sections 3 and 4, respectively, which cover synthesis methods, up-to-date sensing approaches and nonenzymatic hybrid sensors. Finally, we briefly outline the current status and future direction for carbon nanomaterials to be used in the sensing area.
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As a typical phase-change material (PCM) with high heat storage capacity and wide distribution, hydrated salts play broad and critical roles in solar energy utilization in recent years. However, the leakage and supercooling problems of hydrated salts have been a constraint to their further practical applications. In the current work, the super-hydrophilic reduced graphene oxide (RGO) aerogels modified by konjac glucomannan (KGM) as supporting structural materials are prepared by the hydrothermal reaction-freeze-drying, which can effectively absorb and convert visible sunlight energy into thermal energy. In addition, the super-hydrophilic aerogels compounded with PCMs can ameliorate the shortcoming of leakage and suppress the supercooling temperature as low about 0.2-1.5 °C in the freezing process. Under 1 sun irradiation, the prepared sodium acetate trihydrate/KGM-modified graphene oxide aerogel (SAT/KRGO) composite PCM achieves a high photothermal conversion efficiency (86.3%) due to its good light absorption property. The number of cycles has no apparent effect on the supercooling of the composite materials, suggesting their stable thermal cycles and thermal storage.
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A series of polyurethane/graphene oxide (PU/GO) solid-solid phase change materials (SSPCMs) were synthesized by using GO as a light-absorbing filler and polyethylene glycol (PEG) as a phase change matrix. The effects of PEG content on the energy storage capacity, thermal stability and photo-thermal conversion performance of PU were investigated. The results show that the form-stability of PU/GO decreases while the phase change enthalpy and photo-thermal conversion efficiency of PU/GO increases with the increasing PEG content. The introduction of a very low content of GO can maintain comparable energy storage density and greatly improve light absorption by reasonably modulating the soft segment contents. The PU/GO composite with 92 wt% PEG has a phase change enthalpy of 138.12 J/g and a high photo-thermal conversion efficiency (87.6%). The composite solid-solid PCMs have great potential for effective energy storage and solar energy utilization.
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The thermal transport of Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) nanofiber is contributed by the electronic component of thermal conduction and the phonon component of thermal conduction. The relationship between the electrical conductivity and thermal conductivity of these conducting polymers is of great interest in thermoelectric energy conversation. In this work, we characterized the axial electrical conductivities and thermal conductivities of the single PEDOT:PSS nanofibers and found that the Lorenz number L is larger than Sommerfeld value L0 at 300 K. In addition, we found that the L increased significantly in the low-temperature region. We consider that this trend is due to the bipolar contribution of conducting polymers with low-level electrical conductivity and the increasing trend of the electronic contribution to thermal conductivity in low-temperature regions.
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Metal-organic frameworks (MOFs) and their derivatives are promising materials for energy conversion and storage. This study demonstrates a solvent-free method to fabricate a CoOx/carbon composite array derived from ZIF-67 for asymmetric supercapacitors. Tree-like Co metal arrays are electrodeposited on a surface and then directly converted into composite ZIF-67/Co-based MOF arrays via a chemical vapor deposition method (MOF-CVD). Finally, the CoOx/carbon composite array is obtained by regulated calcination of the ZIF-67/Co composite array. The as-prepared CoOx/carbon composite arrays provide a less tortuous pathway for ion diffusion, high pseudocapacitance from transition-metal oxides, and good electrical conductivity from carbon. Moreover, the absence of adhesives in array electrodes is also beneficial to the promotion of the electrochemical performance. The as-fabricated CoOx/carbon composite array electrode shows excellent electrochemical performance with high energy density, high power density, superior rate capability, and long cycle life in an asymmetric supercapacitor. These MOF-derived composite arrays are promising candidate materials for power sources because of their good electrochemical performance.
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Stable ethylene-glycol-based nanofluids containing graphene oxide nanosheets have been prepared. The measurements of thermal conductivity indicate that the nanofluids have substantially higher thermal conductivities than the base fluid. The thermal conductivity enhancement depends strongly on the volume fraction of graphene oxide nanosheets and increases with the increasing loading. When the nanosheet loading is 5.0 vol%, the enhancement ratio is up to 61.0%. The thermal conductivity of the fluids remains almost constant for seven days, indicating their high stability. The level of enhancement is independent of temperature in the measured temperature range.
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As a renewable resource of reducer, biochar prepared by pine sawdust is proposed for direct reduction of copper slag in this paper. Combined with thermodynamic analysis, effects of reduction time, temperature and CaO addition ratio on solid copper slag reduction characteristics are discussed. The oxides of iron in copper slag are Fe3O4 and 2FeO·SiO2. The reduction processes were carried out step by step for Fe3O4 and 2FeO·SiO2, respectively: Fe3O4 â FeO â Fe and 2FeO·SiO2 â Fe. The porous structure of biochar exhibits higher reduction reactivity and reaction rate than that of coal. CaO reduced the Gibbs free energy of reduction reactions and facilitated the reduction of 2FeO·SiO2 with C and CO. When CaO was added, separation reaction of FeO and SiO2 took place and α-SiO2 and ß-SiO2 were produced. When the addition ratio of CaO is above 0.3, CaO·SiO2 and 2CaO·SiO2 are produced. The reduction process of copper slag was established as follows: (a) dehydration and fast pyrolysis; (b) reduction of iron oxides by C and CO; and (c) sweating metallic iron outflows from cracks in pellet. Besides, direct reduction reaction mechanism and transport process of Cu are established based on reduction experiments, XRD and SEM-EDS analysis.
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Carvão Mineral , Cobre , Carbono , Carvão Vegetal , Dióxido de SilícioRESUMO
The direct absorption solar collector (DASCs) with nanofluids can remarkably improve the utilization efficiency of solar energy. However, in the actual applications, the temperature distribution of the receiver is extremely uneven when the concentration of nanofluids is high or the receiver is deep. This makes the temperature of upper layer much higher than that of the lower layer, resulting in much heat loss to the surrounding by convection. Here, we propose a magnetic forced convection nanofluids absorption system, where an external rotating magnetic field is used to change the heat transfer mechanism of working fluids from traditional heat conduction to the thermal convection. It is found that the photothermal conversion efficiency of FeNi/C-EG nanofluids is up to 58.1% in this system, which is 22.7% higher than non-external rotating magnetic field when the nanofluids concentration is 50â¯ppm. Furthermore, the agglomeration of nanofluids can be effectively reduced by an external rotating magnetic field.
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Nanofluids offer the exciting new possibilities to enhance heat transfer performance. In this paper, experimental and theoretical investigations have been conducted to determine the effect of CuO nanowires on the thermal conductivity and viscosity of dimethicone based nanofluids. The CuO nanowires were prepared through a thermal oxidation method, and the analysis indicated that the as-prepared CuO nanowires had high purity, monocrystalline with a monoclinic structure and large aspect ratio compared to CuO nanospheres. The experimental data show that the thermal conductivity of the nanofluids increases with the volume fraction of CuO nanowires or nanospheres, with a nearly linear relationship. For the nanofluid with the addition of 0.75 vol.% CuO nanowires, the thermal conductivity enhancement is up to 60.78%, which is much higher than that with spherical CuO nanoparticles. The nanofluids exhibit typical Newtonian behavior, and the measured viscosity of CuO nanowires contained nanofluids were found only 6.41% increment at the volume fraction of 0.75%. It is attractive in enhanced heat transfer for application. The thermal conductivity and viscosity of CuO nanofluids were further calculated and discussed by comparing our experimental results with the classic theoretical models. The mechanisms of thermal conductivity and viscosity about nanofluids were also discussed in detail.
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A series of Zr-Fe (Zr/Fe = 4:0, 3:1, 2:2, 1:3, 0:4) polymeric pillared interlayered montmorillonite loading 10 wt.% MnOx (Mn/Zr-Fe-PILM) were investigated for the selective catalytic reduction of NOx by NH3 (NH3-SCR) in metallurgical sintering flue gas. The X-ray diffraction (XRD), N2 adsorption-desorption isotherm, scanning electron microscope (SEM), and ammonia temperature-programmed desorption (NH3-TPD) were used to analyze the physicochemical property. The Fe polymerized with Zr exchanged to montmorillonite can improve the Mn/Zr-Fe-PILM low-temperature NOx conversion and N2 selectivity. The Mn/Zr-Fe-PILM (1:3) shows the highest NOx conversion between 140 and 180 °C. The XRD results suggest that the growth of crystalline ZrO2 phase is intensely restrained for the Fe2O3 migration into the ZrO2 lattice. The ZrO2 and MnOx have an excellent dispersion in montmorillonite. The N2 adsorption result illustrates that the increase of Fe molar content in the Zr-Fe-PILM support increases the catalyst-specific surface area. The NH3-TPD results elucidate that the Mn/Zr-Fe-PILM (1:3) has the most total acid sites. Therefore, the low-temperature catalytic activity of the Mn/Zr-Fe-PILM (1:3) has been assigned to the large specific surface area, abundant acid sites, and the dispersion of metallic oxides.