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Synthesis of β-SiC powders by the carbothermal reduction of porous SiO2–C hybrid precursors with controlled surface area
摘要： SiO2–C precursors with various surface areas were derived from tetraethyl orthosilicate and phenolic resin as Si and C sources, respectively, by a modi?ed sol–gel process using the in situ precipitation of phenol resin in a prepared wet gel. The surface area of the SiO2–C precursors was varied from 20 to 175 m2/g by changing the C/Si molar ratio in the preform. β-SiC powders were synthesized using carbothermal reduction in vacuum at the temperature range of 1200–1600 °C. The e?ects of the temperature and heat treatment time as well as that of the surface area of the preform on the formation of β-SiC powders were studied. It was determined that the formation of β-SiC started at 1200 °C and was considerably promoted as the heat treatment temperature and time further increased during the carbothermal reduction of SiO2–C preforms with high surface area. When high surface area SiO2–C preforms were used, highly crystalline SiC powders were synthesized at 1600 °C in vacuum with a high yield of 85%.
关键词： Meso-macro porous,Carbotermal reduction,Sol–gel method,SiC,Synthesis
更新于2025-09-16 10:30:52
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Bionanosensor based on N-doped graphene quantum dots coupled with CoOOH nanosheets and their application for in vivo analysis of ascorbic acid
摘要： Herein, we employ 3D nitrogen-doped porous graphene frameworks (3D NPG) as raw material to prepare emissive nitrogen doped graphene quantum dots (r-NGQDs) via chemical oxidation method. The as-prepared fluorescent r-NGQDs was integrated with CoOOH nanosheets to construct a sensing platform for in vivo ascorbic acid (AA) analysis. Initially, the fluorescence emission intensity of r-NGQDs was quenched by CoOOH nanosheets based on the inner filter effect (IFE). Then the quenched intensity of r-NGQDs and CoOOH nanosheets system was enlightened by the addition of AA, since AA could consume CoOOH nanosheets through redox reaction, leading to the release of r-NGQDs and fluorescence restoration. Moreover, the restored fluorescence intensity of r-NGQDs is highly dependent on the concentration of AA which endows them as a quantitative analysis of AA with a limit of detection (LOD) reach up to1.85 μM (n = 3) in aqueous solution. Finally, the as constructed bionanosensor was further employed for in vivo analysis of AA in living rat brain microdialysate with basal value up to 9.4 ± 1.4 μM (n = 3).
关键词： Nitrogen-doped porous graphene,Graphene quantum dots,Ascorbic acid,In vivo,CoOOH nanosheets
更新于2025-09-16 10:30:52
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Hollow/porous-walled SnO2 via nanoscale Kirkendall diffusion with irregular particles
摘要： Hollow/porous structured SnO2 nanoparticles were synthesized by simple oxidation of dense metal chalcogenide precursors via nanoscale Kirkendall diffusion effect. First, tin chalcogenide (SnS, SnSe) nanoparticles were synthesized by mechanochemical method, which is considered a facile, scalable, and eco-friendly process. Hollow/porous-walled SnO2 nanoparticles were synthesized by simple oxidation of the prepared Sn chalcogenide precursors, for which the transformation mechanism was verified in detail. Nanoscale Kirkendall diffusion process was thoroughly investigated by morphological, crystallographic, and elemental analyses performed at various oxidation temperatures and times. To examine the morphological effect of hollow/porous-walled SnO2 nanoparticles on the electrochemical performance, the synthesized nanoparticles were applied as anode material in a lithium-ion battery. Anode material showed highly improved electrochemical properties compared to its dense counterpart, with 83% capacity retention from the second cycle at the 400th cycle and capacity of 302 mA h g-1 at a high current density of 30 A g-1.
关键词： chalcogenide,hollow structure,mechanochemical synthesis,porous particles,Kirkendall effect
更新于2025-09-16 10:30:52
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The Enhanced Sensitivity of a Porous Silicon Microcavity Biosensor Based on an Angular Spectrum Using CdSe/ZnS Quantum Dots
摘要： To improve the detection sensitivity of porous silicon microcavity biosensors, CdSe/ZnS quantum dots are used to label complementary DNA molecules for the refractive index amplification and angular spectrum method for detection. In this method, the TE mode laser is used as the detection light and the light source is changed into a parallel beam by collimating and expanding the beam, which illuminates the PSM surface and receives the reflected light from the PSM surface through the detector. The angle corresponding to the weakest reflected light intensity before and after the biological reaction between probe DNA and complementary DNA of different concentrations labeled by quantum dots was measured by the detector, and the relationship between the angle change before and after the biological reaction and the complementary DNA concentration labeled by quantum dots was obtained. The experimental results show that the angle change increases linearly with increasing complementary DNA concentration. The detection limit of the experiment, as determined by fitting, is approximately 36 pM. The detection limit of this method is approximately 1/300 of that without quantum dot labeling. Our method has a low cost because it does not require the use of a reflectance spectrometer, and it also demonstrates high sensitivity.
关键词： refractive index amplification,angular spectrum,quantum dot,porous silicon microcavity
更新于2025-09-16 10:30:52
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Electrochemical Studies on CaP Electrodeposition on Three Dimensional Surfaces of Selective Laser Melted Titanium Scaffold
摘要： In this work, calcium phosphate (CaP) coating was electrodeposited on the three dimensional surface of SLM-Ti sca?olds. The in situ measurement showed that the potential variation within 5 mm thickness porous selective laser melting (SLM)-Ti samples was about 80 mV as a result of the low conductivity of CaP coatings. SEM observation results revealed that the coating morphology depended on the distance between the surface position of porous SLM-Ti electrode and the auxiliary electrode. Based on the compared electrochemical experiments, it was found that the top and the bottom surfaces of SLM-Ti sca?olds exhibited continuous nucleation and instantaneous nucleation behavior respectively. The Electrochemical impedance spectroscopy (EIS) results also revealed that the electrodeposition processes at di?erent depth of SLM-Ti sca?olds were not synchronized. These di?erences were ultimately caused by the non-uniform distribution of the potential and the current inside porous SLM-Ti electrodes. The present work provides a basic research method for studying the mechanism of the electrochemical process on three dimensional surfaces of SLM-Ti sca?olds.
关键词： porous titanium,selective laser melting,electrochemical deposition,CaP coating
更新于2025-09-16 10:30:52
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From bulk to porous GaN crystal: precise structural control and its application in ultraviolet photodetectors
摘要： Porous GaN has many unique merits, such as a large specific surface area, adjustable bandgap and excellent optical performance. Here, we develop a simple and effective method for preparing porous GaN single crystals through high temperature annealing. The effects of different annealing temperatures on the porous structure, crystal quality and optical properties of GaN are investigated. The relationship model of annealing temperatures, times and GaN porous structures is summarized. An ultraviolet (UV) photodetector based on porous GaN is fabricated. The effects of porous structures on the performance of the GaN UV photodetector are investigated for the first time. We found that the appropriate GaN porous structure can improve the performance of the photodetector. A possible performance enhancement mechanism has been proposed. Based on the high performance and simple fabrication process, porous GaN crystal can be an excellent candidate for UV photodetectors.
关键词： optical properties,crystal quality,UV photodetector,high temperature annealing,porous GaN
更新于2025-09-16 10:30:52
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In-depth study of annealed porous silicon: Understand the morphological properties effect on negative LiB electrode performance
摘要： Silicon (Si) used as negative electrode in a Li-ion battery (LIB) is highly attractive for its high energy density, safe cycling, and nontoxicity. However its alloying mechanism with Li induces material pulverization, which leads to a rapid capacity fade. In this work, annealing post treatment was used in order to tune the morphological properties of porous silicon. Playing on annealing temperature, the morphological modification induces electrochemical behavior changes in LIB. The porosification is an interesting way to accommodate the volume expansion occurring during the alloying process. Increase of the annealing temperature leads to porous Si pores and walls reorganization, which has a positive impact on battery performance likely due to a higher wettability of the Si electrode with electrolyte. 700 °C appeared to be the optimized annealing temperature.
关键词： Negative electrode,Morphological properties,Li-ion battery,Annealing,Silicon,Electrochemical behavior,Porous silicon
更新于2025-09-16 10:30:52
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Bulk Power System Dynamics with Varying Levels of Synchronous Generators and Grid-Forming Power Inverters
摘要： The conversion of electrical to mechanical power on a sub-centimeter scale is a key technology in many microsystems and energy harvesting devices. In this paper, we present a type of a capacitive energy conversion device that uses capillary pressure and electrowetting to reversibly convert electrical power to hydraulic power. These microhydraulic actuators use a high surface-to-volume ratio to deliver high power at a relatively low voltage with an energy conversion efficiency of over 65%. The capillary pressure generated grows linearly with shrinking capillary diameter, as does the frequency of actuation. We present the pressure, frequency, and power scaling properties of these actuators and demonstrate that power density scales up as the inverse capillary diameter squared, leading to high-efficiency actuators with a strength density exceeding biological muscle. Two potential applications for microhydraulics are also demonstrated: soft-microrobotics and energy harvesting.
关键词： microsystems,electrocapillary,soft robotics,PDMS,actuator,energy conversion,microfluidics,electrowetting,energy harvesting,porous materials,Microhydraulics,microrobotics
更新于2025-09-16 10:30:52
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Formation of Nanoparticles and Plasmonic Structures in Porous Materials Using Laser and SCF Technologies
摘要： A review of the authors’ studies on the processes of metal nanoparticles (silver and gold) formation and of various type structures in polymer and porous materials based on the effects of self-assembly and self-organization in the continuous laser radiation field is presented. Most experiments were performed either with samples saturated with metal precursors in supercritical carbon dioxide or with those exposed to this medium. Structures of various types from metal nanoparticles in polymers and porous glasses: periodic structures of micron and submicron scale, layered structures from nanoparticles with an unusually short period (about 90 nm), filament, ring structures, and island nanoparticle films have been synthesized. Several regularities and mechanisms of the formation of both the nanoparticles and their structures depending on the wavelength of laser radiation have been established. New results on the method for producing composite porous foam materials based on silver nanoparticles and polymer matrices, which combines laser-induced “drawing” of porous structures, their impregnation with precursor molecules using supercritical fluid technology, and subsequent reduction of nanoparticles are presented.
关键词： structures,porous glasses,polymers,carbon dioxide,supercritical fluid,nanoparticles,laser formation,self-assembly
更新于2025-09-16 10:30:52
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Hierarchically porous surface of PEEK/nMCS composite created by femtosecond laser and incorporation of resveratrol exhibiting antibacterial performances and osteogenic activity in vitro
摘要： To further improve the surface properties of polyetheretherketone (PEEK)/nanoporous magnesium calcium silicate (nMCS) composite (PMC), hierarchically porous surface of PMC (PMCF) were created by femtosecond laser, and resveratrol (RV) was incorporated into the porous surface of PMCF (RV@PMCF). Compared to PMC with flat surface, PMCF contained not only two types of micropores with different sizes (around 20 μm and 0.5μm) but also nanopores (around 4 nm), which exhibited remarkably increase in surface roughness and protein adsorption. In addition, PMCF displayed a slow-release of RV while PMC showed a burst-release of RV into cell cultured medium. Moreover, compared with PMC and PMCF, RV@PMCF with antibacterial performances inhibited the growth of E. coli and S. aureus thanks to the release of RV. In addition, compared with PMC, PMCF and RV@PMCF significantly promoted adhesion and proliferation of rat bone mesenchymal stem cells (BMSC). Furthermore, compared with PMCF, RV@PMCF obviously enhanced the proliferation and osteogenic differentiation as well as bone related genes expressions of BMSC. The results demonstrated that PMCF with hierarchically porous surface and incorporating of RV displayed antibacterial performances and osteogenic activity in vitro, Therefore, as a drug-loaded implant, RV@PMCF with good cytocompatibility would have a big potential for applications in orthopaedic fields.
关键词： femtosecond laser,osteogenic activity,antibacterial performances,polyetheretherketone based composite,hierarchically porous surface
更新于2025-09-16 10:30:52