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Investigation of Strongly Hydrophobic and Thick Porous Silicon Stain Films Properties
摘要： Porous silicon (PSi) structures with strong hydrophobicity have been achieved by chemical etching of p-type silicon substrates in a solution based on hydrofluoric acid solution (HF) and vanadium oxide (V2O5). The surface morphology and microstructure of the elaborated structured silicon surfaces were investigated using Scanning Electron Microscope (SEM), contact angle and Fourier Transform Infrared spectroscopy (FTIR). The results show that the obtained structures exhibit hierarchically porous surfaces with porous pillars of silicon (PPSi) and an important hydrophobicity of the surface. The electrical properties of those PPSi structures were investigated in presence of 10 ppm of NO2 gas. The response time was about 30s at room temperature. Our results demonstrate that PPSi/Si are highly hydrophobic for long time and suitable for applications in the field of self-cleaning and may be a good candidate in elaborating practical NO2 sensors.
关键词： Porous silicon,Hydrophobicity,Gas sensing applications,Pillars structures
更新于2025-09-23 15:23:52
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Electrical Properties of Porous Silicon for N2 Gas Sensor
摘要： The application of porous silicon (PSi) for gas sensing devices has gained a considerable attention in the last decade. This work considers the electrical features of PSi layers prepared by electrochemical etching. We find that in order to get a better understanding of the absorption properties of PSi surface, it is necessary to know how the PSi morphology depends on the etching parameters. The physical structure of PSi, i.e., porosity, and pore size distribution can be controlled by changing the Hydrofluoric Acid concentration, current density, anodizing length and etching time in anodizing procedure. We describe our test system for gas sensors and investigate on the electrical behavior of PSi layers (p-type) in N2 gas for various fabrication conditions. The results show that the current density increases significantly as N2 gas is adsorbed. The measurements of the I-V characteristics were carried out at atmospheric pressure, room temperature, and with N2 gas as well.
关键词： Current-voltage curve,N2 gas,Porous silicon,Gas sensor
更新于2025-09-23 15:23:52
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Quasi-one-dimensional silicon nanostructures for gas molecule adsorption: a DFT investigation
摘要： Porous structures offer an enormous surface suitable for gas sensing, however, the effects of their quantum quasi-confinement on their molecular sensing capacities has been seldom studied. In this work the gas-sensing capability of silicon nanopores is investigated by comparing it to silicon nanowires using first principles calculations. In particular, the adsorption of toxic gas molecules CO, NO, SO2 and NO2 on both silicon nanopores and nanowires with the same cross sections was studied. Results show that sensing-related properties of silicon nanopores and nanowires are very similar, suggesting that surface effects are predominant over the confinement. However, there are certain cases where there are remarked differences between the nanowire and porous cases, for instance, CO-adsorbed nanoporous silicon shows a metallic band structure unlike its nanowire counterpart, which remains semiconducting, suggesting that quantum quasi-confinement may be playing an important role in this behaviour. These results are significant in the study of the quantum phenomena behind the adsorption of gas molecules on nanostructure’s surfaces, with possible applications in chemical detectors or catalysts.
关键词： Sensing,Chemical sensors,Silicon nanowires,Density functional theory,Molecule adsorption,Porous silicon
更新于2025-09-23 15:23:52
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Determination of high-temperature radiative properties of porous silica by combined image analysis, infrared spectroscopy and numerical simulation
摘要： The influence of the texture of fused silica glasses ? containing unconnected spherical bubbles ? on their thermal radiative properties was investigated by combining experimental measurements and numerical simulations. Exact numerical replicas of the porous samples were obtained from X-ray microtomography and image analysis showed that their bubble populations include two lognormal distributions of radii. The complex refractive index of the silica matrix was extracted from emittance measurements acquired at 1200 K on two reference silica samples. The comparison between direct measurements of the normal spectral emittance of the porous samples and those generated by applying Monte-Carlo ray tracing, performed on the numerical replicas, validated the use of geometric optics. The OH content of the porous samples was evaluated to be around 210 ppm. Ray tracing simulations carried out on a set of virtual samples having a similar texture proved to be a flexible means to address experimental limits when characterizing semi-transparent materials. The simulations also provided a natural framework to test the ability of the modified two-flux approximation model to predict the thermal radiative response of the porous silica investigated.
关键词： Radiative properties,X-ray microtomography,Porous silica glass,Spectral emittance,Monte-Carlo ray tracing
更新于2025-09-23 15:23:52
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Synthesis of Inorganic-Organic 2D CdSe Slab-Diamine Quantum Nets
摘要： Porous semiconductors attract great interest due to their unique structural characteristics of high surface area as well as their intrinsic optical and electronic properties. In this study, synthesis of inorganic–organic 2D CdSe slabs-diaminooctane (DAO) porous quantum net structures is demonstrated. It is found that the hybrid 2D CdSe-DAO lamellar structures are disintegrated into porous net structures, maintaining an ultrathin thickness of ≈1 nm in CdSe slabs. Furthermore, the CdSe slabs in quantum nets show the highly shifted excitonic transition in the absorption spectrum, demonstrating their strongly confined electronic structures. The possible formation mechanism of this porous structure is investigated with the control experiments of the synthesis using n-alkyldiamines with various hydrocarbon chain lengths and ligand exchange of DAO with oleylamine. It is suggested that a strong van der Waals interaction among long chain DAO may exert strong tensile stress on the CdSe slabs, eventually disintegrating slabs. The thermal decomposition of CdSe-DAO quantum nets is further studied to form well-defined CdSe nanorods. It is believed that the current CdSe-DAO quantum nets will offer a new type of porous semiconductors nanostructures under a strong quantum-confinement regime, which can be applied to various technological areas of catalysts, electronics, and optoelectronics.
关键词： quantum nets,porous materials,semiconductor nanocrystals,CdSe,2D materials
更新于2025-09-23 15:23:52
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Advanced Coating Materials || Anodic Oxide Nanostructures: Theories of Anodic Nanostructure Self-Organization
摘要： This chapter reviews the morphologies, growth kinetics, and theories of growth kinetics of anodic oxide films. Experimentally, it is possible to control the growth conditions of these films to yield several distinct morphologies, including orderly arranged nanoporous and nanotubular films. Fundamental processes that lead to self-ordering of nanoscale features, including interfacial reactions, ionic transport, stress generation, and space charge accumulation, are discussed. Various theories are included to explain the growth mechanism of oxide film.
关键词： barrier film,Anodic oxide film,porous film,EIS,anodization
更新于2025-09-23 15:23:52
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Improved galvanic porous silicon fabrication using patterned electrodes
摘要： On-chip porous silicon can be fabricated in a number of ways, but perhaps the simplest is a galvanic method that requires no external power supply. While this etch process is relatively simple, the etch is highly dependent on the surface area ratio (SAR) of a backside precious metal and frontside silicon surface, which respectively act as the cathode and the anode of an electrochemical cell. The SAR controls the etch current density, and therefore local variations can create high current densities that have detrimental effects on the quality of the final porous silicon film. The present study investigates the use of patterned backside platinum electrodes with the galvanic etch technique. The use of a patterned backside electrode that mimics the silicon pattern on the frontside, provides a more consistent etch current throughout the entire sample, and thus a more uniform porous silicon film. A triangular shape porous silicon film was tested in this work for comparison to a previous study utilizing an unpatterned electrode. With patterned electrodes, an etch depth variation percentage was observed throughout the length of the film of 8%. This is a considerable improvement over a 108% depth variation observed with a similar frontside silicon pattern and an unpatterned backside electrode.
关键词： porous silicon,electrochemical etching,mesoporous,galvanic etching
更新于2025-09-23 15:23:52
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Porous SiO2-coated Au-Ag alloy nanoparticles for the alkyne-mediated ratiometric Raman imaging analysis of hydrogen peroxide in live cells
摘要： We prepared an ultrathin porous silica shell-coated Au-Ag alloy nanoparticle (AuAg@p-SiO2NP) and developed it as a novel alkyne-based surface-enhanced Raman scattering (SERS) nanoprobe for the ratiometric Raman imaging of exogenous and endogenous H2O2 in live cells. The AuAg@p-SiO2NPs functionalized with 4-mercaptophenylboronic acid (MPBA) and 4-mercaptophenylacetylene (MPAE, 1,986 cm-1) as internal standard were first incubated with dopamine (DA) to incorporate the bridging molecules through the formation of borate bond between DA and MPBA on the surface of nanoparticle. Then, the signaling alkyne molecules of 3-(4-(phenylethynyl) benzylthio) propanoic acid (PEB, 2,214 cm-1) were conjugated to the surface of nanoparticle through the formation of amide bond between the carboxyl group on the PEB and the amino group on the DA, forming the ratiometric SERS nanoprobe. In the presence of H2O2, the alkynyl on the PEB is released from the surface of the Au-Ag alloy nanoparticle due to the boronate-to-phenol switch, decreasing the Raman signal at 2,214 cm-1 significantly. Since the Raman signal of MPAE at 1,986 cm-1 remains unchanged, quantitative analysis of H2O2 concentration can be achieved based on the ratiometric value of I1986/I2214. Under the optimized conditions, the plot of the ratiometric value of I1986/I2214 versus the H2O2 concentration in the range from 0.12 to 8 m M revealed a good linear response with a detection limit of 52 nM based on a signal-to-noise ratio of S/N = 3. The porous SiO2-coated Au-Ag alloy nanoparticle provides a novel SERS substrate with excellent biocompatibility, high stability, and effective anti-interference ability. Together with the alkynyl derivatives as internal standard, the SERS nanoprobe reported here allows the ratiometric detection of H2O2 in live cells and can be further applied to quantify many other biomolecules by using different signaling agents.
关键词： porous SiO2-coated Au-Ag alloy nanoparticle,SERS,alkyne,cell imaging,hydrogen peroxide
更新于2025-09-23 15:23:52
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Porous WO3 monolith-based photoanodes for high-efficient photoelectrochemical water splitting
摘要： We report a successful fabrication of low-cost, high-efficient, structurally-rigid, porous WO3 photoelectrochemical (PEC) catalysts using polystyrene as the template by a sol-gel method and a high-temperature annealing treatment. The scanning electron microscopy and Brunauer-Emmett-Teller surface analysis results indicate that such WO3 monoliths possess a porous structure and a large specific surface area, which can supply lots of photogenerated charge transfer pathways as well as more surface PEC active sites. Compared with a commercially available WO3, our highly porous WO3 PEC catalysts show an excellent PEC water splitting activity. Particularly, the porous WO3 photoanodes calcinated in the presence of oxygen atmosphere at 450 °C for 7 h show the best PEC performance exhibiting the photocurrent density of 0.97 mA/cm2 at 1.23 V versus reversible the hydrogen electrode and the incident photon-to-current conversion efficiency up to 48.9% at 420 nm in 0.5 M Na2SO4 electrolyte under AM 1.5 G irradiation. Such excellent PEC performance is due to the high porosity of the WO3, promoting the fast transfer and the separation rate of photogenerated carriers during the PEC water splitting process.
关键词： Water splitting,Porous structures,Energy conversion,WO3,Photoanode
更新于2025-09-23 15:23:52
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Facile fabrication and photocatalytic properties of Cu O (x?=?1 and 2) nanoarrays on nanoporous copper
摘要： Micro-nano CuxO (x = 1 and 2) composite arrays were successfully synthesized on nanoporous copper (np-Cu) via one-step anodic oxidation method. With anodic time prolonging, the surface area and the length of pine-needle CuO clusters increased. The np-Cu/CuxO supported by amorphous layer composite as photocatalyst exhibited excellent photocatalytic activity and cycling stability for the degradation of Rhodamine B. Meanwhile, compared with the dif?culties of powders and nanoparticles in recycling, the ?exible and free-standing composite makes it easy for recovery of heterogeneous catalysts. The photocatalytic mechanism of np-Cu/CuxO was investigated.
关键词： Nanocomposites,Amorphous materials,Porous materials,Functional
更新于2025-09-23 15:23:52