![]() Surface chemistry for native porous silicon (pSi, Si–H). In this review, we have summarized the conventional surface modification methods, newly reported surface modification methods, and our perspectives. Accordingly, surface modification is the most important component in terms of the use of pSi materials. However, the oxidized pSi is necessary in the development of sensors, photoluminescent bio-imaging materials, and drug-delivery systems. In the field of optoelectronics or battery application, the oxidized pSi could degrade performance of materials. The reactive silicon hydrides on the large surface of pSi is susceptible to slow oxidation in humid air. Essentially, freshly etched pSi has silicon hydrides (Si–H) on the surface and residual oxides or fluorides are removed by the HF electrolyte ( Figure 1). With proper surface modification, pSi materials have shown the suppression of pulverization, low volume expansion, and a long-term cycling stability in the lithiation and delithiation stages as next-generation lithium-ion batteries.Īs we described above, the surface modification of pSi materials is imperative to improve the properties of pSi and its usage. ![]() In addition, the nanostructured pSi material is a promising anode material for high-performance lithium-ion batteries. One such approach, “drug loading in the pore and surface functionalization of pSi materials with disease targeting moiety”, was one of the biggest leaps in the field of drug delivery systems. Recently, the pSi micro- and nano-particles have been applied to drug delivery systems and controlled release systems, by using the biodegradation property of pSi. Due to a significant amount of research and the discovery of quantum confinement effects, photoluminescence, and photonic crystal properties of pSi, the focus has mostly been on creating optoelectronic materials, displays, sensors, and bio-imaging materials. The pSi materials have been widely used in various industries and basic science. The surface of the resulting porous silicon is covered mainly with silicon-hydrogen (Si–H) and partly with silicon-oxygen (Si–OH, Si–O–Si). Porous silicon micro- and nano-particles can be prepared using ultrasonication fracturing. A porous silicon layer is generated on the surface of the silicon wafer using electro chemical etching, and the layer can be separated from the wafer using lift-off etch. ![]() Schematic illustration for the preparation of porous silicon by electrochemical etching and ultrasonication. As compared to anodization and sonication processes, recently a new concept in electroless etching of Si powder has been reported that is an easily scalable process for the generation of pSi particles. The porosity, pore size, pore pattern, and particle size can be controlled by the fabrication parameters HF concentration, current density, electrolyte composition, and wafer (dopant type, dopant density, crystallographic orientation). So far, various types of pSi materials have been reported, including pSi chip, pSi film, and pSi micro- and nano-particles ( Figure 1). Silicon (Si) elements in Si wafer can be dissolved out to a hexafluorosilane (SiF 6 2−) ion in the electrochemical etching stage, with each wafer generating a different pore diameter p-type Si wafer (micropores, 50 nm). Porous silicon can be generated by electrochemical etching of crystalline silicon in hydrofluoric acid (HF) containing aqueous or non-aqueous electrolytes. Porous silicon was discovered in the mid-1950s, and its unique physical, chemical, optical, and biological properties allowed us to develop new disciplines. It has a melting point of 1414°c and a boiling point of 3265°c.Porous silicon (abbreviated as pSi) is a silicon formulation that has introduced nanopores in its microstructure. It is located in Group 14 as a metalloid solid at room temperature, it is relatively light weight and strong. Many scientists worked on the discovery of Silicon but it wasn’t until 1823 that Jöns Jacob Berzelius isolated Silicon by his reduction of Potassium fluorosilicate using Potassium metal to produce pure Silicon. This Silicon is often mixed with other metals to increase its conductivity. Silicon is most commonly used in semiconductors the most well known are computer circuits and microelectronics due to its property being able to conduct electricity. The most common forms of Silicon found in the earth’s crust are oxides like sand and quartz. The compounds of silicon are known as silicates and they make up over 90% of the earths crusts. It is most commonly found in compounds and never found naturally. 8th most abundant element in the universe and is the second most abundant element by weight on earth. It is a metalloid that has the atomic number 14 in the periodic table. Silicon (Si) is a crystalline blue-grey solid with a metallic appearance.
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