Potassium fluoride,anhydrous
           Potassium fluoride,extra pure
           Potassium fluoride,Granular
           Silicon Dioxide
           Hydrofluoric acid
           Synthetic Cryolite
           Potassium Fluoaluminate
           Ammonium bifluoride
           Potassium Bifluoride
           Aluminium fluoride
           Sodium fluoride
           Potassium Fluorosilicate
           Fluorosilicic Acid
           Sodium silicofluoride
           Potassium Hydroxide Flakes
           Magnesium Fluoride
           Magnesium fluorosilicate
           Barium Fluoride
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As one can see, this decrease is much more pronounced for the meso-PS sample treated with hydrofluoric acid under UV light (the dashed blue line represents the background spectral evolution according to the Drude's model). It means that the holes concentration is significantly increased in the meso-PS layer after the treatment. This fact is also supported by a huge reduction of general electrical resistivity (more than two orders of magnitude) of the treated porous layer. This increase of the free carrier concentration in the treated samples can be explained by a considerable decrease of the donor-like and amphoteric surface defects responsible for the hole trapping in the p-type Si NCs. Indeed, these kinds of defects are known to be especially dominant in the as-prepared hydrogenated and partially oxidized meso-PS. The hydrofluoric acid treatment efficiently removes the surface defects playing the role of electronic traps for the free charge carriers. For example, the HF-induced disappearance of the donor-like states ensured by water and oxygen is clearly manifested on the spectra.

In conclusion, a continuous permanent treatment of Si NCs by hydrofluoric acid before and during their chemical functionalization with hydrocarbon chains allows not only to efficiently remove original surface defects produced during the fabrication of the NCs by electrochemical etching of bulk Si substrates but also to avoid appearance of the oxidation induced defects on their surface during photoinitiated hydrosilylation procedure. In consequence, stable sols of highly luminescent Si NCs in organic solvents with PL QY up to 20% are shown to be easily obtained. In addition, time control of the hydrofluoric acid action allows precise tuning of the PL wavelengths. Moreover, application of the same HF-based treatment to meso-porous Si (meso-PS) free layers leads to significant concentration increase of free charge carriers due to their liberation from the numerous electronic traps located at the near-surface defect regions. Such the observed effect will unavoidably ensure considerable improvement of the electric transport through the meso-PS network which is still an issue for various photovoltaic and thermoelectric applications.

Due to Hydrofluoric acid is very dangerous, according to the relevant laws of People's Republic of China, sulfuric acid, nitric acid, hydrochloric acid, hydrofluoric acid, sodium hydroxide, toxic agents, strong oxidizing agents, flammable reagents belong tube products. Since hydrofluoric acid belongs to toxic agents, organizations need to buy, such as school laboratory, Institute of Science, Academy of Sciences. From these organizations need to be out to prove, and then to the local Public Security Bureau for the record, out to prove, and the police took the two certification bodies to store to purchase chemical reagents. Here is a related events about hydrofluoric acid: in September 27, 2012 Chemical Manufacturers' Hube Global "is located in the eastern part of Gumi chemical plant exploded, killing five workers, about eight tons of hydrofluoric acid leak. About 3,200 people in the symptoms of poisoning due to inhalation of toxic gases in varying degrees of treatment. October 8 South Korean government decided to hydrofluoric acid spill occurs Gyeongsangbuk Gumi incident area designated as a "special disaster area."