There are a variety of patents that fully disclose how they produce nano sized fumed silica (patents.google.com). The process usually uses some type of halo- or organosilane that is heated to a decomposition temperature. You could also purchase a few different sized silica with very high purity form Sigma.com

Although the actual conditions of the producton of fumed silica are trade secret[ PATENTS], yet a general procedure and the Chemistry behind their production is given below:

(i) Fumed silica is manufactured by a continuous flame hydrolysis process of SiCl4. During this process, SiCl4 is converted into the gas phase and then reacts spontaneously and quantitatively in an oxyhydrogen flame with the intermediately formed water to produce the desired silicon dioxide.

2 H2 + O2 = 2 H2O

SiCl4 + 2 H2O = SiO2 + 4 HCl

2 H2 + O2 + SiCl4 = SiO2 + 4 HCl

(ii)During this chemical reaction a considerable amount of heat is released, which is eliminated in a cooling line. The only by-product is gaseous HCl which is separated from the fumed silica solid matter.

SiO2 is then converted into the HYDROPHOBIC FUMED SILICA dimethyldichlorosilane (DDS) in a fluid-bed reactor. The silane reacts with the silanol groups primarily with the formation of Si-O-Si (CH3)2 units, and as a result the material acquires a hydrophobic character. The number of silanol groups is reduced during the treatment to about 30% of the initial value.

(iii)Analogous reactions can also be carried out with other silanes and other HYDROPHILIC SILICA FUMES.

An abstract from a Patent is reproduced for your perusal:

Patent NO:US 6217840 B1

ABSTRACT

A method for producing fumed silica and a fluorine-containing product from a source of silica in solid form and a solid material containing fluorine, the solid material selected from the group consisting of sodium aluminum tetrafluoride, cryolite, aluminum fluosilicate ammonium bifluoride, sodium aluminum silicofluoride, and sodium fluosilicate. The method comprises the steps of digesting the silica in solid form and the solid material selected from the group consisting of sodium aluminum tetrafluoride, cryolite, aluminum fluosilicate, ammonium bifluoride, sodium aluminum silicofluoride, and sodium flurosilicate in a sulfuric acid digester. The digestion step produces a first gas component comprised of silicon tetrafluoride, hydrogen fluoride and water vapor. The first gas component is removed from the digester. The gas component recovered from the digester is heated to a temperature sufficiently high to convert the silicon tetrafluoride to fumed silica in the presence of the hydrogen fluoride and the finned silica is separated from the hydrogen fluoride.

The way I see it, the whole point of modern materials science is that such basic ingredients have to be purchased and NOT made by yourself. Commercialy available products should not cost a wealth of money and save your time while offering a definite quality standard. Once you are not going to improve the process of production but simply need it in your research as one of the initial components - buy it, don't bother to waste your time with synthesis of something that widespread.

Thank you dear S. Abd.El.Aleem ,,I feel this method is dangerious because of presence of hydrogen