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Silica nanospheres have special optical properties such as relatively stable chemical property, high temperature resistance and corrosion resistance, so they can be widely used in Chemistry, biomedical and materials science fields. However, many existing preparation methods of silica nanospheres not only rely on expensive instruments, but also have long preparation cycles. Here, we propose an optimized Stӧber method to prepare silica nanospheres, which is simple, efficient and low-cost. Silica nanospheres with different sizes can be obtained by repeatedly adding the tetraethoxysilane (TEOS) solution dropwise at a constant speed. The characterizations by transmission electron microscope (TEM) and zeta potential meter reveal that the size of silica nanospheres gradually increases with the increase of the amount of TEOS. In addition, different concentrations of ammonia affect not only the rate of reaction, but also the final particle size of the microspheres. Afterwards, the silica nanospheres with sizes of 190 nm, 235 nm, and 284 nm were prepared into colored photonic crystal thin films by chemical self-assembly, and they appeared blue, green and red under the reflection of natural light. Finally, their reflection spectra were measured using a selfbuild characterization system, and found that their peak reflection wavelengths were 427 nm, 511 nm, and 622nm. These results indicate that the reflection peaks of the films gradually red-shift with increasing silica nanosphere size. The proposed optimized Stӧber method for preparing silica nanospheres is simple and efficient, which can greatly expand their application in various fields. For example, the surface of silica nanospheres can be linked to various chemical groups by silanization, which can be used for biochemical sensing. Colored films prepared from silica nanospheres also have potential applications in decoration and other fields.
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