Raw materials of SiC nanoparticles of 100 - 500 nm in diameter prepared via SHS method, as shown in Figure 1(a), were corroded into the mixture acid of Nitric and Hydrofluoric. The progress of the chemical etching can be expressed by the following three steps:

FirstlySiC + 2HNO₃ + 2H₂O → 2HNO₂ + 4OH⁻ + SiC⁴⁺                   (1)

4OH⁻ + SiC⁴⁺ → SiO₂ + CO₂ + 2H₂                                (2)

In the beginning of the reaction process, due to a large amount of CO₂ and H₂ present at the same time, and release of plenty of the reaction heat, this step was a drastic action. Plastic mixing of the miscible liquids and external temperature controlling can decrease the action.

ThenSiO₂ + 6HF → H₂SiF₆ + 2H₂O                                    (3)

Due to the formation characteristics of material preparation, the self-propagating combustion synthesis of the rapid reaction and fast cooling can lead to the non-equilibrium crystallization conditions. So, many defects on the surface of productions (crystal lattice distortion, dislocation, grain boundary and so on) will be formed, which results in the higher surface energy and lower corrosion activation energy. Rapidly corrosion can be developed without any additional energy like an electric current as reported in literature [7] -[9] . The hollow grid-like structure of the raw materials can be easily obtained after SiC nanoparticles etched for 1 h, as show in Figure 1(b).

The hollow grid-like structure plays very important role in the formation process of SiC QDs. As we know, the ultrasonic cavitation effect can generate strong shock waves and micro-jet in solution [13] , which can break the hollow porous particles into smaller size of SiC nanoparticles and fall to the aqueous solution.

After the aqueous solution has been treated by ultrasonic cavitation, size distribution of the SiC particles was inhomogeneous in the size scope of <10 nm to 200 nm. In an ultra-gravity field (at least 2000 g), centrifugation chromatography for the aqueous phase solution was used to collect the top part of the suspension; containing the uniformly dispersed SiC nanoparticles. TEM imaging and size distribution of the SiC QDs were listed in the Figures 2(a) and (b), respectively. Yellow exhibition of suspension in the aqueous solution under daylight exciting was also displayed in Figure 2(c), which has been reported in many literatures [7] -[9] .

As can be seen, the SiC QD dimensions are below 4 nm, obeying the center of the distribution approximately, the average diameter of 2.5 nm, which is similar to the former results [10] [11] [14] . The microscopic structure

and size distribution of the QDs are the most important factors on its optical properties. Many studies verified that the core-shell spherical structure of QDs with size of less than its exciton Bohr radius will display a strong quantum confinement effect.

As the same results of the former work [10] [11] [14] , the optical properties of SiC QDs can be listed as: 1) the largest value of photo luminescence (PL) will be displayed when it is excited in the scope of 320 nm to 360 nm for exciting light wavelength. The red shift for PL will occur with increasing the exciting light wavelength. 2) The PL of emission light will blue shift with the diameter decreasing of SiC QDs. There is an inherent relationship between the emission color-displaying and the sizes of the SiC QDs. Multi-color fluorescence can be displayed in one exciting wavelength according to the size. 3) The stock shift of SiC QDs will reach the value of 110 nm higher than that of fluorescence isothiocyanate (FITC) of 35 nm.

The Aureobasidium pullulans is aureobasidium of imperfect fungi and second-class fungi with the shape of yeast and hypha. Its pullulan production has excellent physicochemical and biological properties such as filmforming, fibrous, resistance oxygen, and easy decomposition [15] . Therefore, it was widely used in many fields such as medical, food packaging, and sewage treatment because of its non-toxic and harmless to human body.

The Aureobasidium pulluans cells in the culture medium solution with SiC QDs for different times were dropped onto slides and observed under a fluorescence microscope with 340 nm exciting wavelengths, as shown. in Figure 3.

The photoluminescence effect will happen and cause strong fluorescence emission when excited by appropriate light wavelength. At the early stage of cells culturing, 3 days, for example, the Aureobasidium pulluans will be stably marked on the cell membrane, displaying in the left-top position of Figure 3(a). Furthermore, the SiC QD material can be absorbed and swallowed by living cells or its hypha when cultured for over 5 days (Figure 3(b)). Fluorescence experiments have been performed for more time after the intake of nanoparticles in the cell and the cells were found to be still living (Figures 3(c) and (d)). Compared with the control group (normal method in the cell culture medium without SiC QDs), living cells form and grow normally during each period as the same aspects reported in the literature [15] . Therefore, it is believed that the SiC QD material has no cytotoxicity on cells and does not affect functions of the producing polysaccharides. The works of Bluet et al. have the same conclusions [7] -[9] . This has a great significance for tracking fluorescence imaging of the living cells within long-term-distance.

Many results indicate that biological function bondings including carboxyl (COO⁻), oxygroup (O⁻), and hyfroxy (OH⁻) on the surface can be formed after the SiC particles’ etching in mixture acid of HF and HNO₃

[7] -[14] . These biological function bondings play important role in stably fluorescence labeling and imaging the living cells. In the early stage, the SiC QDs will stably label the living cells by means of coupling with biological function bondings and protein of cell membranes. As the culture time extends, SiC QDs can enter the interior of cell, marking the nucleus for example, by endocytosis. Our results are in good agreement with the former reports [10] [11] .