TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The germanium source is germanium dioxide and/or germanium salt, preferably germanium dioxide. The reducing agent is sodium borohydride, sodium citrate or ascorbic acid, preferably sodium borohydride. The alkaline solution is sodium hydroxide at concentration of 2-10, 5-8, or 6 mg/ml. The germanium source solution is 2.6-26, 5-20, or 10 mg/ml germanium content. The acid solution is dilute hydrochloric acid. The resulting germanium source concentration of sodium borohydride solution in the third step is 3.2-12, 4-8, or 6.4 mg/ml. Preferred Method: The method further includes dissolving germanium dioxide in alkaline solution under ultrasonic irradiation, adjusting pH to 6-9 by adding acid solution; adding polyvinylpyrrolidone, stirring and fully dissolving; dropping sodium borohydride, placing in oil bath at 60-80 degrees C, stirring for 10-30 minutes; adjusting pH of solution to slightly alkaline, continuously reacting in oil bath for 7-9 hours until brick-red insoluble material disappears to give blue fluorescent solution; ultrafiltering germanium quantum dot from inorganic salt solution, redispersing dots in water, cleaning, and freeze-drying at - 50 to - 60 degrees C. The pH of germanium source solution is 6-7.5 or 7. Ultrasonic radiation is performed by using ultrasonic cleaning instrument. The stirring method is magnetic stirring for 15-25 minutes, preferably 20 minutes. The oil bath temperature is 65-75 degrees C, preferably 70 degrees C. The fourth step includes adjusting pH to slightly alkaline at 8-9, 8.2-8.8, or 8.5, setting oil bath temperature at 65-75 degrees C, preferably 70 degrees C for 7.5-8.5 hours, preferably 8 hours. The fifth step includes ultrafiltering using 10000-50000 MW ultrafiltration tube, preferably 10000 MW, cleaning by washing with water, and repeating operation for at least 3 times.    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The protecting agent is polyvinylpyrrolidone and/or polyethylene glycols, preferably polyvinyl pyrrolidone. The polyvinylpyrrolidone has average molecular weight of 50000-65000, 55000-60000, or 58000. The resulting concentration of dissolved polyvinylpyrrolidone in germanium source is 2.5-10, 4-8, or 6 mg/ml.