HEPES applied to the preparation of gold nanoparticles CAS7365-45-9 CAS NO.7365-45-9

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HEPES, 4-hydroxyethylpiperazine ethanesulfonic acid, utilizes the reducibility of HEPES to transition metals at a specific pH value, and uses the HEPES-NaOH reduction method to prepare gold nanoparticles. This method is simple to operate, fast in response, and easy to control. There are few products and it is environmentally friendly.

Preparation of gold nanoparticles:
1. Prepare a chloroauric acid solution with a concentration of 0.05-10mmol/L;
2. Prepare hepes buffer with a concentration of 5-50mmol/L, and adjust the pH of the hepes buffer to 7.0-8.0 with sodium hydroxide;
3. Add surfactant to the HEPES buffer prepared in step 2 to prepare a surfactant solution with a concentration of 1-2mmol/L;
4. Introduce the surfactant solution prepared in step 3 into the reaction tank, and slowly add the gold chloride prepared in step 1 to the reaction tank according to the molar ratio of the chloroauric acid solution and the surfactant solution of 1:1-1:10 Acid solution, and uniformly stirring at a speed of 200-300r/min, reacting for 5-30min, to obtain a mixed solution containing nano-gold colloid;
5. The mixed solution prepared in step 4 is dried and purified by the nano-gold colloid to obtain nano-gold particles.
Taking the preparation of 200L of hepes buffer with a concentration of 50mmol/L as an example, the configuration method is: first weigh 2.38kg of HEPES and dissolve in 180L of deionized water, sonicate and shake until it is completely dissolved; then use a pH meter to measure this At this time, the pH value of the solution is about 5.4, so slowly add 0.1 mol/L sodium hydroxide solution and keep stirring until the pH is adjusted to 7.4; finally continue to add deionized water to 200L.

Preparation of HEPES:
method 1:
Using 1,2-dichloroethane directly as the solvent, add hydroxyethylpiperazine (5.00g, 0.02mol) and potassium carbonate K2CO3 (6.00g, 0.04mol) into a 100mL three-necked flask equipped with mechanical stirring and thermometer. , 50mL 1,2-dichloroethane, heating in an oil bath at 90°C (1,2-dichloroethane boiling point 85°C), stirring and reacting for 20h. The reaction was stopped, filtered, and the filtered salt was washed with 200 mL of ethyl acetate (EA). The filtrate was spin-dried to obtain 2.6 g of HEPES solid.

Method 2:
Add 11.0g (84.5mmol) of anhydrous sodium sulfite, 27.0mL (343.6mmol) of dichloroethane, 120mL of water, 110mL of ethanol, 50mg of copper powder, and 50mg of copper powder into a three-necked flask equipped with a magnetic stirrer and reflux condenser. The bath is heated to reflux. After refluxing for 22 hours, the reaction solution was evaporated under reduced pressure to remove water until all white solids were precipitated. This solid is mainly composed of product, unreacted raw materials and formed salt. The obtained solid and 500 mL of ethanol were added to a 1 L flask and heated to reflux for 40 min. It was filtered while it was hot, and the filtrate was cooled, and then placed at 0°C overnight. Suction filtration, vacuum drying, flake crystals were obtained, the yield was 11.40 g, and the yield was 81.0%.
Add sodium chloroethanesulfonate (15.10g, 0.08mol), hydroxyethylpiperazine (9.88g, 0.075mol), 60mL water, and oil bath into a four-necked flask equipped with a magnetic stirrer, reflux condenser and thermometer. Stir the reaction at 105°C. As the reaction progresses, the pH of the reaction solution will drop. Add 5mol/L NaOH aqueous solution dropwise to control the pH at around 9, add a total of 15 mL, and continue the reaction for 5 hours.

At the end of the reaction, the reaction solution was diluted with water to 500mL, and then applied to an ion exchange resin column (about 500g) for desalination purification. After all the reaction solution was applied to the column, rinse with distilled water until the pH of the effluent was 6, and then rinsed with 1mol/L ammonia water. , Collect the effluent (pH about 5-9) with product spots detected by TLC. Concentrate by rotary evaporation to 150mL, add activated carbon for decolorization, oil bath at 110°C, heat and stir for 0.5h, filter, spin-dry the filtrate, add 50mL ethanol, heat to reflux for 0.5h, hot filter, the white solid obtained is 8.63g after drying. Glacial acetic acid was added dropwise to the filtrate, the pH was adjusted to 5, cooled overnight at 0°C, and filtered. The obtained solid was 2.80 g after drying. A total of 11.43g with the aforementioned HEPES solids, with a yield of 64.5%.

The preparation method of 10mmol/L hepes buffer is as follows: accurately weigh 2.383g HEPES, add fresh three-distilled water to make the volume to 1L. Sterilize by filtration and store at 4°C after aliquoting. If it is used as a buffer in the cell culture medium, it is recommended to store the medium in the dark.

Hubei Xindesheng is a biochemical raw material manufacturer with 14 years of R&D and production experience. It can provide various specifications of biological buffers (HEPES, Tris, BICINE, CAPS, TAPS, etc.), chemiluminescence reagents, blood collection tube additives, color The original substrates, enzyme preparations, antigens and antibodies, etc., please call for more details!