Solvothermal Technique Guidelines

Transcription

1 Solvothermal Technique Guidelines When performing a solvothermal reaction, the first thing you need to do is to check the physical properties of your reactants. For a regular solvothermal reaction, there are solvents, metal salts, ligands and any necessary additives. The safety guidelines may vary based on their properties. Here are some general guidelines. Presynthesis-Preparation of Solvothermal Reaction 1. Metal Salts The properties of metal salts vary by what you are going to use. Some of the metal salts are highly water reactive. In such cases, a stock solution containing metal salts in an appropriate solvent is highly recommended. However, the stock solution should not be kept for long time, because unwanted reactions with water vapor, the solvent, and air might eventually take place and reproducibility of crystal synthesis will not be good. 2. Ligands Ligands are generally organic carboxylic acids. They are most stable as dry powders under ambient conditions. Some sensitive ligands might need to be stored together with a drying agent, such as Drierite, in a fridge. It is recommended NOT to make a stock solution of a ligand unless it can be used up within one day. The ligand should be mixed with the metal salts just prior to solvothermal synthesis. 3. Solvents. The majority of your solvothermal reaction is about solvents, and the following attachment is a table of properties of common organic solvents. Check your solvent before use. We sometime use mixed solvents, which usually contain one with high boiling point and the other one with low boiling point to grow crystals. The solvent with a low boiling point will decrease the tolerable temperature limit of the vials. Always double-check this safety issue with more experienced group members. Some solvents (especially DMF, DMSO) can decompose below a boiling temperature, generating toxic fumes.

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3 4. Additives In order to slow down the crystal growth process, some inhibitors, such as benzoic acid, acetic acid, trifluoroacetic acid (TFA), and tetrafluoroboric acid (HBF4), can be added into the reaction. A normal rule to follow is that anhydrous

4 acid should be used for the water-reactive metals salts. Also note that any fluorine-containing acids, such as TFA and HBF4 are extremely acidic and corrosive. They are also very volatile and any extent inhalation must be avoided at your best efforts. It is a good practice to handle all acids inside a fume hood, and all contaminated glass pipets or plastic syringes mush be diluted and rinsed with water before they are appropriately discarded. Unless necessary metal needles should NOT be used to get any acids, as they can react with each other. 5. Reaction Holder We normally use 2 ml and 4 ml (1 dram or 2 dram) vials to hold the solvothermal reactions. However, those vials are not able to withstand temperature higher than C. In this regard, the shorty vial (Borosilicate Glass, Wheaton, 4mL with Cap), sealed tubes or Teflon-lined stainless steel autoclave should be used. Specifically, DMSO must be sealed in either tubes or Teflon-lined autoclaved at temperature above 85 0 C. The sealed tubes will hold the reaction up to C, while the shorty vial (Borosilicate Glass, Wheaton, 4mL with Cap) is able to hold the reaction up to C with water as a solvent. One thing need to notice is that the content of any holder MUST NOT go higher than 2/3 of the vial at high temperature and no higher than the neck of those vials at any temperature. In addition, when we seal tubes, around 3 inches of the space are needed. Because we use a flame to seal the tubes, low boiling point solvents need special attention. 6. Sonication Sonication is usually the last step before you put your reaction into the oven. Most of the reactants will be dissolved by sonication. We have two sonicators one located in Room 2526 nearby the door and the other one in Room The one in Room 2526 set 5 minutes as an increment, while the other one in Room 2526 could be set at any time. Before you use the sonicator, make sure all your caps are tightly secured on the vials. During the sonication, caps can also be loosened. To avoid losing your reactions, it is better to check the caps during sonication as well. Let your vials stand up not laying down, or the water will wipe off some marker on the vials. Shake your sample thoroughly every 5 minutes. It is fine if not all reactants are dissolved, which will be later dissolved at high temperature. 7. For the people who is not familiar with newly designed experiments. After you design a series of reaction, make sure to check your reaction at least one senior group member. They will evaluate your design and check safety issue with you.

5 Synthesis 8. Use of oven If you have a lot of reaction vials going on, a larger container will help you to properly hold all the vials and tubes without disturbing others reactions. Rubber bands are a very BAD choice to hold the reaction vials, since they will melt with a terrible smell or even catch fire at high temperature. Instead, a larger beaker will safely hold a large amount of vials. In Room 2526, we have some ovens commonly set at 60 0 C, 75 0 C, 85 0 C, C, and C. In addition, there are two extra ovens could be set at ambient temperature. Ask the senior group member for guide when you need to set your own temperature. 9. Emergency Some accidents could happen in chemistry experiments. Explosion of vials is one of them. Whenever you find any exploded vials in the oven, close the hood door, report it immediately to the people in charge of lab safety and inform the people who own those vials. They will help to take care of it. The people who own those vials are required to clean the dirt caused by this accident. Post-Synthesis 10. Dealing with products Reaction with DMF, DMSO at higher temperature, must be handled in the fume hood. All the waste solvent must go to the waste container. 11. Recycle and Disposal of Vials Once you are done with your reactions, please collect all your vials and put them away. Please do not let your vials stand in the oven forever, or you will clean the oven whenever. The shorty vial (Borosilicate Glass, Wheaton, 4mL with Cap) costs $1 a piece, so that we d better to recycle them. The Teflon-lined autoclave could be washed as normal glassware. Other regular vials or tubes need to go to the special glass disposal container. The 20 and 40 ml vials can also be easily recycled sometimes. Especially, if the vials have no stains on the surface, recycling the vials are highly recommended.