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Dedicated to splitting water with sunlight
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Another printing option
It appears that keeping the printer up and running is the biggest problem that we and others have been running into as we get going this summer. We started working on a really simple method for preparing libraries at the end of the research class last spring that may be able to keep you going during printer down times. The procedure is to premix the various ratios of nitrate salt solutions in an array of test tubes (8x8 or whatever) and then spot these solutions onto the conductive glass. We prepared the glass by dipping it into an alkylchlorosilane solution to make it hydrophobic so the transfered drops of mixed nitrate salts would bead up. We pipetted only a few microliters onto the glass with an eppendorf pipette. We made a little template with holes in it to guide the pipette tip so we got even spacing of the drops. We used an 8x8 array with a pattern like that in our CoAlFe oxide publication (see downloads section). The concentrations of the metal salts were much less than are loaded into the printer cartridges since we are dropping on much larger volumes than are printed. We found that these larger drops had some problems with uniformity of the spots as they dried and were just beginning to experiment with drying agents as the semester ended. We tried things like polymers, glycols and other water soluble solvent mixtures. Perhaps a dishwashing drying agent such as jet dry might work well (but I really don't know what is in it). This method is very simple and cheap since a printer is not needed but a bit more labor intensive. Another advantage is that some of the lower solubility precursors might work better. The details of how to do this with uniform drying of the spots still needs worked out so feel free to experiment and share your results if you are interested.
Details
Thanks! This should keep us busy until we get our printer unclogged, although we had a few questions about the procedure. What was the concentration of the alkylchlorosilane solution, and what solvent did you use? What was your template made out of, and how did you make it? And what were the approximate concentrations of the precursors in this case?
Pipette method
I think a few percent solution of a dichlorodialkyl silane in methanol will work. Dimethyldichlorosilane or something like surfasil (http://www.piercenet.com/files/0614as4.pdf)
The template was just holes punched in a piece of cardboard such that the dispo pipette tips were tight when the tip was near the glass surface. Probably a two hole template with a larger and smaller hole would work better since it will keep the pipette perpendicular to the substrate.
You can do a simple calculation for the concentration of the precursor by starting with a guess of say 20 mM and calculating the total amount in the volume you pipette and writing a chemical reaction to form the oxide and then assuming a density of the oxide (Fe2O3 = 5.24) and then calculating the volume taken up in a cylinder the diameter of your spot. The final film should be on the order of 100 nm ±50 nm thick.
Good freshman chemistry problem!
Re:Pipette method
Hello to all,
With our printer problems, we decided to give the pipette method a try as well, here is what we have come up with thusfar:
-Make 3 stock solutions of metals at the concentrations calculated from Dr. Parkinson’s post.
-Make 10 different solutions in test tubes based on the ratios of the volumes used (i.e. 1:1:4, 1:2:3…etc.)
-On a slide with 5 X 4 grid, pipette 5 uL from each test tube into it’s respective holes (we allotted two holes per solution)
If we’re right, this will give us ten distinct combinations, all with the same total amount of metal.
If anyone sees any flaw in this method, please let me know. Suggestions are always appreciated.
p.s. We had some dicholodimethylsilane laying around from the 1970’s (at least) and it seems to work just fine on the FTO.
We spent some time yesterday
We spent some time yesterday afternoon preparing a slide for scanning. First we made a grid pattern by drilling holes through a piece. The holes had to be just large enought for the pippetter to fit through.
We then cleaned a slide and coated it with the silane layer. From there is was just a matter of pipptting our solutions onto the slide and putting it into the furnace. We are now ready to give scanning a try.
Question
How did you make up the silane solution?
Silane Solution
We put 3 mL of the dichlorodimethylsilane in 50 mL of methanol. We found that soaking the FTO for much more than ten minutes would leave a cloudy residue on the slide, so we've been using around five minutes, it seems to work well. We're not exactly sure how beaded up the nitrates will have to be, so we'll be working on that this afternoon.
If you're in need of silane, we still have a few rusted out (but unopened) containers from the 70's laying around if you'd like to make the trek up the hill.