Week of 3/13-3/19

Beckman Group 1 started baking their plate (BHS-1-52). This plate had 0.03 M of iron standard and 0.03 M of Al(NO3)3. The ratios of Al: Fe are 4:1, 3:1, 2:1, and 1:1. They are also going to make another plate similar to BHS-1-52 but will increase the ratio of iron standard. Group 2 decided to add a little bit of HCl to their bismuth nitrate solution, specifically 2.0 M in order to help the solution dissolve faster. However, the bismuth just ended up sinking at the bottom of the volumetric flask. Group 3 had made a 0.03 M solution of bismuth nitrate last week. As per the advice that was given, Group 3 also added a little bit of HCl, in order to help the bismuth solution dissolve faster but got the same results as Group 2. Group 4 tested two of their plates, BHS-4-54A and BHS-4-57, which they had made a few weeks back. One of the plates was treated with the UV for 15 mins and the other was treated for 30 minutes.

Canyon Crest got through both of the plates they had ready to test (3 and 5), epoxied five more (6 through 10), and tested plate 6 as well. They also annealed three more (11 through 13), including the product of the evaporation/hot plate mini-experiment. They were also able to create two new plates, Ba:Cr:Sr and Fe(NO3)3:K2Cr2O7:KOCN (14 and 15). They had issues with the spotting template not lining up with the kit, so they made a new template which should hopefully result in less overlap between spots when testing future plates. Next week they hope to be able to test plates 7 through 10, epoxy 11 through 13, anneal 14 and 15, and perhaps make a new plate or two.

San Marino Green Team Tested their Cu and trace amounts of Zn plate from last week (99:1 and 999:1 Cu to Zn). Everything on the plate is different shades of grey but there doesn’t seem to be any predictable trend for why certain spots appear darker than others. Possible explanation could just be slight variations of how much volume is put down for each spot, though that seems unlikely to be responsible for such varying darkness differences.

When a positive bias was applied to the plate before scanning, the area of the plate without spots would peak, while the actual spots themselves were quite low.  However, when negative bias was applied, the peaks were inverted so that the lowest peaks before were now the highest peaks. This means that in the copper reversed the current so that it would read a negative value. Overall, for every scan performed, the same spots peaked, usually the spots that contained the most copper.  To test this hypothesis, they made a plate with only the highest and lowest amounts of copper to ensure that the data is accurate.

Blank Team Testing a plate with Ba because of good results on the SEAL database.  They are using Mn to test it with new metals and see if it still has issues with flaking as it did last year. Both pure Ba(NO)2 and Fe(NO)3 spots were flaking, likely due to too high temp, since this is a brand new Fe solution. Ba and Zn formed Barium Sulfate precipitate (white spots) where the spots become more white/opaque with increasing Zn concentration. Some of the spots flaked or dissolved in the NaOH solution upon testing, which has all blue bars.

Idea for new plate: Paul explained that because the optical band gap acts as a “cutoff point” for light, only higher-energy wavelengths above the band gap are able to excite electrons. The band gap is also the amount of energy released when the electron falls back down to the valence level. We are interested in this energy, so we want larger band gaps. However, larger band gaps mean that more light is excluded. Thus, we want to maximize the size of the band gap without excluding too much light. A possible solution is to link a series of plates in succession, each with different materials that absorb different wavelengths. For example, violet on top, blue, green, and red on bottom. We need 1.23 eV to oxidize water. Thus, we need at least a 1.23 eV band gap. http://pubs.rsc.org/en/content/articlehtml/2009/cs/b719545c

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