happy new year!

Instead of actual chemistry or even pictures[1], I present you with...the top five most random Google searches that ended up here:


5. ouch
Random? Kinda, I guess.

4. firearms curiosities
This one came out of Tehran, IIRC.

3. turns organic solvents pink
Something I would never have thought to google.

2. don't see wheels in carbon
Sounds completely off-the-wall unless you are a car enthusiast.

1. satan's solvent
My absolute favorite. I wonder which solvent they meant? Personally, I hate hate hate DMF.


Next year there will be ten instead of just five, and they will be more random. After all, CBC has only been alive for about three months. There's room for improvement. Thanks for reading, and here's hoping you start 2007 hangover-free! [2]



[1] because I've been lazy and haven't been in the lab

[2] Otherwise, I hear all the sharp pointy hexagons in the background hurt your head.

a new approach to solar cells?

This paper has been out for a while, but I've been meaning to write something about it anyway. Most organic solar cells use nice, normal carbon-based compounds as donor and acceptor materials. While some of these have decent charge carrier mobility ("decent" is a relative term!), there is another important factor to consider--the exciton lifetime. This is the amount of time the exciton can last before recombination. Recombination occurs when the electron and the hole annihilate each other. This may or may not involve release of a photon. (In OLEDs, recombination is the desired outcome. Not so for solar cells.)

Photoexcitation will give a singlet exciton. ΔS=0, no spin flips with excitation, right? In most light-atom-only (read: organic) compounds, L-S coupling is observed, and ΔS=0 holds. For heavier atoms, spin-orbit coupling takes over. Consequentially, ΔS=0 doesn't matter so much.[1] This enables intersystem crossing to a triplet state...which is cool, because triplet excitons last a lot longer than singlet excitons.[2] Increasing the exciton lifetime also increases the exciton diffusion length. This means the solar cell can be thicker! If it's thicker, it can absorb more light.

This is the rationale behind using Pt-OEP. A heavy metal, such as platinum, enables spin-orbit coupling. In other words, the excitons used by the solar cells in the aforementioned paper are triplets! Unfortunately, Pt-OEP has a very low charge carrier mobility and doesn't absorb at all the wavelengths emitted by the sun.

Still, the paper's worth reading if you haven't gotten around to it already (it was published in 2005).

[1] The first rule of quantum is: the rules don't always apply. Forbidden transitions still occur.

[2] Never mind that spin-orbit coupling affects this also...

stalker alert?

This arrived in the mail yesterday:

As much as I appreciate their lovely equipment in the lab, I don't think I'll be buying any for my apartment in the near future. (The kitchen is small enough already.)

It's also a little creepy that they know where I live. Or am I just being paranoid? I know other people must get similar junk mail. What are your thoughts on it?

get your tenderbutton fix

A new column by Dylan Stiles is out! Go read it!

Also, go vote for your favourite chemistry blog. The poll is all the way over on the right side. Owing to Mitch's colourblindness, you may have to highlight the whole thing in order to read any of the text.

On a somewhat-related note, ChemBark is taking nominations for the 2006 Chemmy Awards.


While it is the end-of-year holiday season, I can't seem to stay out of the lab. So, posting will be light over the next week or two, but you will get to see some nice shiny crystals here in a few days.

new background!

Comment if you like it! The dots were really bothering me, and I figured graphite was much more appropriate anyway.

oxygen--part two

Back to something I started a while ago and didn't finish: how to generate singlet oxygen. Probably the best-known means is photosensitization--use a dye (Rose Bengal, Methylene Blue, etc.) and a lamp. The dye is photoexcited and transfers its energy to oxygen, giving the singlet.[1] While this can involve some pretty cool-looking lamps (see left), it doesn't have to--you can do it Dylan's way with a lamp from Home Depot. (This group has even managed to do it without solvent!) Photochemical reactions can have some scale-up issues, though, despite being super-cool.

Alternatively, you can use peroxide and things involving metals (ew, metals, ick). Molybdates, peroxotungstates and La(OH)₃ seem to work alright.[2] CaO₂ appears to be the most popular, but it sounds kinda tricky to make. (Anyone done this?)

And then there's a fun little reaction I did a while ago.[3] Uses a weird little hypervalent iodine compound--[Bis(trifluoroacetoxy)iodo]benzene, oft-abbreviated as "PIFA"--and catalytic H₂O₂ to generate singlet oxygen.

This was dead easy to set up and about the only thing I've done that's given a respectable yield. If a knuckle-dragging undergrad like me can manage not to screw this up, just about anyone can. As an added bonus, the benzofuran I started with was the color of yellow highlighter ink. (No picture, though. Sorry!)

[1] You really don't want to get me started on energy transfer, especially since I am already very excitable. Maybe a nice long post will appear about it in the future.

[2] Found a review on this a while back. Fairly short & sweet. Have fun.

[3] Here is the paper! Go try it! (Especially if it's a bad day and nothing else is working. This will make you feel better.)

Have you seen this girl?

A Japanese artist(?) has made a pretty creepy video of what he calls Ferrofluid sculptures. I have to say, this video creeps me out, but it does use ferrofluids, which are pretty awesome. A ferrofluid is a dispersion of iron nanoparticles in (usually) water, which can interact with magnetic fields to generate corrugated patterns that look like this:



Ferrofluids are more than just artsy and freaky-cool. Its magnetic properties have found use in the IT, optics and defense industries. They will probably be partly responsible for this guy looking for Sarah Connor.

And for the truly bored during this Festivus break, here's how to synthesize your very own ferrofluids. Have fun!

crystals!

Lately there has been some talk about the importance of crystallography on Whistling in the Wind and Chemical Musings. While some interesting points about modeling in general and drug design in particular come up, some of us who are less interested in pharma-chem are still in need of crystallographic data.
Semiconductors, the molecular love-children of people who design materials for use in devices such as transistors (and solar cells and OLEDs and others), have electronic properties that are closely related to their crystal structures.[1] Charge carrier mobility in crystals of organic semiconductors depends on the crystallographic axis along which the mobility is measured. In other words, if you're trying to build a single-crystal transistor, you had better have a crystal structure so you can tell how to orient the thing for highest mobility. More importantly, the band structure of a semiconductor depends on its crystal structure. (Although I would really like to go into more detail here, k-space really hurts my head.) I will probably elaborate on this topic after a semester's worth of crystallography. Until then, ask your local crystallographer or solid-state physicist, or consult the Britney Spears guide to Semiconductor Physics.

Have a picture. Here's the band structure of silicon carbide (not organic, but good enough as an example of sorts.)

Taken from here

[1] Polymers are an exception of sorts, since they are too weird to have regular crystal structures...

alert!

Check out this post on A Synthetic Environment about moonshine! So cool, I had to mention it.

Today's post is brought to you by...

Neodymium. It's interesting enough, for a metal. Makes neat little magnets that will mystify your cats for hours, not to suggest that's difficult. My question for you: Can you tell me what the magnets are sticking to in this photo?

Anyone who has construction experience should know.

I didn't intend to take a week off without posting! Finals are over, by the way, but I've seen so much carbon lately that I need a (brief) break from it. This also explains why You can expect a post or two about magnetic materials soon, and a brief series about how field-effect transistors work and what you can do with them.

For anyone else who is going through a week of exams, my condolences.

JACS: copy editors needed?

Confession: I am a bit of an English nazi.[1] Certain things really drive me nuts. Confusing plurals with possessives, "its" with "it's," little misspellings...all of these things make my left eye twitch a little. It's one thing to see it in a hastily written email or IM or blog post. It's painful, but survivable, to see it on a sign advertising for a newspaper. When you're publishing a paper on transistors, though, and you can't spell "transistor," I go a little nuts. That's just a single-letter lapse of thought, though.[2] There are worse things you can do.

Quick! Before they fix it! This paper isn't really bad at all. There's a cute little crystal structure in there. But there is one grievous error. See the table?


"Something times ten to the fourth" cm²/Vs is not something you usually see for the charge carrier mobility in an organic semiconductor. Most people are very, very happy if they see a mobility of, say, 4 cm²/Vs...and that's kinda pushing it, since a lot of compounds don't see past the 0.1-or-so range.

So this looks like a really big deal. EXCEPT for this little sentence:

As expressed in Table 1, the hole mobility of 1 deposited at 22 °C was found to be 1.5 10-2 cm2 V-1 s-1, which was 100 times as high as that of 2 under the same condition.

In other words, don't panic. Someone just left out a minus sign or two in there.[3]
Maybe, just maybe, JACS should look things over a little more carefully before they're published.

Sometime after finals week I'll maybe do a series of posts covering transistors in plain English.


[1] NOT to be confused with an actual nazi. Nor am I English.
[2] A quick search for "transister" anywhere in the article from the ACS site got two hits. Two too many.
[3] Simple mistake. Happens to me whenever I see that curly S of death.[4]
[4] Curly S of death = integral sign

i <3 pyrex

What chemist doesn't like glassware? Alright, except for the part where it breaks. That's not so fun. So, given that glass is so important to some of us that we hide our round-bottoms[1], I thought I'd post about things made of Pyrex you DON'T see in the lab.

The most obvious is cookware. Lots of chemists also cook. Most of those can cook things that do not involve macaroni. Pyrex is nice stuff for baking.

And then there's art. A good deal of glass sculptures are the kind of things you'd expect to find on your grandmother's shelves collecting dust. Some artists are better than others, though.

There are also the, um, stranger uses. If I ever see either the object to the left or the object to the right in the lab...I'm running.[2]

And then we come to my favorite underappreciated use for glass. It's wonderful for jewelry...but you can't really use any of the above earrings if your holes aren't at least around a 12G. (The way gauging up works? You typically start with 18G and slowly work your way up--smaller numbers are larger sizes. Doesn't hurt if you go up one size at a time, in the shower, with antibacterial soap.) If I remember correctly, these start with 10G on the left, then 8G, 2 pairs of 6G and two pairs of 4G. For the skeptics, and the people who are thinking "ouuuuch," you can also see what one of these looks like in my ear. These can be rather nice for people with nickel allergies or stubborn earlobes. Plus, some of them are sparkly.

[1] I am definitely among "some of us." It's the only way I can keep it clean.

[2] Outside the lab? Maybe a different story.

oh, the irony

Evidently Whistling in the Wind's hiatus is over. To celebrate:

Have you noticed that...
as soon as you have crystals of the compound it took you a month or so to make, someone uses the last of the reagent you needed for the next step?

Self-cleaning cotton ftw

As Ψ*Ψ showed in the last post, pretty colors are awesome. But sometimes, pretty colors are better off in the flask than, say, on your new white shirt. And ugly colors are frankly never appreciated anywhere. Imagine the following situation: you're in lab, drinking coffee and working, it's midnight, and you spill some coffee on your lucky synthesis shirt- a white shirt you got for free from some hot female (or male) sales rep at PittCon. Well crap, now if you want to clean it, you have to go home and do a load of laundry and you're running a column right now and... well, looks like your lucky shirt is now your lucky coffee-stained shirt. "What if," you think... "What if I never had to clean this shirt again?"

Nanocrap to the rescue! A textile group in Hong Kong has developed a type of fabric they call self-cleaning cotton. In it, cotton is doped with nanocrystalline TiO₂ that act as self-cleaning agents. Upon irradiation with sunlight for a few hours, the titania acts as a photobleaching agent to remove common stains such as red wine and coffee. Furthermore, the titania possessed antibacterial properties, rendering the fabric truly self-cleaning, from both a colorimetric and microbial perspective. However, the casting process to embed these titania crystals in the cotton weakens the structure of the cotton, rendering the cotton more prone to tearing. Furthermore, I'm not sure how titania would react to your skin, so wearable self-cleaning cotton adds a whole new challenge to the mix. Still, this is a pretty awesome start to a interesting field, and one that blends nanocrap with materials with useful properties.

Just think: in a few years you'll have one less reason to go home. This is either a good or a bad thing, depending on your boss' thoughts on the matter.

what's in YOUR freezer?

I've come across a fair number of inorganic chemists who seem to think they have a monopoly on the pretty-colored solutions. This post is intended to prove them wrong. See?

I am in the midst of two solid weeks of exams, papers and pretty much hell. So I've been a little behind with this updating thing. Oops! After all this is over with, I'll have several weeks of no classes, and then...THEN I will have some serious chemistry for you. Until THEN, enjoy the pretty colors.