Quantum Dots

me in RiftOMG I didn’t even post in March!  If anyone is still reading, I’m sorry.

I’d like to think that completing the second novel in my Gamers and Gods trilogy is a good excuse — but it isn’t, because there’s no way for you to read it yet.  Oh well.

Word must have gotten out that I am an encyclopedia of useless facts;  some of you even ask me about them.  Quantum Dots have been in the news, in stories ranging from their potential to improve solar cells to their application to quantum computers.  So what, exactly, you may ask is this thing called a “quantum dot?”

I’ve decided to try to answer this question without resorting to the equations, eigenfunctions, and quantum wells that most physicists like me resort to.  (Maybe it’s vanity, but I like to set myself impossible tasks to keep my aging brain active. )  I’m afraid I will have to mention atoms, the tiniest bits of identifiable matter and electrons, those invisible pieces of electricity.  So here goes.

Many of you might still, in spite of the Great Recession, be holding onto the American dream of the two car garage, or at least have two cars in the driveway, because it’s pretty hard to raise a family on one paycheck these days.  Think of your house as an atom — one that can hold onto only two electrons (the cars).

Long before I studied physics and had a career in Web development, my parents, for a time, lived in (I swear!) a place called Webwood Court.  A branch off a main road, it ended in a big disk of asphalt with driveways radiating off  it like the spokes of a wagon wheel.  (A brother of mine lives on one of these places today, although the street that ends in it is called a lane instead of a court.)

My point is this:  although the driveways radiating from a “court” may only hold two cars each,  you can park cars in the central area, instead of in the driveways. That can be rude, if you block the driveways.  But what I’m saying is, if houses were atoms, and driveways the “orbitals” that hold two electrons, this central unclaimed area is like a Quantum Dot:  it can hold more than two car/electrons that are not actually attached to any of the surrounding atom/houses.  A quantum dot is like a parking lot for electrons.  You can push electrons into it, and they will tend to stay there.

If you don’t already know, these quantum dots have some peculiar (and useful) properties.  For example, you may know that different chemicals are usually different colors.  But did you know that when you make quantum dots, you can make them all out of the same chemical –and get different colors?  It’s true.  It turns out that the size of the dot, rather than its ingredients, controls the color.  I won’t waste your time with math.  The relationship is simple.  Big dots are red (lower energy), tiny ones are purple (higher energy), and you can get all the colors of the rainbow from sizes between big and small — and all without having to use a lot of different ingredients.  Basically, this is because red light waves are longer — they need more room.  Purple light waves are shorter — they can fit into smaller regions.

That wasn’t so painful, was it?  Isn’t Nature amazing?  Yes, I said Nature.  You don’t need a lab.  Quantum dots are so easy to make, Nature was doing it a long time before we found out about them.


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