Greetings fellow nerds.
In this video, we’re going to grow tiny crystals of silver metal under the microscope.
We’re going to grow the crystals by electrochemistry. The setup is actually very simple.
I’ve tapped down an aluminum wire cathode and a silver wire anode to this plastic tray.
It’s connected to these batteries through a 470 ohm resistor to limit the current.
Now the electrolyte is a saturated solution of silver nitrate that i’m applying between
the electrodes. I don’t need very much since we’re going to
be doing this under the microscope. Now to slow down evaporation i’m putting this
glass slide over the drop. This also has the advantage of making the
surface shape flat and allowing us to easily keep focus under the microscope.
Okay, let me take it to the microscope. The deposition occurs on the cathode or negative
terminal so that’s where we’ll focus our attention. I haven’t connected the battery and resistor
yet so that gives me time to do so. Now, first we’ll look at highest magnification
at the tip. Let me connect the power through the resistor…
and look at that! Those are microscopic crystals of silver metal
growing at the tip of the aluminum wire. I’m actually time-lapsing this as the growth
is actually very slow and is occurring over the course of three hours.
As it progresses you’ll notice the crystals getting all deformed and no longer looking
like perfect crystals. Two things are causing this, first the crystals
are hitting the glass cover. Second, growing crystals electrically is not
an even process since the parts with highest charge density grow fastest.
Since charge density is not uniform for an irregularly shaped object, crystal deformation
is really hard to avoid. Nonetheless, the time-lapsed results are still
spectacular. Let’s try that again.
This one i filmed over the course of ten hours and under time-lapse you’ll see a lot of things
happening around it as it grows. This is actually me fighting off various side
effects like bubbles forming and the solution crusting over every hour,
forcing me to keep removing and cleaning the slide.
Every time i did so i disturbed the crystal growth and thus it became even more deformed.
Nonetheless, We’re still seeing actual pure silver metal electrically crystallizing out
of solution. Not a salt or metal ion, actual raw metal.
This is not something most of us will ever see in our lifetime.
So what’s happening is that at the anode, which is not on screen,
the silver metal is dissolving and releasing silver ions into solution.
At the cathode the silver ions are electrodepositing on to the aluminum wire form silver metal.
It’s a very simple reaction, but its quite amazing when you have a microscope to see
it. I’m using an aluminum metal wire as the cathode
simply because I didn’t have another silver metal wire available.
Here i tried it again using a diluted silver nitrate solution.
Since its not saturated it doesn’t crust over as quickly or produces as many bubbles,
letting me film longer without disturbing the growth.
But as you can see, instead of hard crystal edges,
the dilute silver nitrate grows a more feathery appearance of many smaller crystals.
Kinda looks like I’m growing a silver tree. A microscopic one.
Now so far I’ve been limiting the current with a resistor to get slow and controlled
growth. Now i’m going to apply the voltage directly
to the electrodes. Ready, go.
That is not time-lapsed, that growth is actually happening in real time with the much higher
current. The solution doesn’t have time to diffuse
in and form large crystals so instead the crystals grow outward in branches
composed of many smaller crystals. OK I’ve stopped the current. These branches
are actually quite fragile and will easily fall apart.
Now I’m putting the resistor in and going with slow growth while time-lapsing the video.
You can see the branches get thicker as now the solution has time to diffuse in and deposit
the silver more evenly. But you’ll notice the tips are growing faster
than the stems. This is because the charge density is greater
at the tips. Let’s try that again.
This time I’m going to use that large silver crystal hunk we grew slowly a few runs back.
Let me prepare the slide and get everything into position.
I’m also using saturated silver nitrate solution for this particular run.
I’m going to apply the current… now. Whoa, that was different.
Look at that, we got a few things happening here.
OK I’ve turned off the current, let’s examine our handy work.
Look at that, these branches are composed of different sized crystals, but mostly cleanly
formed. Back here at the base the original crystal
hunk is now coated in a fine layer of small crystals, kinda like frosting.
Looking around here… oh look at that, looks like some kind of silver metal plant.
I betcha some sci-fi filmmakers are getting ideas for an alien world from this.
Anyway, I hope ya liked this simple experiment into the microscopic beauty of electrochemistry.
Thank you very much for watching. Please subscribe, like and comment.