Golden sandwich could make the world more sustainable
Scientists have developed a photoelectrode that can harvest 85 percent of visible light in a 30 nanometers-thin semiconductor layer between gold layers, converting light energy 11 times more efficiently than previous methods.
[...] In the study published in Nature Nanotechnology, the research team sandwiched a semiconductor, a 30-nanometer titanium dioxide thin-film, between a 100-nanometer gold film and gold nanoparticles to enhance light absorption. When the system is irradiated by light from the gold nanoparticle side, the gold film worked as a mirror, trapping the light in a cavity between two gold layers and helping the nanoparticles absorb more light.
To their surprise, more than 85 percent of all visible light was harvested by the photoelectrode, which was far more efficient than previous methods. Gold nanoparticles are known to exhibit a phenomenon called localized plasmon resonance which absorbs a certain wavelength of light. "Our photoelectrode successfully created a new condition in which plasmon and visible light trapped in the titanium oxide layer strongly interact, allowing light with a broad range of wavelengths to be absorbed by gold nanoparticles," says Hiroaki Misawa.
Enhanced water splitting under modal strong coupling conditions (DOI: 10.1038/s41565-018-0208-x) (DX)
(Score: 3, Informative) by Anonymous Coward on Wednesday September 12 2018, @02:25AM
The videos and internet instructions make it seem more complicated than it is so they can sell you stuff. You can do this at home with some stuff from home depot and Radio Shack / Fry's / Digikey.
First step is to grind everything to powder, chip, circuit board all of it, this can be done with a cement mixer from Harbor Freight and heavy steel balls, the noise is atrocious but it's cheaper than any sort of stamp mill you might try to buy online.
Second step is to heat that powder to the point that anything non-metallic burns to ash, with enough heat the metals will also melt and if you did this correctly and used a container with a rounded spot in the bottom, the molten metals will sink and condense at the bottom into a metal button made up of all kinds of mixed metals at the same time the ash will float to the top. You can use a little steel or lead wool to burn away the not metallic ash.
Third step is to pulverize the metal button into a fine powder.
Fourth step is to prepare a mixture called Aqua Regia,
This is a highly selective acid that will only take up noble metals like gold, platinum etc so the fourth step is that you pour the powdered metal in, shake stir and let sit and then repeat.
Now you have a liquid that has gold in it (amongst other precious metals).
Fifth step is to decant off the liquid, leaving the blackish metal sludge at the bottom, you can discard the sludge there's nothing left of value in it.
Next you add a chloride salt to the aqua regia. This will cause the gold to come out of solution and it will be greenish black to greenish gold.
This is gold salt and it's about 90% pure gold. You can heat it and melt it again to get a 92% pure ingot.
You can further purify the ingot to 99% simply by electrolysis.
Put the ingot in a salt water bath with. Attach the ingot to the anode side and attach a small piece of pure gold film to the cathode side. Run 5 to 12 volts of DC through it.
The gold atoms will leave the anode side and migrate to the cathode side, plating the cathode with 99+% pure gold.
When I started doing this in the early 1990s I could grind about a half ton of motherboards into about 10 ounces of gold ingots.
When I stopped doing this in the mid 2000s I was only getting a quarter of an ounce of gold per ton of source material, at that point it wasn't worth the electricity anymore. Also the local town grew up and was getting upset with me about what was coming out of my drain pipes.
I did find out that you can in fact skip the aqua regia stage if you're willing to settle for 80% when it comes time to do electrolysis.
The trick is to use a high strength magnet under the bath and some zeolite (fish gravel) in the electrolytic bath.
Also helpful is to use a membrane between anode and cathode.
The magnet (under the bath) causes the ferrous metals (which is most of the junk), to settle to the bottom. The zeolyte further traps the non-noble metals along with the noble metals that are being stubborn about their affinity.
This gives the electric current more time to pry the gold from the junk and carry it away.
The membrane (pourous enough for single atoms of gold to come through) , allows the gold to pass and any single atoms smaller than gold, but nothing larger.
This secondary setup saves money on aqua regia which quickly became my major cost center.
Once you're at 80% most refineries will buy your gold at $.60 to $.70 on the dollar, or you can cast it to jewelry such as rings and pendants and sell it to cash for gold places as 14k gold which tends to give you closer to $0.85 on the dollar vs spot.
Hope that's helpful!