Silver nanoprisms grown into structural colors by high power LEDs 

the projects you come up with never cease to amaze me. great work!

Fun fact, this triangular gran of the silver particles is why analog film companies call some of their stock, TRI-grain or Delta. Extar has a tri grain and illford Delta has this shape. it makes for a higher definition exposure.

Oh no. I have a centrifuge in shipping right now that I bought for dewatering nano particles. I did not realize until seeing that separation chart how much of a challenge is ahead for me and my $100 ebay centrifuge. Really excellent project/video as always!

A potentially fun follow-up experiment: Rig up a jig that lets you both illuminate the liquid with a specific wavelength OR sample it with the spectrometer in situ. This way you can turn off the illumination long enough to sample the absorption spectrum at regular intervals. It would be cool to watch the peaks shifting on the absorption spectrum in time-lapse.

Ben, this is super cool, every time I see an upload from you I know I'm going to not only learn something new and cool but then end up down a rabbit hole for the next few weeks, lol so thank you :)

I'm definitely saving this for later. In a few minutes the kids go to bed and roughly 45 minutes later I shall kick back in my recliner with this on the TV. Glorious Saturday Night Commence!

If the reactivity of the particles is "encouraged" by a given wavelength of light, it makes sense to me that they'd therefore react and grow *until* they're no longer (strongly) absorbing that wavelength. If that's the reason, that also explains why irradiating with a lower wavelength of light doesn't shrink the particles. TL;DR: if we assume the reaction occurring here is strictly crystal growth and that reaction is *enhanced* by light absorption, then we expect both effects that you seemed slightly surprised by (absorption wavelength != exposure wavelength; and the inability to reduce the absorption wavelength.)

Ben, one of the ways that nanoparticles are prepared for TEM is to place a droplet onto your substrate, wait for some time for the particles to settle/adhere to the substrate, blot the supernatent out with filter paper, and optionally wash by dropping wash solvent and blotting. There are a lot of surface modification tricks to try to get more particles to stick, such as plasma cleaning, UV-ozone, spin coating charged polymer solutions, etc. It might take a few iterations of sample loading (e.g. apply multiple droplets) to get enough visible sample. Definitely not easy and unfortunately not well described in literature (generally passed down via institutional knowledge in labs studying nanoparticles).

I wish I had a friend like Ben IRL to just unashamedly totally nerd out with over spectroscopy, electron microscopes, cryogenics, lasers, x-rays, and superconductors.... 😿

One sidenote concerning the stability of the NaBH4-solution: You could basify it in advance (to like pH 10-11), which would increase it's lifespan by orders of magnitude. Just seems like a possibility, since the final reaction mixture needs to be basic anyway. So a mixed stock solution of NaOH and NaBH4 could be used instead of two separate ones, since the required amount of NaOH is also known (2mL 50mM NaOH stock solution)

I love your old JEOL JSM T-200. I worked for JEOL for about 10 years in the early 90's. I had several of that model in my service area, along with the later 300 series models. They are a great little scope when working properly. The 10nm resolution is only with Gold on carbon @ maximum KV very short working distance. The sample must be heated to ~ 100C before being transferred to the vacuum. Also must have very good chamber vacuum. low e-6 torr minimum. It is a pain, and I can remember the struggles when resolution had to be demonstrated.

When I needed to image citrate-terminated gold nanoparticles in SEM, I used to deposit them onto poly-electrolyte multilayers. Surprisingly simple to set up. Simply prepare your imaging surface (the CD ROM in your case) by alternatively dipping it in solutions of polystyrene sulfonate (PSS; a negatively charged polyelectrolyte) washing with water, then dipping into poly diallyl dimethyl ammonium chloride (PDAC; positively charged), and washing in water again. Repeat the process 3-5 times to ensure a good coating of the poly electrolytes. Make sure you finish the treatment with PDAC so the surface will tend to be positively charged, so that the negatively charged nanoparticles will adhere to the surface. Simply leave this surface in the nanoparticle solution for an hour or two and you should have a even monolayer of individual particles to look at.

Two ideas for reversing transition: 1) Add precursor silver particles over time to encourage stealing atoms from plates. 2) Try going one wavelength step at a time, preferably try it with a smallest wavelength step you can get.

Dang, I never knew how much I wanted a multispectrum monochromatic LED light, that is a super cool idea! I've got 9 different wavelengths of laser pointers which are also very cool for studying light absorbtion in different materials but now that I see this video I need the LED equivalent. It's amazing how much LED technology has evolved in just the last decade, being able to get this many monochromatic LEDs with such a high output power for the relatively low price they cost is incredible. I also think a flashlight version would be pretty great too, with a wheel inside that rolls through all the different wavelengths so only one is on at a time, that would be neat...

10:08 I have been wanting to build one of these to test out astrophotgraphy light pollution filters. Mouser sells some very specific LED wavelengths, such as 656.28 for Hydrogen Alpha.

The red-shift is due to inherent energy losses in the system (basically non-reactive vibrational modes). If you use flourescent nanoparticle systems as a model, I think it can help make sense of the situation. Basically, not all of the energy you put into the system is available for the output, be it fluorescence or building the particle. This is why the shift is always in the red (aka lower energy) direction comparted to the exciting wavelength.

Great video! I worked and made AgNP for my SERS research in grad school at UCSB. I made "bare" borate capped nanoparticles with just borohydride, but they were very tricky to get right and unstable once any contamination got into them. You can also use citrate directly as a reducing agent to make "nanoegg" ovaloids by heating a AgNO3 and citrate solution. These will provide stable citrate capped AgNP. Also, majority of absorbed light usually goes into creating plasmons (surface plasmon resonance). The electrons excited by this process can go on to participate in reactions, like reducing Ag ions in solution onto their surface. Might be an explanation on why the AgNP grow irreversibly with intense light.

Awesome Project! About the red shift: Did you consider if the refraction index of the medium might have an effect? Or even the shape of the cylindrical container?

"I'd like to show you these silver nanoprisms" Truly a man of my own heart

I think photoelectric effect is interacting with plasmon resonances. Short wavelength (high energy) light causes electrons to be ejected from the particle surfaces and then the solvent captures a silver ion to neutralize the particle. This continues until the particle gets small enough that its plasmon resonance frequency equals the light's frequency; at this point, the plasmon resonance shields the particle's surfaces from the light. Once the particle is too small, no longer wavelength light can reach it to cause dissolution. You could check this model by adding some fresh solution to see whether the color could be reddened in that case. Adding fresh silver ions will allow all particles to grow until the photoelectric effect arrests the growth. Plasmon resonances will have normal modes in triangular prisms. Probably, the underlying fcc structure of silver plays a part in the triangular shape.

What always fascinates me the most is how people somehow managed to figure out this works in the first place. Thanks for sharing.

You are one smort cookie. Truly one of a kind among the RU-vid STEM community. Thank you for the content

This guy made the very best video I have ever seen when he made a very low temperature beaker go below 100 degrees below zero in a two stage cooling beaker that makes the atmosphere separate into liquid components by repairing a unit that can even make dry ice.

I love this channel. Every video is well researched and really well presented. The downside is we get a video every 2 months. 100% quality over quantity.

2:15 I love the branding on that Sodium Citrate. "It's Just"

Hey Ben, you should check out this paper: Bensley, Robert D. “Natural Color Photography in Colloidal Silver.”. As the name suggests, it involves creating color photographs out of colloidal silver using a standard black and white emulsion. Very interesting stuff.

If particles are catalyzed to grow when they absorb light, it makes sense that they keep growing until they are all too large to absorb the LED light. This would make the particle absorption peak longer wavelength than the LED illumination bandwidth.

The brief look I made into gold nanoparticles suggested they were much simpler to make, I think they used citric acid as both a reducing agent and an anti-clumping agent.

Science aside for a moment, your opening clip was framed into an incredibly inviting scene. Seriously, let a few weeks go by and just pause at 0:00 to admire the artistic thought that went into the shot.

This man deserves respect. He is the Bob Vila of shop tech.

Insanely obscure topics demystified and demonstrated is why I love this channel so much!

I have never clicked on a notification quicker than this one.

This is really cool. When I was in school we made something like this but with a rather more mundane size selection... it was CdSe nanocrystals (at the time we were still calling them microdots) and they were grown via Ostwald ripening... basically start with a mixture of Cd and Se mercaptan salts suspended in molten parafin, then set to a specific temperature for several hours and depending on the temperature, that would determine the size/color. I'm sure I've forgotten some critical details... it was almost 20 years ago. One thing I certainly won't forget though... the odor of bezenethiol (or thiolphenol for those who swing that way). It was like an unholy blend of smoke and anus.

I love watching your content when chronic pain wakes me up in the middle of the night and it takes 2 hours for a nerve blocker to do it's thing. Keeps me very focused on what your doing and talking about so I don't feel as much pain. Thanks again. Your awesome! 😎

This guy is so smart, it always hurts me to watch while being interesting at the same time.

It's great to see people so curious that they are willing to go through so much effort, basically just for fun.

Ben, you focus on the coolest of engineering + physics

That's science for ya... the answer to any question provokes several new questions that you otherwise never would have thought to ask. This also illustrates the difference between an experiment and a mere demonstration.

Neat! Sounds a lot like the chemistry of film photography!

I always get excited when the electron microscope gets screen time! I think projects on this scale are some of the most interesting.

As always, thank you for a great video Ben!

Always pumped to see you post. Hope you are doing well!

Another phenomenal video mate! I love all your content! Always engaging!

Your videos are all great, your attempts to taker it further are always interesting.

Every video you release blows my mind. Thank you so much and keep up the amazing research! ☺️

Great video! I love that you explain your process and any adjustments or changes you made along the way. 🙌

so cool to watch thanks Ben, love watching your videos.

There's a sweet irony about mentioning the hydrated forms of chemicals, and using the bag that says "It's just sodium citrate, nothing else!" on it as an example.

Great video! You always have such great content!

Amazing detail and tenacity as usual. Fabulous to see really interesting chemistry in such complete "stories"

Great stuff Ben ! The optical properties of silver are fascinating. Photography, mirrors and now colorful nanoparticles.

I didn't really have time to watch this, but thought I will just watch some introductory part in the beginning. But I couldn't stop, watched the whole thing! Very interesting stuff!

I'm surprised such a low density of a few shattered snowflakes make such good structural pigments. Thanks for the great science again.

I recently discovered that CMDITR channel as well! Some really awesome technical content on there

You’re a wizard, I absolutely love your work

Truly fascinating! Thankyou for your insight and your dedication to experimentation! Your content never ceases to amaze and inspire my mind.

I'd love to see a multispectral photographic imaging project using that light. Put an ancient papyri document (or whatever document you have handy if you don't have any ancient papyri lying about) flat on a vacuum plate with a monochrome astrophotography camera above it with the light at low angle. Image the document at each wavelength. Rotate the light 15deg around the center of the document, image again, and repeat through a full rotation. Then rotate the angle of the light up 15deg and repeat the entire process again. Ideally the light should be collimated (maybe a bigish fresnel?), and maybe place some filters over the LEDs to narrow the frequency range. Write a bit of software to display one of the ~2100 images from the set based on three inputs that select the lighting angles and frequency. The idea is to reveal hidden details in the document.

I gotta watch this when I have some more time - your channel is super interesting! :) I really respect the effort you put into making videos - they are outstanding!

nice to have you back!

This is literally like my biology, physics and chemistry classes from school but for adults that I actually enjoy 👌

Hey Ben always good to hear from you.

Just, wow. Thank you so much. I'm going to be learning about silver nanoparticles for the next week

Love your videos. Really makes me think and wonder. Guess this goes back to the effects of light on silver that was exploited by film for so long. Thanks.

I love these videos. You present knowledge in such an honest and valuable way. Major kudos! Lots of folks can learn a lot from these videos. I can only parody what others have said, which is that you present such advanced knowledge in such a simple way that it makes the knowledge digestible. It greatly appreciate it.

Super project Ben - great to see. :)

Super funky. I've only seen this with gold nano particles, but that was a while ago. Love this.

Thank you for the curious 🧐 work and sharing it with everyone. You are Awesome ManManaMan ✔️

Super interesting! Always a pleasure to watch your videos…

You're an icon of DIY science!

I don't know; this is my first video I've watched from this channel but when I heard that "...pretty crazy. Right?", something clicked in my mind.

Haven't seen the video yet, still gave a thumps up, because i know all his videos are great.

Thank you so much. I snagged all the parts on Digikey to build the broad spectrum LED board. I was planning to use a selection of noble gases for same but this is so much easier! This will also be great for the calibration of my telescopes optical spectrophotometer without having to point at known stars. Awesome content as always.

Brilliant video. Really stimulating and enjoyable.

This is the kind of content that keeps me on youtube.

Rainbow llama blood, fascinating, real research , great choice pf project. a clear energy transfer , the mechanism unknown, exciting. , the frequency shift. Love seeing the SEM images. so the particles are not 600nm like the cd pits but ~10x smaller. , Inspirational science as always. I bow to your use of chemistry. Silver, highest thermal conductivity, made some silver heatsinks for a micromouse competition.

24:41 The way you explained the process so far, that's exactly what I think would happen. The light of X wavelength gives the particles that absorb X wavelength a growth boost. So they would grow so big till they aren't absorbing it anymore.

Thanks, applied science after so many months!

I want one of those lights. Adjusting light color based on it's wavelength. it's so elegant. Genius. I couldn't build one if you gave me a year and unlimited budget.

this is wild. thanks a million for sharing and doing all of this

Nice work! Thank you for experimenting, it keeps me entertained. Very interesting videos!

The only channel where I hit the like button before even watching it. You may want to try raising the temperature (a little) during the reversal experiment. Temp has a huge influence on reaction kinetics, as you know.

Great content! Thanks for the work you put into this!

Really interesting video! It's also refreshing to hear which steps did not work in your process.

Fascinating, as always!

Always interesting. Always well explained. Thank you.

I've work with EM's and know the pain of sample prep !...cheers.

Absolutely amazing. Thank you for sharing this!

Wow, great walkthrough of the process 👍 And what a process Thanks for sharing yourexperiencewith all of us 👍😀

As a layperson with no education in science I watch pretty much all of your videos until the end. You're very good at explaining things and I'm always amazed at the breadth of your skills and knowledge and the amount of work you put into your projects.

An ultra sonic bath also works great for degassing solvents especially if you use it in short bursts. Heating the solvent also is a cheap and easy way to do it. It is great to see what you do in your garage, while we often struggle with stuff in a multi million dollar lab.

As always well done and interesting. Thank you for sharing it. Cheers!

Amazing project. This channel shows what RU-vid can be.

You never disappoint!

Excellent, as always.

@14:10 according to your assumption, one could make an artificial paper with enclose microdroplets of silver nanoprisms, which then could be "imprinted" by projecting a multicolored master image at 3 (or more, here just to stick alongside the RGB concept) specific wavelengths after each other, and so "save" a colored photo on type of "nanoparticle" paper.

Amazing video. I have a few comments and ideas: 1. You're talking about the *absorbance* of your sample at the end, but you are measuring the *extinction.* There is a big difference, because these particles *scatter* very strongly (as seen by the nice color range shown in the thumbnail), and what is transmitted is the source minus scattering and minus absorbance. 2. You could maybe filter the nanoparticles with a reverse osmosis filter. Just an idea, but you already got nice pictures anyway! 3. My theory for the growth mechanism is the following: If you irradiate a sample of silver nanoparticles they will absorb some of the light. However, this absorption may depend on the size of the nanoparticles. If small particles absorb more light than big ones they get fed energy and are more unstable, leading to dissolution and agglomeration into bigger particles. This would explain why you can't shrink particles by illumination - the big particles don't absorb as much energy and therefore have no reason to dissolve into smaller particles. This explanation does not offer a compelling reason for the spectroscopy results at 25:40, but I would argue that the spectrum just shows the emergence of smaller particles from remaining seed material, rather than the dissolution of the bigger prisms. The difference between the blue and black curve at 550nm is not that significant in my opinion (based on the shown sample size of 2, more spectra to compare would be nice) I have not yet found a simulator for silver nanoprism spectra, but there are online tools to calculate mie theory for spherical particles*. The extinction spectrum matches nicely to your measured data, -but the absorbance of the spherical particles does not fully support my explanation, as the difference by particles size (for spheres) is not very large- [EDIT: scrap that, the simulator I used uses a varying y axis. The absorbance is significantly size dependent]. This may very well be different for prisms though, any resources for calculating the spectra of silver nanoprisms are welcome! *RU-vid likes to delete comments with links to further resources, so I'll not link directly here, but instead try in a comment below this one. I'm sure you'll find one by googling "Javascript Mie scattering calculator" or similar.

Awesome video as always.

I love how your electron microscope looks like it was developed at the Los Alamos Trinity Lab.

I did this experiment years ago with nano spheres. The interesting part is that unlike the butterfly scales in that case it was the surface area and not the shape that makes the color,

Oh yes. structural colors in your garage. Why am I not surprised its you back at it again x)