nanoparticles

9 Articles

A 3D-printed case encloses a number of electronic components. In the top left of the case, a laser diode is mounted. In the top right, the laser beam is shining into a cuvette, which is glowing red from scattered light. In the bottom right, a small breadboard has an integrated circuit and a few parts mounted. In the bottom left is a large red circuit board marked “Rich UNO R3.”

Measuring Nanoparticles By Scattering A Laser

August 30, 2025 by 6 Comments

A fundamental difficulty of working with nanoparticles is that your objects of study are too small for an optical microscope to resolve, and thus measuring their size can be quite a challenge. Of course, if you have a scanning electron microscope, measuring particle size is straightforward. But for less well-equipped labs, a dynamic light scattering system, such as [Etienne]’s OpenDLS, fits the bill.

Dynamic light scattering works by shining a laser beam into a suspension of fine particles, then using a light sensor to measure the intensity of light scattered onto a certain point. As the particles undergo Brownian motion, the intensity of the scattered light changes. Based on the speed with which the scattered light varies, it’s possible to calculate the speed of the moving particles, and thus their size.

The OpenDLS uses a 3D printed and laser-cut frame to hold a small laser diode, which shines into a cuvette, on the side of which is the light sensor. [Etienne] tried a few different options, including a photoresistor and a light sensor designed for Arduino, but eventually chose a photodiode with a two-stage transimpedance amplifier. An Arduino samples the data at 67 kHz, then sends it over serial to a host computer, which uses SciPy and NumPy to analyse the data. Unfortunately, we were about six years late in getting to this story, and the Python program is a bit out of date by now (it was written in Python 2). It shouldn’t, however, be too hard for a motivated hacker to update.

With a standard 188 nm polystyrene dispersion, the OpenDLS calculated a size of 167 nm. Such underestimation seemed to be a persistent issue, probably caused by light being scattered multiple times. More dilution of the suspension would help, but it would also make the signal harder to measure, and the system’s already running near the limits of the hardware.

This isn’t the only creative way to measure the size of small particles, nor even the only way to investigate small particles optically. Of course, if you do have an electron microscope, nanoparticles make a good test target.

The green CRT display of a scanning-electron microscope is shown, displaying small particles.

DIY Calibration Target For Electron Microscopes

June 12, 2025 by 3 Comments

It’s a problem that few of us will ever face, but if you ever have to calibrate your scanning electron microscope, you’ll need a resolution target with a high contrast under an electron beam. This requires an extremely small pattern of alternating high and low-density materials, which [ProjectsInFlight] created in his latest video by depositing gold nanoparticles on a silicon slide.

[ProjectsInFlight]’s scanning electron microscope came from a lab that discarded it as nonfunctional, and as we’ve seen before, he’s since been getting it back into working condition. When it was new, it could magnify 200,000 times and resolve features of 5.5 nm, and a resolution target with a range of feature sizes would indicate how high a magnification the microscope could still reach. [ProjectsInFlight] could also use the target to make before-and-after comparisons for his repairs, and to properly adjust the electron beam.

Since it’s easy to get very flat silicon wafers, [ProjectsInFlight] settled on these as the low-density portion of the target, and deposited a range of sizes of gold nanoparticles onto them as the high-density portion. To make the nanoparticles, he started by dissolving a small sample of gold in aqua regia to make chloroauric acid, then reduced this back to gold nanoparticles using sodium citrate. This gave particles in the 50-100 nanometer range, but [ProjectsInFlight] also needed some larger particles. This proved troublesome for a while, until he learned that he needed to cool the reaction temperature solution to near freezing before making the nanoparticles.

Using these particles, [ProjectsInFlight] was able to tune the astigmatism settings on the microscope’s electron beam so that it could clearly resolve the larger particles, and just barely see the smaller particles – quite an achievement considering that they’re under 100 nanometers across!

Electron microscopes are still a pretty rare build, but not unheard-of. If you ever find one that’s broken, it could be a worthwhile investment.

Continue reading “DIY Calibration Target For Electron Microscopes” →

Nanotechnology In Ancient Rome? There Is Evidence

January 26, 2024 by 47 Comments

Anything related to nanotechnology feels fairly modern, doesn’t it? Although Richard Feynman planted the seeds of the idea in 1959, the word itself didn’t really get formed until the 70s or 80s, depending on who you ask. But there is evidence that nanotechnology could have existed as far back as the 4th century in ancient Rome.

That evidence lies in this, the Lycurgus cup. It’s an example of dichroic glass — that is, glass that takes on a different color depending on the light source. In this case, the opaque green of front lighting gives way to glowing red when light is shining through it. The mythology that explains the scene varies a bit, but the main character is King Lycurgus, king of Edoni in Thrace.

So how does it work? The glass contains extremely small quantities of colloidal gold and silver — nanoparticles of gold to produce the red, and silver particles to make the milky green. The composition of the Lycurgus cup was puzzling until the 1990s, when small pieces of the same type of glass were discovered in ancient Roman ruins and analyzed. The particles in the Lycurgus cup are thought to be the size of one thousandth of a grain of table salt — substantial enough to reflect light without blocking it.

The question is, how much did the Romans know about what they were doing? Did they really have the means to grind these particles into dust and purposely infuse them, or could this dichroic glass have been produced purely by accident? Be sure to check out the videos after the break that discuss this fascinating piece of drinkware.

Continue reading “Nanotechnology In Ancient Rome? There Is Evidence” →

Holograms: The Future Of Speedy Nanoscale 3D Printing?

April 9, 2023 by 7 Comments

3D printing by painting with light beams on a vat of liquid plastic was once the stuff of science fiction, but now is very much science-fact. More than that, it’s consumer-level technology that we’re almost at the point of being blasé about. Scientists and engineers the world over have been quietly beavering away in their labs on the new hotness, nanoscale 3D printing with varying success. Recently IEESpectrum reports some promising work using holographic imaging to generate nanoscale structures at record speed.

Current stereolithography printers make use of UV laser scanned over the bottom of a vat of UV-sensitive liquid