Using four-dimensional electron microscopy to track diffusion of nanoparticles in a liquid

August 28, 2017 by Bob Yirka, Phys.org report
4D imaging of nanoparticle diffusion in liquid. Credit: Xuewen Fu

A team of researchers at Caltech has developed a way to capture on film the superfast propulsive motion of Brownian objects, particularly those at the nanoscale. In their paper published on the open-access site Science Advances, the team describes using four-dimensional electron microscopy techniques to capture real-time imagery of gold nanoparticles as they diffused in a liquid.

Tiny particles suspended in hot liquid are observed to move in a seemingly random fashion. Such movement was noted by Robert Brown in the early 19th century, a phenomenon thus called Brownian motion. In more recent times, researchers have focused on Brownian motion as it relates to even smaller particles—micro and . Unfortunately, due to technological limitations, it was previously impossible to capture the action on film—instead, researchers have pieced together stills taken using an electron microscope. In this new effort, the researchers report on a technique they have developed that overcomes this problem, offering a new way to study diffusion of extremely .

The new approach involves the use of four-dimensional microscopy, which entails using both extremely fast laser pulses and transmission electron microscopy—it is based, the researchers note, on a pump-probe working mechanism. The first of two lasers excites the particles, while the second takes a picture of the action—it happens so quickly that the results can be viewed as video.

In their experiments, the researchers fired a first pulse at , then fired a second pulse that captured images of tiny bubbles forming near the surface of the nanoparticles and exciting them. Increasing the energy of the first pulse, the team noted, resulted in merging many of the tiny bubbles, causing different types of movement by the . The researchers suggest their technique could be used by other researchers to study dispersion systems, particularly those that are out of equilibrium. It could also lead the way, perhaps, to the development of light-powered nanorobots working inside liquid systems.

Tracing photoinduced nanoparticle diffusion. Credit: Xuewen Fu

Results of nanoparticle experiment. Credit: Xuewen Fu

Explore further: Combining pulsed laser with electron gun allows for capturing fast motion of nanoparticles in a liquid

More information: Xuewen Fu et al. Photoinduced nanobubble-driven superfast diffusion of nanoparticles imaged by 4D electron microscopy, Science Advances (2017). DOI: 10.1126/sciadv.1701160

Related Stories

The dance of hot nanoparticles

September 8, 2010

(PhysOrg.com) -- "Brownian motion is a very old concept," Klaus Kroy tells PhysOrg.com. "The laws explaining it were formulated more than a century ago by Albert Einstein. However, we are finding some interesting divergences ...

A 'nano-golf course' to assemble precisely nanoparticules

October 3, 2016

Whether it has to do with making pens or building space shuttles, the manufacturing process consists of creating components and then carefully assembling them. But when it comes to infinitely small structures, manipulating ...

Recommended for you

Gravitational wave detectors to search for dark matter

August 16, 2018

Gravitational wave detectors might be able to detect much more than gravitational waves. According to a new study, they could also potentially detect dark matter, if dark matter is composed of a particular kind of particle ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.