Optimize nanobubbles with nanoparticle tracking analysis

Optimize nanobubbles with nanoparticle tracking analysis

Water treatment is a cornerstone of our world: innovations in this area deliver immense improvements in health and quality of life around the world. Nanobubbles show promise in becoming one of these innovations. However, absolute precision is crucial, as any issues in water treatment and quality problems can have serious consequences.

One of the key challenges in water treatment is the control of bacteria. The combination of trace amounts of food, room temperature heat, and low flow rates in reservoirs often make water treatment plants ideal breeding environments for many forms of bacteria.

Many chemicals and purification techniques are forbidden because water runoff from a treatment plant must remain fit for public consumption.  Fortunately, nanoparticles in nanobubble form offer an effective solution, not just in wastewater treatment, but in all hydraulic applications: irrigation, surface water treatment, aquaculture, oil & gas refining, mining, food safety – and more! 

What makes nanobubbles effective bacteria hunters

Nanobubbles are usually categorized as bubbles that are in the 100-200 nanometer diameter range. Inside the nanobubbles are gases – usually air or oxygen, but any gas can be used. These gases are the secret to the nanobubbles’ effectiveness against bacteria. The gases serve as reactive oxygen species (ROS), which are chemicals that act as signals that turn biological functions on and off. When one of these bubbles encounters such a microbe, it binds to it, bursts, and releases the ROS gas that essentially destroys the bacterium.

Nanobubbles effectively ‘find’ microbes and other contaminants: their negative surface charge attracts to positively charged microbes, and the hydrophobicity of nanobubbles means they will strongly attach to anything in the water – like a bacterium.

Another strength is their buoyancy: the balance of negative charges and extremely high surface tension of nanobubbles creates neutral buoyancy. Nanobubbles can therefore remain suspended in liquid for months without rising to the surface and releasing their gases into the atmosphere.

For example, ROS-loaded nanobubbles help locate bacteria in natural water sources, disrupt them as they attempt to form on various surfaces, and destroy them. What determines their effectiveness is nanobubble size, distribution, concentration, and surface tension.

Helping nanobubbles in their fight

Nanobubbles are easily analyzed when they are on the surface of a liquid: liquid-phase transmission electron microscopy (LP-TEM) is a straightforward tool for detecting the presence of these ‘surface nanobubbles’.  ‘Bulk nanobubbles’ are more difficult to analyze since they deeply penetrate liquid to locate and destroy hidden bacteria.

In this ‘bulk’ state, nanobubbles exhibit random Brownian motion: observation can easily lack accuracy and repeatability due to this randomness, especially when dealing with low concentrations of nanobubbles. In this state, a technique called Cryo-TEM that freezes the sample in a specific configuration is advantageous for visualizing nanobubbles.

But for quantitative and reproducible analysis of their size and concentration, nanoparticle tracking analysis (NTA) with Malvern’s Panalytical’s NanoSight series is the best solution. The new NanoSight Pro by Malvern Panalytical utilizes the properties of light scattering and Brownian motion (the random motion of particles) to obtain the particle size and absolute number of nanobubbles in a liquid suspension.

A laser beam is passed through the sample chamber, and the particles or nanobubbles in suspension in the path of the beam scatter light in such a manner that they can easily be visualized via a 20x magnification microscope with a mounted camera.

The camera, which operates at variable frame rates (measured in frames per second), captures a video of the scattered light from the particles or nanobubbles moving under Brownian motion within a field of view of approximately 100 µm x 80 µm x 10 µm. This video is then analyzed to obtain the size, distribution, and concentration measurements of nanobubbles. These data are used to understand the physical properties of the nanobubbles and optimize them.

Malvern Panalytical at the cutting edge of NTA

The higher resolution, combined with the ability to gate and determine size and concentration for sub-populations in a number-based size distribution, makes the NanoSight Pro the superior light-scattering technology for nanobubbles. The Zetasizer, another Malvern Panalytical light scattering instrument, can be used in conjunction with the NanoSight Pro to obtain zeta potential measurements, enabling the control and optimization of nanobubble surface tension.

To further support the development of nanobubble technology, Malvern Panalytical has also been at the forefront of the development of international methods and performance standards. For example, Strategic Account Manager Stephen Ward-Smith has chaired the ISO TC281 standards committee for many years.

The best way to realize the potential of nanobubbles is by combining technology and regulation in all applications involving water, from irrigation and aquaculture to wastewater treatment. Nano-tracking analysis technology and standardization are key to this clean water future.

In the next installment of our blog series on colloidal nanoparticles, we’ll dive into X-ray diffraction. In the meantime, learn more about nanoparticle tracking analysis by heading to the NanoSight range product page!