A new method to study nanoparticles

By Paul Grad |

Researchers from the Singapore-MIT Alliance for Research and Technology (Singapore; https://smart.mit.edu) have discovered a way to study the properties of a nanoparticle without damaging it, which has not been possible so far. The work was led by Michael Strano, a professor at MIT (Cambridge, Mass.; www.mit.edu), and a principal investigator of DiSTAP — the Disruptive & Sustainable Technologies for Agricultural Precision Interdisciplinary Research Group — which is a part of Smart. DiSTAP develops new technologies to enable Singapore to improve its agriculture yield to reduce its dependence on imported food and produce.

The researchers’ method, called molecular probe adsorption (MPA), is based on a non-invasive adsorption of a fluorescent probe on the surface of colloidal nanoparticles in aqueous phase.

The corona phase — the adsorbed layer of polymer, surfactant, or stabilizer molecules around a nanoparticle — is typically used to disperse nanoparticles into a solution or solid phase. However, this phase also controls molecular access to the nanoparticle surface. The MPA method allows measuring the accessible nanoparticle surface using a titration of a quenchable fluorescent molecule.

A material balance on the titration yields certain surface coverage parameters, including the ratio of the surface area (q) to the dissociation constant (Kd) of the fluorophore, q/Kd, as well as Kd itself. Using MPA across a series of corona phases, the researchers found that the Gibbs free energy of probe binding scales inversely with the cubic root of the surface area, q.

The researchers say MPA is the only technique to date capable of discerning critical structure-property relationships for such nanoparticle surface phases. They say the MPA method is also able to characterize a nanoparticle within minutes compared with several hours that the best chemical methods require today. Because it uses only fluorescent light, the MPA method is also substantially cheaper than other methods.

DiSTAP is using the MPA method for nanoparticle sensors in plants and nanocarriers for delivery of molecular cargo into plants. Strano says with better data and insight into plant biochemistry, we can provide optimal nutrient levels for healthier plants and higher yields.

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