Scientists from the University of Oxford have challenged a fundamental principle of physics by demonstrating that particles with the same charge can be attracted over long distances. A study published in the journal Nature Nanotechnology reveals that the interaction between particles with the same charge depends on the solvent in which they are suspended.
A team of researchers from the Oxford University Chemistry Department has discovered that negatively charged particles are attracted to each other at large distances, while positively charged particles repel each other. However, in solvents such as alcohols, the opposite effect was observed.
These findings challenge long-standing beliefs and have significant implications for various processes, including particle interactions and molecule behavior on different scales such as self-assembly, crystallization, and phase separation.
Using light-pushed microscopy during their experiments, the scientists observed negatively charged microparticles of silicate in water being attracted to each other, forming clusters with a hexagonal structure. On the other hand, positively charged silicate particles in water did not exhibit this clustering behavior.
The researchers found that for negatively charged particles in water, attractive forces outweighed electrostatic repulsion over long distances, leading to cluster formation. Conversely, positively charged particles in water always experienced repulsion, preventing cluster formation.
Furthermore, the researchers discovered that the observed effects were dependent on the pH of the environment. By altering the pH, they were able to manipulate the formation or absence of clusters for negatively charged particles; however, no clusters formed for positively charged particles regardless of pH.
By changing the solvent to alcohol, such as ethanol, which behaves differently from water, the researchers were able to induce clustering of positively charged particles while negatively charged particles did not exhibit this behavior.
This groundbreaking discovery prompts a reevaluation of fundamental principles and has the potential to impact various fields, from pharmaceutical and chemical product stability to understanding pathological disorders associated with molecular aggregation within the human body.
Professor Madhavi Krishnan, the head of the research group, commended the graduate and bachelor students for their significant contributions to this discovery. Sida Wang, one of the study’s authors, expressed admiration for the observed particle attraction despite challenges with vision.