Entropic Trapping of a Singly Charged Molecule in Solution.

Area of Science:

• Molecular Biophysics
• Physical Chemistry
• Nanotechnology

Background:

• Previous methods relied on electrostatic trapping, which was insufficient for weakly charged molecules (≤5 e).
• Confining molecules in solution is crucial for studying their properties at the nanoscale.

Purpose of the Study:

• To demonstrate spatial confinement of single molecules in solution using configurational entropy.
• To enable optical imaging and measurement of effective charge for weakly charged molecules.

Main Methods:

• Spatial modulation of local configurational entropy.
• Utilizing a geometrically modulated system for thermally fluctuating molecules.
• Measuring the configurational entropy contribution.

Main Results:

• Successfully confined weakly charged molecules in solution.
• Demonstrated good agreement between measured configurational entropy and theoretical expectations.
• Achieved optical imaging and effective charge measurement of molecules as small as ~1 nm with charges as low as 1 e.

Conclusions:

• Configurational entropy offers a viable method for confining weakly charged molecules in solution.
• This technique facilitates the study of nanoscale molecular properties, comparable to monovalent ions.
• Enables direct optical imaging and precise charge determination of individual molecules.