Radiation-driven rotational motion of nanoparticles

Area of Science:

• Physics
• Materials Science
• Nanotechnology

Background:

• Focused synchrotron beams can interact with samples through heating and radiation pressure.
• High angular sensitivity is required to detect minute forces, such as those from field gradients.

Purpose of the Study:

• To investigate the effects of X-ray heating and radiation pressure on nanoparticles.
• To demonstrate the capability of rotational X-ray tracking to quantify small forces.

Main Methods:

• Tracking the rotational motion of single-crystal nanoparticles using Bragg reflections.
• Embedding nanoparticles in viscous (glycerol) and viscoelastic (colloidal gel) media.
• Utilizing uniform gradient and Gaussian profile X-ray beams.

Main Results:

• Observed changes in viscosity of glycerol due to X-ray heating for 42 µm crystals.
• Measured angular velocities of 10⁻⁶ rad s⁻¹ for 340 nm crystals in a colloidal gel, corresponding to torques of 10⁻²⁴ N m.
• Demonstrated the detection of forces caused by X-ray intensity gradients.

Conclusions:

• Rotational X-ray tracking is a sensitive method for detecting and quantifying small forces.
• X-ray beams can induce measurable physical effects like heating and radiation pressure on nanoparticles.
• This technique allows for the study of material properties (e.g., viscosity) and nanoparticle dynamics under X-ray irradiation.