Cholesterol Template for Synthesizing Non-Polar Chiral Nanoparticles

Yields Colloidal Chiral Nanoparticles with Consistent Size and Useful Optical Properties

This cholesterol ligand template enables the preparation of nonpolar inorganic chiral nanoparticles. Chirality is a fundamental geometrical property with various objects in our universe, enabling matter to adopt three-dimensional arrangements. Chiral molecules have attracted attention in organic and biochemistry for centuries, but chirality is not limited to only organic molecules. Researchers, with the development of nanoscience, discovered chiral inorganic nanostructures with chiroptical activity. These chiral inorganic nanostructures are spin-controlled quantum emitters, which can respond to polarized light more strongly than large biomacromolecules, making them useful for various applications, including bioimaging, sensing, and spin-polarized light-emitting electro-optical devices. Conventional procedures synthesize nanoparticles in water, whose polar environment causes the shape and size of the resulting nanoparticles to vary significantly. Since size and shape, particularly the twist shape, impact the nanoparticle’s chirality and interactions with polarized light, procedures for synthesizing nanoparticles in nonpolar environments, yielding standardized sizes and shapes, are highly beneficial.

Researchers at the University of Florida have synthesized nonpolar chiral nanoparticles by growing the nanoparticles along the ligand template from a chiral cholesterol molecule. This synthesis controls the chirality and optical behavior of the resulting nanoparticles via the number of hydrocarbons attached to the cholesterol.

Application

Cholesterol ligand template for synthesis of inorganic chiral nanoparticles with consistent size and shape in a nonpolar environment

Advantages

• Yields consistent nanoparticle size and shape, resulting in dependable optical properties
• Produces chiral nanoparticles capable of rotating the polarization plane of light and exhibiting circular dichroism, rendering them applicable for detecting and imaging certain substances in biological samples
• Follows a general synthesis strategy, allowing other metals such as lead, mercury, or zinc to substitute for the cadmium, while selenium or tellurium can replace the sulfur

Technology

Assembling nanostructures following the chiral “template” enables the preparation of colloidal chiral nanoparticles. Cholesterol provides a chiral structure for dictating this chiral assembly, its nonpolar nature lending to improved size and shape consistency to the assembly. Cadmium dissolved in a non-aqueous solution forms the metal salt, while sulfur is the inorganic precursor. These combine to form an inorganic chiral nanoparticle, CdS. This nanoparticle has particular optical properties determined by the chemical environment of the cholesterol. The cholesterol links to an anchor group containing methylene units. When interacting with polarized light, the CdS rotates the polarization plane to the left when this number is even but rotates it to the right when this number is odd, a property known as circular birefringence.