Using Circular Dichroism Microspectroscopy to Study Nanoscale Materials

Nanoscale materials are governed by their structures. Once dimensions fall below a micron, geometry becomes a primary driver of optical behavior and often has a greater influence than chemical composition. Subtle asymmetries in nanoscale structures, such as twists, offsets, or handed features can dictate how light is absorbed, transmitted, or rotated, producing optical responses that vary across a sample. Circular dichroism (CD) spectroscopy has long been used to measure chirality, but conventional CD instruments operate at the bulk level, meaning local variation within nanoscale materials is averaged out. Averaging over large areas masks the local variation that defines nanoscale systems. This limitation has led to the use of circular dichroism microspectroscopy, where CD measurements are performed at defined locations rather than across bulk samples. With CD microspectroscopy, the chiroptical properties of nanoscale materials can be examined at the length scale where structural variation occurs.

Chirality as a Structural Property

At the nanoscale, chirality often arises from physical form rather than molecular arrangement. Helical nanowires, twisted plasmonic elements, and asymmetrically patterned surfaces can all exhibit strong optical activity even when composed of chemically achiral materials. In these systems, optical response is controlled by three-dimensional geometry and its interaction with polarized light.

CD microspectroscopy is particularly suited to investigating this type of structural chirality. Instead of collapsing a complex surface into a single averaged spectrum, it allows researchers to examine how optical activity varies between individual nanoscale features. Such a distinction is critical for engineered materials, where small deviations in geometry can lead to measurable changes in performance. Resolving the differences directly improves how the structure and optical behavior of nanoscale materials are understood and controlled during fabrication.

Studying Nanoscale Materials Using Circular Dichroism Microspectroscopy

Examining nanoscale materials requires techniques that can resolve optical behavior at the same scale as structural variation. CD microspectroscopy can link chiroptical measurements to specific nanoscale features rather than relying on bulk averages, Optical activity can therefore be evaluated in relation to local geometry within structurally complex materials.

CD microspectroscopy is useful for nanoscale materials that are patterned or heterogeneous, in which optical responses vary across a surface. Localized measurements can be applied to:

• Nanoparticle clusters, where collective geometry influences chiroptical response.
• Defined regions within metasurfaces, requiring individual patterned elements to be examined rather than inferred from an average signal.
• Nanostructured films, with differences between nanoscale domains affecting overall optical behavior.

When measurements are performed across a surface, changes in optical activity from one region to another become apparent. The spatial differences help identify gradients, defects, or fabrication-related variations that influence the performance of nanoscale materials and would otherwise remain hidden in bulk measurements.

Complementing Circular Dichroism with Raman Microspectrometers

Utilizing CD microspectroscopy in tandem with complementary techniques allows different aspects of nanoscale materials to be examined at comparable spatial scales. Raman spectroscopy provides chemically specific information on molecular composition, bonding, crystallinity, and stress, complementing chiroptical measurements. If implemented with Raman microspectrometers, this information can be obtained from spatially defined regions, aligning naturally with CD-based analysis.

Applied together, these techniques address different aspects of the same material system, with CD microspectroscopy showing how nanoscale structure interacts with polarized light and Raman microspectrometers confirming what the material is made of and how its molecular framework is organized. Such a combined approach is particularly valuable for complex nanoscale materials like functional coatings, chiral polymers, and bio-nano interfaces, since optical behavior reflects the interplay between chemical composition and structure.

High-Impact Applications of CD Microspectroscopy in Nanoscale Materials

CD microspectroscopy is used with nanoscale materials exhibiting spatial variation in optical response across a surface or device. Region-specific measurements allow differences between local features to be examined directly, rather than inferred from bulk analysis.

Key application areas include:

• Nanostructured metasurfaces- where CD microspectroscopy is applied to study nanoscale materials composed of repeating chiral elements. Localized measurements can verify that individual nanoscale features exhibit the intended optical response and that variations in fabrication do not compromise device-level functionality.
• Bio–nano interfaces- where nanoscale materials such as nanoparticles or nanostructured coatings interact with proteins and other biomolecules. CD microspectroscopy detects changes in chiroptical response that arise from structural rearrangements at the nanoscale, delivering insight into how material geometry influences biological structure.
• Self-assembled nanoscale materials- where chirality emerges during assembly rather than being predefined. Spatially resolved CD microspectroscopy measurements identify where symmetry breaking occurs within the nanoscale material and how chiral order develops across individual domains.

In each case, CD microspectroscopy enables optical activity to be correlated with specific nanoscale features, reducing uncertainty introduced through ensemble-averaged measurements.

Practical Insight at the Nanoscale

Chiroptical analysis at the nanoscale depends on the ability to examine optical activity at specific regions within a material, rather than inferring behavior from ensemble measurements. CD microspectroscopy provides this capability by enabling site-specific measurements across surfaces, thin films, and patterned devices where structural variation is inherent. CRAIC Technologies offers equipment to support localized CD microspectroscopy for nanoscale materials, including the 2030 PV PRO™ and FLEX microspectrophotometers. For additional information about the solutions for CD microspectroscopy from CRAIC Technologies, contact our specialists today.