Search for: All records

Polymer‐based chiral materials with exceptional optical activity can dramatically impact integrated chiral photonics due to the tunability of their optical responses coupled with ease of fabrication. Realizing these applications requires increasing the absorbance dissymmetry factor. Here, in situ, the synthesis of gold nanostars is introduced in a chiral polymer medium to produce chiral polymer‐anisotropic plasmonic nanocrystal nanocomposites. The optimized nanocomposite shows a tenfold enhancement of dissymmetry factor,g_abs(up to 0.64) and a corresponding 46‐fold augmented circular dichroism (CD) value upon annealing, relative to the annealed pure chiral polymer film. Moreover, the enhancement relative to the non‐annealed polymer‐gold nanostar nanocomposite is strikingly higher: a 35‐fold increase ing_absand a 4272‐fold increase in CD. Based on computational analysis, it is concluded that the local plasmon field enhancement around the crevices and tips of nanostars is mainly responsible for the observed effect which is further supported by a signal enhancement in Surface Enhanced Raman Scattering (SERS). Thus, this study underscores the significant role of close‐range plasmon interactions in altering the chiroptical response of nanocomposite materials and a practical pathway toward the realization of next‐generation integrated photonics and optoelectronic circuitry with photon spin control.

Microglia are immune cells, which densely populate the central nervous system (CNS), and play essential role in suppression of neurodegenerative diseases, clearance of debris after CNS trauma, as well as serve as the last line of immune defense in response to any potential threat by being activated to eliminate diverse pathogens ranging from bacteria to cancer. The activated microglia cells are commonly used as a diagnostic biomarker of diverse brain conditions, however detection and classification of microglia activated phenotypes is a cumbersome and imprecise procedure. Here, we report on development of optical assay for detection and quantitative analysis of activated microglia. In this study, we investigated overall changes in the metabolism of microglia cells during their activation by monitoring the signal from cellular proteins and lipids using label‐free coherent anti‐Stokes Raman scattering imaging. Our data demonstrate that the activation of microglia in the presence of bacterial liposaccharide is accompanied by intense upregulation of synthesis of proteins and lipids. We further propose that elevated intracellular content of these types of macromolecules can serve as early supplementary marker for identification of active microglia cells in the brain samples by Raman imaging techniques.