Measurement of Raman Optical Activity with High-Frequency Polarization Modulation.

Many chiroptical spectroscopic techniques have been developed to detect chirality in molecular species and probe its role in biological processes. Raman optical activity (ROA) should be one of the most powerful methods, as ROA yields vibrational and chirality information simultaneously and can measure analytes in aqueous and biologically relevant solvents. However, despite its promise, the use of ROA has been limited, largely due to challenges in instrumentation. Here, we report a new approach to ROA that exploits high-frequency polarization modulation. High-frequency polarization modulation, usually implemented with a photoelastic modulator (PEM), has long been the standard technique in other chiroptical spectroscopies. Unfortunately, the need for simultaneous spectral and polarization resolution has precluded the use of PEMs in ROA instruments. We combine a specialized camera system (the Zurich imaging polarimeter, or ZIMPOL) with PEM modulation to perform ROA measurements. We demonstrate performance similar to the current standard in ROA instrumentation while reducing complexity and polarization artifacts. This development should aid researchers in exploiting the full potential of ROA for chemical and biological analysis.

Light-emitting coaxial nanofibers.

Ionic transition-metal complex (iTMCs)-based electro-luminescent nanofibers (TELFs) are developed by using coelectrospinning. A single TELF consists of a Galistan liquid metal core (cathode), an iTMC-based polymer shell, and an ITO thin film coating (anode). Lights emitted from the TELFs can be detected by a CCD camera at 4.2 V and seen by naked eyes at 5.6 V in nitrogen. The TELFs are structurally self-supporting but do not require a physical substrate (generally relatively bulky and heavy) to support them, rendering one-dimensional light sources more flexible, lightweight, and conformable. This technology can be beneficial to many research and development areas such as optoelectronic textile, bioimaging, chemical and biological sensing, high-resolution microscopy, and flexible panel displays, particularly as iTMCs with emission at different wavelengths are available.