Rich valleytronics and diverse defect-induced or interlayer pre-bandgap excitonics have been extensively studied in transition metal dichalcogenides (TMDCs), a system with fascinating optical physics. However, more intense high-energy absorption peaks (∼3 eV) above the bandgaps used to be long ignored their underlying physical origin remains unveiled. Here, we employ momentum resolved electron ...

A novel near-infrared (NIR) electrochromic polyelectrolyte consisting of anthraquinone imide (AQI) pendants and a poly(1-vinylimidazole bromide) main chain was synthesized via radical polymerization. Its AQI content was varied by copolymerization with 1-vinyl-3-butylimidazole bromide to improve the processability of the polymer as well as the monomer conversion. The electrochemical and electroc...

Optical frequency comb-based cavity-ringdown spectroscopy has recently enabled high-sensitivity absorption detection of molecules over a broad spectral range. We demonstrate an improved system based on a mode-locked erbium-doped fiber laser source centered at 1.5 microm, resulting in a spectrometer that is inexpensive, simple, and robust. It provides a very large spectral bandwidth (1.45-1.65 m...

Direct detection of saponins in medicinal plants using Fourier Transform Infrared (FTIR) spectroscopy is reported in this paper. Crude dry plant powders were mixed with potassium bromide (KBr) powder and compressed to a thin pellet for infrared examination. FTIR spectra of the test samples showed -OH, -C=O, C-H, and C=C absorptions characteristic of oleanane triterpenoid saponins. The C-O-C abs...