Dual plasmonic metal–semiconductor hybrids exhibit multifunctionalities for broad photophysical and photochemical applications. In this study, we focus on the magneto-optical (MO) properties of Au@CuS core–shell nanoparticles examined by magnetic circular dichroism (MCD) spectroscopy. The core–shell nanoparticles are prepared by a seeded growth protocol. The MCD response in the CuS (covellite) spectral region [= near-IR (NIR) region] has an inverted sign with respect to that of Au, demonstrating that the charge carriers inducing the surface plasmon behavior are different between CuS (p-type) and Au (n-type). The hole effective mass of covellite CuS is estimated on the basis of the cyclotron-derived MCD signal analysis. The MO activity, defined here as the maximum MCD amplitude normalized to extinction, is significantly damped when the shell is thin and nonuniform. Thicker and more uniform shell formation leads to the MO activity increase in the NIR region, but it is overall smaller than that of pure CuS nanoparticles, suggesting the existence of magnetoplasmonic coupling between the Au and CuS counterparts. We then believe our work will put forward developments toward the realization of flexible controllability of MO responses in dual plasmonic nanostructures.

Owing to their excellent photoluminescence (PL) properties in a narrow linewidth below 30 nm and high photoluminescence quantum yield (PLQY), organometal halide perovskite nanocrystals (PeNCs) are promising photonic sources for wide-color gamut displays. However, with a top-down approach, luminescent PeNCs comparable to those prepared through bottom-up synthesis is still a significant subject, including the optimization of milling processes. Herein, we propose a novel and simple ultrasound-assisted bead milling process based on the characteristics of facile crystallization. During the milling process, irradiated ultrasounds disperse milling beads that facilitate an intense collision between the beads and the perovskite precursors. Thus, this bead milling can be easily performed without planetary ball milling, and it provides brightly luminescent colloidal PeNCs with high PLQY. We established that mechanochemical conditions significantly enhance the optical properties by exploring various milling conditions. Furthermore, the color adjustment can be realized by changing the halide composition. Therefore, this novel milling process has great potential and versatility for preparing diverse perovskite nanomaterials for optoelectronic applications.

Magnetic circular dichroism (MCD) is demonstrated for the first time in substoichiometric molybdenum oxide (MoO 3−x ) nanoarchitectures to explore the origin of their near-IR (NIR) transitions. Various nanostructures of MoO 3−x are synthesized by a simple hydrothermal process using an ionic Mo(VI) or metallic Mo(0) precursor. The phase, morphology, and spectroscopic properties of the obtained nanostructures are dependent both on the reaction temperature and the molybdenum precursor. In particular, hexagonal MoO 3−x nanostructures are colored blue with different degrees. To better understand the nature of the electronic states in these nanomaterials, MCD spectroscopy is conducted. A derivative-like MCD response is detected in the vis-NIR region, but it is not attributed to surface magnetoplasmonic modes because of the absence of the peak-energy shift with the increasing refractive index of the dispersion medium. Then, the bisignate MCD signal can be attributed to Faraday B-terms for small-polaronic transitions, arising from two interacting polaronic states close in energy that would give opposite signs under an applied magnetic field. We believe that MCD evaluation for polaronic nanomaterials will expand promising new applications in fields such as semiconductor-based nanophotonics and magneto-optical devices.

Synthesized MAPbI3 QDs were purified using various alkyl acetates, with differences in the dispersibility of the MAPbI3 QDs in each solvent, and an LED based on the purified MAPbI3 QDs showed narrow emission and a high external quantum efficiency.

Lead halide perovskite quantum dots (PeQDs) have excellent optical properties, such as narrow emission spectra (FWHM: 18–30 nm), a tunable bandgap (λPL: 420–780 nm), and excellent photoluminescence quantum yields (PLQYs: >90%). PeQDs are known as a material that is easily decomposed when exposed to water in the atmosphere, resulting in causing PeQDs to lower performance. On the other hand, according to the recent reports, adding water after preparing the PeQD dispersion decomposed the PeQD surface defects, resulting in improving their PLQY. Namely, controlling the amount of assisting water during the preparation of the PeQDs is a significantly critical factor to determining their optical properties and device applications. In this paper, our research group discovered the novel effects of the small amount of water to their optical properties when preparing the PeQDs. According to the TEM Images, the PeQDs particle size was clearly increased after water-assisting. In addition, XPS measurement showed that the ratio of Br/Pb achieved to be close to three. Namely, by passivating the surface defect using Ostwald ripening, the prepared PeQDs achieved a high PLQY of over 95%.