Manipulation of Chiral Nonlinear Optical Effect by Light-Matter Strong Coupling.

Light-matter strong coupling (LMSC) is an intriguing state in which light and matter are hybridized inside a cavity. It is increasingly recognized as an excellent way to control material properties without any chemical modification. Here, we show that the LMSC is a powerful state for manipulating chiral nonlinear optical (NLO) effects through the investigation of second harmonic generation (SHG) circular dichroism. At the upper polariton band in LMSC, in addition to the enhancement of SHG by more than 1 order of magnitude, the responsivity to the handedness of circularly polarized light was largely modified, where sign inversion and increase of the dissymmetry factor were achieved. Quarter waveplate rotation analysis revealed that the LMSC clearly influenced the coefficients associated with chirality in the NLO process and also contributed to the enhancement of nonlinear magnetic dipole interactions. This study demonstrated that LMSC serves as a great platform for controlling chiral and magneto-optics.

Magneto-chiral Nonlinear Optical Effect with Large Anisotropic Response in Two-Dimensional Halide Perovskite.

The chiral organic-inorganic halide perovskites (OIHPs) are vital candidates for superior nonlinear optical (NLO) effects associated with circularly polarized (CP) light. NLO in chiral materials often couples with magnetic dipole (MD) transition, as well as the conventional electric dipole (ED) transition. However, the importance of MD transition in NLO process of chiral OIHPs has not yet been well recognized. Here, the circular polarized probe analysis of second harmonic generation circular dichroism (SHG-CD) provides the direct evidence that the contribution of MD leads to a large anisotropic response to CP lights in chiral OIHPs, (R-/S-MBACl)2PbI4. The thin films exhibit great sensitivity to CP lights over a wide wavelength range, and the g-value reaches up to 1.57 at the wavelength where the contribution of MD is maximized. Furthermore, it is also effective as CP light generator, outputting CP-SHG with maximum g-factor of 1.76 upon the stimulation of linearly polarized light. This study deepens the understanding of relation between chirality and magneto-optical effect, and such an efficient discrimination and generation of CP light signal is highly applicable for chirality-based sensor and optical communication devices.

Circularly Polarized Light Emission from Nonchiral Perovskites Incorporated into Nanoporous Cholesteric Polymer Templates.

Chiral perovskites have garnered significant attention, owing to their chiroptical properties and emerging applications. Current fabrication methods often involve complex chemical synthesis routes. Herein, an alternative approach for introducing chirality into nonchiral hybrid organic-inorganic perovskites (HOIPs) using nanotemplates composed of cholesteric polymeric networks is proposed. This method eliminates the need for additional molecular design. In this process, HOIP precursors are incorporated into a porous cholesteric polymer film, and two-dimensional (2D) HOIPs grow inside the nanopores. Circularly polarized light emission (CPLE) was observed even though the selective reflection band of the cholesteric polymer films containing a representative HOIP deviated from the emission wavelength of the 2D HOIP. This effect was confirmed by the induced circular dichroism (CD) observed in the absorbance band of the HOIP. The observed CPLE and CD are attributed to the chirality induced by the template in the originally nonchiral 2D HOIP. Additionally, the developed 2D HOIP exhibited a long exciton lifetime and good stability under harsh conditions. These findings provide valuable insights into the development and design of innovative optoelectronic materials.

Safety survey on infusion reaction and cardiac dysfunction when switching from reference trastuzumab (HERCEPTIN®) to biosimilar trastuzumab (Trastuzumab­NK) in the treatment of HER2­positive breast cancer.

The present study is a safety survey of patients with human epidermal growth factor receptor type 2-positive, chemotherapy-naive breast cancer treated with trastuzumab plus paclitaxel at the Saitama Cancer Center (Saitama, Japan) between April 2018 and March 2022. The expression of infusion reaction (IR) and the effect on cardiac function were investigated in patients who switched from reference trastuzumab (HERCEPTIN®) to biosimilar trastuzumab (Trastuzumab-NK) and continued treatment (switching group). The two groups (reference vs. biosimilar trastuzumab) had no significant difference in the expression of IR (P>0.999). In the switching group, IR associated with switching did not occur in all nine eligible patients. Left ventricular ejection fraction (LVEF) was used to assess cardiac function, and no patient in either group experienced a significant decrease in LVEF with treatment, meaning that there was no effect of switching on the decrease in LVEF. These results suggested that switching from reference to biosimilar trastuzumab may not have a significant effect on the frequency of IR expression or the occurrence of cardiac dysfunction.

Preadsorption Effect of Carbon Monoxide on Reactivity of Cobalt Cluster Cations toward Hydrogen.

We report gas-phase reactions of free Con(CO)m+ (n = 3-11, m = 0-2) with H2, expecting a catalytic reaction of coadsorbed CO and H2 on Con+. Preadsorption of CO molecules is found to promote H2 adsorption, in particular, on Con(CO)+ (n = 5, 8-10). Density functional theory (DFT) calculations reveal that the reactivity is governed by the molecular-orbital energy of Con+, which is tuned by preadsorbed CO molecules. Collision-induced-dissociation experiments performed on ConCOH2+ (n = 8-10) imply that at least some of the CO and H2 molecules are bound together on Con+.

Energy Transfer-Assisted Whispering Gallery Mode Lasing in Conjugated Polymer/Europium Hybrid Microsphere Resonators.

Lanthanide metal complexes display luminescence with narrow bandwidth. Here, we present coupling of the luminescence from europium ion (Eu3+ ) with whispering gallery modes (WGMs) in conjugated polymer microsphere resonators. Self-assembly of fluorene-terpyridine alternating copolymer, coordinated by Eu3+ (F8tpy-Eu3+ ), forms well-defined microspheres with an average diameter of 3.2 µm. Upon focused laser excitation, a microsphere of F8tpy copolymer displays WGM photoluminescence (PL) at a wide spectral range from 420 to 680 nm. In contrast, F8tpy-Eu3+ hybrid microspheres exhibit sharp WGM PL at a narrow spectral range of 615-630 nm, which is characteristic of luminescence from Eu3+ . The PL behavior indicates that photoinduced energy transfer from F8tpy to Eu3+ occurs efficiently. Furthermore, the intensity of the PL peak increases nonlinearly upon strong pumping, indicating that a lasing action appears with the threshold of 1.85 mJ cm-2 . These results will pave the way for developing microlasers and photonic devices from soft organic materials.

π-Electronic Co-crystal Microcavities with Selective Vibronic-Mode Light Amplification: Toward Förster Resonance Energy Transfer Lasing.

π-conjugated organic microcrystals often act as optical resonators in which the generated photons in the crystal are confined by the reflection at the crystalline facets and interfere to gain lasing action. Here, we fabricate microcrystals from a mixture of carbon-bridged oligo- para-phenylenevinylenes (COPVs) with energy-donor (D) and energy-acceptor (A) characters. Upon weak excitation of the single D-A co-crystal, Förster resonance energy transfer (FRET) takes place, exhibiting spontaneous emission from A. In contrast, upon strong pumping, stimulated emission occurs before FRET, generating lasing action from D. Lasing occurs with single- and dual-vibronic levels, and the lasing wavelength can be modulated by the doping amount of A. Time-resolved spectroscopic studies reveal that the rate constant of lasing is more than 20 times greater than that of FRET. Furthermore, microcrystals, vertically grown on a Ag-coated substrate, reduce the lasing threshold by one-fourth. This study proposes possible directions toward organic solid FRET lasers with microcrystalline resonators.

Fabrication of Polymer Microspheres for Optical Resonator and Laser Applications.

This paper describes three methods of preparing fluorescent microspheres comprising π-conjugated or non-conjugated polymers: vapor diffusion, interface precipitation, and mini-emulsion. In all methods, well-defined, micrometer-sized spheres are obtained from a self-assembling process in solution. The vapor diffusion method can result in spheres with the highest sphericity and surface smoothness, yet the types of the polymers able to form these spheres are limited. On the other hand, in the mini-emulsion method, microspheres can be made from various types of polymers, even from highly crystalline polymers with coplanar, π-conjugated backbones. The photoluminescent (PL) properties from single isolated microspheres are unusual: the PL is confined inside the spheres, propagates at the circumference of the spheres via the total internal reflection at the polymer/air interface, and self-interferes to show sharp and periodic resonant PL lines. These resonating modes are so-called "whispering gallery modes" (WGMs). This work demonstrates how to measure WGM PL from single isolated spheres using the micro-photoluminescence (µ-PL) technique. In this technique, a focused laser beam irradiates a single microsphere, and the luminescence is detected by a spectrometer. A micromanipulation technique is then used to connect the microspheres one by one and to demonstrate the intersphere PL propagation and color conversion from coupled microspheres upon excitation at the perimeter of one sphere and detection of PL from the other microsphere. These techniques, µ-PL and micromanipulation, are useful for experiments on micro-optic application using polymer materials.

Color-Tunable Resonant Photoluminescence and Cavity-Mediated Multistep Energy Transfer Cascade.

Color-tunable resonant photoluminescence (PL) was attained from polystyrene microspheres doped with a single polymorphic fluorescent dye, boron-dipyrrin (BODIPY) 1. The color of the resonant PL depends on the assembling morphology of 1 in the microspheres, which can be selectively controlled from green to red by the initial concentration of 1 in the preparation process of the microspheres. Studies on intersphere PL propagation with multicoupled microspheres, prepared by micromanipulation technique, revealed that multistep photon transfer takes place through the microspheres, accompanying energy transfer cascade with stepwise PL color change. The intersphere energy transfer cascade is direction selective, where energy donor-to-acceptor down conversion direction is only allowed. Such cavity-mediated long-distance and multistep energy transfer will be advantageous for polymer photonics device application.

Chiroptical switching caused by crystalline/liquid crystalline phase transition of a chiral bowl-shaped molecule.

The liquid crystal of a chiral bowl-shaped molecule having a central-phosphorus atom and long alkyl chains was developed. The DSC and XRD analyses suggested the formation of columnar liquid crystals of both the enantiopure and racemic compounds. The condensed phase of the enantiopure compound in a thin film exhibited a significant signal in CD spectra, which was switched by a reversible phase transition between the crystalline and liquid crystalline states.