Ido Hadar

The bottom‐up assembly of small organic molecules into dynamic optical materials remains a major challenge in materials chemistry. Biological systems, however, demonstrate that hierarchical organization of such molecules can generate diverse optical functionalities. Here we show that zebrafish pigment cells undergo a developmentally regulated phase transition in which pteridine‐rich organelles, known as pterinosomes, transform from disordered ultraviolet (UV)‐absorbing compartments into highly reflective, liquid‐crystal‐like scattering structures. Cryogenic STEM diffraction mapping and electron microscopy reveal that this transition corresponds to the reorganization of a disordered fibrous matrix into a hierarchical, concentrically ordered mesophase. We show that pterinosomes are built from a composite pteridine material whose relative composition is developmentally tuned. We further identify ionic gating as a key regulator of this process: potassium (K ⁺ ) depletion enables π – π stacking‐driven ordering, thereby decoupling metabolite accumulation from crystallization. Optical modeling indicates that the resulting mesoscale organization generates strong dielectric anisotropy and refractive‐index contrast, enabling efficient broadband scattering through collective effects in organelle arrays. Our findings establish ionic gating and hierarchical assembly as strategies for controlling the phase behavior of confined small‐molecule systems and provide design principles for tunable bio‐inspired photonic materials.

Understanding the effect of organic spacers on the fundamental excited-state processes in 2D perovskites is crucial for advancing these novel materials. Mn doping offers a powerful strategy for tuning and enhancing the optoelectronic properties of halide perovskites, yet the role of spacers in Mn emission dynamics remains poorly understood. Herein, we investigate these processes in Mn-doped 2D Ruddlesden–Popper perovskite crystals with aromatic phenethylammonium (PEA) and aliphatic butylammonium (BA) spacers. Notably, PEA-based perovskites exhibit strong dopant emission with a photoluminescence quantum yield of 47%, compared to 15% for BA-based systems at the same doping level. To understand this contrast, we probed the structural dynamics and transient transport properties. We show that the enhanced Mn emission in PEA-based perovskites arises from the structural rigidity and reduced dynamic disorder imparted by the aromatic spacer, enabling efficient carrier transport. In contrast, the softer BA lattice exhibits stronger exciton–phonon coupling and greater dynamic disorder, resulting in slower exciton transport, faster nonradiative decay of Mn ²⁺ states, and consequently weaker Mn emission. This work provides a general framework for understanding spacer effects in 2D perovskites and guiding the design of advanced luminescent materials.

Extending the absorbance range of perovskite nanoparticles to the near-infrared (NIR) region is essential for expanding their optoelectronic applications. In this study, PbS nanoparticles (NPs) were conjugated with CsPbBr₃ NPs via a PbSO₄ matrix, forming hybrid nanostructures with optical responses spanning from the visible to the NIR region achieving a total photoluminescence quantum yield (PLQY) of 66%. The PbSO₄ matrix enables the formation of well-organized 1D nanorods, ensuring a consistent and close proximity between the two types of NPs. Temperature-dependent time-resolved photoluminescence measurements revealed efficient charge transfer from the CsPbBr₃ NPs to the PbS NPs. Surface photovoltage spectroscopy and ambient photoemission spectroscopy were used to construct the energy-level diagram of this unique system, confirming the strong coupling between the two semiconductors. This hybrid approach offers a strategy to conjugate dissimilar semiconductors without the need for lattice matching.

Low-dimensional halide perovskites (LDHPs) are promising candidates for optoelectronic applications, specifically light emission. LDHP’s reduced-dimensional frameworks allow exceptional tunability of the optoelectronic properties. Self-trapped exciton emission (STE) is an intriguing characteristic of some LDHPs, offering a compelling mechanism for white-light emission. In this work, we study the effect of halide substitution and synthetic methods on the optical properties, with a particular focus on STE emission, of one-dimensional LDHPs using (2,5-dmpz)­Pb­(Br _x Cl_1–x )₄ (dmpz = dimethylammonium piperazine) as a model system, exhibiting high emission quantum efficiency and structural consistency. Mechanochemical approaches, including manual grinding and ball milling, were employed to synthesize pure and mixed halide compounds, enabling precise composition control. Structural characterization revealed that ball milling produces materials with improved crystallinity and a homogeneous halide distribution. Optical characterization showed an anticorrelation between the absorption onset and STE emission energies, with STE properties influenced by both halide composition and a synthesis route. Moreover, we found that the STE emission of the mixed halide compounds evolved with time. The post-synthesis evolution of the STE emission spectrum is associated with local lattice distortions rather than long-range structural changes. The emission quantum efficiency of these compounds was measured and reached a value of 35%, among the highest values measured for 1D broad emitters. These findings provide additional insights into the design of next-generation LDHP compounds exhibiting STE emission and development of white-light-emitting devices based on them.

This study explores 2D lead iodide perovskites with varying spacer chains, comparing bulk poly-crystals, colloidal nanoplatelets, and thin films. Their optical properties mainly depend on structural distortion and the bulk-to-surface ratio.

The heterojunction of Co ₃ O ₄ –CdS shows dual functions of photocatalytic dehydrogenation and dehydration to simultaneously produce syngas (H ₂ and CO) from formate, with near zero CO ₂ emission under alkaline conditions.