Hila Shalom

Over the last decade, nanostructures that support exciton–polaritons (EPs) have attracted considerable attention due to their distinctive optical properties and technological promise. WS₂ nanotubes (NTs) sustain strong EP coupling under ambient conditions without external cavities. Quasi-one-dimensional systems enable radius-dependent tuning of light–matter interactions, which evolve from excitonic to polaritonic regimes. Scattering scanning near-field optical microscopy (s-SNOM) imaging of an individual NT reveals intricate coupling among surface-bound waves and the evanescent field at the structure–substrate interface. To disentangle these contributions and assess waveguiding characteristics, s-SNOM observations are combined with finite-difference time-domain simulations of nanowires with varied refractive indices (RIs). Geometric resonances emerge at RI = 2, optical cavity dominates at RI = 4, whereas the dielectric response of WS ₂ induces EP modes. Radius-dependent simulations show a transition from a geometric mode at small diameters to a two-mode regime governed by a strong EP contribution. Polarization-resolved analysis demonstrates enhanced coupling when incident radiation aligns with the NT axis. Surface-bound waves radiate efficiently into the surrounding medium, evidenced by long-range propagation of the evanescent waves and pronounced interference features on their crests. Embedding WS ₂ NTs within polydimethylsiloxane produces flexible nanocomposite fibers exhibiting high quality factors, supporting tunable nanolaser platforms.

Strong coupling between optical cavity modes and excitons in transition-metal dichalcogenides (TMDs) has attracted considerable interest due to its potential applications in nanophotonics and nonlinear optical technologies. Owing to their high refractive index, TMD systems sustain optical cavity modes that strongly couple with excitons to form exciton-polaritons. However, trion-based polaritonic states under ambient conditions without external cavities remain largely unexplored. Here, we demonstrate the photochemical induction and stabilization of exciton-trion-polaritons (ETPs) in multiwalled WS2 nanotubes (NTs) through the combined effects of nanotube diameter, light excitation, and chemical hole scavenging. Large WS2 NTs (~100 nm, NTs-I) support internal cavity modes and pronounced exciton-polariton (EP) coupling, under strong-light excitation, which promotes trion formation due to the intrinsic n-type character of WS2. Potassium iodide (KI) suppresses electron-hole recombination and stabilizes trion populations through efficient hole scavenging. Consequently, distinct low-, medium-, and high-energy trion-polariton branches emerge. Control experiments using neutral-density filters, KCl, solar irradiation, and core-shell WS2@WSe2 NTs confirm the trion-mediated origin and tunability of the observed states. Transient absorption spectroscopy reveals prolonged excitedstate dynamics and stabilized trion-related features in KI solution. Complementary quantum mechanical modeling, finite-difference time-domain simulations, and machine-learning-assisted analysis successfully reproduce the experimental optical response and confirm hybridization between cavity photons, excitons, and trions, with Rabi splitting reaching ~140 meV. These findings establish WS2 NTs as a versatile roomtemperature platform for tunable trion-polaritonic phenomena and open pathways for polaritonic applications in photocatalysis and renewable energy technologies.

This work explores the effect of Eu doping techniques on CsPbBr ₃ NCs. In-situ doping allows Eu ³⁺ incorporation into the lattice and enhances optocatalytic properties, while ex situ sonochemical doping results in surface-bound Eu with limited effects.

Halide perovskite nanowires (HP‐NWs) exhibit fascinating optical properties, making them attractive for advanced technologies. However, instability and lack of an effective synthetic protocol limit their commercialization. To address this, nanoporous anodized aluminum oxide (AAO) metamaterial is used as templates for the growth of CsPbBr₃ NW arrays. AAO functions as a growth template and a stabilizing medium. The NW array exhibits strong light‐trapping ability, and the pore geometric features (pore radius‐R and distance between pores‐d) can potentially enhance the light‐matter interactions (LMI). The impact of R and d on LMI within the AAO/CsPbBr₃ system using theoretical finite difference time domain (FDTD) simulations is demonstrated for the first time. Optimal LMI is observed with _R = d = 25 nm and 50 nm. Ligand‐free synthesis of CsPbBr₃ NW arrays via spin‐coating, drop‐casting, and inverse temperature crystallization (ITC) is reported. While spin‐coating and drop‐casting results in poor pore filling, the modified ITC method achieves >90% pore filling with significant NW lengths. These findings highlight the potential of AAO templates for protecting CsPbBr3 and addressing synthetic challenges in HPs and other semiconductor NW arrays. This study provides key insights for LMI in HPs and advances NW array‐based optical devices and renewable energy applications.

Zero-dimensional (0D) and three-dimensional (3D) halide perovskite nanocrystals (HP-NCs), owing to their unique optoelectronic properties, are extensively studied for photocatalytic activity. However, HPs are highly sensitive to light, humidity, and other environmental factors, which accelerate their decomposition. Understanding the decomposition process is crucial for gaining insights into how to stabilize HP-NCs. Here, we investigate the radical-driven decomposition process and dynamics of the 0D C4PbBr6 and 3D CsPbBr3 NCs under the influence of visible light and a polar solvent by electron paramagnetic resonance (EPR) spectroscopy. Our findings indicate that light accelerates radical formation over time, making the decomposition of HP-NCs a self-sustaining process. Upon illumination of the NCs, hydroperoxyl radicals are formed first, followed by unconventional Br, Cs, and Pb-related radicals, indicating the initiation of NC decomposition. The decomposition of CsPbBr¬3 NCs starts after 3 min of light exposure, while C4PbBr6 NCs take 18 min, indicating the greater stability of the latter. Additionally, we evaluated the photocatalytic activity of the HPs toward degrading organic dyes. The 3D CsPbBr3 NCs performed as superior photocatalysts compared to their 0D Cs4PbBr6 NCs counterparts. Yet, linking the results of EPR measurements with the photocatalytic efficacy suggests that the CsPbBr3 NCs undergo degradation during the photocatalytic process, thereby serving as a sacrificial agent to enhance photocatalytic activity. The understanding derived from EPR spectroscopy in tracking radical formation and dynamics can be extended to enhance the stability and efficiency of various nanomaterials in optoelectronic and photocatalytic applications, thus contributing to advancements beyond the HP family.

Metal halide perovskites (MHPs), particularly CsPbBr3 nanocrystals (NCs), attract significant interest due to their remarkable optoelectronic properties. These properties make them ideally suited for applications such as photovoltaics and ionizing radiation detectors. However, CsPbBr3 NCs suffer from poor luminescence efficiency and short service life. Doping with rare earth (RE) elements, especially europium (Eu), has emerged as a viable method for solving these problems because of their unique electronic structure. Doping with RE improves luminescence efficiency and extends the service life of the MHPs, enhancing their optoelectronic properties and catalytic capabilities. This study examines the effects of in-situ and ex-situ europium doping on the structural, optical, and photocatalytic properties of CsPbBr3 NCs. In-situ doping was achieved by introducing the dopant during the NC synthesis, while ex-situ doping involved adding the dopant to pre-prepared NCs via sonochemical synthesis with an ultrasonic bath. The doped NCs exhibit enhanced emission and boosted photocatalytic activity, showcasing the multifaceted benefits of Eu ions doping. The study concludes that in-situ europium doping, particularly at 5 wt%, significantly enhances the structural and functional characteristics of CsPbBr3 NCs, offering a promising approach for improving their performance in optoelectronic and photocatalytic applications.

Halide perovskite nanowires (HP-NWs) exhibit fascinating optical properties, making them attractive for advanced technologies. However, instability and lack of an effective synthetic protocol limit their commercialization. To address this, we use nanoporous anodized aluminum oxide (AAO) metamaterial as templates for the growth of perovskite (CsPbBr3) NW arrays. AAO functions as both growth template and stabilizing medium. The NW array exhibits strong light-trapping ability, the pore geometric features (pore radius-R and distance between pores-d) have the potential to enhance the light-matter interactions (LMI). We demonstrate the impact of R and d on LMI within the AAO/CsPbBr3 system using theoretical Finite Difference Time Domain (FDTD) simulations for the first time. Optimal LMI was observed with R=d=25 nm and R=d=50 nm. We report ligand-free synthesis of CsPbBr3 NW arrays via spin-coating, drop-casting, and inverse temperature crystallization (ITC). The spin-coating and drop-casting yielded poor pore filling while the modified ITC method yielded nearly complete (>90%) pore filling with significant NW lengths. Our findings highlight the potential of AAO templates for protecting CsPbBr3 and addressing synthetic challenges in HPs and other semiconductor NW arrays. This study provides valuable references for LMI in HPs and advances HPs and NW array-based optical devices and renewable energy applications

Photocatalytic processes are among the prime means for mitigating the pollution caused by toxic effluents. In this context, photocatalysis presents a promising path and is undergoing rapid evolution. Halide perovskite‐nanocrystals (HP‐NCs) are excellent candidates due to their negative conduction band minimum and low work function, essential for photocatalysis. Yet, HP‐NCs face limitations within this domain because they are prone to chemical degradation when exposed to external factors like high temperature, polar solvents, oxygen, and light. A practical approach toward stabilizing HP‐NCs involves hybridizing them with a chemically inert material that can provide steric stabilization and act as a cocatalyst. Transition‐metal dichalcogenides emerge as outstanding candidates to sterically stabilize the HPs as they are stable, chemically inert, and can serve as co‐catalysts, enabling suppressed charge recombination. Herein, the photocatalytic performance of Cs₄PbBr₆/WS₂‐nanocomposites towards organic dye degradation in polar solvents under visible light illumination is investigated. We found that the presence of WS₂ nanostructures significantly stabilizes the HP‐NCs and promotes dye degradation rate compared to pristine Cs₄PbBr₆‐NCs. Using transient absorption measurements, we found that the WS₂‐nanostructures act as an electron transport channel, effectively reducing charge recombination in the NCs. These findings pave the way for implementing Cs₄PbBr₆/WS₂‐nanocomposites as stable and superior photocatalysts.

WS₂ inorganic nanotubes (WS₂-NT) have been incorporated into Polylactic Acid (PLA) by melt mixing to create a bio-degradable, mechanically reinforced nanocomposite filament. The filament was then processed by Fused Filament Fabrication (FFF) 3D-printer, and the morphology and characteristics before and after printing were compared. We found that addition of WS₂-NT to PLA by extrusion mixing increases the elastic modulus, yield strength and strain-at-failure by 20%, 23% and 35%, respectively. Moreover, we found that the printing process itself improves the dispersion of WS₂-NT within the PLA filament, and does not require changing of the printing parameters compared to pure PLA. The results demonstrate the advantage of WS₂-NT as reinforcement specifically in 3D-printable polymers, over more traditional nano-reinforcements such as graphene and carbon nanotubes. WS₂-NT based 3D-printable nanocomposites can be used for variety of applications from custom-made biodegradable scaffold of soft implants such as cartilage-based organs and biodegradable soft stents to the more general easy-to-apply nano-reinforced polymers.