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Abstract The presence of poly‐ and perfluoroalkyl substances (PFAS) in the environment is associated with adverse health effects but measuring PFAS is challenging due to the associated high cost and technical complexities of the analysis. Here, the reactivity of atomically precise metal‐oxo clusters is reported and the foundation for their use is provided as fluorescent nanosensors for PFAS detection. The material comprises crystalline, water soluble, hexanuclear cerium‐oxo clusters [Ce₆(µ₃‐O)₄(µ₃‐OH)₄]¹²⁺decorated with glycine molecules (Ce‐Gly) characterized by fluorescence emission at 353 nm. The Ce‐Gly fluorescence is found sensitive to long chain carboxylated PFAS of CF₃–(CF₂)_n–, where n ≥ 6, such as perfluorooctanoic, perfluorononanoic and perfluorodecanoic acids. This unique reactivity leads to a change in the emission spectra in a concentration dependent manner, enabling PFAS detection through ligand exchange and aggregation‐induced emission (AIE) enhancement. No significant cross‐reactivity from potentially co‐existing species, including sulfonated PFAS, octanoic and dodecanoic acids, humic acid, and inorganic ions is observed. With an optimal concentration of 3.3 µg mL⁻¹Ce‐Gly, the method demonstrated detection limits of 0.24 ppb for PFOA and 0.4 ppb for PFNA. These findings highlight the potential of fluorescence‐based detection strategies utilizing nanoscale probes such as Ce‐Gly as fluorescent probes and nanosensors for PFAS. 

Abstract Rational design of chiral two‐dimensional hybrid organic–inorganic perovskites is crucial to achieve chiroptoelecronic, spintronic, and ferroelectric applications. Here, an efficient way to manipulate the chiroptoelectronic activity of 2D lead iodide perovskites is reported by forming mixed chiral (R‐ or S‐methylbenzylammonium (R‐MBA⁺or S‐MBA⁺)) and achiral (n‐butylammonium (nBA⁺)) cations in the organic layer. The strongest and flipped circular dichroism signals are observed in (R/S‐MBA_0.5nBA_0.5)₂PbI₄films compared to (R/S‐MBA)₂PbI₄. Moreover, the (R/S‐MBA_0.5nBA_0.5)₂PbI₄films exhibit pseudo‐symmetric, unchanged circularly polarized photoluminescence peak as temperature increases. First‐principles calculations reveal that mixed chiral–achiral cations enhance the asymmetric hydrogen‐bonding interaction between the organic and inorganic layers, causing more structural distortion, thus, larger spin‐polarized band‐splitting than pure chiral cations. Temperature‐dependent powder X‐ray diffraction and pair distribution function structure studies show the compressed intralayer lattice with enlarged interlayer spacing and increased local ordering. Overall, this work demonstrates a new method to tune chiral and chiroptoelectronic properties and reveals their atomic scale structural origins. 

Abstract 2D‐on‐3D (2D/3D) perovskite heterostructures present a promising strategy to realize efficient and stable photovoltaics. However, their applicability in inverted solar cells is limited due to the quantum confinement of the 2D‐layer and solvent incompatibilities that disrupt the underlying 3D layer, hampering electron transport at the 2D/3D interface. Herein, solvent‐dependent formation dynamics and structural evolution of 2D/3D heterostructures are investigated via in situ X‐ray scattering. It is revealed that solvent interaction with the 3D surface determines the formation sequence and spatial distribution of quasi‐2D phases withn= 2–4. Isopropanol (IPA) reconstructs the perovskite into a PbI₂‐rich surface, forming a strata with smallernfirst, followed by a thinner substratum of largern. In contrast, 2,2,2‐Trifluoroethanol (TFE) preserves the 3D surface, promoting the formation of uniformly distributed largerndomains first, and smallernlast. Leveraging these insights, Dion–Jacobson perovskites are used with superior charge transport properties and structural robustness to fabricate 2D/3D heterostructures dominated byn≥ 3 and engineer a favorable energy landscape for electron tunneling. Inverted solar cells based on 3‐Aminomethylpyridine and TFE achieve a champion efficiency of 23.60%, withV_ocand FF of 1.19 V and 84.5%, respectively, and superior stabilities witht₉₄of 960 h under thermal stress.