A ferroelectric with a high phase‐transition temperature (Tc) is an indispensable condition for practical applications. Over the past decades, both strain engineering and the isotope effect have been found to effectively improve the Tc within ferroelectric material systems. However, the former strategy seems to prefer working in inorganic ferroelectric thin films, while the latter is also limited to some certain systems, such as hydrogen‐bonded ferroelectrics. It is noted that a mono‐fluorinated molecule is geometrically very similar to its parent molecule and the substitution of H by an F atom can introduce a chiral center on the molecule to template or stabilize polar structures. Significantly, the barrier of rotation of the fluorinated organic molecules is raised, resulting in a remarkable increase in Tc. Herein, by applying the molecular design strategy of H/F substitution to the organic–inorganic perovskite ferroelectric (pyrrolidinium)CdCl3 with a low Tc of 240 K, two high‐Tc chiral perovskite ferroelectrics, (R)‐ and (S)‐3‐F‐(pyrrolidinium)CdCl3 are successfully synthesized, for which the Tc reaches 303 K. The significant enhancement of 63 K in Tc extends the ferroelectric working temperature range to room temperature. This finding provides a new effective way to regulate the Tc in ferroelectrics and to design high‐Tc molecular ferroelectrics.

The past decade has witnessed much progress in designing molecular ferroelectrics, whose intrinsic mechanical flexibility, structural tunability, and easy processability are desirable for next-generation flexible and wearable electronic devices. However, an obstacle in expanding their promising applications in nonvolatile memory elements, capacitors, and sensors is effectively modulating the Curie temperature (T c ).Here, taking advantage of fluorine substitution on the reported molecular ferroelectric, (pyrrolidinium)MnCl 3 , we present enantiomeric perovskite ferroelectrics, namely, (R)and (S)-3-(fluoropyrrolidinium)MnCl 3 . The close van der Waal's radii and the similar steric parameters between H and F atoms ensure the minimum disruption of the crystal structure, while their different electronegativity and polarizability can trigger significant changes in the physical and chemical properties. As expected, the T c gets successfully increased from 295 K in (pyrrolidinium)MnCl 3 to 333 K in these two homochiral compounds. Such a dramatic enhancement of 38 K signifies an important step toward designing high-T c molecular ferroelectrics. In the light of the conceptually new idea of fluorine substitution, one could look forward to a continuous succession of new molecular ferroelectric materials and technology developments.

For nearly 100 y, homochiral ferroelectrics were basically multicomponent simple organic amine salts and metal coordination compounds. Single-component homochiral organic ferroelectric crystals with high-Curie temperature (T c ) phase transition were very rarely reported, although the first ferroelectric Rochelle salt discovered in 1920 is a homochiral metal coordination compound. Here, we report a pair of single-component organic enantiomorphic ferroelectrics, (R)-3-quinuclidinol and (S)-3-quinuclidinol, as well as the racemic mixture (Rac)-3-quinuclidinol. The homochiral (R)-and (S)-3-quinuclidinol crystallize in the enantiomorphic-polar point group 6 (C 6 ) at room temperature, showing mirror-image relationships in vibrational circular dichroism spectra and crystal structure. Both enantiomers exhibit 622F6-type ferroelectric phase transition with as high as 400 K [above that of BaTiO 3 (T c = 381 K)], showing very similar ferroelectricity and related properties, including sharp step-like dielectric anomaly from 5 to 17, high saturation polarization (7 μC/cm 2 ), low coercive field (15 kV/cm), and identical ferroelectric domains. Their racemic mixture (Rac)-3-quinuclidinol, however, adopts a centrosymmetric point group 2/m (C 2h ), undergoing a nonferroelectric high-temperature phase transition. This finding reveals the enormous benefits of homochirality in designing high-T c ferroelectrics, and sheds light on exploring homochiral ferroelectrics with great application. ferroelectricity | homochirality | enantiomer | ferroelectric domains

International audienceSurface grafting from diazonium solutions triggered by localized surface plasmon has been investigated. An organic layer that is 20−30 nm thick is easily grafted onto gold nanoparticles (AuNPs) by visible-light illumination in a few minutes without any reducing agent or molecular photocatalyst. Grafting depends on the wavelength and polarization of the incident light. As a consequence, the orientation of the growth of the layer deposited on the AuNPs can be controlled by polarized light. Grafting is also highly enhanced between adjacent AuNPs or at the corners of triangular AuNPs, that is, in plasmonic hot spots. These results clearly demonstrate plasmon enhancement and strongly suggest that the transfer of hot electrons from the excited plasmonic NPs to the diazonium is the main mechanism. They also confirm that localized surface plasmon resonance can induce nano-localized electrochemical reactions, thus contributing to the field of " plasmonic electrochemistry "