Unveiling the piezoelectric nature of polar α-phase P(VDF-TrFE) at quasi-two-dimensional limit.

Piezoelectric response of P(VDF-TrFE), which is modulated by the dipole density due to the polarization switching on applying an electric field, allows it act as the fundamental components for electromechanical systems. As proposed since the 1970s, its polar α-phase is supposed to yield an enhanced piezoelectric activity. However, its experimental verification has never been reported, hampered by a substantial challenge for the achievement of a smooth, neat α-phase film. Here, we prepare ultrathin crystalline α-phase P(VDF-TrFE) films on the AlOx/Al-coated SiO2/Si substrates via a solution-based approach at room temperature. Thus, we unveil the piezoelectric nature of the polar α-phase P(VDF-TrFE) at a quasi-two-dimensional limit. The obtained values of the relative morphological deformation, the local effective piezoelectric coefficient, and the electric field-induced strain reach up to 37 pm, -46.4 pm V-1, and 4.1%, respectively. Such a robust piezoelectric response is even higher than that of the ß-phase. Besides, the evolution of piezoelectricity, which is related to the piezoelectric properties of two polarization states, is also studied. Our work can enable the exploration of the prospective applications of polar α-phase P(VDF-TrFE) films.

Lu2@C82 Nanorods with Enhanced Photoluminescence and Photoelectrochemical Properties.

One-dimensional (1D) single-crystalline hexagonal nanorods of Lu2@C3v(8)-C82 were prepared for the first time using the liquid-liquid interface precipitation (LLIP) method from the interfaces between carbon disulfide (CS2) and isopropyl alcohol (IPA). The length of the nanorods can be readily controlled by varying the concentration of the Lu2@C82 solution in addition to the volume ratio of CS2 to IPA. The latter factor also exhibits a significant influence on the morphology of the crystals. The crystalline structure of the nanorods has been investigated by XRD and selected area electron diffraction (SAED), suggesting a face-centered cubic structure. Photoluminescence of the Lu2@C82 nanorods shows a remarkable enhancement as compared to that of pristine Lu2@C82 powder because of the high crystallinity. Furthermore, we have investigated the photoelectrochemical properties of Lu2@C82 nanorods, proving their potential applications as photodetectors.

Understanding Charge-Transfer Characteristics in Crystalline Nanosheets of Fullerene/(Metallo)porphyrin Cocrystals.

Cocrystals in the form of crystalline nanosheets comprised of C70 and (metallo)porphyrins were prepared by using the liquid-liquid interfacial precipitation (LLIP) method where full control over the morphologies in the C70/(metallo)porphyrins nanosheets has been accomplished by changing the solvent and the relative molar ratio of fullerene to (metallo)porphyrin. Importantly, the synergy of integrating C70 and (metallo)porphyrins as electron acceptors and donors, respectively, into nanosheets is substantiated in the form of a near-infrared charge-transfer absorption. The presence of the latter, as reflection of ground-state electron donor-acceptor interactions in the nanosheets, in which a sizable redistribution of charge density from the electron-donating (metallo)porphyrins to the electron-accepting C70 occurs, leads to a quantitative quenching of the localized (metallo)porphyrin fluorescence. Going beyond the ground-state characterization, excited-state electron donor-acceptor interactions are the preclusion to a full charge transfer featuring formation of a radical ion pair state, that is, the one-electron reduced fullerene and the one-electron oxidized (metallo)porphyrin.

Rigid Tether Directed Regioselective Synthesis and Crystallographic Characterization of Labile 1,2,3,4-Bis(triazolino)[60]fullerene and Its Thermolized Derivatives.

Labile bis-triazoline adducts of C60 are supposed to be the precursors of bis-azafulleroids, but the formation mechanism is still unclear because of the incomplete isolation of the thermolized products and the lack of X-ray structures. A rigid-tethered reagent 1,2-bis(azidomethyl)benzene (1) was used to regioselectively synthesize the labile 1,2,3,4-bis(triazolino)[60]-fullerene (2), the structure of which was determined by single-crystal X-ray crystallography. Further thermolysis of 2 produces four products (3 a-3 d), which were all characterized by X-ray crystallography. Although 3 a and 3 b have traditional bis-azafulleroid structures, as proposed previously, 3 c and 3 d show unprecedented structures with either the coexistence of [5,6]-open and [6,6]-closed patterns or an oxidized structure with an 11-membered ring on the cage. A thermolysis mechanism is proposed to clarify long-term confusion about the transformation process from bis-triazoline adducts to bis-azafulleroids of C60 .

Facile Method toward Hierarchical Fullerene Architectures with Enhanced Hydrophobicity and Photoluminescence.

A two-step self-assembly strategy has been developed for the preparation of fullerene hierarchical architectures. Typically, the precipitation method is utilized to synthesize the initial fullerene microstructures, and subsequently a drop-drying process is employed to facilitate the fullerene microstructures to self-assemble into the final hierarchical structures. Overall, this methodology is quite simple and feasible, which can be applied to prepare fullerene hierarchical structures with different morphological features, simply by choosing proper solvent. Moreover, the as-obtained C70 hierarchical structures have many superior properties over the original C70 microrods such as superhydrophobicity and unique photoluminescence behaviors, promising their applications as waterproof optoelectronics.