The Journal of Physical Chemistry C最新文献

Grain engineering has long been utilized to modify the electrical poling behavior of piezoelectric ceramics. In this study, we explore the impact of grain boundary engineering on the piezoelectric performance of Pb(Zr_0.52Ti_0.48)O₃ (PZT) epitaxial films. By precisely tuning growth parameters, we produce dense and “rod-like” grain boundary PZT films. These “rod-like” PZT films exhibit a markedly different piezoelectric response compared to dense epitaxial PZT films that are free of grain boundaries. When subjected to 5 N external pressure at 190 °C, the output voltage of the dense PZT film reaches 17.7 mV, while the “rod-like” PZT film’s output drops to 5.6 mV, highlighting the attenuating influence of grain boundaries on piezoelectricity. Both films demonstrate an increasing piezoelectric response with rising temperatures, suggesting a pyro-piezoelectric effect in PZT. Additionally, both films show excellent durability, maintaining performance over 1000 cycles. Piezoelectric force microscopy analysis reveals that grain boundaries hinder reversible domain wall motion, leading to reduced piezoelectric coefficients in the PZT films. This study underscores the critical role of grain boundaries in influencing the piezoelectric behavior of epitaxial films and offers insights for grain boundary engineering in the development of self-sustained, smart sensing applications.

The picene molecules grown on a Pb(111) substrate have been investigated by low-temperature scanning tunneling microscopy. Picene molecules present selective adsorption at low coverage due to the quantum size effect of the Pb(111) film. The lattice of picene exhibits chiral switching and lattice rotation induced by the electric field. When increasing the coverage, two crystalline phases, (110)-like and (211̅) phases, have been found in the picene monolayer regime. Our results provide new choices and ideas for preparing new organic electronic devices.

Materials having room-temperature phosphorescence (RTP) are in limelight due to their advantageous long luminescence lifespan for applications in optoelectronics, bioimaging, and security purpose devices. Development of metal- and halogen-free organics for persistent luminescence and RTP has been envisaged through aggregation, heavy atom substitution, host–guest interactions, etc. In this article, we present experimental evidence for the effect of H-bonding and other nonbonding interactions on types of emission in five carbazole derivatives. An unsubstituted carbazole showed only fluorescence in powder form, while the N-aryl-substituted carbazole having carbonyl and nitrile groups (Benzal-CN-Cbz, Acph-CN-Cbz, and Bnph-CN-Cbz) showed dual emission consisting of fluorescence and phosphorescence in powder form under ambient conditions. Acph-CN-Cbz showed the longest excited-state lifetime exceeding 1.2 ms in powder form. RTP in Benzal-CN-Cbz, Acph-CN-Cbz, and Bnph-CN-Cbz is correlated to H-bonding and nonbonding interactions evident from single-crystal analysis. H-bonding involving the carbonyl group and extensive π–π interactions caused close packing in the solid state and is associated with the long-lived triplet excited state and RTP. Further, persistent luminescence having a lifetime of up to 1.5 s at ambient temperature in air was displayed in drop-casted PVA films. To the best of our knowledge, only a few organics, without halogen and heavy atoms, are available with such long lifetimes.

The sensitization-initiated electron transfer (SenI-ET) mechanism is a well-established concept in photoredox catalysis, yet its kinetic intricacies remain to be fully elucidated. In this study, we have successfully designed and synthesized a dyad, Ru(bpy)₃²⁺–pyrene (Ru-Py), which functions dually as a sensitizer and a reductant. By the use of the rapid intramolecular triplet and singlet energy transfer of Ru-Py, the complex decay pathway of the SenI-ET process was effectively simplified. Notably, we have demonstrated that direct electron transfer from ³Ru*-Py to diisopropyl ethylamine generates Ru(I)-Py, which further drives the catalytic process, rather than the catalytic reaction being driven by the formation of a Ru-Py^•- through electron transfer from Ru-³Py* to diisopropyl ethylamine. Furthermore, we employed Ru-Py as a catalyst for the C–H oxidation of an activated aryl bromide, demonstrating superior catalytic efficiency compared to that of the conventional Ru(bpy)₃²⁺/pyrene system.

Single-crystal (SC) perovskites have emerged as promising contenders for perovskite solar cells (PSCs) and the next generation of optoelectronic devices. Compared to polycrystalline (PLC) perovskites, SC perovskites have reduced trap densities, enhanced carrier mobility, and extended carrier lifetime. However, a comprehensive understanding of carrier dynamics in perovskite SCs is still lacking, primarily due to their bulk dimensions, which are not suitable for ultrafast spectroscopic studies. Here, we prepared spectroscopically thin SC films for investigating their ultrafast photophysical properties. It is found that the excitation above the band gap results in the quasi-thermalization of carrier distributions within 100 fs, with an initial carrier temperature of the SC film three times higher than that of the PLC film. Our results indicate that the contribution of inelastic carrier–carrier scattering in the SC film is significantly lower than that in the PLC film. During carrier cooling, a short-lived sub-band gap transient absorption signal arises only in the SC film, which can be explained by the interplay of band gap renormalization and hot-carrier distributions. However, it is absent in the PLC film until the excitation density surpasses the amplified spontaneous emission threshold. Furthermore, cooling of hot carriers in the SC film is accelerated by a stronger interaction between the photocarrier and the lattice.