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Investigation of the clear structure–property relationship and microscopic mechanism of thermally activated delayed fluorescence (TADF) emitters with high emission quantum yield is a direction wort...

Investigation of the clear structure-property relationship and microscopic mechanism of thermally activated delayed fluorescence (TADF) emitters with high emission quantum yield is a direction worthy of continuous efforts. The instructive theoretical principle of TADF material design is critical and challenging. Here, we carried out theoretical calculation on two experimental Cu(I) complexes with the same 7,8-bis(diphenylphosphino)-7,8-dicarba

Various tetrahedral heteroleptic Cu(I) complexes, as red organic light-emitting diodes (OLEDs), show a concern of maximizing the quantum yield (QY) in order to improve the optoelectronic performance. Herein, three experimental [Cu(N^N) (bis [2-(diphenylphosphino)phenyl]ether)]+ (named 1, 2 and 3) were selected as the jumping-off point, following two complexes (named 4 and 5) were successfully designed by introducing bulky electron-donating substituents into N^N ligands continuously. As expected, the QY of designed complexes 4 (0.26) and 5 (0.13) exhibit over twice higher than that of 3 (5.4 × 10−2). This can be attributed to the enhanced electron-donating property of N^N ligand, which accelerated the radiative transition rate (kr) through the apparently elevated energy level of the lowest triplet excited state (T1) and strengthened transition dipole moments, even though the spin-orbit coupling (SOC) effect is weakened. Simultaneously, the tetrahedral geometric distortion could be effectively restrained by the bulky N^N ligands, but the high vibrational freedom of the terminal substituents could also bring in some unfavorable intra-ligand deformation, resulting in an upward of the nonradiative transition rate (knr) at 5 (knr: 0.30 × 105 s−1 for 4; 0.95 × 105 s−1 for 5). Therefore, it's worth noting that the balance of excited state energy level, SOC effect as well as the reorganization energy ought to be elaborately regulated to achieve the optimal QY. This detailed investigation on the microscopic mechanism of these Cu(I) complexes can provide instructive inspiration for experimentalists.

Montmorillonite (MMT)-supported Ag/TiO(2) composite (Ag/TiO(2)/MMT) has been prepared through a one-step, low-temperature solvothermal technique. Powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) reveal that the Ag particles coated with TiO(2) nanoparticles are well-dispersed on the surface of MMT in the composite. As a support for the Ag/TiO(2) composite, the MMT prevents the loss of the catalyst during recycling test. This Ag/TiO(2)/MMT composite exhibits high photocatalytic activity and good recycling performance in the degradation of E. coli under visible light. The high visible-light photocatalytic activity of the Ag/TiO(2)/MMT composite is ascribed to the increase in surface active centers and the localized surface plasmon effect of the Ag nanoparticles. The Ag/TiO(2)/MMT materials with excellent stability, recyclability, and bactericidal activities are promising photocatalysts for application in decontamination.

Cubic-phase zirconia nanoparticles modified with univalent surface cations have been prepared through a low-temperature solvothermal method. The obtained products were characterized by powder X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). The surface of the nanoparticles has also been modified by divalent and trivalent cations, such as Mg2+ and Al3+, via ion exchange. The surface photovoltage (SPV) spectroscopy and surface photocurrent (SPC) spectroscopy measurements show that the surface cations on nanoscaled ZrO2 exert significant influence on the generation of charge carriers and the transportation of the generated charge carriers between nanoparticles. The effect of surface cations on the photoelectric conversion properties of the zirconia nanoparticles has been elucidated on the basis of theoretical calculation.

High-crystallinity anatase TiO2 nanocrystals with the size of ∼2−4 nm have been prepared by a facile and quick method at low temperature. Ethylene glycol was used to both control the hydrolysis and condensation rates of titanium isopropoxide. H2O used in this reaction system, is the key reagent for the anatase formation, and the amount of H2O has been demonstrated to be an important parameter for the fast anatase phase formation. The plausible reaction mechanism has been discussed on the basis of the results of SEM, TEM, HRTEM, XRD, UV−vis, FT-IR, and TGA measurements. By studying the sensing properties of the as-synthesized anatase nanocrystals, it has been found that the nanocrystals exhibit the fast response to oxygen under the UV illumination at room temperature.

Monodisperse gold-doped titania microspheres have been synthesized under high concentration of a titanium precursor (9.34 mM) by introducing a trace amount of chloroauric acid (CA) into the reaction system; the size of the microspheres can be easily tuned (from approximately 587 to approximately 392 nm) by varying the amount of the CA added. The plausible formation mechanism has been discussed in detail. Chloroauric acid was found to act as the stabilizing agent to induce the formation of monodisperse colloidal spheres. Gold-doped anatase titania spheres with approximately 7 nm gold nanodots on the surface were synthesized by calcination. Interestingly, results from surface photocurrent, surface photovoltage, and transient photovoltage measurements indicate that the gold nanodots exhibit different electronic properties when the gold-doped anatase titania spheres were illuminated by different wavelengths of light: one is an electron acceptor in the UV region, while the other is an electron donor in the visible region. Furthermore, the decay time of the injected plasmon-induced electrons was found to be on the millisecond timescale and increased with increasing amounts of gold doped.