The electron transfer rate of large TPA based compounds: a joint theoretical and electrochemical approach

Site-selective heat boosting electrochemiluminescence for single cell imaging

In operando visualization of local electrochemical reactions provides mechanical insights into the dynamic transport of interfacial charge and reactant/product. Electrochemiluminescence is a crossover technique that quantitatively determines Faraday current and mass transport in a straightforward manner. However, the sensitivity is hindered by the low collision efficiency of radicals and side reactions at high voltage. Here, we report a site-selective heat boosting electrochemiluminescence microscopy. By generating a micron-scale heat point in situ at the electrode-solution interface, we achieved an enhancement of luminescence intensity up to 63 times, along with an advance of 0.2 V in applied voltage. Experimental results and finite element simulation demonstrate that the fundamental reasons are accelerated reaction rate and thermal convection via a photothermal effect. The concentrated electrochemiluminescence not only boosts the contrast of single cells by 20.54 times but also enables the site-selective cell-by-cell analysis of the heterogeneous membrane protein abundance. This electrochemical visualization method has great potential in the highly sensitive and selective analysis of local electron transfer events.

Versatile Donor-π-Acceptor-Type Aggregation-Enhanced Emission Active Fluorophores as Both Highly Efficient Nondoped Emitter and Excellent Host

By employing triphenylamine (TPA) and/or carbazole as donor and cyano group as acceptor, three donor-π-acceptor (D-π-A)-type fluorophores, 4,6-di(4-(diphenylamino)phenyl)isophthalonitrile (DTPAIPN), 4-(4-(diphenylamino)phenyl)-6-(3,5-(9,9'-dicarbazolyl)phenyl)isophthalonitrile (TPAmCPIPN), and 4,6-di(3,5-(9,9'-dicarbazolyl)phenyl)isophthalonitrile (DmCPIPN), were designed, synthesized, and characterized for their thermal, photophysical, electrochemical, and electroluminescent properties. All three compounds exhibited excellent thermal and morphological stabilities with thermal decomposition (T_d) and glass transition temperature (T_g) values ranging from 396 to 516 °C and from 114 to 211 °C, respectively. The investigation into the photophysical properties revealed the aggregation-enhanced emission (AEE) feature of these chromophores. The performances of the nondoped devices were significantly improved as compared to those of the doped devices, further confirming the AEE nature. In particular, DmCPIPN-based nondoped device rendered the maximum current efficiency (CE), power efficiency (PE), and external quantum efficiency (EQE) values of 26.6 cd A^-1, 22.4 lm W^-1, and 8.3%, respectively, in comparison with 9.1 cd A^-1, 4.9 lm W^-1, and 4.2% for the doped device. The versatility of these new luminogens was demonstrated through the utilization of them as host for highly efficient red phosphorescent organic light-emitting diodes (PHOLEDs). The EQE of the DmCPIPN-hosted device reached as high as 19.3% with a reduced efficiency roll-off of 10.3% at 1000 cd m^-2. These results demonstrate that the new luminogens of this work can be used as both nondoped emitter and host for high-performance OLEDs, which facilitates the development of multifunctional materials for OLEDs applications.

DFT investigation on organic dyes with cross-conjugated cyano groups

Organic dye molecules with the acceptor moieties, cyano groups, cross-conjugated to the donor moieties, have been investigated theoretically. Density functional theory (DFT) calculations on such cross-conjugated molecules reveal the effects of cross-conjugation on the geometric and electronic structures of the molecules. The cross-conjugated cyano groups in the dye molecules are found effective to alter the charge population and the frontier orbital energy levels of the dyes. The effects of cross-conjugation of cyano group on the molecular conformation, the charge transfer, and polarity of the dyes are discussed.

Electroactivity of a starburst hole-transport material in Langmuir–Blodgett films. Solid state effects and intervalence charge transfer

Here we report on the electroactivity properties of Langmuir-Blodgett (LB) films of the hole-transport molecule 4,4',4''-tris[3-methylphenyl(phenyl)amino] triphenylamine (m-MTDATA). Fairly stable Langmuir films at the air-water interface are accomplished, despite the non-amphiphilic character of the molecule. The reflection-absorption infrared spectroscopy (RAIRS) and Fourier transform infrared (FT-IR) analysis revealed that the molecules arrange with no neat preferential orientation, in agreement with the amorphous glassy nature of this starburst molecule. However, there is a tendency of the molecules to organize in a more planar conformation due to the intermolecular stacking induced by the LB technique. On the other hand, the fundamental electrochemistry (by cyclic voltammetry, CV) of the films is also analyzed. The CV studies of both solution and films reveal that both the solid state and the electrolyte's anions clearly affect the m-MTDATA's electroactivity, exhibiting a unique and broad redox process instead of the two reversible oxidations observed in solution. The oxidization mechanism is discussed. Finally, the spectroelectrochemistry studies evidence that the oxidization of the films leads to new absorption bands, among which the emerging bands in the NIR region ascribed to intervalence charge transfer (IVCT) between the generated aminyl radical cations should be pointed out.