Alkylboronic esters from copper-catalyzed borylation of primary and secondary alkyl halides and pseudohalides.

Easy access: An unprecedented copper-catalyzed cross-coupling reaction of the title compounds with diboron reagents is described (see scheme; Ts = 4-toluenesulfonyl). This reaction can be used to prepare both primary and secondary alkylboronic esters having diverse structures and functional groups. The resulting products would be difficult to access by other means.

Kramers-Kronig relation between nonlinear absorption and refraction of C(60) and C(70).

Using the Z-scan technique with 532 nm 16 picosecond laser pulses, we observe reverse saturable absorption and positive nonlinear refraction of toluene solutions of both C(60) and C(70). By deducting the positive Kerr nonlinear refraction of the solvent, we notice that the solute molecules contribute to nonlinear refraction of opposite signs: positive for C(60) and negative for C(70). Attributing nonlinear absorption and refraction of both solutes to cascading one-photon excitations, we illustrate that they satisfy the Kramers-Kronig relation. Accordingly, we attest the signs and magnitudes of nonlinear refraction for both solutes at 532 nm by Kramers-Kronig transform of the corresponding nonlinear absorption spectra.

A Method for Reducing the Singlet-Triplet Energy Gaps of TADF Materials for Improving the Blue OLED Efficiency.

We have successfully synthesized a series of blue thermally activated delayed fluorescence emitters, BPy-pC, BPy-pTC, BPy-p2C, and BPy-p3C, bearing a 4-benzoylpyridine core as the electron-accepting unit and carbazolyl, tert-butylcarbazolyl, dicarbazolyl, and tercarbazolyl groups as the electron-donating units, respectively. The density functional theory calculation shows that all of the compounds have their lowest unoccupied molecular orbitals on the benzoylpyridine moiety. However, the highest occupied molecular orbital (HOMO) of BPy-p3C is widely dispersed to the whole tercarbazolyl group, while the HOMOs of BPy-pC and BPy-pTC are mainly on the carbazolyl and extended to the phenyl ring. As a result, ΔEST is reduced from 0.29 eV for BPy-pC to 0.05 eV for BPy-p3C, and the organic light-emitting diodes using these materials as dopants emit blue light and their maximum external quantum efficiencies (EQEs) increase from 4.2% to 23.9% for BPy-pC and BPy-p3C, respectively. The EQE of the BPy-p3C-based device increases 2 times more than that of the BPy-pTC-based device without a significant change in the color coordinates.

Ultraviolet light enhances the bovine serum albumin fixation for acid fast bacilli stain.

The use of a liquid culture system such as MGIT broth has greatly improved the sensitivity of isolating mycobacteria in clinical laboratories. Microscopic visualization of acid fast bacilli (AFB) in the culture positive MGIT broth remains the first routine step for rapidly indicating the presence of mycobacteria. We modified an ultraviolet (UV) light fixation process to increase AFB cells adherence to the slide. The retained haze proportion of a 1-cm circle marked area on the smear slide was quantified after the staining procedure indicating the adherence degree of AFB cells. More AFB cells were preserved on the slide after exposure to UV light of either germicidal lamp or UV crosslinker in a time-dependent manner. We demonstrated both the bovine serum albumin (BSA) in MGIT media and UV light exposure were required for enhancing fixation of AFB cells. While applying to AFB stains for 302 AFB positive MGIT broths in clinics, more AFB cells were retained and observed on smear slides prepared by the modified fixation procedure rather than by the conventional method. The modified fixation procedure was thus recommended for improving the sensitivity of microscopic diagnosis of AFB cells in culture positive MGIT broth.