The photoswitching and competitive processes of the referent photochromic diarylethene derivative 1,2-bis(2,4-dimethyl-5-phenyl-3-thienyl)perfluorocyclopentene (DTE) and a novel bridged analog DTE-m5 have been investigated by state-of-the-art TD-DFT calculations and ultrafast spectroscopy supported by advanced chemometric data treatments. Focusing on DTE, the overall deactivation pathway of both antiparallel (AP) and parallel (P) conformers of the open form (OF) (1 : 1 in solution) has been resolved and rationalized starting from the Franck-Condon (FC) region to the ground state recovery. For the photo-excited P conformer, after ultrafast relaxation (∼200 fs) towards the S relaxed state, an expected ISC occurred (55 ps) to produce a triplet state, P, the latter relaxing within 2.5 μs. Concerning the AP conformer, the photocyclization reaction is reported to proceed immediately (100 fs) starting from the FC region while the relaxed singlet state is populated in parallel. For the first time, we discovered that the latter state evolves through an unexpected ISC process (1 ps) giving rise to a second triplet state,AP. For DTE-m5, by slightly constraining the molecule with the bridge, this triplet becomes reactive and participates in the formation of 10% of closed form (CF) probably through an adiabatic mechanism. Concerning the photoreversion, in accordance with the literature, we report on a two-step process, a 190 fs vibrational relaxation followed by a 6 ps ring-opening reaction. For the overall species at the singlet or triplet manifold, the use of advanced MCR-ALS allows us to obtain specific spectral signatures. This study is therefore a new step within the comprehension of DTE photochemistry.

N-doped carbon synthesized by a room temperature plasma process demonstrated the synergic effect of amino-N and graphitic-N towards advanced ORR activity.

Halogen-doped carbon nanoparticles (CNPs) were synthesized by a simple one-step solution plasma process at room temperature using a mixture of benzene (C6H6) and organics containing halogen atoms as the precursors (i.e., hexafluorobenzene (C6F6), hexachlorobenzene (C6Cl6), and hexabromobenzene (C6Br6)). The experimental results demonstrated that halogen doping, especially F and Cl, could lead to more efficient removal of residual hydrogen compared to carbon synthesized with pure benzene. This phenomenon was related to the different binding energies between hydrogen and halogens to form hydrogen halides. Their crystallinity and morphology did not change and remained the same as non-doped carbon. The electrochemical evaluation of oxygen reduction reaction (ORR) activity in an alkaline solution revealed that halogen doping did not play a significant role in shifting the onset potential for the ORR, while a slight enhancement in diffusion limited current density was observed at high overpotentials. Moreover, the electron transfer number involved in the ORR process determined from the Koutecky-Levich plot at -0.6 V was found to increase for halogen-doped carbons in the following order: F-CNPs > Br-CNPs > Cl-CNPs > CNPs. The improved ORR performance of F-CNPs could reasonably be attributed to the synergistic effects of specific bonding states between the halogen and carbon, structural defects and surface functional groups. Our results confirmed the validity of using halogen doping to improve the ORR catalytic activity of CNPs.

Selective nitrogen bonding within nitrogen-doped carbon nanoparticles was achieved by altering linear and heterocyclic precursor via solution plasma.

Although nitrogen-doped carbon catalysts are promising candidates for oxygen reduction reactions (ORRs), the role of the nitrogen bonding structure, such as pyridinic-N, amino-N, and graphitic-N, on the ORR activity remains controversial. Furthermore, despite recent progress in tuning the CÀN chemical bonding states within the carbon materials by using chemical vapor deposition and post heat treatment, a systematic evaluation of various N moieties remains challenging, owing to the differences in the thermal stabilities of different types of bonds. Herein, we successfully designed a method to tailor pyridinic-N, amino-N, and graphitic-N bonding in N-doped carbon nanoparticles fabricated through a plasma process combined with post heat treatment. Investigations on the electrochemical performance of the fabricated materials suggested that catalysts with dominant amino-N exhibited higher current density, where graphitic-N has a positive effect on the ORR onset potential. This synthetic strategy provides a simple and efficient approach for studying the relationship between the CÀN bonding structure and the electrochemical performance of N-doped carbon catalysts.

For several decades, the development of synthesis processes and designs for carbon materials such as graphites, carbon nanotubes, and graphenes has been continuous because of their superior physicochemical properties. The liquid-phase electric discharge process, known as the solution plasma process (SPP), has emerged as a potential synthesis process for carbon materials; however, liquid discharge in organic solutions has not yet been thoroughly investigated. In this study, plasma discharges in benzene (C 6 H 6 ) and pyridine (C 5 H 5 N) were conducted. During the discharge, two types of nanocarbons with different crystallinities were synthesized simultaneously in different reaction fields: between electrodes and in a liquid phase. The nanocarbons grown between electrodes were collected and then compared with the nanocarbons produced in the liquid phase after discharge. All carbon samples were measured using various techniques such as transmission electron microscopy (TEM), the nitrogen absorption-desorption method, X-ray diffraction (XRD), Raman spectroscopy, CHN elemental analysis, and X-ray photoelectron spectroscopy (XPS). Nanocarbons grown between electrodes in benzene or pyridine were found to be graphite structures, while the nanocarbons produced in the liquid phase were amorphous carbons. On the basis of the results obtained, the formation and growth of the two types of nanocarbon materials synthesized by SPP and their dependence on the position of the reaction field in plasma in the liquid phase are discussed.

Two types of diarylethene, each of which contains a naphthalene and a thiophene ring, were synthesized, and their photochromic properties were studied. The photochromic properties are dependent on the bridge position of the thiophene ring. The cycloreversion of one of the closed forms of some of the diarylethenes occurred almost photon quantitatively, and the photochromic reactions were thermally irreversible, at least at room temperature.

Photochromic thiophenophan-1-ene-S,S,S′,S′-tetraoxides have been synthesized by oxidation of sulfur atoms of thiophenophan-1-enes, and their photochromic properties were studied. The tetraoxides indicated photochromism and the quantum yields for photocyclization reactions became higher than that of nonbridged dithienylethene-S,S,S′,S′-tetraoxide due to fixation of conformations.