Computational Studies on Healing Mechanism of Vacancy of Graphene and Design of Organic Magnetic Materials
소속 :
연사 : Jin Yong Lee(SKKU Chem)
일시 : 2012-11-22 17:00 ~
장소 : 500동 목암홀
일 시 : 2012년 11월 22일, 5:00 PM
장 소 : 500동 목암홀
-Abstract-
In this talk, I will introduce computational studies on three topics; (1) Healing Mechanism of Vacancy of Graphene, (2) Design of Organic Magnetic Materials, and (3) CO2Chemosensor. Using first-principle DFT calculations, we have systematically explored the CO adsorption on the pristine graphene nanodot and the defective one by taking the external electric field into account. It is found that, the electric field can increase the CO adsorption energy and there is a barrier for CO-vacancy recombination which is mostly believed to remerge instantaneously when they come close to each other. Also, we proposed a mechanism for the subsequent healing of monovacancy on graphene nanodot by interaction with CO molecules, leading to the restoration of a pristine hexagonal carbon network. (2) A new series of neutral radicals (DP1–DP6) based on diazaphenalenyl were designed via heteroatomic modifications. As spin sources, the designed radicals were implemented in four different diradical model systems (Model I, II, III, and IV) by changing the reference radical and the linkage, and their magnetic interactions between the designed radicals and the reference radical were investigated by using density functional theory calculations. The trend in strength of magnetic interactions of radicals was found to be identical in different model systems. In particular, as a new family of spin source radical, DP3 could be a potential candidate in designing new organic magnetic materials due to its strong magnetic coupling and high stability in diradical systems. Then, we divided monoradicals into α-group and β-group according to Mulliken spin density values of the connected atoms. The overall trends in the strength of magnetic interactions of diradicals were found to be identical in three different model systems. NN-ethylene-PO was calculated to have the strongest magnetic coupling constant with ferromagnetism, and even stronger (more than twice) than NN-ethylene-NN which was reported to have strong antiferromagnetic interactions in a previous experiment. It was found that the spin density values of the connected atoms are closely related to the determination of magnetic interactions and J values. The spin states of the ground state in diradical systems were explained by means of the spin alternation rule. (3) If allowed, I will introduce a theoretical study on a new sensor for the fluorescent and colorimetric detection of CO2. The system utilizes fluoride to activate the imidazolium group in a tetrapropyl benzobisimidazolium deriative (TBBI) and operates in the absence of an added exogenous base. The calculation could explain the ambiguous experimental NMR spectra, and finally propose the plausible functioning mechanism of the sensor.
장 소 : 500동 목암홀
-Abstract-
In this talk, I will introduce computational studies on three topics; (1) Healing Mechanism of Vacancy of Graphene, (2) Design of Organic Magnetic Materials, and (3) CO2Chemosensor. Using first-principle DFT calculations, we have systematically explored the CO adsorption on the pristine graphene nanodot and the defective one by taking the external electric field into account. It is found that, the electric field can increase the CO adsorption energy and there is a barrier for CO-vacancy recombination which is mostly believed to remerge instantaneously when they come close to each other. Also, we proposed a mechanism for the subsequent healing of monovacancy on graphene nanodot by interaction with CO molecules, leading to the restoration of a pristine hexagonal carbon network. (2) A new series of neutral radicals (DP1–DP6) based on diazaphenalenyl were designed via heteroatomic modifications. As spin sources, the designed radicals were implemented in four different diradical model systems (Model I, II, III, and IV) by changing the reference radical and the linkage, and their magnetic interactions between the designed radicals and the reference radical were investigated by using density functional theory calculations. The trend in strength of magnetic interactions of radicals was found to be identical in different model systems. In particular, as a new family of spin source radical, DP3 could be a potential candidate in designing new organic magnetic materials due to its strong magnetic coupling and high stability in diradical systems. Then, we divided monoradicals into α-group and β-group according to Mulliken spin density values of the connected atoms. The overall trends in the strength of magnetic interactions of diradicals were found to be identical in three different model systems. NN-ethylene-PO was calculated to have the strongest magnetic coupling constant with ferromagnetism, and even stronger (more than twice) than NN-ethylene-NN which was reported to have strong antiferromagnetic interactions in a previous experiment. It was found that the spin density values of the connected atoms are closely related to the determination of magnetic interactions and J values. The spin states of the ground state in diradical systems were explained by means of the spin alternation rule. (3) If allowed, I will introduce a theoretical study on a new sensor for the fluorescent and colorimetric detection of CO2. The system utilizes fluoride to activate the imidazolium group in a tetrapropyl benzobisimidazolium deriative (TBBI) and operates in the absence of an added exogenous base. The calculation could explain the ambiguous experimental NMR spectra, and finally propose the plausible functioning mechanism of the sensor.
