55 research outputs found
Direct Microscopic Analysis of Individual C<sub>60</sub> Dimerization Events: Kinetics and Mechanisms
Modern
transition state theory states that the statistical behavior
of a chemical reaction is the sum of individual chemical events that
occur randomly. Statistical analysis of each event for individual
molecules in a three-dimensional space however is practically impossible.
We report here that kinetics and mechanisms of chemical reactions
can be investigated by using a one-dimensional system where reaction
events can be observed in situ and counted one by one using variable-temperature
(VT) atomic-resolution transmission electron microscopy (TEM). We
thereby provide direct proof that the ensemble behavior of random
events conforms to the Rice–Ramsperger–Kassel–Marcus
theory, as illustrated for [2 + 2] cycloaddition of C<sub>60</sub> molecules in carbon nanotubes (CNTs). This method gives kinetic
and structural information for different types of reactions occurring
simultaneously in the microscopic view field, suggesting that the
VT-TEM opens a new dimension of chemical kinetics research on molecules
and their assemblies in their excited and ionized states. The study
carried out at 393–493 K showed that pristine CNT primarily
acts as a singlet sensitizer of the cycloaddition reaction that takes
place with an activation energy of 33.5 ± 6.8 kJ/mol. On the
other hand, CNT suffers electron damage of the conjugated system at
103–203 K and promotes a reactive radical cation path that
takes place with an activation energy of only 1.9 ± 0.7 kJ/mol.
The pre-exponential factor of the Arrhenius plot gave us further mechanistic
insights
Direct Microscopic Analysis of Individual C<sub>60</sub> Dimerization Events: Kinetics and Mechanisms
Modern
transition state theory states that the statistical behavior
of a chemical reaction is the sum of individual chemical events that
occur randomly. Statistical analysis of each event for individual
molecules in a three-dimensional space however is practically impossible.
We report here that kinetics and mechanisms of chemical reactions
can be investigated by using a one-dimensional system where reaction
events can be observed in situ and counted one by one using variable-temperature
(VT) atomic-resolution transmission electron microscopy (TEM). We
thereby provide direct proof that the ensemble behavior of random
events conforms to the Rice–Ramsperger–Kassel–Marcus
theory, as illustrated for [2 + 2] cycloaddition of C<sub>60</sub> molecules in carbon nanotubes (CNTs). This method gives kinetic
and structural information for different types of reactions occurring
simultaneously in the microscopic view field, suggesting that the
VT-TEM opens a new dimension of chemical kinetics research on molecules
and their assemblies in their excited and ionized states. The study
carried out at 393–493 K showed that pristine CNT primarily
acts as a singlet sensitizer of the cycloaddition reaction that takes
place with an activation energy of 33.5 ± 6.8 kJ/mol. On the
other hand, CNT suffers electron damage of the conjugated system at
103–203 K and promotes a reactive radical cation path that
takes place with an activation energy of only 1.9 ± 0.7 kJ/mol.
The pre-exponential factor of the Arrhenius plot gave us further mechanistic
insights
Direct Microscopic Analysis of Individual C<sub>60</sub> Dimerization Events: Kinetics and Mechanisms
Modern
transition state theory states that the statistical behavior
of a chemical reaction is the sum of individual chemical events that
occur randomly. Statistical analysis of each event for individual
molecules in a three-dimensional space however is practically impossible.
We report here that kinetics and mechanisms of chemical reactions
can be investigated by using a one-dimensional system where reaction
events can be observed in situ and counted one by one using variable-temperature
(VT) atomic-resolution transmission electron microscopy (TEM). We
thereby provide direct proof that the ensemble behavior of random
events conforms to the Rice–Ramsperger–Kassel–Marcus
theory, as illustrated for [2 + 2] cycloaddition of C<sub>60</sub> molecules in carbon nanotubes (CNTs). This method gives kinetic
and structural information for different types of reactions occurring
simultaneously in the microscopic view field, suggesting that the
VT-TEM opens a new dimension of chemical kinetics research on molecules
and their assemblies in their excited and ionized states. The study
carried out at 393–493 K showed that pristine CNT primarily
acts as a singlet sensitizer of the cycloaddition reaction that takes
place with an activation energy of 33.5 ± 6.8 kJ/mol. On the
other hand, CNT suffers electron damage of the conjugated system at
103–203 K and promotes a reactive radical cation path that
takes place with an activation energy of only 1.9 ± 0.7 kJ/mol.
The pre-exponential factor of the Arrhenius plot gave us further mechanistic
insights
The relationship between elastase and lactoferrin in healthy, gingivitis and periodontitis sites
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