Effects of the π-electrons in fused polycyclic aromatic hydrocarbons on positron annihilation

Publication date: Available online 14 May 2019Source: Radiation Physics and ChemistryAuthor(s): Yijun Du, Junhu Zhao, Chen Wang, Chenze Qi, Yan Li, Hongyu Tao, Peng Zhang, Xingzhong Cao, Baoyi WangAbstractThe mesoporous phenol-formaldehyde resins (PFR) were synthesized using formaldehyde, phenol, F127 template as raw materials by high temperature hydrothermal method under different temperatures. Nitrogen doped mesoporous PFR were synthesized in the same way with another additional raw material HMTA. Two series of carbon materials PCs and PCNs were obtained after calcinating PFR at 700, 800, 900 °C. N2 adsorption analysis indicates that both the two kind of carbon materials have relatively large specific surface area (325–619 cm2/g for PCs and 431–580 cm2/g for PCNs). TEM and XRD analyses prove highly ordered mesoporous structure of the samples. Both the elemental analysis and IR results suggest a high carbon content and the abundant fused-ring structure of the test materials. The positron annihilation spectra show that the corresponding intensity I3 of the longest lifetime component τ3 is less than 2%, indicating that the π electrons in the fused rings with low ionization energy are capable of trapping positrons and inhibiting the formation of o-Ps.

Source: Radiation Physics and Chemistry - May 15, 2019 Category: Physics Source Type: research