1 eV is ascribed to the carbon of sp 2-hybridized C-C bonds whereas that at 285.8 eV to carbon of C-N bonds. There are three primary statuses of nitrogen configuration in nitrogen-doped CNMs: graphitic (substitutional nitrogen), pyridine-like, and pyrrole-like. In order to analyze the electronic state of nitrogen atoms in CNMs, we focused our
attention especially to the N1s spectra, as revealed in Figure 3c. The peak around 398.3 eV is attributed to sp 3-hybridized nitrogen of the tetrahedral phase; the nitrogen is pyridine-type and is connected with the defective graphite Selleck BI 2536 sheets. The peak at 399.8 eV is ascribable to nitrogen with a local structure alike that of pyrrole, and the nitrogen is hence considered as Torin 1 research buy pyrrole-type. The peak LOXO-101 in vivo at 401.0 eV corresponds to sp 2-hybridized nitrogen of trigonal phase, and the nitrogen is graphite-type or substitutional type. The composition of the three types of nitrogen is reflected by the area ratio of the corresponding N1s peaks. With rise of reaction temperature from 400°C to 500°C, there is a significant increase of graphitic nitrogen relative to that of pyridine-type nitrogen. It is deduced that the formation
of graphitic configuration becomes more favorable with the rise of temperature. Figure 3 XPS spectra of the purified samples. (a) Survey scan, (b) C1s spectra, (c) N1s spectra, and (d) illustration of nitrogen configuration. Figure 4 shows the Raman spectra of C450, C5N1, C450N, and C500N. Each of the samples exhibits two peaks. The one at about 1,340 cm-1 (called D band) is associated with amorphous carbon relating to the vibration of carbon atoms with dangling bonds of disordered graphite. The peak at about 1,600 cm-1 (called G band) is related to the double-degenerate E2g mode of graphite, corresponding to the vibration of triple-degenerate sp 2 hybrid bond. The intensity ratio of G band and D band (I G/I D) is generally
used to identify the crystallinity of graphite. Lower I G/I D means more defect or vacancy. The intensity ratios of C450, C5N1, C450N, and C500N are listed in Table 3. Figure 4 Raman spectra of C450, C5N1, C450N, and C500N. Table 3 The I G / I D intensity ratios of all samples Sample name I G/I D C450 1.326 C5N1 1.287 C450N 1.255 C500N 1.239 Compared with C5N1, C450N is lower in I G/I D value. The C2H2/NH3 flow rate ratio for the formation of C5N1 is 5:1 whereas that of C450N is CYTH4 1:1. In other words, with a source flow richer in nitrogen, there is rise of nitrogen content, and with more defects or vacancies in N-CNM, there is decline of I G/I D value. With the rise of reaction temperature from 450°C to 500°C, there is slight decrease of nitrogen content but enhanced formation of amorphous carbon, and the net result is the further decline of I G/I D value. The PL spectra of C450, C5N1, and C450N obtained with an excitation source of 220 nm wavelength are showed in Figure 5a. It is known that pristine CNM exhibits strong UV PL at 368 nm at RT.