UV-VIS electronic spectra of OB

UV-VIS electronic spectra of OB, COB, OOBAR, and Mo:OOBAR were estimated in solid state using Nujol mulls procedure. The higher energy of UV spectra bands of OB was performed at 241-265 nm which were attributed to the ?-?* transitions, and 293-340 nm which was attributed to the n-?* transitions localized on the conjugated system. Higher energy adsorption band in COB was assigned to 241-265 nm which was attributed to the ?-?* transitions, the second band was shifted to 293-355 nm and after oxidation process, there was a new band at 368-370 nm which were assigned to the n-?* transitions. UV spectrum of OOBAR was shown that many absorption bands between 200 and 250 nm at (201, 205, 216, 224, 227-229, 232, 237, 241 and 245) nm which were assigned to ?-?* transitions and due to the several functional groups of OOBAR. Also, many lower energy bands have appeared between 300 and 320 nm due to n-?* transitions. Mo:OOBAR has higher energy adsorption bands at 233-245, 250 and 261 nm which were attributed to the ?-?* transitions, and 264-296 nm which was attributed to the ?-?* and n-?* transitions, and also at 299 and 307 nm which were attributed to the n-?* transitions localized on the conjugated system. There are many lower energy bands were appeared at 247, 255 and 259 nm which were assigned to ?-?* transitions, and also between 300 and 340 nm due to n-?* transitions.
Figure 2
Boehm titration offers an identification of the active surface sites such as carboxylic, carbonyl and phenolic 42. Total acidic and basic sites were detected by back titration using 0.1 mol/L HCl and NaOH solutions. Carboxylic, lactonic and phenolic groups were evaluated by using titration with 0.1 mol/L NaHCO3, Na2CO3, and NaOH solutions. The acidic and basic sites of OB were (1.8 and 0.9 mmol/g), COB was (1.6 and 0.9 mmol/g), and OOBAR was (2.6 and 1.3 mmol/g). It is clear that the amount surface of total acidic sites was greater than basic sites in OB, COB, and OOBAR which have mainly acidic character. OB has 0.7 mmol/g carboxylic sites, 0.6 mmol/g lactonic sites and 0.5 mmol/g phenolic sites. The quantity of lactonic and phenolic sites was decreased from 1.1 mmol/g in OB to 0.6 mmol/g of COB while the number of carboxylic sites of COB was increased to 1.0 mmol/g due to an oxidation process. The amount of carboxylic and carbonyl groups of OOBAR is higher than COB due to the addition of phthalic acid.