Before answering your query, let me bring to your kind information that the quantitative PPy estimation can also be done by forming calibration curve in Methylene blue(MB).If asked, I can send the reference/process.
SincePPY.ZnO composite is insoluble in most of organic solvents,so use 0.15 mol of dodecylbenzene sulfonic acid (DBSA) in 500 ml of de-ionized water.
Absorption peak at 360 nm reveals electron transition in the benzenoid rings of DBSA. A broad band at 380 nm is the characteristic band of the hexagonal pure ZnO. (PPy)/ZnO composite film and PPy have the peaks of same shape, but some shifting in the bands is noticed. Further, the increased relative intensity of the peak for (PPy)/ZnO composite film is attributed to the interaction between ZnO NP and Ppy molecules. It is confirmed that the strong guest-host interactions organic/inorganic composites have occurred due to the presence of hydrogen bonding.The interaction between ZnO and PPy composite film contributes to the decrease in the degree of orbital overlap between the( pi) electrons of the phenyl rings with the lone pair of the nitrogen atom in the PPy molecules. It forms strong hydrogen bonding between them. Consequently, the extent of conjugation of PPy, thus resulting in the increased intensity of the peak in (PPy)/ZnO composite film substrate shifted to peaks for 380nm respectively(pi to pi*).