This experiment was conduct to investigate the fluorescent behaviour of Leucophor PAF and to investigate the quenching of QBS with NaCl. It was found that the Leucophor PAF indeed satisfied the characteristic to act as whitening agent. It was also found that the quenching of QBS with NaCl was a diffusion-controlled collision process.
Fluorescence measurement provides very important information about the photochemistry of a particular molecule. The first part of this experiment was dealing with the fluorescence behavior of a Leucophor PAF. Information from both spectrophotometry and fluorimetry was used to measure the quantum yield as well as to explain why Leucophor PAF was use as ...view middle of the document...
Table 1.2. Fluorescence emission spectrum of QBS and Leucophor PAF
Based on Table 1.2, it can be observed that both compounds gave a different maximum intensity at different wavelength. The intensity of Leucophor is less than intensity of QBS.
There are two majors characteristics of optical brightener which are can absorb light in the ultraviolet region and re-emit light in visible spectrum. As can be seen in Figure 1.1, Leucophor PAF has absorbance at 345 nm which in the ultraviolet region. From Table 1.2, Leucophor PAF has maximum intensity at 428 nm which in the visible region. Based on these two characteristics, Leucophor PAF able to act as whitening agent.
Quantum yield is expressed as followed:
Since the fluorescence quantum yield of QBS is given, it is possible to find the fluorescence quantum yield of Leucophor PAF:
∅_QBS/∅_PAF =((1-〖10〗^(-A_2 ) ) n_1^2 α_1)/((1-〖10〗^(-A_1 ) ) n_2^2 α_2 ) where ∅_QBS= 0.546 and both n1and n2=1.33
0.546/∅_PAF = = ((1-〖10〗^(-0..433) )×〖1.33〗^2×58459)/((1-〖10〗^(-0.440) )×〖1.33〗^2×22256)
Based on the graph above, the rate...