Distinguishing motor oils at higher concentration range by evaluating total fluorescence quantum yield as a novel sensing tool

Recently we developed a fluorescence-based fiber optic sensor for polycyclic aromatic hydrocarbons (PAHs) detection and subsequently methods were developed for studying multi-fluorophoric systems at higher concentration using fluorescence. In this paper, it is shown that evaluation of relative total fluorescence quantum yield can be a simpler and fast sensing tool to study various kinds of motor oils. The concentration variation of different kinds of motor oils such as petrol, kerosene, diesel and 2T oil at higher concentration range from 0 to 100% (v/v) shows a unique behavioral change with respect to each other in their total fluorescence quantum yield. Total fluorescence quantum yield makes it easier to distinguish lighter versus heavy motor oils. The excitation and emission spectral maxima shift of petrol, kerosene and 2T oil are found to be similar in the line of diesel as reported earlier but show different class of PAHs present in these motor oils. It is observed that kerosene and petrol contain lower ring PAHs compared to mobil, diesel and 2T oil. The fluorescence change due to energy transfer with concentration also reflects the relative concentration of various classes of PAHs.