In the traditional fluorescence detection, samples are tested in the solvent, and the mutual effect of solvent, micro impurity and sample affects the fluorescence characteristics. Meanwhile, such effect includes vibrational relaxation, electron rearrangement of solvent molecule, special role of the sample with the solvent molecules and so on. The experiment of fluorescence quantum efficiency at atmosphere reduces the interference, because the distance between molecules is much larger in gas phase. In addition, the research of quantum efficiency can also promote the understanding of LIF and expand the range. <p> </p>In this paper, the fluorescence quantum efficiency of 3 different samples at atmosphere was compared, and the electrospray ionization source was selected for its soft ionization characteristics. The ionization method did not spoil the fluorophore of the sample, and the drift tube of ion mobility spectrometry (IMS) was used for ions transport and desolvation. The ionization source was on the one side of the drift tube and the test point was on the other side. The paths of excited laser and emission light were orthogonal at the test point. Meanwhile, stable ions flowed through the drift tube. The emission light was captured by the camera, which was coupled with a long-wave pass filter. The test samples were Rhodamine 6G，Rhodamine B and amino copper indium sulfide quantum dots of the same mass fraction. The energy of excited laser was between 30 mW and 150 mW. Then the results showed that the emission intensity was proportional to the laser power in gas phase, and the sort of the fluorescence quantum efficiency was the quantum dots>Rhodamine 6G>Rhodamine B.
Ion mobility spectrometry (IMS) is widely used in the field of chemical composition analysis. Faraday cup is the most classical method to detect ions for IMS in the atmospheric pressure. However, the performance of Faraday plate was limited by many kinds of factors, including interfering electromagnetic waves, thermal(Johnson) noise, induced current , gain bandwidth product, etc. There is a theoretical limit in detection of ions at ambient condition which is approximately 106 ions per second. In this paper, we introduced a novel way using laser-induced fluorescence (LIF) to bypass the limitation of Faraday plate. Fluorescent ions which were selected by IMS get excited when they fly through the laser excitation area. The fluorescence emitted by the excited ions was captured exponentially and amplified through proper optoelectronic system. Rhodamine 6G (R6G) was selected as the fluorochrome for the reason that excitation wavelength, emission wavelength, and fluorescence quantum yield were more appropriate than others. An orthometric light path is designed to eliminate the adverse impact which was caused by induced laser. The experiment result shows that a fluorescence signal from the sample ions of the IMS could be observed. Compared with Faraday plate, the LIF-IMS may find a potential application in more system at the atmosphere condition.