Fluorescence spectrum analysis
Fluorescence spectrum can provide more information, such as excitation spectrum, emission spectrum, quantum yield, fluorescence lifetime, fluorescence polarization and so on. At the same time, the excitation and emission peaks can be used for qualitative analysis, and the relationship between fluorescence intensity and concentration can be used for quantitative analysis. In addition, the microscope accessories can be used for microscopic analysis.
A fluorophore which is excited by a photon will drop to the ground state with a certain probability based on the decay rates through a number of different (radiative and/or nonradiative) decay pathways. Steady state fluorescence can provide an average signal, and fluorescence lifetime can provide information about excited state molecules.
The experimental results show that many molecules fluorescence information is lost in the time averaged process. The fluorescence lifetime is related to the polarity and viscosity conditions of the microenvironment. We can directly understand the changes in the system studied by fluorescence lifetime. Fluorescence occurs mostly in nanosecond, which is precisely the time scale of molecular motion.
Time-Resolved fluorescence measurement is widely used in fluorescence spectroscopy, including materials science, chemistry, biological research macromolecules and cell imaging. The following are briefly introduced:
1 The measurement and analysis of the fluorescence lifetime of the mixed system:
When the system contains a variety of fluorescent substances, the fluorescence emission spectra of each substance may be overlapped and interfered, and the accurate information of the system cannot be obtained by using the Steady-State fluorescence emission spectrum. By Time-Resolved fluorescence, the composition of fluorescent substances in the system can be resolved through the difference of fluorescence lifetime, thus providing valuable information.
2. The influence of the different batches components on the phosphors quality and monitoring.
Oxygen (nitrogen) phosphor powders have been paid much attention in the field of solid luminescence because of their high luminescence efficiency, effective excitation of visible light, high stability and friendly environment. Among them, rare earth doped phosphors have good application prospects because of their high luminous intensity, high quantum efficiency and excellent thermal stability.
3. ZnO microtubules PL spectroscopy
ZnO is a kind of amphoteric white oxide. As shown, the wurtzite structure ZnO has central symmetry but no axial symmetry, and a dangling bond appears on the crystal surface due to the cross section. The influence of the characteristics of the surface section of ZnO crystal on the overall properties of the crystal increases with the decrease of its size, and even completely changes the original properties of the crystal itself. Therefore, by controlling the structure of Zinc Oxide, such as size, morphology or surface orientation, surface composition and surface charge, the properties of Zinc Oxide can be greatly adjusted or changed, so as to obtain the luminescence, fluorescence enhancement, ferromagnetism, catalytic properties and so on, in which the micrometer size of ZnO is luminescent.
PL spectroscopy is a non destructive and highly sensitive analytical method. It is a conventional test method in the development and production of semiconductor materials. It can detect the intrinsic luminescence of semiconductors and detect the defect luminescence caused by the conditions of doping, production technology and so on. The effects of optical properties provide theoretical guidance for semiconductor applications in photonic crystals, catalysis, sensing and dye-sensitized solar cells.
|Fig.1 ZnO wurtzite structure
||Fig.2 ZnO microtubules
PL spectroscopy at different position,
the photo is the Microimaging
at the fracture of ZnO microtubule.
|Fig.3 Different size of
ZnO microtubules PL spectroscopy
4、Upconversion Fluorescence Measurements
Fluorescence upconversion materials absorb light in the near infrared and produce emission of shorter wavelengths in the visible spectral range. Based on this characteristic, these upconversion materials are currently the focus of research for their use in biological fluorescence labeling, infrared photoelectric detection, and dye sensitized solar cells and so on. The excitation light of the rare earth doped upconversion nanomaterials is infrared light, and the light through the window of the biological tissue is in the infrared band, which means that the fluorescence probe can be realized in the body. In addition, the rare earth doped upconversion nanomaterials also have the advantages of high luminous sensitivity, stable chemical properties and low biotoxicity. Therefore, rare earth doped upconversion luminescent nanomaterials are expected to be ideal fluorescent probes for biological applications.