LUMINESCENCE the full process about it when

LUMINESCENCE the full process about it when

1. Luminescence 1 PREPARED BY PRIYANSHI ASATI

2. INDEX 2 Introduction 2 The nature of absorption process 3 Luminescence 3.1 luminescence process 3.2 Types of luminescence 4 Photoluminescence 4.1 Types of photoluminescence 4.2 It's applications 5 Research Topic .6 Conclusion

3. INTRODUCTION 3 THE WORD LUMINESCENCE WAS FIRST USED BY A GERMAN PHYSICIST, EILHARDTWIEDEMANN, IN 1888. IN LATIN 'LUMEN' MEANS 'LIGHT'. THE MATERIALS EXHIBITING THIS PHENOMENON ARE KNOWN AS 'LUMINESCENT MATERIALS' OR 'PHOSPHORS' MEANING 'LIGHT BEARER' IN GREEK.

4. 4 Luminescence refers to the emission of light by processes other than thermal emission, which is called incandescence. There are many types of luminescence: fluorescence, phosphorescence, chemiluminescence, triboluminescence, radioluminescence, and so on. The luminescent processes that are of interest in oceanography are fluorescence, phosphorescence, and bioluminescence, which is a form of chemiluminescence.When light is absorbed by a molecule, one of three things can happen: the energy is used for photochemisty , e.g. for photosynthesis in a chlorophyll molecule; 2. the energy goes into vibrational modesof the molecule, i.e. into heat; or 3. the energy is re-emitted as light via fluorescence of phosphorescence

5. 5 Figure 1 show a partial energy diagram for a photoluminescence system. One should note that each of the electronic states (ground or exited) has a number of vibrational levels superimposed on it. The vibrational levels arise because a molecule in a given electronic state may absorb small increments of energy corresponding to changes in vibrational modes, although retaining the same electronic configuration. Another significant fact to be noted is the degree of overlap between the vibrational levels of exited states such as S_{2} and S_{1} By convention the singlet states should be stacked in a column while the triplet states are stacked in another vertical column displaced. to the right of the singlet column. One should also notice the overlap between the vibrational levels of the triplet state T_{1} and its corresponding singlet state S_{1 The Nature of Absorption Processes

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7. LUMINESCENCE LUMINESCENCE IS SPONTANEOUS EMISSION OF LIGHT BY A SUBSTANCE NOT RESULTING FROM HEAT. IT CAN BE CAUSED BY CHEMICAL REACTION ELECTRICAL ENERGY SUBATOMIC MOTION OR STRESS ON A CRYSTAL LUMINESCENCE IS EMISSION OF LIGHT BY CERTAIN MATERIALS WHEN THEY ARE RELATIVELY COOL ALSO REFERRED AS A COOL-BODY RADIATION. 7

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9. Type of Luminescence 9

10. CLASSIFICATION OF LUMINESCENCE THERE ARE MANY TYPES OF LUMINESCENCE: ELECTRO-LUMINESCENCE: IT IS PRODUCED BY APPLYING POTENTIAL FOR ELECTRIC FIELD TO LUMINESCENT MATERIAL PHOTO-LUMINESCENCE: IT TAKES THE PLACE BY ABSORPTION OF PHOTON.(U-V RADIATION). THERMO-LUMINESCENCE: IT ORIGINATES WHEN PREVIOUSLY IRRADIATED SUBSTANCE IS HEATED. BIO- BIO-LUMINESCENCE : THIS IS BECAUSE OF THE ENERGY FROM BIOCHEMICAL REACTIONS IN A LIVING ORGANISM. MECHNO-LUMINESCENCE: PRODUCED BY MECHANICAL DEFORMATION OF SOLID. CATHODO-LUMINESCENCE: IT IS DUE TO THE ENERGETIC ELECTRONS OR CATHODE RAY. RADIO-LUMINESCENCE: IT IS PRODUCED BY ANY OR ALL RADIOACTIVE PRODUCTS. HOT LUMINESCENCE : IN SEMICONDUCTING LUMINESCENT MATERIALS, HOT LUMINESCENCE IS CAUSED BY HOT ELECTRON OR HOLES. CHEMI-LUMINESCENCE: IT IS NARRATED BY THE ENERGY RELEASED FROM CHEMICAL REACTION. 10

11. PHOTO-LUMINESCENCE THE PHENOMENA OF TEMPORARY LIGHT ABSORPTION AND SUBSEQUENT LIGHT EMISSION IS CALLEDPHOTO LUMINESCENCE. PHOTOLUMINESCENCE IS A PROCESS IN WHICH A MOLECULE ABSORBS A PHOTON IN THE VISIBLE REGION, EXCITING ONE OF ITS ELECTRON TO A HIGHER ELECTRONIC EXCITED STATE AND THEN RADIATES A PHOTON AS THE ELECTRON RETURNS TO A LOWER ENERGY STATE. The photo-excitation causes the material to jump to a higher electronic state, and will then release energy, (photons) as it relaxes and returns to back to a lower energy level. The emission of light or luminescence through this process is photoluminescence, PL.. 11

12. TYPES OF PHOTO-LUMINESCENCE FLUORESCENCE PHOSPHORESCENCE 12

13. FLUORESCENCE IT IS THE ABSORPTION OF ENERGY BY ATOMS OR MOLECULES FOLLOWED BY IMMEDIATE EMISSION ELECTROMAGNETIC RADIATION. OF LIGHT THE EMISSION OF RADIATION OR LIGHT SUDDENLY STOPS ON REMOVAL OF SOURCE OF EXCITATION. IT IS A FORM OF LUMINESCENCE. IN MOST CASES, THE EMITTED LIGHT HAS A LONGER WAVELENGTH, AND THEREFORE LOWER ENERGY, THAN THE ABSORBED RADIATION. THE MOST STRIKING EXAMPLE OF FLUORESCENCE OCCURS WHEN THE ABSORBED RADIATION IS IN THE ULTRAVIOLET REGION OF THE SPECTRUM, AND THUS INVISIBLE TO THE HUMAN EYE, WHILE THE EMITTED LIGHT IS IN THE VISIBLE REGION, WHICH GIVES THE FLUORESCENT SUBSTANCE A DISTINCT COLOR THAT CAN BE CUEN ONLY WHEN EXPOSED TO UV LIGHT. 13

14. Fluorescence is one of two kinds of emission of light by a substance that has absorbed light or other electromagnetic radiation.Fluorescence involves no change in electron spin multiplicity and generally it immediately follows absorption; phosphorescence involves spin change and is delayed. Thus fluorescent materials generally cease to glow nearly immediately when the radiation source stops, while phosphorescent materials, which continue to emit light for some time after.Fluorescent minerals emit visible light when exposed to ultraviolet. 14

15. PHOSPHORESCENCE IT IS THE ABSORPTION OF ENERGY BY ATOMS OR MOLECULES FOLLOWED BY DELAYED EMISSION OF LIGHT ELECTROMAGNETIC RADIATION. THE EMISSION OF RADIATION REMAINS FOR SOME TIME EVEN AFTER REMOVAL OF SOURCE OF EXCITATION. THE EMITTED PHOTON HAS LOWER ENERGY THAN THE ABSORBED PHOTON AND EMISSION OCCURS AT A LONGER WAVELENGTH THAN FLURESCENCE. PHOSPHORESCENT MATERIALS APPERAS TO "GLOW IN THE DARK" BECAUSE OF SLOW EMISSION OF LIGHT OVER TIME. There are two separate mechanisms that may produce phosphorescence, called triplet phosphorescence (or simply phosphorescence) and persistent phosphorescence (or persistent luminescence). 15

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17. APPLICATION OF PHOTOLUMINESCENCE SEMICONDUCTOR INDUSTRIES CHEMICAL INDUSTRIES SENSOR INDUSTRIES PHOTO LAMINATION PIGMENT CAN ALSO BE USED IN GLASS SILICA GEL AND TOYS INDUSTRY. Medical industry- LED may be used for surface tumors, such as skin cancer, therapy. Phosphorus use many other applications such as traffic signs, power switch, traffic police uniform, watches and clock etc. Phosphorescent paint has been used to mark escape paths in aircraft. 17

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19. Luminescence study of aluminate based phosphor activate with rare earth metal Lanthanide-activated alkaline earth aluminate phosphors are excellent luminescent materials that are designed to overcome the limitations of conventional sulfide-based phosphors. The increasing research attention on these phosphors over the past decade has led to a drastic improvement in their phosphorescence efficiencies and resulted in a wide variety of phosphorescence colors, which can facilitate applications in various areas. This review article discusses the development of lanthanide- activated alkaline earth aluminate phosphors with a focus on the various synthesis methods, persistent luminescence mechanisms, activator and coactivator effects, and the effects of compositions. Particular attention has been devoted to alkaline earth aluminate phosphors that are extensively used, such as strontium-, 19

20. 2. Strontium Aluminate Phosphors Strontium aluminates are the most extensively used alkaline earth aluminates and are convenient host crystals for rare-earth dopants [27]. They have attracted recent research interest that has resulted in their extensive applications in several fields owing to their excellent phosphor properties such as high brightness, long-persistent luminescence, and good chemical stability compared to those of other phosphor materials (Table 1). There are various types of strontium aluminate hosts, such as SrAl2O4, SrAl2B207, SrAl407, SrAl12019, Sr3Al206, and Sr4Al14025, all of which have different structures. For example, SrAl204 has a tridymite structure, whereas SrAl12019 has a magnetoplumbite structure [28,29]. Among these, SrAl204 is a promising host material for ensuring persistent luminescence and acts as a convenient host crystal for rare-earth and transition metal dopants [30]. 20

21. Conclusions Short review is given to show the past and present of luminescent materials. Major phosphor's applications in traditional display, flat panel. display, lighting, medical, security are presented. Multiphase micro and nanoparticle blue-green persistent phosphor with turquoise luminescence was synthesized and applied for painting, medical and biological investigations. A lot of examples show a very large range of applications of persistent luminescence phosphors from bulk materials visible to everyone to high tech products, especially in medicine. The development of high efficiency nanosized phosphor gives the possibility to incorporate it in an organic matrix to produce singlet oxygen, which kill cancer cells. This persistent phosphors are very good candidates for photodynamic therapy of cancer. 21