Chemiluminescence physical chemistr.pptx

Physical chemistry chemiluminescence notes

1. Chemiluminescence and its applications Chemiluminescence is a phenomenon in which molecules excited by a chemical reaction emit excitation energy as light when they return to their ground state.

2. INTRODUCTION Chemiluminescence is the emission of cold light as a result of a chemical reaction. In a chemiluminescent reaction, reactive intermediates are formed which enter electronically excited states. Subsequent transition back to ground state is accompanied by a release of energy in form of light. The mechanism is depicted in Fig1.

3. Natural chemiluminescence F irefly secretes the enzyme luciferase. This enzyme reacts with luciferin which carries out oxidation of magnesium. This happens in the presence of magnesium and oxygen.  Light is emitted because of the oxidation of magnesium . Glowing of ceria red in the gloom of the ocean abyss Black smokers during hydrothermal vents.

4. HISTORY   The best-known and first well-documented example of deliberately induced, man-made chemiluminescence was the discovery of elemental phosphorus by a German alchemist H. Brand (Fig. 2). The waxy white phosphorus is slowly oxidized at room temperature giving off faint greenish glow. The formation of excited reactive intermediate (PO)2 and HPO is responsible for the green glow.

5. Chemiluminescence sensors In recent years, there has been a great deal of interests in the development of CL-based sensors due to their high sensitivity compared with photoluminescence-based sensors.  Types: CL sensors for inorganic compounds e.g. H2O2 CL sensor, ammonium CL sensor, phosphate CL sensor for detection of heamogobin (Fe), NH4 +, and phosphate ion respectively. Also CL sensors for organic and biological compounds e.g. amino acid and vitamin CL sensors.

6. Food analysis Nitrogen compounds exist in a wide variety of analytical samples, from harmful contaminants in refinery streams to important ingredients in certain beverages, spices and condiments. Accurate determination of nitrogen concentrations in these diverse samples is very important for process monitoring, quality control, product development, as well as basic research in these different industries .  For nitrogen CL detection, the chemiluminescent nitrogen species is nitric oxide and the CL is derived from the well-known NO + O 3  reaction. 

7. Bio photon emission and application for cancer cells detection Many, if not all, living organisms, including plants, animals, microbes and even humans, can display ultra-weak emission of photons . Many, if not all, living organisms, including plants, animals, microbes and even humans, can display ultra-weak emission of photons . It occurs without enhancement or excitement by chemical administration or light irradiation and is result of the metabolic activity of cells only. T he BPE of cells is a reflection of the activity occurring in the living organisms and its measurement and analysis, so it can be exploited to gain insight into the life-activity state in these tissues and to monitor non-invasively the underlying physiological process of the living system.

8. BPE BPE from various cancer tissues has been measured. Generally, the results revealed that the intensity of BPE from the cancer tissues was mostly higher than that from normal tissues. It was suggested that a CL-detection technique has potential as a simple, non-invasive tool to localize superficial tumors, not for deeply located ones, without the need for any pre-examination preparation. The detection and enumeration of CTCs(circulating tumor cells) are of great importance for early diagnosis and prognosis of cancer, monitoring of treatment efficacy in cancer patients and predicting their chances of survival.

9. Conclusion Chemiluminescence reactions are used for many analytical and diagnostic applications but their applications are limited as these reactions are very selective to pH, temperature, concentration etc. of the sample, or environmental conditions of the system. Electro generated chemilumenescence reactions are of more importance for next advanced applications.

10. R eferences Zhang, Zhenyu , Sichun Zhang, and Xinrong Zhang. "Recent developments and applications of chemiluminescence sensors."  Analytica Chimica Acta  541.1-2 (2005): 37-46 . Liu, Meilin , Zhen Lin, and Jin-Ming Lin. "A review on applications of chemiluminescence detection in food analysis."  Analytica Chimica Acta  670.1-2 (2010): 1-10 . Iranifam , Mortaza . "Analytical applications of chemiluminescence methods for cancer detection and therapy."  TrAC Trends in Analytical Chemistry  59 (2014): 156-183.