Chemoluminescence Akmal F iruz Firuz

Transcription

1 Chemoluminescence Akmal Firuz

2 Contents Historical background Luminescence Occurrence in nature Chemiluminescence - Requirements -Factors Applications: luminol, glow sticks Bioluminescence References

3 Historical background Luminescence phenomena has been known since ancient times. Multiple written references in ancient Chinese literature emperor s magic paint The first written acknowledgement of chemiluminescent reactions was made by Aristotle who noted weak emission from some dead fungi and fish. 1663: R. Boyle worked on oxygen which opened new doors for scientific explanation of CL. Mentions the CL of phosphorus. 1877: B. Radziszewski studies the CL of Lophine 1888: Theterm chemiluminescence is coined by Eilhardt Weidemann 1901: R. Dubois publishes the first paper on BL and introduces the phrases Luciferin and Luciferase 1905: M. Trautz publishes a review of known CL and BL reactions and attributes them to active oxygen 1928: H. O. Albrecht is attributed with the discovery and characterisation of the chemiluminescence of luminol Luminescence phenomena has a very long historical development!

4 Luminescence What? Emission i of light by a substance not resulting from heat (cold light) When? When electron in excited state falls back to ground state. Types? Chemiluminescence, Bioluminescence, Photoluminescence Compare to incandescence and fluorescence.

5 Occurrence in nature (bioluminescence) Fireflies,,glow worms 90% of deep-sea creatures Bacteria Fungi Dinoflagellate

6 Chemiluminescence Emission of light (usually in visible and near infrared) as a result of a chem. reaction. [A] + [B] [ ] [Products] + light A: chemiluminescent i precursor B: oxidant : excited intermediate Sometimes in a presence of catalyst (reduce activation energy), intermediate in electronically excited state, subsequently relax to ground state by the emission of photon.

7 Requirements Reaction must be exothermic to produce sufficient energy to form electronically excited state. For visible light: kj/mol. Reaction pathway must be favourable to channel the energy for the formation of electronically excited state. Photon emission must be a favourable deactivation process of excited product (figure 3) in relation to other competitive nonradiative process that t may appear in low proportion.

8 For CL to occur, reaction must be sufficiently exothermic such that: : Free Energy : wavelength limit for excitation of luminescent species

9 Factors affecting chemiluminescence emission Chemical structure of CL precursor, including side chain Nature of other substrates affecting CL pathway Selected catalyst Presence of metal ions Temperature ph and ionic strength Hydrophobicity of the solvent and solution composition Presence of energy transfer acceptor

10 Reaction: Application: Luminol (forensics) Luminol must be activated by hydroxide salt forming a dianion. Iron catalyzes hydrogen peroxide to decompose and form Oxygen The dianion reacts with oxygen producing the unstable organic peroxide intermediate: This intermediate decomposes from higher energy states to the ground state, emitting a p g gy g, g photon

11 Floorboard treated with luminol

12 Application: Glow sticks First container contains Phenyl Oxalate and dye. Glass vial contains Hydrogen Peroxide. Reaction produces 2 molecules of phenol and one molecule of peroxyacid ester. Peroxyacid decompose to CO 2 and releases energy which excites the dye. Dye relaxes by releasing a photon. Wavelength is dye dependant!

13 Examples of dyes used:

14 Other applications Pharmaceutical Industry (analysis and quality control) Clinical i l Science Detecting the photoactivity of water through its H 2 O 2 concentration Detecting Nitric Oxide in the breath of Asthma Patients. HPLC (High Performance Liquid Chromatography)

15 Special mention: Bioluminescence In general, involves 2 types of substances: light producing luciferin and enzyme-based catalyst luciferase. Often the process requires the presence of other substances, such as oxygen or ATP. Luciferin is oxidized by oxygen and reaction is catalysed by luciferase and light is emitted. Emission continues until all light is oxidised. Reaction mechanism, luciferin and luciferase vary from organism to organism.

16 Example: Firefly luciferin luciferase luciferin + ATP luciferyl adenylate+ Pyrophosphate luciferyl adenylate + O 2 Oxyluciferin + Adenosine monophosphate + light Light is emitted because the reaction forms oxyluciferin in an electronically excited state. The reaction releases a photon of light as oxyluciferin returns to the ground state.

17 References Ana M. Garcia-Campana (2001) Chemiluminescence in Analytical Chemistry y innovations/light-stick2.htm ce3 t / com/2013/07/30/chemsummer carnival-glow-sticks-how-do-they-work/

18 Thank you for your attention!