The rate of photosynthesis is often lower than expected for several reasons: 1) Dark respiration occurs during the day which reduces net photosynthesis, 2) Not all wavelengths of light are absorbed efficiently by leaves, and 3) Factors like photorespiration and suboptimal conditions can limit carbon fixation and respire photosynthates. Leaf anatomy, physiology, and environmental conditions can prevent photosynthesis from reaching its maximum potential.
History of lighting | quantum dots | PhonsiPhilippe Smet
Talk given at the MSCA Phonsi Summer School in Fréjus, France, May 22 2017. Contains historical overview of lighting technologies, key metrics in lighting. Focus on LED based lighting, with RGB, phosphor converted and quantum dot based LEDs.
EMRS 2018 Replacing rare earth ions in LEDs (?)Philippe Smet
Two decades after the development of the blue light-emitting diode (LED), LEDs have quickly established themselves as the lighting technology of the future. The high efficiency, spectral tunability, lack of toxic compounds and a small footprint makes them far more attractive than other lighting technologies. The high efficiency, now well exceeding 100 lum/W in commercial products, has still the margin to double, promising a strong reduction in electricity consumption.
White LEDs are commonly based on a blue LED, combined with luminescent materials, or phosphors, which convert part of the blue light to longer wavelengths, the mixture providing white light. Besides the workhorse Y3Al5O12:Ce (YAG:Ce, yielding yellow emission), europium doped phosphors are used to provide e.g. the red emission required for warm-white LEDs.
Six main requirements for LED phosphors are discussed and used to explain the discrepancy between the high number of compositions described in literature and the handful of actually used compounds, being almost uniquely based on rare earth ions as luminescent center [1]. Alternative materials avoiding the use of rare earth ions are discussed, including Mn4+ doped fluorides phosphors (e.g. K2SiF6:Mn4+ [2]) and quantum dots. Finally, the impact of phosphor geometries on phosphor use, including remote phosphor applications, are discussed.
[1] Smet PF and Joos JJ, Nat. Mater. 16 (2017) 500.
[2] Sijbom H et al, Opt. Mater. Exp. 7 (2017) 3332.
TechBoost 2015 - Ghent University - Phosphors for lightingPhilippe Smet
Presentation on the history of lighting and the role of phosphors (luminescent materials) in lighting. From fluorescence lamps to white light emitting diodes (LEDs) for displays and general lighting.
History of lighting | quantum dots | PhonsiPhilippe Smet
Talk given at the MSCA Phonsi Summer School in Fréjus, France, May 22 2017. Contains historical overview of lighting technologies, key metrics in lighting. Focus on LED based lighting, with RGB, phosphor converted and quantum dot based LEDs.
EMRS 2018 Replacing rare earth ions in LEDs (?)Philippe Smet
Two decades after the development of the blue light-emitting diode (LED), LEDs have quickly established themselves as the lighting technology of the future. The high efficiency, spectral tunability, lack of toxic compounds and a small footprint makes them far more attractive than other lighting technologies. The high efficiency, now well exceeding 100 lum/W in commercial products, has still the margin to double, promising a strong reduction in electricity consumption.
White LEDs are commonly based on a blue LED, combined with luminescent materials, or phosphors, which convert part of the blue light to longer wavelengths, the mixture providing white light. Besides the workhorse Y3Al5O12:Ce (YAG:Ce, yielding yellow emission), europium doped phosphors are used to provide e.g. the red emission required for warm-white LEDs.
Six main requirements for LED phosphors are discussed and used to explain the discrepancy between the high number of compositions described in literature and the handful of actually used compounds, being almost uniquely based on rare earth ions as luminescent center [1]. Alternative materials avoiding the use of rare earth ions are discussed, including Mn4+ doped fluorides phosphors (e.g. K2SiF6:Mn4+ [2]) and quantum dots. Finally, the impact of phosphor geometries on phosphor use, including remote phosphor applications, are discussed.
[1] Smet PF and Joos JJ, Nat. Mater. 16 (2017) 500.
[2] Sijbom H et al, Opt. Mater. Exp. 7 (2017) 3332.
TechBoost 2015 - Ghent University - Phosphors for lightingPhilippe Smet
Presentation on the history of lighting and the role of phosphors (luminescent materials) in lighting. From fluorescence lamps to white light emitting diodes (LEDs) for displays and general lighting.
Energy storage phosphors @ Phosphor Global Summit 2019Philippe Smet
Presentation on opportunities and limitations of energy storage phosphors, which can be used for glow-in-the-dark roads or safety illumination. Loss mechanisms in phosphors. Presented at the Phosphor Global Summit and Quantum Dot Forum 2019 in San Diego, La Jolla, California. March 19-21.
Defects in energy storage phosphors: friends or enemies? (PRE19 workshop)Philippe Smet
Plenary talk presented at the PRE19 workshop (Photoluminescence in Rare Earths: Photonic Materials and Devices) in Nice, France, on September 4. Dealing with persistent luminescence, afterglow, mechanoluminescence, traps, defects and thermoluminescence. Overview of the activities of the LumiLab research in the past 10 years.
Pfsmet amazing rise of solid state lightingPhilippe Smet
Overview of lighting technologies. Focus on blue LEDs, solid state lighting, colour conversion by luminescent materials. Applications of LEDs. Future of lighting.
Jpc lett 10.1021jz300574u-gates presentation on Atomically Resolved Site-Isol...jpcoffice
This presentation has been moved. To view this presentation, please visit http://pubs.acs.org/iapps/liveslides/pages/index.htm?mscNo=jz300574u
Atomically Resolved Site-Isolated Catalyst on MgO: Mononuclear Osmium Dicarbonyls formed from Os3(CO)12
Abstract: Supported triosmium clusters, formed from Os3(CO)12 on MgO, were treated in helium at 548 K for 2 h, causing fragmentation of the cluster frame and the formation of mononuclear osmium dicarbonyls. The cluster breakup and the resultant fragmented species were characterized by infrared and X-ray absorption spectroscopies, and the fragmented species were imaged by scanning transmission electron microscopy. The spectra identify the surface osmium complexes as Os(CO)2{Osupport}n (n = 3 or 4) (where the braces denote support surface atoms). The images show site-isolated Os atoms in mononuclear osmium species on MgO. The intensity analysis on the images of the MgO(110) face showed that the Os atoms were located atop Mg columns. This information led to a model of the Os(CO)2 on MgO(110), with the distances approximated as those determined by EXAFS spectroscopy, which are an average over the whole MgO surface; the results imply that these complexes were located at Mg vacancies.
This presentation summarizes history and recent development of perovskite solar cells. If you have any questions or comments, you can reach me at agassifeng@gmail.com
Energy storage phosphors @ Phosphor Global Summit 2019Philippe Smet
Presentation on opportunities and limitations of energy storage phosphors, which can be used for glow-in-the-dark roads or safety illumination. Loss mechanisms in phosphors. Presented at the Phosphor Global Summit and Quantum Dot Forum 2019 in San Diego, La Jolla, California. March 19-21.
Defects in energy storage phosphors: friends or enemies? (PRE19 workshop)Philippe Smet
Plenary talk presented at the PRE19 workshop (Photoluminescence in Rare Earths: Photonic Materials and Devices) in Nice, France, on September 4. Dealing with persistent luminescence, afterglow, mechanoluminescence, traps, defects and thermoluminescence. Overview of the activities of the LumiLab research in the past 10 years.
Pfsmet amazing rise of solid state lightingPhilippe Smet
Overview of lighting technologies. Focus on blue LEDs, solid state lighting, colour conversion by luminescent materials. Applications of LEDs. Future of lighting.
Jpc lett 10.1021jz300574u-gates presentation on Atomically Resolved Site-Isol...jpcoffice
This presentation has been moved. To view this presentation, please visit http://pubs.acs.org/iapps/liveslides/pages/index.htm?mscNo=jz300574u
Atomically Resolved Site-Isolated Catalyst on MgO: Mononuclear Osmium Dicarbonyls formed from Os3(CO)12
Abstract: Supported triosmium clusters, formed from Os3(CO)12 on MgO, were treated in helium at 548 K for 2 h, causing fragmentation of the cluster frame and the formation of mononuclear osmium dicarbonyls. The cluster breakup and the resultant fragmented species were characterized by infrared and X-ray absorption spectroscopies, and the fragmented species were imaged by scanning transmission electron microscopy. The spectra identify the surface osmium complexes as Os(CO)2{Osupport}n (n = 3 or 4) (where the braces denote support surface atoms). The images show site-isolated Os atoms in mononuclear osmium species on MgO. The intensity analysis on the images of the MgO(110) face showed that the Os atoms were located atop Mg columns. This information led to a model of the Os(CO)2 on MgO(110), with the distances approximated as those determined by EXAFS spectroscopy, which are an average over the whole MgO surface; the results imply that these complexes were located at Mg vacancies.
This presentation summarizes history and recent development of perovskite solar cells. If you have any questions or comments, you can reach me at agassifeng@gmail.com
Photosynthesis is a oxidation reduction process in which water is oxidized and carbon dioxide is reduced to carbohydrate level, the water and oxygen being by product.
photosynthesis Presentation on AgricultureFayzanKhan10
photosynthesis, the process by which green plants and certain other organisms transform light energy into chemical energy. During photosynthesis in green plants, light energy is captured and used to convert water, carbon dioxide, and minerals into oxygen and energy-rich organic compounds.
this presentation describes light phase of photosynthesis. it explains Evidences for two phases, Photosynthetic unit & Harvesting of light energy, Emerson effect &two photosystem, Hill reaction & Photolysis /photo-oxidation of water, Redox potential & mechanism of light reaction, Cyclic photophosphorylation, Non- cyclic photophosphorylation .
17. 5b. Photorespiration Phosphoglycolate + O 2 + ATP -> PGA + CO 2 + ADP + 2Pi G3P G3P G3P G3P G3P Chloroplast peroxisome mitochondria peroxisome chloroplast Fotorespiratie dus noodzakelijk om C 2 (PG) te regenereren
18. 6. Morpholoigcal & Physiological variation - Low- and high-light leaves: High light - thick leaf Many chloroplasts m -2 High [Rubisco] m -2 Low light - thin leaf Fewer chloroplasts m -2 Low [Rubisco] m -2
Licht wordt gedeeltelijk gereflecteerd of valt door het blad heen.
Absorptie van een chlorofyloplossing is heel sterk bij blauw en rood licht en vertoont een sterke dip bij 550 nm, bekend verhaal
Absorptie van een chlorofyloplossing is heel sterk bij blauw en rood licht en vertoont een sterke dip bij 550 nm, bekend verhaal
Absorptie van een blad laat een veel minder sterke dip bij groen licht zien. Hoe kan dat nou??
Quantum yield is de helling van de PS-I curve bij hele lage LI
Quantum yield is de helling van de PS-I curve bij hele lage LI
Fotosynthese afhankelijk van CO2 concentratie rond blad. Rode pijl is ambient. Maar eigenlijk zitten de stomata als regulerende factor tussen.
Co2 intern lager dan extern door barriere van epidermis. Stomata zijnde ingang, maar dat is een beperking
In het begin volgen de punten de MM kinetiek, maar daarna niet meer. Hierbij is de lichtlimitatie bereikt. Dat de punten toch nog iets doorstijgen komt door fotorespiratie
Rubisco gaat vreemd.
Rubisco gaat vreemd.
If only one third of the Rubisco reactions are oxygenations (a realistic, even conservative figure), no profit is made by the Calvin cycle. This means the phosphoglycolate must be remetabolised. (http://www.steve.gb.com/science/photorespiration.html)
Q: kun je dit verklaren? LL<HL bij veel licht, maar LL>HL bij weinig licht. Hoe wordt dat gestuurd? LL: veel slimme light harvesting, weinig rubisco.
Q: kun je dit verklaren? LL<HL bij veel licht, maar LL>HL bij weinig licht. Hoe wordt dat gestuurd? LL: veel slimme light harvesting, weinig rubisco.