Detecting fluorescence via CW or pulsed LEDs

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SUMMARY

This discussion focuses on building a rudimentary fluorometer using high-power LEDs to excite proteins for fluorescence detection. The key components include a phototransistor sensitive to the fluorescent spectrum and the necessity for nanosecond pulsed measurements to accurately capture the fluorescence decay. The conversation also addresses the effectiveness of optical filters in blocking light and achieving significant attenuation under $200. Understanding the differences between fluorescence and phosphorescence is crucial, as fluorescence involves immediate wavelength conversion while phosphorescence involves a delayed decay.

PREREQUISITES
  • Understanding of fluorescence and phosphorescence principles
  • Knowledge of high-power LED specifications and applications
  • Familiarity with phototransistor functionality and sensitivity
  • Basic concepts of optical filtering and attenuation measurement
NEXT STEPS
  • Research circuit designs for nanosecond pulsed measurement systems
  • Explore optical filter technologies and their attenuation capabilities
  • Investigate specific phototransistor models suitable for fluorescence detection
  • Learn about the properties of various fluorescing materials and their applications
USEFUL FOR

This discussion is beneficial for DIY electronics enthusiasts, researchers in biochemistry, and anyone involved in fluorescence detection and measurement techniques.

Anton Alice
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Hello forums,

in the context of a little DIY-project I am planning to build a rudimentary fluorometer, which is actually doing nothing but checking whether an amount of protein is fluorescing or not, and roughly measuring its intensity.

A highpower LED is used to excite the protein to the fluorescent state, while a phototransistor (specially sensitive to the fluorescent spectrum) starts measuring a short time after the LED has been turned off.
The live time of fluorescence is in the region of a few nano seconds. For example a nanosecond pulsed measurement should (tightly) be able to solve the problem. Do you know circuitries which can handle this measurement cycle?
 
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I know its difficult.

For the continuous approach:
How well can optical filters block light? What is the best possible attenuation (below 200dollars)?
 
Anton Alice said:
The live time of fluorescence is in the region of a few nano seconds.
Why is the time constant so short? What is the fluorescing material?
 
One can distinguish between fast and slow decaying luminscence. The fastest kind of luminescence is fluorescence. There is also phosphorescence, which is more of an "exite, and wait until it decays", whereas fluorescence is more of a direct conversion of one wavelength to another.
http://nic.ucsf.edu/FPvisualization/#ref30
http://nic.ucsf.edu/FPvisualization/#ref30

Fluorescence is always in the nanosecond region.
 
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