Upconversion fluorescence

In summary, upconversion phosphors can generate shorter wavelengths from visible or infrared light, making them suitable for two-photon fluorescence microscopy. They can also be tailored to fluorescence only under simultaneous stimulation by two different wavelengths, opening up many possibilities for imaging and sensing applications.
  • #1
LionFox
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Hi there, I was looking into two photon fluorescence microscopy and was amazed at the light intensity required for the simultaneous two photon absorption to take effect; as it is, the setup is prohibitively expensive, the laser source is particularly problematic.
Are there any compounds that you know of capable of generating shorter wavelengths from visible or infrared? I researched this stuff a bit and I've only come across a definition for this sort of phenomena (the titular UF) and various Jablonski diagrams with metastable states, which are a bit beyond my expertise.
I would also like to know if you reckon they can be tailored to fluorescence only under simultaneous stimulation by two different wavelengths. That would open up a lot of possibilities...

Thanks in advance!
 
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  • #2
Yes, there are compounds that can generate shorter wavelengths from visible or infrared light. These are known as upconversion phosphors. They typically consist of rare earth metal ions doped into a host crystal lattice, such as yttrium aluminum garnet (YAG). The upconversion process involves multiple photon absorption, which is why it is ideal for two-photon fluorescence microscopy. The photons absorbed by the upconversion phosphor can then be re-emitted at shorter wavelengths than the original input. In terms of tailoring the upconversion phosphors to fluorescence only under simultaneous stimulation by two different wavelengths, this is possible with the right combination of host materials and rare earth metal ions. For example, Pr3+ and Er3+ ions in YAG can be excited by 980nm and 1550nm infrared light and emit blue and green light, respectively.
 

1. What is upconversion fluorescence?

Upconversion fluorescence is a process in which lower energy photons are converted into higher energy photons through the absorption of multiple lower energy photons. This results in the emission of light at a shorter wavelength than the excitation wavelength, which is known as anti-Stokes fluorescence.

2. How does upconversion fluorescence work?

Upconversion fluorescence occurs when a material with upconverting properties, such as rare earth ions, is excited by multiple low energy photons. These photons are absorbed and the electrons in the material are excited to a higher energy state. When these electrons return to their ground state, they emit a photon with higher energy, resulting in upconverted fluorescence.

3. What are the applications of upconversion fluorescence?

Upconversion fluorescence has several applications, including bioimaging, biosensing, and energy conversion. In bioimaging, it is used to visualize biological structures and processes at a microscopic level. In biosensing, it can be used to detect and quantify specific biomolecules. In energy conversion, it can be used to convert low energy light into higher energy light, which can be harnessed for solar energy.

4. What are the advantages of upconversion fluorescence over traditional fluorescence techniques?

Upconversion fluorescence has several advantages over traditional fluorescence techniques. It allows for imaging and detection at deeper tissue depths due to the use of near-infrared excitation light, which has lower scattering and absorption in biological tissues. It also has a higher signal-to-noise ratio, resulting in better image contrast and sensitivity.

5. Are there any limitations or challenges associated with upconversion fluorescence?

One of the main challenges with upconversion fluorescence is the low efficiency of the upconversion process, meaning that only a small percentage of the absorbed photons are converted into higher energy photons. This can limit the brightness and sensitivity of the imaging or sensing technique. Additionally, the synthesis and functionalization of upconverting materials can be complex and expensive.

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