Questions tagged [fluorescence]
For questions relating to the radiation emitted by substances as a result of incident radiation.
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Are there any (simple) molecules with very different absorption and emission dipole directions?
When a single molecule absorbs or emits light, it does so perpendicular to the direction of the respective transition dipole. In principle, the directions of the dipoles for absorption and emission ...
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What should the Rehm-Weller equation look like?
The Rehm-Weller equation, which defines the energy change for photoinduced electron transfer according to Lakowicz "Principles of Fluorescence Spectroscopy" [1, p. 337] should look like:
$$\...
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Why is collagen fibre autofluorescent?
Why is collagen fibre autofluorescent? Proteins with increased amount of trp, tyr, phe tend to fluoresce but I don't think collagen fibre has increased percentage of any of them. Some say collagen ...
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Is it right to say that fluorescent lamps are actually fluorescent?
Fluorescence occurs rapidly ($\approx 10^{-6}$ to $10^{-9}$ s) but phosphorescence is slow, and is therefore observable ($> 10^{-4}$ s). So, is it right to say that fluorescent lamps actually ...
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What chemical(s) in peanut butter cause it to glow under UV light?
It is relatively well known that peanut butter glows in the dark under UV light (if you don't believe me, see this short YouTube demo by NileRed).
I've tried it myself and it is clearly a real thing.
...
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What makes scorpions glow under UV light?
What substance (or class of substances) is responsible for the neon blue-colored fluorescence we observe when we shine UV light on scorpions?
Do note, I want to know what substance makes them glow ...
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Help with Forster distance conversion for FRET
For my project on Fluorescence, I'm trying to simplify the equation for the Forster distance (I obtained this from the Lakowicz book). To keep track, the units are in square brackets.
$$R_0 = \left(\...
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Interpretation of Figure - biofunctionalization
In this paper on page 1985 they say:
Fluorescence analysis confirmed that enhanced protein binding at higher electron dose depends only to a small extent on the slight increase in the lateral ...
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Why do different substances containing saturated hydrocarbons burns with different flame?
LPG and Candle wax both contain saturated hydrocarbon, yet LPG gives a clean white flame but a candle gives yellow flame with lots of smoke. Why so?
I have read some answers on web which says that it ...
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What is special about the molecule luciferin that it can emit light?
A classic example of bioluminescence; the protein luciferin is oxidized by the enzyme luciferase, releasing energy as light.
What is it that gives luciferin this ability? Why can't just about any ...
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How does molecular structure contribute in the property of fluorescence?
Fluorescence is the property which is exhibited when electrons emit wavelength of light lower than the one they absorbed so does that mean we can make every molecule to become fluorescent? I wanted to ...
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Why do glow-in-the-dark substances dim gradually?
Related: How do things glow in the dark?
Growing up, I had glow-in-the-dark stars on my ceiling and after being "charged" by having my lights on, they would phosphoresce for quite some time.
...
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Lifetime components in phosphorescence decay
I'm studying the phosphorescence decay of diacetyl in acetonitrile (it has a high quantum yield of intersystem crossing). The fluorimeter than I'm employing has microsecond resolution and, since the ...
user78790
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Excited states and emission lifetimes
I have some doubts about the nomenclature of the lifetimes. Are singlet and fluorescence lifetimes the same? As well as the triplet and phosphorescence lifetimes?
Also, can the triplet/phosphorescence ...
user78790
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Nitrogen dioxide fluorescence quenching and lifetime
Nitrogen dioxide fluorescence quenching:
$$
\begin{align}
\ce{NO2 + h\nu &->[$\varphi_\mathrm{Ia}$] NO2^{\ast}}\tag{I}\\
\ce{NO2^{\ast} &->[$k_2$] NO2 + h\nu'}\tag{II}\\
\ce{NO2^{\ast} +...
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Deriving fluorescence intensity equations
I've been having trouble with deriving the equations in the following problem.
The interaction between DNA and AO to form the AO–DNA complex can be expressed by the following reaction:
$$\ce{...
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Compound with a bright green emission when electrically excited
I rolled back the edit because I really am looking for the following:
I am looking for an element or compound that would have a bright green emission when electrically excited and is a gas at between ...
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Is there any molecule describable by three-level with mixed parity and transition dipole moments in different directions?
I would like to know if there are molecules described by a three-level system with mixed parity and transition dipole moments in different directions. By mixed parity I mean all three transitions can ...
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Why are glow-in-the-dark things usually green?
I've noticed that many glow-in-the-dark objects you can purchase in the store are green. Occasionally I would come across something that was orange or blue, but mostly it seems that green is the ...
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Absorption and emission at same wavelength?
Is it possible for a molecule to absorb and emit at the same wavelength? What is the reason behind it?
I’m working on charged tin porphyrins and got the excitation and emission (fluorescence) ...
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Brilliant fluorescent properties of Na2S(x) obtained from Na2SO3 or Na2S2O3
When $\ce{K2SO3}$ or $\ce{Na2SO3}$ is heated strongly by any method (in a flame, in an electric arc, on a metal plate in an induction heater), the resulting residue should be a mixture of $\ce{Na2SO4/...
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Measuring a high Michaelis constant using fluorescence
We have the task of measuring kinetic parameters of an oxidase reaction that has a $K_M$ of about $2 \,\text{mM}$. For that, we want to use a fluorescence assay based on Amplex Red. The latter is a ...
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Why wouldn't a standard addition fluorometric method return the same starting concentration of a solution used to make the standards?
I am trying out a new standard addition method and having some very basic problems. I am hoping someone could point me in the right direction.
I am using a fluorometric method to quantify ammonium in ...
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How are these green, blue, and purple markers fluorescing under monochromatic 589nm (yellow) light?
I have some green, blue, and purple markers which clearly fluoresce under monochromatic light with a lower wavelength. Here they are illuminated by 589nm light emitted by a low pressure-sodium lamp (...
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How to calculate molecular emission spectra?
Is there free software that can calculate the fluorescence emission spectra of organic molecules?
Let's say, for example, rubrene
There is a bunch of quantum free quantum chemistry software:
https://...
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How does light emission depend on temperature by fluorescence?
I have a glass, which emits green light after charging it with sunlight. I though this is fluorescence, and only photons with shorter wave length (than the green light has) can excite the electrons of ...
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Fluorescence quenching by palladium(II) vs. platinum(II) complexes
Why do we observe much stronger (in most cases complete) fluorescence quenching by $\ce{Pd^2+}$ than $\ce{Pt^2+}?$ I work with complexes of both metals and there is no real 100% explanation I can find ...
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Why do fluorescence intensities decline with replicate number?
I am performing a determination of riboflavin with fluorescence spectrophotometry. I've dissolved my riboflavin in a dilute GAA solution, created a calibration curve and measured my unknown's ...
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Non-binding buffer at pKa of roughly 6 that dissolves in ethanol?
I'm trying to find a proper buffer for my experiment, which I'd appreciate some suggestions on. I have a solution in which I want to measure the concentration of magnesium ions using a fluorescent ...
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Detection of contamination from salicylic acid via either single excitation fluorometer or via absorbance
My colleague detected fluorescent contamination likely from salicylic acid in some water samples. I have made a new batch and want to check whether my new samples also have this contamination.
1. Can ...
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Fluorophores with high quantum yield and low lifetime
Does anyone know of any fluorophore or family of fluorophores with a relatively high fluorescence quantum yield (larger than 0.1) and a short lifetime (below hundreds of picoseconds)?
I have been ...
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Wave Dispersive X-ray Fluoresence and Bragg's Law
Thermo Fisher website explains that "WDXRF uses crystals to disperse the fluorescence spectrum into individual wavelengths of each element, providing high resolution and low background spectra ...
user119534
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How can I set up and process my excitation-emission matrices properly?
I'm running EEMS on some water samples on a Horiba Fluoromax 4 spectrofluorometer. Method below.
$\pu{240-580nm}$ emission, $\pu{5nm}$ interval, $\pu{1nm}$ width.
$\pu{240-480nm}$ excitation, $\pu{...
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Fluorescence Intensity and Fluorescence Quantum Yield
I plan to use ImageJ to analyze some fluorescence experiments where the pH changes. I will be using fluorescein as the indicator for the pH changes and it will be present in low concentration (like is ...
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Why do some molecules show non-symmetric absorption and emission bands?
I'm looking at a molecule of [Ru(bpy)3]2+ in water and the absorption and emission bands are not symmetrical. I want to know why the mirror image rule doesn't apply here. Is this because of the MLCT, ...
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Is the XRF spectroscopy equally sensitive for every element?
I am curious whether or not every element can be equally well detected by using X-Ray-fluorescence-spectroscopy. Might there be any contitions or circumstances that make it hard/impossible to detect a ...
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Why does aqeous fluorescein shine when exposed to UV light?
I know that (aq) fluorescein "absorbs" UV light and releases light in the visible spectrum , but how does it do that. It is a really interesting and useful organic chemical and I just wanted to know ...
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Is Beer-Lambert law also valid for fluorescence and luminescence?
When I measure optical density in a microplate reader the absorbance is proportional to the concentration and the height of the liquid. Is Beer-Lambert law also valid for fluorescence and luminescence?...
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Calculate IC50 from fluorescence kinetic
I have an assay in which a fluorescence signal is generated when the enzyme reaction progresses. The fluorescence signal increases until a maximum is reached. Than it keeps constant. The first 1 h ...
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High voltage arc treatment leads to the appearance of fluorescent granules in soda baking. Perhaps it's the F-centers?
I have a high-voltage converter at home, consisting of a horizontal "flyback" transformer from an old tube TV, field-effect power transistors and a square-wave generator with adjustable ...
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DNA staining agent with good absorbance at 532 nm
I need to stain some double-stranded DNA with an intercalating fluorescent dye. For imaging, I am using a microscope setup equiped with a 532 nm green laser.
What is the staining agent of choice to ...
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What causes horizontal lines on an excitation-emission matrix in fluorometry?
I am doing excitation-emission matrices to test for CDOM, and we just got some brand new quarts cuvettes. When I hold them in front of a light, they're totally clear and clean.
I ran a sample, and in ...
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Data analysis in TCSPC for fluorescene decay (reconvolution with measured IRF)
I am trying to understand the data analysis of fluorescence decay counts measured by TCSPC technique, particularly with reconvolution with measured IRF.
I am able to get the fitted counts (given by ...
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Chemical Potential in the Fluorescent Molecule
I'm reading this paper, which states that the chemical potential $\mu$ is determined by the steady-state balance of up and down transitions in a fluorescent molecule. I am happy with this ...
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What's causing this dip in the FCS curve?
This is a fluorescence correlation spectroscopy measurement of light harvesting complexes. What could be causing the dip at 100 microseconds?
Edit:
The same thing was observed using fluorescence ...
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What fluorescent materials absorb visible light and emit UVC light?
What fluorescent materials, if any, exhibit anti-stokes shift such that they absorb visible light and emit ultraviolet light in the range of 250-285 nm? I'm interested in particular in materials that ...
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What makes a species "fluorescence quencher"?
I just came across an article where they said that sodium fluoride is not quencher (in the context of fluorescence). Why is NaF not a quencher but NaBr is one?
user14874
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Why does isolated chlorophyl emits red light?
If we observe isolated chlorophyl solution with UV light, chlorophyl is seen as red. Explanation suggests that when a specific atom of chlorophyl absorbs UV light, the atom gets excited and in a short ...
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What are the requirements for FRET?
I have a question about fluorescence resonance energy transfer (FRET), and the requirements needed for this technique.
Q: Which of the following need to be met for FRET?
A) Strong overlap between ...
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Is vibronically resolved spontaneous emission temperature dependent, following a distribution defined by the canonical density operator?
Does the lifetime of a molecular excited electronic state, for example the $S_1$ state, suffice for thermal equilibration before spontaneous emission occurs?
For example the fluorescence of coumarine, ...
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