Questions tagged [fluorescence]

For questions relating to the radiation emitted by substances as a result of incident radiation.

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Spectroscopic methods for quantifying peptides/proteins with or without Tryptophan or Tyrosine content

I have several peptides (20-50 amino acids long) which I want to quantify the solubility/concentration in a solvent at certain temperature and pH. These peptides may or may not contain Tryptophan or ...
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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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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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6 votes
2 answers
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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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Dark smudge at the TLC solvent front

I have recently started using TLC in my graduate work to test for the cleavage of a cyclic oligo-adenylate in an enzymatic reaction. The sample I'm spotting on my plate is in an aqueous solution ...
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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 ...
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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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4 answers
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Fluorescence: what mechanism regulates the rate of discharge of energy?

The other day, I noticed a strip of fluorescent tape when the lights in the room were turned off. The energy was discharged as a continued, faint glow, rather than one burst or flash of light. How so? ...
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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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2 votes
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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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Fluorochrome (fluorescein) emission decay when linked to macromolecule

I measure the intensity and polarization of light emitted from a blood sample that contains excited fluorescein (experiment known as fluorescence polarization assay). The excitation is done, as usual, ...
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How can I save an EEM file on a Fluoromax4?

I'm trying to run excitation-emission matrices on some water samples, but I'm running into some software issues that the manuals aren't helpful for. In order to use R studio to extract my data, I need ...
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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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What is the amount of UV light required to make fluorophores glow and what is the minimum amount of electricity needed to achieve this?

So I have heard that fluorophores glow under UV light, so I was wondering what is the minimum amount of UV light needed to make the fluorophores glow and what would be the minimum amount of ...
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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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How ph affects aesculune fluorescence?

I am facing a ween problem. I am trying to find out, how would look like the graph for fluroscence of aesculine (intensity of fluoroscence on Y axis and pH on X axis). I know, that increasing the pH ...
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Microcopy Fluorescence filter set usefulness

I have a brief doubt and maybe someone around here can give as some help. We are doing a pilot study on microplastics using a fluorescence method (red nile). The dye is solvachromic, so it's emission ...
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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 is there a mirror image effect in the absorbance and fluorescence spectra?

I've read some answers online but I still can't seem to understand the mirror image effect. Why is the highest energy absorption (v" = 0 to v' = 4) the lowest energy fluorescence (v' = 4 to v&...
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Which commonly available UV light source to use with fluorescein

I want to start experimenting with fluorescein. I have a 353 nm UV light source, but am thinking that it might be too short since it looks like peak excitation occurs at 494 nm. So am I correct in ...
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5 answers
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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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7 votes
1 answer
137 views

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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Why does the emission of dansyl group diminish with time in this experiment?

I don't know how to make sense of this. I what is happening when an enzyme (carboxypeptidase, which contains tryptophan as its only chromophore and uses a Zn(II) ion in its active center) hydrolises a ...
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1 vote
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Fluorometer for measuring fluorescence in a sheet of water

Does anyone know of a fluorometer that I could use to measure fluorescence in a thin sheet of water. So it would be like holding a piece of writing or printer paper vertically and trying to get a ...
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Implications of the excitation spectra

The fluorescence excitation spectra show the change in fluorescence intensity as a function of the wavelength of the excitation light. I'm interested in the certain physical implications of the above. ...
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1 answer
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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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2 votes
0 answers
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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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Common chemcials that produce phosphorescence

Are there any common lab chemicals or household stuff that produce phosphorescence? I am aware of ZnS, CaS, Fluorescein, Erythrosin B, Vanillin Benzaldehyde, Vitamin B2, Tryptophan etc. I just need ...
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2 votes
1 answer
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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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1 vote
2 answers
545 views

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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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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Are there any fluorophores with lifetimes in the micro to milli second range?

I'm looking for a fluorophore with exceptionally long lifetime to use in an oxygen optode (the longer the lifetime the less timing precision needed in the electronics). So far the longest I have ...
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5 votes
1 answer
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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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1 vote
1 answer
292 views

Latent blood detection with fluorescein

I need help with the reaction between fluorescein and blood in the method of detecting latent blood stains. I find it hard to find any literature on this subject. As far as I am concerned, the ...
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0 answers
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When an electron is excited to a singlet state, must it flip its spin state to enter the triplet state and flip once more to the ground state?

I understand the Jablonski diagram in that it has intersystem crossing from the singlet state to the triplet state, but how many spin switches are necessary to complete to phosphores? When an electron ...
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Is the activation energy always inversely proportional to the reaction rate?

When I obtained the activation energy using the Arrhenius equation for a 10-minute glowstick (rapid, rigorous reaction), it was almost 4 times that of a 12-hour glowstick (slow, mild reaction). ...
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1 answer
108 views

Why has nature evolved to put a porphyrin (i.e. chlorophyll) as the chromophore in a leaf? [closed]

I'm stumped by this question: Why has nature evolved to put a porphyrin (i.e. chlorophyll) as the chromophore in a leaf? I've thought that it might have something to do with how sun emits light ...
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3 votes
1 answer
257 views

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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Does something like a fluorescent foil or a fluorescent film exist?

During my experiments I want the emitted laser beams to come back with a different wavelength than the original wavelength using a fluorescent foil or fluorescent film. The laser I'm currently using ...
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3 votes
1 answer
656 views

Why are most glow-in-the-dark things 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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5 votes
2 answers
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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. However,...
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4 votes
2 answers
118 views

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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1 vote
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Choosing the right wavelength for calibration curve and for analysis of actual results

Introduction: I am currently conducting a series of experiments in which I am studying the transport of polystyrene nanoparticles (PNPs) through sand and soil. This is done in sand/soil columns, into ...
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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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2 answers
295 views

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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1 answer
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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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1 vote
1 answer
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What is the relationship between emission and fluorescence?

A molecule exposed to a photon with some energy is put into an excited state, and emits a photon of some energy when it returns to ground state. The photon that provided the energy for excitation ...
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1 vote
3 answers
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Self tan mousse cannot contain UV, right?

So, I bought this self tanner specificly to avoid UV radiation. Back home I noticed that the bottle says it contains ultra violet: "The inclusion of Ultra Violet fluorescence in the base colour" . I ...
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3 votes
1 answer
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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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