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Questions tagged [fluorescence]

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

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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 ...
Nikita Danilov's user avatar
3 votes
0 answers
23 views

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 ...
Helena's user avatar
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0 answers
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Strange Binding Curve DNA:Protein Interaction

So I did some DNA:Protein Interaction studies using Fluorescence Polarisation Assays. I have fluorescently labelled DNA and add my Protein of interest. Down below you see an exemplary plot of the ...
TheChemist's user avatar
3 votes
1 answer
108 views

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 (...
Henry Marshall's user avatar
2 votes
1 answer
112 views

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 ...
raptorlane's user avatar
8 votes
1 answer
2k views

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. ...
matt_black's user avatar
3 votes
0 answers
37 views

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 ...
claire's user avatar
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1 answer
612 views

Compounds with fluorescence and/or phosphorescence, what can do both? [closed]

What else (besides benzophenone) can both do phosphorescence but not fluorescence, and what else can do both phosphorescence and fluorescence? For example, does pentacene can do both? I'm reading that ...
Neal Conroy's user avatar
0 votes
1 answer
49 views

Why isn't residual standard deviation used in FQY analysis?

I've been measuring relative fluorescence quantum yield (hereafter FQY) for a photosensitive pigment. Most analytical articles and standard operating procedures (SOPs) I've read suggest taking the ...
YHoshi's user avatar
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6 votes
1 answer
263 views

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 ...
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1 vote
1 answer
35 views

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, ...
Hans Wurst's user avatar
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8 votes
1 answer
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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 ...
Yushi Li's user avatar
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1 vote
1 answer
87 views

Calculating total fluorescence based on thin slices in a slab

I am modeling an acid-base reaction that includes a fluorescence indicator. My simple model is a slab of acid next to a slab of base and so on. These slabs are very thin, typically less than 10 ...
rdemyan's user avatar
  • 173
5 votes
3 answers
343 views

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 ...
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1 vote
0 answers
49 views

How the optical fibre pH microsensors work?

Just browsed through the chemical sensor products of the company, called PreSens (https://www.presens.de/products/ph/sensors) in order to look for a precise method to measure pH change in a ...
Ryksa's user avatar
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1 vote
0 answers
79 views

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 ...
littleworth's user avatar
2 votes
0 answers
44 views

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 ...
Brenlla's user avatar
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3 votes
0 answers
76 views

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 ...
Paul Logan's user avatar
6 votes
2 answers
1k views

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 ...
25 Simran Tiwari's user avatar
0 votes
0 answers
145 views

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 ...
Thom Hallmark's user avatar
3 votes
0 answers
40 views

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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1 vote
1 answer
161 views

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 ...
Lasha Bukhnikashvili's user avatar
0 votes
4 answers
178 views

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? ...
Noffica's user avatar
  • 111
4 votes
0 answers
71 views

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 ...
user112717's user avatar
2 votes
0 answers
57 views

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 ...
dogman's user avatar
  • 61
0 votes
1 answer
51 views

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, ...
nicolas005's user avatar
1 vote
0 answers
43 views

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 ...
dogman's user avatar
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3 votes
0 answers
98 views

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{...
dogman's user avatar
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1 vote
0 answers
88 views

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 ...
Tsar Asterov XVII's user avatar
3 votes
0 answers
128 views

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 ...
rdemyan's user avatar
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0 votes
1 answer
99 views

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 ...
HASHTAG's user avatar
  • 11
1 vote
0 answers
38 views

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 ...
AnastD's user avatar
  • 119
3 votes
1 answer
128 views

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 ...
TheChemist's user avatar
0 votes
0 answers
462 views

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&...
Mark's user avatar
  • 31
0 votes
0 answers
99 views

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 ...
rdemyan's user avatar
  • 173
6 votes
5 answers
1k views

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 ...
Harsh Gautam's user avatar
7 votes
1 answer
197 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(\...
Frankie S. Palmer's user avatar
1 vote
0 answers
40 views

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 ...
coffee_pls's user avatar
1 vote
0 answers
116 views

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 ...
rdemyan's user avatar
  • 173
1 vote
2 answers
460 views

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. ...
Treex's user avatar
  • 153
4 votes
1 answer
1k views

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) ...
Pavithra J's user avatar
2 votes
0 answers
1k views

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 ...
Crops's user avatar
  • 139
2 votes
0 answers
49 views

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 ...
Tomi's user avatar
  • 590
1 vote
0 answers
101 views

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 ...
Crops's user avatar
  • 139
2 votes
1 answer
566 views

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 ...
Anni.Lin's user avatar
  • 105
2 votes
2 answers
1k 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, ...
Abu's user avatar
  • 23
5 votes
1 answer
197 views

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} +...
Ecdee 's user avatar
  • 65
1 vote
1 answer
98 views

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 ...
norlesh's user avatar
  • 553
5 votes
1 answer
251 views

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{...
Pöytä Laatikko's user avatar
1 vote
1 answer
558 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 ...
Lasse Karlshøj's user avatar