Emission - Science topic

One possible reason is that there is more lower energy carriers in the conduct band so the spectrum has a tail extending to longer wavelength.

They are not green markets because they are not cleared by a green market price, they are environmental externality management based markets.

I've used it as a solvent for XRF analysis of elements such as S, Cl etc in organic compounds, for which it is very good (as are quite a few other dipolar aprotic solvents!). I've always used helium flushing for this sort of job, but you can probably get away with air atmosphere for a lot of the possible analytes.

There are toxicity concerns about it; the high boiling point means that volatility isn't much trouble (but work in a fume cupboard anyway); however it will probably pass through the skin barrier quite easily, taking with it whatever is dissolved in it, so I've always used HEAVY DUTY nitrile gloves (NOT the cheap disposable ones) for solvents such as this. Wash the gloves with soap and water after use. Check with your local H&S advisor for the local policy on safe use of solvents such as NMP: I'm not aware of any reason why it should be impossible to work with solvents such as this, but as always, make sure you have the best possible advice and follow it.

@Naveen Kishore have you found a way to do this by any chance?

Hi,

Read my article (meticulously) and send me a direct. I will guide you.

Icen

One can construct simple model (Shifted Harmonic Oscillator model) and derive tractable equations to obtain absorption and emission spectra.

1. Absorption and Emission Lite: Assume ground and excited states are shifted classical Harmonic Oscillator. Ground state |g> energy: E_g(R) = 1/2 ω²R² & Excited state |e> energy: E^_e(R) = 1/2 ω²(R - R₀)² + ΔE. Treating R classically one gets absorption (I_a) and emmision (I_e) spectra as:

I_a(e) = exp[(e-ΔE)²/2σ²] I_e(e) = exp[(E-ΔE + ω²R_0²)²/2σ²] (Arbitrary Units)

absorption and emission is peaked at different energies and the difference is ω²R_0² --- stokes shift, see: https://en.wikipedia.org/wiki/Stokes_shift

σ is the linewidth caused by molecules coupling to environment (Homogeneous Broadening) caused because individual molecules see slightly different environment, e.g. ΔE (Inhomogeneous Broadening) is different for different molecule.

2. Absorption and Emission Pro: Same as 1, but treat R quantum mechanically,

this gives |g>|v₀> , |g>|v₁> ... |g>|v^_n> states and |g>|v₀'> , |g>|v₁'> ... |g>|v^_n'> where |v^_n> is nth vibrational state centered around 0 and |v^_n'> nth vibrational state centered around R₀.

With this we write the absorption at T = 0K ( or ℏω >> kT)

I_a(e) = ∑_n |<v_n'|v₀>|² exp[(e-ΔE - nℏω)²/2σ²]

= ∑_n (1/n!) * (ωR_0²/2)ⁿ exp[-(ωR_0²/2)²] exp[(e-ΔE - nℏω)²/2σ²]

I_e(e) = ∑_n |<v₀'|v_n>|² exp[(e-ΔE + nℏω)²/2σ²]

= ∑_n (1/n!) * (ωR_0²/2)ⁿ exp[-(ωR_0²/2)²] exp[(e-ΔE + nℏω)²/2σ²]

|<v₀'|v_n>|² are Franck-Condon factor,

|<v₀'|v_n>|² = |<v_n'|v₀>|² = (1/n!) * (ωR_0²/2)ⁿ exp[-(ωR_0²/2)²].

3. Absorption and Emission Pro Max: Same as 2 but at finite temperature T. Assuming instant thermalization --> states are population according to Bolzmann distribution,

I_a(e) = ∑_m∑_n |<v_n'|v_m>|² exp[(e-ΔE - nℏω)²/2σ²] * P_m

₌ ∑_m∑_n |<v_n'|v_m>|² exp[(e-ΔE - nℏω)²/2σ²] * (exp[-βmℏω] /∑_kexp[-βkℏω])

= ∑_m∑_n (1/n!) * (ωR_0²/2)ⁿ exp[-(ωR_0²/2)²] exp[(e-ΔE - nℏω)²/2σ²] * (exp[-βmℏω] /∑_kexp[-βkℏω])

I_e(e) = ∑_m∑_n (1/n!) * (ωR_0²/2)ⁿ exp[-(ωR_0²/2)²] exp[(e-ΔE + nℏω)²/2σ²] * (exp[-βmℏω] /∑_kexp[-βkℏω])

P_m = (exp[-βmℏω] /∑_kexp[-βkℏω])

Dear Arunangshu Biswas ,

To the best of my knowledge this phenomenon is never observed using ‘normal’ fluorescence. To measure fluorescence, you need a fluorophore like Laurdan as used in the paper you indicated, see enclosed file. You either used a laser source or a highly sensitive spectrofluorometer (like FP-8500, JASCO).

Using FP-8500 there is one paper (see enclosed file) that describes your findings using photoluminescence:

Sekar, S., Muller, J. G., Karthikeyan, J., Murugan, P., & Lakshminarasimhan, N. (2018). Unveiling the multifunctional roles of hitherto known capping ligand oleic acid as blue emitter and sensitizer in tuning the emission colour to white in red-emitting phosphors. Physical Chemistry Chemical Physics, 20(28), 19087-19097.

Here you see the excitation and emission spectra of oleic acid that pretty much answers your question.

Best regards.

Almost all commercially available LEDs (Especially in the range of the visible spectrum) are phosphor-converted LEDs, The table that you provided is for the spectrum of emitted light of the different semiconductor materials.

Hi Jermaine,

Please have a look at the link below, the paper published is an excellent case study, good luck.

Best wishes,

Sofiane

ASSESSMENT OF PARTICULATE MATTER (PM 10 & PM 2.5) AND ASSOCIATED HEALTH PROBLEMS IN DIFFERENT AREAS OF CEMENT INDUSTRY, HATTAR, HARIPUR, January 2013, Journal of Science and Technology 37(2):7-15

Right, SCF + excited state energies - obviously, stupid me... Anyway, I confess I got no theoretical background on the TD-DFT topic. But for my supervisor entirely don't know what I am doing, I ask here, at RG.

Have a look at this useful RG link.

Fluorescence intensity measurements are usually relative, unlike absorbance measurements, because they depend on many factors, such as the instrument settings, the geometry of the sample, the intensity of the exciting light, the sensitivity of the detector, and so forth. So fluorescence intensity measurements are reported as relative fluorescence units (RFU). The size of the numbers has no real meaning. They are arbitrary.

If you wish, you can normalize the fluorescence intensity to some comparator, such as the fluorescence of a reference dye, dividing the first by the second. This could be useful in some circumstances to make it easier to compare measurements made at different times or under different circumstances.

It is better to mention even if you don't know it, that is much better.Regards

Since the energy of fluorescence photons cannot be higher than that of absorbed ones (energy conservation), their wavelenght is longer, since the photon energy is h c/l where h= Planck's constant, c = velocity of light and l is the wavelenght.

Ashish Gupta - ok - somehow when I read the question first the "and" was obscured and I didn't understand what was meant by "Time resolved steady state" as a single term.

Things to be considered are:

(i) as a trivial suggestion, make sure the lamp is properly monochromated.

(ii) what is the material? the difference may be that of CW illumination vs pulsed, and in the former you may have a build up of long lived states. What is the laser pulse width, repitition rate? You could try chopping the lamp to give the sample some time to recover, although you may not get close to the laser pulse width, repitition rate.

Here is a reference for your query...

Visit kindly the following useful RG links:

If you want to calculate N2O emissions, you'll need to take two samples and keep track of how much time passes between them.

Most spectrometers use a grating and what you may be measuring are the higher diffraction orders.

The following RG links are also very useful:

Dear Patricia Román-Carrasco ,

The emission peak is at 568 nm. PE is a comparable dye. You should use the green laser for maximum excitation. Please find attached an image a spectral viewer.

A Statistical Analysis of Carbon Dioxide Emission from ...

https://www.ijert.org › a-statistical-analysis-of-carbon-di...

West Bengal is one of the major contributors among identified states. Undesirable emission of CO2 from different sources

Depends on the cooking fuel, its duration --GC-MS can detect it

A duality between statics and dynamics ie https://www.researchgate.net/post/Whether_Quantum_Mechanics_can_be_justified_with_Quantum_Statics_Quantum_dynamics

Hello.

You need to take the absorption and fluorescence spectra of each concentration of only ligand and subtract them from the corresponding concentration of ligand-protein. If your protein and ligand both absorb at the same wavelengths, UV and fluorescence are not very good methods for the study. You need to correct the absorbance for the inner filter effect as well as the fluorescence intensity by easily available mathematical equations.

Hello René. Thank you for the points raised. I am talking about an open system in an external environment (materials yards). The temperature of the materials dumped is around 100-200°C. The volume of materials is small, 1 or 2 m³. They are wetted before the dumping operation to avoid dust emission, mainly total suspended particles (TSP) and PM10. I would like to measure the particles concentration or any parameter related to the particles emission. The opacity was the easiest way that we found to determine if there is or not PM emission, however, the vapor generated in the process interferes in the measurements.

Please refer this article which will be a help

Dear Sadman, In broad sense, water hyacinth endangers aquatic ecosystems and stifles organic growth.

The exponential increase of water hyacinth responses in increased carbon dioxide (CO2) uptake at rates of 3.4 - 5.4 g C-CO2 m-2 per day, as noted for tropical lakes.

Rapid growth rates demonstrate its ability to mobilise and retain nutrients in the tissues, as well as metabolize large amounts of CO2 (CO2).

I am facing the same problem.Did you find the solution? Diana Uriza

@Abbishek Gururaj, I am facing the same problem. Can you please tell me what happened afterwards.

Thank you, Nagalakshmi, for your answer.

I apologise for not formulating my question clearly enough. I was thinking about biogeoArgo floats. I was wondering how increased aeolian deposition to surface water (from fires for example) could bias say backscattering measurements and chlorophyl measurements made by those floats for example. Same question regarding increased fire emissions in the atmosphere; how do they disturb satellite measurements of Chlorophyll. Is there any acknowledged correction to be applied to such measurements ?

Thanks again

Generally for the cement industry it is a stack emission at 10% O2 dry for 500 mg/NM3 of NOx as NO2. The Power Industry at least in Europe is 200

To calculate CO2 you need a proximate and ultimate analysis plus the gross CV of whatever fuel you are using. To get the Bio %age your need to look at the c14 %age via a mass spec.

I can think of two potential problems, both with simple solutions.

1. The peptide is sticking to the plastic of the microplate. The enzyme can also do this. The solution is to include in the buffer 0.01% Triton X-100 or some other non-ionic detergent at a concentration below its critical micellar concentration.

2. The fluorophore is suffering photodamage as a result of an excessive number of flashes from the light source. There are two simple solutions. One is to reduce the number of flashes per measurement. The other is to make measurements at less frequent intervals.

Make sure you always use the same settings for the measurement for every experiment in order to get consistent results. You can save the setup to prevent accidentally using the wrong settings.

Dear Atakan, it's really appreciable that

you're working towards decarbonisation and sustainable development. Based on your needs, I can share you the relative links, kindly make use of it.

As follows:

Best wishes

Mohamed Khedawy

Thanks a lot!

Hi: It's an "old" fluorophore, but you could try DCM - https://omlc.org/spectra/PhotochemCAD/html/038.html - excitation max ~490 and peak emission ~620 nm (in methanol). Because it's a laser dye it is very stable.

This book - https://www.chem.ucla.edu/~craigim/pdfmanuals/catalogs/Lamdachrome-laser-dyes.pdf seems to be out of print now but contains a lot of good information on laser dyes (fluorophores used in tunable dye lasers). You might be able to find another suitable molecule there?

That's something. Thank you.

Dear Amit Chakraborty ,

you are right.

There are two attenuation coefficients involved:

a) that of the excitation radiation, which has a photon energy a bit higher than the absorption edge energy of the excited atom, and

b) that of the fluorescence radiation, the photon energy of which is smaller than

and the edge energy.

I did not understood what did you obtain, so I may only guess. Generally, suppose you add analyte with absorption at the probe's excitation wavelength, than probe's fluorescence intensity will decrease due to IFE, but lifetime will not change. If there is analyte's abscorption at the probe's emission wavelength, probe's emission intensity could decrease either due to just reabsorption (in this case lifetime will not change) or FRET (if analyte and probe are close; in this case lifetime will decrease). But if probe binds to analyte, both intensity and lifetime could change just due to binding, this should br also accounted for...

What is Food color ?

To identify the mechanism of a detection process, you have to theorize the behavior of our probe depending of the different models. This includes the prediction of behavior of your probe in conditions that you have still not tested. A successful prediction will offer you plenty of confidence.

Spectroscopic evidences are part of the job. And, as you mentioned, a change in the fluorescence spectrum is not predicted by FRET or PET.

Quantitative measurements offer also pieces of evidence. The quenching efficiency can be calculated in the case of FRET and partially calculated for PET.

An example of quatitative analysis of fluorescence quenching experiment was discussed in “Can anyone help me to do stern volmer plot in flourescence quenching?” at

Dear Harsha Agrawal

Indeed, in a polar solvent, upon excitation in the longer wavelength band, the emission is quenched, and upon excitation in the shorter wavelength band, emission is observed in the green region.

Being in a non-polar solvent, when excited in a longer wavelength band, red emission is observed, while when excited in a shorter wavelength band, emission is observed in the red and green regions.

It is sometimes possible that the emission spectra show two bands.

My mini-review will help you answer these questions:

Solvatochromism and Nonradiative Decay of Intramolecular Charge-Transfer Excited States: Bands-of-Energy Model, Thermodynamics, and Self-Organization

Article

Full-text available

I agree

Bhai jate program lako ..copy past na karo

You can normalize your apoptotic activity against the total amount of DNA by applying a DAPI or Hoechst stain.

If you are working with cells a lot you should check-out Cellseeker https://www.cellseeker.org/). This is an easy and free to use app to organize and inventory your cell collection online.

Its depends upon individual level (life style) to industrial, political level and many other factors.

u can check this paper maybe itis help

DOI:https://doi.org/10.1103/PhysRevB.69.115216

If you look closely at the numbers, you will find that the "Excited State Energy" is the difference between the TD-X and the RB3LYP energy and that the excitation energy is the same as the Excited State energy, just with a different unit.

The order of magnitude of that is also at least plausible for a molecule with this stoichiometry.

Sorry please perhaps there is error . Refers to this Article Sir "Study on Appraisal of Per Capita Consumption of Charcoal and Firewood as an Alternative Energy Sources for Domestic Usage in Keffi Nasarawa State Nigeria". You might have some idea related to your area. Thank you

Dear Saptarshi Mandal,

Thank you very much for your helpful tips. Thank you for your valuable reference.

Best Regards

In principle, you could use it. The reason for the application you mentions has to do with the number of treated units. The SCM can reach situations where the rest of the methods are not adequate (e.g., a single treated unit). This is often the case of state-level policies vs firm-level events (we usually have many observations and treated units in the latter case).

You can have a look at Cunningham's Causal inferente: the mitxtape (https://mixtape.scunning.com/), which can be of some help here.

All the best,

José-Ignacio

well,you must read some books related to lighting systems,simply it depend upon lamp type, watt,age,dimension of surface,some factors,watts to lumens factor and angle of inclination (get curve).There is famous equation in this field

Dear Yadi,

could you be more precise on what exactly you mean by "reverse"? I am not quite sure whether you are looking for new techniques (such as remote sensing) to MEASURE greenhouse gases in aquatic ecosystems or whether you are looking for new ways to REDUCE/MITIGATE emissions from aquatic ecosystems (or potentially even ways to enhance their storage capacity as carbon sinks).

Thanks & best wishes to Beijing,

Julius

You may use EBG coomon-mode filter to mitigate the quoted phenomenon

I think the cause is the functionalization of pyrene with functional groups having double bonds with 2 carbon atoms both by sp hybridization and triple bonds (1 sigma and 2 pi bonds). This condition can extend the π-conjugation system leading to a bathochromic shift from the emission band to the visible region. Furthermore, the shift results in the vibrational structure of the emission spectrum and at the same time prove that the ground state interactions occurring of the pyrene with the potential host molecule are provided by the emission spectrum.

Hopefully, this answer can provide some insight.

Since the molecule is fluorescent, have you considered monitoring the fluorescence excitation and emission spectra, intensities or the lifetimes? Self-association would probably have an effect on one or more of these properties.

The challenge is the high concentration of the compound that is likely going to be needed, causing a severe inner filter effect. To deal with this problem, you can use a triangular cross-section cuvette in the spectrofluorometer to allow you to measure the surface fluorescence by reflection, or rectangular cuvette with a short pathlength.

The radiative emission process competes with other non-radiative excited state deactivation mechanisms, like rotational relaxation, vibrational deactivation and the like. Increasing the rigidity of a molecule's surrounding makes those pathways more unlikely. Therefore, cooling a almost always increases fluorescence emission intensity. Or, telling it the other way round: increasing temperatures increases non-radiative deactivation, therefore emission intensity goes down on warming up

If your fluorescence spectrometer allows, I would suggest doing a full EEM (excitation emission matrix) measurement. Or at least measure excitation spectra for your different emission bands. If excitation spectra are the same for two bands, there must be an excited state process leading to those two emissions. If they are differing, there must be two ground state compounds present with different absorbance spectra. A highly fluorescent impurity might get unnoticed from measuring absorbance spectrum or NMR, but still exist in small amounts.

There does not appear to be any public information on this matter. You need to talk to officials at Sohar Port Authority to request information.

Dear Hamza Karmoum,

The study sounds interesting. You might try to go to the enterprise and do field research to get the emission factors. Some LCA emission factors can only be obtained through field research.

Arezoo Setayesh, you should measure your spectrum without a sample (I_o(lambda), where lambda is lights wavelength) and spectrum with sample (I(lambda)). Then you can calculate the spectrum of your sample as

S(lambda) = I(lambda) / I_o(lambda)

This is a correct operation if you avoid saturation of your receiver for any spectral range, otherwise, you should adjust incident light intensity or receiver's sensitivity.

In fact, this is an extended version of Gerhard Martens answer.

I hope it helps.

Someone suggested "Layertec (Germany), they do offer Dichroic Mirror / pump mirror HR 980nm, HT 2-3-3.5um. Costs around $500." You can check it out.

Synchrotron_radiation_energ y_flux.png

Hi Andrii Lesiuk ,

Well, that is an intriguing question because red or blue shifts in the emission spectra is usually interpreted as changes in the environment of the fluorescent probe. Such changes affect the electronic distribution and consequently modify the energy gaps, which reflects in the change of the wavelength emitted.

In that case, I agree with Nilimesh Das , I would take the maximal intensities of each curve, because they are referent to the specific electronic transition that you are tracking, the shift is a secondary effect... Another point is that if you take F0 and F at the same wavelength you will be overestimating the quenching. I think this work can help you: Vivian, James T., and Patrik R. Callis. "Mechanisms of tryptophan fluorescence shifts in proteins." Biophysical journal 80.5 (2001): 2093-2109.

And last but not the least, are you working with a low concentration of quenchers? Did you correct the inner filter effect? I have published results of fluorescence experiments in which a saw shift in the emission spectra, but when I corrected the inner filter, the shift disappeared (Povinelli, Ana Paula Ribeiro, et al. "Details of the cooperative binding of piperlongumine with rat serum albumin obtained by spectroscopic and computational analyses." Scientific reports 9.1 (2019): 1-11.). In that case, the quencher absorbed the light according to its own absorbance spectra causing an “optical ilusion”. In this work we showed the possibility of building Stern-Volmer plot based on the area under the spectra.

Hello Yuhui, sorry to see that your very interesting technical question has not yet received any expert answers. Although we frequently worked with new copper compounds in the past, I'm not really an expert when it comes to fluorescence studies of copper clusters. However, I can recommend to you a few potentially useful literature references. For example, please have a look at the following articles:

(please see attached pdf file)

Of course this is only a small selection potentially helpful articles. You can easily find and access other relevant references when you search the "Publications" section of RG for the term "fluorescence of copper nanoclusters":

I hope this helps. Good luck with your work and best wishes, Frank Edelmann

Dear Zhao Wenxiao

Unlike Enclosed fixtures that do not allow for proper ventilation can have a significant impact on the temperature of the LED bulb, causing it to overheat and shortening its lifespan. That's why some bulbs warn against using them in enclosed ceiling fans or fully enclosed porch light fixtures.

Best Regards

In PL measurement  typically the excitation wavelength ranges from 300nm -450 nm. The emission is at longer wavelengths, ex. the blue emission (430 nm) green emission (510 nm)  or orange luminescence (620 nm). The excitation wavelength must match the absorption band of your material, otherwise there energy transfer will not be possible.

I think that there may be some operational mistakes. Did you correct the line intensities by the efficiency curve of optical system? May the lines you selected be self-absorbed? Maybe you just used the wrong units for variables and constants, just like Boltzmann constant (K or eV?) in your calculation. If there were atomic lines in your spectra and LTE is satisfied, you can use the Saha-Boltzmann plot ( ) to determine the electron temperature.

Ciao Giovanni,

In our paper here you will see that its possible to tune the lifetime of the emission without necessarily sacrificing the brightness of the long-lived luminescence - we were targeting the seconds range:

Regards

Bryce

Monalisha Mohanta When a semiconductor or a dielectric material is excited above the bandgap energy and as a result of relaxation, luminescence is observed is called photoluminescence. As a result of relaxation, if only photons are emitted, the bandgap will be a "direct" bandgap, while, if in addition to photons, phonons are also emitted, the bandgap will be an "indirect" bandgap. Since, the phonons emission is due to the defects, impurities, and dopants between CB and VB. When only photons are emitted, the relaxation is called radiative, while, when only phonons are emitted, the relaxation is called nonradiative. We can only find the bandgap energy from PL data in the case of radiative relaxation (direct bandgap). In nonradiative relaxation, when an electron passes its energy to the phonons, is called Shockley–Read–Hall recombination and when a relaxing electron passes its energy to another electron or hole is called Auger recombination. From PL data, intensity, line edge, and FWHM are the characteristics parameters i.e. higher intensity means low defect density and greater FWHM gives poor structure and vice versa. In addition to all the above, the energy bandgap calculation from PL data is subject to many limitations. For example, PL emissions do not give an exact bandgap like UV-Vis absorbance (Tauc plot). The bandgap calculated by the PL study will always be less than the original bandgap. Emission spectra are usually solvent dependent and are shifted with the change in solvent polarity due to solvent relaxation, the excitation spectra are usually preferred for bandgap calculations.

In the following video, I have explained all the above discussions in detail. Links to the files used in the Origin tutorial video have been provided in the video description. Thanks