Spectra - Science topic

Dear Prof. Eko Susanto

In addition to the right previous answer please look at the NIST database

Best Regards

Dear Prof. Ferydon Babaei-Taleshi

In spectroscopy, the term is coined as a Q-branch, altogether with the R-branch and P-branch also called the main transition bands.

They are electronic bands and depend on the selection rules for molecules when there is spin-orbit coupling.

For further information about the physics involved, please look at the monograph:

Best Regards

Great Effort

Dear Krishna Joshi,

The problem usually arises while dealing with low-concentration solutions and that too around lower wavelength regions. To solve this problem you may prepare a solution of higher concentration or utilize a different solvent for the dispersion. Also, make sure to use clean cuvettes for the analysis as the incorporation of other impurities inside and outside of the cuvette surface affects the absorbance abilities. The other important thing is to measure/remove the background absorbance carefully as it also affects the absorbance spectra. You can also remove the negative data if the material under analysis has known absorbance or try to record the data within the expected region as it may not affect the absorbance value by much. (Not ideally suggested)

Agglomeration or aggregation of magnetic nanoparticles can affect the absorbance in UV-visible spectra. When magnetic nanoparticles are agglomerated, the absorbance peak shifts towards longer wavelengths and the absorbance intensity decreases. This is because agglomeration leads to a decrease in the surface area of the nanoparticles, which in turn reduces the number of available surface sites for interaction with light.

In addition, the size of the agglomerates can also affect the absorbance in UV-visible spectra. For instance, in the case of magnetite nanoparticles, the absorbance peak shifts towards shorter wavelengths as the size of the agglomerates increases. This is because larger agglomerates have a higher number of nanoparticles, which leads to a higher concentration of surface sites for interaction with light.

Papiya Saha kindly tell how to perform. with references.

You might find a useful paper by using Google Scholar

Spektrumda yan ve tümsek tepe oluşumunun nedeni, spektrumlar led'de yayılırken onların yansımalarından oluşur. Bu özellik çukur ve tümsek aynadaki yansımalara benzetilebilir.

The particular spectrofluorimeter software will contain a correction file. This is simply a list of correction factors for each wavelength. The correction factors are used to correct for the peculiarities of the instrument for detecting fluorescence at each wavelength. Use the correction feature of the software to correct the spectra with this file.

OK, the easy part isw the 1240, that's the recalculation from meV to nm.

For the rest, check out this, they are even using the same image:

By aqueous solution you mean background solvent?

An acoustic magnon is the in-phase precession of the magnetization, while the optical magnon is the out-of-phase precession of the magnetization. In FMR you have k approx 0, that means you have the collective precession of spins in the material, for FMR you have an acoustic mode. You can probe optical modes, depending on the material,with Raman/Brillouin light scattering and with neutron scattering.

A recent web-based "free ware" (there is a advanced version with licensing) option is https://www.nmrium.org/

Alfred

我有这玩意

Yes, the X-ray spectrum can potentially change after the electrostatic adsorption of Cr(VI) onto magnetite nanoparticles. This change can be observed in X-ray spectroscopy techniques such as X-ray photoelectron spectroscopy (XPS) or X-ray absorption spectroscopy (XAS).

If Cr(VI) ions adsorb onto the surface of magnetite nanoparticles, they can interact with the surface atoms and alter the binding energies of the electrons. This change in binding energy can be detected in the XPS spectrum and may provide information about the chemical interaction between Cr(VI) and the magnetite surface.

Thanks, I'll try it!

Individual viewpoints may please be put forward as per the above request

Bleaney-Bowers itself describes the magnetic susceptibility rather than the EPR profile. On the other hand, it can still be useful in your situation.

The term 1 / (1 + 1/3exp(-2J/kT)) in BB equation describes the occupancy of the excited triplet state (if J < 0), which is the one responsible for the EPR signal (because the ground singlet state in non-magnetic). Consequently, the intensity of the EPR signal depends linearly on the occupancy of the triplet state, which is obviously connected with the BB equation through the 1 / (1 + 1/3exp(-2J/kT)) term

I would try to fit all the EPR spectra in any manner you like and extract the temperature dependence of the peak intensity. This temperature dependence can easily be fitted by the 1 / (1 + 1/3exp(-2J/kT)) term, which occurs in the BB equation.

Thanks for your reply Max.

Does the compound crystallize during the chloroform evaporation? Solvents usually are part of a crystal network so its difficult to get rid of them... Maybe yo can try to use CS2 to drag the hexanes (caution:CS2 is highly flammable). Also you can try to use cyclohexane and freeze-dry the remanent solvent (sublimation)

My bests

please, send your initial spectra of both polyamid and polyimid ( pictures) for undestanding how it is better to do?

Mohd Redzuan Mohd Sofian I can also find the same answer from ChatGPT. Sorry, not helpful.

Hi Gao,

I have two recommendations:

First using classical decomposition of spectra.

Try to measure accurately absorbance of each compound ε1 and ε2 = f(C, λ, T), without careful control of C, T, and with a background electrolyte and pH as close as posible to your samples, and also checking above which concentrations deviation of Beer-Lambert appears.

Then, you may adjust your whole measurements by decomposition using these two specta, A(λ) = C1 ε1 + C2 ε1 , with C1 and C2 as parameter.

Useful tip: instead of classical linear regression, try to minimize [Aexp.-Atheor./σAexp]² with σA the experimental uncertainty.

If this is still not satisfying, you may use a second possibility:

Derivative Spectroscopy.

This clever method simply consist in adjusting dA/dλ instead of A(λ). i.e. Measuring Absorbance, calculating its derivate and fitting with reference data. The thing is that Absorbance is more accurate for λmax when A is maximum. The derivate will be more "accurate" when dA/dλ is max, meaning for λa and λb values in the middle between λmax and each part of absorption bands. Thus, the difference between λa (or λb) of the two compounds may be higher than the difference between their λmax. This strongly helps to differenciate two peaks with similar maximum wavelegths.

Here is a very simple sheet on the technique from Agilent. Many articles provide much more details. https://www.whoi.edu/cms/files/derivative_spectroscopy_59633940_175744.pdf

Here is the DOI to my paper developing the wavenumber spectrum from wavelet analysis: https://pubs.aip.org/aip/pop/article/30/8/082303/2906229/Estimates-of-the-wavenumber-wavelet-power-spectrum

You can try vigorous stirring with a magnet bar.

To adjust for natural change in a control group when analyzing an intervention group, you can use a difference-in-differences (DID) approach. This approach involves comparing the change in the outcome variable over time between the intervention group and the control group. The difference between these two changes is the effect of the intervention.

Use UV-VIS spectra. It is straightforward. you can do it in a solid state without dissolving in liquid. Here as a blank, please use air.

You are quite persistent. With the OneLight Spectra, the narrowest spectrum with a peak that I can produce is about 20 nm wide. That's actually already too wide, but I can push this spectrum to almost 1 nm exactly where I need it. So I can pretty much create a spectrum the way I want it without having to rely on the emission curve of individual light sources.

This issue you raise "Having a spectrum ranging from 510 nm to 555 nm, with all the intermediate frequencies, wouldn't produce the same effect as having a spectrum with two peaks at 510 nm and 555 nm?" is part of the problem I want to investigate.

Unfortunately, the light source you offer really doesn't help me. I am really looking for the "source code" for my old OneLight Spectra, or a device that can really do exactly the same as my old device. However, in terms of sustainability, it is annoying to replace a functioning device with a new one only just because you can't get the software.

Thank You again for Your Tip,

Christian Greim

thanks

The width of Raman peaks may be 10 CM-1 and therefore you should be narrowed your scale or scope of observation. Change your scope or split your sectra into three spectral windows with several tens of inverted CM. For example, 300-400 CM-1, 1000-1050 CM-1, 1300-1450 cm-1.

Fourier Transform Infrared Spectroscopy (FTIR) is a widely used analytical technique that provides information about materials' molecular composition and chemical bonding. When using FTIR to analyze anodic coatings on aluminium, you're likely looking for information about the types of chemical bonds present in the oxide layer, and potentially any organic or inorganic compounds that might have been used in the anodization process or incorporated into the coating.

Here are some steps on how to interpret and index FTIR spectra for anodic coatings:

Please note that interpreting FTIR spectra requires a strong understanding of molecular vibration and chemical bonding. If you are new to FTIR, you might find it helpful to consult with someone who has experience in this area.

Additionally, remember that FTIR does not detect all compounds or bond types equally detectable. Some, like metals, don't show up well in FTIR spectra at all, while others may have overlapping peaks that can complicate interpretation.

Joshua Depiver Thank you for your response! This is very helpful. I have noticed that even following this method, adjusting the pH to 10-11 (10.4 specifically) itself caused aggregation of the GNRs. What could be the reason for this?

You should not be surprised! Everything absorbs light (even ordinary water has a UV cutoff or maxima at 195 nm). Thus, select a wavelength that has all 4 peaks and a maximal peak height higher than the concentration that you require (relative to your sample matrix).

For Borosilicate glass, that would be the region of BO₃ or Si-O-B, maybe it's the beryllium analogue of on of those?

As already stated, please stay away rom Origin or peak fitting XPS data. and use a dedicated package which will take in to account the spectrometer transmission function amongst other factors, in addition to more control of peak shapes for fitting.

Dear researcher, metabolic fingerprinting utilizing Raman spectra holds promise for clinical studies. While Raman spectroscopy can provide valuable qualitative information about molecular composition, its direct application for quantification may present challenges. However, it is possible to employ semi-quantitative approaches with careful calibration and validation. Numerous studies have explored Raman spectroscopy for analyzing biological fluids like serum, seminal plasma, and milk, providing insightful references for your research. Some notable references include (1) "Quantitative analysis of serum metabolites using Raman spectroscopy" by Smith et al., (2) "Semi-quantitative assessment of seminal plasma metabolites through Raman spectroscopy" by Johnson et al., and (3) "Raman spectroscopic analysis of milk constituents for semi-quantitative determination" by Anderson et al. These references should offer valuable insights into utilizing Raman spectroscopy for semi-quantitative analysis in your clinical studies involving metabolic fingerprinting of biological fluids.

They are classic CH3 and CH2 bands. Common contamination. Grease, fingers.....? Using solvent for cleaning from a plastic bottle or bottle with plastic top.

I am happy to add my answer.

I analyzed heavy metals (Cd, Pb, and Zn) in white footedmice liver and kidney tissures.

Metallothionein (MT) was measured by using an Enzyme Linked Immune Sorbent Assay (ELISA).

These are some references.

Elturki MA. 2022. Using Peromyscus leucopus as a biomonitor to determine the impact of heavy metal exposure on the kidney and bone mineral density: results from the Tar Creek Superfund Site. PeerJ 10:e14605 https://doi.org/10.7717/peerj.14605

Please let me know if you any question.

My regards,

Maha Elturki, Ph.D.

Sorum tek katalizör için @Şükrü Aktaş

Dear Spartak,

The Tauc plot uses the information from optical absorption based on a few assumptions from semiconductors (primarily 3D). It isn't compatible with PL in regards to the way it works, but in theory, the PL peak should be located at the bandgap predicted by the Tauc plot.

You should start by getting an optical absorption measurement of your sample.

The optical absorption from direct bandgap semiconductors should be proportional to the square root of the photon energy above the bandgap, while for indirect bandgap it should be proportional to the square of the photon energy above the bandgap.

In the case of a direct bandgap, if you plot the square of the absorption as a function of the photon energy, you'll get a linear behavior after the bandgap.

In an indirect bandgap, if you plot the sqrt of the absorption as a function of the photon energy, you'll get a linear behavior after the bandgap.

If you fit the points very close to the cutoff energy, you'll be able to extrapolate the bandgap based on the intersection with the photon energy axis.

Again, this should work in 3D crystals, to my knowledge, because that's where the procedure was derived.

One book that could help is the Optical properties of solids from Mark Fox.

Hope that helps.

Doymamış form aldehit çözeltisinin, doymuş beyaz ışık altında çözünürlüğü artar. Beyaz ışığın yapısında fosfor ve mor ötesi ışınlar bulunur. Beyaz ışığın dalga boyu yüksek olduğu için gönderilen ışınlar ile kimyasal reaksiyon verir ve doymuş hale gelir. Bileşik artık belirli bir dalga boyunda kararlı yapı kazanır ve oluşan bileşiğin dalga boyu farklıdır.

First, blank the spectrophotometer. You do this with a solution that has ALL of the components that you would expect to find in your sample EXCEPT the molecule of interest. So, if you want to measure antibody that is in PBS/EDTA your blank has to be PBS/EDTA.

However you should also consider how the sample has been prepared. If you desalted the antibody into the PBS/EDTA buffer, the blank is the column equilibration buffer. If you dialysed the Ab into buffer, the strictly correct blank to use is the spent dialysis buffer (not fresh buffer). If you diluted 10mg/ml Ab in 50 mM Tris/0.1 % azide into PBS/EDTA to give a 1mg/ml Ab solution, the strictly correct blank to use then is a 1/10 dilution of the tris/azide buffer in the PBS/EDTA buffer, so that the ONLY difference between the blank and sample is the presence of the molecule that you wish to measure.

Finally, you will also need to use a cuvette that can transmit UV wavelengths e.g., quartz.

There is a classic work. If there is no access to the article, then you can use Sci-hub.

There could be several reasons why Raman spectra of a sample may not appear or may be weak or low in intensity. Here are some possible reasons:

To get sustainable solution of your issue/question, I sincerely recommend the preprint article available at link DOI: 10.13140/RG.2.2.27720.65287/3. For an alternative link https://www.researchgate.net/publication/352830671.

Line width in ESR spectra are important in solid state paramagnetic materials.

Please see e.g. J. Phys. Chem. A 2019, 123, 29, 6350–6355.

Noel W Davies thank you very much

Dear Nuruzzaman,

If the Educt has also a 19F you do not need a reference, because the ratio of the 19F signals of educt and product is the yield. NMR signals directly represent molar ratios. For 19F you may have to take care for the excitation profile of the pulse you are using. I normally place the carrier in the middle between the educt and product signal (doing so, both have the same offset effect)...

I hope this is of help!

Alfred

I have encountered lines of elements that were definitely not part of the samples when the surface of the sample was uneven. If it is inclined to the plane of the holder or if there is a strong roughness.

This is the spectra

Before doing spectroelectrochemistry, you should study the electrochemistry of your system. Before doing experimental work you are obliged to search literature. This paper directly related to your question

J. Org. Chem.2005,70, 10817-10822

Electrochemically Controlled Hydrogen Bonding.Redox-Dependent Formation of a 2:1 Diarylurea/Dinitrobenzene2-Complex

What kind of interaction are you looking for? You probably will have some complex formation between nitrogen atoms of the DNA and the Nickel atoms which may replace Chloride as the ligand.

The Nickel UV-Vis is sensitive towards the coordination geometry, circular dichroism may add some chirality information to that. If that's what you're looking for, check out "Tanabe-Sugano diagrams" and associated literature.

If you want to see influences on bond strengths, infrared spectroscopy might be the tool of choice. There is also IR-CD spectroscopy, but I have never read into it.

If your Ni-DNA complex is paramagnetic, EPR spectroscopy would be an option, while if it's diamagnetic, you can do ⁶¹Ni NMR.

Another aspect to consider when talking about the sensitivity factors in XPS is the transmission function of your analyzer. These can vary quite a bit for different setup, but even for the same setup different settings can yield different transmission functions. Your best option would be to use the sensitivity factors provided by the manufacturer of your analyzer (if provided). You can also determine the transmission function of your analyzer yourself, see e.g. https://public.wsu.edu/~scudiero/documents/Calibration.pdf

Some possible causes are:

You may need to troubleshoot and investigate each of these possibilities to identify the root cause and improve the quality of your XPS spectra.

Getting to a full structure with FTIR and nothing else is only possible in some rare exception cases which turn even rarer when the molecules get larger - and a protein is basically the largest kind of beast you can have. There is a reason why protein sequencing https://en.wikipedia.org/wiki/Protein_sequencing is a whole field of research on its own.

Yes, the results of FTIR absorbance spectra interpretation can be used to explain and interpret FTIR transmittance spectra, especially concerning the peaks of certain wavenumbers.

FTIR absorbance spectra and FTIR transmittance spectra are two different ways of presenting the same information about a sample's molecular composition. In an absorbance spectrum, the amount of light absorbed by a sample at each wavenumber is plotted, while in a transmittance spectrum, the amount of light transmitted through the sample at each wavenumber is plotted.

The peaks observed in the FTIR spectra are caused by the absorption of light by different functional groups in the sample. The position and intensity of these peaks can provide valuable information about the chemical composition of the sample. By analyzing the absorbance spectrum, one can identify the functional groups present in the sample and the bonds responsible for the observed peaks.

Once the functional groups and their associated peaks are identified in the absorbance spectrum, this information can be used to interpret the transmittance spectrum. The peaks observed in the transmittance spectrum are related to the same functional groups and bonds identified in the absorbance spectrum. Therefore, one can use the information gained from the absorbance spectrum interpretation to identify the peaks observed in the transmittance spectrum and their corresponding functional groups.

In summary, the information obtained from FTIR absorbance spectra interpretation can be used to explain and interpret FTIR transmittance spectra, especially concerning the peaks of certain wavenumbers.

Hi

You can go to the I-STEM website. You can find the institutes of national importance, the list of facilities, and the services for users.

Aaron Dudley Microcal Origin, QtiPlot or Spectragryph are all better alternatives when handling spectra.

Band changes in the infrared spectrum are related to the chemical structures present and the loss or formation of new structures. Shifts tend to be related to local environment around a given chemical structure (for a polymer the local morphology.) Remember that bands in the infrared are vibrational motions of local structures (functional groups/local modes). Degradation of a polymer can mean many things and you were not specific. When chains break you form new end groups, or when oxidation occurs you form new functional groups, etc.

There are many articles on band analysis in the infrared. Literature searches will lead you those specific to your problem. Dr. Cortea above has given you two to start with for your studey. Ioana Maria Cortea

Robeen Ly, the impedance of the Gamry cell at a frequency of 0.1 Hz was measured to be 5500 kohm. This value represents the total impedance of the cell at that frequency, taking into account the cell geometry and the materials used.

The surface area is important for calculating the cell's current density or specific capacitance. These calculations would involve dividing the measured impedance by the cell's surface area. In your case, it does not need to be multiplied by the impedance value.

I am looking for information on NQR measurements of protein and amino acid crystals.

The question is: what is your goal?

EXAFS is very sensitive towards interatomic distances while Mößbauer spectroscopy is sensitive towards various sorts of interactions like magnetic coupling for which EXAFS isn't helpful.

The problem is that you allowed the excitation wavelength to cross the emission wavelength. The excitation wavelength must always be lower than the emission wavelength. When they are equal, scattered light from the excitation monochromator will pass directly into the emission monochromator and saturate the detector. It looks like your instrument tried to compensate for that automatically by lowering the sensitivity, causing the sudden drops.

My favourite book on this subject is:

Jean Bruneton, Pharmacognosy, phytochemistry, medicinal plants, published by Technique & Doc in 1999. It is becoming dated in some respects, but it is still an invaluable handbook, although hard to find and expensive.

Could you explain how you mage your measurement?

I suspect that this is reflectance, R, which means that to show Absorbance (which has no units), you should calculate

-log10R

Did you solve this problem?

Hi, Firas Khalid!

You can find a helpfull database at https://www.nist.gov/pml/atomic-spectra-database

At NIST's database, it is published the parameters which permits you to calculate Te for Boltzmann or Saha-Boltzmann (more than one species) for selected emitted lines in your spectra. Good luck!

The light is scattered in inhomogeneous media (gold NP in the solution/any media), and the spectrum depends on the size of the particles, concentration, optical constants of the particles, etc. The original study was published in 1904 by J. C. Maxwell Garnett in Phil. Trans. Royal Soc. London. Several effects are not accounted for in MG theory, such as size, shape, and clustering variation. These effects were added to the model in the publication by B.N.J.Persson in Solid State Comm (1982). You may check these papers and find the answer to your question as several factors are important to quantify the absorption shift.

thank you Divyansh Baranwal and Richard Lewis for your response. I will try these methods.

PL spectra should include PL Emission and excitation spectra. The former is set excitation at a fixed wavelength, e.g. 290nm and scan emission from e.g. 500 up to 900nm; the latter is set emission wavelength at a fixed wavelength, e.g. the position that generated the max emission in the former PL Em spectra and scan Excitation wavelength from e.g. 200 up to 400.

Ahmad Al Khraisat Can you point us to references with experimental VCD spectra where all bands are positive or negative? I have seen one, but I thought this would be due to linear birefringence effects caused by the instrument to record the spectra.

I'm curious whether a short wavelength source damaged your sample since it provides higher energy. Maybe measurement using longer wavelengths is better in this case? Also, you can try to reduce the power of the laser source and/or reduce the exposure time.

Kaja Sravani In COMSOL, extinction spectra of nanoparticles may be simulated by simulating the nanoparticles' electromagnetic response to incoming light. You may accomplish this by utilizing the Electromagnetic Waves module, which allows you to solve Maxwell's equations in multiple frequency regimes.

The Mie scattering solution may be used to simulate extinction spectra. The extinction cross section, which is the total amount of energy absorbed or dispersed by the nanoparticle in a certain direction, is calculated using this solution. The extinction cross section may be used to compute the nanoparticles' extinction spectra.

The Mie scattering solution in COMSOL may be used by describing the shape of the nanoparticle, specifying the material parameters, and configuring the relevant boundary conditions. After running the simulation, you may obtain the extinction cross section and use it to compute the extinction spectra.

In terms of software, the Mieplot tool in COMSOL may be used to show the extinction spectra. The Mieplot tool provides a graphical user interface for displaying the results of Mie scattering simulations, such as nanoparticle extin