Questions tagged [uv-vis-spectroscopy]
For questions that are related to the ultraviolet and visible spectrum of compounds, mostly due to electronic transitions between orbitals.
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UV-Vis Absorbance against wavelength graph for finding max wavelength
I have plotted the absorbance against wavelength graph to find the optimum wavelength for maximum absorbance of p-nitroaniline. However, the curve (dark blue) of the most concentrated solution (sample ...
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Datasets of Light Absorbance Spectra for Atmospheric Gases
I am currently doing some thermal/aerospace engineering research that involves finding light absorption in different points in Earth's orbit.
What is the best way to find absorbance vs. wavelength ...
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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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How can I compare the UV/Vis absorption difference after metal ion chelating of crown ether-containing polymer?
Recently I have synthesized the polymer that contains 1-aza-18-crown-6 in the repeating unit. I want to know if there is any UV/Vis absorption difference after the chelation of metal ion. Considered ...
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Auxochromic action of an alkyl group attached to a double bond
In the UV-Vis spectra,
$\ce{CH2=CH2}$ has max absorbance at $\pu{171 nm}$.
$\ce{CH3-CH2-CH=CH-CH2-CH3}$ has max absorbance at $\pu{184 nm}$.
The alkyl groups decrease the π-π* gap by raising the π but ...
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The extinction coefficients of oxymyoglobin and ferryl myoglobin
I want to know what the extinction coefficients of oxymyoglobin and ferryl myoglobin are. I was able to find the one for the oxymyoglobin in this pretty old article (it says that it equals $121 \text{...
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UV absorbance titration to determine binding stoichiometry
I previously posted a question but I think I did not explain correctly. I want to construct a Job plot using UV-Vis titration to find binding stoichiometry. I have 20uM of ligand solution and 20uM of ...
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Comparison of two different coloured dyes using UV-vis spectra
I know that Both solutions are a shade of purple due to the lack of absorbances in the red and blue regions, however am I correct in thinking that the peak slightly to the right of the 2 in this ...
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Assigning structure based on EPR spectroscopy
When given two copper(II) complexes - bis(N-3-chlorophenyl-salicydenaminato)copper(II) and bis(N-3-methylphenyl-salicydenaminato)copper(II) - how can you predict their EPR spectrum and hence their g ...
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Absorption wavelength of nickel (II)
One of my students is trying to study a nickel(II) solution, prepared from nickel(II) sulfate, which is green. In solution it is also green, thus I would expect it to absorb red light. Here is a test ...
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Crude palm oil DOBI analysis
I'm performing Crude Palm Oil DOBI spectrum analysis using uv-1900i UV-VIS spectrophotometer at a range of 269nm and 446nm but it's only giving peak absorbance at 446nm but no reading at 269nm,what ...
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Searching for electronic spectroscopy reference book
I'm looking for a reference book that will help me describe UV-VIS spectra of organic compounds in terms of Q band, MLCT band, Soret band, and so on. Is something like that available?
Thanks
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Creating custom spectra graphs
I wanted to make a few custom spectra graphs for some homework questions I'm assigning. The issue is that the Education Board issued datasheets do not reflect online images. They often say that bonds ...
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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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Relationship between transmittance and color of the solution
As I understand, transmittance is light which passes through a material and it determines the color of material (for example green solution transmits green light).
Here’s the transmission spectrum of ...
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The reason for selection of wavelengths in the spectrophotometry of Quinoline Yellow SS
The absorption spectrum for Quinoline Yellow SS has peaks at 224 nm and 414 nm, and a trough at 337 nm.
This experiment (see page 31), selects 224, 337 and 414 nm to be used in the spectrophotometric ...
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How to Combine an Emission spectrum into a colour? [closed]
I am trying to wrap my head around the flame test, and for the most part, it is making sense. My question is their a way to figure out the colour of a flame of an unknown element given the emission ...
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Finding the percent of light absorbed by a sample [closed]
I have an absorbance of $0.266$ and need to find the percent of light absorbed by the sample. Is it found by just turning it back into transmittence% and subtracting 1? So by that, would it be $(1 - 0....
user118463
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How to troubleshoot absorbance analysis when readings fluctuate
I am trying to measure creatinine in fluids by using an enzymatic (creatinine) test. I try to determine the concentration by the difference in absorbance before and after 5 minutes after a reagent is ...
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Is it false that the absorbance of two concentrations is the sum of the absorbances of the concentrations?
I am in the lab and trying to perform the molybdenum blue test for phosphorus using a photometer. It appears common speak in colorimetric lab sheets that
Absorbance of a mix of two concentrations is ...
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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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How can I prove ascorbic acid degradation with Uv-vis spectroscopy?
I have to prove scientifically why a sodium ascorbate solution in water turns yellowish - reddish over time. I know ascorbic acid is supposed to oxidize into dehydroascorbic acid, and the latter then ...
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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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Absorption Curves Normalization
I have absorption curves for three species that are nominally the same concentration that I need in order to calculate spectral overlap. Part of that process is dividing the curve through by the ...
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Why is 295 nm a good wavelength to check absorbance when testing for aspirin?
Take aspirin (acetylsalicylic acid) and hydrolyze it with NaOH. This results in sodium acetylsalicylate and water. I think the sodium is held on with an ionic bond, so it is really salicylate dianions ...
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Invisible spin allowed transitions in Tanabe-Sugano diagrams
In class we are looking at Tanabe-Sugano diagrams, more concretely at transitions for a d2 complex.
I understand that the only spin allowed transitions are those that have a triplet state, therefore ...
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TD-DFT transition dipole moment vector does not align with experimental data
I have been modelling excited states of some molecules with similar stucture using TD-DFT theory, however, I have encountered an issue that sometimes transition dipole moment does not align with the ...
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Why iron(II) spectrometry is not measured in distilled water and it requires a complexing agent like o-Phen?
We know that iron(II) ions in water have a green colour. Why we cannot draw the spectrum of iron(II) directly in distilled water to measure the absorbance then determine the concentration of iron(II)? ...
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How to determine the number of π-electrons in a conjugated system from UV-Vis data?
Is there a way to determine the number of π-electrons in a conjugated system from UV-Vis data? I am modelling the electrons as particles in an infinite box of length $L$ equal to the length of the ...
user85551
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E1 selection rules for transitions between two Σ states
For E1 selection rules (embodied in the electronic transition moment), to have an allowed transition the direct product of irreducible representations (IRs) must contain the totally symmetric IR. So, ...
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What is the best way to clean Lovibond tintometer quartz cuvette used for oil?
I work in a laboratory where we regularly check edible oil color by using a Lovibond colorimeter. Some people suggested me to wash the quartz cuvette using soap solution.
But I am thinking about ...
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How to draw molecular orbital diagrams for protonated/deprotonated methyl red?
Give a molecular structure-based explanation for the differences in the UV-Vis
spectra in I and II. Use detailed MO schemes for A and B for illustration. (12 marks)
Does the double bond of N=N, C=O ...
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How is the UV-visible spectra of carbonatotetraamminecobalt(III) nitrate interpreted?
In a laboratory practice I have done a characterization of the $\ce{[Co(NH3)4CO3]NO3}$ and obtained the following spectra:
I don't know if the band between 300 nm and 400 nm can be due to the effect ...
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Why diethyl ether does not absorb in UV region?
Explain why diethyl ether does not have a UV spectrum, even though it has lone-pair electrons.
Can we say that π* molecular orbital does not exist because there are no π-bonded electrons in diethyl ...
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Beer Lambert law when complex is tetragonal (Jahn-Teller elongated)
I wondered what modifications there would be to the Beer Lambert law to find the molar extinction coefficients for the solution if the solvent contained the ligands which bind to the metal centre of a ...
user85551
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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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Is it possible to make a solution of zinc oxide in a high school chemistry lab?
As part of my IB Chemistry curriculum, we are required to conduct our own experiment researching our own question. I'm in the preliminary research phase and wanted to conduct an experiment looking at ...
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Is there an actual distinction between through-space charge transfer and excimer emission?
Variety of books and literature reviews consider excimer (or exciplex) emission something distinct from through-space charge transfer. Is this actually the case?
This question arises, because the more ...
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How does Mars rover Curiosity's ChemCam's infrared laser produce a 100,000 K plasma plume (kT = 8.6 eV)?
Mars rover Curiosity's ChemCam uses a pulsed diode-pumped solid-state laser (DPSS) at 1064 nm to excite material on the surfaces of rocks up to 7 meters away, and a large aperture telescope to collect ...
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Connecting a computer to Genesys 10S Spectrophotometer
Has anybody ever connected a computer to a Thermo Scientific Genesys 10S Spectrophotometer without their (costly!) software? I'd like to pull absorbance data off of it to perform analyses. There are ...
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Estimate the relative intensities of absorption given the split in energy levels
Estimate the relative intensities at $\pu{25 °C}$ of absorption originated in the ground state and the first excited state when the energy levels involved are separated by:
(a) $\pu{10000 cm^-1};$
(b) ...
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Adsorption of Cu2+ using banana peels for pH 2,2.5,3,3.5,4
so basically I did my experiment which is the title. This is my procedure and results:
Make 0.05M CuSO4
pipette 50ml CuSO4
change to respective pH values using HCl
Add 2g of oven-dried banana peels
...
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How to change pH of CuSO4?
I'm currently very desperate to know this. I'm doing an experiment about adsorption/chelation of Cu ions in CuSO4 using banana peels using the UV-Visible spectroscopy. How do I change the pH of 0.1M ...
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Photoluminescence Spectra of Solids
What information can we gain with the photoluminescence spectra of solids? The bandgap can be determined for example, but are there any other useful properties we can learn? I care about this in the ...
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Why do we see complementary colors in UV/Vis Spectroscopy? [closed]
From what I read, a compound that absorbs visible light will produce a complementary color (using the color wheel), that can be seen. Why is this the case? Is it because, for example, if a molecule ...
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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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Can I make UV-Vis calibrant in the lab?
I have a Thermo Nanodrop 1000 spectrometer that I have reason to believe is out of calibration. After consulting the manual, it appears as though there is a way to check the calibration of the ...
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What type of FDA process does a 222nm Kr-Cl excimer UV-C light have to go through [closed]
There are plenty of articles and preliminary research about this type of light being able to kill virus as effectively as 254nm UVC light, but not harmful to human skin and eye. This is wonderful news ...
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Visible Light Spectrophotometer Recommendations
I’m looking into purchasing a cheap uv-vis spectrophotometer but am not affiliated with an institution at the moment given the whole COVID 19 situation. Are there any good recommendations for cheap ...
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Chemical equation to represent the hydrogen peroxide scavenging experiment, used to determine antioxidant ability of tea
I am currently investigating the antioxidant ability of tea using hydrogen peroxide scavenging. Basically, I will look at absorbance of the tea samples with and without the addition of hydrogen ...
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