Using light to detect metalsUsing light to detect metals

Laura I. Saucedo

http://i138.photobucket.com/albums/q261/newt_album/visiblespectrum.gif

Heavy Metal Ion ContaminationHeavy Metal Ion Contamination

� In chemical solutions� In underground water supplies

Today:Today:

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But first…But first…

Let’s talk about colorLet’s talk about color

Under UV light

a: b:

Why does substance ‘b’ change color?Why does substance ‘b’ change color?

� A) Because our eyes are playing tricks on us.

� B) Light interference � C) Because it now reflecting blue� D) Because of electronic excitation

Under UV light

a: b:

What are some ways that molecules can utilize energy?What are some ways that molecules can utilize energy?

http://preloaders.net/en/search/arrow%20rotating ; http://www2.ess.ucla.edu/~schauble/MoleculeHTML/CO2_html/CO2_page.html

Singlet vs TripletSinglet vs Triplet

Spin multiplicity = 2S + 1S = ms1 + ms2

Singlet Triplet

Absorption

InternalConversionVibrationalRelaxation

Radiative Decay

Absorption

IntersystemCrossing Vibrational

Relaxation

Radiative Decay

PhosphorescencePhosphorescence

http://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Electronic_Spectroscopy/Jablonski_diagram

Absorption

IntersystemCrossing Vibrational

Relaxation

Radiative Decay

Intersystem Crossing?Intersystem Crossing?

http://employees.csbsju.edu/cschaller/Reactivity/photochem/PCfluorescence.htm

What is the relationship of energy to wavelength?What is the relationship of energy to wavelength?� A) E = hc/λ� B) E = hcλ� C) E = hλ/c� D) E = hc/λ2

λ is inversely proportional to Energyhttp://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html

FluorescenceFluorescence

http://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Electronic_Spectroscopy/Jablonski_diagram

Absorption

VibrationalRelaxation

Radiative Decay

Stokes ShiftStokes Shift

http://dc440.4shared.com/doc/3mKIGd6e/preview.html

Fluorescein

Rhodamine

Coumarin

Common fluorescent molecules:Common fluorescent molecules:

What do these molecules have in common that cause them to fluoresce?

a) Ether groupsb) Each contain a

benzene ringc) Extended π

systemd) Electronegative

atoms

BODIPYBODIPY

4,4-difluoro-4-bora-3a, 4a-diaza-s-indacene

Peña, E. et al., Chem. Commun. 2010, 46, 5103-5105 Tram, K. et al., Dyes Pigments, 2009, 392

Meltola, N. et al., J. Fluoresc. 2004, 635-647 Jiang, X. et al., Org. Biomol. Chem. 2012, 6861-6865

Placing this into a polar solvent:Placing this into a polar solvent:

QuenchedQuenched

http://chemwiki.ucdavis.edu/Organic_Chemistry/Organic_Chemistry_With_a_Biological_Emphasis/Chapter__2%3A_Introduction_to_organic_structure_and_bonding_II/Section_2.3%3A_Non-covalent_interactions

+

2

2+3+

Optical Properties Optical Properties

0

0.02

0.04

0.06

0.08

0.1

348 398 448 498 548

AB

S

λ

Absorption

Hex

Ben

DCM

THF

Acetone

Acetonitrile

0.00E+00

5.00E-02

1.00E-01

1.50E-01

2.00E-01

2.50E-01

348 398 448 498 548

Fluo

resc

ence

vol

ts

λ

EmissionsHex

Ben

DCM

THF

Acetone

Acetonitrile

Optical PropertiesOptical Properties

What do these spectra tell you?What do these spectra tell you?

� A) Some of the absorbed energy is lost through non-radiative decay

� B) Polar solvents are interacting with the molecule

� C) A and B� D) none of the above

Future WorkFuture Work

� Currently purifying a protected:

� Working to cleave disulfide bond.

Rate My PresentationRate My Presentation

� A) Best, most informative presentation of your entire life

� B) It was a good informative presentation� C) Meh� D) Are you still up there?� E) BOOO!

Questions?Questions?

This material is based upon work supported by the National Science Foundation under Grant Number DUE-1140469.

Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

Degenerate?Degenerate?