This document discusses various spectroscopy techniques used in inorganic chemistry, with a focus on applications of metal nanoparticles and organic ligands. It describes how surface plasmon resonance gives silver nanoparticles their color and how that color depends on particle size. It also outlines several applications of silver nanoparticles in biosensing, antibacterial materials, conductive inks, and optics. The document then discusses estimating the number of atoms and concentration of nanoparticles from absorption measurements before analyzing samples of silver and gold nanoparticles. Finally, it covers electronic transitions in organic molecules, conjugated pi systems, and fluorescence spectroscopy techniques for inorganic analysis.

1. Spectroscopy in
Inorganic Chemistry
UV-VIS
Part 2
08/2018

2. Electronic
Transitions
2

4. METAL NANOPARTICLES

5. SPR (Surface Plasmon Resonance)
https://www.sigmaaldrich.com/technical-documents/articles/materials-
science/nanomaterials/silver-nanoparticles.html
The strong interaction of the silver nanoparticles
with light occurs because the conduction
electrons on the metal surface undergo a
collective oscillation when excited by light at
specific wavelengths

6. Color (absorption maximum) corresponds to particle size.
Example: AgNP

8. Applications of AgNP
Diagnostic Applications: Silver nanoparticles are used in biosensors and
numerous assays where the silver nanoparticle materials can be used as
biological tags for quantitative detection.
Antibacterial Applications: Silver nanoparticles are incorporated in
apparel, footwear, paints, wound dressings, appliances, cosmetics, and
plastics for their antibacterial properties.
Conductive Applications: Silver nanoparticles are used in conductive inks
and integrated into composites to enhance thermal and electrical
conductivity.
Optical Applications: Silver nanoparticles are used to efficiently harvest
light and for enhanced optical spectroscopies including metal-enhanced
fluorescence (MEF) and surface-enhanced Raman scattering (SERS).

9. Analyze these 4 samples of AgNP

10. Influence of stabilizer
Reduction of AgNO3 by Na-citrate +/- PVP
No PVA + PVA
https://file.scirp.org/pdf/JMP_2015072215535041.pdf

11. Number of atoms in one NP
d = diameter of NP
 = density of the metal
M = molar mass of the metal
http://scholarcommons.usf.edu/ujmm/vol7/iss1/2/

12. Conc. of NP in “solution”
Lambert-Beer applied:
cf curcumin in DMSO: 5.54 * 104 M-1cm-1

13. Gold NP:  max = 517 nm =>  = 1.1 * 10 7 (or 8 !?!)

14. Estimation of particle size for AuNP
d = diameter of NP
0 = 512 nm
L1 = 6.53
L2 = 0.0216
https://pubs.acs.org/doi/pdf/10.1021/ac0702084
{for d > 25 nm)

15. Alternative method using Absorption values:
Experimental parameters:
B1 = 3.00
B2 = 2.20
https://pubs.acs.org/doi/pdf/10.1021/ac0702084

16. ORGANIC MOLECULES (LIGANDS)

17. Normally only 2 types of electronic transitions:

18. Which transitions are possible for Formaldehyde ?

19. Electronic transition selection rules
(1) S = 0 (spin selection)
(2) l= ±1 (orbital selection / Laporte rule)
There must be a change in orbital symmetry
(3) the direct product i,el * j,el transforms like
x, y or z
http://www.southampton.ac.uk/~pileio/peppesoton/Teaching/Entries/2009
/3/10_Symmetry_and_Molecular_Spectroscopy_-
_PG510_files/Lecture_6.pdf
19

20. Example Butadiene
Ground state:
2 el in Au and 2 el in Bg => product: Au x Au x Bg x Bg = Ag
Excited state:
Au x Bg x Au x Au = Bu x Ag = Bu
Transition Ag -> Bu: product is Bu -> has x/y component
=> transition allowed 20

21. Summary of usual electron transitions
http://www.chemguide.co.uk/analysis/uvvisible/theory.html

22. Conjugated  systems

23. More conjugated double
bonds cause
1. Redshift
2. Higher peaks

24. Example: Curcumin Complexes

25. Anti-Cancer activity

26. Ox.no. change on metal
Under certain situations, Cu(II) can be reduced to Cu(I), thereby
forming a radical as intermediate.
This could serve as “radical scavenger”

27. Curcumin in CH3CN
plus Cu(II)
Curcumin in CH3OH
plus Cu(II)
Curcumin in CH3CN

28. SEMICONDUCTORS

30. FLUORESCENCE (LUMINISCENCE)
SPECTROSCOPY

31. Triplet
States

32. Flouresence emission always
occurs from the LOWEST
vibrational excited state
BECAUSE:
the relaxation process is fast !

33. http://micro.magnet.fsu.edu/primer/techniques/fluorescence/fluorescenceintro.html

34. Absorption
Emission (A)
Det
Det
Emission (B)
Det
Det
Excitation

35. We measure the excitation spectrum in order to find out the
best wavelength, which we should use for the emission
spectrum – example:

36. Excitation vs Emission Spectrum

37. Advantages
• More sensitive when compared to other
absorption techniques. Concentrations as low
as μg/ml or ng/ml can be determined.
(One molecule can emit light many times, but in
absorption only one time)
• Precision up to 1% can be achieved easily
• As both excitation & emission wave lengths
are characteristic it is more specific than
absorption methods.

38. Inorganic Analysis
• Is in competition to AAS for metal cations
• Especially useful for uranium salts
• And for certain anions like (a) cyanide:
Absorption at 400 nm,
emission at 480 nm
0.2 – 50 ug/L
(b) Phosphate:
An ion association complex between molybdophosphate and rhodamine B
provides the basis for an assay for phosphorous at 0.04 to 0.6 µg. The
fluorescence is measured at 575 nm with an excitation at 350 nm, after first
extracting excess of the rhodamine with chloroform.
(c) Flouride

39. The End of Part 1