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e -. h +. Plasmon Sensitized TiO 2 Nanoparticles as a Novel Photocatalyst for Solar Applications . George Chumanov . Department of Chemistry, Clemson University, Clemson, SC 29634. Reduction. e -. cb. h +. Oxidation. vb. Titania Photocatalyst. ~3.2ev (UV light).

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plasmon sensitized tio 2 nanoparticles as a novel photocatalyst for solar applications

e-

h+

Plasmon Sensitized TiO2 Nanoparticles as a Novel Photocatalyst for Solar Applications

George Chumanov

Department of Chemistry, Clemson University, Clemson, SC 29634

titania photocatalyst

Reduction

e-

cb

h+

Oxidation

vb

Titania Photocatalyst

~3.2ev (UV light)

Electron-Hole recombination is on the order of < 30ps, hence

efficiency is low (< 5%).

Efficiency of photocatalysis depends on how well one can prevent

this charge recombination

role of metal in metal titania nanocomposites

O2-

e-

e-

O2

cb

h+

Oxidation

vb

Role of metal in metal/titania nanocomposites

metal

~3.2ev (UV light)

Metal nanoparticles act as an electron sink, promoting interfacial charge transfer reducing charge recombination

P. V. Kamat. J. Phys.Chem. B., 2002, 106, 7729-7744

slide4

E

E

E

H

++





++

k

Plasmon Resonance (PR) in Metal Nanoparticles

PR – collective oscillations of conducting electrons in metal nanostructures

p = (ne2/0me)1/2

metal (p) = 0

Ag, Au, Cu nanoparticles exhibit PR in the visible spectral range

slide5

h

E

quadrupole

dipole

H

Opticaldensity

Dipole

Quadrupole

Hexapole

Octapole

200

300

400

500

600

700

800

900

Wavelength (nm)

Optical Properties of Silver Nanoparticles

Extinction Spectra of Ag Nanoparticles as a Function of Size

Local Field is Enhanced Several Orders of Magnitude!

slide6

Wavelength (nm)

Wavelength (nm)

Ag Nanoparticles as Efficient Antennae for Capturing of Solar Energy

Solar Spectrum is from J.H.Seinfeld and S.N.Pandis”Atmospheric Chemistry and Physics” John Wiley &Sons, Inc. New York, Chichester, Brisbane, Singapore, Toronto (1998)

slide7

h

RuO2

Pt

Pt

RuO2

RuO2

Pt

Pt

RuO2

RuO2

Pt

++



Titania Coated Metal Nanoparticles

Au

Ag

Ag/Au

5 ÷ 150 nm

TiO2 1 – 5 nm

Plasmon Enhanced Electron-Hole Pair Generation

slide9

h UV

h visible

SiO2

TiO2

++



Metal core shortens the electron-hole pairs generated in titania shell

metal ion doped titania photocatalyst

e-

Reduction

e-

cb

Migrate to the surface

h+

(Visible light)

Fe3+/4+

Fe2+/3+

vb

Oxidation

h+

Metal Ion Doped-Titania Photocatalyst

Dopants influences intrinsic properties of titania resulting in lowering the

band gap and shifting light absorption into visible spectral range

Dopants should be both good electron and hole traps

Efficiency of photocatalysis depends on various charge transfer events

and migration of charges to the surface

synthesis of fe 3 doped tio 2

Titanium Butoxide/Ethanol

Hydrolysis

sonicate

Fe(III) salt/Ethanol

sonicate

Condensation

Centrifuging

Drying at 100°C

12 hours

Heating at >450°C

Synthesis of Fe3+-doped TiO2
electron microscopy
Electron Microscopy

TiO2 as prepared (amorphous)

TiO2 after heat treatment (crystalline)

electron microscopy15
Electron Microscopy

Fe3+/TiO2 as prepared (amorphous)

Fe3+/TiO2 after heat treatment (semi-

crystalline)

edx spectra and mapping of fe 3 doped tio 2
EDX spectra and Mapping of Fe3+-doped TiO2

EDX spectra shows the presence of iron

at >8 atomic % which arises from both

surface and bulk Fe3+ sites

EDX mapping studies indicate the uniform

dispersion of iron within the TiO2 matrix

photocatalysis using uv light

O2-

e-

UV light

O2

h+

SRB

TiO2

+

O2

SRB•+

SRBOO•+

Conduction Band

(Eg = 3.2 eV)

h+ or •OH

Valence Band

SO42-, NH4+, CO2, H2O

Photocatalysis Using UV light

Degradation of chromophore structure

(diethylamine, N,N-diethylacetamide, etc)

slide18

Photosensitization Using Visible light

SRB*

O2-

e-

e-

O2

Visible light

SRB

h+

+

O2

SRB•+

SRBOO•+

TiO2

Conduction Band

Degradation of chromophore structure

(diethylamine, N,N-diethylacetamide, etc)

(Eg = 3.2 eV)

+

SO42-, NH4+, CO2, H2O

Valence Band

G. Liu, L. J. Zhao. New. J. Chem., 2000, 24, 411-417

role of metal in metal doped titania photocatalyst

e-

Reduction

e-

cb

h+

Fe3+/4+

Fe2+/3+

vb

Oxidation

h+

Role of metal in Metal/Doped-Titania Photocatalyst

Silver

(Visible light)

At the plasmon resonance frequency there would be efficient resonance light

absorption.

Band-gap excitation wavelength should reasonably match

silver plasmon resonance frequency

conclusions
Conclusions

Titania coated silver nanoparticles were synthesized using sol-gel technique.

Fe3+- doped Titania that is sensitive to visible light was synthesized.

From the degradation of sulforhodamine dye experiments true doping effect

was observed in the Fe3+- doped Titania photocatalyst

Efforts are underway to coat silver nanoparticles with Fe3+- doped Titania .

Photocatalytic activity of Fe3+- doped Titania and silver coated

with Fe3+- doped Titania will be compared.

slide22

Current Member of the Group

David Evanoff, Katrina Daniels,

Amar Kumbhar, Steve Hunson,

Mark Kinnan, Sravanti Ambati,

Kenia Parga

EPA