NIRT: Active Nanoparticles in Nanostructured Materials Enabling Advances in Renewable Energy and...
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NIRT: Active Nanoparticles in Nanostructured Materials Enabling Advances in Renewable Energy and Environmental Remediation David A. Dixon, James L. Gole, Andrei Federov, Clemens Burda, Greg Szulczewski Department of Chemistry, The University of Alabama, Departments of Physics & Mechanical Engineering, Georgia Institute of Technology, Department of Chemistry, Case Western University Focus is the modification of interfaces with enhanced catalytic and sensing capabilities. A key property of decorated and decorating nanostructures is that they must undergo changes in their states in order to catalyze a chemical reaction. Doped nanoparticles of TiO 2 such as the oxynitride (TiO 2x N x ) can be used to create improved photocatalytic absorbers in the visible part of the spectrum. These nanoparticles can be doped with metal ions to change how they interact with ligands including water molecules for potential photochemical splitting of water. A combination of materials synthesis, advanced characterization techniques, and computational chemistry are being used to study active nanostructures. Developed first single step etch-liftoff procedure (one step separation) based on the formation and removal of macroporous silicon (PS) layers. With silicon wafers with resistivities in the range from 14 to 22 ohm-cm, films with pore diameters ranging from one to two microns and thickness ranging from 3 to 70 micrometers have been prepared. These silicon-based films (filters), which carry a polarizing negative charge, represent an alternative to porous alumina (films) filters (pore diameter not yet in the one to two micron range) in terms of their size range and their potential interaction-reaction at elevated temperature. Pt and Cu can be introduced to these filters using electroless solutions to create an effective reductive surface. Using these and alternate material combinations, interactive-reactive filters in the one micron size range which operate at temperatures well in excess of porous polymer films can be realized. SEM micrographs of a porous silicon filter. In the top images, the tips of the pores can be seen before (left) and after (right) they begin to spread out in their face directions. The bottom images show the front (left) and back (right) of a filter. Note that pore spreading is significant in the filter back. Direct Lift-off of PS- based film- filter (~ 20 microns) from the surface of an etched PS film. Pore diameter is approximately one micron. Mechanical Lift-off of PS filter using the ability to readily remove the silicon oxyfluoride polymer that forms on the PS surface. The seeding of the high spin transition metal ions Co (II) and Ni (II) into porous nanoscale nitrogen doped titanium oxynitride, TiO 2-x N x structures leads to a significant enhancement of the infrared spectrum due to adventitious water and minor contaminants associated with the oxynitride synthesis from a porous TiO 2 nanocolloid sample. There are a number of contributions to the infrared enhancement (1) the formation of protonated amines near the oxynitride surface; (2) modification of the anatase ionic crystal dipole moment due to the displacement of charged ions by the electric field associated with the high spin Co (II) and Ni (II) ions; and (3) the incorporation of a spinel- like structure into the TiO 2 lattice as demonstrated by Raman spectra. The presence of partial proton transfer from the amines to the surface can lead to enhanced intensities. The higher the proton affinity of the amine, the less proton transfer occurs leading to a higher N-H stretch frequency with less enhancement. A goal is to form improved visible light absorbing oxynitride photocatalysts at the nanoscale. Note enhancement between 2000 and 3000 cm -1 . ν(N-H) 2317 cm -1 2595 cm -1 2743 cm - 1 I (km/mol) 2769 2115 1837 velopment of Porous-Silicon-based Active Microfilters “Development of Porous-Silicon-based Active Microfilters,” J.Campbell, J.A. Corno, Ni.Larsen, and J.L. Gole, J. Electrochem . Soc. Accepted, Oct. 2007 Evidence for High Spin Transition Metal Ion Induced Infrared Spectral Enhancement NIRT: CTS-0608896 0 200 400 600 800 1000 1200 -1000 0 1000 2000 3000 4000 5000 6000 7000 8000 380 690 240 608 440 R am a n In te n sity W avenum ber TiO 2 -x N x C o (C l) 0 .05 TiO 2 -x N x C o (C l) 0 .02 5 TiO 2 -x N x C o (C l) 0 .01 2 5 Raman spectra of TiO 2-x N x nanocolloid for various Co II concentrations, using CoCl 2 . Laser power is less than 10 mW. The surprising room temperature phase conversion of anatase to rutile TiO 2 , a process that normally requires temperatures well in excess of 700 C, is facilitated through the use of transition metal ions with highly unpaired electron spin. Raman spectroscopy is used to demonstrate this unexpected process, facilitated through the use of high spin cobalt (Co II ) and nickel (Ni II ) transition metal ion seeding into a TiO 2 or TiO 2-x N x nanocolloid lattice. In distinct contrast, the effect is not manifest upon seeding with low spin ions including Cu II . The Raman spectra also demonstrate the concomitant incorporation of a spinel-like structure into the titania lattice. Efficient Room Temperature Conversion of Anatase to Rutile TiO 2 Induced by High Spin Ion Doping 300 350 400 450 500 550 600 650 700 R am an In ten sity (A rb.U nits) W avenum ber (cm -1 ) nano T iO 2 F itto d ata 300 400 500 600 700 800 3x10 4 4x10 4 5x10 4 6x10 4 TiO x N 1-x anatase anatase anatase TiO x N 1-x R am an Intensity W avenum ber(cm -1 ) Raman spectra of (a) untreated anatase TiO 2 powder (Degussa P25) and ( b) anatase nitridized TiO 2 nanocolloid powder. The dashed lines represent the fit to the experimental data and the solid line corresponds to the data. (Raman spectrometer extends to 200 cm -1 ) 200 400 600 800 1000 1200 1000 10000 240 690 606 430 R am a n In te n sity W avenum b e r (cm -1 ) TiO 2 - .0 1 2 5 C o TiO 2 - .0 2 5 C o TiO 2 - .0 5 C o TiO 2 - 0 .1 C o w ith C o(C l) 2 200 400 600 800 1000 1200 100 1000 688 244 380 606 442 R am a n In te nsity W avenum b e r (cm -1 ) TiO 2 -(N O 3 ) 0.0 25 TiO 2 -(N O 3 ) 0.0 5 TiO 2 -(N O 3 ) 0 .2 Raman spectra for a TiO 2 nanocolloid (<10 nm) prepared with various concentrations of Co II using a) CoCl 2 and b) Co(NO 3 ) 2 . Note that the Raman signal was obtained using a 1 μm spot size and a power of 25 mW or less. Photoreduction of Copper(II)-Dendrimer Complexes Zero valent Cu polyamidoamine (PAMAM) dendrimer nanocomposites were synthesized using UV irradiation starting from the aqueous Cu(II)/dendrimer system. The size of the nanoparticles is strongly dependent on the generation of the dendrimers and the pH of the solution. Larger nanoparticles are obtained with higher generation dendrimers, as well as in more basic solution. EPR spectra show that the sites bonded to the Cu(II) ion are significantly different at different pH. Density functional theory (DFT) calculations have been used to predict the structures and EPR spectra of the Cu(II)-dendrimer complexes. At pH = 3, the hydrated ion complexes Cu(H 2 O) 6 2+ or Cu(H 2 O) 5 2+ are present, as expected and previously reported. At pH = 7.8, a chelating complex with two tertiary amine sites with or without two amide oxygen sites is present. At pH = 11, the Cu(II) ion binds to either the primary amine and amide oxygen sites on a single branch, or to two tertiary amines and four amide oxygen sites on all four branches. Our results show the importance of the amide sites in Cu(II)-dendrimer complexes in neutral and basic solutions. N N N H NH 2 H N NH 2 N H H N H 2 N H 2 N O O O O HRTEM images of Cu/G0-NH 2 nanoparticles formed upon UV irradiation at pH = 3.0 (top), pH = 7.8 (middle), and pH = 11.0 (bottom). 2.28 2.02 2.28 2.04 2.04 2.01 1.98 2.06 1.98 2.06 2.18 7 12 2.34 2.07 2.18 2.05 2.10 87.3 2.89 2.94 2.09 1.99 2.04 1.98 2.89 2.94 2.09 1.99 2.04 1.98 2.13 2.25 2.05 2.03 2.28 2.03 2.43 2.44 2.13 2.01 2.13 2.01 2.43 2.44 2.13 2.01 2.13 2.01 24 25 30 31 “Evidence for High Spin Transition Metal Ion Induced Infrared Spectral Enhancement,” J. L. Gole, S. M. Prokes, M. G. White, T.-H. Wang, R. Craciun, and D. A. Dixon, J. Phys. Chem., 2007, WEB ASAP, Oct “Efficient Room Temperature Conversion of Anatase to Rutile TiO 2 Induced by High Spin Ion Doping,” J.L. Gole, S. M. Prokes, M. G. White, J. Phys. Chem. B, submitted “Experimental and Theoretical Studies of the Photoreduction of Copper(II)-Dendrimer Complexes,” H. Wan, S. Li, T. A. Konovalova, S. Shuler, D. A. Dixon, and S. C. Street, J. Phys. Chem., accepted, Oct. 2007
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Transcript of NIRT: Active Nanoparticles in Nanostructured Materials Enabling Advances in Renewable Energy and...
NIRT: Active Nanoparticles in Nanostructured Materials Enabling Advances in Renewable Energy and Environmental Remediation
David A. Dixon, James L. Gole, Andrei Federov, Clemens Burda, Greg SzulczewskiDepartment of Chemistry, The University of Alabama, Departments of Physics & Mechanical Engineering, Georgia Institute of
Technology, Department of Chemistry, Case Western University
Focus is the modification of interfaces with enhanced catalytic and sensing capabilities. A key property of decorated and decorating nanostructures is that they must undergo changes in their states in order to catalyze a chemical reaction. Doped nanoparticles of TiO2 such as the oxynitride (TiO2xNx) can be used to create improved photocatalytic absorbers in the visible part of the spectrum. These nanoparticles can be doped with metal ions to change how they interact with ligands including water molecules for potential photochemical splitting of water. A combination of materials synthesis, advanced characterization techniques, and computational chemistry are being used to study active nanostructures.
Developed first single step etch-liftoff procedure (one step separation) based on the formation and removal of macroporous silicon (PS) layers. With silicon wafers with resistivities in the range from 14 to 22 ohm-cm, films with pore diameters ranging from one to two microns and thickness ranging from 3 to 70 micrometers have been prepared. These silicon-based films (filters), which carry a polarizing negative charge, represent an alternative to porous alumina (films) filters (pore diameter not yet in the one to two micron range) in terms of their size range and their potential interaction-reaction at elevated temperature. Pt and Cu can be introduced to these filters using electroless solutions to create an effective reductive surface. Using these and alternate material combinations, interactive-reactive filters in the one micron size range which operate at temperatures well in excess of porous polymer films can be realized.
SEM micrographs of a porous silicon filter. In the top images, the tips of the pores can be seen before (left) and after (right) they begin to spread out in their face directions. The bottom images show the front (left) and back (right) of a filter. Note that pore spreading is significant in the filter back.
Direct Lift-off of PS-based film- filter (~ 20 microns) from the surface of an etched PS film. Pore diameter is approximately one micron.
Mechanical Lift-off of PS filter using the ability to readily remove the silicon oxyfluoride polymer that forms on the PS surface.
The seeding of the high spin transition metal ions Co (II) and Ni (II) into porous nanoscale nitrogen doped titanium oxynitride, TiO2-xNx structures leads to a significant enhancement of the infrared spectrum due to adventitious water and minor contaminants associated with the oxynitride synthesis from a porous TiO2 nanocolloid sample. There are a number of contributions to the infrared enhancement (1) the formation of protonated amines near the oxynitride surface; (2) modification of the anatase ionic crystal dipole moment due to the displacement of charged ions by the electric field associated with the high spin Co (II) and Ni (II) ions; and (3) the incorporation of a spinel-like structure into the TiO2 lattice as demonstrated by Raman spectra. The presence of partial proton transfer from the amines to the surface can lead to enhanced intensities. The higher the proton affinity of the amine, the less proton transfer occurs leading to a higher N-H stretch frequency with less enhancement. A goal is to form improved visible light absorbing oxynitride photocatalysts at the nanoscale.
Note enhancement between 2000 and 3000 cm-1.
ν(N-H) 2317 cm-1 2595 cm-1 2743 cm-1
I (km/mol) 2769 2115 1837
Development of Porous-Silicon-based Active Microfilters
“Development of Porous-Silicon-based Active Microfilters,” J.Campbell, J.A. Corno, Ni.Larsen, and J.L. Gole, J. Electrochem . Soc. Accepted, Oct. 2007
Evidence for High Spin Transition Metal Ion Induced Infrared Spectral Enhancement
NIRT: CTS-0608896
0 200 400 600 800 1000 1200
-1000
0
1000
2000
3000
4000
5000
6000
7000
8000
380690
240
608440
Ra
ma
n In
ten
sity
Wavenumber
TiO2-x
Nx Co(Cl) 0.05
TiO2-x
Nx Co(Cl) 0.025
TiO2-x
Nx Co(Cl) 0.0125
Raman spectra of TiO2-xNx nanocolloid for
various CoII concentrations, using CoCl2.
Laser power is less than 10 mW.
The surprising room temperature phase conversion of anatase to rutile TiO2, a process that normally requires temperatures well in excess of 700 C, is facilitated through the use of transition metal ions with highly unpaired electron spin. Raman spectroscopy is used to demonstrate this unexpected process, facilitated through the use of high spin cobalt (Co II ) and nickel (NiII) transition metal ion seeding into a TiO2 or TiO2-xNx nanocolloid lattice. In distinct contrast, the effect is not manifest upon seeding with low spin ions including CuII. The Raman spectra also demonstrate the concomitant incorporation of a spinel-like structure into the titania lattice.
Efficient Room Temperature Conversion of Anatase to Rutile TiO2 Induced by High Spin Ion Doping
300 350 400 450 500 550 600 650 700
Ram
an I
nten
sity
(A
rb.
Uni
ts)
Wavenumber (cm-1)
nano TiO2
Fit to data
300 400 500 600 700 800
3x104
4x104
5x104
6x104
TiOxN
1-x
anatase
anatase
anatase TiO
xN
1-x
Ram
an I
nten
sity
Wavenumber(cm-1)
Raman spectra of (a) untreated anatase TiO2 powder (Degussa P25) and
( b) anatase nitridized TiO2 nanocolloid powder. The dashed lines represent
the fit to the experimental data and the solid line corresponds to the data. (Raman spectrometer extends to 200 cm-1)
200 400 600 800 1000 1200
1000
10000
240
690
606
430
Ra
ma
n In
ten
sity
Wavenumber (cm -1)
TiO2- .0125 Co
TiO2- .025 Co
TiO2- .05 Co
TiO2- 0.1 Co
with Co(Cl)2
200 400 600 800 1000 1200
100
1000
688244
380
606442
Ra
ma
n In
ten
sity
Wavenumber (cm -1)
TiO2-(NO
3) 0.025
TiO2-(NO
3) 0.05
TiO2-(NO
3) 0.2
Raman spectra for a TiO2 nanocolloid (<10 nm) prepared with various
concentrations of CoII using a) CoCl2 and b) Co(NO3)2. Note that the Raman
signal was obtained using a 1 μm spot size and a power of 25 mW or less.
Photoreduction of Copper(II)-Dendrimer Complexes
Zero valent Cu polyamidoamine (PAMAM) dendrimer nanocomposites were synthesized using UV irradiation starting from the aqueous Cu(II)/dendrimer system. The size of the nanoparticles is strongly dependent on the generation of the dendrimers and the pH of the solution. Larger nanoparticles are obtained with higher generation dendrimers, as well as in more basic solution. EPR spectra show that the sites bonded to the Cu(II) ion are significantly different at different pH. Density functional theory (DFT) calculations have been used to predict the structures and EPR spectra of the Cu(II)-dendrimer complexes. At pH = 3, the hydrated ion complexes Cu(H2O)6
2+ or Cu(H2O)52+ are present, as expected and
previously reported. At pH = 7.8, a chelating complex with two tertiary amine sites with or without two amide oxygen sites is present. At pH = 11, the Cu(II) ion binds to either the primary amine and amide oxygen sites on a single branch, or to two tertiary amines and four amide oxygen sites on all four branches. Our results show the importance of the amide sites in Cu(II)-dendrimer complexes in neutral and basic solutions.
N
N
NH
NH2
HN
NH2
NH
HN
H2N
H2N
O
O
O
OHRTEM images of Cu/G0-NH2 nanoparticles formed upon UV irradiation at pH = 3.0 (top), pH = 7.8 (middle), and pH = 11.0 (bottom).
2.28
2.02
2.28
2.04
2.04
2.011.98 2.06
1.98
2.06
2.18
7 12
2.342.07
2.182.05
2.1087.3
2.89
2.94
2.09
1.99
2.04
1.98
2.89
2.94
2.09
1.99
2.04
1.98
2.13
2.25
2.05
2.03
2.28
2.03
2.43
2.44
2.13
2.01
2.13
2.01
2.43
2.44
2.13
2.01
2.13
2.01
24
25
3031
“Evidence for High Spin Transition Metal Ion Induced Infrared Spectral Enhancement,” J. L. Gole, S. M. Prokes, M. G. White, T.-H. Wang, R. Craciun, and D. A. Dixon, J. Phys. Chem., 2007, WEB ASAP, Oct
“Efficient Room Temperature Conversion of Anatase to Rutile TiO2 Induced by High Spin Ion Doping,” J.L. Gole, S. M. Prokes, M. G. White, J. Phys. Chem. B, submitted
“Experimental and Theoretical Studies of the Photoreduction of Copper(II)-Dendrimer Complexes,” H. Wan, S. Li, T. A. Konovalova, S. Shuler, D. A. Dixon, and S. C. Street, J. Phys. Chem., accepted, Oct. 2007
