Kara Phillips1, Jeremy Eskelsen2, Ursula Mazur2, K. W. Hipps2
NSF REU Characterization of Advanced Materials at WSU
1School
of Materials Science and Engineering, Clemson University
2School of Chemistry and Materials Science and Engineering, Washington State University
RESULTS
INTRODUCTION
Porphyrins are well known for their high
absorption in the visible region making them
prime materials for many applications, such
as:
•catalysts
•photoconductors
•electrical conductors
•sensors
•light harvesting[1]
FIGURE 1: UV-visible spectra of TSPP,
TAPP, and TAPP+TSPP mixture showing
the formation of an H-aggregate in the
mixture [2].
FIGURE 2: UV vis. for differing ratios of
TAPP+TSPP filtered after 20 minutes with
little absorption for 1:1 suggesting a
reaction ratio of around 1:1.
EXPERIMENTAL
FIGURE 8: TEM image of TAPP+TSPP mixed at
room temperature (20 ⁰C). Structures are
around 12.628 nm wide and 47.75 nm long.
TAPP+TSPP Cross Section
100 ⁰C
60
TAPP+TSPP Cross Section
50 ⁰C
25
20
Height (nm)
80
Height (nm)
Samples were made from stock solution then
diluted to desired micromolar
concentrations. Solutions were acidified
with HCl to pH 3. The mixture was made by
first pouring TAPP [meso-tetra (4aminophenyl) porphine] then TSPP [mesotetra (4-sulfonatophenyl) porphine] each
time.
UV-Visible Spectroscopy
•Concentration and time dependent studies
were evaluated.
•Perkin Elmer 330 spectrophotometer was
used.
Microscopy
•Atomic Force Microscopy
• Samples were deposited from the
bottom of solution on peeled mica then
let set for one minute and spun for 30
seconds (process was repeated 5 times).
• Images taken on Digital Instruments AFM
in tapping mode.
•Transmission Electron Microscopy
• Samples were deposited on formvar
coated Nickel TEM grids.
• Images were taken on Phillips CM200
TEM at 200 keV.
FIGURE 3: UV-vis. time study of
TAPP+TSPP mixture suggesting that the
reaction reaches completion after one
day because there is little change in the
absorption peaks after that time.
15
40
10
20
0
0
100
200
Width (nm)
300
400
FIGURE 4: AFM image of TAPP+TSPP structures formed
at 100 ⁰C with cross section showing an average height
of 89 nm and width of 159 nm.
5
Temperature
(⁰C)
Height
(nm)
Width
(nm)
Length
(nm)
0
---
7.68
28.82
20
---
12.628
47.75
50
21
46
414.5
100
89
159
>5000
TABLE 1: Average height, width, and length of
TAPP+TSPP nanorods formed at different temperatures.
Measurements for 50 and 100⁰ samples were taken
from AFM images. Data for 0 and 20⁰ samples was
taken from TEM images.
0
0
100
200
Width (nm)
300
FIGURE 5: AFM image of TAPP+TSPP structures formed
at 50 ⁰C with cross section showing an average height
of 21 nm, width of 46 nm, and length of 414.5 nm.
TSPP
TAPP
CONCLUSIONS & FUTURE WORK
•At pH 3, the TAPP and TSPP compounds react
to form small rod-like structures.
•This reaction is completed in one day and
occurs in approximately a 1:1 ratio (elemental
analysis will be completed in the future to
confirm).
•The size of the rods changes significantly with
reaction temperature.
• Lower temperatures result in more
nucleation sites showing large numbers
of smaller rods.
• Higher temperatures result in more
growth showing larger rods.
• Future studies will concentrate on the
conductive and structural properties of the
self assembled nanostructures.
ACKNOWLEDGEMENTS
FIGURE 6: AFM image of TAPP+TSPP structures
formed at 20 ⁰C.
FIGURE 7: AFM image of TAPP+TSPP structures
formed at 0 ⁰C.
[1] Friesen, Benjamin, Bryan Wiggins, Jeanne L. McHale, Ursula Mazur, and K. W. Hipps. "Differing HOMO and LUMO Mediated Conduction in a Porphyrin Nanorod." Journal of
the American Chemical Society 132.25 (2010): 8554-556. Web.
[2] Eisfeld, A., and J. S. Briggs. "The J- and H-Bands of Organic Dye Aggregates." Chemical Physics 324.2–3 (2006): 376-84. Web.
The funding for this research was provided by
the National Science Foundation grants CHE1152951 and REU Program DMR-1062898 as
well as the Department of Chemistry and
Materials Science and Engineering at WSU.