Scanning Probe Microscopy of Dendrimer Monolayers · Scanning Probe Microscopy of Dendrimer...
Transcript of Scanning Probe Microscopy of Dendrimer Monolayers · Scanning Probe Microscopy of Dendrimer...
Center For Materials For Information TechnologyAn NSF Materials Research Science and Engineering Center
Scanning Probe Microscopy of Dendrimer Monolayers
Jia Sun, Kye-Young Kim, Silas C.Blackstock, and Greg J. Szulczewski
Center For Materials For Information TechnologyAn NSF Materials Research Science and Engineering Center
N
N N
NMeO
N
OMe N
OMe
MeO
MeO OMe
OMe
OMe
OMe
3PD 4AA/PD
TAPD
N N
OMe
OMe
MeO
MeO
N N
N
N
MeO
OMe
N
N
MeO
MeO
MeO
MeO
OMe
OMe
OMe
OMe
S-TAPD
Center For Materials For Information TechnologyAn NSF Materials Research Science and Engineering Center
20nm 3PD/HOPG
Bias –3V,set point 10pA Bias –2V,set point 10pA
Bias 0.656V,set point 5pA Bias 1.59V,set point 5pA Bias 2.59V,set point 5pA
Bias is positive
Tip
Bias is negative
Tip
Electron flow
Electron flow
sample
sample
Center For Materials For Information TechnologyAn NSF Materials Research Science and Engineering Center
STM images of 20nm 3PD/HOPG1st image Zoomed in once and zoomed out
Scanned 6 times and zoomed out Image of small area
Center For Materials For Information TechnologyAn NSF Materials Research Science and Engineering Center
124000
126000128000
130000
132000134000
136000
155160165170
binding energy(ev)
coun
ts
192000194000196000198000200000202000204000206000208000
155160165170
binding energy(ev)
coun
ts
138000140000
142000144000146000
148000150000
155160165170
binding energy (ev)
coun
ts
118000
120000
122000
124000
126000
128000
155160165170
binding energy(ev)
coun
ts
X-ray photo spectra in S(2p) region of S-TAPD/Au
10 S 2 Hr
3Hr50min 26Hr
Center For Materials For Information TechnologyAn NSF Materials Research Science and Engineering Center
0.0015
0.002
0.0025
0.003
0.0035
0.004
0.0045
0.005
0 200 400 600 800 1000 1200 1400 1600 1800
immersion time(min)
ratio
of x
ps p
eak
10s
35min
2hr3hr50min
26hr
Ratio of XPS peak area for Thiolate S(2p) and Au(4f) atvarying immersion time
Center For Materials For Information TechnologyAn NSF Materials Research Science and Engineering Center
Au(111) S-TAPD/Au(111)
1.3nm
Center For Materials For Information TechnologyAn NSF Materials Research Science and Engineering Center
Micro contact printing S-TAPD on HOPG and Au(111)
Fabricate master Cast PDMS prepolymer Cure and peel off
Ink stamp in S-TAPD/toluenesolution and dry
Printed S-TAPD lines
HOPG/Au(111)HOPG/Au(111)
Print and release on substrate
Center For Materials For Information TechnologyAn NSF Materials Research Science and Engineering Center
Printing S-TAPD on HOPG
9.7Х10-4M 3.2Х10-4M 9.7Х10-5M
Center For Materials For Information TechnologyAn NSF Materials Research Science and Engineering Center
AFM image of S-TAPD printed on HOPG
Center For Materials For Information TechnologyAn NSF Materials Research Science and Engineering Center
AFM image of S-TAPD printed on Au(111)
Center For Materials For Information TechnologyAn NSF Materials Research Science and Engineering Center
• Conclusion• To image 3PD on HOPG, bias voltage is important for
STM image contrast. There is a threshold bias of ~2.5V require for imaging.
• Dendrimer with thiol group has been synthesized, becausethiol groups have a strong affinity for Au surface, stable STM images S-TAPD/Au(111) have been acquired.
• Future work• Redox gradient dendrimer with “core” and “shell”structure
will be studied later.• The size of STM image should be decreased in smaller
size(below 50nm)• Apply pulse voltage to STM tip to change redox state.