Download Carbon Nanotubes for Transistor Type-Biosenosor and Therapeutic Applications

5th Korea-US NanoForum, Jeju, Korea, April 17-18, 2008
Carbon Nanotubes for Transistor Type-Biosensor and
Therapeutic Applications
Hee Cheul Choi
Department of Chemistry,
Pohang University of Science and Technology (POSTECH)
South Korea, 790-784
Surface Chemistry of Carbon nanotubes: Hybrid structures
Facile and spontaneous synthetic approaches
Choi, et al., JACS 2002, 124, 9059.
Noble metal-SWNT composites
Lee and Choi, et al., Small 2005, 1, 975.
Transition metal-SWNT
TiO2-SWNT composites
Shin and Choi, et al., Adv. Mater. 2007, 19, 2873.
Mechanism
Surface Chemistry of Carbon nanotubes: Schottky diodes
Intercalation of Li ions in pyrene-functionalized SWNT
Modulation of band energy
Lim and Choi, et al., JACS 2008, 130, 2160.
Schottky diode behavior
Lithium intensity distribution (SPEM, Li 1s)
Surface Chemistry of Carbon nanotubes: Carbothermal Reduction – Etching SiO2
CO
CH4
H2
O2
SiO
C2H4
SiO2
Si
Carbothermal Reduction
Byon and Choi, Nature Nanotech 2007, 2, 162.
Byon and Choi, Nano Lett. 2008, 8, 178.
Sub-10 nm scale Lithography using Nanotrenches
Byon and Choi, Nature Nanotech 2007, 2, 162.
Carbon nanotube electronics:
Carbon nanotube/protein-based memory device
Negative Differential Resistance (NDR) device
- Ferritin captured in metallic SWNT nanogap electrodes
- Electrically cut m-SWNT (gap = ca. 20 nm)
- Electrostatically captured Ferritins
- Peak current density: 4.0 x 106 A cm-2 (record)
- Peak-to-Valley Ratio (PVR): ~ 40 (@ scan rate of 26 mV/s)
- NDR is 1.2 µohm cm2
Apoferrtin
Tang and Choi, et al., JACS 2007, 129, 11018.
Apoferrtin + Fe(III)
Electronic sensing of biomolecular recognitions using SWNTs-FETs
▪ Nonspecific Binding
▪ Specific Binding (using CDI-Tween20)
Robert J. Chen et al,. PNAS. 2003, 100, 4984
Hurdles to overcome
Sensitivity
- At least ~ pM, grateful if it can go lower.
- Protein detection limit of SWNT-FET: >10 nM
(c.f. Lieber group: ~ 10 fM detection limit of proteins using SiNW
devices-Nat. Biotechol. 2005, 23, 1294.)
Feasibility
- Prompt use: currently too long stabilization time
- Nonspecific binding: perfect protection of devices with efficient
chemical blocking is mandatory.
The two regions effecting to a biosensor sensitivity
Buffer Sol’n
Au/Cr
Au/Cr
SiO2/Si
Nanotube aspect: Direct charge communication between
proteins and nanotubes
Metal-nanotube contact aspect: Schottky barrier modulation by protein
adsorptions on metal surfaces
The origin of conductance changes: Schottky Barrier
ƒ Nanotube aspects:
Charge injection from biomolecules
Electric double layer field modulation caused by biomolecules
Strongly depending on the pI (isoelectric point)
values of proteins
Energy
ƒ Metal-nanotube contact aspect:
Adsorbed chemical species may modulate work function level of contact
metals, which consequently change the Schottky barrier height resulting in
the conductance change.
EFM
CB
+
EFS
buffer
VB
Metal
Semiconducting
SWNT
Fermi level matching
(EFM = EFS) &
Band bending of VB,
CB
Experimental evidence for the detection mechanism
PMMA
HIgG
SWNT
-6
.50x10
SiO2/Si
mPEG-SH
SAM
Lift off
s
s s s s ssss s s s s
SiO2/Si
Lift off
ss
ss
SiO2/Si
SiO2/Si
OMe OMe
O
O
n
n
S
Device I
1.48
1.46
1.44
0
Device I
100 nM
400
800
Time (s)
1200
-6
.50x10
100 nM
3.45
Ids (µΑ)
Pd/Au
evaporation
Ids (µΑ)
SiO2/Si
Device II
3.40
3.35
3.30
0
200
400 600
Time (s)
800
1000
S
Device II
Chen, Choi, Dai et al, J. Am. Chem. Soc. 2004, 126, 1563
Increased Schottky contact area for high performance
Au/Cr
Au/Cr
SiO2/Si
▪ Synthesis of network SWNTs
▪ Usage of the thin shadow mask
▪ Thermal evaporator with tilted angle stages
Fabrication of SWNT-FET having increased Schottky contact area
SiO2/Si Substrate with Catalyst
D
S
SiO2/Si
CH4
H2
( R ~ 1 kΩ )
C2H4
S
CVD (900℃ 10 min)
Growth SWNTs
D
(Cu)
In wire
Teflon
electrochemical cell
Protein
Injection
2000 μm
10 mV
1 μM
V
S
D
200 µm
Choi and Dai et al. Nano Lett. 2003, 3, 157.
Yang and Choi et al. Langmuir 2005, 21, 9198.
Fabrication of SWNT-FET having increased Schottky contact area
(a) SWNT FET device fabricated by a photolithography
SWNTs
Au/Cr
Photo Resist
SiO2/Si
(1) Metal Evaporation
SWNTs
SiO2/Si
(2) Lift Off
Au/Cr
Shadow Mask
angle evaporation
(b) SWNT-FET device fabricated by a shadow mask at tilted angle
Byon and Choi. J. Am. Chem. Soc. 2006, 128, 2188.
Highly sensitive SWNT-FET devices: Nonspecific bindings of proteins
Buffer sol’n
Au/C
r
SiO
2 /S i
▪ SA
▪ SpA
a SWNT-FET fabricated by a shadow mask
at tilted angle
Æ 1 pM sensitivity
Byon and Choi. J. Am. Chem. Soc. 2006, 128, 2188.
Highly sensitive SWNT-FET devices: Nonspecific bindings of proteins
(unit : pM)
a SWNT-FET fabricated by a shadow mask
at tilted angle
a SWNT-FET fabricated by a shadow mask
<Protein : SpA>
Æ 1 pM sensitivity
Æ 10 nM sensitivity
Highly sensitive SWNT-FET devices: Specific bindings of proteins
▪ Probe protein: Protein A
▪ Target protein: rabbit IgG
▪ Probe protein: hCG
▪ Target protein: anti β-hCG
Treatment of 0.05% Tween20 after immobilizing probe proteins
Æ 1 pM sensitivity
Acknowledgement
Post Doctors
Dr. Hyeon Suk Shin
Dr. Hye Ryung Byon
Graduate Students
Seok Min Yoon
Yoonmi Lee
Hyun Jae Song
Hyunseob Lim
Hye Kyung Moon
Suphil Kim
Kyoung Ok Kim
Ji Eun Park
Kwangho Chu
UnderGraduate Students
Chee Bum Park
January 8, 2008
Fundings
MOST, KOSEF, KRF, POSTECH
Collaborators
Prof. Joon Won Park (POSTECH)
Prof. Jillian M. Buriak (Univ. Alberta, Canada)
Prof. Insung S. Choi (KAIST)
Prof. Seunghun Hong (SNU)
Prof. Jin Yong Lee (SKKU)
Prof. Young Kyun Kwon (U. Mass)