POTENTIAL APPLICATIONS OF CARBON NANOTUBESBernd Büchner, Institut für Festkörperforschung, IFW DresdenInstitut für Festkörperphysik, TU Dresden

Bernd BüchnerInstitut für Festkörperforschung, IFW Dresden

Institut für Festkörperphysik, TU Dresden

Potential Applications of Carbon Nanotubes

Magnetism of Carbon Nanotube Based Systems

,,Ferromagnetic Grass‘‘ Biomedical applicationsNovel magnetic

SPM Probes

Carbon Nanotubes

Graphite

MWNT (multi walled nanotube)

1 graphenelayer

2 +n graphenelayers

SWNT (single wallednanotube)

Multi-walled Carbon Nanotubes

Multi walled tubes

5nm

Fe

Partially filled MWCNT:

filled MWNT

Pyrolysis of metallocenes

[ Fe (C5H5)2 , Co (C5H5)2 or Ni (C5H5)2 ]

Fe-, Co- and Ni-filled MWNTAlloy-filled MWNT

10 nm

FeNi

10 nm

40 nm

Co

1 µm

40 60 80 100 120 (degrees)2Θ

Fe3C

(102

)

Fe3C

(112

)

C(0

04)

C(1

10)

γ Fe

(222

)

γ Fe

(311

)α F

e (2

00)

γ Fe

(220

)

γ Fe

(200

)

γ Fe

(111

)

S i

S iC(0

02)

α F

e (2

20)

α F

e (2

11)

α F

e (1

10)

S i

In

tens

ity (a

rb.u

.)

X-ray diffraction: bcc (α-Fe), fcc (γ-Fe) and Fe3C, texture for α-Fe (110) and γ-Fe (111)

Synthesis and characterization of filled carbon nanotubes

Synthesis and characterization of filled carbon nanotubes

9 µm

Ni

Co-filled CNTs Ni-filled CNTs Fe-Co alloy-filled CNTs

25 µm

Fe-filled CNTs

Ref.: A. Leonhardt et. al, Diamond and Related Materials 12 (2003) 790.T. Mühl et. al, J. Appl. Phys. 93 (10) (2003) 7894. R. Kozhuharova et. al, Journal of Materials Science: Materials in Electronics 14 (2003) 789.C. M. Schneider et. al, Diamond and Related Materials 13 (2004) 215.R. Kozhuharova et. al, submitted to Applied Surface Science.

20 µm

Magnetic storage

Magnetism of Fe-filled nanotubes

-250 0 250

µ0H / mT

-0.5

0

0.5

m /

msa

tH parallel substrateH perpendicular substrate

Fe22

-1000 0 1000µ0H / mT

-1

0

1m

/ m

sat

uniaxial anisotropy

coercivity of 56 mT at RT (bulk Fe: 0.09 mT)

filled nanotubes(Fe, Co, Ni)

20 µm

Outlook• self-organized growth• well defined diameter (length) • other materials (FePt)• ....

C- shell -> long-time chemically stable Fe nanowires

-1000 -500 0 500 1000-0,15

-0,10

-0,05

0,00

0,05

0,10

0,15

Ms*m

m-2

/mem

u*m

m-2

µ0H / mT

perpenticularparallel

H28d - orginal14d, 22 °C, wet atmosphere5h, 50 °C, O2-atmosphere

2 months in wet atmosphere, RT

5h in O2– atmos-

phere, 50°C (!)

Fe-filled CNT(d = 30nm)

Fe filled MWCNT: Chemically stable Fe nanomagnets

Fe filled MWCNT: Bio-compatible nanomagnets

Ferromagnetic nanocontainer for diagnostic and therapy of cancer

10 nmantibodies

cellantigene

functional groupsferromagnetica

drugs

temperature sensor

Idea: ,,Transfer‘‘ of (functionalized) ferromagnetic nanotubes in cells Manipulation by external magnetic fields (e.g. alignement, heating) Detection of magnetic particals by magnetic probes (SQUID, NMR, etc.)

Cooperation: - Department of Urology, TU Dresden- Systenanix GmbH, Dresden

Biomedical applications of ferromagnetic filled carbon nanotubes

Insertion of nanotubes in cells and tissue

Slice of muscle tissue containingFe-CNTs

TEM-picture of cellscontaining Fe-CNTs

Macroscopic depot (mm area) of Fe-CNTs

Fe-CNTs

Animal experiments: fm-MWCNT nontoxicinvestigation period 4 months

-1000 -500 0 500 1000

µ0H (mT)

-300

-200

-100

0

100

200

300

m

(µem

u)-250 0 250

µ0H (mT)

-200

-100

0

100

200

m

(µem

u)

Magnetisation measurements on cellular suspensions doped with Fe-filled nanotubes

-500 0 500

µ0H (mT)

-600

-400

-200

0

200

400

600

m

(µem

u)

cellular suspension on glass substrate 3∗3mm ⇒air dried ⇒ ≅ 1 mg

cellular suspension ≅ 5µl on fleece paper ⇒ air dried

small anisotropy ⇒

nanotubes tend to be parallel to the glass substrate

no detectable anisotropy in the fleece paper

Magnetisation typical for an ensemble ofnanotubes (saturation field, hystereses)

H parallel to thesubstrateH perpendicular to the substrate

HC=45mT HC=52mT

HC=25mT HC=24mT

Magnetisation curves of “cancer cells“

Biomedical applications of ferromagnetic filled carbon nanotubes

Heating by AC magnetic fields

0

10

20

30

40

50

60

0 2 4 5,5 6 7,5 8 9,5 10 11,5 12 13,5 14,5 15,5

time [min]

tem

pera

ture

[°C

]

without Fe-CNTs

with Fe-CNTs

Fe-CNT/NaCl-suspension 1

Heating of Fe-CNTs inside tissue in a AC magnetic field

f = 231 kHz; H = 25 kA/m

Muscle tissue : before and after AC-heating

40

10

Magnetometry on individualnanotubes using nano-sized Hall devices.(in cooperation with D. Grundler, HamburgS. Wirth, MPI-CPFS)

Fe-filled Carbonnanotube.

Silicon SPM tip

Magnetism of individual Nanotubes

New MFM probe:

Fe-filled nanotube attached at a conventional SPM probe.

Fe-filled Carbonnanotube.

Ferromagnetic coating

Magnetic force microscopy

Cantilever spring constant ccant

Frequency drive = Frequency tip

Amplitude tip = f(frequency, mtip, ceff)

Phase tip = f(frequency, mtip, ceff)

ceff = ccant+ csample-tip

csample-tip ~ dFsample-tip / dz

csample-tip ~ Fsample-tip

tip

Magnetism of individual Nanotubes

MFM on Fe-filled nanotubes:

SEM contrast

BSE contrast

MFM contrast

Bending of Fe-filled nanotubes by AFM-based nanomanipulation

MFM contrastSEM

Before…

After manipulation

-Remanent magnetization (Mr) of an individual Fe nanowire

-Length: 420 nm, diameter: 17 nm

-External magnetic field along the MWCNT axis applied prior tothe MFM measurement.

-Two remanent stray field configurations of opposite sign

Mr is normalised to +1/-1.

MFM of Fe-filled Carbon Nanotubes

New MFM probeFe-filled nanotube attached at a conventional SPM probe

Silicon SPM tip

Successful use as high resolution MFM probe

Outlook: Evaluation of these new MFM probes, e.g. by determination of the effective moments (dipole/monopole)

Fe filling

Silicon SPM tip

New MFM probeFe-filled nanotube attached at a conventional SPM probe

Topography (3 x 1) µm2

MFM contrast (phase)

Outlook – Mechanical stability of the CNT MFM probes?

Vibration??

FIB milled hole

Spin Transport in Carbon NanotubesFM1

FM2

Ferromagnetic contactsSpin injection in CNT

Field dependent transport (MR)Detection of spin direction

Spin transport in CNT

Outlook – Novel spinelectronic devices with f-MWCNT

No influence of the Fe-filling. Idea: Local removal of carbon shells

Magnetism of Carbon Nanotube Based Systems

,,Ferromagnetic Grass‘‘ Spin transport in carbon nanotubes

-0.5 -0.4 -0.3 -0.2 -0.1 0 0.1

B,T

0

2

4

6

8

10

12

14

16

18

[R(B

)-R(0

.1T)

]/R(0

.1T)

, %

I = 5 nA

R(0.1T) = 2.4 MΩ

Biomedical applications Novel magnetic SPM Probes

A. Leonhardt, I. Mönch, M. Ritschel, S. Hampel, R. Koshuva,

T. Mühl, A. Winkler, D. Elefant, S. Menzel,

H. Vinzelberg, C.M. Schneider, T. Gemming

IFW Dresden

A. Meye, K. Krämer, A. Wirth

Urologie, Technische Universität Dresden

G. Hammermann

Systenanics GmbH

DFG and BMBF for financial support