X-ray Photoelectron Spectroscopy of biocompatible polymer based magnetic nanostructures with controlled functionality

(1)

National Institute of Research and Development for Isotopic and Molecular Technologies (INCDTIM) Cluj-Napoca, Romania

http://www.itim-cj.ro

X-ray Photoelectron Spectroscopy of biocompatible polymer based magnetic

nanostructures with controlled functionality

Rodica Turcu

October 24, 2012, Szeged

(2)



Fundamental challenges concerning new specific processes and phenomena induced by the nanostructure, specific molecular interactions, interface effects and phase transitions



Attractive properties of polymers: structural stability, easily shaped, light weight,

noncorrosiveness, mechanical resistence, and dielectric tunability can be used along with magnetic and optical properties of nanoparticles to get multifunctional materials.



Magnetic-polymer nanocomposites  controllable mechanical, thermal, magnetic and electroactive properties; easy functionalization and processing.



Design in a multitude of architectures (dispersed core-shell nanoparticles, gels, selfassembled structures) with tailored properties.

Core-shell systems based on magnetic nanoparticles coated by polymer  tailoring the properties of magnetic nanoparticles in a highly modular fashion by control of the polymer shell structure and composition



Applicability in biotechnology and nanomedicine which undergo an explosive increase in the last decade:

magnetic separation

the increase of the contrast in NMR imaging hyperthermal treatment of the cancerous tumors protein purification

targeting the drug transport artificial muscles

temperature and pH sensors micro-fluidic devices

Why the increasing interest for polymer/magnetic hybrid

nanostructures?

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Magnetic nanoparticles-polymers nanocomposites

Magnetic nanoparticles stabilized with

surfactants

Polymer coating / encapsulation

Polymer /magnetic hybrid nanostructures

Complex characterization by different techniques:

TEM, DLS, XRD, XPS, FTIR, VSM, SQUID

Correlation synthesis-

structure- properties 

to make these materials

suitable for applications

(magnetic separation,

nanomedicine, catalysis)

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X-ray Photoelectron Spectroscopy (XPS)

- a useful surface analysis technique -

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X-ray Photoelectron Spectroscopy (XPS) also known as Electron Spectroscopy for Chemical Analysis (ESCA) provides information about chemical composition of surfaces.

H. Hertz, Ann. Physik 31,983 (1887).

A. Einstein, Ann. Physik 17,132 (1905). 1921 Nobel Prize in Physics.

K. Siegbahn, et. ESCA: Atomic, Molecular and Solid State Structure by means of Electron Spectroscopy, Almqvist snd Wiksells, Uppsala, Sweden, 1967.

XPS technique is based on Einstein’s idea about the photoelectric effect developed around 1905.

During the mid 1960’s Dr. Siegbahn and his research group at the University of Uppsala, Sweden developed the XPS technique.

In 1981, Dr. Siegbahn was awarded the Nobel Prize in Physics for the development of the XPS technique.

X-ray Photoelectron Spectroscopy - Introduction

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XPS as a surface science tool provides:

• Elemental identification and chemical state of element

• Relative composition of the constituents in the surface region

• Depth profile of chemical composition

Applications

• Measuring surface contaminants

• Ultra thin film and oxide thickness measurements

• Characterization of surface defects

• Measuring effect of surface preparation treatments

• Composition of powders and fibers

• Chemical characterization of polymer materials

• Measurement of coating thickness

• Composition depth profiling for multilayer and interface analysis

XPS is considered as non-destructive because it produces soft x-rays to induce

photoelectron emission from the sample surface

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How does XPS work ?

 The sample is irradiated with monoenergetic X-rays:

Mg K , 1253.6 eV Al K , 1486.6 eV

 X-rays penetrate the sample to a depth on the order of 1 m.

 Useful e

^-

signal is obtained only from a depth of around 10 to 100 Å on the surface.

 Ultrahigh vacuum (UHV) environment, p < 10

^-9

Torr

 The energy spectrum of the emitted photoelectrons is determined by a high resolution electron analyser



The binding energies can be determined from the peak positions and the elements present in the sample identified.

Why Does XPS Need UHV?

 Contamination of surface

 XPS is a surface sensitive technique.



Contaminates will produce an XPS signal and lead to incorrect analysis of the surface composition.

 Removing contamination: the sample surface is bombarded with argon ions

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

XPS spectral lines are identified by the shell from which the electron was ejected (1s, 2s, 2p, etc.).



The ejected photoelectron has kinetic energy:

E

_k

= hv-E

_b

- 



Following this process, the atom could release energy by the emission of an Auger Electron

.

XPS – Basic principles

E_b= Electron Binding Energy E_K= Electron Kinetic Energy

 = Work Function

Surface Analysis by Auger and X-ray

Photoelectron Spectroscopy, D. Briggs

and J. T. Grant, Eds., IM Publications,

Chichester, 2003

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X-ray Induced Auger Electrons

• The X-Ray source irradiate and remove the e

^-

from the core level causing the e

^-

to leave the atom

• A higher level e

^-

will occupy the vacancy.

• The energy released is given to a third higher level e

^-

.

• This is the Auger electron that leaves the atom.

Basic principles

KLL

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The XPS measured signal includes contributions from both photoelectron and Auger electron lines.

Exemple: The “survey scan” or “wide scan” XPS spectrum of a polystyrene sample exposed to a nitrogen plasma

Auger line

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 XPS is a very sensitive surface analyzing method, which allows to determine the samples atomic composition as well as the type of the existing chemical bonds and their distribution.

 Using XPS it is possible to detect all elements except for H and He.

 An XPS spectrum shows the number of photoelectrons as a function of binding energy. The spectrum will be a superposition of photoelectron and Auger lines with accompanying satellites and loss peaks and a background due to inelastic scattering in the substrate.

 The main advantage  the binding energy of a photoelectron is sensitive to the chemical surrounding of the atom, i.e. there is a chemical shift in the binding energy. According to the type of chemical bond and to the neighbor atoms, the binding energy of a given state can be shifted from a fraction of eV up to several eV.

 Chemical shifts information is a powerful tool to identify individual chemical states of an element  functional group, chemical environment, oxidation state.

X-ray Photoelectron Spectroscopy - Short summary

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Increase the binding energy of the C1s core orbital.

Binding Energy Shifts - Chemical Shifts –

Carbon bonding to more electronegative atoms decrease the electron density in the valence shell

C 1s

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Quantification of XPS spectra

www.casaxps.com

O1s region

 The number of electrons recorded is proportional to the number of atoms in a given state.

 An XPS spectrum is a combination of the number of electrons leaving the sample surface and the ability of the instrumentation to record these electrons; not all the electrons emitted from the sample are recorded by the instrument.

 The best way to compare XPS

intensities is via, so called, percentage

atomic concentrations - the

representation of the intensities as a

percentage: the ratio of the intensity

to the total intensity of electrons in

the measurement.

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XPS equipment SPECS

INCDTIM Cluj-Napoca Department for Physics of

Nanostructured Systems

 Electron Energy Analyser PHOIBOS 150 CCD;

energy resolution < 2 meV

 X-ray source:

Dual anode – Al/Mg

 Data acquisition software:

SpecsLab 2

 Data analysis software:

CasaXPS

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Applications of XPS to surface

modified magnetic nanoparticles

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Magnetite nanoparticles prepared by co-precipitation method using ionic liquids as a novel reaction medium

A. Nan, R. Turcu, J. Liebscher, RO Patent Nr. A/01357/2010

Ionic liquid (IL) novel reaction medium

1-metyl-3-methylimidazolium tetrafluoroborat [BMIM][BF₄]

2 FeCl₃+ FeCl₂ Baza

Fe₃O₄

80⁰C / Ar / 1 h 80⁰C / Ar / 2 h ac. glicolic

O

HO OO O

OH

O

O OH

O O

HO Fe₃O₄

O O

OH O O

OH

O O

OH O O

HO

Fe₃O₄ /glycolic acid, mean size 10 nm

TEM XRD

50 nm

IL-NP

^[BMIM][BF₄

]

Magnetic nanoparticles

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800 700 600 500 400 300 200 100 0 0.0

2.0x10⁴ 4.0x10⁴ 6.0x10⁴ 8.0x10⁴ 1.0x10⁵ 1.2x10⁵

IL-NP13 IL-NP 6

CPS

Binding energy (eV)

C 1s N 1s

O 1s Fe 2p

XPS survey spectra for Fe

₃

O

₄

/glycolic acid nanoparticles obtained in IL

The presence of N1s in the spectrum shows that the cations from the ionic liquid are adsorbed onto the nanoparticles.

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^[BMIM][BF₄

]

glycolic acid

540 538 536 534 532 530 528 526

0 2000 4000 6000 8000 10000 12000

CPS

Binding energy (eV)

O1s

Fe-O COO^- OH

740 730 720 710 700

0 2000 4000 6000 8000 10000

Fe³⁺ sat.

Fe³⁺

Fe²⁺

Fe2p1/2

Fe2p

CPS

Binding energy (eV) Fe2p3/2

Fe²⁺

sat.

Fe

₃

O

₄

/glycolic acid obtained in IL

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294 292 290 288 286 284 282 280 0

500 1000 1500 2000 2500

O-CH₂

COO^-

CPS

Binding energy (eV)

C1s

C-C, CH₂ C-F

Fe

₃

O

₄

/glycolic acid obtained in IL

408 406 404 402 400 398 396

0 100 200 300 400 500 600 700

CPS

Binding energy (eV)

N1s C-N⁺

C-N

^[BMIM][BF₄

]

glycolic acid

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Magnetite nanoparticles stabilized with (3-Aminopropyl)triethoxysilane

800 700 600 500 400 300 200 100 0 0.0

5.0x10⁵ 1.0x10⁶ 1.5x10⁶

CPS

Binding energy (eV)

O KLL Fe 2p

Fe LMM O 1s

In 3d (support)

N 1s C1s

180 170 160 150 140 130 120 110 100 90 6.0x10⁴

8.0x10⁴ 1.0x10⁵

Si 2p

CPS

Binding energy (eV)

Si 2s

XPS survey spectrum

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294 292 290 288 286 284 282 280 0

1x10⁴ 2x10⁴ 3x10⁴

Binding energy (eV)

Intensity (c.p.s)

C 1s C-C

C-N

538 536 534 532 530 528

0 1x10⁵ 2x10⁵ 3x10⁵

Binding energy (eV)

Intensity (c.p.s)

O 1s Fe-O

Si-O-Si Si-OH

H₂O

408 406 404 402 400 398 396

0.0 5.0x10³ 1.0x10⁴ 1.5x10⁴

Binding energy (eV)

Intensity (c.p.s)

N 1s

NH₂ N⁺

164 162 160 158 156 154 152 150 148 0.0

5.0x10³ 1.0x10⁴

Binding energy (eV)

Intensity (c.p.s)

Si 2s Si-OH

Si-O-Si

730 720 710 700

9x10⁵ 1x10⁶ 1x10⁶ 1x10⁶ 1x10⁶

Fe 2p1/2

Binding energy (eV)

Intensity (c.p.s)

Fe 2p3/2 Fe 2p

High resolution XPS spectra for Fe

₃

O

₄

nanoparticles stabilized with (3-Aminopropyl)triethoxysilane

Name Position (eV)

FWHM

(eV) %At Conc C 1s 284.63 2.23 34.956

C 1s 287.17 3.256 65.044 Name Position

(eV)

FWHM

(eV) %At Conc N 1s 402.72 2.771 63.575 N 1s 400.23 2.222 36.425 Name Position

(eV)

FWHM

(eV) %At Conc O 1s 530.56 1.688 27.565 O 1s 531.61 1.201 6.141

O 1s 533.17 2.372 52.7

O 1s 535.52 2.315 13.594

Name Position (eV)

FWHM

(eV) %At Conc Si 2s 156.62 3.216 60.823 Si 2s 154.2 2.607 39.177

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High resolution XPS spectra for magnetite

nanoparticles prepared by the combustion method

292 288 284 280 276

0 10000 20000 30000 40000 50000

C=O

C-C, CH

iron carbide C1s

Intensity (c.p.s.)

Binding energy (eV)

540 536 532 528 524

0 100000 200000

Fe-O

C-O, O-C=O O1s

Intensity (c.p.s.)

Binding energy (eV)

740 730 720 710 700 690

0 100000 200000 300000

In support satellites

satellites Fe³⁺ Fe²⁺

Fe³⁺

Fe²⁺

Fe 2p1/2

Fe 2p3/2 Fe 2p

Intensity (c.p.s.)

Binding energy (eV)

Fe³⁺/ Fe²⁺ = 1.38

The ratio is different from magnetite (Fe³⁺/ Fe²⁺= 2)

Peak name Position (eV)

FWHM (eV)

% At. conc.

Fe²⁺ 2p3/2 708.66 4.009 4.082 Fe³⁺ 2p3/2 710.74 4.489 8.257 Fe²⁺ 2p1/2 722.04 4.08 3.952 Fe³⁺ 2p1/2 724.22 4.835 7.996 Fe²⁺ satellite 2p3/2 713.96 4.842 3.731 Fe³⁺ satellite 2p3/2 718.21 6 4.406 Fe²⁺ satellite 2p1/2 728.01 6 4.434 Fe³⁺ satellite 2p1/2 732.66 4.801 1.681

O 1s 528.12 2.245 7.4

O1s (Fe-O) 530.11 3.191 23.824 O 1s (C-O, O-C=O) 533.32 3.238 3.325

C 1s (iron carbide) 282.88 2.344 4.087 C 1s (C-C, C-H) 284.85 3.225 12.676

C 1s (C=O) 288.09 3.46 2.843

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Biofunctionalized magnetite nanoparticles from water based magnetic fluid

Fe₃O₄ HOOC COOH

COOH

COOH COOH HOOC COOH

HOOC HOOC

HOOC

COOHCOOH

COOH

COOH COOH HOOC

HOOC

HOOC COOH

COOH

+

O

H

OH

H

OH H

H₂N H OH

HO HCl

EDC, HOBt, DIPEA

Fe₃O₄ H₂O, 24 h

Glucosamine

MF: Fe₃O₄/LA+LA Lab. Magnetic Fluids

Timisoara

100 nm

800 1200 1600 2000 2400 2800 3200 3600 0.2

0.4 0.6 0.8 1.0 1.2 1.4

Absorbance (a. u.)

w (cm^-1) Fe₃O₄

CH₂ , CH₃

amide -C-C- CH

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294 292 290 288 286 284 282 0

10000 20000 30000 40000

Intensity (cps)

B.E. (eV)

C1s C-C / CH_n

C-N / C-O

O-C=O

540 538 536 534 532 530 528 526

0 100000 200000 300000

Intensity (cps)

B.E. (eV) O1s

Fe-O C-OH

O-C=O

406 404 402 400 398 396

0 2000 4000

Intensity (cps)

B.E. (eV)

N1s ^N-H

740 730 720 710 700

0 100000 200000

Fe³⁺

Fe²⁺

Fe³⁺

Fe2p1/2

Intensity (cps)

B.E. (eV)

Fe2p ^Fe2p3/2

Fe²⁺

sat.

XPS spectra  covalent attachment of glucosamine to the carboxyl group from the lauric acid stabilizer of magnetite in the MF

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Applications of XPS to polymer based

hybrid nanostructures

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O1s and C1s regions of XPS spectra of a thin PMMA film, recorded under three different charging conditions. The point of zero charge (PZC) for the C1s peak of the backbone carbon atoms is shown for comparison.

XPS is a surface charge sensitive measurement

The nature of the charging process of polymer surfaces at the molecular level investigated by XPS - poly(methyl methacrylate) (PMMA) films analyzed either in their pristine state or deliberately charged using a flood gun as an external electron source and by applying external bias to control the extent of charging.

E.Yilmaz et al., Angew. Chem. 2012, 124, 5584 –5588

As the system becomes more positively charged:

- the measured BE difference between the O1s and the C1s peaks of the carbonyl groups (-C=O) decreases;

- the difference between the two O1s peaks gradually increases, the full width at half maximum (FWHM) of the carbonyl O1s peaks increases.

Carbonyl groups respond to the charging shifts more.

The carbonyl oxygen atoms are more susceptible to the presence of charges.

(27)

R. De Palma et al., Chem. Mater. 2007, 19, 1821-1831

XPS study - Silane Ligand Exchange to Make Hydrophobic Superparamagnetic

Nanoparticles Water-Dispersible

(28)

Pyrrole based functionalized magnetic core-shell nanostructures

S. Karsten, A. Nan, R. Turcu, J. Liebscher, J. POLYM.

SCI. PART A: POLYMER CHEMISTRY - accepted 2012



Synthesis of azido-functionalized polypyrrole (PPy)-based superparamagnetic core shell nanoparticles (NP) by surface initiated polymerization.



The surface initiated polymerization is carried out at new magnetite NP stabilized by pyrrol- containing fatty acids.



NP 1 of a narrow size distribution below 10 nm were prepared by a known thermal

decomposition method starting with iron (III) acetylacetonate and using oleic acid and oleylamine as colloid stabilizing surfactants .



The ligands of the starting NPs 1 (oleic acid, oleylamine) were exchanged by the pyrrolyl- dodecanoic acids 2 and 4 giving the azido- functionalized NP 5



Ppy-NP equipped with azido groups are very versatile for attaching important applicative functions for biotechnology, catalysis, nanomedicine.

O O

N

3

HN NH O

H HN H

S O

O NH O N N

3

Fe3O4

1

Fe₃O₄

N N

N N N

N

3 1,2-dichlorbenzene,

80°C, 24 h 10 N O

OH

82%

6 HN

O NH

O

N3 3

Fe3O4 N3

N3 N3 N3

N₃

N₃ N3

N3

N₃

Fe₃O₄

O O

3 HN

NH O

H HN H

S

O

1. 0.2 equ. Cu(CH3CN)4PF6, 0.2 equ. DIPEA, MeOH rt, ultrasound, 4 h, 2. Cuprisorb^TM

=

O HN

O N₃ 3

polypyrrole shell

1. (NH4)2S2O8, CHCl3/H2O, rt, ultrasound,1- 24 h 2. 2,6-di-t-butyl-p-cresol

N3 =

7

9 2

8 Fe₃O₄

N N

N N N

N +2

N O

HN

O N₃ 3

10OH + O

1,2-dichlorobenzene, 80°C, 24 h

N3 N3

N₃ N3

4

5

azido group (R-N=N⁺=N^- )

Hybrid nanostructures

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400 800 1200 1600 2000 2400 2800 3200 3600 4000

Transmission

wavenumber [cm^-1] ν_as(N₃)

ν (C=O) δ (CH_Pyrrol)

Hydrodynamic diameter (nm)

7 nm 15 nm

50 nm

b) a)

10 nm

c) d)

2 nm

a, c) TEM-images of NPs 5, (b) SAED, (d) HRTEM.

NPs 5

-6 -4 -2 0 2 4 6

-20 -15 -10 -5 0 5 10 15 20

M (emu/g)

B (T)

M_S=15.4 emu/g

Fe

₃

O

₄

nanoparticles coated with azido-functionalized pyrrole

The FTIR-spectrum of the NPs 5 indicates successful ligand exchange by the appearance of bands typical for amide (1641 cm^-1), pyrrole (719 cm^-1) and the azido groups (2101 cm^-1).

DLS

(30)

XPS spectra of Fe

₃

O

₄

nanoparticles coated with azido-functionalized pyrrole

azido group (R-N=N⁺=N^- )

292 290 288 286 284 282 280

0 100000 200000 300000

C1s

Intensity (cps)

Binding energy (eV) C-C/CH_n

C-N / C-O

N-C=O / O-C=O

540 538 536 534 532 530 528 526

0 10000 20000 30000

40000 O1s

Intensity (cps)

Binding energy (eV) Fe-O C=O / C-O

O-C=O

394 396 398 400 402 404 406

0 800 1600

N1s

Intensity (cps)

Binding energy (eV) N-H/C-N

=N⁺=

=N^-

740 730 720 710 700 690

200000 210000 220000

230000 Fe 2p1/2

Fe 2p3/2

Fe2p

Intensity (cps)

Binding energy (eV)

(31)

294 292 290 288 286 284 282 280 278 0.0

4.0x10⁴ 8.0x10⁴

Intensity (c.p.s.)

Binding energy (eV)

C 1s ^{C-C, C-H}

C-N C=O

538 536 534 532 530 528 526 524 0.0

6.0x10⁴

1.2x10⁵ C=O

In-O (support) Fe-O

Intensity (c.p.s.)

Binding energy (eV) O 1s

408 406 404 402 400 398 396 394 392 0

1x10⁴ 2x10⁴

Intensity (c.p.s.)

Binding energy (eV)

N-H, C-N N 1s

=N^-

=N⁺=

735 730 725 720 715 710 705 700 695 0.0

4.0x10⁴ 8.0x10⁴ 1.2x10⁵

Fe²⁺

Fe³⁺

In support satellites

satellites

Fe²⁺

Fe³⁺

Fe 2p1/2

Fe 2p3/2

Intensity (c.p.s.)

Binding energy (eV) Fe 2p

XPS spectra for azido functionalized nanoparticles

NP 4

The spectrum contains the

contribution from azido group

(R-N=N⁺=N^- )

(32)

Polymer based magnetic core-shell nanostructures

Modification of magnetite surface with glycolic acid:

Fe₃O₄ +

80⁰C 2 h / Ar OH

O

OH Fe₃O₄

O O

HO

O O

HO

O O

HO O

O HO

O O

HO O O

OH O O

OH

O O

OH

O HO O

O

O OH

O O

OH

Modification of magnetite surface with serine:

Fe₃O₄ +

80⁰C 2 h / Ar H₂N CH C

CH₂

OH O

OH

Fe₃O₄

HO O

O O

OH

O O O

OH O

O O

HO O

O O

OH

O

O O

HO

O O

O

O OH O

O OH

O

O O

Surface initiated ring opening polymerization of lactones Surface modification of

magnetite

The magnetic

nanoparticles coated with polylactones (polycaprolactone, polylactic acid)

containing hydroxyl groups offer the

possibility of

subsequent grafting of several functionalized molecules, such as biomolecules or catalytically active groups

.

(33)

O O

Sn(oct)₂ OH OH

OH

OH OH HO HO

HO

Fe3O4 O

O

OH n +

O O

O O O O O

Fe₃O₄

O

OH

n

O

HO n

O

HO n

O

OH n

HO O n

O HO n

HO n

HO O

O

OH n O

O

nOH

O

HO n

O O

HO n

O O HO

n

OH HO

OH

Sn(oct)2

microwave irradiation 100⁰C, Ar

200⁰ C, 200 W, 7 min.

OH OH

HO OH

MNP /PCL

A. Nan, R. Turcu, I. Craciunescu, O.

Pana, H. Scharf, J. Liebscher, J. Polym.

Sci. Part A: Polym. Chem., 47 (2009) 5397-5404

Microwave irradiation:

The mixture of surface functionalized MNP, CL and the catalyst were placed in a dried glass ampoule with a magnetic stirrer and were vacuum sealed.

The reaction was performed at 200 ⁰C , microwave power of 200 W for 7 minutes while the pressure reached 8 bar.

Classical polymerization reaction:

Surface functionalized MNP were mixed with freshly distilled CL and strongly shacked for 30 min. at 1200 rot./min. Tin(II)ethylhexanoate was then added as a catalyst and the reaction mixture was stirred in a shaker at 100 ⁰C for 5 h at 1200 rot./min.

Surface initiated ring opening polymerization of -caprolactone onto

magnetite

Polycaprolactone coated magnetite

(34)

MNP/ PCL

10 20 30 40 50 60 70 80 90

50 100 150

MNP1 (Fe₃O₄/serine) MNP2 (Fe₃O₄/glycolic acid)

intensity [ a.u.]

2 theta (degrees) (311)

(220) (400) (511) (440)

Samples D_eff [nm ] <²>^1/2_hkl

 10² MNP1

serine 9.4 0.546

MNP2

glycolic acid 16.3 0.137 The microstructural parameters of Fe₃O₄ obtained by single X-ray profile Fourier analysis

MNP/glycolic acid MNP/PCL

Magnetite core mean size: 9-16 nm (TEM, XRD) Polymeric shell thickness: 1-2 nm (HRTEM)

Structural and morphological characterization

XRD

(35)

Magnetic characterization of magnetite covered with polycaprolactone

-6 -4 -2 0 2 4 6

-80 -60 -40 -20 0 20 40 60 80

M (emu/g)

B (T)

MNP1 (Fe₃O₄ /serine) MNP1/ PCL (MW) MNP1/ PCL

-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6

-100 -80 -60 -40 -20 0 20 40 60 80

100 MNP2 (Fe

3O

4 /glycolic acid) MNP2 /PCL

M (emu/g)

B (T)

M_S = 79 emu/g

MS = 76 emu/g

0 40 80 120 160 200 240 280 320

0 50 100 150 200 250 300 350 400 450

Bc (G)

T (K) MNP1-PCL

superparamagnetic behaviour

 Superparamagnetic behaviour

 High magnetization values 50 – 79 emu/g.

(36)

X-ray Photoelectron Spectroscopy of magnetite coated with serine

250 300 350 400 450 500 550 600 650 700 750

0.0 2.0x10⁵ 4.0x10⁵ 6.0x10⁵

serine

MNP1 (Fe₃O₄ /serine)

O1s

In3d (support)

Intensity (counts) N1s

Binding energy (eV)

C1s

Fe2p

Due to the deamination of serine in the presence of iron salt, no contribution from N1s core level was observed for MNP1 (Fe₃O₄/serine).

Deamination of serine - detachment of molecular

ammonia due to C-N bond scission

(37)

294 292 290 288 286 284 282 280 0

1x10⁴ 2x10⁴ 3x10⁴ 4x10⁴ 5x10⁴ 6x10⁴ 7x10⁴

Intensity (counts)

Binding energy (eV) C 1s

COO^-

CH, C-C

CH₂

serine

294 292 290 288 286 284 282 280

0 1x10⁴ 2x10⁴ 3x10⁴

MNP1 (Fe₃O₄ /serine)

Intensity (counts)

Binding energy (eV)

C 1s

COO^-

CH, C-C

CH₂

408 406 404 402 400 398 396

0 1x10⁴ 2x10⁴ 3x10⁴ 4x10⁴ 5x10⁴

serine

Intensity (counts)

N 1s

Binding energy (eV)

NH₃⁺

NH₂

540 538 536 534 532 530 528 526

0.0 5.0x10⁴ 1.0x10⁵ 1.5x10⁵

2.0x10⁵ serine

Intensity (counts)

O 1s

Binding energy (eV)

OH C=O

538 536 534 532 530 528 526

0 1x10⁵ 2x10⁵ 3x10⁵ 4x10⁵ 5x10⁵ 6x10⁵

7x10⁵ MNP1 (Fe₃O₄ /serine)

Intensity (counts)

O 1s

Binding energy (eV) OH

COO^-

O-Fe

735 730 725 720 715 710 705 700

0.0 5.0x10⁴ 1.0x10⁵ 1.5x10⁵ 2.0x10⁵ 2.5x10⁵ 3.0x10⁵

3.5x10⁵ MNP1 (Fe

3O

4 /serine)

Fe²⁺

Fe³⁺

Fe²⁺

Fe 2p3/2

Fe 2p

Binding energy (eV)

Intensity (counts)

Fe 2p1/2 Fe³⁺

High resolution XPS spectra

(38)

538 536 534 532 530 528 526 0

1x10⁵ 2x10⁵ 3x10⁵ 4x10⁵ 5x10⁵

O 1s

Intensity (a.u.)

Binding energy (eV) OH

Fe-O

COO

730 725 720 715 710 705

0.0 2.0x10⁴ 4.0x10⁴ 6.0x10⁴ 8.0x10⁴ 1.0x10⁵ 1.2x10⁵ 1.4x10⁵

Fe²⁺

Fe³⁺

Fe²⁺

Fe³⁺

Fe 2p1/2

Fe 2p3/2

Fe 2p

Binding energy (eV)

294 292 290 288 286 284 282 280

0.0 2.0x10⁴ 4.0x10⁴ 6.0x10⁴

8.0x10⁴ C 1s

Intensity (a.u.)

Binding energy (eV) COO (4)

CH₂ (1,2) CH₂ (3)

CH₂ ( CH₂)₃ CH₂ C O

O

3 1 2 4

n PCL

XPS of magnetite coated with polycaprolactone

(39)

Magnetite -Polylactic Acid Core–Shell Nanoparticles I.

A. Nan, R. Turcu, J. Liebscher, J. POLYM. SCI.

PART A: POLYMER CHEMISTRY 2012, 50, 1485–1490

MN-OH

MN-PLA Ring-Opening Polymerization

Under Microwave Irradiation

MN-OH Magnetite core surface functionalized with glycolic acid

(40)

XPS of magnetite stabilized with glycolic acid

The atomic

concentrations ratio:

C/Fe =0.21

(41)

XPS of magnetite coated with polylactic acid

The atomic

concentrations ratio:

C/Fe =0.327

(42)

Magnetite cores surface-functionalized by -D- Glucose-1-phosphate disodium salt

2 FeCl3+ FeCl2

NH4OH

Fe3O4

Synthesis of magnetite

80⁰C / Ar / 1 h

Fe3O4 +

rt. / Ar / 24 h

Fe₃O₄ Surface modification

O HO

HO

OH O OH

P O

ONa ONa

Magnetite -Polylactic Acid Core–Shell Nanoparticles II.

MNP-Glu

DMAP, toluene, reflux, 10 h

OH HO OH

OH HO HO HO

HO Fe₃O₄

OH HO

OH

O O O

O O O O

O Fe₃O₄

O O

O

O HO

OH OH OH

OH OH OH OH HO HO HO

HO +

O

O O

O

Surface-initiated ring opening polymerization of lactic acid

MNP-Glu-PLA

500 1000 1500 2000 2500 3000 3500 0.2

0.4 0.6 0.8 1.0 1.2

Absorbance (a.u.)

Wavenumber (cm^-1)

MNP-Glu-PLA MNP-Glu

(43)

294 292 290 288 286 284 282 280 0

10000 20000 30000

Intensity (c.p.s.)

Binding energy (eV)

C 1s

C-C, CH_n C-O-H, C-O-C

O-C=O

540 538 536 534 532 530 528 526 524 0.0

7.0x10⁴ 1.4x10⁵

Intensity (c.p.s.)

Binding energy (eV)

O 1s

Fe-O OH, C-O-C

O-C=O

138 136 134 132 130

0 1000 2000 3000

P 2p1/2

Intensity (c.p.s.)

Binding energy (eV)

P 2p P 2p3/2

740 730 720 710 700

0.0 6.0x10⁴ 1.2x10⁵

satelite

Fe³⁺

Fe²⁺

Fe³⁺

Fe 2p1/2

Intensity (c.p.s.)

Binding energy (eV)

Fe 2p

In support Fe²⁺

Fe 2p3/2

satelite

XPS of polylactic coated magnetite nanoparticles MNP-Glu-PLA

(44)

-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 -60

-40 -20 0 20 40 60

M (emu/g)

B (T)

MNP-Glu-PLA

M_S= 54 emu/g

The magnetic nanoparticles coated with polylactones offer the possibility of subsequent grafting of several biomolecules for applications in nanomedicine.

100 nm

MNP-Glu

MNP-Glu-PLA

100 nm