Nanoscale coordination polymers exhibiting luminescence properties and NMR relaxivity

Dynamic Article LinksC<Nanoscale

Cite this: Nanoscale, 2011, 3, 1200

www.rsc.org/nanoscale PAPER

Nanoscale coordination polymers exhibiting luminescence properties andNMR relaxivity†

Elena Chelebaeva,ac Joulia Larionova,*a Yannick Guari,*a Rute A. S. Ferreira,b Luis D. Carlos,*b

Alexander A. Trifonov,c Thangavel Kalaivani,d Alessandro Lascialfari,*def Christian Gu�erin,a

Karine Molvinger,g Lucien Datas,h Marie Maynadier,ijkl Magali Gary-Boboijkl and Marcel Garciaijkl

Received 22nd September 2010, Accepted 1st December 2010

DOI: 10.1039/c0nr00709a

This article presents the first example of ultra-small (3–4 nm) magneto-luminescent cyano-bridged

coordination polymer nanoparticles Ln0.333+Gdx

3+/[Mo(CN)8]3� (Ln ¼ Eu (x ¼ 0.34), Tb (x ¼ 0.35))

enwrapped by a natural biocompatible polymer chitosan. The aqueous colloidal solutions of these

nanoparticles present a luminescence characteristic of the corresponding lanthanides (5D0 / 7F0–4

(Eu3+) or the 5D4 / 7F6–2 (Tb3+)) under UV excitation and a green luminescence of the chitosan shell

under excitation in the visible region. Magnetic Resonance Imaging (MRI) efficiency, i.e. the nuclear

relaxivity, measurements performed for Ln0.333+Gdx

3+/[Mo(CN)8]3� nanoparticles show r1p and r2p

relaxivities slightly higher than or comparable to the ones of the commercial paramagnetic compounds

Gd-DTPA� or Omniscan� indicating that our samples may potentially be considered as a positive

contrast agent for MRI. The in vitro studies performed on these nanoparticles show that they maybe

internalized into human cancer and normal cells and well detected by fluorescence at the single cell

level. They present high stability even at low pH and lack of cytotoxicity both in human cancer and

normal cells.

aInstitut Charles Gerhardt Montpellier, UMR5253, Chimie Mol�eculaire etOrganisation du Solide, Universit�e Montpellier II, Place E. Bataillon,34095 Montpellier cedex 5, FrancebDepartment of Physics, CICECO, University of Aveiro, 3810-193 Aveiro,PortugalcG. A. Razuvaev Institute of Organometallic Chemistry of the RussianAcademy of Science, Tropinina 49, GSP-44S, 603950 Nizhny Novgorod,RussiadDipartimento di Scienze Molecolari Applicate ai Biosistemi, Universit�adegli studi di Milano, I-20134 Milano, ItalyeCentro S3, CNR-Istituto di Nanoscienze, I-41125 Modena, ItalyfDipartimento di Fisica ‘‘A. Volta’’, Universit�a degli studi di Pavia, ViaBassi 6, I-27100 Pavia, ItalygInstitut Charles Gerhardt Montpellier, UMR 5253, Mat�eriaux Avanc�espour la Catalyse et la Sant�e, Ecole Nationale Sup�erieure de Chimie deMontpellier, 8, rue de l’�ecole normale, 34296 Montpellier cedex 5, FrancehService commun de Microscopie Electronique TEMSCAN, Universit�ePaul Sabatier, 118 route de Narbonne, 31062 Toulouse cedex 4, FranceiInstitut de Recherche en Canc�erologie de Montpellier, Montpellier,F-34298, FrancejINSERM, U896, Montpellier, F-34298, FrancekUniversit�e Montpellier 1, Montpellier, F-34298, FrancelCentre R�egional de Lutte contre le Cancer, Val d’Aurelle Paul Lamarque,Montpellier, F-34298, France

† Electronic supplementary information (ESI) available: TEM imagesand size distribution histograms, IR and emission spectra, diffractionpattern and HRTEM coupled EDX analysis. See DOI:10.1039/c0nr00709a

1200 | Nanoscale, 2011, 3, 1200–1210

I. Introduction

Multifunctional nanoparticles represent a class of nano-mate-

rials that combines several specific properties, such as mechan-

ical, electronic, optical, and magnetic in a single nano-object

which is capable of exhibiting diverse physical responses when

subjected to certain external stimuli. In recent years, multifunc-

tional nano-materials are at the forefront of research and tech-

nology due to their interesting properties and their potential

applications in different fields.1 In particular, for biomedical

applications, multifunctional nano-objects are able to combine

two or more functions, such as different types of imaging or

imaging with drug delivery, targeting, or various therapies.2 One

of the most promising multifunctional nano-objects should

present a combination of magnetic and optical properties within

a single hybrid nano-system in order to combine luminescence

biolabelling and Magnetic Resonance Imaging (MRI). Generally,

the approaches used for the synthesis of those multifunctional

nanomaterials consist in design complex hybrid nano-objects

containing two or more components with luminescence and

magnetic relaxivity. We can cite numerous works on magnetic

metallic or metal-oxide core–shell nanoparticles where lumines-

cent organic dyes, Au nanoparticles or metal complexes are

incorporated into silica or polymer shells or attached on their

surface.2g,3 Other works concern silica or polymer nanoparticles

used as a platform for incorporation or covalent surface

This journal is ª The Royal Society of Chemistry 2011

http://dx.doi.org/10.1039/c0nr00709a





anchoring of magnetic nanoparticles, luminescent complexes,

organic dyes or paramagnetic Gd3+ complexes.4 Note that in

most cases, superparamagnetic iron oxide nanoparticles or more

rarely Gd–macrocycles are used to confer the magnetic proper-

ties to these hybrid nano-objects.

Very recently, nanoparticles of molecule-based materials as

a new type of magnetic inorganic nanoparticles were explored.5

These nanoparticles present an increasing interest due to their

specific nature, which is different in comparison to other inor-

ganic nano-objects. They present all advantages of bulk molec-

ular-based materials, such as determined and flexible molecular

structures, adjustable physical and chemical properties, porosity,

low density, and the possibility to combine several properties in

the same multifunctional nano-objects. Furthermore, as their

bulk analogous, the nanoparticles may be obtained from

molecular precursors by using ‘‘soft’’ chemistry methods by self-

assembling reactions. On the other hand, it is possible to design

the nano-objects in such a way that they possess controlled size,

shape and organization at the nano-scale level, and thus their

physical and chemical properties may be controlled. Indeed, the

synthesis of nano-objects based on cyanometallates, carboxylates

or phosphate ligands presenting exciting magnetic or optical

properties was performed.6 These nanoparticles present an

increasing interest for biomedical applications, and few works on

the investigation of lanthanides-7 iron-based8 Metal–Organic

Frameworks (MOFs) nanoparticles, and cyano-bridged coordi-

nation polymer nanoparticles9 as new systems of contrast agents

for Magnetic Resonance Imaging (MRI), optical imaging and

drug delivery have been reported recently. Among these, a small

number of examples have been devoted to designing multifunc-

tional nanoparticles. We can cite hybrid polymer or silica coated

nanoparticles of Gd-10 and Mn-based11 MOFs with organic

fluorophores on their surface, supramolecular coordination

polymer networks based on lanthanides ions and phosphate-

modified nucleotides with encapsulated organic fluorophore12 or

silica nanoparticles containing fluorophore coated with magnetic

cyano-bridged coordination poymer.13 Among those, only one

recently published work concerns the synthesis of nanorods with

a bi-functional magneto-luminescent core by a combination of

paramagnetic gadolinium with luminescent europium or terbium

ions in the same MOF in order to achieve a bi-modal MRI-

optical imaging probe.14 However, these nano-objects present

a relatively large size with large size distribution that makes

difficult their internalization into the cells and more importantly

their elimination from the body. In addition, it was shown that

due to their relatively low stability, MOFs nanoparticles release

the metal ions.10,14

In the present work, we demonstrate a new approach to the

synthesis of ultra small magneto-luminescent coordination

polymer nanoparticles designed from octacyanomolybdate

building block and lanthanides ions which can be considered as

a new family of bi-functional probe for MRI and optical

imaging. This approach is based on an association of luminescent

Ln3+ and paramagnetic Gd3+ ions with paramagnetic octacya-

nomolybdate building blocks in order to obtain magneto-lumi-

nescent cyano-bridged core of nanoparticles stabilized by the

biopolymer chitosan. These small nanoparticles of 3–4 nm are

biocompatible, they present high stability event at low pH and

may potentially be used for imaging in specific conditions (for


instance a gastro-intestinal tract). Here, we present the synthesis,

the evaluation of the Nuclear Magnetic Resonance (NMR)

relaxivity and the luminescence properties of ultra-small, bi-

functional magneto-luminescent coordination polymer nano-

particles Ln0.333+Gdx

3+/[Mo(CN)8]3� (Ln ¼ Eu (x ¼ 0.34), Tb

(x ¼ 0.35)) enwrapped by the natural biopolymer chitosan used

as a stabilizing agent. A first characterization of the cells uptake

of these nanoparticles indicates their efficient internalization and

fluorescence detection into human cancer and normal cell line

and the lack of cytotoxicity related to their high stability.

II. Experimental part

Synthesis

All of the chemical reagents used in these experiments are

analytical grade: Ln(NO3)3$6H2O (Eu from Alfa Aesar, Tb and

Gd from Rhone-Poulenc). (N(C4H9)4)3[Mo(CN)8] was prepared

according to the literature procedure.15 The pristine porous

chitosan beads were synthesized as previously described.16 The

degree of acetylation (DA) which is the percent of remaining

acetyl groups was 10% as measured by IR spectroscopy.

Synthesis of Ln0.333+Gdx

3+/[Mo(CN)8]3�/chitosan (Ln¼ Eu (x¼0.34), Tb (x ¼ 0.35)) nanoparticles. The synthesis of

Ln0.333+Gdx

3+/[Mo(CN)8]3�/chitosan nanoparticles (Ln ¼ Eu,

Tb) was performed in two steps, consisting first in the synthesis of

chitosan nanocomposites containing the Ln0.333+Gdx

3+/

[Mo(CN)8]3� nanoparticles (1a, 2a) incorporated into the chito-

san beads and second in the solubilization of the most part of the

chitosan matrix in acidic water in order to obtain aqueous

colloidal solutions of the nanoparticles (1b, 2b). The nano-

composite beads Ln0.333+Gdx

3+/[Mo(CN)8]3�/chitosan (Ln ¼ Eu

1a, Tb 2a) were prepared by subsequent incorporation of

Gd(NO3)3$6H2O, Ln(NO3)3$6H2O and (N(C4H9)4)3[Mo(CN)8]

into the pristine porous chitosan beads. The typical synthesis for

1a or 2a was performed as follows: the pristine chitosan beads

(90 mg) were added to a mixture of methanolic solutions of

Ln(NO3)3$6H2O (Ln ¼ Eu or Tb) (5 g L�1) and of

Gd(NO3)3$6H2O (5 g L�1). The mixture was stirred overnight at

room temperature and then the solution was filtered off. The

beads were washed copiously with methanol and then dried

in vacuo. Then, the composite Ln0.333+Gdx

3+/chitosan (Ln ¼ Eu

(x ¼ 0.34), Tb (x ¼ 0.35)) (90 mg) was added to a 10�2 M

methanolic solution of the (N(C4H9)4)3[Mo(CN)8]. The mixture

was stirred 48 h, the beads were filtered, thoroughly washed with

methanol and dried in vacuo. The consecutive treatment with

a mixture of methanolic solutions of Gd(NO3)3$6H2O and

Ln(NO3)3$6H2O and then with a methanolic solution of

(N(C4H9)4)3[Mo(CN)8] was repeated twice. In the second step, in

order to obtain colloidal solutions of the coordination polymer

nanoparticles (1b, 2b), the respective nanocomposite beads (100

mg) were immersed in a buffer solution (20 mL, pH 4.25) over-

night with stirring. The resulting suspension was centrifuged (15

min, 20 000 trs min�1) and the supernatant containing the

nanoparticles recovered. As a result, colloidal solutions con-

taining nanoparticles Ln0.333+Gdx

3+/[Mo(CN)8]3�/chitosan (Ln¼Eu 1b, or Tb 2b) were obtained. These colloidal solutions are very

stable and no any precipitate was observed even after four

Nanoscale, 2011, 3, 1200–1210 | 1201

months. The solutions may be concentrated or diluted in water.

For biological assays, the pH of solutions was adjusted to 7.2 by

using 0.1 M aqueous KOH solution. The stability tests of the

nanoparticles were performed both in buffered aqueous solution

with pH ¼ 4.25 (acetic acid buffered solution) and in a physio-

logical media McCoy’s 5A, supplemented with 10% fetal bovine

serum, penicillin 100 U mL�1and streptomycin 100 mg mL�1 used

for the maintenance of HCT116 colon cancer cells. The TEM

image of the nanoparticles 1b dispersed into these physiological

media shown that the nanoparticles are well dispersed and not

aggregated (ESI, Fig. S1†). The nanoparticles were then precip-

itated from both solutions with ethanol and the ICP-MS analysis

of the mother solutions shows no detectable presence of Gd3+.

Physical measurements

IR spectra were recorded on a Perkin Elmer 1600 spectrometer

with a 4 cm�1 resolution. TEM measurements were carried out

with a microscope JEOL 1200 EXII operated at 100 kV,

HRTEM observations were performed on a JEOL JEM2010

operated at 200 kV. In the latter, coupled EDS analysis was

performed on single nanoparticles. Samples for TEM measure-

ments were prepared using ultramicrotomy techniques and then

deposited on copper grids for the solids. In the case of the

colloids, samples were prepared simply by depositing a drop of

the nanoparticles’ solutions on carbon coated copper grids. The

nanoparticles’ size distribution histogram was determined using

enlarged TEM micrographs taken at magnification of 100 K on

a statistical sample of ca. 300 nanoparticles. An evaluation of the

Ln/Gd/Mo ratio on assemblies of nanoparticles was performed

by using an Environmental Secondary Electron Microscope FEI

Quanta 200 FEG coupled with an Electrons Dispersive Spec-

troscope Oxford INCA detector. Elemental analyses (ICP-MS)

were performed by the Service Central d’Analyse (CNRS, Ver-

naison, France). Magnetic susceptibility data were collected with

a Quantum Design MPMS-XL SQUID magnetometer. The

photoluminescence spectra were recorded at room temperature

on a Fluorolog-3 Model FL3-2T with double excitation spec-

trometer and a single emission spectrometer (TRIAX 320)

coupled to a R928 photomultiplier, using a front face acquisition

mode. The excitation source was a 450 W Xenon lamp. Emission

was corrected for the spectral response of the monochromators

and the detector using a typical correction spectrum provided by

the manufacturer and the excitation spectra were corrected for

the spectral distribution of the lamp intensity using a photodiode

reference detector. Emission decay curve measurements were

carried out at room temperature with the setup described for the

luminescence spectra using a pulsed Xe–Hg lamp (6 ms pulse at

half width and 20–30 ms tail). We collected the NMR data by

means of a Smartracer Stelar relaxometer (with the use of Fast-

Field-Cycling technique) for frequencies in the range 10 kHz # n

# 10 MHz,17 and of Stelar Spinmaster and Apollo-Tecmag

spectrometers for n > 10 MHz. Standard radio frequency exci-

tation sequences CPMG-like (T2) and saturation-recovery (T1)

were used. From the measured T1 and T2 values, we calculated

the longitudinal and transverse relaxivities with the usual

formula. To perform the confocal analysis, the nanoparticles

solution was added in serum free culture medium of each cell

type at the dose of 100 ng mL�1. The day prior to the experiment,

1202 | Nanoscale, 2011, 3, 1200–1210

HCT116 and Capan-1 cells were seeded onto bottom glass dishes

(World Precision Instrument, Stevenage, UK) at a density of

30 000 cells cm�2. On the day of the experiment, cells were

washed once and incubated in 1 mL red-free medium containing

Eu0.333+Gd0.35

3+/[Mo(CN)8]3�/chitosan nanoparticles 1b at

a concentration of 100 ng mL�1 for 6 h. 30 min before the end of

incubation, cells were loaded with Hoechst 33342 (Invitrogen,

Cergy Pontoise, France) for nuclear staining at a final concen-

tration of 5 mg mL�1. For the lysosome labelling, 3 h before the

end of the experiment, 50 nM of lysotracker red DND-99

(Invitrogen) were added to phenol red-free medium. Before

visualization, cells were washed gently with phenol red-free

medium. Cells were then scanned with a LSM 5 LIVE confocal

laser scanning microscope (Carl Zeiss, Le Pecq, France), with

a slice depth (Z stack) of 0.67 mm and at 489 nm excitation

wavelength. The distributions of fluorescent nanoparticles were

analyzed by CLSM using nucleus and lysosome markers. Merged

images of fluorescent nanoparticles and lysosome marker allow

establishment of the level of nanoparticles into lysosomes.

Cell culture

Cancer cell types were purchased from ATCC (American Type

Culture Collection, Manassas, VA), HUVECs were purchased

from PromoCell and normal fibroblasts were obtained from

Prof. Dr Kurt von Figura (G€ottingen). All cell types were

allowed to grow in humidified atmosphere at 37 �C under 5%

CO2. Capan-1 human pancreatic cancer cells were routinely

maintained in Dulbecco’s Modified Eagle’s Medium (DMEM)

supplemented with 10% fetal bovine serum and 50 mg mL�1

gentamycin. HCT116 colon cancer cells were routinely main-

tained in McCoy’s 5A medium, supplemented with 10% fetal

bovine serum, penicillin 100 U mL�1and streptomycin 100 mg

mL�1. HUVECs (human umbilical vein endothelial cells) were

routinely cultured in Endothelial Cell Growth Medium 2

(ECGM 2) supplemented with fetal calf serum (2%), epidermal

growth factor (5 ng mL�1), basic fibroblast growth factor (10 ng

mL�1), insulin-like growth factor (20 ng mL�1), vascular endo-

thelial growth factor (0.5 ng mL�1), ascorbic acid (1 mg mL�1),

heparin (22.5 mg mL�1), hydrocortisone (0.2 mg mL�1), penicillin

(100 U mL�1) and streptomycin (100 mg mL�1). Human fibro-

blasts were routinely maintained in DMEM supplemented with

7.5% fetal bovine serum, penicillin 100 U mL�1 and streptomycin

100 mg mL�1.

MTT cell viability assay

For cell viability experiments, Capan-1 and HCT-116 cells were

seeded into 96-well plates at 10 000 cells per well in 100 mL of

their respective culture medium. HUVECs and fibroblasts were

seeded into 96-well plates at 5000 cells per well in 100 mL of their

culture medium. One day after seeding, cells were then incubated

4 days with different doses of Eu0.333+Gd0.35

3+/[Mo(CN)8]3�/chi-

tosan nanoparticles 1b (0, 25, 50, 100 ng mL�1). Following this

incubation, cells were incubated for 4 h with 0.5 mg mL�1 of

MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium

bromide; Promega) in media. The MTT/media solution was then

removed and the precipitated crystals were dissolved in ethanol/

DMSO (1/1). The solution absorbance was read at 540 nm.


III. Results and discussion

III.1. Synthesis, structural and textural characterizations of

Ln0.333+Gdx

3+/[Mo(CN)8]3�/chitosan (Ln ¼ Eu (x ¼ 0.34),

Tb (x ¼ 0.35)) nanoparticles

Our approach consists in an association of luminescent Ln3+ (Ln¼Eu, Tb) and paramagnetic Gd3+ ions with the paramagnetic

octacyanomolybdate building block in order to obtain a bi-

functional magneto-luminescent core of the nanoparticles

enwrapped by a biopolymer chitosan. The choice of these

components was performed from the reasons given hereafter.

The paramagnetic [Mo(CN)8]3� do not efficiently absorb visible

light and prevents the quenching of the Ln3+ luminescence by

energy transfer processes contrarily to what is observed for the

[Fe(CN)6]3� building block. In association with lanthanide ions

at the macroscopic level [Mo(CN)8]3� forms very stable bulk two-

dimensional cyano-bridged coordination polymer network pre-

senting magnetic properties and the lanthanides luminescence.18

Further, the choice of the chitosan beads for the formation and

stabilization of nano-sized cyano-bridged coordination polymers

has been done due to its interesting physical and chemical

properties. The chitosan is a biocompatible, biodegradable,

bioactive, and non-toxic polymer derived from the partial

deacetylation of chitin and thus possessing free amino groups

allowing coordination of metal ions (Scheme 1a). It presents high

water solubility and can be produced in the form of porous beads

obtained by drying gel beads of the polymer chitosan under

supercritical CO2 conditions in order to provide easy circulation

of precursors into the pores and increasing the access to the

functional amino groups.16

The synthesis of Ln0.333+Gdx

3+/[Mo(CN)8]3�/chitosan (Ln ¼Eu (x ¼ 0.34), Tb (x ¼ 0.35)) nanoparticles was performed by

using a two-step procedure. The first step consists in the intra-

pore growth of the cyano-bridged network of the nanoparticles

into the chitosan matrix by step-by-step coordination of

lanthanides ions and octacyanomolybdenum in order to obtain

the nanocomposite beads containing the coordination polymer

nanoparticles (1a, 2a). The second step concerns the solubiliza-

tion of the chitosan matrix in acidic water to obtain the corre-

sponding aqueous colloidal solutions containing Ln0.333+Gdx

3+/

[Mo(CN)8]3�/chitosan (Ln ¼ Eu (x ¼ 0.34), Tb (x ¼ 0.35))

nanoparticles (1b, 2b) (Scheme 1).

Scheme 1 Schematic representation of (a) the chemical structure of

chitosan; (b) the synthesis of coordination polymer nanoparticles

Ln0.333+Gdx

3+/[Mo(CN)8]3�/chitosan (Ln¼ Eu (x¼ 0.34), Tb (x¼ 0.35)).


As the first step of our approach, two subsequent treatments of

the pristine porous chitosan beads with methanolic solutions of

Gd(NO3)3$6H2O, Ln(NO3)3$6H2O (Ln ¼ Eu, Tb) and

(N(C4H9)4)3[Mo(CN)8] allow us to obtain two types of nano-

composite beads Eu0.333+Gd0.34

3+/[Mo(CN)8]3�/chitosan 1a and

Tb0.333+Gd0.35

3+/[Mo(CN)8]3�/chitosan 2a. At each step of the

treatment, the chitosan beads were thoroughly washed with

methanol and dried in vacuo. The atomic ratio Ln and Gd vs. Mo

as inferred from elemental and Energy Dispersive Spectroscopy

(EDS) analyses is given in Table 1. Compared to the stoichi-

ometry found for the corresponding bulk compounds18 i.e. 1/1,

the nanoparticles present a lack in lanthanide ion vs. molyb-

denum (ca. 0.65/1). A similar ratio was observed in the case of

coordination polymer nanoparticles containing lanthanide and

hexacyanometallates,19a and may be attributed to the specific

step-by-step growth of the cyano-bridged framework onto the

chitosan matrix instead of the co-precipitation method employed

for the preparation of the bulk materials.

In order to obtain information about the homogeneity of the

cyano-bridged network dispersion into the chitosan beads, EDS

analysis was performed on the total internal surface of a cleaved

nanocomposite bead. As an example, Fig. 1a shows an internal

view of the cleaved nanocomposite bead 1a with the line along

which the EDS analysis was performed. Eu, Gd and Mo contents

are shown to be homogenous on the entire surface of the cleaved

bead (Fig. 1b).

As the second step, the straw-colored nanocomposite beads

were solubilized in slightly acidic water (acetate buffer, pH 4.25)

giving rise to aqueous solutions of the same color of

Eu0.333+Gd0.34

3+/[Mo(CN)8]3�/chitosan 1b or Tb0.333+Gd0.35

3+/

[Mo(CN)8]3�/chitosan 2b (Scheme 1b). It is important to note that

these colloidal solutions are extremely stable over time and no any

precipitation or aggregation of nanoparticles was observed during

few months. Such stability in time was attributed to the presence

of a residual corona of chitosan surrounding the nanoparticles.9a,19

The dry residues of these solutions present the same Ln/Gd/Mo

ratio as for the nanocomposite beads (Table 1).

The infrared (IR) spectra of the nanocomposite beads 1a and

2a and their corresponding aqueous solutions 1b and 2b show the

band at 2113 cm�1 corresponding to the stretching vibrations of

the bridging –Mo5+–CN–Ln3+– indicating the formation of the

cyano-bridged network (Table 1, ESI, Fig. S2†). Similar band

has also been observed in the case of the bulk analogous.18 As

expected, the IR spectra also present chitosan vibration bands at

3237 (NH2 and OH groups), 1660 (acetamide groups) and 1598

cm�1 (NH2 groups).19

Transmission Electronic Microscopy (TEM) observations

were performed on the nanocomposite beads 1a, 2a and on the

corresponding aqueous solutions 1b, 2b. As an example, Fig. 2a

shows a TEM image of the nanocomposite beads 1a. The

porosity of the chitosan matrix can be clearly seen as well as the

presence of non-aggregated homogeneously dispersed nano-

particles appearing as black dots into the chitosan (inset on the

left of Fig. 2a). A High Resolution Transmission Electronic

Microscopy (HRTEM) image of a single nanoparticle displaying

the atomic planes alignment is also given in the inset on the right

of Fig. 2a (ESI, Fig. S3†). The EDS analysis coupled with

HRTEM on isolated nanoparticles 1a confirmed the homoge-

neous dispersion of Mo, Eu and Gd ions in proportions identical

Nanoscale, 2011, 3, 1200–1210 | 1203

Table 1 Some relevant characteristics for the samples 1a,b and 2a,b

Composition Sample Ln/Gd/Mo ratioa IR, n(CN)/cm�1 NPs size in aqueous solution/nm

Eu0.333+Gd0.34

3+/[Mo(CN)8]3�/chitosan

1a,b 0.33/0.34/1 2113 4.5(2.4)

Tb0.333+Gd0.35


2a,b 0.33/0.35/1 2113 2.8(0.8)

a Calculated from elemental analysis.

to those obtained on assemblies of nanoparticles (i.e. a Eu/Gd/

Mo ratio of ca. 0.3/0.3/1) (ESI, Fig. S4†). Fig. 2b and c present

TEM and HRTEM images of nanoparticles 1b obtained after

solubilization of the chitosan matrix in water. They show

spherical in shape, non-aggregated and well dispersed nano-

particles with the size distribution centered at 4.5 nm. The size

distribution histogram for nanoparticles 1b is given in Fig. 2d.

The nanoparticles 2a,b present similar textural characteristics:

narrow sized spherical coordination polymer nanoparticles were

observed with the size distribution centered 2.8 nm (ESI,

Fig. S5†).

Consequently, the step-by-step coordination of the respective

precursors allowed us to achieve cyano-bridged coordination

polymer nanoparticles with a good control of the Ln/Mo stoi-

chiometry in the nanoparticle core as well as of the nanoparticles

size which cannot be achievable by using a co-precipitation

method. Note also that these nanoparticles are perfectly soluble in

aqueous solutions, which may be concentrated or diluted in water

and their pH may be increased up to 7.2. These nanoparticles may

also be dispersed into physiological media without any precipita-

tion (see Experimental part concerning the composition of the

physiological media and ESI Fig. S1† for the TEM images of this

solution). These are important requirements for the use of the

nanoparticles for potential biological applications.

III.2. Investigations on magneto-luminescent properties of

Ln0.333+Gdx

3+/[Mo(CN)8]3�/chitosan nanoparticles

Photoluminescence properties. In order to prove the bi-func-

tionality of the obtained nanoparticles, we investigate both the

Fig. 1 (a) Internal view of a cleaved bead of 1a. The yellow line represents the

(b) EDS profile curves of 1a for Eu, Gd and Mo.

1204 | Nanoscale, 2011, 3, 1200–1210

photoluminescence and the relaxivity studies of their aqueous

colloidal solutions. The photoluminescent properties of the

nanoparticles 1b, 2b were investigated at room temperature.

Fig. 3 shows the emission spectra of Eu0.333+Gd0.34

3+/

[Mo(CN)8]3�/chitosan 1b and Tb0.333+Gd0.35

3+/[Mo(CN)8]3�/chi-

tosan 2b nanoparticles under distinct excitation wavelengths. For

both, the emission is formed by a large broad band ascribed to

the chitosan intrinsic emission20 and by a series of intra-4f lines

attributed to the 5D0 / 7F0�4 (Eu3+) and 5D4 / 7F6�0 (Tb3+)

transitions. The relative intensity between the intra-4f lines and

the chitosan-related emission depends on the excitation

wavelength, in such a way that for lower excitation wavelengths

(280–340 nm) the intra-4f lines dominates, whereas for higher

excitation wavelength (350–464 nm), the opposite is observed, as

illustrated in Fig. 3 for selected excitation wavelengths. The

energy and full width at half maximum (fwhm) of the intra-4f

lines are independent on the excitation wavelength suggesting

that, in each material, the Ln3+ ions occupy the same average

local environment. Moreover, for the particular case of the Eu3+-

containing material 1b the presence of a single line for the non-

degenerated 5D0 / 7F0 transition, the Stark splitting of the 7F1,2

levels into 3 and 4 components and the high relative intensity of

the 5D0 / 7F2 transition (ESI, Fig. S6†), indicates that the Eu3+

ions occupy a low symmetry local coordination site without an

inversion centre.21 Nevertheless, the high fwhm of the intra-4f

lines (e.g. 44 � 1 cm�1 for the 5D0 /7F0 transition) indicates

a high degree of disorder for the Eu3+ local coordination (site-to-

site variations). Accordingly, it should be noted that Eu3+ local

site disorder has been found in the case of the Eu(H2O)5-

[Mo(CN)8] bulk coordination polymer material.18

line (total length¼ 600 mm) along which the profile curves were obtained;


Fig. 2 (a) TEM image of the nanocomposite beads 1a. Insets: magnification of this image and HRTEM image of a single nanoparticle; (b) TEM and (c)

HRTEM images of an aqueous colloidal solution of 1b; (d) Size distribution histogram obtained for the nanoparticles 1b. White circles are given as guide

for the eyes.

Fig. 4 displays the selective excitation spectra monitored

within the large broad band (475 nm) and within the Eu3+ (1b)

and Tb3+ (2b) transitions (612 and 544 nm, respectively). The

excitation spectra monitored within the chitosan-related emis-

sion at 475 nm are similar for the Eu3+ and Tb3+-containing

Fig. 3 Room-temperature emission spectra of (a) 1a and (b) 2a excited

at (1) 280, (2) 340, (3) 420, and (4) 460 nm. The inset shows a magnifi-

cation of the 5D4 / 7F2-0 (Tb3+) transitions.


materials, being formed of a broad band with two main

components at ca. 345 and 375 nm ascribed to the chitosan

excited states.22 For intra-4f monitored wavelengths, the excita-

tion spectra reveal clearly the presence of the chitosan-related

excited states at ca. 345 nm and at ca. 375 nm superimposed on

Fig. 4 Room-temperature excitation spectra of (a) 1b and (b) 2b

monitored at (1) 475, (2) 544, and (3) 612 nm. The inset shows a magni-

fication of the 7F0 / 5D2 (Eu3+) transition.

Nanoscale, 2011, 3, 1200–1210 | 1205

the 7F0 / 5L6, 5D2 (1b) and 7F6 / 5D4 (2b) transitions. The very-

low relative intensity of the intra-4f lines points out that the Ln3+

ions are mainly populated via the chitosan-related excited states,

rather than by direct intra-4f excitation. Chitosan-to-Ln3+ energy

transfer, already reported for lanthanide-containing chitosan–

silica hybrids,20 can occur through the dipole–dipole, dipole–2l

pole (l ¼ 2, 4, and 6) and exchange mechanisms.23

The decay curves of the 5D0 (Eu3+) and 5D4 (Tb3+) excited

states, monitored at 612 and 544 nm, respectively, and under

excitation at 350 nm, are well modeled by a single exponential

function yielding 5D0 (1b) and 5D4 (2b) lifetime values of 0.235 �0.002 ms and 0.415 � 0.046 ms, respectively. The single expo-

nential behavior of the emission decay curves is in good agree-

ment with the presence of a single average local-environment for

the Ln3+ ions.

Thus, the obtained aqueous colloidal solutions of the nano-

particles exhibit at room temperature the typical fluorescence

characteristic for Eu3+ (5D0 / 7F0�4 transitions) or Tb3+ (5D4 /7F6�2 transitions) ions under excitation in UV region, while

a green luminescence of chitosan shell is observed when the

nanoparticles are excited in the visible region. As a result, the

luminescence of our nanoparticles may allow for multiplexing

because different excitation sources provide different color of

luminescence, red for lanthanides and green for chitosan shell.

When compared with other inorganic nanoparticles such as dye-

doped nanoparticles and QDs,24 the Ln333+Gdx

3+/[Mo(CN)8]3(Ln ¼ Eu (x ¼ 0.34), Tb (x ¼ 0.35)) cyano-bridged coordination

polymer nanoparticles combine the advantages of high photo-

bleaching threshold and good chemical stability with readily

tunable spectral properties. In particular, the bimodal emission

with distinct dynamics (the long-lived Ln3+ narrow red lines and

the short-lived chitosan broad green band) may be easily attained

by controlling physical (excitation wavelength) and chemical

(Ln3+ ratio) parameters, rather than making use of the size-

dependent excitation and emission wavelengths typical of

colloidal semiconductor nanoparticles. Note that bimodal (or

multicolored) emission can be applied in multiplexed detection

and imaging of therapeutic cells both in vitro and in vivo,25

multiplex fluorescent detection assays in which a specific fluo-

rescence image could be selected using appropriate optical filters

and innovative barcodes systems.26

Relaxivity properties. The longitudinal and transverse relax-

ivities of the nanoparticles were also estimated at room temper-

ature in aqueous solutions. The 1H NMR relaxometry

characterization of the aqueous solutions Ln0.333+Gdx

3+/

[Mo(CN)8]3�/chitosan nanoparticles (Ln ¼ Eu (x ¼ 0.34),

Tb (x ¼ 0.35)) 1b, 2b was performed by measuring the longitu-

dinal and the transverse nuclear relaxation times T1 and T2, in

the frequency range 10 KHz # n # 100 MHz, for T1, and 8 MHz

# n # 60 MHz, for T2. Relaxivity values, r, are simply defined as

the inverse of the relaxation time normalized for the contrast

agent concentration, once previously corrected by the host

diamagnetic contribution. So, the efficiency of the MRI contrast

agents may be determined by measuring the nuclear relaxivities

r1p,2p defined as:27

rip ¼ [(1/Ti)meas � (1/Ti)dia]/c, i ¼ 1,2

1206 | Nanoscale, 2011, 3, 1200–1210

where (1/Ti)meas is the measured value on the sample with

concentration c (mmol L�1) of magnetic center (0.0267 mmol L�1

in our case), and (1/Ti)dia refers to the nuclear relaxation rate of

the diamagnetic host solution (water in our case).

Fig. 5 reports the frequency dependence of r1p and r2p for

Eu0.333+Gd0.34

3+/[Mo(CN)8]3�/chitosan 1b, together with the

values for the commercial contrast agents Omniscan� and Gd-

DTPA�. As can be seen, the r1p values obtained for 1b are

comparable to or slightly higher than the ones observed for Gd-

DTPA�, while the values of r2p relaxivities of our sample are

higher in comparison to the measured values for Omniscan�.

The same values were observed in the case of 2b. For this reason,

it can be concluded that our nanoparticles behind their lumi-

nescent properties may also be used as a positive contrast agent.

III.3. Nanoparticles internalization, intracellular detection and

cytotoxicity tests

Taking into account that our nanoparticles present magneto-

luminescent properties, we estimate their internalization into the

living cells and the possibility of their intracellular detection.

Note that the uptake of cyano-bridged coordination polymer

nanoparticles has never been reported previously. The cellular

uptake of our nanoparticles was analysed by using a series of

cancer cell lines such as colorectal HCT-116, pancreatic Capan-1

and also normal human fibroblasts and human umbilical endo-

thelial HUVEC cells. For this experiment, cells were incubated

during 6 h at 37 �C with 100 ng mL�1 of the nanoparticles 1b in

serum free culture medium and analyzed by confocal laser

scanning microscopy (CLSM) of living cells in order to assess

internalization and intracellular distribution of the nano-

particles. The confocal microscopy of living cells avoids the cell

fixation step, a potential cause of artefacts on the entry and the

cellular localization of the nanoparticles. Moreover, the 0.6 mm

width of Z stacks ensures that the labelling is intracellular and

not retains at the outside of the plasma membrane. For all

investigated cells the green emission related to the chitosan shell

of the nanoparticles is clearly seen under excitation in the visible

region at 489 nm (Fig. 6b) demonstrating that the nanoparticles

1b were successfully internalized by all used cancer (HCT116 and

Capan-1) and normal cells (HUVEC and fibroblasts). This result

is not surprising regarding with their ultra-small size of 2.8–4.5

nm. More importantly is that the presence of the nanoparticles

into these cells is highly detectable by fluorescence microscopy at

an extremely low dose. Co-staining of cell nuclei and lysosome

were also performed. For this reasons, nuclei were loaded with

5 mg mL�1 Hoechst 33342 (blue) (Fig. 6a) and lysosomes were

labelled by 50 nM lysotracker (red) (Fig. 6c). Merged images of

nanoparticles fluorescence and lysosome marker show that in all

cases the nanoparticles, which appear as orange spots, were

mostly localized into lysosomes (Fig. 6d). Such cell localisation is

typical for the most of the inorganic nanoparticles and is mainly

due to the endocytosis pathway. Note that the effect of particle

uptake and optical detection can be used to label cells and follow

their pathway or fate.

In the in vivo imaging area, some challenges have been iden-

tified and the foremost obstacle is the difficulty to obtain new

contrast agents without cytotoxic effects. To analyse the toxicity

of these nanoparticles, normal human fibroblasts, umbilical vein


Fig. 5 Longitudinal (r1p) (top) and transversal (r2p) (bottom) relaxivities of 1b (-), collected at T z 25 �C, compared to relaxivities reported for the

commercial compounds Gd-DTPA� and Omiscan� (:).

endothelial cells (HUVECs) and human colorectal (HCT-116)

and pancreatic (Capan-1) cancer cell lines were treated 4 days

with increasing doses of Eu0.333+Gd0.34


nanoparticles 1b (with concentrations of 0, 25, 50 and 100 ng

mL�1). Cell viability was monitored for 4 days using MTT assay

to measure mitochondrial enzyme activity. Fig. 7 shows that

these nanoparticles present no toxicity, neither in cancer cells

analysed in this study (human colorectal and pancreatic cancer

cells, Fig. 7a and b) nor in normal cells (human fibroblasts and

umbilical endothelial HUVEC cells, Fig. 7c and d).

The toxicity tests also demonstrate a high stability of these

nanoparticles in aqueous solutions. During 4 days at 37 �C no

toxic Gd3+ or Ln3+ leaching has been detected. The stability of the

nanoparticles in aqueous and physiological solutions has also

been confirmed by the elemental analysis of the mother solution

Fig. 6 Localization of nanoparticles 1b in living cancer (HCT-116 and Capa

nanoparticles 1b. Merged pictures represent the co-localization of nanoparticl

of two independent experiments. Bars represent 4 mm.


after precipitation of the nanoparticles in which no presence of

free Gd3+ ion has been detected. Note that the high stability of

the cyano-bridged coordination polymer nanoparticles is not

surprising because Prussian Blue aggregated nanoparticles are

well known as an effective per os treatment for human radioac-

tive Cs+ and Tl+ decontamination.28

An interesting point to note is that these ultra-small inorganic

nanoparticles maybe interesting for imaging because they may be

rapidly eliminated from the body. Recently three criteria for

distinguishing inorganic nanoparticles that can present potential

clinical utility were proposed: (i) a low hydrodynamic diameter

permitting complete elimination from the body; or (ii) a formu-

lation with completely nontoxic components; or (iii) biodegrad-

ability to clearable components. It was shown that the inorganic

nanoparticles presenting the hydrodynamic diameter lower than

n-1), or normal (HUVECs and fibroblasts) cell lines, incubated 6 h with

es 1b (100 ng mL�1) with the lysosomal marker. Images are representative

Nanoscale, 2011, 3, 1200–1210 | 1207

Fig. 7 Absence of toxicity of Eu0.333+Gd0.34


nanoparticles 1b in human normal and cancer cells. (A) Human colo-

rectal cancer cells (HCT116), (B) human pancreatic cancer cells (Capan-

1), (C) human fibroblasts and (D) human umbilical endothelial HUVEC

cells are incubated for 4 days in the absence (0 ng mL�1) or in the presence

of increasing doses of nanoparticles (25, 50 and 100 ng mL�1). After

treatment, cell proliferation was measured by MTT assay (see Experi-

mental part). Values represent the mean � standard deviations of trip-

licates from a typical experiment and were confirmed in two additive

experiments.

5.5 nm may be rapidly (during around 4 h) and efficiently

excreted from the body by renal filtration while the larger

nanoparticles cannot be evacuated and will be kept in the body

for several days.29 Taking into account the small size (2.8–4.5

nm) of the nanoparticles described here they may be completely

eliminated by a renal clearance that satisfy the first criteria of

potential clinical utility. In addition, high stability of these

nanoparticles at low pH make them interesting in imaging or

labeling of some cell compartments such as lysosomes, large

acidic vesicles also called phagolysosomes or certain tissue

environment such as the gastrointestinal tract where the physi-

ological pH is less than 5.

IV. Conclusion

The development of multifunctional nanoparticles for imaging is

one of the main objectives in the field of biology and nano-

medicine. The main requirements for such nanoparticles include

good image contrast at low dosage, high stability under physi-

ological conditions which may be varying depending on the

imaging objects, organs or body region, low toxicity and rapid

1208 | Nanoscale, 2011, 3, 1200–1210

elimination from the body. The research results described in this

article are to propose a novel approach toward designing a new

family of efficient imaging probes based on cyano-bridged

coordination polymer nanoparticles presenting magneto-lumi-

nescent bi-functionality, ultra small size and high stability. This

approach presents an alternative way to achieve multifunctional

nanoparticles in comparison with designing of large sized

complex hybrid nanoparticles where different components are

incorporated together or attached onto the nanoparticles

surface.

The approach that we adopted in order to obtain aqueous

colloidal solutions of cyano-bridged coordination polymer

nanoparticles Ln0.333+Gdx

3+/[Mo(CN)8]3�/chitosan (Ln ¼ Eu

(x ¼ 0.34), Tb (x ¼ 0.35)) consists in the consecutive growing of

the cyano-bridged metal network at the functional amino groups

into the pores of the chitosan matrix and then in solubilization of

the most part of the chitosan in water. Thus, the as-obtained

nanoparticles are spherical in shape, non-aggregated and well

dispersed in water or alcohols with mean sizes values in the range

2.8–4.5 nm, presenting a narrow size distribution according to

the TEM and HRTEM measurements. The nanoparticles are

perfectly soluble in aqueous solutions which may be concen-

trated or diluted in water and their pH may be increase up to 7.2.

These colloidal solutions are also stable and no aggregation or

nanoparticles degradation has been observed after few months.

These properties are the first requirements for the potential use of

these nanoparticles for biological applications.

In order to prove the bi-functionality of our nanoparticles, we

evaluate their potential for MR contrast enhancement and their

optical properties. The r1p relaxivity of aqueous colloidal solu-

tions of the nanoparticles is slightly higher than or comparable to

the ones of the commercial contrast agents Omniscan� and Gd-

DTPA� indicating that our nanoparticles may be considered as

an efficient positive contrast agent for MRI. In addition to these

properties in terms of relaxivity, the nanoparticles exhibit the

typical fluorescence for Eu3+ (5D0 / 7F0–4 transitions) or

Tb3+(5D4 / 7F6–2 transitions) under excitation in UV region,

while a green luminescence of chitosan shell is observed when the

nanoparticles are excited in the visible region. The magneto-

luminescent property of the nanoparticles is suggestive of their

use both for the luminescence labeling of cells and as new

contrast agents for MRI imaging.

We also evaluate the nanoparticle uptake by living cells and

their fluorescence detection in vitro. The results clearly show that

these nanoparticles not only were rapidly internalized by both

healthy (HUVECs and fibroblasts) and living cancer (HCT-116

and Capan-1) cells, and localised into the lysosomes, but they can

be highly detectable by fluorescence microscopy into these cells at

an extremely low dose. Cell viabilities of human cancer or normal

cells such as colorectal (HCT-116) and pancreatic cancer

(Capan-1) cell lines, human fibroblasts and umbilical vein

endothelial cells (HUVEC) were unaffected by these nano-

particles in the concentration range allowing their cellular

imaging. The toxicity tests also demonstrate a high stability of

these nanoparticles in aqueous solutions and no leaching of toxic

Gd3+ or Ln3+ ions was detected.

These results present the first step toward a design of new

multi-modal imaging probes of interest based on cyano-bridged

metallic nanoparticles. Further works on functionalization of the


nanoparticle surface with biological molecules in view of

particular cells targeting are actually under run.

Acknowledgements

The authors thank Mme Corine Reibel (ICGM, Montpellier,

France) for magnetic measurements. E.C. thanks the Russian

Academy of Science and the French Ministry of Foreign Affairs.

The authors also thank the Network of Excellence MAGMANet

for funds support. M.G. and M.G.-B. thank Prof. Dr Kurt von

Figura (G€ottingen) for cell cultures.

References

1 (a) M. M.-C. Cheng, G. Cuda, Y. L. Bunimovich, M. Gaspari,J. R. Heath, H. D. Hill, C. A. Mirkin, A. J. Nijdam,R. Terracciano, T. Thundat and M. Ferrari, Curr. Opin. Chem.Biol., 2006, 10, 11; (b) F. J.-J. Toublan, S. Boppart andK. S. Suslick, J. Am. Chem. Soc., 2006, 128, 3472.

2 (a) For example: H. Park, Small, 2008, 4, 192; (b) New DeliverySystems for Controlled Drug Release from Naturally OccurringMaterials, ACS Symposium Series, 2008, vol. 992, ch. 9, pp153–173; (c) J. Gao, G. Liang, J. S. Cheung, Y. Pan, Y. Kuang,F. Zhao, B. Zhang, X. Zhang, E. X. Wu and B. Xu, J. Am. Chem.Soc., 2008, 130, 11828; (d) R. Zhang, C. Wu, L. Tong, B. Tang andQ.-H. Xu, Langmuir, 2009, 25, 10153; (e) R. Guo, L. Zhang,H. Qian, R. Li, X. Jiang and B. Liu, Langmuir, 2010, 26, 5428; (f)J. Zhang, H. Sun and P. X. Ma, ACS Nano, 2010, 4, 1049; (g)M. Liong, J. Lu, M. Kovochich, T. Xia, S. G. Ruehm, A. E. Nel,F. Tamanoi and J. I. Zink, ACS Nano, 2008, 2, 889; (h) Nano-Biotechnology in using Enzymes for Environmental Remediation:Single-Enzyme Nanoparticles, Nanotechnology and the Environment,ACS Symposium Series Volume 890, ed. J. Kim and J. W. Grate,2004, vol. 220, ch. 29; (i) M. Chen, Y. N. Kim, H. M. Lee, C. Liand S. O. Cho, J. Phys. Chem. C, 2008, 112, 8870; (j)N. Nasongkla, E. Bey, J. Ren, H. Ai, C. Khemtong, J. S. Guthi, S.-F. Chin, A. D. Sherry, D. A. Boothman and J. Gao, Nano Lett.,2006, 6, 2427; (k) F. M. Brunel, J. D. Lewis, G. Destito,N. F. Steinmetz, M. Manchester, H. Stuhlmann and P. E. Dawson,Nano Lett., 2010, 10, 1093; (l) P. A. Bertin, J. M. Gibbs, C. K.-F. Shen, C. S. Thaxton, W. A. Russin, C. A. Mirkin andS. T. Nguyen, J. Am. Chem. Soc., 2006, 128, 4168; (m) K. C. Weng,C. O. Noble, B. Papahadjopoulos-Sternberg, F. F. Chen,D. C. Drummond, D. B. Kirpotin, D. Wang, Y. K. Hom, B. Hannand J. W. Park, Nano Lett., 2008, 8, 2851; (n) J. Gao, H. Gu andB. Xu, Acc. Chem. Res., 2009, 42, 1097.

3 (a) J. S. Kim, W. J. Reiter, K. M. L. Taylor, H. An, W. Lin andW. Lin, J. Am. Chem. Soc., 2007, 129, 8962; (b) Q. Chang, L. Zhu,C. Yu and H. Tang, J. Lumin., 2008, 128, 1890; (c) M. Chen,Y. Nam Kim, H. Moo Lee, C. Li and S. O. Cho, J. Phys. Chem. C,2008, 112, 8870; (d) L. O. Cinteza, T. Y. Ohulchanskyy, Y. Sahoo,E. J. Bergey, R. K. Pandey and P. N. Prasad, Mol. Pharmaceutics,2006, 3, 415; (e) C.-W. Lai, Y.-H. Wang, C.-H. Lai, M.-J. Yang,C.-Y. Chen, P.-T. Chou, C.-S. Chan, Y. Chi, Y.-C. Chen and J.-K. Hsiao, Small, 2008, 4, 218.

4 (a) M.-J. Li, Z. Chen, V. W.-W. Yam and Y. Zu, ACS Nano, 2008, 2,905; (b) S.-H. Wu, Y.-S. Lin, Y. Hung, Y.-H. Chou, Y.-H. Hsu,C. Chang and C.-Y. Mou, ChemBioChem, 2008, 9, 53; (c) X. Ji, J.Phys. Chem. C, 2007, 111, 6245; (d) L. Wang, J. Bai, Y. Li andY. Huang, Angew. Chem., Int. Ed., 2008, 47, 2439; (e) L. L. Ma,M. D. Feldman, J. M. Tam, A. S. Paranjape, K. K. Cheruku,T. A. Larson, J. O. Tam, D. R. Ingram, V. Paramita, J. W. Villard,J. T. Jenkins, T. Wang, G. D. Clarke, R. Asmis, K. Sokolov,B. Chandrasekar, T. E. Milner and K. P. Johnston, ACS Nano,2009, 3, 2686; (f) Y. S. Lin, Chem. Mater., 2006, 18, 5170; (g)J. Kim, J. Am. Chem. Soc., 2006, 128, 688; (h) Y. H. Xu, J. Bai andJ.-P. Wang, J. Magn. Magn. Mater., 2007, 311, 131; (i) J. Lee,W. Hasan, M. H. Lee and T. W. Odom, Adv. Mater., 2007, 19, 4387.

5 (a) J. Larionova, Y. Guari, C. Sangregorio and C. Guerin, New J.Chem., 2009, 33, 1177; (b) L. Catala, F. Volatron, D. Brinzei andT. Mallah, Inorg. Chem., 2009, 48, 3360; (c) E. Dujardin andS. Mann, Adv. Mater., 2004, 16, 1125.


6 (a) S. Vaucher, M. Li and S. Mann, Angew. Chem., Int. Ed., 2000, 39,1793; (b) S. Mann, J. Fielden, M. Li, E. Dujardin and S. Mann, NanoLett., 2002, 2, 225; (c) L. Catala, T. Gacoin, J.-P. Boilot, E. Riviere,C. Paulsen, E. Lhotel and T. Mallah, Adv. Mater., 2003, 15, 826;(d) Y. Guari, J. Larionova, Ch. Blanc, Ph. Dieudonn�e, A. Tokarevand Ch. Gu�erin, Langmuir, 2009, 25, 1138; (e) E. Chelebaeva,Y. Guari, J. Larionova, A. A. Trifonov and Ch. Gu�erin, Chem.Mater., 2008, 20, 1367; (f) J. Larionova, Y. Guari, A. Tokarev,E. Chelebaeva, C. Luna, C. Sangregorio, A. Caneschi andCh. Gu�erin, Inorg. Chim. Acta, 2008, 361, 3988; (g) J. Larionova,Y. Guari, H. Sayegh and Ch. Gu�erin, Inorg. Chim. Acta, 2007, 360,3829; (h) G. Clavel, J. Larionova, Y. Guari and Ch. Gu�erin,Chem.–Eur. J., 2006, 12, 3798; (i) T. Uemura and S. Kitagawa, J.Am. Chem. Soc., 2003, 125, 7814; (j) L. Catala, A. Gloter,O. Stephan, G. Rogez and T. Mallah, Chem. Commun., 2006, 1018;(k) D. Brinzei, L. Catala, C. Mathoni�ere, W. Wensdorfer,A. Gloter, O. Stephan and T. Mallah, J. Am. Chem. Soc., 2007,129, 3778; (l) J. M. Domingez-Vera and E. Colacio, Inorg. Chem.,2003, 42, 6983; (m) J. Larionova, L. Salmon, Y. Guari, A. Tokarev,K. Molvinger, G. Molnar and A. Bousseksou, Angew. Chem., Int.Ed., 2008, 47, 8236; (n) P. Zhou, D. Xue, H. Luo and X. Chen,Nano Lett., 2002, 2, 845; (o) J. G. Moore, E. J. Lochner,C. Ramsey, N. S. Dalal and A. E. Stiegman, Angew. Chem., Int.Ed., 2003, 42, 2741; (p) J. Larionova, Y. Guari, C. Sangregorio andCh. Gu�erin, New J. Chem., 2009, 33, 1177; (q) B. Folch, Y. Guari,J. Larionova, C. Luna, C. Sangregorio, C. Innocenti, A. Caneschiand Ch. Gu�erin, New J. Chem., 2008, 32, 273; (r) G. Clavel,Y. Guari, J. Larionova and Ch. Gu�erin, New J. Chem., 2005, 29,275; (s) R. Mouawia, J. Larionova, Y. Guari, S. Oh, Ph. Cook andE. Prouzet, New J. Chem., 2009, 33, 2449.

7 (a) K. M. L. Taylor, A. Jin and W. Lin, Angew. Chem., Int. Ed., 2008,47, 7722; (b) M. D. Rowe, C.-C. Chang, D. H. Thamm, S. L. Kraft,J. F. Harmon, Jr, A. P. Vogt, B. S. Sumerlin and S. G. Boyes,Langmuir, 2009, 25, 9487; (c) K. M. L. Taylor, W. J. Rieter andW. Lin, J. Am. Chem. Soc., 2008, 130, 14358; (d) G. A. Pereira,J. A. Peters, F. A. Almeide Paz, J. Rocha and C. F. G. Geraldes,Inorg. Chem., 2010, 49, 2969.

8 P. Horcajada, T. Chalati, Ch. Serre, B. Gillet, C. Sebrie, T. Baati,J. F. Eubank, D. Heurtaux, P. Clayette, Ch. Kreuz, J.-S. Chang,Y. K. Hwang, V. Marsaud, Ph.-N. Bories, L. Cynober, S. Gil,G. F�erey, P. Couvreur and R. Gref, Nat. Mater., 2009, 9, 172.

9 (a) Y. Guari, J. Larionova, M. Corti, A. Lascialfari, M. Marinone,G. Poletti, K. Molvinger and Ch. Gu�erin, Dalton Trans., 2008,3658; (b) M. Shokouhimehr, E. S. Soehnlen, A. Khitrin, S. Basuand S. D. Huang, Inorg. Chem. Commun., 2010, 13, 58; (c)S. D. Huang, Y. Li and M. Sholouhimer, U. S. Pat. Appl. Publ.,2010, US 20100254912 A1 20101007.

10 M. D. Rowe, D. H. Thamm, S. L. Kraft and S. G. Boyes,Biomacromolecules, 2009, 10, 983.

11 K. M. L. Taylor, W. J. Rieter and W. Lin, J. Am. Chem. Soc., 2008,130, 14358.

12 R. Nishiyabu, N. Hashimoto, T. Cho, K. Watanabe, T. Yasunaga,A. Endo, K. Kaneko, T. Niidome, M. Murata, C. Adachi,Y. Katayama, M. Hashizume and N. Kimizuka, J. Am. Chem. Soc.,2009, 131, 2151.

13 E. Chelebaeva, L. Raehm, K.-O. Durand, Y. Guari, J. Larionova,Ch. Gu�erin, A. Trivonfov, M. Willinger, K. Thangavel,A. Lascialfari, O. Mongin, Y. Mir and M. Blanchard-Desce, J.Mater. Chem., 2010, 20, 1877.

14 W. J. Rieter, K. M. L. Taylor, H. An, W. Lin and W. Lin, J. Am.Chem. Soc., 2006, 128, 9024.

15 (a) J. P. Leipoldt, L. D. C. Bok and P. J. Ciliers, Z. Anorg. Allg.Chem., 1974, 407, 350; (b) J. Van de Poel and H. M. Neumann,Inorg. Synth., 1968, 11, 53; (c) C. J. Corden, J. A. Cunningham andR. Eisenberg, Inorg. Chem., 1970, 9, 356.

16 (a) R. Valentin, K. Molvinger, F. Quignard and D. Brunel, New J.Chem., 2003, 27, 1690; (b) K. Molvinger, F. Quignard, D. Brunel,M. Boissi�ere and J.-M. Devoiselle, Chem. Mater., 2004, 16,3367.

17 G. Ferrante and S. Sykora, Adv. Inorg. Chem., 2005, 57, 405.18 (a) E. Chelabaeva, J. Larionova, Y. Guari, R. A. S. Ferreira,

L. D. Carlos, P. A. Almeida Paz, A. Trifonov and Ch. Gu�erin,Inorg. Chem., 2008, 47, 775; (b) E. Chelabaeva, J. Larionova,Y. Guari, R. A. S. Ferreira, L. D. Carlos, P. A. Almeida Paz,A. Trifonov and Ch. Gu�erin, Inorg. Chem., 2009, 48, 5983.

Nanoscale, 2011, 3, 1200–1210 | 1209

19 (a) Y. Guari, J. Larionova, K. Molvinger, B. Folch and Ch. Gu�erin,Chem. Commun., 2006, 2613; (b) B. Folch, J. Larionova, Y. Guari,K. Molvinger, C. Luna, C. Sangregorio, C. Innocenti, A. Caneschiand Ch. Gu�erin, Phys. Chem. Chem. Phys., 2010, 12, 12760.

20 F. Liu, L. D. Carlos, R. A. S. Ferreira, J. Rocha, M. C. Ferro,A. Tourrette, F. Quignard and M. Robitzer, J. Phys. Chem. B,2010, 114, 77.

21 L. D. Carlos, R. A. S. Ferreira, V. D. Bermudez and S. J. L. Ribeiro,Adv. Mater., 2009, 21, 509.

22 S. S. Silva, R. A. S. Ferreira, L. Fu, L. D. Carlos, J. F. Mano,R. L. Reis and J. Rocha, J. Mater. Chem., 2005, 15, 3952.

23 P. P. Lima, S. S. Nobre, R. O. Freire, S. A. J�uior, R. A. S. Ferreira,U. Pischel, O. L. Malta and L. D. Carlos, J. Phys. Chem. C, 2007,111, 17627.

24 (a) E. Herz, H. Ow, D. Bonner, A. Burns and U. Wiesner, J. Mater.Chem., 2009, 19, 6341; (b) S. Hohng and T. Ha, J. Am. Chem. Soc.,2004, 126, 1324; (c) H. C. Fischer, L. C. Liu, K. S. Pang andW. C. W. Chan, Adv. Funct. Mater., 2006, 16, 1299.

1210 | Nanoscale, 2011, 3, 1200–1210

25 Y. T. Lim, Y.-W. Noh, J.-H. Cho, J. H. Han, B. S. Choi, J. Kwon,K. S. Hong, A. Gokarna, Y.-H. Cho and B. H. Chung, J. Am.Chem. Soc., 2009, 131, 17145.

26 K. A. White, D. A. Chengelis, K. A. Gogick, J. Stehman, N. L. Rosiand S. Petoud, J. Am. Chem. Soc., 2009, 131, 18069.

27 S. Laurent, L. Vander Elst, A. Roch and R. N. Muller, in NMR, MRI,mSR and Mossbauer Spectroscopies in Molecular Magnets, ed.P. Carretta and A. Lascialfari, Springer-Verlag, Italia, 2007, p. 71.

28 (a) R. Koncki, Crit. Rev. Anal. Chem., 2002, 32, 79; (b) S. Ayrault,C. Loos-Neskovic, M. Fedoroff and E. Garnier, Talanta, 1994, 41,1435; (c) L. Roberts, Science, 1987, 238, 1028; (d) D. Wenker,B. Spiess and P. Laugel, Food Addit. Contam., 1990, 7, 375; (e)H. J. Byker, in Electrochromic Materials II, ed. K. C. Ho and D. A.MacArthur, The Electrochemical Society, Pennington, NJ, 1994,vol. 94-2, p. 3; (f) S. Ferlay, T. Mallah, R. Ouahes, P. Veillet andM. Verdaguer, Nature, 1995, 378, 701.

29 H. S. Choi, W. Liu, P. Misra, E. Tanaka, J. P. Zimmer, B. I. Ipe,M. G. Bawendi and J. V. Frangioni, Nat. Biotechnol., 2007, 25, 1165.


Nanoscale coordination polymers exhibiting luminescence properties and NMR relaxivity

Documents