Interactions between inorganic nanoparticles and cellulosenanofibrils

Tiina Nypelo • Hanna Pynnonen •

Monika Osterberg • Jouni Paltakari •

Janne Laine

Received: 31 October 2011 / Accepted: 20 January 2012 / Published online: 5 February 2012

� Springer Science+Business Media B.V. 2012

Abstract Nanofibrillated cellulose (NFC) is increas-

ingly utilized in materials and biomedical applications

consequently increasing interest in the modification of

its surface properties. Besides modification using

polyelectrolytes and polysaccharides, NFC can be

combined with solid particles enabling formation of

fibril network loaded with particles. Use of particles

enabling easy functionalization could be beneficial for

the development of hybrid structures, and lead to

preparation of nanocomposites and functional materi-

als. In order to explore interactions related to prepa-

ration of such structures, the interactions between

nanosized precipitated calcium carbonate (nanoPCC)

and nanoclay particles and NFC were examined by

observing adsorption of the particles on NFC substrate

using a quartz crystal microbalance with dissipation

monitoring (QCM-D) and atomic force microscopy

(AFM) imaging. By a treatment with carboxymethy-

lated cellulose (CMC), the anionicity of the NFC

substrate could be increased, providing an additional

tool to affect the interplay between NFC and the

inorganic particles. For slightly cationic nanoPCC

particles an increase in the anionicity of the NFC by

the CMC treatment increased the affinity, while the

opposite was true for anionic nanoclay. Additionally,

for interactions between nanoclay and NFC, disper-

sion stability was an important factor. QCM-D was

successfully used to examine the adsorption charac-

teristics of nanoparticles although the technique is

commonly used to study the adsorption of thin

polymer layers. Distinct adsorption characteristics

were observed depending on the nanoparticle used;

nanoclay particles deposited as a thin layer, whereas

nanoPCC particles formed clusters.

Keywords Cellulose nanofibrils � Hybrid materials �Nanoparticle adsorption � Nanoclay �Precipitated calcium carbonate

Introduction

Demand for environmentally sound materials and

advances in nanotechnology have led to the increasing

development of nanomaterials of sustainable origin.

Among the natural substances, lignocellulosic mate-

rials have gained an extensive amount of research

interest and have been suggested to replace oil-based

plastics in packaging (Aulin et al. 2010a), to benefit in

biomedical (Czaja et al. 2007) as well as in electronics

T. Nypelo (&) � H. Pynnonen � M. Osterberg �J. Paltakari � J. Laine

Department of Forest Products Technology, Aalto

University School of Chemical Technology, P.O. Box

16300, 00076 Aalto, Finland

e-mail: tiina.nypelo@aalto.fi

M. Osterberg

LUT Chemistry, Lappeenranta University of Technology,

P.O. Box 20, 53851 Lappeenranta, Finland

123

Cellulose (2012) 19:779–792

DOI 10.1007/s10570-012-9656-x

applications (Okahisa et al. 2009), to name a few. In

forest products technology, development of cellulose

nanomaterials has provided a way to expand the

research scope to applications outside traditional

paper products leading to the multidisciplinary liaison

of biomaterial, physical and chemical engineering.

In forest products research, cellulose nanomaterials

are typically derived from wood. By combining

chemical pretreatment of pulp with mechanical refin-

ing, cellulose fibers can be disintegrated into nano-

sized fibrils (Paakko et al. 2007) or processed into

cellulose nanocrystals (Habibi et al. 2010). Cellulose

nanofibril material, or nanofibrillated cellulose (NFC)

as it is commonly referred to, is of particular interest as

a strength promoter (Nakagaito and Yano 2004; Ahola

et al. 2008a; Guimond et al. 2010; Taipale et al. 2010).

By combining pretreatment of pulp with mechanical

refining, cellulose fibers can be disintegrated more

easily. Carboxymethylation (Wagberg et al. 2008), for

example, increases the charge of the fibrils, assisting in

preparation of stable dispersions as well as enabling

further modification. A cationic pretreatment also

facilitates efficient disintegration, further widening the

applicability (Aulin et al. 2010b; Olszewska et al.

2011).

Wood-based NFC is partly crystalline (Aulin et al.

2009). However, as expected, its properties depend on

the method of manufacturing as well as the raw

material used. Crystallinity, together with the ability

of the fibrils to form a dense network, makes NFC a

potential barrier material. However, for sufficient

barrier strength, fibril modification or incorporation

with other substances is often required (Hult et al.

2010; Rodionova et al. 2010). In an increasing number

of publications NFC is pressed into thin films (Hen-

riksson et al. 2008). These films are flexible, and

depending on the material properties, transparent

(Yano et al. 2005; Nogi et al. 2009). Besides as

barrier materials, such films are suggested to be

applicable, for example, in flexible screens (Okahisa

et al. 2009). In addition to the foregoing application

possibilities, NFC is increasingly reported to be

applicable in composites, and more specifically, in

nanocomposites (Hubbe et al. 2008; Eichhorn et al.

2010). The majority of the applications are based on

the ability of NFC to affect composite strength

properties, an effect that can be further enhanced by

combining nanofibrils with chitosan (Fernandes et al.

2011) or hydroxyethyl cellulose (Sehaqui et al. 2011).

Besides development of organic nanomaterials,

nanotechnology research is concentrated on utilizing

nanoparticles of inorganic origin. Clay nanoparticles,

for example, are typically used as fillers in polymeric

composites (Utracki et al. 2007). The individual

nanoclay sheet has a thickness of only a few nanome-

ters and they are held together by van der Waals and

electrostatic forces (Van Olphen 1977; Solomon and

Hawthorne 1983; Uddin 2008). If not efficiently

exfoliated, the sheets appear in dispersions as stacks

of particles. The basal planes of the clay sheets have a

permanent anionic charge due to isomorphous substi-

tution in the structure, while the edges possess positive

charges at low pH and negative charges at high pH

(Van Olphen 1977). The net charge of particles is,

however, always negative. Changes in charging of

clay particle edges have been noted to induce varying

particle conformations in aqueous dispersions depend-

ing on the pH and ionic strength of the medium

(Lagaly and Ziesmer 2003). In order to benefit from

the properties of the individual sheets, the particle

clusters need to be exfoliated (Burgentzle et al. 2004;

Zhu and Wilkie 2007). Cations as well as adsorption of

water in the interlayer affect the swelling of the

particles (Pashley and Quirk 1984; Chang et al. 1995;

Fitch et al. 1995; Hensen and Smit 2002) and can

hinder the attraction between them, and consequently,

assist in exfoliation. Furthermore, clay exfoliation can

be assisted by high shear or ultrasonication (Lin et al.

2008; Vartiainen et al. 2010).

Whereas clay particles are plate-like, having a high

aspect ratio, precipitated calcium carbonate (PCC)

particles are typically cubic. PCC particles are

commonly used in paper coatings. Typically these

particles are of micrometer size but nanosized grades

are also available. Applications combining cellulose

nanomaterials and PCC are extant, yet a few examples

combining the particles with pulp fines (Subramanian

et al. 2008) or NFC (Nypelo et al. 2011) exist. The

surface chemistry of precipitated calcium carbonate is

rather complex, consisting of CaCO3 and some

impurities of Na, Mg, Al and Si (Sanders 1992).

The properties of calcium carbonate particles are

suggested to be controlled by the ratio of Ca2? and

CO32- ions (Foxall et al. 1979), the net charge being

mostly dominated by the Ca2? ions. Additional

calcium ions present in the PCC dispersion may

increase the cationic charge of the particles (Huang

et al. 1991).

780 Cellulose (2012) 19:779–792

123

Development of organic and inorganic nanomate-

rials has led to progress in construction of hybrid

materials. Hybrid materials combine the constituents

aiming for a synergy leading to properties exceeding

those of the individual constituents. Nanosized clay

and calcium carbonate particles have been used in

polymer nanocomposites enhancing, for example,

abrasion resistance (Mishra et al. 2005; Subramani

et al. 2007; Kapole et al. 2011). A few studies report

structures combining cellulose and clay particles

suggested for, among others, packaging (Tunc and

Duman 2010), thermoplastic composites (Ludvik et al.

2007; Delhom et al. 2010) and to improve thermal

properties (Cerruti et al. 2008; Lin et al. 2008).

Combination of inorganic particles and NFC is

exiguously reported, yet an example of clay combined

with NFC to form paper coatings to improve paper

properties important in printing, that is, strength and

optical properties, exists (Morseburg and Chinga-

Carrasco 2009). Also preparation of thin nanopaper

from clay and NFC where the fibril network encloses

the clay particles has been reported (Sehaqui et al.

2010; Liu et al. 2011a). Oppositely to the polymer

systems where nanoclay is dispersed in a polymer

matrix enabling the polymer to invade the interlayers

and lead to intercalation or exfoliation of the particles

(Liu et al. 2004; Sun et al. 2007; Choudalakis and

Gotsis 2009; Bitinis et al. 2011; Duncan 2011), due to

their large size, the fibrils are unlikely to be able to

enhance clay exfoliation. Therefore, control of the

clay dispersion and its interactions with NFC is the

defining factor regarding the formed structures.

NFC can be modified using polysaccharides, poly-

electrolytes and chemical treatments (Wagberg et al.

2008; Eronen et al. 2011; Pahimanolis et al. 2011;

Syverud et al. 2011). Additionally, the fibril network can

be modified using solid particles (Maneerung et al.

2008; Dıez et al. 2011; Kettunen et al. 2011; Olsson et al.

2011). Evidently use of easily modifiable non-toxic

particles would increase the amount of the potential

applications, for example, in functional packaging

materials. However, loading of the fibril matrix with

particles requires careful consideration of the constitu-

ent interactions. In order to provide understanding

regarding combination of cellulose nanofibrils and

inorganic nanoparticles, the interactions of nanosized

calcium carbonate (nanoPCC) and clay particles with

NFC in varying solution concentrations were examined.

These nanoparticle materials are readily modifiable

(Kim and Lee 2002; Ras et al. 2004; Choi et al. 2009; Hu

and Deng 2010), and hence, suitable for the purpose.

The quartz crystal microbalance with dissipation mon-

itoring (QCM-D) was utilized to investigate affinity

between the nanoparticles and NFC. QCM-D has been

extensively used to study polymer adsorption to cellu-

lose surfaces (Wagberg et al. 2010) as well as to examine

cellulosic nanomaterials (Ahola et al. 2008b; Aulin et al.

2009; Song et al. 2009). The technique is also commonly

used to monitor deposition of thin films and for

investigating multilayer build-up (Lvov et al. 1997;

Saarinen et al. 2008; Wagberg et al. 2008). Although

QCM-D is widely used in materials science, only a few

studies are available that explore the interactions of

nanosized pigments with other substances, for example,

examination of clay-polyelectrolyte multilayers (Lvov

et al. 1996; Lin et al. 2008) and adsorption of titanium

dioxide nanoparticles onto a silica surface (Thio et al.

2011). Utilizing the frequency and dissipation response

of QCM-D, it is possible to elucidate the interactions

between the pigment particles and the NFC substrate

during particle deposition, information not available

using bulk methods. By combining atomic force

microscope (AFM) imaging with the QCM-D experi-

ments, we clarify these interactions in order to contrib-

ute to the development of structures combining organic

and inorganic substances. Examination of two nanopar-

ticle grades with distinct shape and charge furthermore

adds the value of the observations.

Materials and methods

Chemicals

Nanosized precipitated calcium carbonate was donated

by Schaefer Kalk (Diez, Germany) as a *12%

dispersion containing no dispersant. The average par-

ticle diameter was 50 nm. Nanoclay was a sodium

montmorillonite product of Nanocor Inc. (Arlington

Heights, USA) supplied in powder form with a cation

exchange capacity of 145 meq/100 g. Montmorillonite,

has the following theoretical structure: My?(Al2-yMgy)

(Si4)O10(OH)2*nH2O. The individual nanoclay parti-

cles have a thickness of only one nanometer and length

and width in hundreds of nanometers (aspect ratio

150–200). Nanoparticle stock solutions of 5 g dm-3

were prepared in water one day before the experiments.

NanoPCC was disintegrated in an ultrasonic bath for

Cellulose (2012) 19:779–792 781

123

20 min before preparing the final dispersions. The

nanoPCC and nanoclay dispersions were dispersed

prior to use with a Branson sonifier S-450D (Danbury,

USA), for 10 min at 25% amplitude setting. Sodium

CMC was a product of CP Kelco (Aanekoski, Finland)

with a molecular weight of 80,000 g mol-1. Prior to

use it was diluted with water and dialyzed. CMC

was negatively charged, having a charge density of

3.8 meq g-1, determined by polyelectrolyte titration

against polybrene (5.35 meq g-1). This indicates

degree of substitution of approximately 0.7. Sodium

bicarbonate (NaHCO3), calcium chloride (CaCl2) and

sodium chloride (NaCl) were of commercial grade.

Deionized water further purified using Millipore syn-

ergy UV equipment (Millipore SAS, Molsheim,

France) was used in all experiments.

Ultra-thin films of cellulose nanofibrils on silicon

substrate

NFC obtained from the Finnish Centre for Nanocell-

ulosic Technologies was used as the substrate material

for the adsorption experiments. It was prepared from

never dried birch pulp by disintegrating the pulp

20 times through a fluidizer (Microfluidics Corp.,

Newton, MA, USA) leaving a gel with a consistency

of approximately 1.6%. The charge density of the

material is 0.065 meq g-1 (Eronen et al. in press). The

films were prepared by spin coating (spin coater WS-

650SX-6NPP/Lite Laurell Technologies Corp., North

Wales, PA, USA) the NFC dispersion onto silica

coated QCM-D crystals (Q-Sense AB, Vastra Frolun-

da, Sweden) according to the procedure described by

Ahola et al. (2008c), except that poly(vinyl amine)

was used as an anchoring polymer. Prior to measure-

ments, surfaces were allowed to swell overnight in the

respective buffer solution. The NFC film consists of

approximately 60% of crystalline cellulose in its

native (cellulose I) form (Ahola et al. 2008d; Aulin

et al. 2009). Since no chemical pretreatment was used,

this material has similar chemistry to the cellulose

fibers from wood, including hemicelluloses.

Characterization of nanoparticle dispersion

Stability of the dispersions was studied using a Turbi-

scan Ma 2000 instrument (Formulaction, Toulouse,

France). A Coulter Delsa 440SX Electrophoretic Light

Scattering Analyzer (Coulter Electronic Ltd., USA) was

used to measure electrophoretic mobility and for

calculating the f-potential values, which were used to

determine the stability of the dispersions. The particle

sizes were determined by dynamic light scattering using

an N5 Submicron Particle Size Analyzer (Beckman

Coulter Inc., USA).

Adsorption experiments

Affinity between the substances was studied using the

QCM-D E4 equipment supplied by Q-sense AB

(Vastra Frolunda, Sweden). The equipment simulta-

neously measures the change in frequency and dissi-

pation of a quartz crystal. A voltage applied to the

crystal sets it to oscillate at a fundamental resonance

frequency of 5 MHz; its odd overtones are 15, 25, 35,

45, 55 and 75 MHz. Adsorption is detected as a

decrease in frequency of the oscillation. By shutting

down the driving voltage for a short moment and

monitoring the decay of the oscillation, energy dissi-

pation can be measured. The change in the adsorbed

mass (Dm) can be evaluated using the Sauerbrey

equation (Sauerbrey 1959; Hook et al. 1998a),

Dm ¼ �CDf

n; ð1Þ

where C is a device specific constant

(0.177 mg m-2 Hz-1), Df the change in the oscilla-

tion frequency of the crystal and n the overtone used.

This equation is valid for thin and rigid layers. For

high dissipation values the Sauerbrey equation tends

to underestimate the mass as it is calculated directly

from the change in the frequency of one of the

overtones. Instead, another model taking the visco-

elastic properties of the adsorbed layer into account by

utilizing frequencies of multiple overtones and their

variation has been proposed for analyzing viscoelastic

layers (Johannsmann et al. 1992; Naderi and Claesson

2006). It is described, in short, as:

m� ¼ �ffiffiffiffiffiffiffiffiffiffiqqlqp

2f0

Df

f; ð2Þ

where m* is an equivalent mass, qq the specific density

and lq the elastic shear modulus for quartz, f0 the

fundamental frequency of the crystal in air, Df the

frequency response and f the resonant frequency of

the crystal in the solution. The intercept of the

782 Cellulose (2012) 19:779–792

123

equivalent mass of several overtones plotted against

the squares of the resonance frequencies gives the

sensed mass.

The nanoparticle adsorption experiments were

performed by first pumping a respective buffer solu-

tion through the measurement chambers of the

QCM-D followed by the nanoparticle dispersion at

0.1 mL min-1 flow rate. During pumping the disper-

sions were stirred with a magnetic stirrer. Adsorption of

neat nanoparticle dispersions on NFC and CMC-

modified NFC substrates were studied. The concentra-

tions of the dispersions were 1 g dm-3. The dispersions

were prepared in 1 mM NaHCO3 buffer and ionic

strength was altered using CaCl2 or NaCl solutions.

Mainly the Johannsmann (Eq. 2) equation was used to

calculate the adsorbed mass. The adsorbed mass was

calculated from the frequency change observed after

reaching a plateau in the Df curve and rinsing with the

buffer solution. In graphs presenting frequency change

instead of the modeled adsorbed mass, the Df data has

been normalized with the corresponding overtone

numbers by the Qsoft401 software (version 1.4.4.130,

Qsense, Vastra Frolunda, Sweden).

Atomic force microscope

The morphology of the adsorbed layers was studied

using the Nanoscope IIIa Multimode scanning probe

microscope in air (Digital instruments Inc., Santa

Barbara, CA, USA). The images were scanned in

tapping mode using Si cantilevers (Micromasch,

Estonia) with a resonance frequency of 330–350 Hz.

At least three different areas of the sample were

recorded. Substrate coverage by particles was deter-

mined from the AFM images using Scanning Probe

Image Processor (SPIP) software (version 4.0.6.0,

Image Metrology, Lyngby, Denmark) by the grain

analysis with threshold detection method.

Results and discussion

Nanoparticle dispersions

Dispersion stability is an imperative to obtain a

uniform distribution of particles on a substrate as well

as in a dispersion, and can be achieved if the repulsive

forces dominate over the attractive van der Waals

forces. For charged particles the repulsive forces

depend on surface potential and the thickness of the

electrical double-layer (Evans and Wennerstrom

1999). In the present study, interactions of nanopar-

ticles of precipitated calcium carbonate and montmo-

rillonite nanoclay with NFC were examined by

adsorbing them onto an NFC substrate in varying

electrolyte concentrations enabling observation

regarding preparation of hybrid structures. In addition

to the nanoparticle-NFC interactions, considering

formation of a uniform structure, the particle–particle

interactions are important. Hence, the nanoparticle

dispersion properties were also examined.

The f-potential was used to evaluate the magnitude

of the repulsive electrostatic forces of the nanoparticle

dispersions as it describes the properties of the

slipping plane in the outer layer of the electrical

double-layer of a particle (Cosgrove 2005). The

nanoPCC and nanoclay dispersions were prepared in

1 mM NaHCO3. The electrolyte concentration of the

nanoPCC dispersion was adjusted with CaCl2 and the

nanoclay dispersion with either CaCl2 or NaCl. At

1 mM NaHCO3 the nanoPCC dispersion was slightly

cationic observed as a f-potential value of ?9 mV

(Fig. 1). Increasing CaCl2 concentration increased the

f-potential value of the nanoPCC dispersion until it

reached ?35 mV at 10 mM CaCl2. This is due to

increase in the amount of calcium ions on the

nanoPCC particle surface (Huang et al. 1991). Elec-

trostatically stabilized dispersions are usually stable at

high f-potential values. However, without shear the

nanoPCC particles flocculated and their size could not

be measured. At low ionic strength the f-potential was

-50

-30

-10

10

30

50

0 0.1 1 10

(m

V)

Electrolyte concentration (mM)

NanoPCC, CaCl2

Nanoclay, CaCl2

Nanoclay, NaCl

Fig. 1 Effect of the electrolyte concentration on the f-potential

of the nanoparticle dispersions. The dispersions were prepared

in 1 mM NaHCO3 and the electrolyte concentration was

adjusted using CaCl2 or NaCl

Cellulose (2012) 19:779–792 783

123

low explaining the instability. At 10 mM CaCl2 the

Debye length of the double layer repulsion is 1.76 nm.

Thus, it is possible that the van der Waals attraction

between particles dominate the particle interac-

tions and the dispersion flocculates despite the high

f-potential of the particles.

In the conditions used the nanoclay dispersions had

pH above 8.5, and hence, in addition to the permanent

negative charge on the planes, the edges of the

nanoclay particles have anionic charge decreasing

possibility of edge-to-face aggregation (Van Olphen

1977). Increasing the CaCl2 concentration decreased

the f-potential of the nanoclay dispersion (Fig. 1) and,

at 10 mM CaCl2, the nanoclay dispersion flocculated.

Apparently the electrolyte concentration is high

enough above 1 mM CaCl2 for the Ca2? to replace

all the Na?, and hence, change the f-potential. Unlike

in CaCl2 medium, the f-potential value was not

significantly affected by the increasing NaCl concen-

tration. Evidently the f-potential of the sodium

nanoclay dispersion is affected by the type of the

electrolyte, that is, their valence (Garcıa-Garcıa et al.

2007).

Besides dispersion stability, exfoliation of nanoclay

particles has been noticed to be a critical factor to

improve molecular level interactions between clay

particles and a matrix in nanocomposites (Liu et al.

2004; Sun et al. 2007; Chivrac et al. 2009). Plate-like

and anisotropic particles improve the barrier property

of the matrix, and hence, in barrier applications

exfoliation is critical to create a tortuous path for gas

diffusion (Duncan 2011). As sonication treatment has

been noted to be efficient for nanoclay disintegration

(Lin et al. 2008), the nanoparticle dispersions were

treated prior to use with a high intensity ultrasound

sonication. The neat nanoclay dispersion in water

consisted of particles around 650 nm. Preparation of

nanoclay in 1 mM NaHCO3 decreased the average

particle diameter to around 500 nm, while increasing

CaCl2 concentration resulted in flocculation at 10 mM

concentration. With the monovalent cation (Na?)

flocculation was not detected and at 10 mM concen-

tration the average particle size of the nanoclay

dispersion was approximately 500 nm. Evidently,

the extent of aggregation was related to the thickness

of the electrical double-layer around the particles

(Fig. 1).

Adsorption of nanoparticles on ultra-thin cellulose

nanofibril films

The nanoPCC and nanoclay dispersions in varying

electrolyte concentrations were adsorbed on a swollen

NFC film. The affinity between nanoPCC and NFC

was weak at low CaCl2 concentration leading to a low

adsorbed mass (Fig. 2a). Increase in the CaCl2 con-

centration increases the charge of the nanoPCC

particles, and hence, enhanced the affinity to NFC.

This finding is well in accordance with observations

regarding retention of calcium carbonate particles on

pulp fibers (Fimbel and Siffert 1986). Consequently,

the maximum average change in the frequency,

-44 Hz, which corresponds to adsorbed mass of

*8.3 mg m-2 (Eq. 2), was detected at 10 mM CaCl2concentration. Although the affinity between the

substrate and the particles was noted to be low without

CaCl2, a change in dissipation of approximately 13

was detected (dissipation data is not presented)

0

2

4

6

8

10

12

m(m

g m

-2)

CaCl2 concentration (mM)

NanoPCC

Nanoclay

0

10

20

30

40

0 0.1 1 10 0 0.1 1 10

m (m

g m

-2)

NaCl concentration (mM)

Nanoclay

a b

Δ Δ

Fig. 2 Adsorbed mass of a nanoPCC and nanoclay as a

function of CaCl2 concentration and b nanoclay on NFC as a

function of NaCl concentration. The dispersions were prepared

in 1 mM NaHCO3 and the adsorbed mass was calculated using

the Johannsmann equation (Eq. 2)

784 Cellulose (2012) 19:779–792

123

indicating that due to dispersion instability there are

large aggregates present that are not strongly able to

bind to the substrate, but are still able to affect the

energy dissipation of the system. The dissipation

increased with increasing adsorbed mass, reaching

*44 at 10 mM CaCl2.

Although the nanoclay dispersion and the NFC

substrate were alike charged, nanoclay was able to

adsorb on NFC, detected as a change in the frequency

and dissipation response in QCM-D measurements.

Adsorption of nanoclay particles increased with

increasing CaCl2 concentration, reaching a maximum

(Df * 43 Hz corresponding to Johannsmann mass of

*8.2 mg m-2) at 1 mM concentration (Fig. 2a). At

10 mM CaCl2 concentration the dispersion was noted

to flocculate and no adsorption took place. The

dissipation response followed the trend of the

adsorbed mass and reached the maximum value

(*40) at 1 mM CaCl2. In NaCl the adsorbed mass

increased with increasing electrolyte concentration

and compared to the adsorption in CaCl2, the maxi-

mum change in frequency was high, *208 Hz, which

corresponds to Johannsmann mass of 38 mg m-2

(Fig. 2b). Frequency changes between 100 and

200 Hz of clay adsorption have also been reported

elsewhere (Lvov et al. 1996; Ariga et al. 1999; Lin

et al. 2008). However, the observed adsorbed mass

was notably high, and hence, it is probable that the

layer is very water-rich. Nevertheless, considering the

adsorption trend observed by QCM-D, an increase in

ionic strength of the dispersion medium seems to

assists adsorption. This can be due to decreased

repulsion between the substances until an electrolyte

concentration where the particles flocculate is reached.

As expected, the critical coagulation concentration is

lower with the divalent cation.

At the conditions where the maximum adsorption

of nanoPCC and nanoclay on NFC was observed, that

is, at 10 mM CaCl2 and 10 mM NaCl, respectively,

variation in the measured overtone values were

detected. This indicates heterogeneous depth distribu-

tion of the layer. In the case of nanoPCC, the variation

was seen regardless of the dispersion electrolyte

concentration. With nanoclay, the variance in the

overtones was apparent only with high adsorbed mass.

Adsorption of nanoPCC particles often caused irreg-

ular increase in the frequency and dissipation

response, being emphasized with high adsorbed

amounts as clearly seen in Fig. 3a. In comparison to

nanoclay (Fig. 3b), the nanoPCC adsorption was

slower and detection of a clear plateau in the

adsorption was often not possible. This observation

deviates from a study by Ariga et al. (1999) comparing

adsorption of spherical (SiO2) and sheet-like (clay)

particles on a planar substrate, where the spherical

particles adsorbed fast with limited adsorbed amount.

The slow adsorption of the nanoPCC particles in our

study is presumably due to continuous deposition of

particles forming increasingly large particle islands on

the substrate. Moreover, the adsorption of microme-

tersized particles has been shown to induce positive

frequency changes due to contact between the sub-

strate and the particles (Pomorska et al. 2010). Hence,

the nanoPCC particle clusters are possibly large

enough to be detected as irregularity in the QCM-D

response.

-50

-25

0

25

50

-40

-20

0

20

40

Time (min)

-50

-25

0

25

50

-200

-100

0

100

200

0 50 100 150 0 50 100

Time (min)

3rd

7th

5th

a b

5th3rd

7th

Δ f (Hz) ΔD (10-6) Δ f (Hz) ΔD (10-6)

Fig. 3 QCM-D frequency and dissipation response of 3rd, 5th

and 7th overtone as a function of time of a nanoPCC at 10 mM

CaCl2 and b nanoclay at 10 mM NaCl adsorption on NFC

substrate. The dispersions were prepared in 1 mM NaHCO3.

The frequency change is normalized by the corresponding

overtone number

Cellulose (2012) 19:779–792 785

123

Observations regarding the large amount of nano-

clay adsorbed, accompanied with the significant

dissipation response at 10 mM NaCl (Fig. 3) suggests

that the layer is viscous and contains much water.

However, it is misleading to only consider the quantity

of the frequency and dissipation change, and therefore,

QCM-D response is often presented as a ratio of

dissipation and frequency change (Df-ratio) enabling

examination of the intrinsic layer properties (Plunkett

et al. 2003; Du and Johannsmann 2004). Dissipation as

a function of frequency can indicate variation in the

adsorption kinetics and layer viscosity (Hook et al.

1998b) as well as conformational changes in the layer

(Saarinen et al. 2008). In addition to adsorption of

polymers, the ratio of dissipation and frequency can be

utilized in evaluation of layer formation of solid

particles. If the particle layer formed is homogenous

the dissipation to frequency ratio should be unaffected

by the layer thickness (Tellechea et al. 2009).

Plotting the QCM-D responses of the nanoparticle

adsorption as the dissipation to the frequency ratio as a

function of time showed that the Df-ratio of the

maximum nanoclay adsorption in sodium salt (10 mM

NaCl) was constant (Fig. 4). However, the Df-ratio of

the maximum adsorption in calcium salt (1 mM CaCl2)

showed a slight decrease in the beginning of the

adsorption. This must be due to a larger aggregate size

compared to the dispersion at 10 mM NaCl (1100 vs.

500 nm) causing variation in layer uniformity. It is

noteworthy that the Df-ratio of the nanoclay layer

adsorbed in calcium chloride is higher, indicating that

the dissipation change with respect to frequency was

actually higher in comparison to the adsorption in

sodium chloride. Hence, high water content of the layer,

implied by the significant decrease in the frequency (and

dissipation) at 10 mM NaCl (*208 Hz) compared to

43 Hz at 1 mM CaCl2 alone cannot be the reason for the

high adsorbed mass. Moreover, such a significant

difference cannot be solely explained by changes in

dispersion stability, but be partly affected by differences

between Ca2? and Na? ion adsorption on the nanoclay

particle surface and interlayers (Norrish 1954; Delville

and Laszlo 1990). Nevertheless, these results show that

the choice of the electrolyte can be used to tune nanoclay

affinity towards NFC substrate, an important factor

regarding construction of barrier materials from cellu-

lose and clay (Liu et al. 2011a).

In contrast to the nanoclay adsorption with the

constant Df-ratio, the ratio of the nanoPCC adsorption

decreased with time suggesting changes in the layer

coverage and particle distribution along the adsorption

(Tellechea et al. 2009). This implies that the nanoPCC

particles adsorb forming a layer consisting of particle

clusters which possibly do not fully cover the substrate.

Nanoparticles on NFC substrates were imaged using

AFM to examine the formed layer structures and

particle distribution. The nanoPCC coverage deter-

mined by image analysis using SPIP software of the

fibril substrate after adsorption at 0 and 0.1 mM CaCl2was approximately 30%. The substrates contained few

and aggregated nanoparticle clusters (Fig. 5a, b). The

coverage increased to approximately 40% with

increasing CaCl2 concentration (1 and 10 mM) and

the substrates were covered with more homogenously

distributed small aggregates (Fig. 5c, d). Evidently the

increasing CaCl2 concentration induces nanoPCC

dispersion stability and a more even particle distribu-

tion on the substrate. However, although the particle

distribution became more uniform with the increasing

CaCl2 concentration in the dispersion, the particles did

not fully cover the NFC substrate. This correlates with

the observations regarding the changes in the Df-ratio

during adsorption (Fig. 4).

The nanoclay particles were clearly detected only

on the substrates where the highest adsorbed amounts

were recorded (at 1 mM CaCl2 and 10 mM NaCl).

The particles could not be observed in the topography

images, yet comparison to the phase contrast images

of the neat reference (Fig. 6a) revealed that the

0

1

2

3

10 20 30 40 50

Time (min)

NanoPCC 10 mM CaCl2

Nanoclay 10 mM NaCl

NanoClay 1 mM CaCl2

ΔD

/-Δ

f

Fig. 4 The dissipation to frequency ratio of the 3rd overtone as

a function of time of the adsorption of nanoPCC at 10 mM CaCl2(filled circle), of nanoclay at 1 mM CaCl2 (open circle) and of

nanoclay at 10 mM NaCl (open square) on an NFC substrate.

The dispersions were prepared in 1 mM NaHCO3

786 Cellulose (2012) 19:779–792

123

nanoclay particles deposited on the fibril substrates as

a thin layer (Fig. 6b, c). Presence of the particles was

seen as diminished fibrillar structure of the substrate.

Unfortunately precise surface coverage values could

not be determined with SPIP due to the minute effect

of the particles on the substrate height profile.

Formation of a thin layer and a tight contact between

the substrate and clay particles has been also previ-

ously reported (Kotov et al. 1997; Ariga et al. 1999).

Larger magnification of the substrates (Fig. 6d–f)

enabled individual nanoclay particles to be detected on

the substrate with a flat conformation correlating with

observations by Cadene et al. (2005). The close-up of

the layer adsorbed at 10 mM NaCl (Fig. 6f) seemed

more grainy in comparison to the layer adsorbed at

1 mM CaCl2 (Fig. 6e). However, based on the

observations regarding the AFM images, the adsorbed

amount at 10 mM NaCl does not seem significantly

higher than at 1 mM CaCl2. It is impossible to deem

the substrate to be fully covered with the particles.

However, the structure resembles a nanoclay layer

spin coated on a silicon substrate with a polyvinyl-

amine anchoring layer reported by Vartiainen et al.

(2010).

Adsorption of nanoparticles on ultra-thin cellulose

nanofibril films modified with carboxymethyl

cellulose

The effect of an increase in NFC charge on its

interactions with the nanoparticles was examined by

adsorbing a layer of CMC on the NFC substrate prior

b d

1 µm

a c

1 µm 1 µm 1 µm

Fig. 5 AFM topography images (25 lm2) of NFC substrates after adsorption of nanoPCC particles at a 1 mM NaHCO3, b 1 mM

NaHCO3 ? 0.1 mM CaCl2, c 1 mM NaHCO3 ? 1 mM CaCl2 and d 1 mM NaHCO3 ? 10 mM CaCl2

b

d

c

e

1 µm

a

f

1 µm 1 µm

0.2 µm 0.2 µm 0.2 µm

Fig. 6 AFM phase contrast images (25 lm2) of a a neat NFC substrate, b the substrate after adsorption of nanoclay at 1 mM

NaHCO3 ? 1 mM CaCl2, and c at 1 mM NaHCO3 ? 10 mM NaCl. The corresponding 1 lm2 images are presented in d, e and f

Cellulose (2012) 19:779–792 787

123

to nanoparticle adsorption (Fig. 7). It is recognized

that CMC adsorption can be used to modify cellulose

film surface properties (Liu et al. 2011b), and hence

for simplicity, a CMC layer was used instead of

carboxymethylated fibril material (Walecka 1956;

Wagberg et al. 2008). CMC was adsorbed at 10 mM

CaCl2 as a sufficient CaCl2 concentration enhances

CMC adsorption on cellulose (Laine et al. 2000).

Rinsing of the CMC layer with the buffer solution

caused a small decrease both in frequency (Fig. 7a)

and in dissipation (Fig. 7b). The nanoparticles were

adsorbed at 1 mM NaHCO3 and 1 mM CaCl2. Rinsing

with the 1 mM NaHCO3 and 1 mM CaCl2 electrolyte

solution prior to the nanoparticle adsorption increased

both dissipation response and change in frequency

indicating swelling of the NFC layer. NFC ultra-thin

films behave as polyelectrolyte gel and swell/deswell

depending on the electrolyte concentration (Ahola

et al. 2008c). Hence, swelling upon decrease in ionic

strength is expected. NanoPCC adsorbed on the CMC

layer causing a decrease of *38 Hz in frequency and

a notably high increase in energy dissipation (*40).

Adsorption of nanoclay was lower with a frequency

decrease of *15 Hz, yet showing a clear change in

dissipation (*15).

The coverage of the CMC-treated cellulose fibril

substrate after adsorption of nanoPCC was approxi-

mately 60% (Fig. 8a, b). Consequently, a substantial

increase in the coverage was achieved in comparison

to adsorption on neat NFC (Fig. 5). The substrate after

nanoclay adsorption (Fig. 8c, d) resembled those of

the CMC-free substrates (Fig. 6) with a few detectable

nanoclay clusters.

The mass calculated using Eq. (2) for nanoPCC and

nanoclay adsorption on the CMC-modified NFC sub-

strate was 7.3 and 2.9 mg m-2, respectively. A com-

parison of these values to the adsorbed mass of

nanoPCC and nanoclay in corresponding electrolyte

concentration (1 mM CaCl2) on the neat NFC substrate,

2.9 and 8.2 mg m-2, respectively, reveals that

-150

-100

-50

00 50 100 150 200 250

Δf

(Hz)

Time (min)

CM

C

Rin

se Rin

se

Rin

se

NanoPCC

Nanoclay

0

20

40

60

0 50 100 150 200 250

ΔD

(10-6

)

Time (min)

CM

C

Rin

se

Rin

se

Rin

se

NanoPCC

Nanoclay

a b

Fig. 7 Change in the a frequency and b dissipation (3rd

overtone) during adsorption of CMC at 1 mM NaH-

CO3 ? 10 mM CaCl2 on NFC substrate followed by adsorption

of nanoPCC (dashed line) or nanoclay (solid line) at 1 mM

NaHCO3 ? 1 mM CaCl2. Before and after adsorption of each

layer the substrate was rinsed by pumping the buffer through the

chambers

a b c d

1 µm 1 µm 1 µm 1 µm

Fig. 8 AFM topography and phase contrast images (25 lm2) of (a and b) nanoPCC and (c and d) nanoclay adsorbed on CMC-modified

NFC substrate. The depth scale in nanoPCC topography image is 150 nm and in nanoclay topography image 50 nm

788 Cellulose (2012) 19:779–792

123

nanoPCC affinity to NFC increased when the NFC

substrate charge was increased. This is due to enhanced

attraction between the cationic particles and the anionic

substrate. The affinity between the substances is bene-

ficial regarding formation of a particle layer on the NFC

substrate. However, considering preparation of a struc-

ture of cellulose nanofibril network with uniformly

embedded nanoparticles, the increased affinity between

the substances can lead to flocculation, and hence,

deterioration of the structure. In an earlier work, we have

demonstrated an approach to alter nanoPCC surface

charge with particle surface modification with pectin

transforming the particles anionic (Nypelo et al. 2011).

Such a treatment could be utilized in construction of a

uniform nanoPCC/NFC dispersion.

In contrast to nanoPCC, the nanoclay adsorption on

CMC-modified NFC was lower than on the neat NFC

substrate, as increasing NFC substrate charge increases

the repulsion between the anionic substrate and the

anionic particles. Hence, it seems that treatment of NFC

with CMC can improve the hybrid dispersion stability.

In formation of a planar structure of nanoclay on NFC,

the affinity towards the substrate could be induced by

treatment of the fibrils with cationic polyelectrolyte

(Lin et al. 2008) or utilization of cationic NFC

(Olszewska et al. 2011).

The simplified model system used in this study

enables a detailed examination of inorganic nanopar-

ticle interactions with cellulose nanofibrils. Instead of

exploring, for example, a composite construction,

such a set-up allows to distinguish separate interac-

tions giving valuable indirect information essential for

understanding more complex systems. We consider

that the experiments discussed are valuable for

development of hybrid materials combining inorganic

particles and cellulose nanofibrils. Such structures

could be utilized to construct NFC network loaded

with nanoparticles allowing functionalization.

Conclusions

Fundamental insight into the interactions between

nanoparticles and cellulose nanofibrils was achieved

using the QCM-D technique. The technique was

successfully applied to examine adsorption of inor-

ganic nanoparticles on NFC. Investigation of the

dissipation to frequency ratio revealed the distinct

characteristics of the layers. Clearly the technique,

although not often used for this purpose, is applicable

to study nanopigments.

Considerable differences between the behavior of

two nanoparticle grades, nanoPCC and nanoclay, were

observed. Due to its low surface charge the nanoPCC

dispersion flocculated easily. Increase in Ca2? con-

centration was utilized to enhance the surface charge,

which led to enhanced affinity to NFC. Whereas such

an affinity is beneficial for formation of a uniform

particle layer on NFC film, in a dispersion the affinity

can lead to flocculation and deteriorate the hybrid

structure. The nanoclay particles, on the other hand,

were anionically charged, as was the NFC substrate as

well. Nevertheless, the particles were able to adsorb on

to NFC substrate. The nanoclay dispersion properties

and affinity to NFC may be altered by varying the type

and concentration of a background electrolyte.

Acknowledgments This work was performed as a part of

‘‘Nanosellu I’’ project funded by Tekes (Finnish Funding

Agency for Technology and Innovation) and UPM. Schaefer

Kalk is thanked for donating the nanoPCC and Finnish Center

for Nanocellulosic Technologies for NFC. Ritva Kivela is

acknowledged for performing part of the AFM measurements.

Tekla Tammelin is thanked for valuable comments. Paula

Eronen is acknowledged for guidance in adsorbed mass

calculations and Laura Taajamaa for manuscript proof-

reading. Joseph Campbell is acknowledged for linguistic

support.

References

Ahola S, Osterberg M, Laine J (2008a) Cellulose nanofibrils—

adsorption with poly(amide-amine) epichlorohydrin stud-

ied by QCM-D and application as a paper strength additive.

Cellulose 15:303–314

Ahola S, Turon X, Osterberg M, Laine J, Rojas OJ (2008b)

Enzymatic hydrolysis of native cellulose nanofibrils and

other cellulose model films: effect of surface structure.

Langmuir 24:11592–11599

Ahola S, Salmi J, Johansson LS, Laine J, Osterberg M (2008c)

Model films from native cellulose nanofibrils. Preparation,

swelling, and surface interactions. Biomacromolecules

9:1273–1282

Ahola S, Myllytie P, Osterberg M, Teerinen T, Laine J (2008d)

Effect of polymer adsorption on cellulose nanofibril water

binding capacity and aggregation. Bioresources 3:1315–1328

Ariga K, Lvov Y, Ichinose I, Kunitake T (1999) Ultrathin films

of inorganic materials (SiO2 nanoparticle, montmorillonite

microplate, and molybdenum oxide) prepared by alternate

layer-by-layer assembly with organic polyions. Appl Clay

Sci 15:137–152

Aulin C, Ahola S, Josefsson P, Nishino T, Hirose Y, Osterberg M,

Wagberg L (2009) Nanoscale cellulose films with different

Cellulose (2012) 19:779–792 789

123

crystallinities and mesostructures-their surface properties

and interaction with water. Langmuir 25:7675–7685

Aulin C, Gallstedt M, Lindstrom T (2010a) Oxygen and oil

barrier properties of microfibrillated cellulose films and

coatings. Cellulose 17:559–574

Aulin C, Johansson E, Wagberg L, Lindstrom T (2010b) Self-

organized films from cellulose I nanofibrils using the layer-

by-layer technique. Biomacromolecules 11:872–882

Bitinis N, Hernandez M, Verdejo R, Kenny J, Lopez-Manchado

M (2011) Recent advances in clay/polymer nanocompos-

ites. Adv Mater 23:5229–5236

Burgentzle D, Duchet J, Gerard JF, Jupin A, Fillon B (2004)

Solvent-based nanocomposite coatings: I. Dispersion of

organophilic montmorillonite in organic solvents. J Colloid

Interface Sci 278:26–39

Cadene A, Durand-Vidal S, Turq P, Brendle J (2005) Study of

individual Na-montmorillonite particle size, morphology,

and apparent charge. J Colloid Interface Sci 285:719–730

Cerruti P, Ambrogi V, Postiglione A, Rychly J, Matisova-Ry-

chla L, Carfagna C (2008) Morphological and thermal

properties of cellulose-montmorillonite nanocomposites.

Biomacromolecules 9:3004–3013

Chang FRC, Skipper N, Sposito G (1995) Computer simulation

of interlayer molecular structure in sodium montmoril-

lonite hydrates. Langmuir 11:2734–2741

Chivrac F, Pollet E, Averous L (2009) Progress in nano-bio-

composites based on polysaccharides and nanoclays. Mater

Sci Eng R 67:1–17

Choi YY, Lee SH, Ryu SH (2009) Effect of silane functionali-

zation of montmorillonite on epoxy/montmorillonite

nanocomposite. Polym Bull 63:47–55

Choudalakis G, Gotsis A (2009) Permeability of polymer/clay

nanocomposites: a review. Eur Polym J 45:967–984

Cosgrove T (2005) Colloid science: principles, methods and

applications. Wiley-Blackwell, Chichester

Czaja WK, Young DJ, Kawecki M, Brown RM Jr (2007) The

future prospects of microbial cellulose in biomedical

applications. Biomacromolecules 8:1–12

Delhom CD, White-Ghoorahoo LA, Pang SS (2010) Develop-

ment and characterization of cellulose/clay nanocompos-

ites. Compos B Eng 41:475–481

Delville A, Laszlo P (1990) The origin of the swelling of clays

by water. Langmuir 6:1289–1294

Dıez I, Eronen P, Osterberg M, Linder MB, Ikkala O, Ras RHA

(2011) Functionalization of nanofibrillated cellulose with

silver nanoclusters: Fluorescence and antibacterial activity.

Macromol Biosci 11:1185–1191

Du B, Johannsmann D (2004) Operation of the quartz crystal

microbalance in liquids: derivation of the elastic compli-

ance of a film from the ratio of band width shift and fre-

quency shift. Langmuir 20:2809–2812

Duncan TV (2011) Application of nanotechnology in food

packaging and food safety: barrier materials, antimicrobi-

als and sensors. J Colloid Interface Sci 363:1–24

Eichhorn SJ, Dufresne A, Aranguren M, Marcovich NE,

Capadona JR, Rowan SJ, Weder C, Thielemans W, Toman

M, Renneckar S, Gindl W, Veigel S, Keckes J, Yano H,

Abe K, Nogi M, Nakagaito AN, Mangalam A, Simonsen J,

Benight AS, Bismarck A, Berglund LA, Peijs T (2010)

Review: current international research into cellulose

nanofibres and nanocomposites. J Mater Sci 45:1–33

Eronen P, Junka K, Laine J, Osterberg M (2011) Interaction

between water-soluble polysaccharides and native nano-

fibrillar cellulose thin films. Bioresources 6:4200–4217

Eronen P, Laine J, Ruokolainen J, Osterberg M. (in press)

Comparison of multilayer formation between different

cellulose nano-fibrils and cationic polymers. J Colloid

Interface Sci. doi:10.1016/j.jcis.2011.09.028

Evans DF, Wennerstrom H (1999) The colloidal domain: where

physics, chemistry, biology, and technology meet. Wiley,

New York

Fernandes S, Freire CSR, Silvestre AJD, Pascoal Neto C,

Gandini A (2011) Novel materials based on chitosan and

cellulose. Polym Int 60:875–882

Fimbel P, Siffert B (1986) Interaction of calcium carbonate

(calcite) with cellulose fibers in aqueous medium. Colloids

Surf 20:1–16

Fitch A, Du J, Gan H, Stucki J (1995) Effect of clay charge on

swelling: a clay-modified electrode study. Clays Clay

Miner 43:607–614

Foxall T, Peterson GC, Rendall HM, Smith AL (1979) Charge

determination at calcium salt/aqueous solution interface.

J Chem Soc Faraday Trans 75:1034–1039

Garcıa-Garcıa S, Wold S, Jonsson M (2007) Kinetic determi-

nation of critical coagulation concentrations for sodium-

and calcium-montmorillonite colloids in NaCl and CaCl2aqueous solutions. J Colloid Interface Sci 315:512–519

Guimond R, Chabot B, Law K-, Daneault C (2010) The use of

cellulose nanofibres in papermaking. J Pulp Pap Sci 36:

55–61

Habibi Y, Lucia LA, Rojas OJ (2010) Cellulose nanocrystals:

chemistry, self-assembly, and applications. Chem Rev

110:3479–3500

Henriksson M, Berglund LA, Isaksson P, Lindstrom T, Nishino

T (2008) Cellulose nanopaper structures of high toughness.

Biomacromolecules 9:1579–1585

Hensen EJM, Smit B (2002) Why clays swell. J Phys Chem B

106:12664–12667

Hook F, Rodahl M, Brzezinski P, Kasemo B (1998a) Energy

dissipation kinetics for protein and antibody-antigen

adsorption under shear oscillation on a quartz crystal

microbalance. Langmuir 14:729–734

Hook F, Rodahl M, Kasemo B, Brzezinski P (1998b) Structural

changes in hemoglobin during adsorption to solid surfaces:

effects of pH, ionic strength, and ligand binding. Proc Natl

Acad Sci 95:12271–12276

Hu Z, Deng Y (2010) Superhydrophobic surface fabricated from

fatty acid-modified precipitated calcium carbonate. Ind

Eng Chem Res 49:5625–5630

Huang YC, Fowkes FM, Lloyd TB, Sanders ND (1991)

Adsorption of calcium ions from calcium chloride solutions

onto calcium carbonate particles. Langmuir 7:1742–1748

Hubbe MA, Rojas OJ, Lucia LA, Mohini S (2008) Cellulosic

nanocomposites: a review. Bioresources 3:929–980

Hult E, Iotti M, Lenes M (2010) Efficient approach to high

barrier packaging using microfibrillar cellulose and shel-

lac. Cellulose 17:575–586

Johannsmann D, Mathauer K, Wegner G, Knoll W (1992)

Viscoelastic properties of thin films produced with a

quartz-crystal resonator. Phys Rev B 46:7808–7815

Kapole SA, Kulkarni RD, Sonawane SH (2011) Performance

properties of acrylic and acrylic polyol–polyurethane

790 Cellulose (2012) 19:779–792

123

based hybrid system via addition of nano-CaCO3 and

nanoclay. Can J Chem Eng 89:1590–1595

Kettunen M, Silvennoinen RJ, Houbenov N, Nykanen A,

Ruokolainen J, Sainio J, Pore V, Kemell M, Ankerfors M,

Lindstrom T, Ritala M, Ras RHA, Ikkala O (2011)

Photoswitchable superabsorbency based on nanocellulose

aerogels. Adv Funct Mater 21:510–517

Kim DS, Lee CK (2002) Surface modification of precipitated

calcium carbonate using aqueous fluosilicic acid. Appl Surf

Sci 202:15–23

Kotov N, Haraszti T, Turi L, Zavala G, Geer R, Dekany I,

Fendler J (1997) Mechanism of and defect formation in the

self-assembly of polymeric polycation-montmorillonite

ultrathin films. J Am Chem Soc 119:6821–6832

Lagaly G, Ziesmer S (2003) Colloid chemistry of clay minerals:

the coagulation of montmorillonite dispersions. Adv Col-

loid Interface Sci 100–102:105–128

Laine J, Lindstrom T, Nordmark GG, Risinger G (2000) Studies

on topochemical modification of cellulosic fibers. Part 1.

Chemical conditions for the attachment of carboxymethyl

cellulose onto fibers. Nord Pulp Pap Res J 15:520–526

Lin Z, Renneckar S, Hindman DP (2008) Nanocomposite-based

lignocellulosic fibers 1. Thermal stability of modified

fibers with clay-polyelectrolyte multilayers. Cellulose 15:

333–346

Liu W, Ni Y, Xiao H (2004) Montmorillonite intercalated with

polyaminoamide-epichlorohydrin: preparation, character-

ization, and sorption behavior. J Colloid Interface Sci 275:

584–589

Liu A, Walther A, Ikkala O, Belova L, Berglund LA (2011a)

Clay nanopaper with tough cellulose nanofiber matrix for

fire retardancy and gas barrier functions. Biomacromole-

cules 12:633–641

Liu Z, Choi H, Gatenholm P, Esker AR (2011b) Quartz crystal

microbalance with dissipation monitoring and surface

plasmon resonance studies of carboxymethyl cellulose

adsorption onto regenerated cellulose surfaces. Langmuir

27:8718–8728

Ludvik CN, Glenn GM, Klamczynski AP, Wood DF (2007)

Cellulose fiber/bentonite clay/biodegradable thermoplastic

composites. J Polym Environ 15:251–257

Lvov Y, Ariga K, Ichinose I, Kunitake T (1996) Formation of

ultrathin multilayer and hydrated gel from montmorillonite

and linear polycations. Langmuir 12:3038–3044

Lvov Y, Ariga K, Onda M, Ichinose I, Kunitake T (1997)

Alternate assembly of ordered multilayers of SiO2 and

other nanoparticles and polyions. Langmuir 13:6195–

6203

Maneerung T, Tokura S, Rujiravanit R (2008) Impregnation of

silver nanoparticles into bacterial cellulose for antimicro-

bial wound dressing. Carbohydr Polym 72:43–51

Mishra S, Sonawane S, Singh R (2005) Studies on character-

ization of nano CaCO3 prepared by the in situ deposition

technique and its application in PP-nano CaCO3 compos-

ites. J Polym Sci B: Polym Phys 43:107–113

Morseburg K, Chinga-Carrasco G (2009) Assessing the com-

bined benefits of clay and nanofibrillated cellulose in lay-

ered TMP-based sheets. Cellulose 16:795–806

Naderi A, Claesson PM (2006) Adsorption properties of poly-

electrolyte-surfactant complexes on hydrophobic surfaces

studied by QCM-D. Langmuir 22:7639–7645

Nakagaito AN, Yano H (2004) Novel high-strength biocom-

posites based on microfibrillated cellulose having nano-

order-unit web-like network structure. Appl Phys A Mater

Sci Process 80:155–159

Nogi M, Iwamoto S, Nakagaito AN, Yano H (2009) Optically

transparent nanofiber paper. Adv Mater 21:1595–1598

Norrish K (1954) The swelling of montmorillonite. Discuss

Faraday Soc 18:120–134

Nypelo T, Osterberg M, Laine J (2011) Tailoring surface prop-

erties of paper using nanosized precipitated calcium car-

bonate particles. ACS Appl Mater Interfaces 3:3725–3731

Okahisa Y, Yoshida A, Miyaguchi S, Yano H (2009) Optically

transparent wood-cellulose nanocomposite as a base sub-

strate for flexible organic light-emitting diode displays.

Compos Sci Technol 69:1958–1961

Olsson RT, Azizi Samir MAS, Salazar-Alvarez G, Belova L,

Strom V, Berglund LA, Ikkala O, Nogues J, Gedde UW

(2011) Making flexible magnetic aerogels and stiff mag-

netic nanopaper using cellulose nanofibrils as templates.

Nat Nanotechnol 5:584–588

Olszewska A, Eronen P, Johansson LS, Malho JM, Ankerfors

M, Lindstrom T, Ruokolainen J, Laine J, Osterberg M

(2011) The behaviour of cationic nanofibrillar cellulose in

aqueous media. Cellulose 18:1213–1226

Paakko M, Ankerfors M, Kosonen H, Nykanen A, Ahola S,

Osterberg M, Ruokolainen J, Laine J, Larsson PT, Ikkala

O, Lindstrom T (2007) Enzymatic hydrolysis combined

with mechanical shearing and high-pressure homogeniza-

tion for nanoscale cellulose fibrils and strong gels. Bio-

macromolecules 8:1934–1941

Pahimanolis N, Hippi U, Johansson LS, Saarinen T, Houbenov

N, Ruokolainen J, Seppala J (2011) Surface functionali-

zation of nanofibrillated cellulose using click-chemistry

approach in aqueous media. Cellulose 18:1201–1212

Pashley R, Quirk J (1984) The effect of cation valency on DLVO

and hydration forces between macroscopic sheets of musco-

vite mica in relation to clay swelling. Colloids Surf 9:1–17

Plunkett MA, Wang Z, Rutland MW, Johannsmann D (2003)

Adsorption of pNIPAM layers on hydrophobic gold sur-

faces, measured in situ by QCM and SPR. Langmuir 19:

6837–6844

Pomorska A, Shchukin D, Hammond R, Cooper MA, Grun-

dmeier G, Johannsmann D (2010) Positive frequency shifts

observed upon adsorbing micron-sized solid objects to a

quartz crystal microbalance from the liquid phase. Anal

Chem 82:2237–2242

Ras RHA, Nemeth J, Johnston CT, Dekany I, Schoonheydt RA

(2004) Orientation and conformation of octadecyl rhoda-

mine B in hybrid Langmuir-Blodgett monolayers con-

taining clay minerals. Phys Chem Chem Phys 6:5347–5352

Rodionova G, Lenes M, Eriksen Ø, Gregersen Ø (2010) Surface

chemical modification of microfibrillated cellulose:

improvement of barrier properties for packaging applica-

tions. Cellulose 18:127–134

Saarinen T, Osterberg M, Laine J (2008) Adsorption of poly-

electrolyte multilayers and complexes on silica and cellu-

lose surfaces studied by QCM-D. Colloids Surf A 330:

134–142

Sanders ND (1992) The effect of surface modification of pig-

ments on colloidal stability and structural performance.

J Pulp Pap Sci 18:169–175

Cellulose (2012) 19:779–792 791

123

Sauerbrey G (1959) The use of quartz oscillators for weighing

thin layers and for microweighing. Z Phys 155:206–222

Sehaqui H, Liu A, Zhou Q, Berglund LA (2010) Fast preparation

procedure for large, flat cellulose and cellulose/inorganic

nanopaper structures. Biomacromolecules 11:2195–2198

Sehaqui H, Zhou Q, Berglund LA (2011) Nanostructured bio-

composites of high toughness-a wood cellulose nanofiber

network in ductile hydroxyethylcellulose matrix. Soft

Matter 7:7342–7350

Solomon DH, Hawthorne DG (1983) Chemistry of pigments and

fillers. Wiley, New York

Song J, Li Y, Hinestroza JP, Rojas OJ (2009) Tools to probe

nanoscale surface phenomena in cellulose thin films:

application in the area of adsorption and friction. In: Lucia

LA, Rojas OJ (eds) Nanoscience and technology of

renewable biomaterials. Wiley, Chichester, pp 91–121

Subramani S, Choi SW, Lee JY, Kim JH (2007) Aqueous dis-

persion of novel silylated (polyurethane-acrylic hybrid/

clay) nanocomposite. Polymer 48:4691–4703

Subramanian R, Fordsmand H, Paltakari J, Paulapuro H (2008)

A new composite fine paper with high filler loading and

functional cellulosic microfines. J Pulp Paper Sci 34:

146–152

Sun Q, Schork FJ, Deng Y (2007) Water-based polymer/clay

nanocomposite suspension for improving water and mois-

ture barrier in coating. Compos Sci Technol 67:1823–1829

Syverud K, Xhanari K, Chinga-Carrasco G, Yu Y, Stenius P

(2011) Films made of cellulose nanofibrils: surface modi-

fication by adsorption of a cationic surfactant and charac-

terization by computer-assisted electron microscopy.

J Nanopart Res 13:773–782

Taipale T, Osterberg M, Nykanen A, Ruokolainen J, Laine J

(2010) Effect of microfibrillated cellulose and fines on the

drainage of kraft pulp suspension and paper strength.

Cellulose 17:1005–1020

Tellechea E, Johannsmann D, Steinmetz NF, Richter RP,

Reviakine I (2009) Model-independent analysis of QCM

data on colloidal particle adsorption. Langmuir 25:

5177–5184

Thio BJR, Zhou D, Keller AA (2011) Influence of natural

organic matter on the aggregation and deposition of tita-

nium dioxide nanoparticles. J Hazard Mater 189:556–563

Tunc S, Duman O (2010) Preparation and characterization of

biodegradable methyl cellulose/montmorillonite nano-

composite films. Appl Clay Sci 48:414–424

Uddin F (2008) Clays, nanoclays, and montmorillonite miner-

als. Metall Mater Trans A 39:2804–2814

Utracki LA, Sepehr M, Boccaleri E (2007) Synthetic, layered

nanoparticles for polymeric nanocomposites (PNCs).

Polym Adv Technol 18:1–37

Van Olphen H (1977) An introduction to clay colloid chemistry:

for clay technologists, geologists, and soil scientists.

Wiley-Interscience Publication, New York

Vartiainen J, Tammelin T, Pere J, Tapper U, Harlin A (2010)

Biohybrid barrier films from fluidized pectin and nanoclay.

Carbohydr Polym 82:989–996

Wagberg L, Decher G, Norgren M, Lindstrom T, Ankerfors M,

Axnas K (2008) The build-up of polyelectrolyte multilay-

ers of microfibrillated cellulose and cationic polyelectro-

lytes. Langmuir 24:784–795

Wagberg L, Osterberg M, Enarsson LE (2010) Interactions at

cellulose model surfaces. Encycl Surf Colloid Sci 1:1–19

Walecka JA (1956) Low degree of substitution carboxymeth-

ylcelluloses. Tappi J 39:458–463

Yano H, Sugiyama J, Nakagaito AN, Nogi M, Matsuura T,

Hikita M, Handa K (2005) Optically transparent compos-

ites reinforced with networks of bacterial nanofibers. Adv

Mater 17:153–155

Zhu J, Wilkie CA (2007) Intercalation compounds and clay

nanocomposites. In: Kickelbick G (ed) Hybrid materials.

Synthesis, characterization and applications. Wiley-VCH,

Weinheim, pp 151–173

792 Cellulose (2012) 19:779–792

123