Publication

1. C A R B ON 4 8 ( 2 0 1 0 ) 2 1 0 6 –2 1 2 2
available at www.sciencedirect.com
journal homepage: www.elsevier.com/locate/carbon
Letters to the Editor
Uptake of copper ions by carbon fiber/polymer hybrids
prepared by tandem diazonium salt chemistry and in situ
atom transfer radical polymerization
Samia Mahouche Chergui a, Nourredine Abbas a, Tarik Matrab b, Mireille Turmine c,
Elisabeth Bon Nguyen d, Re´mi Losno d, Jean Pinson b, Mohamed M. Chehimi a,*
a ITODYS, Universite´ Paris-Diderot, Baˆ timent Lavoisier, 15 rue Jean de Baı¨f, 75013 Paris, France
b LECA, Ecole Supe´rieure de Physique et de Chimie Industrielles de la Ville de Paris and CNRS (UMR7195), 10 rue Vauquelin,
75231 Paris Cedex 05, France
c LISE, Universite´ Paris 6 and CNRS (UPR 15), Case 133, 4 Place Jussieu 75252 Paris Cedex 05, France
d LISA, Universite´ Paris Diderot, Universite´ Paris 12 and CNRS, Faculte´ des Sciences, 61 av. du Ge´ne´ral de Gaulle,
F-94010 Cre´teil Cedex, France
A R T I C L E I N F O
Article history:
Received 21 September 2009
Accepted 25 January 2010
Available online 1 February 2010
A B S T R A C T
Cyclam-functionalized polyglycidyl methacrylate, grafted on carbon fibres (CF-PGMA-Cy)
was prepared by atom transfer radical polymerization using aryl diazonium salt initiators.
These adsorption maximum capacity of CF-PGMA-Cy fibres for Cu(II) was found to be
28.6 mg/g at pH 5.2 and the adsorption kinetics fitted to the pseudo-second order model.
Cyclic voltammetry of the (CF-PGMA-Cy)-supported copper ions indicated true electro-chemical
stripping of Cu(II) with detection of as low as 2 pmol of adsorbed Cu0. CF-PGMA-
Cy fibres are thus efficient and reusable adsorbents that hold promises for the
design of electrochemical sensors of metal ions.
2010 Elsevier Ltd. All rights reserved.
1. Introduction
Solid phase adsorbents such as activated carbon [1], clays [2],
alumina [3] and silica [4] have long been exploited for removal
of heavy metal ions from the environment owing to their
chemical and mechanical stability, the simplicity of their pro-duction
process and relatively low cost [5]. However, the main
disadvantage of these adsorbents is their non specific charac-ter.
This limitation can be overcome by immobilizing appro-priate
chelating agents on the adsorbents surfaces [6] either
by physical adsorption or by covalent bonding. The latter op-tion
is by far the most investigated over the recent years as it
favours strong grafting of the chelatant, and thus imparts
good stability of the adsorbent [7].
As alternatives to inorganic adsorbents, chelatant organic
polymers were shown to be promising regarding the selective
uptake of metals [8], due to their ability to form stable metal
complexes. Polymers can be in the form of beads, films, pow-ders
or thin films on insoluble solid supports [9]. This ap-proach
has proved to be effective in terms of detection and
purification of polluted aqueous solutions, due to two main
reasons: (i) a large variety of functional groups offered by
polymers, and (ii) mechanical and chemical stability of the so-lid
supports.
In this context, we aimed at designing novel carbon fibre-grafted
chelatant polymers for the detection of metals ions.
The interest of carbon fibres (CFs) lies in their outstanding
mechanical properties and chemical stability, particularly in
* Corresponding author:
E-mail address: chehimi@univ-paris-diderot.fr (M.M. Chehimi).
0008-6223/$ - see front matter 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carbon.2010.01.050

2. C A R B ON 4 8 ( 2 0 1 0 ) 2 1 0 6 –2 1 2 2 2107
strong acidic media [10], and the possibility to employ them
as working electrodes [11]. They are readily amenable to elec-trochemical
treatments and can be used in electroanalysis
[12]. Additionally, as far as non-porous carbon is concerned,
a simple calculation shows that a single 2 cm long fibre
(7 lm diameter, 1.75 g/cm3) has about 200-fold higher specific
surface area than a traditional 1 mm thick carbon electrode (1
cm2 area base, 1.6 g/cm3).
One strategy to prepare carbon fibre-grafted polymers is
surface-initiated atom transfer radical polymerization (SI-ATRP)
[13]. In order to ensure covalent bonding of the polymer
chains to underlying carbon fibres, the latter were electro-grafted
with aryl groups of the formulae –C6H4–CH(CH3)Br, de-rived
from the diazonium salt precursor BF
4 , +N2–C6H4–
CH(CH3)Br [14–17]. The strategy of electroreduction of diazo-nium
salts [11,18] is simple, quick, ensures good density of
grafted aryl groups (5–10 groups/nm2), and allows for the
modification of substrates with various organic functional-ities
(including ATRP initiators). Since the aryl-graphene bond
is strong as demonstrated by DFT calculations [19], it is clear
that combining aryl diazonium salt electrochemistry and
ATRP ensures the fabrication of robust carbon substrate/poly-mer
systems [16,17]. As far as the polymer graft is concerned,
we have chosen poly (glycidyl methacrylate), PGMA, due to its
relative hydrophilic character and the reactivity of its oxirane
groups towards amine ligands [8,20]. In this regard, 1,4,8,11-
tetraazacyclotetradecane (cyclam, Cy), a macrocyclic ligand,
was selected for its ability to strongly bind copper [21]. Be-sides
the chelating power of polymers, their hydrophilic char-acter
and chain mobility favour high accessibility of ions to
chelating sites [22].
The aim of this work is to elaborate an unprecedented,
chelatant cyclam functionalized-carbon fibre/PGMA system
(CF-PGMA-Cy) by tandem diazonium salt chemistry and
in situ ATRP. The chelatant fibres were evaluated in the up-take
of copper ions by means of XPS and ICP. Towards the
development of electrochemical sensors, the detection of
copper ions was performed using stripping voltammetry with
CF-PGMA-Cy fibres acting as the working electrodes.
2. Experimental
4 , +N2–C6H4–CH(CH3)–Br (D1) was pre-pared
The diazonium salt BF
as in [14,15], and electroreduced at the carbon fibre sur-faces.
The aryl initiator-modified carbon fibres CF–C6H4–
CH(CH3)Br (hereafter CF–Br) served as ATRP macroinitiators.
ATRP of GMA at the surface of CF–Br was carried out in
DMF/water mixture (26.6/13.3 in ml) using 200/1/0.25/2.5 mo-lar
ratio for [GMA]/[Cu(I)]/[Cu(II)/[Bpy], with 28 mmol of GMA.
ATRP was conducted for 6 h at room temperature (RT). Five
hundred milligrams of the resulting CF-PGMA were placed
in 100 ml Schlenk reactor then 50 ml of CHCl3 were added, fol-lowed
by dropwise addition of 0.2 g cyclam/40 ml CHCl3 under
argon. The reaction mixture was kept at reflux for 18 h. The
CF-PGMA-Cy hybrids were washed sequentially with chloro-form,
ethanol and water then dried under argon.
Uptake of Cu(II) was determined at RTas a function of time
and pH, the value of which was adjusted using HNO3 (1 M) or
NaOH (0.5 M).
The adsorption capacity (Q, mmol/g) of copper was calcu-lated
using:
Q ¼
C0 Ce
m
V
where C0 and Ce are the initial and equilibrium concentration
of Cu(II) (mmol/L), m is the mass of chelating material (g) and
V (l), the volume of the solution. Ce was determined by ICP.
XPS spectrawere recorded using a VG ESCALAB 250 system
fitted with Al Ka X-ray source (1486.6 eV, 650 lm spot size).
The operating conditions are similar as published elsewhere
[17].
A DSA10 Kru¨ ss instrument was used to determine contact
angles of water droplets gently deposited on untreated and
modified carbon fibers.
Copper concentration was determined with an axial torch
Inductively Coupled Plasma Atomic Emission Spectrometer
(ICP-AES, Perkin–ElmerTM Optima 3000) equipped with an
ultrasonic nebulizer (CetacTM). Stripping voltammetry of cop-per
was conducted with an EGG Princeton Applied research
263 potentiostat. The experiments were performed in water
with an Ag/AgCl electrode and a platinum wire as counter
electrode.
3. Results and discussion
The four-step strategy for the preparation of CF-PGMA-Cy
adsorbents is schematically shown in Fig. 1: (i) synthesis of
the diazonium salt (D1) bearing ATRP initiating group; (ii)
electrografting of aryl layers from D1; (iii) surface-confined
ATRP; (iv) post-functionalization of PGMA grafts by cyclam
via nucleophilic attack of the oxirane groups.
Cyclic voltammetry was used to determine the D1 cathodic
peak electroreduction, which permitted to set up proper con-ditions
for grafting aryl layers by chronoamperometry (Fig. 2).
In the insert of Fig. 2, the cyclic voltammogram exhibits the
cathodic peak of D1 at 0.37 V (vs SCE). The electron transfer
is concerted with the cleavage of dinitrogen, giving an aryl
radical which binds to the surface [18]. For the chronoamp-erometric
electrografting, a sufficiently low cathodic potential
(200 mV negative to the voltammetric peak of D1) was applied
during 200 s. There is a very steep decrease of the current
with time, suggesting the formation of the organic layer
which inhibits electron transfer from the electrode. These re-sults
demonstrate the efficient grafting of aryl groups at the
carbon fibre surface.
Fig. 3 shows the XPS survey scans and the digital photo-graphs
of water drops gently deposited onto the various fibers
before and after modification. The untreated carbon fibres ex-hibit
C1s, O1s and N1s peaks centred at 285, 530 and 400 eV,
respectively. Functionalization of the CF surfaces with bromi-nated
aryl layers is evidenced by the Br3d and Br3p peaks cen-tered
at 71 and 183–190 eV, respectively. The XPS-determined
O/C ratio for CF-PGMA fibres is 0.26, higher that those deter-mined
for CF, but still lower than the theoretical ratio of 0.43
calculated for pure PGMA. This indicates that CFs are detected
through the PGMA grafts. For CF-PGMA-Cy, the survey region
shows a significant increase of the N1s relative intensity, cor-responding
to four-fold increase of the N/C atomic ratio which
accounts for functionalization of CF-PGMA by cyclam.

3. 2108 C A R B ON 4 8 ( 2 0 1 0 ) 2 1 0 6 –2 1 2 2
CH3
CH3
O
Bpy, CuBr, CuBr2
CH3
m
CH3
CH3
- +
CH3
0
-50
Ep=-372eV
I (a.u.)
The inserts in Fig. 3 shows that the deceasing trend of
water contact angles is CF (112) CF–Br (108) CF-PGMA
(105) CF-PGMA-Cy (70). The oxirane groups in PGMA in-duce
a slight depression of the hydrophobic character of the
fibres due to the ester groups of the GMA repeat units. After
cyclam grafting, the fibres turn to be much more hydrophilic
due to the reaction of oxirane ring and cyclam resulting in –
CH(OH)–CH2–N moieties. Amine groups of grafted cyclam
contribute to the relatively hydrophilic character of the CF-PGMA-
Cy fibres. This behaviour is most probably exacerbated
by the existence of partially protonated nitrogen atoms of the
grafted cyclam.
The amount of copper ion adsorption by the chelatant CF-PGMA-
Cy fibres was determined by (i) direct XPS analysis of
copper immobilized on the fibres, and by (ii) the depletion
method in conjunction with ICP. Note that pH is an important
parameter controlling adsorption, due to the dependence of
CH3
HN
CH3
Br
n
CH3
HN
C1s
N1s
Br3p
Br3d
O1s
CF-PGMA-Cy
CF-PGMA
CF-Br
CF
metal–ligand complexes region stability with pH and the pre-cipitation
of Cu(OH)2 at higher pH.
Fig. 4 shows XPS and ICP results pertaining to copper up-take
by the fibres at indicated pH and versus time. After incu-bation
at pH 5.2, the Cu2p doublet in the 930–960 eV range is
very well detected by XPS at the surface of CF-PGMA-Cy fibres
(insert in Fig. 4a). This is reflected in the Cu/N ratio-pH plot,
showing an optimum at pH 5.2 (Fig. 4a). The depletion method
in conjunction with ICP indicates an optimal pH of 5.2
(Fig. 4b), in excellent agreement with XPS results.
The copper uptake at pH 5.2 was found to be 28.6 mg/g of
CF-PGMA-Cy (55% adsorption efficiency), higher than found
(iii)
Carbon fibre
CH
CH CH2
O
CH2 CH
C O
O
CH2
Br
p
CH
CH2 CH
C O
O
CH2 CH CH N
NH HN
OH
SI-ATRP
DMF/H2O,
Ar
CF CF-Br CF-PGMA
(iv) CHCl3
reflux, Ar
CH CH2
O
CH2 CH
C O
O
CH2
Carbon fibre
CH
NH
NH HN
CF-PGMA-Cy
CH
OH
H2N
CH3
C
CH2
C
O
CH2
O
CH CH2
(ii)
Carbon fibre
CH
Br
BF4,N2
+ e-
Carbon fibre
CH
Br
GMA
(i) two steps
Fig. 1 – Strategy for the preparation of chelatant carbon fibre-grafted PGMA chains.
0 100 200
-100
-1200 -600 0
E(eV)
I(A)
t(s)
Fig. 2 – Electrochemical treatment by diazonium salt via
chronoamperometry in ACN + 0.1 M NBu4BF4, v = 200
mV s1, E = 700 mV. Reference SCE. Insert shows
electroreduction waves obtained D1 at the surface of a
single CF.
0 600 1200
I (a.u.)
Binding energy (eV)
Fig. 3 – XPS survey spectra of untreated carbon fibers CF (O/
C = 0.15; N/C = 0.023; Br/C = 0), CF-Br (O/C = 0.1; N/C = 0.023;
Br/C = 0.002), CF-PGMA (O/C = 0.26; N/C = 0.01; Br/C = 8 ·
104), CF-PGMA-Cy hybrids (O/C = 0.23; N/C = 0.043). Water
drops deposited on untreated and modified fibres are shown
in inserts.

4. 0.4
0.3
0.2
0.1
Cu2p
pH=5.2
O1s
C1s
N1s
I (a.u.)
0.4
0.3
0.2
0.1
C A R B ON 4 8 ( 2 0 1 0 ) 2 1 0 6 –2 1 2 2 2109
for purely polymeric materials [23–25]. As far as activated car-bon
is concerned, Mugisidi et al. [26] reported for this adsor-bent
a capacity of 1.4 mg of Cu(II)/g, which was improved to
3 mg/g using 15% sodium acetate modifier. These authors
showed that capacity can further be increased up to 4.2 mg/
g upon regeneration, much lower than for the CF-PGMA-Cy
system reported here. Elsewhere [27,28], using activated car-bon,
copper adsorption capacity was similar to that reported
in the present work. Still, in [27,28], there was no mention
of the reusability of the adsorbents, which is an important
economical issue. Furthermore, carbon fibres can be handled
as free-standing working electrodes, a situation that is much
more difficult with activated carbon.
It is worth to note the very low uptake of copper capacity
under highly acidic conditions, due to the competing charac-ter
of protons present in high concentration which prevents
the accessibility of copper ions to the amino sites of cyclam.
Indeed, the contribution of protonated nitrogen atoms, esti-mated
by N1s peak-fitting (spectra not shown), was found
to be 14.0%, 13.0% and 7.1% at pH 1.5, 3.2 and 5.2, respec-tively;
hence the lowest extent of cyclam protonation at pH
5.2.
Cu(II) adsorption kinetics was investigated at the optimal
pH 5.2 and for an initial concentration of 1 mM for copper.
Either ICP (Fig. 4c) or XPS (Fig. 4d) results indicate relatively
high adsorption rates at the initial stages of incubation of
the chelatant fibres in Cu(II) solutions, before gradually reach-ing
an adsorption plateau value within 6 h. The high affinity
isotherms shown in Fig. 4 suggest that the chelating sites
are readily accessible to the copper ions, probably owing to
the chain mobility of chelating PGMA grafts [22].
Adsorption kinetics of divalent metal ions is commonly
studied using the pseudo-second order rate model which is
given by [29]:
t
Q
¼
30
20
10
30
20
10
t
Qe
þ
1
k Q2
e
where Q (mg/g) is the adsorption uptake at time t (min), k (g/
(mg min)) is the kinetics rate constant for the pseudo-second-order
model. Plotting t/Q versus t resulted in an excellent lin-ear
correlation (R2 = 0.99) suggesting that copper ion adsorp-tion
kinetics fit very well to the pseudo-second order model.
The adsorption rate constant k was 1.85 · 103gmg1 min1,
and the Qe value equal to 29.6 mg/g, matching the experimen-tal
plateau value of adsorption as determined by ICP.
Regeneration of the CF-PGMA-Cy fibres was investigated
by repeated cycles of adsorption/desorption of copper ions
in a solution of 0.5 M thiourea/1 M HCl, during 24 h. The
desorption ratio was calculated from:
Desorption ratio ¼
Amount of desorbed Cu
Amount of adsorbed Cu
100%
The amounts of copper adsorption and recovery percent-age
from five consecutive adsorption/desorption cycles indi-cate
a desorption efficiency as high as 97%, and that the
copper-free fibres could be reused after neutralization. At
the 5th cycle, the adsorption capacity was found to be
25.7 mg/g, that is 90% of that determined at the 1st cycle
(28.6 mg/g). XPS surface analysis of copper complexed by
CF-PGMA-Cy fibres is in line with ICP measurements, as the
surface Cu/N atomic ratio after the 5th adsorption cycle was
found to be as high as 93.5% of that determined for the freshly
prepared chelatant fibres.
CF-PGMA-Cy fibres were evaluated as working electrodes
for sensing copper via adsorptive stripping voltammetry.
After adsorption and equilibration, Cu(II) should be reduced
to Cu(0) and integration of this stripping peak should provide
the Cu(II) content of the solution after construction of a cali-bration
curve. We shall present the proof of concept of this
1 2 3 4 5 6
0.0
0 400 800 1200
Binding energy (eV)
XPS-determined
copper
Cu/N
pH
2 3 4 5 6
0
ICP-determined
copper
Q (mg/g)
pH
0 10 20
0.0
XPS-determined
copper
Cu/N
time (h)
0 5 10 15 20 25
0
ICP-determined
copper
Q (mg/g)
time (h)
Fig. 4 – pH effect on copper uptake by CF-PGMA-Cy as determined by (a) XPS, in insert XPS survey regions of CF-PGMA-Cy
fibres at pH 5.2, (b) ICP, adsorption rate for copper ions onto CF-PGMA-Cy at pH 5.2 as determined by (c) XPS and (d) XPS.

5. 2110 C A R B ON 4 8 ( 2 0 1 0 ) 2 1 0 6 –2 1 2 2
0.50 Cu0 Cu2++ 2e
0.25
0.00
Cu2+ + e Cu+
analytical determination. Cyclic voltammetry measurements
were performed with a fibre immersed in a 103 M Cu(NO3)2
solution for 6 h. The anodic stripping determination of copper
ions was investigated by immersing the single CF-PGMA-Cy-
Cu fibre in a copper-free aqueous 0.1 M acetate buffered solu-tion
at pH 5, with a scan rate of 10 mV/s.
Fig. 5 shows the large stripping peak of Cu(0) at 0.06 V/
Ag/AgCl, that should permit the use of this modified electrode
for the analytical determination of Cu(II). The voltammogram
can be interpreted in the following way: starting from 0.4 V
and scanning towards negative potentials, one observes the
reduction of Cu(II) to Cu(I) at 0.25 V. The scan was then
stopped at 0.6 V for 30 s and it is possible to observe the in-crease
of the current at this potential: Cu(I) disproportionates
to Cu(0) and Cu(II); Cu(II) is then reduced at 0.6 V, its reduc-tion
to Cu(0) is responsible for the increase of the cathodic
current.
On the reverse scan, the stripping of Cu(0) to Cu(II) is ob-served
at 0.06 V as reported for copper stripping from
EDTA-functionalized polypyrrole [30]. Integration of the
stripping peak corresponds to 2.02 · 1012 mol of Cu0 for
1 cm of fibre immersed in the solution, which corresponds
to 2.85 · 106 mol of Cu0/g of chelatant fibre.
This work shows thus conclusively that picomole detec-tion
of adsorbed copper can be achieved with chelatant CF-PGMA-
Cy fibres.
Acknowledgements
The authors are grateful to Dr. Jinbo Bai (Ecole Centrale, Paris,
France) for the gift of carbon fibres, and to Dr. Minh Ngoc Ngu-yen
(LCPO, Bordeaux, France) for his help in starting this re-search
project.
R E F E R E N C E S
[1] Hilda C, Santos HC, Korn MGA, Ferreira SLC. Enrichment and
determination of molybdenum in geological samples and
seawater by ICP-AES using calmagite and activated carbon.
Anal Chim Acta 2001;642:79–84.
[2] Dias Filho NL, Polito WL, Gushikem Y. Sorption and
preconcentration of some heavy metals by 2-
mercaptobenzothiazole- clay. Talanta 1995;42:1031–6.
[3] Rengaraj S, Kim Y, Joo CK. Removal of copper from aqueous
solution by aminated and protonated mesoporous aluminas:
kinetics and equilibrium. J Colloid Interf Sci 2004;73:14–21.
[4] Sayari A, Hamoudi S, Yang Y. Applications of pore-expanded
mesoporous silica. Removal of heavy metal cations and
organic pollutants from wastewater. Chem Mater
2005;17:212–6.
[5] Bailey SE, Olin TJ, Bricka RM, Adrian DD. A review of
potentially low-cost sorbents for heavy metals. Water Resour
1999;33:2469–79.
[6] El-Nahhal IM, El-Ashga NM. A review on polysiloxane-immobilized
ligand systems: synthesis, characterization and
applications. J Organomet Chem 2007;692:2861–86.
[7] Safavi A, Iranpoor N, Saghir N. Directly silica bonded
analytical reagents: synthesis of 2-mercaptobenzothiazole–
silica gel and its application as a new sorbent for
preconcentration and determination of silver ion using solid-phase
extraction method. Sep Purif Technol 2004;40:303–8.
[8] Rivas BL, Maureira AE, Mondaca MA. Aminodiacetic water-soluble
polymer–metal ion interactions. Eur Polymer J
2008;44:2330–8.
[9] Liu P, Liu Y, Su Z. Modification of poly(hydroethyl acrylate)-
grafted cross-linked poly(vinyl chloride) particles via surface-initiated
atom-transfer radical polymerization (SI-ATRP).
Competitive adsorption of some heavy metal ions on
modified polymers. Ind Eng Chem Res 2006;45:2255–60.
[10] Deng S, Bai RB, Chen JP. Aminated polyacrylonitrile fibers for
lead and copper removal. Langmuir 2003;19:5058–64.
[11] Delamar M, De´sarmot G, Fagebaume O, Hitmi R, Pinson J,
Save´ant JM. Modification of carbon fiber surfaces by
electrochemical reduction of aryl diazonium salts:
application to carbon epoxy composites. Carbon
1993;35:801–7.
[12] Xua H, Zenga L, Huanga D, Xiana Y, Jin L. A Nafion-coated
bismuth film electrode for the determination of heavy metals
in vegetable using differential pulse anodic stripping
voltammetry: an alternative to mercury-based electrodes.
Food Chem 2008;109:834–9.
[13] Barbey R, Lavanant L, Paripovic D, Schu¨ wer N, Sugnaux C,
Tugulu S, et al. Polymer brushes via surface-initiated
controlled radical polymerization: synthesis,
characterization, properties, and applications. Chem Rev
2009;109:5437–527.
[14] Matrab T, Chehimi MM, Perruchot C, Adenier A, Guillez V,
Save M, et al. Novel approach for metallic surface-initiated
atom transfer radical polymerization using Electrografted
initiators based on aryl diazonium salts. Langmuir
2005;21:4686–94.
[15] Matrab T, Save M, Charleux B, Pinson J, Cabet-Deliry E,
Adenier A, et al. Grafting densely-packed poly(n-butyl
methacrylate) chains from an iron substrate by aryl
diazonium surface-initiated ATRP: XPS monitoring. Surf Sci
2007;601:2357–66.
[16] Matrab T, Chehimi MM, Pinson J, Slomkowski S, Basinska T.
Growth of polymer brushes by atom transfer radical
polymerization on glassy carbon modified by electro-grafted
initiators based on aryl diazonium salts. Surf Interface Anal
2006;38:565–8.
[17] Matrab T, Nguyen MN, Mahouche S, Lang P, Badre C, Turmine
M, et al. Aryl diazonium salts for carbon fiber surface-initiated
atom transfer radical polymerization. J Adhes
2008;84:684–701.
[18] Pinson J, Podvorica F. Attachment of organic layers to
conductive or semiconductive surfaces by reduction of
diazonium salts. Chem Soc Rev 2005;34:429–39.
-0.6 -0.4 -0.2 0.0 0.2 0.4
-0.25
Cu2+ + 2e Cu 0 Cu+ Cu2+ + Cu0
I (μA)
E (mV)
Fig. 5 – Cyclic voltammogram (scan rate 10 mV s1) of a
single CF-PGMA-Cy-Cu in 0.1 M acetate buffer (pH 5.0) and
Ref. Ag/AgCl. ATRP time was 2 h resulting in CF-PGMA
hybrids with thinner PGMA coatings; XPS-determined O/
C = 0.23 and Br/C = 0.001.

6. C A R B ON 4 8 ( 2 0 1 0 ) 2 1 0 6 –2 1 2 2 2111
[19] Jiang DE, Sumpter BG, Dai S. How do aryl groups attach to a
graphene sheet? J Phys Chem B 2006;110:23628–32.
[20] Zhi-Ya M, Yue-Ping G, Hui-Zhou L. Synthesis of
monodisperse nonporous crosslinked poly(glycidyl
methacrylate) particles with metal affinity ligands for protein
adsorption. Polym Int 2005;54:1502–7.
[21] Amigoni-Gerbier S, Desert S, Gulik-Kryswicki T. Larpent Ch.
Ultrafine selective metal-complexing nanoparticles:
synthesis by microemulsion copolymerization, binding
capacity, and ligand accessibility. Macromolecules
2002;35:1644–50.
[22] San Miguel V, Catalina F, Peinado C. Self-assembly of
physically crosslinked micelles of poly(2-acrylamido-2-
methyl-1-propane sulphonic acid-co-isodecyl methacrylate)-
copper(II) complexes. Eur Polymer J 2008;44:1368–977.
[23] Coskun R, Soykan C, Sacak M. Removal of some heavy metal
ions from aqueous solution by adsorption using
poly(ethylene terephthalate)-g-itaconic acid/acrylamide
fiber. React Funct Polym 2006;66:599–608.
[24] Seyhan S, Colak M, Demirel N. Solid phase extractive
preconcentration of trace metals using p-tert-butylcalix[
4]arene-1, 2-crown-4-anchored chloromethylated
polymeric resin beads. Anal Chim Acta 2007;584:462–8.
[25] Rutkowska J, Kilian K, Pyrzynska K. Removal and enrichment
of copper ions from aqueous solution by 1, 8-
diaminonapthalene polymer. Eur Polymer J 2008;44:2108–14.
[26] Mugisidi D, Ranaldo A, Soedarsono JW, Hikam M.
Modification of activated carbon using sodium acetate and its
regeneration using sodium hydroxide for the adsorption of
copper from aqueous solution. Carbon 2007;45:1081–4.
[27] Goyal M, Rattan VK, Aggarwal D, Bansal RC. Removal of
copper from aqueous solutions by adsorption on activated
carbons. Colloids Surf, A 2001;190:229–38.
[28] Jaramillo J, Gomez-Serrano V, Alvarez PM. Enhanced
adsorption of metal ions onto functionalized granular
activated carbon prepared from cherry stones. J Hazard Mater
2009;161:670–6.
[29] Febrianto J, Kosasih AN, Sunarso J, Ju YH, Indraswati N,
Ismadji S. Equilibrium and kinetic studies in adsorption of
heavy metals using biosorbent: a summary of recent studies.
J Hazard Mater 2009;161:1355–9.
[30] Heitzmann M, Bucher C, Moutet JC, Pereira E, Rivas BL, Royal
G, et al. Complexation of poly(pyrrole-EDTA like) film
modified electrodes: application to metal cations
electroanalysis. Electrochim Acta 2007;52:3082–7.
The effect of substrate positions in chemical vapor deposition
reactor on the growth of carbon nanotube arrays
Ge Li a, Supriya Chakrabarti a, Mark Schulz b, Vesselin Shanov a,*
a Department of Chemical and Materials Engineering, University of Cincinnati, OH, USA
b Department of Mechanical Engineering, University of Cincinnati, OH, USA
A R T I C L E I N F O
Article history:
Received 9 July 2009
Accepted 26 January 2010
Available online 1 February 2010
A B S T R A C T
The effect of substrate positions inside the chemical vapor deposition reactor on the length
and quality of the grown carbon nanotube (CNT) arrays is reported. It was found that longer
CNT arrays are grown when located downstream on the platform in the reactor. This effect
becomes more pronounced for increased growth time. Related factors such as temperature
of the gas mixture and its flow velocity seem to be responsible for the behavior. The quality
of the CNTs is not affected by the position of the substrates inside the reactor.
Published by Elsevier Ltd.
The interest in carbon nanotubes (CNTs) is increasing
worldwide because of their outstanding mechanical, electri-cal,
and optical properties. Intense research efforts have been
undertaken to synthesize aligned CNTs, but only a handful of
leading research groups can offer consistent quality. Our re-search
group recently developed a novel composite catalyst
for oriented growth of CNT arrays [1], and succeeded to grow
the longest multi-wall CNT forest (18 mm) reported in the lit-erature.
1 Thermal CVD is widely used to synthesis CNTs be-cause
of its potential for mass production, relatively low
deposition temperature, and ability to maintain the growth
conditions for long time [2]. It is well known that the dimen-sions
and structural characteristics of CNT grown by CVD de-pend
on the details of the CVD growth process. Variation in
nanotube growth has been investigated vs. reaction time [3];
catalyst amount (thickness or concentration) and composi-tion
[4–6]; temperature [7]; flow rates, pressure and composi-tion
of reaction gas [3,8–10]. Recent studies by Bronikowski
* Corresponding author: Fax: +1 513 556 3773.
E-mail address: vesselin.shanov@uc.edu (V. Shanov).
1 NSF Press Release (2007): http://www.nsf.gov/news/news_summ.jsp?cntn_id = 108992org = NSFfrom = news.
0008-6223/$ - see front matter Published by Elsevier Ltd.
doi:10.1016/j.carbon.2010.01.054