Redox properties of LDH microcrystals coated with a catechol-bearing phosphonate derived from dopamine

Article abstract of DOI:10.1039/c4ra03660c

The surface of Zn-Al-chloride LDH microcrystals (LDH = Layered Double Hydroxides) was activated by grafting a redox active catechol bearing bis-phosphonate obtained by dopamine derivatization. The obtained phosphonate uniformly coats the LDH crystals surface and the catechol groups are exposed. The redox activity of the catechol was employed for the quick and easy synthesis of Gold NPs, which are supported onto the LDH microcrystal surface. The synthetic procedures and the complete characterization of the hybrid system are reported. This journal is the Partner Organisations 2014.

Full text of DOI:10.1039/c4ra03660c

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Redox properties of LDH microcrystals coated with
a catechol-bearing phosphonate derived from
dopamine†
Cite this: RSC Adv., 2014, 4, 26912
Maria de Victoria Rodrıguez,a Ernesto Brunet,a Morena Nocchetti,b
´
c
cd
*
Federica Presciutti and Ferdinando Costantino
The surface of Zn–Al-chloride LDH microcrystals (LDH ¼ Layered Double Hydroxides) was activated by
grafting a redox active catechol bearing bis-phosphonate obtained by dopamine derivatization. The
obtained phosphonate uniformly coats the LDH crystals surface and the catechol groups are exposed.
The redox activity of the catechol was employed for the quick and easy synthesis of Gold NPs, which are
supported onto the LDH microcrystal surface. The synthetic procedures and the complete
characterization of the hybrid system are reported.
Received 22nd April 2014
Accepted 10th June 2014
DOI: 10.1039/c4ra03660c
www.rsc.org/advances
2D materials, layered double hydroxides (LDHs) epitomize one
of the most prevalent compounds actually used for a huge
number of applications such as catalyst in many processes,9
Introduction
Catechol bearing molecules can be found in a very high number
of natural and biological processes, including neurosignalling,1
photoprotection,2 metal complexation,3 and surface adhesion.4
The latter characteristic is typical of dopamine (3,4-dihy-
droxyphenylalanine) which is responsible of the mussel foot
protein adhesion. This feature has been recently employed as
bio-mimetic tool for the design of highly adhesive mussel
inspired lms and materials, thanks to the facile polymeriza-
tion of dopamine into polydopamine. The catechol-redox
activity of the dopamine was also recently used to induce the
reduction of noble metals into metal nanoparticles (NPs) giving
rise to several hybrid systems, based on polydopamine polymer
and noble metal NPs.5 Among them we can cite the synthesis of
adhesive mussel-inspired lms containing Au and Ag NPs with
high conductive properties,6 with antimicrobial activity7 and
core–shell system for imaging and antitumoral activity.8
controlled drug delivery systems,10 gas capture,11 water purier12
or in biomedical applications.13
Herein we report on the surface modication of well crys-
tallized ZnAl-LDH microcrystals achieved by graing it with a
catechol-bearing phosphonate derived from dopamine, in order
to impart redox properties to the system. The redox properties
of this new hybrid system were then employed for the synthesis
of gold nanoparticles (AuNPs) stabilized onto the LDH surface
through the oxidation to quinone of the catechol groups
exposed on the surface.
Experimental
Instrumental details
XRPD patterns for Rietveld renements were collected with Cu
Ka radiation on a PANalytical X'PERT PRO diffractometer,
PW3050 goniometer equipped with an X'Celerator detector. The
long ne focus (LFF) ceramic tube operated at 40 kV and 40 mA.
To minimize preferential orientations of the microcrystals, the
samples were carefully side-loaded onto an aluminum sample
holder with an oriented quartz monocrystal underneath. Ther-
mogravimetric (TG) measurements were performed using a
Netzsch STA490C thermoanalyser under a 20 mL minꢀ1 air ux
with a heating rate of 5 ꢁC minꢀ1. FE-SEM images were collected
with a LEO 1525 ZEISS instrument working with an acceleration
voltage of 15 kV. TEM images were collected with Philips 208
Transmission Electron Microscope (TEM). A small drop of the
dispersion was deposited on a copper grid that had been pre-
coated with a Formvar lm and then evaporated in air at room
temperature (r.t.). UV-vis spectrometry was performed by using a
Deuterium-Halogen lamp as excitation source, (emitted light
Actually, one of the major challenges of this chemistry is
focused on the coupling of such active hybrid systems with
other materials which can act both as solid support and that
could embody an added value due to their intrinsic properties
(such as TiO2, graphene, carbon nanotubes and so on). Among
a
´
´
´
Departamento de Quımica Organica, Facultad de Ciencias, Universidad Autonoma de
Madrid, 28049 Madrid, Spain
bDipartimento di Scienze Farmaceutiche, University of Perugia, Via del Liceo 1, 06123,
Perugia, Italy
cDipartimento di Chimica, Biologia e Biotecnologie, University of Perugia, Via Elce di
Sotto 8, 06123, Perugia, Italy
dCNR – ICCOM, Via Madonna del Piano 10, Sesto Fiorentino, 50019, Firenze, Italy.
E-mail: ferdinando.costantino@unipg.it
† Electronic supplementary information (ESI) available: Complete synthetic
procedures, Rietveld renement details, FT-IR spectra. See DOI:
10.1039/c4ra03660c
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from 200 to 1100 nm) and a high sensitive CCD spectrometer anchoring group can be introduced. However, conventional
(Avaspec 2048 USB2, 200–1100 nm range, spectral resolution 8 Irani synthesis cannot be directly carried out by using formal-
nm). Three single 400 micron core bres directed the light from dehyde and H3PO3 because, in those strong acidic conditions,
the source to the analysing surface. 1H and 13C spectra were deprotection of catechol and its polymerization readily occurs.
recorded on Bruker AV-300 (300 MHz, 75.5 MHz respectively), 31
P
Therefore, a modied Irani reaction has been performed by
and 19F-NMR spectra were recorded on Bruker AVII-300 (121 MHz reuxing acetonide-protected dopamine in the presence of
and 282 MHz respectively) in the indicated solvents. Trans- paraformaldehyde and diethylphosphite.16 The last stage in the
mittance mid-FT-IR measurements were carried out with a JASCO synthesis of H4P2O6DOPA is the hydrolysis of phosphonate
FT/IR 4000 spectrophotometer. The spectral range collected was groups and deprotection of catechol that was performed on a
400 to 4000 cmꢀ1, with a spectral resolution of 2 cmꢀ1 acquiring single step by reuxing in concentrated HCl. Scheme 1 briey
100 scans. The samples were dispersed on anhydrous KBr pellets. summarizes the synthetic routes with the yields, whereas the full
Metal and phosphorus analyses were performed with Varian 700- detailed procedure is reported in the ESI.†
ES series inductively coupled plasma-optical emission spec-
trometers (ICP-OES). A weighted amount of the samples (about
10 mg) was dissolved in concentrate HCl/HNO3 3/1 v/v and the
solution was brought to a nal volume of 50 mL. The solution
properly diluted was analyzed by ICP. Elemental analysis were
also performed on a LECO CHNS-932 analyzer in the SIdI, UAM.
Total Reection X-Ray Fluorescence (TXRF) measurements were
performed on a 8030C Atomika spectrometer using a direct solid
method. The spectrometer is equipped with a X-ray tube of 3 kW
and a multilayer monocromator. The measurements were per-
formed using 50 kV, 8500 cps of speed and time acquisition of
500 s. The microwave equipment was a Biotage initiator 2.5.
Synthesis of ZnAl-chloride LDH
Crystalline ZnAl-chloride LDH (ZnAl-Cl) was synthesized by
modifying the “Urea-method”.17 ZnCl2 (13.637 g, 100 mmol),
AlCl3$6H2O (10.505 g, 43.5 mmol) and urea (10.44 g, 173.82
mmol) were reuxed in 300 mL of deionized water for 24 h. The
precipitate was centrifuged and washed three times with
deionized water. The Zn–Al molar ratio was evaluated by means
of ICP analysis and the water content was evaluated by ther-
mogravimetric analysis yielding the following formula
[Zn0.67Al0.33(OH)2]Cl0.33$0.6H2O.
Synthesis of ZnAl/H2P2O6DOPA
Syntheses
Synthesis of H4P2O6DOPA
In a microwave tube ZnAl-Cl (750 mg) was dispersed in 6.5 mL
of H2O. Dopamine (417 mg, 1.22 mmol) was dissolved into a
solution of 1 mL of KOH 2 M and added to LDH-Cl. The mixture
was then heated at 120 ꢁC for 45 minutes under nitrogen using
normal absorption into a Biotage initiator 2.5 microwave oven.
The resulting solid was centrifuged, washed twice with deion-
[{[2-(3,4-Dihydroxyphenyl)ethyl]imino}di(methylene)]bis(phos-
phonic acid), hereaer H4P2O6DOPA, was prepared by a modi-
ed Mannich type reaction14 starting from a doubly protected
dopamine. The procedure involved the protection of both
catechol and the amino groups in order to prevent polymeri-
zation of the dopamine and the formation of p-conjugated
complexes like quinidrone.
ꢁ
ized water and dried at 50 C for 6 h.
Synthesis of Au@ZnAl/H2P2O6DOPA
One of the main problems of catechol is its quick oxidation to
the quinone form. Due to this, the key step in the synthesis of
the H4P2O6DOPA is the protection of this group in order to avoid
oxidation. In the presence of an amino group direct protection
of a catechol group, by acetonide formation is not possible due
to the high reactivity of the amino group thus forcing its
protection rst. The procedure of this initial stage was per-
formed at room temperature by treating dopamine hydrochlo-
ride with methyl triuoroacetate in methanol in the presence of
triethylamine.15 This protection would be easily removed as
shown later on in the scheme. Then, the catechol group was
protected building the aforementioned acetonide in high yield
by reuxing triuoracetate-dopamine with 2,2-dimethoxy-
propane (DMP) in the presence of a catalytic amount of p-tol-
uenesulfonic acid (p-TsOH). In order to shi the equilibrium
reaction, the water formed was removed with a soxhlet extractor
lled with CaCl2 or activated molecular sieves. Once the catechol
is protected, the next step is the introduction of the anchoring
phosphonic groups so that the amino protection needs to be
removed, maintaining catechol's. Once more, this reaction was
performed at room temperature under very mild conditions
8 mL of a solution of NaAuCl4 in water (0.0125 M, 4.5 mg mLꢀ1
was added slowly to a suspension of 100 mg of LDH containing
)
Scheme 1 Synthetic procedure to prepare H4P2O6DOPA. Reagents,
conditions and yields: (a) CF3COOMe, Et3N in MeOH, 12 h r.t., 86%; (b)
2,2-dimethoxypropane, p-TsOH in benzene, 4 h reflux, 90%; (c)
LiOH$H2O in THF/H2O 4 h r.t., 87%; (d) HCOH, diethylphosphite, 2 h
using LiOH in a H2O/THF solution. Then the diphosphonate 120 ꢁC, 55%; (e) HCl 37% 12 h reflux, 100%.
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dopamine in 10 mL of CO2-free deionizated water. The reaction
mixture turned into dark red color and was stirred for 12 h at r.t.
under nitrogen and protected from light. The resulting solid
was centrifuged, washed twice with deionizated water and dried
ꢁ
at 50 C for 6 h.
Results and discussion
The surface of ZnAl-Cl was functionalized by using microwaves
with anions of H4P2O6DOPA obtained by partial deprotonation
of the phosphonic group in 2 M KOH. A 2 : 1 molar ratio of
KOH/H4P2O6DOPA (4 acid protons per mol of phosphonic acid)
was used with the aim of obtain H2P2O6DOPA2ꢀ di-anion in
which two acid protons are maintained.
The H2P2O6DOPA2ꢀ anions exchange the Clꢀ anions of the
LDH and, upon dehydration at 50 ꢁC, a graing reaction
between the acid P–OH and the OH– groups of the lamella
occurs. The appearance of a small absorption band around
1000 cmꢀ1 can be ascribed to fully deprotonation of P–OH
groups and the formation of M–O–P bonds (see Fig. 1S, ESI†).18
The loss of one water molecule per phosphonic group also
occurred. The diffraction pattern of ZnAl/H2P2O6DOPA (Fig. 2)
Fig. 2 XRPD patterns of the ZnAl/H2P2O6DOPA and of Au@ZnAl/
H2P2O6DOPA LDH.
Rietveld renement of the Au@ZnAl/H2P2O6DOPA diffrac-
tion pattern allowed to get information on the volume weighted
crystalline domain size of Au nanoparticles and on the relative
quantitative phase analysis of the two components.
Microstructural analysis was performed by using the GSAS
program.19 Table 1S† reports the instrumental and renement
details. First, the instrumental contribution to the peak
broadening was previously evaluated by the Rietveld renement
of the prole of lanthanum hexaboride (LaB6), as an external
peak prole standard. We assumed that the standard was not
affected by microstrain, and the instrumental broadening was
modeled by the renement of W and Y peak shape parameters
for Gaussian and Lorentzian contributions, respectively.
˚
is typical of the ZnAl-Cl, having an interlayer distance of 7.75 A,
indicating that the exchange reaction of H2P2O6DOPA involved
only the LDH surface and that did not occur into the interlayer
region of the LDH.
Fig. 1 schematizes the exchange/graing reaction of the
H2P2O6DOPA anions onto the surface of hexagonal ZnAl-Cl
microcrystals. The content of Zn, Al, P, N, O, C and H in ZnAl/
H2P2O6DOPA was determined by ICP, CHN elemental analysis
and TXRF, considering a quantitative graing reaction the
composition resulted [Zn0.67Al0.33(OH)1.896]Cl0.226(P2O6DO-
PA)0.052$0.23H2O. Analysis calculated C : H : N for ZnAl/
H2P2O6DOPA was 6.01 : 2.92 : 0.70 and found 5.96 : 3.11 : 0.71.
Coherent domain size (volume weighted) parallel (D ) and
k
perpendicular (Dt) to the (200) and to the (111) directions was
calculated by using the following expressions
A
NaAuCl4 aqueous solution was added to a ZnAl/
H2P2O6DOPA aqueous dispersion, the mixture turned into dark
red color indicating that the Au(III) ions were quickly reduced to
gold nanoparticles on the LDH surface by the catechol groups.
X-ray diffraction pattern of the recovered composite Au@LDH/
H2P2O6DOPA shows (Fig. 2) the reections of cubic gold beside
the ZnAl-Cl reections.
D ¼ 1800l/p(X + Xe) and Dt ¼ 1800l/pX
k
Microstrain as source of peak broadening was also consid-
ered. In order to give an average strain value along the selected
direction a simple strain model (%) was also used by rening
the Gaussian and the Lorentzian contribution Y, Ye and Yi where
Yi is the experimental instrumental contribution obtained with
the LaB6 standard. The equation for the strain% 3k and 3t to the
selected broadening axes are
3k ¼ (p/18 000)(Y + Ye ꢀ Yi) and 3t ¼ (p/18 000)(Y ꢀ Yi)
where l is the wavelength and X and Xe are two terms related to
the Lorentzian contribution of the size broadening effect.
The calculation gave as results an average D 200 crystalline
k
domain size of about 16 nm whereas the Dt 200 is about
100 nm.
The D 111 and Dt111 were 34 and 12 nm respectively. These
k
data roughly indicate the crystalline domain sizes measured
along and perpendicular to the selected directions and gener-
ally they do not correspond to the observed size from electron
microscope images. In our case a size anisotropy perpendicular
Fig. 1 Schematic representation of the exchange/grafting reaction of
H2P2O6DOPA anions onto the LDH surface.
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to the (200) seems to be present. Concerning the microstrain the
only predominant effect, nicely related to the peak broadening
effect, can be detected only on the direction perpendicular to
(200) which is 3t (ꢂ103) ¼ 1.9. The calculation carried out on
different directions did not give any valuable result. This means
that, along that direction, strain efficiently contributes to the
broadening. The high D value found for that plane (200) is then
affected by the strain contribution and it is probably over-
estimated. Quantitative phase analysis was carried out by using
the Bish and Howard formula.20
amSm
Wm ¼
k¼m
X
akSk
k¼1
where Wm and ak are the weighed fraction of the mth component
in the sample and its calculated density, respectively; ak is given
as follows: ak ¼ ZkMkUk where Zk, Mk, and Uk are the number of
chemical formula units in a unit cell, the molecular weight, and
the unit-cell volume, respectively. The calculation, in absence of
amorphous phases, gave as result 22% of Au.
Fig. 3 Rietveld plot of Au@ZnAl/H2P2O6DOPA LDH.
Assuming that the only amorphous contribution to the
mixture can be ascribed to the presence of the H2P2O6DOPA
anions coating (calculated on the basis of the molar fraction ¼
18.5 wt%), the normalized relative phase weight percentages
were LDH ¼ 64.9%, Au ¼ 16.6%.
The value calculated from quantitative analysis is 0.138 mol
of Au/mol of Au@LDH/H2P2O6DOPA that is in good agreement
with the value found by elemental analysis (ICP and TXRF)
(0.127 mol of Au/mol of compound). The elemental analysis of
Au@ZnAl/H2P2O6DOPA showed that the content of Zn and Al
was different from the ZnAl/H2P2O6DOPA starting material. In
particular aer Au deposition the solid was enriched in Al. The
oxidation of catechol groups to quinone groups occurs with the
formation of H+ ions that locally decrease the pH.21 LDHs at low
pH value can undergo to a partial dissolution with a preferential
leaching of the more soluble cation that is Zn. This process on
the one hand leads to a partial dissolution of LDH on the other
hand drives the catechol oxidation reaction to right promotion
the formation of metallic gold clusters. Considering that the
maximum aluminium molar fraction possible for LDH is 0.40 a
segregation of Al(OH)3 was hypothesized and the composition of
the solid was then written as [Zn0.60Al0.40(OH)1.834]Cl0.234(P2O6-
DOPA)0.083Au0.127$0.3H2O + 0.04 Al(OH)3. Analysis calculated for
Au@ZnAl/H2P2O6DOPA C : H : N was 6.59 : 2.41 : 0.77 and
found 6.38 : 2.77 : 0.77.
Rietveld plot is shown in Fig. 3 whereas the complete
renement parameters and procedures are reported in ESI,
Table 1S.†
FE-SEM and TEM images of the pristine LDH and of the
Au@LDH/H2P2O6DOPA microcrystals are shown in Fig. 4.
Fig. 4a (FE-SEM) shows the pristine ZnAl-LDH microcrystals;
it should be remarked that the surface of the crystals was well
polished. Aer the modication with H2P2O6DOPA anions the
crystal surface turned into dark colour and, at higher magni-
cation degree (Fig. 4c and d) it also became corrugated. Indeed,
Fig. 4 FE-SEM (a–d) and TEM (e–f) images of pristine (a), and modified
(b–f) ZnAl-LDH microcrystals.
homogeneously present over the entire surface. These struc-
tures cannot be attributed to smaller gold clusters as they are
not present in the equivalent TEM images which are more
sensitive to the atomic weight (Fig. 4e and f).
This also suggests that the modication of the LDH micro-
crystals with H2P2O6DOPA anions occurred efficiently with a
homogeneous covering of the surface with the organic
molecules.
Gold NPs are well dispersed over the entire LDH crystal
surface and apparently they seem to have a spherical shape with
a narrow size distribution ranging from 60 to 90 nm. Some of
them are aggregated in larger clusters formed by 4 or 5 NPs
each.
small globular structures of size
< than 10 nm were
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respect to dopamine, the reactivity of this novel phosphonate is
drastically changed due to the non availability of the –NH2
which precludes the possibility of self-polymerization into
polydopamine.
The H2P2O6DOPA anions have been then used to uniformly
coat the surface of well crystallized LDH hexagonal crystals, the
exposed catechol groups operating as the redox agent for the
stabilization of polydisperse gold NPs. Respect to the conven-
tional methods, this strategy is “template free” and allows to
increase the absolute amount of gold nanoclusters onto the
LDH surface. However, the disadvantage of this system resides
in the scarce control of the gold NPs size and shape. We plan to
address further applications of the catechol-bearing LDH in
different elds, like the graing of magnetic NPs and the
complexation of catalytic metals and/or luminescent lanthanide
ions for advanced applications in heterogenous catalysis,
theranostic and imaging.
Fig. 5 Uv-vis spectrum of Au@ZnAl/H2P2O6DOPA. The SPR signals at
525, 545 and 560 nm are indicated.
Acknowledgements
Surface Plasmonic Resonance (SPR) spectra were also
collected on the bulk solid. The absorption spectrum is reported
in Fig. 5.
F.C. and M. N. thank Project FIRB 2010 no. RBFR10CWDA_003
for the nancial support.
SPR spectrum shows three distinct peaks (determined by
second derivative of the curve) at 525, 545 and 560 nm. This
conrms the polydisperse nature of the gold nanoclusters.
According to El-sayed and Link22 the position of the SPR
signals can be related with the average particle size for mono-
disperse systems. In our case the predominant 560 nm signal is
indicative of 70 to 90 nm size gold clusters. The signals at
545 and 525 nm can be related to 50 and 25 nm clusters size
respectively. A fourth signal around 635 nm can be ascribed to
one of the absorption modes of quinone or metal coordinated
hydro-quinones.23
These data are in good agreement with the FE-SEM and TEM
images. LDH as solid supports for AuNPs have been recently
reported from other authors and these materials were mainly
employed for catalytic purposes.24
The NPs were grown on the LDH crystal surface by using
conventional reduction methods involving citrate or urea as
precipitating agent. The average size of AuNPs reported in other
papers was generally lower than that reported in our work (5 to
20 nm, vs. 40 to 90 nm). Nevertheless, respect to the conven-
tional methods, the catechol coating LDHs appear to be more
efficient in terms of Au(0) conversion, allowing the precipitation
of higher amount of Au, expressed as weight%.
Notes and references
1 (a) S. Callier, M. Snapyan, S. L. Crom, D. Prou, J.-D. Vincent
and P. Vernier, Biol. Cell, 2003, 95, 489–502; (b) A. Zhang,
J. L. Neumeyer and R. J. Baldessarini, Chem. Rev., 2007,
107, 274–302.
2 M. Brenner and V. Hearing, J. Photochem. Photobiol., 2008,
84, 539–549.
3 (a) K. G. Alley, G. Poneti, P. S. D. Robinson, A. Nafady,
B. Moubaraki, J. B. Aitken, S. C. Drew, C. Ritchie,
B. F. Abrahams, R. K. Hocking, K. S. Murray, A. M. Bond,
H. H. Harris, L. Sorace and C. Boskovic, J. Am. Chem. Soc.,
2013, 135, 8304–8323; (b) A. Dei, G. Poneti and L. Sorace,
Inorg. Chem., 2010, 49, 3271–3277.
4 (a) J. H. Waite, Int. J. Adhes. Adhes., 1987, 7, 9–14; (b)
J. H. Waite, Integr. Comp. Biol., 2002, 42, 1172–1180.
5 (a) H. Hartati, M. Santoso, S. Triwahyono and D. Prasetyoko,
Bull. Chem. React. Eng. Catal., 2013, 8, 14–33; (b) I. Reyero,
´
G. Arzamendi and L. M. Gandıa, Key Eng. Mater., 2013, 571,
1–26.
6 (a) Y. Long, J. Wu, H. Wang, X. Zhang, N. Zhao and J. Xu,
J. Mater. Chem., 2011, 21, 4875–4881; (b) G. J Gou,
L. E. Dong, F. J. Bao, Z. Y. Wang, L. Jiao, J. Huang, Y. Sun
and B. Bing Xue, Appl. Mech. Mater., 2013, 320, 495–504.
7 D. E. Fullenkamp, J. G. Rivera, Y. Gong, K. H. A. Lau, L. He,
R. Varshney and P. B. Messersmith, Biomaterials, 2012, 33,
3783–3791.
8 Y. Lee, H. Lee, Y. Beom Kim, J. Kim, T. Hyeon, H. Wook Park,
P. B. Messersmith and T. G. Park, Adv. Mater., 2008, 20,
4154–4157.
Moreover, found density of Au NPs onto the LDH crystal
surface by us was generally higher than that reported in other
papers. The effort to improve the size/shape tuning of the gold
cluster, by changing the initial amount of Au and other
parameters like solvents and temperature, will be carried out in
the near future.
9 (a) A. Vaccari, Appl. Clay Sci., 1999, 14, 161–168; (b) M. Turco,
G. Bagnasco, U. Costantino, F. Marmottini, T. Montanari,
G. Ramis and G. Busca, J. Catal., 2004, 228, 43–55; (c)
T. Montanari, M. Sisani, M. Nocchetti, R. Vivani,
Conclusions
In this paper the organic synthesis of a catechol-bearing phos-
phonic acid, derived from dopamine, has been reported with
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M. Concepcion Herrera Delgado, G. Ramis, G. Busca and
RSC Advances
13269; (f) M. Nocchetti, A. Donnadio, V. Ambrogi,
P. Andreani, M. Bastianini, D. Pietrella and L. Latterini, J.
Mater. Chem. B, 2013, 1, 2383–2393.
U. Costantino, Catal. Today, 2010, 152, 104–109; (d)
G. Busca, U. Costantino, T. Montanari, G. Ramis, C. Resini
and M. Sisani, Int. J. Hydrogen Energy, 2010, 35, 5356–5366; 14 K. Moedritzer and R. R. Irani, J. Org. Chem., 1966, 31, 1603–
(e) A. Fronzo, C. Pirola, A. Comazzi, C. L. Bianchi, A. Di 1606.
Michele, R. Vivani, M. Nocchetti, M. Bastianini, 15 Z. Liu, B. Hu and P. B. Messersmith, Tetrahedron Lett., 2010,
D. C. Boffito and F. Galli, Fuel, 2014, 119, 62–69; (f) 51, 2403.
I. Reyero, G. Arzamendi and L. M. Gandıa, Key Eng. Mater., 16 A. A. Prishchenko, M. V. Livantsov, O. P. Novikova,
´
2013, 571, 1–26.
10 (a) Clays and Health Clays in Pharmacy, Cosmetics,
L. I. Livantsova and V. S. Petrosyan, Heteroat. Chem., 2010,
21, 430–440.
Pelotherapy, and Environmental Protection, Special Issue of 17 (a) U. Costantino, F. Marmottini, M. Nocchetti and R. Vivani,
Appl. Clay Sci., ed. M. I. Carretero and G. Lagaly, 2007, vol.
36; (b) V. Ambrogi, V. Ciarnelli, M. Nocchetti, L. Perioli
and C. Rossi, Eur. J. Pharm. Sci., 2009, 73, 285–291; (c) LDH
Eur. J. Inorg. Chem., 1998, 10, 1439–1446; (b) M. Bastianini,
D. Costenaro, C. Bisio, L. Marchese, U. Costantino,
R. Vivani and M. Nocchetti, Inorg. Chem., 2012, 51, 2560.
in physical, chemical, bio-chemical and life sciences in 18 (a) U. Costantino, M. Casciola, L. Massinelli, M. Nocchetti
Developments in Clay Science – Volume 5B Handbook of
Clay Science: Techniques and Applications, ed. F. Bergaya
and G. Lagaly, 2013, vol. 5B; (d) L. Li, W. Gu, J. Chen,
W. Chen and Z. P. Xu, Biomaterials, 2014, 35, 3331–3339;
and R. Vivani, Solid State Ionics, 1997, 97, 203–212; (b)
U. Costantino, S. Clementi, M. Nocchetti and R. Vivani,
Mol. Cryst. Liq. Cryst. Sci. Technol., Sect. A., 1998, 311, 207–
210.
´
(e) V. Rives, M. del Arco and C. Martın, Appl. Clay Sci., 19 C. Larson and R. B. von Dreele, Generalized Crystal Structure
2014, 88–89, 239–269.
Analysis System, Los Alamos National Laboratory, Los
11 (a) H. H. Q. Wang, Z. Tay, J. Zhong, J. Luo and A. Borgna,
Alamos, NM, 2001.
Energy
Environ.
Sci.,
2012,
5,
7526–7530;
(b) 20 D. L. Bish and S. A. Howard, J. Appl. Crystallogr., 1998, 21, 86–
O. Aschenbrennera, P. McGuireb, S. Alsamaq, J. Wang,
91.
S. Supasitmongkola, B. Al-Durib, P. Styringa and J. Wood, 21 S. A. Mechler, A. A. J. Torriero, A. Nafady, C. Y. Lee,
Chem. Eng. Res. Des., 2011, 89, 1711–1721.
12 F. L. Theiss, S. J. Couperthwaite, G. A. Ayoko and R. L. Frost,
J. Colloid Interface Sci., 2014, 417, 356.
A. M. Bond, A. P. O'Mullane and S. K. Bhargava, Colloids
Surf., A, 2010, 370, 35–41.
22 S. Link and M. A. El-Sayed, J. Phys. Chem. B, 1999, 103, 4212–
4217.
13 (a) U. Costantino, V. Ambrogi, L. Perioli and M. Nocchetti,
Microporous Mesoporous Mater., 2008, 107, 149–160; (b) 23 M. J. Sever and J. J. Wilker, Dalton Trans., 2004, 1061–1072.
J.-M. Oh, S.-J. Choi, G.-E. Lee, S.-H. Han and J.-H. Choy, 24 (a) J. Zhao, X. Kong, W. Shi, M. Shao, J. Han, M. Wei,
Adv. Funct. Mater., 2009, 19, 1617–1624; (c) E. Ruiz-Hitzky,
P. Aranda, M. Darder and G. Rytwo, J. Mater. Chem., 2010,
20, 9306–9321; (d) L. Perioli, V. Ambrogi, M. Nocchetti,
M. Sisani and C. Pagano, Appl. Clay Sci., 2011, 53, 696–703;
(e) U. Costantino, F. Costantino, F. Elisei, L. Latterini and
M. Nocchetti, Phys. Chem. Chem. Phys., 2013, 15, 13254–
D. G. Evans and X. Duan, J. Mater. Chem., 2011, 21, 13926–
13933; (b) F. Zhang, X. Zhao, C. Feng, B. Li, T. Chen,
W. Lu, X. Lei and S. Xu, ACS Catal., 2011, 1, 232–237; (c)
Y. Wang, D. Zhang, M. Tang, S. Xu and M. Li, Electrochim.
Acta, 2010, 55, 4045–4049.
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