Photopatterning Freestanding Chiral Nematic Mesoporous Organosilica Films

Article abstract of DOI:10.1002/adfm.201703346

Chiral nematic mesoporous organosilica (CNMO) films are functionalized with a mixture of hydrophobic silanes and spiropyran compounds to create freestanding photochromic films that can be used for reversible photo-patterning. The mesoporosity and interconnected pore structure of the films imparted by the cellulose nanocrystal template enables a large cross-section of the material to be functionalized. Thus, the materials show intense absorption spectra from the tethered spiropyran and rapid color changes when the porous films are irradiated with UV or white light. The spiropyran-bound CNMO films behave as reversible sensors where metal binding to the spiropyran results in visible color changes detectable by the naked eye. These metals can be removed in the presence of ethanol and white light, regenerating the metal-free film. The proof-of-concept demonstrated in this paper may help to develop new photochromic displays, security features, and patterns.

Full text of DOI:10.1002/adfm.201703346

FULL PAPER
Photochromism
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Photopatterning Freestanding Chiral Nematic Mesoporous
Organosilica Films
Andrea S. Terpstra, Wadood Y. Hamad, and Mark J. MacLachlan*
the host properties (e.g., controlled analyte
Chiral nematic mesoporous organosilica (CNMO) films are functionalized
with a mixture of hydrophobic silanes and spiropyran compounds to create
freestanding photochromic films that can be used for reversible photo­
patterning. The mesoporosity and interconnected pore structure of the films
imparted by the cellulose nanocrystal template enables a large cross­section
of the material to be functionalized. Thus, the materials show intense absorp­
tion spectra from the tethered spiropyran and rapid color changes when the
porous films are irradiated with UV or white light. The spiropyran­bound
CNMO films behave as reversible sensors where metal binding to the spi­
ropyran results in visible color changes detectable by the naked eye. These
metals can be removed in the presence of ethanol and white light, regener­
ating the metal­free film. The proof­of­concept demonstrated in this paper may
help to develop new photochromic displays, security features, and patterns.
diffusion and large surface areas) to tailor
[16,17]
the functions of the hybrid materials.
Previously, photochromic molecules have
[
18]
been incorporated onto silica substrates,
silica particles, and porous silicates
[19]
[9,20]
for applications ranging from drug delivery
to chromatography. Mesoporous (organo)
silica are of particular interest due to their
high surface area, tunable pore diameters,
[21]
and readily modified surface chemistry.
Raboin et al. incorporated spirooxazines
into mesoporous organosilica and inves-
tigated the kinetics of thermal bleaching
within the solid support, but they did not
demonstrate continued reversibility or
[22]
patterning.
In 2000 and 2009, Wirns-
berger et al. and Malfatti et al., respectively,
incorporated SP into hexagonally arranged silica composite mate-
rials that were deposited on glass substrates to make reversibly
1
. Introduction
[23,24]
Stimuli-responsive materials are of immense interest for a
wide variety of applications, such as optically rewritable data
photochromic films.
Park et al. also reported the synthesis
of photochromic dyes in composite and mesoporous organo-
storage,[ smart windows, ophthalmic lenses, and sensors.
1,2]
[3,4]
silica hybrid films with cubic mesostructures. Their materials
[25]
These “smart” materials can undergo reversible changes in the
show slow conversion rates and quenching of the photochromic
response of the SP due to the polar environment of the silica. It
is often difficult to obtain mesoporous silica materials as large,
freestanding films that could be used for photochromic appli-
cations. However, we reported a method to create freestanding
chiral nematic mesoporous silica (CNMS) and mesoporous
organosilica (CNMO) films by condensing silica or organosilica
[
5]
presence of external stimuli such as light, heat, or electricity.
[
6]
Many molecular structures, including diarylethenes, spiro-
pyrans (SPs),[ and azobenzene, have been investigated as
photochromic materials that change color upon exposure to
light. SPs in particular are well-known photochromic molecules
7]
[8]
and are commonly used in the synthesis of responsive mate-
rials.[
9–12]
They can undergo reversible isomerization between
precursors, respectively, with cellulose nanocrystals (CNCs).
[26,27]
their open merocyanine (MC) and closed SP forms (Scheme 1)
through either ultraviolet light-induced cleavage of the CO
Subsequent removal of the CNCs yields mesoporous materials
with a chiral nematic pore structure.
[
7,13]
bond of the SP form or visible irradiation of the MC form.
We identified freestanding films of CNMO as candidates
for the incorporation of photoresponsive molecules in order to
generate new photopatternable and photoswitchable materials.
Here, we report that CNMO films modified with a mixture of
hydrophobic and amino organosilanes can bind photochromic
SP to create mesoporous organosilica films with SP molecules
integrated throughout the pore network. These new hybrid
freestanding films show intense absorption and undergo
reversible photopatterning, and are promising for the devel-
opment of photochromic displays, sensors, and patternable
security features.
Hybrid organic–inorganic porous “smart” materials are an
interesting class of advanced materials that have applications in
tunable optical devices and sensors.[14,15] By integrating respon-
sive components into porous materials, one can take advantage of
A. S. Terpstra, Prof. M. J. MacLachlan
Department of Chemistry
University of British Columbia
2
036 Main Mall, Vancouver, BC V6T 1Z1, Canada
E-mail: mmaclach@chem.ubc.ca
Dr. W. Y. Hamad
FPInnovations
2
665 East Mall, Vancouver, BC V6T 1Z4, Canada
2
. Results and Discussion
The ORCID identification number(s) for the author(s) of this article
can be found under https://doi.org/10.1002/adfm.201703346.
Et-CNMO films were synthesized according to the literature
procedure using 1,2-bis(trimethoxysilyl)ethane as precursor.
[
27]
DOI: 10.1002/adfm.201703346
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hydrogen bonding between the oxygen and Si-OH surface.[30]
This can be overcome by capping OH groups and reducing
the polarity of the silica surface through the addition of tert-
NO
2
UV
vis
[
18,31,32]
N
O
NO2
butyl(chloro)diphenylsilane (TBDS).
TBDS can also be
N
O
R
added to dilute the surface coverage of bound SP to reduce
intermolecular interactions that stabilize the MC form.
The CNMO films were functionalized by placing the films
R
MC
SP
Scheme 1. Photoisomerization of a spiropyran between the SP (color-
less) and MC (purple) forms.
−3
into a solution of 16 × 10 m TBDS in toluene at 100 °C for 12 h
−
3
followed by a solution of 6 × 10 m ATMS in toluene at 100 °C
for 12 h, creating organosilica films modified with TBDS and
ATMS groups; these films are denoted TBDS/ATMS-Et-CNMO.
The TBDS/ATMS-Et-CNMO films were soaked in a well-mixed
The resulting organosilica films are ≈50–60 µm thick and have
2
−1
Brunauer–Emmett–Teller (BET) surface areas of ≈500 m g
−
3
and Barrett-Joyner-Halenda (BJH) pore diameters of ≈7 nm.
Importantly, the CNMO films are iridescent owing to the chiral
nematic pore structure that is introduced by the CNC template.
For a chiral nematic structure, the peak wavelength reflected
from the structure (λmax) is given by λmax = navgP sin θ, where
navg is the average refractive index of the material, P is the pitch
solution of 0.5 × 10 m of 1 and EDC in ethanol at room tem-
perature for 24 h to form the SP-functionalized CNMO films,
denoted SP-Et-CNMO. Films were washed in ethanol overnight
to remove any unreacted SP.
The functionalized films were characterized using UV–vis
spectroscopy, CD spectroscopy, IR spectroscopy (Figure S1,
Supporting Information), nitrogen adsorption, and scanning
electron microscopy (SEM). Surface functionalization caused
a red shift in the wavelength reflected by the chiral nematic
structure (λmax) resulting from an increase in the average
refractive index (navg) of the material (Figure 1a). As TBDS
creates a hydrophobic environment in the pores, the SP form
of the spiropyran is the most stable form and has an absorp-
tion peak at 300–380 nm. A CD spectrum of the SP-Et-CNMO
films showed a peak corresponding to the reflection peak of the
chiral structure but no induced chirality was observed for the
SP component (Figure 1a). This is consistent with our previous
[
28]
of the chiral nematic order, and θ is the angle of incidence.
Normal to the film, sin θ = 1. As the reflection wavelength is
sensitive to the refractive index of components in the pores, the
reflection wavelength can serve as a way to monitor the incor-
poration of guests in the channels and functionalization of the
pores. Owing to the left-handed helical structure in these mate-
rials, left-handed circularly polarized light is selectively reflected
from the films and, thus, the materials show an intense posi-
tive signal by circular dichroism (CD) spectroscopy.
The photochromic SP 1 was selected for this study as it is a
well-studied reversible photochromic substance and is capable
of modifying the surface environment. Scheme 2 shows the
synthesis of 1. Indolenine was reacted with 3-bromopropionic
acid then 5-nitrosalicylaldehyde to produce the carboxylic-acid-
functionalized SP molecule 1. The organosilica films modi-
fied with 3-aminopropyltrimethoxysilane (ATMS) have amino
groups on the surface of the films that could react with 1 using
the coupling reagent 1-ethyl-3-(3-dimethylaminopropyl)carbodi-
imide (EDC), forming an amide bond and tethering the SP to
the surface of the organosilica.
[
33]
[34]
observations with conducting polymers,
molecules,
and
[
35]
other species inside CNMS or CNMO, where no induced CD
signal is observed for the guest.
Morphology of the thin film mesoporous organosilica mate-
rials was directly imaged by SEM (Figure 1c,d). Et-CNMO films
have the long-range chiral structure imparted by the CNC tem-
plate. Postsynthetically modified SP-Et-CNMO films showed
clusters of functionalization on the surface of the films and
along the pores. Nitrogen adsorption–desorption isotherms of
the TBDS/ATMS-CNMO and Et-CNMO films were also meas-
ured (Figure 1b). In a representative sample, treatment of the
films with ATMS and TBDS led to a reduction in the surface
Previous research has shown that photoactivity of tethered
SP molecules is sensitive to steric constraints.[
18,29]
Attempts
to tether 1 to CNMO films functionalized with only ATMS
resulted in deep red films that displayed no photochromic
properties despite long exposure times to UV or white light.
Photoisomerization of SP is hampered at high concentrations
because of intermolecular interactions; the polarity of the silica
environment also stabilizes the charged MC form and allows
2
−1
area by ≈140 m g . A small decrease in the pore size for the
TBDS/ATMS-Et-CMNO films (≈6 nm) was also observed com-
pared to the Et-CNMO films (7–8 nm). These reductions are
due to both the modification of the porous network and some
blockage of pores by aggregated ATMS. Thermogravimetric
H N
2
O
Si
O
Si
O
NO2
O
O
1)
Br
OH
o
N
O
NO2
O
Toluene, 100 C
CNMO FIlm
N
N
OHC
NO2
2)
Ethanol, EDC
rt, 24 hrs
O
O
OH
HO
HN
CNMO film
Piperidine, Ethanol
1
Scheme 2. Synthesis of SP-functionalized ethylene films (SP­Et­CNMO).
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Figure 1. a) Optical characterization of organosilica films by UV–vis spectroscopy (top) and CD spectroscopy (bottom) for the Et­CNMO (dash-dot-
dash), TBDS­Et­CNMO (dashed), TBDS/ATMS­Et­CNMO (dotted), and SP­Et­CNMO (solid). b) Nitrogen adsorption data for ethylene-bridged (solid)
and silane-modified CNMO films (dotted). Inset: BJH pore diameter data. SEM images of c) Et­CNMO (scale bar = 1 µm) and d) SP­Et­CNMO (scale
bar = 1 µm) reveal the well-ordered chiral nematic structure.
analysis of the films showed that ≈1 wt% of compound 1
films allows for the incorporation of a substantial quantity of
SP molecules, resulting in a high-intensity absorption signal.
A set of control experiments was performed to investigate the
binding of 1 onto the surface of the CNMO films (Figures S3
and S4, Supporting Information). CNMO films that did not
contain aminopropyltrimethoxysilane were exposed to com-
pound 1 and EDC similar to the conditions for the synthesis of
SP-Et-CNMO. UV–vis spectroscopy of these films showed no
MC absorption signal at 548 nm after irradiation with UV light
indicating that ATMS is essential to bind 1 onto the surface
of the films. Additionally, TBDS/ATMS-Et-CMNO films were
exposed to solutions of 1 with and without EDC, then washed
with 0.7 m NaOH to remove SP bound only through ionic inter-
actions. UV–vis spectroscopy of these irradiated films showed
that in the presence of EDC, most of the SP is covalently bound
to the surface of the films with some bound through ionic
interactions.
The freestanding nature of the CNMO films allows for
photopatterning of the SP-functionalized films. A photo-
mask containing the characters “UBC” was placed on top of
a SP-Et-CNMO film and the sample was irradiated with UV
light (365 nm) for 2 min (Figure 2d). When the photomask was
removed, the characters were visible due to the emergence of
the purple MC form. The photopattern was successfully erased
by exposure to white LED light for 10 min, regenerating the
−
1
(
0.03 mmol g ) was present in the material after modification
Figure S1, Supporting Information).
(
The SP-Et-CNMO films under ambient light displayed
only the colorless SP form. Films were irradiated for different
lengths of time using an 8 W 365 nm Hitachi black light
(Figure 2a). An increase in the UV–vis signal at 548 nm cor-
responding to the presence of the MC form was observed for
the first minute with a maximum signal reached after ≈20 min.
Slow conversion from MC to SP form can occur under dark
ambient light over 150 min (Figure 2c). A rough estimation of
the amount of photo-switched MC form after irradiation with
UV light was also determined to be 1–20 µmol cm− using a
3
modified Beer–Lambert law formula (see the Supporting Infor-
mation).[
36–38]
The absorption of the SP-Et-CNMO films upon
irradiation was compared to that of SP bound to nonporous
ethylene-bridged organosilica films (SP-Et-films) functionalized
using the same conditions (Figure S2, Supporting Information).
The freestanding nonporous SP-Et-films show a low absorption
of MC after UV irradiation that is comparable to previously
reported SP functionalized on glass surfaces, as these mate-
rials can only support monolayer functionalization.[18] On the
other hand, the SP-Et-CNMO films showed significantly more
absorption due to MC molecules (≈20–30×) after irradiation
than the SP-Et-films. The highly porous structure of the CNMO
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Figure 2. UV–vis spectra of SP­Et­CNMO films: a) transmission at 548 nm after photoirradiation at 365 nm for different lengths of time. Inset: Full scan
after 0, 1, 2, 7, and 15 min of irradiation. b) Repeated cycling for the photoisomerization of SP immobilized on CNMO films monitored by absorbance
of the MC form at 548 nm. c) UV–vis spectra of SP­Et­CNMO films showing the relaxation of irradiated MC­Et­CNMO films (irradiated with 365 mn,
8
W light for 18 min) to SP­Et­CNMO in ambient light over 150 min. d) Illustration of the writable/erasable nature of the freestanding mesoporous
organosilica films through UV irradiation and exposure to white LED light.
colorless film. As illustrated by Figure 2b, the photoisomeriza-
tion of the films is quasireversible, switching from the SP form
to the MC form by irradiating with UV (365 nm, 8 W, 10 min)
then reverting to the SP form using white LED light (10 min).
However, some photodegradation of the SP molecules is
observed by UV–vis after repeated switching. Photodegradation
in a polymer matrix that have limitations such as lack of revers-
ible binding, leaching of dye molecules and blockage of the
[
42]
binding sites over time.
SP-functionalized materials are
of particular interest for metal detection and purification as a
reversible metal ion-binding center can be generated by the
opened MC form through the negatively charged oxygen spe-
[
39–41]
[9,10,43]
of SP can occur through mono- and bimolecular pathways,
cies.
The large absorption band and high surface area of
and has been observed in other silica/SP materials.[ To the
best of our knowledge, this demonstrates the first example of
rewritable photochromism in freestanding mesoporous orga-
nosilica films with an interconnected pore structure. The inter-
connected pore structure within the CNMO films enhances
coverage of the interior surface with the tethered SP molecules,
creating films that can be using for photopatterning and metal
sensing.
18]
the freestanding SP-Et-CNMO films allow for sensitive detec-
tion of metals that create visible color changes upon binding in
the films (Figure 3).
−
3
Several 2 × 10 m ethanol solutions of different metal ions
(Zn(II), Sn(II), Ni(II), and Cu(II)) were prepared. After irradia-
tion of the ring-opened MC form, the films showed an intense
absorption band at 548 nm. Complexation with different metal
ions caused the MC absorbance to decrease accompanied by a
blue shift in the maximum absorption wavelength. This blue
shift is dependent on the metal ion and matched previous
Reversible sensors that can switch between active and passive
states offer advantages over organic indicator dyes immobilized
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Figure 3. UV–vis spectra demonstrating the reversible binding of M2+ in the SP­Et­CNMO films. a) Irradiated MC films (blue line) bind Zn(II) (pink
line). The metal is completely removed using white light and ethanol to return the original MC absorbance (dotted line). b) Blue shifts of MC absorb-
ance for Sn(II), Ni(II), and Cu(II) into the films. c) Freestanding CMNO films show clear color changes upon complexation of metal ions.
shifts seen in SP-polymer systems.[43] Blue shifts of the MC-M2+ 4. Experimental Section
complexes ranged from only ≈5 nm (M = Ni, Cu) to ≈30 nm
Reagents and characterization details are provided in the Supporting
Information.
(
M = Zn) giving the films a pink-orange color (Figure 3). The
2+
film complex with Sn had the largest blue shift of ≈90 nm
appearing slightly yellow and looking similar to the unirra-
diated SP films. No change in the reflection peak due to the
chiral structure of the films was observed from complexation
with metal ions, indicating that they had a negligible influence
on the refractive index of the film. The metal–film complexes
were exposed with white LED light while immersed in an
ethanol solution to dissociate the metal ions and ring-close to
the SP form. The films could be irradiated again with UV light
to the ring-opened MC form free of the metal ion (Figure 3a).
The reversible binding of metal ions resulted in visible color
changes, making these CNMO films good candidates for use as
metal sensors.
Synthesis of 1: SP derivative was prepared as described in the
literature.[ A mixture of 2,3,3-trimethylindolenine (0.69 mL, 4.3 mmol)
and 3-bromopropionic acid (0.66 g, 4.3 mmol) was dissolved in dry
toluene (20 mL) and heated under nitrogen at 100 °C for 12 h. The
product was extracted from toluene using 100 mL of distilled water,
washed with chloroform (50 mL × 4) and dried. The remaining solid was
dissolved in ethanol (18 mL) and combined with 5-nitrosalicylaldehyde
44]
(0.80 g, 4.8 mmol) and piperidine (0.52 mL, 5.3 mmol). The mixture was
heated at reflux for 5 h then cooled in an ice bath, filtered and washed
with cold ethanol. The resulting precipitate was recrystallized from
hot ethanol and dried to yield 1 (640 mg, 1.7 mmol, 40%). 1H NMR
(
3
300 MHz, DMSO-d ): δ 1.07 (s, 3H), 1.20 (s, 3H), 2.45–2.57 (m, 2H),
6
.34–3.40 (m, 2H), 5.99–8.2 (aromatic, 9H). EIMS m/z: calculated for
C H O N 380.4; found: 380.
21
20
5
2,
Postsynthetic Functionalization of CNMO Films: Et­CNMO films
[27]
were prepared according to the literature. Et­CNMO films (50 mg)
were heated under vacuum at 100 °C overnight. Films were placed in
dry toluene (20 mL) and TBDS (320 µL of 1 m in methylene chloride,
3
. Conclusion
0
.32 mmol) and stirred at 100 °C for 12 h. Films were filtered, washed
with methylene chloride (10 mL), then acetone (10 mL) and dried under
vacuum at 100 °C for 3 h. This procedure was repeated for a solution
of ATMS (16 µL, 0.09 mmol) in dry toluene (15 mL) at 100 °C for
CNMO films were functionalized with TBDS, ATMS, and SP
to produce freestanding photochromic films. The mesoporo-
sity and interconnected pore structure of the films engender
intense absorption and allows for rapid conversion from the
SP to MC form. This demonstrates the first example a rewrit-
able and patternable photochromic material based on free-
standing mesoporous organosilica films with an interconnected
pore structure. These new materials can be reversibly photo-
patterned and also have the potential to be used as sensors for
metal ions.
1
2 h. Dried TBDS/ATMS-functionalized films were placed in a solution
of ethanol (20 mL) containing EDC (35 mg, 0.23 mmol) and compound
1 (5.0 mg, 0.01 mmol) at room temperature in the dark for 24 h. Films
were washed in ethanol overnight to obtain SP-functionalized Et-CNMO
films (SP­Et­CNMO). Due to day-to-day changes in humidity and
temperature affecting the drying times of the CNMO films, the chiral
pitch (reflected wavelength) varied between samples. To the best of our
knowledge, the different chiral pitches of the films did not significantly
affect the functionalization of the silica.
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[
[
[
18] R. Rosario, D. Gust, M. Hayes, F. Jahnke, J. Springer, A. A. Garcia,
Supporting Information
Langmuir 2002, 18, 8062.
19] J. Allouche, A. L. Beulze, J.-C. Dupin, J.-B. Ledeuil, S. Blanc,
D. Gonbeau, J. Mater. Chem. 2010, 20, 9370.
20] a) J. Y. Bae, J.-I. Jung, B.-S. Bae, J. Mater. Res. 2004, 19, 2503;
b) L. A. Mühlstein, J. Sauer, T. Bein, Adv. Funct. Mater. 2009, 19,
Supporting Information is available from the Wiley Online Library or
from the author.
2
027; c) I. Casades, M. Álvaro, H. García, M. N. Pillai, Photochem.
Photobiol. Sci. 2002, 1, 219.
[21] a) B. J. Melde, B. T. Holland, C. F. Blanford, A. Stein, Chem. Mater.
999, 11, 3302; b) S. Inagaki, S. Guan, Y. Fukushima, T. Ohsuna,
Acknowledgements
The authors acknowledge financial support from the Natural Sciences
and Engineering Research Council (NSERC). A.S.T. is grateful to NSERC
for a postgraduate scholarship.
1
O. Terasaki, J. Am. Chem. Soc. 1999, 121, 9611; c) T. Asefa,
M. J. MacLachlan, N. Coombs, G. A. Ozin, Nature 1999, 402,
8
67.
[
22] L. Raboin, M. Matheron, J. Biteau, T. Gacoin, J.-P. Boilot, J. Mater.
Chem. 2008, 18, 3242.
Conflict of Interest
The authors declare no conflict of interest.
[23] L. Malfatti, S. Costacurta, T. Kidchob, P. Innocenzi, M. Casula,
H. Amenitsch, D. Dattilo, M. Maggini, Microporous Mesoporous
Mater. 2009, 120, 375.
[
24] G. Wirnsberger, B. J. Scott, B. F. Chmelka, G. D. Stucky, Adv. Mater.
000, 12, 1450.
[25] S. S. Park, S.-H. Hong, S. H. Lee, C.-S. Ha, Sci. Adv. Mater. 2014,
, 1425.
Keywords
2
mesoporous silica, photochromism, photopatterns, spiropyran
6
Received: June 19, 2017
Revised: July 31, 2017
Published online:
[26] K. E. Shopsowitz, H. Qi, W. Y. Hamad, M. J. MacLachlan, Nature
2010, 468, 422.
[27] K. E. Shopsowitz, W. Y. Hamad, M. J. MacLachlan, J. Am. Chem.
Soc. 2012, 134, 867.
[
[
28] H. de Vries, Acta Crystallogr. 1951, 4, 219.
29] R. Rosario, D. Gust, M. Hayes, J. Springer, A. A. Garcia, Langmuir
2003, 19, 8801.
[
[
[
[
[
1] X. Guo, D. Zhang, G. Yu, M. Wan, J. Li, Y. Liu, D. Zhu, Adv. Mater.
004, 16, 636.
2] M.-S. Wang, G. Xu, Z.-J. Zhang, G.-C. Guo, Chem. Commun. 2010,
6, 361.
3] M.-Q. Zhu, L. Zhu, J. J. Han, W. Wu, J. K. Hurst, A. D. Q. Li, J. Am.
Chem. Soc. 2006, 128, 4303.
4] S. Scarmagnani, Z. Walsh, C. Slater, N. Alhashimy, B. Paull,
M. Macka, D. Diamond, J. Mater. Chem. 2008, 18, 5063.
5] M. A. C. Stuart, W. T. S. Huck, J. Genzer, M. Müller, C. Ober,
M. Stamm, G. B. Sukhorukov, I. Szleifer, V. V. Tsukruk, M. Urban,
F. Winnik, S. Zauscher, I. Luzinov, S. Minko, Nat. Mater. 2010, 9,
2
[30] M. Fujimaki, S. Kawahara, Y. Matsuzawa, E. Kurita, Y. Hayashi,
K. Ichimura, Langmuir 1998, 14, 4495.
4
[31] R. P. W. Scott, Silica Gel and Bonded Phases: Their Production; Proper-
ties and use in LC, John Wiley & Sons, Ltd, Chichester 1993.
[32] B. C. Bunker, B. I. Kim, J. E. Houston, R. Rosario, A. A. Garcia,
M. Hayes, D. Gust, S. T. Picraux, Nano Lett. 2003, 3,
1723.
[33] S. H. M. Mehr, M. Giese, H. Qi, K. E. Shopsowitz, W. Y. Hamad,
M. J. MacLachlan, Langmuir 2013, 29, 12579.
[34] M. Giese, J. C. De Witt, K. E. Shopsowitz, A. P. Manning, R. Y. Dong,
C. A. Michal, W. Y. Hamad, M. J. MacLachlan, ACS Appl. Mater.
Interfaces 2013, 5, 6854.
[35] P.-X. Wang, V. M. Zamarion, W. Y. Hamad, M. J. MacLachlan,
Dalton Trans. 2015, 44, 14724.
[36] S. Ardo, G. J. Meyer, J. Am. Chem. Soc. 2011, 133, 15384.
[37] M. Pazoki, P. W. Lohse, N. Taghavinia, A. Hagfeldt, G. Boschloo,
Phys. Chem. Chem. Phys. 2014, 16, 8503.
101.
[
[
[
[
6] M. Irie, Chem. Rev. 2000, 100, 1685.
7] Y. Hirshberg, E. Fischer, J. Chem. Soc. 1954, 297.
8] H. Rau, E. Lueddecke, J. Am. Chem. Soc. 1982, 104, 1616.
9] C. T. Burns, S. Y. Choi, M. L. Dietz, M. A. Firestone, Sep. Sci.
Technol. 2008, 43, 2503.
[
10] A. K. Chibisov, H. Görner, Chem. Phys. 1998, 237, 425.
[
11] I. Vlassiouk, C.-D. Park, S. A. Vail, D. Gust, S. Smirnov, Nano Lett.
[38] M. Ogawa, K. Kuroda, J. Mori, Langmuir 2002, 18, 744.
[39] G. Baillet, G. Giusti, R. Guglielmetti, J. Photochem. Photobiol., A
1993, 70, 157.
[40] M. Sakuragi, K. Aoki, T. Tamaki, K. Ichimura, Bull. Chem. Soc. Jpn.
1990, 63, 74.
2
006, 6, 1013.
12] X. Tian, B. Wang, J. Li, J. Zeng, K. Chen, Carbohydr. Polym. 2017,
57, 704.
[
1
[
13] S. Bénard, P. Yu, Adv. Mater. 2000, 12, 48.
[
14] C. Sanchez, B. Lebeau, F. Chaput, J.-P. Boilot, Adv. Mater. 2003, 15,
[41] R. Klajn, Chem. Soc. Rev. 2014, 43, 148.
1
969.
[42] R. Byrne, D. Diamond, Nat. Mater. 2006, 5, 421.
[43] K. H. Fries, J. D. Driskell, G. R. Sheppard, J. Locklin, Langmuir 2011,
27, 12253.
[44] A. Fissi, O. Pieroni, G. Ruggeri, F. Ciardelli, Macromolecules 1995,
28, 302.
[
[
[
15] B. Lebeau, P. Innocenzi, Chem. Soc. Rev. 2011, 40, 886.
16] P. Yang, S. Gai, J. Lin, Chem. Soc. Rev. 2012, 41, 3679.
17] F. P. Nicoletta, D. Cupelli, P. Formoso, G. De Filpo, V. Colella,
A. Gugliuzza, Membranes 2012, 2, 134.
Adv. Funct. Mater. 2017, 1703346
1703346 (6 of 6)
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