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Article
Core−Shell Pluronic-Organosilica Nanoparticles with Controlled
Polarity and Oxygen Permeability
Cristina De La Encarnacion Bermudez, Elahe Haddadi, Enrico Rampazzo, Luca Petrizza, Luca Prodi,
and Damiano Genovese*
Cite This: Langmuir 2021, 37, 4802−4809
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sı Supporting Information
*
ABSTRACT: Nanostructured systems constitute versatile carriers
with multiple functions engineered in a nanometric space. Yet, such
multimodality often requires adapting the chemistry of the
nanostructure to the properties of the hosted functional molecules.
Here, we show the preparation of core−shell Pluronic-organosilica
“PluOS” nanoparticles with the use of a library of organosilane
precursors. The precursors are obtained via a fast and quantitative
click reaction, starting from cost-effective reagents such as diamines
and an isocyanate silane derivative, and they condensate in building
blocks characterized by a balance between hydrophobic and Hbond-rich domains. As nanoscopic probes for local polarity, oxygen
permeability, and solvating properties, we use, respectively,
solvatochromic, phosphorescent, and excimer-forming dyes covalently linked to the organosilica matrix during synthesis. The results obtained here clearly show that the use of these organosilane
precursors allows for finely tuning polarity, oxygen permeability, and solvating properties of the resulting organosilica core,
expanding the toolbox for precise engineering of the particle properties.
potential to modify the network of silica nanostructures for
this purpose.15−17 Besides controlling the hosting ability of
nanocarriers, a pre-requirement for the design of successful
nanostructures for nanomedicine is their colloidal stability,18
also in biological fluidsthus in the presence of large protein
concentration.12,19 The well-known preparation of core−shell
Pluronic-silica “PluS” nanoparticles20,21 has recently demonstrated to yield small, monodisperse, and colloidally and
photophysically stable nanoparticles, also in vivo. This type of
silica nanoparticles grows templated by micelles of Pluronic
F127a triblock copolymer composed of poly(ethylene
glycol) (PEG) and poly(propylene glycol) (PPO)in acidic
water at 30 °C, and exhibits a silica core diameter of ca. 10 nm
and a hydrodynamic diameter of ca. 25 nm, which corresponds
to the PEG blocks of Pluronic surfactant, which remain as
brushes on the silica surface. Their very small size and the
shielding PEG surface are responsible for long circulation time,
low accumulation rate, and enhanced targeting ability.13,21
INTRODUCTION
Functional nanoarchitectures, defined as materials engineered
at the nanoscale to perform specific functions,1 have revealed
in the last decades an enormous potential for transversal
application in science and technology,2,3 owing to their
versatility and to their small scale, which allows us to easily
and creatively interface them with biological structures.4−6 In
the field of drug delivery, the production of carriers with high
load, fast dissolution rate, and specific targeting ability has been
of capital importance to maximize the action of many
pharmaceuticals. An additional advantage of this sought
specificity is the drastic reduction of the amount of drug
that, after unnecessary contact with nontargeted biological
tissues and organs, will be largely dispersed in the environment
when not causing adverse effects.7 To reach this goal, various
formulation strategies have been developed with the main aims
of optimizing pharmacokinetics and of properly matching the
polarity of the specific drugs. Nowadays, the emergence of
nanomedicine8,9 with the strategic design of nanocarriers
endowed with multiple functions, including targeting, yearns
for transferring this knowledge to the nanoscale.10−14
An efficient nanocarrier is required to host high loads of the
drug molecule, which largely depends on matching its solvating
nanoenvironment to the chemistry of the drug itself. The
possibility to tune the chemistry of the nanocarrier is therefore
of utmost importance, and organosilanes22−24 have the
■
© 2021 The Authors. Published by
American Chemical Society
Received: December 11, 2020
Revised: March 26, 2021
Published: April 14, 2021
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Figure 1. PluOS NP synthesis: organosilane precursors OS1−4, here schematized with two trivalent silane moieties and an organic linker, were
mixed with TEOS to obtain Pluronic-organosilica nanoparticles PluOS NPs, doped with one of the luminescent probes PYS, DSS, or RBS.
Scheme 1. Chemical Structures of Organosilanes OS1−4, Obtained via Reaction of Diamines 1−4 and
Triethoxysylilpropylisocyanate, and of the Silanized Reporter Dyes PYS, DSS, or RBS (c)
In this context, and starting from the robust synthetic
protocol of PluS NPs, we explore here the possibility to modify
this reliable preparation method with the use of organosilane
precursors produced in situ with a fast and quantitative click
reaction. The templating action of Pluronic F127 and the mild
conditions can allow us to obtain nanoparticles with small size
and high colloidal stability, but with a chemical network
different from silica, characterized by a balance between
hydrophobic and H-bond rich domains that allows for finely
tuning polarity and oxygen permeability of the resulting
nanoarchitectures. In addition, we explore the nanoenvironment of the resulting organosilica matrix by means of three
luminescent probes that provide information on local polarity,
permeability to oxygen, and ability to solubilize hydrophobic
molecules.
■
MATERIALS AND METHODS
All reagents and solvents were used as received without further
purification. Nonionic surfactant Pluronic F127, tetraethoxysilane
(TEOS, 99.99%), trimethylsilylchloride TMSCl (≥98%), tetramethoxysilane (TMOS), acetic acid (≥99.8%), reagent-grade dimethylformamide (DMF), 1-pyrenemethylamine hydrochloride (95%), 5(dimethylamino)naphthalene-1-sulfonyl chloride (dansyl chloride,
≥99.0%), hexamethylenediamine (98%), ethylenediamine (≥99.5%),
p-phenylendiamine (98%) and N,N′-diphenylethylenediamine (98%)
were purchased from Sigma-Aldrich. Triethylamine (≥99.5%), 3(triethoxysilyl)propyl isocyanate (≥95%), and NaCl were purchased
from Fluka.
The luminophores dansyl sulfonamide triethoxysilane (DSS),25
pyrene triethoxysilane (PYS),26 and Ru(bpy)32+ triethoxysilane
derivative (RBS)27 were prepared as previously reported. A Milli-Q
Millipore system was used for the purification of water (resistivity
≥18 MΩ).
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Figure 2. (a−c) Hydrodynamic diameter distribution of RBS-doped PluOS with 50, 25, and 12.5% organosilane 1 as obtained by DLS
measurement (distribution by intensity). (d) Average hydrodynamic diameter dH with relative error bars of all NPsprepared with the three
fluorescent probeswith decreasing organosilane content and with or without end-capping agent TMSCl (from DLS). TEM micrographs of some
organosilica NPs end-capped with TMSCl, scale bar = 20 nm: (e) RBS-doped PluOS with 25% organosilane OS1 (core diameter dC = 11 ± 3 nm),
(f) RBS-doped PluOS with 12.5% organosilane OS1 (core diameter dC = 12 ± 2 nm).
The organoethoxysilane derivatives OS1−4 were synthesized by
click reactions between the corresponding diamine (i−iv) and (3isocyanatopropyl)triethoxysilane. In a typical preparation, 0.2 mmol
of a diamine was dissolved in 0.1 mL of dimethylformamide (DMF)
and 0.4 mmol of (3-isocyanatopropyl)triethoxysilane was added. This
mixture was vortexed for 1 min and then stirred for 30 min at room
temperature. Each synthesis was performed prior to the preparation of
nanoparticles and their product used without further purification.
Nanoparticles synthesis: to prepare core−shell organosilica nanoparticles (PluOS NPs), desired amounts of organosilane derivative
(OS1−4), triethoxysilane dye derivative (in 0.1 mL DMF), and
tetraethylorthosilicate (TEOS) were added under magnetic stirring at
room temperature (25 °C) to an acidic aqueous solution (acetic acid
1 M, 1.6 mL) containing Pluronic F127 (100 mg) and NaCl (67 mg).
Detailed information on the exact quantities can be found in Table S1
in the Supporting Information. After 3 h, the capping agent
trimethylsilylchloride (TMSCL, 10 μL, 0.08 mmol) was then added
and the solution was stirred overnight. Nanoparticle suspensions were
purified via dialysis versus ultrapure water for 3 days (RC membrane,
12 KDa cutoff), and finally diluted to a total volume of 5 mL with
water.
started with a click reaction in DMF between a set of diamines
and 3-(triethoxysilyl)propyl isocyanate to yield organosilane
precursors OS1−4 (Scheme 1). The reaction is fast and
quantitative, as it results from NMR and MS characterizations
(see Supporting Information), thus allowing us to use the
precursors without further purification. Analogous reactions
were previously used to functionalize the surface of nanomaterials for catalytic purposes30,31 or to modify mesoporous
nanoparticles for drug delivery.32 OS precursors are then cocondensated with tetraethoxysilane (TEOS) to tune the
chemical nanoenvironment of the resulting organosilica matrix.
Substituting half or more of the TEOS reagent in a typical
synthesis of PluS NPs with an organosilane precursor results in
the formation of nanoparticles of comparable size and
morphology as PluS NPs, as witnessed by transmission
electron microscopy (TEM) (Figure SI2) and by the main
peak of the distribution obtained by dynamic light scattering
(DLS) (distribution by intensity, Figure 2a). Yet, reduced
colloidal stability is observed: aggregation is indeed confirmed
by DLS analysis, which shows the presence of large
sedimenting aggregates.
However, by reducing the fraction of the organosilane
precursors to 25 or 12.5%, we observed enhanced colloidal
stability of the resulting PluOS NPs (Figure 2b−d). Plotting
the dispersion of diameters measured with DLS (distribution
by intensity, Figure 2d) also clearly shows the importance of
the capping agent TMSCl to obtain the sought colloidal
stability in water of core−shell organosilica nanoparticles.33
The average hydrodynamic diameter of PluOS NPs with 25 or
12.5% organosilanes, end-capped with TMSCl, ranges between
20 and 50 nm (Table 1). TEM reveals that in all cases, the
organosilica core features a highly monodispersed diameter of
15 ± 5 nm, suggesting thatas in the synthesis of PluS NPs
also in the presence of the organosilane precursor, the final
core size is determined by the template action of the Pluronic
F127 micelles (Figures 2e−f, S9 and S11).
RESULTS AND DISCUSSION
In a typical preparation of previously reported core−shell
Pluronic-silica “PluS” nanoparticles,28 TEOS was added to a
micellar solution of Pluronic F127 in water containing 1 M
acetic acid; after condensation, trimethylsilylchloride
(TMSCL) was added as an end-capping agent to promote
long-term colloidal stability. Finally, a dialysis-based workup
led to the isolation of monodispersed nanoparticles having a
silica core of 11 ± 1 nm and hydrodynamic diameter of 25 ± 5
nm, well characterized in terms of concentration of nanoparticles, surface chemistry, and resulting photophysical
properties when doped with suitable dyes.29
Starting from this method, we investigated the possibility to
mix TEOS and an organosilane precursor to produce
colloidally stable, long shelf-life, small core−shell organosilica-PEG nanoparticles (Pluronic-organosilica nanoparticles,
here abbreviated as PluOS NPs, Figure 1). The preparation
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25 ± 5 nm) and feature satisfactory stability against
aggregation.
After morphological characterization via TEM and DLS, we
have investigated relevant physicochemical properties of the
so-modified nanoparticle core using specific dyes, derivatized
with silane moieties to be covalently linked within the
organosilica network. Specifically, we have used a solvatochromic dye (dansyl silane, DSS) as a reporter of the local
polarity,35−37 an excimer-forming dye (pyrene silane, PYS) to
monitor the ability of the core to solubilize hydrophobic
molecules,38 and an oxygen-sensitive phosphorescent dye
(Ru(bpy)32+ silane, RBS) to report on the O2 permeability
of the organosilane core.39,40
Three sets of organosilica NPs end-capped with TMSCl
were synthesized, in three different organosilane: TEOS ratios
(50, 25, and 12.5% organosilane molar fraction), for each
silanized dye. The nominal dye doping degree was 1% for DSS
and RBS and 0.2% for PYS, expressed in moles vs moles of
silane moieties.
The solvatochromic DSS dyes provide information on the
micropolarity of the organosilica core, in which they are
entrapped owing to their covalent silane link.36,37,41 Doping
the organosilica matrix during its formation with a small
amount of DSS indicates that the polarity of the nanostructured environment can be tuned by tuning the chemistry
of the diamine (1−4), i.e., of the organosilane linker (OS1−4).
Indeed, as shown in Figure 3a,b, the emission peak
progressively shifts to a higher energy (hypsochromic shift)
with increasing the number of carbon atoms in the aliphatic
chain and the number of phenyl rings of the diamine, following
the expected polarity scale diethylamine > hexanediamine >
phenylenediamine > diphenylethylenediamine. Interestingly,
the “reference” silica network formed by TEOS features
intermediate polarity, suggesting that the organosilanes have a
“double-sided” role on the overall polarity: while the diamine
all-carbon chain linker contributes to make the silica network
more hydrophobic, the urea groups formed by the reaction of
amine and isocyanate provide local H-bond-rich, hydrophilic
spots. The balance between the hydrophilicity of the urea
groups and the lipophilicity of aliphatic and aromatic linkers
results in a fine-tuning of the overall micropolarity of the
organosilica nanoparticles. The comparison of the emission
maxima of PluOS NPs and of DSS in different solvents, as
plotted in Figure 3b, provides evidence of the magnitude of
nanopolarity variations obtained by substituting TEOS with
OS1−4, which ranges from a similar environment to ethanol
with OS1 to a polarity lower than dichloromethane with OS4.
The emission anisotropy of DSS dyes are very high for all
PluOS NPs (0.25 < r < 0.35), and the monoexponential
fluorescence lifetimes and high quantum yields are comparable
to or higher than those of the monomeric DSS dye (Table S2
in Supporting Information), indicating that the dyes are well
dispersed inside the rigid organosilica matrices and do not
suffer from aggregation or self-quenching.
Besides altering the average polarity of the chemical
nanoenvironment within the nanoparticles, the introduction
of organosilane groups may introduce different permeabilities
of the network to relevant chemical species such as O2. It is
important to note, at this point, that the tuning of oxygen
permeability can be an interesting option to address specific
applications. In fact, while a low permeability is desired for
having a high luminescence intensity and photostability, a high
permeability can allow the use of the nanoparticles as
Table 1. Morphological and Photophysical Parameters of
Dye-Doped Organosilica NPs
dye
DSS
% OSa
0%
50%
25%
12.5%
RBS
0%
50%
25%
12.5%
PYS
0%
50%
25%
12.5%
OS
dH/nmb
ndyec
[dye] %
mol/molTEOS
only
TEOS
1
2
3
4
1
2
3
4
1
2
3
4
only
TEOS
1
2
3
4
1
2
3
4
1
2
3
4
only
TEOS
1
2
3
4
1
2
3
4
1
2
3
4
32
14.4
0.180
0.66
57
39
66
114
38
34
60
48
21
27
44
40
37
1.9
8.3
0.7
4.8
4.2
7.5
15.8
8.1
8.2
10.3
17.9
12.6
7.4
0.024
0.104
0.009
0.060
0.053
0.094
0.200
0.101
0.103
0.129
0.224
0.158
0.093
0.74e
0.92e
0.71d,e
0.89d,e
0.66e
0.56e
0.09d,e
0.24d,e
0.56e
0.61e
0.10d,e
0.22d,e
0.070
88
74
40
172
24
36
47
55
32
40
46
44
29
0.28
0.57
0.74
0.62
3.2
3.9
6.2
4.2
7.7
6.9
10.4
7.9
7.03
0.004
0.007
0.009
0.008
0.040
0.049
0.078
0.053
0.096
0.086
0.130
0.099
0.088
0.090
0.072
0.072
0.058
0.061
0.070
0.072
0.053
0.059
0.35
144
30
54
93
77
47
38
42
31
28
44
36
3.65
7.22
0.92
3.37
4.00
4.08
5.27
3.87
5.40
5.31
5.82
4.49
0.046
0.090
0.012
0.042
0.050
0.051
0.066
0.048
0.068
0.066
0.073
0.056
0.38
0.36
0.07
0.28
0.47
0.52
0.025
0.26
0.50
0.51
0.026
0.26
Article
PLQY
f
0.080
f
a
Percentage of organosilane precursor with respect to TEOS.
Hydrodynamic diameter in nanometers, average value, distribution
by intensity, from DLS measurements. cAverage number of dyes per
PluOS NP, obtained from absorbance spectra and assuming constant
NP concentration from synthesis as in previous work.34 dThe
photoluminescence quantum yields (PLQYs) are estimated excluding
an energy transfer contribution from the organosilane matrix (see
excitation spectra in Figures S1). eScattering is excluded from PLQY
calculation, but it still introduces a significant error due to low
absorption and high scattering at the excitation wavelength. fThe
PLQY could not be measured.
b
As a general trend, the increase of the TEOS/organosilane
ratio leads to an increased monodispersity in the hydrodynamic radius, suggesting that the organosilanes introduce
some instability in the colloidal system. DLS shows that
TMSCl end-capped PluOS NPs with equal to or less than 50%
organosilane precursor converges to PluS morphology (dH =
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Figure 3. (a) Emission spectra of DSS-doped PluOS NPs obtained with 50% OS 1−4 and of PluS NPs obtained with TEOS or TMOS as silane
precursors. (b) Trends of the emission peak wavelength of DSS-doped PluOS NPs as a function of OS precursor and of its concentration. The
emission peak wavelengths of PluS NPs obtained with TEOS or TMOS as silane precursors are marked in gray dashed line for reference. The
emission peak wavelengths of DSS dye dissolved in different solvents are marked with colored lines as reference for polarity. Peak wavelengths are
obtained with an error <0.5 nm.
Figure 4. (a) Average lifetime of RBS-doped PluOS NPs at 0% (only TEOS), 12.5, and 25% OS molar ratios, for nanoparticles obtained using
OS1−OS4 as organosilane precursors. (b) Plot of the short (τ1, squares) and long (τ2, circles) components of the phosphorescence decay of RBSdoped PluOS NPs 12.5% (red) and 25% OS molar ratio (black), for nanoparticles obtained using OS1−OS4 as organosilane precursors. In
deareated solution (after purging with N2), the decays are monoexponential and close to the τ2 of the corresponding aerated solution (empty
circles, red and black for 12.5 and 25% OS molar ratios, respectively). The short lifetime of RBS-doped PluS NPs (only TEOS) is 510 ns and is
represented by the gray dashed line.
sensitizers for photodynamic therapy. Finally, if chemosensors
for molecular oxygen are desired, different oxygen permeation
can tune the effective working range for pO2 measurements. We
select RBS dye as a dopant of PluOS NPs to shine light on this
aspect, due to the dependence of its phosphorescence lifetime
on the diffusion of molecular oxygen. Indeed, the quenching
rate of its triplet emissive state increases by increasing the
concentration and diffusion rate of O2.42,43 Compared to the
pure silica network, which forms an almost impenetrable
matrix for oxygen, the core−shell organosilica NPs feature a
shorter emission lifetime, indicating a higher local concentration and diffusion of molecular oxygen (Figure 4c). The
lifetime shortening becomes more evident when the organosilane content of PluOS NPs is higher, highlighting the direct
correlation between the presence of an organic counterpart in
the organosilica network and the resulting oxygen permeability
of the structure. In addition, the most apolar organosilane 4
appears to confer the highest oxygen permeability to the
organosilane matrix. This trend is confirmed both when
looking at the average lifetime (Figure 4a) or at the shortlifetime component τ1, i.e., the one that reports more
accurately on the quenching from O2 (Figure 4b). In addition,
the long-lifetime component τ2, which reports on the
nonquenched fraction of RBS dyes, is comparable for all
PluOS samples, indicating that (i) a fraction of RBS dyes is still
not accessible to O2 and that (ii) RBS dyes are not quenched
by the PluOS matrix. The observed quenching of RBS dyes is
therefore only due to O2 diffusion. A conclusive proof of this
statement is provided by the reversibility of the emission
lifetime in the absence of O2, removed by purging PluOS NPs
solutions with N2: the lifetime becomes monoexponential and
matches at approximately 1.1 μs the long component of the
decays acquired in the presence of O2, proving that also the
quenched RBS dyes can reach the long phosphorescence
lifetime of the fraction of RBS dyes which are not reached by
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the preparation of organosilica matrices with finely tuned
polarity, due to the balance between hydrophobic and H-bondrich domains. Silanized derivatives of fluorescent probes for
polarity (Dansyl), oxygen permeability (Ru(bpy)32+), and
solvating properties (Pyrene) were employed to test the
nanoparticle matrices, yielding clear indication of the broad
range of chemical nanoenvironments featured by the different
organosilica nanoparticles.
O2. Emission lifetimes measured for PluOS NPs with 50% OS
were considered not reliable, due to the relatively high degree
of aggregation that may substantially affect oxygen permeation.
Finally, pyrene dyes are very sensitive to local solubility, with
ready formation of dimers and excimers in unfavorable
conditions that can be sensitively detected owing to their
characteristic broad emission band centered at 480 nm.44,45
Emission from excimers is observed when pyrene dyes can
come in contact during the lifetime of the excited state, which
is possible either for diffusing species at high concentration or
for static (nondiffusing) pyrene dyes when they are located
very close to one another. In the last case, which is the case of
rigid nanoenvironments, excimeric emission greatly depends
on two factors: the local concentration of pyrene moieties and
the ability of the solvating environment to stabilize the pyrene
dyes, keeping them isolated from one another.46,47 We have
observed, at a rather constant local pyrene concentration, the
appearance of a strong excimeric emission from organosilica
NPs containing organosilane OS1 (Figure 5), while pyrene
■
ASSOCIATED CONTENT
sı Supporting Information
*
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.langmuir.0c03531.
Details on synthesis; NMR spectra; characterization
methods; photophysical data; additional TEM images;
spectra of absorbance, emission, excitation, and emission
anisotropy; luminescence decays curves; and fitting
results (PDF)
■
AUTHOR INFORMATION
Corresponding Author
Damiano Genovese − Dipartimento di Chimica “Giacomo
Ciamician”, Università di Bologna, 40126 Bologna, Italy;
orcid.org/0000-0002-4389-7247;
Email: damiano.genovese2@unibo.it
Authors
Cristina De La Encarnacion Bermudez − Dipartimento di
Chimica “Giacomo Ciamician”, Università di Bologna,
40126 Bologna, Italy
Elahe Haddadi − Dipartimento di Chimica “Giacomo
Ciamician”, Università di Bologna, 40126 Bologna, Italy;
Department of Chemistry, College of Sciences, Shiraz
University, Shiraz 71454, Iran
Enrico Rampazzo − Dipartimento di Chimica “Giacomo
Ciamician”, Università di Bologna, 40126 Bologna, Italy
Luca Petrizza − Dipartimento di Chimica “Giacomo
Ciamician”, Università di Bologna, 40126 Bologna, Italy
Luca Prodi − Dipartimento di Chimica “Giacomo Ciamician”,
Università di Bologna, 40126 Bologna, Italy; orcid.org/
0000-0002-1630-8291
Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.langmuir.0c03531
Figure 5. (a) Normalized emission spectra of PYS-doped PluOS NPs
at increasing concentration of OS1. (b) Normalized emission spectra
of PYS-doped PluOS NPs prepared with 25% organosilanes OS1−4.
Normalized emission spectrum of PYS-doped PluS NPs (prepared
only with TEOS, blue line) is shown for comparison. Note that
emission spectra in the presence of organosilane 3 (green spectra) are
relative to residual emission due to heavy quenching from the PluOS
matrix (PLQY = 0.025).
results quenched in formulations containing organosilane 3 (in
which residual excimeric emission can be observed), possibly
due to an electronic interaction with the N-phenyl units (Table
1). From these observations, we can conclude that the urea
groups play the most relevant role in destabilizing the pyrene
dyes, resulting in the observation of excimer-like emission,
while pure silica (formed by TEOS) and organosilica with
bulkier organic moieties provide a favorable environment to
separate the pyrene dyes from one another.
Author Contributions
C.E.B and E.H. contributed equally to the work. The
manuscript was written through the contributions of all
authors. All authors have approved the final version of the
manuscript.
Funding
D.G. and L.P. are grateful to the Università di Bologna
( AL M A I D E A g r a n t ) an d M I U R ( P R I N P r o j ec t
2017EKCS35), respectively, for funding. C.E.B. acknowledges
the Erasmus+ fellowship.
CONCLUSIONS
In conclusion, a new synthetic route is investigated that
broadens the potential of the Pluronic-silica (PluS) nanoparticle preparation technique. Organosilane precursors are
used to prepare core−shell organosilica nanoparticles PluOS
with homogeneous morphology (10−15 nm core size, 20−50
nm hydrodynamic diameter) but with cores featuring different
chemical environments. A click reaction among cost-effective
reagents such as diamines and an isocyanate silane derivative is
here proven useful to synthesize a broad set of precursors for
■
Notes
The authors declare no competing financial interest.
ABBREVIATIONS USED
OS, organosilane; NP, nanoparticle; PluS, pluronic-silica;
PluOS, pluronic-organosilica; PLQY, photoluminescence
quantum yield; TEOS, tetraethoxysilane; TMOS, tetramethoxysilane; TMSCl, trimethylsylilchloride
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Extending the Frontiers of Brightness. Angew. Chem., Int. Ed. 2011,
50, 4056−4066.
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