J. Mattay et al.
based and switchable fluorescent nanoparticles with a high
potential for bio-application. Future studies are in progress
and are focused on clarifying the mechanism of fluorescence
quenching and on improving its efficiency by selecting suita-
ble pairs of donor and acceptors (in the sense of FRET) as
well as developing silica nanoparticles of well-defined archi-
tectures aiming at applications in optical fluorescence mi-
croscopy.
Acknowledgements
Support from the Deutsche Forschungsgemeinschaft (SFB 613) and from
Bielefeld University is gratefully acknowledged.
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Experimental Section
NMR spectra were measured at room temperature on a Bruker DRX
500 spectrometer (500 MHz). [D4]Methanol was used as an internal stan-
dard for H spectra. All UV/Vis absorption spectra were recorded in eth-
anol/water (1:1) on a Perkin–Elmer Lambda 25 UV/Vis spectrometer at
room temperature. Fluorescence spectra were measured on a Perkin–
Elmer 50 B fluorescence spectrometer.
1
[8] B. Seefeldt, R. Kasper, M. Beining, J. Mattay, J. Arden-Jacob, N.
Kemnitzer, K. H. Drexhage, M. Heilemann, M. Sauer, Photochem.
For light-induced generation of the open form of the spiropyran the sam-
ples were irradiated at 365 nm using a Nichia diode. Fluorescence excita-
tion of the fluorophores and photoswitching of the open to the closed
form was induced by irradiation with 568 nm using a laser diode (Cube,
Coherent). The resulting particle-solution was characterized by TEM
(transmission electron microscopy - TWIN Philips CM 200). The sample
preparation was carried out by dropping the particle solution on a
carbon-coated TEM grid and removing the solvent under vacuum.
[11] L. Giordano, T. M. Jovin, M. Irie, E. A. Jares-Erijman, J. Am. Chem.
Synthesis of 3’,3’-dimethyl-1’-(b-hydroxyethyl)-6-nitrospiroACTHNUGTRNEUNG[2H-1]benzo-
[15] S. Bonacchi, D. Genovese, R. Juris, M. Montalti, L. Prodi, E. Ram-
pyran-2,2’-indoline (6): The experimental procedure followed for the syn-
thesis of 6 starting from 3, is the one reported by Raymo et al.[30]
Synthesis of 1’-(3-triethoxysilanpropyl)-3’,3’-dimethylnitrospiroACHTNUTGRNEUNG[2H-1]ben-
zopyran-2,2’-indoline (1): The experimental procedure followed for the
synthesis of 1, is the one reported by Allouche and Gonbeau.[29]
[16] a) M. Montalti, L. Prodi, N. Zaccheroni, A. Zattoni, P. Reschiglian,
chi, R. Juris, M. Montalti, D. Genovese, N. Zaccheroni, L. Prodi,
[19] J. Fçlling, S. Polyakova, V. Belov, A. van Blaaderen, M. L. Bossi,
[20] J. Chen, P. Zhang, G. Fang, P. Yi, X. Yu, X. Li, F. Zeng, S. Wu, J.
[22] J. Chen, F. Zeng, S. Wu, J. Zhao, Q. Chen, Z. Tong, Chem.
Synthesis of rhodamine B 4-(3-hydroxypropyl)piperazine amide (10): The
experimental procedure followed for the synthesis of 10 starting from 8,
is the one reported by Nguyen and Francis.[31]
Synthesis of rhodamine B 4-(3-triethoxysilanpropyl)piperazine amide (2):
A solution of rhodamine B 4-(3-hydroxypropyl)piperazine amide (10;
0.055 g, 0.096 mmol) and 3-triethoxysilylpropylisocyanate (7; 0.024 mL,
0.01 mmol) in dry DMF (20 mL) was stirred under reflux for 24 h. The
1
emulsion of 2 was used without further purification. H NMR (500 MHz,
[D4]MeOH): d=0.58(t, 3J=7, 4 Hz, 2H), 1.15 (t, 3J=7.2 Hz, 12H), 1.19
(t, 3J=7.1 Hz, 9H), 1.61 (m, 4H), 2.46 (t, 3J=7.2 Hz, 2H), 3.14 (t, 3J=
7.2 Hz, 2H), 3.35 (brm, 8H), 3.47 (q, 3J=6.9 Hz, 6H), 3.67 (q, 3J=
7.1 Hz, 8H), 4.12 (t, 3J=7.2 Hz, 2H), 6.93 (s, 1H), 6.96 (s, 1H), 7.05(d,
3
3
3J=9.5 Hz, 1H), 7.07 (d, J=9.6 Hz, 1H), 7.9 (d, J=9.6 Hz, 1H), 7.26 (d,
3J=9.5 Hz, 2H), 7.50 (m, 1H), 7.72 (m, 1H), 7.76 (m, 2H); ESI-MS (pos-
itive): m/z: 816.5 [M]+.
[23] L. Zhu, W. Wu, M.-Q. Zhu, J. J. Han, J. K. Hurst, A. D. Q. Li, J. Am.
Preparation of nanoparticles: The silica nanoparticles doped with the flu-
orophor (2) and the photoswitch (1) were prepared using a modified
Stçber method.[29]
A mixture of ethanol, deionized water, and concentrated ammonia solu-
tion ꢀ25% (Roth) was stirred for 2 min. To this mixture, TEOS (Al-
drich) was slowly added, after 5 min the fluorophor (2) and the photo-
switch (1) were slowly added and the mixture was stirred at room tem-
perature overnight. Two different molar ratios of TEOS/NH3/EtOH/H2O
were used. A: TEOS (2 mL), ammonia solution (2 mL), double distilled
water (6 mL), EtOH (100 mL). B: TEOS (4 mL), ammonia solution
(4 mL), double distilled water (12 mL), EtOH (200 mL). The different
molar ratios for 1 and 2 are given in Table 1, with concentrations of
0.09 m for 1 and 0.0031 m for 2. For workup the reaction solutions were
centrifuged with 3600 R/min over 15 min. After removing of the solvents
the NP were dispersed in distilled water/ethanol (1:1; 50 mL). This pro-
cess was repeated three times. To control the workup and analyze the dif-
ferent reaction setups TEM spectroscopy was used.
[26] J. Piard, R. Mꢆtivier, M. Giraud, A. Lꢆaustic, P. Yu, K. Nakatani,
[27] D. Genovese, M. Montalti, L. Prodi, E. Rampazzo, N. Zaccheroni,
[28] K. Kinashi, S. Nakamura, Y. Ono, K. Ishida, Y. Ueda, J. Photochem.
[29] J. Allouche, A. Le Beulze, J.-C. Dupin, J.-B. Ledeuil, S. Blanc, D.
[30] F. M. Raymo, S. Giordani, A. J. P. White, D. J. Williams, J. Org.
[32] A. M. Powe, S. Das, M. Lowry, B. El-Zahab, S. O. Fakayode, M. L.
Geng, G. A. Baker, L. Wang, M. E. McCarroll, G. Patonay, M. Li,
820
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2012, 18, 814 – 821