well as ratiometric, responses. Luminescence measurements per-
formed in solution confirmed the ability to differentiate between
metal ions such as Ca2+, Cd2+, Zn2+, Mg2+ and Al3+, and show a
strong response to Ca2+, Cd2+, Mg2+ and Al3+. Conversely,
cations such Zn2+ and Hg2+ showed only a weak response, while
Co2+, Cu2+ and Ni2+ showed emission quenching. Both lumi-
nescence turn-on and signal attenuation can be used to identify the
respective cations on a qualitative level in aqueous solutions using
a S2–S6 micro-well array. Partial selectivity with variable intensity
responses and changes in emission wavelengths make sensors
S2–S6 excellent candidates for use in cross-reactive luminescence-
based arrays. Finally, preliminary experiments suggest that
Fig. 5 Fluorescence output from two arrays using sensors S1–S6 in the
presence of chloride salts of various metal ions. Left: Metal ions (1 mM,
400 nL) were administered in de-ionized water. Right: Metal ions were
administered in HEPES buffer (pH = 7.4).
quantitative determination of metal ions is possible at
a
concentration range between 10 mm and 10 mM.{
Notes and references
{ P. A. acknowledges support from the Alfred Sloan Foundation, BGSU
(Technology Innovations Enhancement grant) and the NSF (SENSOR
#0330267). M. A. P. and V. A. M. acknowledge support from the
McMaster Endowment.
1 Principles of Fluorescence Spectroscopy, ed. J. R. Lakowicz, Springer,
New York, 3rd edn, 2006.
2 (a) Topics in Fluorescence Spectroscopy: Volume 9. Advanced Concepts in
Fluorescence Sensing: Small Molecule Sensing, ed. C. D. Geddes and
J. R. Lakowicz, Springer Science, New York, 2005; (b) J. F. Callan,
A. P. de Silva and D. C. Magri, Tetrahedron, 2005, 61, 8551; (c)
B. Valeur and I. Leray, Coord. Chem. Rev., 2000, 205, 3.
3 J. W. Lee, J.-S. Lee, M. Kang, A. I. Su and Y.-T. Chang, Chem.–Eur. J.,
2006, 12, 5691.
4 (a) C. C. Woodroofe and S. J. Lippard, J. Am. Chem. Soc., 2003, 125,
11458; (b) M. Royzen, A. Durandin, V. G. Young, Jr., N. E. Geacintov
and J. W. Canary, J. Am. Chem. Soc., 2006, 128, 3854; (c) S. Maruyama,
K. Kikuchi, T. Hirano, Y. Urano and T. Nagano, J. Am. Chem. Soc.,
2002, 124, 10650.
Fig. 6 Deconvolution of the array images of sensors S1–S6 allows
5 R. G. W. Hollingshead, Oxine and its Derivatives, Butterworth Scientific
Publications, London, 1954–1956, vol. I–IV.
integration of the pixel intensities into the green and blue channels.
6 R. Pohl, D. Aldakov, P. Kuba´t, K. Jurs´ıkova´, M. Marquez and
P. Anzenbacher, Jr., Chem. Commun., 2004, 1282.
7 (a) R. Nishiyabu and P. Anzenbacher, Jr., Org. Lett., 2006, 8, 359; (b)
R. Nishiyabu and P. Anzenbacher, Jr., J. Am. Chem. Soc., 2005, 127,
8270.
regardless of the relative hydrophilicity/lipophilicity of the
individual materials. Most importantly, the polyurethane allows
us to circumvent the incompatibility in solubility of the sensors and
cations, which can be administered in water or buffer without
causing aggregation or precipitation of the sensors.
8 T. L. Nelson, C. O’Sullivan, N. T. Greene, M. S. Maynor and
J. J. Lavigne, J. Am. Chem. Soc., 2006, 128, 5640.
9 M. Schena, Microarray Analysis, John Wiley, Hoboken, NJ, 2003.
10 (a) J. J. Lavigne and E. V. Anslyn, Angew. Chem., Int. Ed., 2001, 40,
3118; (b) A. T. Wright and E. V. Anslyn, Chem. Soc. Rev., 2006, 35, 14.
11 K. Soroka, R. S. Vithanage, D. A. Phillips, B. Walker and
P. K. Dasgupta, Anal. Chem., 1987, 59, 629.
12 (a) E. Bardez, I. Devol, B. Larrey and B. Valeur, J. Phys. Chem. B,
1997, 101, 7786; (b) B. Valeur, F. Badaoui, E. Bardez, J. Bourson,
P. Boutin, A. Chatelain, I. Devol, B. Larrey, J. P. Lefe`vre and A. Soulet,
in NATO ASI Series: Chemosensors of Ion and Molecule Recognition, ed.
J.-P. Desvergne and A. W. Czarnik, Kluwer, Dordrecht, 1997, pp. 195.
13 V. A. Montes, R. Pohl, J. Shinar and P. Anzenbacher, Jr., Chem.–Eur.
J., 2006, 12, 4523.
The response of the array changes depends on the pH of the
analyte. This feature can be further used to increase the data
density used for discrimination between the analytes (Fig. 5).19
While the majority of cations tested provide a response
discernible by the naked eye at 50–5000 mM concentration
(Fig. 5), the scanned images, deconvoluted into their respective
RGB channels, allow the construction of response patterns. Fig. 6
shows a quantitative representation of the changes of the grey pixel
value (8-bit/channel) in their respective RGB channels.
The channel deconvolution of the array images confirms
spectroscopic observations suggesting that sensors S1–S6 will
show varying emission intensities in the blue and green channels,
thus generating response patterns useful for metal ion analysis. The
combination of the turn-on response in the green channel with the
analyte-specific intensity changes in the blue–green channels allows
for ratiometric sensing in solid state arrays.
14 C. H. Chen and J. Shi, Coord. Chem. Rev., 1998, 171, 161.
15 (a) R. Ballardini, G. Varani, M. T. Indelli and F. Scandola, Inorg.
Chem., 1986, 25, 3858; (b) Y. Onoue, K. Hiraki, K. Morishige and
Y. Nishikawa, Nippon Kagaku Kaishi, 1978, 1237.
16 B. Garc´ıa-Acosta, R. Mart´ınez-Man˜ez, F. Sancen˜o´n, J. Soto, K. Rurack,
M. Spieles, E. Garcia-Breijo and L. Gil, Inorg. Chem., 2007, 46, 3123.
17 N. Miyaura, in Metal-Catalyzed Cross-Coupling Reactions, ed. A. De
Meijere and F. Diederich, Wiley-VCH, Weinheim, 2004, pp. 41.
18 V. A. Montes, C. Pe´rez-Bol´ıvar, N. Agarwal, J. Shinar and
P. Anzenbacher, Jr., J. Am. Chem. Soc., 2006, 128, 12436.
19 A. Buryak and K. Severin, J. Am. Chem. Soc., 2005, 127, 3700.
In summary, sensors S2–S6, utilizing extended conjugated
chromophores, were designed to display luminescence turn-on, as
3710 | Chem. Commun., 2007, 3708–3710
This journal is ß The Royal Society of Chemistry 2007