Rational Design of a Minimal Size Sensor Array for Metal Ion Detection

Abstract

The focus of this study was to demonstrate that, in the luminescent sensors, the signal transduction may possibly be the most important part in the sensing process. Rational design of fluorescent sensor arrays for cations utilizing extended conjugated chromophores attached to 8-hydroxyquinoline is reported. All of the optical sensors utilized in the arrays comprise the same 8-hydroxyquinoline (8-HQ) receptor and various conjugated chromophores to yield a different response to various metal cations. This is because the conjugated chromophores attached to the receptor are partially quenched in their resting state, and upon the cation coordination by the 8-HQ, the resulting metalloquinolinolate complex displays a change in fluorescence. A delicate balance of conjugation, fluorescence enhancement, energy transfer, and a heavy metal quenching effect results in a fingerprint-like pattern of responses for each sensor-cation complex. Principal component analysis (PCA) and linear discriminant analysis (LDA) are used to demonstrate the contribution of individual sensors within the array, information that may be used to design sensor arrays with the smallest number of sensor elements. This approach allows discriminating between 10 cations by as few as two or even one sensor element. Examples of arrays comprising various numbers of sensor elements and their utility in qualitative identification of Ca(2+), Mg(2+), Cd(2+), Hg(2+), Co(2+), Zn(2+), Cu(2+), Ni(2+), Al(3+), and Ga(3+) ions are presented. A two-member array was found to identify 11 analytes with 100% accuracy. Also the best two of the sensors were tested alone and both were found to be able to discriminate among the samples with 99% and 96% accuracy, respectively. To illustrate the utility of this approach to a real-world application, identification of enhanced soft drinks based on their Ca(2+), Mg(2+), and Zn(2+) cation content was performed. The same approach to reducing array elements was used to construct three- and two-member arrays capable of identifying these complex analytes with 100% accuracy.

BODIPY-based fluorometric sensor array for the highly sensitive identification of heavy-metal ions

“…Because many heavy-metal ions form insoluble hydroxides at high pH, we studied the spectroscopic properties of indicators 1-3 in the presence of heavy-metal ions at pH = 6.5. [20] Upon addition of Cd 2+ to a dilute solution of 1, its absorption and emission maxima shifted from 484 nm to 530 nm and from 556 nm to 550 nm, respectively; and the emission efficiency nearly quintupled as evidenced by the emission intensity upon excitation at the isosbestic point (510 nm), as shown in Fig. 1a.…”

“…Various sensor arrays for heavy-metal-ion detection using commercial or custom fluorescent indicators have been reported that manifest remarkable selectivity at mM concentrations of the ions. However, extending this performance to the environmentally relevant M concentrations remains a challenge because of the lack of suitable fluorescent indicators [3,[20][21][22][23][24].…”

Array‐Based Sensors

“…Not surprisingly, it has found application in the sensing of various analytes including cations [70][71][72], anions [73], electroneutral small molecules such as amino acids [74], saccharides [75,76], explosives [77], poisonous gases [78], peptides [79] and proteins [80,81], consumer products including sweeteners [82], beverages [26,70,83], and toothpastes [73], and so on.…”

A Selective, Colorimetric and Ratiometric Chemosensor for Hg2+ and Its Application as Test Papers

“…13,14 Mercury represents for one of the most toxic heavy metals due to its thiophilic nature to proteins and enzymes. [15][16][17][18] Exposure to Hg 2+ leads to irreversible damage and dysfunction in biosystems, including brain, stomach, kidney, and central nervous system. 19,20 What is more worrisome is that Hg 2+ may exist in air, water and soil.…”