Sensors transition metal ions

Most PET fluorescent sensors for cations are based on the principle displayed in Figure 10.7, but other photoinduced electron transfer mechanisms can take place with transition metal ions (Fabbrizzi et al., 1996 Bergonzi et al., 1998). In fact, 3d metals exhibit redox activity and electron transfer can occur from the fluorophore... 

Epoxy-based membrane of 2-[(4-chloro-phenylimino)-methyl]-phenol reveals a far Nemstian slope of 43 mV per decade for Pb+2 over a wide concentration range CIO 6 to 10 1 mol dm-3). The response time of the electrode is quite low (< 10 sec) and could be used for a period of 2 months with a good reproducibility. The proposed electrode reveals very high selectivity for Pb(II) in the presence of transition metal ions such as Cu2+, Ni2+, Cr and Cd2+at concentrations l.()xl() 3 M and 1.0><10 4 M. Effect of internal solution concentration was also studied. The proposed sensor can be used in the pH range of 2.50 - 9.0. It was used as an indicator electrode in the potentiometric titration of Pb+2 ion against EDTA. 

Complexation studies of sensors 83 and 84 with the alkali, alkaline earth, and transition metal ions Cu2+, Ni2+, Zn2+, Cd2+, and Pb2+ were performed in Valeur s laboratory.141,142 In these compounds, the chromophores are linked to the azacrowns in such a way that the cations interact directly with the carbonyl group that acts as an electron-withdrawing unit. Therefore, when an ion is coordinated,... 

Macrocycies Functionalized with 8-Hydroxyquinoline and Its Derivatives as Transition Metal Ion Sensors... 

ISEs and CHEMFETs with calix[4]arene 32, bearing two thioether functionalities, are highly selective for Ag+ in the presence of alkaline earth ions (K" ", Ca ) and transition metal ions (Cu, Cd ), with selectivities log/f gj varying from —4.2 to —4.7 [133,135]. The CHEMFETs with 32 also showed selectivity for Ag in the presence of Hg " " ions (log g g = —2.7), which is quite unique since both ions have the same coordination number and preference for a linear interaction with soft donor atoms [133]. McKervey et al. reported Ag selectivity for calix[4]arene 33 in PVC membrane based ISEs [136]. These ISEs show a moderate Ag" selectivity (—1.1 to -2.1). Due to the presence of the hard donating carbonyl atoms in the molecule, a sub-Nemstian response (50mV decade ) was obtained in the presence of alkaline metal ions [137]. Moreover, the sensor was not selective for Ag in the presence of Hg " ions. 

Binyamin, Chen and Heller reported that wired enzyme electrodes constituted of glassy carbon electrodes coated with poly(4-vinylpyridine) complexed with [Os(bpy)2Cl] and quarternized with 2-bromoethylamine or poly[(iV-vinylimidazole) complexed with [Os(4,4 -dimethyl-2,2 -bypyridine)2Cl] or poly(vinylpyridine) complexed with [Os(4,4 -dimethoxy-2,2 -bypyridine)2Cl] quaternized with methyl groups lost their electrocatalytic activity more rapidly in serum or saline phosphate buffer (pH 7.2) in the presence of urate and transitional metal ions such as Zn and Fe " " than in plain saline phosphate buffer (pH 7.2). It was reported that as much as two-thirds of the current is lost in 2 h in some anodes. However, when a composite membrane of cellulose acetate, Nafion, and the polyaziridine-cross-linked co-polymer of poly(4-vinyl pyridine) quaternized with bromoacetic acid was applied, the glucose sensor stability in serum was improved and maintained for at least 3 days [27,50]. 

An anthracene-based fluorescent sensor for transition metal ions (Figure 93) has been developed by Fabbrizzi et al. [120]. They have shown that at an appropriate pH (6-8), the addition of Mn " ", Co or Zn2+ does not affect the fluorescence. However, the addition of Cu or Ni ions results in a sharp... 

Fig. 18 Sensor output characteristics in solutions with transition-metal ions for (a) P2VP-block-P (NlPAAm-co-DMlAAm) (Gel la) and for (b) PDMAEMA-DMIMA (Gel 4) based sensors. Reprinted from (Guenther et al. 2007b, 2007c) with kind permission from Elsevier and Wiley-VCH...

---