Conjugated chemosensors

Fig. 32 Effect of analyte coordination in (a) a traditional molecular chemosensor system, (b) receptors wired in series in a conjugated polymer, (c) chemosensors grafted onto the surface of a nanoparticle, and (d) a fluorescent dendrimer. The curved arrows indicate the active...

Zhou Q, Swager TM (1995) Fluorescent chemosensors based on energy migration in conjugated polymers the molecular wire approach to increased sensitivity. J Am Chem Soc 117 12593-12602... 

Fan L-J, Zhanga Y, Murphy CB, Angell SE, Parker MFL, Flynn BR, Jones WE Jr (2009) Fluorescent conjugated polymer molecular wire chemosensors for transition metal ion recognition and signaling. Coord Chem Rev 253 401 122... 

Yang NC, Jeong JK, Suh DH (2003) A new conjugated polymer chemosensor functionalised with 2, 6-bis(l, 3,4-oxadiazole-2-yl)pyridine for metal ion recognition. Chem Lett 32 40-41... 

Murphy CB, Zhang Y, Troxler T, Ferry V, Martin JJ, Jones WE Jr (2004) Probing Forster and Dexter energy-transfer mechanisms in fluorescent conjugated polymer chemosensors. J Phys Chem B 108 1537-1543... 

Kim J, McQuade DT, McHugh SK, Swager TM (2000) Ion-specific aggregation in conjugated polymers highly sensitive and selective fluorescent ion chemosensors. Angew Chem IntEd 39 3868-3872... 

Fan L-J, Jones WE Jr (2006) Studies of photoinduced electron transfer and energy migration in a conjugated polymer system for fluorescence tum-on chemosensor applications. J Phys Chem B 110 7777-7782... 

Zhou, Q. and T. Swager. Methodology for enhancing the sensitivity of fluorescent chemosensors Energy migration in conjugated polymers. 7. Am. Chem Soc. 117, 7017-7018 (1995). 

Several vibrational modes in the excited singlet states of DPA have been identified from picosecond CARS measurements. The central C—C bond of DPA retains much of its triple-bond-like character in the S2 state however, the central C—C bond has double-bond-like character in the state. By analogy with the trans-bent form of S acetylene, it was proposed that S DPA has a trans-or cis-form bent structure that is consistent a previously proposed strucmre. It has been cautioned that, because of the conjugation between the phenyl groups and the central C—C bond, the S state may assume a structure different from the bent form. The interpretation of recent picosecond IR absorption measurements provide support for the trans-bent planar structure for S of DPA. The diphenylace-tylenic fluorophore has recently been incorporated into several chemosensor structures whose fluorescent signaling properties are controlled by the relative flexibilities of the molecules. ... 

In another approach, a fluorescent conjugated polymer was used as the material for the preparation of a chemosensor to detect 2,4,6-trinitrotoluene (TNT) and its related nitroaromatic compounds. To this end, microparticles, made of three-dimensionally cross-linked poly(l,4-phenylene vinylene) (PPV) via emulsion polymerization, were synthesized [61]. This material was chosen due to its high fluorescence intensity and sensitivity to changes in its microenvironment. The chemosensor was exposed to vapour containing different amounts of TNT and quenching of the polymer luminescence at 560 nm was observed after excitation at 430 nm. The dependence of the fluorescence signal in response to the analyte was described by a modified Stem-Volmer equation that assumes the existence of two different cavity types. The authors proposed the modified Stem-Volmer equation as follows ... 

Molecular imprinting has been used to devise a chemosensor for L-nicotine (Table 6) [178]. For that, poly(methacrylic acid) (PMA) beads, imprinted with the L-nicotine template in chloroform, were incorporated in a film of the conjugated polymer, OCiC10-PPV. EIS has then been utilized for the L-nicotine determination in the 1-10 nM concentration range. This MIP chemosensor showed predominant affinity towards L-nicotine over a structurally related L-nicotine metabolite, L-cotinine. Similarly, the polydopamine-imprinted film prepared by electropolymerization in the phosphate buffer (pH = 7.4) has been used to devise a chemosensor for L-nicotine with LOD of 0.5 pM (Table 6) [106]. This LOD is still much higher than that reported for other L-nicotine determination methods based on MIPs, such as SPE combined with differential pulsed elution, which was 6 nM [31]. 

The incorporation of siloles in polymers is of interest and importance in chemistry and functionalities. Some optoelectronic properties, impossible to obtain in silole small molecules, may be realized with silole-containing polymers (SCPs). The first synthesis of SCPs was reported in 1992.21 Since then, different types of SCPs, such as main chain type 7r-conjugated SCPs catenated through the aromatic carbon of a silole, main chain type cr-conjugated SCPs catenated through the silicon atom of a silole, SCPs with silole pendants, and hyperbranched or dendritic SCPs (Fig. 2), have been synthesized.10 In this chapter, the functionalities of SCPs, such as band gap, photoluminescence, electroluminescence, bulk-heterojunction solar cells, field effect transistors, aggregation-induced emission, chemosensors, conductivity, and optical limiting, are summarized. 

Another interesting application of Jt-conjugated systems is their use as chemosensors. For example, a modified dithienophosphole oxide 160 (see Scheme 49 for the synthesis of its precursor) that incorporates boryl-end caps is a very sensitive and selective sensory material for the fluoride ion (Scheme 126). Treatment of this derivative by fluoride induces a red shift of the emission maximum (160, 452 nm 373, 485 nm) that is visible to the naked eye. This shift in the fluorescence emission can even be detected down to micromolar concentrations of fluoride ion notably, the addition of other halides (CP, Br, P) does not affect the fluorescence in any way <20060L495>. 

Cram, Czech et al. [2] reported the development of chemosensors 1-4 (Figure 1) for commercial use as Na" and assays in serum and other solutions. When a cation binds to the crown portion of these compounds, the complexation is coupled to an increase in acidity of the conjugated aniline NH deprotonation at constant pH... 

Yamamoto has investigated conjugated polymers 225 and 226, incorporating phen in the backbone.128,129 These polymers may function as chemosensors for transition metals as they... 

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