Charge transfer sensors

Fluorescent Internal Charge Transfer Sensors Incorporating the Ortho-(Aminomethyl)Phenylboronic Acid Fragment... 

Thus, the major conclusions of tiie early studies by Volkenshtein and his colleagues applicable to the theory of the method of semiconductor gas sensors are the following a) chemisorption of particles on a semiconductor surface can be accompanied by a charge transfer between adsorption-induced surface levels and volume bands of adsorbent and b) only a certain fraction of absorbed particles is charged, the fraction being dependent on adsorbate and adsorbent. 

VEM excitation energy relaxati( i. Such ways (channels) be probably chemisorption with charge transfer, production of phonons, ejection of electrons from surface states and traps, and the like. The further studies in this field will, obviously, make it possible to give a more complete characteristic of the VEM interaction with the surface of solid bodies and the possibilities of VEM detecting with the aid of semiconductor sensors. 

Bosch LI, Mahon MF, James TD (2004) The B-N bond controls the balance between locally excited (LE) and twisted internal charge transfer (TICT) states observed for aniline based fluorescent saccharide sensors. Tetrahedron Lett 45(13) 2859-2862... 

Arimori S, Bosch LI, Ward CJ, James TD (2001) Fluorescent internal charge transfer (ICT) saccharide sensor. Tetrahedron Lett 42(27) 4553-4555... 

Molecular rotors are fluorophores characteristic for having a fluorescent quantum yield that strongly depends on the viscosity of the solvent [50], This property relies on the ability to resume a twisted conformation in the excited state (twisted intramolecular charge transfer or TICT state) that has a lower energy than the planar conformation. The de-excitation from the twisted conformation happens via a non-radiative pathway. Since the formation of the TICT state is favored in viscous solvents or at low temperature, the probability of fluorescence emission is reduced under those conditions [51]. Molecular rotors have been used as viscosity and flow sensors for biological applications [52], Modifications on their structure have introduced new reactivity that might increase the diversity of their use in the future [53] (see Fig. 6.7). 

Brinkley et al. demonstrated89 a simple to use, easy to interpret, low cost, and environmentally friendly colorimetric detector of the chemical warfare agent - mustard gas (HD, l,l-thiobis(2-chloroethane)). An optically transparent xerogel encapsulating Cu(II) acetate was fabricated to detect HD analogues and can serve as the optical sensor based on metal-ligand charge-transfer mechanism. 

Theoretical insight into the interfacial charge transfer at ITIES and detection mechanism of this type of sensor were considered [61-63], In case of ionophore assisted transport for a cation I the formation of ion-ionophore complexes in the organic (membrane) phase is expected, which can be described with the appropriate complex formation constant, /3ILnI. 

Li YQ, Bricks JL, Resch-Genger U et al (2006) Bifunctional charge transfer operated fluorescent probes with acceptor and donor receptors. 2. Bifunctional cation coordination behavior of biphenyl-type sensor molecules incorporating 2, 2 6, 2"-terpyridine acceptors. J Phys Chem A 110 10972-10984... 

Kovalchuk A, Bricks JL, Reck G et al (2004) A charge transfer-type fluorescent molecular sensor that lights up in the visible upon hydrogen bond-assisted complexation of anions. Chem Commun 1946-1947... 

Class 3 fluorophores linked, via a spacer or not, to a receptor. The design of such sensors, which are based on molecule or ion recognition by a receptor, requires special care in order to fulfil the criteria of affinity and selectivity. These aspects are relevant to the field of supramolecular chemistry. The changes in photophysical properties of the fluorophore upon interaction with the bound analyte are due to the perturbation by the latter of photoinduced processes such as electron transfer, charge transfer, energy transfer, excimer or exciplex formation or disappearance, etc. These aspects are relevant to the field of photophysics. In the case of ion recognition, the receptor is called an ionophore, and the whole molecular sensor is... 

The fluorescent molecular sensors will be presented with a classification according to the nature of the photoinduced process (mainly photoinduced electron or charge transfer, and excimer formation) that is responsible for photophysical changes upon cation binding. Such a classification should help the reader to understand the various effects of cation binding on the fluorescence characteristics reported in many papers. In most of these papers, little attention is often paid to the origin of cation-induced photophysical changes. 

Fluorescent PCT (photoinduced charge transfer) cation sensors 10.3.3.1 Principles... 

Valeur B. and Leray I. (2001) PCT (Photo-induced Charge Transfer) Fluorescent Molecular Sensors for Cation Recognition, in Valeur B. and Brochon J. C. (Eds),... 

---