A series of structurally similar fluorescent probes (1-4), synthesized from rhodamine B, were designed to optically measure pH. Each probe had a unique "off-on" response as the solution went from basic to acidic. Probes 1-3 exhibited a spiro-cyclic quenching of the pyronin B fluorophore, whereas probe 4 is quenched by PET from the amine moiety.A chemical sensor capable of measuring pH by optical methods has important implications in analytical and biological chemistry. Fluorescence based probes have demonstrated a superior ability in the detection of various analytes with high sensitivity and low detection limits. In cellular biology, the pH of specific and localized areas of the cell can be an important indication of cellular events.1 Such information could potentially be useful in the diagnosis of specific diseases. For example, colorectal cancer,2 breast cancer2b , 3, cystic fibrosis,4 and neurodegenerative disorders5 have all been linked to abnormal pH regulation, resulting in localized pH values of 4.5-6.0 that are referred to as the acidic window. Currently, a large number of fluorescence based pH sensors have been reported in the literature and are commercially available.6 However, many of these probes lack sensitivity or are simply non-responsive in the so-called "acidic window". Therefore, it would be of great benefit to aid in the diagnosis of these diseases by developing new and more sensitive probes for the measurement of pH.Many fluorescent probes operate in an "off-on" fashion, where in the "off" state the fluorescence is quenched, while the "on" state the fluorophore is fully fluorescent with a high quantum yield. Among the many fluorophores that potentially could be used as pH sensors, pyronin B has particular advantages in biological imaging because of its high quantum yield (Φ= 0.35), longer excitation and emission wavelength (550-600 nm), spectral insensitivity to solvent polarity, pH, and a high tolerance to photobleaching.7 With these criteria in mind, we set out to design a mode of regulating the fluorescence of this fluorophore by synthesizing various benzylamine derivatives at the 9-position, which have Correspondence to: Daniel J. Dyer, ddyer@chem.siu.edu. Supporting Information Available: Detailed synthetic procedures and spectra. This material is available free of charge via the Internet at http://pubs.acs.org. NIH Public Access Author ManuscriptOrg Lett. Author manuscript; available in PMC 2011 July 16. Starting with commercially available rhodamine B, we synthesized various benzylamine structures; (see supporting information for synthesis details), where the amine moiety is primary, secondary, and tertiary ( Figure 1). The rhodamine-based literature is rife with fluorescent probes that are regulated by a spirocyclic structure. These spirocyclic compounds lack absorbance and fluorescence, in visible spectrum, when engaged in the spirocyclic form but will open upon binding to specific analytes to restore the fluorophore and fluorescence intensity of that compound. Typically, th...

New photoconductive materials are explored from three groups of polyacetylenes: poly-(phenylacetylenes) s[HCdC(C 6 H 5 -p-R)] n s, poly(3-thienylacetylenes) s[HCdC(3-C 4 H 2 S-β-R′)] n s, and poly(1-alkynes) s{HCdC[(CH 2 ) m R′′]} n s, where R ) CH 3 (2), CO 2 (CH 2 ) 6 OCO-Biph-OC 7 H 15 (Biph ) 4,4′-biphenylyl; 3); R′ ) Si(CH 3 ) 3 (4), Br (5); and R′′ ) CO 2 (CH 2 ) 6 OCO-Biph-OC 9 H 19 (m ) 2; 6), 9-carbazolyl (m ) 3; 7) and OCO-Biph-OC 7 H 15 (m ) 9; 8). Photoconduction in the polyacetylenes under illumination of visible light is investigated using photoinduced xerographic discharge technique. In the pure (undoped) state, all the polyacetylenes except 5 show higher photosensitivity than do poly(phenylacetylene) (R ) H; 1), a well-studied photoconducting polyacetylene, and poly(9-vinylcarbazole), the bestknown photoconducting vinyl polymer. Among the polyacetylenes, photoconduction performance of the polymers with electron-donating and/or hole-transporting moieties is superior to those with electron-accepting ones. The liquid crystalline polymer 6 exhibits very high photosensitivity, probably due to the formation of crystalline aggregates of its mesogenic pendants induced by the thermal treatment in the photoreceptor preparation process. C 60 acts as a photoconductivity enhancer when doped to amorphous 3, but functions as a crystallinity-breaking plasticizer when doped to liquid crystalline 6, leading to a large decrease in photoconductivity. While 3 shows a low photosensitivity (2.8 × 10 -3 lx -1 s -1 ) to a 573 nm light in the undoped state, doping with I 2 and sensitization with crystal violet (CV) dramatically increase its photosensitivity (up to 41.2 × 10 -3 lx -1 s -1 ). The CV-sensitized 4 exhibits high photoconductivity in the near-infrared spectral region, which may find technological applications in the digital photoimaging systems.

An approach is presented for the design of photoinduced electron-transfer-based sensors. The approach relies on the computational and theoretical prediction of electron-transfer kinetics based on Rehm-Weller and Marcus theories. The approach allows evaluation of the photophysical behavior of a prototype fluorescent probe/sensor prior to the synthesis of the molecule. As a proof of concept, a prototype sensor for divalent metal ions is evaluated computationally, synthesized, and then analyzed spectroscopically for its fluorescence response to zinc. Calculations predicted that the system would show a competition between electron transfer and fluorescence in the free state. In the zinc-bound state, the compound was predicted to be more highly fluorescent, due to the inhibition of electron transfer. Both predictions were confirmed experimentally. A nonzero fluorescence signal was observed in the absence of zinc and an enhancement was observed in the presence of zinc. Specifically, a 56-fold enhancement was observed over a 10-fold increase in zinc concentration.

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Hyperbranched polyols were grafted onto a PAN membrane via a two-step process for boron removal. The grafted hyperbranched scaffold was utilized to optimize the ligand distribution so that a complexing membrane with both high capacity and high adsorption rate was obtained.

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