Rhodamine photosensitizers (PSs) substituting S or Se for O in the xanthene ring give turnover numbers (TONs) as high as 9000 for the generation of hydrogen via the reduction of water using [Co(III)(dmgH)(2)(py)Cl] (where dmgH = dimethylglyoximate and py = pyridine) as the catalyst and triethanolamine as the sacrificial electron donor. The turnover frequencies were 0, 1700, and 5500 mol H(2)/mol PS/h for O, S, and Se derivatives, respectively (Φ(H(2)) = 0%, 12.2%, and 32.8%, respectively), which correlates well with relative triplet yields estimated from quantum yields for singlet oxygen generation. Phosphorescence from the excited PS was quenched by the sacrificial electron donor. Fluorescence lifetimes were similar for the O- and S-containing rhodamines (∼2.6 ns) and shorter for the Se analog (∼0.1 ns). These data suggest a reaction pathway involving reductive quenching of the triplet excited state of the PS giving the reduced PS(-) that then transfers an electron to the Co catalyst. The longer-lived triplet state is necessary for effective bimolecular electron transfer. While the cobalt/rhodamine/triethanolamine system gives unprecedented yields of hydrogen for the photoreduction of water, mechanistic insights regarding the overall reaction pathway as well as system degradation offer significant guidance to developing even more stable and efficient photocatalytic systems.

The ability to accurately measure real-time pH fluctuations in-vivo could be highly advantageous. Early detection and potential prevention of bacteria colonization of surgical implants can be accomplished by monitoring associated acidosis. However, conventional glass membrane or ion-selective field-effect transistor (ISFET) pH sensing technologies both require a reference electrode which may suffer from leakage of electrolytes and potential contamination. Herein, we describe a solid-state sensor based on oxidized single-walled carbon nanotubes (ox-SWNTs) functionalized with the conductive polymer poly(1-aminoanthracene) (PAA). This device had a Nernstian response over a wide pH range (2–12) and retained sensitivity over 120 days. The sensor was also attached to a passively-powered radio-frequency identification (RFID) tag which transmits pH data through simulated skin. This battery-less, reference electrode free, wirelessly transmitting sensor platform shows potential for biomedical applications as an implantable sensor, adjacent to surgical implants detecting for infection.

We report on the rotational reorientation dynamics associated with loop 1 of domain I within a large multidomain protein (human serum albumin, HSA) when it is dissolved in binary mixtures of ionic liquid (1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C4mim][Tf2N]), 1-butyl-3-methylimidazolium tetrafluoroborate ([C4mim][BF4]), or 1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim][PF6])) and distilled deionized water (ddH2O) as a function of temperature and water loading. In IL/2% ddH2O (v/v) mixtures, loop 1 of domain I is more significantly denatured in comparison to the protein dissolved in aqueous solutions containing strong chemical denaturants (e.g., 8 M guanidine HCl (Gu.HCl) or urea). As water loading increases, there is evidence for progressive refolding of loop 1 of domain I followed by recoupling with domains I, II, and III in the [C4mim][BF4]/ddH2O mixtures at 20 degrees C. Above 30% (v/v) water, where domain I appears refolded, the Ac reporter molecule's semiangle steadily decreases from 35 degrees to 20 degrees with increasing water loading. From the perspective of domain I in HSA, this behavior is similar to the effects of dilution from 4 to 0 M Gu.HCl in aqueous solution. Overall, these results lend insight into the tangle of biocatalytic and structural/dynamical mechanisms that enzymes may undergo in ionic liquid-based systems. It will be particularly motivating to extend this work to include enzyme-attuned ionic liquids shown to improve biocatalytic performance beyond that possible in the native (predominantly aqueous) setting.

Mixtures of n-octadecyltrimethoxysilane (C18, 1-5 mole-%), n-octyltriethoxysilane (C8) and tetraethoxysilane (TEOS) gave xerogel surfaces of varying topography. The 1:49:50 C18/C8/TEOS xerogel formed 100-400-nm-wide, 2-7-nm deep pores by AFM while coatings with ≥3% C18 were free of such features. Segregation of the coating into alkane-rich and alkane-deficient regions in the 1:49:50 C18/C8/TEOS xerogel was observed by IR microscopy. Immersion in ASW for 48 h gave no statistical difference in surface energy for the 1:49:50 C18/C8/TEOS xerogel and a significant increase for the 50:50 C8/TEOS xerogel. Settlement of barnacle cyprids and removal of juvenile barnacles, settlement of zoospores of the alga Ulva linza, and strength of attachment of 7-day sporelings were compared amongst the xerogel formulations. Settlement of barnacle cyprids was significantly lower in comparison to glass and polystyrene standards. The 1:49:50 and 3:47:50 C18/C8/TEOS xerogels were comparable to PDMSE with respect to removal of juvenile barnacles and sporeling biomass, respectively.

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A high-throughput screening system has been developed to rapidly produce, screen, and assess the usefulness of organically modified silane (ORMOSIL)-based xerogel films formed on the surface of porous silicon (pSi) surfaces. The ORMOSILs tested include methyltriethoxysilane, n-octyltriethoxysilane, n-hexyltriethoxysilane, n-propyltriethoxysilane, 2-cyanoethyltriethoxysilane, phenyltriethoxysilane, benzyltriethoxysilane, vinyltriethoxysilane, tetraethoxysilane, and hexafluoroethyltriethoxysilane. Xerogel microarrays were pin-printed on the surface of O(3) oxidized pSi using a computer-controlled robotic pin-printer. The fragile pSi required careful pin-printing parameter optimization to simultaneously ensure sufficient sol application and limit pin-induced damage. These multi-functional xerogel-pSi microarrays were exposed to harsh conditions (0.1 mM NaOH, 15 min) to determine the extent to which the xerogel protected the pSi. Microarray assessment included multispectral photoluminescence and infrared imaging. Results demonstrate that the more hydrophobic/nonpolar xerogel films (n-octyltriethoxysilane, n-hexyltriethoxysilane) protect the pSi surface the most and maintained the pSi photoluminescence. Also, unlike xerogel material doped with a reporter molecule, the uniformity of the printed feature plays a role in the protection of the pSi material underneath. Areas with thinner xerogel distributions allowed the permeation of NaOH whereas the thicker areas prohibit pSi exposure to NaOH.

Diethyl ether added as an entrainer (cosolvent) to near- and supercritical CO2 significantly enhanced the enantioselectivity of photocyclization of 5,5-diphenyl-4-penten-1-ol sensitized by saccharide naphthalenedicarboxylate to give a cyclization product in enantiomeric excesses much larger than those obtained in conventional organic solvents, revealing the unique features of nc- and sc-CO2 as well as the critical role of entrainer clustering to the intervening diastereomeric exciplex pair.

Multipurpose solutions (MPS) are a single solution that functions to simultaneously rinse, disinfect, clean, and store soft contact lenses. Several commercial MPS products contain polyhexamethylene biguanide (PHMB) and/or polyquaternium-1 (PQ-1) as antimicrobial agents. In this paper we have created an in vitro small unilamellar vesicle (SUV) model of the corneal epithelial surface, and we have assessed the interactions of PHMB and PQ-1 with several model biomembranes by using fluorescence spectroscopy, dynamic light scattering (DLS), and liquid chromatography-mass spectrometry (LC-MS). Steady-state and time-resolved fluorescence were used to assess the membrane acyl chain and polar headgroup region local microenvironment as a function of added PHMB or PQ-1. DLS was used to detect and quantify SUV aggregation induced by PHMB and PQ-1. LC-MS was used to determine the liposomal composition from any precipitated materials in comparison to the as-prepared SUVs. The results are consistent with PHMB adsorbing onto and PQ-1 intercalating into the biomembrane structure. The differences between the two interaction mechanisms have substantial impacts on the biomembrane dynamics and stability.