Sodium-Polyacrylate-Based Electrochemical Sensors for Highly Sensitive Detection of Gaseous Phenol at Room Temperature.

The detection of volatile organic compounds with electrochemical gas sensors is still very challenging regarding their sensitivity, selectivity, and operation at room temperature. There is a need for robust, sensitive, inexpensive, and yet easy-to-operate sensors for phenol and other phenolic compounds that function reliably under ambient conditions. Herein, we present a phenol gas sensor based on a combination of a semisolid, alkaline sodium polyacrylate, and commercial screen-printed electrodes. Sodium polyacrylate was employed as a multifunctional sensing material serving as a (i) gel-like electrolyte, (ii) accumulation milieu, and (iii) derivatization medium. Under ambient conditions, the sensor showed excellent sensitivity in the low ppbv (µg m-3) range, a good linear operation in the examined concentration range of 0.1-1.0 ppmv for up to 105 min accumulation, and low sensitivity toward examined interferences. The sensor also indicated a possibility to differentiate between several phenolic compounds based on their oxidation potential. Given its favorable electroanalytical performance, a strong application potential is envisioned in topical fields such as environmental monitoring, cultural heritage preservation, and occupational health and safety.

Nanostructured Bismuth Film Electrode for Detection of Progesterone.

Progesterone is an important hormone responsible, among others, for maintaining pregnancy via inhibition of uterus muscles activity; thus, following its concentration levels in pregnant women is of immense importance in the endeavor to prevent premature birth. In this work, the nanostructured bismuth film electrode (nsBiFE) was studied for detection of progesterone in neutral medium. Due to the ability to accumulate progesterone at the nsBiFE, the adsorptive cathodic stripping voltammetry was beneficially exploited. The nsBiFE was prepared on the surface of a glassy carbon supporting electrode and several parameters influencing the detection of progesterone were investigated. The nsBiFE exhibited superior electroanalytical characteristics in comparison to other bismuth-based electrodes and unmodified glassy carbon electrode together with satisfactory response toward low concentrations of progesterone, which are consistent with clinically significant levels.

"Click" Chemistry: Application of Copper Metal in Cu-Catalyzed Azomethine Imine-Alkyne Cycloadditions.

A series of 16 copper-catalyzed azomethine imine-alkyne cycloaddition (CuAIAC) reactions between four pyrazolidinone-1-azomethine imines and four terminal ynones gave the corresponding fluorescent cycloadducts as bimane analogues in very high yields. The applicability of CuAIAC was demonstrated by the fluorescent labeling of functionalized polystyrene and by using Cu-C and Cu-Fe as catalysts. Experimental evidence, kinetic measurements, and correlation between a clean catalyst surface and the reaction rate are in agreement with a homotopic catalytic system with catalytic Cu(I)-acetylide formed from Cu(0) by "in situ" oxidation. The availability of azomethine imines, mild reaction conditions, simple workup, and scalability make CuAIAC a viable supplement to the Cu-catalyzed azide-alkyne cycloaddition reaction in "click" chemistry.

Amino- and ionic liquid-functionalised nanocrystalline ZnO via silane anchoring - an antimicrobial synergy.

The synthesis of highly antimicrobial nanocrystalline zinc oxide and its covalent modifications are presented. In order to achieve further improvement of antimicrobial activity, the surface of ZnO was effectively modified with selected silanes comprising amino- and ionic liquid-functionalities. We demonstrate for the first time ionic liquid surface immobilization on ZnO and the application of this hybrid material for antimicrobial purposes. Different microscopic and spectroscopic techniques as well as size, surface and elemental composition analyses were employed to prove these modifications. Characterization revealed that surface and antimicrobial properties strongly depend on the modification employed. Most of the amino- and ionic liquid-functionalised nanocrystalline ZnO exhibited improved antimicrobial activity compared to commercially available silane-containing antimicrobial agents attached to nanocrystalline ZnO. Bacterial growth reduction was assessed by following the optical density of bacterial growth with different concentrations of the novel antimicrobial nanomaterials. Complete bacterial inactivation was achieved for specific amino- and ionic liquid-modifications at 0.125 g L-1, revealing the synergistic effect of ZnO and its modifications, exhibiting up to 2-fold improvement compared to unmodified ZnO.

A sulfide/polysulfide-based ionic liquid electrolyte for quantum dot-sensitized solar cells.

Further development of quantum dot-sensitized solar cells (QDSCs) will require long-term stability in addition to the continuous increase of photovoltaic (PV) conversion efficiency achieved in the last years. We report a robust S(2-)/S(n)(2-) electrolyte that has been specifically designed for compatibility with CdSe quantum dots in sensitized solar cells. The new pyrrolidinium ionic liquid reaches 1.86% efficiency and a short-circuit current close to 14 mA·cm(-2) under air-mass 1.5 global illumination and improves the device lifetime with good photoanode stability over 240 h. PV characterization showed that the solar cell limitations relate to poor catalysis of regeneration at the counter electrode and high recombination. Further improvement of these factors in the robust electrolyte configuration may thus have a significant impact for advancing the state-of-the-art in QDSCs.

Structural and water-repellent properties of a urea/poly(dimethylsiloxane) sol-gel hybrid and its bonding to cotton fabric.

A novel diureapropyltriethoxysilane [bis(aminopropyl)-terminated-poly(dimethylsiloxane) (1000)] (PDMSU) sol-gel hybrid was synthesized and applied on cotton to make it water repellent. Surface-energy values of PDMSU deposited on an aluminum substrate were determined, and the contact angle for water was assessed for impregnated cotton fabrics. The stability of the coatings was determined by repetitive washing, and their degradation was investigated with the help of the infrared attenuated total reflection (ATR) technique. The structure of PDMSU was studied by ATR and 29Si NMR spectroscopy. The results showed the active role of the urea groups in PDMSU/cotton interface bonding, but washing led to the relaxation of the urea-urea associations, as inferred from the appearance of a new amide II band at 1541 cm(-1).

Structural studies of trimethoxysilane containing R'R"Im+I- ionic liquid and its nanocomposite with tetramethoxysilane (TMOS).

A dialkylsubstituted imidazolium iodide ionic liquid (1-methyl-3-[3-(trimethoxy-lambda4-silyl)propyl]imida-zolium iodide, MTMSPIm+I-) was prepared with the intention of using it as a quasi-solid-state electrolyte for dye-sensitized photoelectrochemical (DSPEC) cells of Grätzel design, while the analogous electrolyte in a gel state was made by the addition of tetramethoxysilane (TMOS) in the molar ratio MTMSPIm+I-:TMOS = 1:1. The structure of the MTMSPIm+I- in its non-hydrolyzed and hydrolyzed states and in its fully condensed form, obtained after ageing the sols for various times (from a few hours to a few weeks) and heating them at 200 degrees C (fully condensed form), was studied employing time-dependent infrared attenuated total reflection (ATR) and 29Si NMR spectroscopic measurements. The structure of the condensed species was correlated with the viscosity and the specific conductivity measurements of MTMSPIm+I- sols and TMOS/MTMSPIm+I- gels during their ageing. The final product of the condensation of MTMSPIm+I- sols was described as a positively-charged ladder-like polysilsesquioxane with Tn end groups exhibiting a single T3 signal in 29Si NMR spectra and characteristic doublet bands at 1138 and 1049 cm(-1) in IR. This structure was retained to a large extent in TMOS/MTMSPIm+I- gels, confirming their nanocomposite structure. The results of the ATR infrared time-dependent spectroscopic studies showed that in the course of condensation of sols, the refractive index of the modes attributed to the polysilsesquioxane species exhibited strong dispersion, which led to shifts in the vibrational band positions in the experimental ATR spectra. This effect accompanies the sol-to-gel transformations and has not yet been considered as a possible error in analysis of the ATR spectra of sols and gels. The calculation procedure for obtaining the corresponding transmission spectra is briefly outlined and the results applied in this work.

Novel polysilsesquioxane-I-/I3- ionic electrolyte for dye-sensitized photoelectrochemical cells.

A new sol-gel precursor, based on 1-methyl-3-[3-(trimethoxy-lambda(4)-silyl)propyl]imidazolium iodide (MTMSPI(+)I(-)), was synthesized and investigated as a potential novel quasi-solid-state ionic liquid redox electrolyte for dye-sensitized photoelectrochemical (DSPEC) cells of the Graetzel type. MTMSPI(+)I(-) was hydrolyzed with acidified water, and the reaction products of the sol-gel condensation reactions were assessed with the help of (29)Si NMR and infrared spectroscopic techniques. Results of time-dependent analyses showed the formation of a positively charged polyhedral cubelike silsesquioxane species, which still contained a small amount of silanol end groups that were removed after heating at 200 degrees C. After cooling, the material formed was a tough, yellowish, and transparent solid, consisting mainly of ladderlike polysilsesquioxane species. The specific conductivity (sigma) of the nonhydrolyzed MTMSPI(+)I(-) (no I(2)) was 0.23 mS/cm, while the activation energy (E(a)), determined from the Vogel-Tamman-Fulcher (VTF) relation, was 0.29 kJ/mol. After 56 days of aging the sigma value of the hydrolyzed MTMSPI(+)I(-) dropped to 0.11 mS/cm but the viscosity had already increased to 7500 Pa.s after 17 days, demonstrating that a quasi solid state was attained. Apparent diffusion coefficients (D(app)) of I(-) and I(3)(-) obtained from the voltammetric measurements were approximately 10(-7) cm(2)/s and decreased to approximately 10(-8) cm(2)/s after 15 days of sol aging. Time-dependent vibrational spectra, which served in assessing the hydrolysis and condensation reactions of MTMSPI(+)I(-), were measured with the help of the attenuated total reflectance (ATR) IR spectroscopic technique. The results revealed that, in the course of condensation of sols, the refractive index of the modes attributed to the polysilsesquioxane species exhibited strong dispersion, which led to a shift of the vibrational band position in the experimental ATR spectra. This effect accompanies the sol-to-gel transformations and has not yet been considered as a possible error in analysis of the ATR spectra of sols and gels. The calculation procedure for obtaining the corresponding transmission spectra is briefly outlined, and the results are applied in this work.