Metal Hydroxide/Polymer Textiles for Decontamination of Toxic Organophosphates: An Extensive Study of Wettability, Catalytic Activity, and the Effects of Aggregation.

Electrospun nanofibers (NFs) incorporated with catalytically active components have gained significant interest in chemical protective clothing. This is because of the desirable properties of the NFs combined with decontamination capability of the active component. Here, a series of metal hydroxide catalysts Ti(OH)x, Zr(OH)4, and Ce(OH)4 were incorporated into three different polymer NF systems. These new polymer/metal hydroxide composite NFs were then evaluated for their catalytic activity against a nerve agent simulant. Two methods were utilized to incorporate the metal hydroxides into the NFs. Method one used direct incorporation of Ti(OH)x, Zr(OH)4, and Ce(OH)4 catalysts, whereas method two employed incorporation of Ti(OH)x via a precursor molecule. Composite NFs prepared via method one resulted in greatly improved reaction rates over the respective pure metal hydroxides due to reduced aggregation of catalysts, with polymer/Ce(OH)4 composite NFs having the fastest reaction rates out of method one materials. Interestingly, composite samples prepared by method two yielded the fastest reaction rates overall. This is because of the homogeneous distribution of the metal hydroxide catalyst throughout the NF. This homogeneous distribution created a hydroxyl-decorated NF surface with a greater number of exposed active sites for catalysis. The hydroxyl-decorated NF surface also resulted in an unexpected highly wettable composite NF, which also was found to contribute to the observed reaction rates. These results are not only promising for applications in chemical protective clothing but also show great potential for application in areas which need highly wettable membrane materials. This includes areas such as separators, antifouling membranes, and certain medical applications.

Toxic Organophosphate Hydrolysis Using Nanofiber-Templated UiO-66-NH2 Metal-Organic Framework Polycrystalline Cylinders.

Metal organic frameworks (MOFs), the UiO series in particular, have attracted much attention because of the high surface area and ability to capture and decontaminate chemical warfare agents. Much work has been done on incorporating these MOFs into or onto textile materials while retaining the desirable properties of the MOF. Many different techniques have been explored to achieve this. Atomic layer deposition (ALD) of TiO2 followed by solvothermal synthesis of MOF has become one of the most adaptable techniques for growing MOFs on the surface of many different polymer fabric materials. However, little work has been done with using this technique on polymer composite materials. In this work, UiO-66-NH2 was grown onto the surface of poly(methyl methacrylate) (PMMA)/Ti(OH)4 and poly(vinylidene fluoride) (PVDF)/Ti(OH)4 composite fibers by first modifying the surface with ALD of TiO2 (@TiO2) followed by solvothermal synthesis of MOF (@MOF). The catalytic activity of these materials was then evaluated using the simulant paraoxon-methyl (DMNP). These new MOF-functionalized composite fabrics were compared to polyamide-6 (PA-6)@TiO2@MOF- and polypropylene (PP)@TiO2@MOF-functionalized fabrics. PMMA/Ti(OH)4@TiO2@MOF fibers resulted in unique hollowed fibers with high surface area of 264 m2/g and fast catalytic activity. The catalytic activity of these samples was found to be related to the active MOF mass fraction on the MOF-functionalized composite fabric, with the hollowed PMMA/Ti(OH)4@TiO2@MOF having the highest weight percent of active MOF and a DMNP t1/2 of 26 min followed by PA-6@TiO2@MOF with 45 min, PVDF/Ti(OH)4@TiO2@MOF with 61 min, and PP@TiO2@MOF with 83 min.

Chemical Protective Textiles of UiO-66-Integrated PVDF Composite Fibers with Rapid Heterogeneous Decontamination of Toxic Organophosphates.

Metal-organic frameworks (MOFs) are a new and growing area of materials with high porosity and customizability. UiO-66, a zirconium-based MOF, has shown much interest to the military because of the ability of the MOF to catalytically decontaminate chemical warfare agents (CWAs). Unfortunately, the applications for MOFs are limited because of their powder form, which is difficult to incorporate into protective clothing. As a result, a new area of research has developed to functionalize fabrics with MOFs to make a wearable multifunctional fabric that retains the desired properties of the MOF. In this work, UiO-66 was incorporated into poly(vinylidene) fluoride/Ti(OH)4 composite fabric using electrospinning and evaluated for its use in chemical protective clothing. The base triethanolamine (TEA) was added to the composite fabric to create a self-buffering system that would allow for catalytic decontamination of CWAs without the need for a buffer solution. The fabrics were tested against the simulants methyl-paraoxon (dimethyl (4-nitrophenyl) phosphate, DMNP), diisopropyl fluorophosphate (DFP), and the nerve agent soman (GD). The results show that all of the samples have high moisture vapor transport and filtration efficiency, which are desirable for protective clothing. The incorporation of TEA decreased air permeation of the fabric, but increased the catalytic activity of the composite fabric against DMNP and DFP. Samples with and without TEA have rapid half-lives ( t1/2) as short as 35 min against GD agent. These new catalytically active self-buffering multifunctional fabrics have great potential for application in chemical protective clothings.

Facile Synthesis of Fluorescent Conjugated Polyelectrolytes Using Polydentate Sulfonate as Highly Selective and Sensitive Copper(II) Sensors.

Fluorescent conjugated polyelectrolytes represent an exciting area of research into new chemosensors. By virtue of their rapid electron and energy transfer paths, these highly correlated, one-dimensional systems have been depicted as "molecular wires" and show "million-fold" sensitivity compared to monomolecular sensor analogs. In this paper, a novel polyelectrolyte sensor, the ttp-PPESO3, has been designed by incorporating terpyridine and sulfonate functional groups into the polyelectrolyte. This specifically tailored sensor has displayed remarkable quenching response toward copper(II) with a detection limit of 14.7 nM (0.93 ppb). It is capable of selectively screening copper without interference from 12 common cations. Molecular modeling suggests that binding occurs through a coordination interaction of the terpyridine and sulfonate. The additional multidentate nature from the sulfonate offers extraordinary chelating ability to the analyte. We anticipate that this unique binding mode will provide insight for the design of future more sensitive and selective systems.

Pentiptycene-Derived Fluorescence Turn-Off Polymer Chemosensor for Copper(II) Cation with High Selectivity and Sensitivity.

Fluorescent conjugated polymers (FCPs) have been explored for selective detection of metal cations with ultra-sensitivity in environmental and biological systems. Herein, a new FCP sensor, tmeda-PPpETE (poly[(pentiptycene ethynylene)-alt-(thienylene ethynylene)] with a N,N,N'-trimethylethylenediamino receptor), has been designed and synthesized via Sonogashira cross-coupling reaction with the goal of improving solid state polymer sensor development. The polymer was found to be emissive at λmax ~ 459 nm under UV radiation with a quantum yield of 0.119 at room temperature in THF solution. By incorporating diamino receptors and pentiptycene groups into the poly[(phenylene ethynylene)-(thiophene ethynylene)] (PPETE) backbone, the polymer showed an improved turn-off response towards copper(II) cation, with more than 99% quenching in fluorescence emission. It is capable of discriminating copper(II) cation from sixteen common cations, with a detection limit of 16.5 nM (1.04 ppb).