Qualitative and quantitative analyses of hydrophilic and lipophilic antioxidants, such as polyphenols, by simple electrochemical measurements were conducted in a bicontinuous microemulsion (BME), in which water and oil phases coexisted bicontinuously on a microscopic scale. Hydrophilic and lipophilic antioxidants were individually monitored in the same BME solution using a hydrophilic indium tin oxide (ITO) electrode and a lipophilic fluorinated nanocarbon film electrode (F-ECR), respectively. The combination of well-balanced BME and extremely biased electrodes, such as ITO and F-ECR, in terms of hydrophilic-lipophilic balance allowed us to achieve individual monitoring of hydrophilic and lipophilic antioxidants in the same BME solution without extraction. Furthermore, the antioxidant activities of functional liquid foods, such as coffee and olive oil, were also evaluated by means of electrochemical measurements in BME solutions containing analytes in concentrations of several percent. The technique we propose provides a very simple, rapid, easily serviceable, and highly reproducible analysis and can be extended to a wide range of analytes and media.
Quantitative analyses of olive oil for lipophilic antioxidants, such as α-tocopherol and phenolics, by simple electrochemical measurements were conducted in a bicontinuous microemulsion (BME), which was bicontinuously composed of saline and toluene microphases with a surfactant system. Lipophilic antioxidants in oils were directly monitored in BME solutions using a lipophilic, fluorinated nanocarbon-film electrode (F-ECR). The combination of a well-balanced BME and extremely biased electrodes, such as strongly hydrophilic indium/tin oxide and strongly lipophilic (hydrophobic) F-ECR, allowed individual monitoring of hydrophilic and lipophilic antioxidants in the same BME solution without any required extraction. Furthermore, values for the charge Q, integrated from observed currents, showed good linear relationships with the results of conventional assays for antioxidant activity, namely, total phenolics and oxygen radical absorbance capacity assays, even with practical food samples. This proposed methodology provided a very simple, rapid, easily serviceable, and highly reproducible analysis that possesses great potential for applications to a wide range of chemical mixtures, in terms of analyte and media, beyond food oils.
Continuous porous poly(N-isopropylacrylamide) (pNIPAM) gels were prepared by radical polymerization in a bicontinuous microemulsion (BME) consisting of saline and toluene microphases. The BME gels demonstrated good thermoresponsive water swellingshrinking performance, exhibiting high speed and large volume change compared with those of homogeneous pNIPAM gels. The BME gels also exhibited swelling with toluene, while the homogeneous pNIPAM gels could not be swollen with toluene.A number of methods for the mesoscale structural control of swollen soft gels, 1 including porous, 28 composite, 3,9 and bicontinuous 35,10a,10b gels, have been proposed and investigated both as soft materials and self-assembly. Among a variety of unique soft gels such as double-network gels, 2 nanocomposite gels, 9 aqua materials, 11 topological gels, 12 hostguest polymer gels, 13 and stimuli-responsive (intelligent) gels 1,10,12a,1315 have seen particular focus because of their potential as polymer materials for actuators 1,13c,14,16 and drug-release systems. 1,15Recently, we have reported novel hybrid gel systems 3 based on bicontinuous microemulsions (BMEs; Winsor III), in which the water and oil phases coexist microscopically. Three alternative composite gel systems were proposed based on the combination of hydrogelation and/or organogelation. Polymerization in the microphase of a BME allows us to produce continuous porous polymeric materials. These results have encouraged us to develop new soft hybrid or porous materials with stimuli-responsive moieties.In this communication, we report thermoresponsive continuous porous BME gels of poly(N-isopropylacrylamide) (pNIPAM) with N,N¤-methylenebis(acrylamide) (MBAAM, crosslinker) prepared by polymerization in a BME solution. Several methods for the preparation of porous pNIPAM gels 57 have been reported. The continuous porous gels show more rapid deswelling performance than porous gels without a network structure, because a continuous pore acts a channel to supply water to an inner central moiety. 6 We prepared BMEs as a middle phase in macroscopic threephase solutions. The upper and lower phases were an oil phase and an aqueous phase, respectively ( Figure S1). 17 To form the BME phase, the concentrations of salt and 2-butanol in the system were adjusted (Table S1) 17 according to previous studies. 3 The volumes of separated saline and oil phases in the three-phase solution were equalized to provide a BME sample solution that consisted of equal volumes of saline and toluene on a microscopic scale. The BME solution with NIPAM/MBAAM required a relatively lower salt concentration than the BME solution without monomers, because the monomers existed in the saline phase and decreased the hydrophilicity of the surfactant system.Polymerization of NIPAM/MBAAM in the BME was conducted using ammonium persulfate (APS) and tetramethylethylenediamine (TMEDA) as initiator and accelerator, respectively. After 1 h stabilization of the BME solution with APS, the accelerator TMEDA was added to the extracte...
Bicontinuous microemulsion (BME)-based hydrogel films were integrated with screen-printed electrodes (SPEs) comprising working, counter, and reference electrodes to form stand-alone, semi-solid-state electrochemical systems that do not require an outer electrolyte solution. The gel network of the BME hydrogel only exists in the microaqueous phase and retains the structure of the entire BME gel. Following gelation, a microaqueous phase with sufficient ionic strength ensured effective ionic conductivity, even in thin gel films. This enabled the electrochemical reaction to proceed using a thin gel film as an electrolyte solution. However, an intact micro-oil phase with no gel network enabled efficient extraction from an external oil solution and exhibited rapid electrochemistry that was comparable to that of a BME solution. Cyclic voltammograms of lipophilic redox species in oil using the gel-integrated SPE system demonstrated successfully in the oil itself and in the air with dropped oil onto the system.
Large two‐dimensional (2D) nanosheets of crystalline coordination frameworks were prepared on highly oriented pyrolytic graphite (HOPG) by re‐crystallization induced by thermal equilibrium treatment in acetic acid vapor. The nanosheets comprised 5,10,15,20‐tetrakis(4‐carboxyphenyl)‐porphyrin (H2TCPP) cross‐linked by copper ions. We found that an acetic acid vapor environment dramatically decreased the activation energy and accelerated the recombination of coordination bonds between metal ions and carboxylate ligands in the H2TCPP‐Cu frameworks. Ultimately, two‐dimensional horizontal crystal growth was induced to form monomolecular sheets as the most thermodynamically stable crystal structure on a well‐defined surface.
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