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A polystyrene–TiO2 nanosandwich film was fabricated by spin-coating a mixture of PS and Ti(O-n-Bu)4. Phase separation of the two components showed various morphological changes in the film, dependi...

Nafion has been the industry standard membrane for polymer electrolyte membrane fuel cells (PEFCs) for decades due to its high conductivity, mechanical stability and durability. However, it has several drawbacks such as poor performance at high temperatures / low humidity, use of harmful fluorine in its production, and as its high price. Therefore research into new membrane materials is necessary. Basic requirements for next-generation fuel cell membranes are sufficiently high proton conductivity, high mechanical strength, good hydrogen gas barrier, and low cost. Nanocellulose is a biopolymer produced in bulk from abundant cheap cellulosic materials such as wood or cotton. Depending on its source, nanocellulose fiber dimensions can range from a few to several tens of nanometers in diameter, and are several micrometers in length. Nanocellulose paper with high mechanical strength and thermal stability up to 150°C has been reported.1,2 Previously, we showed that the hydrogen barrier of nanocellulose membranes is approximately 1000 times higher than Nafion.3 In addition, reasonable proton conductivity at high temperature (~5 mS/cm at 120°C) was shown by impedance spectroscopy. Based on these results we fabricated the world’s first nanocellulose “paper fuel cells” and successfully operated them as hydrogen fuel cells. The performance was stable, with no degradation over 24 hours. Here, in order to increase the proton conductivity, we perform chemical modification of nanocellulose fibers. This chemical treatment resulted in an increase in the number of acidic functional groups, as well as modifying the microstructure. A strong increase in the proton conductivity was observed, with an associated increase in fuel cell performance. In addition, nanocellulose was composited with more established ionomer materials and the resulting membranes were investigated for their fuel cell properties. References 1. Henriksson, M. et al. Cellulose Nanopaper Structures of High Toughness. Biomacromolecules 9,1579–1585 (2008). 2. Nogi, M. et al. High thermal stability of optical transparency in cellulose nanofiber paper. Appl. Phys. Lett. 102,181911 (2013). 3. Bayer, T. et al. High Temperature Proton Conduction in Nanocellulose Membranes: Paper Fuel Cells. Chem. Mater. 28, 4805–4814 (2016). Figure 1

We developed a new device for the in vitro extraction of small molecule metabolites excreted from cancer cells. The extraction device, which was biocompatible and incubated with cancer cells, consists of a thin Tenax TA film deposited on the surface of a cylindrical aluminum rod. The Tenax TA solid phase was utilized for the direct extraction and preconcentration of the small molecule metabolites from a cell culture sample. The device fabrication and the metabolite extraction were optimized, tested, and validated using HeLa cell cultures. Comparison of metabolic profiles with the control measurement from the culture medium enabled detection of metabolites that were consumed or produced by the cell culture. Tentative identification and semi-quantitative investigation of the excreted metabolites were performed by GC–MS analysis. The proposed approach can be a valuable tool for the characterization of low-volatile cancer cell metabolites that are not covered by use of conventional methods based on headspace solid phase microextraction.

The zeolite material ZSM-5 was combined with Tenax TA, a porous polymer adsorbent, to form a thin film microextraction (TFME) device that was used as a novel alternative tool for headspace (HS) volatile organic compound (VOC) extraction and preconcentration. The ZSM-5/Tenax TA film deposited on a cylindrical aluminium rod (AR) substrate exhibited superior properties for the adsorption and preconcentration of chloroform, hexane, cyclohexane, benzene, and toluene compared with those of a conventional Tenax TA film when applied in both the direct and HS extraction modes. The advantages of the fabricated device include its enhanced chromatographic performance and consequently lower detection limits for certain VOCs, the improved retention of compounds in the film (possibly enabling its application for both HS and direct extractions from aqueous solutions), the exceptional simplicity of its fabrication, and its robustness. The use of the film for HS extraction leads to increased application lifetime, film stability and shorter preparation times, because drying step is not necessary. Desorption of the adsorbed VOCs was achieved by heating in a conventional Curie point injector for less than 2 min. It should be noted that the catalytic properties of the zeolite can be disadvantageous at high VOC concentrations (e.g., 100 μM); abundant background peaks as a result of a range of saturated and unsaturated hydrocarbons generated via catalytic degradation of adsorbed compounds at high temperature in the presence of ZSM-5 appear in the gas chromatograph. This effect is still visible at concentrations as low as 10 μM, but does not influence the measurement results. Thus, safe and accurate analyses are achievable at the liquid VOC concentrations in the submicromalar range, which is sufficient for a number of important analytical applications (e.g., detection of VOCs in waste water).

Fuel cells are the key technology towards establishing a hydrogen energy based society, as they convert the chemical energy of hydrogen into electricity with high efficiency, and without emitting harmful exhaust gases. Polymer electrolyte membrane fuel cells (PEMFCs) are already successfully commercialized and are being used in e.g. fuel cell vehicles such as the Toyota MIRAI and the Honda Clarity Fuel Cell. However, the aim for next-generation PEMFCs is to operate at temperatures above the boiling point of water, therefore new membrane materials are needed. Stable operation at high temperature, sufficient high proton conductivity, high gas barrier as well as low cost are essential requirements. Cellulose is the most abundant biopolymer on earth, and has been utilized in various forms by mankind for thousands of years. Cellulose polymer units form nanofibrils during biosynthesis, with diameters of several tens of nanometers and lengths of up to a few microns. These group together to form micro- and macrofibrils. In 1977 nanofibrils were successfully observed for the first time by Turbak et al., kick-starting the field of nanocellulose science. Paper made from nanocellulose has intriguing properties such as high tensile strength (214 MPa), high gas barrier and thermal stability up to 150°C.1–3 During the fabrication process of nanocellulose, acid group functionalities (i.e. carboxyl and sulfonic acid groups) are introduced,4,5which increase hydrophilicity, and additionally act as proton donors and acceptors, thus enabling proton conduction. We investigated nanocellulose for its suitability as fuel cell membrane in PEMFCs for the first time. Two different nanocellulose materials were characterized for their morphology and chemical composition, as well as mechanical properties and gas barrier. Nanocellulose membranes showed four times higher tensile strength compared to the industry standard membrane Nafion and a roughly three orders of magnitude lower hydrogen permeability. A maximum proton conductivity of 4.7 mS/cm at 120°C and 100% RH was observed. For the first time, nanocellulose membranes were assembled into membrane electrode assemblies and operated as hydrogen fuel cell. We will report latest results of our research. References: 1. Henriksson, M., Berglund, L. A., Isaksson, P., Lindstro, T. & Nishino, T. Cellulose Nanopaper Structures of High Toughness. Biomacromolecules9, 1579–1585 (2008). 2. Nair, S. S., Zhu, J., Deng, Y. & Ragauskas, A. J. High performance green barriers based on nanocellulose. Sustain. Chem. Process.2, 1–7 (2014). 3. Nogi, M. et al. High thermal stability of optical transparency in cellulose nanofiber paper. Appl. Phys. Lett.102, 181911 (2013). 4. Lin, N. & Dufresne, A. Nanocellulose in biomedicine: Current status and future prospect. Eur. Polym. J.59, 302–325 (2014). 5. Barbosa, L. et al. A Rapid Method for Quantification of Carboxyl Groups in Cellulose Pulp. BioResources 8, 1043–1054 (2013). Figure 1

Graphene is increasingly being studied for fuel cell catalysis because of its high conductivity, large surface, and chemical stability.[1,2] Graphene oxide (GO) is a monolayer carbon material with carboxyl, hydroxyl and epoxy oxygen functional groups on the surface and edges. These make GO hydrophilic, and the sp2/sp3-hybridization is believed to make it insulating to electrons.[3] Fuel cell membranes have several important requirements. They must be insulating to electrons, have significant ionomer conductivity, provide sufficient barrier to prevent hydrogen/methanol crossover, and have the mechanical strength to be able to support the cell. GO could potentially fulfil these requirements. [4,5] Here, we investigate the suitability of GO for fuel cell membranes by measuring the gas barrier properties, proton conductivity, anion conductivity, electronic conductivity, tensile strength, and fuel cell performance. Initially we reported the characterization of a graphene oxide membrane fuel cell (GOMFC).[6] Free-standing flexible GO membranes were prepared from GO dispersion in water by vacuum-filtration. GO was found to have higher tensile strength and water uptake compared with Nafion. The power density of a fuel cell with a 30 μm thick GO membrane was 35 mW/cm2 at 30°C, despite the fact that the proton conductivity is several orders of magnitude lower than Nafion. The device had a very high open circuit voltage >1 V indicating low crossover. This indicates that thinner membranes compared with Nafion can be utilized, reducing the overall cell resistance. Indeed, by changing the fabrication method to further reduce the thickness of the GO membranes to several microns, we recently achieved improved power density of up to 80 mW/cm2. We also have performed a detailed study on the through-plane conductivity and permittivity of GO membranes over a wide temperature and humidity range.[7] It was found that the proton conductivity is strongly dependant on humidity, and that under dry warm conditions significant electronic conductivity is observed. This opens the opportunity for tuneable mixed ionic-electronic conductivity and may be extremely useful in sensing application. In addition, we performed in-situ scanning electron microscopy (SEM) and electron energy loss spectroscopy (EELS) on humidified and dried GO membranes, directly observing expansion and contraction (“breathing”) of the membranes.[8] Even after drying and under high vacuum conditions, the EELS signal for crystalline ice was observed after freezing, suggesting that water is extremely strongly bound to GO, which may have implications for proton conductivity. Finally, a novel class of alkaline anion exchange membrane (AAEM) is presented, in the form of KOH-modified multilayer graphene oxide paper (GOKOH).[9] SEM investigations showed that the morphology of GO changes after KOH-treatment, whilst X-ray photoelectron spectroscopy (XPS) measurements and X-ray diffraction (XRD) analysis confirmed successful chemical modification. The hydrogen gas permeability was several orders of magnitude lower than conventional polymer-based ionomer membranes. The maximum anion conductivity was 6.1 mS/cm at 70 °C, and the dominant charge carrier was confirmed to be OH− by utilization of anion and proton-conducting blocking layers. The ion exchange capacity was 6.1 mmol/g, measured by titration. A water-mediated reverse Grotthuss-like mechanism is proposed as the main diffusion mode of OH− ions. A prototype AAEM fuel cell was fabricated using a GOKOH membrane, confirming the applicability to real systems. References: 1. J. Liu, T. Daio, K. Sasaki, S. M. Lyth, Journal of the Electrochemical Society, 161, F834 (2014). 2. J. Liu, T. Daio, D. Orejon, K. Sasaki, S. M. Lyth, Journal of The Electrochemical Society 161, F544-F550 (2014) 3. D. R. Dreyer, S. Park, C. W. Bielawski, and R. S. Ruoff, Chem. Soc. Rev., 39, 228–240 (2010). 4. R. R. Nair, H. A. Wu, P. N. Jayaram, I. V. Grigorieva, and A. K. Geim, Science, 335, 442–444 (2012). 5. K. Hatakeyama et al., Angew. Chemie, 53, 6997–7000 (2014). 6. T. Bayer, S. R. Bishop, M. Nishihara, K. Sasaki, and S. M. Lyth, Journal of Power Sources, 272, 239–247 (2014). 7. T. Bayer, S. R. Bishop, N. Perry, K. Sasaki, S. M. Lyth, ACS Applied Materials and Interfaces, In press (2016) 8. T. Daio, T. Bayer, T. Ikuta, T. Nishiyama, K. Takahashi, Y. Takata, K. Sasaki, S. M. Lyth, Scientific Reports, 5, 11807 (2015) 9. T. Bayer, B. V. Cunning, R. Selyanchyn, T. Daio, M. Nishihara, S. Fujikawa, K. Sasaki, S. M. Lyth, Journal of Membrane Science, 508, 51 (2016)

An analytical TD-GC-MS method was developed and used for the assessment of volatile organic compounds (VOCs) released from the blood plasma of dogs with/without cancer. VOCs released from 40 samples of diseased blood and 10 control samples were compared in order to examine the difference between both sample groups that were showing qualitatively similar results independent from the disease’s presence. However, mild disturbances in the spectra of dogs with cancer in comparison with the control group were observed, and six peaks (tentatively identified by comparison with mass spectral library as hexanal, octanal, toluene, 2-butanone, 1-octen-3-ol and pyrrole) revealed statistically significant differences between both sample groups, thereby suggesting that these compounds are potential biomarkers that can be used for cancer diagnosis based on the blood plasma TD-GC-MS analysis. Statistical comparison with the application of principal component analysis (PCA) provided accurate discrimination between the cancer and control groups, thus demonstrating stronger biochemical perturbations in blood plasma when cancer is present.

Quartz crystal microbalance (QCM) electrodes modified with nano-thin films were used to develop a system for measuring significant environment changes (smoke, humidity, hazardous material release). A layer-by-layer approach was used for the deposition of sensitive coatings with a nanometer thickness on the electrode surface. The QCM electrode was modified with self-assembled alternate layers of tetrakis-(4-sulfophenyl) porphine (TSPP) (or its manganese derivative, MnTSPP) and poly(diallyldimethylammonium chloride) (PDDA). The QCM sensors, which had been reported previously for humidity sensing purposes, revealing a high possibility to recognize significant environmental changes. Identifying of the origin of environmental change is possible via differential signal analysis of the obtained data. The sensors showed different responses to humidity changes, hazardous gas (ammonia) or cigarette smoke exposure. Even qualitative analysis is not yet available; it has been shown that ventilation triggers or alarms for monitoring smoke or hazardous material release can be built using the obtained result.

A respiratory monitoring system based on a quartz crystal microbalance (QCM) sensor with a functional film was designed and investigated. Porphyrins 5,10,15,20-tetrakis-(4-sulfophenyl)-21H,23H-porphine (TSPP) and 5,10,15,20-tetrakis-(4-sulfophenyl)-21H, 23H-porphine manganese (III) chloride (MnTSPP) used as sensitive elements were assembled with a poly(diallyldimethyl ammonium chloride) (PDDA). Films were deposited on the QCM resonators using layer-by-layer method in order to develop the sensor. The developed system, in which the sensor response reflects lung movements, was able to track human respiration providing respiratory rate (RR) and respiratory pattern (RP). The sensor system was tested on healthy volunteers to compare RPs and calculate RRs. The operation principle of the proposed system is based on the fast adsorption/desorption behavior of water originated from human breath into the sensor films deposited on the QCM electrode.

TiO 2 nano-thin films with imprinted ( R )- and ( S )-enantiomers of propranolol, 1,1′-bi-naphthol, and 2-(4-isobutylphenyl)-propionic acid were fabricated on quartz plates by spin-coating their solutions with Ti(O- n Bu) 4 in a toluene-ethanol mixture (1:1, v/v). After template removal, the imprinted films showed better binding for original templates than to the corresponding enantiomers. The assessment of template incorporation, template removal, and re-binding was conducted through UV–vis measurements. Significant enhancement of enantioselectivity was achieved by optimization of the film thickness and by heat-treatment of the imprinted films. After subtraction of non-specific binding, the optimized films provided chiral recognition with the enantioselectivity of almost 100% for ( R )-propranolol and 95% for ( S )-propranolol.

Treatment of graphite by the modified Hummers method results in exfoliation of the graphene layers and the introduction of oxygen-containing surface functional groups.1 The resulting graphene oxide offers interesting possibilities for a wide range of applications in areas as diverse as e.g. humidity sensing,2 molecular sieving,3 gas barriers,4 dielectrics,5 and fuel cells.6,7 Polymer electrolyte membrane fuel cells (PEMFCs) are seen as a sustainable energy source for the future. So far the most commonly used membrane in PEMFCs is Nafion, due to its high mechanical and chemical stability as well as its high proton conductivity. However Nafion is expensive, has limited performance at temperatures > 100°C,8 and has only moderate gas barrier properties (leading to fuel crossover in very thin membranes). Graphene oxide membrane fuel cells (GOMFCs) have displayed reasonable power densities at room temperature,7and with some improvements could act as an electrolyte in low temperature fuel cells. Here, the proton conductivity, fuel cell performance, fuel crossover of graphene oxide paper with different oxygen content, surface morphology, and surface functional groups are investigated by impedance spectroscopy, membrane electrode assembly testing, and gas permeation measurements. The manufacturing techniques for production of graphene oxide membranes and the optimal thickness of membranes are also discussed. References: 1. Zhu, Y. et al., Adv. Mater. 22,3906–3924 (2010). 2. Borini, S. et al., ACS Nano 7,11166–11173 (2013). 3. Joshi, R. K. et al., Science 343,752–4 (2014). 4. Yoo, B. M. et al., Polym. Sci. 131,n/a–n/a (2014). 5. Wang, D.-W. et al., J. Mater. Chem. 22,21085 (2012). 6. Tateishi, H. et al., J. Electrochem. Soc. 160,F1175–F1178 (2013). 7. Bayer, T. et l. , J. Power Sources 272,239–247 (2014). 8. Yee, R. S. L. et al., Chem. Eng. Res. Des. 90,950–959 (2012). Figure 1

An evanescent-wave optical fibre sensor modified with tetrakis-(4-sulfophenyl) porphine (TSPP) and poly(allylamine hydrochloride) (PAH) bilayers using layer-by-layer (LbL) electrostatic self-assembly was tested to measure the gas emitted from human skin. Optical intensity changes at different wavelengths in the transmission spectrum of the porphyrin-based film were induced by the human skin gas and measured as sensor response. Influence of relative humidity, which can be a major interference to sensor response, was thoroughly studied and shown to be significantly different when compared to the influence of skin emanations. Responses of the current optical sensor system could be considered as composite sensor array, where different optical wavelengths act as channels that have selective response to specific volatile compounds. Data obtained from the sensor system was analyzed using principal component analysis (PCA). This approach enabled to distinguish skin odors of different people and their altered physiological conditions after alcohol consumption.