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In this paper is reported the energy generated in a paper-based microfluidic fuel cell (paper-based mFC) using Pd/CX100 as anode and glycerol from three sources: reagent grade glycerol, crude glycerol from sunflower oil biodiesel, and crude glycerol from used cooking oil biodiesel, as fuels. TEM, SEM, XRD, XPS, and cyclic voltammetry were employed for the Pd/CX100 characterization. The paper-based mFC using Pd/CX100 as anode was evaluated employing 0.1 M and 0.5 M glycerol of each glycerol sample and achieving power densities of 0.242 and 0.160; 0.15 and 0.127; and 0.108 and 0.090 mW cm-2 for reagent grade glycerol, glycerol from sunflower oil biodiesel, and glycerol from used cooking oil biodiesel, respectively.

Performance of direct internal reforming (DIR)-solid oxide fuel cell (SOFC) can be improved by the application of the paper-structured catalyst (PSC) on the anode material. In the ceramic fiber network of the PSC, any kinds of functional materials can be easily dispersed during paper-making process. The solid solution based on the equimolar mixture of ceria and zirconia (Ce0.5Zr0.5O2-δ), hereafter called CZ, is a promising oxide support of the Ni metal catalyst due to its high specific surface area and high oxygen storage capacity (OSC). By employing the two-step hydrothermal process developed in this study, we could successfully prepare the CZ with flowerlike geometry, which can prevent Ni from sintering under reducing atmosphere. Ni-loaded PSCs with and without the dispersion of CZ, Ni/CZ-PSC and Ni-PSC, respectively, were prepared. Structures of the PSCs were characterized by X-ray diffractometry (XRD), BET specific surface area measurement, field emission scanning electron microscopy (FESEM), inductively coupled plasma spectrometry (ICP) and thermogravimetric analysis (TG). Catalytic performances of these PSCs for the dry reforming of methane (DRM) in the feed of the equimolar mixture of CH4 and CO2 were evaluated by an automatic gas chromatograph (GC) with the posttest analysis by FESEM observation, temperature-programmed oxidation (TPO) and TG to estimate carbon deposition. In the durability (160 h) tests of the prepared-PSCs for DRM at 750oC under gas hourly space velocity (GHSV) of 2300 h-1 revealed that, for both cases with and without CZ dispersion, methane conversions were stable with the degradation rates (estimated after 10 h) of 13.7 and 21.8% 1000 h-1, respectively. TG measurements after the 160 h tests under oxidizing atmosphere in the range from 300 to 750oC revealed that the weights of the deposited carbon were 0.2 and 3.4 folds of those of PSCs for Ni/CZ-PSC and Ni-PSC, respectively. In the case without CZ dispersion (Ni-PSC), after the TG measurement to burn out the deposited carbon, Ni agglomeration and its detachment from the ceramic fiber could be clearly observed. On the other hand, for the Ni/CZ-PSC, these phenomena were considerably suppressed thanks to the flowerlike morphology for better dispersion of Ni metal particles and higher OSC of CZ solid solution to consume deposited carbon by the lattice oxygen. The developed PSCs will be applied on the anode of electrolyte-supported cell to demonstrate the stable operation of DIR-SOFC fueled by biogas (direct-biogas SOFC).

Jaundice continues to be a serious health concern and is among the leading causes of deaths during the first days of newborn babies’ lives. Serum bilirubin is currently being exploited in the clinic as a key biomarker for the diagnosis and management of neonatal jaundice. The commonly used methods for serum bilirubin determination in clinical settings are direct spectroscopic measurement and the diazo reaction method. These methods have drawbacks such as low sensitivity, matrix interference, poor stability, high-cost, professional training, less specificity and tedious sample preparation. Thus, it is very urgent to develop a rapid and economical route for sensitive and specific detection of free bilirubin directly in human serum. Surface-enhanced Raman scattering (SERS) has emerged as a powerful analytical technique for biosensing applications with high sensitivity, molecular specificity, powerful multiplex detection capability, and excellent photostability. This talk will present our recent study on the development of a paper-based SERS biosensor for label-free detection of bilirubin in serum. This biosensor comprises multifunctional graphene oxide-gold nanostar (GO-GNS) hybrids decorated on the filter paper. This biosensor combines the enrichment for serum bilirubin and plasmonic enhancement for Raman signals of bilirubin for boosting the label-free detection sensitivity directly in blood serum without the need for additional sample preparation. Our results demonstrated the excellent detection performance for detection of bilirubin directly in serum in a label-free manner, and the detection results were compared with the commercial diazo reaction method, which justifies the clinical effectiveness and suitability of the present paper-based SERS biosensor. We believe that the present paper-based SERS biosensor has great potential for clinical translation in accurate diagnosis of jaundice and other related diseases. Reference: Xiang Pan, Linhu Li, Hangduo Lin, Jiayi Tan, Haitao Wang, Mengling Liao, Caiju Chen, Beibei Shan, Yingfan Chen, Ming Li, A graphene oxide-gold nanostar hybrid based-paper biosensor for label-free SERS detection of serum bilirubin for diagnosis of jaundice, Biosensors and Bioelectronics, 2019, 145, 111713.

Point-of-care testing (POCT) of proteins is crucial for on-site and rapid diagnosis of diseases in community and family medicine. Microfluidic paper-based analytical devices (µPADs) have attracted growing attention in POCT of proteins, while the practical applications of µPADs in the analysis of proteins in physiological samples is still limited as physiological samples are usually high-salt and complex. Herein, we developed a three-dimensional (3D) paper-based isoelectric focusing (IEF) platform, which is composed of power supply, reservoirs and separation channel make by origami and stacking of cellulose acetate membrane, to simultaneously separate and enrich proteins in both low-salt samples and high-salt samples, especially for directly pretreating and analyzing proteins in physiological samples. Under the optimized experimental conditions, standard proteins (Phy and BHb) were separated in 18 min under a 36.0 V power supply and obtained 10-fold enrichment using the 3D paper-based IEF platform. Then, the capability of the 3D paper-based IEF platform with using a 12.0 V battery as power supply for direct pre-treatment of high-salt samples was proven through separating three standard proteins in saline (0.9 % NaCl) with separation resolution (SR) >1.29. Through further coupling with colorimetric and lateral flow strip measurements, the 3D paper-based IEF platform was applied to directly pre-treat and quantitatively analyze the two disease biomarkers, i.e., microalbuminuria and C-reactive proteins in clinical human serum. The analytical results had the relative deviations of References [1] J. C. Niu, T. Zhou, L. L. Niu, Z. S. Xie, F. Fang, F. Q. Yang, Z. Y. Wu, Simultaneous Pre-concentration and Separation on Simple Paper-based Analytical Device for Protein Analysis, Analytical and Bioanalytical Chemistry 410.6 (2018): 1689-1695. [2] J. C. Niu, H. X. Shi, H. G. Wei, B. Gao, J. X. Li, F. Xu, X. G. Li, F. Li, Liquid Plasticine Integrated with Isoelectric Focusing for Miniaturized Protein Analysis, Analytical Chemistry 92.13 (2020): 9048–9056.

A helium (He) atmospheric-pressure dielectric barrier discharge jet (DBDjet) is used to pattern 1H, 1H, 2H, 2H-perfluorodecyltrichlorosilane (PFDTS)-coated cellulose paper with a shadow mask. DBDjet processing under appropriate conditions can be used to form hydrophilic patterns. The properties of the DBDjet-patterned PFDTS-coated paper are investigated through water contact angle measurement, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS), and the results indicate the successful deposition and removal of PFDTS before/after DBDjet treatment. The successful routing and mixing of liquid in the hydrophilic stripes are demonstrated, and a glucose concentration colorimetric test is demonstrated using this DBDjet-patterned PFDTS-coated paper.

We have developed paper-based screen-printed biofuel cells using MgO-templated carbon (MgOC) as an electrode material1) in which a mediator and an enzyme were immobilized by dropping the solutions on the MgOC surface. However, the immobilization scheme should be shortened for practical applications. In this study, we newly prepare an enzyme-modified carbon ink using chitosan, which has high bio-affinity as a binder. By preparing chitosan-based enzyme ink, it becomes possible to immobilize the enzyme on the electrode by a simple printing process. A paper-based glucose/O2 biofuel cell was fabricated by screen printing with the enzyme-modified carbon inks. In this abstract, we describe the results of the glucose anode. Firstly, a glucose oxidase (GOx) and 1,2-naphthoquinone (1,2-NQ) were physically adsorbed in the pores of the MgOC. Then a chitosan-based enzyme ink was prepared by mixing the GOD and 1,2-NQ immobilized MgOCwith chitosan, and then cross-linked with genipin. A commercially available carbon ink and the as-prepared chitosan-based enzyme ink were successively printed on a water-repellent Japanese paper and dried overnight in a refrigerator to prepare a bioanode. In this study, we used two kinds of carbon. One is an untreated MgOC (normal MgOC). Another is a “washed MgOC”, which were washed with 0.25M NaOH and pure water before the chitosan-based enzyme ink was prepared. Anodes prepared with chitosan-based enzyme inks using normal MgOC and washed MgOC were evaluated by chronoamperometry (measurement potential: 0.2 V) in phosphate buffer containing 100 mM glucose (Fig.1 (a)). The catalytic oxidation reaction was not observed in the anode using normal MgOC, whereas the catalytic oxidation current of about 0.5 mA/cm2 was obtained after 500 seconds in the anode using the washed MgOC. From the SEM (accelerating voltage: 15.0 kV) of the anode using washed MgOC, a structure with many macroporesof about 5 to 10 µm was observed clearly. (Fig. 1(b)). On the other hand, no such macropores were observed in the anode using normal MgOC. The surface of normal MgOC has many functional groups such as -COOH, and it shows acidity when mixed with water. The cross-linking reaction does not occur sufficiently in between genipin and chitosan under acidic condition. On the other hand, in the neutral condiiton, the cross-linking reaction that accompanies the self-polymerization of genipin proceeds enough to form long and flexible chains 2). Therefore, the neutralization of the MgOC surface by the washing treatment forms an electrode with macropores between carbons, resulting in increase of glucose supply to the GOD immobilized in the mesopore of MgOC. References 1) Isao Shitanda et al., J. Electrochem. Soc, 166(12) (2019) B1063-B1068. 2) Elí Emanuel Esparza Floreset et al., Process Biochemistry, 84, (2019) 73-80. Acknowledgements This work was partially supported by JST-ASTEP Grant Number JPMJTS1513, JSPS Grant Number 17H02162 and Private University Research Branding Project (2017-2019) from Ministry of Education, Culture, Sports, Science and Technology, and Tokyo University of Science Grant for President's Research Promotion． Figure 1

A high-performance paper electrode is fabricated through coating polypyrrole (PPy) on ordinary laboratory filter paper via a traditional interfacial polymerization method with perchloric acid (HClO4) as a dopant. Owing to the superior mechanical flexibility and environmental stability of the free standing PPy paper, the robust electrode displays an ultrahigh capacitance of 1650 mF cm−2 and remarkable cyclic stability of losing 11.66% after cycling for 10000 times in a three-electrode system. More importantly, the areal specific capacitance has only decreased by 0.08% after five months. Furthermore, by employing the synthesized PPy papers as electrodes and the PVA-H2SO4 gel as electrolyte, the assembled all-solid-state supercapacitor with an areal specific capacitance of 566.5 mF cm−2 is achieved, corresponding to an areal energy density of 38.55 μW h cm−2 and power density of 0.17 mW cm−2. These results suggest that the simple synthesis of PPy paper electrode pave a promising way to exploit flexible and durable energy storage applications.

As a renewable energy source to replace traditional fossil fuels, hydrogen is a promising sustainable energy carrier due to its eco-friendly nature and high energy density. Although Pt-based materials are widely used as catalysts for generating hydrogen through water electrolysis because of their high catalytic activity, Pt is expensive, and its scarcity hinders the commercialization of large-scale hydrogen production. The development of alternative low-cost materials with low hydrogen evolution reaction (HER) overpotential is the key to achieve low price and highly efficient hydrogen generators such as proton-exchange membrane water electrolysis (PEMWE). Among the numerous candidates of earth-abundant materials, transition metal-based phosphides (TMPs) are suitable for HER applications due to their low toxicity, high electrical conductivity, and catalytic activity. Especially, FeP is in the spotlight as a HER catalyst due to its high catalytic activity in solutions with a wide pH range, and this is a competitive material for large-scale commercial production of hydrogen, since Fe is one of the most abundant elements on earth. In this study, we synthesized the colloidal FeP nanoparticles (NPs) via a hot injection process, so that the pre-synthesized Fe NPs can be converted to FeP NPs through the phosphorization reactions by various phosphorus sources (trioctylphosphine, triphenylphosphite (TPP), tris(diethylamino)phosphine, and tri-n-butylphosphine). Different HER activities were induced by the phase transformation of NPs over the controlled reaction time for the NP samples synthesized with each phosphorus precursor. The FeP synthesized using TPP achieved excellent HER activity with an overpotential of 76 mV at 10 mA cm-2 in 0.5 M H2SO4 as measured by drop casting the catalyst on Ti foil. In terms of the fabrication for the efficient HER electrode, the prepared FeP NPs were deposited on the carbon paper (CP) via electrophoretic deposition (EPD), which is a suitable method for the fabrication of NP films that can be used for various electronic applications. Different morphologies and catalytic activities of the FeP/CP samples were derived by controlling EPD parameters such as mixing ratio of solvents, NP concentration, and deposition voltage. The optimized EPD process lead to excellent HER activity of the FeP/CP with an overpotential of 38 mV and 91 mV at 10 mA cm-2 in 0.5 M H2SO4 and 1 M KOH, respectively. The maximum activity of the catalyst was mainly attributed to the large active surface area and low charge transfer resistance due to the strong contact between the NPs and CP. A PEMWE single cell with the FeP/CP cathode achieved 1.2 A cm-2 at cell voltage of 2.0 V. This study of the EPD procedure for fabricating the NP film from the colloidal NP catalysts contributes to advance manufacturing of HER electrodes for efficient hydrogen generation through water electrolysis.

This work deals with the development of a paper based fuel cell for application in micro-nano systems. In this cell, a porous paper serves as a transport medium and eliminates the need for any metering devices that are integral to conventional fuel cells. Since only very small flow rates of reagents can be achieved on paper, these cells produce only a few milli-watts of power. In this work, formic acid is used as the fuel and potassium permanganate is used as the oxidant. Since the cell presented here is membraneless, both formic acid and potassium permanganate are mixed with sulfuric acid, and they form the anolyte and the catholyte, respectively. A special cell geometry has been designed and implemented to minimize and delay the fuel and oxidant cross over effects. In order to keep the cost low, graphite sheets without any metal loading are used as the current collectors. Two variants of filter paper are used for implementing the fuel cells. Cell characterization is accomplished by performing detailed potentiometric and impedance studies. Our study on formic acid cell shows that the porous paper cell architecture can be extended to other fuel-oxidant combinations as well.

The escalated contamination of water resources with inorganic pollutants is a pressing global problem for the ecosystem due to their well-documented negative effects. Over the years, the problem has aggravated due to uncontrolled industrialization, urbanization and the subsequent disturbance to natural resources by mankind. The direct discharge of inorganic pollutants and their geogenic mobilization has caused their elevated concentrations in ground, surface and river water. Selenium is amongst the emerging inorganic pollutants of concern besides other and was neglected earlier by the environmentalist due to their occupancy in other major pollutants and lack of sensitive analytical techniques. It is essentially known as a beneficial element, however, when consumed above a permissible limit, it may lead to devastating acute and chronic health effects. With the advancement made in paper analytical devices, we herein present for the first time the in-situ prepared flexible electrodes from “lab grade filter paper” for selenium sensing in water with high selectivity and sensitivity. The paper electrode are modified with nanostructured materials (metallic nanoparticles) to introduce conductivity, and thereafter utilized as a transduction platform in anodic stripping voltametric based detection of selenium. The flexible paper electrodes are also studied for their structural, compositional and electrochemical characteristic. A battery of ions are tested under competitive and comparative performance evaluation of fabricated sensor electrodes to realize their practical applications in real water samples. The analytical performance of the paper sensor is also validated against ion chromatography reference technique. The designed sensor electrode demonstrate a wide detection capability of 5-1000 ppb, high sensitivity, and excellent detection limit

A flexible conductive graphene paper electrode was prepared by a flow directed filtration of graphene oxide dispersion followed by a gentle thermal reduction treatment of the filtrate. The prepared partially reduced graphene oxide paper (GOPpr) showed a dense packing of graphene sheets with a distinct interlayer distance of 4.35 Å. Its electrode quality for energy storage applications was tested by an electrochemical characterization in the aprotic electrolyte 1M TEABF4 in acetonitrile (AN) which is commonly used for supercapacitors. Within either the first positive or negative charging sweep GOPpr features an electrochemical activation. As a result the graphene framework of the GOPpr becomes accessible for ion insertion and release. The achieved specific capacitance in galvanostatic discharge measurements reached up to 199 Fg-1 at 0.1 Ag-1 for a positively activated and polarized electrode. Even at high specific currents of 10 Ag-1 this value didn't drop below 145 Fg-1. An even higher specific capacitance was determined from cyclic voltammetry where the positively activated electrode yielded up to 270 Fg-1 during the discharge sweep. It's flexible nature the simple processability and the outstanding rate handling capability makes GOPpr an excellent candidate for a positive electrode in bendable supercapacitors and lithium capacitors.

Active layers of electrocatalysts were prepared by ion beam assisted deposition (IBAD) of platinum and one of rare earth metals (Ce, Gd, Dy, Yb) on the carbon based Toray Carbon Fiber Paper TGP-H-060 T (TorayCFP) and AVCarb® Carbon Fiber Paper Р50 (AVCarbCFP) catalysts carriers with the aim of electrocatalysts production for direct methanol and ethanol oxidation fuel cells (DMFC, DEFC) with polymer membrane electrolyte. Formation of layers in IBAD mode, by means of the deposition of metal and mixing of precipitating layer with the substrate by accelerated (U = 5 kV) ions of the same metal, was carried out. In this process, a neutral fraction of metal vapor and ionized plasma of vacuum pulsed electric arc discharge were used. According to scanning electron microscopy, electron probe microanalysis, X-ray fluorescence analysis and Rutherford backscattering spectrometry investigations atoms of deposited metals, carbon substrates, and oxygen as impurity enter into the composition of layers. The thickness of the prepared catalytic layers is ~30 nm; content of platinum atoms in the layers – ~2×1016 cm–2, or much less than 0.05 mgPt/cm2. Properties of the prepared electrocatalysts were investigated by cyclic voltammetry in 1M CH3OH + 0.5M H2SO4 and 1M C2H5OH + 0.5M H2SO4 solutions. It was established that the prepared electrocatalysts show activity in the processes of electrochemical oxidation of methanol and ethanol. The inclusion of the rare earth metal in the composition of formed layers enhances the activity of electrocatalysts in a multistage process of oxidation of alcohols. Moreover the activity of prepared electrocatalysts in the oxidation of more complex molecules of ethanol is higher than the activity in oxidation reaction of methanol. The advantages of proposed IBAD method are as follows: possibility of forming a cohesive catalytically active layer on a carbon substrate at low platinum consumption; one stage of deposition of each of metals a comparison against multistage traditional chemical methods of catalysts preparation. Figure 1

Introduction Molecularly imprinted polymers (MIPs) are recognition elements with specific cavities designed for a particular target molecule. Recently, MIPs have been used in various applications explicitly requiring molecular recognition. In MIPs, the crosslinking monomers and functional monomers, having an affinity with a target molecule, are copolymerized in the presence of the target or the template molecule. Upon selective removal of the template molecule, imprinted cavities are formed. MIPs provide a wide range of benefits, including mechanical reliability, cost-effectiveness, and rapid mass production, and have recently been used for various applications, especially in biosensing areas [1]–[3]. Theophylline (THO) is a drug commonly used for the therapy of respiratory diseases. However, owing to its highly toxic nature, an overdose can induce paralysis, seizures, and even death.[4] Additionally, the therapeutic window of THO is relatively small (5-15 mgmL-1) [4],[5], and therefore, the therapeutic drug monitoring (TDM) of theophylline is highly significant [5]. In this study, molecularly imprinted polymers grafted carbon pastes were prepared for THO sensing. The commonly used functional monomer, methacrylic acid, crosslinking monomers, N, N’-methylenebisacrylamide (MBAA), and ethylene glycol dimethacrylate (EDMA) were used, and the MIPs thus formed were evaluated using differential pulse voltammetry on a paper chip. Methods Fig. 1 shows the scheme of the paper chip along with the sensing response of theophylline MIP. The paper chip composed of a photo-paper base with electrodes printed using conductive ink through an inkjet printer. The holes for electrodes (working electrode, a reference electrode, and counter electrode) and reservoir are cut on laminating sheets using a laser cutter. The three parts are then attached using the laminator. The reference electrode is packed with Ag/AgCl ink and dried overnight at 60 ℃. The counter electrode with the printed conductive ink is used as it is. The MIP-grafted carbon paste is packed in the working electrode with the help of a glass tube. The theophylline imprinted poly(methylene bisacrylamide-co-ethylene dimethacrylate-co-methacrylic acid) was grafted on the graphite particle surface by a procedure similar to our previous work [3], [6]. This grafted graphite was mixed with ferrocene containing silicone oil to make a paste used as the sensing material. We performed the differential pulse voltammetry with theophylline sample solution (in saline buffer with pH 7.4, 0-40 mgmL-1 and whole bovine blood) filled in the sample-reservoir. Results and Conclusions The execution time of each voltammetry was 2 min only. The plot in Fig. 1 shows the influence of the theophylline concentration on the redox current at 0.8 V at the MIP-carbon paste electrode in both buffer saline and whole bovine blood. It is quite evident from the figure that MIP is sensitive towards theophylline in both buffer and whole blood. It indicates that MIP activates the electrocatalytic behavior of the carbon-paste electrode. The dynamic range at the MIP electrode versus the concentration of theophylline is seen in the range of 0-40 mgmL-1, which covers the therapeutically effective theophylline concentration level in plasma varying from 5 to 15 mgmL-1. The DPV measurements at each concentration has been done using a new chip every time, i.e. ‘single-use’ of the chip. Additionally, no reagents have been added during the analysis, thus making the procedure of drug level measurement simple. From the results of this study, it can be concluded that the proposed method is useful for quick and straightforward real-time TDM to prevent the toxic side effects of an overdose. References [1] T. Sakata, et al. RSC Adv., 10(29),16999–17013, 2020; doi:10.1039/d0ra02793f. [2] Y. Yoshimi, et al. Sensors, 19(10), 2415, 2019; doi:10.3390/s19102415. [3] Y. Yoshimi, et al. Sensors Actuators, B Chem., 259, 455–462, 2018; doi:10.1016/j.snb.2017.12.084. [4] R. Vassallo, et al. Mayo Clin. Proc., 73(4), 346–354, 1998; doi:10.1016/s0025-6196(11)63701-4. [5] A. Peng, Int. J. Electrochem. Sci., 12(1), 330–346, 2017; doi:10.20964/2017.01.03. [6] Aaryashree et al., Sensors, 20(20), 5847, 2020; doi:10.3390/s20205847 Figure 1

Grafting metal nanoparticles (NPs) on flexible platforms is being increasingly attempted to advance their usage in the field of catalysis, sensing, energy storage, etc. However, anchoring NPs on substrates is nontrivial as it involves surface modification of the NPs and/or the substrate, which makes the whole process tedious. On the other hand , Bimetallic nanoparticles, which are composed of two metal elements in a particle, exhibit much higher catalytic activity than respective monometallic ones due to new bi-functional or synergistic effects, so-called a ligand and/or an ensemble effect. Here we present the green, facile, less-time, one-step process fabrication of 3-dimension porous Au(core)@Ag(shell) NP /filter paper by Microplasma-assisted system. The aim of our work is to develop a high efficient catalytic substrate on common filter paper loaded on Au@Ag NPs. In our work, we found Au@Ag NP /filter paper can be synthesized and in a minute time scale. We further extend this technology to fabricated Au@Ag NP /paper and characterized them by SEM, Raman, XRD and UV-Vis spectroscopies. Besides, The as-prepared Au@Ag NP / filter paper is stable, uniform, and exhibits high efficiency and reusability in the catalytic reduction of 4-nitrophenol (4-NP) with a high rate constant as well as an average conversion of 96% in 3 minutes during 6 times. While acting as catalysts, the composites display excellent surface enhanced Raman scattering (SERS) efficiency, allowing the real-time monitoring of chemical reactions. The obtained Au@Ag bimetallic catalysts /filter paper show an exceptional superior catalytic activity for the reduction of 4-nitrophenol (4-NP) which can be completely reduced to 4-aminophenol (4-AP) in a single step within seconds., surpassing most reported noble metal nanoparticle catalysts. The results have not only paved the way for the wide application of Au@Ag NPs / filter paper but also provide a new road for the application of other bimetallic NPs Figure 1

Room temperature ionic liquid (RTIL) is a unique zwitter-ionic compound, that possesses excellent physical and chemical properties, which enables electrochemical applications such as to be utilized as a transducer for probing a complex matrix such as soil. The wide electrochemical window and elevated double layer capacitance of RTIL helps to gauge soil parameters which is helpful to understand soil state. In this work we investigate the utility of RTIL modified electrodes as viable sensors for decoupling soil electrochemistry. Soil plays the key role in plant and crop production and is a vital parameter in the ecological structure of the planet and indispensable in the food ecosystem cycle. Soil health monitoring in the near past has been highly qualitative and speculative with more recent advancements still trying to fill the void of a holistic soil profile. In fields and crop-circles, testing methods to perform in-situ profiling however from one lab is likely to vary with another and hence results are not universally compatible. Additionally, these normalized techniques ideally involve empirical approaches, extensive sample preparation which adds on to a temporal factor along with equipment for extraction and subsequently-analysis. This therefore-stimulates the need for a testing methodology that is capable of rapid analysis in an in-situ environment that can be applicable universally. In this paper, we focus on: a rapid electrochemical point probing mechanism that acts as a soil state evaluation platform via a 3-electrode sensor modified by a widely characterized-RTIL [BMIM] [BF4] interfacial transducer medium. The proposed quantitative model –‘DENSE’ probes the soil diffuse double layer (DDL) dielectric to evaluate a thorough chemical profile of the soil matrix. The experimental design was implemented to capture the effect of electroactive species in the soil matrix altered by adding nutritional amendments. Non-faradaic probing was then performed in this design to gauge the inherent capacitive modulations of the soil system as a function its compositional changes. Therefore, by looking at the rate of electrochemical activity and inherent soil dielectric changes driven by an RTIL interfacial layer, it is possible to decouple information on nutrient availability in soils with potential for application towards temporal soil analysis. Figure: (A) Equivalent-circuit (DENSE) model of the soil-water matrix and a schematic representation of the model with respect to the electrode-electrolyte interface (B) Impedance nyquist plot and (C) Bode-phase to denote the pseudo-capacitive dominant nature of the soil matrix (1:1, 1:2) and the comparatively resistive behavior of the baseline and 2:1 mixture Figure 1

Electrochemically deposited polymeric film of polyaniline (PANI) is used as a substrate for electrochemical deposition of platinum by using cyclic voltammetry. The electrochemical properties of multi-layered films were analyzed by cyclic voltammetry and AC impedance spectroscopy. The structural properties of multi-layered polymer films were analyzed by SEM, TEM, XRD, XPS, Raman and FTIR. The modified electrode showed strong electrocatalytic activity toward oxidation of toluene in presence of NaNO2/H2SO4 in actetonitrile medium. Toluene gave a sensitive anodic peak at 1.318 V (vs. SCE). Cyclic voltammetry studies suggest that the electrochemical activity of Pt-PANI/CFP electrode is higher than that of Pt/CFP electrode toward toluene oxidation.

In this study, indium modified carbon paper electrode is investigated as the positive electrode for all-vanadium redox flow battery (VRFB). The electrochemical performance is studied using cyclic voltammetry, electrochemical impedance spectroscopy and stability test toward V (IV)/V (V) redox reaction. The results show that the modified carbon paper exhibits excellent electrocatalytic activity and stability after repetitive 100-cycle test in an electrolyte containing 0.5 M VOSO4, while degradation is observed in pristine carbon paper. Such improvement is due to the indium particles deposited on the carbon fibers acting as stable active sites promoting the vanadium redox reactions and reducing charge transfer resistance as indicated by impedance measurement. Full cell performance is assessed via polarization curve analysis at different states of charge. A simple cell set-up (without flow field) employing the modified electrode exhibited limiting current of 125 mA cm2, which is 73% higher than the cell employing pristine carbon paper (72 mA cm2) at SOC of 96%. Overall, the results demonstrate that indium deposition on carbon paper promotes the electrochemical performance and provides an opportunity for further investigation in the exploration of metal modification of carbon materials for VRFB.

2020 H. H. Uhlig Summer Research Fellowship – Summary Report

Free Standing Porous Graphene and Reduced Graphene Papers manufactured from Sedimentation of Arc Discharge of Graphite Rods. At SignEcoTech, novel and newer nano-carbons such as hard carbons, homogenized graphene, low defect highly crystalline graphene’s, and wrinkled graphene [1-14]. Here, Graphene Oxide papers have been synthesized previously by flow-directed assembly, where the pressure of air within the assembly supports graphene oxide sheets in their nano-crystalline colloidal solution being filtered on nano-porous filter paper. However in this research, we haven’t used any filter paper, or directed flow assembly, but sedimentation of the colloidal solution in ethyl alcohol in a dish. Then, the wrinkled the hierarchical GO sheets fall under gravity by sedimentation. Wrinkling in GO was enhanced by low defects, multi-layer clusters, and variegated + edge interaction amongst graphene clusters, as such the sedimented graphene papers were porous, intertwined and free standing. The composition of GO was confirmed by XPS, while the low defect level clearly marked by higher planar order and low ID/IG band. The wrinkled, multilayer clusters and carbonic surface properties of the graphene oxide sheets enhanced fast sedimentation, evaporation of the alcohol and formation of porous GO structure. The porous reduced\GO morphology is captured by optical microscope. Keywords: Wrinkled GO Papers, Reduced Graphene, Arc Discharge, Modified Hummers Method

Introduction Oxide nanofibers consisting of nanoparticles are excellent nanostructures for designing high performance gas sensors. To date, randomly tangled oxide nanofiber networks prepared by far-field electrospinning process (FFES) have been widely explored as the sensing materials. When the distance between spinneret needle and substrate is very short, the straight configuration of nanofibers can be directly written on the substrate without whipping. This is referred as near-field electrospinning (NFES), which can be applied to well-defined patterning of one-dimensional nanofibers for various new applications such as sensors, optoelectronic circuits, and functional nanoelectronics. The patterning of polymeric nanofibers has been demonstrated over a decade ago. In contrast, the fabrication of one-dimensional (1D) metal oxide nanopatterns remains challenging because it becomes difficult to control the chaotic whipping motion of the jet due to the acceleration of metal ions under the electric field. In the present study, grids, diamonds, and hexagrams composed of In2O3, Co3O4, and NiO nanofibers were prepared by NFES and their potential applications as gas sensors were investigated. The sensor using In2O3 nanofiber pattern exhibited an unprecedentedly high response (resistance ratio = 239) to 5 ppm trimethylamine (TMA) with negligible cross-responses to ubiquitous ethanol and other interference gases. Method Transparent solution containing 7 g of methanol (99 %), polyvinylpyrrolidone (PVP, 17.4 wt%, Mw = 1,300,000) and metal nitrates (indium nitrate hydrate, 1.4 wt%, 99.999%; cobalt nitrate hexahydrate, 1.7 wt%, 99.99%; nickel nitrate hexahydrate, 1.7 wt%, 99.99%) were stirred for 24 h at room temperature. The prepared clear solution was transferred to a glass syringe (1000 μL) with a 21-gauge needle, and electrospun onto a 4-inch Si/SiO2 wafer containing 76 sensor substrates (size: 1 × 1 cm2) in which Pt interdigitated electrodes (electrode width: 50 μm, electrode spacing: 5 μm) above a metallic collector. The flow rate is fixed as 0.005 μL min−1 at an applied voltage of 50 V and the distance between the tip and the collector is 1 mm. During electrospinning, the loader and collector moved toward x- and/or y-axis at a controlled moving velocity of 800 mm s−1, leading to the fabrication of precursor fiber patterns, for example, grids, diamonds, and hexagrams. The precursor patterns were annealed at 600 °C for 5 h in an air atmosphere, and converted into the corresponding patterns of In2O3, Co3O4, and NiO pattern sensors, respectively. The sensors were placed in a quartz tube furnace and heated at sensing temperature (In2O3: 350 °C; Co3O4: 225 °C; NiO: 300 °C). The dc-probe resistance of the sensor was measured using an electrometer interfaced with a computer. Results and Conclusions The well-defined patterns of continuous and cylindrical oxide nanofibers could be prepared by using highly volatile solvent (methanol) and by controlling the viscosity and electrical conductivity of spray solution, the distance between spinneret needle and substrate, and the moving velocity of spinneret needle. All the parameters had an optimum window, indicating that the sophisticated control or tuning of the parameters is essential to prepare well-organized and continuous precursor and/or metal oxide fibers via NFES. It is worthwhile to note that the longstanding problem of preparing elaborate nano-architectures consisting of 1D metal oxides has been solved for the first time by investigating the interrelations of the solution/working parameters in NFES systematically. Interestingly, the sensor using In2O3 nanofiber pattern on Pt electrodes exhibited unprecedented high selectivity and responses to TMA compared with other metal oxide nanostructures reported in the literature, whereas random networks of In2O3 nanofibers and dense thin In2O3 film with negligible Pt electrode exposure showed low response and selectivity to TMA. The intriguing trimethylamine sensing characteristics are explained in relation to the promotion of gas sensing reaction by catalytic Pt electrode, which is supported again by the high TMA selectivity of the sensors using the patterns of Co3O4 and NiO nanofibers. In addition, the highly increased sensitivity to analyte gases compared with thin film sensors can be attributed by the increased gas accessibility due to the sensor structures, which is composed of mono-layered In2O3 nanofibers with 200 nm diameter. The NFES-assisted patterning of metal oxide nanofibers can provide a new platform to design high performance gas sensors for a range of emerging applications.

Introduction Viruses are not only infectious agents, they are also known as promising functional building blocks for application in nano- and biotechnologies. The tobacco mosaic virus (TMV) was the first studied plant virus and is widely distributed; it infects vegetables, like tomato, bell pepper, beans and other members of the family Solanaceae, while it is totally harmless for mammals [1]. It is one of the most studied plant viruses and its genome is completely sequenced, whereby genetical and chemical modification is easy. TMV has a nanotube-like shape with a length of 300 nm, an outer diameter of 18 nm and an inner diameter of 4 nm. Since it possesses a high chemical and physical robustness, it can be integrated with different electronic transducers for bio- and chemical sensing applications [2]. Recently, we presented a TMV-based amperometric glucose biosensor [3] and a potentiometric penicillin biosensor [4]. TMV was used as enzyme nanocarrier for the enzyme glucose oxidase and penicillinase, respectively [3,4]. The sensitivity and detection limit of these biosensors, among others, depend on the density of TMVs on the sensor surface. The surface density of the immobilized TMVs is strongly influenced by the electrostatic interactions between the charged TMVs and sensor surface as well as by the inter-TMV-nanotubes repulsion, which could be changed by varying the pH value and the ionic strength of the TMV solution. In this study, we investigated an impact of the pH value and ionic strength of the TMV solution on the surface density of TMV nanotubes immobilized onto Ta2O5-gate capacitive field-effect electrolyte-insulator-semiconductor (EIS) sensors. Materials and Methods TMV particles modified with biotin-linker molecules (TMVBio), which serve as binding sites for streptavidin-conjugated enzymes, have been immobilized onto capacitive field-effect EIS sensors with Ta2O5 as transducer layer, as shown in Fig. 1. Immobilization was performed from TMVBiosolutions with different values of pH between pH 3.0 and pH 9.5 and ionic strength between 0.1 mM and 750 mM. The sensors have been electrochemically characterized before and after TMVBio immobilization by capacitance-voltage- and constant-capacitance methods, respectively. In addition, the density of the immobilized TMVs and morphology of the sensor surface has been investigated by means of scanning electron microscopy (SEM). Results and Conclusions The TMVBio density on the Ta2O5 sensor surface was influenced by varying the pH value (as exemplarily shown in Fig. 1) and ionic strength (not shown) of the TMVBio solution. The amplitude of the field-effect sensor signal correlates well with the density of the immobilized TMVBionanotubes. Thus, optimized conditions for the high-density immobilization of TMVBio nanotubes onto the Ta2O5 surface and thereby enhanced biosensing have been found. Details of the experiments and the obtained results will be presented and discussed. Acknowledgements The authors like to thank Dr. Claudia Koch and Rebecca Hummel, Stuttgart, for scientific and technical support. References [1] X. Z. Fan, E. Pomerantseva, M. Gnerlich, Tobacco mosaic virus: A biological building block for micro/nano/bio systems, Journal of Vacuum Science & Technology A. 31 (2013) 050815. doi: 10.1116/1.4816584. [2] M. Knez, M. Sumer, A. Bittner, C. Wege, H. Jeske, D. Hoffmann, K. Kuhnke, K. Kern, Binding the tobacco mosaic virus to inorganic surfaces, Langmuir 20 (2004) 441–447. doi: 10.1021/la035425o. [3] M. Bäcker, C. Koch, F. Geiger, F. Eber, H. Gliemann, A. Poghossian, C. Wege, M. J. Schöning, Tobacco mosaic virus as enzyme nanocarrier for electrochemical biosensors, Sensors and Actuators B: Chemical 238 (2017) 716– 722. doi: 10.1016/j.snb.2016.07.096. [4] A. Poghossian, M. Jablonski, C. Koch, T. S. Bronder, D. Rolker, C. Wege, M. J. Schöning, Field-effect biosensor using virus particles as scaffolds for enzyme immobilization, Biosensors and Bioelectronics 110 (2018) 168–174. doi: 10.1016/j.bios.2018.03.036 Figure 1: Measurement set-up with schematic layer structure of the capacitive EIS sensor modified with negatively charged TMVBio particles (a). SEM images of the Ta2O5-sensor surface modified with TMVBio nanotubes at pH 4.5 (b) and pH 7.0 (c), respectively. Figure 1

Introduction In food industry, the use and dosing of flavoring substances is an important aspect during fabrication processes. Acetoin and diacetyl are flavoring agents which can be found in many food products, like yogurt, cheese, milk, wine and beer [1]. In beer, acetoin/diacetyl is a critical parameter for the maturation degree of the beverage during fabrication. They are formed during the first phase of beer fermentation and getting reduced during the later phase of fermentation and the maturation. Both can have a negative effect on the beer flavor, when they are above a certain concentration. Typical acetoin concentrations in beer are in the range of 10-50 µM. Measuring the acetoin/diacetyl concentration during the production can serve as a quality control and unnecessary maturation time could be avoided [2]. Until now, the quantitative determination of the acetoin/diacetyl concentration is mostly done “off-line” by gas chromatography. Therefore, a sample has to be sent to an external laboratory, which takes time till results are achieved, or the brewery needs an own laboratory, whereby enormous costs arise and trained staff is needed. Because of that, we recently developed a biosensor for the detection of acetoin based on an enzyme-modified electrolyte-insulator-semiconductor (EIS) sensor, which was characterized in buffer solutions [3]. In this work, the novel biosensor was applied for acetoin measurements in beer samples for the first time. Materials and Methods As sensor structures, capacitive Al-p-Si-SiO2-Ta2O5 field-effect sensors have been used, schematically shown in Fig. 1(a). The Ta2O5 transducer surface was modified with a novel acetoin reductase by means of cross-linking. The acetoin reductase (from B. clausii DSM 8716T) catalyzes the reduction of acetoin to 2,3-butanediol, while NADH serves as a cofactor [4]. The fabricated acetoin biosensors have been electrochemically characterized by capacitance-voltage- and constant-capacitance (ConCap) measurements in buffer solution (0.2 mM Tris-HCl) with varying acetoin concentration and beer samples, spiked with different amounts of acetoin. Results and Conclusions The acetoin sensitivity was investigated in beer solutions and the biosensors showed a linear behavior in the concentration range between 10 µM and 90 μM with a sensitivity of ca. 30 mV/dec, see Fig. 1(b). A detailed description of experiments and the obtained results will be presented and discussed. Acknowledgments The authors thank the ministry of innovation, science and research of the state of North-Rhine-Westphalia for financial support (funding program FH-Struktur 2016). References [1] P. Li, Y. Zhu, H. Shun, J. Fan, Q. Hu, Y. Cao, Development and validation of high-performance liquid chromatography method for the determination of diacetyl in beer using 4-nitro-o-phenylenediamine as the derivatization reagent, Journal of Agricultural and Food Chemistry 60 (2012) 3013–3019. doi: 10.1021/jf3007163. [2] A. D. Haukeli, S. Lie, Formation and removal of acetoin during yeast fermentation, Journal of the Institute of Brewing 81 (1975) 58–64. doi: 10.1002/j.2050-0416.1975.tb03662.x. [3] D. Molinnus, M. Muschallik, L. O. Gonzalez, J. Bongaerts, T. Wagner, T. Selmer, P. Siegert, M. Keusgen, M. J. Schöning, Development and characterization of a field-effect biosensor for the detection of acetoin, Biosensors and Bioelectronics 115 (2018) 1–6. doi: 10.1016/j.bios.2018.05.023. [4] L. Muschallik, D. Molinnus, J. Bongaerts, M. Pohl, T. Wagner, M. J. Schöning, P. Siegert, T. Selmer, (R,R)-Butane-2,3-diol dehydrogenase from Bacillus clausii DSM 8716T: Cloning and expression of the bdhA-gene, and initial characterization of enzyme, Journal of Biotechnology 258 (2017) 41– 50. doi: 10.1016/j.jbiotec.2017.07.020 Figure 1: Schematic measurement set-up with the layer structure of the EIS sensor modified with acetoin reductase (a). Exemplary ConCap-measurement curve recorded in buffer-beer mixture (ratio 20:1) spiked with different acetoin concentrations, respectively (b). Figure 1

Introduction Throughout the last decade, strong emphasis was placed on the development of compact, inexpensive and selective sensors for acetone due to its relevance as a proven breath-marker for non-invasive fat metabolism monitoring [1]. While chemo-resistive sensors bear high potential for low-cost devices [2], they are limited by selectivity [3]. Therefore, researchers have improved the acetone selectivity by tailoring sensing materials through meta-stable phases [4], compositing with graphene oxide [5] or carbon nanotubes [6], and by combining sensors with catalytic ZnO filters [7]. Despite remarkable improvements, these sensors cannot compensate for the high selectivity requirements posed by health and lifestyle applications. Interferants or confounders include compounds present at much higher concentrations (e.g., up to 130 ppm hydrogen [8]) than the target analyte (e.g., acetone, 0.5 ppm in healthy breath [9]) or numerous chemical compounds present in such environments (e.g., >800 volatiles in human breath [9]), whose responses, in sum, can cause severe measurement errors. Here, we exploit a catalytic filter composed of flame-made Pt/Al2O3 nanoparticles [10] upstream of a chemo-resistive Si/WO3 sensor [4]. The filter converts interfering analytes to inactive species on the sensor, while target acetone is hardly affected, resulting in selectivities from 250 to over 1’000 with respect to various interferants [11]. Method Both Pt/Al2O3 nanoparticles for the packed bed filter as well as Si/WO3 sensors were produced with a flame spray pyrolysis (FSP) reactor. Nanoparticles were collected on a glass fiber filter downstream of that reactor and assembled as a packed bed filter, placed upstream of the sensor and heated to 135 °C. The sensors were produced by direct deposition of Si/WO3 nanoparticles onto sensor substrates [12]. The sensors with and without filters were tested for 1 ppm acetone, isoprene, ammonia, ethanol, H2 and CO at 90% relative humidity (RH) and 400 °C. In addition, the filter and sensor were tested in gas mixtures containing 1’000 ppb of each interferant simultaneously, as well as high H2 (up to 100 ppm) and CO (up to 50 ppm) concentrations. The sensor response is defined as S = Rair/Ranalyte -1, where Rair and Ranalyte are the sensing film resistances in air and during analyte exposure, respectively. The selectivity is calculated as the ratio of the acetone to interferant response. Results and Conclusions To investigate the effect of the Pt/Al2O3 filter, the Si/WO3 sensor with and without (i.e., filter at room temperature) the filter upstream was evaluated for a variety of breath relevant gases of different chemical groups [11]. Figure 1 shows the Si/WO3 sensor response to acetone, isoprene, ammonia, ethanol, H2 and CO. Without the filter (a), the sensor responds to all analytes, with highest responses for acetone (S = 5.4) and isoprene (S = 10.4). In contrast, with filter (b), only acetone is detected, resulting in unprecedented selectivity > 250 for all analytes. Then, the detector was evaluated with 50 - 1000 ppb acetone only (Figure 2a, blue dashed line) and in mixture with ethanol, isoprene, ammonia, H2 and CO (i.e., each 1’000 ppb, orange solid line). The perfect overlap between the acetone measurement as single analyte and in mixture indicates complete conversion of all interferants to non-responsive species. Most importantly, this excellent selectivity is maintained even in gas mixtures with up to 50 ppm CO and 100 ppm H2 (Figure 2b), as may be present in the breath after smoking [13] or food intake [14]. References [1] J. C. Anderson, Obesity, 23, (2015), 2327–2334. [2] A. T. Güntner, N. A. Sievi, S. J. Theodore, T. Gulich, M. Kohler, and S. E. Pratsinis, Anal. Chem., 89, (2017), 10578–10584. [3] A. T. Güntner, S. Abegg, K. Königstein, P. A. Gerber, A. Schmidt-Trucksäss, and S. E. Pratsinis, ACS Sensors, 4, (2019), 268–280. [4] M. Righettoni, A. Tricoli, and S. E. Pratsinis, Chem. Mater., 22, (2010), 3152–3157. [5] S. J. Choi, B. H. Jang, S. J. Lee, B. K. Min, A. Rothschild, and I. D. Kim, ACS Appl. Mater. Interfaces, 6, (2014), 2588–2597. [6] M. Narjinary, P. Rana, A. Sen, and M. Pal, Mater. Des., 115, (2017), 158–164. [7] A. T. Güntner, I. C. Weber, and S. E. Pratsinis, ACS Sensors, 5, (2020), 1058–1067. [8] D. J. Calloway, E. L. Murphy, and D. Bauer, Am. J. Dig. Dis., 14, (1969), 811–815. [9] C. Turner, P. Španěl, and D. Smith, SIFT-MS, Physiol. Meas., 27, (2006), 321–337. [10] R. Strobel, W. J. Stark, L. Mädler, S. E. Pratsinis, and A. Baiker, J. Catal., 213, (2003), 296–304. [11] I. C. Weber, H. P. Braun, F. Krumeich, A. T. Güntner, and S. E. Pratsinis, Adv. Sci., 7, (2020), 2001503. [12] M. Righettoni, A. Tricoli, and S. E. Pratsinis, Anal. Chem., 82, (2010), 3581–3587. [13] S. E. Deveci, F. Deveci, Y. Açik, and A. T. Ozan, Respir. Med., 98, (2004), 551–556. [14] D. H. Calloway, Gastroenterology, 51, (1966), 383–389. Figure 1

Voltammetric determination of morin on carbon fiber paper (CFP) electrode modified by electropolymerization of 2,5-dimercapto1,3,4- thiadiazole (DMTD) in phosphate buffer solution (PB, pH 9.0) have been studied. This modified electrode showed strong electrocatalytic activity toward the oxidation of morin, a flavonoid at physiological pH (PB, pH 7.0). Morin gave a sensitive anodic peak at 0.245 V (vs. SCE). The parameters influencing the anodic peak of morin such as effect of pH, effect of scan rate and concentration have been optimized. The electrochemical process was found to be irreversible and adsorption-controlled. Under the optimum conditions, the anodic peak current was linear to concentration of morin in the range of 2.5 x 10(-10)-2.75 x 10(-9) M and detection limit was found to be 8.3 x 10(-11) M. The practical application of the modified electrode was successfully demonstrated for the determination of morin in mulberry leaves. (C) 2016 The Electrochemical Society. All rights reserved.

Germanium is considered as a high mobility channel material for its potential to be introduced in future CMOS technology nodes. Ge surface passivation with a thin silicon layer (Si-cap) has been shown to be efficient for pFETs because of a sufficient valence band offset between Ge and Si-cap, which confines the holes in the Ge layer. Strained Ge pFinFETs outperforming Si pFinFETs due to four times higher mobility have been demonstrated using Si-cap process [1]. Interfacial defects can be further passivated with a high-pressure anneal in H2 resulting in reduced sub-threshold swing and increased mobility in Ge nanowires [2]. Moreover, by using a Si-cap, Negative-bias temperature instability reliability is improved compared to GeOx passivation because of the energy decoupling between holes and defects in SiO2/HfO2 gate stack [3]. However, a Si-cap process poses gate stack scalability issues because in order to achieve sufficient surface passivation, the Si-cap thickness cannot be scaled. An introduction of a high-k interfacial layer instead of a chemical oxide SiO2 could potentially help to scale down equivalent oxide thickness. Integrating thulium silicate (TmSiO) as a replacement of the SiO2 interfacial layer has been demonstrated on silicon, and a hole and electron mobility enhancement compared to SiO2/HfO2 gate stacks has been achieved for an equivalent oxide thickness (EOT) < 1 nm [4]. Moreover, we have previously displayed the compatibility of Tm2O3 with Ge by demonstrating GeOx/Tm2O3 gate stacks with interface state density Dit < 5·1011 eV-1cm-2 [5]. In this work, we integrate TmSiO with a Si-cap process to achieve Dit comparable to GeO2 passivation. In order to evaluate Ge/Si/TmSiO interfaces, MOS capacitors (MOSCAPs) were fabricated on n-type Ge strain relaxed buffers epitaxially grown on n-type Si wafers in a two-step process using GeH4 precursor [6]. Si-caps of different thicknesses were grown at 400 °C using Si2H6. Si growth was confirmed by ellipsometry spectroscopy and testing that the surface is hydrophobic. While trying to keep the Si-cap exposure to air to a minimum, 400 nm PECVD SiO2 was deposited and active areas were defined. After removing the remaining SiO2 from the active areas with 1 % HF, Tm2O3 was deposited by atomic layer deposition (ALD) at 225 °C. Rapid thermal anneal at 550 °C for 60 s in N2 was then employed to form TmSiO layer. High-k HfO2 was deposited by ALD at 350 °C followed by a post deposition anneal in O3 for 10 min. TiN gate metal was deposited at 425 °C by ALD and 500 nm Al was deposited by sputtering for probing purposes. After patterning, the samples were subjected to a forming gas anneal of 10% H2 in N2 at 400 °C for 30 min. Reference MOSCAPs with Ge/GeOx/Tm2O3/HfO2 gate stacks were also fabricated as described in [5] with addition of ALD HfO2. Interface state density in the midgap of Ge/Si/TmSiO/Tm2O3/HfO2 gate stacks was evaluated by CV measurements where measured CV characteristics where compared to calculated ones assuming a parabolic Dit distribution. Dit highly depends on Si-cap thickness, as displayed in Fig. 1. An optimal Si-cap thickness corresponding to 40-50 min deposition time provides Dit at midgap ~5·1011 cm-2eV-1 at CET of 4 nm. Reference MOSCAPs with Ge/GeOx/Tm2O3/HfO2 gates exhibit similar Dit of 4-5·1011 cm-2eV-1. Interface state density distribution within the band gap of Ge/Si/TmSiO interface with 40 min Si-cap deposition time was evaluated using the conductance method at different temperatures and is displayed in Fig. 2. Dit in the midgap is in agreement with the results obtained from CV measurements, and increases towards the valence and conduction band edges. The oxide trapped charge Qox of 2.5·1010 cm-2 (40 times lower than in the Ge reference devices without Si-cap) was determined from CV measurements and corresponds to only 5 mV hysteresis showing the potential of superior reliability. A Si-cap process with high-k TmSiO interface has been demonstrated on Ge MOS devices. A low Dit comparable to GeOx passivation has been shown. In addition, devices with TmSiO potentially have a superior reliability vs GeOx devices due to low oxide trapped charge density. References: [1] J. Mitard et al., Dig. Tech. Pap. - Symp. VLSI Technol., vol. 2016–Septe, 1–2, 2016. [2] H. Arimura et al., 2017 Symposium on VLSI Technology, 2017, T196–T197. [3] J. Franco et al., 2013 Int. Electron Devices Meet., 397–400, 2013. [4] E. Dentoni Litta et al., Eur. Solid-State Device Res. Conf., vol. 2, 155–158, 2013. [5] L. Žurauskaitė et al., ECS Trans., vol. 86, no. 7, 67–73, Jul. 2018. [6] A. Abedin et al., ECS Trans., vol. 75, no. 8, 615–621, 2016. Figure 1

In this work, a miniaturized platform for electrochemical detection of hydrazine, has been developed using droplet paper based three electrode system. Copper oxide cluster (CuO) immobilized on the surface of graphite sheet (Grp@CuO) is used as a working electrode. The developed Grp@CuO showed a surface-confined delayed redox response at an electrode potential (E1/2) −0.24 V vs Ag/AgCl in pH 7 phosphate buffer solution (PBS). The physicochemical characterization of the Grp@CuO revealed the electro deposition of CuO cluster on the surface of graphite sheet. Grp@CuO displayed selective electro-catalytic activity towards the detection of hydrazine in pH 7.0 PBS. A systematic linear increase in the oxidation current is observed in the range of 1 μM to 7 μM at an applied potential of −0.6 to 0.2 V vs Ag/AgCl with an excellent current sensitivity, lower detection limit (0.3482 μM). The fabricated miniaturized droplet-based sensor showed zero interference from other chemicals. Therefore, it is a viable option to be used in detection of hydrazine in real samples. Finally, the prepared platform was harnessed to real water samples for hydrazine detection.

Dual-gate electrostatic modulation gives an attractive approach for transistors performance improvement and operation mode modulation, which is favorable for chemical sensor and logic applications. Here, self-aligned junctionless semiconducting oxide channels are dual-gate electrostatic modulated by solution-processed chitosan-based proton conductors on paper substrates. The low-voltage junctionless paper transistors can be effectively tuned from depletion mode to enhancement mode by a second in-plane gate. Such dual-gate organic/inorganic hybrid paper transistors are promising for portable paper electronics

This paper describes the design and testing of a microfluidic biofuel cell that uses a flow-through bioanode and an air-breathing cathode. The bioanode is Toray carbon paper with glucose dehydrogenase (GDH), multi-walled carbon nanotubes (MWCNTs), and methylene green immobilized within a hydrogel. The cathode consists of a commercially available air-breathing platinum cathode hot pressed to a Nafion membrane. All remaining biofuel cell components were laser-cut from poly(methyl methacrylate) (PMMA) and silicone sheets. Half-cell experiments indicate that cathode variability limits the biofuel cell. An examination of flow rate effects on the biofuel cell showed that the current density increased sharply up to about 1 mL/min. Tested at this flow rate, the flow-through biofuel cell achieved a maximum current and power density of 705 μA/cm 2 and 146 μW/cm 2 . This was a 6% and 29% improvement in the current and power density, respectively, compared to the previously demonstrated bioanode without flow. Fuel utilization was calculated based on the measured current and by measuring UV-Vis absorbance of the reduced form of hydroxybenzhydrazide. The maximum fuel utilization was 5.8% at a flow rate of 0.05 mL/min. Finally, a numerical model of the biofuel cell was designed and its results compare favorably to actual data.

This study explores patterned deposition of cadmium selenide (CdSe) nanocrystalline quantum dot (NQD) thin films on paper substrates using the process of mist deposition. Because NQDs film can be engineered to produce unique emissive response, an application that prompted this research is concerned with printing of security/anti-counterfeiting patterns and identification labels on various substrates, including paper. Among other thin-film techniques using colloidal solution as a precursor, mist deposition is in this study predicted through Monte Carlo simulation and demonstrated through experiments to be particularly suitable for creating NQD micro-patterns on paper. In this experiment, barcode-like patterned NQD films were successfully deposited on various types of paper substrates. The films were characterized for fluorescence intensity, emission spectrum and quality of pattern transfer from shadow mask to the deposited film. Time dependent degradation of the deposited pattern was among key aspects investigated. The results obtained indicate that NQD films deposited on paper and encapsulated using plastic laminate did not show degradation in photoluminescence intensity over a period of nine weeks.

This research introduces the design of a gas-diffusional cathode employing bilirubin oxidase (BOx) immobilized on a complex matrix composed of carbon nanotube (CNT) modified Toray paper (TP) and, encapsulated in silica-gel. The developed enzymatic cathode consists of two layers. One is the hydrophobic gas-diffusional layer (GDL) and the other a hydrophilic catalytic layer (CL) which were combined by pressing at 1000 psi for five minutes. The GDL (35% weight teflonized Vulcan carbon powder (XC35)) that is exposed to air has hydrophobic and porous properties that facilitate oxygen diffusion. The CL consists of a thin, high surface area, 3D CNT/silica-gel matrix where the 3D-enzymatic structure is immobilized and preserved. The nanostructured architecture of the CL was designed to improve conductivity and surface area. Such a design was achieved by modifying the TP surface with CNTs. CNTs are grown on TP by chemical vapor deposition which is possible by electrodepositing Ni seeds via pulse chronoamperometry. Entrapment of BOx was achieved by using tetramethyl orthosilicate (TMOS), a highly volatile compound that results in a polymeric condensation reaction with H2O at room temperature. TMOS polymerization of the cathode surface was performed in a chemical vapor deposition process to form a silica-gel matrix. The gas diffusional cathode was assembled to a capillary driven microfluidic system to be electrochemically characterized. The characterization was performed from electrolyte pH 5 to pH 8 with increments 0.5 in pH. The best performance was observed at pH 5.5 showing a current output of 655.07 ± 146.18 μA.cm −2 and 345.36 ± 30.04 μA.cm −2 at 0 V and 0.3 V, respectively. At a pH of 7.5 the current generated was 287.05 ± 20.37 μA.cm −2 and 205.37 ± 1.57 μA.cm −2 at 0 V and 0.3 V, respectively. The results show the stability of the enzymatic structure, subject to various pH, is maintained within the 3D-CNT silica-gel matrix for pH lower than 8. Future work will focus on storage life and stability over time. © The Author(s) 2014. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any