Rapid Prototyping of Sensors and Conductive Elements by Day‐to‐Day Writing Tools and Emerging Manufacturing Technologies

The growing demand for low cost and easy to use analytical devices requires the development of reliable and rapid deposition strategies suitable for changing easily planned designs and applicable to a wide range of materials for assembling conductive tracks and sensitive elements. Further important challenges to be pursued are the possibility of using readily available instrumentation and reducing power consumption and hazardous chemical waste. This review provides an overview of the use of portable day‐to‐day writing tools, such as pencils and pens, for the rapid and on‐demand deposition of conductive patterns on different substrates, with particular emphasis on the assembly of “Do It Yourself” sensors. Moreover, layer‐by‐layer deposition of simple or even complex three dimensional (3D) circuits, resorting to pressure driven extrusion of conductive filaments is considered. Future perspectives and potentiality of these emerging technologies for assembling sensors are also explored.     

Direct electrochemistry and electroanalysis of hemoglobin adsorbed in self-assembled films of gold nanoshells

Gold nanoshells (GNSs), consisting of a silica core and a thin gold shell, were self-assembled on the surface of 3-aminopropyltrimethoxysilane (APTES) modified indium tin oxide (ITO) electrode. The resulting novel GNSs-coated ITO (GNSs/APTES/ITO) electrode could provide a biocompatible surface for the adsorption of hemoglobin (Hb). The UV-visible (UV-vis) spectra indicated that Hb adsorbed on the GNSs interface retained the native structure. Electrochemical impedance spectra and cyclic voltammetric techniques were employed to evaluate the electrochemical behaviors of Hb, the results demonstrated that GNSs could act as electron tunnels to facilitate electron transfer between Hb and the electrode. Based on the activity of Hb adsorbed on the GNSs/APTES/ITO electrode toward the reduction of hydrogen peroxide, a mediator-free H₂O₂ biosensor was constructed, which showed a broad linear range from 5 μM to 1 mM with a detection limit of 3.4 μM (S/N = 3). The apparent Michaelis-Menten constant was calculated to be 180 μM, suggesting a high affinity.     

基于硼酸-二醇特异性识别作用的层层组装薄膜对肌红蛋白的吸入及其电化学研究

合成了既含有苯硼酸(PBA)基团又含有羧酸基团的聚电解质PAA-PBA(PAA:聚丙烯酸).采用层层组装(Lb L)技术,利用PAA-PBA和葡聚糖(Dex)之间的硼酸-二醇特异性识别作用,在热解石墨电极(PG)表面构筑了{PAA-PBA/Dex}_nLb L薄膜,该薄膜从溶液中吸入肌红蛋白(Mb)形成{PAA-PBA/Dex}_n-Mb薄膜.采用循环伏安方法研究了{PAA-PBA/Dex}_n薄膜中Mb的直接电化学及对氧气和过氧化氢的电催化还原过程.结果表明,该薄膜为保持Mb的生物活性提供了良好的微环境,是一种新型的可固定蛋白质的Lb L薄膜,为设计基于酶的直接电化学生物传感器提供了新思路.     

Is selective hydrogenation of molecular oxygen to H2O2 affected by strong metal–support interactions on Pd/TiO2 catalysts? A case study using commercially available TiO2

In this study, titania-supported Pd catalysts were prepared and their performance evaluated upon H₂O₂ direct synthesis. Typically, the materials contained different ratios of anatase and rutile phases, which gave rise to different surface properties of the supports, e.g., surface area, number of Lewis acidic and basic sites as well as different compositions of the phases, i.e. the amount of anatase phase and crystallite size. Two materials, Pd-A98 and Pd-A05 samples, respectively, apparently hint the existence of the so-called SMSI (strong metal–support interaction) phenomenon giving rise to 1080 and 683 mol_H2O2·mol_Pd⁻¹·h⁻¹ of H₂O₂ productivity and 22 and 14% of H₂O₂ selectivity, respectively. However, the best material, Pd-A82, gave rise to 949 mol_H2O2·mol_Pd⁻¹·h⁻¹ of H₂O₂ productivity and 26% of H₂O₂ selectivity.     

Recent progress in catalytic NO decomposition

Recent progress in catalytic direct NO decomposition is overviewed, focusing on metal oxide-based catalysts. Since the discovery of the Cu-ZSM-5 catalyst in the early 1990s, various kinds of catalytic materials such as perovskites, C-type cubic rare earth oxides, and alkaline earth based oxides have been reported to effectively catalyze direct NO decomposition. Although the activities of conventional catalysts are poor in the presence of coexisting O₂ and CO₂, some of the catalysts reviewed in this article possess significant tolerance toward these coexisting gases. The active sites for direct NO decomposition are different depending on the types of metal oxide-based catalysts. In the case of perovskite type oxides, oxide anion vacancies act as catalytically active sites on which NO molecules are adsorbed. C-type cubic rare earth oxides contain oxide anion vacancies with large cavity space, enabling easy access of NO molecules and their subsequent adsorption. Surface basic sites on alkaline earth based oxides participate in NO decomposition as active sites on which NO molecules are adsorbed as NO₂⁻ species. The reaction mechanisms of direct NO decomposition are also discussed.     

Synthesis of 4-(thien-2-yl)-substituted coumarins through Lewis acid catalyzed Michael addition of thiophenes to 3-benzoylcoumarins followed by oxidation

3-Benzoyl-4-(thien-2-yl)coumarins have been obtained in good yields according to the S_N^H addition–oxidation protocol, involving the diastereoselective addition of thiophenes at C-4 of 3-benzoylcoumarins under BBr₃ catalysis, followed by oxidation of the intermediate 3,4-trans-3-benzoyl-4-(thien-2-yl)-3,4-dihydrocoumarins with DDQ. This two-step procedure can be regarded as nucleophilic substitution of hydrogen (S_N^H) on the heterocyclic ring of coumarins.     

On air-chemistry reduction for hypersonic external flow applications

In external hypersonic flows, viscous and compressibility effects generate very high temperatures leading to significant chemical reactions among air constituents. Therefore, hypersonic flow computations require coupled calculations of flow and chemistry. Accurate and efficient computations of air-chemistry kinetics are of much importance for many practical applications but calculations accounting for detailed chemical kinetics can be prohibitively expensive. In this paper, we investigate the possibility of applying chemical kinetics reduction schemes for hypersonic air-chemistry. We consider two chemical kinetics sets appropriate for three different temperature ranges: 2500 K to 4500 K; 4500 K to 9000 K; and above 9000 K. By demonstrating the existence of the so-called the slow manifold in each of the chemistry sets, we show that judicious chemical kinetics reduction leading to significant computational savings is possible without much loss in accuracy.     

Improving the efficiency of a direct ethanol fuel cell by a periodic load change

We present a simple method to increase the efficiency of a direct ethanol fuel cell by a periodic modulation of the load (pulsed mode). The fuel cell was periodically short circuited with a resistor (1...     

New type of heteroclinic tangency in two-dimensional maps

A new mechanism of heteroclinic tangency is investigated by using two-dimensional maps. First, it is numerically shown that the unstable manifold from a hyperbolic fixed point accumulates to the stable manifold of a nearby period-2 hyperbolic point in a piecewise linear map and that the unstable manifold from a hyperbolic fixed point accumulates to the accumulation of the stable manifold of a nearby period-2 hyperbolic point in a cubic map. Second, a theorem on the impossibility of heteroclinic tangency (in the usual sense) is given for a particular type of map. The notions ofdirect andasymptotic heteroclinic tangencies are introduced and heteroclinic tangency is classified into four types.