Inkjet and microcontact printing of functional materials on foil for the fabrication of pixel-like capacitive vapor microsensors

The work presented demonstrates the utilization of micro-contact printing of self-assembled monolayers (SAMs) of gold nanoparticles (NPs) to pattern the porous thin metallic film composing the top electrode of an ultra-fast capacitive relative humidity sensor based on miniaturized parallel-plates electrodes. The rest of the device, which occupies an area of only 0.0314 mm², is fabricated by inkjet printing stacked individual drops of functional materials, namely gold NPs for the bottom electrode and a polymeric humidity sensing layer, on a polymeric foil. Compared to other printing methods, the use of microcontact printing to pattern the top electrode enables the additive transfer of a solvent-free metallic layer that does not interact chemically with the sensing layer, permitting the thinning of the latter without risk of short-circuits between electrodes, and broadening the range of usable sensing materials for detection of other gases. Thinning the sensing layer yields to ultra-fast response devices with high values of capacitance and sensitivity per surface area. The fabrication process is compatible with low heat-resistant polymeric substrates and scalable to large-area and large-scale fabrication, foreseeing the development of low-cost vapor sensing sheets with high space–time resolution, where every sensor would correspond to a pixel of a large array.     

Challenges towards large-scale fuel cell production: Results of an expert assessment study

Fuel cell electric vehicles are a promising alternative on the way to emission-free mobility. However, there is still a great deal of uncertainty as to how this change can be implemented technologically. Despite various research and development activities on fuel cells in the past two decades, a real breakthrough of fuel cell technology has not yet been reached. The aim of this paper is therefore to identify barriers to a commercialized production of PEM fuel cell stacks. For this purpose, a comprehensive expert study is performed, consisting of a qualitative, exploratory and a quantitative, hypothesis-confirming step. As a result, technical and non-technical barriers are examined and described in this paper. A cost estimation of today's actual manufacturing cost is presented as identified in the study. Conclusively, future research topics and needs for action are derived.     

天麻酵素对失眠小鼠的镇静催眠功效评价

为探究天麻酵素镇静催眠功效,该研究分析了天麻酵素理化指标以及对失眠模型小鼠脑组织内神经递质及氧化应激水平的调节。将KM雄性小鼠随机分为空白组、模型组、枣仁安神液组（阳性对照组1）、天麻粉组（阳性组对照组2）、天麻酵素低（0.10 g/kg）、中（0.30 g/kg）、高（0.49 g/kg）剂量组,以对氯苯丙氨酸建立失眠模型,连续灌胃给药7 d后通过测定小鼠自主活动的变化、小鼠脑组织神经递质和氧化应激水平的变化,分析其对失眠小鼠镇静催眠功能的影响。结果显示,天麻酵素中γ-氨基丁酸含量为0.48 mg/kg,是QB/T 5232-2018标准中要求的16倍;天麻酵素高、中剂量组与模型组相比,小鼠活动时间和站立次数显著减少（p<0.05）,分别减少13.00 s、14.63 s和10.62次、9.12次;小鼠脑组织中5-HT、GABA、IL-1β含量显著增加（p<0.01）、SOD活性显著提高（p<0.05）、MDA含量显著降低（p<0.05）,其中5-HT增加50.62 pg/mL、49.51 pg/mL,GABA增加5.47 ng/mL、5.15 ng/mL。这表明天麻酵可通过调节小鼠脑组织内神经递质及氧化应激水平来达到镇静催眠作用。     

Sulfonated magnetic carbon nanotube arrays as effective solid acid catalysts for the hydrolyses of polysaccharides in crop stalks

The sulfonated magnetic carbon nanotube arrays (MCNAs) were synthesized and characterized by electron microscopy and microanalysis technique and employed as magnetic solid acid catalysts for the hydrolyses of polysaccharides in crop stalks into sugars in present work. The results indicate that the as-prepared sulfonated MCNAs exhibited high activity and selectivity, excellent magnetic property and stability, showing a good potential application for effective hydrolyses of polysaccharides in crop stalks in the future.     

Graphene–NHC–iridium hybrid catalysts built through –OH covalent linkage

Graphene oxide (GO) and thermally reduced graphene oxide (TRGO) were covalently modified with imidazolium salts through their hydroxyl surface groups. The selective reaction of the –OH groups with p-nitrophenylchloroformate produced labile intermediate organic carbonate functions which were used for the covalent anchoring of a hydroxy-functionalized imidazolium salt. Nanohybrid materials containing iridium N-heterocyclic carbene (NHC)-type organometallic complexes were prepared by causing the imidazolium-functionalized materials to react with [Ir(μ-OMe)(cod)]₂. The iridium content of the graphene-based hybrid catalysts, as determined by XPS and ICP-MS was the order of ∼5 and 10 wt.%, for the TRGO and GO-based materials, respectively. The graphene-supported iridium hybrid materials were active in the heterogeneous hydrogen-transfer reduction of cyclohexanone to cyclohexanol with 2-propanol/KOH as the hydrogen source. The thermally reduced graphene–NHC–iridium hybrid catalyst showed the best catalytic performance with an initial TOF of 11.500 h⁻¹, slightly better than the related acetoxy-functionalized NHC iridium homogeneous catalyst. A good catalyst recyclability and stability were achieved.     

Inkjet-defined field-effect transistors from chemical vapour deposited graphene

In this work, inkjet printing methods are used to create graphene field effect transistors with mobilities up to 3000 cm² V⁻¹ s⁻¹. A commercially-available chromium-based ink is used to define the device channel by inhibiting chemical vapour deposition of graphene in defined regions on a copper catalyst. We report on the patterned graphene growth using optical and electronic microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. Silver nanoparticle ink is used to create electrical contacts to the defined graphene regions. The resulting devices were characterised by electrical transport measurements at room temperature. As a result we are able to fabricate high-performance graphene field effect transistors entirely defined by a commercial inkjet printer with channel lengths of 50 μm.     

The oxidative transformation of sodium arsenite at the interface of α-MnO2 and water

Arsenite is acute contaminant to human health in soil and water environment. In this study, Pyrolusite (α-MnO₂) was used to investigate the oxidative transformation of arsenite into arsenate with batch experiments under different reaction conditions. The results showed that arsenite transformation occurred and was accompanied by the adsorption and fixation of both As(III) and As(V) on α-MnO₂. About 90% of sodium arsenite (10 mg/L) were transformed by α-MnO₂ under the conditions of 25 °C and pH 6.0, 36.6% of which was adsorbed and 28.9% fixed by α-MnO₂. Increased α-MnO₂ dosages promoted As (III) transformation rate and adsorption of arsenic species. The transformation rate and adsorption of arsenic species raised with increasing pH values of reaction solution from 4.7 to 8.0. The oxidation rate decreased and adsorbed As(III) and As(V) increased with increasing initial arsenite concentration. The enhancement on oxidative transformation of sodium arsenite may result from abundant active sites of α-MnO₂. Along with adsorption and fixation of arsenic species during the reaction, the crystal structure of α-MnO₂ did not change, but the surface turned petty and loosen. Our results demonstrated that α-MnO₂ has important potential in arsenic transformation and removal as the environmentally friendly natural oxidant in soil and surface water.     

Graphene modified Co–B catalysts for rapid hydrogen production from NaBH4 hydrolysis

Graphene oxide (GO) modified Co–B catalysts for NaBH₄ hydrolysis have been synthesized by the chemical reduction in this work. The structural features and catalytic performance of as-prepared samples have been investigated and discussed as a function of amounts of GO. According to structure characterization, the catalysts still retain the amorphous structure of Co–B alloy with the addition of GO, while GO exists as reduced GO (r-GO). The textural analysis and morphology observation indicate that the appropriate amount of GO in Co–B catalyst results in the obvious increase of specific surface area and uniform clustered morphology, which contributes to improve active surface area for catalytic reactions. The results of surface species characterization show that the electron density at active Co sites increases due to an electron transfer from B to Co facilitated by r-GO. It has been found that 50 mg GO modified Co–B catalyst exhibits especially high activity with a hydrogen generation rate of 14.34 L min⁻¹·g_catalyst⁻¹ and much lower activation energy of 26.2 kJ mol⁻¹ for hydrolysis reaction of NaBH₄. Meanwhile, the reusability evaluations show that the catalyst preserves high stability which can still maintain 81.5% of its initial activity after 5 catalytic cycles.