Interactions of DNA with graphene and sensing applications of graphene field-effect transistor devices: A review

Graphene field-effect transistors (GFET) have emerged as powerful detection platforms enabled by the advent of chemical vapor deposition (CVD) production of the unique atomically thin 2D material on a large scale. DNA aptamers, short target-specific oligonucleotides, are excellent sensor moieties for GFETs due to their strong affinity to graphene, relatively short chain-length, selectivity, and a high degree of analyte variability. However, the interaction between DNA and graphene is not fully understood, leading to questions about the structure of surface-bound DNA, including the morphology of DNA nanostructures and the nature of the electronic response seen from analyte binding. This review critically evaluates recent insights into the nature of the DNA graphene interaction and its affect on sensor viability for DNA, small molecules, and proteins with respect to previously established sensing methods. We first discuss the sorption of DNA to graphene to introduce the interactions and forces acting in DNA based GFET devices and how these forces can potentially affect the performance of increasingly popular DNA aptamers and even future DNA nanostructures as sensor substrates. Next, we discuss the novel use of GFETs to detect DNA and the underlying electronic phenomena that are typically used as benchmarks for characterizing the analyte response of these devices. Finally, we address the use of DNA aptamers to increase the selectivity of GFET sensors for small molecules and proteins and compare them with other, state of the art, detection methods.     

机械剥离石墨烯修饰电极检测食品接触材料中双酚A的迁移量

采用机械剥离石墨烯修饰电极快速检测食品接触材料中双酚A的迁移量。X射线电子衍射表征显示机械剥离石墨烯表面不存在含氧官能团,与化学还原石墨烯相比,机械剥离石墨烯对双酚A具有更好的电催化性能,降低了双酚A的氧化过电位,提高了电流响应。在优化的试验条件下,双酚A的浓度在1.0×10-7~1.5×10-5mol·L-1范围内与氧化峰电流呈线性关系,检出限(3S/N)为3.0×10-8mol·L-1。采用该电极对食品模拟物中的双酚A进行检测,加标回收率在85.1%~104%之间,测定值的相对标准偏差(n=6)在2.7%~5.9%之间。     

超声波促进手性双酰基氧化膦的合成

以L-薄荷醇为原料,经3步反应制备得到中间体薄荷基二氯化膦.该中间体首先通过与超声波辐射制备的微米级钠粒反应形成薄荷基膦二钠盐,然后依次经过偶联及氧化反应合成了目标产物(-)-双(薄荷基甲酰基)薄荷基氧化膦(BMMPO),并经过1 H NMR、13 C NMR、31P NMR和元素分析进行了表征.     

超声提取–离子色谱法测定土壤易溶盐中的氯离子和硫酸根离子

采用超声提取的方式,以离子色谱法测定土壤易溶盐中的氯离子和硫酸根离子。对实验条件进行了优化,色谱柱为NJ–SA–4A柱(250 mm×2 mm),保护柱为SI–92G柱(50 mm×4 mm),淋洗液为1.8 mmol/L Na_2CO_3–1.7mmol/L NaHCO_3,流量为1.0 m L/min;在40℃下,对土壤样品提取10 min。Cl~–和SO_4~(2–)在检测范围内均线性良好,线性相关系数为0.999 8,加标回收率分别为95.0%~99.0%,96.0%~101.0%,测定结果的相对标准偏差分别为1.4%,1.0%(n=4)。与传统的方法相比,该法试剂用量少,操作简单,可用于土壤易溶盐样品的测定。     

A green one-pot three-component synthesis of α-aminophosphonates under solvent-free conditions and ultrasonic irradiation using Fe3O4@SiO2-imid-PMAn as magnetic catalyst

An efficient and environment friendly process for the synthesis of α-aminophosphonates has been devised. Through a one-pot three-component condensation of various aldehydes, amines, and triethyl phosphite in the presence of Fe₃O₄@SiO₂-imid-PMAⁿ nanoparticles as magnetic catalysts under solvent-free conditions and ultrasonic irradiation, α-aminophosphonates were obtained with excellent yields. The reactions under solvent-free conditions at room temperature are compared with the ultrasonic-assisted reactions. This new procedure has notable advantages such as short reaction time, excellent yields, easy purification, and the absence of any tedious workup or purification. The aforementioned catalyst could be easily recovered by an external magnetic field and can be reused for six consecutive reaction cycles without significant loss of activity. In addition, SEM and DLS of the catalyst after the reaction cycle were investigated.     

Fibrillar structure development of polyacrylonitrile fibers treated by ultrasonic etching in oxidative stabilization

Polyacrylonitrile fibers were oxidatively stabilized through 10 gradient‐elevated temperature zones in sequence. The ultrasonic etching method was used for fibril separation of fibers heated at different temperatures, and the fibrillar structure development was studied by scanning electron microscopy. The voids among fibrils are the weak combination points. Under ultrasonic etching, the voids are enlarged. Subsequently, the solvent enters and spreads among fibrils, which results in the separation of fibrils. Separated fibrils with diameters of 100–400 nm appear in fibers heated at less than 235°C. Fibrils in fibers heated from 195°C to 235°C tend to adhere to each other, and the observed macrofibrils are composed of several to dozens of fibrils. For fibers heated from 195°C to 245°C, only a few fibril bundles emerge on the skin near the fiber end, and the fibrils manifest themselves as numerous protuberances on the cross section. In the ranges of 255–275°C, fibrils compactly combine with each other, which suggests insolubility and infusibility, and no separated fibrils appear. The fibrils arrange in a systematic way along the fiber axis and grooves parallel to the fiber axis on the fibers' surface. These grooves are the macro behavior of fibrils arranging on the fiber surface. Copyright © 2017 John Wiley & Sons, Ltd.     

Highly Efficient,Green, and Scalable β‐Cyclodextrin‐Assisted Aqueous Exfoliation of Transition‐Metal Dichalcogenides: MoS2 and ReS2 Nanoflakes

The β‐cyclodextrin‐assisted aqueous‐exfoliation method was used to prepare transition‐metal dichalcogenide (TMD) nanosheets, in a cheap, highly efficient, scalable and environmentally friendly manner. As study cases, MoS₂ and ReS₂ nanoflakes were prepared according to this method. Particularly, the effective exfoliation of ReS₂ crystals in an aqueous environment was observed for the first time. Moreover, exfoliated nanomaterials can be readily utilized in hydrogen evolution reactions (HERs) as noble‐metal‐free catalysts. This work provides new opportunities for highly efficient exfoliation of TMDs and other 2D nanomaterials into few‐layer nanosheets in aqueous media. Their production process showed high biocompatibility, broad applicability and excellent sustainability.     

A Multiple Structure‐Design Strategy towards Ultrathin Niobate Perovskite Nanosheets with Thickness‐Dependent Photocatalytic Hydrogen‐Evolution Performance

Hydrogen production by catalytic water splitting using sunlight holds great promise for clean and sustainable energy source. Despite the efforts made in the past decades, challenges still exist in pursuing solid catalysts with light‐harvesting capacity, large surface areas and efficient utilities of the photogenerated carrier, at the same time. Here, a multiple structure design strategy leading to highly enhanced photocatalytic performance on hydrogen production from water splitting in Dion–Jacobson perovskites KCa₂Na_{n ‐3}Nb_n O_{3n +1} is described. Specifically, chemical doping (N/Nb⁴⁺) of the parent oxides via ammoniation improved the ability of sunlight harvesting efficiently; subsequent liquid exfoliation of the doped perovskites yielded ultrathin [Ca₂Na_{n ‐3}Nb_n O_{3n +1}]⁻ nanosheets with greatly increased surface areas. Significantly, the maximum hydrogen evolution appears in the n =4 nanosheets, which suggests the most favorable thickness for charge separation in such perovskite‐type catalysts. The optimized black N/Nb⁴⁺‐[Ca₂NaNb₄O₁₃]⁻ nanosheets show greatly enhanced photocatalytic performance, as high as 973 μmol h⁻¹ with Pt loading, on hydrogen evolution from water splitting. As a proof‐of‐concept, this work highlights the feasibility of combining various chemical strategies towards better catalysts and precise thickness control of two‐dimensional materials.     

超声波无触点支承陀螺仪技术的理论分析及实现

提出了一种超声无触点支承方案，详细介绍了超声无触点支承原理。通过对声辐射理论的研究，获得超声无触点支承的理论依据。实验证明实现这种超声波无触点支承是可行的。根据这一理论，对三轴无触点支承结构进行了选择设计。     

超声波的光外差接收

激光接收超声是一种非接触式的超声接收技术，它在超声无损评估及检测领域有重要的应用。本文设计研制了激光外差干涉接收超声的实验系统，该系统由声光调制器产生光频的频移，锁相环进行位相解调。文中重点讨论：（１）在光学部分，外差干涉光路空间准直性对信噪比的影响。（２）在信号处理电路部分，锁相环电路特性分析及其参数确定