The status of exploitation techniques of natural gas hydrate

Natural gas hydrate(NGH)has been widely considered as an alternative form of energy with huge potential,due to its tremendous reserves,cleanness and high energy density.Several countries involving Japan,Canada,India and China have launched national projects on the exploration and exploitation of gas hydrate resources.At the beginning of this century,an early trial production of hydrate resources was carried out in Mallik permafrost region,Canada.Japan has conducted the first field test from marine hydrates in 2013,followed by another trial in 2017.China also made its first trial production from marine hydrate sediments in 2017.Yet the low production efficiency,ice/hydrate regeneration,and sand problems are still commonly encountered;the worldwide progress is far before commercialization.Up to now,many gas production techniques have been proposed,and a few of them have been adopted in the field production tests.Nevertheless,hardly any method appears really promising;each of them shows limitations at certain conditions.Therefore,further efforts should be made on the economic efficiency as well as sustainability and environmental impacts.In this paper,the investigations on NGH exploitation techniques are comprehensively reviewed,involving depressurization,thermal stimulation,chemical inhibitor injection,CO2–CH4 exchange,their combinations,and some novel techniques.The behavior of each method and its further potential in the field test are discussed.The advantages and limitations of laboratory studies are also analyzed.The work could give some guidance in the future formulation of exploitation scheme and evaluation of gas production behavior from hydrate reservoirs.

表面自由能对二维结晶的影响

二维分子晶体是一类具有优异光电性能的新兴材料.然而,由于人们对决定二维结晶的因素知之甚少,二维分子晶体的生长极具挑战.我们研究了有机半导体的二维结晶和表面自由能之间的关系,提出了利用表面自由能各向异性因子来衡量二维结晶趋势的设想.以两个BTBT衍生物为例,我们发现具有大的g因子的分子有不受外界条件干扰的二维结晶趋势.这项工作为合理设计可二维结晶的有机半导体提供了指导.

Cocrystal engineering:towards high-performance near-infrared organic phototransistors based on donor-acceptor charge transfer cocrystals

Near-infrared organic phototransistors have wide application prospects in many fields.The active materials with the high mobility and near-infrared response are critical to building high-performance near-infrared organic phototransistors,which are scarce at present.Herein,a new charge transfer cocrystal using 5,7-dihydroindolo[2,3-b]carbazole(5,7-ICZ)as the donor and 2,2’-(benzo[1,2-b:4,5-b’]dithiophene-4,8-diylidene)dimalononitrile(DTTCNQ)as the acceptor is properly designed and prepared in a stoichiometric ratio(D:A=1:1),which not only displays a high electron mobility of 0.15 cm^(2)V^(-1)s^(-1) and very low dark current,but also can serve as the active layer materials in the region of near-infrared detection due to the narrowed band gap and good charge transport properties.A high photosensitivity of 1.8×10^(4),the ultrahigh photoresponsivity of 2,923 A W-1and the high detectivity of 4.26×10^(11)Jones of the organic near-infrared phototransistors are obtained.

Deep insight into the charge transfer interactions in 1,2,4,5-tetracyanobenzene-phenazine cocrystal

A new charge transfer cocrystal of 1,2,4,5-tetracyanobenzene(TCNB)-phenazine(PTC)was prepared by solvent evaporation method.The donor and acceptor molecules of cocrystal are stacked face to face with a mixed-stacking,implying a strong charge transfer(CT)interactions in the cocrystal system.The spectroscopic studies,single-crystal X-ray diffraction structure,density functional theory(DFT)and Hirschfield surfaces calculations are carried out to explore the relationship between structure and properties of cocrystal system,which show that the intermolecular interactions in PTC are stronger than those of single components,leading to the stability and photophysical behaviors of cocrystal different from their constitute units.This study will be helpful for the design and preparation of multifunctional cocrystal materials.

低功耗高迁移率有机单晶场效应晶体管

不断发展的柔性电子产品需要开发兼具高迁移率和低功率的有机场效应晶体管(OFET),这对于新兴的显示器、传感器和标签科技都至关重要.在众多材料中,聚合物栅极电介质和二维有机晶体为构建高性能OFET提供了本征柔性和天然的相容性,但是,两者的结合仍然缺少无杂质、无损伤的构筑策略.在此,我们通过一种无损转移技术将二维有机二萘并[2,3-b:2′,3′-f]噻吩并[3,2-b]噻吩(DNTT)单晶转移到一种独特的聚合物介电层(聚酰胺酸(PAA))上,构筑了一个理想的OFET体系.得益于PAA表面独特的纳米结构和二维有机单晶的长程有序特性,所得的OFET器件表现出优异的性能,包括18.7 cm^(2)V^(−1)s^(−1)的最高迁移率和−3 V的低工作电压.这些结果说明将聚合物栅极介电层与二维有机单晶高质量结合是构筑高性能柔性电子器件的理想途径.

Vertical‐organic‐nanocrystal‐arrays for crossbar memristors with tuning switching dynamics toward neuromorphic computing

Memristors proposed by Leon Chua provide a new type of memory device for novel neuromorphic computing applications.However,the approaching of distinct multi‐intermediate states for tunable switching dynamics,the con-trolling of conducting filaments(CFs)toward high device repeatability and reproducibility,and the ability for large‐scale preparation devices,remain full of challenges.Here,we show that vertical‐organic‐nanocrystal‐arrays(VONAs)could make a way toward the challenges.The perfect one‐dimensional structure of the VONAs could confine the CFs accurately with fine‐tune resistance states in a broad range of 103 ratios.The availability of large‐area VONAs makes the fabrication of large‐area crossbar memristor arrays facilely,and the analog switching characteristic of the memristors is to effectively imitate different kinds of synaptic plasticity,indicating their great potential in future applications.

Phenanthrene derivatives combined charge transport properties and strong solid-state emission

As bifunctional materials, phenanthrene derivatives 2,7-diphenylphenanthrene and 2,7-di(styryl)phenanthrene(DPPa and DSPa) were designed and studied. Both materials show charge transport properties and strong solid-state emission. The hole mobility was measured to be 1.6 and 0.4 cm^2 V-1 s^-1 for DPPa and DSPa, respectively. While the photoluminescence quantum yield of DPPa and DSPa was as high as 37.13% and 62.36%, respectively.

共晶工程:多重刺激下裁剪共晶中电荷转移作用构筑高灵敏度发光开关材料

本论文通过溶液自组装方法制备了吖啶-1,2,4,5-四氰基苯共晶(ATC),这种共晶的发光特性对外部刺激(酸/碱蒸气、研磨和热)表现出敏感的反应.通过光谱测试、理论计算和晶体结构研究表明,交替柱排列的ATC存在明显的分子间电荷转移相互作用,这种相互作用在酸蒸气刺激下减弱,而在机械研磨外力作用下增强,实现了外界刺激下分子间作用力的可逆调控.此外,该共晶的响应时间为秒级,远优于先前报道的大多数刺激响应型共晶.因此, ATC在多种刺激下表现出高灵敏的荧光切换,为开发智能材料提供了一种有效的策略.