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超低温水气转化研究获进展

      近日,大连理工大学化工与环境生命学部化学学院石川教授课题组最新研究成果发表于2017年6月22日的《科学》上。

      水煤气变换反应提供了一条同时制取氢气并净化CO的重要途径,其与水汽重整反应组合是目前廉价制氢的主要技术。传统低温水汽变换催化剂(Cu-Zn-Al)制氢效率偏低,无法满足低温氢燃料电池系统有效整合的需求,研发新一代低温变换催化剂具有重要的科学意义和实用价值。

      石川课题组与北京大学马丁课题组、美国布鲁克海文国家实验室Jose A. Rodriguez、中国科学院大学周武、山西煤化所/中科合成油温晓东等课题组合作,突破以可还原性载体分散贵金属为低温变换催化剂的传统研究思路,利用过渡金属碳化物热稳定性好且与被分散金属有较强相互作用的特点,构建双功能碳化物负载金催化剂Au/α-MoC1-x:立方相α-MoC1-x低温活化解离H2O,被分散的金促进低温CO吸附活化,在界面处完成重整反应并生成H2。该催化剂可将水煤气变换反应温度大幅降低至120oC。在空速高达180,000 h-1的反应条件下,反应活性达到1.05 molCO/(molAu*s),较文献报道提升了20余倍,而CO转化率超过95%,有效解决水煤气变换反应低温条件下高反应转化率与高反应速率不能兼得的难题。结构表征表明:在Au与载体碳化钼的强相互作用影响下,Au形成二维层状纳米结构,并形成缺电子中心,在高温活化和反应条件下表现出优异的结构稳定性。上述电子与几何结构特性是Au/α-MoC1-x催化剂具有优异低温WGS活性的微观机制。

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分类:化学化工研究热点 | 固定链接 | 评论: 0 | 引用: 0 | 查看次数: 52
     近日,《自然—生物技术》在线发表的一篇论文指出,一种基因改造的水藻品系的油脂产量可达野生亲本的两倍,而且能达到与后者类似的生长速度。这些发现使人们向微藻源可持续生物燃料的最终商业化迈近了一步。

     自20世纪70年代末以来,人们一直在积极研究使用光养微藻产生的油脂制造生物柴油,以补充基于石油的运输燃料短缺。光养微藻是一种借助光、水和二氧化碳生长可产生油脂的微生物。截至目前,改造微藻使之油脂产量扩大的工作一直局限于工业品系,它们在数量上无法达到商业化的要求。海洋富油微拟球藻的产油量可达实验室品系的6倍,但尽管经过数十年研究,提升微拟球藻的产油效率都会带来生长受损,该属物种的商业潜力也未得到充分发挥。

    美国加利福尼亚州合成基因组公司(SGI) 的Eric Moellering及同事使用了多种改造工具,包括CRISPR-Cas9基因编辑工具识别ZnCys因子——它调控着工业品系海洋富油微拟球藻的油脂累积。改造ZnCys后,研究人员发现微藻的产油效率翻了一番——最高可达每天每米5克,而且能保持与未受改造的亲本品系相当的生长速度。

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分类:化学化工研究热点 | 固定链接 | 评论: 0 | 引用: 0 | 查看次数: 47

科学家揭示中国湖泊磷污染下降

      近日,我国学者与国际合作者在线发表于《自然—地球科学》的一篇论文指出,在2006到2014年间中国湖泊的磷污染下降了逾1/3。该研究还发现,中国政府于2000年推出的治理水污染政策协助降低了城市地区与磷污染有关的水华风险,但在一些欠发达地区,湖泊的磷浓度上升了。

      富营养化(可用养分增加导致藻类过度生长的情况)可能会在湖泊中自然发生。但是,人为向水体排放营养物已经使全球范围内的富营养化现象明显加重,导致水质下降、鱼类灭绝和生物多样性下降。

      天津大学的童银栋、挪威水研究所的林岩及同事和合作者,分析了2006年至2014年间中国862个湖泊的水化学数据,以及磷来源和磷流入的省级数据。结果发现,磷浓度中值大致降到了可导致富营养化的浓度阈值,重度污染的湖泊数量减少了2/3。其中主要的驱动因素是公共卫生改善和污水减少;一些较偏远地区湖泊磷浓度上升的原因则还不确定,但有可能是受到了森林退化和侵蚀的影响。

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分类:化学化工研究热点 | 固定链接 | 评论: 0 | 引用: 0 | 查看次数: 58

研究识别威士忌真假

      近日来自德国的研究团队提出了一个更加简便的鉴别威士忌真假的方法:使用荧光染料比较不同的饮料。

      当威士忌开始在全球流行起来的时候,骗子也随之而来了。因为他们的伪劣假冒品很便宜,比如混合威士忌冒充纯麦苏格兰威士忌。但除了酿酒大师,很多人难以甄别。虽然,化学家们设计了各种方法甄别伪造威士忌。但这些方法需要对这种酒的复杂化学成分有深入了解才行,要知道普通的酒鬼才不愿意去了解这些。

      据悉,这种新染料是合成的,会根据酒酿的分子构成发出不同的颜色。通过对33种不同的威士忌进行逐个测试,该团队已经能够将荧光信号按照酒的原产地、混合状态(纯麦或混合型)、酒龄、口味(重或清淡)来分类,并将结果发表在日前的《化学》杂志中。

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分类:化学化工研究热点 | 固定链接 | 评论: 0 | 引用: 0 | 查看次数: 60

科学家再组装六足虫纳米钙钛矿

    近日,发表在《自然—通讯》的文章介绍了新南威尔士大学Rose Amal,Hamid Arandiyan,Sean Smith与北京工业大学戴洪兴教授的合作研究,报道了一种三维再组装六足虫纳米介孔钙钛矿催化剂(La0.6Sr0.4MnO3, LSMO),将三维有序大孔镧基钙钛矿结构用超声离心法断裂再组装成六足虫纳米介孔催化剂,该催化剂在断面暴露出的(001)晶面比LSMO常规暴露的(110)晶面对甲烷催化氧化具有更高的催化活性。

    过渡金属氧化物替代贵金属负载型催化剂氧化甲烷的研究一直是热点问题。目前商业化的贵金属催化剂(Pt和Pd)存在成本高且热稳定性差(贵金属颗粒高温团聚失活)等缺点。钙钛矿型催化剂(ABO3)作为一种混合型氧化物,由于其特殊的晶体结构,具有优秀的催化稳定性。作为高效催化剂,钙钛矿的研究关键在于如何提高其催化性能,使得甲烷能够在较低温度下完全氧化。

    该研究指出,相比三维大孔LSMO六足虫纳米介孔LSMO钙钛矿的比表面积有所提高,然而通过计算单位表面积催化剂的反应速率发现高比表面积并不是催化剂活性提高的决定性因素。作者通过高分辨透射电镜发现,六足虫纳米颗粒的断裂面出现新的晶面(001)暴露。因此,作者利用DFT计算研究了三维大孔LSMO表面的常规暴露晶面(110)和六足虫纳米介孔LSMO表面新暴露晶面(001)对甲烷分子中碳氢键(C-H)的断裂,以及这两种晶面对氧气分子的吸附和活化,发现新暴露晶面(110)需要更低的能量断裂C-H键。由此可以通过断裂再组装LSMO钙钛矿,暴露新活性晶面(110),提高材料的催化反应速率并降低表面活化能(Ea从102 kJ mol-1降低到67 kJ mol-1)。(来源:科学网)

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分类:化学化工研究热点 | 固定链接 | 评论: 0 | 引用: 0 | 查看次数: 68
     石墨烯材料具有独特的物理和化学性质,在能源、催化和环境等领域有广阔的应用前景。近年来,铁基磁性纳米粒子因其价格低廉、可磁性分离、催化活性好等优点而被用于设计和制备非均相类Fenton催化剂。经典的芬顿 Fenton (Fe2+/H2O2) 反应可以产生高活性的羟基自由(•OH),然而它在降解有机污染物的应用中,由于催化剂很难进行回收再利用以及反应后产生大量的铁污泥需要进一步处理等问题而受到一定限制。

      近日,中国科学院新疆理化技术研究所资源化学研究室研究员张亚刚带领其团队将Fe0和Fe3O4 在纳米尺度同时均匀地负载到了还原氧化石墨烯(RGO)上,得到了可磁性分离、催化活性高,可多次重复利用的纳米催化剂(Fe0/Fe3O4-RGO),并将其作为非均相类Fenton催化剂用于降解水相中苯酚污染物。

      在前期的研究工作中,张亚刚团队通过探究氧化石墨烯的还原过程,并将其进行磁功能化,制备了不同还原程度的磁性还原氧化石墨烯材料,用于污染物双酚A的吸附,并揭示了氧化石墨烯的还原程度对双酚A的吸附动力学和吸附容量的影响。

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分类:化学化工研究热点 | 固定链接 | 评论: 0 | 引用: 0 | 查看次数: 73
      发光金属团簇是一种由几个到几十个过渡金属原子(如Au、Ag、Cu、Pt、Pd等)组成,具有明显光致发光性质的小尺寸材料(粒径 < 3 nm)。发光金属团簇的性质介于原子金属和金属纳米粒子之间,是这两类物质的中间“过渡态”。金属团簇因其优异的光致发光性质、高活性的催化能力,近年来吸引了研究者们的广泛关注,在各类化学催化反应过程、生物和化学检测、荧光成像标记等领域表现出巨大的应用潜力和研究价值。然而,鉴于极小的尺寸产生的高表面活性,金属团簇极易聚集和氧化。因此,如何合成稳定并具有优异发光性能和催化能力的金属团簇,是一项具有一定难度的研究工作。

      中国科学院新疆理化技术研究所环境科学与技术研究室王传义团队用一种硅烷偶联剂(3-巯基丙基三甲氧基硅烷)作为稳定剂兼还原剂,通过快速且有效的光还原方式制备尺寸、荧光可调的Au纳米团簇。可以简单地调节稳定剂和Au前驱体的比例调节团簇的发射波长,其变化范围为538–580 nm。另外,合成的Au纳米团簇具有相对较长的荧光寿命:34.04到46.83 ns;同时,该团簇的荧光量子产率高达0.26–3.16%,随着发射波长的变化而变化。与体相金相比,该团簇具有特殊的电子结构,有类似于半导体的特性,如紫外-吸收光谱中出现吸收边的性质等。此外,所制备得到的Au纳米簇也具有一定的光催化能力,可以独立作为光催化剂参与光催化反应。在可见光的照射下,该团簇能有效促进亚甲基蓝的降解反应,60分钟的照射时间里亚甲基蓝的降解率高达95.6%。这个发现也进一步拓展了Au纳米簇在催化领域的应用范围。

      相关研究成果发表在《纳米尺度》(Nanoscale)上,并引起同行的广泛关注。该研究工作得到国家自然科学基金、中科院“创新团队国际合作伙伴计划”、“千人计划”(新疆项目)等项目支持。(来源:中国科学院新疆理化技术研究所)

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分类:化学化工研究热点 | 固定链接 | 评论: 0 | 引用: 0 | 查看次数: 63
       新型太阳能电池关键材料一直是清洁能源领域的研究热点。近日,华东理工大学材料科学与工程学院侯宇博士在新型太阳能电池关键材料方面的研究取得新进展,相关研究成果日前发表于《纳米能源》。

      钙钛矿太阳能电池(PSCs)由于其能量转换效率高、成本低廉和制备工艺简单等优点,引起了科研工作者的广泛关注。电子传输层(ETL)作为钙钛矿太阳能电池的重要组件之一,可以选择性传输光生电子,抑制载流子复合,对电池能量转换效率的提高具有重要意义。针对目前传统ETL材料与钙钛矿层本征电子迁移率不匹配这一关键问题,侯宇博士在研究中采用低温化学浴沉积方法,制备了排列规整的In2S3纳米片阵列,并将其首次应用于钙钛矿太阳电池ETL的结构设计中。

      据介绍,研究人员借助时间分辨光致发光光谱技术,探究了PSCs中电荷传输的动力学行为,基于硫化铟的PSCs室温光致发光淬灭现象明显,规整的纳米片阵列结构可以有效收集和传输来自钙钛矿光吸收层中的电子,使得电子空穴寿命更短,加速了钙钛矿材料中光生载流子的分离。此外,硫化铟ETL更为匹配的能带结构以及更高的本征电子迁移率,能够进一步抑制电子的“逆向”传输,降低载流子复合机率,从而使得电池器件的短路电流密度、开路电压以及填充因子均得到提升。基于硫化铟ETL的电池能量转换效率达到18.22%,较基于传统ETL的钙钛矿太阳电池提高了16%。

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分类:化学化工研究热点 | 固定链接 | 评论: 0 | 引用: 0 | 查看次数: 80
      近日,中科院大连化物所吴忠帅研究员带领二维材料与能源器件研究团队发展了一种同时氧化和碱化的新策略,一步法实现了二维金属碳化物纳米片(Ti3C2 MXene)向超薄钛酸钠或钛酸钾纳米带的转变,发现其具有优异的储钠和储钾性能。相关研究成果发表在美国化学会纳米期刊上。

      MXene是一类新型二维金属碳(氮)化物纳米片,具有优异的电化学性能。一般由三元MAX相经化学刻蚀剥离制得,其中M指过渡族金属(如Ti、V、Nb、Ta等),A指Al、Si等,X指C、N。常见的Ti3C2 MXene表面具有大量的含氧/氟官能团, 作为储能电极材料时易产生较大的不可逆容量,导致可逆比容量与库伦效率较低。因此,需要研发结构和性能稳定的MXene基新型电极材料。

      该研究团队通过设计一种同时氧化和碱化的新过程,一步法实现了二维金属碳化物纳米片(MXene)向超薄钛酸钠或钛酸钾纳米带的转变,所制备的纳米带具有较大的层间距(0.90~0.93 nm)、超薄厚度(<11 nm)、较窄宽度(<60 nm)以及开放的大孔结构,有利于充放电过程中电解液离子的快速传输以及结构的稳定。因此,该类钛酸钠纳米带在200 mA g-1电流密度下展现出高达191 mAh g-1的比容量,钛酸钾纳米带具有优异循环稳定性,超过900次的稳定循环且保持较高比容量,明显优于其它的钛基纳米材料。

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分类:化学化工研究热点 | 固定链接 | 评论: 0 | 引用: 0 | 查看次数: 75

数量泛滥 我国专利许可实施率仅为2%

 为进一步推动经济产业升级,国家提出了供给侧改革方案,着力提高供给体系质量和效率。产品质量在很大程度上取决于产品的研发水平、创新程度,并反映在品牌知名度等因素上,因此供给侧结构改革所要实现的全面提升产品质量与知识产权制度息息相关。然而,社科院近日发布的《法治蓝皮书(2017)》披露,当下中国产品供给存在整体质量不高,创新程度不足的情况。中国知识产权还存在量多质低,保护力度不足及保护成本过高等问题,严重制约了企业创新及产品质量的提升。因此,有必要进一步完善知识产权制度,推动供给侧改革目的的实现。

 
研发投入500万以上企业仅占4.1%
 
法治蓝皮书披露,通过对七千多家企业研发项目平均投入的调查发现,企业研发经费投入在100万元以下的占绝大多数(67%),投入500万元以上企业仅占4.1%。而对企业的专利研发周期调查发现,企业研发周期1年及以下的占23.2%,1年到2年的占44.1%,合计占67.3%;而真正愿意在3年以上进行长期研发的占6.2%。这说明绝大多数企业不愿花费太长周期从事研发活动。
 
蓝皮书指出,技术创新决定了企业的核心竞争力,技术创新虽需要资金投入,但也会产生巨额回报,企业不愿意投入更多经费在技术创新领域是需要进行反思和改善的问题。与此同时,一个国家或者企业的技术创新能力又在一定程度上决定了产品供给能力,中国正在进行的供给侧结构改革,恰恰就是要想办法进一步增强中国企业产品的核心技术能力,并且全面提升其品牌信誉度。因此,进一步完善知识产权保护制度,助力供给侧改革也就成为摆在当下的一项重要任务。
 
专利申请数量泛滥利用率不高
 
中国发明专利申请量一直保持稳步增长态势,根据2015年国家知识产权局公布的数据,2015年中国知识产权局共受理发明专利申请110.2万件,同比增长18.7%,连续5年居世界首位。如果仅仅从专利申请数量来看,中国企业的创新能力似乎应是位居“世界首位”的,然而从申请专利的质量来看,事实并非如此,无论是在日用消费品抑或是高科技产品领域,中国企业的创新能力和供给能力与国际同行相比都还存在一定差距。中国企业的创新能力与持续增长的专利申请数量不成正比。
 
然而,法治蓝皮书披露,企业申请的大量专利并没有真正用于提升产品质量。根据中国专利法规定,中国发明专利保护期限为20年,实用新型和外观设计专利保护年限为10年。然而,在绝大多数情况下,专利权人都会中途放弃专利。《2014年度中国有效专利年度报告》显示,国内发明专利平均维持年限3.8年,实用新型专利为3.5年,外观设计专利为3.2年;而真正达到最长维持年限的发明仅占0.02%,实用新型仅占1.1%,外观设计仅占0.5%。上述数据表明,中国绝大多数申请的专利没有真正投入使用。
 
此外,专利许可实施率也能够反映专利实际使用情况。从2012年至2014年,全国共授予国内专利2787707件,签订专利许可合同仅为56067件,仅占授权专利比例的2%。该数据也反映出绝大多数的专利没有真正投入使用。
 
因此,企业申请专利与企业产品供给能力之间并不能直接画上等号。事实上,现有制度中评价政府或企业科技创新能力的重要指标依然是专利量,如:企业要享受诸多优惠福利政策需要专利;企业要减免税收、申请高新企业认证需要有专利指标要求;很多地方和单位的人才引进、人才考评也需要专利。显然,申请专利可以满足多方面的利益需求。加之,很多地方为了争创专利申请数量先进,通过所谓奖励措施为企业申请专利颁发奖金,更加导致专利申请数量泛滥。
 
七成人认为知产保护水平需强化
 
法治蓝皮书介绍,以“中国知识产权保护水平的评价”为题,对8938人进行了调查,总体上,有67%的被调查者认为中国知识产权保护水平需要逐步强化,甚至有24.4%的被调查者认为需要大幅强化,仅有7.2%的被调查者认为比较适当。从调查结果不难看出,中国知识产权保护水平有待进一步提高。
 
事实上,企业作出什么样的选择——是致力于自己创新抑或是模仿和抄袭——在很大程度上取决于对成本和收益的分析。
 
长期以来,中国知识产权保护水平过低,致使许多企业在产品供给过程中不愿意创新,更愿意模仿和抄袭。在专利侵权案件损害赔偿诉讼中,有97.25%的案件适用“法定赔偿”标准,平均赔偿数额仅为7.96万元。相比之下,美国2007-2012年期间专利诉讼赔偿额平均高达2940万元。在商标侵权案件中,法院判赔的平均金额为6.2万元,这与商标经营者长期为维护品牌所花费的巨大心血同样不成正比。知识产权侵权案件赔偿数额过低助长了这种局面的形成:创新者在追求产品品质方面,需要花费大量财力、心力才能有所作为,侵权者只需付出较低成本就可以“抄袭”使用,因此,在中国各类产品供给中模仿痕迹较重,创新能力不足,知识产权纠纷数量居高不下。
 
建议全面引进惩罚性赔偿制度
 
供给侧改革与知识产权密不可分,完善知识产权制度,才能实现真正意义的供给侧改革。基于上述知识产权制度存在的前述问题,蓝皮书建议完善知识产权评价制度,实现供给侧从重数量向重质量转变。在调整专利质量考评体系过程中,应当将原有专利量化的指标调整为专利对于提升产品供给的实际贡献值。无论是涉及到高新技术企业认定,抑或是有关高新企业税收减免,或是专利申请费用减免,以及企业发明创造的相关奖励,有必要取消原有的关于专利量化的规定,而将专利是否实际使用、使用效果、对于产品供给的实际贡献值作为考评指标。在一系列需要企业提交的证明文件中,除专利证书之外有必要提交的是专利对于产品供给发挥实际作用的证明文件。
 
蓝皮书还建议,增加知识产权侵权成本,实现供给侧从模仿向创新转型。虽然专利法在2008年修订时将法定赔偿限额从50万元提升到100万元,但现有赔偿制度对于知识产权侵权依然不具备足够的威慑力,对创新而言也难以发挥有效保障。因此,有必要在知识产权法中全面引进“惩罚性赔偿制度”。
 
同时,降低知识产权保护成本,为供给侧持续创新提供法律保障。为给专利申请人明确的预期,减少预期不确定而带来的成本和风险,专利法有必要就专利申请周期作出明确规范。与其他类型相比较,发明专利因涉及实质审查,其流程最为复杂。专利法有必要针对申请实质审查的期限以及审查结果的期限作出明确规范,其中如涉及提交补正的材料的,也需要就补正时间作出规范。同时,针对实用新型及外观设计专利的审查结果期限作出明确规范。这样,企业在技术升级转型过程中对未来风险就会有相对明确的预期和评估,最大程度减少知识产权申请所带来的成本和风险。
分类:化学化工研究热点 | 固定链接 | 评论: 0 | 引用: 0 | 查看次数: 123

北京大学催化产氢研究取得重大突破

 氢能被誉为下一代二次清洁能源,但氢气的存储和输运一直以来是阻碍氢能源大规模应用的瓶颈。

 
北京大学化学与分子工程学院马丁课题组与中国科学院大学周武、山西煤化所/中科合成油工程有限公司温晓东以及大连理工大学石川等课题组合作,针对甲醇和水液相制氢反应的特点,采用铂-碳化钼双功能催化剂实现对水和甲醇的高效活化,在低温下(150-190oC)获得了极高的产氢效率。此催化体系有望作为下一代高效储放氢新体系得到应用。该研究成果已经在北京大学科技开发部支持下申请专利合作协定(Patent Cooperation Treaty,PCT),相关成果发表于3月23日的Nature上。
 
据悉,氢燃料电池是最具潜力的新一代能量提供系统,它将化学能高效转化为电能,被广泛用于航空航天、汽车以及其他固定和移动能量提供体系中,但是氢气化学性质活泼,氢气的储存就成为氢燃料电池应用的关键。目前,丰田的商业化氢燃料电池汽车的解决方案是使用容量约125L,压力高达700公斤的钢瓶进行储氢,但其安全性不容乐观,并且城市内加氢基础设施建设亦存在一定隐患。
 
此外,目前其他的氢气储放体系,或价格昂贵,或存储容量有限。针对这些不足,一种可能的解决方案是将氢气存储于液体甲醇中,通过水和甲醇的液相重整反应原位产氢供燃料电池使用,在释放出甲醇中存储的氢气的同时也活化等摩尔的水而释放出额外的氢气。
 
具体来说,该研究团队发现将面心立方结构的碳化钼负载的金属铂催化剂应用于甲醇和水液相反应,催化剂表现出超高的产氢活性,在150摄氏度就能以2,276 molH2/(molPt*h)的反应速率释放氢气,进一步提高温度至190摄氏度,放氢速率可达18,046 molH2/(molPt*h),较传统催化剂提升了近两个数量级。
 
仅以产氢活性估计,该催化剂已基本达到商用车载燃料电池组的需求,仅需6克铂即可使产氢速率达到1 kgH2/h。以目前甲醇市场价格(2400元/吨)计算,采用此路径储放氢气,氢燃料电池汽车每百公里燃料价格仅需约13元,而加60-80升甲醇可供家用小轿车行驶600-1000公里。该研究工作构建了化学高效储放氢新体系,为以甲醇为储氢平台分子经燃料电池转化为电能的利用途径提供了新的思路。
 
记者了解到,该团队将进一步优化体系的催化性能,同时积极推动产业化进程。
分类:化学化工研究热点 | 固定链接 | 评论: 0 | 引用: 0 | 查看次数: 89

2016年化学工程领域10大高被引论文

 [1].  Saliba M, Matsui T, Seo J Y, Domanski K, Correa-Baena J P, Nazeeruddin M K, Zakeeruddin S M, Tress W, Abate A, Hagfeldt A, Gratzel M.

Cesium-containing triple cation perovskite solar cells: improved stability, reproducibility and high efficiency[J]. Energy & Environmental Science, 2016, 9(6): 1989-1997.

被引次数:234

[Abstract]Today's best perovskite solar cells use a mixture of formamidinium and methylammonium as the monovalent cations. With the addition of inorganic cesium, the resulting triple cation perovskite compositions are thermally more stable, contain less phase impurities and are less sensitive to processing conditions. This enables more reproducible device performances to reach a stabilized power output of 21.1% and similar to 18% after 250 hours under operational conditions. These properties are key for the industrialization of perovskite photovoltaics.

 

[2].  Berhe T A, Su W N, Chen C H, Pan C J, Cheng J H, Chen H M, Tsai M C, Chen L Y, Dubale A A, Hwang B J.

Organometal halide perovskite solar cells: degradation and stability[J]. Energy & Environmental Science, 2016, 9(2): 323-356.

被引次数:116

[Abstract]Organometal halide perovskite solar cells have evolved in an exponential manner in the two key areas of efficiency and stability. The power conversion efficiency (PCE) reached 20.1% late last year. The key disquiet was stability, which has been limiting practical application, but now the state of the art is promising, being measured in thousands of hours. These improvements have been achieved through the application of different materials, interfaces and device architecture optimizations, especially after the investigation of hole conductor free mesoporous devices incorporating carbon electrodes, which promise stable, low cost and easy device fabrication methods. However, this work is still far from complete. There are various issues associated with the degradation of Omh-perovskite, and the interface and device instability which must be addressed to achieve good reproducibility and long lifetimes for Omh-PSCs with high conversion efficiencies. A comprehensive understanding of these issues is required to achieve breakthroughs in stability and practical outdoor applications of Omh-PSCs. For successful small and large scale applications, besides the improvement of the PCE, the stability of Omh-PSCs has to be improved. The causes of failure and associated mechanisms of device degradation, followed by the origins of degradation, approaches to improve stability, and methods and protocols are discussed in detail and form the main focus of this review article.

 

[3].  Chong Z R, Yang S H B, Babu P, Linga P, Li X S.

Review of natural gas hydrates as an energy resource: Prospects and challenges[J]. Applied Energy, 2016, 1621633-1652.

被引次数:76

[Abstract]Natural gas is the cleanest burning fossil fuel and has been identified as a strong candidate for energy resource compared to oil and coal. Natural gas hydrate is an energy resource for methane that has a carbon quantity twice more than all fossil fuels combined and is distributed evenly around the world. Several field trials on energy production from hydrate resources have been conducted, and their outcomes revealed the possibility of energy production from hydrate resources. In this paper, we review various studies on resource potential of natural gas hydrate, the current research progress in laboratory settings, and several recent field trials. Possible limitation in each production method and the challenges to be addressed for large scale production are discussed in detail. Whilst there are no technology stoppers to exploit or produce methane from hydrates, specific technological breakthroughs will depend on the effective management of the sand and water during production, as well as the appropriate mitigation of environmental risks. (C) 2015 Elsevier Ltd. All rights reserved.

 

[4].  Yi C Y, Luo J S, Meloni S, Boziki A, Ashari-Astani N, Gratzel C, Zakeeruddin S M, Rothlisberger U, Gratzel M.

Entropic stabilization of mixed A-cation ABX(3) metal halide perovskites for high performance perovskite solar cells[J]. Energy & Environmental Science, 2016, 9(2): 656-662.

被引次数:76

[Abstract]ABX(3)-type organic lead halide perovskites currently attract broad attention as light harvesters for solar cells due to their high power conversion efficiency (PCE). Mixtures of formamidinium (FA) with methylammonium (MA) as A-cations show currently the best performance. Apart from offering better solar light harvesting in the near IR the addition of methylammonium stabilizes the perovskite phase of FAPbI(3) which in pure form at room temperature converts to the yellow photovoltaically inactive delta-phase. We observe a similar phenomenon upon adding Cs+ cations to FAPbI(3). CsPbI3 and FAPbI3 both form the undesirable yellow phase under ambient condition while the mixture forms the desired black pervoskite. Solar cells employing the composition Cs(0.2)FA(0.8)PbI(2.84)Br(0.16) yield high average PCEs of over 17% exhibiting negligible hysteresis and excellent long term stability in ambient air. We elucidate here this remarkable behavior using first principle computations. These show that the remarkable stabilization of the perovskite phase by mixing the A-cations stems from entropic gains and the small internal energy input required for the formation of their solid solution. By contrast, the energy of formation of the delta-phase containing mixed cations is too large to be compensated by this configurational entropy increase. Our calculations reveal for the first time the optoelectronic properties of such mixed A-cation perovskites and the underlying reasons for their excellent performance and high stability.

 

[5].  Kim H, Lim K G, Lee T W.

Planar heterojunction organometal halide perovskite solar cells: roles of interfacial layers[J]. Energy & Environmental Science, 2016, 9(1): 12-30.

被引次数:74

[Abstract]Organometal halide perovskites are promising photo-absorption materials in solar cells due to their high extinction coefficient, broad light absorption range and excellent semiconducting properties. The highest power conversion efficiency (PCE) of perovskite solar cells (PrSCs) is now 20.1%. However, a high-temperature processed mesoscopic metal oxide (e.g., TiO2) must be removed to realize flexible PrSCs on plastic substrates using low temperature processes. Although the planar heterojunction (PHJ) structure can be considered as the most appropriate structure for flexible PrSCs, they have shown lower PCEs than those with a mesoscopic metal oxide layer. Therefore, development of interfacial layers is essential for achieving highly efficient PHJ PrSCs, and necessary in fabrication of flexible PrSCs. This review article gives an overview of progress in PHJ PrSCs and the roles of interfacial layers in the device, and suggests a practical strategy to fabricate highly efficient and flexible PHJ PrSCs. We conclude with our technical suggestion and outlook for further research direction.

 

[6].  Albrecht S, Saliba M, Baena J P C, Lang F, Kegelmann L, Mews M, Steier L, Abate A, Rappich J, Korte L, Schlatmann R, Nazeeruddin M K, Hagfeldt A, Gratzel M, Rech B.

Monolithic perovskite/silicon-heterojunction tandem solar cells processed at low temperature[J]. Energy & Environmental Science, 2016, 9(1): 81-88.

被引次数:65

[Abstract]Tandem solar cells combining silicon and perovskite absorbers have the potential to outperform state-of-the-art high efficiency silicon single junction devices. However, the practical fabrication of monolithic silicon/perovskite tandem solar cells is challenging as material properties and processing requirements such as temperature restrict the device design. Here, we fabricate an 18% efficient monolithic tandem cell formed by a silicon heterojunction bottom-and a perovskite top-cell enabling a very high open circuit voltage of 1.78 V. The monolithic integration was realized via low temperature processing of the semitransparent perovskite sub-cell where an energetically aligned electron selective contact was fabricated by atomic layer deposition of tin oxide. The hole selective, transparent top contact was formed by a stack of the organic hole transport material spiro-OMeTAD, molybdenum oxide and sputtered indium tin oxide. The tandem cell design is currently limited by the photo-current generated in the silicon bottom cell that is reduced due to reflectance losses. Based on optical modelling and first experiments, we show that these losses can be significantly reduced by combining optical optimization of the device architecture including light trapping approaches.

 

[7].  Hong Y Z, Jiang Y H, Li C S, Fan W Q, Yan X, Yan M, Shi W D.

In-situ synthesis of direct solid-state Z-scheme V2O5/g-C3N4 heterojunctions with enhanced visible light efficiency in photocatalytic degradation of pollutants[J]. Applied Catalysis B-Environmental, 2016, 180663-673.

被引次数:59

[Abstract]The constructing of direct solid-state Z-scheme heterojunction photocatalytic system has received much attention in environmental purification and hydrogen generation from water. In this study, a novel direct solid-state Z-scheme V2O5/g-C3N4 heterojunctions were synthesized via a facile in-situ growth strategy for the first time. The photocatalytic performance was evaluated by the degradation of rhodamine B (RhB) and tetracycline (TC) under visible light irradiation (lambda > 420 nm). Results show that the as-synthesized heterojunctions can significantly enhance photocatalytic activity in comparison with pure g-C3N4 and V2O5. The optimum photocatalytic efficiency of VC1.0% sample for the degradation RhB was about 7.3 and 13.0 times higher than that of individual g-C3N4 and V2O5, respectively. In addition, the VC1.0% sample as well as can efficiently degrade methyl orange (MO) and methylene blue (MB) under visible light. By further experimental study, the possible for the enhancing photocatalytic mechanism was found to be a direct solid-state Z-scheme heterojunction system based on the active species trapping and electron spin resonance (ESR) experiments, which not only can improve the photogenerated electron-hole pair's separation but also exhibit a strong oxidation and reduction ability for efficiency degradation of organic pollutants. This work will be useful for the design of other direct solid-state Z-scheme photocatalytic systems for application in energy conversion and environmental remediation. (C) 2015 Elsevier B.V. All rights reserved.

 

[8].  An Q S, Zhang F J, Zhang J, Tang W H, Deng Z B, Hu B.

Versatile ternary organic solar cells: a critical review[J]. Energy & Environmental Science, 2016, 9(2): 281-322.

被引次数:57

[Abstract]The power conversion efficiency (PCE) of organic solar cells has been constantly refreshed in the past ten years from 4% up to 11% due to the contribution from the chemists on novel materials and the physicists on device engineering. For practical applications, a single bulk heterojunction structure may be the best candidate due to the cell with a high PCE, easy fabrication and low cost. Recently, ternary solar cells have attracted much attention due to enhanced photon harvesting by using absorption spectral or energy level complementary materials as the second donor or acceptor based on a single bulk heterojunction structure. For better promoting the development of ternary solar cells, we summarize the recent progress of ternary solar cells and try our best to concise out the scientific issues in preparing high performance ternary solar cells.

 

[9].  Hu P D, Long M C.

Cobalt-catalyzed sulfate radical-based advanced oxidation: A review on heterogeneous catalysts and applications[J]. Applied Catalysis B-Environmental, 2016, 181103-117.

被引次数:56

[Abstract]Recently sulfate radical-based advanced oxidation processes (SR-AOP5) attract increasing attention due to their capability and adaptability in decontamination. The couple of cobalt and peroxymonosulfate (PMS) is an efficient way to produce reactive sulfate radicals. This article reviews the state-of-the-art progress on various heterogeneous cobalt-based catalysts for PMS activation, including cobalt oxides, cobalt-ferrite and supported cobalt by diverse substrates. We summarize the intrinsic properties of these catalysts and their fundamental behaviors in PMS activation, as well as synthetic approaches. In addition, influencing factors and synergistic techniques of Co/PMS systems in organic degradation and possible environmental applications are also discussed. Finally, we propose perspectives on challenges related to cobalt-based catalysts, heterogeneous Co/PMS systems and their potential applications in practical environmental cleanup. (C) 2015 Elsevier B.V. All rights reserved.

 

[10].       Li S X, Liu W Q, Shi M M, Mai J Q, Lau T K, Wan J H, Lu X H, Li C Z, Chen H Z.

A spirobifluorene and diketopyrrolopyrrole moieties based non-fullerene acceptor for efficient and thermally stable polymer solar cells with high open-circuit voltage[J]. Energy & Environmental Science, 2016, 9(2): 604-610.

被引次数:55

[Abstract]In this study, we design and synthesize a new non-fullerene electron acceptor, SF(DPPB)(4), in which a spirobifluorene (SF) core is installed with four benzene endcapped diketopyrrolopyrrole (DPP) arms. SF(DPPB)(4) exhibits energy levels matching perfectly with those of the commonly used poly(3-hexyl thiophene) (P3HT) donor in polymer solar cells (PSCs). Furthermore, a designed cross-shaped molecular geometry helps in suppressing strong intermolecular aggregation in the P3HT:SF(DPPB)(4) blend, leading to efficient non-fullerene PSCs. The resultant devices give a maximum power conversion efficiency (PCE) of 5.16% with an extremely high open-circuit voltage (V-oc) of 1.14 V. In contrast, the devices based on P3HT:PC61BM blends provide a PCE of 3.18% with a V-oc of 0.62 V. Finally, we observe that the P3HT:SF(DPPB)(4) devices exhibit significantly improved thermal stability from that of the P3HT:PC61BM devices; upon thermal treatment at 150 degrees C for 3 h, the PCEs of P3HT:SF(DPPB)(4) devices remain unchanged, whereas those of the P3HT:PC61BM devices drop drastically to below 1%. The abovementioned results demonstrate that the new design strategy of employing a high-performance non-fullerene acceptor, SF(DPPB)(4), is promising for the future practical application of PSCs.

分类:化学化工研究热点 | 固定链接 | 评论: 0 | 引用: 0 | 查看次数: 322

2016年有机化学领域10大高被引论文

 [1].  Porta R, Benaglia M, Puglisi A.

Flow Chemistry: Recent Developments in the Synthesis of Pharmaceutical Products[J]. organic Process Research & Development, 2016, 20(1): 2-25.

被引次数:46

[Abstract]Recently, application of the flow technologies for the preparation of fine chemicals, such as natural products or Active Pharmaceutical Ingredients (APIs), has become very popular, especially in academia. Although pharma industry still relies on multipurpose batch or semibatch reactors, it is evident that interest is arising toward continuous flow manufacturing of organic molecules, including highly functionalized and chiral compounds. Continuous flow synthetic methodologies can also be easily combined to other enabling technologies, such as microwave irradiation, supported reagents or catalysts, photochemistry, inductive heating, electrochemistry, new solvent systems, 3D printing, or microreactor technology. This combination could allow the development of fully automated process with an increased efficiency and, in many cases, improved sustainability. It has been also demonstrated that a safer manufacturing of organic intermediates and APIs could be obtained under continuous flow conditions, where some synthetic steps that were not permitted for safety reasons can be performed with minimum risk. In this review we focused our attention only on very recent advances in the continuous flow multistep synthesis of organic molecules which found application as APIs, especially highlighting the contributions described in the literature from 2013 to 2015, including very recent examples not reported in any published review. Without claiming to be complete, we will give a general overview of different approaches, technologies, and synthetic strategies used so far, thus hoping to contribute to minimize the gap between academic research and pharmaceutical manufacturing. A general outlook about a quite young and relatively unexplored field of research, like stereoselective organocatalysis under flow conditions, will be also presented, and most significant examples will be described; our purpose is to illustrate all of the potentialities of continuous flow organocatalysis and offer a starting point to develop new methodologies for the synthesis of chiral drugs. Finally, some considerations on the perspectives and the possible, expected developments in the field are briefly discussed.

 

[2].  Blunt J W, Copp B R, Keyzers R A, Munro M H G, Prinsep M R.

Marine natural products[J]. Natural Product Reports, 2016, 33(3): 382-431.

被引次数:45

[Abstract]This review covers the literature published in 2014 for marine natural products (MNPs), with 1116 citations (753 for the period January to December 2014) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1378 in 456 papers for 2014), together with the relevant biological activities, source organisms and country of origin. Reviews, biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.

 

[3].  Kong L H, Yu S J, Zhou X K, Li X W.

Redox-Neutral Couplings between Amides and Alkynes via Cobalt(III)-Catalyzed C-H Activation[J]. organic Letters, 2016, 18(3): 588-591.

被引次数:37

[Abstract]C-H activation assisted by a bifunctional directing group has allowed the construction of heterocycles. This is ideally catalyzed by earth-abundant and eco-friendly transition metals. We report Co(III)-catalyzed redox-neutral coupling between arenes and alkynes using an NH amide as an electrophilic directing group. The redox-neutral C-H activation/coupling afforded quinolines with water as the sole byproduct.

 

[4].  Meng G R, Szostak M.

Rhodium-Catalyzed C-H Bond Functionalization with Amides by Double C-H/C-N Bond Activation[J]. organic Letters, 2016, 18(4): 796-799.

被引次数:36

[Abstract]The first C-H bond functionalization with amides as the coupling partners via selective activation of the amide N-C bond using rhodium(I) catalysts under highly chemoselective conditions is reported. Notably, this report constitutes the first catalytic activation of the amide N-C(O) bond by rhodium. We expect that this concept will have broad implications for using amides as coupling partners for C-H activation beyond the work described herein.

 

[5].  Hubner S, de Vries J G, Farina V.

Why Does Industry Not Use Immobilized Transition Metal Complexes as Catalysts?[J]. Advanced Synthesis & Catalysis, 2016, 358(1): 3-25.

被引次数:35

[Abstract]Much effort has gone into the immobilization of homogeneous catalysts based on the idea that in this way the catalysts could be not only separated more easily from the product but also reused several times, thus reducing the cost of the catalyst use. So far none of these immobilized catalysts have been used by industry. In this article we critically review the use of immobilized homogeneous catalysts from the point of view of process development for the pharmaceutical and fine chemical industry. The first and foremost question that needs to be answered is: will immobilizing a homogeneous catalyst really lead to lower costs? The answer is thus far always no. This is caused mostly by the fact that homogeneous catalysts are not stable and thus there is little point in immobilizing them. The second reason is the extra added cost that is incurred in immobilizing the catalysts. Other problems are lower rates, sometimes lower selectivities and metal leaching. Three different areas are discussed. The research on immobilized metathesis catalysts is analyzed in detail; in general the immobilized catalysts do not achieve sufficient turnovers to be interesting for industrial use. Very many publications have appeared on immobilized palladium catalysts that were used for C-C bond-forming reactions, such as Suzuki, Heck or Sonoga-shira reactions. These catalysts are invariably converted to nanoparticles after the first run. Although these catalysts can be reused, there is no reason to use an expensive support based on immobilized ligands. This also does not protect the product from palladium contamination. Even more effort has gone into the immobilization of homogeneous hydrogenation catalysts. Most of these catalysts suffer from the same problems as the other immobilized catalysts: catalyst deactivation, low turnover numbers, and leaching of the metal. In addition, the heterogenization adds complexity to the system, increasing risk and prolonging process development.

 

[6].  Shaw M H, Twilton J, MacMillan D W C.

Photoredox Catalysis in organic Chemistry[J]. Journal Of organic Chemistry, 2016, 81(16): 6898-6926.

被引次数:33

[Abstract]In recent years, photoredox catalysis has come to the forefront in organic chemistry as a powerful strategy for the activation of small molecules. In a general sense, these approaches rely on the ability of metal complexes and organic dyes to convert visible light into chemical energy by engaging in single-electron transfer with organic substrates, thereby generating reactive intermediates. In this Perspective, we highlight the unique ability of photoredox catalysis to expedite the development of completely new reaction mechanisms, with particular emphasis placed on multicatalytic strategies that enable the construction of challenging carbon-carbon and carbon-heteroatom bonds.

 

[7].  Wang F, Wang H, Wang Q, Yu S J, Li X W.

Co(III)-Catalyzed Synthesis of Quinazolines via C-H Activation of N-Sulfinylimines and Benzimidates[J]. organic Letters, 2016, 18(6): 1306-1309.

被引次数:32

[Abstract]C-H activation of arenes has been established as an important strategy for heterocycle synthesis via annulations between arenes and unsaturated coupling partners. However, nitriles failed to act as such a coupling partner. Dioxazolones have been employed as a synthon of nitriles, and subsequent coupling with arenes such as N-sulfinylimines and benzimidates bearing a functionalizable directing group provided facile access to two classes of quinazolines under Co(III)-catalysis.

 

[8].  Nam S, French A D, Condon B D, Concha M.

Segal crystallinity index revisited by the simulation of X-ray diffraction patterns of cotton cellulose I beta and cellulose II[J]. Carbohydrate Polymers, 2016, 1351-9.

被引次数:27

[Abstract]The Segal method estimates the amorphous fraction of cellulose I beta materials simply based on intensity at 18 degrees 2 theta in an X-ray diffraction pattern and was extended to cellulose II using 16 degrees 2 theta intensity. To address the dependency of Segal amorphous intensity on crystal size, cellulose polymorph, and the degree of polymorphic conversion, we simulated the diffraction patterns of cotton celluloses (1 beta and II) and compared the simulated amorphous fractions with the Segal values. The diffraction patterns of control and mercerized cottons, respectively, were simulated with perfect crystals of cellulose I beta (1.54 degrees FWHM) and cellulose 11 (2.30 degrees FWHM) as well as 10% and 35% amorphous celluloses. Their Segal amorphous fractions were 15% and 31%, respectively. The higher Segal amorphous fraction for control cotton was attributed to the peak overlap. Although the amorphous fraction was set in the simulation, the peak overlap induced by the increase of FWHM further enhanced the Segal amorphous intensity of cellulose I beta. For cellulose II, the effect of peak overlap was smaller; however the lower reflection of the amorphous cellulose scattering in its Segal amorphous location resulted in smaller Segal amorphous fractions. Despite this underestimation, the relatively good agreement of the Segal method with the simulation for mercerized cotton was attributed to the incomplete conversion to cellulose II. The (1 - 10) and (1 - 10) peaks of cellulose I beta remained near the Segal amorphous location of cellulose II for blends of control and mercerized cotton fibers.

 

[9].  Patel N R, Kelly C B, Jouffroy M, Molander G A.

Engaging Alkenyl Halides with Alkylsilicates via Photoredox Dual Catalysis[J]. organic Letters, 2016, 18(4): 764-767.

被引次数:26

[Abstract]Single-electron transmetalation via photoredox/nickel dual catalysis provides the opportunity for the construction of C-sp3-C-sp2 bonds through the transfer of alkyl radicals under very mild reaction conditions. A general procedure for the cross coupling of primary and secondary (bis-catecholato)alkylsilicates with alkenyl halides is presented. The developed method allows not only alkenyl bromides and iodides but also previously underexplored alkenyl chlorides to be employed.

 

[10].       Jia J H, Liu Z, Xiao X, Liu B X, Chou K C.

iPPBS-Opt: A Sequence-Based Ensemble Classifier for Identifying Protein-Protein Binding Sites by Optimizing Imbalanced Training Datasets[J]. Molecules, 2016, 21(1).

被引次数:26

[Abstract]Knowledge of protein-protein interactions and their binding sites is indispensable for in-depth understanding of the networks in living cells. With the avalanche of protein sequences generated in the postgenomic age, it is critical to develop computational methods for identifying in a timely fashion the protein-protein binding sites (PPBSs) based on the sequence information alone because the information obtained by this way can be used for both biomedical research and drug development. To address such a challenge, we have proposed a new predictor, called iPPBS-Opt, in which we have used: (1) the K-Nearest Neighbors Cleaning (KNNC) and Inserting Hypothetical Training Samples (IHTS) treatments to optimize the training dataset; (2) the ensemble voting approach to select the most relevant features; and (3) the stationary wavelet transform to formulate the statistical samples. Cross-validation tests by targeting the experiment-confirmed results have demonstrated that the new predictor is very promising, implying that the aforementioned practices are indeed very effective. Particularly, the approach of using the wavelets to express protein/peptide sequences might be the key in grasping the problem's essence, fully consistent with the findings that many important biological functions of proteins can be elucidated with their low-frequency internal motions. To maximize the convenience of most experimental scientists, we have provided a step-by-step guide on how to use the predictor's web server (http://www.jci-bioinfo.cn/iPPBS-Opt) to get the desired results without the need to go through the complicated mathematical equations involved.

分类:化学化工研究热点 | 固定链接 | 评论: 0 | 引用: 0 | 查看次数: 93

2016年化学领域10大高被引论文

[1].  Groom C R, Bruno I J, Lightfoot M P, Ward S C.

The Cambridge Structural Database[J]. Acta Crystallographica Section B-Structural Science Crystal Engineering And Materials, 2016, 72171-179.

被引次数:370

[Abstract]The Cambridge Structural Database (CSD) contains a complete record of all published organic and metal-organic small-molecule crystal structures. The database has been in operation for over 50 years and continues to be the primary means of sharing structural chemistry data and knowledge across disciplines. As well as structures that are made public to support scientific articles, it includes many structures published directly as CSD Communications. All structures are processed both computationally and by expert structural chemistry editors prior to entering the database. A key component of this processing is the reliable association of the chemical identity of the structure studied with the experimental data. This important step helps ensure that data is widely discoverable and readily reusable. Content is further enriched through selective inclusion of additional experimental data. Entries are available to anyone through free CSD community web services. Linking services developed and maintained by the CCDC, combined with the use of standard identifiers, facilitate discovery from other resources. Data can also be accessed through CCDC and third party software applications and through an application programming interface.

 

[2].  Saliba M, Matsui T, Seo J Y, Domanski K, Correa-Baena J P, Nazeeruddin M K, Zakeeruddin S M, Tress W, Abate A, Hagfeldt A, Gratzel M.

Cesium-containing triple cation perovskite solar cells: improved stability, reproducibility and high efficiency[J]. Energy & Environmental Science, 2016, 9(6): 1989-1997.

被引次数:234

[Abstract]Today's best perovskite solar cells use a mixture of formamidinium and methylammonium as the monovalent cations. With the addition of inorganic cesium, the resulting triple cation perovskite compositions are thermally more stable, contain less phase impurities and are less sensitive to processing conditions. This enables more reproducible device performances to reach a stabilized power output of 21.1% and similar to 18% after 250 hours under operational conditions. These properties are key for the industrialization of perovskite photovoltaics.

 

[3].  Zhao W C, Qian D P, Zhang S Q, Li S S, Inganas O, Gao F, Hou J H.

Fullerene-Free Polymer Solar Cells with over 11% Efficiency and Excellent Thermal Stability[J]. Advanced Materials, 2016, 28(23): 4734-4739.

被引次数:179

[Abstract]A nonfullerene-based polymer solar cell (PSC) that significantly outperforms fullerene-based PSCs with respect to the power-conversion efficiency is demonstrated for the first time. An efficiency of >11%, which is among the top values in the PSC field, and excellent thermal stability is obtained using PBDB-T and ITIC as donor and acceptor, respectively.

 

[4].  Cavallo G, Metrangolo P, Milani R, Pilati T, Priimagi A, Resnati G, Terraneo G.

The Halogen Bond[J]. Chemical Reviews, 2016, 116(4): 2478-2601.

被引次数:156

[Abstract]The halogen bond occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity. In this fairly extensive review, after a brief history of the interaction, we will provide the reader with a snapshot of where the research on the halogen bond is now, and, perhaps, where it is going. The specific advantages brought up by a design based on the use of the halogen bond will be demonstrated in quite different fields spanning from material sciences to biomolecular recognition and drug design.

 

[5].  Meng D, Sun D, Zhong C M, Liu T, Fan B B, Huo L J, Li Y, Jiang W S, Choi H S, Kim T, Kim J Y, Sun Y M, Wang Z H, Heeger A J.

High-Performance Solution-Processed Non-Fullerene organic Solar Cells Based on Selenophene-Containing Perylene Bisimide Acceptor[J]. Journal Of the American Chemical Society, 2016, 138(1): 375-380.

被引次数:122

[Abstract]Non-fullerene acceptors have recently attracted tremendous interest because of their potential as alternatives to fullerene derivatives in bulk heterojunction organic solar cells. However, the power conversion efficiencies (PCEs) have lagged far behind those of the polymer/fullerene system, mainly because of the low fill factor (FF) and photocurrent. Here we report a novel perylene bisimide (PBI) acceptor, SdiPBI-Se, in which selenium atoms were introduced into the perylene core. With a well-established wide-band-gap polymer (PDBT-T1) as the donor, a high efficiency of 8.4% with an unprecedented high FF of 70.2% is achieved for solution-processed non-fullerene organic solar cells. Efficient photon absorption, high and balanced charge carrier mobility, and ultrafast charge generation processes in PDBT-T1:SdiPBI-Se films account for the high photovoltaic performance. Our results suggest that non-fullerene acceptors have enormous potential to rival or even surpass the performance of their fullerene counterparts.

 

[6].  Shao M H, Chang Q W, Dodelet J P, Chenitz R.

Recent Advances in Electrocatalysts for Oxygen Reduction Reaction[J]. Chemical Reviews, 2016, 116(6): 3594-3657.

被引次数:120

[Abstract]The recent advances in electrocatalysis for oxygen reduction reaction (ORR) for proton exchange membrane fuel cells (PEMFCs) are thoroughly reviewed. This comprehensive Review focuses on the low- and non-platinum electrocatalysts including advanced platinum alloys, core shell structures, palladium-based catalysts, metal oxides and chalcogenides, carbon-based non-noble metal catalysts, and metal-free catalysts. The recent development of orR electrocatalysts with novel structures and compositions is highlighted. The understandings of the correlation between the activity and the shape, size, composition, and synthesis method are summarized. For the carbon based materials, their performance and stability in fuel cells and comparisons with those of platinum are documented. The research directions as well as perspectives on the further development of more active and less expensive electrocatalysts are provided.

 

[7].  Wang J H, Cui W, Liu Q, Xing Z C, Asiri A M, Sun X P.

Recent Progress in Cobalt-Based Heterogeneous Catalysts for Electrochemical Water Splitting[J]. Advanced Materials, 2016, 28(2): 215-230.

被引次数:118

[Abstract]Water electrolysis is considered as the most promising technology for hydrogen production. Much research has been devoted to developing efficient electrocatalysts for hydrogen production via the hydrogen evolution reaction (HER) and oxygen production via the oxygen evolution reaction (OER). The optimum electrocatalysts can drive down the energy costs needed for water splitting via lowering the overpotential. A number of cobalt (Co)-based materials have been developed over past years as non-noble-metal heterogeneous electrocatalysts for HER and OER. Recent progress in this field is summarized here, especially highlighting several important bifunctional catalysts. Various approaches to improve or optimize the electrocatalysts are introduced. Finally, the current existing challenges and the future working directions for enhancing the performance of Co-implicated electrocatalysts are proposed.

 

[8].  Berhe T A, Su W N, Chen C H, Pan C J, Cheng J H, Chen H M, Tsai M C, Chen L Y, Dubale A A, Hwang B J.

Organometal halide perovskite solar cells: degradation and stability[J]. Energy & Environmental Science, 2016, 9(2): 323-356.

被引次数:116

[Abstract]Organometal halide perovskite solar cells have evolved in an exponential manner in the two key areas of efficiency and stability. The power conversion efficiency (PCE) reached 20.1% late last year. The key disquiet was stability, which has been limiting practical application, but now the state of the art is promising, being measured in thousands of hours. These improvements have been achieved through the application of different materials, interfaces and device architecture optimizations, especially after the investigation of hole conductor free mesoporous devices incorporating carbon electrodes, which promise stable, low cost and easy device fabrication methods. However, this work is still far from complete. There are various issues associated with the degradation of Omh-perovskite, and the interface and device instability which must be addressed to achieve good reproducibility and long lifetimes for Omh-PSCs with high conversion efficiencies. A comprehensive understanding of these issues is required to achieve breakthroughs in stability and practical outdoor applications of Omh-PSCs. For successful small and large scale applications, besides the improvement of the PCE, the stability of Omh-PSCs has to be improved. The causes of failure and associated mechanisms of device degradation, followed by the origins of degradation, approaches to improve stability, and methods and protocols are discussed in detail and form the main focus of this review article.

 

[9].  Li X, Yu J G, Jaroniec M.

Hierarchical photocatalysts[J]. Chemical Society Reviews, 2016, 45(9): 2603-2636.

被引次数:114

[Abstract]As a green and sustainable technology, semiconductor-based heterogeneous photocatalysis has received much attention in the last few decades because it has potential to solve both energy and environmental problems. To achieve efficient photocatalysts, various hierarchical semiconductors have been designed and fabricated at the micro/nanometer scale in recent years. This review presents a critical appraisal of fabrication methods, growth mechanisms and applications of advanced hierarchical photocatalysts. Especially, the different synthesis strategies such as two-step templating, in situ template-sacrificial dissolution, self-templating method, in situ template-free assembly, chemically induced self-transformation and post-synthesis treatment are highlighted. Finally, some important applications including photocatalytic degradation of pollutants, photocatalytic H-2 production and photocatalytic CO2 reduction are reviewed. A thorough assessment of the progress made in photocatalysis may open new opportunities in designing highly effective hierarchical photocatalysts for advanced applications ranging from thermal catalysis, separation and purification processes to solar cells.

 

[10].       Studer A, Curran D P.

Catalysis of Radical Reactions: A Radical Chemistry Perspective[J]. Angewandte Chemie-International Edition, 2016, 55(1): 58-102.

被引次数:108

[Abstract]The area of catalysis of radical reactions has recently flourished. Various reaction conditions have been discovered and explained in terms of catalytic cycles. These cycles rarely stand alone as unique paths from substrates to products. Instead, most radical reactions have innate chains which form products without any catalyst. How do we know if a species added in "catalytic amounts" is a catalyst, an initiator, or something else? Herein we critically address both catalystfree and catalytic radical reactions through the lens of radical chemistry. Basic principles of kinetics and thermodynamics are used to address problems of initiation, propagation, and inhibition of radical chains. The catalysis of radical reactions differs from other areas of catalysis. Whereas efficient innate chain reactions are difficult to catalyze because individual steps are fast, both inefficient chain processes and non-chain processes afford diverse opportunities for catalysis, as illustrated with selected examples. 

分类:化学化工研究热点 | 固定链接 | 评论: 0 | 引用: 0 | 查看次数: 98

 上世纪30年代,一名英国化学家做了一项由好奇心驱动的观察,这个观察今天仍处于该化学物质安全性争论的中心。他注意到,合成化学物双酚基丙烷(BPA)能够较弱地模仿人体雌性激素。在接下来的数十年,BPA成为环氧树脂和聚碳酸酯塑料的普遍成分,被用于从塑封到塑料水瓶的各个地方,每年用量可达数百万吨。

但BPA并不会原地不动。20世纪90年代,美国斯坦福大学研究人员发现塑料会渗透微量BPA。研究人员和公众已经在担心其他类似荷尔蒙的化合物会干扰内分泌系统,他们担心BPA的轨迹是否会造成一些危害。
现在,测试已经在超过90%的美国人体内发现这种化学物质。但BPA污染依然处于争议之中。一个原因是研究曾产生冲突性的或非总结性的结论,这在部分程度上是因为内分泌系统的选择可能是细微的,而且很难确定。另一个原因是科学家和管理机构对于哪种研究能够最好地塑造政府对化学品的监管存在分歧。
2014年,美国食药监局(FDA)对关于BPA潜在健康影响的161篇新研究做了审查。其目标是了解科学是否能对这种化合物的安全性做出明确判断,从而为监管人员照亮道路。汇集的证据包括发表于同行评议期刊的论文,其中很多文章发现的证据支持微量BPA能够改变人体的观点。然而,官方科学家则认为这些研究中的大多数对于制定政策没有价值。他们发现决定BPA剂量安全的足够引起注意的文章仅有4篇。但没有一篇文章报告小剂量的影响。
现在,一些科学家和监管人员正在就如何弥补这一分歧全力以赴。其中最雄心勃勃的是由北卡罗来纳州国家环境健康科学研究所(NIEHS)领头的斥资3000万美元的一项计划。它正在让学术界和政府科学家联合他们的方法,以更好地了解BPA的潜在风险,并为评估化学物质的安全性提供新的模型。但这个项目遇到的各种颠簸,说明了它有多难。
 
始于丑闻
 
目前的僵局可追溯到1976年伊利诺伊州芝加哥市区一家充满老鼠的实验室。当时由于FDA一名病理学家怀疑其测试报告良好到有些不真实,联邦办公室于是开始调查这个名为产业生物监测的实验室。彼时,生物监测是美国最大的一家私人化学测试实验室,它被产业界用来尝试满足联邦安全标准。
恶劣的实验室条件和被篡改的数据丑闻,随后引发对该公司3名顶级科学家的国会听证会和刑事定罪。它还促使美国政府采用《良好实验室管理规范》(GLP)。相关规范列出了广泛的监管、审查和做记录的要求,以确保实验室程序遵循流程,数据不会被捏造。
对于在监管竞技场上工作的私人和政府实验室来说,GLP已经成为必要。但却鲜少有学界研究人员使用它,取而代之,他们会依赖资助机构、同行评议期刊和大学委员会对其工作的审核。“文字负担极度繁琐。”伊利诺伊大学再生毒理学家、参与上述大规模BPA研究的Jodi Flaws说,“我觉得大多数学界研究人员都是诚实的,会做良好的记录以重复实验。但我认为GLP报告是一个完全不同的水平。”
随着20世纪80年代化学管理规范的成熟,这些实验室规则被拿来与新标准做对比,新标准说明了监管人员想看到评估一种特殊健康效应有哪些种类的验证,比如一种化学物质是否会导致癌症。今天,这些指导性测试有数百种,它们大多数由经济合作与发展组织(OECD)维护,这是一家由35个国家在二战后建立的位于法国巴黎的联盟。
OECD起草研究指导规范的部门主任Bob Diderich说,监管者应该衡量证据,即便它并非来自按指导规范开展的研究。他表示,很难弄清楚如何应对利用前沿技术如独立基因组学开展的学术研究,它会建立基因活动中因为毒性化学物质而改变的模式。“它在真实世界中意味着什么?它如何转译为对人体和动物的影响?你在判断这些时存在困难。”Diderich说。
 
科学审核
 
FDA对关于小剂量BPA影响的科学应对方式说明了这两种研究之间存在鸿沟。
2008年,该机构宣布人们从食物中吸收的BPA水平不会造成任何健康风险。它主要依赖两项根据GLP指导规范进行的研究,这两项研究并未发现低剂量摄入BPA会造成危害的证据,它们均由一家受塑料产业资助的私人实验室完成。从那时起,FDA就对新出现的研究评估了若干次。现在,它已经因为BPA对大脑、行为和前列腺的影响而表示担忧,但却并未改变其整体评估结果,即人们从食物中摄取到的剂量不会造成风险。而且,它还继续将很多学术研究划归为错误或不能用于制定监管标准的类别。
马里兰州FDA毒理学家、主导这些观点的Jason Aungst说,尽管学界研究能够表现出“极大的灵活性”,但他们更多地聚焦在解释化学物质如何影响有机物的机制上,而不是测量一种化学物质的毒性有多大。“通常,当我们看到遵照指导规范的研究时,它们是已经验证过的研究,在多个实验室测试了很多次,并已经形成可重复性的结果,我们可以有信心地在安全水平上使用。”Aungst补充说。
但一些学界研究人员说,规范指导研究依赖的是过期的测试方法。他们指出,越来越多的研究发现小剂量BPA会导致从焦虑到糖尿病等各种影响。例如,北卡罗莱纳州立大学神经毒理学家Heather Patisaul长期研究小鼠出生前接触微量BPA后对其神经系统产生的影响。通过观察大脑中的信使核糖核酸水平,她发现接触BPA的小鼠下丘脑和杏仁核(这些结构会影响生殖和行为)中含有更丰富的雌激素受体。
 
弥合分歧
 
NIEHS主任、内分泌学家Linda Birnbaum想知道是否能够通过让学界和FDA科学家合作结束这些纷争。
“21世纪的研究和方法正在揭示人类生物学的影响和化学物质或药物的效用,而用一些指导性研究往往并不能得到明确结果。”Birnbaum回忆说。所以“我们提出了传统指导性研究中不会被问及的12个问题”。这个斥资3000万美元的项目名为“学术界和监管机构BPA毒性联合调查”(CLARITY-BPA),于2012年启动。它跨越了12个高校实验室和阿肯色州FDA国家毒理学研究中心。在那里,实验室工作人员根据GLP规范内容饲养了3800多只大鼠,并让其中一部分接触BPA。
相关结果正在逐渐形成。与此前的研究类似,若干所大学科学家说他们看到摄入少量BPA之后的影响。Patisaul的实验室又一次发现小剂量BPA影响大脑雌激素受体的证据。
Birnbaum表示,“我们认为它(CLARITY)可以作为未来研究的一个模型。对于具有重要产业作用的一种大量使用的化合物来说,或者值得再次采取这种方法。”Birnbaum希望,通过学术工作和对同样大规模大鼠的新指导性研究(FDA计划在2018年公布结果),最终能够对BPA的风险作出明确的结论。因为该研究是CLARITY项目的一部分,高校科学家从一开始就参加了研究设计。
 
《科学》文章原文:In BPA safety war, a battle over evidence
http://www.sciencemag.org/news/2017/02/bpa-safety-war-battle-over-evidence
分类:化学化工研究热点 | 固定链接 | 评论: 0 | 引用: 0 | 查看次数: 812

首个金属氢样本“诞生”

 两名物理学家称,他们完成了物理学家为此已尝试了80多年的一项壮举:在巨大压力下压碎了氢气,使其成为一种发光的金属。

 
但其他研究人员则对这个长时间以来反复失败的领域出现的新成果深表怀疑。
 
美国马萨诸塞州哈佛大学物理学家Ranga Dias和Isaac Silvera最初将他们的研究结果于10月1日发表在预印文本服务器arXiv上,文章随即便招来批评。对该报告的一份同行评议于今年1月26日发表于《科学》,但质疑者说它包含的信息量过少。
 
5位专家在接受采访时表示他们并不相信这一论断,还需要更多证据。“我认为这篇文章并不可信。”法国布吕伊埃雷勒沙特原子能委员会物理学家Paul Loubeyre说。
 
Silvera和Dias表示,在通过获得的脆弱材料进一步验证之前,他们想先发表初步观察到的结果。
 
从1935年开始,在实验室中制作金属氢就是高压研究人员的梦想,当时理论首次预言了该物质的存在。当在一个砧中挤压到足够压力时,氢气就能导电,这是金属态的一个特征。理论学家称该材料还有其他的特征,如可以作为没有任何阻力的超导体,即便在室温下也是如此。
 
近年来,物理学家将微小的氢样本放在压力超过地心的金刚石砧之间。这项实验非常复杂,可能会出现潜在的错误。研究人员曾观察到随着压力变化该材料从透明变黑,这表明当电子簇拥在一块儿时,它们能够吸收可见光的光子。但没有人曾证明过可以反光的发出光泽的金属态氢的存在。2011年,由德国马普学会化学所物理学家发表的一项报告引发了争议。带领该团队的Mikhail Eremets表示,他们并未提供结论性的证据。
 
Dias和Silvera则称,他们能够通过比别人更大的压力挤压氢气。为了做到这一点,他们利用可放入一个低温恒温器的砧,使它们可以把氢气样本恰好冷却到绝对零度以上。他们还表示发现了磨光金刚石尖端的更好方法,从而清除可能破坏这些金刚石的不规则行为。随后,他们旋动一个螺丝使压力增加到4950亿帕斯卡,这相当于海平面大气压力的500万倍。
 
“然后,它突然变成了一种强有力的反射样本,你会认为它只有可能金属。”Silvera说。通过一个显微镜观测,该样本似乎会发光、会像金属氢那样反射光。
 
但其他研究人员并不相信。华盛顿特区卡耐基科学研究所地球物理学家Alexander Goncharov说,研究人员看到的闪光材料距离真实的金属氢还相差很远。Goncharov此前就曾批评过Silvera实验室的方法。他认为这种闪光材料可能是氧化铝,它覆盖在砧中金刚石尖端上,可能在压力下表现发生了变化。
 
“如果他们想要让人相信,就需要重新进行实验,切实地测量压力的变化。”英国爱丁堡大学物理学家Eugene Loubeyre说,“他们需要证明在这样的压力范围内,氧化铝并未变成金属。”Loubeyre和其他科研人员认为,Silvera和Dias高估了他们达到的压力水平。
 
但Silvera表示,他只是希望在进行确认实验之前,先将消息公布出来,因为二次试验可能会破坏他们珍贵的样本。“我们希望发表针对这个样本的突破。”他说。为了保存这个材料,他和Dias已经将其放在了低温恒温器中。他表示,该实验室有两台低温恒温器,另一台被用于其他实验。“现在,这篇论文已经被接收,我们将进一步开展实验。”
 
尽管广泛存在质疑,但《科学》杂志和哈佛大学公布的媒体材料仍满怀信心地宣称,科学家已经制作出了金属氢。“这是高压物理学领域的圣杯。”Silvera在哈佛大学的新闻通稿中说,“这是至今为止地球上出现的首个金属氢样本。”

《自然》相关报道:Physicists doubt bold report of metallic hydrogen

http://www.nature.com/news/physicists-doubt-bold-report-of-metallic-hydrogen-1.21379

分类:化学化工研究热点 | 固定链接 | 评论: 0 | 引用: 0 | 查看次数: 112

绿色焦点:环保谣言为啥满天飞

内蒙古风电偷走北京大风导致雾霾,地沟油比砒霜要毒100倍,石油焦是雾霾罪魁祸首……面对这些“论断”,非专业人士可能都会莫衷一是,有些人就稀里糊涂地相信了。其实,这些都是谣言。

谣言年年有,这些年特别多,环保领域也不例外,而且涉及方方面面。

环保谣言是如何产生的,为什么这么有市场,该如何遏制其传播?记者采访了各方专家。

 

谣言刺痛公众神经

查看更多...

分类:化学化工研究热点 | 固定链接 | 评论: 0 | 引用: 0 | 查看次数: 127

两名中国学者获四面体青年科学家奖

 近日,国际出版集团爱思唯尔(Elsevier)宣布,中国科学院上海有机化学研究所李昂研究员、北京大学雷晓光教授获得2017年“四面体青年科学家奖(Tetrahedron Young Investigator Award)”。这是除美国外,四面体青年科学家奖首次授予同一个国家的两名学者。两位获奖者将应邀出席2017年6月27日-30日在匈牙利布达佩斯举办的第18届四面体会议并作大会报告。

 
四面体青年科学家奖由《四面体》系列杂志2005年设立,是有机化学领域的重要国际奖项。该奖分“有机合成”、“生物有机与药物化学”两个领域单独评审,每年仅分别评出一名获奖者,旨在奖励40岁以下的杰出青年有机化学家。该奖的获奖者包括普林斯顿大学戴维·麦克米兰(David MacMillan)、斯坦福大学卡罗琳·贝尔托齐(Carolyn R. Bertozzi)等国际著名的有机合成或生物有机化学家。作为之前唯一获奖的中国学者,北京大学施章杰教授曾于2012年获得有机合成领域的四面体青年科学家奖。
 
李昂研究员主要从事天然产物全合成研究。他发展了6p电环化-芳构化和Prins环化等高效构建多取代六元环的创新策略,完成了虎皮楠生物碱、五味子降三萜、台湾杉醌二萜二聚体、噁唑二萜、吲哚单萜生物碱、吡咯并吲哚生物碱、吲哚萜类等10多个家族天然产物的全合成。电环化-芳构化策略打破了从苯环起始原料出发逐级取代的传统思路,提高了立体化学环境复杂的多取代苯环的合成效率。李昂研究员曾获得2012年优秀青年科学基金项目和2015年国家杰出青年科学基金项目资助(项目编号:21222202,21525209)。
 
雷晓光教授主要从事分子探针导向的化学生物学研究。他系统地利用小分子探针,揭示出一系列新颖的程序性细胞死亡生物作用机制和化学调控方法;高效构建了一系列倍半萜多聚体类、石松生物碱天然产物分子探针,阐明了它们的生物作用靶点和全新的分子作用机制,进而开发出对肿瘤、感染性疾病与自身免疫性疾病有良好治疗前景的、基于天然产物的药物先导。雷晓光教授曾获得2012年优秀青年科学基金项目和2016年国家杰出青年科学基金项目资助(项目编号:21222209,21625201)。
分类:化学化工研究热点 | 固定链接 | 评论: 0 | 引用: 0 | 查看次数: 182

 过程化学:冰箱大小的药物生产机器

 
  提到药物制造,很多人都会想起洁净宽阔的厂房、精密运转的大型机器和众多全副武装的技术人员。的确,目前制药公司通常在大型工厂中批量生产药物,生产过程往往漫长而复杂,不同的步骤甚至有可能在不同的地方完成。不过,制药业也在出现一种新趋势,即通过使用小型连续流系统(continuous-flow system)根据需要定制药物,以降低基础设施的成本。
 
  今年,麻省理工学院(MIT)的Timothy F. Jamison、Klavs F. Jensen、Allan S. Myerson和同事设计了一个冰箱大小的连续流系统设备,作为“迷你工厂”以最终制剂的形式来生产临床上直接可用的药物(点击阅读详细)。该系统将药物生产体系上游的化学反应器单元与下游的沉淀、过滤、重结晶和制剂等单元组合在一起,还具有用于质量控制和过程评估的化学分析和计算模块。这种“迷你工厂”比传统的设备小得多,而且更便宜,可以在大约两个小时内按需要制备数百或甚至数千份剂量的药物,特别适合用于制备保质期较短的药物,病人群体很小的“孤儿药”,或者受突发公共卫生事件影响的少部分患者群体的药物。此外,它将会减少对药物运输和存储的需求,让药物生产更加灵活和有针对性,会更受小公司或发展中国家青睐。
 
  目前,该系统已经可以生产苯海拉明、盐酸利多卡因、地西泮、盐酸氟西汀的口服和外用液体制剂。下一步,MIT的科学家们希望将系统体积再缩小40%,增加合成更复杂药品的能力,并且将这种专利技术商业化。
 
  On-demand continuous-flow production of pharmaceuticals in a compact, reconfigurable system
 
  Science, 2016, 352, 61-67, DOI: 10.1126 /science.aaf1337
 
  高分子:首个“吃”PET塑料的细菌
 
  聚对苯二甲酸乙酯(polyethylene terephthalate,PET)是最常见的塑料之一,和其他塑料一样,在给人类生活带来很大便利的同时,也会给环境带来很大的压力。全世界的PET塑料年产量超过4500万吨,被生产成矿泉水瓶、色拉盒、花生酱罐以及其它各式各样的产品。PET在美国已经是回收最多的塑料,但是仍有超过一半的PET塑料最终只能进入垃圾填满场,而这种聚合物中的酯键很强,很难自然降解。
 
  日本京都工艺纤维大学的小田康平(Kohei Oda)和庆应义塾大学的宫本贤治(Kenji Miyamoto)等人今年报道了一种利用细菌来帮助降解PET的新方法,这是迄今发现的第一种可以“吃掉”PET塑料的细菌,它将PET作为其主要的碳源和能量来源(点击阅读详细)。他们的研究小组筛选了来自一个塑料回收厂的样本,包括沉积物、土壤、废水和活性污泥,经过微生物筛选发现一种细菌能够在PET薄膜上成长。这种首个被发现能“吃掉”PET的细菌被命名为Ideonella sakaiensis。
 
  PET可通过化学水解方法得到单体进行回收,但该方法需要高温和高压。而这种细菌在温和的30 ℃温度条件下就能够“切割”PET聚合物,得到单体对苯二甲酸和乙二醇。研究人员发现,有两种酶对于这种细菌的PET降解能力十分关键:一种被称为PETase,将PET降解为中间产物单(2-羟乙基)对苯二甲酸(MHET);另一种被称为MHETase,将MHET水解成单体对苯二甲酸和乙二醇。
 
  不过,这种细菌目前还是个“挑食的吃货”,更喜欢无定形PET,而不是大多数产品中使用的结晶态PET。另外,两种关键酶的作用也太慢,目前也不太适于在工业上。不过没关系,随着科学家进一步优化和改进,纯生物手段的PET高效率无污染回收,或许不用等待太久。
 
  A bacterium that degrades and assimilates poly(ethylene terephthalate)
 
  Science, 2016, 351, 1196-1199, DOI: 10.1126/science.aad6359
 
  材料学:液态金属的新应用
 
  看到“液态金属”这四个字,除了水银,很多读者脑海里可能都会冒出电影《终结者2》中液态金属终结者机器人T-1000的身影。在科幻电影之外,液态金属也是科学家们长期以来很感兴趣的课题。今年,液态金属的一些新应用再次引起了人们的关注。
 
  镓及其一些合金是一种液态金属,当暴露于空气中时,会自发形成薄的氧化物外皮,从而稳定液滴形态以及研究人员创造的其他任意图案。如果这种材料被挤压,氧化物外皮破裂,金属会恢复流动,直到重新生成氧化物外皮。
 
  北卡罗来纳州立大学(NCSU)Michael D. Dickey领导的团队利用镓(Ga)基合金的这种特性,制造了最小可到10 μm的聚合物包覆的eGaIn线,eGaIn是镓和铟的共晶混合物,熔点15.5 °C,在室温下是液体。与普通的电线不同,由eGaIn制成的线可以很容易地被拉伸、弯曲和成形,同时还能保持导电性。
 
  Drawing liquid metal wires at room temperature
 
  Extreme Mech. Lett., 2016, 7, 55-63, DOI: 10.1016/j.eml.2016.03.010
 
  在今年的另一项研究中,瑞士洛桑联邦理工学院(EPFL)的Stéphanie P. Lacour和同事们设计了一种两相材料,包含固体AuGa2簇和散布其中的液体镓微液滴。他们使用这种材料通过喷墨打印,在手套上制造包含LED和传感器堆叠层的可拉伸装置,能够追踪手指的细微运动。
 
 
  Intrinsically Stretchable Biphasic (Solid–Liquid) Thin Metal Films
 
  Adv. Mater., 2016, 28, 4507-4512, DOI: 10.1002/adma.201506234
 
  爱荷华州立大学的Martin Thuo团队利用铋-铟-锡和相关合金自发形成的氧化物外皮,从而使液态金属微液滴即使在低于其熔点的温度下也不会凝固。对液滴施加温和的力就能破坏氧化物外皮,使得金属在外皮重新形成之前可以短暂地流动。研究人员利用这种特殊的性能可以在室温下将金属部件结合在一起,也就是说,可以在没有电或加热的情况下进行焊接。
 
  Mechanical Fracturing of Core-Shell Undercooled Metal Particles for Heat-Free Soldering
 
  Sci. Rep., 2016, 6, 21864, DOI: 10.1038/srep21864
 
  C-H键活化:亚甲基活化的新高度
 
  美国斯克里普斯研究所(The Scripps Research Institute,TSRI)余金权(Jin-Quan Yu)教授和加州大学洛杉矶分校(UCLA)K. N. Houk教授等化学家今年实现了一个长久以来都未曾实现的目标:选择性活化有机化合物中最常见的基团之一——亚甲基(CH2)中特定的碳氢键并将其转化为手性中心。
 
  具体来说,这篇论文中化学家们通过使用乙酰基保护的胺乙基喹啉配体,实现了单一亚甲基碳中心上前手性碳氢键的不对称钯插入,他们还把这些钯复合物用于了脂肪族酰胺的β-位碳氢键不对称官能团化,使用双齿配体来加速碳氢键的活化对于避免底物诱导的环钯化背景反应是至关重要的,从而可以保证高的对映选择性。作者还将这一配体促进的碳氢键活化反应用于了简单羧酸底物的β-位碳氢键芳基化,而不需要再引入导向基。
 
  瑞士苏黎世联邦理工学院(ETH Zurich)不对称合成专家Erick M. Carreira评论说:“余的团队把之前认为不可能的事情变成了现实。”
 
  这篇论文的背后,是余金权教授14年的努力和坚持。对映选择性的活化β-亚甲基“是我第一个独立工作的项目,那还是在2002年,我还在剑桥大学,”余金权在接受采访时说,“花了14年才终于完成目标。”
 
  论文刊登之后,余金权教授和他的同事们还在进一步扩展他们的方法,例如在其他官能团(如烷基胺)附近创建手性中心。与余教授课题组有合作的百时美施贵宝(BMS)的化学家,已经在用这个反应合成药物候选分子,“但还需要优化以提高复杂底物反应的收率,”余教授说,“我们可能会将这项技术授权给一家化学品开发公司,目前正在谈判。”
 
  Ligand-accelerated enantioselective methylene C(sp3)–H bond activation
 
  Science, 2016, 353, 1023-1027, DOI: 10.1126/science.aaf4434
 
  诊断学:今年流行可穿戴传感器
 
  智能手环、智能手表以及有些手机App可以让人们记录他们的心率、血压以及跑了多远,一些研究人员希望更进一步,开发能够分析人的汗水或环境中化学物质的设备,以监测健康状态、锻炼效果甚至化学品暴露风险。
 
  韩国首尔大学Dae-Hyeong Kim教授领导的研究团队报告了基于石墨烯的可穿戴设备在糖尿病治疗领域的新用途(点击阅读详细)。糖尿病人需要长期监控血糖水平并服用药物,目前的常见的测血糖方法大都需要抽取血液,麻烦且有健康风险。Kim等人发明的这种可穿戴贴片(如下图),贴在皮肤上,通过涉及酶葡萄糖氧化酶的电化学反应测量人体汗水中的葡萄糖含量来检测血糖水平,不会造成任何创伤。另外,与微针阵列相结合,这种可穿戴设备还能够通过皮肤输送治疗糖尿病的药物。
 
  A graphene-based electrochemical device with thermoresponsive microneedles for diabetes monitoring and therapy
 
  Nat. Nanotechnol., 2016, 11, 566-572, DOI: 10.1038/nnano.2016.38
 
  加州大学伯克利分校Ali Javey领导的研究小组开发了一种可穿戴设备,包括柔性PET片上的电路板和传感器阵列,可以检测使用者汗液中的盐水平、乳酸盐和葡萄糖。这样,使用者就有可能在出现健康问题之前接收到警报,例如脱水、肌肉痉挛甚至糖尿病。Javey认为,该设备将来的生产成本有可能控制在10美元左右。
 
  Fully integrated wearable sensor arrays for multiplexed in situ perspiration analysis
 
  Nature, 2016, 529, 509-514, DOI: 10.1038/nature16521
 
  麻省理工学院Timothy M. Swager领导的化学家们设计了一种无线徽章,以检测类似化学武器(如神经毒剂)的分子,灵敏度达十亿分之一。该装置基于浸没在离子液体中的碳纳米管,如果有亲电靶分子存在,它们的电阻会发生改变。
 
  Wireless Hazard Badges to Detect Nerve-Agent Simulants
 
  Angew. Chem. Int. Ed., 2016, 55, 9662-9666, DOI: 10.1002/anie.201604431
 
  药物发现:加强抗生素的“军火库”
 
  传染性病菌和人类之间的战斗持续了成千上万年,而今年人类有可能稍稍占据优势,这是因为有两组科学家设法升级了我们的抗菌“军火库”——一组制造了新的大环内酯类化合物,另一组则是在我们的鼻子里寻找新抗生素。
 
  哈佛大学Andrew G. Myers研究小组的化学家想出了如何用全合成的方法来增加大环内酯类药物的数量(点击阅读详细)。大环内酯类抗生素是含有14至16个碳原子的大环,包括红霉素和阿奇霉素,Myers等人的“积木式”策略使得他们能够制备之前难以获得的大环内酯类化合物。Myers已经成立了一家名为Macrolide Pharmaceuticals的公司,到目前为止,使用该策略全合成了近1,000种大环内酯类化合物。其中许多对革兰氏阴性病原体具有前所未见的活性,包括对目前使用的几种抗生素耐药的大肠杆菌和克雷伯菌。
 
  A platform for the discovery of new macrolide antibiotics
 
  Nature, 2016, 533, 338-345, DOI: 10.1038/nature17967
 
  德国蒂宾根大学微生物学家Andreas Peschel和Bernhard Krismer领导的团队通过人类鼻孔中的细菌筛选,发现了一种能杀死耐甲氧西林金黄色葡萄球菌(MRSA)的化合物(点击阅读详细)。该分子是一种新的含有噻唑烷的环状肽,称为路邓素(lugdunin),由人类鼻子里面的一种细菌——路邓葡萄球菌Staphylococcus lugdunensis分泌,而这种菌落在约70%的人鼻子中都存在。路邓素代表着一种新的抗菌剂种类,是第一个来自主要生活于人体内的细菌的抗生素。这个发现可能刺激科学家在我们身体的其他地方寻找新的武器,以抗击细菌侵入者。
 
  Human commensals producing a novel antibiotic impair pathogen colonization
 
  Nature, 2016, 535, 511-516, DOI: 10.1038/nature18634
 
  生物催化:酶法构建C-Si键
 
  硅是地球上位列氧之后第二丰富的元素,但C-Si键在自然界却从未出现过,无论是生物有机硅化合物,还是生成它们的生物合成途径。加州理工学院(Caltech)的研究人员今年发现,如果提供一些合适的起始材料,一些血红素蛋白可以立体特异性地形成C-Si键。
 
  “因为我们提供了合适的前体,自然的铁血红素化学就实现了这一转化,”领导此项工作的Frances H. Arnold说,“这是一个令人印象深刻的例证,大自然可以很容易的进行创新。”
 
  先前,Arnold实验室以及其他地方的工作已经表明,血红素蛋白可以通过插入N-H和S-H键催化非天然卡宾转移反应。在新的实验中,加州理工学院的研究人员筛选了一系列血红素蛋白,以找到那些能够催化2-重氮基丙酸乙酯插入二甲基(苯基)硅烷Si-H键反应的蛋白。
 
  来自于在冰岛海底温泉中发现的细菌Rhodothermus marinus的细胞色素c催化反应的对映选择性达到97% ee,但转换数较低。不过,细胞色素c蛋白通常不催化化学反应,它们通常在细胞中的生物分子之间转移电子。
 
  通过定向进化,加州理工学院团队发现R. marinus细胞色素c的三个突变可以将新酶的对映选择性提高到大于99% ee,并将其转换数提高约15倍。
 
  “这一发现或许可以用于促进工业相关的反应,例如烯烃的氢硅烷化。”柏林工业大学的Hendrik F. T. Klare和Martin Oestreich在同期发表的观点文章的评论道。
 
  Directed evolution of cytochrome c for carbon–silicon bond formation: Bringing silicon to life
 
  Science, 2016, 354, 1048-1051, DOI: 10.1126/science.aah6219
 
  催化:单原子催化剂
 
  金属氧化物或其它固体载体上负载的催化材料(通常是贵金属,例如铂)对工业规模化学过程非常重要,例如将原油转化为汽油。与常规的多原子催化剂相比,采用单原子分散的金属进行催化反应的单原子催化剂的利用率非常高(理论上达100%),大大降低昂贵和稀缺的贵金属的消耗。此外,原子尺度均匀性使不需要的反应和副产物最小化,并使得研究人员能更简单地推断反应机理,这对改善催化剂至关重要。
 
  在今年的一项研究中,新墨西哥大学的Abhaya K. Datye及同事们发现,将铂纳米颗粒暴露于热氧化条件可导致铂形成挥发性PtO2,可从纳米颗粒解吸附(点击阅读详细)。研究人员指出,在高温处理时Pt以PtO2的形式气化,又因与邻近CeO2表面的强相互作用而被CeO2捕获,并以高度分散的形式负载在CeO2载体表面,得到了原子级分散的Pt催化剂,在高温下保持稳定而不团聚,并表现出了一定的CO氧化活性。
 
  Thermally stable single-atom platinum-on-ceria catalysts via atom trapping
 
  Science, 2016, 353, 150-154, DOI: 10.1126/science.aaf8800
 
  另一项单原子催化剂研究中,由中国科学院大连化学物理研究所所长张涛院士领导的小组开发了一种制备单原子钴催化剂的湿化学方法。这种催化剂避免了贵金属的使用,可催化氢化和其他反应。但在此之前,关于这类催化剂中活性位点的详细知识难以捉摸,这也阻碍了它们的发展。张涛院士课题组确定了催化剂的活性位点结构,钴原子与石墨层中的四个吡啶氮原子配位,并由两个弱吸附的O2分子封端。该催化剂负载量高达3.6 wt.%,可高活性、高选择性地催化硝基苯加氢偶联制备偶氮苯的反应。
 
  Single-atom dispersed Co–N–C catalyst: structure identification and performance for hydrogenative coupling of nitroarenes
 
  Chem. Sci., 2016, 7, 5758-5764, DOI: 10.1039/c6sc02105k
 
  结构生物学:三个生物大分子的结构
 
  结构生物学家通过冷冻电子显微镜、X射线晶体学和其他技术来解析生物大分子的结构,这里列出了C&EN选择的今年三个“明星”生物大分子结构。
 
  DNA酶(DNAzyme)的结构在今年以前一直是个谜,因为研究人员无法结晶这种类型的生物催化剂。德国马克斯普朗克生物物理化学研究所的ClaudiaH?bartner和Vladimir Pena领导的团队解决了这个问题,他们报告了DNAzyme 9DB1的结构,该酶可以连接RNA链(Nature, 2016, DOI: 10.1038/nature16471)。
 
  核孔复合物非常巨大,对细胞核也很重要,它负责着数千种蛋白质、RNA分子和营养物质的进出。两个独立的团队,一个由欧洲分子生物学实验室的Martin Beck领导,另一个由加州理工学院的André Hoelz领导,分别解析了这个包括30种核孔蛋白的超大型细胞机器(Science, 2016, DOI: 10.1126/science.aaf0643; DOI: 10.1126/science.aaf1015)。
 
  组蛋白脱乙酰酶6(HDAC6)的原子分辨率结构对药物开发非常重要,这个蛋白是癌症化疗的“热点靶标”。两个独立的研究小组,一个由宾夕法尼亚大学的David W. Christianson领导,另一个由弗雷德里希?米歇尔生物医学研究所的Patrick Matthias领导,分别解析了HDAC6的结构(Nat. Chem. Biol., 2016, DOI: 10.1038/nchembio.2140; DOI: 10.1038/nchembio.2134)。
分类:化学化工研究热点 | 固定链接 | 评论: 0 | 引用: 0 | 查看次数: 200

德科学家借助人工光合作用高效固碳

 应对气候变化措施中,减少空气中温室气体含量是重要一项。德国研究人员日前报告说,他们在实验室中研究出一种人工光合作用方法,可以更快地固定空气中的二氧化碳。

 
植物光合作用中的卡尔文循环是一种重要的生物固碳形式,大气中的二氧化碳进入卡尔文循环转化成糖,这是减少大气中二氧化碳含量最便宜且副作用最少的一种方法。光合作用需要不同的酶来催化并相互协调,其中对碳起到关键固定作用的酶名为RuBisCo,这种酶的催化速度不但相对较慢,还时常错把氧气分子“认成”二氧化碳分子。
 
德国马克斯·普朗克协会研究人员在美国《科学》杂志上报告说,他们发现自然界中存在一种能够更有效结合固定二氧化碳的酶。这种名为ECR的酶从细菌中提取,几乎从不“犯错”,且催化反应速度可达RuBisCo的20倍,但ECR酶无法与光合作用中的其他酶协调作用。
 
经过不断筛选优化,研究人员为ECR酶设计出了一种名为CETCH循环的人工循环过程。该过程有包括ECR酶在内的17种酶参与,在实验室中固碳的效率较自然界中的光合作用高出20%。
 
此外,目前在实验室发生的CETCH循环中,二氧化碳被吸收后的产物为乙醛酸。研究人员介绍说,他们还可对CETCH循环作出相应调整,使其产物变为生物柴油原材料、抗生素等其他物质。
分类:化学化工研究热点 | 固定链接 | 评论: 0 | 引用: 0 | 查看次数: 156