News on China's scientific and technological development.

Resistive random access memory (RRAM) device is considered as one of the most promising candidates for the next-generation nonvolatile memory (NVM) due to its simple structure, fast switching speed, low power consumption and feasibility of 3D integration. However, the physical mechanism of the resistive switching behavior is still unclear, which hinders further development of RRAM device. Generally, resistive switching behavior is accompanied by the microstructure and composition changes of the functional materials, which affect the current conducting mechanism and dominate the switching behaviors. Therefore, how to directly obtain the microstructure change information is an important issue to clearly understand the nature of resistive switching behavior.

The group of Prof. LIU Ming at the Institute of Microelectronics of Chinese Academy of Sciences (IMECAS), whose work focuses on the optimization of resistive switching characteristics, device integration and resistive switching mechanism of binary-metal-oxide-based RRAM devices, systematically studied switching mechanism by using ZrO2 as resistive switching material. Based on the temperature-dependent resistive switching characteristics, researchers demonstrated that the switching behavior of Cu/ZrO2: Cu/Pt device is responsible for the formation and rupture of the metallic Cu filament (APL, 93, 223506, 2008). By using a dc voltage sweep mode with a very small incremental rate, a stepwise switching phenomenon in Cu/ZrO2: Cu/Pt device was clearly observed in the I-V curve, which implied that multiple conductive filaments are formed between the bottom and top metal electrodes (APL, 95, 023501, 2009). Then, researchers demonstrated that the growth location and direction of conductive filament in the ZrO2-solid-electrolyte-based RRAM can be controlled by inserting a metal nanocrystal layer between the inert bottom electrode and the solid-electrolyte layer, which can greatly reduce the randomness of conductive filaments growth process and effectively improve the resistive switching behaviors (ACS Nano, 4, 6162, 2010).

In order to further study the dynamic of the CF growth and dissolution processes, the group carried out a novel research for the microscopic mechanism of RRAM based on in-situ TEM technology, cooperating with Prof. SUN Litao’s group from Southeast University. By using in-situ TEM technology, nanostructure evolution process of RRAM systems at atomic resolutions can be characterized when adding electrical signals on the device, leading to a more complete understanding of the underlying nature of the switching behavior. Based on the approach, real-time observations of the CF formation and dissolution processes in Cu (or Ag)/ZrO2/Pt devices are conducted. Contrary to the general belief of electrochemical metallization theory, the CFs are found to start growth from anode (Ag or Cu) toward the cathode (Pt), which suggests that the differences of cations solubility and diffusion coefficient between traditional solid-electrolyte and oxide-electrolyte materials should be taken into consideration.

Based on these findings, a modified microscopic mechanism for the switching behavior of oxide-electrolyte RRAM device is built. It is noteworthy that the methodology reported here can be easily extended to other resistive switching material systems, which may guide us to understand the origin nature of resistive switching behavior more clearly and optimize the performances of RRAM device with more effective methods. This research has accepted highly evaluation from the reviewers of Advanced Materials. It is considered to be the "important discovery in this field" and published as the inside front cover article

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According to data gathered by the OECD, China produced 285,000 papers in 2009. That's about 0.2 papers per 1,000 head of the population. Just 0.05 percent were published in top journals.

By comparison, the United States published 473,000 papers, or 1.6 for every 1,000 people. More than half made it into top journals. The figures for the UK, which punches above its weight, are 134,000 papers, just over 2 per 1,000 people, with more than half in top journals.

Tiny Switzerland, which spends about $10.5 billion a year on research and development, produces nearly 4 per 1,000 people; more than half appear in top journals.

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Polymer solar cells (PSCs) have received considerable attention in recent years because of their potential application for low-cost solar energy conversion. The conventional PSCs are composed of a photoactive layer sandwiched between an indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOTSS) positive electrode and a Ca (or LiF)/Al low-work-function negative electrode. However, both the PEDOTSS layer and the low-work-function metal electrode are known to degrade the device lifetime, since the low work-function metal is susceptible to degradation by oxygen and water vapor, and the PEDOTSS layer is acidic and corrosive to the ITO electrode.

Recently developed inverted PSCs solved the problem and improved the stability by using ITO modified by an electron-collecting layer as negative electrode and stable high-workfuntion metal top electrode as positive electrode. A key component in the inverted PSCs is the electron-collecting buffer layer material on ITO electrode. Solution-processing and low temperature treatment of the buffer layer is desirable for low cost and large area fabrication of the PSCs, especially for flexible PSCs with plastic substrate. However, the buffer layersuch as ZnO and TiO2 reported in literatures was prepared ether by vacuum-evaporation or with high temperature treatment (higher than 200oC) after solution-processing. Therefore, high efficiency solution-processed low-work-function buffer layer on ITO electrode still needs to be developed for high performance inverted PSCs.

Under the support of NSFC, Ministry of Science and Technology of China and the Chinese Academy of Sciences, the researchers in CAS Key Laboratory of Organic Solids, in collaboration with the State Key Laboratory of Polymer Physics and Chemistry and North China Electric Power University, fabricated the inverted PSCs based on PBDTTT-C/PC70BM with isopropanol solution-processed TIPD as electron collecting layer on ITO as negative electrode and air-stable MoO3/Al as positive electrode.

The TIPD buffer layer was thermal treated at 150oC for 10 min, which removed the two isopropoxy groups in TIPD and turns the surface of the buffer layer from hydrophilic to hydrophobic. The power conversion efficiency (PCE) of the inverted PSC with a-TIPD buffer layer annealed at 150 oC for 10 min reached 7.4% under the illumination of AM1.5, 100 mW/cm2, which is increased by 16% in comparison with that (6.4%) of the device in the conventional structure. The high PCE of the inverted device is benefitted from the hydrophobic surface (which is beneficial to the active layer formation on it from the organic solution) and the suitable electronic energy levels (which facilitates electron collection and block hole transfer from the active layer to the negative electrode) of the a-TIPD buffer layer. Long lifetime can also be expected for the inverted PSCs with the stable a-TIPD buffer layer and MoO3/Al top electrode.

This work is the extension of their previous work on the TIPD buffer layer in a traditional PSC based on MEH-PPV/PCBM.

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Chinese scientists will attempt the world's deepest manned submersible dive by going 7,000 meters under the surface of the Pacific Ocean between mid-June and early July, according to the mission's leader.

An oceanographic ship carrying nearly 100 scientists and other staff is currently en route to the eastern Chinese city of Jiangyin from the port city of Qingdao.

After reaching Jiangyin, the Jiaolong, a manned submersible, is expected to leave for the Mariana Trench on June 3, said Liu Xincheng, deputy director of the Beihai branch of the State Oceanic Administration.

The vessel will return to Qingdao in mid-July.

The Jiaolong, named after a mythical sea dragon, is the world's first manned submersible designed to reach depths of 7,000 meters below sea level. The submersible succeeded in diving 5,188 meters below sea level in the Pacific Ocean last summer, enabling China to conduct scientific surveys in 70 percent of the world's seabed areas.

However, diving for an additional 1,800 meters will put the submersible's ability to resist pressure to the test.A roundtrip drive, including seabed operations, will take more than 10 hours, said diver Tang Jialing.

After reaching a depth of 7,000 meters, divers will test the submersible's functionality, conduct scientific research and take seabed samples.

China's deep-sea diving program is open, meaning that foreign scientists are welcome to make dives in the Jiaolong as well, Liu said.

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The Chinese Academy of Sciences (CAS) hit number 1 among Chinese institutionsfor high-quality basic research and the Shanghai Institutes for Biological Sciences (SIBS) ranked first among individual institutes within CAS in 2011, according to the Nature Publishing Index 2011 China, published on May 24, 2012 as a supplement to the journal of Nature.

The supplement offers insights into how national investments, institutions and cities have contributed to China’s rapid scientific expansion. The Index measures the output of research articles from nations and institutes in terms of publications in the 18 Nature-branded primary research journals in 2011, with 2010 and 2009 data included for comparison.“The Nature Publishing Index offers a unique way to assess the high quality research output of an institution or a city in China,” said Felix Cheung, Editor of Nature China and of the supplement. “We have analysed the index data and assessed the various strengths of each institution and city.”

In the ranking presented by the supplement, the top ten Chinese institutions of 2011 are: the Chinese Academy of Sciences (CAS), the University of Science and Technology of China (USTC), Peking University, Tsinghua University, Hong Kong University of Science and Technology (HKUST), Xiamen University, Shanghai Jiao Tong University (SJTU), the University of Hong Kong (HKU), Nanjing University and BGI Shenzhen. CAS has an impressive lead, publishing 62 articles in Nature-branded primary research journals in 2011. And SIBS ranks first among individual institutes within CAS with 15 articles in Nature journals.

The Nature Publishing Index 2011 China supplement also presents a ranking by city. The top ten Chinese cities of 2011 for high-quality basic research are: Beijing, Shanghai, Hefei, Hong Kong, Nanjing, Wuhan, Xiamen, Hangzhou, Shenzhen and Xi’an.

According to the supplement, papers with authors from China represent 6.6% (225) of the 3425 papers published in Nature journals in 2011, up from 5.3% (152 papers) in 2010. By comparison, authors from China published just 12 papers in Nature journals in 2000. The Index also presents a new analysis of ISI Web of Knowledge data, showing that China now publishes more than 10% of the world’s most cited scientific research.

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May 18 news, recently an independent R & D company in China has developed a wearable computer: Eyetop which collected fifth-generation wearable computer display screen and a new generation of human-computer interaction technology, not only to create a precedent for civil wearable computer, but also has a leading position in the international area.

The wearable computer is a new concept of personal mobile computing systems, which is the inevitable product of the computer should be people-oriented concept, it frees up computer space bound currently in the United States, Canada, Germany, Britain, Australia, Israel and Japan and other countries has been rapid development.

According to the Austrian, the wearable computer due to its high-end and the high cost of the past used for military, space exploration and other specific areas. Now, Eyetop to break the convention and wearable computer from military to civilian use, making everyone can be confused with life, enjoy the convenience and a better experience of technology....

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The detection of nucleic acid is of central importance for the diagnosis and treatment of genetic diseases, the detection of infectious agents, biowarfare agents, and drug discovery. Dr. ZENG Lingwen’s group at Guangzhou Institutes of Biomedicine and Health (GIBH) developed a new biosensor for visual detection of nucleic acid with a detection limit of 0.01 fM, which is comparable or higher than previously reported fluorescence and colorimetric approaches.

This new biosensor provides a rapid, low cost, and semi-quantitative tool for the detection of nucleic acid samples. It also provides an alternative SNP detection method for genetic diseases, personalized medicine, cancer related gene mutations, and drug resistant mutations of infectious agents. It shows great promise for in-field and point-of-care diagnosis of genetic diseases as well as detection of infectious agents or warning against biowarfare agents.

the biosensor was composed of three parts: a sample pad, a strip of nitrocellulose membrane, and an absorbent pad. A 5’-thiol-modified, 3’-biotin-modifed 41-mer DNA hairpin probe containing the target DNA binding site was coated AuNPs. Another DNA probe was used as strand displacement primer with a sequence tag at the 5’end. A third target DNA probe was used for recognition and hybridization with the hairpin probe, triggering an ISDPR to generate large numbers of sequence tagged duplex DNA complexes. The resulting sequence tagged-duplex DNA complexes were then captured by an anti-tag DNA sequence fixed on the test zone of the nitrocellulose membrane. The red band at the control zone indicates that the biosensor works properly, and the red band at the test zone indicates the presence of target nucleic acid.　

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Researchers from the National Engineering Research Center of Fine Petrochemical Intermediates, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences (LICP), have invented an anti-sulfur poisoning three-way catalyst for the reduction of gasoline engine exhaust. The corresponding Chinese invention patent has been authorized on May 4, 2012.

Gasoline engine exhaust contains a great quantity of CO, HC, SOX and NOX, among which SOX is mainly from sulfide in gasoline. Sulfide will partly turn into SO2 and SO3 after being burned in engine. The combined action of SO2 and SO3 can lead to toxication and deactivation of catalysts, which will in turn cause catalysts to be inefficient in transforming pollutants in exhaust, such as CO, HC, NOX, etc.

As it is known, hydrogenated and isomerized gasoline which contains a small amount of sulfide is mainly used abroad. The content of sulfide in gasoline exerts little influence on the use of gasoline engine catalysts. Thus, the research on anti-sulfur poisoning three-way catalyst for gasoline engine exhaust is relatively rare. However, gasoline containing sulfur from the Middle East is mainly used in China and thereby the content of sulfur in catalytic cracked gasoline is relatively high. That’s why the stability of catalysts is weaker when catalysts are used in China.

In this invention the three-way catalyst uses cordierite honeycomb ceramics as a matrix, and noble metals, namely Pd, Pt, and Rh as main active constituents. A compound aluminum oxide coating layer composed of aluminum oxide powder, rare earth metal, alkali earth metal, transitional metal and La-Y-Ce-Zr solid solution is coated on the surface of the matrix. A presoaking layer composed of rare earth metal and transitional metal is further impregnated on the compound aluminum oxide coating layer. Then soluble salt solution containing the noble metal active constituents of Pd, Pt, and Rh is utilized to impregnate catalyst carrier to get the three-way catalyst. The presoaking layer can prevent active sties of noble metals from being bound or covered with sulfur. In this way the service life of catalysts can be prolonged. This catalyst has excellent anti-sulfur poisoning performance on the basis of maintaining unchanged transform rates of CO, HC and NOx.

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Attapulgite is a magnesium aluminium phyllosilicate. It is abundantly distributed in Jiangsu, Anhui, Gansu provinces of China. Due to its special fibrous structure, extraordinary colloidal and adsorption properties, attapulgite has been widely used. However, attapulgite surfaces are rich in polar silanol groups, which makes it hard for attapulgite to be compatible with non-polar organic solvents. And this has limited the application of attapulgite.

Room temperature ionic liquids have excellent physical and chemical properties and can be compatible with many organic solvents. And the molecular structure of ionic liquids is designable. If ionic liquids can be bonded to the surface of attapulgite, then the modification of the surface structure of attapulgite might be achieved. And the functions of attapulgite can be enlarged and more attapulgite related products will be developed.

Researchers at R&D Center for Eco-material and Eco-chemistry, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, have prepared an attapulgite/ionic liquid composite material by utilizing ionic liquid molecules with a designable molecular structure to modify attapulgite, which provides a novel approach for increasing the compatibility between the attapulgite and diverse organic solvents.

The method bonds a functionalized ionic liquid containing a carboxyl functional group on the surface of the attapulgite through a covalent bond, and utilizes anion exchange to change hydrophilic and hydrophobic properties of the attapulgite.

The preparation process is simple. The attapulgite composite material with controllable solubility and modified by the ionic liquid is expected to be applied in the fields of catalysis, sensors, novel nanometer materials, chemosynthesis, water treatment, food processing, mining, drug synthesis and so on.

The researchers have received a Chinese invention patent for the technique on November 30, 2011.

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