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Fine Tuning of the Sizes and Phases of ZrO_(2)nanocrystals

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Nano Research 2009年第11期2卷 891-902页

作者： Xiangxing Xu Xun Wang Department of Chemistry Tsinghua UniversityBeijing 100084China

Monodisperse and pure phase zirconia(tetragonal:T-ZrO_(2);monoclinic:M-ZrO_(2))nanocrystals with finely tuned sizes as well as ultrathin T-ZrO_(2)nanowires have been selectively synthesized by a facile solvothermal *** the first time,a diagram of the size to effective strain was mapped for both T-ZrO_(2)and M-ZrO_(2),which gives a good explanation for the size-and cation doping-dependent stability of the two phases on the sub-10nm *** work may expand our understanding of the phase properties of not only zirconia,but also various other polymorphic nanocrystals.

关键词： nanocrystals polymorphism phase stability

Magnetic and optical properties of NaGdF4：Nd^3＋, Yb^3＋, Tm^3＋ nanocrystals with upconversion/downconversion luminescence from visible to the near-infrared second window

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Nano Research 2015年第2期8卷 636-648页

作者： Xianwen Zhang Zhi Zhao Xin Zhang David B. Cordes Brandon Weeks Bensheng Qiu Kailasnath Madanan Dhiraj Sardar Jharna Chaudhuri Department of Mechanical Engineering Texas Tech University Lubbock Texas 79409 USA Hefei National Laboratory for Physical Sciences at the Microscale Hefei Anhui 230026 China Department of Chemical Engineering Texas Tech University Lubbock Texas 79409 USA Department of Chemistry & Biochemistry Texas Tech University Lubbock Texas 79409 USA EaStCHEM School of Chemistry University of St. Andrews St. Andrews KY16 9ST UK School of Information Science and Technology University of Science and Technology of China Hefei Anhui 230026 China Department of Physics and Astronomy University of Texas at San Antonio San Antonio Texas 78249 USA International School of Photonics Cochin University of Science and Technology Kochi 682022 India

We have designed and synthesized NaGdF4：Nd^3＋, Yb^3＋, Tm^3＋. magnetic nano- phosphors with combined dual-mode downconversion （DC） and upconversion （UC） photoluminescence upon 800 run excitation. Hexagonal-phase NaGdF4：Nd^3＋, Yb^3＋, Tm^3＋ nanocrystals （NCs） with an average size of 21 nm were synthesized using a solvothermal approach. Nd^3＋, Yb^3＋, Tm^3＋ triple-doped NaGdF4 NCs exhibit a broad range of photoluminescence peaks covering a near infrared first/second window （860-900, 1,000, and 1,060 nm）, and visible emission including blue （475 nm）, green （520 and 542 nm） and yellow （587 nm） after excitation at 800 nm. A mechanism involving circulation of energy over Gd^3＋ sublattices as bridge ions and final trapping by the initial activator ions （Nd^3＋） has been proposed. Penetration depth studies indicate that NIR emission is easily detected even at a large tissue thickness of 10 mm. These paramagnetic nanophosphors demonstrate a large magnetization value of 1.88 emu/g at 20 kOe and longitudinal relaxivity value of 1.2537 mM-1.S-1 as a Tl-weighted magnetic resonance imaging contrast agent. These NaGdF4：Nd^3＋, Yb^3＋ Tm^3＋ NCs are promising for applications in biological and magnetic resonance imaging.

关键词： near-infrared second window photoluminescence energy transfer nanocrystals

Development of carrier-free nanocrystals of poorly water-soluble drugs by exploring metastable zone of nucleation

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Acta Pharmaceutica Sinica B 2019年第1期9卷 118-127页

作者： Xiaoting Ren Jianping Qi Wei Wu Zongning Yin Tonglri Li Yi Lu Key Laboratory of Drug Targeting and Drug Delivery Systems West China School of Pharmacy Sichuan University Department of Pharmaceutics School of Pharmacy Fudan University Department of Industrial and Physical Pharmacy College of Pharmacy Purdue University

There has been increasing interest in research and development of nanocrystals for the delivery of poorly water-soluble drugs that can be directly produced from solution. Compared with traditional carrier-based or encapsulation designs, drug nanocrystals circumvent possible side-effects due to carrier polymers and poor stability issues associated with encapsulation. The production of carrier-free nanocrystals requires careful control of nucleation and thus a thorough understanding of the relevant solution's metastable zone. A solution may stay supersaturated without forming any nuclei and become metastable. The maximal degree of supersaturation is known as the metastable zone width. When nucleation is triggered directly from the metastable zone, it helps to produce homogeneous nuclei leading to uniform nanocrystals. Herein, we report a study in which the solubility and metastable limit of paclitaxel(PTX) in ethanol aqueous solution were measured at 40 °C. A wide range of metastable compositions were studied to prepare carrier-free PTX nanocrystals with particle size smaller than250 nm and PDI less than 0.25. Compared with the raw material, dissolution rate of PTX nanocrystals was significantly increased. The study enables production of high-quality drug nanocrystals for treating patients.

关键词： nanocrystals Metastable zone Nucleation Sonication Dissolution Paclitaxel

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A Green Method for Recycling 2-Propanol from Water during Purification Process of Aqueous nanocrystals

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Chinese Journal of Chemistry 2011年第7期29卷 1389-1394页

作者：王春雷徐淑宏崔一平 Advanced Photonics Center School of Electronic Science and Engineering Southeast University Nanjing Jiangsu 210096 China

During traditional 2-propanol-based purification of aqueous nanocrystals （NCs）, it is very difficult to recycle 2-propanol from the aqueous solution, which brings great consumption of 2-propanol during the purification process. A major contribution of this work is to provide a simple way to reduce the consumption via recycling of 2-propanol during the purification process. The recycled 2-propanol is available for precipitating NCs from aqueous solution in a new round of NC purification process. Due to the recycling of 2-propanol, the great consumption of 2-propanol can be avoided, which makes the purification process of aqueous NCs much greener and at a much lower cost.

关键词： recycling nanocrystals CdTe

Shape Control of CoO and LiCoO_(2) nanocrystals

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Nano Research 2010年第1期3卷 1-7页

作者： Dingsheng Wang Xiaoling Ma Yanggang Wang Li Wang Zhongying Wang Wen Zheng Xiangming He Jun Li Qing Peng Yadong Li Department of Chemistry and State Key Laboratory of New Ceramics and Fine Processing Tsinghua UniversityBeijing 100084China Institute of Nuclear and New Energy Technology Tsinghua UniversityBeijing 102201China

Shape control of nanocrystals has become a significant subject in materials *** this work,we describe a convenient way to achieve morphology-controllable synthesis of CoO nanocrystals including octahedrons and spheres as well as LiCoO_(2) polyhedrons and *** particular,we explain the formation of CoO octahedrons exposing only high-energy(111)facets using theoretical calculations;these should also be a useful tool for directing future face-controlled preparation of other *** importantly,the as-obtained LiCoO_(2) nanocrystals showed different electrochemical performance depending on their morphology,indicating that Li-insertion/deintercalation dynamics might be crystal face-sensitive.

关键词： CoO LiCoO_(2) nanocrystals lithium-ion batteries

Kinetics of dissociative adsorption of formic acid on electrodes of tetrahexahedral platinum nanocrystals

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Science China Chemistry 2009年第10期52卷 1660-1665页

作者： ZHU TianWei TIAN Na KONG DeWen SUN ShiGang State Key Laboratory of Physical Chemistry of Solid Surfaces Department of ChemistryCollege of Chemistry and Chemical EngineeringXiamen UniversityXiamen 361005China

In the present paper we study the kinetics of dissociative adsorption of formic acid on the electrode of tetrahexahedral platinum nanocrystals (THH Pt NCs). In situ FTIR spectroscopic results demonstrate that HCOOH can be oxidized to CO2 at a low potential (-0.2 V(SCE)) on the THH Pt NCs electrode, and the chemical bonds inside formic acid molecule are broken to form adsorbed COL species. The kinetics of the dissociative adsorption of HCOOH was quantitatively investigated by employing programmed potential step technique. It has been determined that, in 5 × 10-3 mol·L-1 HCOOH + 0.1 mol·L-1 H2SO4 solution, the maximal value of the average rate (υamax) of dissociative adsorption of HCOOH on a commercial Pt/C catalyst electrode is 8.58 × 10-10 mol·cm-2·s-1, while on the THH Pt NCs the υamax is 1.5 times larger than the υamax measured on Pt/C and reaches 13.19 × 10-10 mol·cm-2·s-1. The results have revealed that the reactivity of the THH Pt NCs is much higher than that of the Pt/C catalysts.

关键词： platinum nanocrystals electrocatalysis formic acid dissociative adsorption in situ FTIR spectroscopy

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Heterogeneous catalysis for green chemistry based on nanocrystals

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National Science Review 2015年第2期2卷 150-166页

作者： Yuxi Liu Guofeng Zhao Dingsheng Wang Yadong Li Department of Chemistry Tsinghua University

Modern society has an ever-increasing demand for environmentally friendly catalytic processes. Catalysis research is working towards a solution through the development of efective heterogeneous catalysts for environment-related applications. Nanotechnologies have provided efective strategies for the preparation of nanocrystals(NCs) with well-deined sizes, shapes and compositions. Precise control of these NCs provides an important foundation for the studies of structure-performance relationships in catalysis, which is critical to the design of NCs with optimized catalytic performances for practical applications. We focus on recent advances in the development of botom-up strategies to control NCs structures for some key catalytic applications, including CO oxidation, selective oxidation of alcohols, semihydrogenation of alkynes, and selective hydrogenation of unsaturated aldehydes and nitrobenzene. hese key applications have been a popular research focus because of their signiicance in green chemistry. Herein we also discuss the scientiic understandings of the active species and active structures of these systems to gain an insight for rational design of eicient catalytic systems for these catalytic reactions.

关键词： nanocrystals heterogeneous catalysis green chemistry CO oxidation alcohol oxidation selective hydrogenation

Structural transition of BaF_2 nanocrystals under high pressure

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Chinese Physics C 2013年第8期37卷 76-79页

作者：王婧姝马春丽祝洪洋武晓鑫李冬妹丛日东刘景石蕊崔啟良 Jilin Normal University State Key Laboratory of Superhard Materials Jilin University Institute of High Energy Physics Chinese Academy of Sciences

The structural transition of BaF2 nanocrystals is studied by in situ high pressure synchrotron radiation X-ray diffraction measurements up to about 21.2 GPa at ambient temperature. Two phase transformations were observed at 5.8 and 14.4 GPa, and the two high pressure phases are identified as orthorhombic （Pnma） phase and hexagonal （P63/mmc） phase by Rietveld refinement. Upon decompression, the 0c-PbC12-type metastable phase is retained when the pressure is released. Two phase transformations of the BaF2 nanocrystals are higher than that in bulk BaF2. It is proposed that the size effects are found to influence the BaF2 nanocrystals high-pressure behaviors and the surface energy plays a significant role in the structural stability.

关键词： nanocrystals BaF2 synchrotron radiation phase transition

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Preparation,Characterization and Applications of Titanate/Titania nanocrystals

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稀有金属材料与工程 2006年第A3期35卷 638-641页

作者： Junrong Li Zilong Tang Zhongtai Zhang Zhigang Zhou State Key Laboratory of New Ceramics and Fine Processing Department of Materials Science and Engineering Tsinghua University Beijing 100084 China Beijing Institute of Space Medico-Engineering Beijing 100094 China

The present paper focused on the preparation of hydrogen titanate nanotubes and nanowires and their conversion into titania by heat *** structural,morphology and optical properties of as-prepared nanostructured titanate and titania were investigated by transmission electron microscopy (TEM),X-ray diffraction (XRD) and diffusive reflectance *** slim diameter of these nanostructured titanate and titania,the versatile crystal structure and special optical and electronic properties may make them find versatile applications in chemical sensors for multiple purposes.

关键词： titanate titania nanocrystals preparation applications