The applications of copper (Cu) and Cu-based nanoparticles, which are based on the earth-abundant and inexpensive copper metal, have generated a great deal of interest in recent years, especially in the field of catalysis. The possible modification of the chemical and physical properties of these nanoparticles using different synthetic strategies and conditions and/or via postsynthetic chemical treatments has been largely responsible for the rapid growth of interest in these nanomaterials and their applications in catalysis. In addition, the design and development of novel support and/or multimetallic systems (e.g., alloys, etc.) has also made significant contributions to the field. In this comprehensive review, we report different synthetic approaches to Cu and Cu-based nanoparticles (metallic copper, copper oxides, and hybrid copper nanostructures) and copper nanoparticles immobilized into or supported on various support materials (SiO2, magnetic support materials, etc.), along with their applications i...

http://pubs.acs.org/doi/pdfplus/10.1021/acs.chemrev.5b00482

Cu and Cu-Based Nanoparticles: Synthesis and Applications in Catalysis.

A surface science perspective on TiO2 photocatalysis

Tubular and fibrous nanostructures of titanates have recently been
synthesized and characterized. Three general approaches (template assisted, anodic oxidation, and alkaline hydrothermal) for the preparation of nanostructured titanate and TiO2 are reviewed. The crystal structures, morphologies, and mechanism of formation
of nanostructured titanates produced by the alkaline hydrothermal method are critically discussed. The physicochemical properties of nanostructured titanates are highlighted and the links between properties and applications are emphasized. Examples of early applications of nanostructured titanates in catalysis, photocatalysis, electrocatalysis, lithium batteries, hydrogen storage, and solar-cell technologies are reviewed. The stability of titanate nanotubes at elevated temperatures and in acid media is considered.

Protonated Titanates and TiO2 Nanostructured Materials: Synthesis, Properties, and Applications

We report a general synthesis of high-quality cubic (α-phase) and hexagonal (β-phase) NaREF4 (RE:  Pr to Lu, Y) nanocrystals (nanopolyhedra, nanorods, nanoplates, and nanospheres) and NaYF4:Yb,Er/Tm nanocrystals (nanopolyhedra and nanoplates) via the co-thermolysis of Na(CF3COO) and RE(CF3COO)3 in oleic acid/oleylamine/1-octadecene. By tuning the ratio of Na/RE, solvent composition, reaction temperature and time, we can manipulate phase, shape, and size of the nanocrystals. On the basis of its α → β phase transition behavior, along the rare-earth series, NaREF4 can be divided into three groups (I:  Pr and Nd; II:  Sm to Tb; III:  Dy to Lu, Y). The whole controlled-synthesis mechanism can be explained from the point of view of free energy. Photoluminescent measurements indicate that the value of I610/I590 and the overall emission intensity of the NaEuF4 nanocrystals are highly correlative with the symmetries of the Eu3+ ions in both the lattice and the surface.

High-Quality Sodium Rare-Earth Fluoride Nanocrystals: Controlled Synthesis and Optical Properties

Nanofluids, the fluid suspensions of nanomaterials, have shown many interesting properties, and the distinctive features offer unprecedented potential for many applications. This paper summarizes the recent progress on the study of nanofluids, such as the preparation methods, the evaluation methods for the stability of nanofluids, and the ways to enhance the stability for nanofluids, the stability mechanisms of nanofluids, and presents the broad range of current and future applications in various fields including energy and mechanical and biomedical fields. At last, the paper identifies the opportunities for future research.

/pdf/a-review-on-nanofluids-preparation-stability-mechanisms-and-427pko83jc.pdf

A review on nanofluids: preparation, stability mechanisms, and applications

A nanotube material is obtained by the reaction of polycrystalline TiO2 with concentrated NaOH solution for 20 h at 110 °C. From the contents of Na, Ti and the structural water determined, it is concluded that the nanotube material is Na2Ti2O4(OH)2, rather than TiO2, TiOx or H2TiO3. After treating with an HCl solution of pH 1, nanotube Na2Ti2O4(OH)2 can be converted to nanotube H2Ti2O4(OH)2. The crystalline structure of such nanotube materials belongs to an orthorhombic crystalline system. TEM results indicate that nanotube Na2Ti2O4(OH)2 is formed in the reaction stage of TiO2 with concentrated NaOH solution. The formation process is discussed.

Study on composition, structure and formation process of nanotube Na2Ti2O4(OH)2

Nanotubed titanic acid (H2Ti2O4(OH)2) was prepared from nanotubed sodium titanate (Na2Ti2O4(OH)2) by an ion exchange reaction in a pH=1 HCl solution. The effect of annealing temperature on the morphology, structure and photocatalytic behavior of nanotubed H2Ti2O4(OH)2 was studied by means of TEM, XRD, DTG, DSC, BET and ESR. The results showed that nanotubed H2Ti2O4(OH)2 is thermally unstable. Its dehydration consists of two steps. In the first-step dehydration, single-electron-trapped oxygen vacancies (SETOVs) were generated. Accompanying the second-step dehydration, the transition of crystal form from orthorhombic system to anatase took place, at the same time the nanotubes broke. At T>300 °C, when the SETOV concentration greatly increased, the interaction between SETOV happened. (VOo)x formed could play the role of recombination center of photogenerated e−–h+ and make the photocatalytic behavior of TiO2 (anatase, obtained from 500 °C-treated nanotubed H2Ti2O4(OH)2) to become bad.

Effect of annealing temperature on morphology, structure and photocatalytic behavior of nanotubed H2Ti2O4(OH)2

Friction and wear properties of a surface-modified TiO2 nanoparticle as an additive in liquid paraffin

Nanosized Cu, modified by an organic compound containing S and P was synthesized using a surface‐modification method. The size and structure of the Cu nanoparticles were characterized by means of a transmission electron microscope (TEM) and electron diffraction (ED). Their tribological behavior was evaluated on a four‐ball machine. The results showed that Cu nanoparticles as an oil additive have better friction‐reduction and antiwear properties than ZDDP, especially at high applied load. Meanwhile, they can also strikingly improve the load‐carrying capacity of the base oil. The rubbed surface was investigated by electron probe microanalysis (EPMA) and X‐ray photoelectron spectroscopy (XPS). It was found that the boundary film on the worn surface consisted of a Cu nanoparticle deposited film and a tribochemical reaction film containing S and P. A synergistic effect between the deposited film and tribochemical reaction film contributes to the good tribological properties of oil.

Zhijun Zhang

Papers

Study on composition, structure and formation process of nanotube Na2Ti2O4(OH)2

Effect of annealing temperature on morphology, structure and photocatalytic behavior of nanotubed H2Ti2O4(OH)2

Friction and wear properties of a surface-modified TiO2 nanoparticle as an additive in liquid paraffin

Tribological behavior and lubricating mechanism of Cu nanoparticles in oil

Study on an antiwear and extreme pressure additive of surface coated LaF3 nanoparticles in liquid paraffin