Papers by Keyword: Colloid

Abstract: This study proposes a simple method for fabricating metal particles. Metal nanoparticles are synthesized in an aqueous solution. The synthesis method is based on the galvanic replacement of one metal with another, i.e., the deposition of a metal on the surface of another metal using difference between the standard electrode potentials of the metals under ultrasonication. An aqueous colloidal solution of metallic copper (Cu) nanoparticles is prepared using Cu acetate and a metallic zinc (Zn) plate. A similar colloidal solution of metallic Cu nanoparticles is prepared using Cu acetate and a metallic iron plate. No metallic nanoparticles are obtained using metallic aluminum and nickel (Ni) plates because of the formation of passivated layers. An aqueous colloidal solution of metallic Ni nanoparticles is prepared using Ni acetate and a metallic Zn plate; however, Ni_0.7Zn_0.3O is also formed. The results of the study show that the proposed method can be used to produce metallic particles in a simple manner.

Abstract: Simple and low environmental impact methods for producing chemically-stable nanoparticles of metallic zinc (Zn) are asked to be developed, because metallic Zn nanoparticles are easily oxidized in air, and organic solvents, which can be used for the fabrication of metallic Zn particles, give a great environmental impact. The present work focuses on the chemical reaction in protonic solvents containing aqueous solvents, of which the use will give a smaller environmental load, and proposes a method for producing metallic Zn nanoparticles by reduction of Zn ions in the protonic solvent. Two kinds of hydrophilic solvents were examined: water and ethylene glycol (EG). The use of water and EG as the solvents produced Zn oxide. Though the addition of aluminum salt to EG also produced Zn oxide, the crystallinity of Zn oxide was lower than that for with no addition of aluminum salt. In the case of the aluminum salt addition, nanoparticles with a size of 27. 5±13.3 nm were fabricated, and not only bonds of Zn-O-Zn and Zn-OH but also a bond of Zn-Zn were confirmed to be formed, which indicated the production of low crystallinity metallic Zn nanoparticles.

Abstract: This study aimed to investigate the effect of pH value raging from pH 4 - 8 on color development of silver colloids. Silver colloids with different colors were synthesized by chemical reduction method using NaBH₄ as a reducing agent and then adjusted pH value by adding dropwise of acetic acid. These silver colloids were characterized by Transmission Electron Microscopy and UV-Vis spectrophotometer. The results showed that the colors of silver colloids ranging from blue to yellow depended on amount of NaBH₄ added. Due to Localized Surface Plasmon Resonance (LSPR) properties, different shapes and sizes of silver nanoparticles resulting in different colors. It was found that the pH value also affected color development of silver colloids. By adjusting the pH value, the colors of silver colloids changed to different colors or shades, which were clarified by the changes in the center as well as intensity of the absorption spectra. Moreover, the silver colloid in an acidic condition led to aggregation of nanoparticles.

Abstract: New titanium-dioxide (TiO₂) colloids composed of nano-crystalline TiO₂ and polydimethylsiloxane (PDMS) have been developed for use in the working electrodes of dye-sensitized solar cells (DSSCs). The surface morphology and electrical characteristics of the TiO₂ colloid electrodes were studied. The analysis of the surface morphology of the TiO₂ colloids was conducted by an atomic force microscope (AFM) and a field-emission scanning electron microscope (FE-SEM). The photovoltaic characteristics of the TiO₂ colloids with different compositions were investigated. The TiO₂ content of the colloids determined the photovoltaic conversion ability of DSSCs. Colorful colloids were implemented by adding pigments to the TiO₂ colloids. The processes of the TiO₂ colloids demonstrated the advantages of simple fabrication and low cost. The flexible property of the TiO₂ colloids showed great potential for application in flexible optoelectronics.

Abstract: Biomimetic nanocrystalline apatites are analogous to bone mineral. They can be exploited not only for bone regeneration applications, but it is also possible to take advantage of their biomimetic features to explore novel domains of research such as in nanomedicine, if the nanoparticles are stabilized as a colloidal formulation. In this contribution, we concentrate on AEP/HMP-stabilized colloidal apatite nanoparticles (NPs) and on their interaction with different types of cells so as to get experimental evidence on their low cytotoxicity, non-proinflammatory potential, and good compatibility with Red Blood Cells. We then started to explore their interaction with an artificial free-standing phospholipid bilayer, as a simplified model for cell membranes: results indicate, for the first time, that these colloidal apatite NPs can modulate phospholipid bilayer membrane properties, and may even favor the permeation of small molecules (illustrated here with luminescent FITC), which could ultimately be exploited for nanomedicine applications in view of enhancing intracellular drug delivery.

Abstract: This work is devoted to investigation of the way light transmittance of drying drop of Fe₂O₃ nanocolloid deposited on flat surface changes as liquid evaporates. According to results of transmitted light intensity measuring it is assumed that drying process can be divided into separate stages each being characterized by particular quality level of ability to transmit light because of different behavior and, thus, density of suspended nanoparticles inside the droplet. The last stage ends by forming of a ring-shaped pattern (known as “coffee ring”). Temperature of the surface was being changed by applying a varying potential difference to lower layer of transparent substrate made of ITO. Time dependences of integral transmitted light intensity for every single temperature are represented in graphs. They are compared with dependences for water drops of the same volume.

Abstract: The colloidal crystal template or opal with a closed-packed face centered cubic (fcc) lattice was prepared from monodisperse polystyrene (PS) microspheres by gravity sedimentation, and it was used for the fabrication of polyaniline hybrid with inverse opal structure. The template provided void space for the infiltration of Bi₂Te₃ and monomer that was then in situ polymerized to polyaniline. The opal composite was then soaked in toluene for completely removing PS microspheres to form porous polyaniline hybrid with inverse opal structure. The PS microspheres were replaced by air microspheres, which interconnected each other through the windows on the polyaniline hybrid wall. Both the wall and the air void constitute continuous phases. The polyaniline hybrid with inverse opal structure was observed with scanning electronic microscopy.

Abstract: This paper aims to investigate the mass and characteristics of colloid in leaching process to provide useful information for assessing the effects of colloid on leach at vertical and safety assessment of the disposal of (ultra-) low uraniferous radioactive waste. The variation of pH, colloid mass and effects on leach were studied at ambient conditions. The experimental results showed that the formation of colloid was strongly influenced by the pH value, it increased with time from 24 h to 96 h, and mass of colloid showed the opposite trend. The mass of colloid increased by the thick of uranium residual ores from 0.2 m to 0.8 m, but the pH showed opposite trend. The colloid morphology was identified using S-4800 scanning electron microscopy (SEM/EDS), and confirmed Al, Fe, Mg, Cs, U, Pr, O, and C as main composition. It implies that the existence of colloids would retard uranium leaching process. The residue grade of different thick nicely verified this point.

Abstract: In this work, optical K9 glass surface has been flattened by nanoparticle colloid jet machining, which is an ultra-smooth surface processing technique utilizing surface chemical effect between work surface atoms and nanoparticles in alkaline colloid to remove the uppermost surface atoms. The surface removal process of nanoparticle colloid jet machining has been investigated through K9 glass polish experiments. And the characterizations of ultra-smooth K9 glass surface polished by nanoparticle colloid jet machining have also been studied in this paper. Surface profiler and atomic force microscopy (AFM) are used to observe the surface microscopic morphological characteristics of K9 glass sample before and after polishing by nanoparticle colloid jet machining. The measurement results of processed surface prove that the primary scratches on the original surface have been completely wiped off by nanoparticle colloid jet machining and the roughness of the K9 glass surface has been improved to be less than 1 nm (Rq). Autocovariance (ACF) is investigated along a cross section of the K9 glass surface to determine the dominant spatial frequencies. The ACF curves show that the surface morphology of K9 glass processed by nanoparticle colloid jet machining is completely different from the preprocessed surface. The final K9 glass surface has been flattened by nanoparticle colloid jet machining. The microscopic morphological profile of the final K9 glass surface becomes increasingly smooth and eventually close to a flat state.

Abstract: Acid sludge is one of the major oil field acidification increased production ineffective. Therefore, the acid sludge formation of influencing factors on improving acidification effect is of great importance. The Suizhong 36-1 oilfield is selected as the research object , a more in-depth study of the acid sludge formed in the acidification process influencing factors . The results show that: With the increase of crude oil in the colloid and asphaltene content , the amount of oleic acid mixture to form acid sludge also increases . Strong acid ionizing out of the higher concentration of H+ , the faster of the speed, the forming acid slag trend is obvious. The residual acid pH value increased , the amount of acid sludge also will continue to rise.