Nanoparticles preparation methods

Allemann, E., R. Gurny, and E. Doelker. 1993. Drug-loaded nanoparticles preparation methods and drug targeting issues. Eur J Pharm Biopharm 39 173. 

Cheng, J. Davis, M.E. Khin, K.T. Cyclodextrin-Based Polymers for Therapeutics Delivery. US Patent 20040077595 Al, Apr 22, 2004 Insert Therapeutics, Inc. Pasadena, CA. Allemann, E. Gurny, R. Doelker, E. Drug-loaded nanoparticles—preparation methods and drug targeting issues. Eur. J. Pharm. Biopharm. 1993, 39, 173-191. 

Cheow, W., Hadinoto, K. Enhancing encapsulation efficiency of highly watersoluble antibiotic in poly(lactic-co-glycolic acid) nanoparticles modifications of standard nanoparticle preparation methods. Coll. Surf. A Physicochem. Eng. Asp. 2010, 370 (1-3), 79-86. 

Alldmann, E., Gurny, R., Doelker, E. Drug loaded nanoparticles—Preparation methods and drug targeting issues. Eur. J. Pharm. Biopharm., 39, 173,1993. 

For microencapsulation of inorganic nanoparticles, preparation methods like in situ polymerization may be used [102]. However, these methods often require toxic organic solvents and surfactants. Furthermore, the removal of residual surfactants or solvents is needed, since they cause faults in the product An environmentally benign solvent like supercritical carbon dioxide can be used to encapsulate inorganic nanoparticles. But its use is limited because of the low... 

Nakade S, Matsuda M, Kambe S, Saito Y, Kitamura T, Sakata T, Wada Y, Mori H, Yanagida S (2002) Dependence of Ti02 nanoparticle preparation methods and annealing temperature on the efficiency of dye-staisitized solar cells. J Phys Chem B 106 10004-10010... 

Various nanoparticle preparation methods, such as physical vapor deposition, chemical vapor deposition," reactive precipitation, sol-gel,° microemulsion, sonochemical processing and supercritical chemical processing, have been developed and reported in the literature. Among these methods, reactive precipitation is of high industrial interest because of its convenience in operation, low cost and suitability for massive production. The conventional precipitation process is, however, often carried out in a stirred tank or column reactor, and moreover the quality of the product is difficult to control and the morphology and size distribution of the nanoparticles usually change from one batch to another during production. 

In this chapter, we introduce our created nanoparticle preparation methods in RTIL under vacuum condition including electron beam (Imanishi et al., 2009 Tsuda et al., 2009a Tsuda... 

Allemann, E., Gumy, R., and Doelker, E. (1993). Drug-loaded nanoparticles— preparation methods and drug targeting issues. Euro. J. Pharmaceut. Biopharma-ceut. 39 (5), 173-191. 

It must be emphasised that under the optimised preparation conditions, no byproducts, such as carbon nanoparticles or amorphous carbon fragments are formed. Thus this preparation method for PCNTs is promising for large-scale synthesis of MWCNTs, since apart from removal of the metal catalyst tedious purification processes are avoided. 

Electron irradiation (100 keV) of the sample, heated to 800°C, yields MWCNTs (20-100 nm in length) attached to the surface. Such nanotube growth does not take place if natural graphite, carbon nanoparticles or PTFE are subjected to electron irradiation. The result implies that the material may be a unique precursor for CNTs and may constitute a new preparation method. 

Possible applications of MIP membranes are in the field of sensor systems and separation technology. With respect to MIP membrane-based sensors, selective ligand binding to the membrane or selective permeation through the membrane can be used for the generation of a specific signal. Practical chiral separation by MIP membranes still faces reproducibility problems in the preparation methods, as well as mass transfer limitations inside the membrane. To overcome mass transfer limitations, MIP nanoparticles embedded in liquid membranes could be an alternative approach to develop chiral membrane separation by molecular imprinting [44]. 

The bottom up methods of wet chemical nanoparticle preparation rely basically on the following methods ... 

Herein we briefly mention historical aspects on preparation of monometallic or bimetallic nanoparticles as science. In 1857, Faraday prepared dispersion solution of Au colloids by chemical reduction of aqueous solution of Au(III) ions with phosphorous [6]. One hundred and thirty-one years later, in 1988, Thomas confirmed that the colloids were composed of Au nanoparticles with 3-30 nm in particle size by means of electron microscope [7]. In 1941, Rampino and Nord prepared colloidal dispersion of Pd by reduction with hydrogen, protected the colloids by addition of synthetic pol5mer like polyvinylalcohol, applied to the catalysts for the first time [8-10]. In 1951, Turkevich et al. [11] reported an important paper on preparation method of Au nanoparticles. They prepared aqueous dispersions of Au nanoparticles by reducing Au(III) with phosphorous or carbon monoxide (CO), and characterized the nanoparticles by electron microscopy. They also prepared Au nanoparticles with quite narrow... 

The precise control of size, its distribution, shape, composition, and crystal structure of bimetallic nanoparticles is crucial in this field. Some strategies to prepare bimetallic nanoparticles were proposed and subsequently the corresponding methods were developed for the purpose of controlled nanoparticles. These methods enable us to find novel chemical and physical properties of bimetallic nanoparticles depending on their structures. 

Late transition metal or 3d-transition metal irons, such as cobalt, nickel, and copper, are important for catalysis, magnetism, and optics. Reduction of 3d-transition metal ions to zero-valent metals is quite difficult because of their lower redox potentials than those of noble metal ions. A production of bimetallic nanoparticles between 3d-transi-tion metal and noble metal, however, is not so difficult. In 1993, we successfully established a new preparation method of PVP-protected CuPd bimetallic nanoparticles [71-73]. In this method, bimetallic hydroxide colloid forms in the first step by adjusting the pH value with a sodium hydroxide solution before the reduction process, which is designed to overcome the problems caused by the difference in redox potentials. Then, the bimetallic species... 

Bimetallic Ag-core/Au-shell nanoparticles, prepared by a NaBH4 reduction method, were directly confirmed by HRTEM [124],... 

AuPt bimetallic nanoparticles, prepared by polyol method and stabilized with PVP, were studied by UV-Vis spectra [122]. In this preparation the reaction temperature... 

PtRu nanoparticles can be prepared by w/o reverse micro-emulsions of water/Triton X-lOO/propanol-2/cyclo-hexane [105]. The bimetallic nanoparticles were characterized by XPS and other techniques. The XPS analysis revealed the presence of Pt and Ru metal as well as some oxide of ruthenium. Hills et al. [169] studied preparation of Pt/Ru bimetallic nanoparticles via a seeded reductive condensation of one metal precursor onto pre-supported nanoparticles of a second metal. XPS and other analytical data indicated that the preparation method provided fully alloyed bimetallic nanoparticles instead of core/shell structure. AgAu and AuCu bimetallic nanoparticles of various compositions with diameters ca. 3 nm, prepared in chloroform, exhibited characteristic XPS spectra of alloy structures [84]. 

Figure 9. TEM micrographs of nanocrystal superlattices of Au nanoparticles prepared by the inverse micelle method and digestive ripening, (a) and (b) low-magnification images (c (f) regularly-shaped nanocrystal superlattices (g) magnified image of a superlattice edge. Note the perfect arrangement of the Au nanoparticles. (Reprinted with permission from Ref. [30], 2003, American Chemical Society.)...

The potential of morphologically controlled metal nanoparticles should be expanded by further improvement of their preparation method. It is highly required to develop preparation methods to obtain a better morphological control, i.e., perfect facet control on the particles of optional size. Better morphological control of metal nanoparticles is expected to be achieved in near future and the obtained metal particles will find new exciting applications, not only in catalysis but also in other technically important fields. 

In the early work on the thermolysis of metal complexes for the synthesis of metal nanoparticles, the precursor carbonyl complex of transition metals, e.g., Co2(CO)8, in organic solvent functions as a metal source of nanoparticles and thermally decomposes in the presence of various polymers to afford polymer-protected metal nanoparticles under relatively mild conditions [1-3]. Particle sizes depend on the kind of polymers, ranging from 5 to >100 nm. The particle size distribution sometimes became wide. Other cobalt, iron [4], nickel [5], rhodium, iridium, rutheniuim, osmium, palladium, and platinum nanoparticles stabilized by polymers have been prepared by similar thermolysis procedures. Besides carbonyl complexes, palladium acetate, palladium acetylacetonate, and platinum acetylac-etonate were also used as a precursor complex in organic solvents like methyl-wo-butylketone [6-9]. These results proposed facile preparative method of metal nanoparticles. However, it may be considered that the size-regulated preparation of metal nanoparticles by thermolysis procedure should be conducted under the limited condition. 

It is known that Au nanoparticles efficiently catalyze various reactions, but its activity greatly depends on the degree of dispersion, support, and preparation method. We tried to synthesize Au wires and particles by our photo- and H2-reduction. For the S5mthesis of Au nanowires, several groups use HAUCI4 as a precursor. 

The drawbacks of the W/O emulsification method include the use of large amounts of oils as the external phase, which must be removed by washing with organic solvents, heat stability problems of drugs, possible interactions of the cross-linking agent with the drug, and, as with all nanoparticles prepared by emulsification techniques, a fairly broad particle size distribution. 

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