Alcohol nanoparticles

PANI/P-PVA (partially phosphorylated poly(vinyl alcohol)) nanoparticles were successfully dispersed in epoxy resin applied to steel [82]. P-PVA is fundamental to obtain a uniform dispersion of PANI nanoparticles, and this fact is responsible for the uniform formation of Fe Oj passive layer at the interface between coating and substrate and therefore for its effectiveness in corrosion protection. PANI was also used in combination with DBSA to be added to epoxy-ester (EPE) system to form a smart anticorrosion coating [73]. DBSA is used as both surfactant and doping agent. By EIS measurements it is deduced that the better anticorrosion performance of PANI (DBSA)/EPE coatings with respect to simple EPE is due to the formation of a second barrier layer by reaction between released DBSA anions and Fe cations at the defective locations of the coating. 

Li JK, Wang N, Wu XS (1998) Poly(vinyl alcohol) nanoparticles prepared by freezing-thawing process for protein/peptide drug delivery. J Control Release 56 117-126... 

Finally, the term steric stabihzation coifid be used to describe protective transition-metal colloids with traditional ligands or solvents [38]. This stabilization occurs by (i) the strong coordination of various metal nanoparticles with ligands such as phosphines [48-51], thiols [52-55], amines [54,56-58], oxazolines [59] or carbon monoxide [51] (ii) weak interactions with solvents such as tetrahydrofuran or various alcohols. Several examples are known with Ru, Ft and Rh nanoparticles [51,60-63]. In a few cases, it has been estab-hshed that a coordinated solvent such as heptanol is present at the surface and acts as a weakly coordinating ligand [61]. 

Noble metal ions can be easily reduced to the corresponding zero-valent metal atoms. Therefore, bimetallic nanoparticles consisting of two different noble metals have been extensively investigated for purpose of novel catalysts and optical materials. A simultaneous reduction of two noble metal ions with alcohol is a simple and useful technique to prepare bimetallic nanoparticles. The alcohol reduction of metal ions M + is followed by Equation (1). 

Pt/Pd bimetallic nanoparticles can be prepared by refluxing the alcohol/water (1 1, v/v) solution of palla-dium(II) chloride and hexachloroplatinic(IV) acid in the presence of poly(A-vinyl-2-pyrrolidone) (PVP) at ca. 95 °C for Ih [15,16,48]. The resulting Pd/Pt nanoparticles have a Pt-core/Pd-shell structure with a narrow size distribution and the dispersion is stable against aggregation for several years. The core/shell structure was confirmed by the technique of EAXFS. Composition of Pt/Pd nanoparticles can be controlled by the initially feed amount of two different metal ions, i.e., in this case one... 

Our first attempt of a successive reduction method was utilized to PVP-protected Au/Pd bimetallic nanoparticles [125]. An alcohol reduction of Pd ions in the presence of Au nanoparticles did not provide the bimetallic nanoparticles but the mixtures of distinct Au and Pd monometallic nanoparticles, while an alcohol reduction of Au ions in the presence of Pd nanoparticles can provide AuPd bimetallic nanoparticles. Unexpectedly, these bimetallic nanoparticles did not have a core/shell structure, which was obtained from a simultaneous reduction of the corresponding two metal ions. This difference in the structure may be derived from the redox potentials of Pd and Au ions. When Au ions are added in the solution of enough small Pd nanoparticles, some Pd atoms on the particles reduce the Au ions to Au atoms. The oxidized Pd ions are then reduced again by an alcohol to deposit on the particles. This process may form with the particles a cluster-in-cluster structure, and does not produce Pd-core/ Au-shell bimetallic nanoparticles. On the other hand, the formation of PVP-protected Pd-core/Ni-shell bimetallic nanoparticles proceeded by a successive alcohol reduction [126]. 

Recently, Somorjai, Yang et al. [143] examined this reaction over lwt.% Pt/SBA-15 utilizing an elaborate preparation protocol. Preformed Pt nanoparticle sols of five different mean sizes, obtained by alcohol reduction in the presence of a protecting polymer (PVP) were combined with SBA-15 silica exhibiting 9nm pores. After 3h low-power ultrasonic treatment, the Pt particles were evenly distributed throughout the pores of the support (Figure 12 (a)-(e)). 

This alcohol reduction method is applied to the control of size and composition of not only the noble metal/noble metal [7] but the 3d-transition metal/noble metal nanoparticles [8] like magnetic FePt nanoparticles. 

Figure 3. Schematic representation of the selective synthesis of metal nanowires and nanoparticles by the Sintering Controlled Synthesis approach, (a) Mesoporous silica, (b) impregnation of mesoporous silica with metal ions, (c) addition of water/alcohol vapors and UV-irradiation, or wet H2-reduction, (d) formation of metal nanowires, (e) dry H2-reduction, (f) formation of metal nanoparticles.

Chemical reduction of metal salts in solution is the most widely used method of preparation of metal nanoparticles, especially in laboratories. In general, the reducing reagents are added into the solution of the precursor ions, but in some cases, a solvent works as a reductant. Various reducing reagents have been proposed to prepare metal nanoparticles. Ethanol or small alcohols can reduce precious metal ions such as Au, Pt", Pd, Ag, and so on [3j. Polymer-stabilized precious metal nanoparticles and their alloy particles can be used as good catalysts for various reactions. Polyols, such as ethylene glycol, were... 

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