Intentional nanoparticles

The intention of this chapter is to provide a general survey on the preparative methodologies for the size- and shape-selective synthesis of metallic nanoparticles that have emerged from the benches of chemical basic research during the last few decades and become established as practical standard protocols. Industrial scale-up, however, has only just started to test the economic viability of these procedures and to determine whether they can meet the challenges of a number of very specific applications. The commercial manufacture of such thermodynamically extremely unstable nanoparticles in defined sizes and shapes on the kilo-scale is still confronted by a number of major problems and it remains to be seen how these can be solved. 

Nanoparticles produced from anthropogenic sources can either be formed inadvertently as a by-product of combustion activities (i.e. emissions from road vehicles and industries) or produced intentionally (e.g. ENPs) due to their particular characteristics [15]. The following section describes the ENPs in detail and provides only a brief overview of other anthropogenic sources. 

Definition of the nanoscale covers all species having at least one diameter of 100 nm or less. When nanoparticles are intentionally synthesized to be used in a range of consumer goods, they are called nanomaterials. Without doubt, one can say that we are now at the beginning of nanoindustrial revolution. Different types of nanomaterials are frequently applied in electronics, space technology, cosmetics and sunscreens production, medicine and pharmacy, solar energetics, textile industry, sport equipment, and many other areas [22, 23]. 

Although most applications try to avoid agglomeration, the intentional formation of a blockage of magnetic nanoparticles to block blood supply to a tumor has been investigated [67, 70, 137]. Aggregation and selective uptake has been used to destroy cells via the application of pulsed magnetic fields and subsequent rupture of cells [205]. 

Dendrimers appear to have interiors that are, to all intents and purposes, empty and they, therefore, are able to accommodate guest molecules and also nanoparticles. Early theoretical work suggested that dendrimers develop in concentric shells, and enclose a considerable amount of empty space. More recent theoretical studies have suggested that they may not be as much free space as first thought, and this has been confirmed by X-ray diffraction studies. NMR has shown that there is a reasonable free volume within dendrimers though there is some experimental evidence that the amount of free volume varies with the thermodynamic quality of the solvent. This, in turn,... 

In the publications on MEF to-date, silver has been the most studied metal as compared to other metals. Figure 1.3A shows the photogr hs of SIFs deposited onto glass and plastic supports, where the left-half of these siqjports was left intentionally blank to visually demonstrate the deposition of silver nanoparticles... 

Although the connection between SERS and SPPs is established in (1.2), how to effectively produce desirable SERS on a given metallic structure remains challenging. To address this issue, different plasmonic systems at different dimensionalities have been proposed, fabricated, and characterized with the same intention to maximize the local field strength at cOexc and cors [13-16]. A variety of structures have been found to support SERS well, including roughened metal electrodes, metal nanoparticles colloids, metal island films, metal nanorods, etc., or more specifically, substrates that contain nanoscale gaps or hotspots are particularly... 

The first studies that intentionally used colloidal nanocatalysts were reported independently by Beller et al. [50] and Reetz et al. [51] using chemical reduction and electrochemical techniques, respectively, to synthesize colloidal palladium nanoparticles for the Heck reaction. Both Beller and Reetz concluded that the solution-phase catalysis occurred on the surface of the nanoparticle, without confirming that a homogeneous catalytic pathway was nonexistent. Le Bars et al. [52] demonstrated an inverse relationship between the size of Pd nanoparticles and the TOF (normalized to the total number of surface atoms) for the Heck reaction (Fig. 18.4a). After normalizing the rate to the density of defect sites (for each nanoparticle size) (Fig. 18.4b), the TOF for all particle sizes was identical. Colloidal PVP-capped palladium nanoparticles synthesized by ethanol reduction are effective catalysts for Suzuki cross-coupling reactions in aqueous solution [53]. The El-Sayed group reported that the initial rate of reaction increased linearly with the concentration of Pd nanoparticles [53] and the catalytic activity was inversely proportional to the... 

A major new sub-field of cluster chemistry is that of nanoparticles of metals in which there are no intentionally appended ligands. These are not molecular and thus neither homodisperse nor crystalline. 

The aim of this chapter was to examine recent advances in research on nanoparticles as multimodal MRI contrast agents. The discussion was intentionally focused on particles that incorporate Gd " " as aTi or brightening agent because this class of agent is preferred for its radiological characteristics. The nanoparticulate systems discussed above are compositionaUy complex but generally obtainable in high yield by simple reactions. 

The nucleation of crystalline calcium phosphates in aqueous solutions is occasionally preceded by the formation of amorphous calcium phosphate (ACP) [1-6]. Abbona and Baronnet [7], Brecevic et al. [8], and Christoffersen et al. [9] were among the first to report such early-forming i.e., within the first few minutes of synthesis) ACP nanoparticles by using electron microscopy. If such ACP nanoparticles were not intentionally stabilized by adding Mg pyrophosphate or carbonate ions [10] to tbe synthesis media, then they transform into crystalline octacalcium phosphate (OCP, Ca3(HP04)2(P04)4-5H20) or non-stoichiometiic apatitic calcium phosphate with an increase in aging time, even in their native precipitation solutions [11-19]. 

It is notable that ID arrays of nanoparticles is still a great challenge for materials scientists. In this context, coaxial electrospinning is extremely effective and successful in achieving confined arrays of either nanoparticles or nanorods in the inner core of the nanofibers. The organic and inorganic phases are intentionally not mixed instead, they must be weU separated to display a distinct core-shell morphology. 

Biodegradable polymeric nanoparticles have been prepared and used to enhance the stability of proteins and peptides, control their release and pharmacokinetic parameters, furthermore, to improve their bioavailability. For delivery purposes, the polymeric material needs to meet physicochemical and biological requirements, of which, biocompatibility, safety, and biodegradability into non-toxic metabolites are of cmcial importance. The polymers can be easily functionalised towards off opsoni-sation. They are also known to show reduced toxicity in the peripheral healthy tissues. The selection of polymers depends on the method of administration, the bioactive molecules to be loaded, the desired release profile, the intention to target specific tissues, the desired rate of particle degradation, and the biocompatibility. Table 11.3 outlines some of the natural and synthetic polymers currently used in the fabrication of nanoparticles. 

CMP slurries are formulated with a variety of surface active chemical additives that are added to the slurry mixture with the intent of influencing particle behavior. The role of these additives in influencing particle behavior and removal in real wastewater streams needs to be addressed. All waste treatment processes generate a concentrated waste solids product in some form. The fate and ultimate stability of the alumina, ceria, and silica nanoparticles that are removed into waste solids is an important consideration that needs to be addressed by the research community. 

This article reviews the synthesis, characterization, and applications of rare earth oxide and snlphide nanomaterials. Special focus is placed on nanoparticulate materials and the description on nanoscale films and bulk nanoporous materials are intentionally excluded. In the first section, the synthesis methods of nanoparticles in general are reviewed, and examples of the production of rare earth oxides and sulphides are presented. The second section deals with the applications of rare earth oxides and sulphides, and they are discussed in relation to the unique properties of nanoscale particles. 

Sometimes, also polynuclear clusters such as Rh4(CO)j2 or Rh6(CO)26 were submitted to the formation of rhodium catalysts [18]. Metallic rhodium embedded in inorganic materials (carbon, AI2O3) was tested for mini-plant manufacturing. In this context, the frequently phosphorus ligands [PPhj, P(OPh)3] were added with the intention to detach rhodium from the heterogeneous layer (activated rhodium catalyst = ARC) [19, 20] More recently, ligand (Xantphos, PPhj, BIPHEPHOS)-modified or unmodified rhodium(O) nanoparticles were used as catalyst precursors for solventless hydroformylation [21]. It is assumed that under the reaction conditions these metal nanoparticles decompose and merge into soluble mononuclear Rh species, which in turn catalyze the hydroformylation. 

To control the interfacial properties between the nanoparticles and polymeric matrix, various functionalization techniques, such as covalent [109] and noncovalent methods [110], have been developed. Covalent functionalizations involve oxidation step where defects are intentionally introduced within the structure to enable sites for further covalent bonding. The mechanical and electrical properties of the individual carbon nanostructures decrease due to the introduction of these defect sites, i.e. as a result of covalent functionalization. Such deterioration of properties is not anticipated when noncovalent functionalization methods, including solution crystallization, precipitation and physical vapour deposition, are... 

The broad intent of Deliverable 1 was to develop and build multiple reactors that could easily and reproducibly generate robust and stable aerosol nanoparticles so that the technical team could have a readily available supply of aerosol nanoparticles of various chemistries with controlled particle size distributions and number concentrations in order to conduct the different programs within each deliverable. If successful, these aerosol reactors would enable the technical team to attach various aerosol generators upstream of... 

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