Surface-confined nanoparticles

Next, the role of the external dielectric medium on the optical properties of these surface-confined nanoparticles is considered. Just as it is difficult to decouple the effects of size and shape from one another, the dielectric effects of the substrate and external dielectric medium (i.e., bulk solvent) are inextricably coupled because together they describe the entire dielectric environment surrounding the nanoparticles. The... 

Haes, A. J., D. A. Stuart, S. M. Nie, and R. R Van Duyne. 2004. Using solution-phase nanoparticles, surface-confined nanoparticle arrays and single nanoparticles as biological sensing platforms. J. Fluores. 14 (4) 355-367. 

Specific, surface confined reactions not only directly involve catalysis but also the built-up of sdf-assembled multilayers (see Fig. 9.1 (3)) with co-functionalities for more complex (bio-) catalytic systems such as proteins or the directed deposition of active metals. Furthermore, SAM on flat substrates can be used for the study and development of e.g. catalytic systems, but are not useful for large scale applications because they have very limited specific surface. Here, nanoparticle systems covered with 3D-SAMs are the ideal solution of combining the advantages of high surface area, defined surface composition and accessibility of proximal active catalytic centers. 

For example, Mandal et al. have reported the synthesis of Au core-shell NPs containing a gold core and poly(methyl methacrylate) (PMMA) shells by surface-confined living radical polymerization on gold nanoparticles. The synthesis of Au NPs has been carried out in the presence of 11-mercaptoundecanol (MUD) and subsequent esterification with 2-bromoisobutyryl bromide (BIB). Atom transfer... 

Shape The radiative emission from molecules confined within metallic nanocavities and on the surface of nanoparticles is of great relevance to biotechnology. In 1986, it has been suggested that fluorescence enhancement and reduced observation volumes could be obtained from small metal apertures (85). Nanocavities of different shapes could induce different surface plasmon (SP) fields. More recently, some studies has been done for different shapes, such as circular (86-90), elliptical (91), coaxial (92), or rectangular (93, 94) metallic nanocavity(95). In 2003, single-molecule detection from a nanocavity was demonstrated (86). However, it might be difficult to position the biospecies in the nanocavities. 

The use of nanoparticle arrays to generate surface-confined architectures has been extensively studied by Willner and co-workers [6]. The structural motif involves the sequential electrostatic assembly of nanoparticles and the desired molecules on planar electrodes. An ITO substrate is functionalized using an aminosilane molecule to yield a charged surface. Negatively charged citrate-stabilized gold... 

Shipway, A.N. Willner, I. Nanoparticles as structural and functional units in surface-confined architectures. Chem. Commun. (Camb.) 2001, 2035-2045. 

Semiconductors can be used as quantum dots because their nanosize confines the motion of conduction band electrons, valence band holes, or excitons in all three spatial directions. Quantum dots are often highly emissive, but their absorption and emission is much less sensitive on binding phenomena at their surfaces. The nanoparticles size and shape is the only effective means to control their optical properties. 

Preparations of nanoparticles have yielded synthesis methods that are widely used to obtain nanoparticle samples for research pinposes [3-5]. These preparations have led to detailed examinations of the opto-electronic properties of nanostmctures as they deviate from those of the bulk material. For example, the blue shift in the absorption onset as a function of decreasing nanoparticle size can be directly related to quantum confinement of excitons within the nanoparticle [6]. Due to their extremely small size and large specific surface area, nanoparticles usually exhibit unusual physical and chemical properties compared to that of bulk materials [7]. The use of polymer matrix as an environment for in situ nanoparticle growth combines, synergistically. 

Carlberg B, Ye LL, Liu J (2011) Surface-confined synthesis of silver nanoparticle composite coating on electrospun polyimide nanofibers. Small 7 3057-3066... 

Katz E, Baron R, Willner I. Magnetoswitchable electrochemistry gated by alkyl-chain-functionalized magnetic nanoparticles controlling of diffiisional and surface-confined electrochemical process. J Am Chem Soc 2005 127 4060-4070. 

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