Bottom-up preparation

A large volume of work has focused on the controlled, stimuli-responsive immobilization of various materials, including proteins, polymers, and NPs, onto surfaces. Especially in the case of NPs, controlled positioning and assembly of small building blocks is of great interest in the bottom-up preparation of devices. If a surface is first patterned with some supramoiecuiar recognition unit, it is possible to specifically immobilize functional materials into predetermined patterns in a 2D and 3D manner. A series of short reviews exist on the immobilization of NPs on patterned stu-faces using supramoiecuiar interactions. ... 

When a polymer is present in the reaetion environment, organic-inorganic hybrids are formed spherieal or quasi-spherical siliea partieles are obtained, with dimensions from few nanometres to submicron dimension, carrying out the so-called bottom-up preparation of nanofillers. Nanocomposites are thus formed with an intimate mixture of organic and inorganic phases. 

Fig. 6.2 Schematic illustration of the bottom-up preparation processes of metal nanoparticles (left) the chemical reduction process and (right) the physictd vacuum process...

Different synthetic methodologies can be pursued to prepare hierarchical porous zeolites, which can be discriminated as bottom-up and top-down approaches. Whereas bottom-up approaches frequently make use of additional templates, top-down routes employ preformed zeolites that are modified by preferential extraction of one constituent via a postsynthesis treatment For the sake of conciseness, we restrict ourselves here to the discussion of the latter route. Regarding bottom-up approaches, recently published reviews provide state-of-the-art information on these methodologies [8, 9,17-19]. 

In the 1980s, CdSe quantum dots vere prepared by top-dovm techniques such as lithography ho vever, size variations, crystal defects, poor reproducibility, and poor optical properties of quantum dots made them inadequate for advanced applications. Introduction of bottom-up colloidal synthesis of CdSe quantum dots by Murray et al. [3] and its further advancements brought radical changes in the properties of quantum dots and their applications in devices and biology. The colloidal syntheses of CdSe quantum dots are broadly classified into organic-phase synthesis and aqueous-phase synthesis. 

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

The synthesis of bimetallic nanoparticles is mainly divided into two methods, i.e., chemical and physical method, or bottom-up and top-down method. The chemical method involves (1) simultaneous or co-reduction, (2) successive or two-stepped reduction of two kinds of metal ions, and (3) self-organization of bimetallic nanoparticle by physically mixing two kinds of already-prepared monometallic nanoparticles with or without after-treatments. Bimetallic nanoparticle alloys are prepared usually by the simultaneous reduction while bimetallic nanoparticles with core/shell structures are prepared usually by the successive reduction. In the preparation of bimetallic nanoparticles, one of the most interesting aspects is a core/shell structure. The surface element plays an important role in the functions of metal nanoparticles like catal5dic and optical properties, but these properties can be tuned by addition of the second element which may be located on the surface or in the center of the particles adjacent to the surface element. So, we would like to use following marks to inscribe the bimetallic nanoparticles composed of metal 1, Mi and metal 2, M2. 

There are several bottom-up methods for the preparation of nanoparticles and also colloidal nanometals. Amongst these, the salt-reduction method is one of the most powerful in obtaining monodisperse colloidal particles. Electrochemical methods, which gained prominence recently after the days of Faraday, are not used to prepare colloidal nanoparticles on a large scale [26, 46], The decomposition of lower valent transitional metal complexes is gaining momentum in recent years for the production of uniform particle size nanoparticles in multigram amounts [47,48],... 

In this review I have attempted to give a comprehensive overview of the published work on nanoporous materials prepared from ordered block copolymers. Given the numerous successful demonstrations of the block copolymer strategy in the design, synthesis, and applications of nanoporous materials, this methodology holds a great deal of promise for the bottom-up en-... 

When judging the public impact of carbon-capture and storage activities, it should be taken in mind, that apparently only very few people are aware of the extraordinary challenge imposed by the need to reduce greenhouse-gas emissions by 60% to 80% within the next five decades. This finding of Shackley et al. (2004) clearly reveals the need for a bottom-up information policy to prepare the grounds for any new mitigation option. 

Even newer generations of nanomaterials are based on carbon nanotubes using the bottom-up approach. The materials are still very expensive, but the technology is evolving rapidly. Another type of nanotube has been prepared based on self-assembly of specific molecules such as chitosan-based nanoparticles of polypeptides, DNA or synthetic polymers. Phospholipids or dendrimer-coated particles are suitable for the entrapment of actives in very small vesicles. The current materials are still lacking in selectivity and yield (costs). 

Engineered nanoparticles can be prepared in two ways top-down by breaking apart conventional bulk substances, or bottom-up by building up structures from the molecular scale. There also is a growing trend to combine the top-down and bottom-up approaches to produce more sophisticated nanoparticle systems (Horn and Rieger, 2001). 

One of the most promising bottom-up approaches in nanoelectronics is to assemble 7i-conjugated molecules to build nano-sized electronic and opto-electronic devices in the 5-100 nm length scale. This field of research, called supramolecular electronics, bridges the gap between molecular electronics and bulk plastic electronics. In this contest, the design and preparation of nanowires are of considerable interest for the development of nano-electronic devices such as nanosized transistors, sensors, logic gates, LEDs, and photovoltaic devices. 

FIGURE 1. Two types of films with redox complexes on the electrode, (a) Conventional redox polymer film (redox sites (circles) are randomly located), (b) Highly ordered film prepared by the bottom-up method. 

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