Molecular Nanosystems

With hyperbranched polyesterpolyols and polyesteramides, molecular nanosystems have now reached the cost-performance threshold for use in plastics and composites along a broad front. 

The fourth generation will involve research into integrated heterogeneous molecular nanosystems together with coordinated functionalities. This is approaching the way biological systems work, for example evolutionary cells and cell ageing therapies, human-machine interface. 

KE Drexler. Nanosystems Molecular Machinery, Manufacturing, and Computation. New York Wiley, 1992. 

Maurizio Selva (on the right) and Alvise Perosa (left) lead the Green Chemistry group at the Department of Molecular Sciences and Nanosystems of the University Ca Foscari Venezia. 

Fig. 8 Nanosystems that may function as simultaneous drug delivery and imaging agents for targeting T cells (a) liposomal systems, (b) solid biodegradable nanoparticulates, and (c) macro-molecular dendrimer complexes. PEG polyethylene glycol, Gd-DTPA gadolininum-diethylene triamine penta acetic acid. (Adapted from [48])...

As the analytical, synthetic, and physical characterization techniques of the chemical sciences have advanced, the scale of material control moves to smaller sizes. Nanoscience is the examination of objects—particles, liquid droplets, crystals, fibers—with sizes that are larger than molecules but smaller than structures commonly prepared by photolithographic microfabrication. The definition of nanomaterials is neither sharp nor easy, nor need it be. Single molecules can be considered components of nanosystems (and are considered as such in fields such as molecular electronics and molecular motors). So can objects that have dimensions of >100 nm, even though such objects can be fabricated—albeit with substantial technical difficulty—by photolithography. We will define (somewhat arbitrarily) nanoscience as the study of the preparation, characterization, and use of substances having dimensions in the range of 1 to 100 nm. Many types of chemical systems, such as self-assembled monolayers (with only one dimension small) or carbon nanotubes (buckytubes) (with two dimensions small), are considered nanosystems. 

These new methods of nonequihbrium statistical mechanics can be applied to understand the fluctuating properties of out-of-equilibrium nanosystems. Today, nanosystems are studied not only for their structure but also for their functional properties. These properties are concerned by the time evolution of the nanosystems and are studied in nonequilibrium statistical mechanics. These properties range from the electronic and mechanical properties of single molecules to the kinetics of molecular motors. Because of their small size, nanosystems and their properties such as the currents are affected by the fluctuations which can be described by the new methods. 

In nonequilibrium steady states, the mean currents crossing the system depend on the nonequilibrium constraints given by the affinities or thermodynamic forces which vanish at equihbrium. Accordingly, the mean currents can be expanded in powers of the affinities around the equilibrium state. Many nonequilibrium processes are in the linear regime studied since Onsager classical work [7]. However, chemical reactions are known to involve the nonlinear regime. This is also the case for nanosystems such as the molecular motors as recently shown [66]. In the nonlinear regime, the mean currents depend on powers of the affinities so that it is necessary to consider the full Taylor expansion of the currents on the affinities ... 

K. E. Drexler, Nanosystems, molecular machinery, manufacturing and computation Wiley, New-York, 1992. 

Engines of Creation The Coming Era of Nanotechnology, which outlines the general principles involved in molecular manufacturing in terms laypeople can easily understand. Six years later, Drexler wrote a second book on molecular manufacturing, this one intended for the scientific community. In Nanosystems Molecular Machinery, Manufacturing, and Computation, Drexler discussed the fundamental physical and chemical issues involved in the development of nanoscale devices. 

Molecular Metal Oxides and Clusters as Building Blocks for Functional Nanoscale Architectures and Potential Nanosystems... 

Here we start to examine the pivotal role that polyoxometalate clusters can play in the development of nanoscale devices that utilize POM components, and start to conceptualize some example systems in which POM components could have a crucial role [13, 19]. This is because such functional nanosystems can exploit the building block principle already established in this area of chemistry, coupled with the range of physical properties, and the fact that POM systems can really be seen as molecular metal oxides [20]. To demonstrate this point, a number of examples have been selected across the area of POM chemistry, including our contributions, to help highlight new directions and concepts. It should also be noted that metal oxides already play an important role in the electronics and semiconductor industry today and their solid-state properties have been studied extensively [21, 22]. Many of these concepts are not new in isolation, but the possibility of using molecular design in metal oxides to produce... 

The gap between concepts in molecular design to produce polyoxometalate integrated nanosystems or molecular-scale devices is vast due to the problem of fabrication and control of molecular orientation. Molecule-by-molecule assembly is... 

Drexler KE (1992) Nanosystems Molecular machinery, manufacturing, and computation. In Yearbook of science and the future. Encyclopedia Britannica, London, 170 ... 

I am very grateful to all coworkers and collaborators who are mentioned in our publications and who have shaped the understanding of molecular dynamics in nanoporous systems and drug delivery in living cells. The work was supported by the Excellence Clusters Nanosystems Initiative Munich (NIM) and Center for Integrated Protein Science Munich (CIPSM) as well as the collaborative research centers SFB 486 and SFB 749. 

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