Phase changes are ubiquitous in nature, and transformations between solid structures represent a large group of them. They are usually reported on phase diagrams, as coexistence lines between different structures. The phase diagrams, well established for macroscopic 3-dimensional (3D) materials, change drastically when the material’s dimensions are reduced to few nanometers, or if the material is confined in a nano-pore. At the nanoscale the positions of coexistence lines on the phase diagrams are shifted and their new locations depend mainly on the size and shape of the nano-confinement, the structure of the confining walls, and their interaction with the confined substance. Here we show that it is possible to induce structural transformations in a confined system by simply varying the number of molecules adsorbed in the pore. We found that the mechanism of these novel, adsorption-induced structural transformation in nano-pores differs from that of well-known capillary condensation. The confined, equilibrium structures are not characterized by mean positions of molecules but rather by a probability distribution of molecular positions around adsorption centres. The character of transformation depends on temperature: it is strongly discontinuous at low temperature but evolves into a continuous transition when the temperature increases.

A molecular machine, or nanomachine, refers to any nano-sized system that produces quasi-mechanical movements (output) in response to a specific stimuli (input). Nano-engineering is today a rapidly growing, innovative field of science and technology. The 2016 Nobel Prize in Chemistry recompensing the chemical research effort in this area confirmed that engineering of the nano-machines is not any more an object of science-fiction stories. We are at the advent of new engineering methodology, in which the nano-systems can be numerically designed and chemically synthesized. In order to construct a complex machine, several challenging problems must be solved. First, a number of pre-assembled building blocks have to be prepared, as the function of the device is intended to be a consequence of their assembly. Furthermore, to obtain a predetermined function of the machine, this assembly should provide a possibility to precisely controlled translational and rotational movements of the machine components, stimulated by an inflow of external energy. The machine also needs an interface with its environment. Ultimately, it should be able to overcome thermal fluctuation (Brownian motion) that influences its mechanical action, and to operate out of equilibrium in dissipative systems, when controlled and driven by an external fueling, by light or other energy source.Starting from Richard Feynman prediction from 1984 that it would be possible to build machines with nanometric dimensions we show how the notion of the nano-machine has evolved during the last century. In 1983 chemists succeeded to produce molecular chains, catenanes, in which ring-shaped molecules were linked together by mechanical bonds, but the interlocked molecules did not form any intermolecular, strong covalent bonds. The catenanes were not only a new class of macromolecules: they also represented the first step towards creating a molecular machine. Then, in 1994 a rotaxane, a ring-shaped molecule that is mechanically attached to an axle has been created. The first molecular motor was proposed in 1999. Since then the rotaxane has been used to construct numerous molecular machines, including a molecular elevator, which can raise itself 0.7 nanometers above a surface, and an artificial muscle (2000), that is able to bend a very thin gold lamina. Many new ideas have been published and many new systems have been already synthesized. This presentation will be focused on the nanomachines in which the light is used as a photonic factor actuating and allowing control of the nano-machines movements.

It is well know that the properties of nano-objects differ from those of their macroscopic analogs. Any system of nanometric size shows characteristics that strongly depend on its size and geometric form. It is mainly because the major part of atoms (or molecules) of nano-volume are located at the object surface and their cohesive energy is smaller than for the atoms in the bulk. As a consequence, the density of the nanoobjects is not homogeneous, and may decrease close to the object boundary. Here we show that when a fluid is confined in nano-volume, delimited by non-interacting pore walls, its density is on average smaller than the bulk density. The heterogeneous distribution of fluid density results from the nano-confinement, and progressively weakens when the pore size increases: it disappears for pores larger than 5 nm. On the other side, the fluid density approaches the ideal gas values in the limit of very small pores. This effect should be distinguished from the well know heterogeneity of density of fluids adsorbed in nanopores, driven by the difference between the strength of fluid-fluid and fluid-pore wall interactions. The reported observation has non-trivial influence on evaluation of excess/total adsorption in nanopores, as these two quantities are calculated assuming the known – and homogeneous – bulk density of gas in the pore. Additionally, the gas density in the pores depends on the definition of the pore volume which is neither straightforward nor unique. We analyze this phenomenon on an example of five gases: H2, CH4, the two intensively studied energy vectors, and N2, Ar, and Kr, commonly used for characterization of porous structures. Two model pore geometries with not adsorbing soft walls are analyzed (slit-shaped and cylindrical). For H2, the distributions of densities of gas confined in adsorbing and not adsorbing pores are compared and commented.

We study the intrinsic optical spectroscopy (UV-vis-NIR absorption, Raman and photoluminescence) signatures of single wall carbon nanotubes (SWNT) dispersed in degassed water without additives, so called ‘‘eau de nanotubes” (EdN). They are found to be very close to those of SWNT dispersed in aqueous suspensions stabilized with surfactants. Absorption peaks appear to be even slightly better resolved for EdN, suggesting sharper excitonic resonances, which is also supported by the Raman data. On the other hand, the photoluminescence signal is significantly weaker. These signatures suggest that SWNT are dispersed as individuals in degassed water, in a similar way single layer graphene was recently shown to be readily dispersable in degassed water [1-3].References[1]G. Bepete et al, Nat. Chem. 2016, DOI 10.1038/NCHEM2669[2]G. Bepete et al, J. Phys. Chem. C 2016, 120 (49), 28204–28214.[3]G. Bepte et al, Phys. Stat. Solidi 2016, 10 (12), 895-899.

We discuss the intrinsic optical spectroscopy (UV-vis-NIR absorption, Raman and photoluminescence)signatures of single layer graphene (SLG) and single wall carbon nanotubes (SWNT) dispersed indegassed water without additives, so called "eau de graphene" (EdN) [1-3] and ‘‘eau de nanotubes”(EdN) [4].The most characteristic signature of SLG in EdG is a narrow and symmetric 2D band with a widthdepending on processing conditions [2,3]. The position of the G and 2D bands indicate moderate biaxialcompressive strain and weak n doping. The intensity of the D band and the width of the G band arediscussed in terms of point-defect density and flake size. We show that point defects can be easily curedby preparing thin films from EdG and annealing at 800°C.The signatures of SWNT in EdN are found to be very close to those of SWNT dispersed in aqueoussuspensions stabilized with surfactants [4]. Absorption peaks appear to be even slightly better resolvedfor EdN, suggesting sharper excitonic resonances, which is also supported by the Raman data. Thesesignatures support that SWNT are dispersed as individuals in EdN, in a similar way SLG aredispersable in EdG [1-3].[1] G. Bepete et al, Nat. Chem. 2016, DOI 10.1038/NCHEM2669[2] G. Bepete et al, J. Phys. Chem. C 2016, 120 (49), 28204–28214.[3] G. Bepte et al, Phys. Stat. Solidi 2016, 10 (12), 895-899.[4] G. Bepete et al, to be published