The anionic cyanine dye Merocyanine 540 (MC540) dissolved in Aerosol-OT (AOT) solutions of heptane and toluene possesses a significantly higher fluorescence quantum yield and excited singlet lifetime than the acetonitrile solutions of the dye. The difference in the photophysical properties observed upon incorporation of the dye into the AOT micelles is attributed to the decrease in the photoisomerization efficiency. The presence of AOT also controls the aggregation and photosensitization behavior of MC540 adsorbed onto TiO2 semiconductor nanoparticles. MC540 adsorbed onto nanostructured TiO2 films from acetonitrile solutions contains both the aggregated and monomeric forms of the sensitizer, while the dye-modified films obtained from AOT/heptane solutions contain mainly the monomeric form of the sensitizer. Significant enhancement in the photocurrent generation efficiency has been achieved in photoelectrochemical cells using the AOT encapsulated dye films. An electroactive polymer (poly(4-vinylpyridine)) film cast on the dye-modified TiO2 electrode has been found to be effective in promoting charge mediation and minimizing dye desorption from the electrode surface. The incident photon-to-photocurrent generation efficiency (IPCE) exhibited by the monomeric form (∼40%) is nearly five times greater than the corresponding efficiency of the aggregate form (∼8%). The beneficial aspects of incorporating dyes in organized assemblies for the purpose of suppressing nonradiative decay of the excited-state sensitizer and minimizing the aggregation effects on semiconductor surfaces are discussed.

The hydrophilic/hydrophobic nature of cellulose is based on its structural anisotropy. Cellulose chains are arranged in a parallel manner and are organized in sheets stabilized by interchain OH–O hydrogen bonds, whereas the stacking of sheets is stabilized by both van der Waals (vdW) dispersion forces and weak CH–O hydrogen bonds. Cellulose has a strong affinity to itself and materials containing hydroxyls, especially water. Based on the preponderance of hydroxyl functional groups, cellulose polymer is very reactive with water. Water molecular smallness promotes the reaction with the cellulose chains and immediately formed hydrogen bonds. Besides that, vdW dispersion forces play an important role between these two reactive entities. They stabilize the cellulose structure according to the considerable cohesive energy in the cellulose network. Hydrogen bonding, electrostatic interactions, and vdW dispersion forces play an important role in determining the cellulose crystal structure during the cellulose-water interactions. As a result of these interactions, the volume of cellulose undergoes a meaningful change expressed not only by an exponential growth in amorphous regions, but also by an expansion in nanocrystalline regions. In addition, the volume change is associated with the swelling material expressed as a weight gain of the cellulose polymer. Molecular modeling using Accelrys Materials Studio allowed us to open a new horizon and is helpful for understanding cellulose-water interactions.

Cellulose chains are linear and aggregation occurs via both intra- and intermolecular hydrogen bonds. Cellulose has a strong affinity to itself and toward materials containing hydroxyls groups. Based on the preponderance of hydroxyl functional groups, cellulose is very reactive with water. At room temperature, cellulose chains will have at least a monomolecular layer of water associated to it. The formation of hydrogen bonds at the cellulose/water interface is shown to depend essentially on the adsorption site, for example, the equatorial hydroxyls or OH moieties pointing outward from the cellulose chains. The vdW forces also contribute significantly to the adsorption energy. They are a considerable cohesive energy into the cellulose network. At the surface of the cellulose chains, many intermolecular hydrogen bonds of the cellulose chains are lost. However, they are compensated by hydrogen bonds with water molecules. Electronic clouds can be distorted and create electrostatic dipoles. The large antibonding electron cloud that exists around the glucosidic bonds produces an induced polarization at the approach of water molecules. The electron cloud can be distorted and create an electrostatic dipole. It applies to the total displacement of the atoms within the material. Orbitals play a special role in reaction mechanism. Hydrophilic/hydrophobic nature of cellulose is based on its structural anisotropy. Cellulose-water interactions are exothermic reactions. These interactions may occur spontaneously and result in higher randomness of the system. They are denoted by a negative heat flow (heat is lost to the surroundings). Energy does not need to be inputted in order for cellulose-water interactions to occur.