A homogeneous aqueous dispersion of cellulose nanocrystals (CNs) that is left to evaporate in a Petri dish self-organizes into smectic liquid crystals that are actually liquid multilamellar structures. As evaporation proceeds, the liquid multilamellar structures solidify to become a solid multilamellar film. Each solid lamella is in the submicrometer range, and its iridescence is easily explained by classical light interference. A careful inspection of each solid lamella revealed long, oriented arrays of colloids. Interestingly, the array orientation is generally the same for each superposed layer. This is exceptional because the stratification appears first in the liquid, and the solid colloids are formed in each stratum at the very end of the process. Our findings are supported by optical, atomic force, and electron microscope observations and by laser diffraction observations. The multilamellar solid film model is easier to engineer than the helical model currently used to explain the iridescence and optical activities of CN solid films. This new understanding should promote the industrial production of colorful CN coatings and inks as a green alternative for decades to come.

Time-resolved fluorescence lifetime measurements of 5-(4-carboxyphenyl)-10,15,20-tritolylporphyrin (TTPa) with dioleoylphosphatidylcholine (DOPC) in mixed Langmuir-Blodgett (LB) films on quartz slides were performed at two different laboratories. TTPa in the mixed LB film exhibited a simpler and longer decay profile than did a pure TTPa monolayer. At a DOPC/TTPa molar ratio of 50:1, the decay consisted primarily of one lifetime of 10.7 ± 0.2 ns. This mixed LB film is being offered as a standard for time-resolved fluorescence lifetime measurements of LB films. Simplification and lengthening of the lifetime were attributed to reduction of TTPa aggregate formation in the film. This effect is also seen in fluorescence and absorption spectra. The fluorescence lifetime of the standard system at the air-water interface was also measured and found to be essentially the same as that of the LB film.

A novel method to make 2D crystals of fine particles is proposed. It is based on the hydrodynamic properties of thin laminar flow. To explore the possibilities of this method, we chose two variables, the particle diameter and the surface charge density. The spherule diameter varied from 6 μm to 53 nm, and its calculated surface charge density from 1134 to 4 μC/cm2. In every case, we easily obtained a rate of monolayer preparation up to 1 mm/s. Moreover, 2D crystals were always observed. The subphase ionic condition was the key parameter providing an adsorption window wide enough to allow a controlled particle−air/water interface adsorption, while maintaining particle−particle repelling electrostatic forces strong enough to avoid fractal formation during the surface compression. This report demonstrates that the DTLF method is an efficient way of producing monolayers and 2D crystals of colloids and that it could be developed to work in a continuous mode.

This paper describes a new way to make protein monolayers rapidly. This process reduces the protein contact time at the air−water interface, which subsequently prevents structural alteration. High-speed protein monolayer preparations are obtained by confining proteins in a thin laminar flow liquid film at various speeds. A prototype made of a rotating glass cylinder compressing cytochrome P450scc validated this method. The cytochrome P450 monolayers were verified by optical microscopy, TEM, STM, and AFM. Possible protein 1D crystallites were observed. A rate of protein monolayer preparation up to 2 cm/s was easily obtained. This method is suitable for continuous protein monolayer production and fine particle coating.

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