Self-patterned mixed phospholipid monolayers for the spatially selective deposition of metals

ω-Thiolation of Phenolic Surfactants Enables Controlled Conversion between Extended, Bolaform, and Multilayer Conformations

The self-assembly of ω-thiolated surfactants onto gold is a well-studied phenomenon; however, control over the final organization within the thin films is either limited or requires extensive pre- and post-deposition chemical modifications. On the other hand, Langmuir-Blodgett deposition from the air-water interfaces affords a high degree of control over lateral organization within the film, yet it is generally employed to create physisorbed, soft matter films. Despite this, relatively little is known about the impact of the ω-thiolation on either the air-water of deposited film organization. Here, we show that the introduction of a terminal hydrophilic thiol on a phenolic surfactant does not necessarily disrupt a highly organized film nor does it necessarily induce a bolaform conformation at the interface. We show that the relative proportions of different conformations can be controlled using pH, relaxation time, surface pressure, and combinations thereof. Moreover, at high pH, the system undergoes a monolayer-to-multilayer transition wherein well-defined multilayer structures and morphologies are generated. These multilayers appear to comprise a single bolaform conformation atop an extended-chain condensed phase. We demonstrate that these structures can be transferred using Langmuir-Blodgett deposition demonstrating that combining these two approaches has the potential to achieve greater control over the functional properties of robust, chemisorbed films.

Thermal behavior of 1,2-dipalmitoyl-sn-3-phosphoglycerocholine bi- and multi-layers, deposited with physical vapor deposition under ellipsometric growth control

1,2-dipalmitoyl-sn-3-phosphoglycerocholine membranes were deposited onto a silicon substrate (Si/SiO(2)) using physical vapor deposition with in situ ellipsometric thickness control. Along several heating cycles it was possible to identify well-defined boundaries for gel, ripple, liquid crystalline, and fluid-disordered phases. Particularly, the second order transition between gel and ripple phase was clearly identified in the range of ~28-34 °C using Raman spectroscopy. Atomic force microscopy and imaging ellipsometry (IE) were used to observe and characterize the ripple phase undulations of period λ = 20.8 nm and average height h = 19.95 nm along the temperature interval of ~34 to 40 °C. Clusters/agglomerations heights of more than twice the membrane thickness were observed with IE, induced by heating cycles.

Impact of temperature on the LB patterning of DPPC on mica

The influence of the subphase temperature on the stripe pattern formation during Langmuir-Blodgett transfer (LB patterning) is investigated in a combined experimental and theoretical study. According to our experiments on the LB transfer of dipalmitoylphosphatidylcholine (DPPC) on planar mica substrates, even small temperature changes between 21.5 and 24.5 °C lead to significant changes in the monolayer patterns. For a constant surface pressure and dipper speed, the width of the stripes and the overall spatial period of the patterns increase with increasing subphase temperature. Because the stripe patterns are ascribed to alternating monolayer domains in the liquid-expanded and the liquid-condensed phases, the working regime for the formation of stripes is found to depend strongly on the respective surface pressure-area isotherm. These experimental findings are in accordance with the results of a theoretical investigation based on a model that takes hydrodynamics and the monolayer thermodynamics into account.