Pb arachidate Langmuir-Blodgett coatings of silicon wafers: relation between Pb particle density and subphase composition

• Published in: Colloid and polymer science 2018-04, Vol.296 (4), p.771-780
• Main Authors: Klimova, Svetlana A., Sreij, Ramsia, Bratashov, Daniil, Bookhold, Johannes, Teichert, Niclas, Gorobets, Anna S., Hellweg, Thomas
• Format: Article
• Language: English
• Subjects: Atomic force microscopy; Atomic structure; Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Coatings; Complex Fluids and Microfluidics; Electron microscopy; Food Science; Langmuir-Blodgett films; Lead; Microscopy; Monolayers; Nanotechnology and Microengineering; Nitrates; Original Contribution; Particle density (concentration); Physical Chemistry; Polymer Sciences; Silicon; Soft and Granular Matter; Wafers
• ISSN: 0303-402X; 1435-1536
• DOI: 10.1007/s00396-018-4288-9

The formation of lead arachidate (Pb(AA) 2 ) coatings produced by Langmuir tensiometry (LT) was studied in dependence of lead nitrate (Pb(NO 3 ) 2 ) concentration in the aqueous subphase at pH 5.5. The stable Pb(AA) 2 monolayers were transferred to Si wafers and TEM grids at 35 mN/m in the liquid condensed phase of the AA monolayer applying the Langmuir-Blodgett (LB) (ten monolayers) or the Langmuir-Schaefer (LS) technique, respectively. The most homogeneous monolayer was obtained at a Pb(NO 3 ) 2 concentration of 0.1 mM by using the LS method. Most homogeneous films (five bilayers) were obtained for a Pb(NO 3 ) 2 concentration of 0.01 mM by using the LB method. The formed films are investigated by transmission electron microscopy (monolayer produced by LS), X-ray reflectivity (XRR), and atomic force microscopy (films produced by LB). These methods revealed the formation of homogeneously distributed lead inclusions in the formed monolayers and films. Pb aggregates increase in number whereas their average size stays constant at ≈ 50 nm 2 with increasing Pb(NO 3 ) 2 concentration. Thickness parameters were determined by XRR. With increasing Pb(NO 3 ) 2 concentration, the bilayer thickness was found to increase. Furthermore, the patterns (111) and (200) for a cubic lead structure were found. The experimental results are compared with simulations obtained from geometry optimization on a semi-empirical quantum level to discuss the lead-ion binding to the AA molecules at pH 5.5.