(E)-N-Hexadecyl-4-[2-(4-octadecyloxynaphthyl)ethenyl]quinolinium bromide, which has a wide-bodied chromophore and terminal n-alkyl groups, adopts a U-shape when spread at the air–water interface but a stretched conformation when compressed to ca. 35 mN m−1. The high-pressure phase has a narrow stability range prior to collapse but may be extended from 40 to 60 mN m−1 by co-spreading the dye in a 1 ∶ 1 ratio with docosanoic acid. The mixed Langmuir–Blodgett (LB) film has a monolayer thickness of 4.6 ± 0.2 nm which decreases to 2.5 ± 0.1 nm layer−1 in the bulk, the reduction arising from an interdigitating layer arrangement, both top and bottom. It is the first example of LB-Lego® and, in addition, represents the only fully interdigitating
structure with non-centrosymmetrically aligned chromophores. They are tilted 38° from the substrate normal. The second-harmonic intensity increases quadratically with the number of layers, i.e. as I2ω(N) = I2ω(1)N2, with a second-order susceptibility of χ(2)zzz = 30 pm V−1 at 1064 nm for refractive indices of nω = 1.55 and n2ω = 1.73, d = 2.5 nm layer−1 and ϕ = 38°. Angle resolved X-ray photoelectron spectra (XPS) of these films provide no evidence of the bromide counterion, which suggests that it
is replaced by OH− or HCO3−, which occur naturally in the aqueous subphase, or C21H43COO− from the co-deposited fatty acid. This probably applies to all cationic dyes deposited by the LB technique.
(E)-N-
十六烷基-4-[2-(4-
十八烷氧基
萘基)
乙烯基]
溴化
喹啉,具有宽体发色团和末端正烷基,在空气-
水界面铺展时呈 U 形,但在压缩至约 35 mN m-1 时呈拉伸构象。高压相在塌陷前的稳定性范围较窄,但通过以 1 ∶ 1 的比例将
染料与
二十二酸共同铺展,可将高压相从 40 mN m-1 扩展到 60 mN m-1。混合朗缪尔-布洛杰特(LB)薄膜的单层厚度为 4.6 ± 0.2 nm,在大体积中厚度减小到 2.5 ± 0.1 nm layer-1,减小的原因是顶部和底部的层间排列。这是 LB-Lego® 的第一个实例,也是唯一具有非中心对称排列发色团的完全互咬结构。它们与基底
法线倾斜 38°。在折射率为 nω = 1.55 和 n2ω = 1.73、d = 2.5 nm layer-1 和 ϕ = 38° 时,1064 nm 处的二次谐波强度随层数的增加而二次增加,即 I2ω(N) = I2ω(1)N2 ,二阶电感为 χ(2)zzz = 30 pm V-1。这些薄膜的角分辨 X 射线光电子能谱 (XPS) 没有发现
溴化反离子,这表明
溴化反离子是被
水性亚相中自然存在的 OH- 或 HCO3- 或共沉积
脂肪酸中的 C21H43COO- 所取代。这可能适用于所有通过 LB 技术沉积的
阳离子染料。