Surface plasmon resonance and nonlinear optical studies of Langmuir–Blodgett films of a betaine dye

• Published in: Colloids and surfaces. A, Physicochemical and engineering aspects Vol. 155; no. 1; pp. 43 - 46
• Main Authors: Ashwell, Geoffrey J, Skjonnemand, Karl, Roberts, Michael P.S, Allen, David W, Li, Xing, Sworakowski, Juliusz, Chyla, Antoni, Bienkowski, Marcin
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15-09-1999
• Subjects: Betaine dye; Langmuir–Blodgett films; Second-harmonic generation; Sensors; Surface plasmon resonance; Langmuir–Blodgett films; Surface plasmon resonance; Sensors; Second-harmonic generation; Betaine dye
• ISSN: 0927-7757; 1873-4359
• DOI: 10.1016/S0927-7757(98)00392-6

Langmuir–Blodgett (LB) monolayers of 4-(
N-hexadecylpyridinium-4-ylmethylidene-amino)-2,6-dichlorophenolate have been investigated by surface plasmon resonance (SPR) and second-harmonic generation (SHG) techniques. The thickness, the real and imaginary components of the dielectric permittivity and the effective second-order susceptibility are
l=2.4
nm
layer
−1,
ε
r=1.75 and
ε
i=0.08 at 632.8
nm,
χ
(2)
eff
=20
pm
V
−1
at 1.064
μm respectively. The films protonate in air with loss of SHG and the colour changes from purple (
λ
max=510
nm) to yellow (
λ
max=375
nm). The process is reversible upon exposure to NH
3 and, thus, the glass|Ag|LB structures for SPR may be utilised as sensors by monitoring changes in the reflectance at a fixed angle of incidence.