Functional Microstructures by Self-Assembly - Molecular Self-Assembly: Advances and Applications - page 398

steps and the final QD pattern were confirmed using fluorescence
measurements (Fig. 12.8).
The two-layer molecular self-assembly procedure diverges from
the DNA process after hydroxylation of the exposed SiO surface

2

−

(Fig. 12.9). Surface-expressing amines ( ) were created using

immersion of the sample in 3'-aminopropyltriethoxylsilane (APTES)
solution with the substrate hydroxyl groups providing the necessary
binding sites. The second layer consists of carboxylated 655 nm
wavelength emission QDs suspended in a mix of phosphate buffer
solution (PBS) and an amine

NH 3

−

carboxyl coupling reagent, 1-ethyl-
3-(-3-dimethylaminopropyl)-carbodiimide (EDC). The QDs bind to
the sample over time. Excess material was rinsed off using PBS and
ammonium acetate; the PMMA was dissolved by dichloromethane. XPS
confirmed the deposition of APTES. Fluorescence micrographs and
atomic force microscopy images demonstrated successful attachment
of the QDs (Fig. 12.9) with topographical profiling revealing continuous
layers. Figure 12.9 displays a scanning electron micrograph of a dual
500 nm wide array with 200 nm spacing in between.

Figure 12.9 QDWs based on two-layer self-assembly of QDs. (a) Schematic

of the self-assembly chemistry. (b) Fluorescence imaging
shows QD immobilization in 500 nm wide (left micrograph)
and 100 nm wide (right micrograph) QWDs, in (i) single and
pair formation with a spacing of (ii) 200 nm and (iii) 500
nm, from left to right, respectively. The scale bar represents
a length of 1

µ

m. Reprinted with permission from Ref. [6].
Copyright 2006 American Chemical Society.