Study and Optimization of Self-Assembled Polymeric Multilayer Structures with Neutral Red for pH Sensing Applications

Table 1

Measurements of the thickness, roughness, and absorbance at 470 nm. The absorption coefficient at 470 nm was calculated from these data.

pH of the solutions	Bilayer thickness (nm)	Surface roughness (nm, rms)	Absorbance at 470 nm (a.u.)	Absorption coefficient (nm^−1)
2.5	5.5	4.12	0.246	0.00089
3.0	4.9	4.76	0.346	0.00141
3.5	4.8	6.36	0.425	0.00176
4.0	6.8	6.72	0.629	0.00185
4.5	14.5	5.24	1,179	0.00163
5.0	26.7	2.61	1,079	0.00081
5.5	35.2	1.48	0.579	0.00033
6.0	27.0	0.74	0.042	0.00003
6.5	9.7	2.04	0.003	0.00001
7.0	6.4	1.06	0.059	0.00011
7.5	6.6	1.64	0.036	0.00011
8.0	14.8	0.62	0.055	0.00007
8.5	32.3	0.34	0.034	0.00002
9.0	56.6	0.31	0.108	0.00004
9.5	82.8	0.38	0.157	0.00004