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. Author manuscript; available in PMC: 2022 Jan 22.
Published in final edited form as: ACS Appl Nano Mater. 2020 Dec 23;4(1):33–42. doi: 10.1021/acsanm.0c01998

Figure 4.

Figure 4.

Ability of each platform to create an evenly distributed, high concentration of SWNT was tested. (a) Either non-biotinylated or biotinylated SWNT (30 mg/L) was applied to intermediates in the derivatization processes and completely derivatized surfaces. Intermediate surfaces showed little to no retention of SWNT while APTES and avidin showed a significant increase in SWNT retention. The SWNT/substrate combinations of APTES + non-biotinylated SWNT, APTES + biotinylated SWNT, and avidin + non-biotinylated SWNT showed no significant differences (labeled as ns), while the avidin + biotinylated SWNT condition showed a significant increase in fluorescence (labeled *) compared to all electrostatic and nonspecific conditions, indicating that the addition of biotin enhances SWNT retention (n = 3, s = 5). (b) Individual data points are shown for the two main platforms with both biotinylated and non-biotinylated SWNT and (c) SWNT loading was determined for concentrations of 10–50 mg/L. Concentrations of 30 mg/L and greater produced significant increases in loading capacity for the avidin + biotinylated SWNT combination when compared with all other combinations. It is not possible for the APTES + non-biotinylated SWNT, APTES + biotinylated SWNT, and avidin + non-biotinylated SWNT conditions to reach a fluorescence intensity level as high as that of the avidin + biotinylated SWNT conditions, even with the addition of excess SWNT to those conditions. (e–h) Representative images of avidin + biotinylated SWNT, avidin + non-biotinylated SWNT, APTES + biotinylated SWNT, APTES + non-biotinylated SWNT, respectively, show the even distribution of fluorescence that is achieved for all four conditions. (d) Quantification of SWNT distribution was determined via the arithmetic average roughness (Ra). Ra values showed no significant differences between substrate/SWNT combinations, indicating a smooth loading of SWNT across all SWNT concentrations. Statistics performed via one-way ANOVA analysis with multiple comparisons tests, conducted using the Tukey method.