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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 3.

Figure 3.

Substrates were characterized with contact angle and XPS at each step of the process. Contact angle measurements are shown for (a) piranha treated slides, which demonstrated a contact angle of <5° that is consistent with glass substrates treated in this manner. (b) GPTMS treated slides show a characteristic increase in a contact angle of 58.5°. (c) Avidin treated slides show a decrease in the contact angle to 29.6°, which can be attributed to avidin’s hydrophilicity. (n ≥ 3, SE ≤ 1.3 for all three conditions) XPS spectra data are shown for each of these steps. (d) C 1s clearly demonstrates an increase in the total carbon after 3-GPTMS and avidin functionalization indicating their presence on the surface. (e) N 1s peak showed no substantial peaks until avidin functionalization indicating avidin’s presence on the surface. (f,g) Both the O 1s and Si 2p peaks demonstrate shielding effects as the addition of silane and later avidin decrease the signal intensity of the underlying SiO2 framework.