Tapping Mode Atomic Force Microscopy Investigation of Poly(amidoamine) Core−Shell Tecto(dendrimers) Using Carbon Nanoprobes

Carbon nanoprobes were utilized in tapping mode atomic force microscopy investigations to highlight the topographic differences between poly(amidoamine) (PAMAM) dendrimers, two-dimensional arrays of PAMAM dendrimers, and PAMAM core−shell tecto(dendrimers). The PAMAM core−shell tecto(dendrimers) used for this study consist of a shell of generation five (G5) dendrimers covalently linked to a G7 core. The volumes measured for the PAMAM core−shell tecto(dendrimers) suggest a 75−100% saturation of shell G5 dendrimers about the G7 core. This compares favorably with theoretical predictions that 12 G5 dendrimers should pack to form a shell about a G7 core. The effect of different imaging substrates was also explored. Tecto(dendrimers) imaged on hydrophobic surfaces experience a 6-fold increase in maximum peak height and a 3-fold decrease in diameter as compared to those imaged on mica. Measured volume is invariant.