Quantitative Analysis of Scanning Force Microscopy Data Using Harmonic Models

Schröter, Klaus; Petzold, Albrecht; Henze, Thomas; Thurn‐Albrecht, Thomas

doi:10.1021/ma8024464

Cited by 36 publications

(54 citation statements)

References 33 publications

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“…Phase contrast originates from different mechanical properties of crystalline and amorphous regions with higher signal corresponding to stiffer crystalline domains. 39 Fibrillar morphology similar to that of Figure 2b has been reported for RP3HT previously. 8,40 In addition, RP3HT nanofibrils have been suggested to be related with edge-on oriented P3AT chains.…”

Section: Resultssupporting

confidence: 82%

Effects of Polythiophene Surface Structure on Adsorption and Conformation of Bovine Serum Albumin: A Multivariate and Multitechnique Study

et al. 2014

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Protein interactions with surfaces of promising conducting polymers are critical for development of bioapplications. Surfaces of spin-cast and postbaked poly(3-alkylthiophenes), regiorandom P3BT, and regioregular RP3HT are examined prior to and after adsorption of model protein, bovine serum albumin, with time-of-flight secondary ion mass spectrometry, atomic force microscopy, and X-ray photoelectron spectroscopy. The multivariate method of principal component analysis applied to ToF-SIMS data maximizes information on subtle differences in surface chemistry: PCA reveals alkyl side chains and conjugated backbones, exposed for RP3HT and P3BT, respectively. Phase imaging AFM shows semicrystalline microstructure of RP3HT and amorphous morphology of P3BT films. A cellular-like pattern of proteins adsorbed on RP3HT develops with coverage to more uniform overlayer, observed always on P3BT. The amount of adsorbed protein, determined by XPS as a function of BSA concentration (up to 10 mg/mL), is ∼21% lower for RP3HT than P3BT (up to 1.1 mg/m(2)). Although PCA differentiates protein from polythiophene, relative protein surface composition evaluated from ToF-SIMS saturates rather than increases with amount of adsorbed BSA from XPS. This reflects ToF-SIMS sensitivity to outermost layer of proteins, enabling multivariate analysis of protein conformation or orientation. PCA distinguishes between amino acids characteristic for external regions of BSA adsorbed to P3BT and RP3HT. These amino acids are identified for P3BT and RP3HT as hydrophilic and hydrophobic, respectively, by relative hydrophobicity of amino acid side chains. Alternative identification with BSA domains fails, pointing to substrate-induced changes in conformation and degree of denaturation rather than orientation of adsorbed protein.

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Section: Resultssupporting

confidence: 82%

Effects of Polythiophene Surface Structure on Adsorption and Conformation of Bovine Serum Albumin: A Multivariate and Multitechnique Study

et al. 2014

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“…AFM phase contrast is related to the Fourier transform of the interaction force between tip and sample during approach and penetration of the sample. 41 As the corresponding height images do not show the same pattern and as the surface of the film is chemically uniform, it is obvious that the phase signal reflects mainly the different mechanical properties of crystalline and amorphous parts of the sample. For a sample with hard-soft contrast generally higher values of the phase correspond to the stiffer material.…”

Section: Resultsmentioning

confidence: 99%

“…For a sample with hard-soft contrast generally higher values of the phase correspond to the stiffer material. 41 Clearly with increasing molecular weight the thickness of the crystals increased and the arrangement of the crystals became somewhat less well ordered. A direct quantitative determination of the thicknesses of the crystals and the amorphous layers is difficult due to resolution problems.…”

Section: Resultsmentioning

confidence: 99%

Temperature and Molecular Weight Dependent Hierarchical Equilibrium Structures in Semiconducting Poly(3-hexylthiophene)

et al. 2010

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We report on structural investigations of a series of regioregular poly(3-hexylthiophene) with well-defined molecular weight (5-19 kg/mol) using DSC, small angle and wide-angle X-ray scattering, and AFM. With increasing temperature, we identify three ordered phases, namely 3D crystalline, 2D crystalline with disordered side chains, and a layered phase of smectic symmetry, followed by complete melting. Although all samples crystallize in extended chain conformation, the lower molecular weight material exhibits a lower crystallinity, most likely caused by noncrystallizable end groups. The crystallinity increases strongly with increasing molecular weight, which could be a possible explanation for the known dependence of charge transport properties on molecular weight.

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“…We attribute the shape of the PB curves to viscoelastic dissipation processes 19 and note the plateau-like shape of the PS curves, similar to those curves observed on crystalline regions of polypropylene. 24 Figure 1 panels f and g show the analysis of the APD curves according to ref 21. Conservative and dissipative contributions to the total tipϪsample interaction force are expressed by an additional tipϪsample spring constant k TS and the effective damping parameter ␣ eff /m.…”

Section: Resultsmentioning

confidence: 99%

“…Conservative and dissipative contributions to the total tipϪsample interaction force are expressed by an additional tipϪsample spring constant k TS and the effective damping parameter ␣ eff /m. 21 The former is given by where m ϭ k/ 0 2 is the vibrating mass and k eff is the total effective spring constant. The effective damping parameter…”

Section: Sample Preparationmentioning

confidence: 99%

Subsurface Imaging of Soft Polymeric Materials with Nanoscale Resolution

2010

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Nondestructive depth-resolved imaging of ∼20-nm-thick surface layers of soft polymeric materials is demonstrated using amplitude modulation atomic force microscopy (AM-AFM). From a map of amplitude-phase-distance curves, the tip indentation into the specimen is determined. This serves as a depth coordinate for reconstructing cross sections and volume images of the specimen's mechanical properties. Our method reveals subsurface structures which are not discernible using conventional AM-AFM. Results for surfaces of a block copolymer and a semicrystalline polymer are presented.

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Quantitative Analysis of Scanning Force Microscopy Data Using Harmonic Models

Cited by 36 publications

References 33 publications

Effects of Polythiophene Surface Structure on Adsorption and Conformation of Bovine Serum Albumin: A Multivariate and Multitechnique Study

Effects of Polythiophene Surface Structure on Adsorption and Conformation of Bovine Serum Albumin: A Multivariate and Multitechnique Study

Temperature and Molecular Weight Dependent Hierarchical Equilibrium Structures in Semiconducting Poly(3-hexylthiophene)

Subsurface Imaging of Soft Polymeric Materials with Nanoscale Resolution

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