Nanowizard 3 bioscience afm

Atomic force microscopy (AFM) was performed on a JPK Nanowizard 3 BioScience AFM (JPK, Germany). Images were taken operating in the AC mode and analysed by the SPM and DP 4.2 software version. Si-cantilevers with a force constant of 2.8 N/m and a resonance frequency of 75 kHz (Nanoworld AG, Switzerland) were used. The phase signal was set to zero at a frequency 5-10% lower than the resonance one. Drive amplitude was 700 mV and the amplitude set point was 700 mV.

Coverages and morphology were measured by scanning electron microscopy (SEM). All SEM images are taken at 3000x magnification and 25 kV beam energy (LEO VP1400 operated in high vacuum). Atomic Force Microscopy (AFM) is operated in tapping mode, both in air and liquid conditions using a NanoWizard 3 BioScience AFM (JPK Instruments). The resonance frequency of the AFM cantilevers (Nano and More, USA) was 300 kHz with a constant force of 50 N/m.

AFM measurements were carried out using a JPK Nanowizard ® 3 Bioscience AFM equipped with JPK Vortis SPM Control controller with XYZ closed-loop feedback (JPK instrument, Berlin) on an inverted microscope. Silicon cantilevers from Budget sensor (model: Multi-75-Al-G with 30 nm Aluminium reflected coating) were used for the quantitative imaging (QI) mode and force spectroscopy. The samples were first incubated in the pH 5 aqueous solution, where AFM tip was approached to the sample and QI measurement was used to measure the morphology of the samples. Force spectroscopy was carried out later on the sample on various location and the fore spectra were collected. The force spectra are averaged from the multiple force curves. The spring constants of the cantilevers were calibrated according to thermal noise method, which were found to be in the range of 4 -6 N/m. The sensitivity of the probe was subsequently measured on a silicon wafer. All data conversions were done on the JPK Data Processing software. The modulus was obtained by fitting the extended part of the force-penetration curves with simple Hertz model (JPK data analysis software). Individual force curve was fitted and tabulated into the graph.

Samples were prepared by putting a droplet of CNS suspension (0.1 wt%) onto a 1 × 1 cm 2 of a freshly cleaved mica. All samples were left 2 min in an atmospheric condition, rinsed with distilled water and blow-dried with N2 gas. Unattached particles were finally removed from the substrate using distilled water.
Dynamic-mode AFM was used to determine the morphology of the particles using a JPK NanoWizard 3 BioScience AFM. Each measurement was carried out in the air with commercial Bruker nanoprobes. Tips with a spring constant of 40 N/m and an amplitude point of 80% of the fundamental resonance peak, in the attractive regime, were chosen.
The Quantitive Imaging (QI) mode proposed by JPK was used to determine the force/distance curve for each pixel (256 × 256) and tip with a spring constant of 3 N/m (i.e. 2.96 N/m measured) was selected. Sensitivity calibration was derived by measuring thermal noise (30.91 nm/V measured). Optimal resolution was obtained using a 3.0 V free oscillating amplitude and 10-20 ms/pixel scanning speed. Additional information about the Quantitative Imaging is found in A2 section.