Multimode 8 spm

The atomic force microscopy (AFM) measurements were performed by exploiting a Multimode 8 SPM coupled with a Nanoscope-V controller (Bruker-AXS, Santa Barbara, CA, USA). In order to minimize probe-sample interactions during scanning, the topographic images were obtained by tapping-mode AFM where a continuously oscillating probe is used to scan the sample. Briefly, mica coverslips were prepared by first mounting the entire mica stack onto a glass slide with two-sided tape. Scotch tape was applied to the top of the mica and then removed, which pulled off an entire layer of mica, leaving behind a freshly cleaved layer of mica on the glass slide. Therefore, 10 µL drops of MV suspension was deposited onto surface of clean layer of mica. Sample was air-dried at room temperature before of AFM measurements in a scan size of 5 microns square for each acquisition. The surface of a clean mica was used as background reference (data not shown). Images were collected from three different samples and were processed by Gwyddion 2.45 software. For each image, single MVs were analysed to obtain MV diameter. Clustered MVs and MVs with imaging artifacts were excluded from the analysis. MVs adjacent/touching to each other were included in the analysis only if separation between MVs can be clearly established. At least 50 MVs were measured to obtain MV size distribution.

Microfibrillated cellulose (MFC) with a nominal fiber width of 50 nm and several hundred micrometers of length was purchased from Maine University (3.0 wt % aqueous gel) [58 ]. Further characterizations and information about the MFC can be found in [58 ]. Functionalized multiwalled carbon nanotubes (MWCNTs) with hydroxy and carboxyl groups (–OH and –COOH), outer diameter between 20 and 50 nm and an average length of 5 μm were produced at CTNano/UFMG [59 (link)–61 (link)]. Morphological analysis was carried out by scanning electron microscopy (SEM) in a Quanta 200 FEG, using secondary electrons between 2 and 10 kV. Atomic force microscopy (AFM) was carried out on a Bruker MultiMode8 SPM using the intermittent contact mode. AC160TS silicon cantilevers from Olympus with a typical spring constant of k ≈ 46 N/m, a nominal radius of curvature of r ≈ 7 nm, and a resonant frequency of ω₀ ≈ 300 kHz were employed. Heat flow and weight changes of selected solvents were determined by thermogravimetric analysis (TGA) using a PerkinElmer STA 8000 device. Electrical measurements were performed using a lock-in amplifier (SR830 DSP Stanford Research Systems), a pre-amplifier (model 1211 DL instruments), and a multimeter (model 2000 Keithley), which were controlled by a computer.

Graphene transfer coverage and cleanliness is studied using field emission scanning electron microscopy (SEM) (Zeiss LEO 1530 Gemini). The graphene quality after the transfer is assessed via Raman spectroscopy using a 532 nm wavelength laser (Thermo Scientific DXR Raman Microscope). The laser power is kept below 5 mW in order to prevent damage to the graphene. The terrace-step morphology of the annealed sapphire substrates with and without graphene termination is analyzed by AFM (Bruker Multimode 8 SPM) in tapping mode.

The P-E loops of PMN-PT were measured using a Radiant Technologies Precision Premier II system. The strain properties were measured using a strain gauge glued on the PMN-PT^{58 (link)}. XRD with in situ electric fields was characterized by a Rigaku SmartLab 3 kW X-ray diffractometer with a Cu Kα radiation. The morphology was characterized by atomic force microscopy using a commercial scanning probe microscope system (Multimode 8 SPM, Bruker).