2.3. Characterization

Transmission Electron Microscope (TEM) was applied through FEI Tecnai F20 (Thermo Fisher Scientific Inc., Waltham, MA, USA) to examine the nanostructure of NCC particles. The specimen was prepared by staining the samples with 2% uranyl acetate and deposited on copper grid prior to viewing. Besides this, their surface feature after freeze-drying was examined with Field Emission Scanning Electron Microscope (FESEM) using FEI Nova NanoSEM 450 (Thermo Fisher Scientific Inc., Waltham, MA, USA), which operated under 1–15 kV accelerating voltage. Prior to viewing, samples were coated with platinum metal layer before loading on carbon-taped stub. The size of particle was determined for the nanoparticles via ImageJ software analysis. Elemental composition for each NCC sample was also investigated through Energy Dispersive X-ray (EDX) analysis (Thermo Fisher Scientific Inc., Waltham, MA, USA). Meanwhile, the dispersion behavior was studied with zeta potentials by Dynamic Light Scattering (DLS) using an equipment of Malvern Zeta sizer Nano ZS (Malvern Panalytical B.V., Brighton, UK). Additionally, the chemical composition of each treated fibre sample, including NCCs was analyzed to determine their contents of α-cellulose with TAPPI T203cm-99, holocellulose with TAPPI T249-75, and lignin with TAPPI T222 om-88, whilst the hemicellulose was determined by deducting with α-cellulose from holocellulose. The yield (%) of each fibre sample production was also calculated with the Equation (1) provided as below:

in which M₁ represents mass of raw Conocarpus fibres; M₂ represents total mass of treated-fibres within weighing container; M₃ represents mass of weighing container. Triplicate works were also conducted for the chemical composition and yield production to obtain reproducibility proof.

The functional groups of NCCs were investigated using Thermo Nicolet Nexus 670 Fourier Transform Infrared Ray (FTIR) analyzer (Thermo Fisher Scientific Inc., Waltham, MA, USA) with wavenumbers ranging 4000–400 cm⁻¹ maintained at 4 cm⁻¹ resolution. Before analysis, the samples were grinded with potassium bromide (KBr) and then underwent pelletization.

A PANalytical Empyrean X-ray diffractometer (XRD) (Malvern Panalytical B.V., Brighton, UK) was used to study the crystallinity of NCCs. The X-ray generator operated at 45 kV and 40 mA with Cu Kα radiation in 2°/min scan rate, while the powder samples were placed on nickel coated steel holder.

Thermal behavior of NCCs was evaluated with TA-SDT Q600 thermo gravimetric analyzer (Mettler-Toledo International Inc., Columbus, OH, USA). Both analyses of Thermogravimetry (TGA) and Derivative Thermogram (DTG) were conducted in 30–900 °C temperature range at 10 °C/min heating rate under nitrogen purge atmosphere. Meanwhile, Differential Scanning Calorimetry (DSC) (Mettler-Toledo International Inc., Columbus, OH, USA) was run in 30–600 °C temperature range with 10 °C/min heating rate.