MATERIALS AND METHODS

Materials: Surian Wood Bark (SWB) was collected from community forest at Cibugel District, Sumedang Regency, West Java Province, Indonesia. Geographically, sampling site is located at 6°44'-70°83' south latitude and 107°21'-108°21' east longitude.

Methods: SWB was collected from community forest then cut using cleaver into small pieces measuring length by width about 20 by 20 mm and then solar dried until moisture content less than 5%. SWB was made into powder by pounded using a pestle and sieved by 60 mesh size.

Synthesis of bio-based nanomaterial was conducted by two step. First, 0.22 kg of wood bark powder (60 mesh) was further ground by using conventional balls milling for 48 h at 100 rev min^-1 with a ratio of balls to powder of 3.2:1. Second, wood bark powder treated by liquid nitrogen with a ratio of volume of liquid nitrogen to powder of 2:1, then ground using conventional balls milling for 48 h under condition as same as before. Wood bark powder then sieved by four of sieve types equipped with various size of fabric screen printing was called T77, T90, T120 and T200 of sieve types, respectively.

The milling container was made of PVC pipe with diameter size of 101.6 mm and length size of 275 mm. Balls were made of alumina with diameter size of 13-40 mm. Fig. 1 shows the schematic of synthesis of bio-based nanomaterial by using conventional balls milling.

Bio-based nanomaterial was evaluated using Scanning Electron Microscopy (SEM), energy dispersive X-ray Spectroscopy (EDS), Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray Diffraction (XRD). The morphology and diameter size of bio-based nanomaterial from SWB was characterized by using SEM (JEOL-JSM-6510LV SEM type). Samples were taken and coated with platinum with an ion sputter coater. The chemical composition of the SWB was analyzed using SEM that extended with energy dispersive X-ray spectroscopy analysis (SEM-EDS).

The functional groups present in the SWB was examined using Fourier Transform Infrared Spectroscopy (FTIR), Prestige 21, Shimadzu (Japan). Five miligram of samples were mixed with 160 mg KBr (1:32). They were then pressed into transparent thin pellets. A FTIR spectrum of SWB was obtained in the range of 4500 to 500 cm^-1. Spectral output was recorded in the transmittance mode as a function of wavenumber.

The crystallinity and its size of bio-based nanomaterial from SWB was identified by powder X-Ray Diffraction (XRD) instrument (XRD, PW 1710, Philips analytical) operation at 40 kV and 30 mA with Cu/Kα (λ = 1.54060 °A) radiation source. The diffractrograms were scanned using a scanning rate of 0.5° sec^-1 and in steps of 0.02° from 5° to 65° (2 θ) at room temperature.

The crystalline size of nanoparticle of SWB was determined from the X-ray diffraction peaks using Scherrer’s equation (Patterson, 1939), after correction for instrumental broadening as follow:

In the Eq. 1, D is the diameter of crystalline size, K is a shape factor with a value of 0.9-1.4 or the Scherrer’s constant of the order of unity for usual crystals, λ is the wavelength of the X-rays (1.54060 °A), θ is the diffraction angle and β is the value of the full width at half maximum (FWHM). XRD patterns were identified using the PDF2 CD-ROM (JCPDS-International Centre for Diffraction Data).

RESULTS AND DISCUSSION

Diameter size of bio-based nanomaterial: The particle size obtained from SEM analysis was found to be 93-110, 67-165, 68-93 and 42-114 nm produced from T77, T90, T120 and T200 of sieve types respectively with magnifications of 30,000 times and its morphology seemed the formation of agglomeration among particles (Fig. 2).

Fig. 1:	Schematic diagram of synthesis of bio-based nanomaterial using conventional balls milling

Fig. 2:	SEM analysis of particle size were produced from four of sieve types: (a) T77, (b) T90, (c) T120 and (d) T200

Therefore, the nanoparticle of organic materials from SWB was obtained, because their size in the rang e of 10-1000 nm (Allouche, 2013). For comparison, Abdul Khalil et al. (2011) reported that after the oil palm ash milled with high-energy ball milling for 30 h, the diameter size of particles up to 50 nm.

Table 1:	Sieve types and nanoparticle size
*: Based on SEM analysis, **: Based on conversion from T200 of sieve type, ***: Retained on T77 of sieve type

Fig. 3:	Proportion of nanoparticle size

The proportion of nanoparticle size were 39, 29, 24 and 2% produced from T77, T90, T120 and T200 of sieve types, respectively and the last (6%) of nanoparticle retained on T77 of sieve type (Table 1; Fig. 3).

Chemical components of bio-based nanomaterial: The chemical c ompositions of the SWB were studied by scanning electron microscopy equipped with energy dispersive X-ray spectroscopy analysis (SEM-EDS). Figure 4 shows the energy dispersive X-ray spec-troscopy analysis (EDS) spectra with the chemical composition of SWB. An essential ob-servation is that the SWB contained of carbon, oxygen, potassium and calcium.

Wood bark containing about 60-70% of glucose (Harkin and Rowe, 1971) and its nutrient depend on species, tree age, environmental factors and growing site (Buamscha et al., 2007). For comparison, pine wood bark contained of phosphorous, potassium, manga-nese, copper, calcium, magnesium and zinc (Buamscha et al., 2007).

Functional groups of bio-based nanomaterial: The presence of the functional groups that exist in the SWB were detected by fourier transform infrared spectroscopy (FTIR). The FTIR transmission spectrum of the SWB with size in diameter were 93-110, 67-165, 68-93 and 42-114 nm, produced from T77, T90, T120 and T200 of sieve types respectively composed of cellulose, the main constitute in natural fibers that acts as the reinforcing material in the cell wall (Fan et al., 2012; Garside and Wyeth, 2003; Kampeerapappun, 2012; Marchessault, 1962; Poletto et al., 2012) (Table 2; Fig. 5).

On the other hand the FTIR analysis shows the presence of C = O stretching band at 1735 cm^-1 in the nanoparticle of SWB produced from T90 and T120 of sieve types (Fig. 5b, 5c) and C = O stretching band at 1734 cm^-1 of SWB produced from T200 of sieve type (Fig. 5d due to balls milling effect while the nanoparticle of SWB produced from T77 of sieve type not observed (Fig. 5a).

Marchessault (1962) reported that there are correlation between morphology and chemical composition of wood from the bark through the cambium. Whereas Abdul Khalil et al. (2011) reported that the silanol (Si-OH) functional group presented after the oil palm ash milled with high-energy ball milling for 30 h.

Crystallinity of bio-based nanomaterial: According to the XRD results (Fig. 6), samples of bio-based nanomaterial produced from T77 and T200 of sieve types shows the crystalline structure of calcium oxalate hydrate (C₂CaO₄.H₂O).

Fig. 4:	EDS analysis of nanoparticle were produced from four of sieve types: (a) T77, (b) T90, (c) T120 and (d) T200

The reflecting peaks at 2 = 15.02, 24.46, 30.20, 36.04, 38.30 and 39.90° were used to estimate the average of crystalline size produced from T77 of sieve type which was calculated to be 26 nm (Fig. 6a). Whereas the average of crystalline size produced from T200 of sieve type had smaller size. The reflecting peaks at 2 = 15.10, 24.58, 30.28, 36.18, 38.38 and 43.68° were used to estimate the average of crystalline size produced from T200 of sieve type which was calculated to be 14 nm (Fig. 6b). According to Park et al. (2010) accessibility of cellulose affected by crystallinity, lignin and hemicellulose contents and its distribution, porosity and particle size.

Table 2:	Infrared spectrum of bio-based nanomaterial produced from SWB
Note: - no dat

Fig. 5:	FTIR analysis of nanoparticle were produced from four of sieve types: (a) T 77, (b) T 90, (c) T 120 and (d) T200

Fig. 6:	XRD analysis of nanoparticle were produced from : (a) T 77 and (b) T200 of sieve types

CONCLUSION

ACKNOWLEDGMENTS

The authors would like to thank to Prof. Dr. Bambang Sunendar Purwasasmita (head of Advanced Materials Processing Laboratory), Engineering Physics Department, Faculty of Industrial Technology, Institut Teknologi Bandung for research facilities; Board of Research and Community Services, Institut Teknologi Bandung and Ministry of Education and Culture of Republic of Indonesia for the financial support for this research through Decentralization Research Program 2013. The authors also thank to Mr. Rifki Septawendar for his technical assistance of XRD data analysis.