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This work implicates the synthesis of biochar-hematite nanocomposite from bamboo sawdust and its photodegradation characteristic for remazol brilliant blue. The nanocomposite was prepared through a one-step pyrolysis process in a tubular furnace under a flow of nitrogen and impregnation using FeSO4.7H2O and FeCl3.6H2O. The physicochemical properties were characterized by x-ray diffraction and Fourier transform infrared spectroscopy, which confirmed that hematite was successfully identified on the surface of the nanocomposite. The results also show that the nanocomposite is suitable for photodegradation application. The decolorization of remazol brilliant blue is suitable with the Langmuir isotherm model and pseudo-second-order kinetic model. At pH = 1, initial concentration = 200 mg/L, contact time = 60 minute and nanocomposite dosage 0.4 g/L, the decolorization efficiency reached 96.9%.

The composite of green synthesized gold nanoparticles (Au NPs)-doped hydroxyapatite (HA) has been prepared. The gold nanoparticles were produced via bioreduction of HAuCl4 with Clitoria ternatea flower extract, and utilized in the synthesis of hydroxyapatite using Ca(OH)2 and ammonium diphosphate as precursor. The aim of this research is to study the structural analysis of the composite and antibacterial activity test toward Eschericia coli, Staphylococcus aureus, Klebsiela pneumoniae, and Streptococcus pyogenes. In addition, the antioxidant activity was evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging method. The monitoring of gold nanoparticles formation was conducted by UV–vis spectroscopy and particle size analyses, meanwhile the synthesized composite was studied using X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The results showed that homogeneously dispersed gold nanoparticles in HA structure was obtained with the particle size ranging at 5-80 nm. The nanocomposite demonstrated antibacterial activity against tested bacteria. The nanocomposite expressed an antioxidant activity as shown by the DPPH scavenging activity of 66 and 58% at the concentration of 100 μg/mL and 50 μg/mL, respectively.

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