Background: The search for promising and renewable sources of carbohydrates for the production of biofuels and other biorenewables has been stimulated by an increase in global energy demand in the face of growing concern over greenhouse gas emissions and fuel security. In particular, interest has focused on non-food lignocellulosic biomass as a potential source of abundant and sustainable feedstock for biorefineries. Here we investigate the potential of three Brazilian grasses (Panicum maximum, Pennisetum purpureum and Brachiaria brizantha), as well as bark residues from the harvesting of two commercial Eucalyptus clones (E. grandis and E. grandis x urophylla) for biofuel production, and compare these to sugarcane bagasse. The effects of hot water, acid, alkaline and sulfite pretreatments (at increasing temperatures) on the chemical composition, morphology and saccharification yields of these different biomass types were evaluated. Results: The average yield (per hectare), availability and general composition of all five biomasses were compared. Compositional analyses indicate a high level of hemicellulose and lignin removal in all grass varieties (including sugarcane bagasse) after acid and alkaline pretreatment with increasing temperatures, whilst the biomasses pretreated with hot water or sulfite showed little variation from the control. For all biomasses, higher cellulose enrichment resulted from treatment with sodium hydroxide at 130°C. At 180°C, a decrease in cellulose content was observed, which is associated with high amorphous cellulose removal and 5-hydroxymethyl-furaldehyde production. Morphological analysis showed the effects of different pretreatments on the biomass surface, revealing a high production of microfibrillated cellulose on grass surfaces, after treatment with 1% sodium hydroxide at 130°C for 30 minutes. This may explain the higher hydrolysis yields resulting from these pretreatments, since these cellulosic nanoparticles can be easily accessed and cleaved by cellulases. Conclusion: Our results show the potential of three Brazilian grasses with high productivity yields as valuable sources of carbohydrates for ethanol production and other biomaterials. Sodium hydroxide at 130°C was found to be the most effective pretreatment for enhanced saccharification yields. It was also efficient in the production of microfibrillated cellulose on grass surfaces, thereby revealing their potential as a source of natural fillers used for bionanocomposites production.

Gold and Silver nanoparticles were fabricated using Camellia sinensis extracts, the Camellia sinensis serves as a dual role playing the role of reductant and stabilizers in the reduction of silver and gold and silver ions into the free states and potentially stabilized the surface of the synthesized silver nanoparticles. The synthesized Camellia sinensis stabilized silver and gold nanoparticles were characterized using Fourier Transform Infrared spectroscopy, Thermal analysis, Scanning electron microscope, Transmission electron microscope, Powder X-ray diffraction techniques, Microanalysis and uv/visible spectroscope. The localized surface plasmon resonance appeared at 401nm and gold 535nm. The synthesised green tea-AgNPs were used for the detection of heavy metals such as (copper, nickel and gold) and removal of copper from aqueous solution, the results obtained the ability of the Camellia sinensis stabilized AgNPs(GT-AgNPs) to be used as a portable sensor for the detection of heavy metals and subsequently used for the removal of heavy metals from aqueous solutions. The synthesized green tea stabilized gold nanoparticles were used for the detection of silver, nickel and copper.

Cysteine-stabilised silver nanoparticles (cys-AgNPs) were prepared in a one-pot aqueous synthesis in which AgNO₃ was reduced with NaBH₄ and the particles were capped with cysteine at room temperature. Formation of the particles was indicated by a colour change from colourless to yellow and then reddish-brown, with a localised surface plasmon resonance (LSPR) band at 401 nm that changed little over 100 min. UV-vis, FTIR, TGA, CHNS microanalysis, powder XRD, SEM and TEM were used for characterisation. These techniques indicated crystalline face-centred cubic silver of about 5–48 nm with a bimodal size distribution. They also showed a substantial organic fraction (about 40–53 wt%), with cysteine probably bound to the silver surface through the thiol group. Addition of Cu(II), Ni(II) and Au(III) (2–20 ppm) caused a rapid colour change and a marked decrease and shift of the LSPR band within 5 min. Batch experiments with Cu(II) and Ni(II) examined the effects of initial concentration, contact time, adsorbent dose, pH and temperature. Uptake reached about 10 mg g⁻¹ at 20 ppm, was fast (Cu(II) near-complete within 5 min), followed pseudo-second-order kinetics and was best described by the Henry isotherm. Ni(II) uptake increased with temperature and with pH. These results show that cys-AgNPs can bind Cu(II) and Ni(II) rapidly from dilute solution and are a candidate material for combined colorimetric sensing and removal of heavy metals. Selectivity, working capacity and performance in real wastewater still need to be established.