Synthesis of Graphene Oxide from Sugarcane Dry Leaves by Two-Stage Pyrolysis.

Natural or synthetic graphite as precursors for the preparation of graphene oxide (GO) have constraints due to their limited availability, high reaction temperature for processing of synthetic graphite and higher generation cost. The use of oxidants, long reaction duration, the generation of toxic gases and residues of inorganic salts, the degree of hazard and low yield are some of the disadvantages of the oxidative-exfoliation methods. Under these circumstances, biomass waste usage as a precursor is a viable alternative. The conversion of biomass into GO by the pyrolysis method is ecofriendly with diverse applications, which partially overcomes the waste disposal problem encountered by the existing methods. In this study, graphene oxide (GO) is prepared from dry leaves of sugarcane plant through a two-step pyrolysis method using ferric (III) citrate as a catalyst, followed by treatment with conc. H2SO4. The synthesized GO is analyzed by UV-Vis., FTIR, XRD, SEM, TEM, EDS and Raman spectroscopy. The synthesized GO has many oxygen-containing functional groups (-OH, C-OH, COOH, C-O). It shows a sheet-like structure with a crystalline size of 10.08 nm. The GO has a graphitic structure due to the Raman shift of G (1339 cm-1) and D (1591 cm-1) bands. The prepared GO has multilayers due to the ratio of 0.92 between ID and IG. The weight ratios between carbon and oxygen are examined by SEM-EDS and TEM-EDS and found to be 3.35 and 38.11. This study reveals that the conversion of sugarcane dry leaves into the high-value-added material GO becomes realistic and feasible and thus reduces the production cost of GO.

Synthesis of Carbon Quantum Dots with Special Reference to Biomass as a Source - A Review.

Quantum dots (QDs) have received much attention due to their extraordinary optical application in medical diagnostics, optoelectronics and in energy storage devices. The most conventional QDs are based on semiconductors that comprise heavy metals whose applications are limited due to toxicity and potential environmental hazard. Of late, researchers are focusing on carbon-based quantum dots, which have recently emerged as a new family of zero-dimensional nanostructured materials. They are spherical in shape with a size below 10 nm and exhibit excitation-wavelength-dependent photoluminescence (PL). Carbon quantum dots (CQDs) have unique optical, photoluminescence and electrochemical properties. They are environment-friendly with low toxicity as compared to toxic heavy metal quantum dots. Generally, CQDs are derived from chemical precursor materials, but recently researchers have focused their attention on the production of CQDs from waste biomass materials due to the economic and environmental exigency. In this review, recent advances in the synthesis of CQDs from waste biomass materials, functionalization and modulation of CQDs and their potential application of biosensing are focused. This review also brings out some challenges and future perspectives for developing smart biosensing gadgets based on CQDs.

Improving the stability of thyme essential oil solid liposome by using ß-cyclodextrin as a cryoprotectant.

The objective of this study was to investigate the preparation of the freeze-dried ε-polylysine (ε-PLY)-coated thyme essential oil (TEO) liposome, and its application in vegetable juices to control the Escherichia coli O157:H7 growth. Firstly, the solid liposomes (SLP) were obtained via freeze-drying in the presence of ß-cyclodextrins as cryoprotectant under different ratios of ß-cyclodextrin: lipid (w/w) (2:1, 4:1, 6:1 and 8:1). The ultraviolet visible and fourier transformed infrared spectrograms results indicated the presence of TEO and ε-PLY in SLPs. Subsequently, the morphology, antioxidant activity, digestibility, release rate and phase inversion temperature of SLPs were measured respectively. The SLP powders and re-hydrated SLP solutions exhibited the optimal physical and chemical properties when the ratio of ß-cyclodextrin: lipid was 6:1. In addition, SLPs stored at 4 °C and 12 °C possessed favorable particle size, PDI and zeta potential. Finally, the desired antibacterial effects of SLPs on Escherichia coli O157:H7 in 4 vegetable juices were achieved at a concentration of 5 mg/mL.