Abstract: Bioactive compounds such as essential oils (EO), botanical extracts and natural resins are well known to have beneficial properties. Among these properties are their antibacterial activity. A disadvantage of these compounds is that they are volatile. Therefore, encapsulation is a good way to overcome this problem. In this study, the morphology, particle size distribution, Zeta potential and microbiological activity of chitosan nanoparticles incorporated with three different bioactive compounds having antimicrobial properties: ethanol extract of propolis, thyme essential oil and ethanol extract of Byrsonima crassifolia (L.) Kunth were evaluated. Nanoparticles were synthesized using the nanoprecipitation method. The morphology was observed using transmission electron microscopy (TEM). Also, particle size distribution and Zeta potential were measured. Results show spherical in shape nanoparticles. Thyme essential oil-loaded chitosan nanoparticles (TEO-CSNPs) showed the smallest particle size and highest stability as assessed by Zeta potential measurement, followed in stability by ethanol extract of propolis-loaded chitosan nanoparticles (EEP-CSNPs), ethanol extract of Byrsonima crassifolia (L.) Kunth (EEBC-CSNPs) and finally by chitosan nanoparticles (CSNPs). The antibacterial activity of the bioactive compounds-loaded chitosan nanoparticles was evaluated against Staphylococcus aureus. The highest antibacterial activity was observed for TEO-CSNPs with an inhibition halo (IH) value of 10.54±0.78 mm, followed by EEP-CSNPs (8.10±1.19 mm). EEBC-CSNPs and CSNPs did not show zone of inhibition. Bioactive compounds-loaded chitosan nanoparticles represents a good alternative for bacterial control of food borne pathogens in applications for fruits and vegetables conservation.
Abstract: Adsorption of cationic cetyltrimethylammonium bromide (CTAB) and nonionic Triton X100 surfactants from their mixed aqueous solutions on graphitized carbon black (CB) have been studied. The adsorption isotherms of CTAB or Triton X100 from single solutions on CB surface shown to be of the Langmuir type. In the mixed solutions of CTAB and Triton X100 surfactants, the adsorption of CTAB or Triton X100 on CB decreased in the presence of the other surfactant due to competitive adsorption of the components. It was shown that the mole fraction of Triton X-100 on CB surface has been essentialy changed depending on total concentration of the surfactants mixture. At mixture concentration corresponding to the unsaturated monolayer, a strong synergetic effect was found when the surface excess concentration Triton X100 at the CB surface in the presence of CTAB is higher than that for Triton X-100 in the absence of CTAB.
Abstract: This work demonstrates a simple, reproducible and scalable method of producing a potential slow-release fertilizer material. In this study, oxalate-phosphate-amine metal organic frameworks (OPA-MOFs) powder was synthesized from the hydrothermal treatment of ferric chloride (FeCl3•6H2O), orthophosphoric acid (H3PO4), oxalic acid dihydrate (H2C2O4•2H2O), and a common fertilizer, urea (CO(NH2)2). Being a structure directing agent (SDA)-type of MOF, the material is expected to slowly release urea via cation exchange, and eventually trigger the collapse of the framework, thus resulting to the subsequent release of the phosphates and iron-oxalate complexes. Elemental analysis revealed that the synthesized samples contains a promising amount of incorporated nitrogen and phosphorus. In this particular study, increasing in the amount of urea during the synthesis however revealed minimal change in the %N in the final product which tells us that maximum loading has already been achieved. P and N release experiments shall still be done both in vitro and in actual soil samples to monitor the release delivery kinetics and efficiency of the OPA-MOFs for fertilizer release applications.
Abstract: In this research, the nickel nanowire composite is synthesized with the copper foil via a single batch liquid-phase reduction method under a magnetic field. The deposition rate of nickel is investigated by using a quartz crystal microbalance (QCM) measurement. Various magnetic field conditions are used. The effect of magnetic field is investigated based on the changes in the morphology of the synthesized composite nanomaterial. The resulting morphology of the composite structure shows aligned nickel nanowire deposited vertically on the surface of the copper foil in a large area at a higher magnetic field, whereas decreasing the magnetic field leads to a wavy-like nanowire composite structure.
Abstract: The self-organization of COOH-functionalized multiwall carbon nanotubes (MWCNTs) during droplet evaporation of their aqueous suspension in a constant uniform electric field (E) was investigated. It was established that the COOH-functionalization polarizes the MWCNTs in the transverse direction to their axis. Depending on their size, MWCNTs tended to agglomerate into three different stable structures in different drop regions. There were linear, fractal and cluster structures (LS, FS, and CS). Sizes of the FSs decreased as 1/Е, whereas the rate of their growth increased as Е2. The single-walled carbon nanotubes (SWCNTs) were found inside the LSs and CSs. The chiral indices of the SWCNTs were determined, corresponding to metallic and semiconducting conductivities. An analysis showed that as a result of coagulation and amassment of the carbon nanotubes (CNTs) near electrodes, there were formed conductive regions. When the concentration of MWCNTs reached some value in part nearest to an electrode, this part became conductive. The positive and negative electrodes, formed now by MWCNTs, shifted towards each other. The observed effects show that considered self-organization is controllable by the electric field.
Abstract: Silica nanoparticles were synthesized by rice husk ash (RHA) produced from jasmine rice husk and riceberry rice husk via sol-gel method for the use as reinforcing fillers in natural rubber (NR). The obtained silica nanoparticles are spherical in shape and the particle sizes were observed to be in the 10-20 nm range with uniformly size distribution. The surface of silica nanoparticles was treated with a silane coupling agent confirmed by FTIR. The treated silica nanoparticles were then incorporated into NR and vulcanized with electron beam irradiation. The rubber nanocomposites with silica nanoparticles, produced from jasmine rice husk and riceberry rice husk, resulted in higher mechanical properties (tensile strength and modulus) than neat rubber vulcanizate. The modified rubber vulcanizates revealed rougher surface with tear lines as compared to the neat rubber vulcanizates, indicating the improved strength. Interestingly, the rubber nanocomposites with silica nanoparticles from jasmine rice husk showed higher tensile strength and modulus than silica nanoparticles produced from riceberry rice husk. The micrographs indicated better dispersion of NR composites with jasmine rice husk which leads to a strong interaction between silica nanoparticles and rubber matrix, thereby improving the strength.
Abstract: Nanocellulose were extracted from dried rubber tree leaves by acid hydrolysis. The dried rubber tree leaves were treated by the alkali and bleaching process to obtain the bleached cellulose powder. Acid hydrolysis from sulfuric acid (H2SO4) at different concentrations (35 wt.% to 65 wt.%) was performed to obtain the nanocellulose. The extracted nanocellulose were characterized by the transmission electron microscope (TEM), atomic force microscope (AFM), Fourier transform infrared spectroscopy (FTIR) and X-ray powder diffraction (XRD). The produced nanocellulose exhibited rod-like shaped cellulose nanocrystals (CNCs), however, the CNCs structure and crystallinity depended on the H2SO4 concentration. It was revealed that the higher H2SO4 concentration led to the shorter CNCs lengths. In addition, the crystallinity was generally found to increase with increasing acid concentration treatments but slightly reduce at 65 wt.% of H2SO4.
Abstract: Gold or silver nanoparticles (NP) were covered with protein corona by: 1) direct binding with a number of proteins; 2) nanoprecipitation of proteins from their solutions in fluoroalcohols; 3) physisorption of proteins on the NP surface treated with poly (allylamine) s; 4) encapsulation of Ag or Au NP into SiO2 envelope and functionalization with organosilanes. Adsorption of proteins on surfaces of metal NP is reversible and up to 70% of the attached proteins can be eluted. Ag NP possess high affinity for binding with immunoglobulins and fibrinogens but not with any protein. Nanoprecipitation of Ag and Au NP with proteins resulted in combined NP with metal core and protein shell with ligand-binding and enzymatic activities. SiO2 layer on surfaces of metal NP is suitable for silanization and covalent immobilization of any protein. Protein corona prevents Ag and Au NP from oxidation, dissolution and aggregation. Proteins attached to metal NP reduce their antimicrobial activity and cytotoxicity for eukaryotic cells. The developed methods of fabrication of Ag/Au NP with protein shells permit to attach any protein at different distances from metal core to avoid possible inactivation of proteins, to reduce fluorescence fading and to stabilize the nanoconjugates.
Abstract: This research aims to investigate photocatalytic activities of titanium dioxide (TiO2) incorporated with reduced graphene oxide (rGO) nanocomposite catalysts. These TiO2-rGO photocatalysts were easily prepared through a direct-mixing of TiO2 powder suspended in acidic solution under the different amounts of rGO loading (0.25, 0.50, 0.75 and 1.00 wt%). Then, the obtained TiO2-rGO samples were characterized by a several techniques. The results demonstrated that the crystalline phases of all samples are corresponding to pristine TiO2, whereas the characteristic peaks of rGO in the TiO2-rGO nanocomposites could be observed and also well-confirmed by Raman spectroscopy. TEM results showed that the TiO2 nanoparticles were well-combined with rGO nanosheets. Moreover, the photocatalytic activities of all TiO2-rGO photocatalyst samples were evaluated by photodegrading of methylene blue (MB) dye solution under natural sunlight irradiation. The results revealed that all TiO2-rGO nanocatalysts exhibited much higher activity than those of the bare TiO2. The improved photocatalytic activity can be attributed to the presence of rGO nanosheets, leading to the decrease of electron (e-) - hole (h+) recombination of TiO2 catalyst, increasing charge transfer rate of electrons and surface-adsorbed amount of MB molecules which enhances the photocatalytic activity.