Economic and facile approach for synthesis of graphene-titanate nanocomposite for water reclamation.

Graphene and its composites with semiconductor materials have been received highly attention in many research areas because of their unique properties. Efficient application of graphene is hindered by the lack of cost-effective synthesis methods. In this work, an economic and facile route for mass production of graphene-titanate nanocomposite has been discussed. Graphene was prepared by exfoliation of graphite powder in 40% ethanol aqueous solution. Titanate nanotubes were grown on graphene sheets by hydrothermal method, where the dispersed graphene sheets were mixed with titanate solution and then placed in autoclave and placed in oven for 16 h at 160 °C. The prepared composite was characterized by transmission electron microscope (TEM), scanning electron microscope (SEM), Fourier transforms infrared spectroscopy (FTIR), thermogravimetric analysis (TGA). All the obtained results confirmed the synthesis of graphene and its composite with titanate in highly uniform and pure form. The adsorption efficiency of the prepared composite was tested using methylene blue (MB) as a model dye. The adsorption isotherm was investigated using Freundlich and Langmuir models. The adsorption capacity of MB was 270.27 mg/g. The obtained correlation coefficients (R2) by Freundlich and Langmuir model were 0.996 and 0.973, respectively. The adsorption kinetics was investigated and discussed using different models. The thermal stability of the developed composite is improved after MB adsorption.

New sensing platform of poly(ester-urethane)urea doped with gold nanoparticles for rapid detection of mercury ions in fish tissue.

A new electrochemical sensor has been fabricated based on the in situ synthesis of poly(ester-urethane) urea (PUU) doped with gold nanoparticles (AuNPs), and the obtained composite materials (PUU/AuNPs) were used as a new sensing platform for highly sensitive and selective detection of mercury(II) ions in fish tissue. PUU was synthesized and fully characterized by XRD, TGA, DSC, and FTIR to analyze the chemical structure, thermal stability, and morphological properties. As a polymeric structure, the PUU consists of urethane and urea groups that possess pronounced binding abilities to Hg2+ ions. SEM-EDX was carried out to confirm this kind of interaction. Using ferricyanide as the redox probe, PUU alone exhibited weak electrochemical signals due to its low electrical conductivity. Therefore, a new series of nanocomposites of PUU with different nanostructured materials were applied, and their electrochemical performances were evaluated. Among these materials, the PUU/AuNP-modified electrode showed high voltammetric signals towards Hg2+. Consequently, the parameters affecting the performance of the assay, such as electrode composition, scan rate, and sensing time, as well as the effect of electrolyte and pH were studied and optimized. The sensor showed a linear range of 5 ng mL-1 to 155 ng mL-1 with the regression coefficient R 2 = 0.986, while the calculated values of the limit of detection (LOD) and limit of quantification (LOQ) were 0.235 ng mL-1 and 0.710 ng mL-1, respectively. In terms of cross reactivity testing, the sensor exhibited a high selectivity against heavy metals which are commonly determined in seafood (Cd2+, Pb2+, As3+, Cr3+, Mg2+, and Cu2+). For real applications, total Hg2+ ions in fish tissue were determined with very high recovery and no prior complicated treatments.

Exploitation of new approach to control of environmental pathogenic bacteria causing bovine clinical mastitis using novel anti-biofilm nanocomposite.

New approaches are required for prevention and control of biofilm-producing bacteria and consequently mitigating the health problems of bovine clinical mastitis. This work designed to determine prevalence rates of biofilm-producing bacteria that causing bovine clinical mastitis and evaluate the anti-biofilm effectiveness of novel nanocomposite of zinc-aluminum layered double hydroxide intercalated with gallic acid (GA) as chelating agent (Zn-Al LDH/GA) on the prevention and control of environmental pathogenic bacteria; Escherichia coli (E. coli), Klebsiella pneumoniae (K. pneumoniae), Staphylococcus aureus (S. aureus), and Coagulase-negative staphylococci (CNS), besides Listeria monocytogenes (L. monocytogenes) and assess the ability to use as an antimicrobial agent, and/or sanitizer for milking equipment. All samples (n = 230) involved clinical mastitis cow's milk (n = 50) beside environmental samples (n = 180) were collected then examined for isolation and identification of bacterial pathogens. Zn-Al LDH/GA nanocomposite was synthesized using co-precipitation method, then characterized by Fourier-transform infrared spectroscopy (FT-IR); X-ray diffraction (XRD); field emission scanning electron microscopy (FESEM); high-resolution transmission electron microscopy (HRTEM); thermogravimetric analysis (TGA); differential thermal analysis (DTA); zeta potential; DLS analysis; and Brunauer, Emmett, and Teller (BET) surface area. The anti-biofilm activity of nanocomposite against mastitis-causing bacteria was detected using the broth micro-dilution and disc-diffusion assay. Results, the minimum concentration of Zn-Al LDH/GA that inhibited the growth of gram-positive and negative bacteria, were 312-625 and 5000 µg/mL, respectively. The LD50 of Zn-Al LDH/GA was determined in mice at 1983.3 mg/kg b.wt. As a conclusion, Zn-Al LDH/GA nanocomposite proved its efficiency as an antimicrobial agent and/or sanitizer used for cleaning of milking equipment, due to it could inhibit the growth and multiplication of potentially pathogenic bacteria that causing clinical mastitis and its formation of biofilm on the milking equipment. Zn-Al LDH/GA was found to use under varying pH conditions compared with other commercial sanitizer used besides the formation of nanocomposite increases the material stability.

Preparation, characterization and antimicrobial applications of Zn-Fe LDH against MRSA.

Facile and simple processes to get Zn-Fe layered double hydroxide (LDH) with nitrate as the interlayer anion are reported. The method of co-precipitation produced high crystallinity LDH that is marked by XRD, SEM, TEM and FT-IR. Results showed that 99.8% of Cd(+2) removals were at pH11 and 4h. To get the adsorption isotherms, the concentration of metal ions extending from 6 to 18mg/L was utilized. Results supported the Langmuir adsorption model. In contrary, the adsorption process followed the pseudo-second-order reaction kinetics. Interestingly, the prepared LDH shows durable antimicrobial activities against Gram-negative (Proteous vulgaris, Klebsiella pneumoniae, Escherichia coli and Pseudomonas aeruginosa) and Gram-positive (Staphylococcus epidermidis, Staphylococcus aureus, Streptococcus pyogenes and MRSA) and fungi (Candida albicans, Aspergillus fumigatus, Geotricumcandidum, and Trichophyton mentagrophytes). The minimum inhibitory concentration (MIC) of Zn-Fe LDH varied from 0.49 to 15.60µg/mL according to the types of microorganisms. The prepared LDH achieved 90% at pH8.50 which is the pH of wastewater and at the same time exhibited durable antimicrobial activities against MRSA, Gram-negative, Gram-positive and fungi. Results have significant implications in the field of bioremediation of water with little cost, simple operation, high productivity and easiness of the equipment.