Moustafa M.G. Fouda

Comparative study of calcium alginate, activated carbon, and their composite beads on methylene blue adsorption

Three adsorbents, calcium alginate beads (AB), sodium hydroxide activated carbon based coconut shells (C), and calcium alginate/activated carbon composite beads (ACB) were prepared. Their textural properties were characterized by N2-adsorption at -196°C and scanning electron microscopy. The porosity, surface area and total pore volume of C>ACB>AB, but AB adsorbent was more acidic function groups more than the other adsorbents. Adsorption experiments were conducted to examine the effects of adsorbent dosage, pH, time, temperature and initial concentration of methylene blue. Methylene blue adsorption on C, AB and ACB was observed at pH>6 to avoid the competition of H(+). The amount of dye adsorbed increases as the adsorbent dosage increase. Adsorption of dye follows pseudo-second order mechanism. Thermodynamic studies show spontaneous and endothermic nature of the overall adsorption process.

Antimicrobial activity of carboxymethyl chitosan/polyethylene oxide nanofibers embedded silver nanoparticles

A facile method to synthesize silver nanoparticles (AgNPs) using carboxymethyl chitosan (CMCTS), which act as reducing agent for silver ions as well as protecting agent for the formed AgNPs, is reported. CMCTS embedded AgNPs are mixed with polyethylene oxide (PEO). The blend polymers containing AgNPs are electrospun resulting in blend nano-fiber mats. The formation of AgNPs has been confirmed using UV-vis and TEM. The diameter range of 12-18 nm of well-dispersed AgNPs with a concentration of 100 ppm was obtained. The electrospun mats are characterized using SEM, EDX as well as TGA. Antimicrobial activity against different species of pathogenic/nonpathogenic; Staphylococcus aureus ATCC 25923, Pseudomonas aeruginosa ATCC 27853 and Escherichia coli ATCC 25922 in addition to the fungus Candida albicans ATCC 10231 was studied. The results show excellent antimicrobial activity compared with nanofibers without AgNPs and AgNPs alone.

Eco-friendly microwave-assisted green and rapid synthesis of well-stabilized gold and core-shell silver-gold nanoparticles

Herein, we present a new approach for the synthesis of gold nanoparticles (AuNPs) individually and as bimetallic core-shell nanoparticles (AgNPs-AuNPs). The novelty of the approach is further maximized by using curdlan (CRD) biopolymer to perform the dual role of reducing and capping agents and microwave-aided technology for affecting the said nanoparticles with varying concentrations in addition to those affected by precursor concentrations. Thus, for preparation of AuNPs, curdlan was solubilized in alkali solution followed by an addition of tetrachloroauric acid (HAuCl4). The curdlan solution containing HAuCl4 was then subjected to microwave radiation for up to 10 min. The optimum conditions obtained with the synthesis of AuNPs were employed for preparation of core-shell silver-gold nanoparticles by replacing definite portion of HAuCl4 with an equivalent portion of silver nitrate (AgNO3). The portion of AgNO3 was added initially and allowed to be reduced by virtue of the dual role of curdlan under microwave radiation. The corresponding portion of HAuCl4 was then added and allowed to complete the reaction. Characterization of AuNPs and AgNPs-AuNPs core-shell were made using UV-vis spectra, TEM, FTIR, XRD, zeta potential, and AFM analysis. Accordingly, strong peaks of the colloidal particles show surface plasmon resonance (SPR) at maximum wavelength of 540 nm, proving the formation of well-stabilized gold nanoparticles. TEM investigations reveal that the major size of AuNPs formed at different Au(+3)concentration lie below 20 nm with narrow size distribution. Whilst, the SPR bands of AgNPs-AuNPs core-shell differ than those obtained from original AgNPs (420 nm) and AuNPs (540 nm). Such shifting due to SPR of Au nanoshell deposited onto AgNPs core was significantly affected by the variation of bimetallic ratios applied. TEM micrographs show variation in contrast between dark silver core and the lighter gold shell. Increasing the ratio of silver ions leads to significant decrease in zeta potential of the formed bimetallic core-shell. FT-IR discloses the interaction between CRD and metal nanoparticles, which could be the question of reducing and stabilizing metal and bimetallic nanoparticles. XRD patterns assume insufficient difference for the AuNPs and AgNPs-AuNPs core-shell samples due to close lattice constants of Ag and Au. Based on AFM, AuNPs and AgNPs-AuNPs core-shell exhibited good monodispersity with spherical particles possessing different sizes in the studied samples. The average sizes of both metal and bimetallic core-shell were found to be 52 and 45 nm, respectively.

RETRACTED: Antibacterial modification of cotton using nanotechnology

This review article is undertaken with a view to survey important scientific research and developmental works pertaining to antibacterial modification of textiles using nanotechnology as a new means to achieve such textiles. Inevitably, conventional antimicrobial agents and their applications to textiles are reported. This is followed by a focus on inorganic nanostructured materials that acquire good antibacterial activity and application of these materials to the textiles. Evaluation of the antibacterial efficacy is described. An outlook which envisions the importance of using nanotechnology in the antibacterial finishing of textiles is also outlined.

Crosslinking of alginic acid/chitosan matrices using polycarboxylic acids and their utilization for sodium diclofenac release.

Three different ratios of alginic acid/chitosan matrices of ratios 3/1, 1/1 and 1/2, respectively, were crosslinked in their dry state using citric acid (CA)/sodium hypophosphite (SHP) at different conditions controlling the crosslinking process such as citric acid concentration, citric acid/sodium hypophosphite molar ratio as well as time and temperature of reaction. Results indicate that such matrices were crosslinked efficiently on curing at 180°C for 9min in presence of CA/SHP ratio 1 and the citric acid concentration of 0.6 based on the weight of any matrices. The crosslinked matrices were characterized by investigating their swelling properties, FT-IR and thermalgravimetric analysis. Furthermore, such crosslinked matrices were tested as drug release for sodium diclofenac.

Chitin and chitosan from Brazilian Atlantic Coast: Isolation, characterization and antibacterial activity

Chitin and chitosan were obtained by chemical treatments of shrimp shells. Different particle sizes (50-1000 μm) of the raw material were used to study their effect on size distribution, demineralization, deproteinization and deacetylation of chitin and chitosan isolation process. The particle size in the range of 800-1000 μm was selected to isolate chitin, which was achieved by measuring nitrogen, protein, ash, and yield %. Hydrochloric acid (5%, v/v) was optimized in demineralization step to remove the minerals from the starting material. Aqueous solution of sodium hydroxide (5%, w/v) at 90 °C for (20 h) was used in deproteinization step to remove the protein. Pure chitin was consequently impregnated into high concentration of sodium hydroxide (50%) for 3.5 h at 90 °C to remove the acetyl groups in order to form high pure chitosan. The degree of deacetylation (DDA) of chitosan was controlled and evaluated by different analytical tools. The chemical structure of chitin and chitosan was confirmed by elemental analysis, ATR-FTIR, H/C NMR, XRD, SEM, UV-Vis spectroscopy, TGA, and acid-base titration. The isolated chitin and chitosan from shrimp shell showed excellent antibacterial activity against Gram (-ve) bacteria (Escherichia coli) comparing with commercial biopolymers.

Synthesis, characterization and antibacterial activity of new fluorescent chitosan derivatives

The present work aims to the development of innovative new derivatives of chitosan that can be used for medical applications. This innovation is based on the synthesis and characterization of chitosan-g-aminoanthracene derivatives. Thus, N-(anthracen-9-yl)-4,6-dichloro-[1,3,5]-triazin-2-amine (AT) reacted with chitosan by the following steps: at first, cyanuric chloride reacted with 9-aminoanthracene to obtain N-(anthracen-9-yl)-4,6-dichloro-[1,3,5]-triazin-2-amine (AT), then the AT reacted with chitosan to obtain (CH-g-AT). The final product of CH-g-AT was separated, purified and re-crystallized by dioxane. The structure of the prepared chitosan derivatives was confirmed by FTIR-ATR, solid-NMR, TGA, X-RD, and DSC. The new chitosan derivatives showed fluorescence spectra in liquid and in solid state as well. CH-g-AT showed also high antibacterial activity against gram -ve species (Escherichia coli).

Structure and properties of hydroxyapatite/hydroxyethyl cellulose acetate composite films

The main aim of this research work was to develop a new inorganic-organic film. Hydroxyapaptite (HAp) particles that represent the inorganic phase was mixed well with hydroxyethyl cellulose acetate (HECA), which representing the organic phase and then the inorganic-organic films were fabricated by evaporating of the solvent. The structure as well as the properties of the formed films were characterized using different analytical tools such as field emission scanning electron microscopy (FEG-SEM), thermo-gravimetric analysis (TGA), Fourier transform infra-red (FT-IR) spectroscopy. The obtained results revealed that, the HAp nanoparticles was well dispersed and well immobilized throughout the formed films. This can be attributed to the role of the nano- and micropores in the HECA substrate. In addition, a strong interaction occurred between HAp and HECA matrix. The results showed also good thermal stability and miscibility as well.

Synthesis and characterization of composite based on cellulose acetate and hydroxyapatite application to the absorption of harmful substances

The aim of this work is to develop composite materials with hydroxyapatite (HAp) mineral and organic matrix such as cellulosic polymers. We use cellulose acetate with different percentages, and then inorganic-organic films were fabricated by evaporation of solvent. The composite films were characterized using emission scanning electron microscopy (FEG-SEM), thermo-gravimetric analysis (TGA) and Fourier transform infra-red (FT-IR) spectra. Test results show that these films are uniform and have good ductility. A strong interaction existed between HAp and cellulosic polymers, and the method allows the production of very fine particles size of about 92 nm. We have developed a new chromatographic method for the quantification of bisphenol A (BPA) in samples of baby food. The result of this study demonstrates how to use this type of composite materials to remove pollutants.

Removal of heavy metal using poly (N-vinylimidazole)-grafted-carboxymethylated starch

Carboxymethyl starch (CMS) grafted with N-vinyl imidazole was investigated for heavy metal removal from aqueous solutions. Poly (N-vinyl imidazole)-grafted carboxymethyl starch (PVI-g-CMS) was prepared in aqueous solution using potassium persulfate (KPS) as initiator. The produced grafted copolymer was characterized by FTIR, TGA, surface area and elemental analysis. The grafted material was used for the sorption of Mn(II), Zn(II) and Cd(II). Uptake parameters such as affinity of metal ions, effect of metal ion concentration, adsorbent amount and agitation time were investigated. The polymers were more sensitive to Cd(II) and Zn(II) and the order of metal ion binding was Cd(II)>Zn(II)>Mn(II). The adsorption data was fitted very well in a Freundlich isotherm equation and the kinetics of adsorption was found to follow the pseudo-first order kinetic model.