PEG-mesoporous material modified by superparamagnetic nanoparticles as a delivery system of cefotaxime.

The fight against infectious bacterial diseases has been taking major steps forward by designing new nanodrugs and nanoscale biological carriers with unique physicochemical properties. Here, polyethylene glycol (PEG)-silica mesoporous material/superparamagnetic CuFe2O4 nanoparticle nanocomposite was synthesized using a facile chemical approach, and proposed as a carrier for the delivery of cefotaxime (CTX) drug. The resulting nanocomposite material and nanocomposite CTX drug carrier were characterized by different techniques. Antibacterial activity of the nanocomposite drug carrier was investigated against E.coli and S. aureus bacteria, and compared with that of commercial CTX drug. It was found that the minimum inhibitory concentrations of the nanocomposite drug carrier (1.25 and 5 µg/mL) were significantly less than those of the commercial drug (10 and 80 µg/mL) against the bacteria. Furthermore, enhanced performance of the nanocomposite CTX carrier for both the Gram-negative and Gram-positive bacteria was evidenced.

PdZrO2/rGO-FTO as an effective modified anode and cathode toward methanol electro-oxidation and hydrogen evolution reactions.

In the present work, Pd/rGO and PdZrO2/rGO nanostructures were synthesized in a single step by hydrothermal method. Synthesized nanostructures containing 20 wt% Pd nanoparticles were characterized and approved using Fourier-transform infrared spectroscopy, x-ray diffraction, field emission scanning electron microscopy, energy-dispersive x-ray spectroscopy, and transmission electron microscopy techniques. The performance of Pd and PdZrO2hybridized with rGO as catalysts were investigated and compared in the process of hydrogen production by water electrolysis and also in the process of electricity generation by methanol oxidation in the fuel cell. The activity and stability of synthetic nanocatalysts were evaluated using cyclic voltammetry, LSV, and chronoamperometry. The results showed that the presence of ZrO2in the nanostructure increases the current density and reduces the overvoltage of the catalytic process. For methanol oxidation reaction, PdZrO2/rGO catalyst displays 92 mA cm-2current density in alkaline media. For hydrogen evolution reaction, the Tafel slope of 52 mV dec-1and overpotential of -0.198 V at the current density of 10 mA cm-2were obtained in alkaline media. Also, due to high stability, this catalyst can be recommended as an optimal catalyst for industrial processes.

Aspergillus Section Flavi from Four Agricultural Products and Association of Mycotoxin and Sclerotia Production with Isolation Source.

Many agricultural products are susceptible to contamination by aflatoxin-producing species from Aspergillus section Flavi. The objectives of this study were to determine the occurrence of Aspergillus section Flavi in four agricultural products, such as pistachio, walnut, hazelnut, and dried fruits, collected from market and retail shops in various areas of Kerman County and obtain information on the relationships between isolation source and ability to produce sclerotia and potential for aflatoxin production. Aspergillus species were identified based on morphological characteristics as well as subsequent sequencing of the parts of the ß-tubulin and calmodulin genes. From 207 isolated strains, the following species were identified: A. flavus, A. tamarii A. nomius, A. parasiticus, A. arachidicola, A. caelatus, A. pseudotamarii, and A. leporis. To the best of our knowledge, this is the first report of A. pseudotamarii and A. arachidicola with the potential to produce aflatoxins from dried apricots and hazelnuts, respectively. Sclerotial type was significantly different between isolates from different isolation sources. From 192 tested isolates, 38% were aflatoxin producer from which 5% were scored as strong aflatoxin producers and 33% as average aflatoxin producers. A significant difference in the population of aflatoxin-producing strains across the isolation sources was observed which may reflect host adaptation and thereby different vulnerabilities to aflatoxin-producing species among the examined products.

Determination of trace amounts of ochratoxin A in different food samples based on gold nanoparticles modified carbon paste electrode.

In the present study, a carbon paste electrode chemically modified with gold nanoparticles was used as a sensitive electrochemical sensor for determination of ochratoxin A. The differential pulse voltammetric method was employed to study the behavior of ochratoxin A on this modified electrode. The effect of variables such as percent of gold nanoparticles, pH of sample solution, accumulation potential and time on voltammogram peak current were optimized. The proposed electrode showed good oxidation response for ochratoxin A in 0.1 mol L(-1) PBS (pH 7.2) and the peak potential was about +0.8 V (vs. Ag/AgCl). The peak current increased linearly with the ochratoxin A concentration in the range of 0.5-100 nM. The detection limit was found to be 0.2 nM and the relative standard deviation was 6.2 % (n = 7). The method has been applied to the determination of ochratoxin A in cereal derived products such as breakfast cereals, cereal-based baby foods and beer samples.

A microextraction procedure based on a task-specific ionic liquid for the separation and preconcentration of lead ions from red lipstick and pine leaves.

First, the extraction and preconcentration of ultratrace amounts of lead(II) ions was performed using microliter volumes of a task-specific ionic liquid. The remarkable properties of ionic liquids were added to the advantages of microextraction procedure. The ionic liquid used was trioctylmethylammonium thiosalicylate, which formed a lead thiolate complex due to the chelating effect of the ortho-positioned carboxylate relative to thiol functionality. So, trioctylmethylammonium thiosalicylate played the roles of both chelating agent and extraction solvent simultaneously. Hence, there is no need to use a ligand. The main parameters affecting the efficiency of the method were investigated and optimized. Under optimized conditions, this approach showed a linear range of 2.0-24.0 ng/mL with a detection limit of 0.0010 ng/mL. The proposed method was applied to the extraction and preconcentration of lead from red lipstick and pine leaves samples prior to electrothermal atomic absorption spectroscopic determination.

A Quercetin Biosensor Based on Chitosan-Entrapped Carbon Nanotube Paste Electrode Coated with DNA.

This paper presents an easy, fast, low cost, and sensitive approach for the electrochemical determination of quercetin based on its intercalation into DNA double helix. Electrochemical studies of the interaction between quercetin and DNA showed a decrease in peak currents with a reduction in redox reversibility of quercetin in the presence of the DNA. The electrochemical behavior of quercetin at a chitosan-entrapped carbon nanotube paste electrode coated with DNA was studied. A considerable increase was observed in the oxidation signal of quercetin at the DNA-coated electrode compared with a DNA-free electrode, indicating the preconcentration of quercetin due to its interaction with the surface-confined DNA layer. After optimizing the main experimental parameters influencing the biosensor response, its performance was evaluated from an analytical point of view. Two linear dependences of the anodic peak current of quercetin on its concentration were observed in the ranges of 0.40-7.50 and 7.50-30.0 µmol/L, with LOD and LOQ of 0.039 and 0.13 µmol/L, respectively. The proposed biosensor was successfully applied to the analysis of black and green tea extracts for their quercetin content.

Evaluation of cadmium in greenhouse soils and agricultural products of Jiroft (Iran) using microwave digestion prior to atomic absorption spectrometry determination.

This study determines total levels of potentially toxic trace element, Cd (II) in Jiroft (Kerman, Iran) greenhouse soil and agricultural products that are grown in these greenhouses (tomatoes and cucumbers), and the comparison with soil outside of greenhouse using microwave digestion prior to flame atomic absorption spectrometry determination. The results show that the cadmium concentration in greenhouse soil is 0.9-1.9 mg kg(-1) and out of greenhouse is 0.4-1.0 mg kg(-1). Also, cadmium concentration range in tomatoes and cucumbers is about 0.07-0.40 mg kg(-1). The obtained results show that the concentration of this metal in greenhouse soil is higher than outside soil samples and is below the safe limit.

Modelling and experimental investigation on the application of water super adsorbents in waste air biofilters.

In this research work, a synthetic water super absorbent polymer was included in the bed of a perlite-based biofilter for the removal of ethanol from air. The performance of this biofilter was compared with the performance of a control perlite-based biofilter lacking the water super absorbent. With the empty bed residence time of 2 min, both biofilters were able to remove more than 90% of the entering pollutant with the concentration of 1 g /m3, when regular moistening was applied. After last irrigation on day 23, the performance of the control biofilter was unchanged until day 35. From day 36 onwards, the control biofilter lost its activity gradually and became totally inactive on day 45. The performance of the super absorbent containing biofilter, however, was unchanged until day 58 before starting to lose its activity. A mechanistic model was developed to describe the performance of a biofilter under drying effects. The model could predict the trends of experimental results reasonably well. The model was also applied to predict the trends of experimental data from a published paper on the removal of hexane in a perlite/super absorbent containing biofilter.

Determination of nickel in water, food, and biological samples by electrothermal atomic absorption spectrometry after preconcentration on modified carbon nanotubes.

A new and sensitive SPE method using modified carbon nanotubes for extraction and preconcentration, and electrothermal atomic absorption spectrometric determination of nickel (Ni) in real samples at ng/L levels was investigated. First, multiwalled carbon nanotubes were oxidized with concentrated HNO3, then modified with 2-(5-bormo-2-pyridylazo)-5-diethylaminophenol reagent. The adsorption was achieved quantitatively on a modified carbon nanotubes column in a pH range of 6.5 to 8.5; the adsorbed Ni(II) ions were then desorbed by passing 5.0 mL of 1 M HNO3. The effects of analytical parameters, including pH of the solution, eluent type and volume, sample volume, flow rate of the eluent, and matrix ions, were investigated for optimization of the presented procedure. The enrichment factor was 180, and the LOD for Ni was 4.9 ng/L. The method was applied to the determination of Ni in water, food, and biological samples, and reproducible results were obtained.

Determination of trace amounts of zirconium in real samples after microwave digestion and ternary complex dispersive liquid-liquid microextraction.

In this study, a ternary Zr(IV) system with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) and fluoride was chosen on the basis of dispersive liquid-liquid microextraction method. Zirconium was extracted into the fine droplets of dichlorobenzene as extracting solvent. These drops dispersed as a cloud in the aqueous sample with the help of ultrasonic waves, and the procedure was done. Finally, atomic absorption spectrometry was applied for the determination of zirconium. The effects of different factors that influence complex formation and extraction, such as pH, amounts of complexing agents, type and volume of the extracting solvent, as well as sonication and centrifuging time, were optimized. Under optimum conditions, the calibration curve was linear in the range of 150.0-800.0 ng mL(-1) with a limit of detection of 44.0 ng mL(-1). Relative standard deviation was calculated to be 4.1 % (n = 7, c = 400.0 ng mL(-1)). The enrichment factor was 80. The proposed method was successfully used to determine the zirconium in several water, wastewater, and soil samples.

Sonochemical-assisted method for efficient synthesis of Cu-MOF and evaluating its antibacterial properties.

Sonochemical-assisted method was used to synthesize copper metal-organic frameworks (Cu-MOF) nanostructures. The final products were examined by related techniques such as XRD patterns, SEM image, BET N2 adsorption/desorption technique and FTIR spectrum. Microtiter plates microbiological assay were used to investigate antibacterial properties and the results were analyzed using ANOVA and Tukey HSD tests. The results showed that Cu-MOF nanostructures have a mesoporous nature with an average particle size distribution around 60 nm. The final product had the property of preventing the growth of all tested bacteria in certain concentrations. Minimum Inhibitory Concentration (MIC) values were observed in the range of 30-100 ppm. It was also discovered that this nanostructure can not kill bacteria completely. In addition, the minimal inhibitory concentration for biofilm growth (MIC-B) of the nanostructure was investigated. The MIC-B analyzes demonstrated that the growth of bacterial biofilm decreased with increasing Cu-MOF concentration.

Displacement-dispersive liquid-liquid microextraction based on solidification of floating organic drop of trace amounts of palladium in water and road dust samples prior to graphite furnace atomic absorption spectrometry determination.

A new displacement-dispersive liquid-liquid microextraction method based on the solidification of floating organic drop was developed for separation and preconcentration of Pd(ll) in road dust and aqueous samples. This method involves two steps of dispersive liquid-liquid microextraction based on solidification. In Step 1, Cu ions react with diethyldithiocarbamate (DDTC) to form Cu-DDTC complex, which is extracted by dispersive liquid-liquid microextraction based on a solidification procedure using 1-undecanol (extraction solvent) and ethanol (dispersive solvent). In Step 2, the extracted complex is first dispersed using ethanol in a sample solution containing Pd ions, then a dispersive liquid-liquid microextraction based on a solidification procedure is performed creating an organic drop. In this step, Pd(ll) replaces Cu(ll) from the pre-extracted Cu-DDTC complex and goes into the extraction solvent phase. Finally, the Pd(ll)-containing drop is introduced into a graphite furnace using a microsyringe, and Pd(ll) is determined using atomic absorption spectrometry. Several factors that influence the extraction efficiency of Pd and its subsequent determination, such as extraction and dispersive solvent type and volume, pH of sample solution, centrifugation time, and concentration of DDTC, are optimized.

Ultrasound-assisted ion-pair dispersive liquid-liquid microextraction of trace amounts of lead in water samples prior to graphite furnace atomic absorption spectrometry determination.

A new ion-pair dispersive liquid-liquid microextraction method is described for separation and preconcentration of trace amounts of lead in different water samples. Graphite furnace atomic absorption spectrometry was used for determination of lead. The ion association complex between lead and iodide ions that forms is PbI4(-2)-tetradecyl-dimethylbenzylammonium, which is extracted into fine droplets of chlorobenzene. In order to reach the optimized experimental conditions, the influence of different parameters, such as concentration of KI, nature and volume of extraction solvents, pH effect, extraction time, and the period and speed of sonication and centrifugation, were optimized. The LOD was 0.08 ng/mL and the linear dynamic range was 0.20-8.0 ng/mL in initial solution with a correlation coefficient of 0.9985. Under the optimum conditions, the enrichment factor was 555.5. The proposed method was successfully applied for separation and determination of lead in sea, rain, river, and drinking water samples.

Separation and preconcentration of trace amounts of gold(III) ions using modified multiwalled carbon nanotube sorbent prior to flame atomic absorption spectrometry determination.

Multiwalled carbon nanotubes are attractive as sorbents for SPE because they can be used for enrichment of organic compounds and metal ions at trace levels. In this study, multiwalled carbon nanotubes were oxidized with concentrated HNO3, and then the oxidized multiwalled carbon nanotubes were modified with 5-(4'-dimethylamino-benzyliden)-rhodanine. The modified multiwalled carbon nanotubes were used as a solid sorbent for separation and preconcentration of trace amounts of Au(III) ions. The sorption of Au(III) ions was quantitative in the pH range of 2.0-5.0, whereas quantitative desorption occurred instantaneously with 5.0 mL 2.0 M Na2S2O3. The eluted solution was aspirated directly into the flame for atomic absorption spectrometry. The proposed method resulted in an enrichment factor of 94. The RSD of the method was +/- 1.11% (n=10, 2.0 microg/mL) and the LOD was 0.15 ng/mL. The calibration curve for Au(III) was linear between 0.53 ng/mL and 36.0 microg/mL in the initial solution, with an R2 value of 0.9999. The sorbent capacity of the modified multiwalled carbon nanotubes was 7.3 mg Au(III)/g sorbent. The influences of the experimental parameters, including sample pH, sample flow rate, eluent volume and flow rate, sample volume, and interference of some ions on the recoveries of the Au ions, were investigated. The proposed method was applied for preconcentration and determination of Au in different samples.

Determination of trace amounts of Pd(II) ions in water and road dust samples by flame atomic absorption spectrometry after preconcentration on modified organo nanoclay.

This paper describes the application of organo nanoclay, an easily prepared and stable solid sorbent, to the preconcentration of trace amounts of palladium ions in aqueous solution. The organo nanoclay was prepared by adding tetradecyldimethylbenzylamonium chloride onto montmorillonite, which was then modified with 1-(2-pyridylazo)-2-naphthol. The modified nanoclay was used as a solid sorbent for separation and preconcentration of trace amounts of Pd(II) ions, and a simple, sensitive, and economical method was developed for determination of trace amounts of palladium by flame atomic absorption spectrometry. The sorption of Pd(II) ions was quantitative in the pH range of 1.5-5.0, whereas quantitative desorption occurred with 5.0 mL of a mixture containing 1.0 M thiourea and 1.0 M HCl. The RSD of the method was +/- 2.1% (n = 10; concn = 0.5 microg/mL), and the LOD (3sigma(bl); sigma = SD and bl = blank) was 0.1 ng/mL. The calibration curve was linear for concentrations of 0.5-8.0 microg/mL in the initial solution, and the preconcentration factor was 140. The maximum capacity of the sorbent was 2.4 mg Pd(II)/g modified organo nanoclay. The influences of the experimental parameters, including sample pH, eluant volume, eluant type, sample volume, and interfering ions, on the recoveries of the palladium ion were investigated. The proposed method was applied to the preconcentration and determination of palladium in different samples.

Synthesis of novel sepiolite-iron oxide-manganese dioxide nanocomposite and application for lead(II) removal from aqueous solutions.

In this study, the sepiolite-iron oxide-manganese dioxide (Sep-Fe3O4-MnO2) nanocomposite was synthesized and applied as a magnetically separable adsorbent for removal of Pb(II) ions from water in a batch system. The effects of initial Pb(II) concentration, adsorbent dosage, contact time, pH value, and temperature were investigated to optimize the conditions for maximum adsorption. The equilibrium adsorption data were analyzed with the Langmuir, Freundlich, and Temkin models. The adsorption process closely agreed with the Langmuir adsorption isotherm, and the monolayer saturation adsorption value was achieved as 131.58 mg g-1. The adsorption kinetics follow the pseudo-second-order (PSO) model that illustrated the rate controlling step might be chemisorption. Thermodynamic investigations for the removal process were conducted by determining the values of ∆G°, ∆H°, and ∆S°. The adsorption behavior of Pb(II) on the Sep-Fe3O4-MnO2 was a spontaneous and endothermic process. Several consecutive adsorption-desorption cycles confirmed that the proposed Sep-Fe3O4-MnO2 nanocomposite could be reused after successive lead removal. Furthermore, the practical application of the adsorbent was successfully realized by the treatment of real Pb-contaminated water samples.

Chitosan/polyvinyl alcohol nanofibrous membranes: towards green super-adsorbents for toxic gases.

Removal of hazardous gases from the atmosphere has become a big challenge for scientists and engineers alike. Eco-friendly nature of biopolymers has given a new dimension to the debate within the environmental science area but attempts mainly failed to cleanse the air stream of toxic gases as a consequence of design imperfections. In this work, green electrospun nanofibrous membranes based on chitosan (Cs)/polyvinyl alcohol (PVA) composite with a very high carbon monoxide adsorption capacity (much higher than the values one may expect from activated carbon and zeolite adsorbents, and also higher than that of the metal-organic framework) are developed. 2k-1 factorial design, response surface and desirability function analyses are merged to optimize the electrospinning parameters for functional-based carbon monoxide elimination. The best Cs/PVA adsorbent obtained through multi-objective optimization has a very high desirability value level of 0.953. Optimized electrospinning parameters are: Voltage = 17 kV, spinning distance = 13 cm, flow rate = 0.2 mL/h, and PVA concentration = 6 wt.%; and optimized properties are: maximum thermal stability = 329 °C, minimum fiber diameter = 9.8 nm, and maximum surface area = 2204 m2/g. This work opens a new era for taking the next steps towards the design and optimization of green super-adsorbents for gaseous contaminations.

Determination of trace amounts of Cu2+, Ni2+, and Mn2 ions after preconcentration onto PAN-immobilized organo nanoclay as a new sorbent.

The application of organo nanoclay 1-(2-pyridylazo)-2-naphthol (PAN)-immobilized as a new, easily prepared, and stable solid sorbent for preconcentration of trace amounts of Cu2+, Ni2+, and Mn2+ ions in aqueous solution is presented. The organo nanoclay was prepared by adding tetradecyldimethylbenzylammonium chloride onto montmorillonite and then saturating with PAN. A simple, rapid, selective, sensitive, and economical method was developed for the simultaneous separation of trace amounts of copper, nickel, and manganese in aqueous medium using PAN as an analytical reagent. The sorption was quantitative in the pH range of 6-9.5, and quantitative desorption occurred instantaneously with 5.0 mL 3 M HNO3. Linearity was maintained at 0.26-37 ng/mL for copper, 1-52 nglmL for nickel, and 0.2-21 ng/mL for manganese in the original solution. The detection limits were 0.04 ng/mL for Cu(II), 0.15 ng/mL for Ni(II), and 0.03 ng/mL for Mn(II) in the original solution (2delta(bl); delta = standard deviation and bl = blank). Various parameters, such as the effect of pH, breakthrough volume, and interference of a large number of anions and cations, have been studied, and the proposed method was used to determine these metal ions in water and standard samples. Determination of these metal ions in standard samples showed that the proposed method has good accuracy.

A novel synthesis of a new thorium (IV) metal organic framework nanostructure with well controllable procedure through ultrasound assisted reverse micelle method.

Reverse micelle (RM) and ultrasound assisted reverse micelle (UARM) were applied to the synthesis of novel thorium nanostructures as metal organic frameworks (MOFs). Characterization with different techniques showed that the Th-MOF sample synthesized by UARM method had higher thermal stability (354°C), smaller mean particle size (27nm), and larger surface area (2.02×103m2/g). Besides, in this novel approach, the nucleation of crystals was found to carry out in a shorter time. The synthesis parameters of UARM method were designed by 2k-1 factorial and the process control was systematically studied using analysis of variance (ANOVA) and response surface methodology (RSM). ANOVA showed that various factors, including surfactant content, ultrasound duration, temperature, ultrasound power, and interaction between these factors, considerably affected different properties of the Th-MOF samples. According to the 2k-1 factorial design, the determination coefficient (R2) of the model is 0.999, with no significant lack of fit. The Fvalue of 5432, implied that the model was highly significant and adequate to represent the relationship between the responses and the independent variables, also the large R-adjusted value indicates a good relationship between the experimental data and the fitted model. RSM predicted that it would be possible to produce Th-MOF samples with the thermal stability of 407°C, mean particle size of 13nm, and surface area of 2.20×103m2/g. The mechanism controlling the Th-MOF properties was considerably different from the conventional mechanisms. Moreover, the MOF sample synthesized using UARM exhibited higher capacity for nitrogen adsorption as a result of larger pore sizes. It is believed that the UARM method and systematic studies developed in the present work can be considered as a new strategy for their application in other nanoscale MOF samples.

Ultrasound assisted reverse micelle efficient synthesis of new Ta-MOF@ Fe3O4 core/shell nanostructures as a novel candidate for lipase immobilization.

In the present study, Ta-MOF@Fe3O4 core/shell nanostructures were synthesized in optimal conditions using the rapid, efficient, and novel ultrasound assisted reverse micelle method. FTIR, TGA/DTG, XRD, TEM, EDS and N2 adsorption/desorption isotherms were conducted in order to obtain samples with desirable properties. Results showed that the synthesized products had the thermal stability of 200 °C, particle-size distribution of 38 nm and surface area of 740 m2/g. Also, the VSM test showed that these compounds have desirable magnetic properties which provide the opportunity for recovery. Based on these obtained properties, final products were used as a novel candidate for enzyme immobilization. Results of SEM images revealed that the Bacillus licheniformis Km12 lipase is efficiently loaded on the Ta-MOF@Fe3O4 core/shell substrate. The stability test indicated the high stability of the enzyme loaded into these nanostructures. The synthesis method and the results obtained from enzyme immobilization developed in this study can be a new strategy for various applications of these novel compounds in diverse biological fields.