Highly Efficient Photocatalytic Degradation of Imidacloprid Based on Iron Metal-Organic Frameworks of Mesoporous NH2-MIL-88b/Graphite Carbon Nitride Nanocomposites by Visible Light Driven in Aqueous Media.

Pesticides that protect crops from insects and other pests are some of the main causes of water pollution. Imidacloprid (IMC) is the most widely used insecticide in the world and should be removed from the environment. This work aims to prepare mesoporous nanocomposites to increase the photodegradation efficiency of IMC. To improve the surface properties and enhance the photocatalytic activity, mesoporous nanocomposites with different weight ratios of graphite carbon nitride (CN = 125, 250, and 500 mg) were prepared by the solvothermal method. Mesoporous NH2-MIL-88b(Fe)/graphite carbon nitride (CN = 250 mg, NH2-MCN-2) nanocomposites showed the best photocatalytic performance. To save the time and cost of the experiments, central composite design (CCD) and response surface methodology (RSM) were used and the results were obtained as the initial concentration of IMC (20 mg L-1), amount of photocatalyst (0.76 g L-1), pH = 5, and degradation time ∼46 min. The maximum photocatalytic degradation efficiency estimated by the model was obtained at 96.31%, which is very close to the actual value of 95.47%. The mesoporous NH2-MCN-2 nanocomposite showed excellent stability and suitable reusability with a maximum degradation of 84.5% after five cycles. Results obtained from kinetic studies indicated a rate constant value of 0.08 min-1, and isotherm models showed that equilibrium data are more consistent with the Langmuir model in photocatalytic degradation. Electrochemical experiments showed significant improvement in the electron transfer rate and photocatalytic activity of the mesoporous NH2-MCN-2 nanocomposite. Different trapping agents were used to investigate the effective active species in IMC photodegradation, and it was determined that the hole (h+) and OH radical (•OH) play the main role. The possible mechanism for IMC photocatalytic degradation was suggested by Mott-Schottky (M-S) electrochemical impedance.

Adsorption properties of low-cost synthesized nanozeolite L for efficient removal of toxic methylene blue dye from aqueous solution.

In this study, nanozeolite L was applied for the removal of toxic methylene blue dye (MB) to evaluate its feasibility as an effective adsorbent. Synthesized nanozeolite L was characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electronic microscopy (SEM), Brunauer-Emmett-Teller (BET), and energy-dispersive X-ray analysis (EDX) methods to determine its basic physicochemical properties. Batch adsorption studies were performed as a function of pH, adsorbent dose, contact time, initial MB concentration, and temperature. The adsorption behavior of MB was fitted better by the Langmuir isotherm than by the Freundlich isotherm, and the maximum adsorption capacity of nanozeolite L was obtained 80.64 mg g-1. The negative values of Gibbs free energy change (ΔG°) and the positive value of the standard enthalpy change (ΔH°) affirmed that the adsorption process is spontaneous and endothermic. Based on these findings, nanozeolite L, with high surface area, great adsorption capacity, and low synthetic cost, can be an effective and economical adsorbent for MB removal.

Förster resonance energy transfer-based molecularly imprinted polymer /amine-functionalized metal-organic framework nanocomposite for trace level detection of 4-nitrophenol.

Herein, luminescent metal-organic framework (LMOF) is modified with molecularly imprinted polymer (MIP) and employed as an efficient and cost-effective nanoprobe for the determination of 4-nitrophenol (4-NP). Amine-UiO-66 support with unique luminescence property is chosen for creating the template of 4-NP using MIP to construct a highly selective LMOF-based sensor (amine-UiO-66/MIP nanocomposite). The imprinted sites formed at the surface of LMOF significantly enhance the selectivity of the probe for 4-NP over its analogs. 4-NP can effectively quench the fluorescent intensity of the optical sensor via the Förster resonance energy transfer (FRET) mechanism. Amine-UiO-66/MIP sensor provided the linear range of 0.05-50 µM and low limit of detection of 0.009 µM for sensing of 4-NP. The application of probe for the fluorometric analysis of real samples, including drinking and environmental water, provided satisfactory recovery results with low relative standard deviation (RSD).

Design of turn-on luminescent sensor based on nanostructured molecularly imprinted polymer-coated zirconium metal-organic framework for selective detection of chloramphenicol residues in milk and honey.

Herein, an optical sensor based on nanostructured molecularly imprinted polymer (MIP) coated on a luminescent zirconium metal-organic framework (MIP/Zr-LMOF) is introduced, and its performance is investigated for the fluorescent determination of chloramphenicol (CAP) antibiotic residues in milk and honey. To fabricate the sensor, the surface of Zr-LMOF is modified with MIP in the presence of CAP template, resulting in the introduction of recognition sites for antibiotic molecules. The porous structure of Zr-LMOF with specific binding sites for CAP recognition benefiting from coated MIP leads to selective and sensitive detection of antibiotic. The probe yields a linear range for detection of CAP in trace concentrations (0.16-161.56 µg.L-1) and provides a detection limit of 0.013 µg.L-1. Acceptable recoveries are achieved for antibiotic in real samples, which are consistent with that obtained from liquid chromatography-tandem mass spectrometry (LC-MS/MS), confirm the favorable performance of sensor for accurate determination of CAP in practical applications.

Synthesis of zeolite NaY supported Mn-doped ZnS quantum dots and investigation of their photodegradation ability towards organic dyes.

In this work, Mn-doped ZnS quantum dots capped by L-cysteine (Mn@ZnS/L-cyst) and polyethylene glycol (Mn@ZnS/PEG) and also Mn-doped ZnS on zeolite NaY (Mn@ZnS/Y) were synthesized. These compounds were characterized by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), and ultraviolet-visible and fluorescence spectroscopy. Then, the photodegradation ability of these three photocatalysts was investigated for degradation of 4',5'-dibromofluorescein dye under ultraviolet irradiation. In the next stage, the different effective parameters on degradation performance, such as pH, catalyst dosage, and initial dye concentration, were studied. Results demonstrated that the optimum initial concentration was 40 mg L-1 for all three catalysts. The optimum catalyst dosage for both Mn-doped ZnS quantum dots capped by L-cysteine and Mn-doped ZnS on zeolite NaY was 0.017 g L-1 and for Mn-doped ZnS quantum dots capped by polyethylene glycol was 0.033 g L-1. The degradation efficiency of 97% for all three photocatalysts was achieved; therefore, by considering the higher production yield of quantum dots onto zeolite and also the more convenient recovery of the Mn-doped ZnS on zeolite NaY from the solution, it seems synthesis of quantum dots onto the zeolites is a reasonable strategy.

Green synthesis of fluorescent PEG-ZnS QDs encapsulated into Co-MOFs as an effective sensor for ultrasensitive detection of copper ions in tap water.

In this work, a novel and highly fluorescent (FL) metal-organic framework (MOF)-based host-guest hybrid system was developed through encapsulation of polyethylene glycol (PEG)-capped ZnS quantum dots (QDs) into zeolitic imidazolate framework (ZIF)-67 at ambient temperature. This new composite material was characterized by FT-IR, XRD, TEM, UV-Vis absorption and FL spectroscopy, and then exploited as fluorescence sensor for highly sensitive and selective detection of Cu (II) ions in water samples. The as-prepared PEG-ZnS QDs@ZIF-67 nanohybrids took advantages of both accumulation effect in ZIF-67 and FL sensitivity and selectivity in ZnS QDs toward analyte-Cu2+. In this regard, ZIF-67 was treated as absorbents to capture and enrich Cu (II) ions, and ZnS QDs were exploited as tentacle to selectively and sensitively sense the bonding interactions between ZIF-67 and Cu (II) ions, and further transduce these chemical events to the detectable fluorescence signals. By this approach, Cu2+ could be detected in a wide concentration range of 3 to 500 nM with a LOD as low as 0.96 nM. The proposed FL-sensor can be promising in the field of preparation of various QDs@MOFs platforms for application in high-performance optical sensing.

High-efficiency purification of sulforaphane from the broccoli extract by nanostructured SBA-15 silica using solid-phase extraction method.

Sulforaphane, a promising phytochemical, has received much attention in recent decades as a potential anticarcinogenic compound. In this research work, a novel, specific and affordable method has been developed for the separation and purification of natural sulforaphane from broccoli extract using SBA-15 mesoporous silica. SBA-15 was found to be the most efficient in the purification of sulforaphane compared to some of the conventionally used adsorbents and zeolites. The nanoparticles of SBA-15 mesoporous silica were synthesized using the hydrothermal method from natural amorphous silica extracted from rice husk ash with a silica purity of 96%. Structural and morphological analysis of the synthesized SBA-15 mesoporous silica were performed by the XRD, FT-IR, FE-SEM, and BET techniques. The method includes the primary immiscible solvent extraction of autolyzed broccoli sample with dichloromethane, followed by purification of the extract by SBA-15 mesoporous silica using solid-phase extraction (SPE) method. The recovery of the purified sulforaphane from broccoli extract was >98% using SBA-15 mesoporous silica, which is higher compared to that obtained using current purification methods. The highest purity of sulforaphane product was measured 94% based on the results of analytical HPLC chromatograms. Moreover, the effects of different parameters on the sulforaphane purification by using SBA-15 were studied and optimized.

Gold-copper bimetallic nanoparticles supported on nano P zeolite modified carbon paste electrode as an efficient electrocatalyst and sensitive sensor for determination of hydrazine.

In this report, a facile, efficient and low cost electrochemical sensor based on bimetallic Au-Cu nanoparticles supported on P nanozeolite modified carbon paste electrode (Au-Cu/NPZ/CPE) was constructed and its efficiency for determination of hydrazine in trace level was studied. For this purpose, agro waste material, stem sweep ash (SSA) was employed as the starting material (silica source) for the synthesis of nano P zeolite (NPZ). After characterization of the synthesized NPZ by analytical instruments (scanning electronic microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy), construction of Au-Cu/NPZ/CPE was performed by three steps procedure involving preparation of nano P zeolite modified carbon paste electrode (NPZ/CPE), introducing Cu+2 ions into nano zeolite structure by ion exchange and electrochemical reduction of Cu+2 ions upon applying constant potential. This procedure is followed by partial replacement of Cu by Au due to galvanic replacement reaction (GRR). The electrochemical properties of hydrazine at the surface of Au-Cu/NPZ/CPE was evaluated using cyclic voltammetry (CV), amperometry, and chronoamperometry methods in 0.1 M phosphate buffer solution (PBS). It was found that the prepared sensor has higher electrocatalytic activity at a relatively lower potential compared to other modified electrodes including Au/NPZ/CPE, Cu/NPZ/CPE, Au-Cu/CPE and etc. Moreover, the proposed electrochemical sensor presented the favorable analytical properties for determination of hydrazine such as low detection limit (0.04 µM), rapid response time (3 s), wide linear range (0.01-150 mM), and high sensitivity (99.53 µA mM-1) that are related to the synergic effect of bimetallic of Au-Cu, porous structure and enough surface area of NPZ. In addition, capability of Au-Cu/NPZ/CPE sensor was successfully tested in real samples with good accuracy and precision.

Quantum dots and ionic liquid-sensitized effect as an efficient and green catalyst for the sensitive determination of glucose.

A novel fluorescence (FL) method using water-soluble CdSe quantum dots (QDs) is proposed for the fluorometric determination of hydrogen peroxide and glucose. Water-soluble CdSe QDs were synthesized by using thioglycolic acid as stabilizer in aqueous solutions. The nanoparticles were structurally and optically characterized by X-ray powder diffraction (XRD), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), UV-Vis absorption spectroscopy, photoluminescence (PL) emission spectroscopy and transmission electron microscope (TEM). Ionic liquid-sensitized effect in aqueous solution was then investigated. In the presence of ionic liquid as catalyst, H2O2 was decomposed into radical that could quench the fluorescence of CdSe QDs more efficiently and rapidly. Then the oxidization of glucose by glucose oxidase was coupled with the fluorescence quenching of CdSe QDs by H2O2 producer with ionic liquid catalyst, which can be used to detect glucose. Therefore, a new FL analysis system was developed for the determination of glucose. Under the optimum conditions, there is a good linear relationship between the relative PL emission intensity and the concentration of glucose in the range of 5.0×10(-7)-1.0×10(-4) M of glucose with a correlation coefficient (R(2)) of 0.9973. The limit of detection of this system was found to be 1.0×10(-7) M. This method is not only simple, sensitive and low cost, but also reliable for practical applications.

Synthesis and characterization of NaX nanozeolite using stem sweep as silica source and application of Ag-modified nanozeolite in electrocatalytic reduction of H2O2.

Nanozeolite is one of the three dimensional nanoporous materials consisting of extremely accessible surface area and shorter diffusion pathways. In this study, NaX nanozeolite is synthesized using the hydrothermal method from natural silica source of stem sweep ash (SSA). The synthesized nanoparticles were characterized using X-ray diffraction, scanning electronic microscopy, Brunauer-Emmett-Teller (BET) and FT-IR techniques. The synthesized nanozeolite is used incorporating Ag (I) ions for preparing modified carbon paste electrode (Ag/X-CPE) as an electrochemical sensor for the reduction of H2O2. Electrochemical results demonstrate that nanozeolite provides a promising platform for the development of electrochemical sensors in biosensing and Ag/X-CPE electrode possesses the remarkable catalytic activity toward the H2O2 reduction. Amprometric results show that this sensor could detect H2O2 in linear ranges of 20 µM to 1.76 mM and 1.76-11.76 mM with a detection limit of 9.1 µM at a signal-to-noise ratio of 3 and a response time of 2s. Furthermore, this sensor exhibited good anti-interference and selectivity.

The use of imidazolium ionic liquid/copper complex as novel and green catalyst for chemiluminescent detection of folic acid by Mn-doped ZnS nanocrystals.

A novel chemiluminescence (CL) method using water-soluble Mn-doped ZnS quantum dots (QDs) as CL emitter is proposed for the chemiluminometric determination of folic acid in pharmaceutical formulation. Water-soluble Mn-doped ZnS QDs were synthesized by using L-cysteine as stabilizer in aqueous solutions. The nanoparticles were structurally and optically characterized by X-ray powder diffraction (XRD), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), UV-Vis absorption spectroscopy and photoluminescence (PL) emission spectroscopy. The CL of ZnS QDs induced by directly chemical oxidation and its ionic liquid-sensitized effect in aqueous solution were then investigated. It was found that oxidants, especially hydrogen peroxide, could directly oxidize ZnS QDs to produce weak CL emission in basic conditions. In the presence of 1,3-dipropylimidazolium bromide/copper a drastic light emission enhancement is observed, related to a strong interaction between Cu(2+) and the imidazolium ring. Therefore, a new CL analysis system was developed for the determination of folic acid. Under the optimum conditions, there is a good linear relationship between the relative CL intensity and the concentration of folic acid in the range of 1×10(-9)-1×10(-)(6) M of folic acid with a correlation coefficient (R(2)) of 0.9991. The limit of detection of this system was found to be 1×10(-)(10) M. This method is not only simple, sensitive and low cost, but also reliable for practical applications.

A novel luminol chemiluminescent method catalyzed by silver/gold alloy nanoparticles for determination of anticancer drug flutamide.

It was found that silver/gold alloy nanoparticles enhance the chemiluminescence (CL) of the luminol-H2O2 system in alkaline solution. The studies of UV-Vis spectra, CL spectra, effects of concentrations luminol, hydrogen peroxide and silver/gold alloy nanoparticles solutions were carried out to explore the CL enhancement mechanism. Flutamide was found to quench the CL signals of the luminol-H2O2 reaction catalyzed by silver/gold alloy nanoparticles, which made it applicable for the determination of flutamide. Under the optimum conditions, the CL intensity is proportional to the concentration of the flutamide in solution over the range 5.0 × 10(-7) to 1.0 × 10(-4)mol L(-1). Detection limit was obtained 1.2 × 10(-8)mol L(-1)and the relative standard deviation (RSD) γ5%. This work is introduced as a new method for the determination of flutamide in commercial tablets. Box-Behnken experimental design is applied to investigate and validate the CL measurement parameters.

Determination of epinephrine in pharmaceutical formulation by an optimized novel luminescence method using CdS quantum dots as sensitizer.

In this article, a novel chemiluminescence method using water-soluble CdS quantum dots (QDs) as sensitizers is proposed for the chemiluminometric determination of epinephrine. The method is based on the quenching effect of epinephrine on the chemiluminescence emission generated by the mixing of CdS quantum dots (QDs) with hydrogen carbonate (HCO3(-)) in the presence of hydrogen peroxide (H2O2) in an alkaline medium. The optimization of variables influencing the chemiluminescence response of the method has been carried out by using experimental design. Under the optimal conditions, there is good linear relationship between the relative chemiluminescence intensity and the concentration of epinephrine over the range of 5 × 10(-9)-1 × 10(-6) molL(-1) with a 3σ detection limit of 5 × 10(-11) molL(-1). The method has been successfully applied to the determination of epinephrine in pharmaceutical formulation and the recovery test was done in human urine.

Removal of Cd(II) from aquatic system using Oscillatoria sp. biosorbent.

Biosorption of Cd(II) ions from aqueous solutions by native and dried Oscillatoria sp. Cyanobacterium biomass was investigated in the batch mode. The Oscillatoria sp. was prepared from Molecular and Cell Laboratory of University of Mazandaran and grown in BG-11 medium. A comparison of Cd(II) adsorption properties of dried with native Oscillatoria sp. biomass was made, the dried one showed a higher biosorption capacity and faster kinetic. The influence of solution pH, contact time, biomass concentration, initial metal ion concentration, and presence of coions using dried Oscillatoria sp. biomass as well as pretreatment on the biosorption capacity of the biomass were studied. Various pretreatments of Oscillatoria sp. increased biosorption of Cd(II) at pH 7 in comparison with native biomass. However, heating at 100 °C in a water bath showed significant improvement in Cd(II) biosorption capacity. The experimental biosorption data was well fitted to the Freundlich model compared to the Langmuir model, and the amount of Cd(II) removed from solution increased with increasing Cd(II) concentration. In addition, the dried biomass was investigated for Cd(II) removal from the simulated real sample containing about 14 mg/l Cd(II) at pH 7, under the same experimental condition.