Journal of the Iranian Chemical Society
Volume:8 Issue: 1, Feb 2011

In this study, nanoscale MCM-41 molecular sieve was prepared under a basic condition by a hydrothermal method using cetyltrimethylammonium bromide as a template and tetraethyl orthosilicate as a silica source. Methylated nanoscale MCM-41 molecular sieve was prepared from the nanoscale MCM-41 by post-synthesis method using trimethylchlorosilane (TMCS) as coupling agent. The product was characterized by means of element analysis, powder X-ray diffraction, Fourier transform infrared (FT-IR) spectroscopy, low-temperature nitrogen adsorption-desorption technique at 77 K, scanning electron microscopic (SEM), thermogravimetry-differential thermal analysis (TG-DTA). Powder XRD showed that the framework of the molecular sieve was well retained and the degree of ordering of the methylated MCM-41 decreases. IR spectra and the low-temperature nitrogen adsorption-desorption technique suggested that methyl was successfully grafted to the inner surface of the methylated MCM-41 and the mesoporous channels of the methylated MCM-41 were still maintained. Scanning electron microscopic results showed that the average size of the methylated MCM-41 prepared was 112 nm. Differential thermal analysis showed that the prepared material has preferable thermal stability and the methylated MCM-41 can be stable at 903 °C.

Magnetic solid phase extraction (MSPE) based on cetyltrimethylammonium bromide (CTAB)-coated magnetic iron oxide nanoparticles (C-MIONPs) was investigated for the separation, preconcentration and determination of Rose Bengal (RB) in aqueous solutions. The influences of different analytical parameters such as pH, temperature, ionic strength, volume of desorbent solvent, amount of adsorbent and interfering ions in the adsorption of RB on C-MIONPs were investigated. The RB adsorption on C-MIONPs follows Langmuir isotherm. The sizes of C-MIONPs were in the range of 20-80 nm. The method was capable of determining RB concentration in the range of 0.01-1.20 µg ml-1. The limit of detection (LOD) of RB based on three times the standard deviation of the blank (3Sb) was found to be 5.91 × 10-3mg ml-1 (n = 8). The relative standard deviation (RSD) for 0.3 µg ml-1 and 0.8 µg ml-1 of RB were 4.1% and 1.1%, respectively. The proposed method was applied to the determination of RB in Brucella Antigen solution and water samples from the Karoon River.

Nano-SiO2 solid acid efficiently and selectively catalyzed the cyclocondensation reaction of arylnitriles with 3-amino-1-proopanol or 1,3-diaminopropane to afford their respective 2-substituted oxazines and tetrahydropyrimidines in high yields under thermal conditions and microwave irradiation. This methodology works effectively for the selective synthesis of mono-1,3-oxazines and mono-tetrahydropyrimidnes from dinitriles. The catalyst could be recycled and reused several times without a noticeable decrease in its activity.

Engelhard titanosilicate (ETS-10) supported cadmium sulphide (CdS) nanoparticles were synthesized and characterized by various solid state techniques including: XRD, DR UV-Vis, TEM and FESEM. The effect of different synthesis routes of CdS nanoparticles on its physicochemical character was studied. It was observed that CdS nanoparticles prepared by both in situ sulphur reduction (CdS-IS) and reverse micelle (CdS-RM) methods showed similar properties. However, CdS-IS nanoparticles are more feasible and economically practical. The reflectance measurements of the as-synthesized CdS nanoparticles are apparently blue-shifted compared to bulk CdS. This phenomenon of blue-shifted absorption edge has been ascribed to an increase in bandgap energy with a decrease in particle sizes. The bandgap of the as-synthesized CdS samples was calculated from the linear correlation of [F(R) hν]2 and hν. The bandgap of CdS in ETS-10 was noticeably slightly reduced when compared with the as-synthesized CdS (8 nm) due to the formation of cluster arrays on the pores of ETS-10.

Bi-sized and separable gold nanoparticles (AuNps) with smaller sizes were synthesized by treatment of cysteine with tetrachloroauric acid solution. These nanoparticles were made stable with further reduction in size after adding very small volume of NaOH solution before controlled heating. In NaOH treated solution the AuNps stopped precipitation as compared to untreated solution. Various methods such as UV-Vis spectroscopy, Transmission Electron Microscopy (TEM), X-ray Diffractometry (XRD), FTIR and Raman spectroscopy were used for characterization of surface properties and interaction between AuNps and cysteine. The results showed good correlation with literature regarding the interaction but interesting differences in size distribution as evident from high resolution TEM micrograph. Zeta potential studies revealed that these particles are negatively charged. Surprisingly, the Raman of the cysteine-derived AuNps without NaOH showed tremendous enhancement as compared to pure cysteine and cysteine-derived AuNps treated with NaOH. The NaOH treated Cyst-AuNps sol proved as excellent homogeneous catalyst for reduction of methylene blue (MB).

Polycrystalline ZnO/HZSM-5 nanocomposites were synthesized by the impregnation method using a home prepared HZSM-5 zeolite as porous support and Zn(C5H7O2)2 or Zn(NO3)2 as zinc precursors. As-prepared samples were characterized by ICP, XRD, SEM (EDS), TEM (SAED), BET and DRS techniques. A small amount of sub-nanometeric ZnO clusters were introduced into the channels of HZSM-5 zeolite. These ZnO clusters exhibited absorption band onset at about 280 nm, different from ZnO particles at about 370 nm. The significant blue shift possesses high quantum size effect in sub-nanometeric ZnO clusters. SAED and TEM images revealed that the ZnO nanoparticles, supported on the surface of HZSM-5 zeolite, were identified as polycrystalline structure with the particle size of about 20-25 nm. XRD results provided evidence of the strong host-guest interactions between HZSM-5 framework and ZnO structure. The samples prepared by Zn(C5H7O2)2 were more porous and smaller than those prepared from the Zn(NO3)2. This was confirmed by SEM and XRD results.

The electrochemical oxidation of ascorbic acid (AA), dopamine (DA) and uric acid (UA), as three important biological molecules, have been studied at the bare, activated and multi-wall carbon nanotubes modified glassy carbon electrodes (MWCNT-GCE) using different voltammetric methods. MWCNT-GCE not only exhibited both the roles of mediator and promoter for AA oxidation, but also performed the role of an excellent promoter for electrochemical oxidation of DA and UA when compared with bare GCE (BGCE) or activated GCE (AGCE). The results show that the oxidation of AA at MWCNT-GCE exhibits the characteristic shape typical of an EC catalytic (EiC’i) mechanism. In differential pulse voltammetric measurements, MWCNT-GCE and AGCE could separate the oxidation peak potentials of AA, DA and UA present in the same solution, though the MWCNT-GCE remarkably improves the sensitivity of determination of the analytes and also reduces the fouling effects as compared to AGCE. Furthermore, the hydrodynamic amperometry at rotating MWCNT-GCE at constant potential was used for determination of AA, DA and UA individually in the presence of the other two species. It has been shown that using MWCNT-GCE, these three species can be determined by amperometry with high sensitivity and selectivity. Finally, MWCNT-GCE has been applied to simultaneous determination of AA and DA in the related injection solutions and UA in a human urine sample with satisfactory results.

Mesoporous carbon was synthesized for the removal of a cationic dye malachite green (MG) from aqueous solution. The studies were carried out under various experimental conditions such as contact time, dye concentration, adsorption dose and pH to assess the potentiality of mesoporous carbon for the removal of malachite green dye from wastewater. The sorption equilibrium was reached within 30 min. In order to determine the adsorption capacity, the sorption data were analyzed using linear form of Langmuir and Freundlich equation. Langmuir equation showed higher conformity than Freundlich equation. More than 99% removal of MG was reached at the optimum pH value of 8.5. From kinetic experiments, it was concluded that the sorption process followed the pseudo-first-order kinetic model. This study showed that mesoporous carbon can be recommended as an excellent adsorbent at high pH values.

A new catalytic system based on palladium nanoparticles supported on poly(4-vinylpyridine) (P4VPy)-grafted silica is introduced. Aminopropylsilica was reacted with acryloyl chloride to form acrylamidopropylsilica. Onto this functionalized silica, 4-vinylpyridine monomer was polymerized by free radical polymerization. The P4VPy-grafted silica was characterized by FT-IR spectroscopy and the amount of (P4VPy) grafted was determind by thermogravimetric analysis (TGA). The complexation of (P4VPy)-grafted silica with Pd(Cl)2 was carried out to obtain the heterogeneous catalytic system. Transmission electron microscopy images (TEM) showed that palladium dispersed through polymer surface in nanoparticle size. This catalytic system exhibited excellent activity in cross-coupling reactions of aryl iodides, bromides and also chlorides, with olefinic compounds in Heck-Mizoraki, and with benzylbronic acid in Suzuki-Miyaura reactions. The use of aryl chlorides in cross-coupling reactions is usually hardly successful, but excellent results were gained in the presence of terta-n-butylammonium bromide (TBAB) as an additive. The turnover number (TON) of this catalyst reaches up to 9 × 104 in these C-C bond forming reactions. High efficiency of the catalyst along with short reaction time, high yields, easy purification, recyclability, large scale synthesis and simple procedure are among the advantages of this catalytic system

The use of 2 mol% of Cu/C nanoparticles, as an easily accessible and inexpensive heterogeneous catalyst, promoted a one-pot three-component condensation of an amine, aldehyde, and an alkyne in water to produce the corresponding propargylamine in good to high yields. This method was proved to be applicable to a wide range of substrates and is especially practical for the synthesis of new azacrown ether derivatives. The catalyst was quantitatively recovered from the reaction by a simple filtration and reused for at least ten times with almost consistent activity.

Nanocrystals provide a confinement effect for nanoscale engineering. In this work the cadmium selenide quantum dot and its nanoparticle films have been deposited by chemical bath deposition method (CBD). Effects of deposition time, pH and annealing operation on the optical and structural of CdSe nanoparticle film were studied. The energy band gap, structure and morphology of the samples are investigated by X-ray diffraction (XRD), UV-Vis spectrometer and scanning electron microscope (SEM). It was found that the optical band gap, nanoparticle size and thin film configuration are changed by varying pH, deposition time and annealing operation.

Behavior of a single CH4 molecule adsorbed on external surface of H-capped (4,4) (5,5), (6,6) and (5,0) single-walled carbon nanotubes (SWCNTs) is studied via B97D hybrid density functional and 6-31G* basis set. Binding energies clearly exhibit adsorption dependence on tube diameter. 13C and 1H chemical shielding tensors are calculated at the B971 level using GIAO method. The 1H and 13C(CH4) NMR results reveal that chemical shielding due to CH4 molecule adsorption are also dependent upon the nanotube electronic structure, and radius. 2H nuclear quadrupole coupling constants, CQ, and asymmetry parameter, ·, reveal the remarkable effect of CH4 adsorption on electronic structure of the SWCNTs.

Catalytic activity of nano-flake ZnO for synthesis of quinoline derivatives and their related polyheterocycles under solvent-free conditions has been studied. Nano-flake ZnO has been successfully synthesized by conventional heating of a solution approach using ZnOAc.2H2O and Urea. This method is simple, cost-effective, and environmentally benign and the catalyst can be reused for several times.

Synthesis of 14-aryl or alkyl-14H-dibenzo[a,j]xanthenes using nano-TiO2 as eco-friendly and efficient catalyst is reported. Short reaction times, high yields, a clean process, simple methodology, easy work-up and green conditions are advantages of this protocol.

3,4-Dihydropyrimidin-2(1H)-ones and 3,4-dihydropyrimidin-2(1H)-thione were synthesized under solvent free condition in the presence of nano-silica supported boron trifluoride (nano-BF3.SiO2). The reactions were carried out at 80 °C for 15 min under solvent free condition. This methods have some advantages such as good to excellent yield, mild reaction condition, ease of operation and workup, short reaction time and high product purity.

In this work clinoptilolite nanoparticles were modified with conducting polyaniline by the polymerization of anilinium cations in and out side of the clinoptilolite channels and a nanocomposite of polyaniline/clinoptilolite was obtained. Cations (Na+, K+, Mg2+, Ca2+…) in the natural clinoptilolite structure were exchanged with anilinium cations by the treatment of clinoptilolite nanoparticles in an acidic solution of aniline monomer. The cation exchange process was confirmed by elemental analysis of nitrogen and carbon atoms of anilinium cations in clinoptilolite dry powder after treatment. The polyaniline/clinoptilolite nanocomposite was obtained by the oxidative polymerization of anilinium cations within the clinoptilolite structure. The polyaniline/clinoptilolite nanocomposite was characterized utilizing FT-IR and X-ray diffraction measurements and was used for the removal of Cr(VI) from aqueous solutions in chromate anion form as an important water pollutant. The effect of a number of parameters such as initial concentration of Cr(VI), amount of nanocomposite and contact time on the removal efficiency of Cr(VI) by polyaniline/clinoptilolite nanocomposite were determined and optimized. It was found that after 5 min of exposure of nanocomposite powder with Cr(VI) solutions in the concentration range of 25 to 100 ppm, more than 98% of chromate anions can be removed and the Cr(VI) removal capacity per one gram of nanocomposite is about 0.3 mmol of Cr(VI).

The present work is an attempt to design new electrochemical biosensor that easily determines the concentration of phenolic compounds in water and wastewaters. It is well-known that enzymes can add selectivity towards one or limited number of compounds. Thus, in the present study, horseradish peroxidase (HRP) was coated on CuO nanoparticles and immobilized on the electrode using a thin polymeric film. The electrochemical studies of modified electrode were carried out by using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The voltammetric and EIS results confirm the possibility of HRP direct electron transfer at CuO nanoparticles. Our results revealed that the modified electrode can be used to determine the phenol concentration in the standard solutions and real samples. The present biosensor has good relative standard deviation (RSD% = 7%) and detection limit (DL of 0.1 µM), in addition to high stability.

Thin films of polystyrene and polystyrene-TiO2 nanocomposite were prepared by spin coating from a polystyrene solution in which TiO2 nanoparticles were dispersed by mechanical mixing. Thin films of polystyrene (PS) and polystyrene-TiO2 nanocomposite were exposed to UV irradiation for varied time intervals. The effect of UV radiation on the optical properties, crystallinity, surface energy and degradation of PS-TiO2 nano-composite has been studied. X-Ray diffraction analysis (XRD), UV-Vis and FTIR spectroscopy, Atomic Force Microscopy (AFM) and contact angle measurement were used to study the induced changes of the properties of the irradiated PS-TiO2 nanocomposite. Optical band gaps and hydrophilicity in UV-irradiated samples were altered by destruction processes. The optical band gap values were found to reduce from 4.54 eV in pure PS to 4.45 eV for PS-TiO2 nanocomposite prior to irradiation. This value is further reduced to 3.46 after UV irradiation for 45 h.

In the present study, photocatalytic degradation of methylene blue (MB) on ZnS nanoparticles, prepared in aqueous solution of a room-temperature ionic liquid (RTIL), was studied and the results were compared with commercial ZnS. Influence of various operational parameters such as calcination temperature, catalyst weight, pH of solution, and initial concentration of MB on the photodegradation reaction was investigated to achieve maximum degradation efficiency. The optimum value of pH and catalyst dose was found to be 9.5 and 0.6 g l-1. It was demonstrated that the photodegradation of MB follows a pseudo first-order kinetic. At optimized conditions, the rate constant of the reaction on ZnS nanoparticles prepared in aqueous solution of the RTIL is about five and four times greater than the prepared sample in water and commercial ZnS, respectively.