Journal of the Iranian Chemical Society
Volume:7 Issue: 1, July 2010

Superparamagnetic iron oxide nanoparticles (SPIONs) are promising materials for various biomedical applications including targeted drug delivery and imaging, hyperthermia, magneto-transfections, gene therapy, stem cell tracking, molecular/cellular tracking, magnetic separation technologies (e.g. rapid DNA sequencing), and detection of liver and lymph node metastases. The most recent applications for SPIONs for early detection of inflammatory, cancer, diabetes and atherosclerosis have also increased their popularity in academia. In order to increase the efficacy of SPIONs in the desired applications, especial surface coating/characteristics are required. The aim of this article is to review the surface properties of magnetic nanoparticles upon synthesis and the surface engineering by different coatings. The biological aspects, cytotoxicity, and health risks are addressed. Special emphasis is given to organic and inorganic-based coatings due to their determinant role in biocompatibility or toxicity of the final particles.

Phase changes of Lennard-Jones clusters containing 4N3 (N = 1-20) identical atoms in terms of solid and liquid phase-like forms have been studied by performing molecular dynamics (MD) simulation at sharply-bounded range of temperatures between freezing temperature (Tf) and melting temperature (Tm) and at constant pressure. The small differences between the free energies of clusters in different phase-like forms and also the non-rigidity of the cluster (0 ≤ γ ≤ 1) as an order-parameter, which characterizes the phase transition, have been calculated. Plots of the free energy of phase change versus the non-rigidity indicate that the free energy is a continuous function of the non-rigidity and also different crystalline-like cores with different free energies correspond to the same non-rigidity factor at any given temperature.

The density profile of molecules is an interesting property in the theoretical study of inhomogeneous fluids. In this work, the density profile of a hard sphere fluid around various hard and soft spheres is studied using a well-established version of the density functional theory called “modified fundamental measure theory”. The results obtained from this study show that an increase in the size of the central molecule leads to both an enhanced density profile at the contact point and an amplified layering structure. Similar effects can be observed when attraction between original and bulk molecules increases. Another finding of the present study is that increasing the size of the central molecule has a quasi-attractive role of an entropic origin called ‘depletion potential’. Since the molecule is not very large, the depletion potential can be mapped in a hard core with an attractive Yukawa tail. Increasing molecule softness, however, has an opposite effect and causes the height of the first peak of the density profile to diminish and the inhomogeneity of the structure to lighten.

The anion of hippuric acid, hippurate (A-), as an organic guest was intercalated into the interlayers of anionic clay, Zn/Al hydrotalcite-like or layered double hydroxides (LDH) host by direct co-precipitation method from aqueous solution for the formation of new nanohybrid compounds, Zn/Al-hippurate nanohybrids (ZAHs). Various Zn/Al molar ratios (R) = 3-5 and concentrations of HA (0.06-0.15 M) were used for the synthesis. ZAHs synthesized, using 0.15 M HA, was found to give well-ordered layered nanohybrid materials with an increase of the basal spacing to 19.6-21.0 Å compared to 8.8-9.0 Å in the LDHs. The increase in the basal spacing is due to the insertion of A- organic moiety into the LDH interlayers. Formation of the host-guest type of material was confirmed by XRD, FTIR, TGA/DTG and compositional analysis. The release of the intercalated guest was found to be tunable in a controlled manner by Zn/Al molar ratio and is governed by pseudo-second order kinetics. Thus, by varying the experimental conditions, the release property of the guest anion can be tailored as required.

Cobalt doped titania nanoparticles were synthesized by sol-gel method using titanium(IV) isopropoxide and cobalt nitrate as precursors. X-Ray diffraction (XRD) results showed that titania and Co/TiO2 nanoparticles only include anatase phase. The framework substitution of Co in TiO2 nanoparticles was established by XRD, scanning electron microscopy equipped with energy dispersive X-ray microanalysis (SEM-EDX) and Fourier transform infrared (FT-IR) techniques. Transmission electron microscopy (TEM) images confirmed the nanocrystalline nature of Co/TiO2. The increase of cobalt doping enhanced "red-shift" in the UV-Vis absorption spectra. The dopant suppresses the growth of TiO2 grains, agglomerates them and shifts the band absorption of TiO2 from ultraviolet (UV) to visible region. The photocatalytic activity of samples was tested for degradation of methyl orange (MO) solutions. Although the photocatalytic activity of undoped TiO2 was found to be higher than that of Co/TiO2 under UV irradiation, the presence of 0.5% Co dopant in TiO2 resulted in a catalyst with the highest activity under visible irradiation.

Ultra fine thin films of pure and SnO doped ZnO nanosensor were grown on gold digitated ceramic substrate from bis(2, 4-pentanedionate)dimethylethanolamine zinc (II) using bis(2, 4-pentanedionate) tin(II) chloride as a dopant by ultrasonic aerosol assisted chemical vapor deposition technique (UAACVD) at temperature range of 400"450 °C under oxygen atmosphere at 5 Pa pressure. The sensitivity, selectivity, fast recovery, and reliability test performed on nanosensor suggested that both doped and undoped ZnO thin films are suitable for detecting ethanol vapor in the temperature range of at 60 to 150 °C, whereas at room temperature (25 °C) response and recovery time of the sensor increases many folds compared to 60 °C. Sensitivity of the ZnO sensor shows linear relationship with the increase of gas concentration. Electrical properties show that 1 % SnO doped ZnO enhanced the sensitivity of the film drastically and thus improved its detecting efficiency. Physico-chemical techniques like, CHNS-O, atomic absorption analyzer, and infra red and multinuclear nuclear magnetic resonance spectrometers were used for precursor characterization. X-ray diffractometer, scanning electron microscope, sigma scan analyzer and energy dispersive x-ray techniques were used for thin film characterization.

Fast, simple and template-free method is proposed for preparation of ZnO nanocrystallines in the presence of 1-ethyl-3-methylimidazolium ethyl sulfate, [EMIM][EtSO4], a room-temperature ionic liquid (RTIL) under microwave irradiation. The powder X-ray diffraction (XRD) studies display that products are excellently crystallized in the form of wurtzite hexagonal structure. Energy dispersive X-ray spectroscopy (EDX) investigations reveal that the products are extremely pure. The results obtained by scanning electron microscopy (SEM) demonstrate that mean size of ZnO nanocrystallines decreases with microwave irradiation time and the RTIL content of media. Diffuse reflectance spectra (DRS) of the ZnO nanocrystallines shows blue shift relative to the bulk ZnO, which can be attributed to quantum confinement effect of ZnO nanocrystallines. A possible formation mechanism of the ZnO nanocrystallines in aqueous solution of the RTIL is presented. Photocatalytic activity of the ZnO nanocrystallines towards photodegradation of methylene blue (MB) was carried out. The results demonstrate that photocatalytic activity of the ZnO nanocrystallines increases with microwave irradiation time and the RTIL content of media.

A simple and effective procedure is proposed for spectrophotometric determination of catecholamines; Dopamine (1), L-Dopa (2) and Adrenaline (3). It was found that the reduction of Ag+ to silver nanoparticles (Ag-NPs) by these catecholamines in the presence of polyvinylpyrrolidone (PVP) as a stabilizing agent produced very intense surface plasmon resonance peak of Ag-NPs. The plasmon absorbance of the Ag-NPs allows the quantitative spectrophotometric detection of the catecholamines. The calibration curves derived from the changes in absorbance at λ = 440 nm were linear with concentration of Dopamine, Levodopa and Adrenaline in the range of 3.2×10-6- 2.0×10-5 M, 1.6×10-7 - 1.0×10-5 M, 1.5×10-6- 4.0×10-5 M, respectively. The detection limits (3σ) were 1.2×10-6 M, 8.6 ×10-8 M, 9.7 ×10-7 M for the Dopamine, L-Dopa and Adrenaline, respectively. The method was applied successfully to the determination of catecholamines in Ringer’s injection serum.

Adsorption of molecular hydrogen on single-walled carbon nanotube (SWCNT), sulfur-intercalated SWCNT (S-SWCNT), and boron-doped SWCNT (BSWCNT), have been studied by means of density functional theory (DFT).Two methods KMLYP and local density approximation (LDA) were used to calculate the binding energies. The most stable configuration of H2 on the surface of pristine SWCNT was found to be on the top of a hexagonal at a distance of 3.54 Å in good agreement with the value of 3.44 Å reported by Han and Lee (Carbon, 2004, 42, 2169). KMLYP binding energies for the most stable configurations in cases of pristine SWCNT, S-SWCNT, and BSWCNT were found to be -2.2 kJ mol-1, -3.5 kJ mol-1, and -3.5 kJ mol-1, respectively, while LDA binding energies were found to be -8.8 kJ mol-1, -9.7 kJ mol-1, and -4.1 kJ mol-1, respectively. Increasing the polarizability of hydrogen molecule due to the presence of sulfur in sulfur intercalated SWCNT caused changes in the character of its bonding to sulfur atom and affected the binding energy. In H2-BSWCNT system, stronger charge transfer caused stronger interaction between H2 and BSWCNT to result a higher binding energy relative to the binding energy for H2-SWCNT.

A simple procedure was developed to prepare a carbon-ceramic electrode (CCE) modified with multi wall carbon nanotube (MWCNT). The electrochemical behavior of pyridoxine was investigated on the obtained electrode in phosphate buffer solution (PBS), pH 7.0. During oxidation of pyridoxine on the MWCNT/CCE, one irreversible anodic peak at Ep = 716 mV vs. SCE appeared. Cyclic voltammetric study indicated that the oxidation process is irreversible and diffusion controlled. The number of exchanged electrons in the electro-oxidation process was obtained, and the data indicated that pyridoxine is oxidized via two one-electron steps. The results revealed that MWCNT promotes the rate of oxidation by increasing the peak current, so that pyridoxine is oxidized at lower potentials, which thermodynamically is more favorable compared with on the bare CCE. A sensitive, simple and time-saving differential pulse voltammetric procedure was developed for the analysis of pyridoxine. Using the proposed method, pyridoxine can be determined with a detection limit of 95 nM. The applicability of the method to direct assays of some commercial pharmaceutical samples is described.

Reduction of the transition metal complexes in aqueous solution has been investigated systematically by ascorbic acid as the reducing agent without the assistance of any surfactant. Nanoparticles of ±-Mn2O3, Ag and Cu were synthesized directly through aqueous phase reduction at room temperature. Nanoscale metal oxides such as Co3O4, ±-Fe2O3 and MoO2 were obtained through ascorbic acid reduction in alkali medium at 40šC. All the products were characterized on their structure and micro-morphology by the X-ray diffraction (XRD) and atomic force microscopy (AFM). The particle size of metal and metal oxides was about 10-50 nm. The reaction details and features were described and discussed.

We synthesized a series of cobalt-iron Prussian blue analogues in the form of nanocubes with which we tuned the amount of Cesium cation in the tetrahedral sites of the structure and varied nature of the alkali cation in the compound adopting a single microemulsion technique. Structure and morphology of the compound had been investigated by combining energy-dispersive X-ray spectroscopy (EDS), inductively coupled plasma (ICP), thermo-gravimetry analysis (TGA), infrared spectroscopy (IR), powder X-ray diffraction (XRD) and Transmission electron microscopy experiments (TEM). To directly determine the coercivity, remanence and Curie temperature, superconducting quantum interference device magnetometer (SQUID) was performed. Our investigation suggests that the amount and nature of the alkali cation are critical parameters for understanding the magnetic properties of the nanoparticles.

The utilization of modified magnetite nanoparticles (Fe3O4 NPs) with a cationic surfactant (cetyltrimethylammonium bromide (CTAB)) as an efficient adsorbent was successfully carried out to remove reactive black 5 (RBBA), reactive red 198 (RRR) and reactive blue 21 (RTB) dyes from aqueous solutions. First, a reactor was designed to be simple, repeatable and efficient in its synthesis of Fe3O4 NPs via co-precipitation method. Then, an orthogonal array design (OAD), four factor-four level (44) matrix was applied to assign affecting factors on removing of the dyes from aqueous solutions. The obtained results from ANOVA showed that the amount of CTAB and NaCl% significantly affect the adsorption of RBBA, RRR and RTB dyes. The sorption kinetics of the dyes were best described by a second-order kinetic model, suggesting chemisorptions mechanism. Also, dye adsorption equilibrium state data were fitted well to the Langmuir isotherm rather than Freundlich isotherm. Also, the maximum monolayer capacity, qmax, obtained from the Langmuir was 312.5, 163.9 and 556.2 mg g''1 for RBBA, RRR and RTB, respectively. The obtained results in the present study indicated that the CTAB-coated Fe3O4 NPs can be an efficient adsorbent material for removal of reactive dyes form aqueous solutions.

Magnetic nanoparticles can promote many attractive functions in biomedicine, which may contribute to the prevention of human disease but also may be potentially harmful. In the present study, the interaction of Fe2O3 nanoparticles with human hemoglobin (Hb) was studied by fluorescence, circular dichroism and UV/vis spectroscopies. Fluorescence data revealed that the fluorescence quenching of Hb by Fe2O3 nanoparticles was the result of the formed complex of Fe2O3 nanoparticles-Hb. Binding constants and other thermodynamic parameters were determined at three different temperatures. The hydrophobic interactions are the predominant intermolecular forces to stabilize the complex. Circular dichroism studies did not show any changes in the content of secondary structure of hemoglobin after Fe2O3 nanoparticles treatment. This study provides important insight into the interaction of Fe2O3 nanoparticles with hemoglobin, which may be a useful guideline for further using of these nanoparticles in biomedical applications.

In this work the titanium dioxide powder was prepared by the optimized and simple Sol-Gel method and then characterized. The gelling pH was set to values of 3 (TiO2-A), 7 (TiO2-N) and 9 (TiO2-B) to observe the effect on the properties of the material. In these three cases nanoparticulated materials were obtained with particle sizes between 10nm and 20nm. The larger surface areas were obtained at pH 3, which is several times larger than the others. Furthermore, with the gelling condition pH 3, it was possible to synthesize pure anatase phase titania. Some preliminary results on the test of the photocatalytic activity of the synthesized materials in the reduction of nitric oxide are presented. Based on these results the nanoparticle TiO2, which was prepared in acidic pH 3 with the pure anatase phase and the lowest particle size has the highest reactivity for the photocatalytic reduction of nitric oxide.

A new photocatalyst, nanoporous anatase TiO2 crystalline particles coupled by Na5PV2Mo10O40 Keggin units, TiO2-PVMo, was prepared by combination of the methods of sol-gel and hydrothermal treatment. The catalyst was characterized by X-ray diffraction (XRD), UV diffuse reflectance spectroscopy (UV-DRS), FT-IR spectroscopy, Scanning Electron Microscopy (SEM) and cyclovoltametery (CV). This photocatalyst exhibited a good photocatalytic (UV region) and sonocatalytic activity in the decomposition of different dyes in aqueous systems. The TiO2-PVMo composite showed higher photocatalytic and sonocatalytic activity than pure polyoxometalate or pure TiO2.

A simple and low temperature method is proposed for preparation of CdS nanoparticles in presence of 1-ethyl-3-methylimidazolium ethyl sulfate, [EMIM] [EtSO4], a room-temperature ionic liquid (RTIL). The powder X-ray diffraction (XRD) studies display that the products are excellently crystallized in the form of cubic structure and size of the nanparticles prepared in presence of the RTIL is smaller than that prepared in water. Energy dispersive X-ray spectroscopy (EDX) investigations reveal that the products are very pure and nearly stoichiometric. The results obtained by scanning electron microscopy (SEM) demonstrate that the CdS nanoparticles prepared in presence of the RTIL have lower tendency for aggregation relative to the prepared sample in water. Diffuse reflectance spectra (DRS) of the product prepared in the neat RTIL, shows 1.52 eV blue shift relative to bulk CdS, which can be attributed to quantum confinement effect of the CdS nanoparticles. A possible formation mechanism for CdS nanoparticles in presence of the RTIL is presented. Photocatalytic activity of the CdS nanoparticles towards photodegradation of methylene blue (MB) using UV and visible lights was performed. The results demonstrate that observed first-order rate constant for photodegradation of MB on CdS nanoparticles prepared in the neat RTIL are about 20 and 6 times greater than the prepared sample in water using visible and UV lights, respectively.