Nanochemistry Research
Volume:2 Issue: 1, Winter and Spring 2017

The adsorption of hydrogen sulfide molecule on undoped and N-doped TiO2/Au nanocomposites was investigated by density functional theory (DFT) calculations. The results showed that the adsorption energies of H2S on the nanocomposites follow the order of 2N doped (Ti site)>N-doped (Ti site)>Undoped (Ti site). The structural properties including bond lengths, angles and adsorption energies and electronic properties in view of the projected density of states (PDOSs) and molecular orbitals (MOs) were analyzed in detail. The results indicated that the interaction between H2S molecule and N-doped TiO2/Au nanocomposite is stronger than that between H2S and undoped nanocomposite, suggesting that N-doping helps to strengthen the interaction of H2S with TiO2/Au nanocomposite. Mulliken population analysis was conducted to analyze the charge transfer between the nanocomposite and H2S molecule. Although H2S molecule has no significant interaction with undoped nanocomposite, it tends to be strongly adsorbed on the N-doped nanocomposite. The results also suggest that the two doped nitrogen atoms in TiO2 greatly strengthen the adsorption process, being a helpful procedure to help in the design and development of improved sensor devices for H2S detection.

In this review, we examine the greenest nanoparticles of zero-valent metals, metal oxides and metal salts, with emphasis on recent developments routes. Products from nature or those derived from natural products, such as extracts of several plants or parts of plants, tea, coffee, banana, simple amino acids, as well as wine, table sugar and glucose, have been used as reductants and as capping agents during the present synthesis method. Polyphenols found in plant material often play a key role in the processes mentioned here. The techniques involved are generally one-pot processes, environmentally friendly and simple. Green synthesis of gold nanoparticles using several extracts and spices extracts was conducted, in which aqueous extracts HAuCl4.3H2O reduce to Au° has establishing themselves in specific crystal phase. Synthesized nanoparticles were confirmed by the color change of auric chloride which is yellow. The growth of nanoparticles was monitored by the behavior of surface Plasmon using UV-Vis spectroscopy; also the pH was determined meanwhile. Moreover, this approach is not only of a green rapid synthesis kind and considered as a better alternative to chemical synthesis, but also found to be effective for large scale synthesis of gold nanoparticles.

Titanium dioxide-based nanofibers (TiO2 nanofiber) were prepared by an electrospinning technique. The electrospun composite fibers were synthesized at different concentrations of titanium isopropoxide (25.35, 50.69, 76.05 wt%) and calcinated at different temperatures (450 oC, 650 oC and 850 oC) for 2 h. The diameters of nanofibers decreased by increasing the inorganic part of composite nanofibers and principally depicted anatase, anatase- rutile and rutile phases. By increasing temperature from 450 oC to 850 oC, the anatase phase decreased whereas the rutile phase increased. The different optimized TiO2 nanofibers were prepared and utilized as a sufficient scattering layer for the photoanode in dye sensitized solar cells. Then, the electron transport and recombination in TiO2 nanofiber based dye sensitized solar cells (DSSCs) was investigated. It was shown that the electron life time in DSSCs with TiO2 nanofibers, as a scattering layer, increases in different photoanode electrodes compared to that on DSSCs based on nanoparticles. As a result, conversion efficiency of 5.6% is realized, which is 55.37% higher than TiO2 photoanodes without addition of nanofibers as a scattering layer.

The new magnetic amine-functionalized graphene oxide (Fe3O4-GO-NH2) nanocatalyst was prepared through the reaction of 3-aminopropyltriethoxysilane (APTES) with magnetic graphene oxide (Fe3O4-GO). It was characterized by XRD, TEM, SEM, FT-IR and EDX techniques. The intrinsic carboxylic acids on the edges of Fe3O4-GO along with the amine groups post grafted to the surface of Fe3O4-GO led to preparation of an acid-base bifunctional magnetically recyclable nanocatalyst. It proved to be efficient nanocatalyst for solvent-free synthesis of pyrano[3,2-c]pyridine derivatives under mild reaction conditions with good to excellent yields. This heterogeneous catalyst also exhibited higher activities than acid or base functionalized mesoporous silica, magnetic GO or basic Al2O3 an even higher than some basic homogeneous catalysts such as triethylamine and piperazine. More importantly, due to the loaded iron oxide nanoparticles, this catalyst could be easily recovered from the reaction mixture using an external magnet and reused without significant decrease in activity even after 7 runs.

Ghezeljeh montmorillonite nanoclay or “Geleh-Sar-Shoor” (means head-washing clay) used as a native adsorbent to extraction-preconcentration mercury ions from a variety of real water and fish samples have been investigated in a batch system followed by atomic absorption spectroscopy (AAS) with vapor generation accessory (VGA) system. The clay was characterized by using FT-IR, SEM-EDS, XRF, XRD, CEC, Specific surface area and Zeta potential. The results of XRD, FT-IR, Zeta potential and CEC of the Ghezeljeh clay confirm that montmorillonite is the dominant mineral phase. On the basis of on SEM images, the distance between the layers is in nm level. The outcome of varying parameters and interfering ions were studied. Detection and quantification limits, preconcentration factor, and adsorption capacity were calculated. The Langmuir and Freundlich equations showed the finest fit to the equilibrium data. The adsorption procedure follows a pseudo-second-order reaction pattern. Calculation of ΔG0, ΔH0 and ΔS0 displayed that the nature of Hg(II) ions adsorption is endothermic and favorable at upper temperature.

A new, sensitive and fast dispersive liquid-liquid microextraction (DLLME) coupled with micro-solid phase extraction (μ-SPE) was developed for determination of zearalenone (ZEN) in wheat samples. The DLLME was performed using acetonitrile/water (80:20 v/v) as the disperser solvent and 1-octanol as the extracting solvent.  The acetonitrile/water (80:20 v/v) solvent was also used to extract ZEN from solid wheat matrix, and was directly applied as the disperser solvent for DLLME process. Additionally, hydrophobic oleic-acid-modified magnetic nanoparticles were used in μ-SPE approach to retrieve the analyte from the DLLME step. So, the method uses high surface area and strong magnetism properties of these nanoparticles to avoid time-consuming column-passing processes in traditional SPE. Main parameters affecting the extraction efficiency and signal enhancement were investigated and optimized. Under the optimum conditions, the calibration curve showed a good linearity in the range of 0.1-500 μg kg−1 (R2=0.9996) with low detection limit of 83 ng g−1. The intra-day and inter-day precisions (as RSD %) in the range of 2.6-4.3 % and high recoveries ranging from 91.6 to 99.1 % were obtained. The pre-concentration factor was 3. The method is simple, inexpensive, accurate and remarkably free from interference effects.

Crystal engineering has recently emerged as a method of choice for the design and construction of organic as well as metal-organic functional materials. Crystal engineering attempts to establish packing trends in whole families of compounds and seeks to establish connections between structure and function. The utility of crystal engineering has also been expanded to the nanoscience and the development of nanomaterials. The crystal engineering of materials on the nanoscale has attracted attention from various fields of research. Using bottom-up assembly strategies, a wide range of functional systems can be accessed. Materials of nanometer-scale dimensions having unique physicochemical properties are of great interest in various fields such as synthetic chemistry, materials science, catalysis and medicine. This review concerns to the recent advances in crystal engineering from nanoscience views. This study was conducted in four categories; nanococrystals, nano metal-organic frameworks, composites of polyoxometalates and also some of the nanocarbons.

In this study, Zinc oxide nanoparticles were synthesized by gel-combustion method using a novel bio-fuel tapioca starch pearls, derived from the tubers of Mannihot esculenta, to investigate the photocatalytic degradation of ccaffeine. The ZnO photocatalyst was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV-visible spectroscopy. X-ray diffractometry result for the ZnO nanoparticles exhibit normal crystalline phase features. All observed peaks can be indexed to the pure hexagonal wurtzite crystal structures. There are no other impurities in the diffraction peak. In addition, SEM measurement shows that most of the nanoparticles are spongy and spherical in shape and fairly mono dispersed. A significant degradation of the Caffeine was observed when the catalyst was added into the solution even without the UV light exposure. In addition, the photo degradation increaseds with the photocatalyst loading. Besides the photocatalyst loading, the effect of some parameters on the photo degradation efficiency such as initial concentration and pH were also studied.

A novel sulfonated polybenzimidazole/organoclay (Cloisite-30B) (SPBI/clay) nanocomposite membranes was successfully synthesized based on aromatic diacide (1) and diaminobenzidine. Nanocomposite membranes were fabricated using 1, 4-bis (hydroxymethyl) benzene (BHMB) as cross-linker, and Cloisite-30B organoclay as the pseudo cross-linker. The cross-linked SPBI/clay nanocomposite membranes were prepared via solution intercalation method. Participation of reactive organoclay in the cross-linking process was established from ion exchange capacity (IEC) measurements and FTIR studies. Wide angle X-ray diffraction (WAXD), field emission-scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM) techniques confirmed the presence of a combination of the intercalated and partially exfoliated clay confirmed mixed clay dispersion morphology of intercalation and partial exfoliation of the clay platelets in the cross-linked SPBI/clay nanocomposite membrane. The cross-linked SPBI/clay nanocomposite membranes showed higher tensile strength, modulus and lower elongation at break compared to neat cross-linked SPBI. Water and methanol uptake studies revealed superior barrier properties of cross-linked SPBI/clay nanocomposite membranes compared to cross-linked SPBI. Furthermore, thermal stability, residual solvent in the membrane film, and structural ruination of membranes were analyzed by thermal gravimetric analysis (TGA). TGA data indicated an increase in thermal stability of the SPBI/clay nanocomposite membranes in compared to the pure polymer. The oxidative stability of SPBI improved remarkably with cross-linking and subsequent clay addition. These improvements in the thermo-mechanical, barrier and oxidative stability of the membranes could be achieved without significantly affecting the protonic conductivity.

CdS-coupled TiO2 nanocrystals were prepared by the microemulsion-mediated solvothermal method at pretty low temperatures. The semiconductor nanocrystals were modified with tyrosine, phenyl alanine, glysine and glutamate aminoacids and then were characterized by BET, SEM, EDX, XRD, UV–Vis spectroscopy, and FTIR analysis methods. The specific surface area and the average pore diameter were found to be about 470 m2 g−1 and 2.8 nm, respectively. Moreover, the average size of the CdS-TiO2 particles was evaluated to be 28 nm. The results showed that the modification process with the aminoacids improves the adsorption capability and photoactivity of the samples. Among them, tyrosine was determined to be the best choice. According to the results, modification of CdS-TiO2 heterojunction photocatalyst with electron-donating groups is an efficient strategy to increase the photoreduction of nitroaromatic compounds. Reusability experiments were also carried out and confirmed the high capacity of the prepared samples for the photoconversion of nitrobenzene after being repeated for four times.

In current study, nanoparticles and single crystals of a Zn(II) coordination complex, [Zn(dmph)I2](1), {dmph=2,9-dimethyl-1,10-phenanthroline(neocuproine)}, have been synthesized by the reaction of zinc(II) acetate, KI and neocuproine as ligand in methanol using sonochemical and heat gradient methods, respectively. The nanostructure of 1 was characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), FT-IR spectroscopy and elemental analyses, and the structure of compound 1 was determined by single-crystal X-ray diffraction. The thermal stability of nano-sized 1 has been studied by thermogravimetric (TG) and differential thermal analyses (DTA). Structural determination of compound 1 reveals the Zn(II) ion is four-coordinated in a distorted tetrahedral configuration by two N atoms from a 2,9-dimethyl-1,10-Phenanthroline ligand and two terminal I atoms. The effect of supercritical condition on stability, size and morphology of nano-structured compound 1 has also been studied. The XRD pattern of the residue obtained from thermal decomposition of nano-sized compound 1 at 600 °C under air atmosphere provided pure phase of ZnO with the average particles size of about 31 nm.

The nucleation and growth of sol-gel derived TiO2 colloidal nanoparticles have been studied using  experiment and theory as well. In this study, the temperature effect on the formation of TiO2 nanoparticles was discussed and some effective parameters such as the supply rate of solute (Q0), the mean volumic growth rate of stable nuclei during the nucleation period (u), the diffusion coefficient of [Ti]+4 ions and the nucleus size were determined. The formation of TiO2 nanoparticles in three different temperatures (60, 70 and 80°C) was studied. The obtained results showed that the process temperature has a considerable impact on the nucleation and growth of TiO2 nanoparticles. It can be concluded that  increasing the temperature leads to a decrease of the supersaturation and an increase of the nucleus size, supply rate of monomer, nanoparticles density and growth rate as evident from LaMer diagram.

In the present study, the extract of the plant of Oenothera biennis was used to green synthesis of silver nanoparticles (Ag NPs) as an environmentally friendly, simple and low cost method. And Additionally, TiO2/SiO2 was prepared via facile sol-gel method using starch as an important, naturally abundant organic polymer as an ideal support. The Ag NPs/TiO2/SiO2 as an effective catalyst was prepared through reduction of Ag+ ions using Oenothera biennis extract as the reducing and stabilizing agent and Ag NPs immobilization on TiO2/SiO2 surface in the absence of any stabilizer or surfactant. Several techniques such as FT-IR spectroscopy, UV-Vis spectroscopy, X-ray Diffraction (XRD), sScanning eElectron mMicroscopy (FE-SEM), Eenergy dDispersive X-ray sSpectroscopy (EDS), and Ttransmission Eelectron Mmicroscopy (TEM) were used to characterize TiO2/SiO2, silver nanoparticles (Ag NPs), and Ag NPs/TiO2/SiO2. Moreover, the catalytic activity of the Ag NPs/ TiO2/SiO2 was investigated in the reduction of 4-nitrophenol (4-NP) at room temperature. On the basis of the results, the Ag NPs/TiO2/SiO2 was found to be high catalytic activity highly active catalyst according to the experimental results in this study. In addition, Ag NPs/TiO2/SiO2 can be recovered and reused several times in the reduction of 4-NP with no significant loss of catalytic activity.

Paracetamol is a non-steroidal anti-inflammatory drug used as an antipyretic agent for the alternative to aspirin. Conversely, the overdoses of paracetamol can cause hepatic toxicity and kidney damage. Hence, the determination of paracetamol receives much more attention in biological samples and also in pharmaceutical formulations. Here, we report a rapid and sensitive detection of the paracetamol based on screen-printed modified electrode (SPE) with Cu nanocomplex (Cu) in pH=7.0. The paracetamol is not stable in strong acidic and strong alkaline media, and is hydrolyzed and hydroxylated. However, it is stable in intermediate pHs due to the dimerization of paracetamol. The kinetics of the paracetamol oxidation was briefly studied and documented in the schemes. In addition, the characterization of Cu nanocomplex was probed by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). Moreover, the voltammetry determined the paracetamol with the linear concentration ranging from 10.0 to 1000.0 μM and the lower detection limit of 1.0 μM. This method was also successfully used to detect the concentration of paracetamol in pharmaceutical formulations and urine samples.