Journal of Nano Structures
Volume:4 Issue: 2, Spring 2014

Isotherm equation is one of the important scientific bases for adsorbent selection. There are different isotherms that do not account for an adsorbate, different chemisorption geometries on the nanoporous surface. It is interesting to introduce a general isotherm, which considers different chemisorption geometries of an adsorbate on nanoporous surfaces. In this study, an isotherm for non- dissociative gas adsorption on nanoporous surface was derived by classical thermodynamics. Theoretical study of thermodynamics of adsorption leads to the concept of a constant parameter which shows the ratio of the number of occupied sites to the number of adsorbed molecules. The derived isotherm was analyzed by several experimental systems of non-dissociative gas adsorption on nanoporous surfaces. By using experimental data, a comparison between the derived isotherm with some famous isotherms like Langmuir, Sips, Toth and Frumkin was provided.

In the present study, tin-promoted Pd/MWNTs nanocatalystwas synthesized via polyol technique for application in hydrogenation of high-concentrated acetylene feedstocks. TEM images showed a restricted distribution of nanoparticles in the range of 3-5 nm. The results indicated that nanoparticles sizes were resistant to further catalyst deactivation. XRD patterns signified alloying between Pd and Sn which contained a high percentage of ordered intermetallic structures (70.8%), as confirmed by XPS. According to the results, pore blocking and/or fouling was known as the main reasons of the catalyst deactivation. Here, we supposed a novel deactivation mechanism based on which dehydrogenation susceptibility of carbonaceous species (green oil) played a significant role in the formation of the isolated adsorption sites and then, catalyst deactivation.

The Cu doped NiO (NiO:Cu) nanoparticles were synthesized by co- precipitation method using NiCl2.6H2O, CuCl2.2H2O for Ni and Cu sources, respectively. Sodium hydroxide has been used as a precipitator agent. Effect of Cu doping agent on the structural and optical properties of nanostructures were characterized by XRD, SEM, AFM, spectrophotometry, FTIR and VSM techniques. XRD revealed that NiO:Cu has a FCC structure. Optical absorption spectra of the samples obtained using UV-Vis spectrophotometer shows a blue-shift when copper amount increase which indicates decreasing particle size. The study of magnetization property at room temperature shows weak ferromagnetic behavior of NiO:Cu nanoparticles. Hysteresis loops were show that magnetization increasing with Cu doping up to 13% and then with further doping decreasing.

Substitution of two or four carbon atoms by nitrogen in the corannulene molecule as a carbon nanostructure was done and the obtained structures were optimized at MP2/6-31G(d) level of theory. Calculations of the nucleus-independent chemical shift (NICS) were performed to analyze the aromaticity of the corannulene rings and its derivatives upon doping with N at B3LYP/6-31G(d) level of theory. Results showed NICS values in six-membered and five-membered rings of two and four N atoms doped corannulene are different and very dependent to number and position of the N atoms. The values of the mean NICS of all N-doped structures are more positive than intact corannulene that show insertion of N atom to the structures causes to decreasing aromaticity of them.

The electrochemical oxidation of sulfamethazine (SMZ) has been studied at a multi-walled carbon nanotubes modified glassy carbon electrode (MWCNT-GCE) by cyclic voltammetry. This modified electrode (MWCNT-GCE) exhibited excellent electrocatalytic behavior toward the oxidation of SMZ as evidenced by the enhancement of the oxidation peak current and the shift in the anodic potential to less positive values (170 mV) in comparison with the bare GCE. The formal potential, E0'', of SMZ is pH dependent with a slope of 54 mV per unit of pH, close to the anticipated Nerstian value of 59 mV for a 2-electron and 2-proton oxidation process. A detailed analysis of cyclic voltammograms gave fundamental electrochemical parameters including the electroactive surface coverage (Г), the transfer coefficient (), the heterogeneous rate constant (ks). Under the selected conditions, the peak current shows two dynamic linear ranges of 10-200 M and 300-3000 Mwith the detection limit of 6.1 M. The method was successfully applied to analyze SMZ in serum sample.

In this paper, surface and piezoelectric effects on the vibration behavior of nanowires (NWs) are investigated by using a Timoshenko beam model. The electric field equations and the governing equations of motion for the piezoelectric NWs are derived with the consideration of surface effects. By the exact solution of the governing equations, an expression for the natural frequencies of NWs with simply-supported boundary conditions is obtained. The effects of piezoelectricity and surface effects on the vibrational behavior of Timoshenko NWs are graphically illustrated. A comparison is also made between the predictions of Timoshenko beam model and those of its Euler-Bernoulli counterpart. Additionally, the present results are validated through comparison with the available data in the literature.

Piezoelectric nanobeams having circular, rectangular and hexagonal cross-sections are synthesized and used in various Nano structures; however, piezoelectric nanobeams with hexagonal cross-sections have not been studied in detail. In particular, the physical mechanisms of the surface effect and the role of surface stress, surface elasticity and surface piezoelectricity have not been discussed thoroughly. The present study investigated post-buckling behavior of piezoelectric nanobeams by examining surface effects. The energy method was applied to post-buckling of hexagonal nanobeams and the critical buckling voltage and amplitude are derived analytically from bulk and surface material properties and geometric factors.

The Atmospheric Pressure Chemical Vapor Synthesis (APCVS) route is a process that can be used for the synthesis of doped-nanocrystalline powders with very small crystallite sizes having a narrow particle size distribution and high purity. In this study, APCVS technique was used to prepare boron-doped titania nanopowders. The effects of temperature, borate flow rate and water flow rate on the amount of doped boron were studied. The resultant powders were characterized by inductively coupled plasma (ICP), X-ray diffraction (XRD), nitrogen adsorption technique (BET), UV-visible DRS spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The optimum boron precursor flow rate was 80 sccm. The highest amount of doped boron was attained when water flow rate was 900 sccm. In comparison to the pristine TiO2, the boron-doped TiO2 nanoparticles showed blue-shift in band-gap energy of the samples.

In this report, we present a facile approach for the synthesis of luminescent CdS and CdS:Mn+2 nanocrystals by reaction of CdSO4 and Na2S2O3 in the presence of thioglycerol (C3H8O2S) as capping agent. The influence of various experimental variables including, pH values and percentage of dopant, on the growth rate and optical properties of the obtained CdS nanocrystals has been systematically investigated. Experimental results show that by lapsing time and increasing particles size, red shift has occurred in the absorption edge and peak of luminescence. Luminescence of CdS nanoparticles covers 480-650nm of visible range. This luminescence arises from trap states and reaches to its maximum in pH=6 after 5 days. Doping of CdS with Mn+2 is found to enhance the photoluminescence (PL)intensity. PL Peak in CdS:Mn+2 sample has shifted towards 580nm due to  1614A T  transition in Mn+2 ions.

Several novel composite membranes were prepared to separate and recycle amoxicillin from pharmaceutical wastewater via nanofiltration process. The synthesis of these membranes included three stages: 1- preparation of polysulfone ultrafiltration membranes as a support via phase separation process, 2- modification of its surface by interfacial polymerization as a selective layer (polyamide), and 3- self-assembly of TiO2 nanoparticles on the selective layer as an anti-fouling agent. The rejection of all nanofiltration membranes was more than 99% and only its flux was changed proportional to different conditions. In the presence and absence of TiO2 nanoparticles, the pure water flux of polyamide thin-film membrane also obtained 44.4 and 38.4 L/h.m2 at 4 bar pressure, respectively. These were equal to 34 L/h.m2 for amoxicillin solutions. The results showed that TiO2 nanoparticles increased hydrophilicity of polyamide selective layer and therefore,nanoparticlesdecreasedthefoulinglevel.SEMimages illustrated the excellent establishment of polyamide layer and distribution of TiO2nanoparticles on the selective layer. The properties of membrane surface were taken into consideration by using AFM, indicating the increment of surface roughnesswith interfacial polymerization and TiO2 nanoparticles self-assembly. The pore sizeofmembranes was in the nanoscale (2.653 and 2.604 nm without and with TiO2nanoparticles self-assembly, respectively).

Electrosynthesis process has been used for preparation of zinc sulfide nanoparticles. Zinc sulfide nanoparticles in different size and shapes were electrodeposited by electrolysis of zinc plate as anode in sodium sulfide solution. Effects of several reaction variables, such as electrolysis voltage, sulfide ion concentration as reactant, stirring rate of electrolyte solution and temperature on particle size of prepared zinc sulfide were investigated. The significance of these parameters in tuning the size of zinc sulfide particles was quantitatively evaluated by analysis of variance (ANOVA). Also, optimum conditions for synthesis of zinc sulfide nanoparticles via electrosynthesis reaction were proposed. The structure and composition of prepared nanoparticles under optimum condition was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV-Vis spectrophotometry techniques.

In this study the effects of Fe2O3 and Fe3O4 magnetic nanoparticles and EDTA on urease activity was investigated. The effect of nano-Fe2O3 and nano-Fe3O4 on urease activity were investigated. Urease activity was studies by UV-Vis spectrophotometry at 40 °C at pH = 7.2 using sodium phosphate as buffer. Measurements were carried out using 0.075 mg/ml of urease and a range of nano-Fe2O3 and nano-Fe3O4 concentrations between 0.002-0.006 mg/ml. It was found that by increasing the concentration of nano-Fe2O3 and nano-Fe3O4, urease activity will be decreased. On the other hand, nano-Fe2O3 and nano-Fe3O4 act as non competitive inhibitor for urease. Urease protection studies were corried out by using different concentration of EDTA (0.004-0.008 mg/ml). It was shown by increasing the concentration of EDTA, the activity of enzyme increased.

Bismuth sulfide nano-rods and nano-flowers were synthesized via a hydrothermal reaction at a relatively low temperature. Thioglycolic acid is used as sulfur source and capping agent simultaneously. Bi2S3 nanostructures were then added to acrylonitrile-butadiene-styrene (ABS) copolymer. The thermal stability behavior of ABS filled with bismuth sulfide nano-rods were investigated by thermogravimetric analysis (TGA). Nanostructures were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The flame retardancy behavior of ABS-Bi2S3 was studied by UL-94 analysis.