JOURNAL OF PHYSICAL AND THEORETICAL CHEMISTRY
Year:2010 | Volume:7 | Issue:1|Papers Count:10

Polychlorinated Biphenyls (PCBs) have been widely used to flame-retard products common in homes and the workplace, and subsequently. Polychlorinated biphenyls (PCBs) typify a class of highly toxic, stable aromatic pollutants. PCBs are recently being scrutinized for potential environment damage in groundwater and in the atmosphere. The elimination of chemical pollutants from a contaminated environment is one of the most important steps towards achieving the goal of environmental remediation.Recent studies have used carbon nanotubes (CNTs) for adsorption of pollution in environment, which are significantly higher dioxin elimination efficiencies. In this study, mechanism and interaction of single-walled carbon naotube (SWNT) for removal of PCBs are calculated by Gaussian program package. Inter SWNT; there are four situations for PCBs near SWNT (6, 6) with length of 1.54 nm that we calculated simulation of passing PCB through SWNT. The thermodynamics properties are calculated for passing PCBs across from SWNT that their results are showed this method can use for removal PCBs in environmental and their interaction are low potential in SWNT middle. So there is a place for adsorption of PCBs into SWNT, PCBs trap in it. This passing is exothermic, spontaneous, and favorable.

The [M (18c6)]+ (M=Li, Na, K and 18c6=18-crown-6) complexes have been chosen as the model systems to investigate the nature of chemical bonds between alkali metal cations and large multidentate organic ligands.The B3LYP/6-31+G (d, p) level of calculation has been used for obtaining equilibrium geometries andρ (r) functions (electron density distributions). By the aid of fundamental physical theorems implemented in Quantum Theory of Atoms in Molecules (QTAIM), the structures and the physical nature of chemical bonds have been determined for cited species at the mentioned theoretical level. These results establish the metaloxygen in all complexes in this work as ionic. The Li+ shows the coordination number of 3 with 18c6 crown ether and Na+ and K+ exhibits the coordination number of 6.

Nowadays application of nanotubes in biology and medicinal science is more investigated. Nanotubes can pass through cell walls and transport and release drugs in special tissues. The purpose of this paper is to investigate the interaction of a nanotube having hydroxyl functional groups (OH) with an anticancer agent. In this work transporting of an anticancer drug named 2- (2-amino 6, 7-dimethyl Pteridine 4-ylamino) -ethanol by a zigzag nanotube with 60 C atoms (5, 0) is investigated. The methods used are quantum mechanics and semiempirical.Two composites of the drug and nanotube are under studying: 1-compose of drug and nanotube's wall 2-compose of drug and one of the two heads of nanotube. At first some hydroxylic functional groups are put on the head of nanotube and then an etheric bond formed between agents. The results show that the composite is more stable than the single agent. Also binding of drug with the head of the nanotube is more stable than the wall. In the other case the interaction between a carbon nanotube (9, 0) and Levothyroxine as a drug is investigated. All of above composites are investigated by semiempirical methods and Molecular Mechanics/Molecular Dynamics simulation in body temperature (310 K) and their heat capacities are obtained in water, methanol and ethanol solutions separately. The results show that by increasing initial temperature in most of the cases heat capacity increases. Also it can be seen that by increasing of solvent molecular mass, the heat capacity increases too.

Energy gaps, DXS–t (X=E, H and G) (DXS–t=X(singlet) -X(triplet)) between singlet (s) and triplet (t) states were calculated at B3LYP/6-311++G** level of theory. Our results showed that electron donating substituents (G=-NH2, -OH, -CH3, -F, -Cl and -Br) at phenyl group cause to increase and electron withdrawing substituents (G=-CF3 and –NO2) lead to decrease the singlet-triplet energy gaps of Ar-C4H3 C.

Diminishing protein aggregation by chaperone is very important factor in medicine and industry. In this paper, it is induced the chaperone ability for; b-casein upon modification of its acidic residues by Woodward reagent K (WRK) and examined on lysozyme as a target protein at pH 7.2 and outlined the mechanism for chaperone ability of modified system by UV-Vis and fluorescence spectroscopy and theoretical calculation methods.

The dried nitrate-urea gels exhibit the combination of auto-catalytic combustion behavior and ultrasonic, which can be used to synthesize the nanocatalyst ferrite powders. Cu and Ni ferrites nanocatalyst powders with composition of CuFe2O4 and NiFe2O4 were synthesized by a sol–gel auto catalytic combustion process. The molar ratio between metal ions and urea was 1: 1.2. The sol- gel process was done at 800C. The nanoparticle crystallines have been calcined at 8000C.Combustion behavior and crystallite size of synthesized powders were investigated with the help of Scanning Electron Microscopy observation and X-ray diffraction technique. X- ray diffraction and Scanning Electron Microscopy were carried out for characterization of the powders. The grain size of the prepared ferrite powders is found to be in the range 30-35 nm.

Plane-wave pseudopotential Density Functional Theory (DFT) periodic slab calculations were performed using the generalized gradient approximation (GGA) to investigate the adsorption of nitric oxide (NO) on the (111) surface of Cu. Copper surface was simulated using the Periodic Slab Method consisting of five atomic layers.Four different adsorption sites (Atop, Bridge, HCP Hollow, and FCC Hollow) were considered. Results specified that the suitable site for NO adsorption in molecular form is the Hollow FCC site, and molecular adsorption is more stable than dissociative adsorption energetically.

We optimized the geometries of the graphene and graphene with hydrogen using PW91VWN, PW91PL, MPWLYP, G96LYP, G96PL/3-21G, 6-31G, 6-31G*levels of theory and compared our results with each other.We present the most important structural parameters determined for the addition of a hydrogen atom to graphene and the outward movement of the carbon atom that is bonded to hydrogen is 0.48 A. Also we calculateed vibrational frequencies at the same levels. All thermodynamic parameters of including DG, DH, DS were calculated.

The catalyst Pt-Ta supported on g-alumina was prepared by impregnation with solution containing compounds of H2PtCl6 and Ta2O5. The Pt concentration was kept constant at 0.2 wt% while the concentration of the tantalum was 0.4 wt%. The activity and selectivity of catalyst were determined under conditions at 450-500 ºC and 15-30 atm., with molar ratio H2/C7H6=5 and VVH=1.5mL/h for converted n-heptane. The results showed that in the presence the catalyst is stable and has much higher selectivity for aromatization reaction. It was shown that Ta modifies the acidity of support, resulting to higher selectivity for aromatization, and modifies the properties of the Pt catalyst.

As drug delivery systems Nanoparticulate widely investigated because of many advantages such as smaller size, controlled drug release potential, targeting ability, enhancement of therapeutic efficacy and reduction of toxicity. So, carbon nanotubes have recently received considerable attention as alternative drug delivery carrier.In this study we investigate interaction of tamoxifen with open-end of single-walled carbon nanotubes (SWNTs) using the Gaussian 98 program. We have computed NMR shielding tensors at B1LYP and HF levels by using 3-21G and STO-3G basis sets in the water. Our results reveal that NMR chemical shielding parameters are strongly affected by inducing solvent media. Regarding to our plotted graphs of siso, saniso, Ds,  h,  d in different methods and basis sets, the largest siso values obtained for O43 atom at the HF in STO-3G whereas the smallest one belonged to C34. It is interesting to note that the opposite trend have been observed for asymmetry parameters (h).