The simplest all-nitrogen ring: photolytically filling the cyclic-N3 well

We report evidence that cyclic-N(3) is exclusively produced in the 157-nm photolysis of ClN(3). Photoproduct translational energy measurements reveal a single-peaked distribution for an N(3)-formation channel with maximum and minimum translational energies matching the theoretically predicted minimum and maximum binding energies of cyclic-N(3), respectively. The absence of linear-N(3) greatly simplifies the data analysis. The zero-Kelvin heat of formation of cyclic-N(3) is derived experimentally (142+/-3.5 kcal/mol) and is in excellent agreement with the best existing determinations from other studies.     

A theoretical study on the electronic structure of GaAs/AlAs and AlAs/GaAs core/shell nanoparticles

Results of theoretical investigation on the structural and electronic properties of GaAs/AlAs and AlAs/GaAs core/shell nanoparticles are presented. We have considered relaxed structures of essentially spherical parts of the zinc-blende crystal structure. The electronic properties and the total energy were calculated using density-functional tight-binding method. Our results include the charge distribution, density of states (DOSs), electronic energy levels (in particular HOMO and LUMO), HOMO-LUMO gap, excitation spectra and their variation with shell thickness for both GaAs/AlAs and AlAs/GaAs core/shell systems.     

Syndiotactic Polystyrene / Fullerene Composites: Elucidation of Structural Aspect

Summary: Syndiotactic polystyrene (sPS), an attractive polymer due to its wide range of application, forms polymer-solvent intercalates with a large variety of solvent molecules ranging from liquids to solids. Recently, it has been realized that sPS intercalate prepared from SPS/naphthalene gel is more promising of making mesoporous materials. Here, the composite of sPS/fullerene have been prepared by taking advantage of sublimation of naphthalene. The different techniques as like XRD, SEM, HRTEM, FT-IR, DSC, TGA etc have been employed to characterized sPS/fullerene composite. XRD investigation shows the presence of δ form sPS in the composite. SEM and HRTEM reveal the fibrillar network with fringe like structure in presence of fullerene only and the average diameter of fibril has increased as compared to pure sPS fibrils. The conductivities of these fibrils have been increased with increasing amount of fullerene.     

The heat of formation of chlorine-isocyanate and the relative stability of isoelectronic molecules: an experimental and theoretical study

Accurate thermochemical data of small molecules are invaluable to the progress of every aspect of chemistry, especially in the atmosphere, combustion and industry. In this work, photofragmentation translational spectroscopy and 1st principles electronic structure theory reveal the literature value of the heat of formation of chlorine-isocyanate to be in error by more than 40 kcalmol. We report a revised experimental value for D0(Cl-NCO) = 51+/-3 kcal/mol which leads to a Delta Hf (ClNCO) = 8.5+/-3 kcal/mol. High level ab initio (CCSD(T)) electronic structure calculations extrapolated to the complete basis set limit give D0(Cl-NCO) = 6.3 kcal/mol, in good agreement with experiment. In light of the present results, the destabilization of azides relative to isoelectronic isocyanates has been evaluated empirically for three pairs of related molecules. It is found to be 90-110 kcal/mol, and has been attributed mainly to the weakening of the N-NN bond relative to the N-CO bond. Electronic structure calculations employing decomposition analysis suggest that, compared to homopolar N2, the (+delta)CO(-delta) pi polarity provides better orbital interaction (charge transfer) and electrostatic attraction and results in a closer encounter and larger stabilization between the fragments and that this is the origin of isoelectronic destabilization of azides relative to the isocyanates.     

Collision-free photochemistry of methylazide: observation of unimolecular decomposition of singlet methylnitrene

Methylazide photolysis at 248 nm has been investigated by ionizing photofragments with synchrotron radiation in a photofragmentation translational spectroscopy study. CH3N and N2 were the only observed primary products. The translational energy release suggests a simple bond rupture mechanism forming singlet methylnitrene, 1CH3N, and N2. Thus, these experiments reveal the unimolecular decomposition of this highly unstable species. We explain our observations through a mechanism which is initiated by the isomerization of 1CH3N to a highly internally excited methanimine H2C=NH isomer, which decomposes by 1,1-H2 elimination forming HNC+H2 as well as sequential H-atom loss (N-H followed by C-H bond cleavage), to form HCN. No evidence for dynamics on the triplet manifold of surfaces is found.     

Lysinated Multiwalled Carbon Nanotubes with Carbohydrate Ligands as an Effective Nanocarrier for Targeted Doxorubicin Delivery to Breast Cancer Cells

Multiwalled carbon nanotubes (MWCNTs) are elongated, hollow cylindrical nanotubes made of sp2 carbon. MWCNTs have attracted significant attention in the area of drug delivery due to their high drug-loading capacity and large surface area. Furthermore, they can be linked to bioactive ligands molecules via covalent and noncovalent bonds that allow for the targeted delivery of anticancer drugs such as doxorubicin. The majority of methodologies reported for the functionalization of MWCNTs for drug delivery are quite complex and use expensive linkers and ligands. In the present study, we report a simple, cost-effective approach for functionalizing MWCNTs with the carbohydrate ligands, galactose (GA), mannose (MA) and lactose (LA), using lysine as a linker. The doxorubicin (Dox)-loaded functionalized MWCNTs were characterized using FT-IR, NMR, Raman, XRD and FE-SEM. The drug–loaded MWCNTs were evaluated for drug loading, drug release and cell toxicity in vitro, in breast cancer cells. The results indicated that the carbohydrate-modified lysinated MWCNTs had greater Dox loading capacity, compared to carboxylated MWCNTs (COOHMWCNTs) and lysinated MWCNTs (LyMWCNTs). In vitro drug release experiments indicated that the carbohydrate functionalized LyMWCNTs had higher Dox release at pH 5.0, compared to the physiological pH of 7.4, over 120 h, indicating that they are suitable candidates for targeting the tumor microenvironment as a result of their sustained release profile of Dox. Doxorubicin-loaded galactosylated MWCNTs (Dox-GAMWCNTs) and doxorubicin loaded mannosylated MWCNTs (Dox-MAMWCNTs) had greater anticancer efficacy and cellular uptake, compared to doxorubicin–loaded lactosylated MWCNTs (Dox-LAMWCNTs) and pure Dox, in MDA-MB231 and MCF7 breast cancer cells. However, neither the ligand conjugated multiwall blank carbon nanotubes (GAMWCNTs, MAMWCNTs and LAMWCNTs) nor the lysinated multiwalled blank carbon nanotubes produced significant toxicity in the normal cells. Our results suggest that sugar-tethered multiwalled carbon nanotubes, especially the galactosylated (Dox-GAMWCNTs) and mannosylated (Dox-MAMWCNTs) formulations, may be used to improve the targeted delivery of anticancer drugs to breast cancer cells.     

Preparation of Hierarchical Porous Activated Carbon from Banana Leaves for High-performance Supercapacitor: Effect of Type of Electrolytes on Performance

We demonstrate a facile efficient way to fabricate activated carbon nanosheets (ACNSs) consisting of hierarchical porous carbon materials. Simply heating banana leaves with K₂CO₃ produce ACNSs having a unique combination of macro-, meso- and micropores with a high specific surface area of ∼1459 m² g⁻¹. The effects of different electrolytes on the electrochemical supercapacitor performance and stability of the ACNSs are tested using a two-electrode system. The specific capacitance (C_sp) values are 55, 114, and 190 F g⁻¹ in aqueous 0.5 M sodium sulfate, organic 1 M tetraethylammonium tetrafluoroborate in acetonitrile, and pure ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF₆]) electrolytes, respectively. The ACNSs also shows the largest potential window of 3.0 V, the highest specific energy (59 Wh kg⁻¹) and specific power (750 W kg⁻¹) in [BMIM][PF₆]. A mini-prototype device is prepared to demonstrate the practicality of the ACNSs.     

Photodissociation dynamics of vinyl fluoride (CH2CHF) at 157 and 193 nm: Distributions of kinetic energy and branching ratios

Using photofragment translational spectroscopy and tunable vacuum-ultraviolet ionization, we measured the time-of-flight spectra of fragments upon photodissociation of vinyl fluoride (CH2CHF) at 157 and 193 nm. Four primary dissociation pathways--elimination of atomic F, atomic H, molecular HF, and molecular H2--are identified at 157 nm. Dissociation to C2H3 + F is first observed in the present work. Decomposition of internally hot C2H3 and C2H2F occurs spontaneously. The barrier heights of CH2CH --> CHCH + H and cis-CHCHF --> CHCH + F are evaluated to be 40+/-2 and 44+/-2 kcal mol(-1), respectively. The photoionization yield spectra indicate that the C2H3 and C2H2F radicals have ionization energies of 8.4+/-0.1 and 8.8+/-0.1 eV, respectively. Universal detection of photoproducts allowed us to determine the total branching ratios, distributions of kinetic energy, average kinetic energies, and fractions of translational energy release for all dissociation pathways of vinyl fluoride. In contrast, on optical excitation at 193 nm the C2H2 + HF channel dominates whereas the C2H3 + F channel is inactive. This reaction C2H3F --> C2H2 + HF occurs on the ground surface of potential energy after excitation at both wavelengths of 193 and 157 nm, indicating that internal conversion from the photoexcited state to the electronic ground state of vinyl fluoride is efficient. We computed the electronic energies of products and the ionization energies of fluorovinyl radicals.     

Deficiently extremal Cohen-Macaulay algebras

The aim of this paper is to study homological properties of deficiently extremal Cohen-Macaulay algebras. Eagon-Reiner showed that the Stanley-Reisner ring of a simplicial complex has a linear resolution if and only if the Alexander dual of the simplicial complex is Cohen-Macaulay. An extension of a special case of Eagon-Reiner theorem is obtained for deficiently extremal Cohen-Macaulay Stanley-Reisner rings.