Loading of a Phenanthroline-Based Platinum(II) Complex onto the Surface of a Carbon Nanotube via pi–pi Stacking

Stacking of the metal complex [(5,6-dimethyl-1,10-phenanthroline)(1S,2S-diaminocyclohexane)platinum(II)]2þ (56MESS) onto the surface of two different fullerenes, a carbon nanotube (CNT), and a C60-buckyball was examined. The metal complex forms a supramolecular complex with multi-walled CNTs but not with buckyballs. Binding of 56MESS to the CNTs is highly efficient (90 %) but can be further stabilized by the addition of the surfactant, pluronic F-127, which resulted in a loading efficiency of 95 %. Molecular modelling shows that binding of 56MESS to the CNT is supported by the large surface area of the fullerene, whereas the more pronounced curvature and lack of a flat surface on the buckyball affects the ability of 56MESS to form bonds to its surface. The loading of 56MESS onto the CNT is via p–p stacking from the metal complex phenanthroline ligand and C–H p bonding fromthe diaminocyclohexane ligand. 56MESS has 13 critical bonding points with the CNT, eight of which are p–p stacking bonds, but the metal complex forms only seven bonds with the buckyball. In addition, the loading of 56MESS onto the CNT results in a charge transfer of 0.111 eV; however, charge transfer is almost negligible for binding to the buckyball

Probing the Structure, Stability and Hydrogen Adsorption of Lithium Functionalized Isoreticular MOF-5 (Fe, Cu, Co, Ni and Zn) by Density Functional Theory

Li adsorption on isoreticular MOFs with metal Fe, Cu, Co, Ni and Zn was studied using density function theory. Li functionalization shows a considerable structural change associated with a volume change in isoreticular MOF-5 except for the Zn metal center. Hydrogen binding energies on Li functionalized MOFs are seen to be in the range of 0.2 eV, which is the desired value for an ideal reversible storage system. This study has clearly shown that Li doping is possible only in Zn-based MOF-5, which would be better candidate to reversibly store hydrogen

Recent advances in MXenes: from fundamentals to applications

The family of MAX phases and their derivative MXenes are continuously growing in terms of both crystalline and composition varieties. In the last couple of years, several breakthroughs have been achieved that boosted the synthesis of novel MAX phases with ordered double transition metals and, consequently, the synthesis of novel MXenes with a higher chemical diversity and structural complexity, rarely seen in other families of two-dimensional (2D) materials. Considering the various elemental composition possibilities, surface functional tunability, various magnetic orders, and large spin$-$orbit coupling, MXenes can truly be considered as multifunctional materials that can be used to realize highly correlated phenomena. In addition, owing to their large surface area, hydrophilicity, adsorption ability, and high surface reactivity, MXenes have attracted attention for many applications, e.g., catalysts, ion batteries, gas storage media, and sensors. Given the fast progress of MXene-based science and technology, it is timely to update our current knowledge on various properties and possible applications. Since many theoretical predictions remain to be experimentally proven, here we mainly emphasize the physics and chemistry that can be observed in MXenes and discuss how these properties can be tuned or used for different applications

Cucurbit[7]uril encapsulated cisplatin overcomes cisplatin resistance via a pharmacokinetic effect

The cucurbit[n]uril (CB[n]) family of macrocycles has been shown to have potential in drug delivery where they are able to provide physical and chemical stability to drugs, improve drug solubility, control drug release and mask the taste of drugs. Cisplatin is a small molecule platinum-based anticancer drug that has severe dose-limiting side-effects. Cisplatin forms a host–guest complex with cucurbit[7]uril (cisplatin@CB[7]) with the platinum atom and both chlorido ligands located inside the macrocycle, with binding stabilised by four hydrogen bonds (2.15–2.44 A ˚ ). Whilst CB[7] has no effect on the in vitro cytotoxicity of cisplatin in the human ovarian carcinoma cell line A2780 and its cisplatin-resistant sub-lines A2780/cp70 and MCP1, there is a significant effect on in vivo cytotoxicity using human tumour xenografts. Cisplatin@CB[7] is just as effective on A2780 tumours compared with free cisplatin, and in the cisplatin-resistant A2780/cp70 tumours cisplatin@CB[7] markedly slows tumour growth. The ability of cisplatin@CB[7] to overcome resistance in vivo appears to be a pharmacokinetic effect. Whilst the peak plasma level and tissue distribution are the same for cisplatin@CB[7] and free cisplatin, the total concentration of circulating cisplatin@CB[7] over a period of 24 hours is significantly higher than for free cisplatin when administered at the equivalent dose. The results provide the first example of overcoming drug resistance via a purely pharmacokinetic effect rather than drug design or better tumour targeting, and demonstrate that in vitro assays are no longer as important in screening advanced systems of drug delivery

A prospective cohort study examining medical and social factors associated with engagement in life activities following total hip replacement

Objectives: Studies show limited improvement in the frequency of engaging in life activities after joint replacement. However, there is a paucity of research that has examined factors, including other life events, which influence engagement following total hip replacement (THR). This research sought to identify factors associated with engaging in life activities following THR. Methods: A prospective cohort study was conducted with 376 people who had a THR for osteoarthritis (OA). Data were collected pre-surgery and 1 year post-surgery. The primary outcome was change in frequency in engagement in life activities (Late Life Disability Index (LLDI): higher scores indicate higher frequency of engagement (range 0e80)). Analyses included multivariable regression. Factors considered included: positive/negative life events, a new comorbidity, another joint replacement and complications post-surgery. Results: Participants' mean age was 64 years; 46% were male. 68% of participants had at least one comorbidity pre-surgery; 36% reported at least one new comorbidity after surgery. The mean change in LLDI frequency was an increase of 6.29 (+/- 8.10). 36% reported one or more positive impact life events in the year following surgery; 63% reported one or more negative life events. The number of positive life events (beta=1.24; 95% CI: 0.49, 1.99) was significantly associated with change in LLDI frequency after adjusting for age, sex, education, body mass index (BMI), comorbidities pre-surgery, number of symptomatic joints and pre-surgery pain and function, LLDI limitations and depression. Conclusions: These findings highlight the significant influence of social factors and life circumstances on engagement in life activities following THR. (C) 2017 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.Peer reviewe

Chemical engineering of adamantane by lithium functionalization: A first-principles density functional theory study

Using first-principle density functional theory, we investigated the hydrogen storage capacity of Li functionalized adamantane. We showed that if one of the acidic hydrogen atoms of adamantane is replaced by Li/Li+, the resulting complex is activated and ready to adsorb hydrogen molecules at a high gravimetric weight percent of around ~ 7.0 %. Due to polarization of hydrogen molecules under the induced electric field generated by positively charged Li/Li+, they are adsorbed on ADM.Li/Li+ complexes with an average binding energy of ~ -0.15 eV/H2, desirable for hydrogen storage applications. We also examined the possibility of the replacement of a larger number of acidic hydrogen atoms of adamantane by Li/Li+ and the possibility of aggregations of formed complexes in experiments. The stabilities of the proposed structures were investigated by calculating vibrational spectra and doing MD simulations.Comment: 8 pages, 6 figures, 2 tables, accepted for publication in Physical Review

First-principles study of hydrogen storage over Ni and Rh doped BN sheets

Absorption of hydrogen molecules on Nickel and Rhodium doped hexagonal boron nitride(BN) sheet is investigated by using the first principle method. The most stable site for the Ni atom was the on top side of nitrogen atom, while Rh atoms deservers a hollow site over the hexagonal BN sheet. The first hydrogen molecule was absorbed dissociatively over Rh atom, and molecularly on Ni doped BN sheet. Both Ni and Rh atoms are capable to absorb up to three hydrogen molecules chemically and the metal atom to BN sheet distance increases with the increase in the number of hydrogen molecules. Finally, our calculations offer explanation for the nature of bonding between the metal atom and the hydrogen molecules, which is due to the hybridization of metal d orbital with the hydrogen s orbital. These calculation results can be useful to understand the nature of interaction between the doped metal and the BN sheet, and their interaction with the hydrogen molecules

PREPARATION AND PROPERTIES OF DIAMOND-LIKE CARBON FILMS AND INTERCALATED GRAPHITE FIBERS (PLASMA DEPOSITION)

Experimental methods are outlined for the preparation of hard, semitransparent, \u27Diamond-like\u27 carbon films on oriented, polished crystal wafers of silicon and gallium arsenide as well as on potassium bromide flats, quartz plates and glass plates. Properties of the films are determined using infrared and visible absorption spectroscopy, ellipsometry, Auger, ESCA and conductance - capacitance spectroscopy. Preparation techniques include r.f. plasma decomposition of hydrocarbons (methane, ethylene, propane and propylene) and dual ion beam sputtering. In general, the films showed slight, or no traces of oxygen. The maximum optical bandgap obtained was 2.7 e.v. The optical absorption studies indicate a downward trend for the optical bandgap with increasing negative d.c. bias on the substrates. The annealed samples indicate a gradual narrowing of optical bandgap with increasing anneal temperatures, as well as a loss in their diamond-like quality. Infrared spectra showed the presence of hydrogen in these films. Ellipsometry studies indicated a range of refractive index of 1.8-2.2 for wavelengths in the visible region of the spectrum. The low frequency dielectric constant was found to be 3.4. In the other part of the work, highly graphitized pitch based carbon fibers were intercalated with copper chloride, antimony pentachloride, iodine chloride, nitric acid and bromine. These were reacted either singly or sequentially. The electrical resistivities were measured before and after intercalation, in air, and tests for air and thermal stability were done. A quantitative measurement of mobility was made using the Shubnikov-deHaas effect. The procedures adopted were successful in reducing the resistivity of the intercalated fibers to as low as 15.7 micro ohm-cm. For the first time negative magnetoresistance, and the Shubnikov-deHaas effect were found to be present simultaneously in intercalated fibers. The intercalated fibers exhibited a scattering time a factor of 5 smaller than typically found in Highly Oriented Pyrolytic Graphite

Theoretical Investigation of the Binding of Nucleobases to Cucurbiturils by Dispersion Corrected DFT Approaches

The encapsulation of nucleobases inside CB7 has gained prominence due to its use as anticancer and antiviral drugs. With this respect, the nonconvalent interactions existing in the nucleobases encapsulated inside the CB7 cavity have been analyzed employing the dispersion corrected density functional theory. The CB<i>n</i> cavity has the ability to encapsulate two guest nucleobases molecules when they are aligned in parallel configuration. The computed association energy using the two- and three-body correction method computed at B3LYP-D3 level is close to the experimental estimate. The use of dispersion corrected DFs is essential to identify the correct binding energies. The solvation energy plays a vital role in the estimation of association energy. QTAIM analysis shows that the Laplacian of the charge density (∇²ρ) is negative and the presence of covalent interaction between the guest and host molecule. The NCI-RDG isosurface shows the presence of noncovalent intermolecular interactions such as van der Waals and hydrogen bonding. The existence of “splattering” of charges in guanine@CB7 molecule is responsible for its higher stability. From the AIM, NCI-RDG, and EDA results, we conclude that noncovalent and electrostatic interaction with partial covalent character exists in the intermolecular bonding between the host and the guest nucleobases. The ramification of such intermolecular bonds is reflected in the ¹H NMR and ¹³NMR spectra