Redox properties of undoped 5 nm diamond nanoparticles

This paper demonstrates the promoting effects of 5 nm undoped detonation diamond nanoparticles on redox reactions in solution. An enhancement in faradaic current for the redox couples Ru(NH(3))(6)(3+/2+) and Fe(CN)(6)(4-/3-) was observed for a gold electrode modified with a drop-coated layer of nanodiamond (ND), in comparison to the bare gold electrode. The ND layer was also found to promote oxygen reduction. Surface modification of the ND powders by heating in air or in a hydrogen flow resulted in oxygenated and hydrogenated forms of the ND, respectively. Oxygenated ND was found to exhibit the greatest electrochemical activity and hydrogenated ND the least. Differential pulse voltammetry of electrode-immobilised ND layers in the absence of solution redox species revealed oxidation and reduction peaks that could be attributed to direct electron transfer (ET) reactions of the ND particles themselves. It is hypothesised that ND consists of an insulating sp(3) diamond core with a surface that has significant delocalised pi character due to unsatisfied surface atoms and C[double bond, length as m-dash]O bond formation. At the nanoscale surface properties of the particles dominate over those of the bulk, allowing ET to occur between these essentially insulating particles and a redox species in solution or an underlying electrode. We speculate that reversible reduction of the ND may occur via electron injection into available surface states at well-defined reduction potentials and allow the ND particles to act as a source and sink of electrons for the promotion of solution redox reactions.     

Investigation on Optical and Biological Properties of 2-(4-Dimethylaminophenyl)benzothiazole Based Cycloplatinated Complexes

The optical and biological properties of 2-(4-dimethylaminophenyl)benzothiazole cycloplatinated complexes featuring bioactive ligands ([{Pt(Me₂N-pbt)(C₆F₅)}L] [L=Me₂N-pbtH 1 , p-dpbH (4-(diphenylphosphino)benzoic acid) 2 , o-dpbH (2-(diphenylphosphino)benzoic acid) 3 ), [Pt(Me₂N-pbt)(o-dpb)] 4 , [{Pt(Me₂N-pbt)(C₆F₅)}₂(μ-PR_nP)] [PR₄P=O(CH₂CH₂OC(O)C₆H₄PPh₂)₂ 5 , PR₁₂P=O{(CH₂CH₂O)₃C(O)C₆H₄PPh₂}₂ 6 ] are presented. Complexes 1 – 6 display ¹ILCT and metal-perturbed ³ILCT dual emissions. The ratio between both bands is excitation dependent, accomplishing warm-white emissions for 2 , 5 and 6 . The phosphorescent emission is lost in aerated solutions owing to photoinduced electron transfer to ³O₂ and the formation of ¹O₂, as confirmed in complexes 2 and 4 . They also exhibit photoinduced phosphorescence enhancement in non-degassed DMSO due to local oxidation of DMSO by sensitized ¹O₂, which causes a local degassing. Me₂N-pbtH and the complexes specifically accumulate in the Golgi apparatus, although only 2 , 3 and 6 were active against A549 and HeLa cancer cell lines, 6 being highly selective in respect to nontumoral cells. The potential photodynamic property of these complexes was demonstrated with complex 4 .     

Human frataxin: iron and ferrochelatase binding surface

The coordinated iron structure and ferrochelatase binding surface of human frataxin have been characterized to provide insight into the protein's ability to serve as the iron chaperone during heme biosynthesis.     

Structural Distortion of the Epoxy Groups in Norbornanes: A Rotational Study of exo‐2,3‐Epoxynorbornane

Exo‐2,3‐epoxynorbornane is studied in the gas phase by pulsed jet Fourier transform microwave spectroscopy in the 4–18 GHz region. Six isotopologues were observed and characterized in their natural abundance. The experimental substitution and effective structures were obtained. Comparison with the structure of norbornane shows significant differences in several bond lengths and valence angles upon introduction of the epoxy group. All the work is supported by quantum chemical calculations.     

Impact of Zeolite Framework Composition and Flexibility on Methanol-To-Olefins Selectivity: Confinement or Diffusion?

The methanol-to-olefins reaction catalyzed by small-pore cage-based acid zeolites and zeotypes produces a mixture of short chain olefins, whose selectivity to ethene, propene and butene varies with the cavity architecture and with the framework composition. The product distribution of aluminosilicates and silicoaluminophosphates with the CHA and AEI structures (H-SSZ-13, H-SAPO-34, H-SSZ-39 and H-SAPO-18) has been experimentally determined, and the impact of acidity and framework flexibility on the stability of the key cationic intermediates involved in the mechanism and on the diffusion of the olefin products through the 8r windows of the catalysts has been evaluated by means of periodic DFT calculations and ab initio molecular dynamics simulations. The preferential stabilization by confinement of fully methylated hydrocarbon pool intermediates favoring the paring pathway is the main factor controlling the final olefin product distribution.     

Application of the solid state NMR to the study of the alcohol/alkane mixtures adsorption onto graphite

The mixing of molecules adsorbed from solution to different interfaces has both industrial and academic relevance and the mixing behaviour at the interface is a key to understanding for example, that the surface tension of a mixture of two surfactants is lower than either of the two pure materials and many other effects. In this paper, we report, for the first time, the application of Solid State NMR to the study of alkane/alcohol mixtures, in a range of relative size ratio between 0 and 0.35, adsorbed onto graphite at high, multilayer coverage. Moreover, this paper evaluated, for the first time, the utility of the combined used of 1H and 2H NMR for: (i) determining the surface composition and (ii) making a theoretical approach to the sorption isotherm. A variety of preferential adsorption behaviour is reported. Preferential adsorption of the longer molecule (decane vs. heptanol) from a mixture has been observed. However, if both components are of similar length, the alcohol is preferentially adsorbed (heptanol vs. octane and octanol vs. octane). Finally, a linear relation between the relative size ratio and the amount of alcohol at monolayer coverage is observed.     

Metal-free highly luminescent silica nanoparticles

Stable, cost-effective, brightly luminescent, and metal-free organosilica nanoparticles (NPs) were prepared using the St?ber method without any thermal treatment above 318 K. The white-light photoluminescence results from a convolution of the emission originated in the NH(2) groups of the organosilane and oxygen defects in the silica network. The time-resolved emission spectra are red-shifted, relative to those acquired in the steady-state regime, pointing out that the NPs emission is governed by donor-acceptor (D-A) recombination mechanisms. Moreover, the increase of the corresponding lifetime values with the monitored wavelength further supports that the emission is governed by a recombination mechanism typical of a D-A pair attributed to an exceptionally broad inhomogeneous distribution of the emitting centers peculiar to silica-based NPs. These NPs exhibit the highest emission quantum yield value (0.15 ± 0.02) reported so far for organosilica biolabels without activator metals. Moreover, the emission spectra and the quantum yield values are quite stable over time showing no significant aging effects after exposure to the ambient environment for more than 1 year, stressing the potential of these NPs as metal-free biolabels.     

X-Ray Natural Circular Dichroism in Langasite Crystal at the Ga and La Edges

X-ray natural circular dichroism (XNCD) and its structural nature have been investigated in a langasite (La₃Ga₅SiO₁₄) crystal at an incident radiation energy close to the Ga K-absorption edge and the La L_2,3-absorption edges. An XNCD signal was observed mainly beyond the absorption edge, which confirmed the existence of delocalized mixed p–d electronic states in Ga and d–f and d–p electronic states in La. Calculations with application of the multiple scattering method have made it possible to separate the contributions from three crystallographically nonequivalent Ga sites to the absorption spectrum and the XNCD signal and explain adequately the largest contribution of the Ga atom occupying the 1a site to the XNCD signal.     

Biphasic catalysis with RuCl2(DMSO)(TPPMS)3

A mononuclear RuCl₂(DMSO)(TPPMS)₃ complex (1) (TPPMS = triphenylphosphine monosulfonate) has been synthesized. Spectroscopic analysis by i.r., u.v.–vis., ¹H-, ¹³C-, ³¹P-n.m.r., cyclic voltammetry, m.s. analysis and MO calculations were in agreement with a possible octahedral structure. Biphasic (H₂O/PhMe) catalytic studies have shown good olefin hydrogenation activity by the complex at moderate temperature and pressure.