N-doped carbon nanomaterials have received increased attention from electrochemists due to their applications in the metal-free electrocatalysis of important redox processes. In this work, a series of graphitized undoped and nitrogen-doped carbon electrodes prepared by thermal annealing of sputtered amorphous carbon films were prepared and characterized using a combination of X-ray photoelectron spectroscopy and Raman spectroscopy. Adsorption of the surface-sensitive redox probe dopamine at each electrode surface was then studied using cyclic voltammetry and the results correlated to the physico-chemical characterisation. Results indicate that dopamine adsorption is influenced by both the nitrogen surface chemistry and the degree of graphitization of the carbon scaffold. N-doping, with predominantly graphitic-N sites, was found to increase adsorption of dopamine more than 6 fold on carbon surfaces when the introduction of N atoms did not result in substantial alterations to the sp 2 network. However, when an identical type and level of N-doping is accompanied by a significant increase in disorder in the carbon scaffold, adsorption is limited to levels comparable to those of nitrogen-free carbon. Density functional theory studies of dopamine adsorption on graphene and N-doped graphene model surfaces showed that dopamine interacts via π-stacking at the graphene surface. The Gibbs free energy of adsorption on N-doped graphenes were estimated at 12-13 kcal mol-1 , and found to be approximately twice that of undoped graphenes. Results suggest that chemical changes resulting from N-doping enhance adsorption; however, high coverage values depend on the availability of sites for π-stacking. Therefore, the structurally disruptive effects of N-incorporation can significantly depress the dopamine response by limiting the availability of basal sites, ultimately dominating the overall electrochemical response of the carbon electrode.

Abnormal levels of the neurotransmitter dopamine have been linked to a variety of neurochemical disorders including depression and Parkinson's disease. Dopamine concentrations are often quantified electrochemically using biosensors prepared from carbon electrode materials such as carbon paste or glassy carbon. The charge transfer kinetics of dopamine are highly sensitive to carbon surface termination, including the presence of certain oxygen functional groups and adsorption sites. However, the nature of the binding sites and the effects of surface oxidation on the voltammetry of dopamine are both poorly understood.In this work the electrochemical response of dopamine at glassy carbon model surfaces was investigated to understand the effects of altering both the carbon nanostructure and oxygen surface chemistry on dopamine charge transfer kinetics and adsorption. Glassy carbon electrodes with low oxygen content and a high degree of surface graphitisation were prepared via thermal annealing at 900 o C, whilst highly oxidised glassy carbon electrodes were obtained through electrochemical anodisation at 1.8 V vs Ag/AgCl. The carbon surface structure and composition in each case was studied via X-Ray Photoelectron Spectroscopy.Voltammetry in solutions of dopamine at acidic pH confirmed that both annealing and anodisation treatments result in carbon surfaces with rapid charge transfer kinetics. However, dopamine adsorption occurs only at the low-oxygen, highly-graphitized carbon surface.Density functional theory studies on graphene model surfaces reveal that this behaviour is due to non-covalent interactions between the π-system of dopamine and the basal sites in the annealed surface. Simulations also show that the introduction of oxygen moieties disrupt these interactions and inhibit dopamine adsorption, in agreement with experiments. The results clarify the role of oxygen moieties and basal plane sites in facilitating both the adsorption of and charge transfer to DA at carbon electrodes.

C-O bond formation in reactions of olefins with oxygen is a long standing challenge in chemistry for which the very complicated-sometimes controversial-mechanistic panorama slows down the design of catalysts for oxygenations. In this regard, the mechanistic details of the oxidation of the complex [Rh(cod)(Ph N )] (1) (cod=1,5-cyclooctadiene) with oxygen to the unique 2-rhodaoxetane compound [{Rh(OC H )(Ph N )} ] (2) has been investigated by DFT calculations. The results of this study provide evidences for a novel bimetallic mechanism in which two rhodium atoms redistribute the four electrons involved in the cleavage of the O=O bond. Furthermore, both oxygen atoms are used to create two new C-O bonds in a controlled fashion with 100 % atom economy. The key intermediates that we have found in this process are a mononuclear open-shell triplet superoxo compound, an open-shell singlet "μ-(peroxo)" derivative, and a closed-shell singlet "bis(μ-oxo)" complex. Some of the findings are used to predict the reactions of Rh complexes with oxygen, exemplified by that of the complex [Rh(cod)(OnapyMe )] (3). Starting from 3, [{Rh(OC H )(OnapyMe )} ] (4) has been prepared and characterized, which represents the second example of a 2-rhodaoxetane compound coming from an oxygenation reaction with oxygen.