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The long-term future of information storage requires the use of sustainable nanomaterials in architectures operating at high frequencies. Interfaces can play a key role in this pursuit via emergent functionalities that break out from conventional operation methods. Here, spin-filtering effects and photocurrents are combined at metal-molecular-oxide junctions in a hybrid magneto-capacitive memory. Light exposure of metal-fullerene-metal oxide devices results in spin-polarized charge trapping and the formation of a magnetic interface. Because the magnetism is generated by a photocurrent, the writing time is determined by exciton formation and splitting, electron hopping, and spin-dependent trapping. Transient absorption spectroscopy measurements show changes in the electronic states as a function of the magnetic history of the device within picoseconds of the optical pumping. The stored information is read using time-resolved scanning magneto optic Kerr effect measurements during microwave irradiation. The emergence of a magnetic interface in the picosecond timescale opens new paths of research to design hybrid magneto-optic structures operating at high frequencies for sensing, computing, and information storage.

Disentangling the origin of the optical activity of non-aromatic proteins is challenging due to their size and thus their high computational requisites. Here we show, in a much smaller model system, that the single amino acid glutamine undergoes a chemical transformation leading to an unreported glutamine-like structure which has a similar broad absorption spectrum reported previously for non-aromatic proteins. We further show computationally that the optical activity of the glutamine-like structure is directly coupled to short-hydrogen bonds, but also displays charge and vibrational fluctuations, the latter of which are also present in less optically active structures such as in L-glutamine. Since experimentally the glutamine-like structure is the brightest structure, we conclude that short-hydrogen bonds are the ones responsible for the large Stokes shift observed in optically active non-aromatic proteins.

Determination of the atomic structure of inorganic single-walled nanotubes with complex stoichiometry remains elusive due to the too many atomic coordinates to be fitted with respect to X-ray diffractograms inherently exhibiting rather broad features. Here we introduce a methodology to reduce the number of fitted variables and enable resolution of the atomic structure for inorganic nanotubes with complex stoichiometry. We apply it to recently synthesized methylated aluminosilicate and aluminogermanate imogolite nanotubes of nominal composition (OH)3Al2O3Si(Ge)CH3. Fitting of X-ray scattering diagrams, supported by Density Functional Theory simulations, reveals an unexpected rolling mode for these systems. The transferability of the approach opens up for improved understanding of structure–property relationships of inorganic nanotubes to the benefit of fundamental and applicative research in these systems., Structural determination of inorganic nanotubes has lagged far behind that of their carbon-based counterparts. Here, the authors present a transferable methodology, combining wide angle X-ray scattering and computation, to quantitatively resolve the atomic structure of inorganic nanotubes with complex stoichiometry.

Linear-scaling density functional theory simulation of methylated imogolite nanotubes (NTs) elucidates the interplay between wall-polarization, bands separation, charge-transfer excitation, and tunable electrostatics inside and outside the NT-cavity. The results suggest that integration of polarization-enhanced selective photocatalysis and chemical separation into one overall dipole-free material should be possible. Strategies are proposed to increase the NT polarization for maximally enhanced electron–hole separation.

Prompted by growing environmental and energy concerns, increasing research is dedicated to\ud the development of technologies capable of sustainably converting sunlight into commercially\ud viable forms of energy such as chemical fuels. Crucial to this energy conversion is the\ud availability of materials, photo-catalysts (PCs), capable of promoting redox chemistry\ud following absorption of light. Since the macroscopic efficiency of PCs is governed by the\ud atomistic details of the PCs interfaces with media and reactants, increasingly large efforts have\ud been dedicated to the characterization and understanding of these interfaces, also by mean of\ud first principle simulations.\ud In this context, we present a theoretical investigation of a rapidly growing class of onedimensional\ud nanomaterial, Imogolite nanotubes (Imo NTs), whose potential for photocatalysis\ud has so far been overlooked.\ud The first Chapter of the Thesis provides an overview of the current state of the art for research\ud in PCs, and the theoretical framework needed for atomic-scale understanding and informed\ud development of PCs. The computational underpinning of the research carried out for this\ud Thesis, namely Density Functional Theory (DFT) and its linear-scaling (LS) implementation\ud in the ONETEP program is presented and discussed in Chapter 2.\ud Ahead of presentation of the results of my original research, a small literature review on Imo\ud NTs is provided in Chapter 3. Chapter 4 illustrates the applicability of LS-DFT to Imo NTs\ud and, by mean of detailed benchmarking, sets best practice for simulations of these systems.\ud The potential of Imo NTs as (co-)PCs is explored in Chapter 5, where an extensive study of\ud the structure, wall-polarization, absolute band-alignment, band-separation, and optical\ud properties of several Imo NTs is presented and discussed. The simulations suggest possible\ud profitable use of Imo NTs for both photo-reduction and hole-scavenging purposes. The\ud occurrence of (near-)UV charge-transfer excitations is also observed, which may be effective\ud for electron-hole separation and enhanced photo-catalytic performances. Finally, the effects of the NTs’ wall-polarization on the absolute alignment of electron and hole acceptor states of\ud interacting water (H2O) molecules are quantified and discussed.\ud Chapter 6 reports an extensive study of defects in Imo NTs. Electronic and optical\ud characterization of the defective Imo NTs suggests energetically favourable separation of\ud photo-generated electrons and holes via relaxation to different defect-sites, with the ensuing\ud possibility of defect-centred photo-redox activity in defective Imo NTs.\ud The Thesis ends with the investigation of termination effects in Imo NTs. Chapter 7 presents\ud results on the structural, electronic and optical characterization of representative finite Imo\ud NTs models capable of simultaneous description of the NT-ends and bulk-like NT-core. The\ud simulations reveal the presence of longitudinal band-bending and of NT core-end bandsseparations,\ud which in turn suggests advantageous relaxation mechanisms for photo-generated\ud e*-h pairs along the NT axis, to the potential benefit of Imo NTs photo-catalytic reactivity.

The high experimental control over inorganic Imogolite-like open-ended nanotubes (Imo-NTs) composition, dimensions and monodispersity together with the potentially huge range of tuneable properties that can be introduced by chemical functionalisation and doping make Imo-NTs appealing substrates for nanotechnology, as artificial ion-channels and in chemical separation. Investigation of Imo-NTs electronic and spectroscopic properties has so far been hampered by the large size of the systems repeat unit (+300 atoms), which pose severe challenges and accuracy-viability compromises for standard plane-wave (fixed atomic basis set) density functional theory (DFT) simulations. These challenges can, however, be met by linear-scaling DFT (LS-DFT) approaches based on in situ optimisation of minimal basis sets. Here, we illustrate the applicability of LS-DFT to Imo-NTs by providing structural and electronic characterisation of periodic and finite models of aluminosilicate (AlSi) and methylated-AlSi Imo-NTs. It is shown that adoption of moderate kinetic energy cutoff (1000 eV) and basis set truncation radius (8 Bohr) leads to optimal accuracy-viability compromised for geometrical optimisation of Imo-NTs. These results should be useful for future LS-DFT investigation of Imo-NTs and other AlSi-based functional materials.\ud