Optoelectronic devices typically require low-resistance Ohmic contacts between the optical active layers and metal electrodes. Failure to make such a contact often results in a Schottky barrier which inhibits charge extraction and, in turn, reduces device performance. Here, we introduce a universal solution processable metal-oxide/organic interfacial bilayer which forms a near-perfect ohmic contact between both organic and inorganic semiconductors and metals. This bilayer comprises a Nb-doped TiO2 metal oxide with enhanced electron mobility and reduced trap density compared to pristine TiO2, in combination with a metal-chelating organic molecule to make an intimate electrical contact with silver metallic electrodes. Using this universal interfacial bilayer, we demonstrate substantial efficiency improvements in organic solar cells (from 9.3% to 12.6% PCE), light emitting diodes (from 0.6 to 2.2 Cd W-1) and transistors (from 19.7 to 13.9 V threshold voltage). In particular, a boost in efficiency for perovskite solar cells (from 18.7% up to 20.7% PCE) with up to 83% fill factor is achieved with no-operational lifetime loss for at least 1000 hours under continuous, full-spectrum illumination.

The peculiar magnetic properties of rare earth nitrides (RENs) make them suitable for a wide range of applications. Here, we report on a density functional theory (DFT) study of an interesting member of the family, two-dimensional (2D) NdN film, using the generalized gradient approximation (GGA), including the Hubbard (U) parameter. We consider different film thicknesses, taking into account the effects of N vacancies (VN) and dopants (C and O). Formation energy values show that, even though N vacancy is the predominant defect, C and O dopants are also probable impurities in these films. Individual Nd and N magnetic moments oscillate in the presence of VN and dopants owing to the induced lattice distortions. The density of states calculations show that the 2D NdN film has a semi-metallic nature, while the f orbitals are separated into fully filled and empty bands. A magnetic anisotropy energy of ∼50 μeV is obtained, and the easy axis aligns along the film orientation as the film thickness increases, revealing that such films are ideal candidates for spintronic applications.

We report the synthesis of the first stable, solution-processable and photocrosslinkable hybrid organic/inorganic titanium dioxide nanorods as 'hairy rods' coated with phosphonate ligands with photoreactive coumarin groups located in a terminal position. The relationships between the chemical structure of the diethyl-ω-[(7-oxycoumaryl)-n-alkyl]phosphonate ligands on the ligand exchange rate (LER) and the solubility of the resultant ligand-stabilized titanium dioxide nanorods in organic solvents are elucidated. These TiO2 nanorods, with an organic ligand coating, are short enough (aspect ratio = 5-8) to be dissolved in chlorobenzene at high concentrations, but long enough to form lyotropic nematic liquid crystals. These colloidal solutions are used to deposit a thin, uniform layer of hybrid organic/inorganic TiO2 nanorods with their long axes in the plane of a flat, smooth substrate through a self-organization process. Standard photolithographic patterning creates an insoluble dielectric layer of the desired thickness, smoothness and uniformity and with a dielectric constant of sufficient magnitude, k = 8, suitable for the fabrication of multilayer, plastic electronic devices using solution-based fabrication techniques, such as ink-jet printing, used in roll-to-roll manufacturing.

Bilayers of two-dimensional (2D) transition metal chalcogenides (TMDs) such as WSe2 have been attracting increasing attention owing to the intriguing properties involved in the different stacking configurations. The growth of bilayer WSe2 by chemical vapor deposition (CVD) has been facilely obtained without proper control of the stacking configuration. Herein, we report the controlled growth of bilayer WSe2 crystals as large as 30 μm on c-plane sapphire by the CVD method. Combining second harmonic generation (SHG), low-frequency Raman and scanning transmission electron microscopy (STEM), we elucidate the as-grown bilayer WSe2 with a 2H stacking configuration. Atomic force microscope (AFM) measurements reveal that the prominent atomic steps provide the energetically favorable templates to guide the upper layer nuclei formation, resembling the “graphoepitaxial effect” and facilitating the second WSe2 layer following the layer-by-layer growth mode to complete the bilayer growth. Field-effect charge transport measurement performed on bilayer WSe2 yields a hole mobility of up to 40 cm2 V−1 s−1, more than 3× higher than the value achieved in monolayer WSe2-based devices. Our study provides key insights into the growth mechanism of bilayer WSe2 crystals on sapphire and unlocks the opportunity for potential bilayer and multilayer TMD electronic applications.

Two novel dithieno[3,2-b:2,3-d]pyrrol fused electron acceptors (FREAs) with branched alkyl side-chains have been developed. With 2-ethylhexyl and 2-butyloctyl introduced on the N-position of the pyrrol unit, the sidechain engineered acceptors (INPIC-EH and INPIC-BO) were evaluated for organic solar cells (OSCs) by comparison with our reference INPIC-4F bearing a linear octyl chain. The optoelectronic properties of the FREAs and their bulk-heterojunction (BHJ) with a PBDB-T donor for OSCs are systematically studied. All FREAs exhibit similar absorption spectra and energy levels. Notably, the charge dissociation process, charge mobility, and morphology of the BHJ films make a distinct difference. Consequently, the OSCs constructed with INPIC-EH and INPIC-BO delivered a power conversion efficiency (PCE) of 11.9% and 11.2%, lower than that of INPIC-4F devices (13.1%). The lower short-circuit current density (JSC) and fill factor (FF) of INPIC-EH and INPIC-OB based devices are attributed to unfavorable morphology of the active layers and more bimolecular recombination and unbalanced charge transport. Our investigation demonstrates that side-chain engineering on FREAs has a great impact on the morphology of blends and thus the photovoltaic properties of their OSCs.

Nanocarbons continue to stimulate the scientific community while their production has also started to reach the industrial scale. With the commercialization of products that are based on materials such as carbon nanotubes (CNTs), it has become imperative to implement reliable quality control protocols for the routine analysis of their chemical composition and structure. Herein, we propose alkaline oxidation (a.k.a., fusion) as a valuable approach to disintegrate the graphitic structure of carbon nanotubes. Using the certified reference material SWCNT-1, it was shown that fusion enables the subsequent determination of elemental concentrations (Ni, Co and Mo) by a routine analytical tool such as inductively coupled plasma optical emission spectroscopy (ICP-OES). Furthermore, the fusion residues were investigated, clarifying that the process does not result in the formation of non-intentional carbon compounds (e.g., carbides or carbonates) or lattice doping (e.g., B doping or Li intercalation).

The fundamental development on the design of novel self-powered ozone sensing elements operating at room temperature based on p-type metal oxides pave the way to a new class of low cost highly promising gas sensing devices. Here, we synthesize a p-Type Cu2O nanocubes by a simple solution-based method and tested as self-power ozone sensing element, at room temperature (25°C) for a first time. High crystalline Cu2O nanocubes with 30nm size, were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM) and Transmission Electron Microscopy (TEM). Self – powered sensing elements of Cu2O nanocubes has been succesfully fabricated by deposit of Cu2O nanocubes on interdigitated electrodes (IDE’s) consisting of two connection tracls with 500digits and a gap of 5μm in order to investigate their response to ozone at room temperature. The experimental results showed that the use of nanocubes as sensing element was suitable for detecting ultra – low concentrations of O3 down to 10 ppb at room temperature with very high sensitivity (28%) and very low response/recovery time. The reversible sensing process to the relatively weak binding of O3 species by trapping sites on Cu2O facets with increased oxygen content calculated by using density functional theory calculations.

The aim of this study was the design of a 3D scaffold composed of poly(vinyl) alcohol (PVA) for cardiac tissue engineering (CTE) applications. The PVA scaffold was fabricated using a combination of gas foaming and freeze-drying processes that did not need any cross-linking agents. We obtained a biocompatible porous matrix with excellent mechanical properties. We measured the stress–strain curves of the PVA scaffolds and we showed that the elastic behavior is similar to that of the extracellular matrix of muscles. The SEM observations revealed that the scaffolds possess micro pores having diameters ranging from 10 μm to 370 μm that fit to the dimensions of the cells. A further purpose of this study was to test scaffolds ability to support human induced pluripotent stem cells growth and differentiation into cardiomyocytes. As the proliferation tests show, the number of live stem cells on the scaffold after 12 days was increased with respect to the initial number of cells, revealing the cytocompatibility of the substrate. In addition, the differentiated cells on the PVA scaffolds expressed anti-troponin T, a marker specific of the cardiac sarcomere. We demonstrated the ability of the cardiomyocytes to pulse within the scaffolds. In conclusion, the developed scaffold show the potential to be used as a biomaterial for CTE applications.

Nanoscaled spinel-structured ferrites bear promise as next-generation contrast agents for magnetic resonance imaging. However, the small size of the particles commonly leads to colloidal instability under physiological conditions. To circumvent this problem, supports onto which the dispersed nanoparticles can be anchored have been proposed. Amongst these, flakes of graphene have shown interesting performance but it remains unknown if and how their surface texture and chemistry affect the magnetic properties and relaxation time (T2) of the ferrite nanoparticles. Here, it is shown that the type of graphene oxide (GO) precursor, used to make composites of cobalt ferrite (CoFe2O4) and reduced GO, influences greatly not just the T2 but also the average size, dispersion and magnetic behaviour of the grafted nanoparticles. Accordingly, and without compromising biocompatibility, a judicious choice of the initial GO precursor can result in the doubling of the proton relaxivity rate in this system.

CoP is considered as an efficient electrocatalyst for the hydrogen evolution reaction (HER) in acidic electrolytes but its performance in alkaline solutions is generally poor because of its slow reaction kinetics, which further limits its application in overall water splitting. Herein, we demonstrate a strategy to greatly accelerate its HER and OER kinetics in alkaline solutions through Mn incorporation. Ternary MnxCo1−xP microcubes with a tunable Mn/Co ratio strongly anchored on rGO were synthesized using Prussian blue analogues as precursors. The synergy between the high activity of MnxCo1−xP microcubes and the good conductivity of rGO leads to the superior performance of the hybrid toward water splitting in 1 M KOH. The optimized Mn0.6Co0.4P–rGO electrocatalyst shows high activity and stability towards both the HER and OER with low overpotentials of 54 and 250 mV at 10 mA cm−2, respectively. Furthermore, the water electrolyzer using Mn0.6Co0.4P–rGO as both the cathode and anode only requires a cell voltage as low as 1.55 V to reach a current density of 10 mA cm−2, making Mn0.6Co0.4P–rGO a competitive and cost-effective electrocatalyst for water splitting.