Controlling charge transport through molecules is challenging because it requires engineering of the energy of molecular orbitals involved in the transport process. While side groups are central to maintaining solubility in many molecular materials, their role in modulating charge transport through single-molecule junctions has received less attention. Here, using two break-junction techniques and computational modeling, we investigate systematically the effect of electron-donating and -withdrawing side groups on the charge transport through single molecules. By characterizing the conductance and thermopower, we demonstrate that side groups can be used to manipulate energy levels of the transport orbitals. Furthermore, we develop a novel statistical approach to model quantum transport through molecular junctions. The proposed method does not treat the electrodes' chemical potential as a free parameter and leads to more robust prediction of electrical conductance as confirmed by our experiment. The new method is generic and can be used to predict the conductance of molecules.

A way to obtain graphene-based materials on a large-scale level is by means of chemical methods for the oxidation of graphite to obtain graphene oxide (GO), in combination with thermal, laser, chemical and electrochemical reduction methods to produce reduced graphene oxide (rGO). Among these methods, thermal and laser-based reduction processes are attractive, due to their fast and low-cost characteristics. In this study, first a modified Hummer’s method was applied to obtain graphite oxide (GrO)/graphene oxide. Subsequently, an electrical furnace, a fusion instrument, a tubular reactor, a heating plate, and a microwave oven were used for the thermal reduction, and UV and CO₂ lasers were used for the photothermal and/or photochemical reduction. The chemical and structural characterizations of the fabricated rGO samples were performed by Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), scanning electron microscope (SEM) and Raman spectroscopy measurements. The analysis and comparison of the results revealed that the strongest feature of the thermal reduction methods is the production of high specific surface area, fundamental for volumetric energy applications such as hydrogen storage, whereas in the case of the laser reduction methods, a highly localized reduction is achieved, ideal for microsupercapacitors in flexible electronics.

We present two approaches for fabricating shadow masks for the evaporation of electrodes onto nanomaterials. In the first one, we combine the use of a commercial fiber laser engraving system with readily available aluminum foil. This method is suitable for fabricating shadow masks with line widths of 50 µm and minimum feature separation of 20 µm, and using it to create masks with complex patterns is very straightforward. In the second approach, we use a commercially available vinyl cutting machine to pattern a vinyl stencil mask, and we use a glass fiber to define the separation between the electrodes. With this approach, we achieve well-defined electrodes separated by 15 µm, but this technique is less versatile in creating complex masks as compared with the laser-based one. We demonstrate the potential of these techniques by fabricating field-effect transistor devices based on MoS₂. Our approach is a cost-effective and easily accessible method for fabricating shadow masks with high resolution and accuracy, making it accessible to a wider range of laboratories.

Thermoelectric materials have garnered significant interest for their potential to efficiently convert waste heat into electrical energy at room temperature without moving parts or harmful emissions. This study investigated the impact of the HOMO-LUMO (H-L) gap on the thermoelectric properties of three distinct classes of organic compounds: conjugated aromatics (isoindigos (IIGs)), quinoidal molecules (benzodipyrrolidones (BDPs)), and donor-acceptor systems (bis(pyrrol-2-yl)squaraines (BPSs)). These compounds were chosen for their structural simplicity and linear π-conjugated conductance paths, which promote high electrical conductance and minimize complications from quantum interference. Single-molecule thermoelectric measurements revealed that despite their low H-L gaps, the Seebeck coefficients of these compounds remain low. The alignment of the frontier orbitals relative to the Fermi energy was found to play a crucial role in determining the Seebeck coefficients, as exemplified by the BDP compounds. Theoretical calculations support these findings and suggest that anchor group selection could further enhance the thermoelectric behavior of these types of molecules.

This work demonstrates the fabrication and characterization of single-layer MoS₂ field-effect transistors using biodegradable albumen (chicken eggwhite) as gate dielectric. By introducing albumen as an insulator for MoS₂ transistors high carrier mobilities (up to ~90 cm² V⁻¹ s⁻¹) are observed, which is remarkably superior to that obtained with commonly used SiO₂ dielectric which we attribute to ionic gating due to the formation of an electric double layer in the albumen MoS₂ interface. In addition, the investigated devices are characterized upon illumination, observing responsivities of 4.5 AW⁻¹ (operated in photogating regime) and rise times as low as 52 ms (operated in photoconductivity regime). The presented study reveals the combination of albumen with van der Waals materials for prospective biodegradable and biocompatible optoelectronic device applications. Furthermore, the demonstrated universal fabrication process can be easily adopted to fabricate albumen-based devices with any other van der Waals material.

Two-dimensional semiconducting materials such as MoS₂ have gained significant attention for potential applications in electronic components due to their reduced dimensionality and exceptional electrical and optoelectronic properties. However, when reporting the performance of such 2D-based devices, one needs to consider the effect of the environment in which the characterization is carried out. Air exposure has a non-negligible impact on the electronic performance and vacuum thermal annealing is an established method to decrease the effects of adsorbates. Nevertheless, when measurements are performed in ambient conditions these effects arise again. In this work, we study the changes in the electrical and optoelectronic properties of single-layer MoS₂-based devices at air exposure after thermal annealing treatment. Measurements are carried out in an in-situ vacuum thermal annealing system, enabling the recording of electrical performance degradation over time. Moreover, this work shows how hexagonal boron nitride (hBN) capping improves device performance, both in vacuum and after venting, as well as stability, by decreasing the degradation speed by around six times. The results suggest that vacuum thermal annealing and hBN capping are methods to mitigate the effects of air environment on these devices.