Part 1: Carbon nanotube (CNT) wires are a promising material for electric applications. This study focuses on the interaction between CNTs and organic solvents. A scheme for finding optimal adsorption sites without any assumptions is implemented based on Monte Carlo methods and molecular dynamics. Systems with several molecules can be produced to model different levels of coverage. Density functional theory is used to calculate the binding energy and charge transfer. 6 different organic solvents are studied: 3 non-polar (methane, benzene, cyclohexane) and 3 polar (dichloromethane, isopropanol, and pyridine), as well as iodine for reference. Iodine and dichloromethane act as electron donors, while the hydrocarbons and pyridine have small charge transfer. At higher concentrations iodine forms polyiodide chains that bind more strongly with CNTs and become electron acceptors. This understanding can help studies in which CNT wires are doped through solutions containing an organic solvent. Part 2: In the past years hundreds of new 2D materials have been discovered or predicted. The rise of materials databases detailing the electronic structure of thousands of predicted 2D materials, and high-throughput calculations and filtering can help select materials for specific applications. This work takes advantage of this to study 2D van der Waals heterostructures (VDWH) for water splitting. Results show which transition metal dichalcogenides (TMDs), MXenes and MXY Janus layers are the most promising candidates for photocatalytic water splitting. Solar power to electron conversion efficiencies of up to 29% are calculated for VDWH MXene/TMD and MXY Janus/TMD heterostructures. It is also discovered that the ideal heterostructure for light absorption consists of two 2D semiconductor materials with similar conduction band maxima but different valence band maxima.