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Abstract Excitons play an essential role in the optical response of two-dimensional materials. These are bound states showing up in the band gaps of many-body systems and are conceived as quasiparticles formed by an electron and a hole. By performing real-time simulations in hBN, we show that an ultrashort (few-fs) UV pulse can produce a coherent superposition of excitonic states that induces an oscillatory motion of electrons and holes between different valleys in reciprocal space, leading to a sizeable exciton migration in real space. We also show that an ultrafast spectroscopy scheme based on the absorption of an attosecond pulse in combination with the UV pulse can be used to read out the laser-induced coherences, hence to extract the characteristic time for exciton migration. This work opens the door towards ultrafast electronics and valleytronics adding time as a control knob and exploiting electron coherence at the early times of excitation.

Recirculation of process water (PW) from hydrothermal carbonization (HTC) has revealed as an effective strategy for the residual aqueous phase valorization in order to make the process energetically more efficient while reducing its environmental footprint. The effects of temperature, solid load and consecutive conversion phases on PW recirculation were assessed by using Ferula Communis plant residues as feedstock in HTC experiments. Recirculation of solvent promoted strong synergistic interactions between biomass and PW aimed at increasing hydrochar mass recovery. Hydrochar yield increased by 4-12 wt% on a dry basis (d.b.) according to reaction conditions. Biomass degradation was catalyzed by the reactive intermediates dissolved in the PW. The energy balance results showed that the energy recovery almost doubled by recycling PW when compared to the experiments carried out using only deionized water as HTC solvent.