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This is the peer reviewed version of the following article: Marin, R., Lifante, J., Besteiro, L. V., Wang, Z., Govorov, A. O., Rivero, F., . & Jaque, D. (2020). Plasmonic Copper Sulfide Nanoparticles Enable Dark Contrast in Optical Coherence Tomography. Advanced Healthcare Materials 2020 9.5 (2020): 1901627, which has been published in final form at https://onlinelibrary.wiley.com/doi/full/10.1002/adhm.201901627. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions ; Optical coherence tomography (OCT) is an imaging technique affording noninvasive optical biopsies. Like for other imaging techniques, the use of dedicated contrast agents helps better discerning biological features of interest during the clinical practice. Although bright OCT contrast agents have been developed, no dark counterpart has been proposed yet. Herein, plasmonic copper sulfide nanoparticles as the first OCT dark contrast agents working in the second optical transparency window are reported. These nanoparticles virtually possess no light scattering capabilities at the OCT working wavelength (≈1300 nm); thus, they exclusively absorb the probing light, which in turn results in dark contrast. The small size of the nanoparticles and the absence of apparent cytotoxicity support the amenability of this system to biomedical applications. Importantly, in the pursuit of systems apt to yield OCT dark contrast, a library of copper sulfide nanoparticles featuring plasmonic resonances spanning the three optical transparency windows is prepared, thus highlighting the versatility and potential of these systems in light-controlled biomedical applications ; This project was partially funded by the European Commission through the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie Grant agreement No. 797945 "LANTERNS". This work was partially supported by the Ministerio de Economía y Competitividad de España (MAT2016-75362-C3-1-R) and (MAT2017-83111R), by the Instituto de Salud Carlos III (PI16/00812), by the Comunidad Autónoma de Madrid (B2017/BMD-3867RENIMCM), and co-financed by the European Structural and investment fund. Additional funding was provided by the European Commission Horizon 2020 project NanoTBTech. L.V.B was supported by the Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China and China Postdoctoral Science Foundation (2017M622992 and 2019T120820). Z.W. was supported by the National Basic Research Program of China (Project 2013CB933301) and the National Natural Science Foundation of China (Project 51272038). A.G. was funded via the 1000-talent Award of Sichuan and by the Volkswagen Foundation. Prof. Jorge Rubio-Retama is gratefully acknowledged for granting access to the dynamic light scattering instrument and for the fruitful discussion

We report on the modification of graphene oxide (GO) with poly(vinyl alcohol) (PVA) leading to the mechanical improvement of GO based materials. First, GO was covalently functionalised with PVA by esterification of carboxylic groups on GO with hydroxyl groups of PVA resulting in functionalised f-(PVA)GO. This was carried out for PVA of six different molecular weights. This functionalised graphene oxide could be formed into a paper-like material by vacuum filtration. Papers prepared from f-(PVA)GO showed significant increases in mechanical properties compared to those prepared with GO or with simple mixtures of GO and PVA. The best performance was achieved for PVA functional groups with molecular weights between 50 and 150 kg/mol. Improvements in Young's moduli of 60% and tensile strength of 400% were observed relative to GO-only paper. The improved mechanical properties are attributed to enhanced inter-flake stress transfer due to the covalently bonded PVA. Second, functionalised f-(PVA)GO was used as filler in * Corresponding author. Tel/Fax: +34 976 73-3977 / -3318. E-mail address: wmaser@icb.csic.es (W.K. Maser) 2 PVA-based composites. The application of a pre-selection method allowed the use of only the largest functionalised f-(PVA)GO flakes. This resulted in substantially reinforced PVA-f-(PVA)GO composites. Both modulus and strength increased by 40% relative to the pure polymer for f- (PVA)GO loadings below 0.3 vol.%. ; The authors would like to acknowledge Science Foundation Ireland, (grant number 07/IN.7/I1772), Spanish Ministry of Science and Innovation (MICINN) under project MAT2010-15026, Spanish Research Council CSIC under project 201080E124 and the Government of Aragon (DGA) under Project DGA-T66 CNN. M.C. thanks MICINN for her PhD contract and funding for research stay at TCD under FPI Programme BES-2008-003503. ; Peer reviewed

Van der Waals heterostructures consisting of graphene and transition metal dichalcogenides have shown great promise for optoelectronic applications. However, an in-depth understanding of the critical processes for device operation, namely, interfacial charge transfer (CT) and recombination, has so far remained elusive. Here, we investigate these processes in graphene-WS heterostructures by complementarily probing the ultrafast terahertz photoconductivity in graphene and the transient absorption dynamics in WS following photoexcitation. We observe that separated charges in the heterostructure following CT live extremely long: beyond 1 ns, in contrast to ~1 ps charge separation reported in previous studies. This leads to efficient photogating of graphene. Furthermore, for the CT process across graphene-WS interfaces, we find that it occurs via photo-thermionic emission for sub-A-exciton excitations and direct hole transfer from WS to the valence band of graphene for above-A-exciton excitations. These findings provide insights to further optimize the performance of optoelectronic devices, in particular photodetection. ; S.F. acknowledges fellowship support from Chinese Scholarship Council (CSC). X.J. acknowledges financial support by DFG through the Excellence Initiative by the Graduate School of Excellence Materials Science in Mainz (MAINZ) (GSC 266) and support from the Max Planck Graduate Center mit der Johannes Gutenberg-Universität Mainz (MPGC). A.J.H. acknowledges support from the European Research Council Horizon 2020 ERC grant no. 678004 (Doping on Demand). ICN2 was supported by the Severo Ochoa program from Spanish MINECO (grant no. SEV-2017-0706). K.-J.T. acknowledges funding from the European Union's Horizon 2020 Research and Innovation Programme under grant agreement no. 804349 (ERC StG CUHL) and financial support through the MAINZ Visiting Professorship.