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Cadmium sulfide quantum dots (CdS-QDs) can be generated along poly(propylene imine) (PPI) dendrimerbased self-assembled nanofibers through a simple approach based on ionic substitution. Supramolecular nanofibers are obtained via self-assembly of cationic PPI dendrimers in aqueous solution containing cadmium acetate. The dissociated asymmetric acetate ions (AcO À ) are the ''glue'' for the self-assembly process. The semiconductive CdS nanoparticles are synthesized at room temperature along the selfassembled nanofibers by the addition of sodium sulphide (Na 2 S) in solution. Molecular dynamics (MD) simulation shows that the higher affinity of SH À ions (from dissociated Na 2 S) for Cd 2+ , compared to that of AcO À , triggers ionic substitution at the interface between the dendrimers. TEM and AFM measurements confirm the self-assembly of the fibers and the formation of CdS quantum dots along the filaments having a final size of B2 nanometers. The obtained absorbance results show the presence of quantum confinement effect. Since these self-assembled fibers can be disassembled by a simple addition of sodium chloride in solution (ionic competition), this work proposes a new facile route to obtain functional materials in a convenient way.

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To fabricate graphene-based high-frequency electronic and optoelectronic devices, there is a high demand for scalable low-contaminated graphene with high mobility. Graphene synthesized via chemical vapor deposition (CVD) on copper foil appears promising for this purpose, but residues from the polymethyl methacrylate (PMMA) layer, used for the wet transfer of CVD graphene, drastically affect the electrical properties of graphene. Here, we demonstrate a scalable and green PMMA removal technique that yields high-mobility graphene on the most common technologically relevant silicon (Si) substrate. As the first step, the polarity of the PMMA was modified under deep-UV irradiation at λ = 254 nm, due to the formation of ketones and aldehydes of higher polarity, which simplifies hydrogen bonding in the step of its dissolution. Modification of PMMA polarity was confirmed by UV and FTIR spectrometry and contact angle measurements. Consecutive dissolution of DUV-exposed PMMA in an environmentally friendly, binary, high-polarity mixture of isopropyl alcohol/water (more commonly alcohol/water) resulted in the rapid and complete removal of DUV-exposed polymers without the degradation of graphene properties, as low-energy exposure does not form free radicals, and thus the released graphene remained intact. The high quality of graphene after PMMA removal was confirmed by SEM, AFM, Raman spectrometry, and by contact and non-contact electrical conductivity measurements. The removal of PMMA from graphene was also performed via other common methods for comparison. The charge carrier mobility in graphene films was found to be up to 6900 cm2/(V·s), demonstrating a high potential of the proposed PMMA removal method in the scalable fabrication of high-performance electronic devices based on CVD graphene.

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