Carbon nanomaterials are promising adsorbents for dye removal from wastewater also due to their possible surface functionalization that, in principle, can increase the adsorption rate and provide regeneration. To investigate the real advantages of functionalization, we synthesized and characterized through IR, TGA, TEM, XPS and DLS measurements a multi-walled carbon nanotube (MWCNT) derivative bearing benzenesulfonate groups (MWCNT-S). The obtained material demonstrated to have good dispersibility in water and better capability to adsorb methylene blue (MB) compared to the pristine MWCNT adsorbent. Adsorption kinetic studies showed a very fast process, with a constant significantly higher with respect not only to that of the unfunctionalized MWCNT adsorbent but also to those of widely used activated carbons. Moreover, the adsorption capacity of MWCNT-S is more than doubled with respect to that of the insoluble pristine MWCNT adsorbent, thanks to the dispersibility of the derivatives, providing a larger available surface, and to the possible electrostatic interactions between the cationic MB and the anionic sulfonate groups. Additionally, the reversibility of ionic interactions disclosed the possibility to release the adsorbed cationic pollutant through competition with salts, not only regenerating the adsorbent, but also recovering the dye. Indeed, by treating the adsorbed material for 1 h with 1 M NaCl, a regeneration capacity of 75% was obtained, demonstrating the validity of this strategy.

Gold nanoparticles have been extensively studied due to their unique optical and electronic properties which make them attractive for a wide range of applications in biomedicine, electronics, and catalysis. Over the past decade, atmospheric pressure plasma jets in contact with a liquid have emerged as a sustainable and environmentally friendly approach for synthesizing stable and precisely controlled dispersions. Within the context of plasma jet/liquid configurations, researchers have explored various power sources, ranging from kHz frequencies to nanopulse regimes. In this study, we investigated the effects of coupling two distinct power supplies: a high-voltage micropulse and a radio frequency (RF) generator. The variations within the plasma induced by this coupling were explored by optical and electrical measurements. Our findings indicated a transition from a bullet plasma propagation mechanism to a capacitive coupling mechanism upon the introduction of RF energy. The impact on the production of metal nanoparticles was also examined as a function of the radio frequency power and of two distinct process gases, namely helium and argon. The characterization of gold nanoparticles included UV-visible spectroscopy, dynamic light scattering, and scanning electron microscopy. The results showed that the size distribution depended on the type of process gas used and on the power supplies coupling. In particular, the incorporation of RF power alongside the micropulse led to a decrease in both average particle size and distribution width. The comparison of the different set up suggested that the current density can influence the particle size distribution, highlighting the potential advantages of the use of a dual-frequency atmospheric pressure plasma jet configuration.

Carbon nanotube (CNT) composite hydrogels are promising materials for tissue engineering due to the biocompatibility of the matrix and the electrical conductivity of the filler. However, specific chemical functionalization of CNT is required to disperse them homogeneously within an aqueous matrix. Therefore, we synthesized and characterized (through XPS, TGA, Raman, DLS and Zeta Potential) a water-soluble CNT derivative (fCNT) bearing quaternary ammonium groups, and we used it to prepare alginate-based nanocomposite hydrogels. We employed two different gelation techniques (external and internal) to obtain two plain hydrogels (HG1 and HG2 respectively) and two fCNT-filled composites (HG1-fCNT and HG2-fCNT respectively) and we compared the physical properties of the four different materials. Hydrogels were characterized through SEM microscopy and elastic modulus measurements. Moreover, an exhaustive investigation of the electrical properties of the hydrogel samples was carried on by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy in the range of 1-104 Hz. Notably, the addition of fCNT enhanced the conductivity of the hydrogel from internal gelation (HG2-fCNT) by more than one order of magnitude, thereby making it a promising candidate as a scaffold for electroactive tissues such as muscle. The observed features are even more appealing when considering active electrostimulation of cells. The stability of the scaffolds in the culture medium was improved by an enhanced calcium concentration. Finally, the behavior of the four hydrogels as scaffolds for muscle tissue engineering was investigated through comprehensive studies of myoblast viability, proliferation, and differentiation. While similar and satisfying behaviours were observed for all samples in terms of cytocompatibility and proliferation, a relevant improvement in differentiation was obtained by the addition of fCNT in the case of HG2-fCNT. These outcomes hint at the feasibility of using the fCNT combined with the alginate hydrogel in order to support the myoblasts growth and proliferation.

Carbon-based nanomaterials are increasingly investigated for water purification due to their high surface area, tunable reactivity, and versatile adsorption mechanisms. Among them, graphene and its derivatives have demonstrated superior performance over activated carbon and carbon nanotubes, although their use is often hindered by sheet aggregation and limited dispersibility. In this work, we report the synthesis and characterization of a sulfonated reduced graphene oxide derivative (rGO-S), obtained through a diazotization reaction with sodium sulfanilate. The covalent introduction of benzenesulfonate groups was confirmed by TEM, EDX, XPS, FTIR, and TGA, revealing a homogeneous functionalization and enhanced water dispersibility (0.49 mg/mL). rGO-S exhibited a highly negative zeta potential (−45.3 mV), preventing aggregation and increasing the number of accessible adsorption sites. Using methylene blue (MB) as a model cationic pollutant, adsorption studies demonstrated remarkable performance: equilibrium was reached in less than one minute, with kinetics best described by a pseudo-second-order model and a two-fold increase in adsorption capacity (326 mg/g) compared to pristine rGO. Moreover, rGO-S displayed efficient regeneration through ion-exchange with NaCl solutions, achieving up to 92% desorption in multiple cycles, in combination with ethanol, while maintaining stable adsorption capacity upon reuse. Selectivity tests against a mixture of dyes confirmed the preferential uptake of MB, highlighting the role of electrostatic interactions with sulfonate groups. Overall, the sulfonated graphene derivative combines fast kinetics, good efficiency, selectivity, and reusability, providing promising perspectives for scalable water treatment applications and pollutant recovery within a circular economy framework.