Understanding the Wettability of Graphene Coatings: Insights, Measurements, and Implications for Diverse Applications

Graphene’s (GR) wettability is a contentious subject marked by conflicting reports. Some studies claim superhydrophobicity with up to 150° contact angles indicating limited wettability. Conversely, other research suggests factors like surface roughness, contaminants, and lattice defects modify GR’s wettability, revealing moderate hydrophilicity in defect-free GR. Persistent disagreements center around the impact of GR production processes, substrate interactions, and environmental factors. This paper addresses the controversy by scrutinizing wetting measurement techniques and sample preparation. We present a comprehensive framework for sample preparation and characterization for a few GR layers. Key findings highlight the significance of sample preparation and the identification of Atomic Force Microscopy (AFM) and Vibrational Sum Frequency Generation (VSFG) spectroscopy as particularly valuable techniques for assessing GR wettability. These insights contribute to tailored GR-based applications, from surface coatings to catalysis and energy storage

Biowaste valorization: multifunctional hybrid lignin/TiO2 nanostructures for bacterial-biocide disinfection and dye removal

An urgent goal is to enhance the economic and the environmental value of biowaste via recycling and conversion techniques. Lignin, a plentiful plant polymer, holds significant potential for the development of sustainable multifunctional materials. Despite its advantages in terms of red-ox and pollutant adsorption properties, challenges in lignin valorization must address its chemical complexity and tendency to aggregate in water. We demonstrate that lignin and TiO2 can be intimately combined through a versatile in situ hydrothermal strategy to obtain hybrid multifunctional nanostructures with tunable functionalities. An in-depth physicochemical analysis elucidates the structure-property-function correlations. The synergistic combination of lignin and TiO2 in hybrid nanoparticles enhances ROS-scavenging/generating properties. Indeed, lignin content of 20% wt/wt within nanostructures (TiO2_DL200 sample) resulted in nanoparticles with improved antibacterial/antimycotic properties (15 mm increase in the diameter of bacterial growth inhibition (DDK) and 3-fold decrease in the in the minimum inhibitory concentration (MIC) against fungi compared to neat TiO2 nanoparticles and around 1.3 mm DDK increase and 3-fold MIC decrease against fungi compared to neat lignin) and 90% radical scavenging activity in only 2 minutes. In addition, TiO2_DL200 nanoparticles achieved nearly 80% and 90 % of removal of methylene blue (MB) and fuchsin (F) dyes, respectively, by adsorption within 5 minutes. Conversely, by tuning the lignin content within the hybrid nanomaterial, a trade-off between the adsorption capacity and the photocatalytic activity is achieved, with MB and F removal efficiencies exceeding 80% in 120 minutes under UV-A conditions for TiO2_DL50. These outcomes prove the potential uses of the obtained hybrid nanoparticles as antioxidant, antibacterial and antifungal additives and for the decontamination of dyes in water remediation

Unravelling the photoactivity of metal-loaded TiO2 for hydrogen production: Insights from a combined experimental and computational analysis

Despite being the most employed material for photocatalytic hydrogen generation, TiO2 suffers limitations such as a high rate of electron-hole recombination and poor light absorption in the visible spectrum. Among the various strategies developed to overcome these drawbacks, combining TiO2 with a metal co-catalyst emerged as one of the most promising. In this study, we integrated experimental findings, advanced characterization techniques, and computational methods to shed light on how different noble metals influence the enhancement of the photocatalytic activity of TiO2. Among the tested noble metal co-catalysts, the hydrogen production rate under UV and visible light irradiation followed the trend Pt > Au ≈ Pd > Ag > bare TiO2, with Pt-decorated TiO2 exhibiting a hydrogen production rate of 28 mmol/h g. The noble metals were found to significantly suppress the electron-hole recombination rate compared to bare TiO2. Upon photodeposition, Pd and Pt formed the smallest nanoparticles with average sizes of 13.4 nm and 4.1 nm, respectively. Computational analyses were conducted to rationalize the difference in nanoparticle sizes by analyzing the binding and cohesive energies of the metal clusters on the TiO2 surface. Additionally, calculations demonstrated the strong interaction of Pt, Au, and Pd nanoclusters with adsorbed hydrogen, with Pt achieving the closest-to-zero Gibbs free energy of hydrogen adsorption and displaying the most polar interaction with hydrogen. These findings align closely with the observed hydrogen production rates, where UV/Vis-driven hydrogen production is governed by the coupling of hydrogen radicals on the co-catalyst surface, while visible-light-driven production is limited by charge carrier lifetimes

Photocatalytic applications in wastewater and air treatment: A patent review (2010–2020)

In this work, we reviewed the most significant patents of the last decade (2010–2020) in the fields of water and air photocatalytic treatment. Patents were discussed by identifying the recurrent addressed issues and presenting the proposed solutions. Adoption of TiO2 and/or modified-TiO2-based material is still the most common choice of inventors, whereas many patents focus on the design of the plants/devices to improve efficiency of photocatalytic treatment by improving light utilization and contact between the phases. The review also highlights issues deriving from specific applications and outlines future trends in the field, such as the need for standardized testing and digitalization of monitoring and control

Interaction of urea and urea derivatives with cyclohexamylose in aqueous solutions at 25°C

The interaction in water of urea, monomethylurea, monoethylurea, monopropylurea, and monobutylurea with α-cyclodextrin(hexacycloamylose) was studied calorimetrically at 25°C. The results show that the last three substances form inclusion complexes with α-cyclodextrin. The enthalpy and the association constants relative to the inclusion process were determined. The association constant values are low, indicating weak complexing that increases with increasing length of the alkyl chain. Urea and monomethylurea, on the other hand, do not form inclusion complexes. For these systems the calorimetric data were treated in terms of excess enthalpies, and the McMillan-Mayer approach was used to get an insight into the weak, non-bonding molecular interactions occurring in these solutions. © 1986 Plenum Publishing Corporation

Risk analysis of the sodium hypochlorite production process: Focus on the chlorine line

Mainly in the first part of COVID-19 pandemics, sodium hypochlorite was used as disinfectant, surprisingly also to spray over people. Several hazards may be associated to the production of this compound, such as chlorine gas toxicity and explosive hazards, due to the presence of hydrogen and chlorine, and corrosive hazards. Thus, loss prevention strategies must be ad-hoc developed to mitigate the risks. In the present work, the risk assessment of the first block of the process was performed, focusing the attention on chlorine risks. To this end, HAZOP analysis was first performed to identify the most critical top event, noticing the major issues in the quality of the final product and in the release of chlorine from pipes. Then, the fault tree analysis was built to calculate its failure rate. CFD simulations were used instead of empirical model to assess with a rigorous approach the chlorine dispersion, taking into account all the boundary conditions. In particular, by setting a hazardous chlorine concentration of 180 ppm corresponding to 50% fatalities for chlorine exposition for an exposure of 60 min, results without aspiration demonstrate the possibility for the cloud to impact workers at ground level also very far from the source point, while the chlorine cloud is moved upwards with a maximum length of 6.5 m when an aspiration is used, although the air ventilation speed is kept low