The historical stone heritage that we inherit must be passed on to future generations, not only in the same conditions that we found it but, if possible, in better ones. Construction also demands better and more durable materials, often stone. The protection of these materials requires knowledge of the types of rocks and their physical properties. The characterization of these properties is often standardized to ensure the quality and reproducibility of the protocols. These must be approved by entities whose purpose is to improve the quality and competitiveness of companies and to protect the environment. Standardized water absorption tests could be envisaged to test the effectiveness of certain coatings in protecting natural stone against water penetration, but we found that some steps of these protocols neglect any surface modification of the stones, and hence may not be completely effective when a hydrophilic protective coating (i.e., graphene oxide) is present. In this work, we analyze the UNE 13755/2008 standard for water absorption and propose alternative steps to adapt the norm for use with coated stones. The properties of coated stones may invalidate the interpretation of the results if the standard protocol is applied as is, so here we pay special attention to the characteristics of the coating applied, the type of water used for the test, the materials used, and the intrinsic heterogeneity of the specimens.

In the present study, we explored the interaction of bovine serum albumin (BSA) with oxidized graphene oxide (GO) nanosheets. Nanosheets, synthesized with 4, 6, 8, 10 and 12 wt equivalents of KMnO4 as oxidant, were coded as GO-4, GO-6, GO-8, GO-10 and GO-12, respectively. After incubating sheets with a fixed concentration of BSA at room temperature, interactions were monitored with time. The analysis is based on UV-vis spectroscopy, fluorescence quenching, dynamic light scattering (DLS), small angle neutron scattering (SANS), Fourier transform infrared (FTIR) spectroscopy and circular dichroism (CD) techniques. Binding of BSA over sheets was recorded in the following order; GO-04 >> GO-06 > GO-08 > GO-10 ≈ GO-12. Our observations suggest that these interactions are largely regulated by the availability of pure graphitic domains and density of oxygen functionalities on sheet surface. This led us to the conclusion that GO-protein interactions can be minimized by modulating the extent of sheet oxidation. Moreover, we show that adsorption of proteins as colloidal aggregates contributes to improved biosafety of sheets. The protein molecule did not exhibit depletive changes in its conformation. However, from the viewpoint of drug delivery applications, density of oxygen groups must be optimized for maximizing the loading efficiency of oxidized sheets.

This work provides a new perception toward the application of the graphenic-biopolymeric composites as a solid-bed for separation and purification of bioactive compounds. Graphene oxide nanocomposites with functionalized sheets by soluble and insoluble nanocomplexes of chitosan and Arabic gum, were successfully synthesized and employed for the adsorption and purification of crocin, a nutraceutical from saffron. The composites exhibited a nanostructured scaffold with a particle size of 10 nm and experienced an unprecedented increase in the surface area by about 300% and improved d-spacing sheets by 17%. The optimum conditions for crocin separation were temperature = 318 K, stirring rate = 300 rpm, initial concentration = 100 mg L-1 and pH = 6. Under these conditions, the nanocomposites separated 99.1% of crocin in an equilibrium time of 30 min. The adsorption data were best represented by Freundlich isotherm and pseudo-second-order kinetic models. The thermodynamic studies indicated that the crocin adsorption on nanocomposites was an endothermic, spontaneous and physisorption process. The high-performance liquid chromatography (HPLC) analysis revealed that produced nanocomposites adsorbed crocin efficiently from saffron extract with a purity similar to the standard sample. The possible interaction mechanisms between crocin and nanocomposites were electrostatic interactions and hydrogen bonding.

Graphenic substrates (GS), such as reduced graphene oxide (rGO) and graphene oxide (GO), are 2D materials known for their unique physicochemical properties such as their ability to enhance vibrational spectroscopic signals and quench the fluorescence of adsorbed molecules. These properties provide an opportunity to develop nanostructured GS-based systems for detecting and identifying different analytes with high sensitivity and reliability through molecular spectroscopic techniques. This work evaluated the capacities of different GS to interact with a highly fluorescent compound, thereby changing its optical emission response (fluorescence quenching) and amplifying its vibrational signal, which is the base of graphene-enhanced Raman scattering (GERS). To test these properties, we used a derivative of highly fluorescent BODIPY (BP) compounds, which cover a wide range of applications from solar energy conversion to photodynamic cancer therapy. GS prepared by using the Langmuir-Blodgett (LB) technique allowed us to quench the fluorescence emission of BP and improve its Raman spectroscopy detection limit due to the GERS effect. These results were interpreted in light of the π-π interactions taking place between the Csp2 domains of GS and the aromatic core of the BP fluorophore.

The formation of highly concentrated and stable graphene derivatives dispersions remains a challenge towards their exploitation in various applications, including flexible optoelectronics, photovoltaics, 3D-printing, and biomedicine. Here, we demonstrate our extensive investigation on the dispersibility of graphene oxide (GO) and reduced graphene oxide (RGO) in 25 different solvents, without the use of any surfactant or stabilizer. Although there is a significant amount of work covering the general field, this is the first report on the dispersibility of: a) RGO prepared by a HI/AcOH assisted reduction process, the method which yields RGO of higher graphitization degree than the other well-known reductants met in the literature, b) both GO and RGO, explored in such a great range of solvents, with some of them not previously reported. In addition, through calculation of their Hansen Solubility Parameters (HSP), we confirmed their dispersibility behavior in each solvent, while we indirectly validated the most advanced graphitization degree of the studied RGO compared to other reported RGOs, since its HSPs exhibit the highest similarity with the respective ones of pure graphene. Finally, high concentrations of up to 189 μg mL-1 for GO and ~ 87.5 μg mL-1 for RGO were achieved, in deionized water and o-Dichlorobenzene respectively, followed by flakes size distribution and polydispersity indices estimation, through dynamic light scattering as a quality control of the effect of a solvent\'s nature on the dispersion behavior of these graphene-based materials.

In cold climate regions, the energy associated with indoor heating constitutes a large portion of energy consumption. Increasing energy utilization efficiency is critically important for both economic and environmental reasons. Directly converting electrical energy to thermal energy using joule heating construction elements can save energy and investment to the water pipelines which have been extensively used for indoor heating in China. The fired brick has been extensively used to make pavements, walls and other masonry. Taking advantage of the high dispersion quality of graphene oxide (GO) in water, as well as the firing process used to make fired bricks, graphene nanocomposite bricks with excellent electrical properties and improved mechanical performance were prepared in China. The compressive strength of the bricks showed a substantial increase from 3.15 MPa to 7.21 MPa when GO concentration was 0.1 wt.%. Through applying 5 volts of electrical field within 5 minutes, the nanocomposites can be heated from room temperature to 60 °C, 110 °C and 160 °C for the nanocomposite bricks with graphene concentration of 3 wt.%, 4 wt.% and 5 wt.%, respectively, due to the extremely low percolation threshold (~0.5 wt.%) and high conductivity (10 Ω·cm at 1 wt.%). The sheets were connected more tightly when the GO content was increased. The thermal efficiency can reach up to 88% based on the applied voltage, measured resistance and temperature rise curves.

In this Review article, recent progress in matter of graphene oxide (GO) synthesis and its functionalization via a vast range of materials, including small molecules, polymers, and biomolecules, were reported and systematically summarized in order to overcome the inherent drawbacks of GO nanocarriers and thereby make these nanocarriers suitable for delivering chemotherapeutic agents, genes, and short interfering RNAs. Briefly, this work describes current strategies for the large scale production of GO and modification of graphene-based nanocarriers surfaces through practical chemical approaches, improving their biocompatibility and declining their toxicity. It also describes the most relevant cases of study suitable to demonstrate the role of graphene and graphene derivatives (GD) as nanocarrier for anti-cancer drugs and genes (e.g. miRNAs). Moreover, the controlled release mechanisms within the cell compartments and blood pH for targeted therapeutics release in the acidic environment of tumor cells or in intracellular compartments are mentioned and explored.

The application of graphene oxide (GO) has attracted increasing concerns in the past decade regarding its environmental impacts, except for the impact of GO on a metal-contaminated soil system, due to its special properties. In the present work, the effects of GO on the migration and transformation of heavy metals and soil bacterial communities in Cd-contaminant soil were systematically evaluated. Soil samples were exposed to different doses of GO (0, 1, and 2 g kg-1) over 60 days. The Community Bureau of Reference (BCR) sequential extraction procedure was used to reflect the interaction between GO and Cd. Several microbial parameters, including enzyme activities and bacterial community structure, were measured to determine the impacts of GO on polluted soil microbial communities. It was shown that Cd was immobilized by GO throughout the entire exposure period. Interestingly, the structure of the bacterial community changed. The relative abundance of the major bacterial phyla (e.g., Acidobacteria and Actinobacteria) increased, which was possibly attributed to the reduced toxicity of Cd in the presence of GO. However, GO exerted an adverse influence on the relative abundance of some phyla (e.g., WD272 and TM6). The diversity of bacterial communities was slightly restricted. The functional bacteria related to carbon and the nitrogen cycling were also affected, which, consequently, may influence the nutrient cycling in soil.

Graphene oxide (GO) is an important carbon nanomaterial (NM) that has been used, but limited literature is available regarding the impacts induced in aquatic organisms by this pollutant and, in particular in invertebrate species. The polychaete Diopatra neapolitana has frequently been used to evaluate the effects of environmental disturbances in estuarine systems due to its ecological and socio-economic importance but to our knowledge no information is available on D. neapolitana physiological and biochemical alterations due to GO exposure. Thus, the present study aimed to assess the toxic effects of different concentrations of GO (0.01; 0.10 and 1.00mg/L) in D. neapolitana physiological (regenerative capacity) and biochemical (energy reserves, metabolic activity and oxidative stress related biomarkers) performance, after 28days of exposure. The results obtained revealed that the exposure to GO induced negative effects on the regenerative capacity of D. neapolitana, with organisms exposed to higher concentrations regenerating less segments and taking longer periods to completely regenerate. GO also seemed to alter energy-related responses, especially glycogen content, with higher values in polychaetes exposed to GO which may result from a decreased metabolism (measured by electron transport system activity), when exposed to GO. Furthermore, under GO contamination D. neapolitana presented cellular damage, despite higher activities of antioxidant and biotransformation enzymes in individuals exposed to GO.