Recently, an increase in the production of intelligent nanomaterials has been reported for the application of solid surface coating. These nanomaterials provide a wide number of functionalities such as anticorrosive, antibacterial, and self-cleaning properties. Hence, titanium dioxide (TiO2) and zinc oxide (ZnO) nanoparticles were synthesized using a green chemistry approach. These nanoparticles were fully characterized by scanning electron microscopy, energy-dispersive X-ray, high-resolution transmission electron microscopy, X-ray diffraction, ultraviolet (UV)–visible spectroscopy, Brunauer–Emmett–Teller test, and nitrogen adsorption–desorption isotherm. Then, a commercial enamel-type paint was modified by using different concentrations (2, 3.5, and 5 w/v%) of nanoparticles. These nanofilled paints were then brushed onto the surface of different types of materials such as carbon steel sheets, wood sheets, and aluminum disks. Anticorrosive, self-cleaning, and antibacterial properties of the nanofilled paints were evaluated, with the aim to determine the capability for this application. According to the characterization results, TiO2 and ZnO nanoparticles exhibited similar physicochemical properties compared to those synthesized using traditional methods. The anticorrosion results revealed that nanofilled paints provide a barrier using low concentrations of nanoparticles, due to the decrease of agglomerates on the surface avoiding the presence of high porosity. In the case of self-cleaning, a proposed mechanism of degradation demonstrated that the presence of both nanoparticles in the paint provided high degradation of methylene blue due to the high surface area offered by the nanoparticles. On the other hand, antibacterial activity under UV light was observed only for ZnO nanoparticles, which may be related to the diffusion of nanoparticles into the cell membrane of the bacteria, affecting the normal function. These results showed to be promising for the modification of paints with TiO2 and ZnO nanoparticles, and the application on solid surfaces for the construction, and even in textile fields.

No abstract

Magnetite (Fe3O4) and magnetic core‐shell mesoporous silica (Fe3O4‐mSiO2) nanoparticles are employed to coat cotton fibers using a room temperature water‐based direct electrostatic assembly method with polyelectrolytes. Core‐shell nanoparticles are fabricated by coating super‐paramagnetic magnetite clusters with a mesoporous silica layer (mSiO2) using a surfactant‐templating approach. The Fe3O4 clusters are initially synthesized by a co‐precipitation process. The cotton fibers are modified through a layer‐by‐layer technique using dipping cycles with PDDA and PSS polyelectrolytes solutions to enable further nanoparticles attachment. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) images provides morphologic information of the synthesized nanoparticles and the modified cotton fibers. Composition and physicochemical properties are studied by powder XRD, FTIR, and SEM‐EDX methods, and thermogravimetric analysis (TGA) are carried out to determine the amount of nanoparticles adsorbed onto cotton samples. The saturation magnetization (MS) of nanoparticles determined by a vibrating sample magnetometer (VSM) is greater than that of the cotton‐nanoparticles nano‐composites. Potential applications of these composite materials can include protective clothing and transdermal drug delivery systems.

Polycyclic aromatic hydrocarbons (PAHs) are complex molecules produced by the thermal decomposition of organic matter in anthropogenic activities. Novel composites with enhanced physicochemical properties aim to overcome limitations such as adsorption capacity, affinity, and stability for PAHs adsorption. Composites based on chitosan are promising due to the good biocompatibility and adsorption properties. This study focuses on the facile preparation of chitosan beads modified with iron oxide (FeO) and titanium dioxide (TiO 2 ) nanoparticles via ionic cross-linking (Ch-FeO/TiO 2 ). FeO and TiO 2 were synthesized performing co-precipitation and green chemistry methods, respectively. The characterization evidenced the formation of Ch-FeO/TiO 2 with good crystallinity, excellent thermal stability, and superparamagnetic response, attributed to the presence of FeO and TiO 2 nanoparticles. High thermal stability up to 270 °C was related to the cross-linked chitosan network. The enhanced adsorption mechanism of Ch-FeO/TiO 2 was determined by removing naphthalene from water and seawater samples. The Ch-FeO/TiO 2 showed a higher adsorption capacity of 33.1 mg/g compared to 29.8 mg/g of the unmodified chitosan (un-Ch) beads. This is due to the higher functional surface area of 27.13 m 2 /g, compared to that of 0.708 m 2 /g for un-Ch. We found a rapid adsorption rate of 240 min and the maximum adsorption capacity of 149.3 mg/g for Ch-FeO/TiO 2 . A large number of actives sites allows for increasing the naphthalene molecules interaction. Adsorption in seawater samples from Cartagena Bay (Colombia) exhibits an outstanding efficiency of up to 90%. These results suggest a promising, cheap, and environmentally friendly composite for remediation of water sources contaminated with complex compounds.

Green synthesis, based on green chemistry, is replacing the traditional methods, aiming to contribute with an enhanced environmental sustainability, which can be achieved using nontoxic compounds from biological resources, such as natural extracts from plants. In this study, the life cycle assessment (LCA) of iron oxide nanoparticles prepared through the green synthesis and the coprecipitation method is reported by following a cradle-to-gate approach. The LCA allowed quantifying and normalized the environmental impacts produced by the green synthesis (1.0 × 10 –9 ), which used a Cymbopogon citratus ( C. citratus ) extract and sodium carbonate (Na 2 CO 3 ). The impacts were also determined for the coprecipitation method (1.4 × 10 –8 ) using the iron(II) salt precursor and sodium hydroxide (NaOH). The contribution of C. citratus extract and Na 2 CO 3 as the precursor and pH-stabilizing agents, respectively, was compared regarding the iron(II) and NaOH compounds. Environmental sustainability was evaluated in human toxicity, ecosystem quality, and resource depletion. The major environmental contribution was found in the marine aquatic ecotoxicity (7.6 × 10 –10 and 1.22 × 10 –8 for green synthesis and the coprecipitation method) due to the highest values for ethanol (3.5 × 10 –10 ) and electricity (1.4 × 10 –8 ) usage since fossil fuels and wastewater are involved in their production. The C. citratus extract (2.5 × 10 –12 ) presented a better environmental performance, whereas Na 2 CO 3 (4.3 × 10 –11 ) showed a slight increase contribution compared to NaOH (4.1 × 10 –11 ). This is related to their fabrication, involving toxic compounds, land occupation, and excessive water usage. In general, the total environmental impacts are lower for the green synthesis, suggesting the implementation of environmentally friendlier compounds based on natural sources for the production of nanomaterials.