Direct Measurement of Surfactant-Mediated Picoforces among Nanoparticles in a Quasi-Two-Dimensional Environment.

The lack of methodologies which enable us to measure forces acting between nanomaterials is one of the factors limiting the full comprehension of their behavior and their more effective exploitation in new devices. Here we exploit the irreversible adsorption of surfactant-decorated nanoparticles at the air/water interface to investigate interparticle forces and the effect of the surfactant structure on them. We measured the interparticle repulsive forces as a function of the modulation of the interparticle distance by simultaneously performing compression isotherms and the grazing incidence small-angle X-ray scattering (GISAXS) structural characterization of the monolayers at water-vapor interfaces. Our results demonstrate that the short-range interparticle forces are strongly affected by the presence of the organic ligands, which are shown to be able to influence the interparticle repulsions even when added in micromolar amounts. In particular, we demonstrate the predominant steric nature of short-range forces, which are accounted for in terms of the compression-induced stretched-to-coiled conformational transition of the ligand hydrophobic tail.

TiO2-MoS2-PMMA Nanocomposites for an Efficient Water Remediation.

An improvement of water supply and sanitation and better management of water resources, especially in terms of water reuse, is one of the priorities of the European Green Deal. In this context, it is crucial to find new strategies to recycle wastewater efficiently in a low-cost and eco-friendly manner. The immobilization of inorganic nanomaterials on polymeric matrices has been drawing a lot of attention in recent years due to the extraordinary properties characterizing the as-obtained nanocomposites. The hybrid materials, indeed, combine the properties of the polymers, such as flexibility, low cost, mechanical stability, high durability, and ease of availability, with the properties of the inorganic counterpart. In particular, if the inorganic fillers are nanostructured photocatalysts, the materials will be able to utilize the energy delivered by light to catalyze chemical reactions for efficient wastewater treatment. Additionally, with the anchoring of the nanomaterials to the polymers, the dispersion of the nanomaterials in the environment is prevented, thus overcoming one of the main limits that impede the application of nanostructured photocatalysts on a large scale. In this work, we will present nanocomposites made of polymers, i.e., polymethyl methacrylate (PMMA), and photocatalytic semiconductors, i.e., TiO2 nanoparticles (Evonik). MoS2 nanoflakes were also added as co-catalysts to improve the photocatalytic performance of the TiO2. The hybrid materials were prepared using the sonication and solution casting method. The nanocomposites were deeply characterized, and their remarkable photocatalytic abilities were evaluated by the degradation of two common water pollutants: methyl orange and diclofenac. The relevance of the obtained results will be discussed, opening the route for the application of these materials in photocatalysis and especially for novel wastewater remediation.

Site-specific halloysite functionalization by polydopamine: A new synthetic route for potential near infrared-activated delivery system.

Halloysite nanotubes (HNTs) represent a versatile core structure for the design of functional nanosystems of biomedical interest. However, the development of selective methodologies for the site-controlled functionalization of the nanotubes at specific sites is not an easy task. This study aims to accomplish a procedure for the site-selective/specific, "pin-point", functionalization of HNTs with polydopamine (HNTs@PDA). This goal was achieved, at pH 6.5, by exploiting the basicity of ZnO nanoparticles anchored on the HNTs external surface (HNTs@ZnO) to induce a punctual polydopamine polymerization and coating. The morphology and the chemical composition of the nanomaterial was demonstrated by several techniques. Turbidimetric analysis showed that PDA coating affected the aqueous stability of HNTs@PDA compared to both HNTs@ZnO and HNTs. Notably, hyperthermia studies revealed that the nanomaterial induced a local thermic rise, up to 50 °C, under near-infrared (NIR) irradiation. Furthermore, secondary functionalization of HNTs@PDA by selective grafting of biotin onto the PDA coating followed by avidin binding was also accomplished.

Smartphone-Assisted Sensing of Trinitrotoluene by Optical Array.

Here we report the design and fabrication of an array-based sensor, containing functionalized Carbon Dots, Bodipy's and Naphthalimide probes, that shows high fluorescence emissions and sensitivity in the presence of low amounts of TNT explosive. In particular, we have fabricated the first sensor device based on an optical array for the detection of TNT in real samples by using a smartphone as detector. The possibility to use a common smartphone as detector leads to a prototype that can be also used in a real-life field application. The key benefit lies in the possibility of even a nonspecialist operator in the field to simply collect and send data (photos) to the trained artificial intelligence server for rapid diagnosis but also directly to the bomb disposal unit for expert evaluation. This new array sensor contains seven different fluorescent probes that are able to interact via noncovalent interactions with TNT. The interaction of each probe with TNT has been tested in solution by fluorescence titrations. The solid device has been tested in terms of selectivity and linearity toward TNT concentration. Tests performed with other explosives and other nitrogen-based analytes demonstrate the high selectivity for TNT molecules, thus supporting the reliability of this sensor. In addition, TNT can be detected in the range of 98 ng∼985 µg, with a clear different response of each probe to the different amounts of TNT.

Ag/ZnO/PMMA Nanocomposites for Efficient Water Reuse.

This work attempts to produce photocatalytic surfaces for large-scale applications by depositing nanostructured coatings on polymeric substrates. ZnO/poly(methyl methacrylate) (PMMA) composites were prepared by low-temperature atomic layer deposition (ALD) of ZnO on PMMA substrates. In addition, to increase the photocatalytic and antibacterial activities of ZnO films, Ag nanoparticles were added on ZnO surfaces using plasma-enhanced ALD. The morphology, crystallinity, and chemical composition of the specimens were meticulously examined by scanning and transmission electron microscopies, energy-dispersive X-ray spectroscopy, and X-ray diffraction analyses. The noteworthy photocatalytic activity of the nanocomposites was proved by the degradation of the following organic pollutants in aqueous solution: methylene blue, paracetamol, and sodium lauryl sulfate. The antibacterial properties of the samples were tested using Escherichia coli as a model organism. Moreover, the possible toxic effects of the specimens were checked by biological tests. The present results unambiguously indicate the Ag/ZnO/PMMA nanocomposite as a powerful tool for an advanced wastewater treatment technology.

Chelating Surfaces for Native State Proteins Patterning: The Human Serum Albumin Case.

The paper reports a new "soft" surface functionalization strategy, based on a highly selective ion metal chelation process. The proposed stepwise methodology implies at first the construction of a monolayer of terpyridine-based thiol (Tpy), whose highly packed structuring has been followed in situ by using quartz crystal microbalance (QCM-D) measurements, showing that the monolayers consist of about 2.7 × 10(14) Tpy/cm(2). Then, the tridentate sites of the each Tpy moiety are employed to partially chelate divalent metal ions, providing an effective platform to anchoring proteins by completing the metal ion coordination with an available site on the protein of interest. We report the case study of the application of the process to the HSA immobilization onto various surfaces, including Tpy-Fe(II) and Tpy-Cu(II) complexes, as well as hydrophilic bare gold substrates and hydrophobic self-assembled Tpy-based monolayers. It is shown that the chelation interaction between Tpy-Cu(II) complexes and HSA produces the highest and most robust HSA immobilization, with an adsorbed mass at the steady state of ∼800 ng/cm(2), with respect to an average adsorption of ∼350 ng/cm(2) for the other surfaces. Furthermore, Cu(II)-chelated surfaces seem to promote a sort of protein "soft" landing, preventing the ubiquitous surface-induced major unfolding and transmitting an orientation information to the protein, owing to the highly specific symmetry coordination of the Tpy-Cu(II)-protein complex. Indeed, the interaction with a specific monoclonal antiboby (anti-HSA) indicated the lack of a significant protein denaturation, while a massive reorientation/denaturation process was found for all the remaining surfaces, including the Tpy-Fe(II) complex. Finally, the metal-ion-dependent HSA immobilization selectivity has been exploited to obtain micropatterned surfaces, based on the strikingly different strength of interaction and stability observed for Fe(II) and Cu(II) complexes.