Voronoi Tessellation as a Tool for Predicting the Formation of Deep Eutectic Solvents.

Deep eutectic solvents (DESs) have attracted increasing attention in recent years due to their broad applicability in different fields, but their computer-aided discovery, which avoids a time-consuming trial-and-error investigation, is still lagging. In this paper, a set of nine DESs, composed of choline chloride as a hydrogen-bond acceptor and nine functionalized phenols as hydrogen bond donors, is simulated by using classical molecular dynamics to investigate the possible formation of a DES. The tool of the Voronoi tessellation analysis is employed for producing an intuitive and straightforward representation of the degree of mixing between the different components of the solutions, therefore permitting the definition of a metric quantifying the propensity of the components to produce a uniform solution. The computational findings agree with the experimental results, thus confirming that the Voronoi tessellation analysis can act as a lightweight yet powerful approach for the high-throughput screening of mixtures in the optics of the new DES design.

Inulin-Coated ZnO Nanoparticles: A Correlation between Preparation and Properties for Biostimulation Purposes.

Within the framework of plant biostimulation, a pivotal role is played by the achievement of low-cost, easily prepared nanoparticles for priming purposes. Therefore, in this report, two different synthetic strategies are described to engineer zinc oxide nanoparticles with an inulin coating. In both protocols, i.e., two-step and gel-like one-pot protocols, nanoparticles with a highly pure ZnO kernel are obtained when the reaction is carried out at T ≥ 40 °C, as ascertained by XRD and ATR/FTIR studies. However, a uniformly dispersed, highly homogeneous coating is achieved primarily when different temperatures, i.e., 60 °C and 40 °C, are employed in the two phases of the step-wise synthesis. In addition, a different binding mechanism, i.e., complexation, occurs in this case. When the gel-like process is employed, a high degree of coverage by the fructan is attained, leading to micrometric coated aggregates of nanometric particles, as revealed by SEM investigations. All NPs from the two-step synthesis feature electronic bandgaps in the 3.25-3.30 eV range in line with previous studies, whereas the extensive coating causes a remarkable 0.4 eV decrease in the bandgap. Overall, the global analysis of the investigations indicates that the samples synthesized at 60 °C and 40 °C are the best suited for biostimulation. Proof-of-principle assays upon Vicia faba seed priming with Zn5 and Zn5@inu indicated an effective growth stimulation of seedlings at doses of 100 mgKg-1, with concomitant Zn accumulation in the leaves.

Seed Priming with Zinc Oxide Nanoparticles to Enhance Crop Tolerance to Environmental Stresses.

Drastic climate changes over the years have triggered environmental challenges for wild plants and crops due to fluctuating weather patterns worldwide. This has caused different types of stressors, responsible for a decrease in plant life and biological productivity, with consequent food shortages, especially in areas under threat of desertification. Nanotechnology-based approaches have great potential in mitigating environmental stressors, thus fostering a sustainable agriculture. Zinc oxide nanoparticles (ZnO NPs) have demonstrated to be biostimulants as well as remedies to both environmental and biotic stresses. Their administration in the early sowing stages, i.e., seed priming, proved to be effective in improving germination rate, seedling and plant growth and in ameliorating the indicators of plants' well-being. Seed nano-priming acts through several mechanisms such as enhanced nutrients uptake, improved antioxidant properties, ROS accumulation and lipid peroxidation. The target for seed priming by ZnO NPs is mostly crops of large consumption or staple food, in order to meet the increased needs of a growing population and the net drop of global crop frequency, due to climate changes and soil contaminations. The current review focuses on the most recent low-cost, low-sized ZnO NPs employed for seed nano-priming, to alleviate abiotic and biotic stresses, mitigate the negative effects of improper storage and biostimulate plants' growth and well-being. Taking into account that there is large variability among ZnO NPs and that their chemico-physical properties may play a role in determining the efficacy of nano-priming, for all examined cases, it is reported whether the ZnO NPs are commercial or lab prepared. In the latter cases, the preparation conditions are described, along with structural and morphological characterizations. Under these premises, future perspectives and challenges are discussed in relation to structural properties and the possibility of ZnO NPs engineering.

The Addition of Co into CuO-ZnO Oxides Triggers High Antibacterial Activity and Low Cytotoxicity.

In the present work, a simple two-step method is proposed for mixed oxide synthesis aimed at the achievement of antibacterial nanomaterials. In particular, Cu, Zn and Co have been selected to achieve single-, double- and triple-cation oxides. The synthesized samples are characterized by XRD, IR, SEM and EDX, indicating the formation of either crystalline or amorphous hydrocarbonate precursors. The oxides present one or two crystalline phases, depending on their composition; the triple-cation oxides form a solid solution of tenorite. Also, the morphology of the samples varies with the composition, yielding nanoparticles, filaments and hydrangea-like microaggregates. The antibacterial assays are conducted against E. coli and indicate an enhanced efficacy, especially displayed by the oxide containing 3% Co and 9% Zn incorporated into the CuO lattice. The oxides with the highest antibacterial properties are tested for their cytotoxicity, indicating a low toxicity impact, in line with literature data.

CuO Nanoparticles and Microaggregates: An Experimental and Computational Study of Structure and Electronic Properties.

The link between morphology and properties is well-established in the nanoparticle literature. In this report, we show that different approaches in the synthesis of copper oxide can lead to nanoparticles (NPs) of different size and morphology. The structure and properties of the synthesized NPs are investigated with powder X-ray diffraction, scanning electron microscopy (SEM), and diffuse reflectance spectroscopy (DRS). Through detailed SEM analyses, we were able to correlate the synthetic pathways with the particles' shape and aggregation, pointing out that bare hydrothermal pathways yield mainly spheroidal dandelion-like aggregates, whereas, if surfactants are added, the growth of the nanostructures along a preferential direction is promoted. The effect of the morphology on the electronic properties was evaluated through DRS, which allowed us to obtain the electron bandgap in every system synthesized, and to find that the rearrangement of threaded particles into more compact structures leads to a reduction in the energy difference. The latter result was compared with Density Functional Theory (DFT) computational models of small centrosymmetric CuO clusters, cut from the tenorite crystal structure. The computed UV-Vis absorption spectra obtained from the clusters are in good agreement with experimental findings.

Syntheses of APTMS-Coated ZnO: An Investigation towards Penconazole Detection.

Extrinsic chemiluminescence can be an efficient tool for determining pesticides and fungicides, which do not possess any intrinsic fluorescent signal. On this basis, (3-aminopropyl) trimethoxysilane (APTMS)-coated ZnO (APTMS@ZnO) was synthesized and tested as an extrinsic probe for the fungicide penconazole. Several synthetic routes were probed using either a one-pot or two-steps method, in order to ensure both a green synthetic pathway and a good signal variation for the penconazole concentration. The synthesized samples were characterized using X-ray diffraction (XRD), infrared (IR), Raman and ultraviolet-visible (UV-Vis) spectroscopy, scanning electron microscopy (SEM) imaging and associated energy-dispersive X-ray (EDX) analysis. The average size of the synthesized ZnO nanoparticles (NPs) is 54 ± 10 nm, in line with previous preparations. Of all the samples, those synthesized in two steps, at temperatures ranging from room temperature (RT) to a maximum of 40 °C, using water solvent (G-APTMG@ZnO), appeared to be composed of nanoparticles, homogeneously coated with APTMS. Chemiluminescence tests of G-APTMG@ZnO, in the penconazole concentration range 0.7-1.7 ppm resulted in a quenching of the native signal between 6% and 19% with a good linear response, thus indicating a green pathway for detecting the contaminant. The estimated detection limit (LOD) is 0.1 ± 0.01 ppm.

Influence of Cortisol on the Fibril Formation Kinetics of Aß42 Peptide: A Multi-Technical Approach.

Amyloid-ß peptide (Aß) aggregates are known to be correlated with pathological neurodegenerative diseases. The fibril formation process of such peptides in solution is influenced by several factors, such as the ionic strength of the buffer, concentration, pH, and presence of other molecules, just to mention a few. In this paper, we report a detailed analysis of in vitro Aß42 fibril formation in the presence of cortisol at different relative concentrations. The thioflavin T fluorescence assay allowed us to monitor the fibril formation kinetics, while a morphological characterization of the aggregates was obtained by atomic force microscopy. Moreover, infrared absorption spectroscopy was exploited to investigate the secondary structure changes along the fibril formation path. Molecular dynamics calculations allowed us to understand the intermolecular interactions with cortisol. The combined results demonstrated the influence of cortisol on the fibril formation process: indeed, at cortisol-Aß42 concentration ratio (ρ) close to 0.1 a faster organization of Aß42 fragments into fibrils is promoted, while for ρ = 1 the formation of fibrils is completely inhibited.

"For Asia Market Only": A Green Tattoo Ink between Safety and Regulations.

Due to the increasing tattoo practicing in Eastern countries and general concern on tattoo ink composition and safety, the green tattoo inks Green Concentrate by Eternal, for European and "for Asia Market Only" were analyzed, under the premise that only the former falls under a composition regulation. A separation of the additives from the pigment was carried out by successive extraction in solvents of different polarities, i.e., water, acetone and dichloromethane. The solid residues were analyzed by IR and Raman spectroscopies, the liquid fractions by GC/mass spectrometry. The relative pigment load and element traces were also estimated. We found that the European and the Asian inks are based on the same pigment, PG7, restricted in Europe, though at different loads. They have a similar content of harmful impurities, such as Ni, As, Cd and Sb and both contain siloxanes, including harmful D4. Furthermore, they have different physical-chemical properties, the European ink being more hydrophilic, the Asian more hydrophobic. Additionally, the Asian ink contains harmful additives for the solubilization of hydrophobic matrices and by-products of the phthalocyanine synthesis. Teratogenic phthalates are present as well as chlorinated teratogenic and carcinogenic compounds usually associated to the laser treatment for removal purposes, to a larger extent in the European ink. The composition of the inks does not seem to reflect regulatory restrictions, where issued.

Recent Advances in the Synthesis of Inorganic Materials Using Environmentally Friendly Media.

Deep Eutectic Solvents have gained a lot of attention in the last few years because of their vast applicability in a large number of technological processes, the simplicity of their preparation and their high biocompatibility and harmlessness. One of the fields where DES prove to be particularly valuable is the synthesis and modification of inorganic materials-in particular, nanoparticles. In this field, the inherent structural inhomogeneity of DES results in a marked templating effect, which has led to an increasing number of studies focusing on exploiting these new reaction media to prepare nanomaterials. This review aims to provide a summary of the numerous and most recent achievements made in this area, reporting several examples of the newest mixtures obtained by mixing molecules originating from natural feedstocks, as well as linking them to the more consolidated methods that use "classical" DES, such as reline.

Comparative treatments of a green tattoo ink with Ruby, Nd:YAG nano- and picosecond lasers in normal and array mode.

The tattoos removal has become an issue upon spread of the tattooing practice worldwide and hindsight regrets. Lasers are typically used for the purpose, though some colours such as green are considered "recalcitrant" to the treatment. In the current investigation, we aim at determining the efficacy of removal of a green ink water dispersion, using 5 laser treatments: Nd:YAG nano- and picosecond lasers in normal and array mode and Ruby nanosecond laser, keeping the total irradiated energy constant. The UV-Vis spectroscopy of the treated samples indicate that Nd:YAG picosecond laser is most effective, and the Ruby nanosecond laser is the least efficient. Fragment compounds generated from the pigment and siloxanes are common to all treatments, whereas hydrocarbon emerge by a larger amount upon Nd:YAG nanosecond treatment. Fibres are formed upon picosecond treatments and when operating in array mode, and lamellae are achieved by Ruby nanosecond laser treatment. Residual particles suspensions are very heterogeneous upon nanosecond treatments.

Novel Thienyl DPP derivatives Functionalized with Terminal Electron-Acceptor Groups: Synthesis, Optical Properties and OFET Performance.

Three novel diketopyrrolopyrrole (DPP) based small molecules have been synthesized and characterized in terms of their chemical-physical, electrochemical and electrical properties. All the molecules consist of a central DPP electron acceptor core symmetrically functionalized with donor bi-thienyl moieties and flanked in the terminal positions by three different auxiliary electron-acceptor groups. This kind of molecular structure, characterized by an alternation of electron acceptor and donor groups, was purposely designed to provide a significant absorption at the longer wavelengths of the visible spectrum: when analysed as thin films, in fact, the dyes absorb well over 800 nm and exhibit a narrow optical bandgap down to 1.28 eV. A detailed DFT analysis provides useful information on the electronic structure of the dyes and on the features of the main optical transitions. Organic field-effect transistors (OFETs) have been fabricated by depositing the DPP dyes as active layers from solution: the different end-functionalization of the dyes had an effect on the charge-transport properties with two of the dyes acting as n-type semiconductors (electron mobility up to 4.4 ⋅ 10-2  cm2 /V ⋅ s) and the third one as a p-type semiconductor (hole mobility up to 2.3 ⋅ 10-3  cm2 /V ⋅ s). Interestingly, well-balanced ambipolar transistors were achieved by blending the most performant n-type and p-type dyes with hole and electron mobility in the order of 10-3  cm2 /V ⋅ s.

Functionalization of Gold Nanoparticles with Ru-Porphyrin and Their Selectivity in the Oligomerization of Alkynes.

Gold nanoparticles (AuNPs) were functionalized by ruthenium porphyrins through a sulfur/gold covalent bond using a three-steps reaction. The catalyst was characterized by scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) in order to control the binding of ruthenium porphyrin on AuNPs' surface. The catalyst was tested and compared with an analog system not bound to AuNPs in the oligomerization reaction using 1-phenylacetylene as the substrate.

Critical Assessment of the Sustainability of Deep Eutectic Solvents: A Case Study on Six Choline Chloride-Based Mixtures.

An outline of the advantages, in terms of sustainability, of Deep Eutectic Solvents (DESs) is provided, by analyzing some of the most popular DESs, obtained by the combination of choline chloride, as a hydrogen bond acceptor, and six hydrogen bond donors. The analysis is articulated into four main issues related to sustainability, which are recurrently mentioned in the literature, but are often taken for granted without any further critical elaboration, as the prominent green features of DESs: their low toxicity, good biodegradability, renewable sourcing, and low cost. This contribution is intended to provide a more tangible, evidence-based evaluation of the actual green credentials of the considered DESs, to reinforce or question their supposed sustainability, also in mutual comparison with one another.

Colorimetric Detection of Chromium(VI) Ions in Water Using Unfolded-Fullerene Carbon Nanoparticles.

Water pollution caused by hexavalent chromium (Cr(VI)) ions represents a serious hazard for human health due to the high systemic toxicity and carcinogenic nature of this metal species. The optical sensing of Cr(VI) through specifically engineered nanomaterials has recently emerged as a versatile strategy for the application to easy-to-use and cheap monitoring devices. In this study, a one-pot oxidative method was developed for the cage opening of C60 fullerene and the synthesis of stable suspensions of N-doped carbon dots in water-THF solutions (N-CDs-W-THF). The N-CDs-W-THF selectively showed variations of optical absorbance in the presence of Cr(VI) ions in water through the arising of a distinct absorption band peaking at 550 nm, i.e., in the transparency region of pristine material. Absorbance increased linearly, with the ion concentration in the range 1-100 µM, thus enabling visual and ratiometric determination with a limit of detection (LOD) of 300 nM. Selectivity and possible interference effects were tested over the 11 other most common heavy metal ions. The sensing process occurred without the need for any other reactant or treatment at neutral pH and within 1 min after the addition of chromium ions, both in deionized and in real water samples.

Detection of Heavy Metals in Water Using Graphene Oxide Quantum Dots: An Experimental and Theoretical Study.

In this work, we investigate by ab initio calculations and optical experiments the sensitivity of graphene quantum dots in their use as devices to measure the presence, and concentration, of heavy metals in water. We demonstrate that the quenching or enhancement in the optical response (absorption, emission) depends on the metallic ion considered. In particular, two cases of opposite behaviour are considered in detail: Cd2+, where we observe an increase in the emission optical response for increasing concentration, and Pb2+ whose emission spectra, vice versa, are quenched along the concentration rise. The experimental trends reported comply nicely with the different hydration patterns suggested by the models that are also capable of reproducing the minor quenching/enhancing effects observed in other ions. We envisage that quantum dots of graphene may be routinely used as cheap detectors to measure the degree of poisoning ions in water.

Top-Down N-Doped Carbon Quantum Dots for Multiple Purposes: Heavy Metal Detection and Intracellular Fluorescence.

In the present study, we successfully synthesized N-doped carbon quantum dots (N-CQDs) using a top-down approach, i.e., hydroxyl radical opening of fullerene with hydrogen peroxide, in basic ambient using ammonia for two different reaction times. The ensuing characterization via dynamic light scattering, SEM, and IR spectroscopy revealed a size control that was dependent on the reaction time, as well as a more pronounced -NH2 functionalization. The N-CQDs were probed for metal ion detection in aqueous solutions and during bioimaging and displayed a Cr3+ and Cu2+ selectivity shift at a higher degree of -NH2 functionalization, as well as HEK-293 cell nuclei marking.

Laser vs. thermal treatments of green pigment PG36: coincidence and toxicity of processes.

Comparative laser and thermal treatments were carried out on PG36, a green phthalocyanine-based pigment, permitted in European countries where legislation on tattoo composition was issued. Prior to the treatments, PG36 was characterized by SEM imaging, EDX, IR and UV-Vis spectroscopies, revealing an excess of Si and C and O as compared to the pure halogenated Cu-phthalocyanine. Laser treatments were carried out with a Nd:YAG device applied to H2O and propan-2-ol dispersions. Pyrolysis and calcinations were carried out in air or under N2 flow. The outcome of the different procedures was analyzed by UV-Vis spectroscopy, GC-mass spectrometry, X-ray diffraction of the solid residues, SEM microscopy and dynamic light scattering. The comparative analysis indicated the production of different fragment compounds depending on the treatment, (pyrolysis or laser), and, to some extent, to the solvent of the dispersion, with pyrolysis generating a larger number of hazardous compounds. Hydrocarbons and cyclic siloxanes present as additives in PG36 were stable or degraded depending on the treatment. The morphology of the products is also treatment-dependent with nanoparticles < 20 nm and fibers being produced upon laser treatments only. Based on the experimental findings, the equivalence of laser and thermal treatments is evaluated.

Treatments of a phthalocyanine-based green ink for tattoo removal purposes: generation of toxic fragments and potentially harmful morphologies.

Since tattoos became overwhelmingly fashionable worldwide, the demand for removal has proportionally increased, Nd:YAG Q-switch laser being the most commonly used tool for the purpose. In this framework we investigated the composition and products of laser treatment of green tattoo ink, the Green Concentrate from Eternal. The ink characterization has been carried out by IR, UV-Vis, EDX spectroscopies, and SEM imaging. It revealed the presence of the pigment PG7, rather than PG36 as reported on the bottle label, along with non-fully halogenated analogues. The morphology is an extended sheath with embedded grains. Subsequent laser treatments were performed on both dried and extracted inks, dispersed either in water or in propan-2-ol, chosen for their different polarities, as it is the case in the skin layers. The products were analyzed by gas chromatography-mass spectrometry, UV-Vis spectroscopy, SEM imaging, and dynamic light scattering. The outcome is a complex fragmentation pattern that depends both on the solvent and on the initial aggregation state. The fragment compounds are toxic at various degrees according to the Classification Labelling and Packaging regulations. Several shapes of aggregates are produced as an effect of both downsizing and re-aggregation, with potentially harmful aspect ratios.

NiO Grained-Flowers and Nanoparticles for Ethanol Sensing.

Grained-flower and nanoparticles NiO samples were synthesized with a straightforward, surfactant-free hydrothermal procedure, and probed with respect to ethanol gas-sensing. Both morphologies displayed excellent performances in terms of gas response vs. temperature and concentration and are very reproducible. The grained-flower, however, performed better than the nanoparticles NiO, probably due to the shorter travelling distance of the electrons and/or adsorbates during the detection process. Both sensors displayed high stability over three weeks. The grained-flower NiO sensor also has a good selectivity.

NiO Pseudocapacitance and Optical Properties: Does The Shape Win?

In the present paper, we investigate the effects of alkali and operational temperature on NiO capacitive and optical properties. The NiO samples were prepared by a straightforward, surfactant-free hydrothermal synthesis, employing Ni(NO3)2 and either urea or moderately sterically hindered triethylamine (TEA). The syntheses were followed by calcinations at either 400 or 600 °C. NiO samples were characterized by XRD, scanning electron microscopy, and nitrogen adsorption isotherms. The optical properties were investigated by reflectance spectroscopy, and the pseudocapacitance was studied by cyclic voltammetry and galvanostatic charge charge-discharge measurements. We found that the synthesis with TEA yielded nanoflowers whereas the morphology of the synthesis with urea varied with the calcination temperature and resulted in nanoparticles or nanoslices at calcination temperatures of 400 and 600 °C, respectively. The NiO samples prepared at a lower temperature displayed a favorable combination of surface area and porosity that allowed for high performance with capacitances of 502 and 520 F g-1 at a current density of 1 A g-1 for nanoflowers and nanoparticles, respectively. The band gaps of all the samples were compatible with the estimated nanoparticle sizes. Finally, we used the synthesized NiO samples for the preparation of screen-printed electrodes (SPEs) modified by drop-casting and probed them against a [Fe(CN)6]3-/4- probe.