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.

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.

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.

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.

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.

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.

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.

Choline Hydrogen Dicarboxylate Ionic Liquids by X-ray Scattering, Vibrational Spectroscopy and Molecular Dynamics: H-Fumarate and H-Maleate and Their Conformations.

We explore the structure of two ionic liquids based on the choline cation and the monoanion of the maleic acid. We consider two isomers of the anion (H-maleate, the cis-isomer and H-fumarate, the trans-isomer) having different physical chemical properties. H-maleate assumes a closed structure and forms a strong intramolecular hydrogen bond whereas H-fumarate has an open structure. X-ray diffraction, infrared and Raman spectroscopy and molecular dynamics have been used to provide a reliable picture of the interactions which characterize the structure of the fluids. All calculations indicate that the choline cation prefers to connect mainly to the carboxylate group through OH⋯O interactions in both the compounds and orient the charged head N(CH3)3+ toward the negative portion of the anion. However, the different structure of the two anions affects the distribution of the ionic components in the fluid. The trans conformation of H-fumarate allows further interactions between anions through COOH and CO2- groups whereas intramolecular hydrogen bonding in H-maleate prevents this association. Our theoretical findings have been validated by comparing them with experimental X-ray data and infrared and Raman spectra.

Excitonic Fine Structure in Emission of Linear Carbon Chains.

We studied monatomic linear carbon chains stabilized by gold nanoparticles attached to their ends and deposited on a solid substrate. We observe spectral features of straight chains containing from 8 to 24 atoms. Low-temperature PL spectra reveal characteristic triplet fine structures that repeat themselves for carbon chains of different lengths. The triplet is invariably composed of a sharp intense peak accompanied by two broader satellites situated 15 and 40 meV below the main peak. We interpret these resonances as an edge-state neutral exciton and positively and negatively charged trions, respectively. The time-resolved PL shows that the radiative lifetime of the observed quasiparticles is about 1 ns, and it increases with the increase of the length of the chain. At high temperatures a nonradiative exciton decay channel appears due to the thermal hopping of carriers between parallel carbon chains. Excitons in carbon chains possess large oscillator strengths and extremely low inhomogeneous broadenings.

Coupled hydroxyl and ether functionalisation in EAN derivatives: the effect of hydrogen bond donor/acceptor groups on the structural heterogeneity studied with X-ray diffractions and fixed charge/polarizable simulations.

We present a study by energy-dispersive X-ray diffraction of liquid 2-(2-hydroxyethoxy)ethan-1-ammonium nitrate, NH3CH2CH2(OCH2CH2OH)+NO3- (22HHEAN). This ionic liquid is derived from the parent ethylammonium nitrate (EAN) with an ether link in the chain and a hydroxyl group in the terminal position. The absence of peaks at low-q values in the experimental diffraction curve indicates that the added polar groups and the high conformational isomerism of the cations alter strongly the nanosegregation of the parent EAN liquid. Aggregation between ionic species may involve hydrogen bonding between cations and anions and a variety of intermolecular hydrogen bonds between cations. Diffraction patterns are compared with the results of molecular dynamics simulations with two different force fields: the fixed point charge force field (GAFF) with different charge scaling protocols and the polarizable AMOEBA force field. Most point charge models lead to the appearance of a quite evident low q-peak which decreases gradually, when the percentage and type of the scaling (uniform vs. non-uniform) are increased. In the polarisable model and in the model where only anion charges are scaled to 20%, instead, the pre-peak is absent in agreement with our experiments.

Microscopic Structural and Dynamic Features in Triphilic Room Temperature Ionic Liquids.

Here we report a thorough investigation of the microscopic and mesoscopic structural organization in a series of triphilic fluorinated room temperature ionic liquids, namely [1-alkyl,3-methylimidazolium][(trifluoromethanesulfonyl)(nonafluorobutylsulfonyl)imide], with alkyl = ethyl, butyl, octyl ([Cnmim][IM14], n = 2, 4, 8), based on the synergic exploitation of X-ray and Neutron Scattering and Molecular Dynamics simulations. This study reveals the strong complementarity between X-ray/neutron scattering in detecting the complex segregated morphology in these systems at mesoscopic spatial scales. The use of MD simulations delivering a very good agreement with experimental data allows us to gain a robust understanding of the segregated morphology. The structural scenario is completed with determination of dynamic properties accessing the diffusive behavior and a relaxation map is provided for [C2mim][IM14] and [C8mim][IM14], highlighting their natures as fragile glass formers.

Biologically friendly room temperature ionic liquids and nanomaterials for the development of innovative enzymatic biosensors: Part II.

A newly modified electrode based on glassy carbon (GC) has been prepared and characterized electrochemically for application in electroanalytical chemistry. In particular, a GC screen-printed electrode (SPE) has been modified with nanostructures, namely multi-walled carbon nanotubes (MWCNTs), and TiO2 nanoparticles, and combined with a new generation of eco-friendly room-temperature ionic liquids (RTILs). The green RTILs here used are suitable for the immobilization of enzymes on the electrode surface and, additionally, facilitate the kinetics of electron transfer due to their intrinsic electrical conductivity. Upon evaluation of these newly modified electrodes we found an improvement in terms of electrochemically active area (Aea) with respect to the electrodes we previously reported. The modified SPEs were then used as substrates for the construction of two enzymatic biosensors for analytical applications: the first is an enzymatic biosensor based on alcohol dehydrogenase (ADH) for the analysis of ethyl alcohol; the second biosensor is based on lipase enzyme and has been tested for the analysis and the classification of Extra Virgin Olive Oil (EVOO). The performances of the here projected sensors appear comparable with biosensors having similar finalities. It is here envisaged that such a kind of electrodes could represent the starting tool for the construction and the definition of new portable devices for screening and field analyses.

X-Ray structure and ionic conductivity studies of anhydrous and hydrated choline chloride and oxalic acid deep eutectic solvents.

In this study, we report the structural, thermodynamic and electrochemical properties of deep eutectic solvents (DESs) formed from choline chloride and oxalic acid in anhydrous and di-hydrated form in a 1 : 1 molar ratio. As far as we are aware, this is the first joint X-ray diffraction-molecular dynamics study focussed on analyzing the structural features of DESs.

New Experimental Evidences Regarding Conformational Equilibrium in Ammonium-Bis(trifluoromethanesulfonyl)imide Ionic Liquids.

The X-ray scattering patterns of the two ionic liquids, N-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl)imide (TMPA-TFSI) and N-trimethyl-N-hexylammonium bis(trifluoromethanesulfonyl)imide (TMHA-TFSI), sharing a common anion and differing in the length of the alkyl chain of the cation, were measured at room temperature. Molecular dynamics calculations supported the interpretation of the data. The two force-field models, GAFF and DLPOLY 4, were adopted to simulate the scattering patterns. Both of them are able to reproduce the main peaks of the experimental data; however, the DLPOLY model seems to better reproduce the finer details. Moreover, from the simulations, the concentration of the two conformers of TFSI are derived. The comparison with previously reported infrared spectroscopy measurements suggests that also under this aspect the DPOLY model has a better agreement with the experiments.

Communication: Anion-specific response of mesoscopic organization in ionic liquids upon pressurization.

One of the outstanding features of ionic liquids is their inherently hierarchical structural organization at mesoscopic spatial scales. Recently experimental and computational studies showed the fading of this feature when pressurising. Here we use simulations to show that this effect is not general: appropriate anion choice leads to an obstinate resistance against pressurization.

Choline-amino acid ionic liquids: past and recent achievements about the structure and properties of these really "green" chemicals.

The structure of choline-amino acid ionic liquids, atoxic task-specific solvents composed of materials originated from renewable feedstocks, is reviewed in this letter. The varied and strong interactions that these liquids are capable of establishing are largely dependent on their structure and confer them outstanding solvating properties with respect to a large number of different solutes. Among the experimental methods capable of yielding structural insight, the energy-dispersive version of X-Ray diffraction, that uses the Bremsstrahlung radiation of the X-Ray tube, is a technique very well suited to investigate these liquid systems. The diffraction spectra of five choline-amino acid ionic liquids, recently measured, are reported and discussed; in particular, the presence or absence of the medium-range order pre-peak is related to the presence of polar groups within the amino acid side chain that destroys the hydrophobic interactions between aliphatic chains. In the final section, a recent example of choline-amino acid ionic liquids as for ancient paper preservation and two other interesting results are discussed at the end.

Structure and dynamics of propylammonium nitrate-acetonitrile mixtures: An intricate multi-scale system probed with experimental and theoretical techniques.

In this article, we report the study of structural and dynamical properties for a series of acetonitrile/propylammonium nitrate mixtures as a function of their composition. These systems display an unusual increase in intensity in their X-ray diffraction patterns in the low-q regime, and their 1H-NMR diffusion-ordered NMR spectroscopy (DOSY) spectra display unusual diffusivities. However, the magnitude of both phenomena for mixtures of propylammonium nitrate is smaller than those observed for ethylammonium nitrate mixtures with the same cosolvent, suggesting that the cation alkyl tail plays an important role in these observations. The experimental X-ray scattering data are compared with the results of molecular dynamics simulations, including both ab initio studies used to interpret short-range interactions and classical simulations to describe longer range interactions. The higher level calculations highlight the presence of a strong hydrogen bond network within the ionic liquid, only slightly perturbed even at high acetonitrile concentration. These strong interactions lead to the symmetry breaking of the NO3- vibrations, with a splitting of about 88 cm-1 in the ν3 antisymmetric stretch. The classical force field simulations use a greater number of ion pairs, but are not capable of fully describing the longest range interactions, although they do successfully account for the observed concentration trend, and the analysis of the models confirms the nano-inhomogeneity of these kinds of samples.

Hydrogen Bonding Features in Cholinium-Based Protic Ionic Liquids from Molecular Dynamics Simulations.

We explore the structure of a series of protic Ionic Liquids based on the choline cation and amino acid anions. In the series, the length and the branching of the amino acid alkyl chain varies. Ab initio molecular dynamics, X-ray diffraction measurements, and infrared spectra have been used to provide a reliable picture of the short-range structure and of the short-time dynamic process that characterize the fluids. We have put special emphasis on the peculiar and complicated network of hydrogen bonds that stem from the amphoteric nature of the anion moiety. The use of ab initio molecular dynamics allows us to calculate the "exact" charge density of the system and hence to obtain fairly accurate infrared spectra that, in turn, have been used to assign the experimental ones.

Intriguing transport dynamics of ethylammonium nitrate-acetonitrile binary mixtures arising from nano-inhomogeneity.

Binary mixtures of ethylammonium nitrate and acetonitrile show interesting properties that originate from the structural and dynamical nano-heterogeneity present in ionic liquids. These effects are most pronounced when the ionic liquid is the minority compound. In this study the transport properties of such mixtures are studied, including viscosity, self-diffusion and conductivity. The results strongly support the presence of structural inhomogeneity and show an interesting composition-dependent behaviour in the mixtures.