Polar Aprotic Solvents Research Articles

Low-temperature mineralization of perfluorocarboxylic acids.

Per- and polyfluoroalkyl substances (PFAS) are persistent, bioaccumulative pollutants found in water resources at concentrations harmful to human health. Whereas current PFAS destruction strategies use nonselective destruction mechanisms, we found that perfluoroalkyl carboxylic acids (PFCAs) could be mineralized through a sodium hydroxide-mediated defluorination pathway. PFCA decarboxylation in polar aprotic solvents produced reactive perfluoroalkyl ion intermediates that degraded to fluoride ions (78 to ~100%) within 24 hours. The carbon-containing intermediates and products were inconsistent with oft-proposed one-carbon-chain shortening mechanisms, and we instead computationally identified pathways consistent with many experiments. Degradation was also observed for branched perfluoroalkyl ether carboxylic acids and might be extended to degrade other PFAS classes as methods to activate their polar headgroups are identified.

Cosolvent effect on morphogenic changes of self-assembled aggregates from biodegradable polylactones

The solvent variation effect on the self-assembly phenomenon is discussed in this article. Two different biodegradable backbones of the same community (polycaprolactone and polylactide) were selected to visualize the morphological changes upon treatment of different solvents/cosolvents. The curiosity was to observe if the change occurred only with the solvents or it was assisted to the backbones also. Tetrahydrofuran, acetonitrile and 1,4 dioxane were used as polar aprotic solvent whereas, methanol was used as polar protic one with the common solvent water in each case. The macromolecular aggregates were formed using the solvent mixture and their morphological or conformational changes were monitored using different conventional techniques such as Dynamic Light Scattering (DLS), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and cryo-Transmission Electron Microscopy (cryo-TEM).The spontaneously formed superstructures were thoroughly characterized and well documented here. The hierarchical aggregates disclosed here bears the potential of vast usage in the field of nanotechnology.

Effect of additives on hydrogen release reactivity of magnesium hydride composites

Magnesium hydride, a compound potentially applicable as a hydrogen carrier and energy storage material, releases hydrogen via hydrolysis or thermolysis.Ball-milled MgH2 composites were studied to optimize the kinetics and yield of the dehydriding process. Milling MgH2, under inert atmosphere increased the susceptibility to oxidation: the amount of MgO produced following air exposure of pulverized MgH2 was found to be proportional to the milling duration.Incorporation of protective coatings to avoid undesirable oxidation was studied: addition of anionic surfactants or expanded graphite as milling aids reduces the susceptibility of MgH2 to oxidation, presumably via formation of a protective layer. Such coatings minimize the access of oxygen to the particle surface upon exposure to air and facilitate manipulations, such as performing analysis, under ambient atmosphere.Improved dehydriding efficiency of oxidation-protected milled composites was demonstrated.Hydrolysis of pristine magnesium hydride and MgH2-composites with aqueous hydrolysates containing aprotic polar solvents demonstrated a significant increase of dehydriding efficiency.

Bistable colloidal orientation near a charged surface

Anisotropic particles oriented in a specific direction can act as artificial atoms and molecules, and their controlled assembly can result in a wide variety of ordered structures. Towards this, we demonstrate the orientation transitions of uncharged peanut-shaped polystyrene colloids, suspended in a non-ionic aprotic polar solvent, near a flat surface whose potential is static or time-varying. The charged surface is coated with an insulating dielectric layer to suppress electric currents. The transition between several orientation states such as random, normal or parallel orientation with respect to the surface, is examined for two different colloid sizes at low-frequency ( ~ 10 − 350 kHz) or static fields, and at small electric potentials. In time-varying (AC) field, a detailed phase diagram in the potential-frequency plane indicating the transition between particles parallel or normal to the surface is reported. We next present the first study of orientation switching in static (DC) fields, where no electro-osmotic or other flow is present. A reversible change between the two colloidal states is explained by a theory showing that the sum of electrostatic and gravitational energies of the colloid is bistable. The number of colloids in each of the two states depends on the external potential, particle and solvent permittivities, particle aspect ratio, and distance from the electrode.

Synthesis of dimethyl‐ and diphenylsilane‐based oligo(azine)s: Thermal, optical, electronic, and morphological properties

AbstractFour new oligo(azine)s were synthesized from dimethyldiphenylsilane and tetraphenylsilane core‐based dialdehydes and hydrazine by high‐temperature polycondesation and proposed as materials for optoelectronic applications. The oligo(azine)s were characterized by EA, FT‐IR, and NMR. Although most of samples were poorly soluble, TPS‐containing PAZ‐4 was soluble in aprotic polar solvents. According to SEC and FT‐IR studies, the samples were oligomers with up to five repeating units long. TGA showed highly stable samples with TDT10% over 420°C except for PAZ‐1 that contains a DMS core along with phenyl units, and thus, the lowest carbon content in the series. From DSC analysis, the substitution of phenyl groups in PAZ‐1/3 by biphenyl moieties in PAZ‐2/4 allowed to obtain oligo(azine)s with lower Tg values. PAZ‐4 showed a UV‐A absorption with optical band‐gap values of 2.91 and 2.65 eV from UV–vis (solution) and DRS (films), respectively. PL analysis showed a violet emission. PAZ‐4 showed resistivity of 29.24 Ω cm, similar to wide‐band gap materials. Their contact angle measurements showed a critical surface tension of 42.29 dynes/cm, revealing its hydrophobicity. AFM analysis indicated that the PAZ‐4 films had homogeneous surfaces. Young's modulus close to 4.46 GPa was established by microindentation for the PAZ‐4 thin‐films.

Aprotic Solvent Accumulation Amplifies Ion Current Rectification in Conical Nanopores.

Ion current rectification is highly reported in aqueous electrochemical systems and sensors but lacks exploration in organic systems due to the additional complexity introduced by non-aqueous solvents. Herein, a detailed study on ion current rectification with highly polar and mildly polar aprotic organic solvents as a function of tetraethylammonium tetrafluoroborate supporting electrolyte concentration is presented. To explain our experimental results, we introduce a previously unreported phenomenon: the formation of a double-junction diode within the nanopore that arises due to a complex interplay between ion and solvent enrichment effects. Finite element simulations are used to explore this phenomenon and the subsequent effect on the rectifying behavior of conical quartz nanopores.

Copper(II) Ion Promoted Reverse Solvatochromic Response of the Silatrane Probe to Spectral Shifts: Preferential Solvation and Computational Approach.

The unique solvatochromic attitude of an analyte owing to its coordination with metal ions in solvents of different polarities is challenging. Herein, we introduce two new solvatochromic 4-(pentan-3-yl) benzaldehyde-based triazolyl silatrane probes (5 and 6). The solvatochromic behavior of both probes 5 and 6 was studied using Reichardt's E (30) and the Kamlet-Taft empirical scale by UV-visible spectra in 14 solvents (hydrogen-bond donor (HBD) and non-HBD), and the results show that probes 5 and 6 exhibit reverse solvatochromism. Probe 5 witnessed an enhancement in this behavior upon coordination with the Cu2+ ion in MeCN/MeOH solvents due to the intramolecular charge transfer (ICT) process. Interestingly, the binding of probe 5 with Cu2+ ions resulted in an instant color change in MeCN and MeOH from pale yellow to light blue and brown-red, respectively, which can be easily detected by the "naked eye". A solvatochromic study of the complex 5-Cu2+ in binary mixtures of polar aprotic and polar protic solvents (MeCN/MeOH) discloses that the latter are more preferred over polar aprotic solvents in the solvation microsphere. The entire metal coordination process of probe 5 toward the Cu2+ ion can be visualized and was further evaluated by UV-vis/fluorescence spectral titrations, Fourier transform infrared (FT-IR) spectroscopy, and theoretical calculations employing density functional theory (DFT) and time-dependent-DFT (TD-DFT). The proposed analytical approach is believed to play a crucial role in the solvatochromic study of higher coordinated silicon compounds, which may be utilized to develop a solvent-dependent sensor.

Solvent effect investigation on the acid-catalyzed esterification of levulinic acid by ethanol aided by a Linear Solvation Energy Relationship

When processing lignocellulosic biomass materials to obtain platform molecules such as levulinic acid (LA), alkyl levulinates or γ-valerolactone (GVL), the choice of solvent is of prime importance for kinetics. The knowledge of relationships between reaction kinetics and solvent serves as a decision tool for process design. To determine such relationships, esterification reactions was chosen because such reaction steps are present in several biomass conversion processes. In this work, kinetic models of LA esterification by ethanol over sulfuric acid in polar aprotic solvent (GVL) and polar protic solvents (water or ethanol) were developed and evaluated by Bayesian statistics. The apparent dissociation constants in solvents were estimated by ePC-SAFT approach to distinguish the proton concentration from the rate constants. The developed models can fit the experimental concentrations of ethyl levulinate and predict the proton concentration. Using the Kalmet-Abboud-Taft equation, linear relationships between estimated rate constants and solvent properties were established at different temperatures. We observed that solvents with low polarizability and high hydrogen-bond acceptor capacity should be favored for this reaction. Hence, the reaction of esterification is faster in ethanol solvent than in GVL solvent than in water solvent.

SOLVATOCHROMISM OF THE FREE BASE CORROLES

For two free base corroles with different architecture of peripheral substitution, the solvatochromic shifts of absorption bands in a series of solvents of different nature are herein determined, and the nature of the solvatochromic effects is analyzed by the Valentine method. It is found that the solvatochromism of the free bases of corroles originates due to universal nonspecific interactions, and the short-wavelength T2 tautomer experiences stronger solvation. It is shown that in polar aprotic solvents (acetone, acetonitrile, dimethylformamide,
 and dimethylsulfoxide), specific acid-base interactions occur simultaneously, leading to the formation of the deprotonated form. It is found that both deprotonated and protonated forms of corroles also show nonspecific solvation, leading to solvatochromic shifts, the magnitude of which exceeds that for free base corroles. It is proposed that this feature is due to an excess (negative or positive) electronic charge of the macrocycle.

Molecular structure, electronic properties, ESP map (polar aprotic and polar protic solvents), and topology investigations on 1-(tert‑Butoxycarbonyl)-3-piperidinecarboxylic acid- Anticancer therapeutic agent

The theoretical elucidation of 1-(tert‑Butoxycarbonyl)-3-piperidinecarboxylic acid (1TB3PC) was achieved in this work by using DFT/6–311++G(d,p) as the basis set level -B3LYP approach for the gas phase, polar aprotic, and protic solvents phases, respectively. Potential energy scan (PES) analysis and the optimized geometrical parameters for the gas, polar aprotic and polar protic solvent phases were attained and corresponding parameters were compared with the closely related molecule. The FMO's molecular orbitals (HOMO-LUMO) and the energy gap, FLU indices, and molecular electrostatic potential map (ESP) surface were carried out to predict the nucleophilic and electrophilic regions for the three phases (gas, polar aprotic, and polar protic solvents) were discussed. Further, the electron-hole distribution for the excited states and topological analyses (AIM, ELF, LOL and RDG) were also deliberated. To discern the biological activity of the title compound, drug likeness and ADMET predictions were carried out. Molecular docking approach was performed against ligand with various AKT /Protein Kinase B inhibitors targets and their corresponding parameters were conferred. Thus, the header composite designates as an alternative anticancer therapeutic agent.

Cleavable epoxy networks using azomethine-bearing amine hardeners

This work is a proof-of-concept of the use of azomethine-bearing diamines as novel hardeners of standard epoxy compounds to yield cleavable and thermoformable covalent adaptable networks (CANs), with functional properties otherwise comparable to conventional epoxy networks. A suitable aromatic diamine (TPA-o-PD) was synthesised at acceptable purity for the intended use and successfully reacted with DGEBA. The resulting azomethine-bearing cured epoxy networks exhibited glass transition temperature values and a thermal stability profile similar to conventional epoxy network counterparts. In contrast to their conventional counterparts however, the azomethine-bearing networks were shown to dissolve in mixtures of chloroform and methanesulfonic acid, due to acid hydrolysis of at least some of the azomethine bonds of the network. The resulting recyclate material after evaporating the solvent was consistent with the profile of a thermoplastic polymer of high molecular weight, suggesting limited depolymerisation/network cleavage during dissolution in the chloroform/methanesulfonic acid mixture. The recyclates were soluble in polar aprotic solvents and showed good thermal stability, high Tg and molecular weight values, consistent with the attributes of engineering thermoplastics. Lastly, the cured networks were shown to be thermoformable at 200 °C, yielding self-standing films with only minor reduction of properties.

What Nanomaterials Can Do for Energy Storage: Production of Charged, Individualised Nanomaterials (CINs) As Novel Materials for Electrochemical Energy Storage Devices

Electrochemical energy storage devices, such as batteries and supercapacitors, allow us to store electrical energy as chemical energy. They are a vital component of the UK’s plans to achieve net-zero carbon emissions by 2050.1 Nanomaterials offer properties such as short ion diffusion distances, high percolation to form conductive networks, and structural frameworks that can withstand mechanical stresses from successive volume expansion-contraction cycles on insertion-deinsertion of guest ions. Thanks to these properties, incorporation of nanomaterials into electrochemical energy storage devices could allow them to store more energy, last longer, and cope with the load cycles required for grid storage.2 However, the use of nanomaterials in commercial devices is limited by their low density and tendency to agglomerate. In addition, established synthesis methods such as high energy sonication and Hummer’s method yield nanomaterials with properties that fall short of those predicted theoretically, by resulting in a distribution of few-layer materials, and introducing defects that might not benefit electrochemical performance.This work uses highly reducing solutions, such as alkali metal-ammonia solutions or sodium naphthalide solutions, and subsequent spontaneous dissolution in polar aprotic solvents, to individualise nanomaterials and introduce negative charge to the surface in a single step (Figure 1).3,4 This produces exclusively monolayer, pristine, negatively-charged, individualised nanomaterials (CINs). This synthesis route can be applied to a wide range of materials, such as layered materials like graphite and transition metal dichalcogenides, as well as carbon nanotubes and other carbonaceous materials. The negative charge introduced can be used in subsequent synthesis steps to add functionality, grow nanoparticles, and control assembly into 3D structure. Using starting materials such as graphite, carbon nanotubes, and phosphorus,5 this work presents the application of these methods to investigate what new materials can be made. Furthermore, their electrochemical performance in batteries and supercapacitors is discussed. References 1HM Government, Dep. Business, Energy Ind. Strateg., 2020, 1–38. 2E. Pomerantseva, F. Bonaccorso, X. Feng, Y. Cui, Y. Gogotsi, Science, 2019, 366, 969. 3P. L. Cullen, K. M. Cox, M. K. Bin Subhan, L. Picco, O. D. Payton, D. J. Buckley, T. S. Miller, S. A. Hodge, N. T. Skipper, V. Tileli, C. A. Howard, Nat. Chem., 2017, 9, 244–249. 4A. Clancy, J. Melbourne, M. S. P. Shaffer, J. Mater. Chem. A, 2015, 3, 16708–16715. 5M. C. Watts, L. Picco, F. S. Russell-Pavier, P. L. Cullen, T. S. Miller, S. P. Bartus, O. D. Payton, N. T. Skipper, V. Tileli, C. A. Howard, Nature, 2019, 568, 216–220. Figure 1

New insights into the Van Krevelen diagram: Automated molecular formula determination from HRMS for a large chemical profiling of lichen extracts.

In recent years, LC-MS has become the golden standard for metabolomic studies. Indeed, LC is relatively easy to couple with the soft electrospray ionization. As a consequence, many tools have been developed for the structural annotation of tandem mass spectra. However, it is sometimes difficult to do data-dependent acquisition (DDA), especially when developing new methods that stray from the classical LC-MS workflow. An old tool from petroleomics that has recently gained popularity in metabolomics, the Van Krevelen diagram, is adapted for an overview of the molecular diversity profile in lichens through high-resolution mass spectrometry (HRMS). A new method is benchmarked against the state-of-the-art classification tool ClassyFire using a database containing most known lichen metabolites (n ≈2,000). Four lichens known for their contrasted chemical composition were selected, and extractions with apolar, aprotic polar, and protic polar solvents were performed to cover a wide range of polarities. Extracts were analyzed with direct infusion electrospray ionization mass spectrometry (DI-ESI-MS) and atmospheric solids analysis probe mass spectrometry (ASAP-MS) techniques to be compared with the chemical composition described in the literature. The most common lichen metabolites were efficiently classified, with more than 90% of the molecules in some classes being matched with ClassyFire. Results from this method are consistent with the various extraction protocols in the present case study. This approach is a rapid and efficient tool to gain structural insight regarding lichen metabolites analyzed by HRMS without relying on DDA by LC-MS/MS analysis. It may notably be of use during the development phase of novel MS-based metabolomic approaches.

An efficient p‐TSA catalyzed synthesis of some new substituted‐(5‐hydroxy‐3‐phenylisoxazol‐4‐yl)‐1,3‐dimethyl‐1H‐chromeno[2,3‐d]pyrimidine‐2,4(3H,5H)‐dione/3,3‐dimethyl‐2H‐xanthen‐1(9H)‐one scaffolds and evaluation of their pharmacological and computational investigations

We have developed an easy and efficient protocol for the synthesis of a series of some novel substituted-(5-hydroxy-3-phenylisoxazol-4-yl)-1,3-dimethyl-1H-chromeno[2,3-d]pyrimidine-2,4(3H,5H)-dione/3,3-dimethyl-2H-xanthen-1(9H)-one derivatives (4a–j) via p-TSA catalyzed reaction of 1,3-dimethylbarbituric acid/dimedone, substituted salicylaldehyde/2-hydroxy-nepthaldehyde and 3-phenyl-5-isoxazolone was administered in refluxed temperature in the presence of aqueous ethanol. All the obtained compounds were evaluated for their therapeutic effect using pharmacological and computational investigations, and structures were confirmed using analytical and spectroscopic techniques. Absorption spectra were recorded in six different solvents such as polar protic, polar aprotic, and nonpolar solvents, λmax of all the compounds are appeared at bathochromic shift towards the longer wavelength due to the π-π* & n-π* transitions. The results of pharmacological investigations revealed that the compounds 4c, 4e, and 4h possess excellent cytotoxicity efficacy, and compounds 4c, 4d, 4h, and 4i have shown better anti-TB efficiency. The SAR study shows the importance of the electron-withdrawing group and additional phenyl nucleus enhancing the biological potency of the compounds. The results of the in silico molecular docking studies revealed that the compounds 4c and 4h effectively interacted with P38 MAP kinase (-10.9 kcal/mol) and InhA-Enoyl-Acyl Carrier Protein Reductase (-11.0 kcal/mol), respectively. Further, the molecular dynamics (MD) simulation studies revealed that the compounds 4c and 4h stabilized the macromolecular structures in terms of RMSD, RMSF, the Radius of gyration, and SASA compared to their unbound and standard compound bound structures. DFT study suggested that the compounds are chemically and biologically more reactive due to less energy gap.

Fabrication of sustainable organic solvent nanofiltration membranes using cellulose–chitosan biopolymer blends

Membrane technologies have emerged as a promising alternative to energy-intensive separation processes in various industrial sectors. To address the sustainability challenge associated with the fabrication of separation membranes, a paradigm shift from the use of petrochemical-based raw materials to greener biobased sources is highly desired. In this study, blends of cellulose — as a plant-based material — and chitosan — obtained from shrimp farming waste and used as a biomass material — were investigated for the fabrication of oil and solvent-resistant nanofiltration membranes. The structural, thermal, mechanical, and morphological properties of the prepared membranes were characterized. Molecular simulations were performed to study the fractional free volume and interaction energy among membrane constituents. Adjusting the cellulose–chitosan ratio allowed fine-tuning the molecular sieving properties of the membranes, which exhibited outstanding separation performance and chemical stability even in harsh solvents, such as polar aprotic solvents, at the maximum temperature of 100 °C. Cellulose membranes containing 25 wt% chitosan achieved the lowest molecular weight cutoff value of 413 g mol−1 and a permeance of 24 L m−2 h−1 bar−1 in acetonitrile. The membranes showed stable separation performance over 7 days of continuous cross-flow nanofiltration. Moreover, the cellulose membranes blended with 10–25 wt% chitosan showed decreased water permeance from 52 to 38 L m−2 h−1 bar−1 and increased oil-removal efficiency from 73.8% to 98.6%. Furthermore, the membranes successfully underwent biodegradation, confirming their potential to close the loop of the sustainable lifecycle of membranes from cradle to grave.

Dissolution thermodynamic properties calculation and intermolecular interaction analysis of diacerein in different pure and mixed solvents

The purpose of the present work is to improve the solubility of insoluble diacerein with cosolvent. The solubility of diacerein in pure polar aprotic solvent is significantly higher than that in other solvents. In mixtures of ethyl acetate + isopropanol, the solubility of diacerein increases firstly and then decreases with the addition of cosolvent at a certain temperature. However, in N, N-dimethylacetamide (DMAC) + water systems, the solubility and DMAC concentration shows a monotonic increasing trend at a given temperature. Multiple linear regression analysis of various solvent property parameters indicates that hydrogen bonding and the enhancement of solvent polarity are helpful to the dissolution of diacerein. The calculation results of preferential solvation show that diacerein molecules are preferentially solvated by isopropanol and water in isopropanol / water-rich mixtures. In the DMAC-rich region, solute are preferentially solvated by DMAC, while in the ethyl acetate + isopropanol system, with the increase of ethyl acetate concentration, the solute is solvated firstly by cosolvent and then solvated by isopropanol again. The calculation of apparent thermodynamic properties indicates that the dissolution process is an endothermic and entropy driven process.

N-Cholyl d-Penicilamine Micelles Templated Red Light-Emitting Silver Nanoclusters: Fluorometric Sensor for S2- Ions and Bioimaging Application Using Zebrafish Model.

Red-light-emitting silver nanoclusters (AgNCs) are recently emerged as a promising nanoprobe in the field of biomedical applications, because of their attractive properties, including brightness, luminescence stability, and better biocompatibility. In this report, we have developed highly water-soluble red-light-emitting AgNCs by using N-cholyl d-penicilamine (NCPA) as a biosurfactant at above the critical micelle concentration (CMC) at room temperature. Moreover, the NCPA was initially synthesized by demonstrating the reaction between cholic acid and d-penicilamine via a simple coupling reaction strategy. The primary and secondary critical micellar concentration (CMC) of NCPA surfactant was measured using pyrene (1 × 10-6 M) as a fluorescent probe, and the values were found to be 3.18 and 10.6 mM, respectively. Steady-state fluorescence measurements reveal that the prepared AgNCs shows the excitation and emission maxima at 365 and 672 nm, respectively, with a large Stokes shift (307 nm). The average lifetime measurements and quantum yield of the AgNCs were calculated to be 143.43 ns and 16.34%, respectively. Also, the red luminescent NCPA-templated AgNCs was synthesized in various protic and aprotic polar solvents, among which DMF and DMSO exhibit bright emission at longer wavelength as synthesized in aqueous medium. At higher concentration of AgNO3, bright luminescent and highly stable solid AgNCs was obtained with excitation and emission maxima at 607 and 711 nm, respectively. Furthermore, the synthesized AgNCs has been successfully utilized as a fluorescent probe for selective and sensitive detection of S2- ions at nanomolar level in water samples, showing its potential applicability for the detection of S2- ions in drinking, river, and tap water samples. Finally, toxicity and bioimaging studies of NCPA-templated AgNCs was demonstrated using zebrafish as in vivo model, showing no significant toxicity up to 200 μL/mL. The AgNCs-stained embryos exhibited red fluorescence with high intensity, which shows that AgNCs are stable in a living system.

Preparation of high-solid-loading and highly dispersible ZrB2 slurry in non-aqueous solvent via surface functionalization of cationic/anionic polymers

Zirconium diboride (ZrB2) is used as a component in applications under extreme conditions. It is necessary to prepare the ZrB2 slurry with high dispersity and low viscosity for applying their applications. Therefore, investigations were carried out on the surface functionalization of ZrB2 with cationic or anionic polymers that impart repulsive force to the particles. Differences in motion behavior of particles caused by changes in the surface properties were compared for each of the positive or negative surface functionalization. Consequently, it was noted that functional groups adhering to the surface improved the dispersity of the ZrB2 particles, in view of the increase in the absolute value of the zeta potential and improved particle size distribution at neutral pH. A high-solid-loaded ZrB2 slurry with low viscosity was also prepared by a selection of an appropriate solvent among polar aprotic solvents. Consequently, the ZrB2 slurry with high dispersity and low viscosity was prepared.

Degradation of parathion methyl by reactive sorption on the cerium oxide surface: The effect of solvent on the degradation efficiency

A simple and easily scalable “wet” procedure was used to prepare nanocrystalline cerium oxide capable of destroying the toxic organophosphate pesticide parathion methyl. The synthetic procedure consists of the direct precipitation of cerous salt with aqueous ammonia in the absence of CO 2 . The prepared cerium oxide was able to decompose the organophosphate compounds both in nonpolar (e.g., heptane) and polar aprotic (e.g., acetonitrile) solvents. However, in solvents with hydrogen-bond donating ability, the –OH groups on the cerium oxide surface were solvated and inactivated. The preferential solvation model was used to express the experimental dependencies of the cerium oxide degradation efficiency on the composition of the water-acetonitrile mixture. In certain solvent systems, some empirical polarity scales, such as the alpha-scale or the Dimrodth-Richardt parameter E T (30), may be correlated with the degradation efficiency of cerium oxide.

Deposition of Nanosized Amino Acid Functionalized Bismuth Oxido Clusters on Gold Surfaces.

Bismuth compounds are of growing interest with regard to potential applications in catalysis, medicine, and electronics, for which their environmentally benign nature is one of the key factors. One thing that currently hampers the further development of bismuth oxido-based materials, however, is the often low solubility of the precursors, which makes targeted immobilisation on substrates challenging. We present an approach towards the solubilisation of bismuth oxido clusters by introducing an amino carboxylate as a functional group. For this purpose, the bismuth oxido cluster [Bi38O45(NO3)20(dmso)28](NO3)4·4dmso (dmso = dimethyl sulfoxide) was reacted with the sodium salt of tert-butyloxycabonyl (Boc)-protected phenylalanine (L-Phe) to obtain the soluble and chiral nanocluster [Bi38O45(Boc–Phe–O)24(dmso)9]. The exchange of the nitrates by the amino carboxylates was proven by nuclear magnetic resonance, Fourier-transform infrared spectroscopy, as well as elemental analysis and X-ray photoemission spectroscopy. The solubility of the bismuth oxido cluster in a protic as well as an aprotic polar organic solvent and the growth mode of the clusters upon spin, dip, and drop coating on gold surfaces were studied by a variety of microscopy, as well as spectroscopic techniques. In all cases, the bismuth oxido clusters form crystalline agglomerations with size, height, and distribution on the substrate that can be controlled by the choice of the solvent and of the deposition method.