Apolar Media Research Articles

Particle synthesis based on the concerted effect of mixed acid-base functional groups for electrophoretic display

The development of fast-response and full-color Electrophoretic Displays (EPDs) requires both rapid migration of electrophoretic particles and adjustable mobility of particles with different colors in apolar media, which is determined by the charged properties of the particle surface. Herein, five electrophoretic particles were synthesized with different ratios of acidic and basic functional groups to explore the impact of mixed functional groups on the effective pH of the particle surface. The prepared particles were characterized by FTIR, TGA and zeta potential measurements. The results show that the effective acidity of TiO2-NH2-COOH particles, which contain both acidic and basic functional groups, was higher than that of TiO2-COOH-COOH particles containing a single functional group. The surface charge of the electrophoretic particles increased from − 43 mV to − 90 mV. Similarly, TiO2-COOH-NH2 particles had a higher surface charge than TiO2-NH2-NH2 particles. The effective pH value of the particle surface depends on the synergism of mixed acid-base functional groups. The appropriate amounts of basic (or acidic) functional groups promote the acid-base interaction between acidic (or alkaline) functional groups and surfactant molecules, leading to an increase in the charge value of the particles. Thus, the effective acid-base of the particles can be precisely controlled by adjusting the mixing ratio of acid-base functional groups during particle modification. The application of electrophoretic particles with mixed acid-base functional groups was also demonstrated in two-color and three-color electrophoretic inks, achieving fast response (switching time decreased from 1170 ms to 130 ms) and colored display. This work may help to enhance the comprehension of the interaction mechanism between acid-base groups and particle-reverse micelle interfaces in non-polar solvents. Additionally, it may contribute to the precise modulation of the effective pH value on the particle surface, thereby facilitating the development of advanced functional materials.

Tribo-Dependent Photoluminescent Behavior of Oleylamine-Modified AgInS2 and AgInS2-ZnS Nanoparticles as Lubricant Additives

The content of Cu2+ in lubricants is an essential indicator for determining the quality of the lubricant and predicting mechanical failure. Finding an effective and sensitive method for detecting Cu2+ in lubricants is of great importance in oil monitoring. In this work, AgInS2 (AIS) and AgInS2-ZnS (ZAIS) nanoparticles (NPs) were synthesized by a simple one-step approach via in-situ surface modification by oleylamine. The as-synthesized AIS and ZAIS NPs exhibit good dispersion stability in various apolar media. The photoluminescence (PL) of AIS and ZAIS NPs as lubricating additives could reflect and monitor the lubrication state of steel-copper pairs due to the quenching effect of Cu2+ from the friction process. With an optimum concentration of 0.5 wt% in paraffin oil, the friction coefficient of the AIS and ZAIS NPs at 100 N was decreased by 56.8 and 52.1% for steel-steel contacts, respectively. ZAIS was observed to be more effective than AIS in improving anti-wear (AW) and extreme pressure (EP) properties, with a load-bearing capacity of up to 1100 N. Characterization of the wear tracks by SEM and XPS indicates that a tribofilm composed of metal sulfides and oxides was formed during the lubricating process. This work not only reveals AIS and ZAIS NPs as a new class of promising candidates for lubricating additives but also unveils their potential for monitoring lubricant conditions and exploring lubricant service life.

A bioinspired sequential energy transfer system constructed via supramolecular copolymerization

Sequential energy transfer is ubiquitous in natural light harvesting systems to make full use of solar energy. Although various artificial systems have been developed with the biomimetic sequential energy transfer character, most of them exhibit the overall energy transfer efficiency lower than 70% due to the disordered organization of donor/acceptor chromophores. Herein a sequential energy transfer system is constructed via supramolecular copolymerization of σ-platinated (hetero)acenes, by taking inspiration from the natural light harvesting of green photosynthetic bacteria. The absorption and emission transitions of the three designed σ-platinated (hetero)acenes range from visible to NIR region through structural variation. Structural similarity of these monomers faciliates supramolecular copolymerization in apolar media via the nucleation-elongation mechanism. The resulting supramolecular copolymers display long diffusion length of excitation energy (> 200 donor units) and high exciton migration rates (~1014 L mol−1 s−1), leading to an overall sequential energy transfer efficiency of 87.4% for the ternary copolymers. The superior properties originate from the dense packing of σ-platinated (hetero)acene monomers in supramolecular copolymers, mimicking the aggregation mode of bacteriochlorophyll pigments in green photosynthetic bacteria. Overall, directional supramolecular copolymerization of donor/acceptor chromophores with high energy transfer efficiency would provide new avenues toward artificial photosynthesis applications.

Nanoporous-crystalline and amorphous films of PPO including off-on vapochromic fluorescent 7-hydroxy coumarin guests

This study examines the preparation of nanoporous-crystalline and amorphous films of poly(2,6-dimethyl-1,4-phenylene)oxide (PPO) containing 7-hydroxy coumarin (i.e., umbelliferone) for the detection of chloroform vapours. Chloroform is selected as the volatile contaminant model being considered harmful and possibly carcinogenic after prolonged exposure. Umbelliferone is chosen as a fluorescent molecule being mostly unemissive in the solid-state and apolar media. α and β nanoporous-crystalline and amorphous PPO films presenting ≈40 μm thickness have been prepared by casting from carbon tetrachloride, benzene and chloroform solutions, respectively, whereas umbelliferone inclusions (1–2 wt%) have been realized in saturated methanol mixtures. Films show fluorescence maximum at about 430 nm with very low quantum yield (Φ F ) of around 1–2%, and particularly reduced in the α and β PPO films, thus suggesting stronger molecular interactions which might facilitate fluorescence self-quenching. It has demonstrated that the exposure to chloroform vapours under saturated conditions (10 5 ppm) turns rapidly on the fluorescence of the polymer films thanks to the solvation effect of the solvent and in agreement with the Φ F of 7% of umbelliferone in chloroform. Notably, a slower response was detected by using dichlorometane as VOC, possibly due to the weaker H-donor strength with respect to chloroform. It was worth noting, that the phenomenon results fastest for the α PPO films, i.e., in case of the lowest Φ F and quenched emission. Vapochromism appears therefore sensitive to the different fluorophore confinement, and the reported results may open new avenues for the rapid detection of VOC vapours. • Nanoporous-crystalline PPO films were prepared and characterized by WAXD and FTIR. • Umbelliferone inclusions in PPO films showed very low Φ F of around 1–2%. • Exposure to CHCl 3 vapours turned the fluorescence on. • Faster vapochromism for the α and β co-crystalline PPO films.

The effects of surfactant and oil chemical structures on self-assembly in apolar media.

The thermodynamic and chemical structural aspects of surfactant self-assembly in aqueous systems have been much studied. On the other hand, for oil-water interfaces the effects of chemical structures of surfactants and solvents have received less attention. This review focuses on the surfactant chemical effects in low dielectric solvents, in particular formation and properties of surfactant films at oil-water interfaces. For this purpose, reversed micelles (RMs) and water-in-oil (W/O) microemulsions (μEs) serve as model systems, since electrostatic effects are minimized, allowing a focus on chain architecture of the surfactants and oil solvents themselves. It is noted that chemical structure can have profound effects on stability and self-assembly, suggesting a possibility of identifying unified chemical principles for designing and formulating systems across various thermodynamic conditions.

Co(iii) 2-ethylhexanoate, a hydrophobic and highly soluble Co(iii) precursor for thin coatings for water electrolysis

Co(iii) 2-ethylhexanoate (Co(iii)eh) is the first Co(iii) species soluble in a wide spectrum of solvents including strong apolar media. At modest T or by laser irradiation, Co(iii)eh films convert to state-of-the-art cobalt oxide catalytic layers.

Synthesis and analytical characterization of all N\u2013N-coupled, dimeric oxidation products of \u03b1-tocopheramine: hydrazo-, azo-, and azoxy-tocopherol

Tocopherols are a mixture of antioxidants which are commonly referred to as vitamin E. Tocopheramines differ from tocopherols by an amino function in lieu of the phenolic OH group. They are potent antioxidants which are used in biomedical scenarios as well as stabilizers for polymers against aging. While in aqueous media α-tocopheramine is mainly oxidized to α-tocopherylquinone and N-oxidized by-products, oxidation in apolar media or in polymeric matrices mainly leads to dimeric compounds of hitherto unknown structure. In the present study, we synthesized the whole array of N,N-dimerization product of α-tocopheramine, including the hydrazo, azo, and azoxy derivatives for the first time, and provided comprehensive analytical data as well as general protocols to access the compounds in straightforward syntheses. These results can now be used to identify the common oxidation by-products of α -tocopheramine in different reaction systems.Graphic abstract

Internal conversion of singlet and triplet states employing numerical DFT/MRCI derivative couplings: Implementation, tests, and application to xanthone.

We present an efficient implementation of nonadiabatic coupling matrix elements (NACMEs) for density functional theory/multireference configuration interaction (DFT/MRCI) wave functions of singlet and triplet multiplicity and an extension of the Vibes program that allows us to determine rate constants for internal conversion (IC) in addition to intersystem crossing (ISC) nonradiative transitions. Following the suggestion of Plasser et al. [J. Chem. Theory Comput. 12, 1207 (2016)], the derivative couplings are computed as finite differences of wave function overlaps. Several measures have been taken to speed up the calculation of the NACMEs. Schur's determinant complement is employed to build up the determinant of the full matrix of spin-blocked orbital overlaps from precomputed spin factors with fixed orbital occupation. Test calculations on formaldehyde, pyrazine, and xanthone show that the mutual excitation level of the configurations at the reference and displaced geometries can be restricted to 1. In combination with a cutoff parameter of tnorm = 10-8 for the DFT/MRCI wave function expansion, this approximation leads to substantial savings of cpu time without essential loss of precision. With regard to applications, the photoexcitation decay kinetics of xanthone in apolar media and in aqueous solution is in the focus of the present work. The results of our computational study substantiate the conjecture that S1 T2 reverse ISC outcompetes the T2 ↝ T1 IC in aqueous solution, thus explaining the occurrence of delayed fluorescence in addition to prompt fluorescence.

Lipase-catalyzed selective esterification of catechin

Catechins show strong antioxidant, antitumoral, antiviral, and anti-inflammatory activities. The uses of catechins in food, cosmetic, and pharmaceutical formulations seem very attractive. Unfortunately, solubility and stability of catechins are poor in apolar media, which limits their efficient uses. In order to improve the solubility of catechins in the oil phase and maintain their oxidation resistance, a regioselective enzymatic acylation was investigated. The effects of reaction medium, water content, carbon chain length of acyl donor and other factors on the acylation reaction were studied, catechins were enzymatically esterified with an aliphatic acid (stearic acid) using an immobilized lipase Novozym 435 in n-butanol. The results show that when the ratio between catechins and stearic acid was 1:5, adding molecular sieves 4A after 11 h of reaction and the temperature of 60 °C led to the maximum conversion yield of 60.36%. Studies have shown that catechin stearate has a higher antioxidant activity than vitamin E and dibutyl hydroxytoluene (BHT).

Revisiting doping mechanisms of n-type organic materials with N-DMBI for thermoelectric applications: Photo-activation, thermal activation, and air stability

Understanding doping mechanisms is essential for optimizing the doping efficiency and rationally designing next generations of dopants and organic materials. Over the last few years, N-DMBI became a reference solution-processed n-type dopant, affording decent air-stability and record power factor for thermoelectric energy generation. Nevertheless, a complete description of doping mechanism including the activation conditions, the doping pathways, and possible side reactions is still lacking. In this work, we combined experimental and theoretical evidence to clarify the activation conditions of N-DMBI and elucidate the prevalent doping pathway depending on the dielectric constant of the medium. In polar media, direct doping via hydride H− transfer is largely dominant, while, in apolar media, singly occupied molecular orbital-mediated doping after H• release is thermodynamically favored. We show that N-DMBI can be activated not only by thermal annealing above 100 °C, but also by UV-light irradiation at low fluences even in thin films. Our findings stress the importance of working in strictly anoxic environment to avoid parasitic O2-mediated side reactions, even in the presence of a host.

A Highly Ordered Quantum Dot Supramolecular Assembly Exhibiting Photoinduced Emission Enhancement

AbstractMulticomponent supramolecular assembly systems enable the generation of materials with outstanding properties, not obtained from single‐component systems, via a synergetic effect. Herein, we demonstrate a novel supramolecular coassembly system rendering highly ordered quantum dot (QD) arrangement structures formed via the self‐assembly of azobenzene derivatives, where the photocontrollable photoluminescence (PL) properties of the QDs are realized based on photoisomerization. Upon mixing the assembled azobenzene derivatives and QDs in apolar media, a time‐evolution coaggregation into hierarchical nanosheets with a highly ordered QD arrangement structure occurs. Upon photoirradiation, the nanosheets transform into ill‐defined aggregates without arranged QDs together with enhancing the PL intensity. In days, the photoirradiated coaggregates undergo recovery of the PL properties corresponding to the arranged QDs through thermal isomerization.

A Highly Ordered Quantum Dot Supramolecular Assembly Exhibiting Photoinduced Emission Enhancement.

Multicomponent supramolecular assembly systems enable the generation of materials with outstanding properties, not obtained from single-component systems, via a synergetic effect. Herein, we demonstrate a novel supramolecular coassembly system rendering highly ordered quantum dot (QD) arrangement structures formed via the self-assembly of azobenzene derivatives, where the photocontrollable photoluminescence (PL) properties of the QDs are realized based on photoisomerization. Upon mixing the assembled azobenzene derivatives and QDs in apolar media, a time-evolution coaggregation into hierarchical nanosheets with a highly ordered QD arrangement structure occurs. Upon photoirradiation, the nanosheets transform into ill-defined aggregates without arranged QDs together with enhancing the PL intensity. In days, the photoirradiated coaggregates undergo recovery of the PL properties corresponding to the arranged QDs through thermal isomerization.

Design and NMR conformational analysis in solution of β5i-selective inhibitors of immunoproteasome

The identification of effective and selective immunoproteasome inhibitors could greatly promote smart treatment of many autoimmune, inflammatory and tumor diseases. This paper explores the activity of some pyridone derivatives which are taking advantage of peptide mimicking moieties and other functional groups whose related effects are taken into consideration. The target compounds were designed and synthesized starting from a lead, next their in vitro biological activity was tested; the following structural and conformational analysis sheds light over the different activity of the tested compounds. Compound 3 bearing a phenylalanine at the P2 site and an allyloxycarbonyl group spanning the P3 region, was found to be a selective inhibitor of β5 subunit of immunoproteasome. It has been demonstrated by Nuclear Magnetic Resonance (NMR) that, in solution, this substrate displays a more rigid conformation respect to the others, especially in apolar media, this feature is likely crucial for the enhancement of the activity towards immunoproteasome. The specific conformational analysis enables insights of the biological activity of new chemicals driving possible advancements based on the suitable structural features to identify novel selective β5 immunoproteasome inhibitor.

Towards a better understanding of odor removal from post-consumer plastic film waste: A kinetic study on deodorization efficiencies with different washing media

Mechanical recycling is to date the most commonly applied recycling technology. However, mechanical recycling of post-consumer plastics still faces many challenges, such as the presence of odorous constituents. Accordingly, recycling industry is looking for cost-effective solutions to improve the current washing efficiencies. However, scientific literature and basic understanding of deodorization processes are still scarce, which impedes efficient industrial optimization. Therefore, this study aims to obtain more fundamental insights in the deodorization mechanisms of plastic films in different washing media such as water, detergent, caustic soda, and ethyl acetate as organic solvent. The removal efficiencies of 19 odor components with a wide range of physicochemical properties were quantified via GC-MS analysis. The results revealed that deodorization depends on various factors such as temperature and physicochemical properties as polarity, volatility, and molecular weight of the odor components and the washing media. It was shown that polar washing media are less efficient compared to apolar media or media containing a detergent, achieving efficiencies of around 50% and 90%, respectively. The desorption processes can be accurately modeled by the isotherm model of Fritz-Schlunder in combination with a reversible first order kinetic model for the deodorization kinetics. Aspen Plus® process simulations of a water-based washing process reveal that at least 60% fresh water is needed to avoid saturation of the medium and undesired (re-)adsorption of odor components onto the plastics, which results in a substantial ecological footprint.

Pyranine Based Ion‐Paired Complex as a Mechanophore in Polyurethanes

A new mechanophore for polyurethane thermoplastic elastomers based on ion-paired complexes is developed. 8-(2-hydroxyethoxy)pyrene-1,3,6-trisulfonate (HEPTS) is incorporated into polyurethanes as an end-capper and aggregates in apolar media. Aggregation of the ionic HEPTS end groups in solution depends on concentration solvent polarity. The addition of dimethylformamide to a tetrahydrofuran solution of the polymer results in the dissociation of the aggregates and a significant shift in fluorescence emission from yellow to blue. The same shift in fluorescence emission is induced by stretching the solid polymer at strains larger than 1 and stresses above 7.5MPa, with a clear increase above 12.5MPa. Strain induced dissociation of HEPTS aggregates not attached to the polymer chain leads to fluorescence changes that are much less reproducible.

Anionic polymerization of butadiene by dialkylmagnesium / alkali metal alkoxide systems in apolar medium: Polybutadiene microstructure and polymerization control

Lithium based anionic polymerization of butadiene in apolar media allows the obtention of polybutadiene with a high vinyl content by using polar modifier or alkali metal alkoxide. For instance, butadiene polymerization with alkyllithium and potassium tert-pentoxide produces polybutadiene with 50% of vinyl content. The aim of this paper is to develop an approach without any alkyllithium moieties in order to synthesize polybutadiene with a high vinyl content (50%–70%) in a controlled way. To do so bi-metallic systems based on di-n-butylmagnesium in association with potassium or sodium tert-pentoxide were studied in apolar medium. The influence of parameters such as the initiator preformation time and the [Mt]/[Mg] ratio were assessed (Mt = K, Na). The potassium tert-pentoxide-based system was found to produce polybutadienes in a controlled way with 50% of vinyl content, while polybutadienes with up to 70% of vinyl content were obtained in a controlled way with Na based systems.

Cyan Ni1-x Al2+2x/3□ x/3O4 Single-Phase Pigment Synthesis and Modification for Electrophoretic Ink Formulation.

Cyan Ni1–xAl2+2x/3O4 single-phase pigments with various Ni/Al atomic ratios (from 1:2 down to 1:4) have been prepared by a sol–gel route (Pechini) followed by postannealing treatments. Nickel aluminates crystallize in the well-known spinel structure (Fd3m space group), where metals are located at two different Wyckoff positions: 16d (octahedron) and 8a (tetrahedron). Based on X-ray diffraction (XRD) Rietveld refinements, Ni2+ cations are shown to be partially located in both tetrahedral and octahedral sites and, in addition, cationic vacancies occupy the Oh environment. In the pure-phase series, Ni/Al = 0.35, 0.40, 0.45, as the Al content increases, the Ni2+ rate in the Td site decreases for Ni/Al = 0.45, thus altering the cyan color; within this series, the most saturated cyan coloration is reached for the highest Al concentration. Inorganic pigment drawbacks are their high density and hydrophilic surface, which induce sedimentation and aggregation in nonpolar media used in electrophoretic inks. Hybrid core–shell particle pigments have been synthesized from cyan pigments using nitroxide-mediated radical polymerization (NMRP) with methyl methacrylate monomer in Isopar G, leading to a dispersion of electrically charged hybrids in apolar media. Surface functionalization of the pigments by n-octyltrimethoxysilane (OTS) and n-dodecyltrimethoxysilane (DTS) modifiers has been compared. The inorganic pigments are successfully encapsulated by organic shells to allow a strong decrease in their density. Cyan inks, adequate for their use in e-book readers or other electrophoretic displays, taking further advantage of the high contrast ratio and reflectivity of inorganic pigments in regard to organic dyes, have been stabilized.

Ion-Pair Selective Conformational Rearrangement of Sulfonamide Calix[6]arene-Based Pseudorotaxanes.

We describe the synthesis of a new class of trisulfonamide calix[6]arene-based wheels that can bind dialkylviologen salts, in apolar media. The threading process occurs through a selective ion-pair recognition, established by the sulfonamide groups with the counterions of the bipyridinium salts, that dictates a conformational rearrangement of the corresponding pseudorotaxanes.

Structural Isomerism Effect in Platinum(II) Acetylide-Based Supramolecular Polymers.

The self-assembly of π-aromatic organic and organometallic molecules into long-range-ordered supramolecular polymers is dictated by a variety of molecular parameters and external conditions. In this work, structural isomerism, representing one of the potent molecular parameters, has been investigated to modulate the self-assembly behaviors. Two platinum(II) acetylide-based structural isomers, with different N-hexyl substitution positions on the inner benzotriazole core, have been designed. Thanks to the synergistic participation of hydrogen-bonding and π-π-stacking interactions, both platinum(II) acetylide-based compounds are prone to forming supramolecular polymers via a nucleation-elongation cooperative mechanism in apolar media. Thermal hysteresis phenomena are observed for both compounds, suggesting the different supramolecular polymerization pathways upon cooling and heating. Remarkably, in addition to the spectroscopic difference, these two supramolecular polymers display distinct thermostability and rheological moduli, ascribing to different binding enthalpies of the neighboring monomers. Overall, it is evident that a minor variation at the molecular level brings huge differences to the properties of long-range-ordered supramolecular polymers. The current study illustrates the importance of the structural isomerism effect for the rational design of π-functional supramolecular materials.

Highly fluorescent lipophilic 2,1,3-benzothiadiazole fluorophores as optical sensors for tagging material and gasoline adulteration with ethanol

Lipophilic 2,1,3-benzothiadiazoles were obtained in a short synthesis with excellent yields by a Sonogashira coupling reaction followed by a 1,3-dipolar cycloaddition reaction with alkyl azides. The obtained compounds presented high solubility in a wide range of solvents with different polarities. The benzothiadiazoles present absorption in the violet region due to fully spin- and symmetry-allowed π-π* electronic tansitions and an emission located in the blue-green region with a large Stokes shift. The high solubility in apolar media, along with their photophysical properties allowed their use as tagging materials up to a detection limit of 0.005 ppm. Moreover, their application as chemosensors for the detection of fuel adulteration in commercial gasoline in the range of 5–50 % ethanol/gasoline (v/v) was also sucesfully presented and discussed.