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Nanomaterials are integrated within consumer products to enhance specific properties of interest. Their release throughout the lifecycle of nano-enabled products raises concerns; specifically, mechanical strains can lead to the generation of fragmented materials containing nanomaterials. We investigated the potential release of single-walled carbon nanotubes (SWCNTs—brand TUBALL™) from epoxy composite materials. A pin-on-disk-type tribometer was used for the accelerated mechanical aging of the nanocomposites. A pristine nanocomposite material, abraded material and debris obtained from the abrasion in the tribometer were analyzed by Raman spectroscopy. The airborne-produced particles were captured using particle collectors. Stat Peel's Identifier C2 system was used to monitor the SWCNT content of respirable particles produced during the abrasion test. The SWCNT amounts found were below the LoQ. The Raman spectra conducted on the Stat Peel filters helped identify the presence of free SWCNTs released from the epoxy matrix, although they were notably scarce. Raman spectroscopy has been proved to be a crucial technique for the identification, characterization and assessment of structural changes and degradation in SWCNTs that occurred during the abrasion experiments. [ABSTRACT FROM AUTHOR]

A notable application of polymeric nanocomposites is the design of water vapor permeable (WVP) membranes. "Breathable" membranes can be created by the incorporation of micro/nanofillers, such as CaCO3, that interrupt the continuity of the polymeric phase and when subjected to additional uniaxial or biaxial stretching this process leads to the formation of micro/nanoporous structures. Among the candidate nanofillers, carbon nanotubes (CNTs) have demonstrated excellent intrinsic WVP properties. In this study, chemically modified MWCNTs with oligo olefin-type groups (MWCNT-g-PP) are incorporated by melt processes into a PP matrix; a β-nucleating agent (β-ΝA) is also added. The crystallization behavior of the nanocomposite films is evaluated by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The WVP performance of the films is assessed via the "wet" cup method. The nanohybrid systems, incorporating both MWCNT-g-PP and β-NA, exhibit enhanced WVP compared to films containing only MWCNT-g-PP or β-NA. This improvement can be attributed to the significant increase in the growth of α-type crystals taking place at the edges of the CNTs. This increased crystal growth exerts a form of stress on the metastable β-phase, thereby expanding the initial microporosity. In parallel, the coexistence of the inherently water vapor-permeable CNTs, further enhances the water vapor permeability reaching a specific water vapor transmission rate (Sp.WVTR) of 5500 μm.g/m2.day in the hybrid composite compared to 1000 μm.g/m2.day in neat PP. Notably, the functionalized MWCNT-g-PP used as nanofiller in the preparation of the "breathable" PP films demonstrated no noteworthy cytotoxicity levels within the low concentration range used, an important factor in terms of sustainability. [ABSTRACT FROM AUTHOR]

The global trend in restrictions on pollutant emissions requires the use of catalytic converters in the automotive industry. Noble metals belonging to the platinum group metals (PGMs, platinum, palladium, and rhodium) are currently used for autocatalysts. However, recent efforts focus on the development of new catalytic converters that combine high activity and reduced cost, attracting the interest of the automotive industry. Among them, the partial substitution of PGMs by abundant non-PGMs (transition metals such as copper) seems to be a promising alternative. The PROMETHEUS catalyst (PROM100) is a polymetallic nanosized copper-based catalyst for automotives prepared by a wet impregnation method, using as a carrier an inorganic mixed oxide (CeO2-ZrO2) exhibiting elevated oxygen storage capacity. On the other hand, catalyst deactivation or ageing is defined as the process in which the structure and state of the catalyst change, leading to the loss of the catalyst's active sites with a subsequent decrease in the catalyst's performance, significantly affecting the emissions of the catalyst. The main scope of this research is to investigate in detail the effect of ageing on this low-cost, effective catalyst. To that end, a detailed characterization has been performed with a train of methods, such as SEM, Raman, XRD, XRF, BET and XPS, to both ceria–zirconia mixed inorganic oxide support (CZ-fresh and -aged) and to the copper-based catalyst (PROM100-fresh and -aged), revealing the impact of ageing on catalytic efficiency. It was found that ageing affects the Ce–Zr mixed oxide structure by initiating the formation of distinct ZrO2 and CeO2 structures monitored by Raman and XRD. In addition, it crucially affects the morphology of the sample by reducing the surface area by a factor of nearly two orders of magnitude and increasing particle size as indicated by BET and SEM due to sintering. Finally, the Pd concentration was found to be considerably reduced from the material's surface as suggested by XPS data. The above-mentioned alterations observed after ageing increased the light-off temperatures by more than 175 °C, compared to the fresh sample, without affecting the overall efficiency of the catalyst for CO and CH4 oxidation reactions. Metal particle and CeZr carrier sintering, washcoat loss as well as partial metal encapsulation by Cu and/or CeZrO4 are identified as the main causes for the deactivation after hydrothermal ageing. [ABSTRACT FROM AUTHOR]

Self-healing materials and self-healing mechanisms are two topics that have attracted huge scientific interest in recent decades. Macromolecular chemistry can provide appropriately tailored functional polymers with desired healing properties. Herein, we report the incorporation of glycidyl methacrylate-based (GMA) copolymers in waterborne polyurethanes (WPUs) and the study of their potential healing ability. Two types of copolymers were synthesized, namely the hydrophobic P(BA-co-GMAy) copolymers of GMA with n-butyl acrylate (BA) and the amphiphilic copolymers P(PEGMA-co-GMAy) of GMA with a poly(ethylene glycol) methyl ether methacrylate (PEGMA) macromonomer. We demonstrate that the blending of these types of copolymers with two WPUs leads to homogenous composites. While the addition of P(BA-co-GMAy) in the WPUs leads to amorphous materials, the addition of P(PEGMA-co-GMAy) copolymers leads to hybrid composite systems varying from amorphous to semi-crystalline, depending on copolymer or blend composition. The healing efficiency of these copolymers was explored upon application of two external triggers (addition of water or heating). Promising healing results were exhibited by the final composites when water was used as a healing trigger. [ABSTRACT FROM AUTHOR]

The collection of surface‐enhanced Raman scattering (SERS) by silver nanocolloids was used to identify the critical micelle concentration (CMC) of three cationic surfactants in 0.5‐M NaCl solutions: hexadecyltrimethylammonium bromide, dodecyltrimethylammonium bromide, and benzalkonium chloride. Despite structural similarity between the three test surfactans, differences of the shape and size of the respective micelles affected the corresponding SERS signals. The CMC values determined by this method agreed with the respective values measured by conventional methods, including fluorescence probing and electrical conductivity measurements. The potential for the application of SERS technique for low CMC determination without surface modification of silver nanoparticles by a Raman‐active molecule was also demonstrated. [ABSTRACT FROM AUTHOR]

Carbon nanotubes are among the stiffest and strongest fibres known and they are thus considered as ideal fillers for polymeric fibre reinforcement. Carbon nanotube polymer composites have consequently attracted huge academic and industrial interest with thousands of relevant research works being published every year. In current work, we present a quite integrated study of multiwall carbon nanotube (MWCNT)-reinforced poly ethylene terephthalate (PET) composites prepared at laboratory scale along with industrial melt-spun fibres. For an optimum dispersion of the nanomaterial in the polymer matrix, we proceeded to appropriate functionalization of multiwall carbon nanotubes. The morphology of the composites was inspected by scanning electron microscope and transmission electron microscope, while the physical properties, such as crystallinity and orientation, by differential scanning calorimetry, X-ray diffraction and Raman spectroscopy. The addition of well-dispersed carbon nanotubes acts as a nucleation agent increasing the crystallization of poly ethylene terephthalate matrix, however, decreasing the orientation of either films or fibres. Carbon nanotubes /poly ethylene terephthalate polymer composite films present an increment of Young’s modulus and tensile strength to detriment of failure strain; namely, stiffness is accompanied by a less ductile behaviour. With the addition of carbon nanotubes to poly ethylene terephthalate fibres, a decrease in shrinkage and only a slight improvement in dimensional stability was attained; this once more explains the slow growth of their commercial applications since the mechanical properties of these materials still remain a fraction of the expected theoretical values. [ABSTRACT FROM AUTHOR]

The reactions of copper(ii) carboxylate sources with acetylacetone dioxime (acacdoH2) in Me2CO have been studied and a novel, metal ion-assisted ligand transformation has been discovered. The reaction of [Cu2(diba)4(dibaH)2] and acacdoH2 (1 : 1.5) in Me2CO has provided access to the complex {[Cu2(diba)4(qunx)]}n (1) in low yield (25–30%), where dibaH is 3,3-dimethylbutyric acid and qunx is quinoxaline. The [Cu2(piv)4(pivH)2]/acacdoH2 (1 : 1.5) reaction system in warm Me2CO, where pivH is pivalic acid, gave the analogous complex {[Cu2(piv)4(qunx)]}n (2) in moderate yield (∼50%). Complexes 1 and 2 can be easily prepared by the direct 1 : 1 reactions between the corresponding copper(ii) carboxylate starting materials and qunx in Me2CO and MeOH, respectively. The formation of coordinated qunx in 1 and 2 is CuII-promoted (assisted) as suggested by the failure to synthesize the free qunx by a variety of reactions of acacdoH2 and Me2CO under aerobic conditions in the absence or even the presence of dibaH and pivH, respectively. The observed acacdoH2→ qunx transformation is catalytic and new in the chemistry of the dioximes of β-diketones, and a mechanism has been proposed based on well-established reactions of organic chemistry. The mechanism is based on a double Beckmann rearrangement-type transformation and the overall scheme is represented by the 1 : 1 : 1 reaction between acacdoH2, Me2CO and O2. Complexes 1 and 2 have similar molecular structures consisting of paddle-wheel {Cu2(η1:η1:μ-O2CR)4} units bridged by qunx ligands in a zigzag 1D chain arrangement. The geometry of the CuII ions is square pyramidal with a quinoxaline nitrogen atom occupying the apical position at each metal ion. Weak H bonds are present within the chains, the donors being qunx carbon atoms and the acceptors being coordinated carboxylate oxygen atoms. Neighbouring chains interact through C–H…π interactions between diba−/piv− methyl groups and the “pyrazine” part of qunx forming layers which are stacked along the b (1) or a (2) axis through weak van der Waals interactions. The packing of the layers is different in the two structures, due to the different nature of the carboxylate ligands. Hirshfeld surface analysis of the two structures reveals the similarity of the interchain (intralayer) interactions. The IR and Raman data of 1 and 2 are discussed in terms of the coordination mode of the carboxylate groups and permit assignments of some characteristic bands/peaks of coordinated qunx. Dc magnetic susceptibility studies in the 1.8–310 K range reveal very strong antiferromagnetic CuII…CuII exchange interactions within the carboxylate-bridged Cu2 units (J = −479 K for 1 and −532 K for 2 using the H = −J∑S1·S2 spin Hamiltonian) and weaker antiferromagnetic interactions between the Cu2 units via the qunx superexchange pathways, with the latter being ∼10% in strength compared to the former. A critical discussion of the acacdoH2→ qunx transformation in 1 and 2 is provided in the light of other impressive, recently discovered CuII-assisted transformations of acacdoH2, pointing out the key role of the solvent in the processes known to date. [ABSTRACT FROM AUTHOR]

Microcapsules (MCs) containing isocyanate compounds for use as self-healing materials in waterborne polyurethane coatings have been synthesized, in the presence of modified Novolac resins. With modification of Novolac resin, it is succeeded partial or total protection (Benzylation and Acetylation) of its hydroxyl groups. The idea here is to use a protected Novolac resin as the organic substrate for the encapsulation of the less reactive Isophorone isocyanate (IPDI) while the more reactive one, Methylene diphenyl diisocyanate (MDI), is used for the shell formation. Based on that strategy microcapsules of different morphologies and sizes were obtained, depending on the agitation conditions, as revealed using SEM and optical microscopy. Selective extraction was performed to determine the amount of the less reactive isocyanate (IPDI) stored inside the capsules through FTIR-ATR spectroscopy and isocyanate titration as well as the stability of IPDI inside the capsules over time. As determined, microcapsules based on Acetyl-modified Novolac resin encapsulated 96 wt% of IPDI monomer; this amount is about five and ten times higher than that encapsulated in MCs based on by Benzyl-modified Novolac resin or unprotected Novolac resin, respectively. At the same time, MCs based on Acetyl-modified Novolac resin were stable, maintaining approximately 80 % of the initial isocyanate content after two months of storage under inert conditions. Finally, the self-healing ability of the microcapsules was tested by adding selected IPDI-loaded microcapsules in waterborne polyurethane dispersions. It was proven that the Acetyl-modified Novolac-based MCs showed efficient healing behavior, in the absence of any catalyst, on the polyurethanes' surfaces when scratched artificially. • Two derivatives of Novolac resin through benzylation and acetylation were prepared • Novolac-based microcapsules (MCs) loaded with isocyanates (IPDI) were synthesized • High IPDI loading and stability has been found for acetyl-modified Novolac MCs • MCs can be well incorporated into waterborne polyurethane films • Acetyl-modified Novolac-based MCs were proved efficient self-healing materials [ABSTRACT FROM AUTHOR]

Purpose: To assess the potential impact of corneal crosslinking treatment (365 nm ultraviolet (UV)A irradiation with riboflavin) on the material properties of Intracorneal Rings Segments (ICRS). Materials and methods: Material properties were studied using FT-IR spectroscopy and UV-Vis spectroscopy. Rings were examined: (1) after installation of riboflavin solution, (2) after irradiation with UV-A light and (3) after instillation of riboflavin solution followed by instillation and coeval irradiation. The experiments followed the standard corneal cross-linking (CXL) protocol of corneal crosslinking treatment. Results: After instillation of riboflavin solution, a permanent intense yellow staining of the samples was observed. UV-Vis spectroscopy confirmed that a certain amount of riboflavin solution was absorbed into the samples after CXL procedure. FT-IR spectroscopic analysis showed alterations in the spectra of ICRS mainly at the 2800-3200 cm−1 spectral region [modification in band intensities of CH2 (2925 cm−1) and CH3 (2950 cm−1)]. Conclusions: Our results suggest crosslinking reaction in ICRS material. This should be taken into consideration prior to any CXL treatment of post ICRS-implanted cornea. [ABSTRACT FROM AUTHOR]

The effect of different pretreatment approaches based on alkali (NaOH)/hydrogen peroxide (H2O2) on willow sawdust (WS) biomass, in terms of delignification efficiency, structural changes of lignocellulose and subsequent fermentation toward ethanol, was investigated. Bioethanol production was carried out using the conventional yeast Saccharomyces cerevisiae, as well as three non-conventional yeasts strains, i.e., Pichia stipitis, Pachysolen tannophilus, Wickerhamomyces anomalus X19, separately and in co-cultures. The experimental results showed that a two-stage pretreatment approach (NaOH (0.5% w/v) for 24 h and H2O2 (0.5% v/v) for 24 h) led to higher delignification (38.3 ± 0.1%) and saccharification efficiency (31.7 ± 0.3%) and higher ethanol concentration and yield. Monocultures of S. cerevisiae or W. anomalus X19 and co-cultures with P. stipitis exhibited ethanol yields in the range of 11.67 ± 0.21 to 13.81 ± 0.20 g/100 g total solids (TS). When WS was subjected to H2O2 (0.5% v/v) alone for 24 h, the lowest ethanol yields were observed for all yeast strains, due to the minor impact of this treatment on the main chemical and structural WS characteristics. In order to decide which is the best pretreatment approach, a detailed techno-economical assessment is needed, which will take into account the ethanol yields and the minimum processing cost. [ABSTRACT FROM AUTHOR]

The aim of the study was to assess the effect of anode materials, namely a carbon nanotube (CNT)-buckypaper and a commercial carbon paper (CP) on the performance of a two-chamber microbial electrolysis cell (MEC), in terms of hydrogen production and main electrochemical characteristics. The experiments were performed using both acetate-based synthetic wastewater and real wastewater, specifically the effluent of a dark fermentative hydrogenogenic reactor (fermentation effluent), using cheese whey (CW) as substrate. The results showed that CP led to higher hydrogen production efficiency and current density compared to the CNT-buckypaper anode, which was attributed to the better colonization of the CP electrode with electroactive microorganisms, due to the negative effects of CNT-based materials on the bacteria metabolism. By using the fermentation effluent as substrate, a two-stage process is developed, where dark fermentation (DF) of CW for hydrogen production occurs in the first step, while the DF effluent is used as substrate in the MEC, in the second step, to further increase hydrogen production. By coupling DF-MEC, a dual environmental benefit is provided, combining sustainable bioenergy generation together with wastewater treatment, a fact that is also reinforced by the toxicity data of the current study. [ABSTRACT FROM AUTHOR]

Polymeric composites constitute an appealing class of materials with applications in various fields. Spin crossover (SCO) coordination complexes are switchable materials with potential use in data storage and sensors. Their incorporation into polymers can be considered an effective method for their wider practical application. In this study, Fe(II) SCO/polylactic acid hybrid polymeric composites have been prepared by film casting. The mononuclear coordination complex [Fe{N(CN)2}2(abpt)2] was incorporated into polylactic acid. The morphological, structural and thermoanalytical characterization of the composite films were performed via scanning electron microscopy (SEM), attenuated total reflectance (ATR/FTIR), Raman spectroscopy and differential scanning calorimetry (DSC). In addition, the migration release study (MRS) of the SCO compound from the polymeric matrix into the food simulant 50% v/v water/ethanol solution was also examined via UV/Vis absorption. Of particular interest was the investigation of the SCO behavior of the coordination complex after its incorporation into the polymer matrix; it was accomplished by temperature-dependent micro-Raman spectroscopy. The described attempt could be considered a preparatory step toward the development of SCO-based temperature sensors integrated into food packaging materials. [ABSTRACT FROM AUTHOR]

Hybrid polymeric materials incorporating carbon nanostructures or inorganic constituents stand as a promising class of materials exhibiting distinct but also complementary features. Carbon nanotubes have been proposed as unique candidates for polymer reinforcement; however, sustained efforts are further needed in order to make full use of their potential. The final properties of the reinforced polymer are controlled in part by the morphology and the eventual molecular orientation of the polymer matrix. In the present study, multiwall carbon nanotubes (MWCNTs) were utilized in order to reinforce polyethylene terephthalate (PET) composites. The effect of CNTs on the crystallization and the orientation of the structurally hybridized polymeric material has been investigated from the perspective of assessing their impact on the final properties of a relevant nanocomposite product. Functionalized MWCNTs were used to achieve their optimal dispersion in the polymer matrix. The physical properties of the composites (i.e., crystallinity and orientation) were characterized via differential scanning calorimetry, X-ray diffraction, and polarized Raman microscopy. The addition of well-dispersed CNTs acted as a nucleation agent, increasing the crystallization of the polyethylene terephthalate matrix and differentiating the orientation of both CNTs and macromolecular chains. [ABSTRACT FROM AUTHOR]

The reactions of copper(ii) carboxylate sources with acetylacetone dioxime (acacdoH 2 ) in Me 2 CO have been studied and a novel, metal ion-assisted ligand transformation has been discovered. The reaction of [Cu 2 (diba) 4 (dibaH) 2 ] and acacdoH 2 (1 : 1.5) in Me 2 CO has provided access to the complex {[Cu 2 (diba) 4 (qunx)]} n (1) in low yield (25-30%), where dibaH is 3,3-dimethylbutyric acid and qunx is quinoxaline. The [Cu 2 (piv) 4 (pivH) 2 ]/acacdoH 2 (1 : 1.5) reaction system in warm Me 2 CO, where pivH is pivalic acid, gave the analogous complex {[Cu 2 (piv) 4 (qunx)]} n (2) in moderate yield (∼50%). Complexes 1 and 2 can be easily prepared by the direct 1 : 1 reactions between the corresponding copper(ii) carboxylate starting materials and qunx in Me 2 CO and MeOH, respectively. The formation of coordinated qunx in 1 and 2 is Cu II -promoted (assisted) as suggested by the failure to synthesize the free qunx by a variety of reactions of acacdoH 2 and Me 2 CO under aerobic conditions in the absence or even the presence of dibaH and pivH, respectively. The observed acacdoH 2 → qunx transformation is catalytic and new in the chemistry of the dioximes of β-diketones, and a mechanism has been proposed based on well-established reactions of organic chemistry. The mechanism is based on a double Beckmann rearrangement-type transformation and the overall scheme is represented by the 1 : 1 : 1 reaction between acacdoH 2 , Me 2 CO and O 2 . Complexes 1 and 2 have similar molecular structures consisting of paddle-wheel {Cu 2 (η 1 :η 1 :μ-O 2 CR) 4 } units bridged by qunx ligands in a zigzag 1D chain arrangement. The geometry of the Cu II ions is square pyramidal with a quinoxaline nitrogen atom occupying the apical position at each metal ion. Weak H bonds are present within the chains, the donors being qunx carbon atoms and the acceptors being coordinated carboxylate oxygen atoms. Neighbouring chains interact through C-Hπ interactions between diba - /piv - methyl groups and the "pyrazine" part of qunx forming layers which are stacked along the b (1) or a (2) axis through weak van der Waals interactions. The packing of the layers is different in the two structures, due to the different nature of the carboxylate ligands. Hirshfeld surface analysis of the two structures reveals the similarity of the interchain (intralayer) interactions. The IR and Raman data of 1 and 2 are discussed in terms of the coordination mode of the carboxylate groups and permit assignments of some characteristic bands/peaks of coordinated qunx. Dc magnetic susceptibility studies in the 1.8-310 K range reveal very strong antiferromagnetic Cu II Cu II exchange interactions within the carboxylate-bridged Cu 2 units (J = -479 K for 1 and -532 K for 2 using the H = - J∑S 1 ·S 2 spin Hamiltonian) and weaker antiferromagnetic interactions between the Cu 2 units via the qunx superexchange pathways, with the latter being ∼10% in strength compared to the former. A critical discussion of the acacdoH 2 → qunx transformation in 1 and 2 is provided in the light of other impressive, recently discovered Cu II -assisted transformations of acacdoH 2 , pointing out the key role of the solvent in the processes known to date.