Solid Matrices Research Articles

Triggered and controlled release of active gaseous/volatile compounds for active packaging applications of agri-food products: A review.

Gaseous and volatile active compounds are versatile to enhance safety and preserve quality of agri-food products during storage and distribution. However, the use of these compounds is limited by their high vapor pressure and/or chemical instability, especially in active packaging (AP) applications. Various approaches for stabilizing and controlling the release of active gaseous/volatile compounds have been developed, including encapsulation (e.g., into supramolecular matrices, polymer-based films, electrospun nonwovens) and triggered release systems involving precursor technology, thereby allowing their safe and effective use in AP applications. In this review, encapsulation technologies of gases (e.g., CO2 , ClO2 , SO2 , ethylene, 1-methylcyclopropene) and volatiles (e.g., ethanol, ethyl formate, essential oils and their constituents) into different solid matrices, polymeric films, and electrospun nonwovens are reviewed, especially with regard to encapsulation mechanisms and controlled release properties. Recent developments on utilizing precursor compounds of bioactive gases/volatiles to enhance their storage stability and better control their release profiles are discussed. The potential applications of these controlled release systems in AP of agri-food products are presented as well.

Probiotic bacteria and plant-based matrices: An association with improved health-promoting features

• Probiotic/solid plant matrix combinations may provide improved health benefits. • Vegetable matrices are eligible to host and deliver probiotic bacteria to the gut. • Fibers and bioactive molecules modulate gut microbiota composition and metabolism. • Vegetable products have been validated as a probiotic carrier in human trials. The performance of probiotic bacterial strains is influenced by the carrier food and its functional components which while buffering the probiotic through the gastro-intestinal tract, contribute to an efficient implantation of bacterial cells and regulate probiotic features. Particularly, plant-based matrices are eligible substrate for hosting and delivering microbial populations because of their richness in nutrients, fibers, vitamins, minerals and dietary bioactive phytochemicals. The available data indicate that the intrinsic health-promoting properties of diverse plant-based matrices can be successfully exploited and improved developing effective association with probiotics, whose beneficial activity could be in turn improved and modulated by components of the plant-based carrier. In this review, the health-promoting properties of solid plant-based matrices (particularly artichokes, table olives, apple and cabbage) and their association with probiotic bacteria are also described indicating the role of the food matrix in sustaining probiotic cells during product processing, digestive process, gut implantation, and finally in exerting beneficial effects.

α-Glucosidase enzyme entrapped superporous poly(amphoteric) cryogel reactor with improved enzymatic activity and stability over wide pH ranges

Cryogels are one of the most unique materials for enzyme immobilization due to their super-porous elastic structures, and fast response times. Not only can cryogels act as flexible compartmentalization supports for enzymes, but they can also serve as solid protective matrices capable of preserving enzymatic activity over extreme conditions. The contributions of individual anionic and cationic cryogels to improve enzymatic activity can be combined into one as a cyrogels of poly(ampholyte). The present study targets the development of p(Amphoteric) cryogel as support for immobilization of enzymes and modeled in-depth characterizations and applications of α-Glucosidase (α-Glu) enzyme by entrapment ((α-Glu@p(Amphoteric)) during cryogelation. The α-Glu@p(Amphoteric) cryogels had 91.3 ± 1.7% activity at pH 6.8 and 37 °C the optimum conditions for free enzyme. They exhibited excellent pH tolerability with more than 70% activity between pH 5–8 at 37 °C, and more than 50% activity between 20–50 °C at pH 6.8. They showed improved storage stability even at 25 °C with almost 50% activity on the 10th days of storage and extraordinary reusability performances with more than 50% activity after 10th consecutive usages, respectively.

Sorption and desorption behavior of four antibiotics at concentrations simulating wastewater reuse in agricultural and forested soils

Due to rises in antibiotic resistance, fate and transport of antibiotics in soil systems requires greater understanding to determine potential risks to human and animal health. Adsorption coefficients (Kd and Kf) are standard measures for determining sorption capacity and partitioning behavior of organic contaminants in solid matrices. Frequently, sorption studies use higher antibiotic concentrations (mg L−1) and larger spiked water volume to mass of soil (>5:1), which may not reflect sorption behaviors of antibiotics at low concentrations (ng L−1 - μg L−1) in natural soils. The aim of this study was to determine sorption and desorption behaviors of four antibiotics commonly found in soils due to wastewater reuse using parameters replicating typical soil conditions. Concentrations (μg L−1) of sulfamethoxazole (SMX), trimethoprim (TMP), lincomycin (LIN) and ofloxacin (OFL) were equilibrated with four soil types at a 2:1 ratio of spiked water volume to mass of soil, which better represents field conditions. Log Kf and log Kfoc value ranges in this study were 1.88–1.95 and 3.2–4.7 for TMP, 0.43–1.4 and 2.7–3.2 for SMX, and 0.65–1.4 and 2.0–4.1 for LIN, respectively. Ofloxacin adsorbed tightly to soil particles, and adsorption coefficients could not be calculated. Sorption values were higher than previous studies that used similar soil types but had higher ratios of spiking solution to mass of soil (>5:1). Overall, OFL and TMP are expected to strongly interact with soil particles and be less mobile, while SMX and LIN are expected to be more mobile due to weaker sorption interactions.

Long-lived room temperature phosphorescent system: Phenanthrene–β-cyclodextrin–tert-butylbenzene. Spectra and structure computer simulations

The room temperature phosphorescence (RTP) of phenanthrene (PH) was studied before and after oxygen removal in a suspension formed by adding tert-butylbenzene (TBB) to an aqueous solution of PH and β-cyclodextrin (CD). The RTP decay curves indicate that PH molecules are located inside solid aggregates within two types of the self-assembled phosphorescent complexes. The structure of one of them, PH@2CD@2TBB (I), was proposed by the method of fluorescence spectroscopy and confirmed by the quantum-chemical (QC) calculation indicating the presence of the direct contact between PH and TBB inside the CD dimer in aggregate. The structure of the second, PH@3CD@2TBB (II), was calculated by the QC method. The molecular dynamics simulation (MD) was performed to elucidate the stability in an aqueous solution and in solid matrices of both I and II characterized by different degrees of PH packing density inside the aggregate. Due to the higher stability, I turned out to be the preferred structure as the basis of the phosphorescent center in a solid aggregate. To elucidate the mechanism of RTP quenching the O2 molecules was added to the solution and solid systems of both I and II. Oxygen mobility and penetration statistics to PH in these systems were calculated. Both the fluorescence data and computer simulations show that the longest-lived component of the RTP decay belongs to structure I, in which PH is sandwiched between two TBB molecules in the CD dimer, owing to which RTP is characterized by the minimum values of the quenching and nonradiative relaxation constants. PH molecules located in a less rigid environment like complex II, or as part of other less ordered structures, are characterized by shorter RTP lifetimes. The results demonstrate a high degree of protection of the substrate encapsulated in the CD dimer from oxygen.

Evaluation of low cost immobilized support matrices in augmentation of biohydrogen potential in dark fermentation process using B. licheniformis AP1

In this study, the impact of immobilized (cell adsorbed and cell entrapped) matrices or beads on biohydrogen production potential has been reported. The novelty of this research is to investigate the impact of natural waste matrices or carriers (coconut coir-CC, wood shaving-WS) and low cost carriers (foam-FM, and alginate) on biohydrogen production potential. The study for dark fermentation process was performed for 2 days with four batch tests using cell adsorption method and six batch tests using cell entrapment method at initial pH (6.5), and temperature 38 ± 2 °C temperature. Cell adsorbed solid matrices reported maximum biohydrogen potential results as 62 ± 5.6 mL H2/30 mL (control), 138 mL ± 7 mL H2/30 mL (foam), 103.75 ± 6.7 mL H2/30 mL (coconut coir), and 96 ± 6.36 mL H2/30 mL (wood shaving). In cell entrapment, alginate supplemented TiO2-NP reported results as 32 mL ± 2.8/30 mL (control- 0 TiO2 mg/L), 35 ± 2.4 mL/30 mL (200 TiO2 mg/L), 40 ± 2.8 mL/30 mL (400 TiO2 mg/L), 53 ± 4 mL/30 mL (600 TiO2 mg/L), 75 ± 4.2 mL/30 mL (800 TiO2 mg/L), and 93 ± 3 mL/30 mL (1000 TiO2 mg/L) respectively. The SEM observation displayed that foam was the best carrier for high cell adhesion on its surface in comparison to other carriers due to surface characteristics. The current study achieved maximum yield 2.07 mol/mol of glucose using foam carrier. Majorly, acetic acid followed by butyric acid is analyzed as by-products at the end of dark fermentation.

Calorimetric Investigation of the Relaxation Phenomena in Amorphous Lyophilized Solids.

Studying the thermal history and relaxation of solid amorphous drug product matrices by calorimetry is a well-known approach, particularly in the context of correlating the matrix parameters with the long-term stability of freeze-dried protein drug products. Such calorimetric investigations are even more relevant today, as the application of new process techniques in freeze-drying (which strongly influence the thermal history of the products) has recently gained more interest. To revive the application of calorimetric methods, the widely scattered knowledge on this matter is condensed into a review and completed with new experimental data. The calorimetric methods are applied to recent techniques in lyophilization, such as controlled nucleation and aggressive/collapse drying. Phenomena such as pre-Tg events in differential scanning calorimetry and aging shoulders in isothermal microcalorimetry are critically reviewed and supplemented with data of freeze-dried products that have not been characterized with these methods before.

Solid Polymer Electrolytes with Increased Polymer Polarizability for Solid-State Lithium Batteries

Solid polymer electrolytes (SPE) are light-weight, flexible, and non-flammable, thus providing a promising technical route to practical solid-state lithium batteries. Although a broad variety of molecular structures of the solid polymer matrices are described in the literature, commercially available materials are scarce. The mostly widely studied example of SPE are the poly(ethylene oxide) (PEO)-based electrolytes that contain a small molecule Li-salt (e.g., LiPF6, LiTFSI, etc). However, solid-state batteries made with a PEO-based SPE are only operational above 60 °C, corresponding to the melting of PEO, where their mechanical strength is poor. The room-temperature performance of PEO-SPEs are too low (< 10-5 S/cm) to be practical [1]. Thus, new polymer electrolytes that have high Li+ conductivity and high mechanical strength are needed.The migration of Li+ in PEO-SPE depends on the coordination of Li+ by the ethylene oxide (EO) segment, which normally involves 6-8 EO moieties. The interaction of Li+ with an EO segment is strongly influenced by the polarizability of the EO groups. The relative permittivity (ε) of a single ethylene oxide (CH2CH2O) is only about 13 – 14 [2]. This implies that Li ions experience much weaker interactions with EO groups than other polar molecules, like water (ε = 80) or cyclic carbonates (e.g., ethylene carbonate, ε = 90). Thus, one approach to increase the interaction of Li+ with the polymer chain could be to increase the polarizability of the polymers themselves. Many functional groups are highly polarizable. But only those groups that can be linked to the PEO main chain are worthy of consideration here. An example is vinylene carbonate (VC, ε = 126), which contains double bonds and can be added to the EO chains to form new polymer electrolytes.In order to link VC groups to EO chains, a PEO-like SPE may be formed using in-situ radical polymerization of the EO precursors. Examples of such precursors include poly(ethylene glycol) dimethacrylate, poly(ethylene glycol) diacrylate or their derivatives. Small molecule Li-salts may be incorporated in the precursor solution. The polymerization can be initiated by UV light irradiation or by thermal heating, depending on the type of radical initiator. In this method, the intimate interactions between Li-ions and EO groups are ensured and the crystallization of the EO segments is largely prevented.In this work, we combine these approaches to form a new solid polymer electrolyte that has good conductivity and high mechanical strength. The membrane is formed in-situ using UV irradiation of a blend of precursors and salts and chain additive functional molecules. This resulting SPE has high conductivity (0.3 mS/cm at room temperature and 1.1 mS/cm at 70 °C), a wide electrochemical stability window up to 4.8 V (vs. Li+/Li) and is thermally stable to ~200 °C, while resisting penetration of Li metal dendrites. The application of the polymer electrolyte in a SiO composite electrode is also demonstrated to achieve high capacity.

Hydrophilic-interaction-based magnetically assisted matrix solid-phase dispersion extraction of carbadox and olaquindox in feeds.

Carbadox and olaquindox have been banned from feeds since 1998 by the EU because of their mutagenic, photoallergic, and carcinogenic effects. Unfortunately, owing to their outstanding effect, they are frequently abused or misused in animal husbandry. There is an urgent need to develop a sensitive and reliable method for monitoring these drugs in animal feeds. This work reported a new method of hydrophilic-interaction-based magnetically assisted matrix solid-phase dispersion (MMSPD) extraction coupled with reversed-phase liquid chromatography-mass spectrometry for simultaneous determination of carbadox and olaquindox in animal feeds. 3-Trimethoxysilylpropyl methacrylate (γ-MAPS)-modified attapulgite (ATP) was crosslinked with γ-MAPS-modified iron(II,III) oxide (Fe3 O4 ), 1-vinyl-3-(butyl-4-sulfonate) imidazolium (VBSIm), acrylamide (AM), and N,N'-methylene-bis(acrylamide) (MBA) to synthesize ATP@Fe3 O4 @poly(VBSIm-AM-MBA) particles. The resultant particles were characterized by scanning electron microscopy, energy dispersive spectrometer, transmission electron microscopy, vibrating sample magnetometer, and Fourier transform infrared spectroscopy. Crosslinking of ATP into the magnetic particles has significantly increased the adsorption capacity of the particles. Under optimum conditions, the limits of detection (S/N=3) were 0.3μg kg-1 and 0.9μg kg-1 for carbadox and olaquindox respectively. The intra-day and inter-day recoveries of the spiked targets in feed samples were in the range 83.5-98.3% with relative standard deviations of 1.0-8.3%. With a simplified procedure and a low amount of sample, the proposed hydrophilic-interaction-based MMSPD method is not only useful for the determination of carbadox and olaquindox in feeds but also holds great promise for the analysis of other polar targets in solid or semisolid matrices. © 2021 Society of Chemical Industry.

Improvement of the QuEChERS extraction step by matrix-dispersion effect and application on beta-lactams analysis in wastewater sludge by LC-MS/MS

In the last decade, beta-lactams use in veterinary and human medicine increased to represent today about 15% of the overall consumption. Beta-lactams tend to degrade and metabolize in the environment. Therefore, analytical methods must be sensitive enough to quantify low concentrations of the parent molecules and also allow detection of metabolites. This study presents the development of a modified QuEChERS method for the extraction of seven beta-lactams and one degradation product (Amoxicillin, Ampicillin, Cefapirin, Cefoperazone, Cefquinome, Ceftiofur, Cloxacillin, and Amoxicillin-Diketopiperazine) from sewage treatment plant sludge and their analysis by liquid chromatography coupled with tandem mass spectrometry. Before the QuEChERS extraction, a dispersion step of the sample with EDTA-treated sand was optimized and added, allowing to facilitate the exchanges between the matrix and the extraction solvent. Then, to decrease the interferences present in the extract, a fast and efficient pass-through SPE was implemented.The optimized method was validated and showed satisfactory performances, in adequacy with the analysis of beta-lactams in solid environmental matrices. Limits of quantification lower than 20 ng.g−1 for all analytes, high accuracy (96%–114% quantification on spiked samples nominal concentration) and interday precision (2%–12% RSD) were obtained. This method was then applied to eight sludge samples. Cefapirin and amoxicillin-diketopiperazine were detected in four samples each, at concentrations of 10.2–53.3 ng.g−1 and 3.0–9.5 ng.g−1 respectively. Thus, the developed method is very effective for the extraction of beta-lactams from environmental solid matrices.

Chemical Fate and Partitioning Behavior of Antibiotics in the Aquatic Environment-A Review.

Antibiotics in the aquatic environment is a major problem because of the emergence of antibiotic resistance. The long-term ecological impact on the aquatic environment is unknown. Many sources allow entry of antibiotics into the environment, including wastewater-treatment plants (WWTPs), agricultural runoff, hospital effluent, and landfill leachate. Concentrations of antibiotics in the aquatic environment vary significantly; studies have shown fluoroquinolones, tetracycline, macrolides, sulfonamides, and penicillins to reach 2900, 1500, 9700, 21 400, and 1600 ng L-1 in wastewater effluent samples, respectively. However, concentrations are highly variable between different countries and depend on several factors including seasonal variation, prescription, and WWTP operating procedures. Likewise, the reported concentrations that cause environmental effects vary greatly between antibiotics, even within the same class; however, this predicted concentration for the antibiotics considered was frequently <1000 ngL-1 , indicating that when discharged into the environment along with treated effluent, these antibiotics have a potentially detrimental effect on the environment. Antibiotics are generally quite hydrophilic in nature; however, they can ionize in the aquatic environment to form charged structures, such as cations, zwitterions, and anions. Certain classes, particularly fluoroquinolones and tetracyclines, can adsorb onto solid matrices, including soils, sediment, and sludge, making it difficult to fully understand their chemical fate in the aquatic environment. The adsorption coefficient (Kd ) varies between different classes of antibiotics, with tetracyclines and fluoroquinolones showing the highest Kd values. The Kd values for fluoroquinolones, tetracyclines, macrolides, and sulfonamides have been reported as 54 600, 7600, 130, and 1.37 L kg-1 , respectively. Factors such as pH of the environment, solid matrix (sediment/soil sludge), and ionic strength can influence the Kd ; therefore, several values exist in literature for the same compound. Environ Toxicol Chem 2021;40:3275-3298. © 2021 SETAC.

Repeatable separation of microplastics integrating mineral oil extraction and a PDMS-Ni foam adsorbent in real soil

The accumulation of microplastics (MPs) in the environment has accelerated. It is very challenging to separate MPs from complicated solid substrate matrices such as soil and sediments not only because solid substrates usually adhere to or surround MPs but also because there is no standardized method for extracting MPs. Here, we report a novel adsorption-based repeatable process for separating and efficiently recovering MPs from environmental matrices using mineral oil and a polydimethylsiloxane (PDMS)-coated nickel (Ni) foam adsorbent. The hydrophobic/magnetic adsorbent was produced by chemical vapor deposition of PDMS on Ni foam. This process created a hydrophobic surface throughout three-dimensional (3D) porous Ni network, providing high porosity, high surface area, and robustness. Compared to tested vegetable oils, mineral oil was superior at extracting seven types of MPs (LDPE, PP, PS, PC, PET, PVC, and PTFE) with different densities of 0.94 ∼ 2.2 g/cm3 from real soil samples. After the mineral oil extraction, by stamping the PDMS-Ni foam on the floating oil layer of the extracted materials, oil-captured MPs of various types and sizes (70 ∼ 1200 μm) were successfully recovered and identified in seconds without accompanying unwanted particles. In addition, due to the reusability of the PDMS-Ni foam, the MPs were isolated several times simply by supplementing the sample with mineral oil, and this procedure results in over 99% of MPs becoming isolated from complex solid matrices. Thus, our adsorption-based repeatable process for separating MPs can allow for an accurate quantitative analysis of microplastic accumulation in solid matrices.

Polycyclic Aromatic Hydrocarbon Sorption by Functionalized Humic Acids Immobilized in Micro- and Nano-Zeolites

Polycyclic aromatic hydrocarbons (PAHs) are hazardous compounds originating from anthropogenic activity. Due to their carcinogenic properties for humans, several technologies have been developed for PAH removal. Sorption with natural and organic materials is currently one of the most studied due to its low cost and its environmentally friendly nature. In this work, a hybrid sorbent involving functionalized humic acids (HAs) and nano-zeolite is proposed to entrap PAHs. The use of functionalized HAs immobilized in a porous support is designed to address the instability of HAs in solution, which has been already reported. HA functionalization was carried out to increase the non-polarity of HAs and aliphatic group formation. The HAs were functionalized by esterification/etherification with alkyl halides, and their chemical changes were verified by FTIR and NMR. The sorption isotherms of the functionalized HAs in micro- and nano-zeolites were used to assess the performance of the nano-zeolites in adsorbing these HAs. The hybrid support allowed the removal of anthracene and pyrene at percentages higher than 90%; fluoranthene, of angular molecular structure, was adsorbed at 85%. PAHs are ubiquitous in the environment, and a stable sorption of them in solid matrices will allow their removal from the environment through effective and environmentally friendly methods.

Fe(III)-Complex-Imprinted Polymers for the Green Oxidative Degradation of the Methyl Orange Dye Pollutant.

One of the biggest problems worldwide is the pollution of natural water bodies by dyes coming from effluents used in the textile industry. In the quest for novel effluent treatment alternatives, the aim of this work was to immobilize Fe(III) complexes in molecularly imprinted polymers (MIPs) to produce efficient Fenton-like heterogeneous catalysts for the green oxidative degradation of the methyl orange (MO) dye pollutant. Different metal complexes bearing commercial and low-cost ligands were assayed and their catalytic activity levels towards the discoloration of MO by H2O2 were assessed. The best candidates were Fe(III)-BMPA (BMPA = di-(2-picolyl)amine) and Fe(III)-NTP (NTP = 3,3′,3″-nitrilotripropionic acid), displaying above 70% MO degradation in 3 h. Fe(III)-BMPA caused the oxidative degradation through two first-order stages, related to the formation of BMPA-Fe-OOH and the generation of reactive oxygen species. Only the first of these stages was detected for Fe(III)-NTP. Both complexes were then employed to imprint catalytic cavities into MIPs. The polymers showed catalytic profiles that were highly dependent on the crosslinking agent employed, with N,N-methylenebisacrylamide (MBAA) being the crosslinker that rendered polymers with optimal oxidative performance (>95% conversion). The obtained ion-imprinted polymers constitute cheap and robust solid matrices, with the potential to be coupled to dye-containing effluent treatment systems with synchronous H2O2 injection.

Low-viscosity matrix suspension culture enables scalable analysis of patient-derived organoids and tumoroids from the large intestine

Cell embedment into a solid support matrix is considered essential for the culture of intestinal epithelial organoids and tumoroids, but this technique presents challenges that impede scalable culture expansion, experimental manipulation, high-throughput screening and diagnostic applications. We have developed a low-viscosity matrix (LVM) suspension culture method that enables efficient establishment and propagation of organoids and tumoroids from the human large intestine. Organoids and tumoroids cultured in LVM suspension recapitulate the morphological development observed in solid matrices, with tumoroids reflecting the histological features and genetic heterogeneity of primary colorectal cancers. We demonstrate the utility of LVM suspension culture for organoid and tumoroid bioreactor applications and biobanking, as well as tumoroid high-throughput drug sensitivity testing. These methods provide opportunities for the study and use of patient-derived organoids and tumoroids from the large intestine.

Multiresidue antibiotic-metabolite quantification method using ultra-performance liquid chromatography coupled with tandem mass spectrometry for environmental and public exposure estimation

This manuscript describes a new multiresidue method utilising ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) via multiple reaction monitoring (MRM), for the identification and quantification of 58 antibiotics and their 26 metabolites, in various solid and liquid environmental matrices. The method was designed with a ‘one health’ approach in mind requiring multidisciplinary and multisectoral collaborative efforts. It enables comprehensive evaluation of antibiotic usage in surveyed communities via wastewater-based epidemiology, as well as allowing for the assessment of potential environmental impacts. The instrumental performance was very good, demonstrating linearity up to 3000 μg L−1, and high accuracy and precision. The method accuracy in several compounds was significantly improved by dividing calibration curves into separate ranges. This was accompanied by applying a weighting factor (1/x). Microwave-assisted and/or solid-phase extraction of analytes from liquid and solid matrices provided good recoveries for most compounds, with only a few analytes underperforming. Method quantification limits were determined as low as 0.017 ng L−1 in river water, 0.044 ng L−1 in wastewater, 0.008 ng g−1 in river sediment, and 0.009 ng g−1 in suspended solids. Overall, the method was successfully validated for the quantification of 64 analytes extracted from aqueous samples, and 45 from solids. The analytes that underperformed are considered on a semi-quantitative basis, including aminoglycosides and carbapenems. The method was applied to both solid and liquid environmental matrices, whereby several antibiotics and their metabolites were quantified. The most notable antibiotic-metabolite pairs are three sulfonamides and their N-acetyl metabolites; four macrolides/lincomycins and their N-desmethyl metabolites; and five quinolone metabolites.Graphical abstract

Block Copolymer Stabilized Liquid Nanodroplets Facilitate Efficient Triplet Fusion-Based Photon Upconversion in Solid Polymer Matrices.

Sensitized triplet-triplet annihilation-based photon upconversion is a photophysical process that affords anti-Stokes-shifted emission after annihilation of two metastable triplet excitons of an emitter dye and the formation of a fluorescent singlet state. While this process readily occurs in solutions under conditions where the mobility of the dye molecules is high, particular architectures are required to facilitate efficient energy transfers in solid polymers. One possibility is to incorporate liquid upconverting domains into solid polymer matrices. Another possibility is to reduce the intermolecular distance between the dyes below the Dexter radius, allowing exciton migration via triplet hopping. We introduce herein nanostructured materials that combine both of these features. These glassy nanostructured polymer systems contain liquid upconverting nanodroplets that are stabilized with a block copolymer surfactant and are fabricated under ambient conditions in a facile one-step protocol. The dyes concentrate in the nanostructured liquid domains, and this enables hopping-mediated ET and TTA between the dyes and leads to an upconversion efficiency of ∼20%.

Infrared spectroscopy of carbocations upon electron ionization of ethylene in helium nanodroplets

The electron impact ionization of helium droplets doped with ethylene molecules and clusters yields diverse CXHY + cations embedded in the droplets. The ionization primarily produces C2H2 +, C2H3 +, C2H4 +, and CH2 +, whereas larger carbocations are produced upon the reactions of the primary ions with ethylene molecules. The vibrational excitation of the cations leads to the release of bare cations and cations with a few helium atoms attached. The laser excitation spectra of the embedded cations show well resolved vibrational bands with a few wavenumber widths-an order of magnitude less than those previously obtained in solid matrices or molecular beams by tagging techniques. Comparison with the previous studies of free and tagged CH2 +, CH3 +, C2H2 +, C2H3 +, and C2H4 + cations shows that the helium matrix typically introduces a shift in the vibrational frequencies of less than about 20cm-1, enabling direct comparisons with the results of quantum chemical calculations for structure determination. This work demonstrates a facile technique for the production and spectroscopic study of diverse carbocations, which act as important intermediates in gas and condensed phases.

Matrix Isolation Spectroscopic and Relativistic Quantum Chemical Study of Molecular Platinum Fluorides PtFn (n=1-6) Reveals Magnetic Bistability of PtF4.

Molecular platinum fluorides PtF n , n=1–6, are prepared by two different routes, photo‐initiated fluorine elimination from PtF6 embedded in solid noble‐gas matrices, and the reaction of elemental fluorine with laser‐ablated platinum atoms. IR spectra of the reaction products isolated in rare‐gas matrices under cryogenic conditions provide, for the first time, experimental vibrational frequencies of molecular PtF3, PtF4 and PtF5. Photolysis of PtF6 enabled a highly efficient and almost quantitative formation of molecular PtF4, whereas both PtF5 and PtF3 were formed simultaneously by subsequent UV irradiation of PtF4. The vibrational spectra of these molecular platinum fluorides were assigned with the help of one‐ and two‐component quasirelativistic DFT computation to account for scalar relativistic and spin–orbit coupling effects. Competing Jahn‐Teller and spin–orbit coupling effects result in a magnetic bistability of PtF4, for which a spin‐triplet (3B2g, D 2h) coexists with an electronic singlet state (1A1g, D 4h) in solid neon matrices.

The microstructure of magnetorheological materials characterized by means of computed X-ray microtomography

AbstractMagnetorheological materials are a class of “smart materials”, where mechanical material properties can be tuned by the application of externally applied fields. To accomplish the magneto-sensitive quality, magnetic particlesare distributed in a host matrix. In the last year’s interest gained in materials based on solid matrices. In contrast to fluid systems, within a solid matrix, the particles are fixed within the material. This enables an evaluation of the structures formed by the particles by means of computed X-ray microtomography. As known from past investigations, the arrangement and movement of the magnetic particles within the matrix play a major role in determining the overall material properties. Computed X-ray microtomography proved to be a convenient tool, providing important new knowledge about those materials. This paper gives an overview of the application of the method of computed X-ray microtomography on several kinds of solid magnetorheological materials, the broad possibilities of data evaluation, and fundamental results obtained with this method and the described materials.