Molecular profiling of naphthenic acids in technical mixtures and oil sands process‐affected water using polar reversed‐phase liquid chromatography–mass spectrometry

In this work, a reversed‐phase ultra‐HPLC (UHPLC) ultrahigh resolution MS (UHRMS) method was evaluated for the comprehensive profiling of NAs containing two O atoms in each molecule (O2NAs; general formula C_nH_{2n + z}O₂, where n is the number of carbon atoms and z represents hydrogen deficiency). Using a polar cyanopropyl‐bonded phase column and negative‐ion electrospray ionization mass spectrometric detection at 120,000 FWHM (m/z 400), 187 and 226 O2NA species were found in two naphthenic acid technical mixtures, and 424 and 198 species with molecular formulas corresponding to O2NAs were found in two oil sands process‐affected water samples (one from a surface mining operation and the other from a steam‐assisted gravity drainage operation), respectively. To our knowledge, these are the highest numbers of molecular compositions of O2NAs that have been profiled thus far in environmental samples. Assignments were based on accurate mass measurements (≤3 ppm) combined with rational molecular formula generation, correlation of chromatographic behavior of O2NA homologues with their elemental compositions, and confirmation with carboxyl group‐specific chemical derivatization using 3‐nitrophenylhydrazine. Application of this UHPLC–UHRMS method to the quantitation of O2NAs in the surface mining operation‐derived water sample showed excellent linearity (R² = 0.9999) with external calibration, a linear range of 256‐fold in concentration, and quantitation accuracies of 64.9 and 69.4% at two “standard substance” spiking levels.     

Nitroanilines as Quenchers of Pyrene Fluorescence

The quenching of pyrene and 1‐methylpyrene fluorescence by nitroanilines (NAs), such as 2‐, 3‐, and 4‐nitroaniline (2‐NA, 3‐NA, and 4‐NA, respectively), 4‐methyl‐3‐nitroaniline (4‐M ‐3‐NA), 2‐methyl‐4‐nitroaniline (2‐M‐4‐NA), and 4‐methyl‐3,5‐dinitroaniline (4‐M‐3,5‐DNA), are studied in toluene and 1,4‐dioxane. Steady‐state fluorescence data show the higher efficiency of the 4‐NAs as quenchers and fit with a sphere‐of‐action model. This suggests a 4‐NA tendency of being in close proximity to the fluorophore, which could be connected with their high polarity/hyperpolarizability. In addition, emission and excitation spectra evidence the formation of emissive pyrene—NA ground‐state complexes in the case of the 4‐NAs and, in a minor degree, in the 2‐NA. Moreover, time‐resolved fluorescence experiments show that increasing amounts of NA decrease the pyrene fluorescence lifetime to a degree that depends on the NA nature and is larger in the less viscous solvent (toluene). Although the NA absorption and the pyrene (Py) emission overlap, we found no evidence of dipole–dipole energy transfer from the pyrene singlet excited state (¹Py) to the NAs; this could be due to the low NA concentration used in these experiments. Transient absorption spectra show that the formation of the pyrene triplet excited state (³Py) is barely affected by the presence of the NAs in spite of their efficiency in ¹Py quenching, suggesting the involvement of ¹Py—NA exciplexes which—after intersystem crossing—decay efficiently into ³Py.     

One‐Step Nucleic Acid Purification and Noise‐Resistant Polymerase Chain Reaction by Electrokinetic Concentration for Ultralow‐Abundance Nucleic Acid Detection

Nucleic acid amplification tests (NAATs)integrated on a chip hold great promise for point‐of‐care diagnostics. Currently, nucleic acid (NA) purification remains time‐consuming and labor‐intensive, and it takes extensive efforts to optimize the amplification chemistry. Using selective electrokinetic concentration, we report one‐step, liquid‐phase NA purification that is simpler and faster than conventional solid‐phase extraction. By further re‐concentrating NAs and performing polymerase chain reaction (PCR) in a microfluidic chamber, our platform suppresses non‐specific amplification caused by non‐optimal PCR designs. We achieved the detection of 5 copies of M. tuberculosis genomic DNA (equaling 0.3 cell) in real biofluids using both optimized and non‐optimal PCR designs, which is 10‐ and 1000‐fold fewer than those of the standard bench‐top method, respectively. By simplifying the workflow and shortening the development cycle of NAATs, our platform may find use in point‐of‐care diagnosis.     

Structure and mechanical properties controlling of elastomer modified polypropylene by compounded β/α nucleating agents

Previous work showed that there was a synergistic effect of nucleating agent (NA) and elastomer in improving the fracture resistance of isotactic polypropylene (PP), relating to the formation of large amounts of β‐PP (β‐NA nucleated system) or the decrease of the spherulites diameters of α‐PP (α‐NA nucleated system). To find the direct relation between the synergistic efficiency of NA/elastomer and the microstructures of the materials, in this work, the ethylene‐propylene‐diene terpolymer (EPDM) modified PP blends with compounded NAs (β/α) were adopted and the changes of the microstructure and mechanical properties were investigated comparatively. The results showed that, with the adjustment of the mass fraction of compounded NAs, the microstructures of PP matrix including supermolecular structure and the relative fraction of β‐PP (K_β) change accordingly. Specifically, the K_β of β‐PP was successfully adjusted in the wide range of 0–78.9%. Consequently, the stiffness and the fracture resistance of the PP/EPDM blends were easily controlled in different degrees. It is believed that this work could provide a guide map for the design and preparation of certain polymer blends satisfying certain requirement. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Macrocyclic Mechanism‐Based Inhibitor for Neuraminidases

A macrocyclic mechanism‐based inhibitor for neuraminidases (NAs) bearing a 2‐difluoromethylphenyl aglycone and a linker between the aglycone and C‐9 positions of sialic acid was synthesized and evaluated. The macrocyclic structure was designed to keep the aglycone moiety in the active site of the neuraminidase after cleavage of the glycoside bond. When Vibrio chorelae neuraminidase (VCNA) was treated with a similar acyclic derivative in the presence of detergent, the irreversible inhibition property was disabled. In contrast, this macrocyclic compound acted as an irreversible inhibitor for VCNA in the presence of detergent. Inhibition assay for various NAs using this macrocyclic compound revealed that the irreversible inhibition property depends on the k_cat of the neuraminidase treated. NAs having small k_cat values, such as Influenza viruses, Clostridium, Trypanosoma cruzi, and Human, were also inhibited irreversibly. However, Salmonella typhimurium NA, which has an extremely high k_cat, was not affected irreversibly by the inhibitor. Interestingly, in contrast to common k_cat inhibitors, the irreversibility of inhibition by this macrocyclic compound is inversely proportional to the k_cat of the target neuraminidase.     

Characterization of oil sands naphthenic acids treated with ultraviolet and microwave radiation by negative ion electrospray Fourier transform ion cyclotron resonance mass spectrometry

Naphthenic acids (NAs) are concentrated in oil sand process water (OSPW) as a result of caustic oil sands extraction processes. There is considerable interest in methods for treatment of NAs in OSPW. Earlier work has shown that the combination of ultraviolet (UV) and microwave treatments in the laboratory was effective in reducing the concentration of classical NAs. Here we apply Fourier transform ion cyclotron resonance mass spectrometry (FT‐ICR MS) to further characterize NAs treated with (a) UV (254 nm) in the presence of TiO₂ catalyst; and/or (b) microwave irradiation (2.45 GHz). FT‐ICR MS was used to characterize the NA fraction before and after treatment. Acidic oxygen‐containing classes were most abundant in all samples whereas other heteroatomic classes were least abundant or not present in some samples. For example, the SO₂‐containing species were absent in UV‐ or combined UV‐ and microwave‐treated samples. The O₂ class was dominant in all samples, indicative of NAs. However, samples treated with UV and microwave radiation have a lower relative abundance of other heteroatomic classes. We observed O₂, S₁O₂, O₃, S₁O₃, O₄, O₅, and O₆ classes, whereas the species with relatively high O_n content, namely, the O₃, O₅, and O₆ classes, were present only in UV‐ and microwave‐treated samples. The relatively high O_n content is consistent with oxidation of the parent acids in treated samples. There may thus be potential implications for environmental forensics. For example, the monitoring of the ratio of SO₂:O₂ or tracking the relative abundances of O₂, O₃, O₄, O₅, and O₆ classes may provide insights for distinguishing naturally derived oil sands components from those that are process‐related in aquatic environments. Copyright © 2010 John Wiley & Sons, Ltd.     

One-Step Nucleic Acid Purification and Noise-Resistant Polymerase Chain Reaction by Electrokinetic Concentration for Ultralow-Abundance Nucleic Acid Detection

Nucleic acid amplification tests (NAATs)integrated on a chip hold great promise for point-of-care diagnostics. Currently, nucleic acid (NA) purification remains time-consuming and labor-intensive, and it takes extensive efforts to optimize the amplification chemistry. Using selective electrokinetic concentration, we report one-step, liquid-phase NA purification that is simpler and faster than conventional solid-phase extraction. By further re-concentrating NAs and performing polymerase chain reaction (PCR) in a microfluidic chamber, our platform suppresses non-specific amplification caused by non-optimal PCR designs. We achieved the detection of 5 copies of M. tuberculosis genomic DNA (equaling 0.3 cell) in real biofluids using both optimized and non-optimal PCR designs, which is 10- and 1000-fold fewer than those of the standard bench-top method, respectively. By simplifying the workflow and shortening the development cycle of NAATs, our platform may find use in point-of-care diagnosis.     

Effect of the Metal Phenylphosphonates on the Nonisothermal Crystallization and Performance of Isotactic Polypropylene

The use of metal phenylphosphonates as efficient nucleating agents (NAs) for isotactic polypropylene (iPP) is reported and a possible structural correlation to the nucleation efficiency is studied. First, three kinds of metal phenylphosphonates are synthesized via reflux method: Ca(C₆H₅PO₃)?2H₂O (CaPPA), Ca(C₆H₅PO₃H)₂ (CaPPA2), and Al(HO₃PC₆H₅)(O₃PC₆H₅)?H₂O (AlPPA2). Then, the nonisothermal crystallization behaviors, mechanical, and optical properties of iPP composites are investigated. Compared to CaPPA2 and AlPPA2, CaPPA exhibits more effective heterogeneous nucleation effect during iPP crystallization. Furthermore, the nucleation efficiency of CaPPA is similar to industrial standard NAs NA‐21 and NA‐11. With the addition of 0.1 wt % CaPPA, the crystallization temperature is enhanced and the parameter F(T) of Mo method is decreased appreciably. Moreover, the flexural modulus, impact strength, and haze values of iPP composites are improved remarkably by introducing CaPPA. The CH/π interaction between polymer and aromatic cleft of CaPPA is considered to facilitate the attachment of iPP chains and subsequent nucleation and crystallization, which is verified by the viscoelastic properties of pure iPP and composites. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 161–173     

Microfluidic capillary zone electrophoresis mass spectrometry analysis of alkaloids in Lobelia cardinalis transgenic and mutant plant cell cultures

Application of a microfluidic CE^* device for CZE‐MS allows for fast, rapid, and in‐depth analysis of large sample sets. This microfluidic CZE‐MS device, the 908 Devices ZipChip, involves minimal sample preparation and is ideal for small cation analytes, such as alkaloids. Here, we evaluated the microfluidic device for the analysis of alkaloids from Lobelia cardinalis hairy root cultures. Extracts from wild‐type, transgenic, and selected mutant plant cultures were analyzed and data batch processed using the mass spectral processing software MZmine2 and the statistical software Prism 8. In total 139 features were detected as baseline resolved peaks via the MZmine2 software optimized for the electrophoretic separations. Statistically significant differences in the relative abundance of the primary alkaloid lobinaline (C₂₇H₃₄N₂), along with several putative “lobinaline‐like” molecules were observed utilizing this approach. Additionally, a method for performing both targeted and untargeted MS/MS experiments using the microfluidic device was developed and evaluated. Coupling data‐processing software with CZE‐MS data acquisition has enabled comprehensive metabolomic profiles from plant cell cultures to be constructed within a single working day.     

Functional Microgels Tailored by Droplet‐Based Microfluidics

Monodisperse polymer gel particles with micrometer‐scale dimensions serve for a variety of applications, including those as microcapsules for actives or as micrometer‐sized matrixes for mesoscopic additives. These particles can be produced with exquisite control through the use of droplet‐based microfluidic templating followed by subsequent droplet solidification. This can be achieved by two ways: One way is to use pre‐microgel solutions of low molecular weight monomers and to form microgels by polymerizing these monomers. Another way is to use pre‐polymerized, high molecular weight precursors and to gel them by polymer‐analogous crosslinking. Both approaches have their specific advantages, allowing microgels to be tailored and optimized for specific needs such as those as delivery systems or scaffolds for living cells. This article highlights some recent achievements in the development and use of these microfluidic techniques to fabricate functional microgel particles.

     

Constructing Hierarchical Tectorum‐like α‐Fe2O3/PPy Nanoarrays on Carbon Cloth for Solid‐State Asymmetric Supercapacitors

The design of complex heterostructured electrode materials that deliver superior electrochemical performances to their individual counterparts has stimulated intensive research on configuring supercapacitors with high energy and power densities. Herein we fabricate hierarchical tectorum‐like α‐Fe₂O₃/polypyrrole (PPy) nanoarrays (T‐Fe₂O₃/PPy NAs). The 3D, and interconnected T‐Fe₂O₃/PPy NAs are successfully grown on conductive carbon cloth through an easy self‐sacrificing template and in situ vapor‐phase polymerization route under mild conditions. The electrode made of the T‐Fe₂O₃/PPy NAs exhibits a high areal capacitance of 382.4 mF cm⁻² at a current density of 0.5 mA cm⁻² and excellent reversibility. The solid‐state asymmetric supercapacitor consisting of T‐Fe₂O₃/PPy NAs and MnO₂ electrodes achieves a high energy density of 0.22 mWh cm⁻³ at a power density of 165.6 mW cm⁻³.     

Recent trends in nanomaterial-based microanalytical systems for the speciation of trace elements: A critical review

Trace element speciation in biomedical and environmental science has gained increasing attention over the past decade as researchers have begun to realize its importance in toxicological studies. Several nanomaterials, including titanium dioxide nanoparticles (nano-TiO₂), carbon nanotubes (CNTs), and magnetic nanoparticles (MNPs), have been used as sorbents to separate and preconcentrate trace element species prior to detection through mass spectrometry or optical spectroscopy. Recently, these nanomaterial-based speciation techniques have been integrated with microfluidics to minimize sample and reagent consumption and simplify analyses. This review provides a critical look into the present state and recent applications of nanomaterial-based microanalytical systems in the speciation of trace elements. The adsorption and preconcentration efficiencies, sample volume requirements, and detection limits of these nanomaterial-based speciation techniques are detailed, and their applications in environmental and biological analyses are discussed. Current perspectives and future trends into the increasing use of nanomaterial-based microfluidic techniques for trace element speciation are highlighted.     

Synergistic tuning of electrochemical surface area and surface Co3+ by oxygen plasma enhances the capacities of Co3O4 lithium–oxygen battery cathodes

Modifying electrochemical surface area (ECSA) and surface chemistry are promising approaches to enhance the capacities of oxygen cathodes for lithium–oxygen (Li–O₂) batteries. Although various chemical approaches have been successfully used to tune the cathode surface, versatile physical techniques including plasma etching etc. could be more effortless and effective than arduous chemical treatments. Herein, for the first time, we propose a facile oxygen plasma treatment to simultaneously etch and modify the surface of Co₃O₄ nanosheet arrays (NAs) cathode for Li–O₂ batteries. The oxygen plasma not only etches Co₃O₄ nanosheets to enhance the ECSA but also lowers the oxygen vacancy concentration to enable a Co³⁺-rich surface. In addition, the NA architecture enables the full exposure of oxygen vacancies and surface Co³⁺ that function as the catalytically active sites. Thus, the synergistic effects of enhanced ECSA, modest oxygen vacancy and high surface Co³⁺ achieve a significantly enhanced reversible capacity of 3.45 mAh/cm² for Co₃O₄ NAs. This work not only develops a promising high-capacity cathode for Li–O₂ batteries, but also provides a facile physical method to simultaneously tune the nanostructure and surface chemistry of energy storage materials.     

Nonisothermal crystallization behaviors of polypropylene with α/β nucleating agents

In this work, the nonisothermal crystallization and subsequent melting behaviors of polypropylene (PP) nucleated with different nucleating agents (NAs) have been studied. α‐phase NA 1,3:2,4‐bis (3,4‐dimethylbenzylidene) sorbitol (DMDBS, Millad 3988), β‐phase NA aryl amides compound (TMB‐5), and their compounds were introduced into PP matrix, respectively. The results show that the nonisothermal crystallization behaviors and crystalline structures of PP with compounded NAs are dependent on the composition of NAs. In the sample of PP with 0.1 wt % DMDBS and 0.1 wt % TMB‐5, the nucleation efficiency (NE) of TMB‐5 is much higher than that of DMDBS and PP crystallizes mainly nucleated by TMB‐5, and in this condition, β‐phase PP is the main crystallization structure. For the sample of PP with 0.2 wt % DMDBS and 0.2 wt % TMB‐5, 0.2 wt % DMDBS has higher NE than 0.2 wt % TMB5, and α‐phase is the main crystalline structure. The cooling rate is proved to be very important in controlling the nonisothermal crystallization behavior and the final crystalline structure of nucleated PP. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1853–1867, 2008     

Electrochemical hematocrit determination in a direct current microfluidic device

Hematocrit (HCT) tests are widely performed to screen blood donors and to diagnose medical conditions. Current HCT test methods include conventional microhematocrit, Coulter counter, CuSO₄ specific gravity, and conductivity‐based point‐of‐care (POC) HCT devices, which can be either expensive, environmentally inadvisable, or complicated. In the present work, we introduce a new and simple microfluidic system for a POC HCT determination. HCT was determined by measuring current responses of blood under 100 V DC for 1 min in a microfluidic device containing a single microchannel with dimensions of 180 μm by 70 μm and 10 mm long. Current responses of red blood cell (RBC) suspensions in PBS or separately plasma at HCT concentrations of 10, 20, 25, 30, 35, 40, 45, 50, 55, 60, and 70 vol% were measured to show feasibility of the microfluidic system for HCT determination. Key parameters affecting current responses included electrolysis bubbles and irreversible RBC adsorption; parameters were optimized via addition of nonionic surfactant Triton X‐100 into sample solution and carbonizing electrode surfaces. The linear trend line of current responses over a range of RBC concentrations were obtained in both PBS and plasma. This work suggested that a simple microfluidic device could be a promising platform for a new POC HCT device.     

A Novel Three‐Electrode System Fabricated on Polymethyl Methacrylate for On‐Chip Electrochemical Detection

A new strategy of three‐electrode system fabrication in polymer‐based microfluidic systems is described here. Standard lithography, hot embossing and UV‐assisted thermal bonding were employed for fabrication and assembly of the microfluidic chip. For the electrode design the gold working (WE) and counter electrodes (CE) are placed inside a main channel through which the sample solution passes. A silver reference electrode (RE) is embedded in a small side channel containing KCl solution that is continuously pushed into the main channel. In the present work, the overall electrochemical set up and its microfabrication is described. Conditions including silver ion concentration, cyclic voltammetry (CV) settings, and the flow rate of KCl solution in the RE channel were optimized. The electrochemical performance of the three‐electrode system was evaluated by CV and also by amperometric oxidation of ferro hexacyanide ([Fe(CN)₆]^4?) and ruthenium bipyridyl ([Ru(bipy)₃]²⁺) at 400 mV and 1200 mV, respectively. CV analysis using ferri/ferro hexacyanide showed a stable, quasi‐reversible redox reaction at the electrodes with 96 mV peak separation and an anodic/cathodic peak ratio of 1. Amperometric analysis of the electrochemical species resulted in linear correlation between analyte concentration and current response in the range of 0.5–15 µM for [Fe(CN)₆]^4?, and 0–1000 µM for [Ru(bipy)₃]²⁺. Upon the given experimental conditions, the limit of detection was found to be 3.15 µM and 24.83 µM for [Fe(CN)₆]^4? and [Ru(bipy)₃]²⁺, respectively. As a fully integrated three‐electrode system that is fabricated on polymer substrates, it has great applications in microfluidic‐based systems requiring stable electrochemical detection.     

Microfluidics for Miniaturized Laboratories on a Chip

Microfluidic systems promise solutions for high throughput and highly specific analysis for biology, medicine and chemistry while consuming only tiny amounts of reactants and space. On these lab‐on‐a‐chip platforms often multiple physical effects such as electrokinetic, acoustic or capillary phenomena from various disciplines are exploited to gain the optimal functionality. The fluidics on these small length scales differ significantly from our experience of the macroscopic world. In this Review we survey some of the approaches and techniques to handle minute amounts of fluid volumes in microfluidic systems with special focus on surface acoustic wave driven fluidics, a technique developed in our laboratory. Here, we outline the basics of this technique and demonstrate, for example, how acoustic mixing and fluid actuation is realized. Furthermore we discuss the interplay of different physical effects in microfluidic systems and illustrate their usefulness for several applications.     

A Single‐Atom Manipulation Approach for Synthesis of Atomically Mixed Nanoalloys as Efficient Catalysts

Synthesis of well‐defined atomically mixed alloy nanoparticles on desired substrates is an ultimate goal for their practical application. Herein we report a general approach for preparing atomically mixed AuPt, AuPd, PtPd, AuPtPd NAs(nanoalloys) through single‐atom level manipulation. By utilizing the ubiquitous tendency of aggregation of single atoms into nanoparticles at elevated temperatures, we have synthesized nanoalloys on a solid solvent with CeO₂ as a carrier and transition‐metal single atoms as an intermediate state. The supported nanoalloys/CeO₂ with ultra‐low noble metal content (containing 0.2 wt % Au and 0.2 wt % Pt) exhibit enhanced catalytic performance towards complete CO oxidation at room temperature and remarkable thermostability. This work provides a general strategy for facile and rapid synthesis of well‐defined atomically mixed nanoalloys that can be applied for a range of emerging techniques.     

Activation of CO2 by Vanadium Nitrogenase

The reduction of CO₂ into useful products, including hydrocarbon fuels, is an ongoing area of particular interest due to efforts to mitigate buildup of this greenhouse gas. While the industrial Fischer–Tropsch process can facilitate the hydrogenation of CO₂ with H₂ to form short‐chain hydrocarbon products under high temperatures and pressures, a desire to perform these reactions under ambient conditions has inspired the use of biological approaches. Particularly, enzymes offer insight into how to activate and reduce CO₂, but only one enzyme, nitrogenase, can perform the multielectron, multiproton reduction of CO₂ into hydrocarbons. The vanadium‐containing variant, V‐nitrogenase, displays especial reactivity towards the hydrogenation of CO and CO₂. This Focus Review discusses recent progress towards the activation and reduction of CO₂ with three primary V‐nitrogenase systems. These systems span both ATP‐dependent and ATP‐independent processes and utilize approaches with whole cells, isolated proteins, and extracted cofactors.     

Molecular Spintronics Based on Single‐Molecule Magnets Composed of Multiple‐Decker Phthalocyaninato Terbium(III) Complex

Unlike electronics, which is based on the freedom of the charge of an electron whose memory is volatile, spintronics is based on the freedom of the charge, spin, and orbital of an electron whose memory is non‐volatile. Although in most GMR, TMR, and CMR systems, bulk or classical magnets that are composed of transition metals are used, this Focus Review considers the growing use of single‐molecule magnets (SMMs) that are composed of multinuclear metal complexes and nanosized magnets, which exhibit slow magnetic‐relaxation processes and quantum tunneling. Molecular spintronics, which combines spintronics and molecular electronics, is an emerging field of research. Using molecules is advantageous because their electronic and magnetic properties can be manipulated under specific conditions. Herein, recent developments in [LnPc]‐based multiple‐decker SMMs on surfaces for molecular spintronic devices are presented. First, we discuss the strategies for preparing single‐molecular‐memory devices by using SMMs. Next, we focus on the switching of the Kondo signal of [LnPc]‐based multiple‐decker SMMs that are adsorbed onto surfaces, their characterization by using STM and STS, and the relationship between the molecular structure, the electronic structure, and the Kondo resonance of [TbPc₂]. Finally, the field‐effect‐transistor (FET) properties of surface‐adsorbed [LnPc₂] and [Ln₂Pc₃] cast films are reported, which is the first step towards controlling SMMs through their spins for applications in single‐molecular memory and spintronics devices.