Ongoing Reaction Research Articles

Reaction-driven casing expansion: potential for wellbore leakage mitigation

It is generally challenging to predict the post-abandonment behaviour and integrity of wellbores. Leakage is, moreover, difficult to mitigate, particularly between the steel casing and outer cement sheath. Radially expanding the casing with some form of internal plug, thereby closing annular voids and fractures around it, offers a possible solution to both issues. However, such expansion requires development of substantial internal stresses. Chemical reactions that involve a solid volume increase and produce a force of crystallisation (FoC), such as CaO hydration, offer obvious potential. However, while thermodynamically capable of producing stresses in the GPa range, the maximum stress obtainable by CaO hydration has not been validated or determined experimentally. Here, we report uniaxial compaction/expansion experiments performed in an oedometer-type apparatus on precompacted CaO powder, at 65 °C and at atmospheric pore fluid pressure. Using this set-up, the FoC generated during CaO hydration could be measured directly. Our results show FoC-induced stresses reaching up to 153 MPa, with reaction stopping or slowing down before completion. Failure to achieve the GPa stresses predicted by theory is attributed to competition between FoC development and its inhibiting effect on reaction progress. Microstructural observations indicate that reaction-induced stresses shut down pathways for water into the sample, hampering ongoing reaction and limiting the magnitude of stress build-up to the values observed. The results nonetheless point the way to understanding the behaviour of such systems and to finding engineering solutions that may allow large controlled stresses and strains to be achieved in wellbore sealing operations in future.

Procalcitonin Impairs Endothelial Cell Function and Viability.

Procalcitonin is used as a diagnostic tool for the identification and risk stratification of septic patients. Procalcitonin plasma concentrations tightly correlate with the severity of the ongoing inflammatory reaction and can rise up to 10,000-fold. Impairment of endothelial cell function plays an important role in the pathogenesis of hypotension and disturbed organ perfusion during sepsis. We investigated the possible effects of procalcitonin itself on endothelial cell function and viability. Human endothelial cells were exposed to 0.01 to 100 ng/mL procalcitonin and investigated for endothelial permeability using transwells, migration in a scratch wound assay and new capillary formation on extracellular matrix in vitro. Tumor necrosis factor-α and vascular endothelial growth factor served as positive controls. Procalcitonin's impact on the response of endothelial cells toward ischemia was investigated in vivo in the murine model of unilateral femoral artery ligation. Procalcitonin-exposed endothelial cells were subjected to immunoblot for the investigation of vascular endothelial-cadherin expression and angiogenic signaling pathways. Flow cytometry was used for the detection of inflammatory activation and viability, and genomic analysis was performed. Data are presented as difference in means and 95% confidence intervals; statistical analyses were performed using analysis of variance/Bonferroni, and P values are reported as adjusted for multiple comparisons (Padjust). Tumor necrosis factor-α and 0.1 ng/mL procalcitonin induced endothelial barrier disruption after incubation of endothelial monolayers for 6 hours (-2.53 [-4.16 to -0.89], P = .0008 and -2.09 [-3.73 to -0.45], Padjust = .0064 compared with vehicle-treated control, respectively). Procalcitonin beginning at concentrations of 0.02 ng/mL reduced endothelial cell migration (0.26 [0.06 to 0.47], Padjust = .0069) and new capillary formation in vitro (0.47 [0.28 to 0.66], Padjust < .0001) contrasting the proangiogenic action of vascular endothelial growth factor. Left ventricular injection of procalcitonin in mice on postoperative day 1, 3, and 5 after induction of ischemia impaired new capillary formation and recovery of hindlimb perfusion in vivo (number of capillaries/mm in the ischemic leg of vehicle-treated versus procalcitonin-treated mice, 852.6 [383.4-1322], Padjust = .0002). Twenty-four-hour incubation with procalcitonin reduced the expression of vascular endothelial-cadherin at 100 ng/mL (0.39 [0.06-0.71], Padjust = .0167) and induced endothelial cell death (apoptosis, -5.4 [-10.67 to -0.13], Padjust = .0431). No alteration in the expression of intercellular adhesion molecule-1, vascular cell adhesion molecule-1 or extracellular signal-regulated kinase 1/2, and AKT signaling pathways was observed. Genomic analysis revealed regulation of a variety of genes involved in inflammation, angiogenesis, and cell growth. This study found that procalcitonin itself impaired several aspects of endothelial cell function. Procalcitonin-induced loss of endothelial barrier function may contribute to capillary leakage and therapy-refractory hypotension during sepsis. Anti-angiogenic properties of procalcitonin at low concentrations could also identify procalcitonin as a mediator of vascular disease associated with the metabolic syndrome. Future studies are needed to further test procalcitonin as a potential therapeutic target for preserving vascular dysfunction during acute and chronic inflammatory disorders.

Direct ink writing of geopolymeric inks

The development of geopolymeric inks with optimized rheological properties for DIW is presented; several inks with different water content and additives were compared to determine which parameters enable extrusion as well as shape retention. It is a challenging task, because the inks are subjected to ongoing poly-condensation reactions which continuously modify their rheological properties over time.Highly porous ceramic lattices (porosity up to ∼71vol%) were fabricated with ∼0.8mm struts and unsupported features with very limited sagging. Their physical and mechanical properties were characterized and correlated. Our approach can be successfully extended to other formulations.Geopolymeric foams have recently been proven as suitable for water filtration; the use of precisely designed, non stochastic printed structures could enhance the mechanical properties of the porous components, provide a better control of pressure drop and fluid dynamics inside the part and improve their performances consistently.

On the complex •OH/•O−-induced free radical chemistry of arylalkylamines with special emphasis on the contribution of the alkylamine side chain

A full account of the •OH-induced free radical chemistry of an arylalkylamine is given taking all the possible reaction pathways quantitatively into consideration. Such knowledge is indispensable when the alkylamine side chain plays a crucial role in biological activity. The fundamental reactions are investigated on the model compound N-methyl-3-phenypropylamine (MPPA), and extended to its biologically active analog, to the antidepressant fluoxetine (FLX). Pulse radiolysis techniques were applied including redox titration and transient spectral analysis supplemented with DFT calculations. The contribution of the amine moiety to the free radical-induced oxidation mechanism appeared to be appreciable. •O− was used to observe hydrogen atom abstraction events at pH 14 giving rise to the strongly reducing α-aminoalkyl radicals (∼38% of the radical yield) and to benzyl (∼4%), β-aminoalkyl (∼24%), and aminyl radicals (∼31%) of MPPA. One-electron transfer was also observed yielding aminium radicals with low efficiency (∼3%). In the •OH-induced oxidation protonated α-aminoalkyl (∼49%), β-aminoalkyl (∼27%), benzyl radicals (∼4%), and aminium radicals (∼5%) are initially generated on the side chain of MPPA at pH 6, whereas hydroxycyclohexadienyl radicals (∼15%) were also produced. These initial events are followed by complex protonation–deprotonation reactions establishing acid–base equilibria; however, these processes are limited by the transient nature of the radicals and the kinetics of the ongoing reactions. The contribution of the radicals from the side chain alkylamine substituent of FLX totals up to ∼54% of the initially available oxidant yield.

Influence of re-activation and ongoing CO oxidation reaction on the chemical and electronic properties of Au on a Au/CeO2 catalyst: A XANES study at the Au LIII edge

The influence of oxidative/reductive pretreatment, oxidative re-activation and ongoing CO oxidation on the chemical/electronic properties of a 4.5wt.% Au/CeO2 catalyst was investigated by in operando X-ray absorption spectroscopy at the Au LIII edge. Experimental data on the electronic structure and the size of the Au nanoparticles are correlated with findings from kinetic and deactivation measurements. The results of this study show that oxidative re-activation as well as reductive and oxidative pretreatment significantly affect the Au electronic structure and, in consequence, the catalytic properties. Independent of the type of the treatment, however, the Au nanoparticles rapidly reach a metallic state during reaction, both after oxidative pretreatment and after oxidative re-activation, and can therefore not be responsible for the long-term deactivation of the catalyst. Correlations between electronic/chemical structure, evaluated in a semi-quantitative model, and the catalytic performance are discussed.

A Photoswitchable Olefin Metathesis Catalyst

A dithienylethene-functionalized N-heterocyclic carbene-Ru(II) complex was synthesized and found to undergo a reversible photoisomerization which influenced its intrinsic catalytic activity. UV-induced ring-closure enhanced the rate of ring-closing metathesis reactions (kclosed/kopened = 1.4–1.7) and attenuated the rate of ring-opening metathesis polymerizations (kclosed/kopened = 0.56–0.66). Visible light irradiation promoted cycloreversion and restored the initial activity. The ability to switch between the isomeric states of the catalyst was also utilized to modulate the rate of ongoing olefin metathesis reactions via photoirradiation. A computational investigation revealed how steric and electronic effects separately influence the transition states adopted by each form of the catalyst and afforded activation energies that were in agreement with the relative reaction rate constants determined by experiment.

Quick Detection of DNase II-Type Breaks in Formalin-Fixed Tissue Sections.

Blunt-ended DNase II-type breaks with 5' hydroxyls are generated in phagocytic cells of any lineage during digestion of the engulfed DNA. These breaks indicate the ongoing active phagocytic reaction. They are produced by the acid deoxyribonuclease-DNase II which is the primary endonuclease responsible for DNA degradation after its engulfment.Here, we present an express approach that detects blunt-ended 5' OH DNA breaks in fixed tissue sections. The technique is simple to perform and takes only 60 min to complete. It can be useful in studies of the clearance of dying cells in oncological, inflammatory, and autoimmune disorders.

What we know about the cellular microenvironment of clinically healthy human gingiva? An immunohistochemical and histological study

AbstractThe present study deals with histological descriptions of clinically healthy human gingivae through the methods of light, electron microscopy and immunohistochemistry. Even clinically healthy human gingivae are subject to constant bacterial and mechanical influences present in the oral cavity; therefore, the term “normal gingiva” is misleading. The aim of this study was to identify, in clinically healthy gingiva, all active cells through immunohistochemical markers and light and electron microscope examination. In tissue samples from clinically healthy gingivae of nine patients, we observed the presence of different cells (e.g., T- and B-lymphocytes, macrophages, Merkel cells, Langerhans cells, proliferating cells) and some components of their extracellular matrix that use antibodies against S-100 protein, CD68, CD20, CD45RO, CD20, and Ki67. The presence of immunologically active cells and the ultrastructural characteristics of gingivae were also confirmed. The stratified squamous epithelium of human gingiva contains a population of Langerhans cells and intraepithelial Tlymphocytes. The underlying dense connective tissue contains primarily fibroblasts, but also T-lymphocytes, occasionally B-lymphocytes, plasma cells, and macrophages can be seen. As a border between the oral cavity and the internal environment of the human body, the gingivae are an important part of the immune system. Such findings show that, in healthy gingival tissue, there are constantly ongoing anti-inflammatory, immunological, and regenerative reactions and processes.

Simulation and experimental validation of reactive bubble column reactors

Bubble columns are widespread in chemical process engineering. The overall performance of these reactors relies on the interaction between the hydrodynamics, interfacial mass transfer and chemical reactions. The layout of these columns is commonly based on simplified integral models that are not able to track the complex interactions between the local hydrodynamics and the reactions. Hence, a detailed knowledge about the ongoing interactions is required. The local and temporal evolution of the carbon dioxide (CO2) chemisorption in aqueous NaOH solution in a cylindrical bubble column is investigated. Therefore, local measurements of hydrodynamics, bubble size and velocity, liquid velocity and concentration (pH-value) are done using a high speed PIV/LIF system combined with shadowgraphy. The results are compared to Euler-Euler based computational fluid dynamics simulations that take into account the ongoing reaction.

Multifold C-C Coupling and Unorthodox Cyclization Catalysis for Selective Synthesis of Indolotriarylmethanes, Indolocarbazoles, and Their Analogues: A Control Experiment Study.

The selective construction of medicinally and synthetically important indole-based unsymmetrical triarylmethanes using indoles and aldehydes is challenging because the significant nucleophilicity of indole leads to C-C coupling with an azafulvene intermediate to build up the alternative bis(indolyl)methane products, which may be useful synthons. A new, straightforward, ligand-free CuII catalytic strategy for easy syntheses of unsymmetrical indolotriarylmethanes and new bisindolylbenzoyl analogues is established through the dual C-C coupling of an assembly of three reaction partners comprising aldehydes, indoles, and arylboronic acids. More importantly, this approach is exploited for multifold C-C coupling cyclization reactions with C-C cleavage using symmetrical bisindolylbenzoylmethanes in the presence of an organic base and aerial molecular oxygen as a stoichiometric oxidant. In contrast to the formation of a simple cyclocondensation product indolocarbazole, it undergoes unprecedented selective pseudo-four-component tandem oxidative cyclization with fragmentation from a 1,3-dicarbonyl compound to produce valuable fused 5,7-dihydroindolo[2,3-b]carbazoles through the functionalization of two indole C(sp2)-H and one C(sp3)-H bond of the active methylene residue. For a better understanding of the new reactions, we have studied various competition experiments and ESI-MS and 3D Mid-IR-ATR spectral analyses of the ongoing reactions. The predicted DFT transition state model is also in agreement with the experimental results.

Interleukin (IL)-10 Is an Effective Therapeutic for Murine Transfusion Related Acute Lung Injury (TRALI)

Transfusion related acute lung injury (TRALI) is the leading cause of transfusion-induced fatalities and is characterized by acute respiratory distress following blood transfusion. Donor antibodies present in the transfused blood product such as anti-human leukocyte antigen (HLA) or anti-human neutrophil antigen (HNA) antibodies are frequently involved. Currently, there is no treatment available for TRALI apart from supportive measures such as oxygen. The pathogenesis the disorder is incompletely understood, however, several animal models have contributed to our understanding of TRALI disease pathology. Most TRALI reactions are considered to be due to a two-hit paradigm where the first hit is a predisposing patient factor such as inflammation while the second hit is the transfusion. It is widely believed that the second hit delivers antibodies that trigger TRALI in the recipient. The anti-MHC class I antibody, 34-1-2s, has been widely used as an agent that delivers the second TRALI hit in mice. We have previously shown that CD4+ T cells, more specifically, CD4+CD25+FoxP3+ T-regulatory cells (Tregs) convey protection against TRALI (Blood. 126 (23):2342, 2015; abstract #82075, manuscript submitted). In the current study, we utilized a C57BL/6 mouse model of severe TRALI by first depleting mice of CD4+ T cells and then injecting them with the anti-MHC class I monoclonal antibodies (34-1-2s+AF6-88.5.5.3) and we examined the effects of the anti-inflammatory cytokine IL-10 on the antibody-mediated TRALI reaction.IL-10 (45 µg/kg iv) or volume-matched PBS was injected 15 minutes after the administration of anti-MHC antibodies when the onset of TRALI symptoms (e.g. a 2 degree drop in rectal temperature indicative of systemic shock) began. Results show that 90 minutes after anti-MHC class I antibody injection, control mice injected with PBS exhibited a high degree of pulmonary edema as assessed by significantly elevated lung wet-to-dry weight ratios (W/D: 5.84 ± 1.02). Pulmonary neutrophil levels were also found to be increased and lung tissue histology confirmed severe signs of acute lung injury. In contrast, mice injected with IL-10 completely recovered from TRALI; after 90 minutes post-antibody injection they displayed no signs of pulmonary edema (W/D: 4.76 ± 0.04, ** p<0.004 compared to mice injected with PBS) and no signs of severe acute lung injury as assessed by lung tissue histology. Pulmonary neutrophil levels, however, were equally increased in both groups indicating that although IL-10 rescues the mice from acute lung injury, it does not interfere with pulmonary neutrophil recruitment. Preliminary data suggests that IL-10 administration interferes with the ability of neutrophils to generate reactive oxygen species (ROS) that mediate lung injury. Our results suggest that IL-10 therapy significantly rescues an ongoing severe TRALI reaction and this may prove to be an effective and feasible therapeutic strategy in combating human TRALI. DisclosuresNo relevant conflicts of interest to declare.

Assessing the Immunosafety of Engineered Nanoparticles with a Novel in Vitro Model Based on Human Primary Monocytes

The possibility that nanomaterials could perturb the normal course of an inflammatory response is a key issue when assessing nanoimmunosafety. The alteration of the normal progress of an inflammatory response may have pathological consequences, since inflammation is a major defensive mechanism and its efficiency maintains the body's health. The immunosafety of engineered nanoparticles at nontoxic concentrations was investigated with the use of a human primary monocyte-based in vitro system, which reproduces in a simplified fashion the full course of the physiological inflammatory response, from initiation and development to resolution. The kinetics of expression and production of inflammatory and anti-inflammatory cytokines and the proteomic profiles were used for describing the inflammatory defensive response. We assessed the ability of gold and silver nanoparticles to trigger inflammation and to interfere with the course of an ongoing defensive reaction. While neither nanoparticle type was able to directly activate monocytes, silver nanoparticles could exacerbate the inflammatory response of monocytes but did not interfere with the resolution of the inflammatory reaction. These findings support the use of human primary monocyte-based in vitro assays for realistically investigating the effects of engineered nanoparticles on human innate immune responses, in order to predict the immunological risk of nanomaterials and implement safe nanoparticle-based applications.

Reaction monitoring using hyperpolarized NMR with scaling of heteronuclear couplings by optimal tracking

Off-resonance decoupling using the method of Scaling of Heteronuclear Couplings by Optimal Tracking (SHOT) enables determination of heteronuclear correlations of chemical shifts in single scan NMR spectra. Through modulation of J-coupling evolution by shaped radio frequency pulses, off resonance decoupling using SHOT pulses causes a user-defined dependence of the observed J-splitting, such as the splitting of 13C peaks, on the chemical shift offset of coupled nuclei, such as 1H. Because a decoupling experiment requires only a single scan, this method is suitable for characterizing on-going chemical reactions using hyperpolarization by dissolution dynamic nuclear polarization (D-DNP). We demonstrate the calculation of [13C, 1H] chemical shift correlations of the carbanionic active sites from hyperpolarized styrene polymerized using sodium naphthalene as an initiator. While off resonance decoupling by SHOT pulses does not enhance the resolution in the same way as a 2D NMR spectrum would, the ability to obtain the correlations in single scans makes this method ideal for determination of chemical shifts in on-going reactions on the second time scale. In addition, we present a novel SHOT pulse that allows to scale J-splittings 50% larger than the respective J-coupling constant. This feature can be used to enhance the resolution of the indirectly detected chemical shift and reduce peak overlap, as demonstrated in a model reaction between p-anisaldehyde and isobutylamine. For both pulses, the accuracy is evaluated under changing signal-to-noise ratios (SNR) of the peaks from reactants and reaction products, with an overall standard deviation of chemical shift differences compared to reference spectra of 0.02ppm when measured on a 400MHz NMR spectrometer. Notably, the appearance of decoupling side-bands, which scale with peak intensity, appears to be of secondary importance.

Column percolation test for contaminated soils: Key factors for standardization

Column percolation tests may be suitable for prediction of chemical leaching from soil and soil materials. However, compared with batch leaching tests, they are time-consuming. It is therefore important to investigate ways to shorten the tests without affecting the quality of results. In this study, we evaluate the feasibility of decreasing testing time by increasing flow rate and decreasing equilibration time compared to the conditions specified in ISO/TS 21268-3, with equilibration periods of 48h and flow rate of 12mL/h. We tested three equilibration periods (0, 12⿿16, and 48h) and two flow rates (12 and 36mL/h) on four different soils and compared the inorganic constituent releases. For soils A and D, we observed similar values for all conditions except for the 0h⿿36mL/h case. For soil B, we observed no appreciable differences between the tested conditions, while for soil C there were no consistent trends probably due to the difference in ongoing oxidation reactions between soil samples. These results suggest that column percolation tests can be shortened from 20 to 30days to 7⿿9days by decreasing the equilibration time to 12⿿16h and increasing the flow rate to 36mL/h for inorganic substances.

Pain rather than induced emotions and ICU sound increases skin conductance variability in healthy volunteers.

Assessing pain in critically ill patients is difficult. Skin conductance variability (SCV), induced by the sympathetic response to pain, has been suggested as a method to identify pain in poorly communicating patients. However, SCV, a derivate of conventional skin conductance, could potentially also be sensitive to emotional stress. The purpose of the study was to investigate if pain and emotional stress can be distinguished with SCV. In a series of twelve 1-min sessions with SCV recording, 18 healthy volunteers were exposed to standardized electric pain stimulation during blocks of positive, negative, or neutral emotion, induced with pictures from the International Affective PictureSystem (IAPS). Additionally, authentic intensive care unit (ICU) sound was included in half of the sessions. All possible combinations of pain and sound occurred in each block of emotion, and blocks were presented in randomized order. Pain stimulation resulted in increases in the number of skin conductance fluctuations (NSCF) in all but one participant. During pain-free baseline sessions, the median NSCF was 0.068 (interquartile range 0.013-0.089) and during pain stimulation median NSCF increased to 0.225 (interquartile range 0.146-0.3175). Only small increases in NSCF were found during negative emotions. Pain, assessed with the numeric rating scale, during the sessions with pain stimulation was not altered significantly by other ongoing sensory input. In healthy volunteers, NSCF appears to reflect ongoing autonomous reactions mainly to pain and to a lesser extent, reactions to emotion induced with IAPS pictures or ICU sound.

Synergistic Inhibition of Oxide Formation in Oxidation Catalysis: A First-Principles Kinetic Monte Carlo Study of NO + CO Oxidation at Pd(100)

Oxide formation under oxygen-rich reaction conditions has independently been reported for both CO oxidation and NO oxidation with Pd single-crystal model catalysts. We present a first-principles kinetic Monte Carlo study addressing the simultaneous occurrence of both reactions at Pd(100) exposed to CO- and NO-containing feeds. Even in most oxygen-rich feeds, very small amounts of NO are found to reduce the surface oxygen coverage well below the level required to induce oxide formation. Even though NO and CO compete for the same surface sites and surface oxygen, the ongoing NO oxidation reactions furthermore lead to a partially strong enhancement of the CO oxidation activity. This highlights synergistic effects of multicomponent gas feeds on both surface composition and catalytic activity that cannot be captured, nor extrapolated from prevalent studies focusing on individual reactions.

Core/Shell Approach to Dopant Incorporation and Shape Control in Colloidal Zinc Oxide Nanorods

Tunable aliovalent doping is critical to controlling the optoelectronic properties of semiconductor nanocrystal systems. However, unintentional dopant-induced shape evolution and kinetically limited doping reactions in low-temperature nanocrystal syntheses make it difficult to independently control shape and incorporate dopants in colloidal metal oxide nanocrystals. Here, we demonstrate a synthetic strategy for achieving simultaneous control of both nanorod shape and dopant concentration in colloidal zinc oxide nanorods. We show that this approach succeeds in doping zinc oxide nanorods using Group III dopants (indium or aluminum) in varying concentrations, and we quantify the effects of dopant incorporation on the structural, optical, and plasmonic properties of the nanorods. The synthesis of undoped zinc oxide nanorod templates and subsequent addition of dopant salts to the ongoing reaction enables both shape retention and dopant incorporation. Subsequent growth of an undoped shell on the nanorods incorp...

Pathogenic conversion of Foxp3+ T cells into Th1 and Th17 cells in Stromal Keratitis

Abstract Ocular infection with herpes simplex virus 1 (HSV-1) can result in a chronic immuno-inflammatory lesion that is a significant cause of human blindness. IFN-γ producing CD4 + T cells are generally considered the main orchestrators, and lesions are more severe if the regulatory T cell (Treg) response is compromised. Tregs have been shown to lose FoxP3 (Treg lineage factor) and adopt alternate lineage fates in a changing cytokine environment. Moreover, little is known about the stability of Treg cells in an ongoing inflammatory reaction such as is the case of SK. In this study-using fate mapping mice, we were able to demonstrate that the population of ex-Tregs increased at the site of infection that is the cornea and also at the secondary lymphoid organs after HSV-1 infection. In vivo studies showed that these ex-Tregs acquired the Th1 and Th17 phenotype, which may play a destructive role in stromal keratitis. We also demonstrate in vivo that CD25lo subset of Tregs is less suppressive and more prone to conversion than CD25hi Tregs. Additionally, in-vitro studies suggested that Tregs in the presence of IL-12 converted into ex-Tregs, however this plasticity was prevented when Tregs were generated in the presence of DNMT inhibitor (Azacytidine). Thus, plasticity of Tregs might represent a problem during SK, which needs to be controlled with appropriate therapeutic procedures. Overall, our results indicate that Tregs lose FoxP3 expression in ocular inflammatory setting and drugs that reverse Treg plasticity could be useful to restore Treg function and to inhibit ocular immunopathology.

Enzyme assays using sensor arrays based on ion-selective carbon nanotube field-effect transistors

In the fields of clinical diagnostics and point-of-care diagnosis as well as food and environmental monitoring there is a high demand for reliable high-throughput, rapid and highly sensitive assays for a simultaneous detection of several analytes in complex and low-volume samples. Sensor platforms based on solution-processable electrolyte-gated carbon nanotube field-effect transistors (CNT-FETs) are a simple and cost-effective alternative for conventional assays. In this work we demonstrate a selective as well as direct detection of the products of an enzyme-substrate interaction, here the for metabolic processes important urea-urease system, with sensors based on spray-coated CNT-FETs. The selective and direct detection is achieved by immobilizing the enzyme urease via certain surface functionalization techniques on the sensor surface and further modifying the active interfaces with polymeric ion-selective membranes as well as pH-sensitive layers. Thereby, we can avoid the generally applied approach for a field-effect based detection of enzyme reactions via detecting changes in the pH value due to an on-going enzymatic reaction and directly detect selectively the products of the enzymatic conversion. Thus, we can realize a buffering-capacity independent monitoring of changes in the substrate concentration.

Pb⋯N interactions and π-stacking in lead(II) bis(hydrazone) compounds

2,6-Diacetylpyridine-bis(benzoylhydrazone), H2LPh, reacts with Pb(OAc)2·3H2O and NEt3 as a supporting base forming a polymeric solid of the composition [Pb(LPh)]n. A reaction with pyridine results in cleavage of the polymer and formation of the dimeric, crystalline compound [Pb(py)(LPh)]2.Similar reactions with PbX2 salts (X=Cl, Br, I) also give almost insoluble solids of the tentative composition [Pb(H2LPh)X2]n. After ongoing reactions with DMSO, single deprotonation of the organic ligand and the formation of pseudo-dimeric [Pb(HLPh)X]2 complexes was observed. Depending on the presence of solvent molecules they form different supramolecular aggregates by π–π interactions.The use of Pb(NO3)2 results in a dimeric structure with relatively short Pb–O bonds of 2.442(2)Å between the monomeric sub-units. The formed dimers aggregate to a polymeric assembly by hydrogen bonds.The products were studied by spectroscopic methods and X-ray diffraction.