The translocation of single-walled carbon nanotubes (SWNTs) across MCF7 breast cancer cells was demonstrated with radioisotope labeling. Hybrids of SWNT−RNA polymer poly(rU) were formed through a ...nonspecific binding mechanism which could allow for the dissociation of the poly(rU) from the SWNTs upon delivery. The cellular uptake of the hybrids was examined by confocal fluorescence microscopy. Through cell growth and MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assays, we showed the negligible cytotoxicity of SWNTs (up to 0.5 mg/mL) to MCF7 cells.
Molten salts (MSs) are an attractive medium for chemical and electrochemical processing and as a result there is demand for MS-compatible analysis technologies. However, MSs containing redox species ...present a challenging environment in which to perform analytical measurements because of their corrosive nature, significant thermal convection and the high temperatures involved. This paper outlines the fabrication and characterization of microfabricated square microelectrodes (MSMs) designed for electrochemical analysis in MS systems. Their design enables precise control over electrode dimension, the minimization of stress because of differential thermal expansion through design for high temperature operation, and the minimization of corrosive attack through effective insulation. The exemplar MS system used for characterization was lithium chloride/potassium chloride eutectic (LKE), which has potential applications in pyrochemical nuclear fuel reprocessing, metal refining, molten salt batteries and electric power cells. The observed responses for a range of redox ions between 400 and 500 °C (673 and 773 K) were quantitative and typical of microelectrodes. MSMs also showed the reduced iR drop, steady-state diffusion-limited response, and reduced sensitivity to convection seen for microelectrodes under ambient conditions and expected for these electrodes in comparison to macroelectrodes. Diffusion coefficients were obtained in close agreement with literature values, more readily and at greater precision and accuracy than both macroelectrode and previous microelectrode measurements. The feasibility of extracting individual physical parameters from mixtures of redox species (as required in reprocessing) and of the prolonged measurement required for online monitoring was also demonstrated. Together, this demonstrates that MSMs provide enhanced electrode devices widely applicable to the characterization of redox species in a range of MS systems.
Novel thin‐film materials have been produced from indolo3,2,1‐jkcarbazole (see picture). These are conducting and redox‐active and, unusually, consist of three distinct covalently coupled luminescent ...dimer species, consistent with a specific radical‐cation coupling mechanism.
Indolo3,2,1‐jkcarbazole (IC) has been synthesised on a gram scale by flash vacuum pyrolysis. In contrast to a previous suggestion, IC is planar and it is also highly fluorescent, with a solution quantum yield of 0.41. Electro‐oxidation of IC at a rotating disc electrode resulted in the passage of steady‐state currents and the reproducible formation of conducting, redox‐active films with constituent species that are also highly fluorescent. Unusually for coupled electroactive N‐heterocyclic systems, electrochemical and spectroscopic characterisation revealed the film to consist exclusively of three redox‐active (2,2′, 5,5′ and 2,5′ coupled) IC dimers with no polymeric products. Calculations showed this coupling pattern to be consistent with IC radical‐cation coupling through the accessible sites of highest unpaired electron density. The unusual combination of a high dimer second oxidation potential and a negligible dimer–dimer coupling rate explains the lack of further coupling. The identities of the dimeric species were confirmed by independent syntheses involving the Suzuki–Miyaura coupling of IC boronic acids as the key step. Electro‐oxidation of the IC system therefore offers a ready route to novel conducting, redox‐active molecular films and their redox‐active, luminescent dimer constituents.
Novel thin‐film materials have been produced from indolo3,2,1‐jkcarbazole (see picture). These are conducting and redox‐active and, unusually, consist of three distinct covalently coupled luminescent dimer species, consistent with a specific radical‐cation coupling mechanism.
Microfabricated square electrodes with finely controlled highly reproducible dimensions have been developed for electrochemical analysis of high-temperature molten salt (MS). These microelectrodes ...have been fabricated using photolithographic techniques on silicon wafers and have been designed for operation in lithium chloride/potassium chloride eutectic salt at and ~500 °C. The electrodes are constructed from a series of patterned layers, and their development has involved a systematic study and optimization of a number of different material combinations. This has resulted in a process for making electrodes that represents a step change in capability, delivering the first robust microelectrode device capable of quantitative electroanalysis in a MS system at 500 °C.
We describe a novel glucose biosensor based on a nanoband array electrode design, manufactured using standard semiconductor processing techniques, and bio-modified with glucose oxidase immobilized at ...the nanoband electrode surface. The nanoband array architecture allows for efficient diffusion of glucose and oxygen to the electrode, resulting in a thousand-fold improvement in sensitivity and wide linear range compared to a conventional electrode. The electrode constitutes a robust and manufacturable sensing platform.
•Glucose oxidase was covalently attached to thiol-modified nanoband array electrodes.•The response of the sensor to hydrogen peroxide and glucose was monitored electrochemically.•Comparing with a conventional electrode, a thousand-fold improvement in sensitivity and wide linear range was obtained.•The superior performance of the nanoband sensor can be attributed to the nanoband array architecture.•The nanoband structure allows for efficient diffusion of substrate to the electrode and provides low background currents.
Characterizing the first event of biological production of calcium carbonate requires a combination of microscopy approaches. First, intracellular pH distribution and calcium ions can be observed ...using live microscopy over time. This allows identification of the life stage and the tissue with the feature of interest for further electron microscopy studies. Life stage and tissues of interest are typically higher in pH and Ca signals. Here, using H. elegans, we present a protocol to characterize the presence of calcium carbonate structures in a biological specimen on the scanning electron microscope (SEM), using energy-dispersive X-ray spectroscopy (EDS) to visualize elemental composition, using electron backscatter diffraction (EBSD) to determine the presence of crystalline structures, and using transmission electron microscopy (TEM) to analyze the composition and structure of the material. In this protocol, a focused ion beam (FIB) is used to isolate samples with dimension suitable for TEM analysis. As FIB is a site specific technique, we demonstrate how information from the previous techniques can be used to identify the region of interest, where Ca signals are highest.
Single-walled carbon nanotubes (SWNTs), being hydrophobic by nature, aggregate in water to form large bundles. However, isolated SWNTs possess unique physical and chemical properties that are ...desirable for sensing and biological applications. Conventionally isolated SWNTs can be obtained by wrapping the tubes with biopolymers or surfactants. The binding modes proposed for these solubilization schemes, however, are less than comprehensive. Here we characterize the efficacies of solubilizing SWNTs through various types of phospholipids and other amphiphilic surfactants. Specifically, we demonstrate that lysophospholipids, or single-chained phospholipids offer unprecedented solubility for SWNTs, while double-chained phospholipids are ineffective in rendering SWNTs soluble. Using transmission electron microscopy (TEM) we show that lysophospholipids wrap SWNTs as striations whose size and regularity are affected by the polarity of the lysophospholipids. We further show that wrapping is only observed when SWNTs are in the lipid phase and not the vacuum phase, suggesting that the environment has a pertinent role in the binding process. Our findings shed light on the debate over the binding mechanism of amphiphilic polymers and cylindrical nanostructures and have implications on the design of novel supramolecular complexes and nanodevices.
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