Knightguthrie6723

The continued growth of the nanotechnology industry and the incorporation of nanomaterials into consumer applications will inevitably lead to their release into environmental systems. Single-walled carbon nanotubes (SWCNTs) in particular have exhibited many attractive optical, mechanical, and electrical properties that lend themselves to new and exciting applications. Assessing their environmental impact upon release into the environment is contingent upon quantifying and characterizing SWCNTs in environmental matrixes. In this study, SWCNTs were isolated from estuarine sediments using density gradient ultracentrifugation (DGU), followed by online flow-through analysis of the density fractions via near-infrared spectroscopy. This approach yielded significant improvements in the quantitative detection limit, from 62 to 1.5 μg g-1. In addition, fractions of the density gradient were also obtained for further analysis by bulk inductively coupled plasma mass spectrometry (ICP-MS) and single-particle ICP-MS. Using fluorescent, semiconductive SWCNTs, the primary fluorescent nanotube fraction was found to be separated from the sediment matrix during DGU; however, the residual metal catalyst particles that had been assumed to be physically bound to the SWCNTs were found to form a separate band in the density gradient apart from the fluorescent SWCNTs. This result was repeated for a number of SWCNT types regardless of the metal catalyst and synthesis method, with a 0.1 g cm-3 density difference between most fractions. The apparent disconnect between the fluorescent fraction of SWCNTs and their metal-containing constituents potentially complicates CNT risk assessment as analysis techniques focusing solely on either CNT fluorescence or metal fingerprints may misrepresent exposure concentrations and their toxicological implications.Gold nanoparticles (AuNPs) have been widely used in catalytic electrochemistry. Heterogeneity in size, shape, and surface sites leads to variable, particle-specific catalytic activities. Conventional electrochemical methods can only obtain the collective responses from all the catalytic nanoparticles on the electrode surface; the heterogeneity of particle performance will be averaged. Alternatively, plasmonic electrochemical imaging (PECi) is capable of imaging the electrochemical activity at individual nanoparticles. In this work, PECi was used to image the oxidation and reduction of the gold surface at individual AuNPs, and their associated structural alterations were successfully measured. We have studied the electrochemical responses from gold nanocubes, gold nanorods, and gold nanowires with PECi and observed different surface redox activities. We have also demonstrated the capability of monitoring the surface dynamics at individual AuNPs utilizing characteristic PECi derived cyclic voltammograms (CVs).Organophosphorus esters (OPs) were originally developed as pesticides but were repurposed as easily manufactured, inexpensive, and highly toxic chemical warfare agents. Acute OP toxicity is primarily due to inhibition of acetylcholinesterase (AChE), an enzyme in the central and peripheral nervous system. OP inhibition of AChE can be reversed using oxime reactivators but many show poor CNS penetration, indicating a need for new clinically viable reactivators. However, challenges exist on how to best measure restored AChE activity in vivo and assess the reactivating agent efficacy. This work reports the development of molecular imaging tools using radiolabeled OP analog tracers that are less toxic to handle in the laboratory, yet inhibit AChE in a similar fashion to the actual OPs. Carbon-11 and fluorine-18 radiolabeled analog tracers of VX and sarin OP agents were prepared. Following intravenous injection in normal Sprague-Dawley rats (n = 3-4/tracer), the tracers were evaluated and compared using noninvasive tracer relative to the other tracers studied and suitable for future in vivo OP exposure and reactivation studies.In quantitative mass spectrometry imaging (MSI), the gold standard adds a single structural homologue of the target compound at a known concentration to the sample. This internal standard enables to map the detected intensity of the target molecule against an external calibration curve. This approach, however, ignores local noise levels and disproportional ion suppression effects, which might depend on the concentration of the target compound. To overcome these issues, we propose a novel approach that applies several isotopically labeled versions, each at a different concentration, to the sample. This allows creating individual internal calibration curves for every MSI pixel. selleck products As proof of principle, we have quantified an endogenous peptide of histone H4 by matrix-assisted laser desorption/ionization-Q-MSI (MALDI-Q-MSI), using a mixture of three isotopically labeled versions. The usage of a fourth label allowed us to compare the gold standard to our multilabel approach. We observed substantial heterogeneity in ion suppression across the tissue, which disclosed itself as varying slopes in the per-pixel regression analyses. These slopes were histology-dependent and differed from each other by up to a factor of 4. The results were validated by liquid chromatography-mass spectrometry (LC-MS), exhibiting a high agreement between LC-MS and MALDI-Q-MSI (Pearson correlation r = 0.87). A comparison between the multilabel and single-label approaches revealed a higher accuracy for the multilabel method when the local target compound concentration differed too much from the concentration of the single label. In conclusion, we show that the multilabel approach provides superior quantitation compared to a single-label approach, in case the target compound is inhomogeneously distributed at a wide concentration range in the tissue.It is a challenge to acquire, realize, and comprehend highly emissive phosphorescent molecules. Herein, we report that, using persulfurated benzene compounds as models, phosphorescence can be strongly enhanced through the modification of molecular conformation and crystal growth conditions. By varying the peripheral groups in these compounds, we were able to control their molecular conformation and crystal growth mode, leading to one- (1D), two- (2D), and three-dimensional (3D) crystal morphologies. Two kinds of typical molecular conformations were separately obtained in these crystals through substituent group control or the solvent effect. Importantly, a symmetrical 3,3-conformer exhibits that a planar central benzene ring prefers a 3D-type crystal growth mode, demonstrating high phosphorescence efficiency. Such outcome is attributed to the strong crystal protection effect of the 3D crystal and the bright global minimum (GM) boat-like T1 state of the symmetrical 3,3-conformer. The conformation studies further reveal small deformation of the inner benzene ring in both singlet and triplet states.