Trends in Carbon, Oxygen, and Nitrogen Core in the X-ray Absorption Spectroscopy of Carbon Nanomaterials: A Guide for the Perplexed
14 Jan 2021-Journal of Physical Chemistry C (American Chemical Society)-Vol. 125, Iss: 1, pp 973-988
TL;DR: In this article, the success of carbon nanomaterials in many applications, such as sensing, energy storage, and catalysis, relies on the selection, synthesis, and tailoring of the surface properties.
Abstract: Successful deployment of carbon nanomaterials in many applications, such as sensing, energy storage, and catalysis, relies on the selection, synthesis, and tailoring of the surface properties. Pred...
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29 Sep 2021TL;DR: In this article, the authors examined the effect of electrochemical fouling, caused by the analyte and its reaction products, and biofouling caused by proteins and other species in the measurement environment.
Abstract: Electrode fouling is a major factor that compromises the performance of biosensors in in vivo usage. It can be roughly classified into (i) electrochemical fouling, caused by the analyte and its reaction products, and (ii) biofouling, caused by proteins and other species in the measurement environment. Here, we examined the effect of electrochemical fouling [in phosphate buffer saline (PBS)], biofouling [in cell-culture media (F12-K) with and without proteins], and their combination on the redox reactions occurring on carbon-based electrodes possessing distinct morphologies and surface chemistry. The effect of biofouling on the electrochemistry of an outer sphere redox probe, [Ru(NH3)6]3+, was negligible. On the other hand, fouling had a marked effect on the electrochemistry of an inner sphere redox probe, dopamine (DA). We observed that the surface geometry played a major role in the extent of fouling. The effect of biofouling on DA electrochemistry was the worst on planar pyrolytic carbon, whereas the multiwalled carbon nanotube/tetrahedral amorphous carbon (MWCNT/ta-C), possessing spaghetti-like morphology, and carbon nanofiber (CNF/ta-C) electrodes were much less seriously affected. The blockage of the adsorption sites for DA by proteins and other components of biological media and electrochemical fouling components (byproducts of DA oxidation) caused rapid surface poisoning. PBS washing for 10 consecutive cycles at 50 mV/s did not improve the electrode performance, except for CNF/ta-C, which performed better after PBS washing. Overall, this study emphasizes the combined effect of biological and electrochemical fouling to be critical for the evaluation of the functionality of a sensor. Thus, electrodes possessing composite nanostructures showed less surface fouling in comparison to those possessing planar geometry.
14 citations
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TL;DR: In this paper , a manganese doped ZIF-67 derived nitrogen doped carbon based sulfide Mn/Co/NC/S electrode is synthesized for augmented performance in supercapacitors.
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TL;DR: In this paper, the authors acknowledge the provision of facilities by RawMatters Finland Infrastructure (RAMI, no. 292884), Aalto University Bioeconomy, and OtaNano - Nanomicroscopy Center (Aalto-NMC).
Abstract: Funding Information: We acknowledge the provision of facilities by RawMatters Finland Infrastructure (RAMI, no. 292884), Aalto University Bioeconomy, and OtaNano - Nanomicroscopy Center (Aalto-NMC). Use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under contract no. DE-AC02-76SF00515. We acknowledge CSC – IT Center for Science, Finland, for computational resources. S.S. acknowledges funding from the Walter Ahlstrom Foundation. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement no. 841621 and the Business Finland FEPOD 2117731 project. M.A.C. acknowledges funding from the Academy of Finland under project number 30488. Publisher Copyright: © 2021 The Authors. Published by American Chemical Society.
8 citations
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TL;DR: The effect of surface topography and chemistry on fouling without additional protective layers is investigated and oxygen functionalities were significantly increased on nanograss surfaces compared to the flat counterparts.
Abstract: Biofouling imposes a significant threat for sensing probes used in vivo. Antifouling strategies commonly utilize a protective layer on top of the electrode but this may compromise performance of the electrode. Here, we investigated the effect of surface topography and chemistry on fouling without additional protective layers. We have utilized two different carbon materials; tetrahedral amorphous carbon (ta-C) and SU-8 based pyrolytic carbon (PyC) in their typical smooth thin film structure as well as with a nanopillar topography templated from black silicon. The near edge X-ray absorption fine structure (NEXAFS) spectrum revealed striking differences in chemical functionalities of the surfaces. PyC contained equal amounts of ketone, hydroxyl and ether/epoxide groups, while ta-C contained significant amounts of carbonyl groups. Overall, oxygen functionalities were significantly increased on nanograss surfaces compared to the flat counterparts. Neither bovine serum albumin (BSA) or fetal bovine serum (FBS) fouling caused major effects on electron transfer kinetics of outer sphere redox (OSR) probe Ru(NH3)63+ on any of the materials. In contrast, negatively charged OSR probe IrCl62- kinetics were clearly affected by fouling, possibly due to the electrostatic repulsion between redox species and the anionically-charged proteins adsorbed on the electrode and/or stronger interaction of the proteins and positively charged surface. The OSR probe kinetics were less affected by fouling on PyC, probably due to conformational changes of proteins on the surface. Dopamine (DA) was tested as an inner sphere redox (ISR) probe and as expected, the kinetics were heavily dependent on the material; PyC had very fast electron transfer kinetics, while ta-C had sluggish kinetics. DA electron transfer kinetics were heavily affected on all surfaces by fouling (ΔEp increase 30-451%). The effect was stronger on PyC, possibly due to the more strongly adhered protein layer limiting the access of the probe to the inner sphere.
8 citations
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TL;DR: In this article, the atomic structure of pristine and functionalized graphene was characterized from a combination of computational simulation of X-ray spectra and computer-aided interpretation of experimental spectra.
Abstract: In this work, we demonstrate how to identify and characterize the atomic structure of pristine and functionalized graphene materials from a combination of computational simulation of X-ray spectra, on the one hand, and computer-aided interpretation of experimental spectra, on the other. Despite the enormous scientific and industrial interest, the precise structure of these 2D materials remains under debate. As we show in this study, a wide range of model structures from pristine to heavily oxidized graphene can be studied and understood with the same approach. We move systematically from pristine to highly oxidized and defective computational models, and we compare the simulation results with experimental data. Comparison with experiments is valuable also the other way around; this method allows us to verify that the simulated models are close to the real samples, which in turn makes simulated structures amenable to several computational experiments. Our results provide ab initio semiquantitative information and a new platform for extended insight into the structure and chemical composition of graphene-based materials.
6 citations