1,721,116 research outputs found
Role of the material electrodes on resistive behaviour of carbon nanotube-based sensores for H2S detection
Full text linkDensity functional study of H-induced sites in hybrid carbon nanomaterials
No full textRecently we have reported on the growth of an exciting new class of hybrid nanostructured carbon
materials, coupling nanosized diamond with single-walled carbon nanotubes. The inner structures were
shown to be single-walled C nanotubes or bundles of single-walled nanotubes up to 15 ím long, and the
outer deposit consisted of faceted diamond crystallites with diameters in the range of 20-100 nm. To
aid in understanding the mechanisms responsible for the formation of such materials, the present study
uses density functional theory to examine the role of atomic hydrogen in creating localized sp3 hybridized
defects on the outer wall of carbon nanotubes. The results illustrate that certain absorption configurations
may produce defects containing dangling carbon bonds, and thus promote the formation of suitable sites
for nanodiamond nucleation
Functionalised single-walled carbon nanotubes modified microsensors for the selective response of epinephrine in presence of ascorbic acid
No full textModified stainless steel microelectrodes (microwire diameter: 300 mm) were assembled using functionalized singlewalled
carbon nanotubes (SWCNTs) deposited by the EPD method (electrophoretical deposition process). The
functionalized SWCNTs, which covered the microelectrode surfaces, showed an improved sensitivity and selectivity
toward the electrochemical detection of epinephrine. These chemical sensors hampered the voltammetric responses of
ascorbic acid (AA) and uric acid (UA), while the electrochemical oxidation of epinephrine was significantly
enhanced. Using the differential pulse voltammetry (DPV) technique, epinephrine showed a very well resolved peak
centered around 240mV, while 1 mM of AA (present in the same solution) was not detected. The corresponding
permeability and permselectivity parameters were also evaluated for ascorbic acid and uric acid. To investigate the
sensor selectivity, a comparative study performed using microsensors assembled with non functionalized carbon
nanotubes, deposited on the microelectrode surfaces by a chemical vapor deposition (CVD) technique, was also
carried out. This study was useful to highlight that the presence, or the absence of electrostatic barriers on SWCNT<s
walls (due to the presence of some chemical functional groups), can be able to control the electrochemical response of
these sensors. This optimization resulted in microsensors with a good linear range (2 – 100 mM) epinephrine; a good
sensitivity (28.1 A M 1 cm 2) and interelectrodes reproducibility (RSD%¼7.0, n¼6), a detection of limit (LOD¼
3s) of 2 mM; a response time of 6 s; a significant operational stability (of 13 hours in continuous working conditions)
and long term stability (1 month)
Synthesis and characterization of polymeric films and nanotubule nets used to assemble selective sensors for nitrite detection in drinking water
Full text linkSingle-walled carbon nanotubes on tungsten wires: a new class od microelectrochemical sensors
No full textThis paper reports the fabrication and the outstanding performance characteristics of novel microelectrodes consisting
of tungsten (W) wires coated with homogeneous layers of single-walled C nanotubes (SWNT). A series of studies
using cyclic voltammetry indicate that the SWNT-modified Welectrodes possess interesting electrochemical features.
In fact, they are able to catalyse electron transfer reactions involving a series of inorganic and biological molecules.
These electrodes are characterized by a fast electron transfer, a wide working potential window, and a low background
current. Moreover they demonstrate excellent reproducibility, good stability in various chemical media, and very high
sensitivity towards a series of inorganic and organic compounds. The SWNT modified microelectrodes have been
tested for the capacity to electrochemically detect ferrocene monocarboxylic acid and potassium hexacyanoferrate as
well of a series of interesting biological molecules which include catechol, caffeic acid, DOPAC, ascorbic acid, ltyrosine,
acetaminophen, guanine, uric acid, and the neurotransmitters dopamine, epinephrine, and serotonin (5-HT)
hydrochloride. The advantages of the SWNT-modified W electrodes are illustrated by comparing their analytical
performance with that of conventional electrodes
Charge transport and tunneling in single-walled crbon nanotube bundles
Full text linkWe investigate experimentally the transport properties of single-walled carbon nanotube bundles as a
function of temperature and applied current over broad intervals of these variables. The analysis is
performed on arrays of nanotube bundles whose axes are aligned along the direction of the externally
supplied bias current. The data are found consistent with a charge transport model governed by the
tunneling between metallic regions occurring through potential barriers generated by a nanotube’s contact
areas or bundle surfaces. Based on this model and on experimental data, we describe quantitatively the
dependencies of the height of these barriers upon bias current and temperature.
DOI: 10.1103/PhysRevLett.101.24680
Understanding the way eumelanin works: a unique example of properties and skills driven by molecular heterogeneity
No full textHere we revisit recent scientific discoveries and technological advancements related to the eumelanin (EU) biopolymer. Starting from EU extracted from living species, the settling of laboratory-scale synthesis strategies and of characterization methodologies are now allowing to clarify and reproduce the unique combination of chemical/compositional/structural features of this biomaterial. The 5,6-dihydroxyindole (DHI) and 5,6-dihydroxyindole 2-carboxylic acid (DHICA) substructures constituting EU present indeed a remarkable variability in electron delocalization, redox states, types of free radicals and localization of paramagnetic centers. Moreover, the EU building blocks can be packed following several supramolecular organizations. The high heterogeneity accounts for the abandonment of the notion "one-material/one-set-of-properties". The interplay of mixed and sometimes conflicting functionalities - electronic/protonic conduction, radiative/non-radiative decays of optical active states, antioxidant/pro-oxidant behavior, chemical/physical mechanisms for withstand radioactivity - leads to countless opportunities to employ EU in several cutting-edge technologies. The critical analysis of literature highlights advantages and drawbacks related to the realization of biomedical supports, electronic/ optoelectronic devices, energy storage/delivery systems, bioremediation and radioprotection means. The focus is on the state-of-art, on the translation of major concepts into novel applications, and on the main remaining challenges for the use of a biomaterial characterized by unusual precious characteristics
Nanomechanical characterizations of soft materials and nanocomposites by atomic force microscopy
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