8 research outputs found
Characterization of Graphene-Nanoplatelets Structure via Thermogravimetry
The
rapid increase in graphene-based applications has been accompanied
by novel top-down manufacturing methods for graphene and its derivatives
(e.g., graphene nanoplatelets (GnPs)). The characterization of the <i>bulk</i> properties of these materials by imaging and surface
techniques (e.g., electron microscopy and Raman spectroscopy) is only
possible through laborious and time-consuming statistical analysis,
which precludes simple and efficient quality control during GnP production.
We report that thermogravimetry (TG) may be utilized, beyond its conventional
applications (e.g., quantification of impurities or surfactants, or
labile functional groups) to characterize <i>bulk</i> GnP
properties. We characterize the structural parameters of GnP (i.e.,
defect density, mean lateral dimension, and polydispersity) by imaging
and surface techniques, on one hand, and by a systematic TG, on the
other. The combined data demonstrate that the combustion temperature
of commercially available and laboratory-prepared GnPs is correlated
with their mean lateral dimension and defect density, while the combustion
temperature range is proportional to their polydispersity index. Mapping
all these parameters allows one to evaluate the GnPs’ structure
following a simple thermogravimetric experiment (without necessitating
further statistical analysis). Finally, TG is also used to detect
and quantify different GnP constituents in powder and to conduct rapid
quality-control tests during GnP production
Solid-state solvent-free catalyzed hydrogenation: Enhancing reaction efficiency by spillover agents
Development of a specific radioimmunoassay for the detection of clenbuterol residues in treated cattle
A radioimmunoassay for clenbuterol detection in cattle has been validated and used to monitor treated cattle. The tracer used was 4-amino-3,5-dichloro-α (tert-butylaminomethyl) benzyl alcohol (benzyl-3H) (clenbuterol) prepared by catalytic tritiation with tritium gas of 4-amino-3,5-dibromo-α-(tert-butylamino)-acetophenone, followed by chlorination at positions 3 and 5 in the aromatic ring. The rabbit antiserum was raised against a diazotized clenbuterol/human serum albumin conjugate. The assay described was sensitive (7.8 pg/tube) and reproducible. The intra- and inter-assay variability, which was assessed by measuring known quantities of clenbuterol in plasma, urine and faeces, was satisfactory for RIA. When this assay was used to monitor treated cattle the concentrations of clenbuterol in plasma, urine and faeces were directly related to the administered dose. The absorption and elimination of clenbuterol in cattle was rapid. Data obtained were consistent with results obtained in other species where a rapid clearance rate was also demonstrated. © 1991 Taylor & Francis Group, LLC.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
Carbon Allotropes Accelerate Hydrogenation via Spillover Mechanism
Solid-phase hydrogenation kinetics
can be substantially increased by utilizing hydrogen spillover phenomenon.
Carbonaceous allotropes are considered as promising spillover agents
(SOAs) for improved hydrogen transport rate. We studied the effect
of carbon-based SOA properties on irreversible hydrogenation. We divided
the reaction into two major stages, near- and far-field hydrogenation
(with respect to a catalyst), and determined their rate-limiting steps.
The hydrogenation kinetics was analyzed for hydrogen originating from
either catalyst on activated carbon or catalyst-decorated carbon nanotubes.
The far-field hydrogenation is investigated for three types of loaded
nanocarbons: 1D (nanotubes), 2D (graphene), and 3D (activated carbon).
We found that the kinetics acceleration is strongly correlated with
the nanocarbon dimension, 1D > 2D > 3D, and could reach almost
2 orders of magnitude. These findings are useful for the study of
reversible hydrogen storage applications