Search results for "Thermal desorption"

Emerging switchable ultraviolet photoluminescence in dehydrated Zn/Al layered double hydroxide nanoplatelets

2019

AbstractLayered double hydroxides show intriguing physical and chemical properties arising by their intrinsic self-assembled stacking of molecular-thick 2D nanosheets, enhanced active surface area, hosting of guest species by intercalation and anion exchanging capabilities. Here, we report on the unprecedented emerging intense ultraviolet photoluminescence in Zn/Al layered double hydroxide high-aspect-ratio nanoplatelets, which we discovered to be fully activated by drying under vacuum condition and thermal desorption as well. Photoluminescence and its quenching were reproducibly switched by a dehydration–hydration process. Photoluminescence properties were comprehensively evaluated, such a…

Analysis of ecstasy in oral fluid by ion mobility spectrometry and infrared spectroscopy after liquid-liquid extraction.

2014

We developed and evaluated two different strategies for determining abuse drugs based on (i) the analysis of saliva by ion mobility spectrometry (IMS) after thermal desorption and (ii) the joint use of IMS and infrared (IR) spectroscopy after liquid-liquid microextraction (LLME) to enable the sensitivity-enhanced detection and double confirmation of ecstasy (MDMA) abuse. Both strategies proved effective for the intended purpose. Analysing saliva by IMS after thermal desorption, which provides a limit of detection (LOD) of 160μgL(-1), requires adding 0.2M acetic acid to the sample and using the truncated negative second derivative of the ion mobility spectrum. The joint use of IMS and IR spe…

Catalytic cracking of n-alkane naphtha: The impact of olefin addition and active sites differentiation

2015

An extended dual kinetic model allows to fit the n-heptane cracking results working in a wide range of reaction conditions. The duality of the model is provided by the contribution of monomolecular and bimolecular cracking mechanisms. It takes into account the role played by the olefins formed on the global cracking or added within the feed. Furthermore by means of this model and the kinetic parameters obtained when cracking n-heptane on ZSM-5, it has been observed that, while some characterization techniques show a homogeneous zeolite surface from the point of view of the active sites, rigorous kinetic experiments point to the possibility that the reactant sees a heterogeneous surface with…

2011

Abstract. The detection of primary biological material in submicron aerosol by means of thermal desorption/electron impact ionization aerosol mass spectrometry was investigated. Mass spectra of amino acids, carbohydrates, small peptides, and proteins, all of which are key building blocks of biological particles, were recorded in laboratory experiments. Several characteristic marker fragments were identified. The intensity of the marker signals relative to the total organic mass spectrum allows for an estimation of the content of primary biological material in ambient organic aerosol. The developed method was applied to mass spectra recorded during AMAZE-08, a field campaign conducted in the…

The influence of various synthesis methods on the catalytic activity of cerium oxide in one-pot synthesis of diethyl carbonate starting from CO2, eth…

2013

Different synthesis methods such as homogeneous precipitation at room temperature and supercritical water (T > 647 K and P > 22.1 MPa) were employed for cerium oxide preparation. Additionally, deposition of ceria on silica mesoporous material, SBA-15, was carried out. The obtained materials were characterized by means of X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, nitrogen physisorption, X-ray photoelectron spectroscopy and CO2 temperature programmed desorption. Considerable variations in physico-chemical properties of the resulting materials were observed. The catalytic activities of pristine cerium oxide and ceria loaded on SBA-15 support were…

Experimental setup for analysis of sorption and desorption of tritium in liquid lithium under different external conditions

2013

An original complex device has been designed and created specially for this research. Some of tritium sorption and thermal desorption in liquid lithium experiments has been successfully done already. First experiment series were carried out under reduced pressure (vacuum) to rule out other operating gases (like Ar) that may squeeze out tritium from lithium. Experiments showed good tritium desorption from lithium which highly depends on the temperature. A proportional gas counter tritium monitor was used to collect data from tritium thermal desorption experiments.

Real-space observation of xenon adsorption and desorption kinetics on graphite (0001) by photoemission electron microscopy

2003

Abstract The growth and desorption of Xe monolayers on the basal plane of graphite has been investigated by real-space imaging using photoemission electron microscopy. Adsorption kinetics was studied at different substrate temperatures (39–65 K), corresponding to different growth modes. Coexisting phases showed up as different grey values in the image. Typical domain sizes of the 2D solid phases around 60 K are of the order of one to several μm. The domains exhibit an elongated shape with their long axis oriented preferentially parallel to step edges of the substrate. With increasing coverage the brightness of the domains increases, the 2D gas-phase regions shrink and finally disappear at h…

Determination of 129I/127I isotope ratios in liquid solutions and environmental soil samples by ICP-MS with hexapole collision cell

2003

The determination of I-129 in environmental samples at ultratrace levels is very difficult by ICP-MS due to a high noise caused by Xe impurities in argon plasma gas (interference of Xe-129(+)), possible (IH2+)-I-127 interference and an insufficient abundance ratio sensitivity of the ICP mass spectrometer for I-129/I-127 isotope ratio measurement. A sensitive, powerful and fast analytical technique for iodine isotope ratio measurements in aqueous solutions and contaminated soil samples directly without sample preparation using ICP-MS with a hexapole collision cell (ICP-CC-QMS) was developed. Oxygen is used as reaction and carrier gas for iodine thermal desorption via the gas phase from solid…

Determination of n-alkanes, polycyclic aromatic hydrocarbons and hopanes in atmospheric aerosol: evaluation and comparison of thermal desorption GC-M…

2019

Organic aerosol (OA) constitutes a large fraction of fine particulate matter (PM) in the urban air. However, the chemical nature and sources of OA are not well constrained. Quantitative analysis of OA is essential for understanding the sources and atmospheric evolution of fine PM, which requires accurate quantification of some organic compounds (e.g., markers). In this study, two analytical approaches, i.e., thermal desorption (TD) gas chromatography mass spectrometry (GC-MS) and solvent extract (SE) GC-MS, were evaluated for the determination of n-alkanes, polycyclic aromatic hydrocarbons (PAHs) and hopanes in ambient aerosol. For the SE approach, the recovery obtained is 89.3 %–101…

Improvement of the detection limit for determination of 129I in sediments by quadrupole inductively coupled plasma mass spectrometer with collision c…

2004

The previously developed sample introduction device for the hot extraction of iodine from environmental samples (soils or sediments) and on-line introduction of analyte via the gas phase in quadrupole inductively coupled plasma mass spectrometry with hexapole collision cell (ICP-CC-QMS) was equipped with a cooling finger, which allowed intermediate iodine enrichment and improved the detection limits for I-129 down to 0.4 pg g(-1) without any additional sample preparation. A mixture of oxygen and helium as reaction gases in the hexapole collision cell was used for reducing the disturbing background intensity of Xe-129(+). Oxygen was also used as the carrier gas for iodine thermal desorption …