Radiofrequency plasma methods

Polypropylene (PP) is a hydrophobic and chemically inert polymer which needs to be activated in order to be functional as a support for NA immobilization. Typically, PP membranes are aminated by exposure to an ammonia plasma generated by radiofrequency plasma discharge. Once aminated, the PP membranes can be reacted with derivatized ONDs using common coupling methods [56-58]. 

The direct formation of polymer films on electrode surfaces from their monomeric constituents is an attractive method for the preparation of PMEs. One such method is the polymerization of vinyl monomers from the gas phase using a radiofrequency plasma discharge. However note that polyvinylferrocene (PVF) films formed by plasma polymerization have been found to be cross-linked to a greater degree than electrodeposited PVF films, thus limiting penetration of electrolyte ions. ... 

A method for preparing a wettability gradient on various polymer surfaces was developed by our group (11-13) and by Pitt et aL (14,15). The wettability gradient was produced via radiofrequency plasma discharge treatment by exposing the polymer sheets continuously to plasma. 

Ullrafine particles (UFPs) of metal and semiconductor nitrides have been synthesized by two major techniques one is the reactive gas condensation method, and the other is the chemical vapor condensation method. The former is modified from the so-called gas condensation method (or gas-evaporation method) (13), and a surrounding gas such as N2 or NII2 is used in the evaporation chamber instead of inert gases. Plasma generation has been widely adopted in order to enhance the nitridation in the particle formation process. The latter is based on the decomposition and the subsequent chemical reaction of metal chloride, carbonate, hydride, and organics used as raw materials in an appropriate reactive gas under an energetic environment formed mainly by thermal healing, radiofrequency (RF) plasma, and laser beam. Synthesis techniques are listed for every heal source for the reactive gas condensation method and for the chemical vapor condensation method in Tables 8.1.1 and 8.1.2, respectively. 

Chemically modified celluloses have been analyzed by conventional wet methods and by various Instrumental methods designed to differentiate bulk and surface properties. Electron emission spectroscopy for chemical analyses (ESCA) used alone and In combination with radiofrequency cold plasmas yielded elemental analyses, oxidative states of the element, and distribution of the element. Techniques of electron paramagnetic resonance (EPR), chemiluminescence, reflectance infrared spectroscopy, electron microscopy, and energy dispersive X-ray analyses were also used to detect species on surfaces and to obtain depth profiles of a given reagent in chemically modified cottons. 

Jimenez et al. also used the ICP-MS method for the determination of Al, Ba, Bi, Cd, Co, Cu, Mn, Ni, Pb, Sn, and V. The main differences that they initiated focused on the on-line formation of olive oil-in-water emulsions, the considerable time-gain, and the automatic sample preparation process. Among the various experimental parameters studied and optimized for the development of this method were emulsifier concentration at the mixing point, emulsifier concentration in the carrier solutions in the valves, injected sample emulsifier volumes, emulsion formation flow rate, design of the FIA manifold used (emulsion formation, reactor length, and size of the different connections), and the radiofrequency power in the plasma. 

A plasma may be defined as a gas containing a relatively large number of ions and free electrons. To produce a plasma, an energy source is required and for analytical atomic spectroscopy three different excitation methods have been used. They are (1) a dc arc, (2) radiofrequency energy coupled through a microwave cavity, and (3) radiofrequency energy inductively coupled to the plasma. 

The most widespread type of emission spectroscopy method used to excite the analyte atoms is a plasma that consists of electrons, ions, and excited atoms. In the most frequently deployed system, the plasma is indnced in argon gas by a strong radiofrequency (RF) field (or by microwaves), and is thns called indnctively coupled plasma (ICP) and the method is known as ICP-AES. The plasma is formed when argon gas flows through a torch made of three concentric glass tnbes surrounded by a cooled metal coil with the RF field (Figure 1.18). 

Some mediators can be immobilized to the electrode surface by a strong covalent bond. For example, the cyanurchlorid method is based on a carbon (graphite or glassy carbon) with its surface worked up in a radiofrequency oxygen plasma. Such a surface contains hydroxyl groups... 

Thermal plasmas have been used for decades as a source of heat for gas-phase reactions. The use of a radiofrequency (RF) plasma has been investigated at a laboratory level for the production of very fine powders of oxides and to a greater extent for nonoxides such as nitrides and carbides (110). The process parameters that control the powder characteristics are the frequency and power level of the plasma source, the temperature of the plasma jet, the flow rate of the gases, and the molar ratio of the reactants. While powders with high purity and very fine particle size (e.g., 10-20 nm) can be produced by this method, a major problem is that the powders are highly agglomerated. 

Cubic BN can also be obtained at low pressure in the field of stability of h-BN under nonequilibrium conditions, in analogy to the formation of diamond or diamond-Hke carbon films. As in the case of diamond, CVD, plasma-assisted chemical vapor deposition (PACVD), and PVD methods such as ion beam bombardment, radiofrequency sputter deposition, laser ablation, and magnetron sputtering can each be appHed. 

Among the different types of pretreatment methods proposed, plasma treatment represents probably the most versatile and efficient method for surface modification. The properties of plasma-modified surfaces mainly depend on parameters controlled by the reaction conditions (i.e., type of gas, pressure, radiofrequency, effective power, and time of treatment) and by the physicochemical properties of the polymer used. By using short plasma treatments, the surface modification can be confined to the first atomic layers of the polymer surface. Moreover, plasma treatment offers the ability to choose the nature of the chemical modification as a function of the gas used. As an example, the introduction of amine functionalities on PHB surfaces has been achieved using ammonia plasma [47, 51]. However, the number of functional groups formed at the surface is difficult to control. 

Inductively coupled plasma-mass spectrometry is a very rapid technique for the determination of long-lived radionuclides. This technique is based on the ionization of elements in the plasma source. Typically, radiofrequency and argon are used to reach plasma excitation temperatures ranging from 4900 to 7000 K [18,19]. The ions produced are introduced through an interface into a vacuum chamber and are analyzed by a quadru-pole mass spectrometer. Other attempts are being made to use faster mass-spectrometer detectors, such as time-of-flight mass spectrometers, but methods are still not available. 

In inductively coupled plasma mass spectrometry (ICP-MS), atomization and ionization are achieved in a radiofrequency argon plasma at atmospheric pressure. Since a seminal publication in 1980 [19], ICP-MS has become one of the most frequently employed methods of elemental MS (Chap. 7.3 in [3], Chap. 4 in [6], Chap. 5 in [7]). The wide acceptance of ICP-MS is due to its comparatively robust, yet versatile sampling mode. An ICP not only offers high ionization efficiency for elements of low IE, e.g., 98% for IE = 1 eV, it is still applicable to nonmetals such as P and even Cl (ionization efficiency is 1% for IE = 13 eV). 

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