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This study aimed to obtain the title spectra and verify the temperature dependence of δDSS of the HOD signal from D2O of the NMR sample. However, the analysis of the collected δX data, extended by the results of other closely related measurements reported in the literature, provided important guidelines for performing routine 1H/13C NMR spectra in aqueous solvents externally referenced to neat liquid TMS contained in a coaxial capillary. Therefore, it is recommended that the previously proposed correction of δX data thus determined, which is mainly due to the difference in volume magnetic susceptibility χv between the sample and the external standard used, usually called the bulk magnetic susceptibility (BMS) correction, has been increased by +0.05 ppm (7%). The new value of this correction, +0.73 ppm, based on NMR experiments carried out at a standard temperature of 25°C, was confirmed in a classical approach using critically reviewed χm, χM, and ρ data for TMS, D2O, and H2O. The BMS correction for H2O solutions is +0.75 ppm. Important issues concerning magnetic susceptibility measurements for D2O and H2O, coaxial bulb‐ended inserts, and the geometry of two‐tube NMR cells (shape factor αav) are also critically discussed here, partly from a historical perspective. [ABSTRACT FROM AUTHOR]

Since its introduction, about 15 years ago, the cyclic siloxane Cyclomethicone D5 has become increasingly used in the conservation of Cultural Heritage. In free form it allows the temporary hydrophobization of sensitive surfaces that must be treated in an aqueous environment; in the commercially available gelled form it allows the formulation of water-in-oil particle emulsions for surface cleaning or removal of film-forming substances, depending on the conditions of the aqueous phase. Over time, doubts have arisen about the real inertness of this solvent towards modern oil media. In addition, European regulations have restricted its use in consideration of its environmental impact, and so the already difficult availability of the material could further complicate; this advises the search for a substitute solvent. These two arguments motivated this study, conducted on two modern oil paintings: one unvarnished on paper, the other varnished on canvas. Samples of these paintings were treated under different conditions with D5 and the potential substitute chosen: dodecamethylpentasiloxane. The GC–MS and SEM-EDS analysis of the treated samples made it possible to evaluate and compare the degree of interaction with the oil binder in terms of leaching and topographic alterations of the surface, for both the free solvents and their gelled forms. Tests conducted on specially prepared paint samples also made it possible to evaluate the degree of solvation and consequent swelling produced by the two solvents on the different binders. [ABSTRACT FROM AUTHOR]

The quite popular, simple but imperfect method of referencing NMR spectra to residual 1H and 13C signals of TMS-free deuterated organic solvents (referred to as Method A) is critically discussed for six commonly used NMR solvents with respect to their δH and δC values that exist in the literature. Taking into account the most reliable data, it was possible to recommend 'best' δX values for such secondary internal standards. The position of these reference points on the δ scale strongly depends on the concentration and type of analyte under study and the solvent medium used. For some solvents, chemically induced shifts (CISs) of residual 1H lines were considered, also taking into account the formation of 1:1 molecular complexes (for CDCl3). Typical potential errors that can occur as a result of improper application of Method A are considered in detail. An overview of all found δX values adopted by users of this method revealed a discrepancy of up to 1.9 ppm in δC reported for CDCl3, most likely caused by the CIS mentioned above. The drawbacks of Method A are discussed in relation to the classical use of an internal standard (Method B), two 'instrumental' schemes in which Method A is often implicitly applied, that is, the default Method C using 2H lock frequencies and Method D based on Ξ values, recommended by the IUPAC but only occasionally used for 1H/13C spectra, and external referencing (Method E). Analysis of current needs and opportunities for NMR spectrometers led to the conclusion that, for the most accurate application of Method A, it is necessary to (a) use dilute solutions in a single NMR solvent and (b) to report δX data applied for the reference 1H/13C signals to the nearest 0.001/0.01 ppm to ensure the precise characterization of new synthesized or isolated organic systems, especially those with complex or unexpected structures. However, the use of TMS in Method B is strongly recommended in all such cases. [ABSTRACT FROM AUTHOR]

In this work, the spherically propagating flame method was applied to the measurements of laminar flame propagation for the flame synthesis precursors. The laminar burning velocities of a typical precursor of silica nanoparticles, i.e. tetramethylsilane (TMS, Si(CH 3) 4), were measured, and a comparative study was carried out on its hydrocarbon counterpart, neopentane. The laminar burning velocities of the two fuels were measured at the initial pressure of 1 atm, initial temperature of 323 K and equivalence ratios of 0.7–1.5. The results show that the laminar burning velocities of TMS are much higher than those of neopentane, showing remarkable fuel molecular structure effects. Kinetic models of TMS and neopentane combustion were constructed and validated against the new experimental data in this work. Based on the rate of production analysis and sensitivity analysis, the critical pathways in the flames of TMS and neopentane were revealed. The fictitious diluent gas method was adopted to provide insight into the fuel molecular structure effects on the laminar burning velocities of TMS and neopentane. It is concluded that the relatively high adiabatic flame temperature of TMS is the driven force of the rapid laminar flame propagation of TMS compared with neopentane, while the chemical effect also promotes the laminar flame propagation of TMS, especially under near stoichiometric conditions. [ABSTRACT FROM AUTHOR]

Nanomaterials from gas-phase synthesis are tapping into new fields of application in research and industry due to their unique size-dependent properties. To produce tailored nanoparticles, the synthesis starting from the precursor decomposition to the particle formation must be fully understood. Tetramethylsilane is used as a precursor for the synthesis of silica nanomaterials in flames. The precursor starts to decompose by H-abstraction. Reaction rates for H-abstraction of tetramethylsilane (TMS) by +O/+H/+OH radicals are determined by means of quantum chemical calculations. The rate expressions are obtained in the temperature range from 300 to 1400 K: kH = 6,025,735 (T/K)2.1731exp(-(+2613.840 K)/T) cm3mol−1s−1 for the total bimolecular reaction coefficient of TMS with hydrogen atoms, kOH = 10,179,818 (T/K)1.7790 exp(-(+152.739 K)/T) cm3mol−1s−1 for TMS with OH radicals, and kO = 93,100 (T/K)2.4797 exp(-(+889.166 K)/T) cm3mol−1s−1 for TMS with O(3P) radicals, respectively. The reaction rates are implemented into the TMS reaction mechanism of Janbazi et al. [1], and a better agreement of the TMS reactivity in the flame is achieved. Experiments are conducted to obtain the mass deposition rates with a Quartz-Crystal-Microbalance (QCM) in a wide range of different equivalence ratios. The equivalence ratio is varied between ϕ = 0.6–1.2, and precursor amounts of 400, 600 and 800 ppm are used. These QCM-experiments are complementary to the MBMS-studies from Karakaya et al. [1–3] but use the same flame conditions to extend the data set. The results reveal that metastable particles exist in the reaction zone of the flame. Depending on flame conditions, their concentration decreases towards the end of the reaction zone, but particles subsequently grow again in the recombination zone of the flame. The mechanisms, which describe the reactivity of the metastable nanoparticles, are tentatively proposed. The understanding of the mechanisms can open up the way for tailored nanoparticles with different structures and stoichiometries.

The quite popular, simple but imperfect method of referencing NMR spectra to residual 1H and 13C signals of TMS-free deuterated organic solvents (referred to as Method A) is critically discussed for six commonly used NMR solvents with respect to their δH and δC values that exist in the literature. Taking into account the most reliable data, it was possible to recommend ‘best’ δX values for such secondary internal standards. The position of these reference points on the δ scale strongly depends on the concentration and type of analyte under study and the solvent medium used. For some solvents, chemically induced shifts (CISs) of residual 1H lines were considered, also taking into account the formation of 1:1 molecular complexes (for CDCl3). Typical potential errors that can occur as a result of improper application of Method A are considered in detail. An overview of all found δX values adopted by users of this method revealed a discrepancy of up to 1.9 ppm in δC reported for CDCl3, most likely caused by the CIS mentioned above. The drawbacks of Method A are discussed in relation to the classical use of an internal standard (Method B), two ‘instrumental’ schemes in which Method A is often implicitly applied, that is, the default Method C using 2H lock frequencies and Method D based on Ξ values, recommended by the IUPAC but only occasionally used for 1H/13C spectra, and external referencing (Method E). Analysis of current needs and opportunities for NMR spectrometers led to the conclusion that, for the most accurate application of Method A, it is necessary to (a) use dilute solutions in a single NMR solvent and (b) to report δX data applied for the reference 1H/13C signals to the nearest 0.001/0.01 ppm to ensure the precise characterization of new synthesized or isolated organic systems, especially those with complex or unexpected structures. However, the use of TMS in Method B is strongly recommended in all such cases.

Theoretical kinetics and thermochemistry investigations on the H‐atom abstraction reactions by H and O atoms and OH and HO2 radicals from Si−C−O‐containing species such as Si(CH3)4, Si(CH3)3(OH), Si(CH3)2(OH)2, and Si(CH3)(OH)3 have been carried out in this work. The geometry, vibrational frequencies, and hindrance potential for each species are calculated at the B3LYP/6‐31G(2df,p) level of theory with the single‐point energies calculated at the G4 level of theory. The composite methods G3 and G4 are utilized to derive enthalpies of formation at 0 K by the atomization reaction methodology. ΔHf(298 K), S(298 K), and Cp(T) are calculated by using the statistical thermodynamics method. Conventional transition state theory is used over a wide temperature range (298.15−2000 K) for H‐atom abstraction reactions by H, O, and HO2 radicals from the species mentioned above, and variational transition state theory is used for H‐atom abstraction reactions by the OH radical. The kinetic and thermodynamic parameters based on high‐level theoretical calculations are compared with the literature data. Reactivity comparison between the similar hydrocarbons and silicon‐organic compounds for H‐atom abstractions is explored. A large difference exists between these two different systems when H‐atom abstractions are on hydroxyl sites. [ABSTRACT FROM AUTHOR]

This study aimed to obtain the title spectra and verify the temperature dependence of δ DSS of the HOD signal from D 2 O of the NMR sample. However, the analysis of the collected δ X data, extended by the results of other closely related measurements reported in the literature, provided important guidelines for performing routine 1 H/ 13 C NMR spectra in aqueous solvents externally referenced to neat liquid TMS contained in a coaxial capillary. Therefore, it is recommended that the previously proposed correction of δ X data thus determined, which is mainly due to the difference in volume magnetic susceptibility χ v between the sample and the external standard used, usually called the bulk magnetic susceptibility (BMS) correction, has been increased by +0.05 ppm (7%). The new value of this correction, +0.73 ppm, based on NMR experiments carried out at a standard temperature of 25°C, was confirmed in a classical approach using critically reviewed χ m , χ M , and ρ data for TMS, D 2 O, and H 2 O. The BMS correction for H 2 O solutions is +0.75 ppm. Important issues concerning magnetic susceptibility measurements for D 2 O and H 2 O, coaxial bulb-ended inserts, and the geometry of two-tube NMR cells (shape factor α av ) are also critically discussed here, partly from a historical perspective., (© 2024 John Wiley & Sons Ltd.)

Thermodynamic modeling of the chemical vapor deposition (CVD) of films of complex composition in the Si—B—N—C—H system under reduced pressure (0.01 or 10 Torr) in a wide temperature range of 500–1500 K using various organoelement compounds was carried out. An example with mixtures of tetramethylsilane SiMe4 and hexamethyldisilane (SiMe3)2 with trimethylamine borane Me3N · BH3 or triethylamine borane Et3N · BH3 illustrates a possibility to produce films of various compositions: from boron and silicon nitrides to their mixtures with carbides and/or carbon. According to the CVD diagrams, the prevailing equilibrium condensed phases are various phase complexes containing SiC, Si3N4, BN, and C. [ABSTRACT FROM AUTHOR]

A time-dependent, spatially one-dimensional fluid-Poisson model is applied to analyze the impact of small amounts of tetramethylsilane (TMS) as precursor on the discharge characteristics of an atmospheric-pressure dielectric barrier discharge (DBD) in argon. Based on an established reaction kinetics for argon, it includes a plasma chemistry for TMS, which is validated by measurements of the ignition voltage at the frequency f = 86.2 kHz for TMS amounts of up to 200 ppm. Details of both a reduced Ar-TMS reaction kinetics scheme and an extended plasma-chemistry model involving about 60 species and 580 reactions related to TMS are given. It is found that good agreement between measured and calculated data can be obtained, when assuming that 25% of the reactions of TMS with excited argon atoms with a rate coefficient of 3.0 × 10 - 16 m 3 / s lead to the production of electrons due to Penning ionization. Modeling results for an applied voltage U a , 0 = 4 kV show that TMS is depleted during the residence time of the plasma in the DBD, where the percentage consumption of TMS decreases with increasing TMS fraction because only a finite number of excited argon species is available to dissociate and/or ionize the precursor via energy transfer. Main species resulting from that TMS depletion are presented and discussed. In particular, the analysis clearly indicates that trimethylsilyl cations can be considered to be mainly responsible for the film formation. [ABSTRACT FROM AUTHOR]

Heavy bituminous oil is the main source of Nigerian unconventional resources. The resources represent oil sand and bitumen oil forming a belt of bitumen oil covering about 120 km extending from Lagos, Ogun, Ondo and Edo. Huge reserves of the resources are located in the state of Ondo. A nuclear magnetic resonance (NMR) method was used in the research to study bitumen oil in South West Nigeria. The NMR spectroscopy on the nuclei of 1H and 13C uses signals from protons and carbon nuclei, respectively, tetramethylsilane molecules Si(CH3)4. Regions of absorption of aliphatic (7–65 ppm) and aromatic (108–170 ppm) nuclei of carbon atoms are clearly defined in the NMR spectra of 13C of the objects under consideration. Signals of carbon atoms of olefinic fragments make a significant contribution to the last range of spectra of the cores of Nigerian bitumen deposits. An analysis of more known methods of defining the aromatic region of the nuclear magnetic resonance spectrum of 13C showed that for fractions that do not contain condensed cyclic and heteroatomic compounds, the definition of chemical shift subranges (CS) corresponding to aromatic carbon atoms 110–130 ppm not substituted, 130–137 ppm substituted by methyl, another alkyl – and naphthyl substituted – 137–148 ppm is sufficienly reasonable. There are regions of absorption of quaternary carbon atoms bonded to oxygen or nitrogen (148–170 ppm), carbonyl carbon atoms (170–200 ppm), as well as tertiary aromatic carbon atoms, located in the ortho position to the hydroxyl or other oxygen atom (108–118 ppm) in objects containing larger amounts of heteroatoms.

We report on mass spectrometry of residual gases after dissociation of tetramethylsilane (TMS) during the synthesis of silicon carbide (SiC) nanocrystals (NCs) by an atmospheric pressure microplasma. We use these results to provide details that can contribute to the understanding of the formation mechanisms of NCs. Mass spectrometry reveals the presence of high‐mass polymerization products supporting the key role of neutral fragments and limited atomization. On this basis, we found that the loss of methyl groups from TMS, together with hydrogen abstraction, represents important paths leading to nucleation and growth. The combination of TMS concentration and NC residence time controls the NC mean size and the corresponding distributions. For higher precursor concentrations, the reaction kinetics is sufficiently fast to promote coalescence. [ABSTRACT FROM AUTHOR]

Passivated emitter and rear contact (PERC) silicon solar cell is one of the most promising high-efficiency solar cells, which uses aluminum oxide (Al 2 O 3) and hydrogenated silicon nitride (SiN x :H) stack as the rear passivation layer. The SiN x :H not only serves as a protective layer but can provide hydrogen atoms that further passivate the dangling bonds on silicon wafer surface. In this study, the SiN x :H cover layers are deposited using high density plasma chemical vapor deposition with a silane-free gas mixture of tetramethylsilane (TMS) and ammonia (NH 3). Effects of the TMS gas flow rate on properties of the SiN x :H cover layers and effective minority carrier lifetime of silicon wafers are investigated. The experimental results show that the film density is positively related to the Si N bond proportion. The secondary ion mass spectrometry measurement shows that the dense SiN x :H can make hydrogen atoms move toward wafer surface instead of out-diffusion to the environment. The best SiN x :H film is deposited at a TMS flow rate of 35 sccm. The minority carrier lifetime can be improved from 70 μs for as-cleaned wafer to 373 μs for wafer/Al 2 O 3 and to 1006 μs for wafer/Al 2 O 3 /SiN x :H. The surface recombination rate of 23 cm/s is obtained. Therefore, this study demonstrates the dense, silane-free SiN x :H films with high passivation quality for PERC solar cells. • SiN x :H are deposited by ICPCVD with a silane-free gas mixture of TMS and NH 3. • Effects of the TMS flow rate on Si passivation quality are studied. • SiN x :H provides hydrogen atoms toward Si surface to improve chemical passivation. • SiN x :H can protect Al 2 O 3 against high temperature treatments. [ABSTRACT FROM AUTHOR]

The self-diffusion of parabens (methylparaben, propylparaben) and tetramethylsilane in the binary solvents carbon tetrachloride – co-solvent (methanol‑ d 4 , acetone‑ d 6) has been investigated by the pulsed gradient spin-echo nuclear magnetic resonance (PGSE NMR) method in the range of temperatures from 278 to 318 K. The self-diffusion coefficients of paraben and tetramethylsilane increase as the concentration of acetone‑ d 6 increases and have a minimum for paraben and an inflection point for tetramethylsilane when the methanol‑ d 4 concentration increases. Based on the Stokes-Einstein equation it is shown that the paraben hydrodynamic radius in the binary solvent acetone‑ d 6 – carbon tetrachloride is practically independent of the acetone‑ d 6 concentration and has a maximum in the binary solvent methanol‑ d 4 – carbon tetrachloride. This behavior in both cases is explained by the paraben self-association degree and the heteroassociation degree of paraben – co-solvent. Unlabelled Image • Self-diffusion of parabens and TMS in two binary solvents has been investigated. • Co-solvents have a different effect on solute self-diffusion. • The paraben hydrodynamic radius is independent of acetone‑ d 6 concentration. • The paraben hydrodynamic radius has a maximum if the co-solvent is methanol‑ d 4. [ABSTRACT FROM AUTHOR]

Abstract The conditions for the deposition of stable superhydrophobic coatings on glass substrates using a dielectric barrier discharge plasma jet with tetramethylsilane (TMS) and 3-aminopropyl(diethoxy)methylsilane (APDMES) as precursors were investigated. The coatings, which were formed under different plasma conditions, were characterized by various methods including atomic force microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, static water contact angle (WCA) and sliding angle measurement, and a scratch test. The results presented that superhydrophobic and mechanically stable plasma coatings could be obtained by optimizing the treatment time, applied voltage, gas flow rate into the plasma chamber, and APDMES/TMS ratio. The results indicated that the use of TMS on its own as the coating precursor led to the formation of unstable coatings. However, the mechanical stability increased significantly when APDMES and TMS were used in combination. As a result, a durable coating layer with a WCA of 163° and sliding angle of 3° was achieved for an APDMES/TMS ratio of 1.7. Highlights • Superhydrophobic coatings using non-thermal atmospheric-pressure plasma jet. • Plasma copolymerization of tetramethylsilane and an aminosilane for stable coating. • Maximum water contact angle of 163° with a sliding angle of 3°. [ABSTRACT FROM AUTHOR]

Abstract High density of the inductively coupled plasma chemical vapor deposition (ICPCVD) enables growth of films on soft substrate such as polyethylene terephthalate (PET) that otherwise curls at temperatures higher than 100 °C. In this study, dense silicon oxide (SiO x) films are prepared on PET by ICPCVD. Intrusive optical emission spectroscopy is employed to monitor distribution of the plasma radicals during the deposition process. The study discovers a direct relationship between the dense structure of the deposited film and the CH/(CH + OH) plasma radical intensity ratio. The deposition plasma with the lowest CH radical ratio results in the SiO x film with the least CH x incorporation and densest film structure. The film exhibits the smallest etched area in hydrochloric acid etching tests and the minimal water-vapor transmission rate of about 1.5 × 10−1 g/m2/day. Highlights • Dense ICPCVD SiO x layer is deposited on PET under 100 °C. • Optimization of film density can be achieved by monitoring plasma radicals. • Intensity ratio of CH/(CH + OH) plasma radical is correlated to SiO x film density. • Lowest CH radical ratio leads to the densest SiO x and the least carbon in films. • The densest film with a WVTR of 1.5 × 10−1 g/m2/day is obtained. [ABSTRACT FROM AUTHOR]

This paper describes the effect of tetramethylsilane (TMS) on diamond nucleation on Si substrate under an applied bias voltage of 120 V, performed in a modified microwave plasma chemical vapor deposition (MPCVD) reactor. The introduction of TMS in the CH 4 /H 2 plasma leads to a significant enhancement of nucleation density of diamond nuclei, namely from (3.7 ± 0.2) × 10 7 /cm 2 without the introduction of TMS to (4.7 ± 0.5) × 10 10 /cm 2 at the TMS flow rate of 4 sccm. On the contrary, further increasing in the TMS flow rate to 8 sccm slightly reduces the nucleation density of diamond nuclei to (2.1 ± 0.3) × 10 10 /cm 2 , along with the increase in average size of diamond nuclei. High-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) allow us to study the microstructural and chemical composition evolution of Si/diamond interface. The obtained results suggest that bias-enhanced nucleation of diamond on Si substrate exhibits a direct relationship with the TMS flow rate. [ABSTRACT FROM AUTHOR]

Thin films of hydrogenated silicon carbide (SiCx:H) and carbonitride (SiCxNy:H) are synthesized in a reactor with inductively coupled RF plasma with the introduction of tetramethylsilane vapors and additive gases—argon and/or nitrogen. The process is carried out at different synthesis temperatures, plasma power, and partial pressure of tetramethylsilane and additive gases in the reactor. The dependences on the synthesis conditions of the films’ growth rate, chemical composition, and properties such as the light transmission coefficient, refractive index, optical band gap, and dielectric constant are obtained. The weak dependence of the films’ composition and properties on the preset synthesis conditions is a characteristic feature of the studied process within the investigated range of conditions. The possible reasons of this phenomenon and the results of in situ studies of the gas phase composition in the plasma are examined. [ABSTRACT FROM AUTHOR]

Purpose The use of liquid ionization chambers can provide useful information to endeavors with radiation dosimetry for highly modulated beams. Liquid ionization chambers may be particularly suitable for computed tomography applications where conventional ionization chambers do not present a high enough sensitivity for the spatial resolution required to characterize common X-ray beams. Due to the sensitivity, which leads to high charge densities, liquid ionization chambers can suffer from large recombination losses leading to degradation in signal to dose rate linearity. To solve this problem, a two-dose-rate method for general recombination correction has been proposed for liquid ionization chambers. However, the valid range of recombination losses that the method can accurately account for has been found to vary depending on radiation quality. The present work provides an in-depth analysis of the performance of the two-dose-rate method. Furthermore, the soundness of applying gas theory to liquids is investigated by using the two-dose-rate method. Methods In the present work, the two-dose-rate method for general recombination correction of liquid ionization chambers used in continuous beams is studied by employing theory for gas-filled ionization chambers. An approximate relation for the general collection efficiency containing a material-specific parameter that is traceable to liquids has been derived for theoretical and experimental investigation alongside existing theory. Furthermore, the disassociation between initial and general recombination in the method is analyzed both theoretically and experimentally. Results The results indicate that liquids and gases share general recombination characteristics, where the liquids investigated (isooctane and tetramethylsilane) to a large extent mimic the behavior theoretically expected in gases. Furthermore, it is shown that the disassociation between initial and general recombination in the two-dose-rate method is an approximation that depends on the relation between initial recombination and the collecting electric field strength at the dose rates used. Conclusions Due to the approximation used to separate initial and general recombination the valid range of collection efficiencies for the two-dose-rate method will not only depend on the model used to describe general recombination but also on the type of liquid and radiation beam quality. As there is no robust theory for initial recombination in liquids to apply, the valid range of general collection efficiencies for the two-dose-rate method should be experimentally evaluated for each radiation dosimetry application. [ABSTRACT FROM AUTHOR]

The reaction chemistry of four methyl-substituted silane molecules, including monomethylsilane (MMS), dimethylsilane (DMS), trimethylsilane (TriMS), and tetramethylsilane (TMS), has been studied in the hot-wire (catalytic) chemical vapor deposition (HWCVD) process, both on heated tungsten or tantalum filaments and in the gas phase. The four molecules dissociate catalytically on hot W or Ta surfaces to form ·CH 3 , ·H and H 2 . In a HWCVD reactor setup where the pressure is relatively high at 8–533 Pa, two reaction mechanisms involving silylene and free radical intermediate, respectively, operate with the four precursor gases. For MMS, its reaction chemistry is characterized by the exclusive involvement of methylsilylene intermediate. Reaction products when using DMS as a precursor gas come from silylene chemistry and free-radical chain reactions. Filament temperature and pressure affect strongly the competition between the two mechanisms. Specifically, silylene chemistry dominates at low temperatures of 1200–1300 °C and a low pressure of 16 Pa, and free-radical chain reactions take over at high temperatures and pressures. With the increasing methyl substitutions in TriMS and TMS, free-radical chain reactions become predominant. A clear transition in the operating reaction mechanism from silylene chemistry to free-radical chain reactions has been shown when the number of Si CH 3 bonds increases in the methyl-substituted silane molecules. [ABSTRACT FROM AUTHOR]

DNA samples were extracted from ethanol and formalin-fixed decapod crustacean tissue using a new method based on Tetramethylsilane (TMS)-Chelex. It is shown that neither an indigestible matrix of cross-linked protein nor soluble PCR inhibitors impede PCR success when dealing with formalin-fixed material. Instead, amplification success from formalin-fixed tissue appears to depend on the presence of unmodified DNA in the extracted sample. A staining method that facilitates the targeting of samples with a high content of unmodified DNA is provided.

Assignments of photoabsorption spectra of tetramethylsilane (TMS) recorded in 6–11.5 eV region using synchrotron radiation are reexamined. The broad band spectra up to first ionization potential at 10.6 eV is explained to consists of mixed valence–Rydberg character arising from first two occupied molecular orbitals to 4s, 4p, 3d, 5s and 5p Rydberg states with the help of computational calculations, using TDDFT methodology. TMS is found to have two stable conformers viz. staggered and eclipsed, where the eclipsed conformer lies higher in energy by 6.88 kcal/mol. Presence of a broad continuum devoid of vibronic features is attributed to large change in geometry of molecule, high density of states due to triply degenerated highest occupied molecular orbitals and unimolecular dissociation of molecule as it is excited to its molecular ionization limit. Results from theoretical computations help in relating observed photoabsorption spectra of TMS on the basis of geometry changes in the ground and electronically excited states on excitation of molecule up to its first ionization potential. [ABSTRACT FROM AUTHOR]

Thermal decomposition of tetramethylsilane (TMS) diluted in argon was studied behind the reflected shock waves in a single pulse shock tube (SPST) in the temperature range of 1058-1194 K. The major products formed in the decomposition are methane (CH ) and ethylene (C H); whereas ethane and propylene were detected in lower concentrations. The decomposition of TMS seems to be initiated via Si-C bond scission by forming methyl radicals (CH ) and trimethylsilyl radicals ((CH ) Si). The total rate coefficients obtained for the decomposition of TMS were fit to Arrhenius equation in two different temperature regions 1058-1130 K and 1130-1194 K. The temperature dependent rate coefficients obtained are k (1058-1130 K) = (4.61±0.70) ×10 exp (−(79.9 kcal mol ±3.5)/RT) s , k (1130-1194 K) = (1.33 ± 0.19) ×10 exp (−(15.3 kcal mol ±3.5)/RT) s . The rate coefficient for the formation of CH is obtained to be k (1058-1194 K) = (4.36 ± 1.23) ×10 exp (−(61.9 kcal mol ±4.9)/RT) s . A kinetic scheme containing 21 species and 38 elementary reactions was proposed and simulations were carried out to explain the formation of all the products in the decomposition of tetramethylsilane. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The structural properties and hydrodynamic size of a molecule in solution at infinite dilution are connected to its diffusion coefficient through the Stokes–Einstein–Sutherland equation. In this study, buckyballs (C 60 ) and mixtures of tetramethylsilane and CDCl 3 which closely approximate spherical molecules in solution were investigated using nuclear magnetic resonance (NMR) self-diffusion experiments. It was found that the change in diffusion coefficient of mixtures of TMS and CDCl 3 was only correlated to the viscosity of the solution. The C 60 PGSE NMR data was then analysed using various models of obstruction. It was found that the decrease in C 60 diffusion with increasing concentration can be explained on the basis of aggregation alone, and thus C 60 self-obstruction must be negligible under these experimental conditions. [ABSTRACT FROM AUTHOR]

Thermal decomposition of tetramethylsilane (TMS) and tetramethylgermane (TMG) was studied on a short time scale of 20–100 μs using flash pyrolysis vacuum ultraviolet single-photon ionization time-of-flight mass spectrometry (VUV-SPI-TOFMS). Primary decomposition of TMS and TMG occurred via loss of a methyl radical to form Si(CH 3 ) 3 and Ge(CH 3 ) 3 , respectively. Both the Si(CH 3 ) 3 and Ge(CH 3 ) 3 radicals underwent secondary loss of a second methyl radical to form :Si(CH 3 ) 2 and :Ge(CH 3 ) 2 , respectively. A previously unobserved secondary decomposition process in TMS involving loss of H atom from Si(CH 3 ) 3 followed by elimination of H 2 to form SiC 3 H 8 , SiC 3 H 6 , and SiC 3 H 4 was also identified. Sequential loss of the third and fourth methyl radical with significant formation of Ge and Ge 2 was observed in the TMG pyrolysis. Loss of a third methyl radical in the TMS pyrolysis was not significant, while Si and SiC products were possibly produced. Secondary reactions of methyl to form unsaturated C x H y species, particularly in the TMG decomposition, were also observed. [ABSTRACT FROM AUTHOR]