Decomposition Of Acetone Research Articles

Precursor-free synthesis of carbon quantum dots and carbon microparticles in supercritical acetone

Carbon quantum dots (CQDs) have recently received a lot of attention due to their unique physical properties, and their environmentally friendly features such as low toxicity and high biocompatibility. Supercritical fluids, which possess unusual properties such as high solubility, high diffusivity, low viscosity and zero surface tension, are now commonly used particularly in the fields of electronic, chemical and materials science and engineering. Here, we synthesise carbon nano/microparticles in supercritical acetone, in which neither external molecules nor starting materials are dissolved/dispersed. We find that carbon microparticles and nano structures such as graphene quantum dots (GQDs), carbon nano onions (CNOs) and elongated carbon nano onions (eCNOs) are self-assembled via thermal decomposition of acetone under its supercritical conditions. We also find that the carbon microparticles are in fact formed by GQDs, CNOs and eCNOs, the microparticles being physically resolved into GQDs, CNOs and eCNOs with sonication. The fluorescence features of the carbon nano structures are clarified, noting that no photobleaching was observed for at least one month. The present result may well lead to the development of facile bottom-up methodologies for synthesising nano materials in solvents under their supercritical conditions without using any external precursors/starting materials.

Understanding Decomposition Mechanism of Acetone under Electric Pulsed Discharge: Generation of C3O+ and C3H4O+ ions

AbstractGas‐phase investigations on acetone, under the influence of electric pulsed discharge has provided distinct insight related to its decomposition. Time‐of‐flight mass spectrometry has been utilized to identify different products generated upon dissociation/ionization of acetone, under the influence of electric discharge. In addition to molecular (C3H6O+) and protonated acetone (C3H7O+) ions, predominant ions signal corresponding to C3H4O+, C3O+ and CH3CO+ were observed in the mass spectrum. Under discharge condition, acetone undergoes soft dissociation/ionization producing C3H4O+ and C3O+ ions, which are distinctive from usual fragment ions reported upon decomposition of acetone, in the gas‐phase. Though metastable in nature, significant ion yield has been obtained for C3O+ ions. Computational studies have been carried out to understand the mechanism of acetone decomposition in gas‐phase. Based on experimental and computational findings, generation of these ions (C3O+ and C3H4O+) has been ascribed to step‐wise H2 elimination reaction originating from acetone molecule, followed by ionization of resultant fragments under the influence of electric pulsed discharge. Present studies are of relevance for plasma pyrolysis of volatile organic compounds and laboratory astrochemical investigations.

Dual-functional membranes of CQDs/TiO2 @PI/PES nanofibers for the high filter efficiency of ultrafine particles and photocatalytic activity

The carbon quantum dot/titanium dioxide (CQDs/TiO2), fabricated on highly porous polyimide (PI)/polyether sulfone (PES) nanofiber via electrospinning process, called the dual-functional CQD/TiO2 @PI/PES membrane, was developed and evaluated for its performance, including both removal of volatile organic compounds (VOCs) and ultrafine particulate matters (PM0.1). The photocatalytic activity of synthesized CQD/TiO2 @PI/PES membranes with 5% CQD loading on the decomposition of acetone was significantly enhanced compared with that of TiO2(P25)@PI/PES. The comprehensive results of photoluminescence emission, X-ray photoelectron spectroscopy, and photocatalytic experiments suggest that up-conversion properties of CQD can enhance the absorption of visible light on TiO2 and reduce the reorganization of electron-hole pairs. Further, the optimized CQD/TiO2 @PI/PES membrane could effectively photodegrade of acetone (>94.5%) and also maintained a good PM0.1 filtration efficiency (> 99%) and a differential pressure of 0.34 Pa for creating level 3 medical face masks as per the standards of ASTM F2299 and EN 14683. Therefore, the dual-functional CQD/TiO2 @PI/PES membrane could be applied as a promising photocatalytic filter for air purification that simultaneously and remarkably filters PM0.1 and decompose VOCs.

Catalytic Oxidation of Acetone on SmMn2O5: Effect of Acid Etching and Loading Treatment.

The key of catalytic oxidation technology is to develop a stable catalyst with high activity. It is still a serious challenge to achieve high conversion efficiency of acetone with an integral catalyst at low temperature. In this study, the SmMn2O5 catalyst after acid etching was used as the support, and the manganese mullite composite catalyst was prepared by loading Ag and CeO2 nanoparticles on its surface. By means of SEM, TEM, XRD, N2-BET, XPS, EPR, H2-TPR, O2-TPD, NH3-TPD, DRIFT, and other characterization methods, the related factors and mechanism analysis of acetone degradation activity of the composite catalyst were discussed. Among them, the CeO2-SmMn2O5-H catalyst has the best catalytic activity at 123 and 185 °C for T50 and T100, respectively, and shows excellent water and thermal resistance and stability. In essence, the surface and lattice defects of highly exposed Mn sites were formed by acid etching, and the dispersibility of Ag and CeO2 nanoparticles was optimized. Highly dispersed Ag and CeO2 nanoparticles have a highly synergistic effect with the support SmMn2O5, and the reactive oxygen species provided by CeO2 and the electron transfer brought by Ag further promote the decomposition of acetone on the carrier SMO-H. In the field of catalytic degradation of acetone, a new catalyst modification method of high-quality active noble metals and transition metal oxides supported by acid-etched SmMn2O5 has been developed.

Theoretical and experimental research on growth and doping mechanisms of diamond films fabricated using liquid carbon source precursors

Fabricating diamond films using liquid carbon source precursors in hot filament chemical vapor deposition (HFCVD) is an emerging technology. Although some experiments have demonstrated the feasibility of depositing doped diamond films using liquid carbon source precursors such as acetone, the theoretical explanation still needs to be elucidated. In this study, the density functional theory (DFT) method was used to analyze the decomposition and adsorption processes of acetone and methane on the surface of a diamond (111) models and to clarify the advantages of liquid carbon source precursors. The decomposition and adsorption reaction processes of trimethyl borate, urea, and ethyl orthosilicate on the surface of diamond (111) model were also analyzed to elucidate the doping mechanisms of B, N, and Si elements. Additionally, undoped diamond films were fabricated using acetone and methane precursors, illustrating that liquid precursors have higher growth rates than gas precursors. B-, N-, and Si-doped diamond films were also fabricated using liquid-doped carbon source precursors. Element detection by TOF-SIMS illustrates that all three elements had been doped into the diamond films and were uniformly distributed. Conversely, no doping elements were detected in N-doped diamond film fabricated with nitrogen and methane precursors.

Improving the anodic packing and harmonizing the proton exchange membrane of bioelectrochemical systems for treating waste gases and generating electricity

Conductive (carbonized porous ceramic ring, CPCR or Cp) and non-conductive filters (porous ceramic ring, PCR or P) were used as anode packing materials in a biotrickling filter microbial fuel cell (BTF-MFC). The optimal packing ratio (2:1 for CPCR: PCR, expressed as Cp2P1) yielded 1.1 times and 1.5 times higher rates of decomposition of acetone than did Cp1P2. Nano zero-valent iron (nZVI) in the proton exchange membrane (PEM) not only reduces the oxygen diffusion rate, but also improves the proton transfer capacity. The tensile strength of the PEM to which was added nZVI (5 mg ml−1) was 1.29 times higher than that of conductive carbon black (CCB) and polyvinyl alcohol (PVA) hydrogel (PVA/CCB-H) before drying and 1.23 times higher after drying. A combination of this composite material and BTF-MFC can be used to treat gaseous pollutants, increasing both removal efficiency and power generation. The microbial population could be increased by controlling the characteristics of the packing materials. On the non-conductive materials near the PEM, the dominant species of bacteria were aerobic, while on the conductive materials far from the PEM, more bacteria were anaerobic, so the filter materials could be distributed to improve the acetone removal capacity and power output of the BTF-MFC.

Experimental and modeling study of acetone combustion

The pyrolysis and oxidation of acetone were studied using three complementary experimental setups. Jet-stirred reactor experiments were performed at four equivalence ratios (ϕ = 0.5, 1, 2, and ∞), at pressure of 1.067 bar (800 Torr) and over the temperature range of 700–1200 K for pyrolysis and 600–1150 K for oxidation. The decomposition of acetone starts around 800 K with a conversion rate of 50% obtained around 1000 K in both pyrolysis and oxidation studies. The main stable products detected in both conditions are small hydrocarbons (methane, ethane, and ethylene), with also acetaldehyde, CO and CO2 for oxidation. Oscillation behavior was detected beyond 1000 K under oxidation conditions and the products were followed with on-line mass spectrometry. Ignition delay times were measured using a rapid compression machine at pressures of 20 and 40 bar under non-diluted stoichiometric conditions over the temperature range 850–1100 K. The ignition delay times measured in the present study, combined with shock tube data of literature, exhibit a slight inflexion to the Arrhenius behavior, but no negative temperature coefficient. Laminar burning velocities were measured using a flat flame burner at atmospheric pressure for three fresh gas temperatures: ambient temperature, 358 and 398 K. A detailed kinetic model of the combustion of acetone including 852 species and 3265 reactions was developed. This new kinetic mechanism predicts relatively well the experimental measurements of ignition delay times, the mole fraction of the products in the jet-stirred reactor including oscillations and laminar burning velocities. Related flow rate and sensitivity analysis are also presented providing new insights into the acetone reaction network.

Achieving acetone efficient deep decomposition by strengthening reactants adsorption and activation over difunctional Au(OH)Kx/hierarchical MFI catalyst

Realizing the simultaneous adsorption and activation of O2 and reactants over supported noble metal catalysts is crucial for the oxidation of organic hydrocarbons. Herein, we report a facile one-step ethylene glycol reduction method to synthesize difunctional Au(OH)Kx sites, which were anchored on a hierarchical hollow MFI support and adopted for acetone decomposition. The alkali ion-associated adjacent surface hydroxyl groups were coordinated with Au nanoparticles, resulting in partially oxidized Au1+ sites with improved dispersion. The results obtained from exclusive ex situ and in situ experiments illustrated that the proper content of K and hydroxyl groups significantly enhanced the adsorption of surface O2 and acetone molecules around the Au sites simultaneously, whereas the excess K species inhibited the catalytic performance by blocking the pore structure and decreasing the acidity of catalysts. The Au(OH)K0.7/h-MFI catalyst exhibited the highest efficiency for acetone oxidation, over which 1500 ppm acetone can be completely oxidized at just 280 °C with an extremely low activation energy of 32.5 kJ mol−1. The carbonate species were detected as the main intermediates during acetone decomposition over the difunctional Au(OH)Kx sites through a Langmuir − Hinshelwood (L − H) mechanism. This finding paves the way for designing and constructing efficient functional active sites for the complete oxidation of hydrocarbons.

Insights into non-thermal plasma chemistry of acetone diluted in N2/O2 mixtures: a real-time MS experiment.

Understanding non-thermal plasma reactivity is a complicated task as many reactions take place due to a large energy spectrum. In this work, we used a well-defined photo-triggered non-filamentous discharge to study acetone decomposition in N2/O2 gas mixtures. The plasma reactor is associated to a compact chemical ionization FTICR mass spectrometer (BTrap) in order to identify and quantify in real-time acetone and by-products in the plasma. Presence of oxygen (1 to 5%) decreased notably acetone degradation. A tremendous change is observed in the by-products distribution concomitantly to a global decrease of their total concentration. While main products observed in oxygen-free gas mix are nitrile compounds, in oxygenated media they are replaced by formaldehyde, methanol and ketene. Methanol is maximum for 1% of O2 whereas formaldehyde and ketene concentration reach their maximum value at the highest oxygen concentration tested (5%). A number of nitrate, nitrite and isocyanate organic compounds (C1 and C2) are observed as well with HNO2, HNO3 and HNCO.

Catalytic Activation of Cobalt Doping Sites in ZIF-71-Coated ZnO Nanorod Arrays for Enhancing Gas-Sensing Performance to Acetone.

Developing acetone gas sensors with high sensitivity is crucially important for many applications including nonevasive diagnosis of diabetes. In the present work, cobalt doping is used to catalyze acetone gas-sensing reactions and hence to promote the sensitivity of acetone gas sensors. In order to achieve this, ZIF-71 metal-organic framework (MOF) is synthesized onto ZnO nanorod arrays with various concentrations of Co doping to form composite ZnO@ZIF-71(Co) sensors, which are then evaluated as sensing materials for acetone detection. Such sensors are shown to be sensitive to a trace amount of acetone (50 ppb) and have a massively enhanced response of about 100 times that for the undoped sensor at an optimal Co/Zn ratio and operating temperature. Fourier-transform infrared spectroscopy and temperature-programmed desorption with density functional theory calculations are also made to assist in elucidating the catalytic gas-sensing mechanism for the Co-doped composite sensors ZnO@ZIF-71(Co). It demonstrated that the introduced Co site in ZIF-71(Co) can activate oxygen catalytically and increase active oxygen released to the ZnO surface. Meanwhile, the Co sites also promote the decomposition of acetone. These two steps together affect the catalytic oxidation of gases and finally enhance the sensitivity. This work introduces the catalytic effect of the MOF into the gas-sensing mechanism and provides an idea for broadening the application of MOF catalysis.

Application of Wastewater Reuse with Photocatalyst Prepared by Sol-Gel Method and Its Kinetics on the Decomposition of Low Molecular Weight Pollutants.

The development of immobilized photocatalyst as a strategy for problematic electronics wastewater reuse is described in this study. The strategy was to perform separate rinsing, mostly consisting of low molecular weight compounds, and to decompose them with a simple process, based on the advanced oxidation process (AOP). Extensive studies were performed on the preparation conditions of immobilized photocatalysts by sol-gel method under various amount of precursor and support, water to precursor ratio, pH, aging time, and calcination conditions. The optimized preparation conditions were chosen by measuring removal efficiencies of isopropyl alcohol as a representative target compound with supportive SEM and XRD analyses. Removal efficiencies with photocatalyst and UV irradiation in synthetic wastewater simulating electronics wastewater were evaluated over time. Removal efficiencies of alcohol, acetone, ethanol, and acetaldehyde reached 97.2%, 71.2%, 99.0%, and 99.0%, respectively, in 2 h. Reaction constants of each compound were determined by fitting experimental data to the first order kinetic equation and the trial and error method with consecutive reaction pathway. As analysis results of reaction constants, UV with prepared photocatalyst was found to be effective and the decomposition of acetone was found to be the rate-determining step. The immobilized photocatalyst developed in this study would be useful for application of wastewater reuse with high removal efficiencies, mild preparation conditions, and mechanical stability.

Room temperature oxidation of acetone by ozone over alumina-supported manganese and cobalt mixed oxides

Volatile organic compounds (VOCs) are among the major sources of air pollution. Catalytic ozonation is an efficient process for removing VOCs at lower reaction temperature compared to catalytic oxidation. In this study, a series of alumina supported single and mixed manganese and cobalt oxides catalysts were used for ozonation of acetone at room temperature. The influence of augmenting the single Mn and Co catalysts were investigated on the performance and structure of the catalyst. The manganese and cobalt single and mixed oxides catalysts of the formula Mn10%-CoX and Co10%-MnX (where X = 0, 2.5%, 5%, or 10%) were prepared. It was found that addition of Mn and Co at lower loading levels (2.5% or 5%) to single metal oxide catalysts enhanced the catalytic activity. The mixed oxides catalysts of (Mn10%-Co2.5%) and (Mn10%-Co5%) led to acetone conversion of about 84%. It is concluded that lower oxidation state of the secondary metal improves ozone decomposition and oxidation of acetone.

Formation of two kinds of carbon with different properties by acetone decomposition using in-liquid plasma method

Most waste solvent treatment methods involve combustion; however, such methods emit carbon dioxide and are also problematic relative to energy costs. As well as reducing carbon dioxide generate, in-liquid plasma has been used to generate valuable substances and hydrogen energy from the waste solvent. As a waste solve treatment model, decomposition of acetone using 27.12 MHz in-liquid plasma was performed at atmospheric pressure. The produced gases were H2, CO, CH4, C2H2, C2H4, C2H6, and CO2, where proportion of CO2 was less than 0.25%. Two types of carbons with different properties were obtained as byproducts during the acetone decomposition. These carbons analyzed using elemental analysis and Raman spectroscopy. The analysis results revealed that the crystallinity of the carbons different significantly. Undesirable organic matter, such as benzene, was also produced during acetone decomposition. The acetone decomposition efficiency at 407 W discharge power was 0.9 μmol J−1.

Gas-Phase Synthesis and Reactivity of Ligated Group 10 Ions in the Formal +1 Oxidation State.

Electrospray ionization of the group 10 complexes [(phen)M(O2CCH3)2] (phen=1,10-phenanthroline, M = Ni, Pd, Pt) generates the cations [(phen)M(O2CCH3)]+, whose gas-phase chemistry was studied using multistage mass spectrometry experiments in an ion trap mass spectrometer with the combination of collision-induced dissociation (CID) and ion-molecule reactions (IMR). Decarboxylation of [(phen)M(O2CCH3)]+ under CID conditions generates the organometallic cations [(phen)M(CH3)]+, which undergo bond homolysis upon a further stage of CID to generate the cations [(phen)M]+· in which the metal center is formally in the +1 oxidation state. In the case of [(phen)Pt(CH3)]+, the major product ion [(phen)H]+ was formed via loss of the metal carbene Pt=CH2. DFT calculated energetics for the competition between bond homolysis and M=CH2 loss are consistent with their experimentally observed branching ratios of 2% and 98% respectively. The IMR of [(phen)M]+· with O2, N2, H2O, acetone, and allyl iodide were examined. Adduct formation occurs for O2, N2, H2O, and acetone. Upon CID, all adducts fragment to regenerate [(phen)M]+·, except for [(phen)Pt(OC(CH3)2)]+·, which loses a methyl radical to form [(phen)Pt(OCCH3)]+ which upon a further stage of CID regenerates [(phen)Pt(CH3)]+ via CO loss. This closes a formal catalytic cycle for the decomposition of acetone into CO and two methyl radicals with [(phen)Pt]+· as catalyst. In the IMR of [(phen)M]+· with allyl iodide, formation of [(phen)M(CH2CHCH2)]+ was observed for all three metals, whereas for M = Pt also [(phen)Pt(I)]+ and [(phen)Pt(I)2(CH2CHCH2)]+ were observed. Finally, DFT calculated reaction energetics for all IMR reaction channels are consistent with the experimental observations.

Gas-Phase Reactions of the Group 10 Organometallic Cations, [(phen)M(CH3)]+ with Acetone: Only Platinum Promotes a Catalytic Cycle via the Enolate [(phen)Pt(OC(CH2)CH3)]+

Abstract Electrospray ionisation of the ligated group 10 metal complexes [(phen)M(O2CCH3)2] (M = Ni, Pd, Pt) generates the cations [(phen)M(O2CCH3)]+, whose gas-phase chemistry was studied using multistage mass spectrometry experiments in an ion trap mass spectrometer with the combination of collision-induced dissociation (CID) and ion-molecule reactions (IMR). A new catalytic cycle has been discovered. In step 1, decarboxylation of [(phen)M(O2CCH3)]+ under CID conditions generates the organometallic cations [(phen)M(CH3)]+, which react with acetone to generate the [(phen)M(CH3)(OC(CH3)2)]+ adducts in competition with formation of the coordinated enolate for M = Pt (step 2). For M = Ni and Pd, the adducts regenerate [(phen)M(CH3)]+ upon CID. In the case of M = Pt, loss of methane is favored over loss of acetone and results in the formation of the enolate complex, [(phen)Pt(OC(CH2)CH3)]+. Upon further CID, both methane and CO loss can be observed resulting in the formation of the ketenyl and ethyl complexes [(phen)Pt(OCCH)]+ and [(phen)Pt(CH2CH3)]+ (step 3), respectively. In step 4, CID of [(phen)Pt(CH2CH3)]+ results in a beta-hydride elimination reaction to yield the hydride complex, [(phen)Pt(H)]+, which reacts with acetic acid to regenerate the acetate complex [(phen)Pt(O2CCH3)]+ and H2 in step 5. Thus, the catalytic cycle is formally closed, which corresponds to the decomposition of acetone and acetic acid into methane, CO, CO2, ethene and H2. All except the last step of the catalytic cycle are modelled using DFT calculations with optimizations of structures at the M06/SDD 6-31G(d) level of theory.

Real-time monitoring and quantification of organic by-products and mechanism study of acetone decomposition in a dielectric barrier discharge reactor.

Non-thermal plasma (NTP) degradation of low-concentration acetone was investigated in a cylindrical dielectric barrier discharge reactor. The effects of oxygen content and flow rate on the removal efficiency at various discharge powers were examined in real-time. The acetone removal efficiency decreases drastically and then remains stable or increases gradually as the O2 content increases from 0 to 25%, and further to 50%. The organic by-products were characterized and quantified using a real-time proton transfer reaction time-of-flight mass spectrometry (PTR-TOF-MS) instrument. The observed organic compounds, with concentrations about ppbv/ppmv by volume, were mainly formaldehyde, methanol, ketene, acetaldehyde, formic acid, acetone, and acetic acid. The discharge power was a critical factor affecting the concentration of the organic by-products and the selectivity toward CO2. The mechanism study based on the by-product monitor in real-time showed that acetone firstly fragments into methyl radicals, acetyl radicals, and H; then, the methyl and acetyl radicals are oxidized by O or OH radicals into acetaldehyde, methanol, and other compounds. It seems that acetaldehyde could be an intermediate in acetone decomposition. Firstly, most of the acetone molecules were decomposed into acetaldehyde molecules; then, the acetaldehyde molecules continued to be decomposed and oxidized into other compounds, such as acetic acid and formaldehyde. These investigations not only proposed a detail decomposition mechanism for acetone in dielectric barrier discharge reactor, but also provided a potential way to analyze and evaluate the practicability of NTP removal of VOCs.

Carbon material formation and residue characteristics of SBA-15 and nickel impregnated SBA-15 as exemplified by acetone decomposition

Abstract In this research, SBA-15 (Santa Barbara Amorphous-15) is used as the template and nickel serves as the impregnating catalyst for conversion to Ni-SBA-15. In the present test, the BET surface area of SBA-15 is 652 m2/g and Ni-SBA-15 477 m2/g. The average pore size for SBA-15 is 41 A and for the Ni-SBA-15 is 56 A. The carbon material synthesized between 650 and 850 °C using scarping acetone solvent on the templates. Analysis reveals that the bigger the average pore diameter, the smaller the BET surface area and pore volume of the carbon materials which form on SBA-15 and Ni-SBA-15. The exterior of the SBA-15 becomes coated with soot particles; acetone and Ni-SBA-15 combine to form carbon nanotubes at 650, 750, and 850 °C. Less than 10% of the acetone forms carbon materials on the templates, with the majority decomposing to form tar or be discharged as exhaust gas. During the gas phase, BETX (benzene, ethyltoluene, toluene, and xylene), propene and isopentane are the main VOC compositions during solvent pyrolysis. PAHs are mainly composed of naphthalene and pyrene during the acetone breakdown on the SBA-15 and Ni-SBA-15. These results reveal that Ni catalyst can enhance PAH formation to form carbon materials and decrease VOC concentration.

Spontaneous Shape Alteration and Size Separation of Surfactant-Free Silver Particles Synthesized by Laser Ablation in Acetone during Long-Period Storage.

The technique of laser ablation in liquids (LAL) has already demonstrated its flexibility and capability for the synthesis of a large variety of surfactant-free nanomaterials with a high purity. However, high purity can cause trouble for nanomaterial synthesis, because active high-purity particles can spontaneously grow into different nanocrystals, which makes it difficult to accurately tailor the size and shape of the synthesized nanomaterials. Therefore, a series of questions arise with regards to whether particle growth occurs during colloid storage, how large the particle size increases to, and into which shape the particles evolve. To obtain answers to these questions, here, Ag particles that are synthesized by femtosecond (fs) laser ablation of Ag in acetone are used as precursors to witness the spontaneous growth behavior of the LAL-generated surfactant-free Ag dots (2–10 nm) into different polygonal particles (5–50 nm), and the spontaneous size separation phenomenon by the carbon-encapsulation induced precipitation of large particles, after six months of colloid storage. The colloids obtained by LAL at a higher power (600 mW) possess a greater ability and higher efficiency to yield colloids with sizes of <40 nm than the colloids obtained at lower power (300 mW), because of the generation of a larger amount of carbon ‘captors’ by the decomposition of acetone and the stronger particle fragmentation. Both the size increase and the shape alteration lead to a redshift of the surface plasmon resonance (SPR) band of the Ag colloid from 404 nm to 414 nm, after storage. The Fourier transform infrared spectroscopy (FTIR) analysis shows that the Ag particles are conjugated with COO– and OH– groups, both of which may lead to the growth of polygonal particles. The CO and CO2 molecules are adsorbed on the particle surfaces to form Ag(CO)x and Ag(CO2)x complexes. Complementary nanosecond LAL experiments confirmed that the particle growth was inherent to LAL in acetone, and independent of pulse duration, although some differences in the final particle sizes were observed. The nanosecond-LAL yields monomodal colloids, whereas the size-separated, initially bimodal colloids from the fs-LAL provide a higher fraction of very small particles that are <5 nm. The spontaneous growth of the LAL-generated metallic particles presented in this work should arouse the special attention of academia, especially regarding the detailed discussion on how long the colloids can be preserved for particle characterization and applications, without causing a mismatch between the colloid properties and their performance. The spontaneous size separation phenomenon may help researchers to realize a more reproducible synthesis for small metallic colloids, without concern for the generation of large particles.

Multichannel Gas-Phase Unimolecular Decomposition of Acetone: Theoretical Kinetic Studies.

The multichannel thermal decomposition of acetone is studied theoretically. The isomerization of acetone molecule to its enol form, 1-propene-2-ol, is of especial interest in this research. Steady-state approximation is applied to the thermally activated species CH3COCH3* and CH2C(CH3)OH*, and by performing some statistical mechanical manipulations, integral expressions for the rate constants for the formation of different products are derived. The geometries of the reactant, intermediates, transition states, and products of the reaction are optimized at the MP2(full)/6-311++G(2d,2p) level of theory. More accurate energies are evaluated by single-point energy calculations at the CBS-Q, G4, and CCSD(T,full)/augh-cc-pVTZ+2df levels of theory. In order to account correctly for vibrational anharmonicities and tunneling effects, microcanonical rate constants for various channels are computed by using semiclassical transition state theory. It is found that the isomerization of CH3COCH3 to the enol form CH2C(CH3)OH plays an important role in the unimolecular decomposition reaction of CH3COCH3. The possible products originating from unimolecular decomposition of CH3COCH3 and CH2C(CH3)OH are investigated. It is revealed from present computed rate coefficients that the dominant product channel is the formation of CH2C(CH3)OH at low temperatures and high pressures due to the low barrier height for the isomerization process CH3COCH3 → CH2C(CH3)OH. However, at high temperatures and low pressures, the product channel CH3 + CH3CO becomes dominant. Also, the roaming product channels CH2CO + CH4 and C2H6 + CO could be important at high temperatures.

Deposition of defected graphene on (001) Si substrates by thermal decomposition of acetone

We present results on the deposition and characterization of defected graphene by the chemical vapor deposition (CVD) method. The source of carbon/carbon-containing radicals is thermally decomposed acetone (C2H6CO) in Ar main gas flow. The deposition takes place on (001) Si substrates at about 1150–1160 °C. We established by Raman spectroscopy the presence of single- to few- layered defected graphene deposited on two types of interlayers that possess different surface morphology and consisted of mixed sp2 and sp3 hybridized carbon. The study of interlayers by XPS, XRD, GIXRD and SEM identifies different phase composition: i) a diamond-like carbon dominated film consisting some residual SiC, SiO2 etc.; ii) a sp2- dominated film consisting small quantities of C60/C70 fullerenes and residual Si-O-, CO etc. species. The polarized Raman studies confirm the presence of many single-layered defected graphene areas that are larger than few microns in size on the predominantly amorphous carbon interlayers.