Thermolysis Temperatures Research Articles

Hydrogen evolution with hot electrons on a plasmonic-molecular catalyst hybrid system

Plasmonic systems convert light into electrical charges and heat, mediating catalytic transformations. However, there is ongoing controversy regarding the involvement of hot carriers in the catalytic process. In this study, we demonstrate the direct utilisation of plasmon hot electrons in the hydrogen evolution reaction with visible light. We intentionally assemble a plasmonic nanohybrid system comprising NiO/Au/[Co(1,10-Phenanthrolin-5-amine)2(H2O)2], which is unstable at water thermolysis temperatures. This assembly limits the plasmon thermal contribution while ensuring that hot carriers are the primary contributors to the catalytic process. By combining photoelectrocatalysis with advanced in situ spectroscopies, we can substantiate a reaction mechanism in which plasmon-induced hot electrons play a crucial role. These plasmonic hot electrons are directed into phenanthroline ligands, facilitating the rapid, concerted proton-electron transfer steps essential for hydrogen generation. The catalytic response to light modulation aligns with the distinctive profile of a hot carrier-mediated process, featuring a positive, though non-essential, heat contribution.

Triazine-Augmented Catalytic Activity of Cyclobutadiene Tricarbonyl Fe(0) Complexes for Thermal Decomposition of Ammonium Perchlorate

The employment of combustion catalysts is an effective way to improve ammonium perchlorate (AP) decomposition performance during the combustion process of composite solid propellants. A classic half-sandwich iron carbonyl complex was proposed as the leading structure for exploring high-performance combustion catalysts, in which functionalized cyclobutadienes (Cb) tune the thermal stability and catalytic activity. The thermolysis of Fe2(CO)9 and substituted alkynes initiated [2 + 2] cyclization of alkyne triple bonds and gave η4-cyclobutadiene iron(0) tricarbonyl complexes, CbR1,R2-Fe-CO (1–6), with decent yields. A molecular structure analysis found that the conjugation of the aromatic substituents aryl, ferrocenyl (Fc), and triazinyl (Tz) finely tuned the coordination bonds around the Fe(0) center. The DSC/TG experiments found a remarkable thermal stability of CbTz,R-Fe-CO (3–6) with characteristic thermolysis temperatures (CTT) as high as 500 °C. The catalytic experiments demonstrated that the CTT of Cb-Fe-CO (2-6) overlapped with AP high-temperature decomposition (HTD). The thermal cross-coupling of HTD of AP and CTT of CbTz,Fc-Fe-CO (6) significantly augmented catalytic AP decomposition, resulting in a maximum energy release as high as 2828 J/g.

Morphology-controllable synthesis of hierarchical hollow GaFeO3 microcubes with selective triethylamine gas-sensing properties

Hierarchical multi-metal oxide-based gas sensors with high surface area and abundant active sites have attracted intensely research interests for their highly sensitive and fast gas detection performance. Developing synthetic strategies for obtaining novel hierarchical metal oxides with high sensing performance remains eminently challenging. Herein, hierarchial hollow GaFeO3 microcubes were successfully prepared via a Ga3+-modified Fe-based Prussian Blue (PB) mediated template conversion strategy. The microsized morphologies and hollow interior structures of GaFeO3 microcubes can be feasibly modulated by controlling the thermolysis temperatures. The ultrasmall nanoparticle-assembly of GaFeO3 architecture obtained at 500 °C exhibited an optimum response value (Ra/Rg) of 7.4, and rapid response/recovery times (9 s/49 s) toward 200 ppm triethylamine (TEA) at a working temperature of 200 °C, as well as remarkable selectivity and excellent long-term stability (for at least 31 days), which are intrinsically beneficial from the unique interior loose structure with good permeability for diffusion of target gases. This work provides a promising approach for synthesizing various hierarchical multimetal oxides with intriguing nanoparticle-assembled hollow structure and broad prospects for practical gas sensing applications.

Influence of thermolysis temperature on the morphology, structural and optical properties of nanocomposite ZnS-polyvinyl alcohol thin films: Fabrication and characterization of indium tin oxide/ZnS-polyvinyl alcohol/Al Schottky diode

Zinc sulfide-polyvinyl alcohol (ZnS-PVA) nanocomposite thin films were synthesized on glass substrates via solvent casting method followed by thermolysis technique. The thermolysis reactions were carried out at different thermolysis temperatures (Tt) ~80, 100, 120, 150, 200 and 250 °C to study the induced changes in the growth process. Thin films synthesized at Tt ~ 200 and 250 °C consist of ZnS nanoparticles with high crystallinity and distinct lattice fringes were observed by high-resolution transmission electron microscope. At Tt ~ 250 °C the PVA contents in the film diminishes given that agglomeration of crystallites takes place. X-ray diffraction and selected area electron diffraction patterns confirm the cubic phase of the ZnS-PVA thin films with preferred orientation along (111). The scanning electron micrographs reveal the homogeneous morphology and increase in grain size on the surface of thin films at higher thermolysis temperature. The thickness of the films determined using Swanepoel's method was found to decrease from 1700 to 350 nm when thermolysis temperature increases. The presence of different functional groups and the formation of bonds between Zn and S were confirmed by fourier transform infra-red spectrum analysis. The metal-semiconductor junction was synthesized by forming an indium tin oxide/ZnS-PVA/Al heterostructure. The behavior of metal-semiconductor junction was analyzed by current- voltage characteristics.

Effect of thermolysis condition on characteristics and nonsteroidal anti-inflammatory drugs (NSAIDs) absorbability of Fe-MIL-88B-derived mesoporous carbons

Discharge of nonsteroidal anti-inflammatory drugs (NSAIDs) from wastewater has been increasingly alarmed, led to the advent of the treatment techniques. Among these methods, adsorption is regarded as a tunable and green approach with the utilization of mesoporous carbon (MC) as an efficient and recyclable adsorbent. Herein, we described the strategy for the synthesis of novel MC from Fe-MIL-88B as a self-sacrificial template. Three thermolysis temperatures (550, 750, and 950 °C) were investigated to compare the structural characteristics and absorbability towards selected NSAIDs compounds including diclofenac sodium (DCF), aspirin (APR), and ibuprofen (IBU). Effect of contact time (0–480 min), concentration (10–40 mg/L), pH (2–10), and MC dosage (0.1–0.5 g/L) was systematically studied. Kinetic and isotherm models were also used to find out the adsorption mechanism and behavior of NSAIDs pharmaceutical over MC materials. Proposed mechanism and recyclability test were rigorously studied to gain more insight into how the NSAIDs molecules adsorb on the MC materials and their potential towards drug treatment.

General Strategy for the Synthesis of Transition-Metal Phosphide/N-Doped Carbon Frameworks for Hydrogen and Oxygen Evolution.

Transition metal phosphides (TMPs) have been identified as promising nonprecious metal electrocatalyst for hydrogen evolution reaction (HER) and other energy conversion reactions. Herein, we reported a general strategy for synthesis of a series of TMPs (Fe2P, FeP, Co2P, CoP, Ni2P, and Ni12P5) nanoparticles (NPs) with different metal phases embedded in a N-doped carbon (NC) matrix using metal salt, ammonium dihydrogen phosphate, and melamine as precursor with varying molar ratios and thermolysis temperatures. The resultant TMPs can serve as highly active and durable bifunctional electrocatalyst toward HER and oxygen evolution reaction (OER). In particular, the Ni2P@NC phase only requires an overpotential of ∼138 mV to derive HER in 0.5 M H2SO4, and ∼320 mV for OER in 1.0 M KOH at the current density of 10 mA cm-2. Because of the encapsulation of NC that can effectively prevent corrosion of embedded TMP NPs, Ni2P@NC exhibits almost unfading catalytic performance even after 10 h under both acidic and alkaline solutions. This synthesis strategy provides a new avenue to exploring TMPs as highly active and stable electrocatalyst for the HER, OER, and other electrochemical applications.

The effect of thermolysis temperatures of two silver(I) supramolecular polymers on the formation of silver nanostructures

Two silver(I) supramolecular polymers, [Ag(8-HqH)(8-Hq)] n (1) and {[Ag(8-HqH)2]NO3} n (2), (8-HqH = 8-hydroxyquinoline), have been synthesized and characterized by X-ray powder diffraction, IR, 1H-NMR and 13C-NMR spectroscopies. These supramolecular polymers were used as new precursors for preparation of silver nanostructures. The effect of thermolysis temperature on preparation of silver nanoparticles from these precursors was investigated. The morphology of silver nanostructure is strongly dependent on thermolysis temperature. With increase in temperature, the tendency of silver nanoparticles to agglomerate was increased.

Thiourea sole doping reagent approach for controllable N, S co-doping of pre-synthesized large-sized carbon nanospheres as electrocatalyst for oxygen reduction reaction

The co-doping of heteroatoms into the pre-synthesized graphitic carbons normally requires the use of different doping reagents as heteroatom sources, leading to difficulties in controlling the contents of doped heteroatoms and their chemical bonding forms with graphitic structures. Graphitic carbon-based electrocatalysts with a relatively large size, rich microporous structure and high surface area could possess better structural stability and enhanced conductivity than those of small-sized carbon nanostructures (e.g., nanodots). This study reported the use of a sole reagent (thiourea) as heteroatoms doping source to achieve controllable N, S co-doping of the pre-synthesized graphitic microporous carbon nanospheres (∼100nm in diameter) via a facial thermolysis process to produce high performance oxygen reduction reaction electrocatalysts. Results showed that the contents of the doped N, S and their chemical bonds with graphitic carbon structures could be simply controlled by controlling the thermolysis temperatures. With the experimental conditions investigated, the best performed electrocatalyst was obtained from 1100°C doping process that possessed the most suitable N, S doping contents with 100% of doped N being in electrocatalytically active pyridinic-N and graphitic-N forms. The approach reported in this work could be useful for controllable heteroatoms co-doping of other types of new generation graphitic carbon materials.

Catalytic epoxidation of fatty acid methyl esters by modified metalloporphyrins with variable metals and electron-donating substituents

The catalytic efficiency of modified tetraphenylporphyrins with various metals (Mn, Fe, Co, Ni and Zn) and different electron-donating substituents (–OCH3, –OH, –N(CH3)2, –SO3Na) at the phenyl para-positions using hydrogen peroxide (H2O2, 30 wt%) as the oxidant has been researched in the epoxidation of unsaturated fatty acid methyl esters (FAMEs) under mild conditions. In the present system, the co-catalyst effect of inorganic salts had a crucial role in enhancing catalytic performance. According to the yields, the catalytic activities of metalloporphyrins were in the following order: Mn(TPP)Cl ≈ Fe(TPP)Cl > CoTPP > NiTPP > ZnTPP, and Mn(TPP)Cl > Mn(TMOPP)Cl ≈ Mn(THPP)Cl > Mn(TDMPP)Cl > Mn(TPPS4)Cl. Moreover, metalloporprhyrins after modification by electron-donating substituents displayed promoted thermolysis temperatures. Remarkably, the formation of intermediate porMnV=O has also been indicated, which was verified by both a kinetic study of FAMEs epoxidation and UV–Vis spectroscopy.

Colloidal Synthesis of ZnS, CdS and Zn x Cd1−x S Nanoparticles from Zinc and Cadmium Thiobiuret Complexes

ZnS, CdS and Zn x Cd1−x S nanoparticles were synthesised from the thermolysis of 1,1,5,5-tetra-iso-propyl-4-thiobiuret complexes of Zn and/or Cd in oleylamine. The influence of the different reaction parameters (precursor concentration, growth temperature, reaction time and injection solvent/capping agent combination) on the size, morphology and optical properties of the produced nanoparticles were studied. ZnS nanoparticles with size smaller than 4.3 nm had the cubic phase whereas the particles with size larger than 4.3 nm had a hexagonal crystal structure as suggested by the selected area electron diffraction. Transmission electron microscopy showed the formation of spherical ZnS nanoparticles in addition to few ZnS nanorods only at growth temperature of 280 °C. Powder X-Ray diffraction (p-XRD) showed that the obtained CdS nanoparticles were cubic under all reaction conditions except when dodecanethiol was used as an injection solvent which produced hexagonal CdS. The change in the crystal structure of the CdS nanoparticles was accompanied with a change in morphology from spherical to triangular. Cubic Zn x Cd1−x S nanoparticles were obtained under all reaction conditions. Lattice spacing of the Zn x Cd1−x S nanoparticles showed a very good agreement with Vegard’s law. The optical properties of the Zn x Cd1−x S nanoparticles were highly dependent on the ZnS to CdS precursor ratio and the solvents/capping agent combinations. This in detail study on the relationship of solvent systems (capping agents), thermolysis temperatures, time of reactions and precursors will help in understanding to control the morphology, size of the crystallites and phase of the materials.

Sulfophthalide cycle cleavage and formation of fluorenyl structures upon poly(diphenylene sulfophthalide) thermolysis

Thermolysis of poly(diphenylene sulfophthalide) (PDSP) in the temperature range from 100 to 500 °C was studied by IR and UV-Vis spectroscopy and thermogravimetric analysis. A series of absorption bands in the IR spectrum of PDSP were assigned on the basis of the theoretical calculations of the IR spectrum of diphenyl sulfophthalide used as a model compound, in particular, νas(S=O) = 1352 cm−1, νs(S=O) = 1196 cm−1, ν(C-O) ∼ 920 cm−1, ν(S-O) = 824 cm−1, and δ(SO2) = 576 cm−1. The sulfophthalide cycle (SPC) in PDSP decomposes at the thermolysis temperatures in a range of 260–400 °C. An analysis of the IR spectra of the thermolyzate and the quantum chemical calculations of the IR spectra of the model compounds confirmed the predominant formation of fluorenyl structures in the thermolyzed polymer. The changes in the UV-Vis spectra observed upon the thermolysis of thin films of PDSP (the hypsochromic shift of the long-wavelength absorption band from 271 to 263 nm and the appearance a shoulder at ∼310 nm) and the results of TD-DFT calculations of the UV-Vis spectra of the model compounds are consistent with the hypothesis about the formation of fluorenyl structures. The general scheme of PDSP thermolysis at 260–400 °C was proposed in which the major process is the formation of fluorenyl fragments in macromolecules of the polymer due to the intramolecular ring closure in biradicals formed by the SPC cleavage.

Flexible and Semitransparent Strain Sensors Based on Micromolded Pd Nanoparticle–Carbon μ-Stripes

Flexible resistive strain sensors have been fabricated by micromolding Pd alkanethiolate on polyimide substrates and subjecting to thermolysis in air. Thus produced stripes were ∼1 μm wide with spacing of ∼0.5 μm and contained Pd nanoparticles in carbon matrix. The nanoparticle size and the nature of carbon are much dependent on the thermolysis temperature as is also the resistance of the microstripes. Generally, lower thermolysis temperatures (<230 °C) produced stripes containing small Pd nanoparticles with significant fraction of carbon from the precursor decomposition. The stripes were poorly conducting yet interestingly, exhibited change of resistance under tensile and compressive strain. Particularly noteworthy are the stripes produced from 195 °C thermolysis, which showed a high gauge factor of ∼390 with strain sensitivity, 0.09%. With molding at 230 °C, the stripes obtained were highly conducting, and amazingly did not change the resistance with strain even after several bending cycles. The latter are ideal as flexible conduits and interconnects. Thus, the article reports a method of producing flexible sensitive strain sensors on one hand and on the other, flexible conduits with unchanging resistance, merely by fine-tuning the precursor decomposition under the molding conditions.

Deposition of iron sulfide nanocrystals from single source precursors

Symmetrical and unsymmetrical dithiocarbamato complexes of iron(III) with the general formula [Fe(S2CNRR′)3] where R = Et, R′ = iPr (1); R,R′ = Hex (2); R = Me, R′ = Et (3); and R,R′ = Et (4) have been used as single source precursors to synthesize iron sulfide nanocrystals by thermolysis in oleylamine, hexadecyleamine and octadecene at different temperatures. The nanocrystals obtained were studied by p-XRD and TEM and magnetic measurements. Nanocrystals of iron sulfide with greigite, pyrrhotite and mixed phase were grown at different thermolysis temperatures from each precursor. The precursors with shorter alkyl chain length required higher temperature to give the product. Symmetrical alkyl groups with longer chain alkyl groups gave pure greigite phase at lower thermolysis temperature of 170 °C but a mixture of greigite and pyrrhotite at higher temperatures. The unsymmetrical alkyl groups gave mixed phase (greigite and pyrrhotite) iron sulfide nanocrystals at all temperatures.

Effect of vapor thermolysis on microstructure development of sol–gel-derived lead zirconate–titanate (PZT) and PZT-Sr(K0.25Nb0.75)O3 solid solutions

Ceramic granules of PZT (Pb(Zr53,Ti47)O3) and fibers of SKN-doped PZT (1 Mol-% Sr(K0.25Nb0.75)O3 substitution in PZT) were fabricated from sol–gel precursors. The transformation of the metal–organic gel to the oxide and its crystallization behavior was investigated by thermogravitmetry, and XRD. The formation of pyrochlore or perovskite phase was sensitive to the preceeding heat treatment conditions in moist atmosphere (termed vapor thermolysis). Lower thermolysis temperatures resulted in the preferred formation of metastable pyrochlore phase. Higher thermolysis temperatures favored the formation of perovskite. Investigation of sintered materials revealed a superior sintering activity for samples with pronounced intermediate pyrochlore content whereas low-pyrochlore samples remained highly porous after sintering. For constant chemical precursors the vapour thermolysis conditions (220–280 °C) siginificantly affected crystallization and sintering behavior of the PZT and SKN-PZT material.

Thermal fragmentation of the guanidinato aluminum amide precursor [Me 2NC(N iPr) 2]Al(NMe 2) 2: An investigation of reactive species by matrix-isolation FTIR spectroscopy and time-of-flight mass spectrometry

The gas-phase thermolysis of the guanidinato aluminum amide precursor [Me 2NC(N i Pr) 2]Al(NMe 2) 2 ( 1) in the oven temperature range of ambient temperatures to 600 °C has been investigated with matrix-isolation FTIR spectroscopy and time-of-flight mass spectrometry (argon as carrier gas). Precursor 1 fragments above 300 °C to form iPrCNC iPr ( 2) and monomeric Al(NMe 2) 3 ( 3m). Independent thermolysis series with 2 and the aluminum amide dimer 3d, [Al(NMe 2) 3] 2, were conducted and been used to interpret the results of the fragmentation of precursor 1. Compound 3m was present in the thermolysis range of 350–450 °C and has been identified for the first time. Through a comparison of measured FTIR spectra with the calculated spectrum of 3m ( D 3 point group symmetry; B3LYP/6-31G(d) level of theory) all expected IR bands were found and could be assigned to normal modes. At thermolysis temperatures of ⩾500 °C signals indicative for H 2CNCH 3 ( 4) were found, showing that 3m fragments further at higher temperature. The thermolysis product 2 ( iPrCNC iPr) withstands the higher thermolysis temperatures. From our study one can conclude that precursor 1 cleanly delivers the monomeric aluminum alane 3m, which then acts as the reactive material forming species.

Mechanism of formation of nanosized copper particles in a nanoreactor based on the [LiAl2(OH)6]2[Cuedta]·nH2O supramolecular system

The formation of nanosized copper particles in a nanoreactor based on the [LiAl2(OH)6]2[Cuedta]·nH2O supramolecular system [Li-Al-Cu(edta)] was studied by the DTA, XRPA, FMR, IR, and mass spectrometry methods. Thermal decomposition of Li-Al-Cu(edta) below 200°C occurs as two-stage removal of the interlayer water molecules. Above 200°C dehydration of [LiAl2(OH)6]+ metal hydroxide layers occurs simultaneously with destruction of [Cuedta]2− complexonate ions. The first stage of destruction (below 250–260°C) is a redox process that forms metallic copper and liberates gaseous carbon oxide and dioxide. At higher thermolysis temperatures, other gaseous products evolve (ammonia, hydrogen). The copper phase appeared during thermal decomposition as 20–50 nm isometric particles on the surface, while lenslike copper nanoparticles formed in the bulk substance.

Thermolysis of Fluorinated Single-Walled Carbon Nanotubes: Identification of Gaseous Decomposition Products by Matrix Isolation Infrared Spectroscopy

The thermal decomposition of fluorinated single-walled carbon nanotubes (F-SWNTs), known to result in pristine SWNTs, has been investigated by freezing the gaseous products formed at temperatures between 50 and 500 degrees C under high vacuum in an argon matrix at 10-20 K and analyzing the trapped species by IR spectroscopy. The major products of F-SWNT decomposition are carbonyl fluoride (COF2) below 300 degrees C and CF4 above 300 degrees C. For comparison, graphite fluoride is stable thermally up to 300 degrees C under these conditions, and the major gas-phase species at temperatures below 500 degrees C are CF4 and the CF3 radical. F-SWNTs are thermally less stable than graphite fluoride, and etching of the nanotubes is observed at lower thermolysis temperatures.

N-alkyldithiocarbamato complexes [Cd(S2CNHR)2] (R = C2H5, C4H9, C6H13, C12H25); Synthesis, Characterisation and Deposition of II/VI Nanoparticles.

AbstractA series of N-alkyldithiocarbamato complexes of cadmium have been synthesised and characterized. [Cd(S2CNHC12H25)2] complex was used as a single source precursor to synthesize CdS nanoparticles. Synthesis of CdS nanoparticles was carried out at various thermolysis temperatures and concentration of the precursor to observe the morphological changes. At moderate or high temperature the 1D nanostructures (single-rods, bend rods or multi-rods) are generated. The shape of CdS nanocrystals varied from longer rods to shorter rods with increased width (average size: 4nm wide and 27nm long vs. 9nm wide and 27nm long) by simply increasing the quantity of precursor in the bulk solution from 0.05g/8ml HDA to 1g/8ml HDA at 250°C.

Occurrence of highly mature organic matter in marine black shale petroleum source rocks of basal cambrian from northern tarim basin, China

More and more evidence indicates that organic matter (OM) in immature organicrich sediments and sedimentary rocks is chemically adsorbed onto the outer surfaces of minerals and into interlayer (inner) surfaces of smectitic clay minerals in the form of amorphous molecular-scale carbon. But there have been few reports about the occurrence of highly mature OM in marine black shales (petroleum source rocks). The occurrence of highly mature OM in the black shales of basal Cambrian from northern Tarim Basin is studied in this paper. Based on the comprehensive analyses of total organic carbon contents (TOC), maximum thermolysis temperatures (T max) of OM, mineral surface areas (MSA), and scanning electronic microscopic (SEM) and transmission electronic microscopic (TEM) observations of the black shales, it is concluded that the highly mature OM in the marine black shales of the basal Cambrian from northern Tarim Basin occurs in particulates ranging in size from 1 to 5 µm in diameter. Through the contrast of the occurrence of the highly mature OM in the black shales with that of the immature ones in modern marine continental margin sediments, some scientific problems are proposed, which are worth to study further in detail.

The thermolysis of ε-halodisilanes: a preference for 1,2-Si Si → O rearrangement or Si—O cleavage over Si=O bond formation

Tris(trimethylsilyl)-2,2,2-trifluoroethoxysilane 6, tris(trimethylsilyl)-2-fluoroethoxysilane 7, and tris(trimethylsilyl)-2-chloroethoxysilane 8 were synthesized and characterized by 1H, 13C and 29Si NMR, IR spectroscopy, and EI and CI mass spectrometry. Thermodynamic considerations would suggest that, as a result of the driving force provided by the formation of a Si—F or Si—CI bond, the thermolyses of these compounds would lead to the formation of bis(trimethylsilyl)silanone 4. To examine this question, gas chromatography–mass spectrometry was as used a detection technique for products resulting from the high-pressure thermolyses of 6–8. The elimination of (Me3Si)3SiCl appears to be the major thermolytic pathway of decomposition for 8 at ambient or higher pressures, although it is accompanied by the formation of other products, some of which could have arisen from the addition of various halosilanes to a silanone. Neither 6 nor 7 thermolyzed cleanly; the former compound was essentially unreactive under the thermolysis temperatures used (850 °C). Of the products produced in the thermolysis of 7, no evidence for the formation of the silanone was obtained. Independently, mass spectrometry was used to study unimolecular reactions of molecular ions derived from 6–8. The major route to solitary ions appears to involve a 1,2-trimethylsilyl migration from Si to O (9 → 10) prior to decomposition, for example, of the m/z 346 parent ion in the decomposition of 6. The preparation of the ionized silanone may be a minor pathway. Some of the other fragmentation pathways for 6–8 are discussed. Key words: gas phase thermolysis, ion rearrangements, silyl group migration, silanone, halosilane.