Evaluation of Mono and Bimetallic Ferrocene-Based 1,2,3-Triazolyl Compounds as Burning Rate Catalysts for Solid Rocket Motor.

We reported mono and bimetallic ferrocene-based 1,2,3-triazolyl compounds as potential burning rate catalysts in their neutral and ionic forms. All complexes reported here were characterized using 1H and 13C NMR, elemental analysis, and Mössbauer spectroscopy, which was performed for neutral and oxide compounds. The complexes present quasireversible redox potentials with higher oxidative ability than ferrocene and catocene under the same conditions. The complexes were tested as catalysts on the thermal decomposition of ammonium perchlorate (AP) and examined by a differential scanning calorimetry technique to gain further knowledge about their catalytic behavior. Compound 1 causes a decrease of the high-temperature decomposition (HTD) of AP positively, decreasing the decomposition temperature of AP to 345 °C and consequently increasing the energy release to 1939 J·g-1. We took the residues from the pans after testing from the DSC to elucidate the underlying reaction pathways. We obtained the size of the nanostructures formed after thermal decomposition of AP determined by the TEM technique. The diameter and size distribution of iron oxide nanoparticles formed depend on the alkyl sidechain of the triazolium ring, which induces the formation of nanoparticles with a double diameter and size distribution compared to their neutral analogues, suggesting that the possible intermediate for the mechanism degradation of AP by ferrocene derivatives is nanoscale Fe2O3 or similar oxides.

Porous chitosan-based nanocomposites containing gold nanoparticles. Increasing the catalytic performance through film porosity.

The preparation of porous and non-porous chitosan thin-films containing gold nanoparticles was carried out, aiming to evaluate the effect of porosity on their catalytic response using the p-nitrophenol reduction as model reaction. To achieve this, both types of samples were decorated with gold nanoparticles having similar characteristics in terms of amount, size and shape, which were synthesized following a two-step adsorption-reduction process. The results demonstrated that the presence of porosity generates a considerable enhancement of the catalytic property. This behavior is reflected in higher kinetic constant and conversion values, along with a better recyclability after consecutive cycles. The inclusion of porosity in nanocomposites afforded kobs values 7.5 times higher than the non-porous material, as well as conversion values as high as 80 % in <20 min. On the other hand, as an additional experiment, a porous sample prepared with half the amount of gold also exhibited a better performance than the non-porous catalyst, revealing that the porosity allowed to decrease the amount of catalytic metal used and still exhibiting kobs values 5.9 times higher than the non-porous specimen. These studies demonstrate that there is an important synergistic support-nanostructure relationship, which strongly influences the performance of the nanomaterial.

Mechanistic Insights into the Thermal Decomposition of Ammonium Perchlorate: The Role of Amino-Functionalized Magnetic Nanoparticles.

This work reports the characterization and application of two promising nanocatalysts for the thermal decomposition of ammonium perchlorate (AP). To obtain these composite materials, magnetite nanoparticles (Fe3O4 NPs) were functionalized with two different amine derivative groups, tertiary amine (Fe3O4 NPs-A1) and quaternary amine. X-ray photoelectron spectroscopy and differential scanning calorimetry provided mechanistic insights into the thermal decomposition of AP. Furthermore, tertiary and quaternary amine groups play a critical role, where the presence of an extra proton could favor an electron-proton transfer as the rate-determining step. Moreover, Fe3O4 NPs-A1 causes a diminution of the high-temperature decomposition of AP positively to 335 °C, increasing the energy release by 278 J g-1 and consequently affording the lowest activation energy (102 kJ mol-1), indicating a low degree of thermal stability, and accelerating the thermal decomposition of AP.

Heterobimetallic Catalysts for the Thermal Decomposition of Ammonium Perchlorate: Efficient Burning Rate Catalysts for Solid Rocket Motors and Missiles.

We show the synthesis and characterization of four heterobimetallic compounds derived from s-indacene of general formula [{(CO)3Mn}-s-Ic-{MCp*}]q with M = Fe, Co, Ni, and Ru; q = 0, 1+. The complexes reported here were characterized by 1H and 13C NMR, elemental analysis and FT-IR. Additionally, the X-ray crystal structure of [(CO)3Mn-s-Ic-FeCp*] (1) and Mössbauer spectra are reported. The heterobimetallic compounds exhibit higher quasireversible redox potentials compared with ferrocene and catocene under the same reaction conditions. The complexes were tested as catalysts on the thermal decomposition of ammonium perchlorate examined by a differential scanning calorimetry technique to study their catalytic behavior. Compound (1) causes a decrease of ammonium perchlorate's decomposition temperature to 315 °C, consequently increasing the heat release by 138 J·g-1. Conversely, [{(CO)3Mn}-s-Ic'-{CoCp*}] (2) presents a higher heat release (2462 J·g-1), comparable to catocene.

Data of interaction of supported ionic liquids phases onto copper nanoparticles: A density functional theory study.

This work contains data on the computational, structural, and electronic characterization of supported ionic liquids phases anchored to copper nanoparticles using Density Functional theory calculations. The data supplement the paper "Interaction of supported ionic liquids phases onto copper nanoparticles: A Density Functional Theory study" [1], based on the adsorption of ionic liquid onto a Cu nanoparticle is analyzed from a chemical and physical point of view. The chemical analysis is based on Atoms in Molecule theory (AIM) and allows us to differentiate the chemical binding nature between ionic liquid and copper nanoparticle. On the other hand, the energy decomposition analysis based on absolutely localized molecular orbital (ALMO-EDA) describes the physical contributions that govern the interaction between ionic liquid and the copper nanoparticles. Herein, detailed and extended information in the synthesis and computational characterization are presented.

Nanohybrids of reduced graphene oxide and cobalt hydroxide (Co(OH)2|rGO) for the thermal decomposition of ammonium perchlorate.

The catalytic activity of nanoparticles of cobalt hydroxide supported on reduced graphene oxide, Co(OH)2|rGO, was studied for the decomposition of ammonium perchlorate (AP), the principal ingredient of composite solid propellants. Co(OH)2|rGO was synthesized by an in situ reduction method, which avoided the application of extremely high temperatures and harsh processes. rGO stabilized the nanoparticles effectively and prevented their agglomeration. The performance of Co(OH)2|rGO as a catalyst was measured by differential scanning calorimetry. Co(OH)2|rGO affected the high-temperature decomposition (HTD) of AP positively, decreasing the decomposition temperature of AP to 292 °C, and increasing the energy release to 290 J g-1. The diminution of the HTD of AP by Co(OH)2|rGO is in between the best values reported to date, suggesting its potential application as a catalyst for AP decomposition.

Highly modulated supported triazolium-based ionic liquids: direct control of the electronic environment on Cu nanoparticles.

A series of new triazolium-based supported ionic liquids (SILPs), decorated with Cu NPs, were successfully prepared and applied to the N-arylation of aryl halides with anilines. The triazoles moieties were functionalised using copper-catalysed azide-alkyne cycloaddition. SILP surface characterisation showed a strong correlation between the triazolium cation volume and textural properties. STEM images showed well-dispersed Cu NPs on SILPs with a mean diameter varying from 3.6 to 4.6 nm depending on the triazolium cation used. Besides, XPS results suggest that the Cu(0)/Cu(i) ratio can be modulated by the electronic density of triazolium substituents. XPS and computational analysis gave mechanistic insights into the Cu NP stabilisation pathways, where the presence of electron-rich groups attached to a triazolium ring plays a critical role in leading to a cation adsorption pathway (E ads = 72 kcal mol-1). In contrast, less electron-rich groups favour the anion adsorption pathway (E ads = 63 kcal mol-1). The Cu@SILP composite with electron-rich groups showed the highest activity for the C-N Ullmann coupling reaction, which suggests that electron-rich groups might act as an electron-like reservoir to facilitate oxidative addition for N-arylation. This strategy firmly suggests the strong dependence of the nature of triazolium-based SILPs on the Cu NP surface active sites, which may provide a new environment to confine and stabilise MNPs for catalytic applications.

Correction: Highly modulated supported triazolium-based ionic liquids: direct control of the electronic environment on Cu nanoparticles.

[This corrects the article DOI: 10.1039/D0NA00055H.].

Novel in situ synthesis of copper nanoparticles supported on reduced graphene oxide and its application as a new catalyst for the decomposition of composite solid propellants.

The catalytic activity of graphene oxide (GO), reduced graphene oxide (rGO), copper nanoparticles (CuNP) and rGO supported copper nanoparticles (rGO|CuNP) was investigated for the thermal decomposition of ammonium perchlorate (AP). GO was synthesized using a methodology based on hydrophilic oxidation, while an environmentally friendly and non-toxic reducing agent, l-ascorbic acid, was applied for the in situ reduction of copper and GO. The supporting rGO reduced the mean size of the copper nanoparticles from approximately 6 to 2 Å due to the presence of stabilizing functional groups on the graphitic structure. Theoretical studies through Density Functional Theory revealed the important role of the epoxy and carbonyl groups of rGO on the stabilization of copper. The thermal decomposition process was studied based on DSC and TGA. GO, and rGO did not show a significant catalytic influence in the decomposition of AP. CuNP reduced the decomposition temperature of AP in greater magnitude than rGO|CuNP however, the synergistic effect of the rGO and CuNP increased the energy release significantly.

Tuning the structure and magnetic behavior of Ni-Ir-based nanoparticles in ionic liquids.

We report on a simple preparation of extremely small diameter (ca. 2 nm) Ni-Ir-based NPs using Ni(COD)2 and [Ir(COD)OCH3]2 in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIm·NTf2). The prepared NPs had either core-shell-like or alloy-like structures with the presence of Ni,Ir-oxides, depending on the synthetic approach. X-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), extended X-ray absorption fine structure (EXAFS), and magnetic measurements are combined to describe the influence of nanostructure on the magnetic behavior of these nanosystems. The present findings reveal that the alloy NPs display a disordered magnetic state, similar to a spin glass (SG)-like system (Tf = 7.2 K). Core-shell NPs are formed by a magnetically blocked/unblocked core with a magnetically disordered shell as deduced from the two magnetic responses peaking at TB = 75 K and Tf = 5.8 K. Coupling at the core-shell interface leads to an exchange bias revealed at low temperature as horizontal shifts in the hysteresis loops of 0.12 kOe at 2 K.

Imprinted Naked Pt Nanoparticles on N-Doped Carbon Supports: A Synergistic Effect between Catalyst and Support.

A synergistic effect resulting from the interaction of small (2.4-3.1 nm) naked Pt nanoparticles (NPs) imprinted on N-doped carbon supports is evidenced by structural, electronic and electrochemical characterization. The size and distribution of the sputtered Pt NPs are found to be related to the nature of the support because Pt NPs are preferentially located at Ngraphitic sites. In addition, Rutherford backscattering shows that a deeper penetration of the Pt NPs is obtained in the N-doped carbon support with larger pore diameters. The ligand effect of the N-doped carbon supports is found to occur by electron donation from Npyrrolic and Ngraphitic sites to the Pt NPs and the electron acceptor behavior of the C=Npyridinic sites. The carbon matrix acquires a basic characteristic (electron-richer, metallic behavior) capable of interacting with metallic NPs akin to a bimetallic-like system. The imprinted Pt NPs are active catalysts for oxidation, although displaying poor catalytic activity for reduction reactions. The catalyst N-doped carbon supports play an important role in the overall catalytic process, rather than only acting as a simple active phase carrier.

Sputtering deposition of gold nanoparticles onto graphene oxide functionalized with ionic liquids: biosensor materials for cholesterol detection.

Ionic liquid (IL)-functionalized graphene oxide (GO) containing gold nanoparticles (Au NPs) (5.4-5.9 nm) deposited by sputtering combined with cholesterol oxidase appears to be a suitable and efficient biosensor for total cholesterol detection. These biosensors showed good linear range (25-340 µmol L-1) for total cholesterol determination by colorimetric tests. In addition, control experiments in the presence of interferents demonstrated that the hybrid materials provided a selective detection of total cholesterol. The biosensing activities obtained for the hybrid materials indicate that these compounds are potential biosensors for clinical applications.