Elucidating the reaction mechanism of SO with Cu-CHA catalysts for NH-SCR by X-ray absorption spectroscopy.

The application of Cu-CHA catalysts for the selective catalytic reduction of NO by ammonia (NH-SCR) in exhaust systems of diesel vehicles requires the use of fuel with low sulfur content, because the Cu-CHA catalysts are poisoned by higher concentrations of SO. Understanding the mechanism of the interaction between the Cu-CHA catalyst and SO is crucial for elucidating the SO poisoning and development of efficient catalysts for SCR reactions. Earlier we have shown that SO reacts with the [Cu(NH)O] complex that is formed in the pores of Cu-CHA upon activation of O in the NH-SCR cycle.

Cyclic or Linear? Parameters Determining the Outcome of Glycine Polymerization in Silica Surface Prebiotic Scenarios.

The parameters that determine the formation of linear peptides and cyclic dimers (diketopiperazine, DKP) on silica surfaces of different surface area, silanol and siloxane ring populations, controlled by thermal treatments, are investigated upon glycine deposition from gas and liquid phases. The formed products were characterized by infrared and Raman spectroscopies, X-ray diffraction and thermogravimetric analysis. The results reveal the importance of "nearly-free" silanols to form ester centers as primers for the formation of linear peptides over DKP, on surfaces with medium silanol density (1.

Polypeptide Chain Growth Mechanisms and Secondary Structure Formation in Glycine Gas-Phase Deposition on Silica Surfaces.

Peptide formation by amino acids condensation represents a crucial reaction in the quest of the origins of life as well as in synthetic chemistry. However, it is still poorly understood in terms of efficiency and reaction mechanism. In the present work, peptide formation has been investigated through thermal condensation of gas-phase glycine in fluctuating silica environments as a model of prebiotic environments.

Influence of ion mobility on the redox and catalytic properties of Cu ions in zeolites.

This contribution aims at analysing the current understanding about the influence of Al distribution, zeolite topology, ligands/reagents and oxidation state on ions mobility in Cu-zeolites, and its relevance toward reactivity of the metal sites. The concept of Cu mobilization has been originally observed in the presence of ammonia, favouring the activation of oxygen by formation of NH oxo-bridged complexes in zeolites and opening a new perspective about the chemistry in single-site zeolite-based catalysts, in particular in the context of the NH-mediated Selective Catalytic Reduction of NO (NH-SCR) processes. A different mobility of bare Cu/Cu ions has been documented too, showing for Cu a better mobilization than for Cu also in absence of ligands.

Assessing the Influence of Zeolite Composition on Oxygen-Bridged Diamino Dicopper(II) Complexes in Cu-CHA DeNO Catalysts by Machine Learning-Assisted X-ray Absorption Spectroscopy.

Cu-exchanged chabazite is the catalyst of choice for NO abatement in diesel vehicles aftertreatment systems via ammonia-assisted selective catalytic reduction (NH-SCR). Herein, we exploit X-ray absorption spectroscopy powered by wavelet transform analysis and machine learning-assisted fitting to assess the impact of the zeolite composition on NH-mobilized Cu-complexes formed during the reduction and oxidation half-cycles in NH-SCR at 200 °C. Comparatively analyzing well-characterized Cu-CHA catalysts, we show that the Si/Al ratio of the zeolite host affects the structure of mobile dicopper(II) complexes formed during the oxidation of the [Cu(NH)] complexes by O.

SO Poisoning of Cu-CHA deNO Catalyst: The Most Vulnerable Cu Species Identified by X-ray Absorption Spectroscopy.

Cu-exchanged chabazite zeolites (Cu-CHA) are effective catalysts for the NH-assisted selective catalytic reduction of NO (NH-SCR) for the abatement of NO emission from diesel vehicles. However, the presence of a small amount of SO in diesel exhaust gases leads to a severe reduction in the low-temperature activity of these catalysts. To shed light on the nature of such deactivation, we characterized a Cu-CHA catalyst under well-defined exposures to SO using X-ray absorption spectroscopy.

Investigating the role of Cu-oxo species in Cu-nitrate formation over Cu-CHA catalysts.

The speciation of framework-interacting Cu sites in Cu-chabazite zeolite catalysts active in the selective catalytic reduction of NO with NH is studied, to investigate the influence of the Al content on the copper structure and their reactivity towards a NO/O mixture. To this aim, three samples with similar Cu densities and different Si/Al ratios (5, 15 and 29) were studied using in situ X-ray absorption spectroscopy (XAS), FTIR and diffuse reflectance UV-Vis during pretreatment in O followed by the reaction. XAS and UV-Vis data clearly show the main presence of ZCu sites (with Z representing a framework negative charge) at a low Si/Al ratio, as predicted.

Structure and Reactivity of Oxygen-Bridged Diamino Dicopper(II) Complexes in Cu-Ion-Exchanged Chabazite Catalyst for NH-Mediated Selective Catalytic Reduction.

The NH-mediated selective catalytic reduction (NH-SCR) of NOx over Cu-ion-exchanged chabazite (Cu-CHA) catalysts is the basis of the technology for abatement of NOx from diesel vehicles. A crucial step in this reaction is the activation of oxygen. Under conditions for low-temperature NH-SCR, oxygen only reacts with Cu ions, which are present as mobile Cu diamine complexes [Cu(NH)].

EXAFS wavelet transform analysis of Cu-MOR zeolites for the direct methane to methanol conversion.

Cu-exchanged zeolites have been shown to possess Cu-oxo species active towards the direct methane to methanol (DMTM) conversion, carried out through a chemical-looping approach. Different Cu-zeolites have been investigated for the DMTM process, with Cu-mordenite (Cu-MOR) being among the most active. In this context, an accurate determination of the local structure and nuclearity of selective Cu-oxo species responsible for an efficient DMTM conversion still represents an ongoing challenge for characterization methods, including synchrotron-based X-ray absorption spectroscopy (XAS).

Sonochemically-Promoted Preparation of Silica-Anchored Cyclodextrin Derivatives for Efficient Copper Catalysis.

Silica-supported metallic species have emerged as valuable green-chemistry catalysts because their high efficiency enables a wide range of applications, even at industrial scales. As a consequence, the preparation of these systems needs to be finely controlled in order to achieve the desired activity. The present work presents a detailed investigation of an ultrasound-promoted synthetic protocol for the grafting of β-cyclodextrin (β-CD) onto silica.

Uptake and intracellular distribution of different types of nanoparticles in primary human myoblasts and myotubes.

The use of nanoparticles as drug carriers in the field of skeletal muscle diseases has been poorly addressed and the interaction of nanoparticles with skeletal muscle cells has been investigated almost exclusively on C2C12 murine myoblasts. In this study we investigated the effects poly(lactide-co-glycolide) nanoparticles, mesoporous silica nanoparticles and liposomes, on the viability of primary human myoblasts and analyzed their cellular uptake and intracellular distribution in both primary human myoblasts and myotubes. Our data demonstrate that poly(lactide-co-glycolide) nanoparticles do not negatively affect myoblasts viability, contrarily to mesoporous silica nanoparticles and liposomes that induce a decrease in cell viability at the highest doses and longest incubation time.

Uptake and intracellular fate of biocompatible nanocarriers in cycling and noncycling cells.

Aim: To elucidate whether different cytokinetic features (i.e., presence or absence of mitotic activity) may influence cell uptake and distribution of nanocarriers, in vitro tests on liposomes, mesoporous silica nanoparticles, poly(lactide-co-glycolide) nanoparticles and nanohydrogels were carried out on C2C12 murine muscle cells either able to proliferate as myoblasts (cycling cells) or terminally differentiate into myotubes (noncycling cells).

Strategies to Obtain Encapsulation and Controlled Release of Pentamidine in Mesoporous Silica Nanoparticles.

Pentamidine (PTM), an antiprotozoal agent used in clinics as pentamidine isethionate salt (PTM-S), recently showed high potential also for the treatment of cancer and myotonic dystrophy type I. However, a severe limit to the systemic administration of PTM is represented by its nephrotoxicity, leading to the need for a system able to achieve a controlled release of the drug. In this study, mesoporous silica nanoparticles (MSNs) were employed for the first time to encapsulate PTM.

The Nuclearity of the Active Site for Methane to Methanol Conversion in Cu-Mordenite: A Quantitative Assessment.

The direct conversion of methane to methanol (MTM) is a reaction that has the potential to disrupt a great part of the synthesis gas-derived chemical industry. However, despite many decades of research, active enough catalysts and suitable processes for industrial application are still not available. Recently, several copper-exchanged zeolites have shown considerable activity and selectivity in the direct MTM reaction.

Investigating the Low Temperature Formation of Cu -(N,O) Species on Cu-CHA Zeolites for the Selective Catalytic Reduction of NO.

In this work, we show the potentiality of operando FTIR spectroscopy to follow the formation of Cu -(N,O) species on Cu exchanged chabazite zeolites (Cu-CHA), active for the selective catalytic reduction of NO with NH (NH -SCR). In particular, we investigated the reaction of NO and O at low temperature (200 and 50 °C) on a series of Cu-CHA zeolites with different composition (Si/Al and Cu/Al ratios), to investigate the nature of the formed copper nitrates, which have been proposed to be key intermediates in the oxidation part of the SCR cycle. Our results show that chelating bidentate nitrates are the main structures formed at 200 °C.

Hyaluronated mesoporous silica nanoparticles for active targeting: influence of conjugation method and hyaluronic acid molecular weight on the nanovector properties.

We have prepared and evaluated the physico-chemical and biological properties of four different hyaluronated mesoporous silica nanoparticles (MSNs) samples (MSN/HA). Hyaluronic acid (HA) with two different molecular weights (200 and 6.4 kDa) was used for the conjugation of aminopropyl-functionalized MSN (NH-MSN), following two different procedures.

Composition-driven Cu-speciation and reducibility in Cu-CHA zeolite catalysts: a multivariate XAS/FTIR approach to complexity.

The small pore Cu-CHA zeolite is attracting increasing attention as a versatile platform to design novel single-site catalysts for deNO applications and for the direct conversion of methane to methanol. Understanding at the atomic scale how the catalyst composition influences the Cu-species formed during thermal activation is a key step to unveil the relevant composition-activity relationships. Herein, we explore by XAS the impact of Cu-CHA catalyst composition on temperature-dependent Cu-speciation and reducibility.

Methane to Methanol: Structure-Activity Relationships for Cu-CHA.

Cu-exchanged zeolites possess active sites that are able to cleave the C-H bond of methane at temperatures ≤200 °C, enabling its selective partial oxidation to methanol. Herein we explore this process over Cu-SSZ-13 materials. We combine activity tests and X-ray absorption spectroscopy (XAS) to thoroughly investigate the influence of reaction parameters and material elemental composition on the productivity and Cu speciation during the key process steps.

Poly(NIPAM--MPS)-grafted multimodal porous silica nanoparticles as reverse thermoresponsive drug delivery system.

Hybrid drug delivery systems (DDS) have been prepared by grafting poly(NIPAM--MPS) chains on multimodal porous silica nanoparticles having an inner mesoporous structure and an outer thin layer of micropores. The hybrid thermoresponsive DDS were fully characterized and loaded with a model drug. The drug release tests are carried out at below and above the lower critical solution temperature (LCST) of the copolymer.

Metal-organic framework mixed-matrix disks: Versatile supports for automated solid-phase extraction prior to chromatographic separation.

We present for the first time the application of metal-organic framework (MOF) mixed-matrix disks (MMD) for the automated flow-through solid-phase extraction (SPE) of environmental pollutants. Zirconium terephthalate UiO-66 and UiO-66-NH MOFs with different size (90, 200 and 300nm) have been incorporated into mechanically stable polyvinylidene difluoride (PVDF) disks. The performance of the MOF-MMDs for automated SPE of seven substituted phenols prior to HPLC analysis has been evaluated using the sequential injection analysis technique.

The Cu-CHA deNOx Catalyst in Action: Temperature-Dependent NH3-Assisted Selective Catalytic Reduction Monitored by Operando XAS and XES.

The small-pore Cu-CHA zeolite is today the object of intensive research efforts to rationalize its outstanding performance in the NH3-assisted selective catalytic reduction (SCR) of harmful nitrogen oxides and to unveil the SCR mechanism. Herein we exploit operando X-ray spectroscopies to monitor the Cu-CHA catalyst in action during NH3-SCR in the 150-400 °C range, targeting Cu oxidation state, mobility, and preferential N or O ligation as a function of reaction temperature. By combining operando XANES, EXAFS, and vtc-XES, we unambiguously identify two distinct regimes for the atomic-scale behavior of Cu active-sites.