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We probed the solid-state formation of gold nanoparticles through mechanochemically-activated aging. The acquired data allowed for the establishment of the first kinetic model for solid-state nanoparticle formation.

We use a gold nanoparticle synthesis as a model system to study the morphological and compositional changes in gold(III) precursor particles, while reduction is taking place during aging after mechanical activation. Scanning transmission electron microscopy coupled with a high-angle annular dark field detector revealed the nanoscale changes in particle morphology, while electron energy loss spectroscopy mapped the changes in the chemical landscape during the reduction process. Tracking a specific region of interest on the sample grid allowed for comparisons to be made of the same particles across a two day monitoring period. High-angle annular dark field images permitted the visualization of particle size reduction of the gold salt while electron energy loss spectroscopy captured the surprising mobility of the lighter chlorine and sodium ions in a solid matrix during the reduction process. This system offers unique insight into precursor particle reactivity in the solid phase, which is relevant for many mechanochemical and aging-based reactions.

To unlock nature's potential for functional biomaterials, many efforts have been devoted to isolating the nanocrystalline domains within the supramolecular structure of polysaccharides. Yet, low reactivity and yield in aqueous systems along with excessive solvent usage hinders its development. In this report, the first solvent-free pathway to access carboxylated chitin and cellulose nanocrystals with excellent mass balance is described, relying on a new method coined high-humidity shaker aging (HHSA). The method involves a mild grinding of the polysaccharide with ammonium persulfate followed by an aging phase under high-humidity and on a shaker plate. Insights into the mechanism were uncovered, which highlighted the unique role of high humidity to afford a gradual uptake of water by the material up to deliquescence when the reaction is complete. This process was then validated for direct synthesis of nanocrystals from biomass sources including crab and soft wood pulp.

Commercially used quantum dots (QDs) exemplify complex nanomaterials with multiple components, though little is known about the type of interactions between these components in determining the overall toxicity of this material. We synthesized and characterized a functional QD (CdSe/ZnS_PE) that was identical in structure and composition to a patented and commercially applied QD and the combinations of its components (CdSe, CdSe/ZnS, ZnS, CdSe_PE, ZnS_PE, and PE). Cells exposed to incremental concentrations of these materials were investigated for cell viability and cellular perturbations, contributing to a final common pathway of cell death using high-content screening assays in model human intestinal epithelial cells (HIEC-6). The concentrations that resulted in a loss of 20% cell viability (EC

Cu(I) catalysts were studied for the synthesis of a propargylamine via A3-coupling of aldehyde, amine, and alkyne, under solvent-free and low loading conditions, using batch microwave or flow thermal heating. We explored ultra-low loading conditions with Cu(I) salts as fast and active catalysts featuring turnover frequencies (TOFs) above 105 h−1. Well-defined octahedral and cubic Cu2O microcrystals were also successfully applied and compared with this reaction. Both types of microcrystals exhibited excellent catalytic activities within minutes, via in situ generation of low dose of Cu(I) ions within the reaction medium, to achieve TON beyond 2000 and recycling up to 10 times in a flow reactor. The study of the catalytic system demonstrated that the activity was surface-structure dependent and allowed for the design of low Cu contamination A3-coupling systems, affording a product at the decigram scale, with Cu contamination below FDA recommendations for drug synthesis, without the need for a purification procedure.

Chitosan is typically produced by the deacetylation of biopolymer chitin. Its molecular weight (Mw) is a function of the chitin source and the deacetylation conditions. It remains a challenge to both control the Mw of chitosan and obtain good polydispersity, essential for optimal function of chitosan in different applications. This study explores the use of mechanochemistry and aging as effective methods towards the controlled reduction of the Mw of commercial high Mw chitosan (HMwChs) with phosphoric acid where Mw was measured by gel permeation chromatography (GPC). In comparison to conventional solution-based methods, this new mechanochemical process features improved process mass intensity in comparison to conventional techniques and affords low Mw chitosan (LMwChs) samples in a range of 200 to as low as 19.5 kDa, with a polydispersity of 1.8.

Confinement effects offer unique opportinuties to facilitate reactions in a way to favor sustainability... in an almost magical way.

6:2 Fluorotelomer sulfonate (6:2 FTSA) is a ubiquitous environmental contaminant belonging to the family of per- and polyfluoroalkyl substances. Previous studies showed that hydroxyl radical (

Alcohol amination via hydrogen borrowing is an established method for the clean and simple alkylation of amines with alcohols, which are stable and available in bulk; it also does not require the addition of hydrogen to reduce the imines or the use of coupling agents. A common problem however in those systems is the need to employ additives to prevent stagnation of the product at the imine stage, which indicates inefficient usage of the borrowed hydrogen atoms. In this work, we designed a catalyst series to demonstrate that confined environments can assist with improved selectivity. To this end, we encapsulated Al2O3/Ru(OH)x nanocatalysts inside mesoporous silica in a yolk-shell architecture and were able to trap the hydrogens to increase the amine yield from 12% to 82%, with a 3-fold increase in selectivity without the need of any additive; we found the presence of mesopores in the silica shells to be essential to enable access to the cata-lytic sites and the yolk-shell gap size to be the key parameter influencing the reactivity of the catalytic system. To the best of our knowledge, this is the first report of a confined hydrogen borrowing reaction, an approach that can be extended to the other types of cascade reactions that produce labile intermediates.

As we strive to perform chemical transformations in a more sustainable fashion, inducing reactions through the absorption of mechanical energy has emerged as a highly successful approach. Due to the wide-ranging applications of gold nanoparticles (AuNPs), mechanochemical strategies have already been employed for their synthesis. However, we do not yet fully understand the underlying processes surrounding the gold salt reduction, nucleation and growth of AuNPs in the solid state. Herein, we present a mechanically activated aging synthesis of AuNPs, through a solid-state Turkevich reaction. Solid reactants are only briefly exposed to mechanical energy before being aged statically for a period of six weeks at different temperatures. The aging step grants a greater period of time to analyze the initial reduction and subsequent nanoparticle formation processes. During the aging period the reaction was monitored using a combination of X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy (DRS), powder X-ray diffraction (PXRD) and transmission electron microscopy (TEM) to gain meaningful insights into the solid-state formation of gold nanoparticles.

Hydrogenation and dehydrogenation reactions are one of the pillars of the chemical industry, with applications from bulk chemicals to pharmaceuticals manufacturing. The ability to selectively add hydrogen across double and (or) triple bonds is key in the chemist’s toolbox and the enabling component in the development of sustainable processes. Traditional solution-based approaches to these reactions are tainted by significant consumption of energy and production of solvent waste. This review highlights the development and applications of recently emerged solvent-free approaches to conduct the hydrogenation of organic molecules using mechanochemistry, i.e., chemical transformations induced or sustained by mechanical force. In particular, we will show mechanochemical techniques such as ball-milling enabled catalytic or stoichiometric metal-mediated hydrogenation and dehydrogenation reactions that are simple, fast, and conducted under significantly milder conditions compared with traditional solution routes. Importantly, we highlight the current challenges and opportunities in this field, while also identifying exciting cases in which mechanochemical hydrogenation strategies lead to new, unique targets and reactivity.

To unlock nature’s potential for functional biomaterials, many efforts have been devoted to isolating the nanocrystalline domains within the supramolecular structure of polysaccharides. Yet, low reactivity and yield in aqueous systems along with excessive solvent usage hinders its development. In this report, the first solvent-free pathway to access carboxylated chitin and cellulose nanocrystals with excellent mass balance is described, relying on a new method coined high humidity shaker-aging. The method involves a mild grinding of the polysaccharide with ammonium persulfate followed by an aging phase under high humidity and on a shaker plate. Insights into the mechanism were uncovered, which highlighted the unique role of high humidity to afford a gradual uptake of water by the material up to deliquescence when the reaction is complete. This process was then validated for direct synthesis of nanocrystals from biomass sources including crab and soft wood pulp.

Heteroatom-doped carbon nitride (CN) materials have shown much potential as metal-free photocatalysts for water splitting. Graphitic phosphorus-linked triazine network (g-PCN) materials are a unique class within this family of materials, but remain difficult to access due to long reaction times annealing at temperatures above 500 °C and often afford ill-understood structures. Here, we reveal a milder, lower temperature approach for the synthesis of catalytically active g-PCN materials through combining a room-temperature mechanochemical reaction of sodium phosphide and cyanuric chloride with brief (1 hour) annealing of the milled material at 300 °C. This rapid, low temperature procedure yields ordered g-PCN catalysts whose layered structure was determined through a combination of magic-angle spinning nuclear magnetic resonance (MAS NMR), X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (PXRD) and transmission electron microscopy (TEM). An excellent level of accuracy to simulated 31P MAS NMR signals and PXRD patterns were obtained for the structure of the synthesized layered phosphorus-linked triazine networks following dispersion-corrected density functional theory (DFT). The mechanochemically-generated g-PCN is a highly effective photocatalyst for the hydrogen evolution reaction, producing 122 µmol H2 h-1 g-1 under broad spectrum irradiation.

While a key reaction for oil upgrade, the hydrogenation of arenes substrates remains a challenging one, requiring the use of transition-metal catalysts and harsher reaction conditions than classic ...

Mechanochemistry by milling, grinding, extrusion or other types of shear and mechanical agitation has shown novel reactivity for a wide range of reactions, not seen in traditional solution-based environments. While the area has been extensively investigated and reviewed in the context of organic and solid-state supramolecular chemistry, less attention has been given to the recent advances in the context of inorganic transformations. Here we provide a perspective of inorganic mechanochemical reactions, focusing on transformations that are based on transfer of charged species: exchange of ions and electrons (redox reactions). These types of mechanochemical transformations typically lead to the formation of new nanoparticles and organometallic complexes. Herein, we provide an overview of mechanochemical reactivity that complements the recent developments in organic synthesis and catalysis.

In this report, chitin and chitosan nanocrystals were used as biomass-based supports for Pd nanoparticles (NPs) used as a heterogeneous catalyst for the Heck coupling reaction. By using a one-pot fabrication method, a Pd salt precursor was directly reduced and deposited onto these nanocrystal catalysts. Characterization of these nanocomposites showed disperse Pd NPs on the surfaces of the chitinous nanocrystals. Heck coupling model reactions revealed full product yield in relatively benign conditions, outcompeting the use of other catalysts supported on biomass-based nanomaterials, including cellulose nanocrystals. These initial results show the potential for using chitinous nanomaterials as effective catalyst supports in cross-coupling reactions.

The photocatalytic (PC) splitting of water into oxygen and hydrogen has attracted considerable attention in the past decade. Despite the promise of hydrogen gas as a new energy resource, the enviro...

Peroxymonosulfate (PMS)-based advanced oxidation processes generate highly reactive SO4•- and are promising for water treatment. In this study, we investigated the reaction mechanism of 6:2 fluorotelomer sulfonate (6:2 FTS) with Co2+-activated PMS. 6:2 FTS was simultaneously transformed to perfluoroalkyl carboxylic acids (C2-C7 PFCAs) of different chain lengths, with perfluorohexanoic acid (C6) as the predominant one. The mass balance of the intermediates and products versus the initially added 6:2 FTS was close to 100% over the reaction period. Using chemical scavenging methods, we identified that •OH, instead of SO4•-, was the oxidant initiating the reaction of 6:2 FTS. •OH was mainly produced from SO4•- reacting with H2O. Thus, the reactivity of 6:2 FTS was controlled by the factors affecting the production and scavenging of both SO4•- and •OH. Density functional theory calculations showed that •OH oxidizes 6:2 FTS by H-abstraction from ethyl carbons. This is the first study that demonstrates that •OH in Co2+-activated PMS can play a significant role in contaminant transformations. The results indicate that great caution should be taken when PMS or other agents that generate •OH are used for the treatment of water containing 6:2 FTS or its structural analogs.

Plasmonic polymeric nanoassemblies offer valuable opportunities in photoconversion applications. Localized surface plasmon mechanisms behind such nanoassemblies govern their functionalities under light illumination. However, an in-depth investigation at the single nanoparticle (NP) level is still challenging, especially when the buried interface is involved, due to the availability of suitable techniques. Here, we synthesized an anisotropic heterodimer composed of a self-assembled polymer vesicle (THPG) capped with a single gold NP, enabling an 8-fold enhancement in hydrogen generation compared to the nonplasmonic THPG vesicle. We explored the anisotropic heterodimer at the single particle level by employing advanced transmission electron microscopes, including one equipped with a femtosecond pulsed laser, which allows us to visualize the polarization- and frequency-dependent distribution of the enhanced electric near fields at the vicinity of Au cap and Au–polymer interface. These elaborated fundamental findings may guide designing new hybrid nanostructures tailored for plasmon-related applications.

Biomass is one of the promising alternatives to petroleum-derived materials and plays a major role in our fight against climate change by providing renewable sources of chemicals and materials. Owing to its chemical and structural complexity, the transformation of biomass into value-added products requires a profound understanding of its composition at different scales and innovative methods such as combining physical and chemical processes. In this context, the use of mechanochemistry in biomass valorization is currently growing owing to its potentials as an efficient, sustainable, and environmentally friendly approach. This review highlights the latest advances in the transformation of biomass (i. e., chitin, cellulose, hemicellulose, lignin, and starch) to functional materials using mechanochemical-assisted methods. We focused here on the methodology of biomass processing, influencing factors, and resulting properties with an emphasis on achieving functional materials rather than breaking down the biopolymer chains into smaller molecules. Opportunities and limitations associated this methodology were discussed accordingly for future directions.

ispartof: Acs Sustainable Chemistry & Engineering vol:9 issue:49 pages:16528-16530 status: published

Polymer-inorganic hybrid Janus nanoparticles (PI-JNPs) have attracted extensive attention due to their special structures and functions. However, achieving the synergistic enhancement of photochemical activity between polymer and inorganic moieties in PI-JNPs remains challenging. Herein, we report the construction of a novel Janus Au-porphyrin polymersome (J-AuPPS) heterostructure by a facile one-step photocatalytic synthesis. The near-field enhancement (NFE) effect between porphyrin polymersome (PPS) and Au nanoparticles in J-AuPPS is achieved to enhance its near-infrared (NIR) light absorption and electric/thermal field intensity at their interface, which improve the energy transfer and energetic charge carrier generation. Therefore, J-AuPPS shows a higher NIR-activated photothermal conversion efficiency (48.4%) and generates more singlet oxygen compared with non-Janus core-particle Au-PPS nanostructure (28.4%). As a result, J-AuPPS exhibits excellent dual-mode (photothermal/photodynamic) antibacterial and antibiofilm performance and thereby significantly enhances in vivo therapeutic effect on the implant-associated infection rat model. We believe this work will motivate the rational design of advanced hybrid Janus nanoparticles with the desirable NFE effect and further extend their biological applications. This article is protected by copyright. All rights reserved.

We demonstrate the unprecedented ability to induce hypergolic behavior, i.e. rapid and spontaneous ignition upon contact with an oxidizer, in non-hypergolic metal fuels by blending them with hypergolic metal-organic frameworks (HMOFs). Using magnesium, aluminum or zinc metal as the fuel, we demonstrate materials with ignition delays (IDs) below 50 ms, and calculated specific impulse (Isp) in the 220-250 s range. These parameters are comparable to those of toxic and carcinogenic hydrazine-based hypergols conventionally used in aerospace technologies, suggesting a route to develop cleaner, safer propulsion systems.

Amine N‐alkylation is a process involved in the production of a wide range of chemicals. Here we describe the synthesis of well‐defined (Ni0.5Cu0.5)Fe2O4 magnetic nanoparticles by plasma induction, and their successful application to amine N‐alkylation using alcohols as coupling agents through a borrowing hydrogen pathway. Plasma induction allows precise morphology and size control over nanoparticle synthesis, while allowing the one‐pot production of decagram quantities of material. Up to date, such nanoparticles have never been applied for organic reactions. By coupling high‐end characterization techniques with catalytic optimization, we showed that small Cu(0) satellite nanoparticles played an essential role in alcohol oxidation, whereas both Ni and Cu were required for the last step of the reaction. Using elemental mapping, we demonstrated that catalyst deactivation occurred through a leaching/re‐deposition mechanism of Cu and Ni. The reactions were conducted under microwave conditions, which exerted a positive effect on catalytic activity. Finally, the catalyst was active at low metal loadings (2 mol%) even on the gram‐scale, and affording unprecedented TON for this reaction catalyzed by Ni/Cu bimetallic systems (19).

Herein, we present a study of the impact of the jar and ball medium on the performance in the mechanochemical amorphization of chitin. We measured the crystallinity index of chitin after milling it in a vibration mill in an apparatus made of copper, aluminum, brass, tungsten carbide, zirconia, stainless steel, polytetrafluoroethylene (PTFE), or poly(methyl methacrylate) (PMMA). These materials offer a range of Vickers hardness values and the impact of these parameters is discussed. The role of the size and mass of the balls is also studied in the case of stainless steel. This study also highlights one of the major challenges during milling, which is contamination of the studied samples.

The study of catalysts activity at ultralow concentration is of prime importance for the development of more sustainable catalytic processes. In this work, we designed a mesoporous MCM-41 silica wi...

Phosphorylated polymers are versatile materials for a broad range of applications from flame-retardant coatings to bioactive scaffolds. Traditionally, they are synthesized in solution using corrosi...

Marine biomass waste is a remarkable source of functional molecules and materials. Yet material extraction, conversion and processing are often chemically intensive, preventing the widespread and clean use of these abundant resources for high-end applications. Moreover, current challenges in biomedicine call for the design of novel materials with better functional and mechanical properties. Herein, we present a novel chemical process to afford chitosan nanocrystals (ChsNCs), which uniquely combine a high degree of deacetylation, rod shape and high crystallinity for mechanical robustness. This method is a simple solid-state aging process starting from chitin nanocrystals (ChNCs) and requiring limited chemical and energetic input, which we have quantified using process mass intensity as the sustainability metric. This method, as well as a previously reported solution-based method, afforded a family of novel nanomaterials, which we used to form alginate hydrogels. The resulting materials are the first examples of ChsNC-based hydrogels and featured superior performances in terms of both rheological properties, as well as sustained drug release, as compared to previously reported chitosan/alginate systems. This work opens an avenue for functional soft materials using a green resource via a clean process.

Light emissive organics and inorganic nanoparticles are substance classes competing for applications in displays in the form of organic LEDs (OLEDs) and quantum LEDs (QLEDs), respectively. Upcoming substance classes (perovskites) and Q-OLED displays also contain novel nanomaterials and organics for these applications. However, the sustainability of these emissive substances is difficult to assess quickly and broadly because of their complexity, their inherently different structures, and their rapid evolution in the literature. We propose the use of an alternatives assessment to compare the hazard, cost, and performance of these competing substances, with a focus on replacing cadmium-containing quantum dots. The cost assessment highlights competitiveness of OLEDs because of their low amounts needed per display, but performance assessments do not identify a preferred alternative. The hazard results indicate there is no clear alternative either, with each novel nanomaterial or organic substance having different negative aspects. These results identify the need for a low-hazard high-performing alternative substance, and the assessment provides a framework for researchers to evaluate their own novel substances.

Cadmium-containing quantum dot nanoparticles (QDs) are integrated into electronic displays because of their ability to efficiently convert colors. There are conflicting accounts as to whether these particles present a hazard to the environment, as they have been studied either as (1) embedded QDs in display screen films or (2) as model QDs with small, hydrophilic ligands. We synthesized QDs featuring the core-shell structure and the thick polymer coating present in commercial devices, to probe their fate under low pH conditions. The role of dioxygen was also explored in this context. We also used liver cells to compare the toxicity of pristine QDs to those subjected to acid dissolution.