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1.
Food Chem ; 460(Pt 3): 140731, 2024 Aug 02.
Artigo em Inglês | MEDLINE | ID: mdl-39106757

RESUMO

17ß-E2 is used in animal growth regulation and agricultural fertilizer, and even ng L-1 mass concentration levels can show biological effects. In this work, Ag NPs was used as surface-enhanced Raman spectroscopy (SERS) source and WS2 was synthesized by a simple method to provide a uniform distribution platform for Ag NPs. The MIP was the shell, which can selectively enrich the target molecule, pull the distance between the target molecule and SERS source, and protect Ag NPs. A cyclable SERS substrate with high sensitivity for detecting 17ß-E2 in food was constructed. The optimized WS2/Ag@MIP as SERS substrate has the advantages of high Enhanced Factor (EF = 2.78 × 109), low detection limit (LOD = 0. 0958 pM), strong anti-interference ability, and good recycling performance. Moreover, the detection of 17ß-E2 in real samples still has good accuracy. This work provides a new possibility for the trace detection of 17ß-E2 in food.

2.
Int J Biol Macromol ; 278(Pt 3): 134933, 2024 Aug 22.
Artigo em Inglês | MEDLINE | ID: mdl-39173795

RESUMO

Thermosetting resins are widely used in high-tech applications for excellent mechanical robustness and chemical resistance. With increasing attention to the environmental and usage safety issues, it is necessary to develop bio-derived, recyclable, tough, and fire-retardant thermosetting resins. Herein, a high-performance, vanillin-based vitrimer (CIP1.0) was prepared. The CIP1.0 with 1.0 wt% phosphorus passes vertical burning (UL-94) V-0 rating with a limiting oxygen index (LOI) of 27.2%. The phosphorus-containing and Schiff base groups act synergistically in gas and condensed phases during combustion, endowing CIP1.0 with outstanding fire retardancy. The CIP1.0 shows excellent toughness with high elongation at break of 45.0% due to the π-π stacking of numerous rigid aromatic groups and appropriate cross-linking density. The highly symmetrical structure and low polarizability of CIP1.0 result in a low dielectric constant. The CIP1.0 exhibits superior antimicrobial properties. The CIP1.0 can be reprocessed by hot-pressing at 140 °C for 10 min. The non-destructive, closed-loop recycling of carbon fibers in the carbon fiber-reinforced CIP1.0 composite can be achieved under mild conditions due to the degradable Schiff base groups of CIP1.0. In this work, a bio-derived, tough, fire-retardant, low dielectric, and antimicrobial vitrimer is prepared to provide a rational strategy for the design of advanced environmentally friendly thermosetting resins.

3.
Environ Geochem Health ; 46(10): 401, 2024 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-39196434

RESUMO

A surface-modified mesoporous silica nanoparticle containing dimercaprol monomers was created utilizing the sol-gel condensation process, using tetraethyl orthosilicate (TEOS) as the silica source and poloxamer as the structure directing agent. To accomplish this synthesis, 3-glycidoxypropyl triethoxysilane (GPTS, 20 mol%) was incorporated into the silica walls during the sol-gel condensation process, along with TEOS. Furthermore, dimercaprol (DM) monomers were incorporated onto silica surfaces by a ring-opening reaction between GPTS epoxy groups, and dimercaprol hydroxyl groups. The prepared dimercaprol-modified silica adsorbent (MSN-DT NPs) material has been studied using a variety of instruments, including XRD, FT-IR, N2 adsorption-desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric (TG) analysis, and zeta potential analysis. The MSN-DT NPs material selectively adsorbs mercury ions, with a high adsorption amount of 125 mg/g and a removal capability of roughly ~ 90% from the original metal ion mixture comprising other competing metals such as Pb2+, Ni2+, Fe2+, and Zn2+. The MSN-DT NPs adsorbent shows recyclable qualities for up to five cycles when treated with an acidic aqueous solution (0.1 M HCl). As a result, the MSN-DT NPs adsorbent may be regenerated and reused up to five times without losing its adsorption effectiveness. The experimental findings showed that the MSN-DT NPs adsorbent may be employed to selectively remove hazardous Hg2+ ions from an aqueous solution.


Assuntos
Mercúrio , Nanopartículas , Dióxido de Silício , Poluentes Químicos da Água , Purificação da Água , Dióxido de Silício/química , Adsorção , Nanopartículas/química , Poluentes Químicos da Água/química , Mercúrio/química , Purificação da Água/métodos , Porosidade , Microscopia Eletrônica de Varredura , Microscopia Eletrônica de Transmissão , Difração de Raios X , Espectroscopia de Infravermelho com Transformada de Fourier
4.
Chempluschem ; : e202400111, 2024 Aug 26.
Artigo em Inglês | MEDLINE | ID: mdl-39187435

RESUMO

Nitroaromatic compounds (NACs) cause severe hazardous impacts on human health as well as on the environment. Therefore, there is dire need to develop a robust material to reduce the toxicity of these organic pollutants. In this regard, our group developed a series of porous MOF materials viz., Pdx@IRMOF-9 (x=2%, 5% and 10%) by loading different concentration of Pd(II) on IRMOF-9 and explored them towards reduction of different nitroaromatic compounds. Pd10%@IRMOF-9 showed ~30% greater efficiency for the reduction of 4-NP as compared to Pd2%@IRMOF-9. Pd10%@IRMOF-9 showed excellent reduction ability (>85%) towards 4-NP, 2-NP, 2-NA, 3-NA and 2,4-DNPH. The kinetic studies indicates that the reduction follows the pseudo-first-order kinetics. Moreover, the rate constant value for reduction of 3-NA was ~9 times higher than that of 2-NP. Based on the kinetic parameters, the t1/2 values for all the nitroaromatics have been calculated. The kinetic parameters, Km and Vmax have been calculated from double reciprocal Lineweaver-Burk plot and found 65.984 µM and 116 x10-6 Mmin-1 respectively. Pd10%@IRMOF-9 showed excellent recyclability towards the reduction of 4-NP for few consecutive cycles without any remarkable loss in its activity. Thus, highly efficient, porous and robust material for reduction of nitroaromatic compounds in aqueous media have been demonstrated.

5.
Environ Sci Pollut Res Int ; 31(35): 47475-47504, 2024 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-39017873

RESUMO

The production of renewable materials from alternative sources is becoming increasingly important to reduce the detrimental environmental effects of their non-renewable counterparts and natural resources, while making them more economical and sustainable. Chemical surfactants, which are highly toxic and non-biodegradable, are used in a wide range of industrial and environmental applications harming humans, animals, plants, and other entities. Chemical surfactants can be substituted with biosurfactants (BS), which are produced by microorganisms like bacteria, fungi, and yeast. They have excellent emulsifying, foaming, and dispersing properties, as well as excellent biodegradability, lower toxicity, and the ability to remain stable under severe conditions, making them useful for a variety of industrial and environmental applications. Despite these advantages, BS derived from conventional resources and precursors (such as edible oils and carbohydrates) are expensive, limiting large-scale production of BS. In addition, the use of unconventional substrates such as agro-industrial wastes lowers the BS productivity and drives up production costs. However, overcoming the barriers to commercial-scale production is critical to the widespread adoption of these products. Overcoming these challenges would not only promote the use of environmentally friendly surfactants but also contribute to sustainable waste management and reduce dependence on non-renewable resources. This study explores the efficient use of wastes and other low-cost substrates to produce glycolipids BS, identifies efficient substrates for commercial production, and recommends strategies to improve productivity and use BS in environmental remediation.


Assuntos
Recuperação e Remediação Ambiental , Glicolipídeos , Tensoativos , Tensoativos/química , Recuperação e Remediação Ambiental/métodos , Biodegradação Ambiental
6.
Environ Geochem Health ; 46(8): 283, 2024 Jul 04.
Artigo em Inglês | MEDLINE | ID: mdl-38963423

RESUMO

Phosphorus (P) scarcity and eutrophication have triggered the development of new materials for P recovery. In this work, a novel magnetic calcium-rich biochar nanocomposite (MCRB) was prepared through co-precipitation of crab shell derived biochar, Fe2+ and Fe3+. Characteristics of the material demonstrated that the MCRB was rich in calcite and that the Fe3O4 NPs with a diameter range of 18-22 nanometers were uniformly adhered on the biochar surface by strong ether linking (C-O-Fe). Batch tests demonstrated that the removal of P was pH dependent with an optimal pH of 3-7. The MCRB exhibited a superior P removal performance, with a maximum removal capacity of 105.6 mg g-1, which was even higher than the majority lanthanum containing compounds. Study of the removal mechanisms revealed that the P removal by MCRB involved the formation of hydroxyapatite (HAP-Ca5(PO4)3OH), electrostatic attraction and ligand exchange. The recyclability test demonstrated that a certain level (approximately 60%) was still maintained even after the six adsorption-desorption process, suggesting that MCRB is a promising material for P removal from wastewater.


Assuntos
Carvão Vegetal , Nanocompostos , Fosfatos , Poluentes Químicos da Água , Carvão Vegetal/química , Nanocompostos/química , Poluentes Químicos da Água/química , Fosfatos/química , Adsorção , Concentração de Íons de Hidrogênio , Cálcio/química , Purificação da Água/métodos , Águas Residuárias/química
7.
Chempluschem ; : e202400341, 2024 Jul 08.
Artigo em Inglês | MEDLINE | ID: mdl-38975963

RESUMO

Dynamic covalent chemistry is a promising strategy for developing recyclable thermosets and their carbon fiber reinforced composites, in line with the goal of green and sustainable development. However, a significant challenge lies in balancing the dynamic reversibility and the desired service performances, such as thermal, mechanical properties, and flame retardancy. It has hindered the broader application of dynamic materials beyond the initial proof of concept. This concept provides an overview of the current state of research on phosphorus-containing covalent adaptable networks (CANs), highlighting key designing and regulating principles for tailoring comprehensive properties including flame retardancy, mechanical and thermal properties, as well as dynamic behaviours such as malleability, reprocessability and degradability. Finally, new frontiers and opportunities in developing high-performance sustainable CANs-based thermosets and their carbon fiber composites for structural engineering applications are prospected.

8.
Spectrochim Acta A Mol Biomol Spectrosc ; 322: 124847, 2024 Dec 05.
Artigo em Inglês | MEDLINE | ID: mdl-39032227

RESUMO

Fluorescent turn-on receptors are extensively employed for the detection of Zn ions contamination in the environment due to its simplicity, convenience and portability. However, developing highly sensitive and cell-imageable fluorescent turn-on probe for the recognition of Zn ions in living organisms remains a significant challenge. Herein, we have successfully synthesized a novel Schiff base probe (H2L) with a significant fluorescence turn-on response (Zn ions) by one-step synthetic method. In this work, H2L exhibited high sensitivity to Zn2+ ions upon interaction with various common metal ions in HEPES buffer solution. Its detection limit is 1.87 × 10-7 M, which is lower than the requirement of Environmental Protection Agency (EPA) and World Health Organization (WHO) guidelines. The fluorescence titration and Job's plot analysis suggested a 1:1 binding ratio between the probe and Zn ion, and the single-crystal structures obtained further confirmed this inference. In addition, the fluorescent sensor demonstrated recyclability, maintaining its fluorescence intensity for up to 6 cycles without significant decrease, which holds promise for future investigations on reversible fluorescent chemosensors. Notably, fluorescence imaging experiments demonstrated that H2L could be successfully used for the detection of Zn2+ in live cells.


Assuntos
Corantes Fluorescentes , Bases de Schiff , Espectrometria de Fluorescência , Zinco , Bases de Schiff/química , Bases de Schiff/síntese química , Zinco/análise , Zinco/química , Corantes Fluorescentes/química , Corantes Fluorescentes/síntese química , Humanos , Espectrometria de Fluorescência/métodos , Limite de Detecção , Células HeLa , Íons , Imagem Óptica
9.
Angew Chem Int Ed Engl ; : e202408969, 2024 Jul 20.
Artigo em Inglês | MEDLINE | ID: mdl-39032118

RESUMO

Due to their remarkable features of lightweight, high strength, stiffness, high-temperature resistance, and corrosion resistance, carbon fiber reinforced polymers (CFRPs) are extensively used in sports equipment, vehicles, aircraft, windmill blades, and other sectors. The urging need to develop a resource-saving and environmentally responsible society requires the recycling of CFRPs. Traditional CFRPs, on the other hand, are difficult to recycle due to the permanent covalent crosslinking of polymer matrices. The combination of covalent adaptable networks (CANs) with carbon fibers (CFs) marks a new development path for closed-loop recyclable CFRPs and polymer resins. In this review, we summarize the most recent developments of closed-loop recyclable CFRPs from the unique paradigm of dynamic crosslinking polymers, CANs. These sophisticated materials with diverse functions, oriented towards CFs recycling and resin sustainability, are further categorized into several active domains of dynamic covalent bonds, including ester bonds, imine bonds, disulfide bonds, boronic ester bonds, and acetal linkages, etc. Finally, the possible strategies for the future design of recyclable CFPRs by combining dynamic covalent chemistry innovation with materials interface science are proposed.

10.
ChemSusChem ; : e202400899, 2024 Jul 16.
Artigo em Inglês | MEDLINE | ID: mdl-39010791

RESUMO

The selective conversion of biomass fermentation derived from an acetone-butanol-ethanol (ABE) mixture into high-value biofuels is of paramount importance for industrial applications. However, challenges persist in effectively controlling the selectivity of long carbon chain ketones in elevated ABE conversion. In this research, a Ca-doped Ni-CaO-SiO2 catalyst was designed and employed to achieve a remarkable conversion of 89.9% into ketone products from the extracted ABE mixture. The selectivity for C8+ ketones reaches 41.8%, demonstrating exceptional performance. The reversible phase transition between Ca2SiO4 and CaCO3 enhances the recyclability, thereby improving the sustainability of the process. Additionally, the trace intermediate 3-hepten-2-one was successfully detected using two-dimensional GC×GC-MS, elucidating the conversion pathway in the catalytic upgrading of the ABE mixture. This finding offers a potential route for the efficient utilization of biomass and the highly selective production of value-added chemicals.

11.
ChemSusChem ; : e202400888, 2024 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-39078804

RESUMO

The oxidation of representative bio-based benzyl-type alcohols has been successfully carried out in a multiphase (MP) system comprised of three mutually immiscible liquid components as water, isooctane, and a hydrophobic ionic liquid as methyltrioctylammonium chloride ([N8881][Cl]), a heterogeneous catalyst (either ad-hoc synthesized carbon-supported Mo or a commercial 5% Ru/C), and air as an oxidant. The MP-reaction proceeded as an interfacial process with Mo/C or Ru/C perfectly segregated in the ionic liquid phase and the reactant(s)/products(s) dissolved in the aqueous solution. This environment proved excellent to convert quantitatively benzyl alcohols into the corresponding aldehydes with a selectivity up to 99%, without overoxidation to carboxylic acids. The nature of the catalyst, however, affected the operating conditions with Ru/C active at a lower T and t (130 °C, 4-6 h) compared to Mo/C (150 °C, 24 h). The phase confinement was advantageous also to facilitate the products isolation and the recycle of the catalyst. Notably, in the Mo/C-catalyzed oxidation of benzyl alcohol, benzaldehyde was achieved with unaltered selectivity (>99%) at complete conversion, for 5 subsequent reactions through a semicontinuous procedure in which the catalyst was reused in-situ, without ever removing it from the reactor or treating it in any way.

12.
Environ Geochem Health ; 46(9): 357, 2024 Jul 31.
Artigo em Inglês | MEDLINE | ID: mdl-39083123

RESUMO

Rapid growth in the industry has released large quantities of contaminants, particularly metal discharges into the environment. Heavy metal poisoning in water bodies has become a major problem due to its toxicity to living organisms. In this study, we developed a 3-chloropropyl triethoxysilane incorporated mesoporous silica nanoparticle (SBA-15) based adsorbent utilizing the sol-gel process and Pluronic 123 (P123) as a structure-directing surfactant. Furthermore, the produced SBA-15 NPs were functionalized with bis(2-aminoethyl)amine (BDA) using the surface grafting approach. The physical and chemical properties of the prepared SBA-15@BDA NPs were determined using a variety of instruments, including small-angle X-ray diffraction (SAXS), Fourier-transform infrared (FTIR), scanning electron microscope (SEM), N2 adsorption-desorption, thermogravimetric, particle size distribution, and zeta potential analysis. The MSN has a large surface area of up to 574 m2/g, a pore volume of 0.57 cm3/g, and a well-ordered mesoporous nanostructure with an average pore size of 3.6 nm. The produced SBA-15@BDA NPs were used to adsorb selectively to lead (Pd2+) ions from an aqueous solution. The adsorption study was performed under various conditions, including the influence of solution pH, adsorbent dose, adsorption kinetics, adsorption selectivity in the presence of competing metal ions, and reusability. The results of the kinetic study demonstrated that SBA-15@BDA NPs absorb selectively Pb2+ ions via chemisorption. The SBA-15@BDA NPs show Pb2+ ions with a maximum adsorption capacity of ~ 88% and an adsorbed quantity of approximately ~ 112 mg/g from the studied aqueous solution. The adsorption mechanism relies on coordination bonding between Pb2+ ions and surface-functionalized amine groups on SBA-15@BDA NPs. Furthermore, the proposed SBA-15@BDA NPs adsorbent demonstrated excellent reusability over five cycles without significantly reducing adsorption performance. As a consequence, SBA-15@BDA NPs might serve as an effective adsorbent for the selective removal of Pb2+ ions from aqueous effluent.


Assuntos
Chumbo , Dióxido de Silício , Águas Residuárias , Poluentes Químicos da Água , Dióxido de Silício/química , Adsorção , Chumbo/química , Poluentes Químicos da Água/química , Águas Residuárias/química , Porosidade , Purificação da Água/métodos , Nanopartículas/química , Difração de Raios X , Espectroscopia de Infravermelho com Transformada de Fourier , Microscopia Eletrônica de Varredura
13.
Angew Chem Int Ed Engl ; : e202410127, 2024 Jul 18.
Artigo em Inglês | MEDLINE | ID: mdl-39030819

RESUMO

Polyrotaxanes (PRs) have attracted significant research attention due to their unique topological structures and high degrees of conformational freedom. Herein, we take advantage of an oligo[2]rotaxane to  construct a novel class of dynamically cross-linked rotaxane network (DCRN) mediated by metal-coordination. The oligo[2]rotaxane skeleton offers several distinct advantages: In addition to retaining the merits of traditional polymer backbones, the ordered intramolecular motion of the [2]rotaxane motifs introduced dangling chains into the network, thereby enhancing the stretchability of the DCRN. Additionally, the dissociation of host‒guest recognition and subsequent sliding motion, along with the breakage of metal-coordination interactions, represented an integrated energy dissipation pathway to enhance mechanical properties. Moreover, the resulting DCRN demonstrated responsiveness to multiple stimuli and displayed exceptional self-healing capabilities in a gel state. Upon exposure to PPh3, which induced network deconstruction by breaking the coordinated cross-linking points, the oligo[2]rotaxane could be recovered, showcasing good recyclability. These findings demonstrate the untapped potential of the oligo[2]rotaxane as a polymer skeleton to develop DCRN and open the door to extend their advanced applications in intelligent mechanically interlocked materials.

14.
Environ Res ; 260: 119610, 2024 Jul 14.
Artigo em Inglês | MEDLINE | ID: mdl-39004393

RESUMO

Photocatalysis has been widely used as one of the most promising approaches to remove various pollutants in liquid or gas phases during the last decade. The main emphasis of the study is on the synergy of vacancy engineering and heterojunction formation, two widely used modifying approaches, to significantly alter photocatalytic performance. The vacancy-induced Ag2CO3/BiOBr/WO3-x heterojunction system has been fabricated using a co-precipitation technique to efficiently abate methylene blue (MB) dye and doxycycline (DC) antibiotic. The as-fabricated Ag2CO3/BiOBr/WO3-x heterojunction system displayed improved optoelectronic characteristic features because of the rational combination of dual charge transferal route and defect modulation. The Ag2CO3/BiOBr/WO3-x system possessed 97% and 74% photodegradation efficacy for MB and DC, respectively, with better charge isolation and migration efficacy. The ternary photocatalyst possessed a multi-fold increase in the reaction rate for both MB and DC, i.e., 0.021 and 0.0078 min-1, respectively, compared to pristine counterparts. Additionally, more insightful deductions about the photodegradation routes were made possible by the structural investigations of MB and DC using density functional theory (DFT) simulations. This study advances the understanding of the mechanisms forming visible light active dual Z-scheme heterojunction for effective environmental remediation.

15.
Waste Manag ; 186: 293-306, 2024 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-38954921

RESUMO

The compositions of Dutch lightweight packaging waste (LWP) and sorted products named "PET (Polyethylene terephthalate) trays" have been determined on object level. Additionally, the PET trays from both waste types were sorted in 16 categories representing their packaging use and material build-up. The material composition of at least 10 representative trays from each category was determined with chemical and thermal analysis, based on which the average material composition per category was established. Based on this data the average material composition of sorted PET tray products was approximated. The recyclability of the various categories of PET trays was assessed based on their material build-up. The most ubiquitous PET trays in Dutch LWP and sorted products were only found to be suitable to produce opaque recycled PET with mechanical recycling processes. Whereas only some more uncommon PET trays can be used to produce transparent recycled PET with mechanical recycling processes. Depolymerisation is deemed to be a more appropriate recycling process that will allow the production of transparent food-grade recycled PET.


Assuntos
Polietilenotereftalatos , Embalagem de Produtos , Reciclagem , Reciclagem/métodos , Gerenciamento de Resíduos/métodos , Países Baixos , Resíduos , Eliminação de Resíduos/métodos
16.
Adv Mater ; : e2407170, 2024 Jul 08.
Artigo em Inglês | MEDLINE | ID: mdl-38978419

RESUMO

Ubiquitous anti-counterfeiting materials with a rapidly rising annual consumption (over 1010 m2) can pose a serious environmental burden. Biobased cellulosic materials with birefringence offer attractive sustainable alternatives, but their scalable solvent-free processing remain challenging. Here, a dynamic chemical modification strategy is proposed for multi-modal melt-processing of birefringent cellulosic materials for eco-friendly anti-counterfeiting. Relying on the thermal-activated dynamic covalent-locking of the spatial topological structure of preferred oriented cellulose, the strategy balances the contradiction between the strong confinement of long-range ordered structures and the molecular motility required for entropically-driven reconstruction. Equipped with customizable processing forms including mold-pressing, spinning, direct-ink-writing, and blade-coating, the materials exhibit a wide color gamut, self-healing efficiency (94.5%), recyclability, and biodegradability. Moreover, the diversified flexible elements facilitate scalable fabrication and compatibility with universal processing techniques, thereby enabling versatile and programmable anti-counterfeiting. The strategy is expected to provide references for multi-modal melt-processing of cellulose and promote sustainable innovation in the anti-counterfeiting industry.

17.
Chemistry ; : e202401728, 2024 Jun 18.
Artigo em Inglês | MEDLINE | ID: mdl-38888459

RESUMO

Transitioning towards a circular economy, extensive research has focused on dynamic covalent bonds (DCBs) to pave the way for more sustainable materials. These bonds enable debonding and rebonding on demand, as well as facilitating end-of-life recycling. Acylhydrazone/hydrazone chemistry offers a material with high stability under neutral and basic conditions making it a promising candidate for materials research, though the material is susceptible to acid degradation. However, this degradation under acidic conditions can be exploited, making it widely applicable in self-healing and biomedical fields, with potential for reprocessing and recycling. This review highlights studies exploring the reversibility of acylhydrazone/hydrazone bonds in various polymers, altering their properties, and utilizing them in applications such as self-healing, reprocessing, and recycling. The review also focuses on how the mechanical properties are affected by the presence of dynamic linkages, and methods to improve the mechanical performance.

18.
Macromol Rapid Commun ; : e2400330, 2024 Jun 25.
Artigo em Inglês | MEDLINE | ID: mdl-38924588

RESUMO

Poly(thiourethane)-based covalent adaptable networks are synthesized by reacting a trimer of hexamethylene diisocyanate (Desmodur N3300) containing isocyanurate groups in its structure with 1,6-hexanedithiol. The catalysts evaluated for this process include dibutyltin dilaurate (DBTDL), lanthanum triflate (La(OTf)3), and a thermal precursor of 1,8-diazabicyclo[5.4.0]undec-7-ene (BGDBU). The use of DBTDL results in the initiation of curing upon mixing, while the other two catalysts exhibit a latency period in the reactive mixture, with curing starting at about 90 °C. Notably, the use of the lanthanum salt produces an additional minor exothermic reaction at 80 °C. This phenomenon corresponds to the trimerization of isocyanates rending isocyanurates, leaving a portion of unreacted thiols. Materials prepared with BGDBU or La(OTf)3 present shorter relaxation times than those prepared with DBTDL. Nevertheless, the materials containing the lanthanum salt do not reach complete relaxation, likely due to the reinforcement of the permanent network through increased isocyanurate content. The formation of isocyanurates produces a stoichiometric imbalance, leaving unreacted thiols. This transforms the exchange process into a dual mechanism involving a dissociative process of thiourethanes to isocyanate and thiol, along with an interchange through thiol attacking the thiourethane group. The materials exhibit good recyclability and self-healing characteristics.

19.
Chemistry ; 30(44): e202400242, 2024 Aug 06.
Artigo em Inglês | MEDLINE | ID: mdl-38805006

RESUMO

Singlet oxygen is a powerful oxidant used in various applications, such as organic synthesis, medicine, and environmental remediation. Organic and inorganic photosensitizers are commonly used to generate this reactive species through energy transfer with the triplet ground state of oxygen. We describe here a series of novel benzophenazine derivatives as a promising class of photosensitizers for singlet oxygen photosensitization. In this study, we investigated the structure-activity relationship of these benzophenazine derivatives. Akin to a molecular compass, the southern fragment was first functionalized with either aromatic tertiary amines, alkyl tertiary amines, aromatic sulfur groups, alkyl sulfur groups, or cyclic ethers. Enhanced photophysical properties (in terms of triplet excited-state lifetime, absorption wavelength, triplet state energy, and O2 quenching capabilities) were obtained with cyclic ether and sulfur groups. Conversely, the presence of an amine moiety was detrimental to the photocatalysts. The western and northern fragments were also investigated and slightly undesirable to negligible changes in photophysical properties were observed. The most promising candidate was then immobilized on silica nanoparticles and its photoactivity was evaluated in the citronellol photooxidation reaction. A high NMR yield of 97 % in desired product was obtained, with only a slight decrease over several recycling runs (85 % in the fourth run). These results provide insights into the design of efficient photosensitizers for singlet oxygen generation and the development of heterogeneous systems.

20.
Macromol Rapid Commun ; : e2400239, 2024 May 25.
Artigo em Inglês | MEDLINE | ID: mdl-38794989

RESUMO

Polymeric foams derived from bio-based resources and capable of self-healing and recycling ability are of great demand to fulfill various applications and address environmental concerns related to accumulation of plastic wastes. In this article, a set of polyester-based covalent adaptable biofoams (CABs) synthesized from carbohydrates and other bio-derived precursors under catalyst free conditions to offer a sustainable alternative to conventional toxic isocyanate-based polyurethane foams is reported. The dynamic ß-keto carboxylate linkages present in these biofoams impart self-healing ability and recyclability to these samples. These CABs display adequate tensile properties especially compressive strength (≤123 MPa) and hysteresis behavior. The CABs swiftly stress relax at 150 °C and are reprocessable under similar temperature conditions. These biofoams have displayed potential for use as attachment on solar photovoltaics to augment the output efficiency. These CABs with limited swellability in polar protic solvents and adequate mechanical resilience are suitable for other commodity applications.

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