Foldamer Structuring by Covalently Bound Macromolecules

We used fluorescence and electronic absorption spectroscopy to study the molecular weight dependence of macromolecule-induced folding in a chain-centered meta-phenylene ethynylene (mPE) oligomer. Analogous to the ability of intrinsically unstructured proteins (IUPs) to induce folding of globular proteins in cellular environments, we show that macromolecules attached to both ends of an mPE dodecamer induce the foldamer to collapse into a presumed helical conformation. The collapse is especially prominent once the macromolecule segments become larger than ca. 50 kDa. For sufficiently large macromolecules, the conformational structuring occurs even in solvents that normally denature the foldamer. Based on these findings, chain-centered foldamers might find use as models to investigate the fundamental macromolecular physics of IUPs

Oxidative C–H/C–H Annulation of Imidazopyridines and Indazoles through Rhodium-Catalyzed Vinylene Transfer

Transition-metal-catalyzed C–H activation followed by oxidative annulation with alkynes has been an efficient synthetic tool for the assembly of various polyaromatic scaffolds. Despite the substantial progress in this field, it is still a significant challenge to achieve the synthesis of nonsubstituted vinylene-fused compounds. In this contribution, we report a Rh-catalyzed C–H/C–H vinylene cyclization adopting vinylene carbonate as a “vinylene transfer” agent. This protocol achieves the direct annulative π-extension of imidazole- and pyrazole-fused aromatics

Rhodium-Catalyzed Annulative Coupling Using Vinylene Carbonate as an Oxidizing Acetylene Surrogate

Transition-metal-catalyzed C–H activation and subsequent oxidative cyclization with alkynes has been a powerful tool for the synthesis of polycyclic aromatic compounds. Despite the substantial progress in this field, it is still a significant challenge to establish synthetic methodologies for the construction of nonsubstituted vinylene-fused aromatics. We herein report a Rh­(III)-catalyzed C–H/N–H annulation with vinylene carbonate as an acetylene surrogate. Vinylene carbonate also acts as an internal oxidant to regenerate the Rh­(III) species in situ; thus, no external oxidant is required to trigger the oxidative annulation. This protocol is applicable to the direct synthesis of various N-heteroaromatics

Accordion-like Multilayered Two-Dimensional Ti₃C₂T_<i>x</i> MXenes for Catalytic Elimination of Organic Dyes from Wastewater <i>via</i> the Fenton Reaction

Two-dimensional (2D) MXenes have attracted tremendous research interest due to their layered structure and exceptional properties. Herein, we have synthesized accordion-like multilayered titanium carbide MXenes (m-Ti3C2Tx) via a single-step HF etching method from titanium aluminum carbide (Ti3AlC2). We demonstrate that the as-grown m-Ti3C2Tx acts as an efficient catalyst for dye degradation through a Fenton reaction in water without requiring any heterostructure due to the presence of a large amount of low-valence Ti states (Ti2+ and Ti3+). Post-growth annealing studies establish the critical roles of Ti2+ and Ti3+ species of m-Ti3C2Tx in dye degradation. Our quantitative analysis reveals a direct correlation between the catalytic efficiency of m-Ti3C2Tx MXene and its Ti2+ content. Under optimum experimental conditions, the degradation efficiency of 100% was achieved from 50 mL of 20 μM concentration methylene blue (MB) solution within 24 min without the need for light illumination. The effect of MB concentration and pH of solutions on the degradation efficiency was investigated, and excellent degradation efficiency was found in acidic as well as basic media, which is significant. Furthermore, the free radical scavenging test indicates that •OH radicals are the main active species involved in this degradation process. We also explored the effect of the nature of dyes on the catalytic degradation efficiency, which reveals that the cationic dye (e.g., rhodamine B) has much higher degradation efficiency than the anionic dye (e.g., methyl orange). This work paves the way for the direct use of 2D MXenes for efficient catalysis without requiring any heterostructure or light illumination, and it provides significant insights for the practical application of m-Ti3C2Tx for polluted water treatment through an advanced oxidation process

Rhodium-Catalyzed Annulative Coupling Using Vinylene Carbonate as an Oxidizing Acetylene Surrogate

Transition-metal-catalyzed C–H activation and subsequent oxidative cyclization with alkynes has been a powerful tool for the synthesis of polycyclic aromatic compounds. Despite the substantial progress in this field, it is still a significant challenge to establish synthetic methodologies for the construction of nonsubstituted vinylene-fused aromatics. We herein report a Rh­(III)-catalyzed C–H/N–H annulation with vinylene carbonate as an acetylene surrogate. Vinylene carbonate also acts as an internal oxidant to regenerate the Rh­(III) species in situ; thus, no external oxidant is required to trigger the oxidative annulation. This protocol is applicable to the direct synthesis of various N-heteroaromatics

Rhodium-Catalyzed Annulative Coupling Using Vinylene Carbonate as an Oxidizing Acetylene Surrogate

Transition-metal-catalyzed C–H activation and subsequent oxidative cyclization with alkynes has been a powerful tool for the synthesis of polycyclic aromatic compounds. Despite the substantial progress in this field, it is still a significant challenge to establish synthetic methodologies for the construction of nonsubstituted vinylene-fused aromatics. We herein report a Rh­(III)-catalyzed C–H/N–H annulation with vinylene carbonate as an acetylene surrogate. Vinylene carbonate also acts as an internal oxidant to regenerate the Rh­(III) species in situ; thus, no external oxidant is required to trigger the oxidative annulation. This protocol is applicable to the direct synthesis of various N-heteroaromatics

Stoichiometric Control of Multiple Different Tectons in Coordination-Driven Self-Assembly: Preparation of Fused Metallacyclic Polygons

Stoichiometric Control of Multiple Different Tectons in Coordination-Driven Self-Assembly: Preparation of Fused Metallacyclic Polygon

2D MXene Electrode-Enabled High-Performance Broadband Photodetector Based on a CVD-Grown 2D Bi₂Se₃ Ultrathin Film on Silicon

Topological insulators, such as Bi2Se3, show great promise in the quest for materials with exceptional optoelectronic capabilities in the visible to mid-infrared range due to their unique Dirac-like surface states with a small bulk band gap and broadband light absorption. Here, we report a low-temperature chemical vapor deposition (CVD) of a highly crystalline Bi2Se3 ultrathin film on a Si substrate, and the Si/Bi2Se3 heterojunction shows a very broadband absorption in the range of 300–2000 nm. A Si/Bi2Se3 heterostructure photodetector with two-dimensional MXene electrodes was constructed for the first time. The MXene electrode-enabled photodetector exhibits a truly broadband light detection in the range of 300–1550 nm and a very fast response of a few microseconds (rise time of 19.7 μs and fall time of 35.2 μs). The device demonstrates a high responsivity of 6.96 A/W, a high detectivity of 6.31 × 1012 Jones, a large linear dynamic range of 92.93 dB, and an excellent on/off ratio of 1.9 × 104 at 808 nm. It also exhibits self-biased (0 V) photodetection with a reasonably high responsivity of 24.7 mA/W and excellent detectivity of 4.16 × 1011 Jones under illumination. The highest responsivity and detectivity of the device are found to be 7.56 A/W and 6.85 × 1012 Jones, respectively, at 980 nm. The exceptional crystallinity of the Bi2Se3 film characterized by superior crystal quality and low defect density at the Si/Bi2Se3 interface, along with the presence of a strong built-in electric field, contributes to the observed superior performance of the heterojunction photodetectors. Additionally, the synthesis and functionalization of Ti3C2Tx MXene allow for the preparation of high-quality electrodes by a simple spin-casting process at a low cost. The van der Waals MXene–Bi2Se3 interface effectively reduces the dark current and enhances the collection of photon-excited carriers due to the low density of chemical disorders and negligible defects

Additional file 1 of Plastisphere community assemblage of aquatic environment: plastic-microbe interaction, role in degradation and characterization technologies

Additional file 1: Table S1. Global scenario of microplastic abundance on major aquatic bodies. Table S2. Potential microbial consortia associated with plastic biodegradation. Fig. S1. Common radical reactions in non-hydrolyzable polymers [269]. A The auto-oxidation process involves initiation by light and heat, followed by propagation and termination of a reaction which is influenced by the physical properties of the polymer. B Intramolecular and C Intermolecular hydrogen transfer reaction in polymer occurs through the abstraction and exchange of hydrogen atoms. Fig. S2. Polyethylene (PE), polypropylene (PP), and polyvinylchloride (PVC) are known to consist of similar carbon-carbon backbone chains. Pyrolysis (in the absence of air) is an effective depolymerization method to convert them to the respective low molecular weight aliphatic hydrocarbons [270]. According to the reports [118, 271, 272], the pyrolytic hydrocarbon products of PE are degraded through a terminal oxidation mechanism which is analogous to the n-alkane degradation pathway facilitated by microbes. Fig. S3. Polystyrene (PS) is broken down to its aromatic monomer styrene through pyrolysis [273] and according to O’Leary et al., (2002) [274] several microbes utilize it as a carbon source with the help of two different catabolic pathways. In the first one, which is the direct aromatic ring cleavage pathway, styrene dioxygenase (SDO) hydroxylates the aromatic ring of styrene to styrene cis-glycol. Ultimately it will generate β-D-Hydroxybutyryl-CoA by PhaB (an acetoacetyl-CoA reductase) or can be converted to PHA by PhaC (known as a PHA synthase) [275]. Another styrene metabolism pathway encompasses oxidation of its vinyl side-chain forming polyhydroxyalkanoate (PHA) as an end product

Self-Assembly of Three-Dimensional M₃L₂ Cages via a New Flexible Organometallic Clip

The simple combination of tritopic pyridine donor linkers with a new flexible acceptor “clip” in a 2:3 stoichiometric ratio generates three-dimensional M3L2 cages which possess large cavities in essentially quantitative yields