Producing Pyridines via Thermocatalytic Conversion and Ammonization of Waste Polylactic Acid over Zeolites

In this study, polylactic acid served as raw material to produce fine chemicals (pyridines) via a thermocatalytic conversion and ammonization (TCC-A) process. Ammonia was employed as not only carrier gas but also a reactant in this process. The thermal decomposition behavior of PLA under N₂ or NH₃ atmosphere was investigated. Different catalysts, including MCM-41, β-zeolite, ZSM-5 (Si/Al = 50) and HZSM-5 with different Si/Al ratios (Si/Al = 25, 50, 80) were also screened. Reaction temperature and residence time, which may affect the pyridines production, were investigated systematically. It was verified that all the investigated factors, including catalyst structure, catalyst acid amounts, reaction temperature, and residence time, influenced the PLA conversion and the pyridines production. The highest pyridines yield, 24.8%, was achieved by using HZSM-5 (Si/Al = 25) at around 500 °C. The catalyst regeneration tests were carried out. It demonstrated that the catalyst was stable after five regenerations and the catalytic activity did not change significantly. A possible reaction pathway from PLA to pyridines was also proposed. PLA initially thermally decomposed to form lactic acid and some byproducts such as acetaldehyde, acetone, etc., and then lactic acid, the mixture of acetaldehyde and acetone, or other byproducts reacted with ammonia to form imines and finally underwent complicated reactions to form pyridines

Selective Conversion of Furfural to Cyclopentanone with CuZnAl Catalysts

A new catalytic system was developed for the selective conversion of biomass-derived furfural to cyclopentanone in aqueous solution. CuZnAl catalysts with different Cu/Zn molar ratios (0.5, 1, 2, and 3) and calcination temperatures (350, 500, and 700 °C) were investigated, and the CuZnAl-500–0.5 catalyst (Cu/Zn = 0.5, calcined at 500 °C) showed a remarkable catalytic performance in the reaction. A 62% yield of cyclopentanone was obtained at the optimized conditions (150 °C, 4 MPa H₂, 6 h), and the TOF was 9.4 h^–1. The catalysts were characterized by nitrogen adsorption, XRD, TEM, N₂O titration, ICP, XPS, and a carbon–sulfur analyzer. The factors that influenced the activity of catalysts were also investigated. Additionally, the CuZnAl-500–0.5 was recycled five times and maintained good activity and stability. Hence, the current work presents a new and efficient catalytic system for the conversion of furfural to cyclopentanone. The low-cost nature of the CuZnAl makes it a potential catalyst for the production of cyclopentanone in industry

Synthesis and Assessment of Peptide Gd–DOTA Conjugates Targeting Extradomain B Fibronectin for Magnetic Resonance Molecular Imaging of Prostate Cancer

Contrast enhanced MRI is commonly used in imaging and treatment planning of prostate cancer. However, no tumor targeting contrast agent is commercially available for accurate detection and characterization of prostate cancer with MRI. Extradomain B fibronectin (EDB-FN), an oncoprotein present in aggressive tumors, is a promising molecular target for detection and stratification of high-risk prostate cancer. In this work, we have identified four small peptides (GVK, IGK, SGV, and ZD2) specific to EDB-FN for tumor targeting. <i>In silico</i> simulations of the binding patterns and affinities of peptides to the EDB protein fragment revealed different binding site to different peptide in the ligand–receptor interactions. Tumor specificity and organ distribution of the peptides were assessed using fluorescence imaging in male mice bearing PC-3 human prostate cancer xenografts. Targeted contrast agents were synthesized by conjugating tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) to the peptides in the solid phase, followed by complexation with GdCl₃. The contrast agents were characterized by MALDI-TOF mass spectrometry and relaxivity measurements. All four peptide Gd–DOTA conjugates resulted in robust tumor contrast enhancement in MR imaging of the PC3 mouse prostate cancer model. The peptide Gd–DOTA conjugates specific to EDB-FN are promising targeted small molecular macrocyclic contrast agents for MR molecular imaging of prostate cancer

Multianalysis of 35 Mycotoxins in Traditional Chinese Medicines by Ultra-High-Performance Liquid Chromatography–Tandem Mass Spectrometry Coupled with Accelerated Solvent Extraction

A generic procedure, which involved accelerated solvent extraction and homemade cleanup cartridges, has been developed for the extraction and purification of 35 mycotoxins in various traditional Chinese medicine (TCM) matrixes, i.e., rhizomes and roots, seeds, flowers, and grasses and leaves, for subsequent analysis by ultra-high-performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS). All target analytes could be simultaneously quantitated in less than 17 min per run, showing narrow symmetrical peaks. The developed method was also successfully applied in routine monitoring programs, which implied a significant reduction of both effort and time, to investigate the contamination of TCMs. Among 60 commercial TCMs analyzed, 50 were positive. The achieved data underpin the practical application of the UHPLC–MS/MS method as a valuable tool for the trace analysis of multiple mycotoxins in TCMs

Renewable N‑Heterocycles Production by Thermocatalytic Conversion and Ammonization of Biomass over ZSM‑5

Chemical conversion of biomass to value-added products provides a sustainable alternative to the current chemical industry that is predominantly dependent on fossil fuels. N-Heterocycles, including pyrroles, pyridines, and indoles, etc., are the most abundant and important classes of heterocycles in nature and widely applied as pharmaceuticals, agrochemicals, dyes, and other functional materials. However, all starting materials for the synthesis of N-heterocycles currently are derived from crude oil through complex multistep-processes and sometimes result in environmental problems. In this study, we show that N-heterocycles can be directly produced from biomass (including cellulose, lignocelluloses, sugars, starch, and chitosan) over commercial zeolites via a thermocatalytic conversion and ammonization process (TCC-A). All desired reactions occur in one single-step reactor within seconds. The production of pyrroles, pyridines, or indoles can be simply tuned by changing the reaction conditions. Meanwhile, N-containing biochar can be obtained as a valuable coproduct. We also outline the chemistry for the conversion of biomass into heterocycle molecules by the addition of ammonia into pyrolysis reactors demonstrating how industrial chemicals could be produced from renewable biomass resources. Only minimal biomass pretreatment is required for the TCC-A approach

Antiresonances in the Mid-Infrared Vibrational Spectrum of Functionalized Graphene

We report anomalous antiresonances in the infrared spectra of doped and disordered single layer graphene. Measurements in both reflection microscopy and transmission configurations of samples grafted with halogenophenyl moieties are presented. Asymmetric transparency windows at energies corresponding to phonon modes near the Γ and K points are observed, in contrast to the featureless spectrum of pristine graphene. These asymmetric antiresonances are demonstrated to vary as a function of the chemical potential and defect density. We propose a model that involves coherent intraband scattering with defects and phonons, thus relaxing the optical selection rule forbidding access to <b>q</b> ≠ Γ phonons. This interpretation of the new phenomenon is supported by our numerical simulations that reproduce the experimental features

Electrical Switch to the Resonant Magneto-Phonon Effect in Graphene

We report a comprehensive study of the tuning with electric fields of the resonant magneto-exciton optical phonon coupling in gated graphene. For magnetic fields around <i>B</i> ∼ 25 T that correspond to the range of the fundamental magneto-phonon resonance, the electron–phonon coupling can be switched on and off by tuning the position of the Fermi level in order to Pauli block the two fundamental inter-Landau level excitations. The effects of such a profound change in the electronic excitation spectrum are traced through investigations of the optical phonon response in polarization resolved magneto-Raman scattering experiments. We report on the observation of a splitting of the phonon feature with satellite peaks developing at particular values of the Landau level filling factor on the low or on the high energy side of the phonon, depending on the relative energy of the discrete electronic excitation and of the optical phonon. Shifts of the phonon energy as large as ±60 cm^–1 are observed close to the resonance. The intraband electronic excitation, the cyclotron resonance, is shown to play a relevant role in the observed spectral evolution of the phonon response

Controllable Phase Transition for Layered β‑FeSe Superconductor Synthesized by Solution Chemistry

Low-temperature synthesis of β-FeSe superconductor from soluble precursors is a great challenge in the chemical solution approaches. Here, we develop a new and facile solution-based synthetic route to first fabricate narrow-phased β-FeSe superconductor with soluble iron and selenium sources as starting materials. The growth mechanism of β-FeSe superconductors is discussed by kinetically controllable syntheses in various reaction conditions. Chemically engineering the stoichiometry of β-FeSe products by selenium-diffusion process gives rise to a transition of antiferromagnetic-superconducting-antiferromagnetic (AFM-SC-AFM) order. Once the AFM order is suppressed, SC β-FeSe nanosheets show a tunable initial superconducting transition temperature (<i>T</i>_C) from 3.2 to 10 K in the superconducting regime. Electrical measurements on superconducting β-FeSe exhibit an upper critical magnetic field higher than 14 T, showing potential application of β-FeSe nanosheet for superconducting device. This method provides guidance for future applications in such chemical solutions for diffusion-controlled synthesis of narrow-phased functional materials, which are enriched of abundant fundamental physics and potentials for future applications

Strain Superlattices and Macroscale Suspension of Graphene Induced by Corrugated Substrates

We investigate the organized formation of strain, ripples, and suspended features in macroscopic graphene sheets transferred onto corrugated substrates made of an ordered array of silica pillars with variable geometries. Depending on the pitch and sharpness of the corrugated array, graphene can conformally coat the surface, partially collapse, or lie fully suspended between pillars in a fakir-like fashion over tens of micrometers. With increasing pillar density, ripples in collapsed films display a transition from random oriented pleats emerging from pillars to organized domains of parallel ripples linking pillars, eventually leading to suspended tent-like features. Spatially resolved Raman spectroscopy, atomic force microscopy, and electronic microscopy reveal uniaxial strain domains in the transferred graphene, which are induced and controlled by the geometry. We propose a simple theoretical model to explain the structural transition between fully suspended and collapsed graphene. For the arrays of high density pillars, graphene membranes stay suspended over macroscopic distances with minimal interaction with the pillars’ apexes. It offers a platform to tailor stress in graphene layers and opens perspectives for electron transport and nanomechanical applications

Buchwald-Hartwig Amination Using Pd(I) Dimer Precatalysts Supported by Biaryl Phosphine Ligands

We report the synthesis of air-stable Pd(I) dimer complexes featuring biaryl phosphine ligands. Catalytic experiments suggest that these complexes are comptent precatalysts that can mediate cross-coupling amination reactions between aryl halide electrophiles with both aliphatic and aromatic amine nucleophiles. This work represents an expansion of the air-stable precatalyst toolbox for Pd-catalyzed cross-coupling transformations