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SYNTHESIS AND CHARACTERIZATION OF CERIUM FLUORITES BASED ON Ce1-xLn xO2-δ SYSTEM (Ln: Nd3+, Sm3+, Eu3+, Gd3+, Dy3+ AND Ho3+)
摘要： This paper describes the synthesis of 18 oxides of Ce1-xLnxO2 (Ln: Nd3+, Sm3+, Eu3+, Gd3+, Dy3+ and Ho3+), with x = 0.05, 0.10 and 0.15 mol% by use of a wet chemical route that involving the obtention of coordination compounds type citrate, which allow the generation of a number of chemical and surface properties with potential catalytic applications in solid oxide fuel cells technologies. The materials obtained by this route, has a high purity and homogeneity, enabling calcination temperatures and residence times considerably brief, in comparison with conventional synthetic routes. All oxides, were calcined at 300 °C under flow oxygen and were characterized by X-ray diffraction (XRD), from obtained results, we confirmed the presence of a pure fluorite structure of CeO2 consistent with the ICSD pattern reference of 072155 with space group Fm-3m (225). Subsequent physicochemical characterization by TPR and electron microscopy (SEM-TEM), confirm that cerium oxides could be reduced in two single steps at different temperatures, kinetically detectable and clearly prolonged as well as the obtention of nanostructured solids with a crystallite size between 32-47 nm. According with obtained results, the solids show a high surface area as result of the low calcination temperature. The electrical characterization by impedance spectroscopy (IS), revealed an important concentration of charge carriers in fluorite oxides, mainly in the sample of GDC5, which is a crucial characteristic in advanced materials for SOFC applications. The catalytic studies, conducted on materials at 700 °C under stable reaction conditions, confirm that the methane conversion levels change throughout the series GDC5 → NDC5 → HDC5 → EDC5 → DDC5 → SDC5, which established that the GDC5 solid, exhibits the most promising results. Finally, a stability test was achieved with the GDC5 catalyst under the same reaction conditions established in previous form, for a period of 240 hours of continuous flux, establishing the effectiveness of the proposed method to choice the most promissory material. The results confirmed as the methane conversion vary as function of time and the obtained syngas levels change for potential technological applications.
关键词： TPB,Impedance,Polymerization,Fluorite
更新于2025-09-09 09:28:46
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Synthesis of C-C bonded Two-dimensional Conjugated Covalent Organic Framework Films via Suzuki Polymerization on Liquid/liquid Interface
摘要： Synthesis of free standing two-dimensional (2D) conjugated covalent organic framework (COF) films linked by C-C bonds can be considered as a holy grail of synthetic chemistry. However, reactions for their synthesis are quite rare. Herein we developed a very simple and mild strategy to synthesize them via the Nobel Prize reaction (Suzuki polymerization) on water/toluene interface in a fridge. The versatility of this strategy was proved by the successful synthesis of two different 2D-COF films: a porous graphene and a porphyrin-contained 2D-COF. Both 2D-COF films have large lateral size and their crystalline domains were visualized by high resolution TEM. Based on the wide compatibility of Suzuki reaction, our breakthrough work opened a door for the synthesis of various 2D conjugated COF films. For application studies, the porous graphene exhibits a good carrier mobility which is much higher than -C=N- linked 2D COF films and a good catalytic activity for hydrogen evolution reaction which is comparable with nitrogen or phosphorus doped graphene.
关键词： porous graphene,interface,porphyrin,2D conjugated COF,Suzuki polymerization
更新于2025-09-09 09:28:46
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Photo-control of poly(N-[4-[(4-Nitrophenyl)azo]phenyl]acrylamide) brushes on graphene oxide coated silicon surface
摘要： Poly(N-[4-[(4-Nitrophenyl)azo]phenyl]acrylamide [poly(NPAPAA)] brushes were obtained via interface-mediated reversible addition–fragmentation chain transfer polymerization to design new photoresponsive surface on the graphene oxide coated silicon substrate. Switchable surface wettability was controlled successfully by these densely packed polymer brushes using light as the exterior stimulation. The relatively nonpolar trans azobenzene polymer brushes were converted to a polar cis form (with a larger dipole moment) utilizing light of the suitable wavelength. This conversion is reversible and can be switched back by employing visible light. Cis–trans photo-induced isomerization provided a reversible contact angle change (~ 9o) with UV and visible light for the poly(NPAPAA) brushes under successive irradiation cycles. This study may be promised to control cell culture surface without leaving any residual in terms of alternative medicine.
关键词： Interface-mediated RAFT polymerization,Photoresponsive polymer brushes,Switchable surface wettability
更新于2025-09-09 09:28:46
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High-Throughput Template-Free Continuous Flow Synthesis of Polyaniline Nanofibers
摘要： The large-scale and high-throughput synthesis of conjugated polymer based nanofibers always remain a challenge for the chemists due to the issues related to secondary nucleation in traditional batch processes. Typically polyaniline (PANI) nanofibers are synthesized under highly dilute conditions resulting in a very low throughput of few hundred mg per hour and a low space-time yield (STY) of 1-2 g·L-1·h-1. In this manuscript, we report the continuous flow synthesis of PANI nanofibers which results in high throughput (17-30 g·h-1) and high space-time yield (140-450 g·L-1·h-1). These polyaniline nanofibers show high surface area (42 m2·g-1), high specific capacitance (577 F·g-1) and high crystallinity. Finally, the present method is generic in nature and, in principle, can be extended for the synthesis of nanofibers of other conjugated polymers via oxidative polymerization.
关键词： Chemical oxidative polymerization,One-dimensional nanomaterials,Polyaniline nanofiber,Space-time yield,Electrochemical capacitor,Throughput,Continuous flow synthesis
更新于2025-09-09 09:28:46
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A Modified Photoactivation Protocol Using Two Simultaneous Light-Curing Units for Bonding Brackets to Enamel
摘要： This study investigated the effect of a modified photoactivation protocol using two simultaneous light-curing units on the shear bond strength (SBS) of brackets to enamel. Metal brackets were bonded to bovine incisors using the resin-based orthodontic cement Transbond XT (3M Unitek). Four photoactivation protocols of the orthodontic cement were tested (n=15): Control: photoactivation for 10 s on each proximal face of the bracket at a time; Simultaneous: photoactivation for 10 s on both proximal faces of the bracket at the same time; One side-20s: photoactivation for 20 s at one proximal face of the bracket only; and One side-10s: photoactivation for 10 s only at one proximal face of the bracket. SBS was tested immediately or after 1000 thermal cycles. Adhesive remnant index (ARI) was classified. Data were subjected to two-way ANOVA and Student-Newman-Keuls’ test (α=0.05). Pooled means ± standard deviations for SBS to enamel (MPa) were: 10.2±4.2 (Control), 9.7±4.5 (Simultaneous), 5.6±3.1 (One side-20s), and 4.6±1.9 (One side-10s). Pooled SBS data for immediate and thermal cycled groups were 6.3±2.6 and 8.8±5.2. A predominance of ARI scores 1-2 and 0-1 was observed for the immediate and thermally cycled groups, respectively. In conclusion, simultaneous photoactivation of the orthodontic cement using two light-curing units, one positioned at each proximal face of the bracket, yielded similar bonding ability compared to the conventional light-curing method. Photoactivation of the orthodontic cement at one proximal face of the bracket only is not recommended, irrespective of the light-curing time used.
关键词： composite,polymerization,aging,Orthodontics,shear bond strength
更新于2025-09-04 15:30:14
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Rotational Efficiency of Photo-Driven Archimedes Screws for Micropumps
摘要： In this study, we characterized the rotational efficiency of the photo-driven Archimedes screw. The micron-sized Archimedes screws were fabricated using the two-photon polymerization technique. Free-floating screws trapped by optical tweezers align in the laser irradiation direction and rotate spontaneously. The influences of the screw pitch and the number of screw blades have been investigated in our previous studies. In this paper, the blade thickness and the central rod of the screw were further investigated. The experimental results indicate that the blade thickness contributes to rotational stability, but not to rotational speed, and that the central rod stabilizes the rotating screw but is not conducive to rotational speed. Finally, the effect of the numerical aperture (NA) of the optical tweezers was investigated through a demonstration. The NA is inversely proportional to the rotational speed.
关键词： two-photon polymerization,micropump,optical torque,Archimedes screw,optical tweezers
更新于2025-09-04 15:30:14
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Preparation of erythromycin imprinted polymer by metal-free visible-light–induced ATRP and its application in sensor
摘要： Erythromycin (ERY) molecular imprinted polymer was prepared on the surface of Au electrode modified with Ni and Au nanoclusters (MIP/AuNCs/Ni/Au) via metal-free visible-light–induced atom transfer radical polymerization, which was very easy, controllable, and environmentally benign. MIP/AuNCs/Ni/Au was examined by energy dispersive spectrometer (EDS), scanning electron microscope (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). Further, MIP/AuNCs/Ni/Au was successfully used for the determination of ERY by differential pulse voltammetry (DPV). Under the optimal conditions, MIP/AuNCs/Ni/Au gave a linear correlation over the ERY concentration from 1.0 × 10?8 to 1.0 × 10?1 mg/L with the detection limit of 3.2 × 10?9 mg/L (S/N = 3). Comparing with the similar sensors, the larger linear range and lower detection limit indicated the promising prospect of this electrochemical sensor. Hence, this study was of great importance for the polymer-modified electrodes and the sensitive detection of ERY.
关键词： Molecular imprinted polymer (MIP),Metal-free visible-light–induced atom transfer radical polymerization (MVL ATRP),Erythromycin (ERY)
更新于2025-09-04 15:30:14
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Conductive Fused Porphyrin Tapes on Sensitive Substrates by a Chemical Vapor Deposition Approach
摘要： Oxidative polymerization of nickel(II) 5,15-diphenyl porphyrin and nickel(II) 5,15-bis(di-3,5-tert-butylphenyl) porphyrin by an oxidative chemical vapor deposition (oCVD) approach yields multiply fused porphyrin oligomers in thin film form. The oCVD technique enables the formation, deposition and p-doping of conjugated poly(porphyrins) coatings in a single step without the use of solvents or post-treatments. The decisive reactions and side reactions during the oCVD process are evidenced by high-resolution mass spectrometry. Due to the highly conjugated structure of the fused porphyrin tapes the thin films exhibit an electrical conductivity of 3.6×10–2 S·cm–1 and strong absorption in the visible to near-infrared spectral region. The formation of smooth conjugated poly(porphyrins) thin films, even on sensitive substrates, is demonstrated by their successful deposition and patterning on glass, silicon and printer paper. The ability to form conductive poly(porphyrins) thin films could enable the design of a new category of optoelectronic devices using the oCVD approach.
关键词： Porphyrins,Oxidative Coupling,Chemical Vapor Deposition,Thin Films,Polymerization
更新于2025-09-04 15:30:14
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Preparation of Ag2Se QDs with excellent aqueous dispersion stability by organic coating with aqueous ATRP
摘要： In this article, water-dispersible Ag2Se quantum dots (QDs) were prepared by the facile and environmental-friendly method. In our approach, atom transfer radical polymerization (ATRP) was adopted in aqueous media to grow polymer chains from the surface of Ag2Se QDs. The aqueous ATRP allows the very mild synthetic conditions. In the present work, the polymerization reaction of methoxy[oligo(ethylene glycol)] methacrylate (OEGMA) was carried out at room temperature under aqueous conditions after the incorporation of 2-bromopropionyl moiety as the ATRP initiator on the surface of Ag2Se QDs by the ligand exchange method. OEGMA-coated Ag2Se QDs were successfully obtained without significant morphological change. The aqueous dispersion stability of OEGMA-coated Ag2Se QDs was compared with that of conventional water-dispersible Ag2Se QDs prepared by the simple modification with 11-mercaptoundecanoic acid. As a result, OEGMA-coated Ag2Se QDs showed the extremely high aqueous dispersion stability.
关键词： Aqueous dispersion stability,Methoxy[oligo(ethylene glycol)] methacrylate,Ag2Se quantum dot,Organic coating,Aqueous atom transfer radical polymerization
更新于2025-09-04 15:30:14
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Kinetic Study of Degrafting Poly(methyl methacrylate) Brushes from Flat Substrates by Tetrabutylammonium Fluoride
摘要： Polymer degrafting is a process in which surface-attached polymer brushes are removed from the substrate by breaking a chemical bond in proximity to the substrate. This paper provides insight into the kinetics of degrafting poly(methyl methacrylate) (PMMA) brushes using tetrabutylammonium fluoride (TBAF) and demonstrates how the process can be modeled using a series of degrafting reactions. The trichlorosilane-based polymerization initiator utilized here to synthesize PMMA grafts by surface-initiated atom transfer radical polymerization anchors to the silica substrate by up to three potential attachment points. During the degrafting sequence this anchoring reduces to two and one chemical bond and finally results in complete liberation of the PMMA macromolecule from the substrate. We investigate the effect of TBAF concentration, the initial grafting density of PMMA grafts on the substrate, and TBAF exposure time on degrafting of PMMA by monitoring the instantaneous areal grafting density of PMMA on the substrate.
关键词： PMMA brushes,Polymer degrafting,TBAF,kinetics,surface-initiated atom transfer radical polymerization
更新于2025-09-04 15:30:14