In this article, we addressed the applicability of time-of-flight secondary ion mass spectrometry (TOF-SIMS) to examine the effects of molecular weight and of flexible-segment length on the polymer ...chain arrangement at the folding surfaces of the lamellae. Poly(bisphenol A−etheralkane) (Cn) contains both rigid aromatic and flexible aliphatic CH2 segments. The number of CH2 units per flexible segment, n, varies from 8 to 12. Principal component analysis (PCA) of TOF-SIMS data revealed the chemical and structural variations of the folding surfaces of these polymers and identified the ion peaks contributing to these variations. We highlighted the discriminating power of PCA to distinguish the structural conformations of the amorphous and flat-on lamellar surfaces of these polymers. PCA loadings analyses showed that relatively more flexible structures were deposited on the folding surfaces when the flexible-segment length increased from 8 to 10 CH2 units. The concentration of short loops at folding surfaces and the disorder of folding surfaces increased when the molecular weight increased. All these results led us to conclude that TOF-SIMS has great potential for probing the chemical composition of the folding surfaces of polymers.
In article number 1903525, Wei Han, King Lun Yeung, and co‐workers develop a synthesis approach to binary metal oxides by controlled thermal transformation of bimetallic metal–organic framework ...precursors. The approach is capable of manipulating the morphology and structure of binary metal oxides as high‐performance environmental catalysts for complete oxidation of volatile organic compounds under the conditions of low temperature and high humidity.
Mixed transition metal oxides (MTMOs) have enormous potential applications in energy and environment. Their use as catalysts for the treatment of environmental pollution requires further enhancement ...in activity and stability. This work presents a new synthesis approach that is both convenient and effective in preparing binary metal oxide catalysts (CeCuO
) with excellent activity by achieving molecular-level mixing to promote aliovalent substitution. It also allows a single, pure MTMO to be prepared for enhanced stability under reaction by using a bimetallic metal-organic framework (MOF) as the catalyst precursor. This approach also enables the direct manipulation of the shape and form of the MTMO catalyst by controlling the crystallization and growth of the MOF precursor. A 2D CeCuO
catalyst is investigated for the oxidation reactions of methanol, acetone, toluene, and o-xylene. The catalyst can catalyze the complete reactions of these molecules into CO
at temperatures below 200 °C, representing a significant improvement in performance. Furthermore, the catalyst can tolerate high moisture content without deactivation.
Fluorescent organic hybrid nanosheets were generated by crystallization of polymers capped with luminogenic molecules exhibiting aggregation-induced emission characteristics (AIE). During ...crystallization of polymers, AIE molecules were expelled out of lamellar crystals of polymers, and finally resided on the surface. The fluorescent nanosheets with dangling AIE molecules showed sensitive and specific response to explosives. Such polymer crystallization-induced fluorescent nanomaterials offers a unique avenue to fabricate functional nanomaterials with AIE molecule-enriched domains for potential applications in nanodevices, biological engineering, and so on.
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•Fe@C with magnetic iron core and graphene shell is biocompatible and safe.•Fe@C has high loading capacity for ferulic acid and allows its constant dosing.•Fe@C subcutaneously ...injected in diabetic mice lowers blood sugar level.
Iron nanoparticles encapsulated within graphene shells (Fe@C) were examined for cellular internalization, subcellular behavior, biocompatibility, and influence on cell viability and proliferation. Studies on human lung (adenocarcinoma human alveolar basal epithelial) and skin (epidermoid carcinoma) cells indicate Fe@C is less toxic and more biocompatible than the magnetite nanoparticles coated by an amorphous carbon (Fe3O4@C). Fe3O4@C exhibited more signs of degradation than Fe@C when exposed to murine macrophages (mouse monocyte-macrophages J774). Unlike Fe3O4@C, Fe@C has a high drug loading capacity (0.18 g/g) for ferulic acid, an active pharmaceutical ingredient found in the traditional Chinese herbAngelica sinensisand releases the drug at a constant dosing rate of 8.75 mg/g/day over 30 days. Ferulic acid released by Fe@C injected subcutaneously in diabetic BALB/c mice is effective in lowering the blood glucose level.
In this study, a series of suspensions were fabricated by dispersing calcium carbonate (CaCO 3 ), cement and silica fume into a polycarboxylate-ether plasticizer (PCE)/water solution. The PCE used ...was a comb-like copolymer containing a sodium polymethacrylate (PMA) backbone partially esterified with polyethyleneglycol (PEG) side chains. Sedimentation and optical microscopy tests indicated that both CaCO 3 and cement could form homogeneous suspensions. The crystallization behavior of the PEG side chains revealed that PEG had stronger interactions with CaCO 3 than with cement and silica fume particles, which was further confirmed by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). A detailed time-of-flight secondary ion mass spectrometry (ToF-SIMS) examination suggested that PEG was mainly located on the surfaces of the CaCO 3 , and the PMA backbones were mainly located on the surfaces of the cement and silica fume, respectively. The different interactions between copolymer and inorganic particles were associated with their interfacial tensions, and had a remarkable influence on the paste fluidity.
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The surface chain conformations of poly(methyl methacrylate) (PMMA) at different temperatures were extensively studied by time-of-flight secondary ion mass spectrometry (ToF-SIMS). ...Similar to our previous experimental studies on polystyrene (PS) and poly(2, 3, 4, 5, 6-pentafluorostyrene) (5FPS), a transition temperature (TT) could be identified through the principal component analysis (PCA) of the ToF-SIMS spectra obtained from the PMMA samples annealed at different temperatures. Interestingly, our results show that the TT depended on molecular weight and was about 50–60˚C below the bulk glass transition temperature (Tg) and therefore could possibly be related to the surface glass transition temperature (TgS). These results were confirmed by contact angle measurements. ToF-SIMS results showed higher peak intensities of several low-mass oxygen-containing positive ions, hydrocarbon positive ions and OCH3− negative ion at higher temperatures, which can be interpreted by a higher surface concentration of methoxy groups at the surface.
In this study, a series of poly(l-lactic acid) (PLLA)/poly(ethylene oxide) (PEO) blends with different PLLA concentrations was prepared. Films of these blends crystallized with and without a ...coverslip were characterized by the presence and absence of banded structures, respectively. This difference in morphology was observed because the PEO component of the blends was oxidized at a high temperature (125 °C) in air without the protection of a coverslip. X-ray photoelectron spectroscopy (XPS) results showed that the surface of the blends crystallized in nitrogen without a coverslip contained mostly PLLA while the surfaces of the same blends crystallized under a coverslip contained only a moderately higher concentration of PLLA than their bulks. The migration of PLLA to the surface of the blends during crystallization in nitrogen when no coverslip was used was due to its low surface tension. Phase images obtained using atomic force microscopy (AFM) indicated that the banded structures consisted of valleys and ridges, which were in fact flat-on and edge-on lamellae, respectively. A detailed time-of-flight secondary ion mass spectrometry (ToF-SIMS) examination suggested that PLLA and PEO were located mainly on the surfaces of the ridges and valleys, respectively.
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Hydrogenated graphite powder was obtained through Birch reduction of graphite powder and characterized by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry ...(ToF-SIMS) at 500 °C. The sp 3 carbons formed at the edges of the surface of the hydrogenated graphite powder exhibited an sp 3 carbon peak in the XPS C1s spectrum. The sp 3 -to-sp 2 carbon ratio calculated from the XPS spectra increased from 0.08 to 1.19 after hydrogenation. Two sets of peaks, the C x − and C x H − ion series (where x = 1, 2, 3…), were identified in the ToF-SIMS spectra of both the graphite powder and hydrogenated graphite powder. The difference between these two spectra represented an increase in the normalized intensities of the H − and C x H − ions in the spectrum of the hydrogenated graphite powder, indicating the formation of more sp 3 carbons on the surface.
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