A Novel Approach to High-Performance Aliovalent-Substituted Catalysts-2D Bimetallic MOF-Derived CeCuO Microsheets.

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.

Scalable and ultrafast epitaxial growth of single-crystal graphene wafers for electrically tunable liquid-crystal microlens arrays.

The scalable growth of wafer-sized single-crystal graphene in an energy-efficient manner and compatible with wafer process is critical for the killer applications of graphene in high-performance electronics and optoelectronics. Here, ultrafast epitaxial growth of single-crystal graphene wafers is realized on single-crystal CuNi(1 1 1) thin films fabricated by a tailored two-step magnetron sputtering and recrystallization process. The minor nickel (Ni) content greatly enhances the catalytic activity of Cu, rendering the growth of a 4 in.

Modular functionalization of crystalline graphene by recombinant proteins: a nanoplatform for probing biomolecules.

Graphene, as well as other two-dimensional materials, is a promising candidate for use in bioimaging, therapeutic drug delivery, and bio-sensing applications. Here, we developed a protocol to functionalize graphene with recombinant proteins using genetically encoded SpyTag-SpyCatcher chemistry. SpyTag forms a covalent isopeptide bond with its genetically encoded partner SpyCatcher through spontaneous amidation under physiological conditions.

Reactions of SO and NH with epoxy groups on the surface of graphite oxide powder.

Graphite oxide powder was obtained using the modified Hummers' method and characterized using X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The XPS results indicated that the epoxy groups were the main functional groups on the graphite oxide powder surface. The graphite oxide powder was then reacted with SO and NH gases, respectively, at 25 °C.

Surface Characterization of Polymer Blends by XPS and ToF-SIMS.

The surface properties of polymer blends are important for many industrial applications. The physical and chemical properties at the surface of polymer blends can be drastically different from those in the bulk due to the surface segregation of the low surface energy component. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary mass spectrometry (ToF-SIMS) have been widely used to characterize surface and bulk properties.

Transition temperature of poly(methyl methacrylate) determined by time-of-flight secondary ion mass spectrometry and contact angle measurements.

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 (T) 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 T depended on molecular weight and was about 50-60˚C below the bulk glass transition temperature (T) and therefore could possibly be related to the surface glass transition temperature (T).

Mussel-Inspired Adhesive and Tough Hydrogel Based on Nanoclay Confined Dopamine Polymerization.

Adhesive hydrogels are attractive biomaterials for various applications, such as electronic skin, wound dressing, and wearable devices. However, fabricating a hydrogel with both adequate adhesiveness and excellent mechanical properties remains a challenge. Inspired by the adhesion mechanism of mussels, we used a two-step process to develop an adhesive and tough polydopamine-clay-polyacrylamide (PDA-clay-PAM) hydrogel.

Fast Single-Cell Patterning for Study of Drug-Induced Phenotypic Alterations of HeLa Cells Using Time-of-Flight Secondary Ion Mass Spectrometry.

A facile single-cell patterning (ScP) method was developed and integrated with time-of-flight secondary ion mass spectrometry (TOF-SIMS) for the study of drug-induced cellular phenotypic alterations. Micropatterned poly(dimethylsiloxane) (PDMS) stencil film and centrifugation-assisted cell trapping were combined for the preparation of on-surface single-cell microarrays, which exhibited both high site occupancy (>90%) and single-cell resolution (>97%). TOF-SIMS is a surface-sensitive mass spectrometry and is increasingly utilized in biological studies.

A Mussel-Inspired Conductive, Self-Adhesive, and Self-Healable Tough Hydrogel as Cell Stimulators and Implantable Bioelectronics.

A graphene oxide conductive hydrogel is reported that simultaneously possesses high toughness, self-healability, and self-adhesiveness. Inspired by the adhesion behaviors of mussels, our conductive hydrogel shows self-adhesiveness on various surfaces and soft tissues. The hydrogel can be used as self-adhesive bioelectronics, such as electrical stimulators to regulate cell activity and implantable electrodes for recording in vivo signals.

Super stretchable hydrogel achieved by non-aggregated spherulites with diameters <5 nm.

The scope of hydrogel applications can be greatly expanded by the improvement of mechanical properties. However, enhancement of nanocomposite hydrogels (NC gels) has been severely limited because the size of crosslinking nanoparticles is too large, at least in one dimension. Here we report a new strategy to synthesize non-aggregated spherulite nanoparticles, with diameters <5 nm, in aqueous solution, and their enhancement to hydrogel.

Crystallization-Induced Redox-Active Nanoribbons of Organometallic Polymers.

Polymer/inorganic functional nanostructures are essential for the fabrication of high-performance nanodevices in the future. The synthesis of hybrid nanostructures is hindered by complicated synthetic protocols or harsh conditions. Herein, we report a facile and scalable method for the synthesis of organometallic polymer nanoribbons through crystallization of polymers capped with a ferrate complex.

Mussel-inspired adhesive and transferable free-standing films by self-assembling dexamethasone encapsulated BSA nanoparticles and vancomycin immobilized oxidized alginate.

This study developed an adhesive and transferable free-standing (FS) film with dual function of osteoinductivity and antibacterial activity, which was obtained by sequentially assembling vancomycin immobilized oxidized sodium alginate and dexamethasone encapsulated chitosan coated BSA nanoparticles on a poly-dopamine layer. The FS films enabled the dual release of vancomycin and dexamethasone. The FS films had excellent osteoinductivity and antibacterial activity by cell culture and antibacterial assay.

Insights into the aggregation/deposition and structure of a polydopamine film.

Surface-adherent polydopamine (PDA) films as multifunctional coatings can be easily deposited onto a wide range of materials through dopamine self-polymerization. However, a lack of in-depth understanding of PDA aggregation and deposition processes and definite structure elucidation of PDA make it challenging to tailor the surface characteristic and functionality of the PDA films. Herein, we demonstrate that the surface characteristics of the PDA films can be readily tuned by controlling the competitive interplay between PDA aggregation in solution and deposition on the substrate.

Detection of surface mobility of poly (2, 3, 4, 5, 6-pentafluorostyrene) films by in situ variable-temperature ToF-SIMS and contact angle measurements.

Poly (2, 3, 4, 5, 6-pentafluorostyrene) (5FPS) was prepared by bulk radical polymerization. The spin-cast films of this polymer were analyzed using time-of-flight secondary ion mass spectrometry (ToF-SIMS) at various temperatures ranging from room temperature to 120°C. Principal component analysis (PCA) of the ToF-SIMS data revealed a transition temperature (T(T)) at which the surface structure of 5FPS was rearranged.

Crystallization-Induced Hybrid Nano-Sheets of Fluorescent Polymers with Aggregation-Induced Emission Characteristics for Sensitive Explosive Detection.

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.

Evidence of enhanced mobility at the free surface of supported polymer films by in situ variable-temperature time-of-flight-secondary ion mass spectrometry.

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) spectra of polystyrene (PS) films supported on silicon wafers were obtained at temperatures ranging from room temperature to 100 °C. Principal component analysis (PCA) of the TOF-SIMS data revealed a transition temperature (TT) at which the surface structure of PS was rearranged. The TT of a 120-nm thick PS (weight-average molecular weight of 3,000 g/mol) thin film was determined to be about 36 °C, which is approximately 30 °C lower than the bulk glass transition temperature (Tg) of that PS.

Hollow interior structure of spin-coated polymer thin films revealed by ToF-SIMS three-dimensional imaging.

Surface patterns were observed on spin-coated poly(bisphenol A decane ether) (BA-C10) films prepared with chloroform and tetrahydrofuran as the solvents. The interior structure of these surface patterns were analyzed using a time-of-flight secondary ion mass spectrometry (ToF-SIMS) equipped with a bismuth cluster source for ion imaging and a C(60)(+) cluster source for depth profiling. For the first time, the surface patterns have been shown to be hollow rather than solid using ToF-SIMS three-dimensional (3D) analysis and optical techniques.

Induction of molecular organization of oligomers by low-energy electrons.

We reveal that a beam of low-energy electrons (18 eV) can directly trigger long-range molecular ordering of an amorphous, semi-flexible oligomer in a few minutes without the prerequisite of pre-orientation. A strong endothermic transition was detected with a micro-thermal analyzer on the areas that had been exposed to the electron irradiation while the areas that were shielded from the irradiation by a protective mask remained amorphous as usual. This result suggests that long-range molecular ordering only develops in the area of the oligomer film under electron irradiation.

Time-of-flight-secondary ion mass spectrometry and principal component analysis: determination of structures of lamellar surfaces.

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 CH(2) segments. The number of CH(2) units per flexible segment, n, varies from 8 to 12.

Control of the fold surface conformation of the lamellae of an oligomer.

Small-angle X-ray scattering revealed that a semirigid oligomer of bisphenol-A-co-ether-octane with a monodisperse chain length is capable of forming ciliated-folded, once-folded, ciliated-extended and fully extended lamellar structures. Isothermal crystallization studies suggested a sequence of structures with increasing crystallization temperature, from a ciliated-folded to a once-folded form and then to a ciliated-extended form as the degree of supercooling is decreased. The crystal surface thus changed from octane cilia to bisphenol A segments and then back to octane cilia as the lamellar structure changed.

Spectroscopic analysis of titanium surface functional groups under various surface modification and their behaviors in vitro and in vivo.

In the present study, surface functional groups of titanium surfaces gone through different treatments, including acid etched treatment (AE), nitric acid treatment (NT), heat treatment (HT), and alkali treatment (AT), and their behaviors in vitro and in vivo was thoroughly studied by spectroscopic analysis. In vitro and in vivo results revealed that the rank of bioactivity of various surfaces was AE < NT < HT < AT. XPS analysis indicated that AT greatly increased the OH group concentration on the titanium surface whereas HT reduced the OH group concentration.

Morphology-driven surface segregation in a blend of poly(epsilon-caprolactone) and poly(vinyl chloride).

A blend of poly(epsilon-caprolactone) (PCL) and poly(vinyl chloride) (PVC) with 90 wt % PCL was prepared. Two films of this blend, which were grown at 35 and 45 degrees C, showed the absence and presence of banded spherulites, respectively. A detailed examination conducted with time-of-flight secondary ion mass spectrometry (ToF-SIMS) found that the surface composition of the film grown at 45 degrees C was related to its structure, which was shown to contain ridges and valleys.

Combined X-ray photoelectron spectroscopy and time-of-flight secondary ion MS surface quantitative analysis of polymer blends with varying mixing thermodynamics.

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) was used to quantitatively correlate to the surface chemical composition determined from XPS in poly(styrene-co-p-hexafluorohydroxyisopropyl-alpha-methyl styrene)/poly(4-vinyl pyridine) (PS(OH)/PVPy) blends or complexes when the p-(hexafluoro-2-hydroxyisopropyl)-alpha-methylstyrene (HFMS) contents in PS(OH) copolymers were gradually increased. It was found that different mixing thermodynamics, such as immiscibility, miscibility, and complexation, have little effect on the quantitative analysis of PS(OH) copolymers in the blends or complexes using TOF-SIMS. In the positive spectra, either the normalized intensities or relative peak intensities can be used to quantitatively analyze the surface HFMS, PS(OH), or PVPy concentration when peaks at m/z = 257, 271, 285, and 373 are used for HFMS, peaks at m/z = 91, 103, 105, 115 for styrene, and peaks at m/z = 132, 195, 209 for PVPy.

Solventless polymerization: spatial migration of a catalyst to form polymeric thin films in microchannels.

This paper reports a simple, additive process to generate patterned polymer films without using any solvent. This process involves a highly efficient catalyst, a Grubbs's catalyst, and a volatile monomer, norbornene. The catalyst and monomers have higher local concentrations inside the microchannels, formed by contacting poly(dimethylsiloxane) stamps to a solid surface, and allow the polymeric thin films to be defined by the microchannels.

Characterization of chemical inhomogeneity in plasma-sprayed hydroxyapatite coatings.

Successful applications of plasma-sprayed hydroxyapatite (HA) coating for implants rely on understanding characteristics of the coating's microstructure, particularly its inhomogeneity. We explored three new techniques for characterizing the chemical inhomogeneity of sprayed HA coatings on titanium substrate: micro-Raman spectroscopy (MRS), positive and negative ion ratios of time-of-flight secondary ion mass spectrometry (ToF-SIMS) and the energy loss peaks of X-ray photoelectron spectroscopy (XPS). The results showed that MRS effectively revealed a chemical gradient in the direction of the coating thickness and a decrease in crystallinity from the surface to interface within the as-sprayed coatings.