Enhancing bioactivity and stability of polymer-based material-tissue interface through coupling multiscale interfacial interactions with atomic-thin TiO2 nanosheets.

Stable and bioactive material-tissue interface (MTF) basically determines the clinical applications of biomaterials in wound healing, sustained drug release, and tissue engineering. Although many inorganic nanomaterials have been widely explored to enhance the stability and bioactivity of polymer-based biomaterials, most are still restricted by their stability and biocompatibility. Here we demonstrate the enhanced bioactivity and stability of polymer-matrix bio-composite through coupling multiscale material-tissue interfacial interactions with atomically thin TiO2 nanosheets. Resin modified with TiO2 nanosheets displays improved mechanical properties, hydrophilicity, and stability. Also, we confirm that this resin can effectively stimulate the adhesion, proliferation, and differentiation into osteogenic and odontogenic lineages of human dental pulp stem cells using in vitro cell-resin interface model. TiO2 nanosheets can also enhance the interaction between demineralized dentinal collagen and resin. Our results suggest an approach to effectively up-regulate the stability and bioactivity of MTFs by designing biocompatible materials at the sub-nanoscale. Electronic Supplementary Material: Supplementary material (further details of fabrication and characterization of TiO2 NSs and TiO2-ARCs, the bioactivity evaluation of TiO2-ARCs on hDPSCs, and the measurement of interaction with demineralized dentin collagen) is available in the online version of this article at 10.1007/s12274-022-5153-1.

Interfacial compatibility critically controls Ru/TiO2 metal-support interaction modes in CO2 hydrogenation.

Supports can widely affect or even dominate the catalytic activity, selectivity, and stability of metal nanoparticles through various metal-support interactions (MSIs). However, underlying principles have not been fully understood yet, because MSIs are influenced by the composition, size, and facet of both metals and supports. Using Ru/TiO2 supported on rutile and anatase as model catalysts, we demonstrate that metal-support interfacial compatibility can critically control MSI modes and catalytic performances in CO2 hydrogenation. Annealing Ru/rutile-TiO2 in air can enhance CO2 conversion to methane resulting from enhanced interfacial coupling driven by matched lattices of RuOx with rutile-TiO2; annealing Ru/anatase-TiO2 in air decreases CO2 conversion and converts the product into CO owing to strong metal-support interaction (SMSI). Although rutile and anatase share the same chemical composition, we show that interfacial compatibility can basically modify metal-support coupling strength, catalyst morphology, surface atomic configuration, MSI mode, and catalytic performances of Ru/TiO2 in heterogeneous catalysis.

Promotion of the Co3O4/TiO2 Interface on Catalytic Decomposition of Ammonium Perchlorate.

Supports can widely affect or even dominate the catalytic activity and selectivity of nanoparticles because atomic geometry and electronic structures of active sites can be regulated, especially at the interface of nanoparticles and supports. However, the underlying mechanisms of most systems are still not fully understood yet. Herein, we construct the interface of Co3O4/TiO2 to boost ammonium perchlorate (AP) catalytic decomposition. This catalyst shows enhanced catalytic performance. With the addition of 2 wt % Co3O4/TiO2 catalysts, AP decomposition peak temperature decreases from 435.7 to 295.0 °C and activation energy decreases from 211.5 to 137.7 kJ mol-1. By combining experimental and theoretical studies, we find that Co3O4 nanoparticles can be strongly anchored onto TiO2 supports accompanied by charge transfer. Moreover, at the interfaces in the Co3O4/TiO2 nanostructure, NH3 adsorption can be enhanced through hydrogen bonds. Our research studies provide new insights into the promotion effects of the nanoparticle/support system on the AP decomposition process and inspire the design of efficient catalysts.

A mussel glue-inspired monomer-etchant cocktail for improving dentine bonding.

OBJECTIVES: The humid oral environment adversely affects the interaction between a functionalised primer and dentine collagen after acid-etching. Robust adhesion of marine mussels to their wet substrates instigates the quest for a strategy that improves the longevity of resin-dentine bonds. In the present study, an etching strategy based on the incorporation of biomimetic dopamine methacrylamide (DMA) as a functionalised primer into phosphoric acid etchant was developed. The mechanism and effect of this DMA-containing acid-etching strategy on bond durability were examined. METHODS: Etchants with different concentrations of DMA (1, 3 or 5 mM) were formulated and tested for their demineralisation efficacy. The interaction between DMA and dentine collagen, the effect of DMA on collagen stability and the collagenase inhibition capacity of the DMA-containing etchants were evaluated. The effectiveness of this new etching strategy on resin-dentine bond durability was investigated. RESULTS: All etchants were capable of demineralising dentine and exposing the collagen matrix. The latter strongly integrated with DMA via covalent bond, hydrogen bond and Van der Waals' forces. These interactions significantly improve collagen stability and inhibited collagenase activity. Application of the etchant containing 5 mM DMA achieved the most durable bonding interface. CONCLUSION: Dopamine methacrylamide interacts with dentine collagen in a humid environment and improves collagen stability. The monomer effectively inactivates collagenase activity. Acid-etching with 5 mM DMA-containing phosphoric acid has the potential to prolong the longevity of bonded dental restorations without compromising clinical operation time. CLINICAL SIGNIFICANCE: The use of 5 mM dopamine methacrylamide-containing phosphoric acid for etching dentine does not require an additional clinical step and has potential to improve the adhesive performance of bonded dental restorations.

A new type of noncovalent surface-π stacking interaction occurring on peroxide-modified titania nanosheets driven by vertical π-state polarization.

Noncovalent π stacking of aromatic molecules is a universal form of noncovalent interactions normally occurring on planar structures (such as aromatic molecules and graphene) based on sp2-hybridized atoms. Here we reveal a new type of noncovalent surface-π stacking unusually occurring between aromatic groups and peroxide-modified titania (PMT) nanosheets, which can drive versatile aromatic adsorptions. We experimentally explore the underlying electronic-level origin by probing the perturbed changes of unoccupied Ti 3d states with near-edge X-ray absorption fine structures (NEXAFS), and find that aromatic groups can vertically attract π electrons in the surface peroxo-Ti states and increase their delocalization regions. Our discovery updates the concept of noncovalent π-stacking interactions by extending the substrates from carbon-based structures to a transition metal oxide, and presents an approach to exploit the surface chemistry of nanomaterials based on noncovalent interactions.

Direct synthesis of defective ultrathin brookite-phase TiO2 nanosheets showing flexible electronic band states.

We report a one-pot protocol to prepare ultrathin nanosheets of brookite-phase TiO2 through hydrolyzing TiCl3 in formamide. This 2D titania is defective and shows flexible electronic states and enhanced surface reactivity, which is probed by H2O2 adsorption, catalytic TMB oxidation, and X-ray absorption fine structure. The nanosheets provide a new 2D platform to exploit the applications of TiO2 in catalysis, energy conversion and storage.

Reconstructing 1D Fe Single-atom Catalytic Structure on 2D Graphene Film for High-Efficiency Oxygen Reduction Reaction.

The ordinary intrinsic activity and disordered distribution of metal sites in zero/one-dimensional (0D/1D) single-atom catalysts (SACs) lead to inferior catalytic efficiency and short-term endurance in the oxygen reduction reaction (ORR), which restricts the large-scale application of hydrogen-oxygen fuel cells and metal-air batteries. To improve the activity of SACs, a mild synthesis method was chosen to conjugate 1D Fe SACs with 2D graphene film (Fe SAC@G) that realized a composite structure with well-ordered atomic-Fe coordination configuration. The product exhibits outstanding ORR electrocatalytic efficiency and stability in 0.1 M KOH aqueous solution. DFT-D computational results manifest the intrinsic ORR activity of Fe SAC@G originated from the newly-formed FeN4 -O-FeN4 bridge structure with moderate adsorption ability towards ORR intermediates. These findings provide new ways for designing SACs with high activity and long-term stability.

Facet effect of Co3O4 nanocatalysts on the catalytic decomposition of ammonium perchlorate.

Crystal facets can affect the catalytic decomposition of ammonium perchlorate, but the underlying mechanisms have long remained unclear. Here, we use the nanorods, nanosheets and nanocubes of Co3O4 catalysts exposing {110}, {111} and {100} facets as model systems to investigate facet effects on catalytic AP decomposition. The peak temperature of high temperature decomposition (HTD) process (THTD) of AP by nanorods, nanosheets and nanocubes Co3O4 decrease from 437.0 °C to 289.4 °C, 299.9 °C and 326.3 °C, respectively, showing obvious facet effects. We design experiments about AP decomposition under different atmospheres to investigate its mechanism and verify that the accumulation of ammonia (NH3) on AP surface can inhibit its decomposition and that the facet effects are related to the adsorption and oxidation of NH3. The binding energies of NH3 on the {110}, {111} and {100} planes calculated via density functional theory (DFT) are -1.774 eV, -1.638 eV, and -1.354 eV, respectively, indicating that the {110} planes are more favorable for the adsorption of NH3. Moreover, the {110} planes are readily to form CoNO structure, which benefits the further oxidation of the NH3.

Tailoring N-Coordination Environment by Ligand Competitive Thermolysis Strategy for Efficient Oxygen Reduction.

The synergy of fully exposed active sites and optimized N-dopant configurations in three-dimensional (3D) N-doped carbon (N/C) is highly pivotal for efficient catalysis and energy conversion but lacks effective methods. Meanwhile, to understand the active sites, excluding the size effect of the π-conjugated system, especially in N/C derived from metal-organic frameworks (MOFs) is significant but challenging. Herein, an elegant and general strategy, ligand competitive thermolysis, was developed to construct hierarchical pore structures and tailor their N-coordination environment in the MOF-derived 3D N/C catalysts. Due to sufficient interior mesopores and predominant active N species, the metal-free catalysts achieved an efficient activity (E1/2 = 0.84 V) and impressive durability (20,000 cycles, ΔE1/2 = 5 mV). The relationship between half-wave potential and the content of N species was also investigated. This work not only offers valuable inspiration for developing high-performance electrocatalysts but also motivates deep understanding of the active sites in N/C catalysts.

Enhanced Electrocatalytic Activity of Trace Pt in Ternary CuCoPt Alloy Nanoparticles for Hydrogen Evolution.

We report an enhanced high electrocatalytic hydrogen evolution activity of trace Pt and Co diluted in ternary CuCoPt alloy nanoparticles with Cu as the substrate. Using only 10% Pt atoms can display even better activity and stability in hydrogen evolution reactions than using pure Pt nanoparticles.

Ultrathin Tellurium Oxide/Ammonium Tungsten Bronze Nanoribbon for Multimodality Imaging and Second Near-Infrared Region Photothermal Therapy.

Developing nanophotothermal agents (PTAs) with satisfied photothermal conversion efficiency (PTCE) in the second NIR window (1000-1350 nm, NIR II) holds great promise for enhanced photothermal therapy effect. Herein, we develop a NIR-II PTA with advanced PTCE, based on a new two-dimensional ultrathin tellurium oxide/ammonium tungsten bronze (TeO2/(NH4) xWO3) nanoribbons (TONW NRs). The doped ammonia ions-mediated-free-electrons injection into the lowest unoccupied molecular orbital band of WO3 combined with the electronic transitions between W6+ ions and the lone pair of electrons in Te atoms achieve excellent NIR absorption of TONW NRs resulting from localized surface plasmon resonance. The polyethylene glycol functionalized TONW NRs (PEG-TONW NRs) exhibit good stability and biocompatibility, displaying a PTCE high to 43.6%, surpassing many previous nano-PTAs active in the NIR II region, leading to remarkable tumor ablation ability both in vitro and in vivo. Meanwhile, advanced X-ray computed tomography (CT) and photoacoustic (PA) imaging capability of PEG-TONW NRs were also realized. Given the admirable photothermal effect in NIR II region, good biocompatibility, and advanced CT/PA imaging diagnosis capability, the novel PEG-TONW NRs is promising in future personalized medicine applications.

Probing Ligand-Induced Cooperative Orbital Redistribution That Dominates Nanoscale Molecule-Surface Interactions with One-Unit-Thin TiO2 Nanosheets.

Understanding the general electronic principles underlying molecule-surface interactions at the nanoscale is crucial for revealing the processes based on chemisorption, like catalysis, surface ligation, surface fluorescence, etc. However, the electronic mechanisms of how surface states affect and even dominate the properties of nanomaterials have long remained unclear. Here, using one-unit-thin TiO2 nanosheet as a model surface platform, we find that surface ligands can competitively polarize and confine the valence 3d orbitals of surface Ti atoms from delocalized energy band states to localized chemisorption bonds, through probing the surface chemical interaction at the orbital level with near-edge X-ray absorption fine structure (NEXAFS). Such ligand-induced orbital redistributions, which are revealed by combining experimental discoveries, quantum calculations, and theoretical analysis, are cooperative with ligand coverages and can enhance the strength of chemisorption and ligation-induced surface effects on nanomaterials. The model and concept of nanoscale cooperative chemisorption reveal the general physical principle that drives the coverage-dependent ligand-induced surface effects on regulating the electronic structures, surface activity, optical properties, and chemisorption strength of nanomaterials.

Molecule Channels Directed by Cation-Decorated Graphene Oxide Nanosheets and Their Application as Membrane Reactors.

Highly selective macromembranes, fabricated by cation-decorated graphene oxide, exhibit an excellent selectivity toward a wide range of solvents. Mixed solvents are successfully separated, based on which a membrane reactor is designed to promote a series of chemical reactions. The cations bonding to the graphene oxide nanosheets are found to be responsible for this selectivity by cation-π, electrostatic interactions, and hydrogen bonding.

Insights into the electrochemical performances of Bi anodes for Mg ion batteries using 25Mg solid state NMR spectroscopy.

Bi nanowires as anode materials for Mg ion batteries exhibit excellent electrochemical behaviour, forming Mg3Bi2; this is in part ascribed to the rapid Mg mobility between the two Mg sites of Mg3Bi2, as revealed by the 25Mg NMR spectra of Mg3Bi2 formed electrochemically and via ball-milling. A mechanism involving hops into vacant Mg sites is proposed.

Unusual enrichment and assembly of TiO2 nanocrystals at water/hydrophobic interfaces in a pure inorganic phase.

We report an unusual enrichment and assembly of TiO2 nanocrystals at water/hydrophobic interfaces through oxidative hydrolysis of TiCl3 in water. The assembly is a spontaneous process that involves on-water inorganic reaction and assembly in the absence of any organic phases. In this process, TiO2 nanoparticles are preferentially produced at water/hydrophobic interfaces. When the surface tension of the aqueous phase is above a critical value, ca. 25-35 mN m(-1), these TiO2 nanocrystals can spontaneously accumulate at water/air interfaces to produce macroscopic sized sheets and tubes.

Well-defined metal-organic framework hollow nanocages.

Metal-organic frameworks (MOFs) have demonstrated great potentials in a variety of important applications. To enhance the inherent properties and endow materials with multifunctionality, the rational design and synthesis of MOFs with nanoscale porosity and hollow feature is highly desired and remains a great challenge. In this work, the formation of a series of well-defined MOF (MOF-5, Fe(II) -MOF-5, Fe(III) -MOF-5) hollow nanocages by a facile solvothermal method, without any additional supporting template is reported. A surface-energy-driven mechanism may be responsible for the formation of hollow nanocages. The addition of pre-synthesized poly(vinylpyrrolidone)- (PVP) capped noble-metal nanoparticles into the synthetic system of MOF hollow nanocages yields the yolk-shell noble metal@MOF nanostructures. The present strategy to fabricate hollow and yolk-shell nanostructures is expected to open up exciting opportunities for developing a novel class of inorganic-organic hybrid functional nanomaterials.

Surface-specific interaction by structure-match confined pure high-energy facet of unstable TiO2(B) polymorph.

Surface structures and surface interactions are key factors that influence the reactivity and stability of nanomaterials. Combining experimental and theoretical investigations, we illustrate the roles of surface interactions in the formation and phase stability of an unusual TiO2(B) polymorph that preferentially exposes the plane of the highest surface energy. We find that the favorable bidentate adsorption of ethylene glycol on the TiO2(B)(010) plane enables the formation and confines the phase stability of TiO2(B) ultrathin nanosheets. The essence of such selective generation of the unusual nanostructure with ultrahigh purity both in phase and morphology lies in the specific adsorption driven by the matched interface structures. The general roles of structural match for the activity and stability in physical interactions are elucidated.

Size effects in atomic-level epitaxial redistribution process of RuO2 over TiO2.

Controls over the atomic dispersity and particle shape of noble metal catalysts are the major qualities determining their usability in industrial runs, but they are usually difficult to be simultaneously realized. Inspired from the Deacon catalyst in which RuO(2) can form epitaxial layers on the surfaces of Rutile TiO(2), here we have investigated the shape evolution process of RuO(2) nanoparticles on the surface of P25 TiO(2). It is found that size effects exist in this process and RuO(2) nanoparticles with sizes ~sub-2 nm can be transformed into epitaxial layers while nanoparticles with bigger sizes are not apt to change their shapes. Based on a thermodynamic model, we infer such transformation process is jointly driven by the surface tension and interfacial lattice match between the nanoparticles and substrates, which may be suggestive for the design of noble metal catalysts integrating both active crystal planes and high atomic exposure ratios.

Hydrogen bond nanoscale networks showing switchable transport performance.

Hydrogen bond is a typical noncovalent bond with its strength only one-tenth of a general covalent bond. Because of its easiness to fracture and re-formation, materials based on hydrogen bonds can enable a reversible behavior in their assembly and other properties, which supplies advantages in fabrication and recyclability. In this paper, hydrogen bond nanoscale networks have been utilized to separate water and oil in macroscale. This is realized upon using nanowire macro-membranes with pore sizes ~tens of nanometers, which can form hydrogen bonds with the water molecules on the surfaces. It is also found that the gradual replacement of the water by ethanol molecules can endow this film tunable transport properties. It is proposed that a hydrogen bond network in the membrane is responsible for this switching effect. Significant application potential is demonstrated by the successful separation of oil and water, especially in the emulsion forms.