Upshift of the d Band Center toward the Fermi Level for Promoting Silver Ion Release, Bacteria Inactivation, and Wound Healing of Alloy Silver Nanoparticles

Computer-aided nanodrug discovery: recent progress and future prospects

Nanodrugs, which utilise nanomaterials in disease prevention and therapy, have attracted considerable interest since their initial conceptualisation in the 1990s. Substantial efforts have been made to develop nanodrugs for overcoming the limitations of conventional drugs, such as low targeting efficacy, high dosage and toxicity, and potential drug resistance. Despite the significant progress that has been made in nanodrug discovery, the precise design or screening of nanomaterials with desired biomedical functions prior to experimentation remains a significant challenge. This is particularly the case with regard to personalised precision nanodrugs, which require the simultaneous optimisation of the structures, compositions, and surface functionalities of nanodrugs. The development of powerful computer clusters and algorithms has made it possible to overcome this challenge through in silico methods, which provide a comprehensive understanding of the medical functions of nanodrugs in relation to their physicochemical properties. In addition, machine learning techniques have been widely employed in nanodrug research, significantly accelerating the understanding of bio-nano interactions and the development of nanodrugs. This review will present a summary of the computational advances in nanodrug discovery, focusing on the understanding of how the key interfacial interactions, namely, surface adsorption, supramolecular recognition, surface catalysis, and chemical conversion, affect the therapeutic efficacy of nanodrugs. Furthermore, this review will discuss the challenges and opportunities in computer-aided nanodrug discovery, with particular emphasis on the integrated "computation + machine learning + experimentation" strategy that can potentially accelerate the discovery of precision nanodrugs.

Increased Cytotoxicity of Bimetallic Ultrasmall Silver-Platinum Nanoparticles (2 nm) on Cells and Bacteria in Comparison to Silver Nanoparticles of the Same Size

Ultrasmall nanoparticles (diameter 2 nm) of silver, platinum, and bimetallic nanoparticles (molar ratio of Ag:Pt 0:100; 20:80; 50:50; 70:30; 100:0), stabilized by the thiolated ligand glutathione, were prepared and characterized by transmission electron microscopy, differential centrifugal sedimentation, X-ray photoelectron spectroscopy, small-angle X-ray scattering, X-ray powder diffraction, and NMR spectroscopy in aqueous dispersion. Gold nanoparticles of the same size were prepared as control. The particles were fluorescently labeled by conjugation of the dye AlexaFluor-647 via copper-catalyzed azide-alkyne cycloaddition after converting amine groups of glutathione into azide groups. All nanoparticles were well taken up by HeLa cells. The cytotoxicity was assessed with an MTT test on HeLa cells and minimal inhibitory concentration (MIC) tests on the bacteria Escherichia coli and Staphylococcus xylosus. Notably, bimetallic AgPt nanoparticles had a higher cytotoxicity against cells and bacteria than monometallic silver nanoparticles or a physical mixture of silver and platinum nanoparticles. However, the measured release of silver ions from monometallic and bimetallic silver nanoparticles in water was very low despite the ultrasmall size and the associated high specific surface area. This is probably due to the surface protection by a dense layer of thiolated ligand glutathione. Thus, the enhanced cytotoxicity of bimetallic AgPt nanoparticles is caused by the biological environment in cell culture media, together with a polarization of silver by platinum.

Coordination Structure Modulation in Group-VIB Metal Doped Ag3PO4 Augments Active Site Density for Electrocatalytic Conversion of N2 to NH3

Doping is considered a promising material engineering strategy in electrochemical nitrogen reduction reaction (NRR), provided the role of the active site is rightly identified. This work concerns the doping of group VIB metal in Ag3PO4 to enhance the active site density, accompanied by d-p orbital mixing at the active site/N2 interface. Doping induces compressive strain in the Ag3PO4 lattice and inherently accompanies vacancy generation, the latter is quantified with positron annihilation lifetime studies (PALS). This eventually alters the metal d-electronic states relative to Fermi level and manipulate the active sites for NRR resulting into side-on N2 adsorption at the interface. The charge density deployment reveals Mo as the most efficient dopant, attaining a minimum NRR overpotential, as confirmed by the detailed kinetic study with the rotating ring disk electrode (RRDE) technique. In fact, the Pt ring of RRDE fails to detect N2H4, which is formed as a stable intermediate on the electrode surface, as identified from in-situ attenuated total reflectance-infrared (ATR-IR) spectroscopy. This advocates the complete conversion of N2 to NH3 on Mo/Ag3PO4-10 and the so-formed oxygen vacancies formed during doping act as proton scavengers suppressing hydrogen evolution reaction resulting into a Faradaic efficiency of 54.8% for NRR.

Interfacial Se-O Bonds Modulating Spatial Charge Distribution in FeSe2/Nb:Fe2O3 with Rapid Hole Extraction for Efficient Photoelectrochemical Water Oxidation

Surface engineering is an effective strategy to improve the photoelectrochemical (PEC) catalytic activity of hematite, and the defect states with abundant coordinative unsaturation atoms can serve as anchoring sites for constructing intimate connections between semiconductors. On this basis, we anchored an ultrathin FeSe2 layer on Nb5+-doped Fe2O3 (FeSe2/Nb:Fe2O3) via interfacial Se-O chemical bonds to tune the surface potential. Density functional theory (DFT) calculations indicate that amorphous FeSe2 decoration could generate electron delocalization over the composite photoanodes so that the electron mobility was improved to a large extent. Furthermore, electrons could be transferred via the newly formed Se-O bonds at the interface and holes were collected at the surface of electrode for PEC water oxidation. The desired charge redistribution is in favor of suppressing charge recombination and extracting effective holes. Later, work function calculations and Mott-Schottky (M-S) plots demonstrate that a type-II heterojunction was formed in FeSe2/Nb:Fe2O3, which further expedited carrier separation. Except for spatial carrier modulation, the amorphous FeSe2 layer also provided abundant active sites for intermediates adsorption according to the d band center results. In consequence, the target photoanodes attained an improved photocurrent density of 2.42 mA cm-2 at 1.23 V versus the reversible hydrogen electrode (RHE), 2.5 times as that of the bare Fe2O3. This study proposed a defect-anchoring method to grow a close-connected layer via interfacial chemical bonds and revealed the spatial charge distribution effects of FeSe2 on Nb:Fe2O3, giving insights into rational designation in composite photoanodes.

Boosting N2 Conversion into NH3 over Ru Catalysts via Modulating the Ru-Promoter Interface

Promoters are indispensable components of Ru-based catalysts to promote N2 activation in ammonia (NH3) synthesis. The rational addition and regulation of promoters play a critical role in affecting the NH3 synthesis rate. In this work, we report a simple method by altering the loading sequence of Ba and Ru species to modulate the Ru-promoter interface, thus significantly boosting the NH3 synthesis rate. The Ba-Ru/GC BM catalyst via the prior loading of Ba rather than Ru over graphitic carbon (GC) exhibits a high NH3 synthesis rate of 18.7 mmol gcat-1 h-1 at 400 °C and 1 MPa, which is 2.5 times that of the Ru-Ba/GC BM catalyst via the conventional prior loading of Ru rather than Ba on GC. Our studies reveal that the prior loading of Ba benefits the high dispersion of the basic Ba promoter over an electron-withdrawing GC support, and then Ba species serve as structural promoters to stabilize Ru with small particle sizes, which exposes more active sites for N2 activation. Additionally, the intimate Ba and Ru interface enables facile electron donation from Ba to Ru sites, thus accelerating N2 dissociation to realize efficient NH3 synthesis. This work provides a simple approach to modulating the Ru-promoter interface and maximizing promoter utilization to enhance NH3 synthesis performance.

Procedural Promotion of Wound Healing by Graphene-Barium Titanate Nanosystem with White Light Irradiation

Background

Wound healing is a continuous and complex process that comprises multiple phases including hemostasis, inflammation, multiplication (proliferation) and remodeling. Although a variety of nanomaterials have been developed to control infection and accelerate wound healing, most of them can only promote one phase but not multiple phases, resulting in lower efficient healing. Although various formulations such as nitric oxide releasing wound dressings were developed for dual action, the nanostructure synthesis and the encapsulation process were complex.

Materials and Methods

Here, we report on the design of graphene-barium titanate nanosystem to procedural promote the wound healing process. The antibacterial effect was assessed in Gram-negative Escherichia coli bacteria (E. coli) and Gram-positive Staphylococcus aureus bacteria (S. aureus), the cell proliferation and migration experiment was investigated in mouse embryonic fibroblast (NIH-3T3) cells, and the wound healing effect was analyzed in female BALB/c mice with infected skin wound on the back.

Results

Results showed that graphene-barium titanate nanosystem could generate abundant ROS to kill both E. coli and S. aureus. The growth curves, bacterial viability, colony number formation and scanning electron microscopy (SEM) images of E. coli and S. aureus all confirmed the antibacterial effect. Cell Counting Kit-8 (CCK-8) assay displayed that GBT possesses great biocompatibility. EdU assay showed that GBT plus white light irradiation significantly promoted the proliferation and migration of NIH-3T3 cells. Scratch assay found that GBT could achieve a fast scratch closure compared to the control. In vivo wound healing effect indicates that GBT can accelerate wound repair procedure.

Conclusion

GBT nanocomposite is capable of programmatically accelerating wound healing through multiple stages, including production of a large amount of ROS after white light exposure to effectively kill E. coli and S. aureus to prevent wound infection and as a scaffold to accelerate fibroblast proliferation and migration to the wound to accelerate wound healing.

Nano- and Microemulsions in Biomedicine: From Theory to Practice

Nano- and microemulsions are colloidal systems that are widely used in various fields of biomedicine, including wound and burn healing, cosmetology, the development of antibacterial and antiviral drugs, oncology, etc. The stability of these systems is governed by the balance of molecular interactions between nanodomains. Microemulsions as a colloidal form play a special important role in stability. The microemulsion is the thermodynamically stable phase from oil, water, surfactant and co-surfactant which forms the surface of drops with very small surface energy. The last phenomena determines the shortage time of all fluid dispersions including nanoemulsions and emulgels. This review examines the theory and main methods of obtaining nano- and microemulsions, particularly focusing on the structure of microemulsions and methods for emulsion analysis. Additionally, we have analyzed the main preclinical and clinical studies in the field of wound healing and the use of emulsions in cancer therapy, emphasizing the prospects for further developments in this area.

Effects of the Donor Unit on the Formation of Hybrid Layers of Donor-Acceptor Copolymers with Silver Nanoparticles

Donor-acceptor (D-A) copolymers containing perylene-3,4,9,10-tetracarboxydiimide (PDI) electron-acceptor (A) units belonging to n-type semiconductors are of interest due to their many potential applications in photonics, particularly for electron-transporting layers in all-polymeric or perovskite solar cells. Combining D-A copolymers and silver nanoparticles (Ag-NPs) can further improve material properties and device performances. Hybrid layers of D-A copolymers containing PDI units and different electron-donor (D) units (9-(2-ethylhexyl)carbazole or 9,9-dioctylfluorene) with Ag-NPs were prepared electrochemically during the reduction of pristine copolymer layers. The formation of hybrid layers with Ag-NP coverage was monitored by in-situ measurement of absorption spectra. The Ag-NP coverage of up to 41% was higher in hybrid layers made of copolymer with 9-(2-ethylhexyl)carbazole D units than in those made of copolymer with 9,9-dioctylfluorene D units. The pristine and hybrid copolymer layers were characterized by scanning electron microscopy and X-ray photoelectron spectroscopy, which proved the formation of hybrid layers with stable Ag-NPs in the metallic state with average diameters <70 nm. The influence of D units on Ag-NP diameters and coverage was revealed.

Bismuth Tungstate-Silver Sulfide Z-Scheme Heterostructure Nanoglue Promotes Wound Healing through Wound Sealing and Bacterial Inactivation

Rapid wound closure and bacterial inactivation are effective strategies to promote wound healing. Herein, a versatile nanoglue, bismuth tungstate (Bi₂WO₆)-silver sulfide (Ag₂S) direct Z-scheme heterostructure nanoparticles (BWOA NPs), was designed to accelerate wound healing. BWOA NPs' hollow structure and rough surface could effectively close wound tissues acting as a barrier between external bacteria and the wound. More importantly, the unique Z-scheme heterostructure endows BWOA NPs with an effective electron and hole separating ability with potent redox potential, where electrons and holes could effectively react with water and oxygen to produce reactive oxygen species, leading to a higher antibacterial activity against both endogenous and external bacteria at the wound site. A series of in vitro and in vivo biological assessments demonstrated that BWOA NPs could rapidly close wounds and promote wound healing. With sunlight irradiation, the inhibiting rates of BWOA NPs against Escherichia coli and Staphylococcus aureus are 61.62 ± 2.85 and 73.40 ± 3.28%, respectively. Also, the wound healing rate in BWOA NP-treated mice is 25.90 ± 5.85% higher than PBS. This design provides a new effective strategy to promote bacterial inactivation and accelerate wound healing.

Tuning Fe Spin Moment in Fe-N-C Catalysts to Climb the Activity Volcano via a Local Geometric Distortion Strategy

As the most promising alternative to platinum-based catalysts for cathodic oxygen reduction reaction (ORR) in proton exchange membrane fuel cells, further performance enhancement of Fe-N-C catalysts is highly expected to promote their wide application. In Fe-N-C catalysts, the single Fe atom forms a square-planar configuration with four adjacent N atoms (D4h symmetry). Breaking the D4h symmetry of the FeN4 active center provides a new route to boost the activity of Fe-N-C catalysts. Herein, for the first time, the deformation of the square-planar coordination of FeN4 moiety achieved by introducing chalcogen oxygen groups (XO2 , X = S, Se, Te) as polar functional groups in the Fe-N-C catalyst is reported. The theoretical and experimental results demonstrate that breaking the D4h symmetry of FeN4 results in the rearrangement of Fe 3d electrons and increases spin moment of Fe centers. The efficient spin state manipulation optimizes the adsorption energetics of ORR intermediates, thereby significantly promoting the intrinsic ORR activity of Fe-N-C catalysts, among which the SeO2 modified catalyst lies around the peak of the ORR volcano plot. This work provides a new strategy to tune the local coordination and thus the electronic structure of single-atom catalysts.

Flexible, Strong and Multifunctional Anf@Ag Nanocomposite Film for Human Physiology and Motion Monitoring

To expand the application range of flexible pressure sensors, endowing them with multifunction capabilities becomes extremely important. Herein, a flexible, strong and multifunctional nanocomposite film was prepared by introducing silver nanoparticles (Ag NPs) into aramid nanofiber (ANF) film using a simple two-step vacuum filtration method. When the Ag content was 27.6 vol%, the electrical resistance of the resulting ANF@Ag nanocomposite film was as low as 1.63 Ω/cm2, and the water contact angle of the nanocomposite film reached 153.9 ± 1°. Compared to the ANF film, the tensile strength of the nanocomposite film increased from 55 MPa to 66.3 MPa with an increase of 20.5%. After being applied to the human body, the nanocomposite film served as a pressure sensor that was able to recognize different stimuli for healthcare monitoring. Based on the advantages, it may become a potential candidate for electronic skin, intelligent wearable devices and medical detection equipment.

Controlling the D-band for improved oxygen evolution performance in Ni modulated ultrafine Co nanoparticles embedded in Nitrogen-doped carbon microspheres

Despite the challenges on tuning the d-band structure of transition metals, the d-band is of great importance for promoting the interaction between catalytic and intermediates during the oxygen evolution reaction (OER) process. Herein, ultrafine Co nanoparticles embedded in the surface layer of nitrogen-doped carbon microspheres are prepared through an in-situ co-coordination strategy, and its d-band is modulated by introducing different Ni amounts. The introduction of Ni in the Co crystal lattice can tune the d-band center and unpaired electrons, which collectively result in an enhancement of OER activity and kinetics. By investigating the catalysts with Ni content from 0% to 75%, it is concluded that the catalyst with 25% Ni shows optimal OER activity, lower overpotential (285 mV at 10 mA cm^-2) and higher current densities (73.75 mA cm^-2 at 1.63 V). Moreover, the good stability is also demonstrated with the negligible decrease on current densities after 3000 CV cycles or 100 h of continuous test in alkaline media. This concept of modulating the d-band structure by introducing a transition metal with different contents in another transition metal crystal lattice could present an alternative pathway to the development of highly active catalytic materials for OER and beyond.

Bismuth Oxychloride Nanomaterials Fighting for Human Health: From Photodegradation to Biomedical Applications

Environmental pollution and various diseases seriously affect the health of human beings. Photocatalytic nanomaterials (NMs) have been used for degrading pollution for a long time. However, the biomedical applications of photocatalytic NMs have only recently been investigated. As a typical photocatalytic NM, bismuth oxychloride (BiOCl) exhibits excellent photocatalytic performance due to its unique layered structure, electronic properties, optical properties, good photocatalytic activity, and stability. Some environmental pollutants, such as volatile organic compounds, antibiotics and their derivatives, heavy metal ions, pesticides, and microorganisms, could not only be detected but also be degraded by BiOCl-based NMs due to their excellent photocatalytic and photoelectrochemical properties. In particular, BiOCl-based NMs have been used as theranostic platforms because of their CT and photoacoustic imaging abilities, as well as photodynamic and photothermal performances. However, some reviews have only profiled the applications of dye degradation, hydrogen or oxygen production, carbon dioxide reduction, or nitrogen fixation of BiOCl NMs. There is a notable knowledge gap regarding the systematic study of the relationship between BiOCl NMs and human health, especially the biomedical applications of BiOCl-based NMs. As a result, in this review, the recent progress of BiOCl-based photocatalytic degradation and biomedical applications are summarized, and the improvement of BiOCl-based NMs in environmental and healthcare fields are also discussed. Finally, a few insights into the current status and future perspectives of BiOCl-based NMs are given.

Theoretical Roadmap for Best Oxygen Reduction Activity in Two-dimensional Transition Metal Tellurides

Developing highly active and cost-effective electrocatalysts to replace Pt-based catalysts for the sluggish oxygen reduction reaction (ORR) is a major challenge in the commercialization of fuel cells. Although two-dimensional (2D) transition-metal tellurides have recently been proposed as alternative low-cost ORR catalysts, a fundamental study on the origin of the activity is required to further optimize their composition and performance. Herein, we investigated the electronic properties and ORR catalytic performances of a series of exfoliable 2D transition-metal tellurides to uncover the underlying mechanisms by means of density functional theory simulations. Our in-depth analysis shows that the activation of the ORR mainly depends on the partially filled p_z state of active Te atoms, which can simultaneously accept and donate electrons behaving similarly to both the occupied and unoccupied d orbitals of Pt atoms. This results in a linear relationship between the p_z-band center and the adsorption free energies of O₂ and intermediates, indicating that the p_z-band center might be used as an effective descriptor to probe the performance of telluride catalysts. On this basis, we predicted several 2D transition-metal tellurides with promising catalytic performance and reduced precious-metal contents, where NbRhTe₄ reaches the top of the activity volcano with a limiting potential of 0.96 V. This study provides theoretical guidance to design high-performing 2D telluride ORR catalysts, and its principle might be applicable to other electrochemical reactions in 2D chalcogenides.

Using proposed theoretical guidelines, we designed several high-performing 2D telluride ORR catalysts, where NbRhTe₄ reaches the top of the activity volcano with a limiting potential of 0.96 V.

Bismuth telluride functionalized bismuth oxychloride used for enhancing antibacterial activity and wound healing efficacy with sunlight irradiation

Bacterial infection can lead to chronic non-healing wounds and serious tissue damage. The wound healing process could be accelerated through bacterial inactivation using some semiconductor nanomaterials with the irradiation of light. Herein, we develop sunlight triggered bismuth telluride-bismuth oxychloride heterostructure nanosheets as antibacterial agents for promoting wound healing, in which bismuth telluride can effectively narrow the bandgap of bismuth oxychloride, resulting in more sunlight absorption and higher antibacterial activity. In fact, the bandgap of bismuth oxychloride has been narrowed from 3.25 eV to 2.37 eV as proved by ultraviolet-visible diffuse reflectance spectroscopy. With simulated sunlight irradiation, bismuth telluride-bismuth oxychloride nanosheets could effectively produce reactive oxygen species and inhibit the growth of both Gram-positive and Gram-negative bacteria. In vivo experiments further confirmed the excellent wound healing capability of bismuth telluride-bismuth oxychloride nanosheets. This work may provide a facile strategy for designing sunlight triggered bacterial inactivation agents.

Microenvironment-responsive multifunctional hydrogels with spatiotemporal sequential release of tailored recombinant human collagen type III for the rapid repair of infected chronic diabetic wounds

Recently, the incidence of chronic diabetic wounds increases continuously, and the existing clinical treatment is less effective. Thus, it is an urgent need to solve these problems for better clinical treatment effects. Herein, we prepared a brand-new tailored recombinant human collagen type III (rhCol III) and constructed a multifunctional microenvironment-responsive hydrogel carrier based on multifunctional antibacterial nanoparticles (PDA@Ag NPs) and our tailored rhCol III. The multifunctional smart hydrogel disintegrated quickly at the chronic diabetic wound sites and achieved the programed on-demand release of different therapeutic substances. The first released PDA@Ag NPs showed great antibacterial properties against S. aureus and E. coli. They could kill bacteria rapidly, and also showed antioxidant and anti-inflammatory effects at the wound site. The subsequent release of our tailored rhCol III could promote the proliferation and migration of mouse fibroblasts and endothelial cells during the proliferation and remodeling process of wound healing. Relevant results showed that the multifunctional smart hydrogel could promote the expression levels of basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF), decrease the inflammatory response, accelerate the deposition of collagen and increase cell proliferation and angiogenesis, thereby speeding up the healing of infected chronic wounds. In a word, the hydrogel, which took into consideration the complex microenvironment at the wound site and multi-stage healing process, could achieve programmed and responsive release of different therapeutic substances to meet the treatment needs in different wound healing stages. More importantly, our work illustrated the great application potential of our brand-new rhCol III in promoting chronic wound repair and regeneration.

Symbolic Transformer Accelerating Machine Learning Screening of Hydrogen and Deuterium Evolution Reaction Catalysts in MA2Z4 Materials

Two-dimensional (2D) materials have been developed into various catalysts with high performance, but employing them for developing highly stable and active nonprecious hydrogen evolution reaction (HER) catalysts still encounters many challenges. To this end, the machine learning (ML) screening of HER catalysts is accelerated by using genetic programming (GP) of symbolic transformers for various typical 2D MA₂Z₄ materials. The values of the Gibbs free energy of hydrogen adsorption (ΔG_H*) are accurately and rapidly predicted via extreme gradient boosting regression by using only simple GP-processed elemental features, with a low predictive root-mean-square error of 0.14 eV. With the analysis of ML and density functional theory (DFT) methods, it is found that various electronic structural properties of metal atoms and the p-band center of surface atoms play a crucial role in regulating the HER performance. Based on these findings, NbSi₂N₄ and VSi₂N₄ are discovered to be active catalysts with thermodynamical and dynamical stability as ΔG_H* approaches to zero (-0.041 and 0.024 eV). In addition, DFT calculations reveal that these catalysts also exhibit good deuterium evolution reaction (DER) performance. Overall, a multistep workflow is developed through ML models combined with DFT calculations for efficiently screening the potential HER and DER catalysts from 2D materials with the same crystal prototype, which is believed to have significant contribution to catalyst design and fabrication.

Controlling alloy to core-shell structure transformation of Au-Pd icosahedral nanoparticles

The structure transformation between Au-Pd alloy and core-shell icosahedral nanoparticles was achieved by a one-step aqueous-phase strategy. This strategy provided a way to tune the structure and atomic distribution of Au-Pd icosahedral nanoparticles. It could modulate the electronic structure of Pd, achieving promoted electrocatalytic ability toward the hydrogen evolution reaction.

Fermi Level Equilibration at the Metal-Molecule Interface in Plasmonic Systems

We highlight a new metal-molecule charge transfer process by tuning the Fermi energy of plasmonic silver nanoparticles (AgNPs) in situ. The strong adsorption of halide ions upshifts the Fermi level of AgNPs by up to ∼0.3 eV in the order Cl^- < Br^- < I^-, favoring the spontaneous charge transfer to aligned molecular acceptor orbitals until charge neutrality across the interface is achieved. By carefully quantifying, experimentally and theoretically, the Fermi level upshift, we show for the first time that this effect is comparable in energy to different plasmonic effects such as the plasmoelectric effect or hot-carriers production. Moreover, by monitoring in situ the adsorption dynamic of halide ions in different AgNP-molecule systems, we show for the first time that the catalytic role of halide ions in plasmonic nanostructures depends on the surface affinity of halide ions compared to that of the target molecule.

Construction of a Unique Structure of Ru Sites in the RuP Structure for Propane Dehydrogenation

It is an important task to develop low-cost and anticoking catalysts for the propane dehydrogenation (PDH) reaction. In this work, the P element is introduced to the Ru-based catalyst to obtain Ru sites with a unique structure and the obtained Ru_xP_y (x/y = 2:1, 1:1, 1:2) catalysts are then employed in PDH. Density functional theory (DFT) results show that the addition of P leads to the formation of separated Ru sites and the adjustment of the valance band state of Ru. The upward shift of the d-band center leads to a reduction of the reaction energy barrier for dehydrogenation of propane and an enhancement of catalytic activity. The analysis of the competition between propylene deep dehydrogenation and propylene desorption for each catalyst shows that desorption of propylene is preferred on the RuP(112) surface. Considering both catalytic activity and propylene selectivity, the RuP catalyst is potential for the propane dehydrogenation reaction. On the RuP surface, the PDH reaction proceeds by the dehydrogenation of the H atom on the methylene group (isopropyl pathway), thus restraining the deep dehydrogenation of propylene. The Ru_xP_y catalysts are also synthesized in experiments, and PDH evaluation shows that the RuP structure is a remarkable PDH catalyst with a stable structure, anticoking ability, and low cost.

Single-Particle Hyperspectral Imaging Reveals Kinetics of Silver Ion Leaching from Alloy Nanoparticles

Gold-silver alloy nanoparticles are interesting for multiple applications, including heterogeneous catalysis, optical sensing, and antimicrobial properties. The inert element gold acts as a stabilizer for silver to prevent particle corrosion, or conversely, to control the release kinetics of antimicrobial silver ions for long-term efficiency at minimum cytotoxicity. However, little is known about the kinetics of silver ion leaching from bimetallic nanoparticles and how it is correlated with silver content, especially not on a single-particle level. To characterize the kinetics of silver ion release from gold-silver alloy nanoparticles, we employed a combination of electron microscopy and single-particle hyperspectral imaging with an acquisition speed fast enough to capture the irreversible silver ion leaching. Single-particle leaching profiles revealed a reduction in silver ion leaching rate due to the alloying with gold as well as two leaching stages, with a large heterogeneity in rate constants. We modeled the initial leaching stage as a shrinking-particle with a rate constant that exponentially depends on the silver content. The second, slower leaching stage is controlled by the electrochemical oxidation potential of the alloy being steadily increased by the change in relative gold content and diffusion of silver atoms through the lattice. Interestingly, individual nanoparticles with similar sizes and compositions exhibited completely different silver ion leaching yields. Most nanoparticles released silver completely, but 25% of them appeared to arrest leaching. Additionally, nanoparticles became slightly porous. Alloy nanoparticles, produced by scalable laser ablation in liquid, together with kinetic studies of silver ion leaching, provide an approach to design the durability or bioactivity of alloy nanoparticles.

Antimicrobial efficacy of platinum-doped silver nanoparticles

Silver nanoparticles (AgNPs) have been proposed to combat oral infection due to their efficient ionic silver (Ag+ ) release. However, concentrations required for antimicrobial efficacy may not be therapeutically viable. In this work, platinum-doped silver nanoparticles (Pt-AgNPs) were explored to evaluate their potential for enhanced Ag+ release, which could lead to enhanced antimicrobial efficacy against S. aureus, P. aeruginosa, and E. coli. AgNPs doped with 0.5, 1, and 2 mol% platinum (Pt0.5 -AgNPs, Pt1 -AgNPs, and Pt2 -AgNPs) were synthesized by a chemical reduction method. Transmission electron microscopy revealed mixed morphologies of spherical, oval, and ribbon-like nanostructures. Surface-enhanced Raman scattering revealed that the surface of Pt-AgNPs was covered with up to 93% Pt. The amount of Ag+ released increased 16.3-fold for Pt2 -AgNPs, compared to AgNPs. The initial lag phase in bacterial growth curve was prolonged for Pt-AgNPs. This is consistent with a Ag+ release profile that exhibited an initial burst followed by sustained release. Doping AgNPs with platinum significantly increased the antimicrobial efficacy against all species. Pt2 -AgNPs exhibited the lowest minimum inhibitory concentrations, followed by Pt1 -AgNPs, Pt0.5 -AgNPs, and AgNPs, respectively. Doping AgNPs with a small amount of platinum promoted the release of Ag+ , based on the sacrificial anodic effect, and subsequently enhanced their antimicrobial efficacy.

Hierarchical Acceleration of Wound Healing through Intelligent Nanosystem to Promote Multiple Stages

Wound healing is a dynamic, interactive, and complex process, including multiple stages. Although various nanomaterials are applied to accelerate the wound healing process through exhibiting antibacterial activity or promoting cell proliferation, only a single stage is promoted during the process, lowering healing efficacy. It is necessary to develop programmable nanosystems for promoting multiple wound healing stages in sequence. Herein, arginine-loaded and detachable ceria-graphene nanocomposites (_ACG NCs) were designed to achieve this purpose. Ceria NPs and graphene were linked by base-cleavable N-hydroxysuccinimide ester. At inflammation stage, _ACG NCs could effectively generate reactive oxygen species (ROS) and kill bacteria under white light irradiation due to their efficient electron-hole separation between ceria NPs and graphene. At proliferation stage, ceria NPs could be detached from _ACG NCs and taken up by cells to scarify intracellular ROS and promote cell proliferation, while the separated graphene could act as a scaffold to promote fibroblast migration to wound site. A series of in vitro and in vivo assessments demonstrated that _ACG NCs could effectively accelerate wound healing process.

Hollow, Rough, and Nitric Oxide-Releasing Cerium Oxide Nanoparticles for Promoting Multiple Stages of Wound Healing

Wound healing is a complex and sequential biological process that involves multiple stages. Although various nanomaterials are applied to accelerate the wound healing process, only a single stage is promoted during the process, lacking hierarchical stimulation. Herein, hollow CeO₂ nanoparticles (NPs) with rough surface and l-arginine inside (_Ah CeO₂ NPs) are developed as a compact and programmable nanosystem for sequentially promoting the hemostasis, inflammation, and proliferation stages. The rough surface of _Ah CeO₂ NPs works as a nanobridge to rapidly closure the wounds, promoting the hemostasis stage. The hollow structure of _Ah CeO₂ NPs enables the multireflection of light inside particles, significantly enhancing the light harvest efficiency and electron-hole pair abundance. Simultaneously, the porous shell of _Ah CeO₂ NPs facilitates the electron-hole separation and reactive oxygen species production, preventing wound infection and promotion wound healing during the inflammation stage. The enzyme mimicking property of _Ah CeO₂ NPs can alleviate the oxidative injury in the wound, and the released l-arginine can be converted into nitric oxide (NO) under the catalysis of inducible NO synthase, both of which promote the proliferation stage. A series of in vitro and in vitro biological assessments corroborate the effectiveness of _Ah CeO₂ NPs in the wound healing process.