A chitosan-based hydrogel with ultrasound-driven immuno-sonodynamic therapeutic effect for accelerated bacterial infected wound healing.

Sonodynamic therapy has attracted much attention as a noninvasive treatment for deep infections. However, it is challenging to achieve high antibacterial activity for hydrogels under ultrasonic irradiation due to the relatively weak sono-catalysis capability of sonosensitizers. Herein, an ultrasound-responsive antibacterial hydrogel (Fe3O4/HA/Ber-LA) composed of Fe3O4-grafted-Berberine, chitosan molecules modified with L-arginine and poly (vinyl alcohol) is prepared for enhanced sonodynamic therapy and immunoregulation. The formation of heterojunction between berberine and Fe3O4 with different work function promotes the charge separation and electron flow and disrupts the conjugated structure of berberine, causing a significant decrease in the band gap, eventually enhancing the sonocatalytic activity. The combination of berberine with Fe3O4 also significantly improves the oxygen adsorption energy, enabling more O2 molecules to react with the electron-rich regions on the surface of Fe3O4 to generate more reactive oxygen species (ROS). L-arginine grafted in the hydrogel is catalyzed by the ROS to release nitric oxide, which not only possesses antibacterial activity, but also positively affects macrophage M1 polarization to display potent phagocytosis to Staphylococcus aureus, thus achieving immuno-sonodynamic therapy. Hence, Fe3O4/HA/Ber-LA hydrogel under ultrasound irradiation shows excellent antibacterial activity. Furthermore, the antioxidative activity and anti-inflammatory effect of berberine released from the hybrid hydrogel induces macrophages to polarize towards the anti-inflammatory M2 status as infection comes under control, thus accelerating the wound healing. The hybrid hydrogel based on the immuno-sonodynamic therapy may be an extraordinary candidate for the treatment of deep infections.

In Situ Study of Precipitates' Effect on Grain Deformation Behavior and Mechanical Properties of S31254 Super Austenitic Stainless Steel.

Grain boundary (GB) precipitation-induced cracking is a significant issue for S31254 super austenitic stainless steel during hot working. Investigating the deformation behavior based on precipitate morphology and distribution is essential. In this study, continuous smaller and intermittent larger precipitates were obtained through heat treatments at 950 °C and 1050 °C. The microstructure evolution and mechanical properties influenced by precipitates were experimentally investigated using an in situ tensile stage inside a scanning electron microscope (SEM) combined with electron backscatter diffraction (EBSD). The results showed that continuous precipitates at 950 °C had a stronger pinning effect on the GB, making grain rotation difficult and promoting slip deformation in the plastic interval. Continuous precipitates caused severe stress concentration near GB and reduced coordinated deformation ability. Additionally, the crack propagation path changed from transcrystalline to intercrystalline. Furthermore, internal precipitates were a crucial factor affecting the initial crack nucleation position. Interconnected precipitates led to an intergranular fracture tendency and severe deterioration of the material's plasticity, as observed in fracture morphology.

Ultrasound-driven radical chain reaction and immunoregulation of piezoelectric-based hybrid coating for treating implant infection.

The poor efficiency of US-responsive coatings on implants restricts their practical application. Immunotherapy that stimulates immune cells to enhance their antibacterial activity is expected to synergize with sonodynamic therapy for treating implant infection effectively and safely. Herein, US-responsive hybrid coatings composed of the oxygen-deficient BaTiO3 nanorod arrays and l-arginine (BaTiO3-x/LA) are designed and prepared on titanium implants for sonocatalytic therapy-cooperated immunotherapy to treat Methicillin-resistant Staphylococcus aureus (MRSA) infection. BaTiO3-x/LA can generate more oxidizing reactive oxygen species (ROS, hydroxyl radical (·OH)) and reactive nitrogen species (RNS, peroxynitrite anion (ONOO-)). The construction of nanorod arrays and oxygen defects balances the piezoelectric properties and sonocatalytic capability during US treatment. The generated piezoelectric electric field provides a sufficient driving force to separate electrons and holes, and the oxygen defects attenuate the electron-hole recombination efficiency, consequently increasing the yield of ROS during the US treatment. Moreover, nitric oxide (NO) released by l-arginine reacts with the superoxide radical (·O2-) to produce ONOO-. Since, this radical chain reaction improves the oxidizing ability between bacteria and radicals, the cell membrane (argB, secA2) and DNA (dnaBGXN) are destroyed. The bacterial self-repair mechanism indirectly accelerates bacterial death based on the transcriptome analysis. In addition to participating in the radical chain reaction, NO positively affects macrophage M1 polarization to yield potent phagocytosis to MRSA. As a result, without introducing an extra sonosensitizer, BaTiO3-x/LA exhibits excellent antibacterial activity against MRSA after the US treatment for 15 min. Furthermore, BaTiO3-x/LA facilitates macrophage M2 polarization after implantation and improves osteogenic differentiation. The combined effects of sonodynamic therapy and immunoregulation lead to an effective and safe treatment method for implant-associated infections.

A multifunctional nano-hydroxyapatite/MXene scaffold for the photothermal/dynamic treatment of bone tumours and simultaneous tissue regeneration.

After resection of bone tumour, the risk of cancer recurrence and numerous bone defects continues to threaten the health of patients. To overcome the challenge, we developed a novel multifunctional scaffold material consisting mainly of nano-hydroxyapatite particles (n-HA), MXene nanosheets and g-C3N4 to prevent tumour recurrence and promote bone formation. N-HA has the potential to restrict the growth of osteosarcoma cells, and the combination of MXene and g-C3N4 enables the scaffolds to produce photodynamic and photothermal effects simultaneously under near infrared (NIR) irradiation. Surprisingly, n-HA can further enhance the synergistic anti-tumour function of photodynamic and photothermal, and the scaffolds can eradicate osteosarcoma cells in only 10 min at a mild temperature of 45 ℃. Moreover, the scaffold exhibit exceptional cytocompatibility and possesses the capacity to induce osteogenic differentiation of bone marrow mesenchymal stem cells. Therefore, this multifunctional scaffold can not only inhibits the proliferation of bone tumour cells and rapidly eradicate bone tumour through NIR irradiation, but also enhances osteogenic activity. This promising measure can be used to treat tissue damage after bone tumour resection.

Engineering multilayer catalytic interfaces with N, S co-regulation for high performance water splitting.

The rational design of hierarchical nano-heterojunction electrocatalysts with efficient and durable water splitting performance is a hot research topic in the field of sustainable energy conversion. Herein, chemical vapor deposition methods are exploited to dope N and S elements in a core-shell structured Co3O4@NiMoO4 with a layered structure (N, S-Co3O4@NiMoO4/NF400). The close contact between Co3O4 nanowires and N, S co-doped NiMoO4 cubic arrays facilitates electron transfer. The electronic structure of Ni, Co and Mo atoms could be optimized to enhance their electrical conductivity by modulation of N and S atoms. At current densities of 10 and 200 mA cm-2, N, S-Co3O4@NiMoO4/NF400 has an overpotential of 200, 300 and 71 160 mV for the oxygen evolution reaction and hydrogen evolution reaction, respectively. Its water splitting voltages are 1.45 V and 2 V at 10 and 200 mA cm-2. In addition, N, S-Co3O4@NiMoO4/NF400 can operate stably for 100 h at a current density of 50 mA cm-2. This work provides a new approach to designing bifunctional catalysts with hierarchical heterogeneous structures co-regulated by dual elements.

The enhanced visible light driven photocatalytic activity of zinc porphyrin/g-C3N4 nanosheet for efficient bacterial infected wound healing.

Graphitic carbon nitride (g-C3N4) has received much attention as a metal-free polymeric two-dimensional photocatalyst for antibiotic-free antibacterial application. However, the weak photocatalytic antibacterial activity of pure g-C3N4 stimulated by visible light limits its applications. Herein, g-C3N4 is modified with Zinc (II) meso-tetrakis (4-carboxyphenyl) porphyrin (ZnTCPP) by amidation reaction to enhance the utilization of visible light and reduce the recombination of electron-hole pairs. The composite (ZP/CN) is used to treat bacterial infection under visible light irradiation with a high efficacy of 99.99% within 10 min due to the enhanced photocatalytic activity. Ultraviolet photoelectron spectroscopy and density flooding theory calculations indicate the excellent electrical conductivity between the interface of ZnTCPP and g-C3N4. The formed built-in electric field is responsible for the high visible photocatalytic performance of ZP/CN. In vitro and in vivo tests have demonstrated that ZP/CN not only possesses excellent antibacterial activity upon visible light irradiation, but also facilitates the angiogenesis. In addition, ZP/CN also suppresses the inflammatory response. Therefore, this inorganic-organic material can serve as a promising platform for effective healing of bacteria-infected wounds.

Ti3 C2 TX MXene Modified with ZnTCPP with Bacteria Capturing Capability and Enhanced Visible Light Photocatalytic Antibacterial Activity.

Light-assisted antibacterial therapy is a promising alternative to antibiotic therapy due to the high antibacterial efficacy without bacterial resistance. Recent research has mainly focused on the use of near-infrared light irradiation to kill bacteria by taking advantage of the synergistic effects rendered by hyperthermia and radical oxygen species. However, photocatalytic antibacterial therapy excited by visible light is more convenient and practical, especially for wounds. Herein, a visible light responsive organic-inorganic hybrid of ZnTCPP/Ti3 C2 TX is designed and fabricated to treat bacterial infection with antibacterial efficiency of 99.86% and 99.92% within 10 min against Staphylococcus aureus and Escherichia coli, respectively. The porphyrin-metal complex, ZnTCPP, is assembled on the surface of Ti3 C2 TX MXene to capture bacteria electrostatically and the Schottky junction formed between Ti3 C2 TX and ZnTCPP promotes visible light utilization, accelerates charge separation, and enhances the mobility of photogenerated charges, and finally increases the photocatalytic activity. As a result of the excellent bacteria capturing ability and photocatalytic antibacterial effects, ZnTCPP/Ti3 C2 TX exposed to visible light has excellent antibacterial properties in vitro and in vivo. Therefore, organic-inorganic materials that have been demonstrated to possess good biocompatibility and enhance wound healing have large potential in bio-photocatalysis, antibacterial therapy, as well as antibiotics-free treatment of wounds.

Interfacial Design on Graphene-Hematite Heterostructures for Enhancing Adsorption and Diffusion towards Superior Lithium Storage.

Hematite (α-Fe2O3) is a promising electrode material for cost-effective lithium-ion batteries (LIBs), and the coupling with graphene to form Gr/α-Fe2O3 heterostructures can make full use of the merits of each individual component, thus promoting the lithium storage properties. However, the influences of the termination of α-Fe2O3 on the interfacial structure and electrochemical performance have rarely studied. In this work, three typical Gr/α-Fe2O3 interfacial systems, namely, single Fe-terminated (Fe-O3-Fe-R), double Fe-terminated (Fe-Fe-O3-R), and O-terminated (O3-Fe-Fe-R) structures, were fully investigated through first-principle calculation. The results demonstrated that the Gr/Fe-O3-Fe-R system possessed good structural stability, high adsorption ability, low volume expansion, as well as a minor diffusion barrier along the interface. Meanwhile, investigations on active heteroatoms (e.g., B, N, O, S, and P) used to modify Gr were further conducted to critically analyze interfacial structure and Li storage behavior. It was demonstrated that structural stability and interfacial capability were promoted. Furthermore, N-doped Gr/Fe-O3-Fe-R changed the diffusion pathway and made it easy to achieve free diffusion for the Li atom and to shorten the diffusion pathway.

Critical Role of Surface Defects in the Controllable Deposition of Li2S on Graphene: From Molecule to Crystallite.

Uncontrollable electrochemical deposition of Li2S has negative impacts on the electrochemical performance of lithium-sulfur batteries, but the relationship between the deposition and the surface defects is rarely reported. Herein, ab initio molecular dynamics (AIMD) and density functional theory (DFT) approaches are used to study the Li2S deposition behaviors on pristine and defected graphene substrates, including pyridinic N (PDN) doped and single vacancy (SV), as well as the interfacial characteristics, in that such defects could improve the polarity of the graphene material, which plays a vital role in the cathode. The result shows that due to the constraint of molecular vibration, Li2S molecules tend to form stable adsorption with PDN atoms and SV defects, followed by the nucleation of Li2S clusters on these sites. Moreover, the clusters are more likely to grow near these sites following a spherical pattern, while a lamellar pattern is favorable on pristine graphene substrates. It is also discovered that PDN atoms and SV defects provide atomic-level pathways for the electronic transfer within the Li2S-electrode interface, further improving the electrochemical performance of the Li-S battery. It is found for the first time that surface defects also have strong impacts on the deposition pattern of Li2S and provide electronic pathways simultaneously. Our work demonstrated the interior relationship between the surface defects in carbon substrates and the stability of Li2S precipitates, which is of high significance to understand the electrochemical kinetics and design Li-S battery with long cycle life.

Alloyed Crystalline CdSe1-xSx Semiconductive Nanomaterials - A Solid State 113Cd NMR Study.

Solid-state NMR analysis on wurtzite alloyed CdSe1-xSx crystalline nanoparticles and nanobelts provides evidence that the 113Cd NMR chemical shift is not affected by the varying sizes of nanoparticles, but is sensitive to the S/Se anion molar ratios. A linear correlation is observed between 113Cd NMR chemical shifts and the sulfur component for the alloyed CdSe1-xSx (0

Enhanced Thermoelectric Performance of Zintl Phase Ca9Zn4+xSb9 by Beneficial Disorder on the Selective Cationic Site.

Zintl phase compounds Ca9Zn4+xSb9 have promising thermoelectric properties due to their complex crystal structure and tunable interstitial Zn. In this work, we prepared nominal Ca9Zn4+xSb9 (x = 0.5, 0.6, 0.7, and 0.8) using ball milling and hot pressing. Further decreased lattice thermal conductivity was obtained by isoelectronic substitution of Eu on the selective Ca site, which is farther away from the framework of [Zn4+xSb9]δ- for the smaller disturbance of carrier transport. Together with the intensively enhanced carrier mobility, which is attributed to the decreased effective mass and the increased interstitial Zn by inclusion of Eu, an increased peak ZT value to ∼1.05 at 773 K and an enhanced average ZT value to ∼0.73 from 300 to 823 K were achieved in Ca6.75Eu2.25Zn4.7Sb9.

Theoretical insights into photo-induced electron transfer at BiOX (X = F, Cl, Br, I) (001) surfaces and interfaces.

The electron transfer process (ETP) of a photocatalyst plays a crucial role in clarifying its photoelectrochemical catalytic mechanism. BiOX (X = F, Cl, Br, I) (001) surfaces display excellent photocatalytic performance due to the high separation efficiency of photogenerated electron-hole (e--h+) pairs in their own efficient internal electric field (IEF). The oxygen vacancies (OVs) on the surfaces could cause a change in localized electronic states, then improve the photocatalytic activity of BiOX. Here, the ETP at BiOX (001) surfaces with and without surface OVs were calculated and investigated using a DMol3 module based on density functional theory (DFT). The results showed that the electron transfer at the BiOX (001) surfaces and interfaces should be like this: firstly, the [-O-Bi-] layer at the interface received the photon energy, which made the electrons on the O atoms preferentially photo-induced to Bi atoms and left photo-induced holes on the interface O atoms. Then, the effective electrons on the interface Bi atoms were diffused to one- or multi- electron reactions, and at the same time, electrons from the bulk were transferred through the path of O → Bi → X → X → Bi → O on BiOX (001) surfaces under the IEF effect to interface O atoms, and consequently, maintain the stable proceeding of the photocatalytic reaction. More importantly, we found that the X atoms indeed played a key role in connecting the non-bonding interlayers of the BiOX nanocrystals and affecting the ETP on BiOX (001) surfaces as electron transmitters. The exploration of the OV introduction on BiOX (001) surfaces suggested that the OV-induced localized electronic states should increase the electron mobility and the charge carrier density to improve the photocatalytic activity of BiOX, especially for BiOCl and BiOBr. Our findings could provide new insight for deeply understanding the transfer and catalytic behaviour of photo-induced electrons at BiOX (001) surfaces and interfaces.

A combined experimental and first-principle study on the oxidation mechanism of super austenitic stainless steel S32654 at 900 °C.

A combined experimental and first-principle study on the oxidation mechanism of super austenitic stainless steel S32654 at 900 °C for a short time period (1, 3, and 5 h) in air is presented. The samples exhibit excellent oxidation resistance because of the initial and gradual formation of the denser Fe- and Cr-rich layer with increasing oxidation time. Meanwhile, the Mo-rich layer gradually forms because of the Mo diffusion, which results in the formation of the oxide layer with two distinct regions: an inner Fe- and Cr-rich layer and an outer Mo-rich layer. Density functional theory is applied to investigate the diffusion behaviour of Mo atom in the Fe-Cr-Ni/Cr2O3 interface and the effects of alloying elements (Fe, Ni, and Mn) on the Mo diffusion. The Mo originating from the alloy matrix tends to diffuse into the Cr2O3 part, thereby resulting in the formation of the continuous Mo-rich layer, which is consistent with the experimental behaviour. Moreover, the introduction of Ni to the Cr2O3 part can promote the Mo diffusion and the formation of the Mo-rich oxide layer, whereas Fe and Mn can hinder the Mo diffusion. The calculated results provide a microcosmic explanation of the experimental results.

Theoretical Study on Free Fatty Acid Elimination Mechanism for Waste Cooking Oils to Biodiesel over Acid Catalyst.

A theoretical investigation on the esterification mechanism of free fatty acid (FFA) in waste cooking oils (WCOs) has been carried out using DMol(3) module based on the density functional theory (DFT). Three potential pathways of FFA esterification reaction are designed to achieve the formation of fatty acid methyl ester (FAME), and calculated results show that the energy barrier can be efficiently reduced from 88.597kcal/mol to 15.318kcal/mol by acid catalyst. The molar enthalpy changes (ΔrHm°) of designed pathways are negative, indicating that FFA esterification reaction is an exothermic process. The obtained favorable energy pathway is: H(+) firstly activates FFA, then the intermediate combines with methanol to form a tetrahedral structure, and finally, producing FAME after removing a water molecule. The rate-determining step is the combination of the activated FFA with methanol, and the activation energy is about 11.513kcal/mol at 298.15K. Our results should provide basic and reliable theoretical data for further understanding the elimination mechanism of FFA over acid catalyst in the conversion of WCOs to biodiesel products.

Investigation of diffusion length distribution on polycrystalline silicon wafers via photoluminescence methods.

Characterization of the diffusion length of solar cells in space has been widely studied using various methods, but few studies have focused on a fast, simple way to obtain the quantified diffusion length distribution on a silicon wafer. In this work, we present two different facile methods of doing this by fitting photoluminescence images taken in two different wavelength ranges or from different sides. These methods, which are based on measuring the ratio of two photoluminescence images, yield absolute values of the diffusion length and are less sensitive to the inhomogeneity of the incident laser beam. A theoretical simulation and experimental demonstration of this method are presented. The diffusion length distributions on a polycrystalline silicon wafer obtained by the two methods show good agreement.

DFT study of the effects of interstitial impurities on the resistance of Cr-doped γ-Fe(111) surface dissolution corrosion.

Using density-functional calculations, we studied the interaction between interstitial impurities (N, C) and γ-Fe(111) surfaces doped, or not, with Cr, as well as the effect of Cr doping on the dissolution corrosion resistance of the γ-Fe(111) surface. The elementary processes studied afforded microscopic insights into the formation of a Cr-depleted zone, a phenomenon that leads to local corrosion of the stainless steel surface. The aim of this work was to study, at the atomic scale, the effects of N and C on the segregation behavior of Cr and the synergetic effect between co-doped atoms on the resistance to dissolution corrosion of austenitic stainless steel surfaces. The results showed that interstitial impurities prefer to be trapped at near-surface sites, which can impact the segregation behavior of Cr such that it shifts from the surface to the subsurface. Electrode potential calculations and density of states analysis demonstrated that doping with Cr or inserting interstitial impurities into the solid solution can improve the surface corrosion resistance of an fcc Fe substrate, but detrimental effects on the surface corrosion resistance are induced by interactions between Cr and interstitial impurity atoms in co-doped surfaces. The formation of near-surface Cr carbides and nitrides (speculated to be Cr2N and Cr23C6 due to the results obtained for particular co-doped surfaces) was also noted. The results of our theoretical calculations explain some of the experimental results observed at the atomic scale.

Effects of alloying on oxidation and dissolution corrosion of the surface of γ-Fe(111): a DFT study.

Effects of alloying elements in popular steels on the oxidation and dissolution corrosion of the surface of γ-Fe(111) have been investigated by performing density functional theory calculations within the local density approximation. First, the segregation of alloying atoms as well as preferential adsorption sites for oxygen and water were carefully examined, and it was found that all of the alloying elements considered had a tendency to segregate to the surface, and that the most preferred adsorption sites were the hexagonal closed packed (hcp) site and the top site for oxygen and water, respectively. The adsorption energies that characterized the tendency for oxygen or water to be adsorbed on the alloy surface showed that all ten alloying elements (especially Cr, Si, and Cu) were able to inhibit the adsorption of oxygen, and that all of the alloying elements except for Nb, Mo, and Ti inhibited water adsorption. The electrode potentials, which indicate the electrochemical stabilities of the surfaces of the alloys, suggested that all of these alloying elements (especially Cr, Mo, and Si) were able to suppress the adsorption of oxygen and water on the investigated surfaces, except for Nb and Ti in the case of water adsorption. Density of states analysis further indicated that all ten alloying elements (especially Cr, Si, Mo, and Cu) enhanced the corrosion resistance of the fcc Fe substrate, except for Nb and Ti with respect to dissolution corrosion.

Metallofullerenes encaging mixed-metal clusters: synthesis and structural studies of Gdx Ho3-x N@C80 and Gdx Lu3-x N@C80.

Metallofullerenes of Gdx Ho3-x N@C80 and Gdx Lu3-x N@C80 encapsulating mixed-metal nitride clusters were synthesized. Spectroscopic characterization of Gdx Ho3-x N@C80 and Gdx Lu3-x N@C80 was employed to reveal their structural and vibrational properties. The structural properties of these species were analyzed by using theoretical calculations. The studies of Gdx Ho3-x N@C80 and Gdx Lu3-x N@C80 laid the foundations for these species to be used as multifunctional molecules.

Laser beam homogenizing system design for photoluminescence.

Based on waveguide coupling technology, we set a kaleidoscope homogenizer to get an intensity redistributed uniform multimode laser beam and then shape the uniform beam into a large area square beam with an imaging system. The simulation results of overall light intensity uniformity are both greater than 89% under the irradiation areas of 3.5 cm × 3 cm and 10 cm × 10 cm. In the practical application, it is also greater than 85%. After that, we apply this technology to the photoluminescence imaging detection of semiconductor devices, proving that this technology can be widely used in a variety of research requiring large areas of uniform laser illuminating spots.

Effect of surface hydroxyls on dimethyl ether synthesis over the γ-Al2O3 in liquid paraffin: a computational study.

In a recent paper (Zuo et al., Appl Catal A 408:130-136, 2011), the mechanism of dimethyl ether (DME) synthesis from methanol dehydration over γ-Al2O3 (110) was studied using density functional theory (DFT). Using the same method, the effect of surface hydroxyls on γ-Al2O3 in liquid paraffin during DME synthesis from methanol dehydration is investigated. It is found that DME is mainly formed from two adsorbed CH3O groups via methanol dehydrogenation on both dehydrated and hydrated γ-Al2O3 in liquid paraffin. No close correlation between catalytic activity and acid intensity was found. Before and after water adsorption at typical catalytic conditions (e.g., 553 K), the reaction rate is not obviously changed on γ-Al2O3(100) surface in liquid paraffin, but the reaction rate decreases by about 11 times on the (110) in liquid paraffin. Considering the area of the (110) and (100) surfaces under actual conditions, the catalytic activity decreased mainly because the Al3 sites on the (110) surface gradually become inactive. Catalytic activity decreased mainly due to surface hydrophilicity. The calculated results were consistent with the experiment.