Elastic Aerogels of Cellulose Nanofibers@Metal–Organic Frameworks for Thermal Insulation and Fire Retardancy

Metal–organic frameworks(MOFs)with high microporosity and relatively high thermal stability are potential thermal insulation and flame-retardant materials.However,the difficulties in processing and shaping MOFs have largely hampered their applications in these areas.This study outlines the fabrication of hybrid CNF@MOF aerogels by a stepwise assembly approach involving the coating and cross-linking of cellulose nanofibers(CNFs)with continuous nanolayers of MOFs.The cross-linking gives the aerogels high mechanical strength but superelasticity(80%maximum recoverable strain,high specific compression modulus of^200 MPa cm3 g−1,and specific stress of^100 MPa cm3 g−1).The resultant lightweight aerogels have a cellular network structure and hierarchical porosity,which render the aerogels with relatively low thermal conductivity of^40 mW m−1 K−1.The hydrophobic,thermally stable MOF nanolayers wrapped around the CNFs result in good moisture resistance and fire retardancy.This study demonstrates that MOFs can be used as efficient thermal insulation and flame-retardant materials.It presents a pathway for the design of thermally insulating,superelastic fire-retardant nanocomposites based on MOFs and nanocellulose.

Disinfection Kinetics and Contribution of Reactive Oxygen Species When Eliminating Bacteria with TiO_(2) Induced Photocatalysis

Titania (TiO2) induced photocatalysis has been widely investigated and applied as a disinfection strategy in many industrial and clinical applications. Reactive oxygen species (ROS), including hydroxyl radicals (&8226OH), superoxide radicals () and hydrogen peroxide (H2O2), generated in the photocatalytic reaction process are considered to be the active components prompting the bactericidal effect. In the present work, the kinetics of photocatalytic inactivation of Staphylococcus epidermidis and specific contributions of &#8226OH, and H2O2 to the bactericidal process were studied using two disinfection settings sutilizing photocatalytic resin-TiO2 nanocomposite surfaces and suspended TiO2 nanoparticles, respectively. In antibacterial tests against S. epidermidis with a layer of bacterial suspension on the resin-TiO2 surfaces, H2O2 was found to be the most efficient ROS component contributing to the antibacterial effect. Disinfection kinetics showed a two-step behavior with an initial region having a lower disinfection rate followed by a higher rate region after 10 min of UV irradiation. By contrast, in antibacterial tests with suspended bacteria and photocatalytic TiO2 nanoparticles, &#8226OH and H2O2 showed equal significance in the bacterial inactivation having a typical Chick-Watson disinfection kinetics behavior with a steady disinfection rate. The results contribute to the understanding of the bactericidal mechanism and kinetics of photocatalytic disinfection that are essential for designing specific antibacterial applications of photocatalytic materials.

Cytotoxicity,in Vivo Skin Irritation and Acute Systemic Toxicity of the Mesoporous Magnesium Carbonate Upsalite^(█)

Upsalite®is a mesoporous magnesium carbonate synthesized without using surfactants and therefore highly attractive from environmental and production economy points of view. The material has recently been suggested as drug delivery vehicle and as topical bacteriostatic agent. In order to continue exploring these and other bio-related applications of the material, primary biocompatibility studies are needed. Herein we present the first in vivo acute systemic toxicity and skin irritation analyses as well as in vitro cytotoxicity evaluations of Upsalite®. The material was found to be non-toxic for human dermal fibroblasts cells up to a concentration of 1000 μg/ml and 48 h exposure in contrast to the mesoporous silica material SBA-15, used as reference, which significantly affected cell viability at particle concentration of 500 and 1000 μg/ml after the same exposure time. Topical application of Upsalite®resulted in negligible cutaneous reactions in a rabbit skin irritation model and no evidence of significant systemic toxicity was found when saline extracts of Upsalite®were injected in mice. Injection of sesame oil extract, however, resulted in transient weight loss, most likely due to injection of particles, and not toxic leachables. The presented results form the basis for future development of Upsalite®and similar mesoporous materials in biomedical applications and further toxicity as well as biocompatibility studies should be directed towards specific areas of use.

Calculating buoy response for a wave energy converter-A comparison of two computational methods and experimental results

When designing a wave power plant, reliable and fast simulation tools are required. Computational fluid dynamics （CFD） software provides high accuracy but with a very high computational cost, and in operational, moderate sea states, linear potential flow theories may be sufficient to model the hydrodynamics. In this paper, a model is built in COMSOL Multiphysics to solve for the hydrodynamic parameters of a point-absorbing wave energy device. The results are compared with a linear model where the hydrodynamical parameters are computed using WAMIT, and to experimental results from the Lysekil research site. The agreement with experimental data is good for both numerical models.

Impact of Biomechanical Forces on Antibiotics Release Kinetics from Hydroxyapatite Coated Surgical Fixation Pins

This work investigates the impact of biomechanical wear and abrasion on the antibiotic release profiles of hydroxyapatite (HA) coated fixation pins during their insertion into synthetic bone. Stainless steel fixation pins are coated with crystalline TiO2 by cathodic arc evaporation forming the bioactive layer for biomimetic deposition of Tobramycin containing HA. Tobramycin is either introduced by co-precipitation during HA formation or by adsorption-loading after HA deposition. The samples containing antibiotics are inserted into bone mimicking polyethylene foam after which the drug release is monitored using high performance liquid chromatography. This analysis shows that HA coating wear and delamination significantly decrease the amount of drug released during initial burst, but only marginally influence the sustained release period. Spalled coating fragments are found to remain within the synthetic bone material structure. The presence of HA within this structure supports the assumption that the local release of Tobramycin is not only expected to eliminate bacteria growth directly at the pin interface but as well at some distance from the implant. Furthermore, no negative effect of gamma sterilization could be observed on the drug release profile. Overall, the observed results demonstrate the feasibility of a multifunctional implant coating that is simultaneously able to locally deliver clinically relevant doses of antibiotics and an HA coating capable of promoting osteoconduction. This is a potentially promising step toward orthopaedic devices that combine good fixation with the ability to treat and prevent post-surgical infections.

Effect of Calcium and Strontium on Mesoporous Titania Coatings for Implant Applications

Increasing interest in the role of ions such as calcium and strontium in bone formation has called for the investigation of multifunctional ion-doped implant coatings. Mesoporous titania coatings incorporating calcium or strontium enabled a unique pore morphology and potential for drug delivery. Coatings were produced on titanium by an evaporation induced self-assembly method with the addition of calcium or strontium to the sol causing a shift in morphology from a hexagonally-packed to a worm-like porous network. Pore sizes ranged from 3.8 - 5 nm and coatings exhibited high surface areas between 181 - 215.5 m2/g, as measured by N2 adsorption-desorption. Coatings were loaded with 1 mg/ml Cephalothin, and showed sustained release of the antibiotic over one week in vitro. Cell studies confirmed that the ion addition had no toxic effect on human-like osteoblastic SaOS-2 cells. The results of this study suggest the potential for mesoporous coatings with calcium or strontium incorporation for direct bone-interfacing and combined drug delivery implant applications.

The Effect of Si-Doping on the Release of Antibiotic from Hydroxyapatite Coatings

Herein, we show that incorporation of ions during biomimetic coating deposition may be utilized to tailor the drug loading capacity of hydroxyapatite (HA) coatings. Pure biomimetic HA (HA-B) and Si-doped equivalents (SiHA-B) where deposited by a biomimetic process onto titanium dioxide covered titanium substrates. The antibiotic Cephalothin was incorporated into the coatings by adsorptive loading and the release was studied in-vitro. SiHA-B coatings exhibited superior drug incorporation capacity compared to pure HA-B coatings, resulting in a drug release profile dominated by an initial 10 min burst effect while a more prolonged 10 hour release was observed from HA-B coatings. The results emphasize the possibility to impact the drug release kinetics from implant coatings by selective doping elements and the use of thin, biomimetic HA-coatings as drug delivery vehicles. Functionalizing metal implants with SiHA-B coatings presents an interesting strategy towards creating synergetic effects through ion- and antibiotic release and, hence, contributing both towards preventing post-surgical infections while at the same time enhancing the bone-bonding ability.

Biomimetic Hydroxyapatite Coated Titanium Screws Demonstrate Rapid Implant Stabilization and Safe Removal In-Vivo

The early fixation of bone screws after surgical implantation still remains a challenge in the field of traumatology. Whilst hydroxyapatite (HA) coatings are known to enhance the fixation of implants;their removal at a later time-point may be problematic. An HA coating has been developed to demonstrate that both implant fixation and safe removal are feasible in the same design. Accordingly the aim of this study was to compare the In-Vivo performance of thin biomimetic HA coated titanium screws to uncoated counterparts used as control after bilateral implantation in the femoral condyle of 36 New Zealand White Rabbits. The screws were analysed macroscopically, by histology, micro-CT and biomechanically at both two and six weeks post-implantation. The HA coated screws demonstrated excellent biocompatibility. At two weeks the HA coated screws demonstrated a significant increase in removal torque values as well as a strong trend towards higher pull-out forces. In addition histology confirmed a higher degree of osseointegration and direct bone to implant contact. At six weeks no difference in pull-out force and removal torque could be detected. SEM images confirmed the absence of any residual HA coating indicating a fast coating degradation In-Vivo. The low level of removal torque after full osseointegration at 6 weeks supports the feasibility of safe and easy removal of the implant. The HA coating under study appears to offer a unique characteristic of enhanced fixation with a minimal increase in removal torque after full osseointegration. This may be of value in clinical applications where it is necessary to assure both screw fixation and later removal.

Controlling Osteogenic Differentiation through Nanoporous Alumina

Nanotopographical features are found to have significant effects on bone behavior. In the present study, nanoporous aluminas with different pore sizes (20, 100 and 200 nm in diameter), were evaluated for their osteoinductive and drug eluting properties. W20-17 marrow stromal cells were seeded on nanoporous alumina with and without the addition of BMP-2. Although cell proliferation was not affected by pore size, osteogenic differentiation was 200 nm as compared to 20 and 100 nm pores induced higher alkaline phosphatase activity (ALP) and osteocalcin expression levels, thus indicating osteoblastic differentiation. Cell morphology revealed that cells cultured on 20 nm pores adopted a rounded shape, while larger pores (200 nm) elicited an elongated morphology. Furthermore, ALP expression levels were consistently higher on BMP-2 loaded nanoporous alumina surfaces compared to unloaded surfaces, indicating that not only is nanoporous alumina osteoinductive, but also has the potential to be used as a drug eluting bone-implant coating.

Effects of europium concentration on luminescent and scintillation performance of Cs_(0.2)Rb_(0.8)Ca_(1-x)Eu_(x)Br_(3)(0≤x≤0.08)crystals

A series of Cs_(0.2)Rb_(0.8)Ca_(1-x)Eu_(x)Br_(3)(0≤x≤0.08)crystals doped with different concentrations of Eu^(2+)were grown using the Bridgman-Stockbarger method.The work describes the influence of Eu^(2+)concentration on the luminescent and kinetic properties of Cs_(0.2)Rb_(0.8)Ca_(1-x)Eu_(x)Br_(3) crystals,as well as on their scintillation performance.The maximum in the radioluminescence spectra of these crystals shifts from 439 to446 nm with increasing europium concentration.The scintillation decay times of Cs_(0.2)Rb_(0.8)Ca_(1-x)Eu_(x)Br_(3) lengthen with the Eu^(2+)content.The best light output of 33600photons/MeV is obtained for Cs_(0.2)Rb_(0.8)Ca_(0.93)Eu_(0.07)Br_(3),and the best energy resolution of 6.9%is found for Cs_(0.2)Rb_(0.8)Ca_(0.94)Eu_(0.06)Br_(3).

Isolation and Identification of Pseudo Seven-Coordinate Ru(Ⅲ)Intermediate Completing the Catalytic Cycle of Ru-bda Type of Water Oxidation Catalysts

Isolation of RuⅢ-bda(17-electron specie)complex with an aqua ligand(2-electron donor)is challenging due to violation of the 18-electron rule.Although considerable efforts have been dedicated to mechanistic studies of water oxidation by the Ru-bda family,the structure and initial formation of the Ru^(Ⅲ)-bda aqua complex are still controversial.Herein,we challenge this often overlooked step by designing a pocketshape Ru-based complex 1.The computational studies showed that 1 possesses the crucial hydrophobicity at the Ru^(V)(O)state as well as similar probability of access of terminal O to solvent water molecules when compared with classic Ru-bda catalysts.Through characterization of single-crystal structures at the Ru^(Ⅱ) and Ru^(Ⅲ) states,a pseudo seven-coordinate“ready-togo”aqua ligand with Ru^(Ⅲ)…O distance of 3.62A was observed.This aqua ligand was also found to be part of a formed hydrogen-bonding network,providing a good indication of how the Ru^(Ⅲ)-OH_(2)complex is formed.

Optical Design and Preparation of High Performance Mo/NiAlN/NiAlON/SiO_2 Solar Selective Absorbing Coating

A new solar selective absorbing coating of Mo/NiAlN/NiAlON/SiO_2 multilayer was prepared on stainless steel(SS) substrates by magnetron sputtering for solar thermal power applications. The optical constants and thickness of individual layers were simulated using the Scout software based on the experimentally measured reflectance and transmittance spectra of individual layers. The coating of Mo/NiAlN/NiAlON/SiO_2 with an ideal solar absorptance(α) of 0.945 in the solar spectrum range was designed via the optical constants of each layer in the Scout software. The Mo/NiAlN/NiAlON/SiO_2 coating was deposited via the optimized layer thickness. A good spectral selectivity with absorptance(α=0.936) and emittance(ε=0.09, T=80 ℃) was obtained. This method, which incorporates the optical simulation with the related experiments, provides a convenient approach to obtain the ideal solar selective absorbing coatings.

Influence of surface preparation on atomic layer deposition of Pt films

We report Pt deposition on a Si substrate by means of atomic layer deposition（ALD） using（methylcyclopentadienyl） trimethylplatinum（CH_3C_5H_4Pt（CH_3）_3） and O_2.Silicon substrates with both HF-last and oxidelast surface treatments are employed to investigate the influence of surface preparation on Pt-ALD.A significantly longer incubation time and less homogeneity are observed for Pt growth on the HF-last substrate compared to the oxide-last substrate.An interfacial oxide layer at the Pt-Si interface is found inevitable even with HF treatment of the Si substrate immediately prior to ALD processing.A plausible explanation to the observed difference of Pt-ALD is discussed.

低场诱导液-气界面纳米颗粒组装体自旋玻璃行为和可控各向异性

利用纳米尺度结构单元堆积成具有丰富物理性能的一维(1D)组装体,是材料设计的研究前沿.然而,弱磁场诱导1D阵列的制备及其磁性能机制的揭示仍然具有挑战性.本文采用强度不同的组装场(0/1/3/5/30/50 mT),在二甘醇-空气界面上制备了由无序四氧化三铁纳米立方体组成的低维组装体.随着组装场从0增长到50 mT,环形组装体先变为细长多孔网状,再逐步变为细丝阵列,其中细丝阵列的合成条件为组装场≥3 mT且施加组装场时间t>14 min.通过调控组装场强度可得到自旋玻璃特性和静(动)各向异性~2(3).在弱组装场下磁偶极和无序排列易磁化轴之间相互作用导致自旋玻璃特性,进一步增大组装场将加强磁偶极作用和易磁化轴排列,导致自旋玻璃特性消失和强各向异性.本研究不仅提出了一种制备自旋玻璃和可控各向异性组装体的策略,还为理解低维组装磁相互作用提供了新思路.

通过瞬态可见和瞬态中红外光谱研究InP/ZnS QDs无机配体诱导的表面空穴转移和构型调整过程

光生载流子动力学过程可以显著影响材料光催化活性.通常,光生电子的转移速率远高于光生空穴的,致使空穴的转移和累积成为影响光催化效率的关键因素.因此,深入探究光生空穴转移过程和动力学可以极大地帮助我们认识和理解光催化机理,但该工作鲜有人关注研究.本工作中,时间分辨荧光光谱(TRPL)和飞秒瞬态可见吸收光谱(fsTA)表明空穴会从InP转移至表面S^(2-)配体.此外,瞬态中红外光谱(TRIR)中S^(2-)配体伸缩振动信号表明该空穴转移时间为4.2 ps.转移至S^(2-)配体的空穴具有明显的长寿命特征(>4.5 ns)并且会导致表面活性物的静电解离和构型重组.最后,通过与其他无机配体(Cl^(-)、PO_(4)^(3-))比较,我们发现S^(2-)配体具有最合适平衡的离子半径和净电荷,因此带有该配体的InP/ZnS量子点(InP/ZnS QDs)光催化剂具有最高的光解硫化氢产氢活性(213.6μmol mg^(-1)).本文的研究结果为理解InP QDs光催化过程和机理提供了有价值的见解.

Mechanistic Insight into Supramolecular Polymerization in Water Tunable by Molecular Geometry

Supramolecular self-assembly in water based on non-covalent bonding is attracting major attention due to the potential of hydrogels and aqueous polymers in biomedical applications.Although supramolecular polymerization in organic solvents is well established,the key design features,the assembly mechanisms in water and achieving control over the aggregate structures remain challenging.Here,we present the assembly and disassembly of geometrical isomers of a stiff-stilbene bis-urea amphiphile(SA)in pure water.A remarkable feature of this system is that the(E)-isomer forms supramolecular polymers in both pure water and organic solvents.Taking advantage of this unique property,the hydrophobic effect was studied by comparing the supramolecular assembly in both systems.The assembly process inwater follows an enthalpy-driven nucleation-elongation(cooperative)supramolecular polymerization mechanism with a standard Gibbs free energy(ΔG°=−53 kJ mol^(−1))double the value of the one found in toluene.We attributed this distinctive feature to the hydrophobic effect in water.Furthermore,we discovered an isomer-dependent assembly process,which can be used to control aggregation in aqueous media.Due to the substantial geometric difference between(E)-SA and(Z)-SA,we compared their assembly in water to study the influence of different driving forces involved in the process.The supramolecular polymerization of(E)-SA was cooperatively influenced by hydrogen bonding,π-stacking,and hydrophobic effects,whereas the assembly of(Z)-SAwasmainly driven by hydrophobic effects.As a result,the fiber length of(E)-SA in water is much longer than that of(Z)-SA,presenting opportunities for geometrical control of aggregation in aqueousmedia.