Renishaw Invia

Multifunctional fiber-reinforced composites play a significant role in advanced aerospace and military applications due to their high strength and toughness resulting in superior damage tolerance. However, early detection of structural changes prior to visible damage is critical for extending the lifetime of the part. MXenes, an emerging class of two-dimensional (2D) nanomaterials, possess hydrophilic surfaces, high electrical conductivity and mechanical properties that can potentially be used to identify damage within fiber-reinforced composites. In this work, conductive Ti3C2Tx MXene flakes were successfully transferred onto insulating glass fibers via oxygen plasma treatment improving adhesion. Increasing plasma treatment power, time and coating layers lead to a decrease in electrical resistance of MXene-coated fibers. Optimized uniformity was achieved using an alternating coating approach with smaller flakes helping initiate and facilitate adhesion of larger flakes. Tensile testing with in-situ electrical resistance tracking showed resistances as low as 1.8 kΩ for small-large flake-coated fiber bundles before the break. Increased resistance was observed during testing, but due to good adhesion between the fiber and MXene, most connective pathways within fiber bundles remained intact until fiber bundles were completely separated. These results demonstrate a potential use of MXene-coated glass fibers in damage-sensing polymer-matrix composites.

Christine B. Hatter, Asia Sarycheva, Ariana Levitt, Babak Anasori, Latha Nataraj, Yury Gogotsi. C, 6 (4), 64, 2020.

Nanocrystalline cobalt spinel has been recognized as a very active catalytic material for N2O decomposition. Its catalytic performance can be substantially modified by proper doping with alien cations with precise control of their loading and location (spinel surface, bulk, and spinel-dopant interface). Various doping scenarios for a rational design of the optimal catalyst for low-temperature N2O decomposition are analyzed in detail and the key reactivity descriptors are identified (content and topological localization of dopants, their redox vs. non-redox nature and catalyst work function). The obtained results are discussed in the broader context of the available literature data to establish general guidelines for the rational design of the N2O decomposition catalyst based on a cobalt spinel platform.

Sylwia Wójcik, Gabriela Grzybek, Paweł Stelmachowski, Zbigniew Sojka, Andrzej Kotarba. Catalysts, 10 (1), 41, 2019.

A series of cobalt spinel catalysts doped with bismuth in a broad range of 0–15.4 wt % was prepared by the co-precipitation method. The catalysts were thoroughly characterized by several physicochemical methods (X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), Raman spectroscopy (µRS), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption analyzed with Brunaer-Emmett-Teller theory (N2-BET), work function measurements (WF)), as well as aberration-corrected scanning transmission electron microscopy (STEM) coupled with energy-dispersive X-ray spectroscopy (EDX) and electron energy-loss spectroscopy (EELS). The optimal bismuth promoter content was found to be 6.6 wt %, which remarkably enhanced the performance of the cobalt spinel catalyst, shifting the N2O decomposition (deN2O) temperature window (T50%) down from approximately 400 °C (for Co3O4) to 240 °C (for the 6.6 wt % Bi-Co3O4 catalyst). The high-resolution STEM images revealed that the high activity of the 6.6 wt % Bi-Co3O4 catalyst can be associated with an even, atomic-level dispersion (3.5 at. nm−2) of bismuth over the surface of cobalt spinel nanocrystals. The improvement in catalytic activity was accompanied by an observed increase in the work function. We concluded that Bi promoted mostly the oxygen recombination step of a deN2O reaction, thus demonstrating for the first time the key role of the atomic-level dispersion of a surface promoter in deN2O reactions.

Sylwia Wójcik, Thomas Thersleff, Klaudia Gębska, Gabriela Grzybek, Andrzej Kotarba. Catalysts, 10 (3), 351, 2020.

Aiming to achieve enhanced photocatalytic activity and stability toward the generation of H2 from water, we have synthesized noble metal-free core-shell nanoparticles of graphene (G)-wrapped CdS and TiO2 (CdS@G@TiO2) by a facile hydrothermal method. The interlayer thickness of G between the CdS core and TiO2 shell is optimized by varying the amount of graphene quantum dots (GQD) during the synthesis procedure. The most optimized sample, i.e., CdS@50G@TiO2 generated 1510 µmole g−1 h−1 of H2 (apparent quantum efficiency (AQE) = 5.78%) from water under simulated solar light with air mass 1.5 global (AM 1.5G) condition which is ~2.7 times and ~2.2 time superior to pure TiO2 and pure CdS respectively, along with a stable generation of H2 during 40 h of continuous operation. The increased photocatalytic activity and stability of the CdS@50G@TiO2 sample are attributed to the enhanced visible light absorption and efficient charge separation and transfer between the CdS and TiO2 due to incorporation of graphene between the CdS core and TiO2 shell, which was also confirmed by UV-vis, photoelectrochemical and valence band XPS measurements.

Muhammad Zubair, Ingeborg-Helene Svenum, Magnus Rønning, Jia Yang. Catalysts, 10 (4), 358, 2020.

Mixed-phase nanoTiO2 materials attract a lot of attention as advanced photocatalysts for water decontamination due to their intrinsic structure that allows better photo-excited e−cb-h+vb charge separation, hence improved photocatalytic efficiency. Currently, the best-known mixed-phase TiO2 photocatalyst is P25 with approximate composition 80% Anatase/20% Rutile (A/r). Apart from Anatase (A) and Rutile (R) phases, there is Brookite (B) which has been evaluated less as photocatalyst in mixed-phase nanoTiO2 systems. In this work we present a sustainable solution process to synthesize tunable composition mixed-phase nanotitania photocatalysts in a continuously stirred tank reactor (CSTR) by modulating conditions like pH, CTiCl4 and time. In particular three mixed-phase TiO2 nanomaterials were produced, namely one predominantly anatase with brookite as minor component (A/b), one predominantly brookite with minor component rutile (B/r), and one predominantly rutile with minor component brookite (R/b) and evaluated as photocatalysts in the degradation of methyl orange. The three semiconducting nanomaterials were characterized by XRD and Raman spectroscopy to quantify the phase ratios and subjected to nano-morphological characterization by FE-SEM and TEM/HR-TEM. The new mixed-phase nanoTiO2 materials are shown to be endowed with large specific surface area, ranging from 90–125 m2 g−1, double of that of P25, to be mesoporous and be surface-rich in Ti–OH molecular groups varying from 12%–20% versus 4% for P25. These properties though impact the adsorptive capacity with R/b and B/r removing > 50% of MO but not photocatalytic activity. The latter depends on nanograined mixed-phase structure and not mere assembly of different phase nanoparticles. First-order rate constants reveal essentially equivalent photocatalytic activity for anatase nanocrystals with either rutile (P25) or brookite (this work) domains.

Konstantina Chalastara, Fuqiang Guo, Samir Elouatik, George P. Demopoulos. Catalysts, 10 (4), 407, 2020.

A series of layered birnessite (AMn4O8) catalysts containing different alkali cations (A = H+, Li+, Na+, K+, Rb+, or Cs+) was synthesized. The materials were thoroughly characterized using X-ray diffraction, X-ray fluorescence, X-ray photoelectron spectroscopy, Raman spectroscopy, specific surface area analysis, work function, thermogravimetry/differential scanning calorimetry, and transmission electron microscopy. The catalytic activity in soot combustion in different reaction modes was investigated (tight contact, loose contact, loose contact with NO addition). The activity in the oxidation of light hydrocarbons was evaluated by tests with methane and propane. The obtained results revealed that alkali-promoted manganese oxides are highly catalytically active in oxidative reactions. In soot combustion, the reaction temperature window was shifted by 195 °C, 205 °C, and 90 °C in tight, loose + NO, and loose contact conditions against uncatalyzed oxidation, respectively. The catalysts were similarly active in hydrocarbon combustion, achieving a 40% methane conversion at 600 °C and a total propane conversion at ~450 °C. It was illustrated that the difference in activity between tight and loose contacts can be successfully bridged in the presence of NO due to its facile transformation into NO2 over birnessite. The particular activity of birnessite with H+ cations paves the road for the further development of the active phase, aiming at alternative catalytic systems for efficient soot, light hydrocarbons, and volatile organic compounds removal in the conditions present in combustion engine exhaust gases.

Tomasz Jakubek, Camillo Hudy, Paweł Stelmachowski, Ewa Nowicka, Stan Golunski, Andrzej Kotarba. Catalysts, 10 (5), 507, 2020.

The aim of this work was the optimization of the performance of the cold plasma technology coupled with a structured catalyst for the discoloration and mineralization of “acid orange 7” (AO7) azo dye. The structured catalyst consists of Fe2O3 immobilized on glass spheres, and it was prepared by the “dip coating” method and characterized by different chemico-physical techniques. The experiments were carried out in a dielectric barrier discharge (DBD) reactor. Thanks to the presence of the catalytic packed material, the complete discoloration and mineralization of the dye was achieved with voltage equal to 12 kV, lower than those generally used with this technology (approximately 20–40 kV). The best result in terms of discoloration and mineralization (80% after only 5 min both for discoloration and mineralization) was obtained with 0.25 wt% of Fe2O3 immobilized on the glass spheres, without formation of reaction by-products, as shown by the HPLC analysis. The optimized catalyst was reused for several reuse cycles without any substantial decrease of performances. Moreover, tests with radical scavengers evidenced that the most responsible oxidizing species for the degradation of AO7 dye was O2•−.

Giuseppina Iervolino, Vincenzo Vaiano, Giacomo Pepe, Pietro Campiglia, Vincenzo Palma. Catalysts, 10 (8), 888, 2020.

A series of Nb-doped (0–23 wt%) cryptomelane catalyst (Nb-K-OMS-2) was synthesized and thoroughly characterized by XRD, TEM/EDX, XRF, XPS, XAS, UV-Vis, and Raman techniques corroborated by the work function measurements. The obtained catalysts were tested for soot oxidation (Printex U) in model tight and loose contact modes. It was shown that the catalytic properties of the Nb-K-OMS-2 are controlled by the amount of Nb dopant in a strongly non-monotonous way. The introduction of niobium gives rise to the strain in the cryptomelane lattice, accompanied by significant Mn+3/Mn+4 ratio variations and concomitant work function changes. The isotopic exchange experiments revealed that the catalytic activity of the Nb-OMS-2 catalysts in soot combustion proceeds via the pathways, where both the activated suprafacial 18O and the surface 16O2− species participate together in the reaction. The niobium doping level controls the non-monotonous changes of the catalyst work function and the lattice strain, and variations of these parameters correlate well with the observed deSoot activity. To our best knowledge, the role of the lattice strain of the cryptomelane catalysts was documented for the first time in this study.

Piotr Legutko, Joanna Gryboś, Monika Fedyna, Janusz Janas, Anna Wach, Jakub Szlachetko, Andrzej Adamski, Xuehua Yu, Zhen Zhao, Andrzej Kotarba, Zbigniew Sojka. Catalysts, 10 (12), 1390, 2020.

High sodium ion (Na+) consumption leads to high blood pressure which causes many health issues. Real-time determination of Na+ content in food is still important to limit Na+ intake and control the taste of food. In this work, we have developed an electrochemical sensor based on agglomeration of silver nanoparticles (AgNPs) and graphene oxide (GO) modified on a screen-printed silver electrode (SPE) for Na+ detection at room temperature by using cyclic voltammetry (CV). The AgNPs were synthesized through a simple green route using Pistia stratiotes extract as a reducing agent under blue light illumination and mixed with the GO to be a Na+ selective sensing nanocomposite. The AgNPs/GO/SPE sensor showed high sensitivity (0.269 mA/mM/cm2), high selectivity, linear relationship (0–100 mM), good stability, and excellent reproducibility to Na+ detection as well as low limit of detection (9.344 mM) for food application. The interfering species such as K+, Zn2+, Na+, Mg2+, glucose, and ascorbic acid did not have any influence on the Na+ determination. The AgNPs/GO/SPE sensor was successfully applied to determine Na+ in real samples such as fish sauce and seasoning powder of instant noodle.

Pranlekha Traiwatcharanon, Wilai Siriwatcharapiboon, Chatchawal Wongchoosuk. Chemosensors, 8 (3), 58, 2020.

The AlCrN and AlCrON coatings were deposited on plasma nitrided H13 steels through ion-source-enhanced arc ion plating, and their structures, mechanical properties, thermal stabilities, and tribological properties were investigated. Structural analysis showed that the monolayer AlCrN and AlCrON bilayered coatings were mainly composed of fcc-AlCrN and fcc-AlCrON solid solution phases respectively. Upon the addition of thin AlCrON layer, the hardness of AlCrN/AlCrON coating slightly decreased from about 30.5 GPa to 28.6 GPa, and the thermal stability was improved after annealing at 700 °C. Both coatings exhibited excellent wear resistance at room temperature, while all wear process involved a combination of wear mechanisms, including severe abrasion and oxidation at an evaluated temperature. The AlCrON bilayered coating showed better wear resistance than that of AlCrN coating due to a dense anti-oxidation layer and better adhesion at a high temperature, making it suitable for die tool protection coatings.

Farooq Ahmad, Lin Zhang, Jun Zheng, Iram Sidra, Shihong Zhang. Coatings, 10 (4), 306, 2020.

In this study, P25-titanium dioxide (TiO2) was doped with ruthenium (Ru) by systematically varying the Ru content at 0.15, 0.30, 0.45 and 0.6 mol%. The synthesized Ru-doped TiO2 nanomaterials have been characterized by X-ray diffraction (XRD), Raman spectroscopy, energy-dispersive X-ray (EDX) analysis, UV-visible (UV–Vis) spectroscopy, and electrochemical impedance (EIS) spectroscopy. The XRD patterns of undoped and Ru-doped TiO2 nanomaterials confirm the presence of mixed anatase and rutile phases of TiO2 while EDX spectrum confirms the presence of Ti, O and Ru. Further, UV-visible absorption spectra of doped TiO2 nanomaterial reveal a slight red shift on Ru-doping. The short circuit current density (JSC) of the cells fabricated using the Ru-doped TiO2 photoanode was found to be dependent on the amount of Ru present in TiO2. Optimized cells with 0.3 mol% Ru-doped TiO2 electrodes showed efficiency which is 20% more than the efficiency of the control cell (η = 5.8%) under stimulated illumination (100 mWcm−2, 1 sun) with AM 1.5 filter. The increase in JSC resulted from the reduced rate of recombination upon doping of Ru and this was confirmed by EIS analysis.

Tharmakularasa Rajaramanan, Muthukumarasamy Natarajan, Punniamoorthy Ravirajan, Meena Senthilnanthanan, Dhayalan Velauthapillai. Energies, 13 (7), 1532, 2020.

In this study, a novel method called selective proteolysis was applied to the glycinin component of soy protein isolate (SPI), and a degraded glycinin hydrolysate (DGH) was obtained. The effects of high-intensity ultrasound (HIU) treatment (20 kHz at 400 W, 0, 5, 20, and 40 min) on the physical, structural, and aggregation properties of DGH were investigated with the aim to reveal the influence of the selectively hydrolyzing glycinin component on the HIU treatment of soy protein. The effects of HIU on DGH and a control SPI (CSPI) were both time-dependent. HIU induced the formation of soluble aggregates in both samples at an early stage, while it dissociated these newly formed aggregates after a longer duration. Selectively hydrolyzing glycinin contributed to the soluble aggregation by exposing the compact protein structure and producing small protein fractions. The larger extent of hydrophobic interactions and disulfide bonds imparted a higher stability to the soluble protein aggregates formed in DGH. As a result, DGH displayed more ordered secondary structures, a higher solubility, and better gelling properties after the HIU treatment, especially at 20 min. The results of this study will be beneficial to the scientific community as well as industrial application.

Wenjie Xia, Siyi Pan, Zhe Cheng, Yan Tian, Xingjian Huang. Foods, 9 (6), 839, 2020.

Citrate-capped gold nanoparticles (AuNPs) were functionalized with three distinct antitumor gold(III) complexes, e.g., [Au(N,N)(OH)2][PF6], where (N,N)=2,2′-bipyridine; [Au(C,N)(AcO)2], where (C,N)=deprotonated 6-(1,1-dimethylbenzyl)-pyridine; [Au(C,N,N)(OH)][PF6], where (C,N,N)=deprotonated 6-(1,1-dimethylbenzyl)-2,2′-bipyridine, to assess the chance of tracking their subcellular distribution by atomic force microscopy (AFM), and surface enhanced Raman spectroscopy (SERS) techniques. An extensive physicochemical characterization of the formed conjugates was, thus, carried out by applying a variety of methods (density functional theory—DFT, UV/Vis spectrophotometry, AFM, Raman spectroscopy, and SERS). The resulting gold(III) complexes/AuNPs conjugates turned out to be pretty stable. Interestingly, they exhibited a dramatically increased resonance intensity in the Raman spectra induced by AuNPs. For testing the use of the functionalized AuNPs for biosensing, their distribution in the nuclear, cytosolic, and membrane cell fractions obtained from human lymphocytes was investigated by AFM and SERS. The conjugates were detected in the membrane and nuclear cell fractions but not in the cytosol. The AFM method confirmed that conjugates induced changes in the morphology and nanostructure of the membrane and nuclear fractions. The obtained results point out that the conjugates formed between AuNPs and gold(III) complexes may be used as a tool for tracking metallodrug distribution in the different cell fractions.

Aleksandra M. Bondžić, Andreja R. Leskovac, Sandra Ž. Petrović, Dragana D. Vasić Anićijević, Marco Luce, Lara Massai, Amanda Generosi, Barbara Paci, Antonio Cricenti, Luigi Messori, Vesna M. Vasić. International Journal of Molecular Sciences, 20 (24), 6306, 2019.