Synthesis of gemini basic ionic liquids and their application in anion exchange membranes

A gemini-type basic morpholine ionic liquid ([Nbmd][OH]) was synthesized via a two-step method with morpholine, bromododecane and 1,4-dibromobutane as raw materials, and its structure was characterized by ¹H NMR and FT-IR spectroscopy. Meanwhile, a series of anion exchange membranes ([Nbmd][OH]_x–QCS) were prepared with quaternized chitosan (QCS) as the polymer matrix and [Nbmd][OH] as the dopant owing to its strong alkalinity and good solubility. The structures of the [Nbmd][OH]_x–QCS composite membranes were characterized in detail by FT-IR spectroscopy, the OH⁻ conductivity by AC impedance spectroscopy, and the morphological features by scanning electron microscopy (SEM), thermal gravity analysis (TGA), etc. The results show that the [Nbmd][OH]_x–QCS composite membranes have uniform surfaces and cross-section morphology. Increasing the content of [Nbmd][OH] not only enhances the thermal stability but also increases the OH⁻ conductivity; the thermal decomposition temperature of the [Nbmd][OH]₄₀–QCS membrane is nearly 20 °C higher than that of the pristine QCS membrane, and the maximum OH⁻ conductivity is approximately 1.37 × 10⁻² S cm⁻² at 70 °C. The methanol permeability of the [Nbmd][OH]₄₀–QCS membrane in 1 M methanol at room temperature is 2.21 × 10⁻⁶ cm⁻² s⁻¹, which is lower than that of Nafion®115, indicating a promising potential use in alkaline direct methanol fuel cells. Moreover, the [Nbmd][OH]₄₀–QCS membrane exhibits the best alkaline stability of all the membranes prepared in this work, retaining approximately 81% of its initial conductivity after immersion in 3 M KOH solution for 120 h at 70 °C.

A gemini-type basic morpholine ionic liquid ([Nbmd][OH]) was synthesized via a two-step method with morpholine, bromododecane and 1,4-dibromobutane as raw materials, and its structure was characterized by ¹H NMR and FT-IR spectroscopy.     

Temperature dependent structure and dynamics in smectite interlayers: 23Na MAS NMR spectroscopy of Na-hectorite

²³Na MAS NMR spectroscopy of the smectite mineral hectorite acquired at temperatures from −120 °C to 40 °C in combination with the results from computational molecular dynamics (MD) simulations show the presence of complex dynamical processes in the interlayer galleries that depend significantly on their hydration state. The results indicate that site exchange occurs within individual interlayers that contain coexisting 1 and 2 water layer hydrates in different places. We suggest that the observed dynamical averaging may be due to motion of water volumes comparable to the dripplons recently proposed to occur in hydrated graphene interlayers (Yoshida et al. Nat. Commun., 2018, 9, 1496). Such motion would cause rippling of the T-O-T structure of the clay layers at frequencies greater than ∼25 kHz. For samples exposed to 0% relative humidity (R.H.), the ²³Na spectra show the presence of two Na⁺ sites (probably 6 and 9 coordinated by basal oxygen atoms) that do not undergo dynamical averaging at any temperature from −120 °C to 40 °C. For samples exposed to R.H.s from 29% to 100% the spectra show the presence of three hydrated Na⁺ sites that undergo dynamical averaging beginning at −60 °C. These sites have different numbers of H₂O molecules coordinating the Na⁺, and diffusion calculations indicate that they probably occur within the same individual interlayer. The average hydration state of Na⁺ increases with increasing R.H. and water content of the clay.

²³Na MAS NMR spectroscopy of the smectite mineral hectorite acquired at temperature from −120 °C to 40 °C shows the presence of complex dynamical processes in the interlayer galleries that depend significantly on their hydration state.     

Evaluation of Rodent Cage Processing Using Reduced Water Temperatures

Studies published in 1994 and 2000 established a temperature range of 143–180 °F for effective cage sanitization in animal facilities. These 2 studies were, respectively, theoretical and based on experiments using hot water to sanitize bacteria-coated test tubes. However, such experimental methods may not capture the practical advantages of modern washing technology or account for the routine use of detergent in cage wash. Moreover, these methods may not translate to the challenges of removing adhered debris and animal waste from the surfaces being sanitized. A sample of highly soiled cage bottoms, half of which were autoclaved with bedding to create challenging cleaning conditions, were processed at 6 combinations of wash and rinse cycles with 125 °F, 140 °F, and 180 °F water with detergent. All cycles were equipped with a data logging device to independently verify temperatures. After washing, cages underwent visual inspection and microbial sampling consisting of organic material detection using ATP detection and Replicate Organism Detection and Counting (RODAC) plates. Cages with any amount of visible debris failed inspection, as did cages that exceeded institutional sanitization thresholds. Results indicate that wash and rinse temperatures of 140 °F for a programmed wash duration of 450 s and rinse of 50 s effectively clean and disinfect both highly soiled and autoclaved cages. Accounting for both steam and electrical energy, these parameters result in an annual savings of $21,867.08 per washer on an equivalent run basis using the current institutional standard of 180 °F.

The Guide for the Care and Use of Laboratory Animals states that “effective disinfection can be achieved with wash and rinse water at 143–180°F or more.”¹³ Disinfection is defined as the reduction or elimination of microorganisms, whereas sanitization is the combined effect of cleaning, or removal of gross debris, with disinfection.¹³ In pursuing regulatory compliance and biosecurity, institutions commonly operate at the higher end of this range for both the wash and rinse stages, resulting in high utility usage and high-cost operation. Early research underlying recommendations for disinfection with water alone used a theoretical approach to establish time-heat combinations, known as cumulative heat factors.²⁶ Disinfection combinations are 1800 s at 143 °F (61.7 °C), 15 s at 161 °F (71.7 °C), and 0.1 s at 180 °F (82.2 °C).²⁶ Subsequent research has shown that contact times ranging from 2 to 5 s at 168 °F to 180 °F (75.6 to 82.2 °C) are sufficient to kill Pseudomonas aeruginosa, Salmonella cholerasuis, and Staphylococcus aureus,²⁷ and contact times of 2 min or more at 140 °F (60 °C) will kill Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Providencia rettgeri, and Staphylococcus epidermidis.²¹ When accounting for chemical and mechanical factors in tunnel washers, washing at the domestic hot water temperature (110 °F [43.3 °C]), followed by a rinse at 180 °F, can adequately prevent transmission of mouse parvovirus, Helicobacter spp., Mycoplasma pulmonis, Syphacia obvelata, and Myocoptes musculinus.⁶ The current study used performance standards in a practical study design to build on these disinfection principles and inform sanitization parameters for modern cage washing. Modern washers not only operate longer than the times required in the described cumulative heat factors, but they also use sophisticated mechanical delivery of water via high-pressure jets, dispense detergent, and allow programming of different temperatures at the wash and rinse stages. Test tube models and organism-directed research previously used to determine cage wash efficacy may not capture the challenges of debris removal encountered in day-to-day operation in an animal facility. Assessment of visible debris is recommended by cage processing working groups,¹² and should be included as a practical metric when establishing performance-based standards.The purpose of this study was to compare sanitization performance of reduced-temperature wash conditions to the standard wash cycle temperature of 180 °F. Experimental conditions combined wash and rinse temperatures of 125 °F, 140 °F, and 180 °F. Water sourced to the wash room in our facility is 125 °F (51.7 °C) and was therefore the minimal testable parameter. 140 °F (60 °C) is both commonly used in European facilities¹² and falls in the midrange of temperatures recommend for use with cage wash detergent (120 to 160 °F [48.9 to 71.1 °C]).²³ Highly soiled cages, half of which were autoclaved with bedding to represent the most challenging subset of cages to clean, were evaluated for disinfection and cleanliness. We hypothesized that cages washed and rinsed at 125 °F for 120 s would pass institutional sanitization standards, as assessed with visual inspection, ATP monitoring, and replicate organism detection and counting (RODAC). Given the energy usage, time, and utility costs necessary to reach temperatures of 180 °F, study aims were to verify sanitization performance at reduced temperatures, estimate time savings of operating at these various temperature parameters, and quantify cost and utility savings factoring in both electrical and steam-boosted heating.     

Knecorticosanones C–H from the fruits of Knema globularia (Lam.) warb

Six undescribed polyketides, 1–6, were discovered from the fruits of Knema globularia (Lam.) warb. Two known polyketides and three known lignans were also isolated. Cytotoxicities against HepG2 and KKU-M156 cells of all polyketides were evaluated. Compound 1 displayed the most cytotoxic activity against HepG2 and KKU-M156 cell lines with IC₅₀ values of 1.57 ± 0.37 and 1.78 ± 0.14 μg mL⁻¹, respectively. The structure of all isolates was identified using spectroscopic methods including NMR, IR, MS and ECD.

Compound 1 displayed the most cytotoxic activity against HepG2 and KKU-M156 cell lines with IC₅₀ values of 1.57 ± 0.37 and 1.78 ± 0.14 μg mL⁻¹, respectively.     

Linear and nonlinear optical properties of transfer ribonucleic acid (tRNA) thin solid films

We successfully obtained transfer ribonucleic acid (tRNA) thin solid films (TSFs) using an aqueous solution precursor in an optimized deposition process. By varying the concentration of RNA and deposition process parameters, uniform solid layers of solid RNA with a thickness of 30 to 46 nm were fabricated consistently. Linear absorptions of RNA TSFs on quartz substrates were experimentally investigated in a wide spectral range covering UV–VIS–NIR to find high transparency for λ > 350 nm. We analyzed the linear refractive indices, n(λ) of tRNA TSFs on silicon substrates by using an ellipsometer in the 400 to 900 nm spectral range to find a linear correlation with the tRNA concentration in the aqueous solution. The thermo-optic coefficient (dn/dT) of the films was also measured to be in a range −4.21 × 10⁻⁴ to −5.81 × 10⁻⁴ °C⁻¹ at 40 to 90 °C. We furthermore characterized nonlinear refractive index and nonlinear absorption of tRNA TSFs on quartz using a Z-scan method with a femtosecond laser at λ = 795 nm, which showed high potential as an efficient nonlinear optical material in the IR spectral range.

Optical measurements of one of the vital biological molecules (RNA) in the human body.     

Formation and dissociation of synthetic hetero-double-helix complex in aqueous solutions: significant effect of water content on dynamics of structural change

A 1 : 1 mixture of the ethynylhelicene pseudoenantiomers (M)-tetramer and (P)-pentamer, which possess hydrophilic terminal tri(ethyleneglycol) (TEG) groups, changes their structures in the water–THF (10 μM) solvent system between dissociated random-coils and an associated hetero-double-helix upon heating and cooling. A small change in water content between 30 and 33% significantly affects the dynamics of structural changes. At 30% water content, heating to 60 °C causes rapid formation of random-coil and cooling to 10 °C causes the rapid formation of hetero-double-helix, accompanied by repeated changes in Δε at 369 nm between 0 and −2000 cm⁻¹ M⁻¹. Heating and cooling experiments at constant rates between 60 and 10 °C resulted in sigmoidal curves in Δε/temperature profiles, which indicate rapid structural changes. Different phenomena occurred at 33% water content. Heating to 60 °C and cooling to 0 °C initially induced changes in Δε between 0 and −2000 cm⁻¹ M⁻¹, and repeated cycles gradually reduced the range between 0 and −500 cm⁻¹ M⁻¹. Heating and cooling experiments at constant rates between 60 and 10 °C caused small changes in Δε, and repeated cycles at 10 °C gradually increased Δε to −500 cm⁻¹ M⁻¹. These phenomena involved rapid changes in molecular structure and slow structural changes in the water–THF solvent system. The sharp switching of the dynamics of structural changes at water content between 30 and 33% indicated discontinuous structural changes in the hydration of TEG and/or in water clusters in the vicinity of oligomer molecules.

Significant structural changes by small change in water content from 30 to 33%.     

Surface and thermal properties of synthesized cationic poly(ethylene oxide) gemini surfactants: the role of the spacer

The solubility and heat stability of surfactants are the prerequisites for their oilfield applications. Most commercial surfactants undergo hydrolysis at high temperature and prolonged heating at 40 °C or above leads to decomposition. In this report, three cationic poly(ethylene oxide) gemini surfactants (GSs) containing flexible and rigid spacers were synthesized for oilfield applications. The chemical structures of the GSs were elucidated with the aid of ¹³C NMR, ¹H NMR, FT-IR, and MALDI-TOF MS. The GSs exhibit pronounced solubility in deionized water, seawater, and formation brine and no cloudiness, phase separation, or precipitation were detected after keeping GS solutions in an oven at 90 °C for three weeks. According to thermal gravimetric analysis, the degradation temperature of all the GSs was above 240 °C, which is higher than the existing oilfield temperature (≥90 °C). The critical micelle concentration (CMC) of the synthesized GSs decreases upon increasing the temperature. Additionally, CMC values were observed to increase even further with increasing salinity. The low CMC values of gemini surfactants containing a flexible structure indicate that they create a more closely packed micelle structure compared with gemini surfactants with a rigid structure. The distinct surface and thermal features of the synthesized GSs reveal them to be appropriate materials for high salinity and elevated temperature reservoirs.

Synthesis of new cationic poly(ethylene oxide) gemini surfactants containing flexible and rigid spacer groups to tolerate harsh reservoir condition.     

Synthesis of cyclic α-pinane carbonate – a potential monomer for bio-based polymers

This work reports the first known synthesis of α-pinane carbonate from an α-pinene derivative. Pinane carbonate is potentially useful as a monomer for poly(pinane carbonate), which would be a sustainable bio-based polymer. α-Pinene is a major waste product from the pulp and paper industries and the most naturally abundant monoterpene in turpentine oil. α-Pinene is routinely converted to pinene oxide and pinanediol, but no study has yet demonstrated the conversion of pinanediol into α-pinane carbonate. Here, α-pinane carbonate was synthesised via carboxylation of α-pinanediol with dimethyl carbonate under base catalysis using triazabicyclodecene guanidine (TBD). 81.1 ± 2.8% α-pinane carbonate yield was achieved at 98.7% purity. The produced α-pinane carbonate was a white crystalline solid with a melting point of 86 °C. It was characterised using FTIR, NMR, GCMS and a quadrupole time-of-flight (QTOF) mass spectrometer. The FTIR exhibited a C O peak at 1794 cm⁻¹ confirming the presence of a cyclic carbonate. GCMS showed that the α-pinane carbonate fragments with loss of CO₂, forming pinene epoxide. Base hydrolysis of the α-pinane carbonate using NaOH/ethanol/water regenerated the pinanediol with formations of Na₂CO₃.

Synthesis of α-pinane carbonate from an α-pinene derivative.     

Sulfonic acid functionalized metal–organic framework (S-IRMOF-3): a novel catalyst for sustainable approach towards the synthesis of acrylonitriles

A sulfonic acid functionalized metal–organic framework (S-IRMOF-3) has been synthesized by dropwise addition of chlorosulfonic acid (0.5 mL) in IRMOF-3 (1 g) containing 20 mL of CHCl₃ at 0 °C under simple stirring. The catalyst was applied in Knoevenagel condensation of various aromatic and hetero-aromatic aldehydes forming acrylonitrile derivatives. The catalyst was characterized thoroughly by using FT-IR, XRD, ¹³C MAS NMR, SEM, EDX, elemental mapping, TEM, BET, NH₃-TPD and TGA/DTA techniques. The presence of characteristic bands at 1694 cm⁻¹, 1254–769 cm⁻¹ and 1033 cm⁻¹ in the FT-IR spectrum, 2θ ≃ 6.7° and 9.8° in the XRD pattern and δ = 31.79, 39.55, 129.61, 131.46 (4C, CH), 133.54, 140.07 (2C), 167.71, 171.47 ppm (2C, 2C O) in the solid state ¹³C MAS NMR spectrum confirmed the successful formation of catalyst. This new eco-friendly approach resulted in a significant improvement in the synthetic efficiency (90–96% yield), high product purity, and minimizing the production of chemical wastes without using highly toxic reagents for the synthesis of acrylonitriles with selectivity for (Z)-isomer. Steric interactions seem to have an influence on the control of the Z-configurational isomers. By performing DFT calculations, it was found that the (Z)-isomer 3a is stabilized by 1.64 kcal mol⁻¹ more than the (E)-isomer. The catalyst could be reused for five consecutive cycles without substantial loss in catalytic activity.

Sulfonic acid functionalized metal–organic framework (S-IRMOF-3) as an efficient heterogeneous catalyst has been synthesized and employed for sustainable approach towards the synthesis of acrylonitriles in high yield and shorter reaction time period.     

Enhancement of alkaline conductivity and chemical stability of quaternized poly(2,6-dimethyl-1,4-phenylene oxide) alkaline electrolyte membrane by mild temperature benzyl bromination

A series of quaternized polyphenylene oxide (QPPO) based alkaline electrolyte membranes with different degrees of quaternization were synthesized via a benzyl bromination method at mild temperature (75 °C). Quite a high hydroxide conductivity under the reduced water uptake and swelling was exhibited by this method. When the degree of bromination measured from ¹H NMR analysis was 30%, the corresponding hydroxide ion conductivity was 0.021 S cm⁻¹. The chemical stability of the QPPO membranes was excellent, showing only 3% weight loss in 3 M NaOH solution during 1 month. The fuel cell performance test under H₂/O₂ exhibited the power density of 77 mW cm⁻² and the current density of 190 mA cm⁻² at 70 °C. Such excellent properties of QPPO membranes resulted from the achievement of the quaternization at the benzyl position, specifically.

A series of quaternized polyphenylene oxide (QPPO) based alkaline electrolyte membranes with different degrees of quaternization were synthesized via a benzyl bromination method at mild temperature (75 °C).     

Alkali metal impact on structural and phonon properties of Er3+ and Tm3+ co-doped MY(WO4)2 (M = Li,Na, K) nanocrystals

The Pechini and microwave-assisted hydrothermal syntheses of nanocrystalline Er³⁺ and Tm³⁺ co-doped MY(WO₄)₂, where M = Li, Na, K, double tungstates are reported. The obtained samples were characterized using standard X-ray powder diffraction (XRD) technique, Rietveld method, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and IR spectroscopy. The smallest crystallites (about 13 nm) could be obtained for the sodium samples synthesized by both the Pechini (for the resin calcined at 550 °C) and hydrothermal methods (synthesis at 230 °C). The average particle size of nanocrystalline powders increases with increasing temperature. It was found that nanocrystals retain the bulk structure with tetragonal and monoclinic symmetry for the sodium and potassium analogues, respectively. In contrast to this behaviour, LiY(WO₄)₂ undergoes a size-induced structural transformation from monoclinic (space group P2/n) to tetragonal (space group I4₁/a) symmetry. IR spectra of the synthesized sodium and potassium compounds are very similar to their bulk counterparts. IR spectra of the lithium analogues show, however, abrupt changes when the calcination temperature increases to 850 °C or higher. This behaviour is consistent with the size-induced phase transition in this compound.

TEM images of NaY(WO₄)₂:Er, Tm nanocrystalline powders synthesized by the Pechini method after calcination at (a) 550 °C, (b) 600 °C and (c) 700 °C.     

Efficient and stable catalyst of α-FeOOH for NO oxidation from coke oven flue gas by the catalytic decomposition of gaseous H2O2

Goethite (α-FeOOH) possesses excellent catalytic activity, high selectivity and good stability as a catalyst for NO oxidation through the catalytic decomposition of gaseous H₂O₂. as the primary reactive oxygen species is involved in the NO oxidation process together with ·OH, and N₂O₅ is found for the first time in the products of NO oxidation.

A catalyst α-FeOOH possesses excellent catalytic activity for NO oxidation, and N₂O₅ is first found in NO oxidation products.

Sulphur dioxide (SO₂) and nitrogen oxides (NO_x) yielded by fossil fuels and ore combustion are the major air pollutants produced by traditional chemical industries, including iron and steel, coking, and boilers, and these pollutants cause acid rain, fog, and haze. Wet flue gas desulphurisation (WFGD) and selective catalytic reduction (SCR) are efficient methods used in power plants for desulphurisation and denitration, respectively.¹ However, in traditional chemical industries, for example, coke oven flue gas yielded by coke oven gas combustion has a flue gas temperature of about 200–230 °C and the composition is complex,² which limits the utilisation of SCR.³Recently, we proposed a promising process of gas-phase oxidation combined with wet scrubbing using steel slag slurry to treat NO_x from low-temperature flue gas.^4,5 In this process, the sparingly soluble NO could be oxidised into soluble NO₂, HNO₃ or N₂O₅ through the gas-phase oxidation process, and then the oxidation products could be absorbed together with SO₂ in a wet scrubbing device. This method can achieve the simultaneous removal of SO₂ and NO_x using the oxidisers. Some oxidisers, such as O₃,^6,7 H₂O₂,^8–12 NaClO₂,¹³ NaClO,¹⁴ persulphate salt (S₂O₈²⁻)¹⁵ and ferrate (Fe[vi]),¹⁶ can be used as the gas-phase oxidiser for NO oxidation after being gasified if needed.H₂O₂ is a green and low-cost oxidizer, which can be used as the gas-phase oxidizer for NO oxidation after liquid H₂O₂ is gasified at low temperature. Furthermore, the oxidation potential of H₂O₂ (1.77 eV) is lower compared with that of O₃ (2.08 eV) and ·OH (2.80 eV) and thus its efficiency in oxidising NO is low.^12,17 Thermal decomposition of gaseous H₂O₂ can decompose H₂O₂ into radicals (·OH or ) with high oxidation potential for NO oxidation. However, this technology requires high H₂O₂ consumption (H₂O₂/NO = 80) and excessive residence time (34 s) and results in low NO oxidation efficiency (∼60%).¹⁸ Introducing catalysts into the H₂O₂ decomposition process can effectively decompose H₂O₂ into radicals and considerably reduce the consumption of H₂O₂.¹¹ Iron-based materials, such as hematite (α-Fe₂O₃),⁸ nanoscale zero-valent iron,⁹ Fe₃O₄,¹⁰ γ-Fe₂O₃@Fe₃O₄,¹¹ Fe₂(MoO₄)₃ ¹⁹ and Fe₂(SO₄)₃,¹² have been used as catalysts to decompose gaseous H₂O₂ for NO oxidation. These catalysts have high removal efficiencies as heterogeneous catalysts for the simultaneous removal of NO and SO₂ in an integrated catalytic oxidation/wet scrubbing process. However, the use of these catalysts results in relatively high H₂O₂ consumption^8,9,12,20 and relatively low gas hourly space velocity (GHSV)¹⁹ and catalytic stability.^9,12 Therefore, a catalyst with low H₂O₂ consumption and high GHSV and catalytic stability for NO oxidation through catalytic decomposition of gaseous H₂O₂ should be developed.Goethite (α-FeOOH) is a ubiquitous natural mineral in soils and sediments at the Earth''s surface that is widely used as a heterogeneous Fenton catalyst for wastewater treatment due to its abundance, availability, relative stability and low cost.²¹ He et al. explored the catalytic performance of α-FeOOH and found that it can be used to catalyse H₂O₂ vapour for NO oxidation under low-temperature (<160 °C) flue gas;²² however, coke oven flue gas has a higher flue gas temperature (200–230 °C), and the reaction products and catalytic mechanism may be different under different temperature regions. Therefore, the performance of α-FeOOH for NO oxidation through catalysing gaseous H₂O₂ under high flue gas temperature should be investigated, and the SO₂ oxidation efficiency of this process should also be evaluated. Herein, NO and SO₂ conversions and NO₂ yield using α-FeOOH with gaseous H₂O₂ were performed under the wide temperature range of 100–350 °C, and the catalytic stability and reaction mechanism were determined.Fresh α-FeOOH catalyst was prepared via precipitation reaction of Fe³⁺ followed by crystal transformation according to the method of Böhm.²³ All chemicals used in the experiments were of analytical grade, and deionised water was used. NO, NO₂, and SO₂ concentrations in simulated flue gas were analysed using a UV differential optical absorption spectroscopy (DOAS) flue gas comprehensive analyser (Laoying3023, Qingdao Laoying Environmental Technology Co., Ltd.). The presence of HNO₃ and N₂O₅ in the flue gas were detected using a Fourier transform infrared (FTIR) spectrometer (Tensor 27, Bruker Optik, Inc.), which was equipped with a 2.4 m gas cell. Catalysts were characterised via X-ray diffraction (XRD) spectroscopy (Empyrean, PANalytical Instruments) and FTIR spectrometry. Hydroxyl radical (·OH) and superoxide anion radical decomposed by H₂O₂ were detected via electron paramagnetic resonance (EPR) spectroscopy (A300-10/12, Bruker Optik Inc.), and 5,5-dimethyl-1-pyrroline N-oxide (DMPO) was used for capturing ·OH and . Specifically, DMPO–H₂O solvent was used to capture the ·OH generated after H₂O₂ was catalysed, whereas DMPO–CH₃OH was used to capture The experimental equipment for evaluating the catalytic performance of α-FeOOH was established (Fig. S1, ESI^†). In brief, the bypass of N₂ carried the gaseous H₂O₂ generated by the evaporation of H₂O₂ solution and mixed with the simulated flue gas, and then the mixture gas contacted with the catalyst, in which gaseous H₂O₂ was decomposed into radicals over the catalyst and oxidised NO and SO₂. At the outlet of the catalytic reactor, the simulated flue gas after being oxidised was detected using a UV DOAS flue gas comprehensive analyser and an FTIR spectrometer equipped with a gas cell. Each experiment was conducted for 20 min after the temperature was stabilised.According to Christensen et al., α-FeOOH is transformed to hematite (α-Fe₂O₃) within the temperature range of 171–311 °C, and α-FeOOH is totally converted to α-Fe₂O₃ at 350 °C.²⁴ The fresh catalyst and the catalyst calcinated at 350 °C were characterised via XRD and FTIR spectrometry. The FTIR and XRD spectra (Fig. S2 and S3, ESI^†) indicated that the fresh catalyst was α-FeOOH and the catalyst calcinated at 350 °C was α-Fe₂O₃ in an N₂ atmosphere. The colour of the fresh catalyst (yellow) and the calcinated catalyst (red) also proved the above results (Fig. S4, ESI^†). An FTIR spectrometer equipped with a gas cell was used to analyse the water vapour and further investigate the transformation temperature of α-FeOOH. Results (Fig. S5, ESI^†) showed that α-FeOOH began to decompose into α-Fe₂O₃ and H₂O when the temperature was above 200 °C in an N₂ atmosphere. However, when H₂O(g) and H₂O₂(g) were existed in N₂ atmosphere, they could improve the thermal stability of α-FeOOH. The reason may be that (1) multiple types of surface hydroxyls (–OHs) generated by the adsorption of water on α-FeOOH surface prevented the dehydration of –OHs;^25,26 and (2) H₂O(g) from the injected H₂O₂ solution were adsorbed on the reduced Fe(ii) and generated Fe(ii)–OH viaeqn (1) and (2), and Fe(ii)–OH was converted to Fe(iii)–OH viaeqn (3).^{12,19,22,27,28} The catalyst α-FeOOH was still stable when temperature was up to 225 °C, and little α-FeOOH close to the wall of the reactor was converted to α-Fe₂O₃ (the color of catalyst was changed from yellow to red) when temperature was up to 350 °C. Therefore, the catalyst α-FeOOH possesses great thermal stability under the simulated flue gas condition (e.g., the experimental condition in Fig. 1).1 Fe(ii) + V_o + H₂O → Fe(ii)–OH₂⁺ → Fe(ii)–OH + H⁺2 Fe(ii)–OH + H₂O₂ → Fe(iii)–OH + ·OH3Open in a separate windowFig. 1Effects of temperature on NO and SO₂ conversions and NO₂ yield (H₂O₂/NO, 2.0; H₂O₂ solution feeding rate, 148.9 μL min⁻¹; catalyst dosage, 0.5 g; GHSV, 137 747 h⁻¹; NO concentration, 200 ppm; SO₂ concentration, 660 ppm; O₂ concentration, 6%).As shown in Fig. 1, NO conversion and NO₂ yield were both lower than SO₂ conversion when gaseous H₂O₂ only was used for NO oxidation. This result indicated that SO₂ was more easily oxidised by gaseous H₂O₂ than NO, which consumed a large amount of H₂O₂. NO conversion and NO₂ yield were higher, but SO₂ conversion was considerably lower than using gaseous H₂O₂ only when α-FeOOH was used to catalyse gaseous H₂O₂ for NO oxidation. Therefore, α-FeOOH performed excellent catalytic activity and high selectivity for NO oxidation. Specifically, NO conversion achieved 98.8% and NO₂ yield reached 77.0% at H₂O₂/NO of 2.0, reaction temperature of 225 °C, catalyst dosage of 0.5 g and GHSV of 137 747 h⁻¹. The catalyst of α-FeOOH achieved a higher NO oxidation efficiency under low H₂O₂ consumption and high GHSV compared with those reported by previous studies (Table S1, ESI^†).^{8,9,12,17,19,20} Fig. 1 shows that NO conversion was higher than NO₂ yield within the temperature range of 100–225 °C, and NO conversion was closer to NO₂ yield when the temperature further increased from 250 °C to 350 °C. This trend indicated that the products of NO oxidation was not just NO₂ within the temperature range of 100–225 °C, and the product of NO oxidation might only be NO₂ within the temperature range of 250–350 °C. The products of NO oxidation were determined via FTIR spectroscopy. As shown in Fig. 2, the peaks for NO₂ (1599 cm⁻¹), HNO₃ (886 cm⁻¹) and N₂O₅ (1719 cm⁻¹) were observed in the FTIR spectra within the temperature range of 100–200 °C.^29,30 However, no obvious peaks for NO₂, HNO₃, and N₂O₅ were detected in the FTIR spectra when H₂O₂ was not added. This result indicated that NO₂, HNO₃ and N₂O₅ were the main products of NO oxidation through the catalytic decomposition of gaseous H₂O₂ over α-FeOOH in low-temperature (100–200 °C) region. Furthermore, the peaks for HNO₃ and N₂O₅ in the FTIR spectra disappeared when the temperature increased from 225 °C to 350 °C. The reason is that HNO₃ and N₂O₅ decomposed in the high-temperature region (225–350 °C) (eqn (4) and (5)).²⁹ In summary, NO₂, HNO₃ and N₂O₅ were the main products of NO oxidation in the low-temperature region (100–200 °C), whereas NO₂ was the main product in the high-temperature region (225–350 °C).N₂O₅ → NO + NO₂ + O₂42HNO₃ → NO + NO₂ + O₂ + H₂O5Open in a separate windowFig. 2FTIR spectra of simulated flue gas oxidised by gaseous H₂O₂ over α-FeOOH under different temperature conditions. (Experimental condition was the same as that in Fig. 1.) Fig. 1 shows that NO conversion sharply increased when the temperature increased from 100 °C to 200 °C and then decreased when the temperature further increased from 225 °C to 350 °C. The increase in NO conversion with temperature was because high temperatures enhance H₂O₂ decomposition into radicals according to the Arrhenius law,¹² which further accelerates NO conversion. The decrease in NO conversion at temperatures above 200 °C could be explained by (1) the thermal decomposition of gaseous H₂O₂ under high temperature and/or (2) the transformation of α-FeOOH under high temperature. On the one hand, gaseous H₂O₂ can be decomposed under high temperature. An FTIR spectrometer equipped with a gas cell was used to detect gaseous H₂O₂ under different temperature conditions (free of catalyst) to investigate the decomposition temperature of gaseous H₂O₂,³¹ and the variations in H₂O₂ content were measured by their homologous infrared absorption characteristic peaks (Fig. S6, ESI^†). Results (Fig. S7, ESI^†) indicated that H₂O₂ almost did not decompose at 100–300 °C, and the thermal decomposition of gaseous H₂O₂ occurred when the temperature increased further to 300 °C. On the other hand, NO-TPD (Fig. S8, ESI^†) showed that the absorbed NO began to desorb when the temperature was above 200 °C. Therefore, when the temperature was above 200 °C, NO conversion decreased when the temperature was above 200 °C. Overall, the transformation of α-FeOOH under high temperature (>200 °C) led to the decrease in NO conversion when the temperature was above 200 °C, and the thermal decomposition of gaseous H₂O₂ also resulted in the decrease in NO conversion when the temperature was above 300 °C.The catalytic stability of α-FeOOH was also investigated. As shown in Fig. 3, NO conversion was maintained at a high level (>97.0%) within the first 15 h and then fluctuated slightly but remained at >90.0% at 15–45 h. SO₂ conversion remained stable at about 2.0%. Results indicated that α-FeOOH possesses excellent catalytic activity, good stability and high selectivity for NO oxidation. According to the results in Fig. 1 and ​and3,3, the catalyst has an ideal temperature window of 175–250 °C; therefore, α-FeOOH can be applied in coke oven flue gas (200–230 °C) treatment.Open in a separate windowFig. 3Catalytic stability of α-FeOOH. (H₂O₂/NO, 2.0; H₂O₂ solution feeding rate, 148.9 μL min⁻¹; catalyst dosage, 0.5 g; GHSV, 137 747 h⁻¹; temperature, 225 °C; NO concentration, 200 ppm; SO₂ concentration, 660 ppm; O₂ concentration, 6%.)Fresh and used (after the 45 h test) α-FeOOH were characterised via FTIR and XRD spectroscopy. The bands at 3363, 3127 and 1628 cm⁻¹ are the O–H stretching mode in α-FeOOH, the stretching mode of surface water and the bending mode of H₂O, respectively. The characteristic strong bands at 795 and 891 cm⁻¹ were assigned to the Fe–O–H bending vibrations of α-FeOOH. The band at 638 cm⁻¹ was assigned to the Fe–O stretching vibration of pure α-FeOOH. The characteristic absorption peaks of α-FeOOH in the catalyst after the 45 h test did not change compared with that of the fresh catalyst (Fig. S9, ESI^†), indicating that the catalyst maintained the structure of α-FeOOH even after the 45 h test. The band at 999 cm⁻¹ was assigned to ν₁(SO₄) frequency, and the bands at 1076, 1136 and 1229 cm⁻¹ were interpreted as ν₃(SO₄) frequencies. These vibrational frequencies are attributed to specifically adsorbed SO₄²⁻ ions on the external and internal surfaces of catalyst particles after the 45 h test.^32,33 The XRD patterns showed that the phase of the catalyst before and after the stability test was still α-FeOOH (Fig. S10, ESI^†). This result also indicated that α-FeOOH possessed good stability in the NO oxidation process.EPR test was conducted to detect the radicals generated by H₂O₂ decomposition and analyse the oxygen species of the α-FeOOH/H₂O₂ system. Fig. 4 shows the 4-fold characteristic peak of DMPO–·OH adducts with an intensity ratio of 1 : 2 : 2 : 1 and four notable signals ascribed to adducts. These peaks and signals indicate the formation of ·OH and in the α-FeOOH/H₂O₂ system.^21,34 Furthermore, the intensity of the 4-fold characteristic peak of DMPO–·OH adducts was significantly weaker than that of adducts, indicated that the quantity of produced by the α-FeOOH/H₂O₂ system was larger than that of ·OH. Therefore, α-FeOOH can decompose H₂O₂ into ·OH and and may be dominant among ·OH and for NO oxidation. Radical trapping experiments (Fig. S11, ESI^†) further proved the roles of radicals (·OH and ) in the NO oxidation process. Benzoquinone (BQ, scavenger²⁰) was added into the H₂O₂ solutions, and H₂O₂ and BQ in the mixture solution was vapoured together. NO conversion substantially decreased from 92.9% to 6.1% when the molar ratio of BQ to H₂O₂ increased from 0 to 1.0. The reason was that the addition of BQ captured the generated by gaseous H₂O₂ decomposition over α-FeOOH, thereby decreasing NO conversion. NO conversion decreased from 92.9% to 8.0% when isopropanol (i-PrOH, ·OH scavenger²⁰) was introduced into the same system as the molar ratio of i-PrOH to H₂O₂ increased from 0 to 8.0. The reason was that ·OH generated in the α-FeOOH/H₂O₂ system was captured by i-PrOH instead of oxidised NO. These results indicated that when the addition concentration of the ·OH scavenger (i-PrOH) was eight times that of scavenger (BQ), both systems obtained the similar decrease in NO conversion. Therefore, as the primary reactive oxygen species was involved in the NO oxidation process together with ·OH.Open in a separate windowFig. 4EPR spectra of the α-FeOOH/H₂O₂ system.In this catalytic process, the reaction between H₂O₂ as an oxidant and iron ions as a catalyst to produce highly active species (·OH and ).³⁵ The conversion between Fe²⁺ and Fe³⁺ was proceed according to the Haber–Weiss mechanism. Fe(iii)–OH and Fe(iii) are reduced by H₂O₂ and generate Fe(ii)–OH and Fe(ii) (eqn (6) and (1)), the resulting Fe(ii)–OH and Fe(ii) also can be oxidized by H₂O₂ and produce Fe(iii)–OH and Fe(iii) (eqn (3) and (7)).^{12,19,22,27,28,36}6 Fe(ii) + H₂O₂ → Fe(ii) + ·OH + OH⁻7The proposed mechanism of NO oxidation by H₂O₂ decomposition over α-FeOOH is presented in Fig. 5 based on the study of the products of NO oxidation and reactive oxygen species ( and ·OH) in the NO oxidation process. (1) Gaseous H₂O₂ decomposed into ·OH and on the active sites ( Fe(ii)–OH and Fe(ii), Fe(iii)–OH and Fe(iii)) of the catalyst (eqn (1)–(3), (6) and (7)) according to the Haber–Weiss mechanism, a result that was proved through EPR analysis and scavenger experiments. (2) NO was oxidised by the generated ·OH and and produced NO₂ and HNO₃viaeqn (8) and (9). (3) The produced HNO₃ reacted with ·OH and produced NO₃ or NO₂ (eqn (10) and (11)). (4) NO₂ reacted with NO₃ and produced N₂O₅viaeqn (12).³⁷ The production of NO₂, HNO₃ and N₂O₅ during the NO oxidation process was proved by the FTIR spectra (Fig. 2).NO + 2·OH → NO₂ + H₂O89HNO₃ + ·OH → NO₃ + H₂O10HNO₃ + ·OH → NO₂ + H₂O₂11NO₂ + NO₃ → N₂O₅12Open in a separate windowFig. 5Catalytic mechanism of NO oxidation by H₂O₂ decomposition over α-FeOOH ( Fe^III: Fe(iii), Fe(iii)–OH; Fe^II: Fe(ii), Fe(ii)–OH).In summary, α-FeOOH can be used as an efficient catalyst for coke oven flue gas to enhance NO oxidation efficiency through the catalytic decomposition of gaseous H₂O₂. Moreover, α-FeOOH showed high selectivity for NO oxidation in the presence of SO₂. In this study, NO conversion achieved 98.8% under the following experimental conditions: H₂O₂/NO of 2.0, reaction temperature of 225 °C, catalyst dosage of 0.5 g and GHSV of 137 747 h⁻¹. The 45 h test indicated that α-FeOOH has good catalytic stability. The EPR test and radical trapping experiments revealed that as the primary reactive oxygen species was involved in the NO oxidation process together with ·OH. Furthermore, NO₂, HNO₃ and N₂O₅ were the products of NO oxidation through the catalysis of gaseous H₂O₂ over α-FeOOH within the temperature range of 100–200 °C, and NO₂ was the only oxidation product within the temperature range of 225–350 °C.The catalyst α-FeOOH can be used to decompose gaseous H₂O₂ into radicals and oxidise NO into high-valence NO_x, and then the oxidation products can be absorbed together with SO₂ in existing industrial-scale WFGD systems.^4,5 This process can achieve the simultaneous removal of SO₂ and NO_x from coke oven flue gas.     

Antioxidant activity of cerium dioxide nanoparticles and nanorods in scavenging hydroxyl radicals

Cerium oxide nanoparticles (CeNPs) have been shown to exhibit antioxidant capabilities, but their efficiency in scavenging reactive oxygen species (ROS) and the underlying mechanisms are not yet well understood. In this study, cerium dioxide nanoparticles (CeNPs) and nanorods (CeNRs) were found to exhibit much stronger scavenging activity than ·OH generation in phosphate buffered saline (PBS) and surrogate lung fluid (SLF). The larger surface area and higher defect density of CeNRs may lead to higher ·OH scavenging activity than for CeNPs. These insights are important to understand the redox activity of cerium nanomaterials and provide clues to the role of CeNPs in biological and environmental processes.

Cerium dioxide nanoparticles and nanorods were found to exhibit much stronger scavenging activity than ·OH generation in quasi-physiological conditions.

Reactive oxygen species (ROS) generally describe reduction products of oxygen molecules, including H₂O₂ and hydroxyl radicals (·OH).¹ ROS play a central role in biological processes exerting both beneficial and adverse health effects.² Several studies have looked into the redox balance between ROS and antioxidants³ as well as the underlying mechanisms.⁴ Among all ROS, ·OH is considered as one of the most reactive species; it can attack biomolecules and cause irreversible damage.⁵ Thus, experimental quantification and abiotic regulation of ·OH under physiologically relevant conditions is an important yet challenging task.In the last decade, cerium dioxide nanoparticles (CeNPs) have drawn much attention due to their redox properties⁶ and potential therapeutic applications (such as treating cardiac ischemia).^7–9 Efforts have been made to explore the potential use of CeNPs as medicine.^7,10,11 The ability of CeNPs in switching the oxidation state of Ce³⁺ and Ce⁴⁺ makes it a good candidate to mediate ROS.^6,12 Direct scavenging of ·OH (process ① in Scheme 1), NO·, and OONO⁻ by CeNPs have been investigated.^13–16 Moreover, previous studies indicated that CeNPs have catalase- and superoxide dismutase (SOD)-like effects (processes ③ and ⑤ in Scheme 1).^17,18 Both effects are closely correlated with the Ce³⁺ and Ce⁴⁺ surface concentrations, pH, H₂O₂ and chelating ligand concentrations.^19–23Open in a separate windowScheme 1Fenton reaction and reactive oxygen chemistry of CeNPs. Red and green colors indicate ROS formation and scavenging processes, respectively.In contrast to research about the antioxidant activity of CeNPs, inhalable CeNPs have been detected in ambient air and concerns have been raised about their potential adverse health effect.^24,25 Besides this, additional studies suggested that CeNPs can induce oxidative stress, inflammatory signaling response, and cell death upon generating ROS (processes ④–⑥ in Scheme 1) or ROS-messengers.^26–30 Given the controversies about the beneficial and toxic effects of CeNPs, it is necessary to distinguish the anti- and prooxidant activities of CeNPs under physiologically relevant conditions.³¹ In this study, we compared the ·OH formation and scavenging ability of commercial CeNPs (∅ 25 and 50 nm) and homemade cerium nanorods (CeNRs) with different physicochemical properties in phosphate buffered saline (PBS) buffer, antioxidant solutions, and a surrogate lung fluid (SLF). The SLF was used to mimic the key interface between human respiratory tract and inhaled air. Fig. 1 shows the size, morphology, surface composition, and mass normalized surface area of CeNPs and cerium dioxide nanorods (CeNRs). More information about the applied techniques, sample handling and instrument settings is compiled in Sections S1–S5.^†Fig. 1A and B indicate that CeNPs (∅ 50 nm) and CeNPs (∅ 25 nm) have a heterogeneous size distribution with average diameters of <50 nm and <25 nm respectively. Moreover, samples of these commercial CeNPs contain predominantly cubic NPs. In contrast, the morphology of CeNRs (Fig. 1C) is more uniform with a length of ∼100 nm. Details about the CeNRs can be found from our previous study.³² In addition to the detection of size and morphology, the specific surface areas of the cerium nanoparticles were determined to be 24.8 ± 0.4 m² g⁻¹ (∅ 50 nm CeNPs) (Fig. 1D), 39.2 ± 0.7 m² g⁻¹ (∅ 25 nm CeNPs) (Fig. 1E), and 106.5 ± 2.4 m² g⁻¹ (CeNRs) (Fig. 1F). Moreover, the similar Ce 3d XPS spectra of CeNPs (∅ 50 nm) (Fig. 1G), CeNPs (∅ 25 nm) (Fig. 1H), and CeNRs (Fig. 1I) indicate that the distribution of the cerium surface oxidation states (Ce³⁺ and Ce⁴⁺) on these NPs are quite similar. The six most prominent peaks of these spectra are attributable to Ce⁴⁺ ions.³³ This indicates that Ce⁴⁺ was the dominant cerium species in all three samples. The peak fittings (dashed lines) in panels G, H and I are based on the method by Maslakov et al..³³ The fitting based deconvolution of Ce 3d XPS spectra indicates that the concentration of surface Ce³⁺ in all these samples is <3%. Such a low abundance of surface Ce³⁺ is also supported by the absence of a shoulder peak of Ce 4f electrons at ∼1.1 eV in the XPS valence band spectrum of the CeNRs samples (Fig. S3^†). Furthermore, the deconvolution of the XPS spectrum of the O 1s region of the NPs (Fig. S2 and Table S3^†) indicates that the CeNRs surface contains a much higher concentration of hydroxide than CeNPs. This may correlate with the synthesis method of CeNRs using NaOH as reagent³⁴ and may play a role in the higher ·OH scavenging activity of CeNRs. These differences in chemical composition, morphology, and surface area between CeNPs and CeNRs may result in variations of their redox activity.Open in a separate windowFig. 1Physicochemical characteristics of CeNPs (∅ 50 nm) (A, D, and G), CeNPs (∅ 25 nm) (B, E, and H), and CeNRs (C, F, and I). (A–C) TEM images. (D–F) Surface areas determined by BET. (G–I) Ce 3d XPS spectra. The error bars in panels (D–F) represent standard deviations based on three replicates. The dashed lines in panels (G–I) are fitting curves. Fig. 2 shows the trapping mechanism of 5-tert-butoxycarbonyl-5-methyl-1-pyrroline-N-oxide (BMPO, panel A) and EPR spectra of aqueous mixtures of Fe²⁺, H₂O₂, SLF, and CeNPs (panel B). Fig. 2A shows that BMPO can react with OH radicals and form a BMPO–OH radical adduct. In this way, short lifetime radicals can be probed and characterized by electron paramagnetic resonance (EPR) spectroscopy (EMXplus10/12, Bruker, Germany, see details in Section S5 and Table S4^†). The grey dashed lines in panel B indicate the characteristic hyperfine splitting of BMPO–OH, in agreement with previous assignment.³⁵ The peak intensities of the spectra in Fig. 2B decrease in the order A (Fe²⁺ + H₂O₂) > B (Fe²⁺ + H₂O₂ + CeNPs) > C (Fe²⁺ + H₂O₂ + SLF) > D (Fe²⁺ + H₂O₂ + CeNPs + SLF). This implies that the amount of ·OH decreases accordingly. Based on the spin-counting method,³² we quantified the concentration of BMPO–OH in these solutions. The results are shown in Fig. 3 and Tables S5–S7.^†Open in a separate windowFig. 2(A) Reaction mechanism of the spin-trapping agent BMPO with a hydroxyl radical. (B) EPR spectra of the BMPO-radical adduct in different aqueous mixtures. The four peaks (dotted lines) are characteristic of BMPO–OH adducts. The concentrations of Fe²⁺, H₂O₂, and CeNPs (∅ 50 nm) are 1 mM, 10 mM, and 10 mg mL⁻¹, respectively.Open in a separate windowFig. 3Concentrations (A, B, and E) or remaining fractions (C, D, and F) of BMPO–OH in different aqueous mixtures. (A) and (B) Concentrations of BMPO–OH formed by pure CeNPs (∅ 50 nm) (○) or their mixtures within H₂O₂ (Δ) in pH = 4.7 (A) and 7.4 (B) PBS. (C) and (D) Remaining fraction (c/c₀) of BMPO–OH without (c₀) and with (c) mixing CeNPs (∅ 50 nm) or CeNRs (□) with 1 mM Fe²⁺ and 10 mM H₂O₂ in pH = 4.7 (C) and 7.4 (D) PBS. (E) Concentration of BMPO–OH formed by Fenton reactions in neutral PBS, antioxidant solutions, and SLF. (F) c/c₀ of BMPO–OH with and without mixing CeNPs (∅ 50 nm) (□), CeNPs (∅ 25 nm) (□), and CeNRs (□) with 1 mM Fe²⁺ and 10 mM H₂O₂ in pH = 4.7 SLF. The values of c₀ in panels B, D and F are ∼53, ∼17, and ∼26 μM. The x-axis errors in panels A, B, C, D, and F represent uncertainties from weighing and pipetting. All the y-errors represent standard deviation of more than three replicates. Fig. 3A and B show the positive correlation of ·OH yields of CeNPs (∅ 50 nm) without (black circles) and with the addition of H₂O₂ (black triangles) under different CeNPs (∅ 50 nm) loading conditions. In the absence of H₂O₂, 0.1–30 mg mL⁻¹ CeNPs (∅ 50 nm) can generate 0–0.8 and 0–0.5 μM ·OH in pH = 4.7 (Fig. 3A) and 7.4 (Fig. 3B) PBS, respectively. The generation of ·OH by pure CeNPs (∅ 50 nm) in acidic PBS is consistent with previous hypothesis that acid can catalyze the ·OH formation by CeNPs.³⁶ In contrast to pure CeNPs (∅ 50 nm), mixtures of 0.1–30 mg mL⁻¹ CeNPs (∅ 50 nm) with 10 mM of H₂O₂ can generate 0–5 (pH = 4.7) and 0–3 μM (pH = 7.4) ·OH, which also shows a positive correlation with the loading of CeNPs (∅ 50 nm) as shown in Fig. 3A and B. These hydroxyl radicals may be formed through Fenton-like reactions initiated by CeNPs:³⁷ H₂O₂ + Ce³⁺ → Ce⁴⁺ + ·OH + OH⁻.To evaluate the ·OH scavenging activity of CeNPs in aqueous solution, we measured the ·OH yield by mixtures of CeNPs (∅ 50 nm) or CeNRs, Fe²⁺, and H₂O₂ in acidic and neutral PBS. Fig. 3C and D show that the ·OH concentration decreased with increasing CeNPs or CeNRs loading, characterized by the decreasing remaining OH radical concentration. In the absence of CeNPs, Fenton reactions of 1 mM Fe²⁺ and 10 mM H₂O₂ generated ∼53 and ∼17 μM ·OH in pH = 4.7 (Fig. 3C) and 7.4 (Fig. 3D) PBS. At 30 mg mL⁻¹ CeNPs (∅ 50 nm), concentration of ·OH decreased to 15 μM (pH = 4.7) and 11 μM (pH = 7.4), respectively (Tables S5 and S6^†). In contrast to CeNPs, CeNRs exhibited higher ·OH scavenging efficiency, with 20–50% of ·OH to be scavenged by 0.1–20 mg mL⁻¹ CeNRs. This implies that the scavenging activity of CeNPs (∅ 50 nm) is more pronounced under acidic conditions. The decrease of ·OH concentration may be induced by the following processes: first, CeNPs (∅ 50 nm) or CeNRs could scavenge ·OH directly (process ① in Scheme 1).¹³ Second, the adsorption of H₂O₂ on CeNPs (∅ 50 nm) or CeNRs surfaces (like process ② in Scheme 1) may decrease the available H₂O₂ concentration.³⁸ In this case, due to the lower availability of the H₂O₂ precursor, the amount of ·OH formed by Fenton reactions will decrease. Third, the surface-bound H₂O₂ can be decomposed via catalase-like reactions (process ③ in Scheme 1).²¹ This process will form H₂O and O₂ rather than ·OH. Beyond these two pathways, iron ion-initiated redox processes may also influence the measured ·OH concentrations. For instance, it has been suggested that upon interaction with the surface of CeNPs, Fe²⁺ can enhance the dissolution of Ce³⁺ and cause the formation of 6-line ferrihydrite, which can increase the colloidal stability of the CeNPs.³⁹ Such a reaction may alter the redox activity of CeNPs (∅ 50 nm) or CeNRs.Recently Baldim et al.³⁸ measured the H₂O₂ surface adsorption potential of CeNPs with different sizes. They found that 5–28 nm diameter CeNPs could adsorb 2–20 H₂O₂ molecules nm⁻², depending on the surface composition of the nanomaterial. We used the adsorption potential from Baldim et al. and estimated that only <1% of H₂O₂ (∼8 μM) can be adsorbed on the surface of the CeNPs. Therefore, the surface adsorption of H₂O₂ by CeNPs cannot fully explain the reduction of ·OH concentration in Fig. 3. Furthermore, Pirmohamed et al.²¹ observed a H₂O₂ decomposition rate of ∼2.7 nmol min⁻¹ through catalase-like reactions. Based on this value, we estimate that a concentration of 0.1 mg mL⁻¹ of CeNPs would result in a H₂O₂ loss of <2% in our studies. Therefore, we suggest the direct scavenging process (① in Scheme 1), rather than the surface adsorption (② in Scheme 1) and catalase-like (③in Scheme 1) processes to be the dominant reduction pathways of ·OH. Fig. 3E shows the ·OH scavenging activity of typical epithelial lung fluid antioxidants and a surrogate lung fluid (SLF). Here, 0.1 mM of glutathione, 0.1 mM of uric acid, and 0.2 mM of ascorbate solutions could scavenge ∼8%, ∼14%, and ∼39% of hydroxyl radicals originating from Fenton reactions of 1 mM Fe²⁺ and 10 mM H₂O₂ in PBS. The SLF showed a similar activity as 0.2 mM ascorbate, i.e. the ·OH scavenging activities of individual antioxidants are not additive and decrease in the order ascorbate > uric acid > glutathione. This trend is consistent with previous findings.³⁸To assess the antioxidant activity of CeNPs under quasi-physiological conditions, we explored the ·OH scavenging activity of CeNPs and CeNRs in SLF. Fig. 3F shows the hydroxyl radical yield by Fenton reactions in SLF as a function of the CeNPs (∅ 25 and 50 nm) and CeNRs loading. As the loading of CeNPs (∅ 50 nm) increased from 0.1 to 10 mg mL⁻¹, the concentration of ·OH in SLF decreased by 38–85%. Within the same loading range, the CeNPs (∅ 25 nm) exhibited a similar efficiency. Whereas at higher loadings (1–5 mg mL⁻¹), the ·OH scavenging potential of CeNPs (∅ 25 nm) was 9–55% higher than that of their 50 nm counterparts. In contrast to CeNPs, the CeNRs showed a much higher ·OH scavenging efficiency. Even with a loading as low as 0.1 mg mL⁻¹, the CeNRs could reduce 88% of the ·OH. For CeNRs loadings that exceeded 1 mg mL⁻¹, no ·OH could be observed. The trend of the ·OH scavenging efficiency according to CeNRs > CeNPs (∅ 25 nm) >CeNPs (∅ 50 nm) is in the same order as the surface area of these NPs (Fig. 1D–F). Given the low abundance of Ce³⁺ on fresh CeNPs and CeNRs surface (Fig. 1G–H), we suggest that substantial amount of Ce³⁺ may be formed upon interactions of NPs with water.¹³ The larger surface area of CeNRs may increase the density of Ce³⁺ per unit particle mass and subsequently their ·OH scavenging activity. Previous works showed that CeNRs are prone to expose their (110) facets to reactive species.³⁴ These facets were described as reactive “hybrid structures” between the (111) and (100) surfaces of CeNPs. Furthermore, the distinct crystallographic surface structure of CeNRs may act as binding site for reactive species (·OH and H₂O₂) exerting peroxidase-like effects. Additionally, Fe²⁺-dependent reactive oxygen chemistry may contribute to the observed ·OH scavenging processes.³⁹ Finally, it has been suggested that glutathione could interact with CeNPs and influence the redox couple of Ce³⁺/Ce⁴⁺.⁴⁰It is worthy to note that a real physiologic environment is more complicated than SLF. A large number of redox chemistry processes may alter the agglomeration and distribution of CeNPs and relevant materials,⁴¹ which may eventually influence its properties including ·OH scavenging efficiency and SOD-like characteristics.⁴² Thus, characterizing CeNPs or their functionalized derivatives in more realistic environments will be beneficial and promising in follow-up studies.     

Optimization extraction and functional properties of soluble dietary fiber from pineapple pomace obtained by shear homogenization-assisted extraction

Response surface methodology (RSM) was used to optimize the extraction conditions for shear homogenization-assisted extraction of soluble dietary fiber from pineapple pomace (s-SDF), and the absorption capacities and antioxidant activities of the obtained s-SDF were also investigated. The optimum extraction conditions consisted of a cutting speed of 9000 rpm, a cutting time of 20 min, a cellulase content of 5.0%, a hydrolysis time of 120 min, a pH value of 4.5, a hydrolysis temperature of 50 °C, and a raw material to water ratio of 1 : 45 g mL⁻¹. Under these conditions, the theoretical and actual extraction yields of s-SDF were 8.80% and 8.76%, respectively. An absorption capacity analysis indicated that s-SDF exhibited higher absorption abilities to sodium cholate, cholesterol and fat. In addition, s-SDF possessed higher antioxidant activities, showing a positive concentration effect relationship for DPPH˙, ABTS⁺, ·OH and O₂⁻˙. The concentration of 1.0 mg mL⁻¹ scavenged 76.72% DPPH˙, 58.40% ABTS⁺, 23.47% ·OH and 48.47% O₂⁻˙, respectively, and the reduction power was 0.70. These results indicated that pineapple pomace is a potential source of natural dietary fiber and a potential functional food ingredient.

Shear homogenization-assisted extraction method was successfully applied to extract soluble dietary fiber from pineapple pomace, and the absorption capacities and antioxidant activities of the obtained s-SDF were also investigated.     

Hyper-branched structure—an active carrier for copolymer with surface activity,anti-polyelectrolyte effect and hydrophobic association in enhanced oil recovery

Herein, a hyper-branched polymer h-PMAD with, simultaneously, surface activity, an anti-polyelectrolyte effect and a hydrophobic association was prepared via aqueous solution free radical polymerization, and characterized by IR, NMR, TG–DTG and SEM. The polymer h-PMAD provided excellent comprehensive properties in terms of surface activity, thickening, water solubility, rheology and aging, which were compared with studies of HPAM and the homologous linear polymer PMAD. Specifically, the IFT value was 55.40 mN m⁻¹, 789.24 mPa s apparent viscosity with a dissolution time of 72 min, 97.72, 90.77 and 105.81 mPa s with Na⁺, Ca²⁺ and Mg²⁺ of 20 000, 2000 and 2000 mg L⁻¹, respectively. Meanwhile, the non-Newtonian shear thinning behavior had a 96.33% viscosity retention while the shear rate went from 170 s⁻¹ to 510 s⁻¹ and then returned to 170 s⁻¹ again and 0.12 Hz curve, with an intersection frequency of G′ and G′′. Also, it had 33.51% and 50.96% viscosity retention in formation and deionized water at 100 °C and a low viscosity loss in formation water at 80 °C over 4 weeks. Moreover, the h-PMAD had an EOR of 11.61%, was obviously higher than PMAD with 8.19% and HPAM with 5.88%. Most importantly, the better EOR of h-PMAD over that of PMAD testified that the hyper-branched structure provided an active carrier for copolymers with functionalized monomers to exert greater effects in displacement systems, which is of an extraordinary meaning.

Herein, a hyper-branched polymer h-PMAD with, simultaneously, surface activity, an anti-polyelectrolyte effect and a hydrophobic association was prepared via aqueous solution free radical polymerization, and characterized by IR, NMR, TG–DTG and SEM.     

Steps towards highly-efficient water splitting and oxygen reduction using nanostructured β-Ni(OH)2

β-Ni(OH)₂ nanoplatelets are prepared by a hydrothermal procedure and characterized by scanning and transmission electron microscopy, X-ray diffraction analysis, Raman spectroscopy, and X-ray photoelectron spectroscopy. The material is demonstrated to be an efficient electrocatalyst for oxygen reduction, oxygen evolution, and hydrogen evolution reactions in alkaline media. β-Ni(OH)₂ shows an overpotential of 498 mV to reach 10 mA cm⁻² towards oxygen evolution, with a Tafel slope of 149 mV dec⁻¹ (decreasing to 99 mV dec⁻¹ at 75 °C), along with superior stability as evidenced by chronoamperometric measurements. Similarly, a low overpotential of −333 mV to reach 10 mA cm⁻² (decreasing to only −65 mV at 75 °C) toward hydrogen evolution with a Tafel slope of −230 mV dec⁻¹ is observed. Finally, β-Ni(OH)₂ exhibits a noteworthy performance for the ORR, as evidenced by a low Tafel slope of −78 mV dec⁻¹ and a number of exchanged electrons of 4.01 (indicating direct 4e⁻-oxygen reduction), whereas there are only a few previous reports on modest ORR activity of pure Ni(OH)₂.

β-Ni(OH)₂ nanoplatelets produced via a hydrothermal method exhibit good performance as trifunctional electrocatalysts for the ORR, OER, and HER in alkaline media along with excellent stability under cathodic/anodic polarisation conditions.     

Low-cost VO2(M1) thin films synthesized by ultrasonic nebulized spray pyrolysis of an aqueous combustion mixture for IR photodetection

We report detailed structural, electrical transport and IR photoresponse properties of large area VO₂(M1) thin films deposited by a simple cost-effective two-step technique. Phase purity was confirmed by XRD and Raman spectroscopy studies. The high quality of the films was further established by a phase change from low temperature monoclinic phase to high temperature tetragonal rutile phase at 68 °C from temperature dependent Raman studies. An optical band gap of 0.75 eV was estimated from UV-visible spectroscopy. FTIR studies showed 60% reflectance change at λ = 7.7 μm from low reflectivity at low temperature to high reflectivity at high temperature in a transition temperature of 68 °C. Electrical characterization showed a first order transition of the films with a resistance change of four orders of magnitude and TCR of −3.3% K⁻¹ at 30 °C. Hall-effect measurements revealed the n-type nature of VO₂ thin films with room temperature Hall mobility, μ_e of 0.097 cm² V⁻¹ s⁻¹, conductivity, σ of 0.102 Ω⁻¹ cm⁻¹ and carrier concentration, n_e = 5.36 × 10¹⁷ cm⁻³. In addition, we fabricated a high photoresponsive IR photodetector based on VO₂(M1) thin films with excellent stability and reproducibility in ambient conditions using a low-cost method. The VO₂(M1) photodetector exhibited high sensitivity, responsivity, quantum efficiency, detectivity and photoconductive gain of 5.18%, 1.54 mA W⁻¹, 0.18%, 3.53 × 10¹⁰ jones and 9.99 × 10³ respectively upon illumination with a 1064 nm laser at a power density of 200 mW cm⁻² and 10 V bias voltage at room temperature.

We report detailed structural, electrical transport and IR photoresponse properties of large area VO₂(M1) thin films deposited by a simple cost-effective two-step technique.     

Variable temperature solid-state NMR spectral and relaxation analyses of the impregnation of polyethylene glycol (PEG) into coniferous wood

To investigate the behaviours of polyethylene glycol (PEG) and its interaction with biomass constituents in coniferous wood (Japanese cypress), variable temperature solid-state NMR spectra and relaxation times were measured from 20–80 °C. Signal intensities in the ¹H and ¹³C PST-MAS NMR spectra changed depending on both the measurement temperature and the melting point of the impregnated PEG. In the ¹³C CP-MAS NMR spectra with increasing temperature, although the signal intensities of biomass constituents slightly decreased, signal intensities of PEG molecules in the cypress maximized at 80 °C. PEG impregnation into cypress decreased the T₁H values at 80 °C for short to medium chain PEG in the liquid phase while it decreased T₁H values at ambient temperature for long chain PEG in the solid phase because the interactions of PEG molecules and the biomass constituents of coniferous wood were different for different chain lengths of the PEG. These variable temperature measurements of both solid-state NMR spectra and relaxation time indicated that impregnation of longer chain PEG molecules produced higher hydrophobicity because of the increased steric hinderance of PEG attached to carbohydrates. The variable temperature measurements also showed that long chain PEG molecules were restricted to the lumen while short to medium chain length PEG molecules infiltrated into the intercellular region of the cell wall in addition to the lumen. These results obtained from the variable temperature NMR measurements were also supported by ATR-IR spectroscopy analyses.

To investigate the behaviours of polyethylene glycol (PEG) and its interaction with biomass constituents in coniferous wood (Japanese cypress), variable temperature solid-state NMR spectra and relaxation times were measured from 20–80 °C.     

Comparative study of atrazine degradation by magnetic clay activated persulfate and H2O2

To effectively remove the endocrine disrupting chemicals (EDCs) in water, Fe₃O₄ was loaded on the surface of modified sepiolite clay by the method of co-precipitation to catalyze potassium persulfate (K₂S₂O₈) and hydrogen peroxide (H₂O₂) respectively to generate SO₄˙⁻ and ·OH for atrazine (ATZ) removal. The magnetic clay catalyst was characterized by XRD, SEM, N₂ adsorption–desorption and isoelectric point. The degradation efficiency of ATZ in the two systems was systematically compared in terms of initial pH, oxidant dosage and oxidant utilization rate. The results revealed that, after 90 minutes, systems with K₂S₂O₈ and H₂O₂ can remove 65.7% and 57.8% of the ATZ under the given conditions (30 °C, catalyst load: 1 g L⁻¹, initial pH: 5, [ATZ]₀: 10 mg L⁻¹, [H₂O₂]₀: 46 mmol L⁻¹, [PDS]₀: 46 mmol L⁻¹). The magnetic clay catalyst still maintained good catalytic activity and stability during the four consecutive runs. Based on the quenching experiments, it was demonstrated that the dominant radical species in the two systems were SO₄˙⁻/·OH and ·OH, respectively. However, the degradation efficiency of the two systems presented different responses toward the condition variations; the system with K₂S₂O₈ was relatively more sensitive to solution pH, the oxidant efficiency was generally higher than that of the H₂O₂ system (except 184 mmol L⁻¹).

To effectively remove the EDCs in water, Fe₃O₄ was loaded on the surface of modified sepiolite clay by co-precipitation to catalyze K₂S₂O₈ and H₂O₂ respectively to generate SO₄˙⁻ and ·OH for ATZ removal.     

Effect of Cage-Wash Temperature on the Removal of Infectious Agents from Caging and the Detection of Infectious Agents on the Filters of Animal Bedding-Disposal Cabinets by PCR Analysis

Efficient, effective cage decontamination and the detection of infection are important to sustainable biosecurity within animal facilities. This study compared the efficacy of cage washing at 110 and 180 °F on preventing pathogen transmission. Soiled cages from mice infected with mouse parvovirus (MPV) and mouse hepatitis virus (MHV) were washed at 110 or 180 °F or were not washed. Sentinels from washed cages did not seroconvert to either virus, whereas sentinels in unwashed cages seroconverted to both agents. Soiled cages from mice harboring MPV, Helicobacter spp., Mycoplasma pulmonis, Syphacia obvelata, and Myocoptes musculinus were washed at 110 or 180 °F or were not washed. Sentinels from washed cages remained pathogen-free, whereas most sentinels in unwashed cages became infected with MPV and S. obvelata. Therefore washing at 110 or 180 °F is sufficient to decontaminate caging and prevent pathogen transmission. We then assessed whether PCR analysis of debris from the bedding disposal cabinet detected pathogens at the facility level. Samples were collected from the prefilter before and after the disposal of bedding from cages housing mice infected with both MPV and MHV. All samples collected before bedding disposal were negative for parvovirus and MHV, and all samples collected afterward were positive for these agents. Furthermore, all samples obtained from the prefilter before the disposal of bedding from multiply infected mice were pathogen-negative, and all those collected afterward were positive for parvovirus, M. pulmonis, S. obvelata, and Myocoptes musculinus. Therefore the debris on the prefilter of bedding-disposal cabinets is useful for pathogen screening.Abbreviations: ABDC, animal bedding disposal cabinet; MAV, murine adenovirus K87; MHV, mouse hepatitis virus; MNV, murine norovirus; MPV, mouse parvovirus; MVM, minute virus of mice; MMBTU, million British thermal units; SW, Swiss WebsterThe use of evidence-based standard operating procedures in animal resource centers is crucial to cost containment and sustainable energy use. Understandably, biosecurity is a major driver of procedures and processes in rodent facilities and permeates virtually all aspects of animal resource operations, making it necessary to balance the cost: benefit of detection, prevention, and control of infection. As an example, recent publications that suggested that mouse parvovirus (MPV) infection can be caused by MPV-contaminated grains that were not inactivated during their processing into pelleted rodent feed^25,36,47 have led to changes in husbandry procedures including the use of autoclaved or irradiated food. Although the successful control and prevention of MPV infections in our facilities has been attributed to the practice of autoclaving mouse cages preassembled with bedding and food prior to their use in the facility, this procedure was not definitively proven to be the sole factor in MPV eradication.³⁰ Because wash centers are historically the largest utilities consumer in animal facilities,¹⁵ this practice of autoclaving cages prior to use is not only labor-intensive but also energy-intensive, and the labor and energy consumption is amplified in facilities that lack a bulk autoclave and in which the cages must be transported to be autoclaved. In addition, during outbreaks with MPV and other infectious agents, our long-standing standard operating procedure for soiled cages is to autoclave them to inactivate infectious agents prior to removing the soiled bedding and cage washing. This labor- and energy-intensive practice of using autoclaving to decontaminate cages has historically been justified because MPV is a nonenveloped virus that is highly stable in the environment and difficult to inactivate.^{5,6,16,27,38,42,49} Despite the environmental stability of the virus, infections with MPV are difficult to detect because the amount of virus shed is low; transmission can be inefficient, resulting in inconsistent seroconversion of mice housed in the same cage; and PCR analysis can detect low levels of MPV DNA in the feces of mice that are unable to transmit virus to contact sentinels.^4,30,31 We recently demonstrated that cage washing alone removed or inactivated MPV from 14 cages that had housed outbred mice acutely infected with MPV; these findings are not surprising when the inefficiencies of MPV transmission are considered.¹¹ These initial results challenge the cost:benefit ratio of autoclaving cages as a means to decontaminate them prior to cage washing during an MPV outbreak. Our findings with MPV led us to question whether cage washing alone might be effective for decontaminating cages after exposure to other infectious agents that are stable in the environment, even if they are shed for longer periods of time or at higher levels than is MPV.In our previous study,¹¹ we showed that cage washing was effective at preventing fomite-based transmission of MPV by cage components, and we postulated that water temperature and detergent type contribute to MPV decontamination either directly through inactivation of the virus and/or indirectly through effective mechanical removal of organic waste and residual virus from the cage. The Guide for the Care and Use of Laboratory Animals²⁴ states that “disinfection from the use of hot water alone is the result of the combined effect of temperature and the length of time at a given temperature” and that “effective disinfection can be achieved with wash and rinse water at 143–180 °F or more.” Theoretically, contact times to disinfect equipment at these temperatures would need to be 1800 s at 143 °F (61.7 °C) and 0.1 s at 180 °F (82.2 °C).⁴⁶ Contact times of 6 s or more at 168 to 180 °F (75.6 to 82.2 °C) killed 3 types of bacteria (Pseudomonas aeruginosa, Salmonella cholerasuis, and Staphylococcus aureus) in one study,⁴⁵ and contact times of 2 min or more at 160 °F (71.1 °C) killed 5 types of bacteria (Escherichia coli, Klebsiella pneumonia, Proteus mirabilis, Providencia rettgeri, and Staphylococcus epidermidis) in another.³⁹ However, these 2 studies were performed by using hot water in a test tube and, therefore, detergent and mechanical spraying action that occur within rack washers was not a factor.Traditionally, the temperature used for the wash and rinse water in our facilities has been 180 °F (82.2 °C) with a belt speed of 2 to 3 ft./min (0.6 to 0.9 m/min). We postulated that if the volume and force of the wash water, combined with detergents, consistently diluted or removed infectious agents to below the level necessary for the transmission of infection, then wash temperatures high enough to inactivate the agents would be unnecessary. Given the energy usage and infrastructure necessary to boost ‘domestic’ hot water to 180 °F, the purpose of this study was to compare the efficacy of cage washing by using the domestic hot-water temperature (110 °F [43.3 °C]) and the traditional steam-boosted wash temperature (180 °F [82.2 °C]) on preventing the transmission from contaminated caging of 3 of the most prevalent viral agents (MNV, MPV, MHV; prevalence, 32.6%,1.8%, and 1.6%, respectively ) and bacterial and parasitic agents (Helicobacter spp. and pinworms; prevalence,15.9% and 0.3%, respectively).³⁵Effective and efficient decontamination of caging goes hand-in-hand with effective and efficient detection of infection. Timely detection of infection is important to biosecurity, and environmental sampling is a promising adjunct to sentinel exposure programs for the early detection of infectious agents. PCR analysis of cage and rack components, including the outflow prefilter of ventilated racks, has been shown to be of use for several infectious agents including MPV, MHV, Helicobacter spp., and fur mites.^10,26,31 The ability to reliably detect infectious agents from a site where soiled bedding debris is aerosolized and concentrated might provide an efficient adjunct for infectious agent screening. In the current study, we determined whether monitoring by PCR analysis of dust and debris collected from the animal bedding disposal cabinet (ABDC) prefilter could be used as an efficient adjunct to sentinel programs to screen for contamination by infectious agents.