Chromium-free Cu@Mg/γ-Al2O3 – an active catalyst for selective hydrogenation of furfural to furfuryl alcohol

Development of a chromium (Cr)-free hydrogenation catalyst is very important to replace the existing hazardous Cr based catalyst used in the furfural hydrogenation to furfuryl alcohol. Herein, we report synthesis of well-dispersed copper nanoparticles supported on hydrothermally stable magnesium doped alumina (Cu@Mg/γ-Al₂O₃) for selective hydrogenation of furfural to furfuryl alcohol. The prepared catalyst was characterized by X-ray Photoelectron Spectroscopy (XPS), Auger Electron Spectroscopy (AES), Powder X-ray Diffraction (PXRD), Surface Area Analysis (SAA), High Resolution-Transmission Electron Microscopy (HR-TEM), Temperature Programmed Reduction/Desorption (TPR/TPD) and Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) to understand textural properties of the catalyst. The prepared catalyst was found to be highly active and selective with 99% conversion of furfural and 94% selectivity for furfuryl alcohol under solvent free conditions at 443.15 K and 2 MPa of hydrogen pressure. It was also observed that the Cu@Mg/γ-Al₂O₃ catalyst is reusable (up to six runs) while maintaining its high activity and selectivity (≥94%) in the hydrogenation of furfural to furfuryl alcohol.

A catalyst for selective hydrogenation of furfural to furfural alcohol in a solvent free environment.     

Preparation of α-Fe2O3/rGO composites toward supercapacitor applications

Reduced graphene oxide (rGO) integrated with iron oxide nanoparticles (α-Fe₂O₃/rGO) composites with different morphologies were successfully obtained through the in situ synthesis and mechanical agitation methods. It was found that the α-Fe₂O₃ was densely and freely dispersed on the rGO layer. By comparing electrochemical properties, the sheet-like α-Fe₂O₃/rGO composites demonstrate excellent electrochemical performance: the highest specific capacitance, and excellent cycling stability and rate capacity. The specific capacitance is 970 F g⁻¹ at a current density of 1 A g⁻¹ and the capacitance retention is 75% after 2000 cycles with the current density reaching 5 A g⁻¹. It is mainly due to the synergistic effect between the α-Fe₂O₃ and rGO, and the high conductivity of the rGO offers a fast channel for the movement of electrons.

Preparation of α-Fe₂O₃/rGO composites for supercapacitor application using in situ synthesis and a mechanical agitation method.     

Self-assembled membrane manufactured by metal–organic framework (UiO-66) coated γ-Al2O3 for cleaning oily seawater

In order to effectively clean oily seawater with anionic polyacrylamide (APAM), UiO-66 coated γ-Al₂O₃ (UA) composites were firstly synthesized using γ-Al₂O₃ as a template to induce the growth of high hydrophilic UiO-66 on its surface to form a uniform UA self-assembled membrane. The UA composites and self-assembled membrane were characterized and analyzed. Also, the membrane performance was investigated. The results show that the hydrophilicity of particles is enhanced with the water contact angle decreasing from 39.8° (γ-Al₂O₃ particles) to 26.2° (UA composites) by introducing the UiO-66 coating. Moreover, the UA self-assembled membrane performs attractive water yield and separation performance. The oil concentration in the permeate treated by the first class of UA self-assembled membrane declines apparently from 91.22 to 18.90 mg L⁻¹, while the water yield is as high as 657.89 L m⁻² h⁻¹. The reclaimed separation experiments show that the membrane materials could be recycled by calcination at 200 °C and hydraulic cleaning, which gives the material potential application in cleaning oily seawater.

The self-assembled membrane manufactured by UA composites exhibits excellent separation performance and water yield in the treatment of oily seawater.     

Comparative study on La-promoted Ni/γ-Al2O3 for methane dry reforming – spray drying for enhanced nickel dispersion and strong metal–support interactions

Dry reforming of methane (DRM) enables an efficient utilization of two abundant greenhouse gases by converting them into syngas, a versatile feedstock for chemical synthesis. Aiming for high catalyst performance and enhanced coke resistance, different preparation techniques of La-promoted Ni/γ-Al₂O₃ catalysts for DRM were compared facilitating structure–performance correlations. The studied synthesis techniques comprehend incipient wetness impregnation and co-precipitation as well as alternative techniques such as spray drying. All catalysts were fully characterized before and after reaction by N₂-physisorption, XRD, H₂-TPR and STEM-EDX elemental mapping. Additionally, a thorough investigation of carbon deposits has been carried out by TGA/DSC and STEM-EDX, respectively. The different preparation techniques led generally to very different physical properties, structure, chemical species and anti-coking properties of the catalyst. However, some catalysts with similar physicochemical characteristics differed in catalytic performance and coking resistance. Superior catalytic performance could be reached for catalysts prepared by spray drying and related to excellent Ni dispersion, strong metal–support interaction and very low coke formation of only 2.7% of the catalyst weight. After 6 h time on stream only minor sintering occurred, with few Ni nanoparticles up to 10 nm.

Clear structure-performance correlation for the dry reforming of methane – spray drying for excellent sintering and cocking resistivity.     

The CD3-γδε and CD3-ζ/η Modules Are Each Essential for Allelic Exclusion at the T Cell Receptor β Locus but Are Both Dispensable for the Initiation of V to (D)J Recombination at the T Cell Receptor–β, –γ, and –δ Loci

The pre–T cell receptor (TCR) associates with CD3-transducing subunits and triggers the selective expansion and maturation of T cell precursors expressing a TCR-β chain. Recent experiments in pre-Tα chain-deficient mice have suggested that the pre-TCR may not be required for signaling allelic exclusion at the TCR-β locus. Using CD3-ε– and CD3-ζ/η–deficient mice harboring a productively rearranged TCR-β transgene, we showed that the CD3-γδε and CD3-ζ/η modules, and by inference the pre-TCR/CD3 complex, are each essential for the establishment of allelic exclusion at the endogenous TCR-β locus. Furthermore, using mutant mice lacking both the CD3-ε and CD3-ζ/η genes, we established that the CD3 gene products are dispensable for the onset of V to (D)J recombination (V, variable; D, diversity; J, joining) at the TCR-β, TCR-γ, and TCR-δ loci. Thus, the CD3 components are differentially involved in the sequential events that make the TCR-β locus first accessible to, and later insulated from, the action of the V(D)J recombinase.     

Adsorption of an Au atom and dimer on a thin θ-Al2O3/NiAl(100) film: dependence on the thickness of the θ-Al2O3 film

With calculations based on density-functional theory (DFT) we investigated the adsorption of a single Au atom and a dimer on thin θ-Al₂O₃(001) films supported on NiAl(100). The interaction of the Au adsorbates with the surface was shown to depend on the thickness of the film. The adsorption energy for an Au atom on θ-Al₂O₃(001)/NiAl(100) of film thickness ≤four atomic layers was significantly enhanced—over three times that on a bulk θ-Al₂O₃(001) surface, and accompanied with a shortened Au-oxide bond and an uplifted Au-binding Al. The strong Au-surface interaction involved a decreased work function of θ-Al₂O₃(001)/NiAl(100) and consequently drove charge to transfer from the substrate to the adsorbed Au atom; the charge was transferred from NiAl, through alumina, on monolayer θ-Al₂O₃(001)/NiAl(100), but directly from alumina on thicker layers. For an Au dimer, both upright (end-on) and flat-lying (side-on) geometries existed. The flat-lying dimer was preferred on mono- and tri-layer alumina films, having a greater adsorption energy but a weakened Au–Au bond, whereas the upright geometry prevailed for films of other thickness, having a weaker adsorption energy and being less charged, similar to that on a bulk θ-Al₂O₃(001) surface. The results imply an opportunity to control the properties and morphologies of metal clusters supported on an oxide film by tuning its thickness.

The adsorption behavior of a single Au atom and a dimer on thin-film θ-Al₂O₃(001)/NiAl(100) varies with the thickness of the film.     

In-plasma-catalysis for NOx degradation by Ti3+ self-doped TiO2−x/γ-Al2O3 catalyst and nonthermal plasma

In an attempt to realize the efficient treatment of NO_x, a mixed catalyst of Ti³⁺ self-doped TiO_2−x and γ-Al₂O₃ was constructed by reducing commercial TiO₂. The degradation effect on NO_x was evaluated by introducing the mixed catalyst into a coaxial dual-dielectric barrier reactor. It was found that the synthesized TiO_2−x could achieve considerable degradation effects (84.84%, SIE = 401.27 J L⁻¹) in a plasma catalytic system under oxygen-rich conditions, which were better than those of TiO₂ (73.99%) or a single plasma degradation process (26.00%). The presence of Ti³⁺ and oxygen vacancies in TiO_2−x resulted in a relatively narrow band gap, which contributed to catalyzing deeply the oxidation of NO_x to NO₂⁻ and NO₃⁻ during the plasma-induced “pseudo-photocatalysis” process. Meanwhile, the TiO_2−x showed an improved discharge current and promoted discharge efficiency, explaining its significant activation effect in the reaction. Reduced TiO_2−x could achieve an impressive degradation effect in a long-time plasma-catalysis process, and still maintained its intrinsic crystal structure and morphology. This work provides a facile synthesis procedure for preparing Ti³⁺ self-doped TiO_2−x with practical and scalable production potential; moreover, the novel combination with plasma also provides new insights into the low-temperature degradation of NO_x.

TiO_2−x has a smaller forbidden band width, more abundant Ti³⁺ and oxygen vacancies, so as to obtain a better and more stable degradation effect of NO_x in plasma-catalysis process.     

Copper–cobalt catalysts supported on mechanically mixed HZSM-5 and γ-Al2O3 for higher alcohols synthesis via carbon monoxide hydrogenation

Mechanically mixed γ-Al₂O₃ and HZSM-5 (Si/Al = 50) with different mass ratio were utilized as support for Cu–Co higher alcohol synthesis catalysts prepared through incipient wetness impregnation. The textural and structural properties were studied using Ar low temperature adsorption and desorption, H₂-temperature programmed reduction (H₂-TPR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM) and catalytic performance measurements. The results indicated that the mechanically mixed HZSM-5 and γ-Al₂O₃ supported copper–cobalt catalysts were superior to either γ-Al₂O₃ or HZSM-5 supported ones with the same metal loading. The results revealed that using HZSM-5 and γ-Al₂O₃ mechanically mixed benefited the dispersion of metallic phases and stronger synergetic functions between smaller nanoparticles containing copper and/or cobalt, which is essential for HAS from CO hydrogenation. Under working conditions of P = 5.0 MPa, T = 300 °C, V(H₂) : V(CO) : V(N₂) = 4 : 2 : 1 and GHSV = 7200 mL g⁻¹ h⁻¹, mechanically mixed HZSM-5 and γ-Al₂O₃ supported catalysts showed higher catalytic activity than those over single support. For CuCo catalysts upon support containing 50.0 wt% HZSM-5 and 50.0 wt% γ-Al₂O₃, the CO conversion was 21.3% and the C₂₊ alcohol selectivity was 41.8%.

CuCo bimetallic catalysts over the mixed supports showed smaller average particle size, better dispersion of cobalt and copper species, and good activity for higher alcohols synthesis.     

Heterostructures of ε-Fe2O3 and α-Fe2O3: insights from density functional theory

Many materials used in energy devices or applications suffer from the problem of electron–hole pair recombination. One promising way to overcome this problem is the use of heterostructures in place of a single material. If an electric dipole forms at the interface, such a structure can lead to a more efficient electron–hole pair separation and thus prevent recombination. Here we model and study a heterostructure comprised of two polymorphs of Fe₂O₃. Each one of the two polymorphs, α-Fe₂O₃ and ε-Fe₂O₃, individually shows promise for applications in photoelectrochemical cells. The heterostructure of these two materials is modeled by means of density functional theory. We consider both ferromagnetic as well as anti-ferromagnetic couplings at the interface between the two systems. Both individual oxides are insulating in nature and have an anti-ferromagnetic spin arrangement in their ground state. The same properties are found also in their heterostructure. The highest occupied electronic orbitals of the combined system are localized at the interface between the two iron-oxides. The localization of charges at the interface is characterized by electrons residing close to the oxygen atoms of ε-Fe₂O₃ and electron–holes localized on the iron atoms of α-Fe₂O₃, just around the interface. The band alignment at the interface of the two oxides shows a type-III broken band-gap heterostructure. The band edges of α-Fe₂O₃ are higher in energy than those of ε-Fe₂O₃. This band alignment favours a spontaneous transfer of excited photo-electrons from the conduction band of α- to the conduction band of ε-Fe₂O₃. Similarly, photo-generated holes are transferred from the valence band of ε- to the valence band of α-Fe₂O₃. Thus, the interface favours a spontaneous separation of electrons and holes in space. The conduction band of ε-Fe₂O₃, lying close to the valence band of α-Fe₂O₃, can result in band-to-band tunneling of electrons which is a characteristic property of such type-III broken band-gap heterostructures and has potential applications in tunnel field-effect transistors.

Electron–hole pair recombination is reduced in heterostructures if used in devices in place of single material.     

Expression of concern: Self-assembled membrane manufactured by metal–organic framework (UiO-66) coated γ-Al2O3 for cleaning oily seawater

Expression of concern for ‘Self-assembled membrane manufactured by metal–organic framework (UiO-66) coated γ-Al₂O₃ for cleaning oily seawater’ by Cunlong Li et al., RSC Adv., 2019, 9, 10702–10714, DOI: 10.1039/C9RA00521H.

The following article ‘Self-assembled membrane manufactured by metal–organic framework (UiO-66) coated γ-Al₂O₃ for cleaning oily seawater’ has been published in RSC Advances.The XRD data shown in Fig. 6b is the same for the UA composites (shown in green) and UiO-66 particles (shown in red), with the exception of two peaks that are not present in the UiO-66 pattern.In Fig. 7a, the panel for 0.03 MPa is a rotated and processed duplicate of the panel for 0.02 MPa.The authors were contacted for comment and asked to provide raw data but have not responded to these concerns. RSC Advances is publishing this Expression of Concern to alert readers to the concerns raised. An Expression of Concern will continue to be associated with the article until we receive conclusive evidence regarding the reliability of the reported data.Laura Fisher11^th February 2022Executive Editor, RSC Advances     

Optical and dielectric properties of NaCoPO4 in the three phases α, β and γ

In this work, we are interested in the synthesis of monophosphate α-NaCoPO₄, β-NaCoPO₄ and γ-NaCoPO₄ compounds by mechanochemical method and their characterization by X-ray powder diffraction patterns. These compounds are crystallized in the orthorhombic, hexagonal and monoclinic system, in Pnma, P6₅ and P2₁/n space groups, respectively. The optical properties were measured by means of the UV-vis absorption spectrometry in order to deduce the absorption coefficient α and optical band gap E_g. The calculated values of the indirect band gaps (E_gi) for three samples were estimated at 4.71 eV, 4.63 eV and 3.8 for compounds α, β and γ, respectively. The Tauc model was used to determine the optical gap energy of the synthesized compounds. Then, the results of the dielectric proprieties measured by varying the frequency are described.

In this work, we are interested in the synthesis of monophosphate α-NaCoPO₄, β-NaCoPO₄ and γ-NaCoPO₄ compounds by mechanochemical method and their characterization by X-ray powder diffraction patterns.     

K2S2O8-promoted C–Se bond formation to construct α-phenylseleno carbonyl compounds and α,β-unsaturated carbonyl compounds

A novel K₂S₂O₈-promoted C–Se bond formation from cross-coupling under neutral conditions has been developed. A variety of aldehydes and ketones react well using K₂S₂O₈ as the oxidant in the absence of catalyst and afford desired products in moderate to excellent yields. This protocol provides a very simple route for the synthesis of α-phenylseleno carbonyl compounds and α,β-unsaturated carbonyl compounds.

K₂S₂O₈-promoted C–Se bond formation from the cross-coupling of C(sp³)–H bond adjacent to carbonyl group with diphenyl diselenide under metal-free conditions.

Selenium (Se) is an essential trace mineral nutrient that exerts multiple and complex effects on human health.¹ Selenium has been widely applied in a variety of fields such as the organic synthesis, catalysis, agriculture chemistry, materials science and even the environment protection.² Se-containing compounds have attracted vast interest because of their extensive bioactive functions and important roles in chemical reactions.³ As metabolites of Se in humans, phenylseleno (–SePh) groups are extremely important.⁴ It has been reported that SePh-containing compounds can act as redox agents suitable for targeting cancer cells or play a role in steroid chemistry. Several reported SePh-containing compounds that imitate glutathione peroxidase, like ebselen,⁵ that act as redox agents suitable for targeting cancer cells (naphthoquinone derivatives)⁶ or are important in steroid chemistry (estrogen derivatives)⁷ are shown in Fig. 1. Furthermore, α-phenylseleno carbonyl compounds have a special place since these substances also serve as versatile intermediates in organic synthesis.⁸ They can be converted into the corresponding synthetically useful α,β-unsaturated aldehydes or ketones through oxidation by H₂O₂ or NaIO₄ followed by selenoxide elimination⁹ and Sahani''s group has used α-phenylselanyl ketones as substrates to obtain α-arylated ketones through organic photoredox catalysis.¹⁰Open in a separate windowFig. 1Examples of Se-containing biologically active compounds.Oxidative functionalization of carbonyl compounds has been known since 1935 (ref. 11) and was studied further by Saegusa, Mislow, Baran and others.¹² While there generally exist various means, either direct or indirect, of accessing particular target molecules, in order to continue to advance this field, we must constantly study more efficient and green methods. Currently, several procedures have been developed for the preparation of α-phenylseleno aldehydes and ketones. One typical method to synthesize such compounds is by using an enolate coupling reaction.¹³ This approach suffers from the use of a stoichiometric amount of a strong base and metal oxidant to produce the enolate followed by an oxidative coupling reaction (see Scheme 1). In 2015, Yan''s group demonstrated that with the participation of a suitable oxidant, ketones can undergo direct oxidation functionalization.¹⁴ Despite the improvement of not using strong base, it still needed multiple times the amount of metal-free oxidants. In addition, K₂S₂O₈ was found to be a useful oxidant in oxidative reactions because of its characteristics of easy availability, good stability, and low toxicity. Thus, studies focusing on the development of K₂S₂O₈-mediated oxidative reactions meet the requirement of sustainable chemistry.¹⁵ Based on our research on the functionalization of the C(sp³)–H bond, and in connection to our continued interest in developing efficient metal-free functionalization strategies,¹⁶ herein we report an efficient K₂S₂O₈-mediated C–Se bond formation for the synthesis of α-phenylseleno carbonyl compounds.Open in a separate windowScheme 1Synthesis of α-phenylseleno carbonyl compounds (M = metal).Initially, we utilized acetone (1a) as a standard substrate to evaluate the coupling of C(sp³)–H bonds adjacent to a carbonyl group with diphenyl diselenide (2). Treatment of 1a with 1.0 equiv. of (NH₄)₂S₂O₈ in DMSO at 80 °C under air for 3 h afforded the desired product 3a in 29% yield (17 Then various reaction parameters were screened, including the oxidant, solvent, and temperature. A range of oxidants such as PhI(OAc)₂, IBX, Ag₂O, Na₂S₂O₈, K₂S₂O₈, and oxone were tested, and K₂S₂O₈ showed the highest efficiency (entries 2–7). The solvent also played a key role in this transformation. The product yield decreased when DMSO was replaced by DMF, DMA, CH₃CN or EtOH (entries 8–11). Taking the place of air with argon, the reaction gave the desired product 3a in a similar yield (87%) (entry 12). Notably, a similar yield of 3a was obtained by lowering the amount of K₂S₂O₈ to 0.5 equiv. (entry 13). However, a further decrease of the oxidant amount resulted in a lower yield of 3a (entry 14). The reaction temperature had little influence on the reaction efficiency, and 80 °C was still the best choice (entries 15 and 16). A control experiment revealed that K₂S₂O₈ was necessary for the success of this reaction (entry 17).Optimization of the reaction conditions^a,b

A nontoxic biocompatible nanocomposite comprising black phosphorus with Au–γ-Fe2O3 nanoparticles

Black phosphorus (BP) has emerged as the latest 2D material within the post-graphene scenario, which can be used for various biomedical applications. In this study, we reported a promising nanocomposite material, which could be assembled with Au nanoparticles and γ-Fe₂O₃ nanoparticles on BP nanosheets (AIB), and studied its biocompatibility that promises to be useful for various biomedical applications. The synthesis of the Au–γ-Fe₂O₃ nanomaterial was attained through low-temperature solution synthesis and the exfoliation of BP nanosheets was performed through a liquid ultrasonication process. The individual components were then composited by ultrasonication and stirring. X-ray diffraction and transmission electron microscopic analyses confirmed the existence of Au and γ-Fe₂O₃ nanoparticles (NPs) assembled over BP nanosheets. Moreover, the surface chemical composition and valence state of the elements present in the AIB nanocomposite were evaluated with the help of an X-ray photoelectron spectroscopy study. The AIB nanocomposite exhibited excellent biocompatibility with HCT-15 cells after evaluating through WST assay. Therefore, the excellent biocompatible nature of this BP nanocomposite could be beneficial for various potential biomedical applications.

Synthesis of the Au–γ-Fe₂O₃–BP nanocomposite and its activity.     

Characteristics and mechanism of toluene removal by double dielectric barrier discharge combined with an Fe2O3/TiO2/γ-Al2O3 catalyst

Removal of volatile organic compounds (VOCs) by non-thermal plasma technology produced by dielectric barrier discharge has become a hotspot due to its rapid reaction at room temperature, convenience without preheating and high removal efficiency of VOCs. Ways to improve the removal efficiency of mixed VOCs and the control of by-products in the discharge process are urgently needed. In view of the above shortcomings, the research progress of catalysts to improve the removal efficiency of VOCs by dielectric barrier discharge in recent years was reviewed; in this research, we conducted experiments on the removal efficiency of toluene under high flow rate experimental conditions (input voltage 10–70 V, mixed gas flow rate 1 m³ h⁻¹, inlet concentration 1000 mg m⁻³). The research used γ-Al₂O₃, TiO₂/γ-Al₂O₃ and Fe₂O₃/TiO₂/γ-Al₂O₃ as catalysts in a reactor with a discharge gap of 6 mm, and a 99.7% removal efficiency of toluene was achieved when the SIE was 183.4 J L⁻¹. The added catalyst significantly reduced the concentration of by-products. At the same time, experiments with multiple catalysts to improve the removal efficiency and the performance of the discharge effect under different humidity levels were analyzed. The removal efficiency of toluene was optimized and recyclable, the formation of by-products was effectively suppressed when the catalysts in the reactor were Fe₂O₃/TiO₂/γ-Al₂O₃, TiO₂/γ-Al₂O₃ and γ-Al₂O₃, and the discharge length was 1 : 2 : 2.

The removal efficiency of toluene and CO₂ selectivity were improved and the production of O₃ and NO_x was reduced by using DBD combined with different catalysts.     

Selection and Characterization of β-Lactam–β-Lactamase Inactivator-Resistant Mutants following PCR Mutagenesis of the TEM-1 β-Lactamase Gene

Mechanism-based inactivators of β-lactamases are used to overcome the resistance of clinical pathogens to β-lactam antibiotics. This strategy can itself be overcome by mutations of the β-lactamase that compromise the effectiveness of their inactivation. We used PCR mutagenesis of the TEM-1 β-lactamase gene and sequenced the genes of 20 mutants that grew in the presence of ampicillin-clavulanate. Eleven different mutant genes from these strains contained from 1 to 10 mutations. Each had a replacement of one of the four residues, Met69, Ser130, Arg244, and Asn276, whose substitutions by themselves had been shown to result in inhibitor resistance. None of the mutant enzymes with multiple amino acid substitutions generated in this study conferred higher levels of resistance to ampicillin alone or ampicillin with β-lactamase inactivators (clavulanate, sulbactam, or tazobactam) than the levels of resistance conferred by the corresponding single-mutant enzymes. Of the four enzymes with just a single mutation (Ser130Gly, Arg244Cys, Arg244Ser, or Asn276Asp), the Asn276Asp β-lactamase conferred a wild-type level of ampicillin resistance and the highest levels of resistance to ampicillin in the presence of inhibitors. Site-directed random mutagenesis of the Ser130 codon yielded no other mutant with replacement of Ser130 besides Ser130Gly that produced ampicillin-clavulanate resistance. Thus, despite PCR mutagenesis we found no new mutant TEM β-lactamase that conferred a level of resistance to ampicillin plus inactivators greater than that produced by the single-mutation enzymes that have already been reported in clinical isolates. Although this is reassuring, one must caution that other combinations of multiple mutations might still produce unexpected resistance.     

Inhibition of β-Lactamases by β-Lactam Antibiotics

The inhibitory properties of a selected number of beta-lactam antibiotics were studied, with the use of three distinct types of beta-lactamases. The three enzymes were found to be distinguishable on the basis of their susceptibility to inhibition. Not one of the potential inhibitors tested was found to be a potent inhibitor of all three enzymes, but nafcillin possessed the broadest inhibitory activity. The enzyme isolated from Enterobacter cloacae was found to be the most susceptible. In some cases, the degree of inhibition varied with the time of incubation, and, depending upon the time chosen, widely different observations could be made. It is suggested that, in studies such as these, every consideration should be given to the period of incubation and to the concentration of inhibitor employed. Mixtures of inhibitor and cephaloridine did not always act synergistically against growing bacteria, and a number of reasons for failure are suggested.     

Enhanced legume root growth with pre-soaking in α-Fe2O3 nanoparticle fertilizer

The rising demand for food and energy crops has triggered interest in the use of nanoparticles for agronomy. Specifically, iron oxide-based engineered nanoparticles are promising candidates for next-generation iron-deficiency fertilizers. We used iron oxide and hybrid Pt-decorated iron oxide nanoparticles, at low and high concentrations, and at varied pHs, to model seed pre-soaking solutions for investigation of their effect on embryonic root growth in legumes. This is an environmentally friendly approach, as it uses less fertilizer, therefore less nanoparticles in contact with the soil. Analysis from varied material characterization techniques combined with a statistical analysis method found that iron oxide nanoparticles could enhance root growth by 88–366% at low concentrations (5.54 × 10⁻³ mg L⁻¹ Fe). Hybrid Pt-decorated iron oxide nanoparticles and a higher concentration of iron oxide nanoparticles (27.7 mg L⁻¹ Fe) showed reduced root growth. The combined materials characterization and statistical analysis used here can be applied to address many environmental factors to finely tune the development of vital nanofertilizers for high efficiency food production.

A new approach to increase root growth in legumes by pre-soaking seeds in iron oxide nanoparticle growth solution.     

Structural and electronic properties of α-, β-, γ-, and 6,6,18-graphdiyne sheets and nanotubes

α-, β-, γ- and 6,6,18-graphdiyne (GDYs) sheets, as well as the corresponding nanotubes (GDYNTs) are investigated systematically by using the self-consistent-field crystal orbital method. The calculations show that the GDYs and GDYNTs with different structures have different electronic properties. The α-GDY sheet is a conductor, while 2D β-, γ- and 6,6,18-GDYs are semiconductors. The carrier mobilities of β- and γ-GDY sheets in different directions are almost the same, indicating the isotropic transport characteristics. In addition, the electron mobility is in the order of 10⁶ cm² V⁻¹ s⁻¹ and it is two orders of magnitude larger than the hole mobility of 2D γ-GDY. However, α- and 6,6,18-GDY sheets have anisotropic mobilities, which are different along different directions. For the 1D tubes, the order of stability is γ-GDYNTs > 6,6,18-GDYNTs > β-GDYNTs > α-GDYNTs and is independent of the tube chirality and size. β- and γ-GDYNTs as well as zigzag α- and 6,6,18-GDYNTs are semiconductors with direct bandgaps, while armchair α-GDYNTs are metals, and armchair 6,6,18-GDYNTs change from semiconductors to metals with increasing tube size. The armchair β- and γ-GDYNTs are more favourable to transport holes, while the corresponding zigzag tubes prefer to transport electrons.

Theoretical investigation of α-, β-, γ- and 6,6,18-graphdiyne sheets as well as their corresponding nanotubes.     

Dimpled SiO2@γ-Fe2O3 nanocomposites – fabrication and use for arsenic adsorption in aqueous medium

We report the synthesis of nanocomposites made of silica nanoparticles whose six surface dimples are decorated with magnetic maghemite nanoparticles and their use for detection and recovery of arsenic in aqueous media. Precursor silica nanoparticles have aminated polystyrene chains at the bottom of their dimples and the maghemite nanoparticles are surface functionalized with carboxylic acid groups in two steps: amination with 3-aminopropyltrimethoxysilane, then derivatization with succinic anhydride in the presence of triethylamine. In the end, the colloidal assembly consists of the regioselective grafting of the carboxylic acid-modified iron oxide nanoparticles onto the 6-dimple silica nanoparticles. Several characterization techniques such as transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), dynamic light scattering (DLS) are employed to assess the grafting process and study the influence of the maghemite functional groups on the quality of the composites formed. The resulting magnetic nanocomposites are used for the environmentally benign detection and removal of arsenic from aqueous medium, being readily extracted through means of magnetic separation.

The process of grafting maghemite NFs onto silica dimples.