Modulating low-frequency tribocatalytic performance through defects in uni-doped and bi-doped SrTiO_(3)

Triboelectrification,a process that transforms mechanical energy into electrical energy through friction,holds promise for eco-friendly wastewater treatment.This study delves into the enhancement of tribocatalytic dye degradation using SrTiO_(3),a material notable for its non-piezoelectric and centrosymmetric properties.The synthesis of uni-and bi-doped SrTiOs particles,achieved through a solid-state reaction at 100℃,results in a high-purity cubic perovskite structure.Doping with rhodium(Rh)and carbon(C)causes crystal lattice contraction,internal stress,and significant oxygen vacancies.These changes notably improve tribocatalytic efficiency under solar irradiation,with Rh-doped SrTiO_(3) demonstrating an impressive degradation rate of approximately 88% for Rhodamine B(RhB),along with reaction rate constants near 0.9 h^(-1) at 554 nm and a noticeable blueshift.This study highlights that defects introduced by doping are integral to this process,boosting catalytic activity through energy state modification and enhancing surface redox radical production.Additionally,these defects are instrumental in generating a flexoelectric field,which markedly influences the separation of electron-hole pairs under solar irradiation.Our findings illuminate the complex interplay between material composition,defect states,and environmental conditions,paving the way for advanced strategies in environmental remediation through optimized tribocatalytic activity.

古老而充满魅力的红曲菌

红曲菌(Monascus spp.)又称红曲霉,是我国传统特色的药食同源发酵微生物.红曲菌可产生天然食品着色剂红曲色素(Monascus pigments,MPs)、降血脂成分莫纳可林K(monacolin K,MK)以及丰富的淀粉酶和酯化酶等酶系,红曲菌的发酵产品红曲在我国有近2000年的应用历史.但是某些红曲菌株也可产生真菌毒素桔霉素(citrinin,CIT),污染红曲产品,导致食品安全问题.研究人员通过不懈努力,目前已经解决了红曲产品中CIT污染的问题,关于MPs、MK和CIT等红曲菌主要次级代谢产物生物合成途径及其调控机理的研究也取得了重大突破.同时,研究还发现,红曲菌具有独特的繁殖调控机制以及对光照和磁场(光磁)的感应机理.本文系统梳理了近30年来所取得的关于红曲菌独特繁殖调控与光磁感应机理,以及MPs、MK和CIT等主要次级代谢产物的生物合成途径及其调控机制的研究进展,并展望了红曲菌的未来研究方向,最后阐述了红曲行业面临的挑战及其应对策略.

Gas sensing capabilities of TiO_(2) porous nanoceramics prepared through premature sintering

Pure and noble metal(Pt,Pd,and Au)doped TiO_(2)nanoceramics have been prepared from TiO_(2)nanoparticles through traditional pressing and sintering.For those samples sintered at 550℃,a typical premature sintering occurred,which led to the formation of a highly porous microstructure with a Brunauer-Emmett-Teller(BET)specific surface area of 23 m^(2)/g.At room temperature,only Pt-doped samples showed obvious response to hydrogen,with sensitivities as high as~500 for 1000 ppm H_(2)in N_(2);at 300℃,all samples showed obvious responses to CO,while the responses of noble metal doped samples were much higher than that of the undoped ones.The mechanism for the observed sensing capabilities has been discussed,in which the catalytic effect of Pt for hydrogen is believed responsible for the room-temperature hydrogen sensing capabilities,and the absence of glass frit as commonly used in commercial thick-film metal oxide gas sensors is related to the high sensitivities.It is proposed that much attention should be paid to metal oxide porous nanoceramics in developing gas sensors with high sensitivities and low working temperatures.

Boosting tribo-catalytic conversion of H_(2)O and CO_(2)by Co_(3)O_(4)nanoparticles through metallic coatings in reactors

In recent years,more and more metal oxides have been finding critical tribo-catalytic applications.Presently,we have explored the tribo-catalytic conversion of H_(2)O and CO_(2)using Co_(3)O_(4)nanoparticles and obtained some surprising results.In an as-received 150 mL glass reactor enclosed with 10 mL of H_(2)O,0.10 g of Co_(3)O_(4)nanoparticles,1 atm of CO_(2),and a Teflon magnetic rotary disk,we observed the production of as much as 57.41μmol/L of H_(2),0.15μmol/L of CH_(4),and 0.21μmol/L of CO after 5 h of magnetic stirring.Metallic coatings of Cu,Ni,SUS316,Ti,Nb,Mo,and W were further introduced on reactor bottoms separately.For those coatings of Ni,SUS316,Ti,and Nb,the reduction of CO_(2)was dramatically enhanced,and C_(2+)products of C_(2)H_(6)and C_(2)H_(4)were observed.Especially for the Ti coating,the amounts of H_(2)and CH_(4)were increased by 2 and 26 times from those for the glass bottom,respectively,and the amounts of C_(2)H_(6)and C_(2)H_(4)were very impressive.The Co_(3)O_(4)nanoparticles were proven chemically stable under magnetic stirring in water,and hydroxyl radicals and superoxide radicals have been detected for the Co_(3)O_(4)nanoparticles under magnetic stirring through fluorescence spectroscopy and electron paramagnetic resonance spectroscopy analyses.These findings not only reveal outstanding capability of Co_(3)O_(4)to generate multicarbon products from H_(2)O and CO_(2)through tribo-catalysis but also highlight a promising potential of tribo-catalysis as a whole to harness mechanical energy for addressing energy shortages and environmental pollution.

Contrasting room-temperature hydrogen sensing capabilities of Pt-SnO2 and Pt-TiO2 composite nanoceramics

Contrasting room-temperature hydrogen sensing behaviors have been revealed for Pt-TiO2 and Pt-SnO2 composite nanoceramics. In the case of the Pt-TiO2 nanoceramics, the ultrahigh hydrogen sensitivities are lost abruptly when the oxygen/hydrogen concentration ratio in ambient atmosphere reaches a critical value. However, in the case of the Pt-SnO2 nanoceramics, such a phenomenon does not occur, and the extraordinary room-temperature hydrogen sensing capabilities are observed in the presence of oxygen in air. Our combined experimental and theoretical investigations establish a unified mechanism for both the systems, which is rooted in hydrogen chemisorption on the surface and interstitial lattice sites of SnO2 and TiO2; the difference in stability of the chemisorbed hydrogen on SnO2 and TiO2 is considered responsible for the contrasting hydrogen sensing capabilities. The central findings are helpful in enriching our microscopic understanding of hydrogen interaction with various metal oxide semiconductors （MOSs） at room temperature in varying mixed gaseous concentrations, and they could be instrumental in developing reliable room-temperature hydrogen sensors based on bulk MOSs.

Flammable gases produced by TiO_(2) nanoparticles under magnetic stirring in water

The friction between nanomaterials and Teflon magnetic stirring rods has recently drawn much attention for its role in dye degradation by magnetic stirring in dark.Presently the friction between TiO_(2) nanoparticles and magnetic stirring rods in water has been deliberately enhanced and explored.As much as 1.00 g TiO_(2) nanoparticles were dispersed in 50 mL water in 100 mL quartz glass reactor,which got gas-closed with about 50 mL air and a Teflon magnetic stirring rod in it.The suspension in the reactor was magnetically stirred in dark.Flammable gases of 22.00 ppm CO,2.45 ppm CH_(4),and 0.75 ppm H_(2) were surprisingly observed after 50 h of magnetic stirring.For reference,only 1.78 ppm CO,2.17 ppm CH_(4),and 0.33 ppm H_(2) were obtained after the same time of magnetic stirring without TiO_(2) nanoparticles.Four magnetic stirring rods were simultaneously employed to further enhance the stirring,and as much as 30.04 ppm CO,2.61 ppm CH_(4),and 8.98 ppm H_(2) were produced after 50 h of magnetic stirring.A mechanism for the catalytic role of TiO_(2) nanoparticles in producing the flammable gases is established,in which mechanical energy is absorbed through friction by TiO_(2) nanoparticles and converted into chemical energy for the reduction of CO_(2) and H_(2)O.This finding clearly demonstrates a great potential for nanostructured semiconductors to utilize mechanical energy through friction for the production of flammable gases.

Effects of Ba and Ti co-doping on BiFeO3 multiferroic ceramics optimized through two-step doping

Ceramics of Bi0.9Ba0.1Fe0.925TixO3 (x = 0.0625, 0.08125, 0.0875, and 0.11) were prepared according to two doping strategies: one is called single-step doping in which Ba and Ti were doped together in calcination, while the other one is called two-step doping in which Ba and Ti were doped in calcination and sintering, respectively. Compared with samples prepared with single-step doping, those prepared with two-step doping have obviously different XRD patterns and small grains, and are dramatically improved in dielectric loss, resistivity, and remnant magnetization. A low dielectric loss of 0.05 at 10(3) Hz, a high resistivity of 4x10(12) Omega.cm, and a large remnant magnetization of 1.5 emu/g, have been obtained simultaneously for Bi0.9Ba0.1Fe0.925Ti0.11O3 prepared with two-step doping. The contrast between these two doping strategies clearly reveals the importance of establishing a proper doping strategy when two or more elements are co-doped to BiFeO3.

Balancing the piezoelectric coefficient and carrier concentration of Bi_(2)WO_(6−x) for ultrahigh piezocatalysis

Balancing the piezoelectric coefficient and carrier concentration of materials is key in the field of piezocatalysis.In this work,Bi_(2)WO_(6) material with both piezoelectric and semiconductor properties was chosen as a model material.A one-step ethylene glycol(EG)-assisted solvothermal method was used to synthesize Bi2WO6 with oxygen vacancies.By controlling the solvothermal time and temperature,the oxygen vacancy concentration(COV)was regulated.As COV increases,the piezoelectric coefficient decreases,the carrier concentration increases,and the hydrogen production rate first increases but then decreases.When COV reaches 1.45×10^(12) spins·mg^(−1),the corresponding piezoelectric coefficient and carrier concentration are 13.9 pm·V^(−1) and 2.90×10^(20) cm^(−3),respectively.The optimal hydrogen production rate per power of 2.21μmol·g^(−1)·h^(−1)·W^(−1) is equivalent to or even better than that of most reported piezocatalysts.The piezoelectric coefficient and carrier concentration,as two factors,jointly determine the piezocatalytic performance.The findings of this research can provide important and deep-seated insights for better piezocatalysts in the future.

Characterization of key upstream asexual developmental regulators in Monascus ruber M7

Monascus species are traditional edible and medicinal filamentous fungi with a very long history in East Asia,but their sparse production of asexual spores(conidia)limits their large-scale industrial application.Previous studies have revealed that the flbA ortholog plays a negative role in the conidiation of Monascus ruber M7.FlbA,together with FlbB,FlbC,FlbD,FlbE,and FluG,were shown to be upstream development activators(UDAs)in the asexual development pathway in the model fungus Aspergillus nidulans.In the present study,homologs of these UDAs in M.ruber M7 were identified and functionally characterized.Disruption of MrflbB,MrflbD,and MrflbE delayed and decreased conidiation in M7,whereas the deletion of MrflbC or MrfluG resulted in no detectable change in sporulation.Deletion of MrflbA not only increased conidial number but also postponed sexual development in M7.Furthermore,the deletion of some UDAs also affected the production of secondary metabolites,particularly citrinin,whose yields were dramatically decreased in theΔMrflbC andΔMrflbA mutants.These findings provide new insights and opportunities to further explore the asexual development mechanism and modify the conidial production in Monascus spp.