Small Crystal Size Research Articles

Reservoir characteristics and distribution of the Majiagou Formation in Fuxian area of Ordos Basin, China

The Majiagou Formation in the Fuxian area of the southeastern Ordos Basin has undergone a complex diagenetic evolution history under the influence of eustacy and the Caledonian karstification, resulting in several complex reservoir types. Through analyses of mineralogy, petrology, and reservoir geology, three major types of dolomite reservoirs with different genetic mechanisms, including anhydritic moldic-dissolved pore type, dolomitic intercrystalline-pore type, and fractured type were identified, and their formation mechanisms and distribution patterns were examined. The aphanocrystalline to very fine-crystalline anhydritic dolomite was resulted from Sabhak dolomitization, and is characterized by small size of crystals, high content of anhydrite. Dolomite reservoirs of anhydritic moldic-dissolved pore type were developed in multi-stage dissolution processes and mainly distributed at higher positions of the paleogeomorphology where the filling was weak. The very fine to fine-crystalline dolomite of shoal facies was formed under seepage-reflux dolomitization, and characterized by larger sizes of crystals and well-developed intercrystalline pores. Dolomite reservoirs of intercrystalline-pore type were mainly developed at the lower positions of the paleogeomorphology where bedding-parallel karst dissolution was strong. The fractured dolomite reservoirs, generated by the anhydrite swelling and karst cave collapse, occur in multiple horizons but within limited areas due to multi-stage fillings.

Composition Determination of Heterometallic Trinuclear Clusters via Anomalous X-ray and Neutron Diffraction.

Anomalous X-ray diffraction (AXD) and neutron diffraction can be used to crystallographically distinguish between metals of similar electron density. Despite the use of AXD for structural characterization in mixed metal clusters, there are no benchmark studies evaluating the accuracy of AXD toward assessing elemental occupancy in molecules with comparisons with what is determined via neutron diffraction. We collected resonant diffraction data on several homo and heterometallic clusters and refined their anomalous scattering components to determine metal site occupancies. Theoretical resonant scattering terms for Fe0, Co0, and Zn0 were compared against experimental values, revealing theoretical values are ill-suited to serve as references for occupancy determination. The cluster featuring distinct cation and anion metal compositions [CoCp2*][(tbsL)Fe3(μ3-NAr)] was used to assess the accuracy of different f' references for occupancy determination (f'theoretical ± 15-17%; f'experimental ± 10%). This methodology was applied toward calculating the occupancy of three different clusters: (tbsL)Fe2Zn(py) (6), (tbsL)Fe2Zn(μ3-NAr)(py) (7), and [CoCp*2][(tbsL)Fe2Zn(μ3-NAr)] (8). The first two clusters maintain 100% Fe/Zn site isolation, whereas 8 showed metal mixing within the sites. The large crystal size of 8 enabled collection of neutron diffraction data which was compared against the results found with AXD. The ability of AXD to replicate the metal occupancies as determined by neutron diffraction supports the AXD occupancy methodology developed herein. Furthermore, the advantages innate to AXD (e.g., smaller crystal sizes, shorter collection times, and greater availability of synchrotron resources) versus neutron diffraction further support the need for its development as a standard technique.

Developing a novel toffee-type soft candy process by sonocrystallization: A preliminary study

This study aimed to evaluate the applicability of sonocrystallization, an innovative process, as a low-cost and time-efficient alternative for the crystallization of confectionery dough, which is a crucial step in the production of conventional toffee-type soft candy. In this regard, according to the design plan, sonocrystallization time and current were selected as independent variables. The samples (36 run) nucleated by sonocrystallization using the optimum conditions (1600 and 2400 mA, 20 min) were allowed to aging under different times (0, 2, 4, 6, 8, and 10 min) and temperatures (60, 65, and 70 °C) in order to determine crystal growth. According to the texture profile analysis results, all parameters except for cohesiveness were significantly affected by both the sonocrystallization and aging conditions (p < 0.05), and dramatically higher hardness values were obtained for samples sonocrystallized at 2400 mA. Micrographs showed the formation of a crystalline network with more crystals of smaller size, fragmentation of larger crystals, and a more homogenous crystallization, especially in the samples sonocrystallized at 2400 mA and allowed to aging at >65 °C for durations of >6 min. The targets of the study were achieved by subjecting the samples to sonocrystallization at 2400 mA and aging at 70 °C for 8 min for crystal growth.

Preparation of nano magnesium oxide by mechanochemical method using magnesium chloride

Magnesium chloride is a magnesium resource that is widely present in seawater and salt lakes. Therefore, the use of magnesium chloride is of great significance for the low-cost preparation of high-performance magnesium materials. In this work, mechanical ball milling was used for the preparation of magnesium oxide nanoparticles from magnesium chloride. Ball milling improves the unevenness of the reaction process and generates magnesium oxide with a more uniform particle size distribution. First, a magnesium chloride complex was obtained by heating and evaporating a mixture of magnesium chloride and ethanol with a mass ratio of 1:2 at 110 °C. Next, pure magnesium hydroxide with a smaller crystal size was obtained by ball milling the prepared magnesium chloride complex with calcium hydroxide at 600 rpm for 3 h. Finally, the magnesium hydroxide was calcined at 1000 °C for 60 min to obtain nano magnesium oxide particles with a particle size of 670 nm.

Study on the homologous effects on the performance of alkali metal-doping MgO-based adsorbents for CO2 capture

In this article, MgO-based adsorbents with different structure and surface property were prepared by combustion of the colloids containing Mg and alkali metal. At the same time, CO2 adsorption performance tests are conducted to compare the doping effect of alkali metal on MgO adsorbents. As confirmed, the introduction of lithium, sodium, and potassium can reduce the grain size of MgO and enhance the basicity, especially increasing the concentration of oxygen vacancies on MgO surface which exposed more basic adsorption active sites and was more conducive to CO2 adsorption. Among them, the one doped with 0.5 % K which had more electron shell numbers showed larger surface area and smaller crystal size. Most importantly, it provided more number of basic sites along with the improved strength of surface basicity due to the more oxygen vacancies. As a result, the maximum CO2 uptake (1.09 mmol/g) at the adsorption time of 60 min can be obtained which still remained at 0.67 mmol/g after 16 cycles of CO2 adsorption–desorption. With the aid of N2 physical adsorption, inductively coupled plasma-optical emission spectroscopy, powder X-ray diffraction, scanning electron microscope, X-ray photoelectron spectroscopy, electron paramagnetic resonance, and chemical adsorption, the relationship between CO2 adsorption capacity of MgO-based adsorbent and homologous regularity of alkali metal was disclosed. In other words, by comparing the CO2 adsorption performance of MgO adsorbents prepared by doping different alkali metals, CO2 adsorption capacity increased with the increase of electron shell numbers. Such a configuration is in favor of the electron supply of the p-orbitals and weakens the Mg–O bonds which promoted the formation of oxygen vacancies. The found will provide in-depth understanding for the modification and performance improvement of MgO-based adsorbents.

Optimization of three-dimensional electron diffuse scattering data acquisition

The diffraction patterns of crystalline materials with local order contain sharp Bragg reflections as well as highly structured diffuse scattering. In this study, we quantitatively show how the diffuse scattering in three-dimensional electron diffraction (3D ED) data is influenced by various parameters, including the data acquisition mode, the detector type and the use of an energy filter. We found that diffuse scattering data used for quantitative analysis are preferably acquired in selected area electron diffraction (SAED) mode using a CCD and an energy filter. In this study, we also show that the diffuse scattering in 3D ED data can be obtained with a quality comparable to that from single-crystal X-ray diffraction. As electron diffraction requires much smaller crystal sizes than X-ray diffraction, this opens up the possibility to investigate the local structure of many technologically relevant materials for which no crystals large enough for single-crystal X-ray diffraction are available.

A comparative study of crystal geometry, material, and reconstruction algorithms on MicroPET scanner performance

Small-animal PET, also known as microPET, has been developed to enhance image quality by improving spatial resolution and sensitivity due to its smaller ring and crystal size. However, the reduction of crystal size and the presence of gaps between cuboidal crystals could reduce sensitivity. MicroPET with tapered arrays has been developed to simultaneously improve sensitivity and spatial resolution. This study compared the performance of 14 × 14 and 28 × 28 array microPETs using LSO and CZT crystal materials. The impact of crystal design and reconstruction algorithms on image quality and performance parameters was investigated, using GATE Monte Carlo simulation toolkit. The findings showed that sensitivity increased with crystal thickness, particularly in LSO. The 14 × 14 arrays consistently exhibited higher sensitivity, while the 28 × 28 arrays had superior spatial resolution. NECR values increased with crystal thickness, with LSO outperforming CZT. Scatter and random fractions were low. Different reconstruction algorithms had negligible effects on FWHM and CNR but influenced SNR, with the COSEM algorithm achieving significantly reduced noise. The small size of crystals and tapered arrays contributed to improved sensitivity and spatial resolution. However, there was a trade-off between sensitivity and spatial resolution. LSO crystals showed better performance, but the choice between array sizes depended on specific imaging requirements. This study provides insights into optimizing microPET design for enhanced imaging capabilities.

Nanocarbons decorated TiO2 as advanced nanocomposite fabric for photocatalytic degradation of methylene blue dye and ciprofloxacin

In this research, C [graphene (Gr), multi-walled carbon nanotubes (MWCNTs), and single-walled carbon nanotubes (SWCNTs)] decorated TiO2 nanostructures were developed and further utilized to modify textile to achieve high-performance photocatalytic degradation of mixed water pollutants including methylene blue (MB) dye and pharmaceutical active compound, Ciprofloxacin (CPF) on solar radiation exposure (∼105 Lumens). The crystallite sizes of TiO2, TiO2-MWCNT, TiO2-SWCNT, and TiO2-Gr nanocomposites were observed in the 7.2–10.4 nm range. The bandgap, Eg of nanostructured C-TiO2, was observed in the 3.09–3.14 eV range. The photocatalytic performance of C-TiO2 showed almost complete removal of MB under the irradiation of the solar spectrum in just 120 min. Among C-based TiO2 nanocomposites, nanostructured TiO2-SWCNT showed the highest degradation efficiency of ∼98.86 % for MB dye. Further, the textile membrane showed a good degradation efficiency of 99.49 % for MB dye and 95.7 % for CPF within 120 min. An impressive removal efficiency of ∼93 % was observed for the mixture of MB and CPF solution due to a combination of several properties like surface groups (OH− & O2−), low charge recombination rate due to CNTs, and small crystal size. This proof-of-the-concept study can be the potential platform to manage water quality according to sustainability goals.

Effects of Rapid Heat Treatments on the Properties of Cu2O Thin Films Deposited at Room Temperature Using an Ammonia-Free SILAR Technique

We report herein the analysis of the properties of copper(I) oxide thin films deposited by an optimized ammonium-free successive ion layer adsorption and reaction (SILAR) technique. The Cu2O thin film deposition process was carried out at room temperature using copper acetate monohydrate, sodium citrate as complexing agent, and hydrogen peroxide as precursors of copper and oxygen ions, respectively. The harmless and easy-to-handle sodium citrate replaces the volatile NH4OH commonly employed as complexing agent in the SILAR technique for the deposition of metal oxide thin films. The optical, structural, morphological, and electrical properties of the as-deposited Cu2O thin films were studied as a function of the number of cycles during deposition, as well as their modifications produced by the effect of rapid thermal annealing (RTA) in vacuum in a temperature range of 200–250°C for 1 min, 3 min, and 5 min. The as-deposited thin films had cubic crystalline structure corresponding to the Cu2O phase as determined by x-ray diffraction (XRD), with a direct energy bandgap of 2.43–2.51 eV depending on the number of cycles, and electrical resistivity of the order of 103 Ω cm. The XRD and x-ray photoelectron spectroscopy (XPS) analysis of the Cu2O thin films treated by RTA demonstrated an increase of the crystal size with time and temperature of the RTA and reduction effects from Cu2+ to Cu1+ oxidation states. On the other hand, the RTA treatments also decreased their energy bandgap to 2.38 eV and electrical resistivity to 102 Ω cm. The high energy bandgap values of the Cu2O thin films were attributed to quantum confinement effects produced by their small crystal size in the range of 3.6–8.6 nm.Graphical

Nanosized “rice ball” like hierarchical beta zeolites with inter-crystalline mesopores for efficient catalytic synthesis of lactide

A series of nanosized “rice ball” like hierarchical beta zeolite aggregates (RBZxAy, x = 6, 9, 12 or 15; y = 2, 4 or 6) with hierarchical structures are successfully synthesized via gel aging and hydrothermal method without mesoporous template. The as-prepared RBZxAy zeolites possess two ranges of inter-crystalline mesoporous that formed by zeolite nanoparticles aggregation compared to the non-aged samples (B12Z4). The effects of Si/Al ratio and crystallization time on the morphology, structure and surface acidic properties of RBZxAy were systematically investigated. Meanwhile, RBZxAy as catalysts were applied in the conversion of lactic acid (LA) to lactide (LT) to investigate their catalytic performance. Benefitting from smaller crystal size, hierarchical structures and higher acid content, the representative catalyst (RBZ12A4) exhibited outstanding catalytic activity that the LA conversion was high to 98 % and the LT yield up to 94 %. In addition, RBZ12A4 presented perfect regeneration ability after 10 times recycles. This work provides an effective and facile route to directly synthesis nanocrystals aluminosilicate zeolite with hierarchal structure, and constructs an approach for efficiently converting LA to LT, it has greatly significance for the development of polylactic acid industry.

Efficient electrochemical oxidation of antibiotic wastewater using a graphene-loaded PbO2 membrane anode: Mechanisms and applications

This paper aims to develop a flow-through electrochemical system with a series of graphene nanoparticles loaded PbO2 reactive electrochemical membrane electrodes (GNPs-PbO2 REMs) on porous Ti substrates with pore sizes of 100, 150, 300 and 600 μm, and apply them to treat antibiotic wastewater. Among them, the GNPs-PbO2 with Ti substrate of 150 μm (Ti-150/GNPs-PbO2) had superior electrochemical degradation performance over the REMs with other pore sizes due to its smaller crystal size, larger electrochemical active specific area, lower charge-transfer impedance and larger oxygen evolution potential. Under the relatively optimized conditions of initial pH of 5, current density of 15 mA cm−2, and membrane flux of 4.20 m3 (m2·h)−1, the Ti-150/GNPs-PbO2 REM realized 99.34% of benzylpenicillin sodium (PNG) removal with an EE/O of 6.52 kWh m−3. Its excellent performance could be explained as the increased mass transfer. Then three plausible PNG degradation pathways in the flow-through electrochemical system were proposed, and great stability and safety of Ti-150/GNPs-PbO2 REM were demonstrated. Moreover, a single-pass Ti-150/GNPs-PbO2 REM system with five-modules in series was designed, which could consistently treat real antibiotic wastewater in compliance with disposal requirements of China. Thus, this study evidenced that the flow-through electrochemical system with the Ti-150/GNPs-PbO2 REM is an efficient alternative for treating antibiotic wastewater.

Crystallization behaviors of chain extended poly (lactic acid) modified with ST‐NAB3 and its improvement for mechanical and thermal properties

AbstractThe widespread use of traditional petroleum‐based plastics is causing significant environmental pollution for example microplastics issues, due to its non‐biodegradability. Poly (lactic acid) (PLA) as a representative biodegradable polymer is a promising candidate to replace petroleum‐based plastics in some fields of disposable packaging materials and tableware. In this work, in order to improve the poor crystallization, mechanical and heat resistance performances of PLA, styrene–acrylonitrile‐glycidyl methacrylate (SAG) as a chain extender and octamethylenedicarboxylic dibenzoylhydrazide (ST‐NAB3) as a heterogeneous nucleating agent (HNA) were added simultaneously into PLA matrix. The chain‐extended PLA (CPLA) with branch structures had smaller crystal sizes and higher crystal density, compared with those of pure PLA. In addition, thanks to the nucleation effect of ST‐NAB3 and the development of “shish‐kebab”, this tendency became more pronounced in CPLA/HNA systems. It was worth mentioning that, CPLA with the ST‐NAB3 content of 1 wt% (CPLA‐1) possessed the highest crystallinity of 43.6%. Meanwhile, CPLA‐1 had the best impact strength and heat deformation temperature of 38.9 kJ/m2 and 91.3°C respectively, which had increased by 11.3 kJ/m2 and 32.4°C contrast to pure PLA. On the whole, this study proposed a simple and effective method, which provided a new possibility for PLA modification research.

Morphology and size modulation of Mn2O3 catalysts derived from MnBDC to enhance propane complete oxidation

Three Mn2O3 with different morphologies and particle sizes were synthesized using MnBDC as precursor. Interestingly, the morphology and size of MnBDC can be easily regulated by changing the reaction solvents slightly. The Mn2O3-L catalyst with large layers and small crystal size exhibited the best catalytic activity for complete oxidation of propane, with T50 of 266℃ and T90 of 311℃ at the WHSV of 120 L g−1 h−1. The multi-layered structure and small crystal size of Mn2O3-L allowed it to possess a high surface area and more interfacial oxygen defects that facilitated oxygen mobility, improving the catalytic activity. It seems that the large precursor size of MnBDC-L slowed down the decomposition rate of ligands, promoting the formation of large layered structure and small crystal size of Mn2O3-L. This study offers a simple strategy to control the structure and crystal size of Mn2O3 catalysts.

Genesis of Carboniferous aluminous-bearing strata in the northern part of the North China Craton: A case study of the Xingxian bauxite deposit

More than five billion tons of karstic bauxites were formed in the North China Craton (NCC) during the Late Carboniferous period. Compared to the bauxite ore, the genesis of the entire aluminous-bearing strata has received less attention. In this study, we conducted geological, mineralogical, and geochemical analyses on core samples from the aluminous-bearing strata located in Xingxian area, situated within the northern NCC, aiming to elucidate the genetic process of these formations. The aluminous-bearing strata consist of a bauxite layer (diaspore–anatase–kaolinite–florencite) sandwiched between the upper sandy claystone horizon (kaolinite–illite–quartz) and the lower berthierine-bearing claystone horizon (berthierine–diaspore–hematite–goethite). Based on the upper continental crust-normalized patterns of rare earth elements and yttrium (REY), immobile trace element ratios, mineral inheritance diagrams, and previous findings, it is suggested that the lower berthierine-bearing claystone was weathered from the impure limestone at the bottom, whereas the upper bauxite and sandy claystone mainly originated from intermediate-felsic igneous rocks of the northern margin of the NCC, granite from the North Qinling Orogenic Belt, and aluminosilicate rocks of the surrounding paleo-uplifts. During the early diagenetic stage, the berthierine was transformed under alkaline and reducing conditions from iron-rich clays (composed of clay minerals, ferric minerals, etc.) formed in acidic and oxidizing conditions from the underlying impure limestone. The coexistence of berthierine with low-temperature stability and diaspore is observed in the berthierine-bearing claystone, which precludes a high-temperature origin of diaspore in the aluminous-bearing strata. Moreover, diaspore is characterized by a small crystal size and is usually poorly crystallized, suggesting a supergene precipitation-diagenesis origin. The paragenetic minerals assemblages (e.g., diaspore, berthierine, goethite, hematite, etc.) suggest that the aluminous-bearing strata primarily formed in a transition zone nearer to the phreatic environment. Large-scale volcanism and warm, humid climatic conditions accelerated the decomposition of allochthonous weathering materials, resulting in the downward migration of metal ions. These ions then precipitated in a reducing and weakly alkaline environment, giving rise to form bauxite ore dominated by diaspore, anatase, and REY minerals.

Synthesis and characterizations of random copolyamide PA(56-co-66): Excellent toughness and transparency

Random copolyamides PA(56-co-66) (coPA-n) with various comonomer compositions were synthesized by a one-pot polycondensation reaction of pentamethyleneammonium adipate (PMA) salt and hexamethyleneammonium adipate (HMA) salt in aqueous solution. All copolymers have high Mn (≥15000 g/mol). The molecular segment composition can be regulated by controlling the feed ratio of PMA salt and HMA salt. Tc and Tm of copolymers obtained by nonisothermal crystallization depend on the composition, showing a clear pseudo-eutectic behavior. Copolyamide coPA-50 exhibits a eutectic phenomenon with the melting point decreasing to a minimum of 218.9 °C. WAXD and SAXS results confirm that the crystalline structure of the copolyamides follows that of the rich component, exhibiting a typical isodimorphic characteristic. Mechanical properties of the copolyamides indicate that the elongation at break could be improved significantly with slight sacrifice of strength, which provides a promising approach for fabricating polyamide materials with desired properties. The tensile strength, tensile modulus, and elongation at break of coPA-50 was 65.2 MPa, 1.0 GPa, and 758.1 %, respectively. These copolymers can be melt-spun into fibers with excellent mechanical properties. Especially, the transmittance of coPA-60 reaches a high value of 88.01 % due to its low crystallinity and small crystal size.

Enhancement of selective monoaromatic hydrocarbon and syngas products from fast pyrolysis of cassava stalks over Co, Mo promoted Ni catalysts

Catalytic fast pyrolysis of cassava stalks has been intriguing as a promising, feasible chemical refinery method in terms of waste-to-energy conversion from cassava cultivation. This study aims to determine the synergetic influence of Mo and Co on Ni catalysts (Ni, Ni–Mo, and Ni–Co) prepared via ultrasonic-assisted incipient wetness impregnation method for catalytic pyrolysis vapor upgrading. The results indicated that Co and Mo enhance the reducibility of NiO and promote weak-to-medium acidity, thereby enhancing Ni's performance. Mono-Ni favors cracking deoxygenation, whereas oxophilicity promoters particularly enhance the oxygen absorbability efficiency to selective deoxygenated production. A fine Ni dispersion on CoNi/SiO2 catalyst was observed to positively affect the production of monoaromatic hydrocarbons (46.10 %), in contrast to those without promoters (21.63 %). This is attributed to an optimal Ni-metallic distribution with a small crystal size of 7.01 nm and a high surface area of 342.6 m2 g−1, highlighting the effectiveness of the promoter-assisted Ni catalyst. Additionally, a high yield of H2 (66.9 %) in non-condensable gas was recorded at 550 °C. The study suggests that a simplified approach to developing Ni-based catalysts could enhance the eco-friendliness of commercial catalysts, thereby facilitating the scale-up of biomass pyrolysis applications.

Heat-Insulated Regenerated Fibers with UV Resistance: Silk Fibroin/Al2O3 Nanoparticles.

The various wastes generated by silkworm silk textiles that are no longer in use are increasing, which is causing considerable waste and contamination. This issue has attracted widespread attention in countries that use a lot of silk. Therefore, enhancing the mechanical properties of regenerated silk fibroin (RSF) and enriching the function of silk are important directions to expand the comprehensive utilization of silk products. In this paper, the preparation of RSF/Al2O3 nanoparticles (NPs) hybrid fiber with different Al2O3 NPs contents by wet spinning and its novel performance are reported. It was found that the RSF/Al2O3 NPs hybrid fiber was a multifunctional fiber material with thermal insulation and UV resistance. Natural light tests showed that the temperature rise rate of RSF/Al2O3 NPs hybrid fibers was slower than that of RSF fibers, and the average temperature rose from 29.1 °C to about 35.4 °C in 15 min, while RSF fibers could rise to about 40.1 °C. UV absorption tests showed that the hybrid fiber was resistant to UV radiation. Furthermore, the addition of Al2O3 NPs may improve the mechanical properties of the hybrid fibers. This was because the blending of Al2O3 NPs promoted the self-assembly of β-sheets in the RSF reaction mixture in a dose-dependent manner, which was manifested as the RSF/Al2O3 NPs hybrid fibers had more β-sheets, crystallinity, and a smaller crystal size. In addition, RSF/Al2O3 NPs hybrid fibers had good biocompatibility and durability in micro-alkaline sweat environments. The above performance makes the RSF/Al2O3 NPs hybrid fibers promising candidates for application in heat-insulating and UV-resistant fabrics as well as military clothing.

Extraordinary synergy on 3D hierarchical porous Co-Cu nanocomposite for catalytic elimination of VOCs at low temperature and high space velocity

It is still a challenge to develop hierarchically nanostructured catalysts with simple approaches to enhance the low-temperature catalytic activity. Herein, a set of mesoporous Co-Cu binary metal oxides with different morphologies were successfully prepared via a facile ammonium bicarbonate precipitation method without any templates or surfactants, which were further applied for catalytic removal of carcinogenic toluene. Among the catalysts with different ratios, the CoCu0.2 composite oxide presented the best performance, where the temperature required for 90% conversion of toluene was only 237°C at the high weight hour space velocity (WHSV) of 240,000 mL/(gcat·hr). Meanwhile, compared to the related Co-Cu composite oxides prepared by using different precipitants (NaOH and H2C2O4), the NH4HCO3-derived CoCu0.2 sample exhibited better catalytic efficiency in toluene oxidation, while the T90 were 22 and 28°C lower than those samples prepared by NaOH and H2C2O4 routes, respectively. Based on various characterizations, it could be deduced that the excellent performance was related to the small crystal size (6.7 nm), large specific surface area (77.0 m2/g), hollow hierarchical nanostructure with abundant high valence Co ions and adsorbed oxygen species. In situ DRIFTS further revealed that the possible reaction pathway for the toluene oxidation over CoCu0.2 catalyst followed the route of absorbed toluene → benzyl alcohol → benzaldehyde → benzoic acid → carbonate → CO2 and H2O. In addition, CoCu0.2 sample could keep stable with long-time operation and occur little inactivation under humid condition (5 vol.% water), which revealed that the NH4HCO3-derived CoCu0.2 nanocatalyst possessed great potential in industrial applications for VOCs abatement.

Wireless Gas Sensor Based on the Mesoporous ZnO-SnO2 Heterostructure Enables Ultrasensitive and Rapid Detection of 3-Methylbutyraldehyde.

Achieving ultrasensitive and rapid detection of 3-methylbutyraldehyde is crucial for monitoring chemical intermediate leakage in pharmaceutical and chemical industries as well as diagnosing ventilator-associated pneumonia by monitoring exhaled gas. However, developing a sensitive and rapid method for detecting 3-methylbutyraldehyde poses challenges. Herein, a wireless chemiresistive gas sensor based on a mesoporous ZnO-SnO2 heterostructure is fabricated to enable the ultrasensitive and rapid detection of 3-methylbutyraldehyde for the first time. The mesoporous ZnO-SnO2 heterostructure exhibits a uniform spherical shape (∼79 nm in diameter), a high specific surface area (54.8 m2 g-1), a small crystal size (∼4 nm), and a large pore size (6.7 nm). The gas sensor demonstrates high response (18.98@20 ppm), short response/recovery times (13/13 s), and a low detection limit (0.48 ppm) toward 3-methylbutyraldehyde. Furthermore, a real-time monitoring system is developed utilizing microelectromechanical systems gas sensors. The modification of amorphous ZnO on the mesoporous SnO2 pore wall can effectively increase the chemisorbed oxygen content and the thickness of the electron depletion layer at the gas-solid interface, which facilitates the interface redox reaction and enhances the sensing performance. This work presents an initial example of semiconductor metal oxide gas sensors for efficient detection of 3-methylbutyraldehyde that holds great potential for ensuring safety during chemical production and disease diagnosis.

Boosting photoelectrocatalytic oxygen evolution activity of BiVO4 photoanodes via caffeic acid bridged to NiFeOOH

Bismuth vanadate (BiVO4) is a promising n-type photoanode material for photoelectrochemical (PEC) water splitting. However, its activity is impeded by poor charge carrier transport and sluggish oxygen evolution kinetics. In this study, we reports a Fe doping and caffeic acid (CA)/NiFeOOH (NiFe) modification with BiVO4 photoanode (NiFe/CA/Fe-BiVO4) to enhance the PEC water oxidation performance and stability. The modified BiVO4 demonstrates significant advantages in promoting the PEC performance and stability. Specifically, Fe doping via in-situ electro-deposition results in smaller crystal sizes, larger specific surface areas, and more exposed active sites. Furthermore, co-catalyst NiFe connects with Fe-BiVO4 through CA bridge facilitates a more uniform self-assembly distribution of NiFe on BiVO4 surface. The NiFe/CA/Fe-BiVO4 exhibits an excellent photocurrent density of 6.2 mA/cm2 at 1.23 VRHEand demonstrates good stability at 0.8 VRHE. In addition, the composite photoanode shows a high applied bias photon-to-current efficiency (ABPE) value of 2.15% at 0.65 VRHE. EPR and in-situ FTIR confirm the generation of superoxide active species (O2- and ·O2-) during the PEC water oxidation reaction.