One-step Co-precipitation Method Research Articles

Multienzyme Mimicking Cascade Mn3O4 Catalyst to Augment Reactive Oxygen Species Elimination and Colorimetric Detection: A Study of Phase Variation upon Calcination Temperature.

Over decades, nanozyme has served as a better replacement of bioenzymes and fulfills most of the shortcomings and intrinsic disadvantages of bioenzymes. Recently, manganese-based nanomaterials have been highly noticed for redox-modulated multienzyme mimicking activity and wide applications in biosensing and biomedical science. The redox-modulated multienzyme mimicking activity was highly in tune with their size, surface functionalization, and charge on the surface and phases. On the subject of calcination temperature to Mn3O4 nanoparticles (NPs), its phase has been transformed to Mn2O3 NPs and Mn5O8 NPs upon different calcination temperatures. Assigning precise structure-property connections is made easier by preparing the various manganese oxides in a single step. The present study has focused on the variation of multienzyme mimicking activity with different phases of Mn3O4 NPs, so that they can be equipped for multifunctional activity with greater potential. Herein, spherical Mn3O4 NPs have been synthesized via a one-step coprecipitation method, and other phases are obtained by direct calcination. The calcination temperature varies to 100, 200, 400, and 600 °C and the corresponding manganese oxide NPs are named M-100, M-200, M-400, and M-600, respectively. The phase transformation and crystalline structure are evaluated by powder X-ray diffraction and selected-area electron diffraction analysis. The different surface morphologies are easily navigated by Fourier transform infrared, field-emission scanning electron microscopy, and high-resolution transmission electron microscopy analysis. Fortunately, for the mixed valence state of Mn3O4 NPs, all phases of manganese oxide NPs showed multienzyme mimicking activity including superoxide dismutase (SOD), catalase, oxidase (OD), and peroxidase; therefore, it offers a synergistic antioxidant ability to overexpose reactive oxygen species. Mn3O4 NPs exhibited good SOD-like enzyme activity, which allowed it to effectively remove the active oxygen (O2•-) from cigarette smoke. A sensitive colorimetric sensor with a low detection limit and a promising linear range has been designed to detect two isomeric phenolic pollutants, hydroquinone (H2Q) and catechol (CA), by utilizing optimized OD activity. The current probe has outstanding sensitivity and selectivity as well as the ability to visually detect two isomers with the unaided eye.

Preparation of Spherical δ-MnO2 Nanoflowers by One-Step Coprecipitation Method as Electrode Material for Supercapacitor.

Spherical δ-MnO2 nanoflower materials were synthesized via a facile one-step coprecipitation method through adjusting the molar ratio of KMnO4 to MnSO4. The influence of the molar ratio of the reactants on the crystal structure, morphology, and electrochemical performances was investigated. At a molar ratio of 3.3 for KMnO4 to MnSO4, the spherical δ-MnO2 nanoflowers composed of nanosheets with the highest specific surface area (228.0 m2 g-1) were obtained as electrode materials. In the conventional three-electrode system using 1 M Na2SO4 as an electrolyte, the specific capacitance of the spherical δ-MnO2 nanoflowers reached 172.3 F g-1 at a current density of 1 A g-1. Moreover, even after 5000 cycles at a current density of 5 A g-1, the GCD curves remained essentially unchanged, and the specific capacitance still retained 86.50% of the maximum value. The kinetics of the electrode reaction were preliminarily studied through the linear potential sweep technique to observe diffusion-controlled contribution toward total capacitance. For the spherical δ-MnO2 nanoflower electrode material, diffusion-controlled contribution accounted for 65.1% at low scan rates and still remained significant at high scan rates (100 mV s-1), indicating excellent utilization efficiency of the bulk phase. The as-fabricated asymmetric supercapacitor HFC-7//MnO2-3.3-ASC presented a prominent specific energy of 16.5 Wh kg-1 at the specific power of 450 W kg-1. Even when the specific power reached 9.0 kW kg-1, the energy density still retained 9.5 Wh kg-1.

Enhancing Oxygen Evolution Reaction through In Situ Electrochemical Oxidation for the Structural Control of Co-Fe Prussian Blue Analogue

The development of exceptionally efficient catalysts for the oxygen evolution reaction (OER) and gaining a deep understanding of their activity is essential for advancing electrochemical conversion technologies. Prussian blue analogues (PBAs) serve as promising pre-catalysts for the OER. However, PBAs, typically prepared through the conventional co-precipitation method, exhibit a lower active site density and limited electrical transport, making them suitable precursors for the derivation of PBA derivatives. In this research, we identified a significant enhancement in the electrocatalytic performance of Co-Fe Prussian blue analogue (CoFe PBA) through electrochemical oxidation. The cubic CoFe PBA was synthesized by one-step co-precipitation method using adjusting the amount of sodium citrate and potassium ferricyanide. After the electrochemical treatment, CoFe PBA demonstrates remarkable attributes, including a low overpotential of 331mV at a current density of 10mA·cm-2, a small Tafel slope of 50.4mV·dec-1, and excellent long-term stability during electrolysis in a 1M KOH alkaline medium for over 37h. Moreover, the electrochemical oxidation of CoFe PBA was comprehensive, employing techniques such as Transmission electron microscope, Powder X-ray diffraction, and X-ray photoelectron spectroscopy. These analyses confirmed the presence of real active substances, including CoOOH and a part of FeOOH species, further supporting the observed improvements in electrocatalytic activity.

One-Step Synthesis of Ultrathin High-Entropy Layered Double Hydroxides for Ampere-Level Water Oxidation

The development of high-entropy anodes, known for their excellent catalytic activity for water oxidation, can depress the energy consumption of hydrogen production by water electrolysis. However, the complex preparation methods and poor stability hindered their practical application. In this work, a one-step co-precipitation method has been modified to rapidly synthesize ultrathin high-entropy layered double hydroxide containing Ni, Co, Fe, Cr, Zn. Through the rational selection of metal elements, the stability of the optimized anode under Ampere-level current density has been significantly improved. Compared to NiFe-LDH, the active site leaching of high-entropy LDH is reduced by 42.7%, and as a result, it achieves a performance decay that is approximately eight times lower than that of NiFe-LDH. Experiment results show that the active sites in the high-entropy LDH can maintain a relatively low oxidation state both before and after activation, thus preventing material deactivation caused by excessive oxidation.

Polyrhodanine-Functionalized Magnetic-Activated Carbon for Efficient Removal of Lead Ions and Malachite Green From Wastewater

The development of wastewater treatment agents with high treatment capacity and efficient separation is crucial for the remediation of heavy metal ions and organic dye wastewater. In this study, a polyrhodanine functional magnetic-activated carbon composite (PR-mAC) was synthesized via a one-step co-precipitation method combined with chemical oxidation polymerization. As an innovative water treatment agent, PR-mAC possesses not only environmentally friendly and easily obtainable raw materials but also magnetic properties that facilitate its reusability. Notably, PR-mAC exhibited remarkable removal efficiency towards lead ion (Pb(II)) and malachite green (MG). Experimental results demonstrated that the adsorption of Pb(II) and MG followed quasi-second-order kinetic model, while the Hill isothermal adsorption model and Redlich–Peterson isothermal adsorption model were suitable for Pb(II) and MG removal, respectively. All adsorption processes were spontaneous endothermic reactions. The maximum adsorption capacities reached 223.71 mg/g and 315.46mg/g, respectively. Even after undergoing 5 cycles, the material maintained satisfactory removal performance for Pb(II) and MG pollutants. Therefore, the prepared PR-mAC represents an optimal agent for wastewater treatment due to its effective capability in removing both metal ions and dyes.

Facile preparation of a Ni-imidazole compound with high activity for ethylene dimerization.

A compound consisting of Ni and imidazole (Ni-imidazole) was synthesized in large quantities by a one-step co-precipitation method. The structure and stability of this Ni-imidazole were well studied by a series of characterization methods. The Ni-imidazole compound exhibited excellent catalytic properties for the dimerization of ethylene to 1-butene.

Empirical correlation of ferromagnetism and electronic structure in Fe and Ni co-doped SnO2 solid solutions: An X-ray analysis using maximum entropy method

The phase-pure magnetic semiconducting Fex/2Nix/2Sn1-xO2 solid solutions with x = 0.03, 0.06, 0.09, and 0.12, were prepared by a cost-effective room-temperature one-step co-precipitation method. XRD peak red-shift reveals lattice compression due to the doping of low/similar ionic radii of Fe3+, Ni3+, and Ni2+ in the Sn4+ lattice, which is also confirmed by the EPR results. Maximum entropy method (MEM)-based electronic structure confirmed interstitial charge accumulation of 6.79 % and 6.05%, forming non-nuclear maxima in 3% and 12% doping systems, respectively, which reduces considerably the ferromagnetism. In addition, pure polar covalent apical and equatorial (Fe/Ni/Sn) – O bonding without interstitial charge accumulation is a key factor for maximum ferromagnetism. A perfect-fitting of the pair distribution function (PDF) and its correlation to charge accumulation at interstitial and regular lattice points in comparison with MEM results provides hope in PDF using low-Q XRD data. The samples with 9% and 6% dopants showed soft ferromagnetism with magnetization (0.0416 and 0.0372) emu/g respectively, which are helpful for magnetic semiconducting applications. The ferromagnetic and antiferromagnetic coupling between interstitial charges' local magnetic domains causes positive exchange anisotropy (exchange bias) in 3% and 12% compositions. The novel and empirical correlation between magnetism and the MEM-based electronic structure is the highlight of this study.

Nanostructured Zr-Mn binary hydrous oxide as an effective adsorbent for arsenic removal from water and groundwater

It is well known that arsenic is a very harmful toxin to humans. Among arsenic species, arsenite is more toxic and more difficult to remove from water than arsenate. In this study, a nanostructured Zr-Mn binary hydrous oxide was synthesized using one-step simultaneous oxidation and coprecipitation method, aiming at removing both arsenate and arsenite effectively and simultaneously. The Zr-Mn binary hydrous oxide particles were aggregated with smaller nanosized particles, resulting in a rough surface. The hydrous oxide was very effective for both As(V) and As(III) removal from water. The maximal sorption capacities for As(V) and As(III) were 52 and 96 mg/g at neutral environment, respectively. The higher sorption capacity for As(III) may be attributed to the As(III) oxidation and reductive dissolution of manganese dioxide, which resulted in the formation of new sorptive sites for arsenic at the solid surface. The presence of sulfate and carbonate had no significantly influence in the arsenic removal. However, the presence of phosphate greatly decreased the removal, especially at high concentrations. Furthermore, the performance of Zr-Mn binary hydrous oxide was further confirmed by an adsorption study with a groundwater. Additionally, the leaching of arsenic from the used sorbent was less serious, indicating that it may not be hazard to the environment after the landfill disposal. Due to its excellent arsenic removal performance and the simple, low-cost synthesis process, the Zr-Mn binary hydrous oxide could be a promising alternate for both As(V) and As(II) simultaneous removal from water or groundwater without the oxidation pretreatment.

Upgrading renewable biogas into syngas via bi-reforming over high-entropy spinel-type catalysts derived from layered double hydroxides

The bi-reforming of biogas is of great significance for the consumption of greenhouse gases and the generation of valuable syngas. In this study, porous high-entropy spinel-type HE-MgAlO (up to quinary metals: Ni, Co, Zn, Ga, Mn,) catalysts derived from layered double hydroxide were prepared by the one-step co-precipitation method. The catalysts were characterized comprehensively via XRD, XRF, H2-TPR, CO2-TPD, XPS, SEM, HR-TEM, STEM-EDS, CH4-TPSR/CO2-TPO, TG-DSC, Raman, and so on. Compared to the monometallic Ni/MgAlO and binary NiCo/MgAlO catalysts, the HE-MgAlO catalyst exhibits higher initial CH4 (∼98 %) and CO2 (∼55 %) conversion and high stability up to 100 h under certain reaction conditions. The homogeneously-dispersed and electronically-enriched Ni sites, the oxophilic property and medium-strong basic sites of HE-MgAlO catalyst, lead to efficient activation of CH4 and CO2 (H2O), respectively, and high catalytic activity ultimately. The generation of reactive O* from CO2 (H2O) over oxophilic and medium-strong alkaline sites of HE-MgAlO catalyst prompts the rapid removal of coke precursors, leads to satisfying coke-resistant behavior. The spinel structure and strong metal-support interaction in HE-MgAlO catalyst enhances the thermal stability and results in satisfying anti-sintering performance.

Preparation of La2O3/ZnO dodecahedral nanopowders induced by ZIF-8 via an innovative mild aqueous solvent approach and evaluation of their gas-sensitive properties towards H2S

Investigating high-performance and low-energy consumption H2S sensors has become a hot research topic. This study adopted a one-step co-precipitation method to synthesize La-doped ZIF-8 deprotonating zinc acetate, lanthanum nitrate, and 2-Methylimidazole in an aqueous. La2O3/ZnO were synthesized with different La3+ doping concentrations (0, 0.5, 1, and 1.5 at%). We found that La3+ doping at a concentration of 1 at% showed the highest response value of 140 for 5 ppm H2S, at a low operating temperature of 100 °C, which is 2.4 times higher than that of pure ZnO. Additionally, La3+ doping led to a lower detection limit of 1.9 ppb. The enhanced performance can be attributed to the widening of the difference in electron concentration, the increase in vacant oxygen content, and the spillover effect of H2S sensing. These factors were analyzed in detail by means of porosity, P-N heterojunctions, and the increased in adsorbed oxygen content caused by La3+doping.

One-Step Fabrication of Magnetic Polymer/Montmorillonite Adsorbent for Highly Efficient Phenol Adsorption

AbstractPhenol contaminants are highly biotoxic and have become a global problem threatening the environment and human health. The objective of the present study was to develop a very efficient and easily recyclable adsorbent to remove phenol. A magnetic montmorillonite composite with organic co-intercalation was fabricated by a simple one-step co-precipitation method and exhibited excellent phenol removal. Two surfactants, cetyltrimethylammonium bromide (CTAB) and erucic acid amide (EA), were successfully co-intercalated into the interlayer of Ca-montmorillonite, and Fe3O4 nanoparticles were simultaneously decorated to obtain Fe3O4-CTAB/EA-montmorillonite composite (Fe3O4-C/E-Mnt). The morphology and structure of Fe3O4-C/E-Mnt composite were explored by using different techniques such as X-ray diffraction, Fourier-Transform infrared spectroscopy, X-ray photoelectron microscopy and so on. The adsorption capacity of Fe3O4-C/E-Mnt for phenol was investigated under various conditions including temperature, pH, contact time, various phenol concentrations, and adsorbent dosage. The results showed that Fe3O4-C/E-Mnt retained a lamellar structure of Ca-Mnt with mesopores. Its interlayer space, surface area, and pore volume were increased. The Fe3O4-C/E-Mnt composite exhibited a good adsorption capacity (31.45 mg·g–1) for phenol with a removal efficiency of 85.46% at optimized conditions. Moreover, the adsorbent still maintained 78.32% of the adsorption capacity after five cycles. The adsorption test data of Fe3O4-C/E-Mnt followed the pseudo-second order kinetic model and the Langmuir model. The adsorption was a spontaneous, exothermic, entropy-decreasing process, and a possible adsorption mechanism of Fe3O4-C/E-Mnt was finally proposed.

Magnetic coffee residue biosorbent for selective extraction of zinc oxide nanoparticles in water samples

ABSTRACT. Quantification of engineered nanomaterials in the environment has attracted researchers’ interest recently because of their increased release to the environment. In this study, a recyclable and easily accessible magnetized coffee residue (MCR) is proposed for magnetic solid-phase extraction (MSPE) of zinc oxide nanoparticles (ZnO-NPs) from water samples. The MCR was synthesized using a simple one-step chemical co-precipitation method from coffee residue and was characterized by state-of-the-art techniques. Various parameters affecting the MSPE efficiency of ZnO-NPs were optimized and 8.5 pH, 75 mg adsorbent, 120 min extraction time, 10 mL sample volume, 4 mL of 0.001 M HCl as an eluting solvent, and 30 min elution time were identified as the optimum conditions. Under these conditions, the method showed excellent linearity (R2 = 0.995) and good sensitivity (detection limit, 0.12 mg L-1, and quantification limit, 0.4 mg L-1). Intra and inter-day percent standard deviations were 1.4 and 2.2%, respectively, for the analysis of 6 mg L-1 ZnO-NPs. The practical applicability of the method for the extraction of ZnO-NPs in environmental samples was evaluated, and recovery values in the range of 93.0–98.2% were obtained, confirming its successful performance. Generally, the technique is easy, economical, and eco-friendly that can be considered for the extraction of metal oxide nanoparticles.
 
 KEY WORDS: Zinc oxide nanoparticles, Magnetic coffee residue, Magnetic solid-phase extraction, Flame atomic absorption spectroscopy, Environmental waters
 
 Bull. Chem. Soc. Ethiop. 2023, 37(4), 859-873. 
 DOI: https://dx.doi.org/10.4314/bcse.v37i4.5

Defect-Healing Induced Monoclinic Iron-Based Prussian Blue Analogs as High-Performance Cathode Materials for Sodium-Ion Batteries.

Prussian blue analogs (PBAs) have attracted wide interest as a class of ideal cathodes for rechargeable sodium-ion batteries due to their low cost, high theoretical capacity, and facile synthesis. Herein, a series of highly crystalline Fe-based PBAs (FeHCF) cubes, where HCF stands for the hexacyanoferrate, is synthesized via a one-step pyrophosphate-assisted co-precipitation method. By applying this proposed facile crystallization-controlled method to slow down the crystallization process and suppress the defect content of the crystal framework of the PBAs, the as-prepared materials demonstrate high crystallization and a sodium-rich induced rhombohedral phase. As a result, the as prepared FeHCF can deliver a high specific capacity of up to 152.0mAhg-1 (achieving ≈90% of its theoretical value) and an excellent rate capability with a high-capacity retention ratio of 88% at 10C, which makes it one of the most competitive candidates among the cathodes reported regarding both capacity and rate performance. A highly reversible three-phase-transition sodium-ion storage mechanism has been revealed via multiple in situ techniques. Furthermore, the full cells fabricated with as-prepared cathode and commercial hard carbon anode exhibit excellent compatibility which shows great prospects for application in the large-scale energy storage systems.

Boosting the H2O resistance and NH3-SCR activity over sulfated FeCe0.5 SmaTi4Ox-S catalysts by Sm modification

In this work, a series of Sm modified sulfated FeCe0.5Ti4Ox-S catalysts were successfully prepared by a concise one-step co-precipitation method for application in flue gases denitrifications (de-NOx) generated from high sulfur content coal-fired power plants. The catalysts were carried out by XRD, Raman, N2 adsorption and desorption, TEM, EDS spectroscopy, NH3-TPD, H2-TPR, XPS, and in-situ DRIFTS characterization. Among these catalysts, FeCe0.5Sm0.3Ti4Ox-S showed the best catalytic activity, maintaining 100% NO conversion in 260–450 °C, high N2 selectivity and good resistance to water and SO2 poisoning. The results demonstrated that the addition of appropriate amount of Sm promoted the interaction between Sm, Ce, Fe and Ti, which increased the oxidation capacity and L-acid sites on the catalyst surface, improving the catalytic activity. Additionally, the increase of L acid sites also contributed to the improvement of water resistance of the catalyst. In-situ DRIFTS studies also indicated that the Sm addition promoted NH3 adsorption in the presence of water due to the reaction of special surface sulfates with H2O to form additional B acid sites, which may be the reason for the negligible effect of water on the catalytic activity. Based on various characterizations, the NH3-SCR de-NOx processes are proposed over FeCe0.5Sm0.3Ti4Ox-S in presence of H2O.

Single-atom Pt-CeO2/Co3O4 catalyst with ultra-low Pt loading and high performance for toluene removal

The design and manufacture of high activity and thermal stability catalysts with minimal precious metal loading is essential for deep degradation of volatile organic compounds (VOCs). In this paper, a novel single-atom Pt-CeO2/Co3O4 catalyst with ultra-low Pt loading capacity (0.06 wt%, denoted as 0.06Pt-SA) was fabricated via one-step co-precipitation method. The 0.06Pt-SA exhibited excellent toluene degradation activity of T90 = 169 °C, matched with the nanoparticle Pt-supported CeO2/Co3O4 catalyst with more than six times higher Pt loading (0.41 wt%, denoted as 0.41Pt-NP). Moreover, the ultra-long durability (toluene conversion remains 99% after 120 h stability test) and excellent toluene degradation ability in a wide space speed range of 0.06Pt-SA were superior to that of 0.41Pt-NP catalyst. The excellent performance was derived from the strong metal-support interaction (SMSI) between the single atomic Pt and the carrier, which induced more Pt0 and Ce3+ for oxygen activation and more Co3+ for toluene removal. The in situdiffuse reflectance infrared spectroscopy (DRIFTS) experiments confirmed that the conversion of intermediates was accelerated in the reaction process, thereby promoting the toluene degradation. Our results should inspire the exploitation of noble single-atomic modification strategy for developing the low cost and high performance VOCs catalyst.

Surface synergistic effect of sub-2 nm NiFeCr hydroxide nanodots yielding high oxygen evolution mass activities

Designing cost-effective electrocatalysts with high efficiency and stability for oxygen evolution reaction (OER) is crucial for hydrogen generation by water splitting and meta-air batteries. NiFe catalysts doped with transition-metal cations have offered an efficient approach to tuning the atomic and electronic structure, thus enhancing OER activity. However, most research focused on regulating the composition of atoms in large-sized catalysts, which remains a major challenge to achieving high atom utilization efficiency and optimal surface synergistic effect. Herein, a one-step co-precipitation method is presented to directly synthesize ultrafine NiFeCr trimetallic amorphous hydroxide nanodots (AND-NiFeCr, < 2 nm) to fully expose the atoms at the surface and near-surface region. Electronic-structure investigation revealed a strong synergistic electronic interaction between Ni, Fe, and Cr cations, which subtly tailors ternary catalysts' local atomic and electronic configuration. Due to the refined ultrafine nano- and electronic-structure modulation, the optimized AND-NiFeCr (Ni:Fe:Cr = 5:3:2) catalysts demonstrated superior OER activity with a low overpotential of 271 mV at 10 mA cm−2. Moreover, an extraordinarily high mass activity of 4926 A gMetal-1 at the overpotential of 300 mV was achieved. This work provides a novel surface synergistic effect strategy to design highly efficient NiFe-based ultrafine hydroxide OER catalysts with high atomic utilization efficiency.

Electron transfer degradation of ciprofloxacin by peroxydisulfate intercalated MgAlFe-layered double hydroxides: Roles of laminate structure and interlayer peroxydisulfate

Peroxydisulfate intercalated MgAlFe-layered double hydroxides (S2O8·LDHs) are synthesized by the one-step co-precipitation method. The Fe content in LDH laminates affects the insertion of S2O82−, and further affects the catalytic activity of S2O8·LDHs. Fe-S2O8·LDH-0.2 with Fe/(Al + Fe) = 0.2 shows superior performance that 1 g/L of dosage leads to 99.55 % degradation of ciprofloxacin (CIP, 10 mg/L) within 60 min. It is fully clarified that electron transfer rather than SO4•−, •OH, O2•− and 1O2 is responsible for CIP degradation. Interlayer S2O82− with longer OO bond length than free S2O82− exists in metastable form, which deprives electrons from the piperazine ring of CIP mainly through the transport of LDH laminates, leading to the degradation of CIP through the cleavage and oxidation of piperazine ring. The efficient degradation of other fluoroquinolones and the modest even negligible influence of Cl−, NO3–, HCO3–/CO32– and natural organic matter on the performance prove the practical application potential of S2O8·LDHs. This work not only provides an in-depth study on the degradation of emerging pollutants by PDS intercalated LDHs, but also provides some new insights into the non-radical mechanism.

Sustainable synthesis of vanadate/fluorapatite nano-crystallites from solid waste for enhanced photocatalysis and pollution removal

In this work, vanadate-fluorapatite, V2O5/Ca10(PO4)6F2, nanocrystals were successfully synthesized through a straightforward one-step co-precipitation method. This method was based on two toxic solid wastes, which are mainly generated as by-products during sulfuric acid manufacturing and in the phosphate industry. The two solid wastes were mainly based on phosphogypsum as a source of calcium and vanadium pentoxide as a source of vanadate. In comparison to numerous conventional methods for FAP synthesis, this innovative method is not laborious, not complex, cost-effective, and environmentally friendly, thanks to the recovery of toxic solid wastes. Furthermore, it consists of mixing various contents of anhydrous gypsum with phosphoric acid, vanadium pentoxide, and ammonium fluoride at one time and at room temperature with no further adjustment of the pH. Several physicochemical characterization techniques were used, including X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), and Ultraviolet-Visible Spectroscopy (UV-vis). Whereas SEM analysis of the crystals obtained showed a nanometer-scale fluorapatite crystallites was obtained. The obtained results offer exciting potential for applying the prepared nanomaterial in both photocatalysis and pollution removal. They hold great promise and are expected to generate significant interest in these fields.

Ultra-small manganese dioxide nanoparticles with high T1 relaxivity for magnetic resonance angiography.

Gadolinium (Gd)-based contrast agents (CAs) for clinical magnetic resonance imaging are facing the problems of low longitudinal relaxivity (r1) and toxicity caused by gadolinium deposition. Manganese-based small molecule complexes and manganese oxide nanoparticles (MONs) are considered as potential alternatives to Gd-based CAs due to their better biocompatibility, but their relatively low r1 values and complicated synthesis routes slow down their clinical translation. Herein, we presented a facile one-step co-precipitation method to prepare MONs using poly(acrylic acid) (PAA) as a coating agent (MnO2/PAA NPs), which exhibited good biocompatibility and high r1 values. A series of MnO2/PAA NPs with different particle sizes were prepared and the relationship between the particle size and r1 was studied, revealing that the MnO2/PAA NPs with a particle size of 4.9 nm exhibited higher r1. The finally obtained MnO2/PAA NPs had a high r1 value (29.0 Mn mM-1 s-1) and a low r2/r1 ratio (1.8) at 1.5 T, resulting in a strong T1 contrast enhancement. In vivo magnetic resonance angiography with Sprague-Dawley (SD) rats further proved that the MnO2/PAA NPs showed better angiographic performance at low-dosage administration than commercial Gadovist® (Gd-DO3A-Butrol). Moreover, the MnO2/PAA NPs could be rapidly cleared out after imaging, which effectively minimized the toxic side effects. The MnO2/PAA NPs are promising candidates for MR imaging of vascular diseases.

Metal-organic frameworks-derived In2O3/ZnO porous hollow nanocages for highly sensitive H2S gas sensor

The detection of hydrogen sulfide (H2S) is critical because of its potential harm and widespread presence in the oil and gas sectors. The zeolitic imidazolate framework-8 (ZIF-8) derived ZnO nanostructures manufactured as gas sensors have exceptional sensitivity and selectivity for H2S gas. In/Zn-ZIF-8 template material was synthesized by a simple one-step co-precipitation method followed by thermal annealing in air. The heat treatment resulted in In2O3/ZnO nanostructures with mixed heterostructures. The crystal structure (XRD), morphology (SEM/TEM), chemical state (XPS), surface area (BET), etc were investigated to ascertain the nature of the as-prepared material. SEM imagery revealed that the as-prepared In2O3/ZnO sensitive material had a microstructure of porous hollow nanocages with an average particle size of about 200 nm, which is beneficial to the diffusion and adsorption of gas molecules. The gas sensing performance test results of the In2O3/ZnO hollow nanocages show that their response to H2S gas is significantly improved 67.5 @50 ppm H2S (about 11 times that of pure ZnO nanocages) at an optimal temperature of 200 °C, better selectivity, lower theoretical detection limit and good linearity between gas concentration and response values. The enhanced gas sensing feat to H2S gas is mainly attributed to the formation of n-n heterojunction and the wide surface area of the newly formed In2O3/ZnO porous hollow nanocages.