Fabrication of Porous ZrO2 Nanostructures with Controlled Crystalline Phases and Structures via a Facile and Cost-Effective Hydrothermal Approach

Enhanced acetic acid sensing of MOF-derived α-Fe2O3/ZrO2 arising from phase junction and defects

The coexistence of phase junction, heterojunction and defects allows α-Fe2O3/ZrO2 to display an significant response towards acetic acid.

Surface-Enhanced Raman Scattering Activity of ZrO2 Nanoparticles: Effect of Tetragonal and Monoclinic Phases

The effect of the ZrO₂ crystal form on surface-enhanced Raman scattering (SERS) activity was studied. The ratio of the tetragonal (T) and monoclinic (M) phases of ZrO₂ nanoparticles (ZrO₂ NPs) was controlled by regulating the ratio of two types of additives in the hydrothermal synthesis method. The SERS intensity of 4-mercaptobenzoic acid (4–MBA) was gradually enhanced by changing the M and T phase ratio in ZrO₂ NPs. The degree of charge transfer (CT) in the enhanced 4–MBA molecule was greater than 0.5, indicating that CT was the main contributor to SERS. The intensity of SERS was strongest when the ratio of the T crystal phase in ZrO₂ was 99.7%, and the enhancement factor reached 2.21 × 10⁴. More importantly, the proposed study indicated that the T and M phases of the ZrO₂ NPs affected the SERS enhancement. This study provides a new approach for developing high-quality SERS substrates and improving the transmission efficiency of molecular sensors.

Highly efficient catalytic transfer hydrogenation of furfural over defect-rich amphoteric ZrO2 with abundant surface acid-base sites

Currently, the catalytic transformation and utilization of biomass-derived compounds are of great importance to the alleviation of environmental problems and sustainable development. Among them, furfural alcohol derived from biomass resources has been found to be one of the most prospective biomass platforms for high-value chemicals and biofuels. Herein, high-surface-area ZrO₂ with abundant oxygen defects and surface acid-base sites was synthesized and used as a heterogeneous catalyst for the catalytic transfer hydrogenation of furfural into furfural alcohol using alcohol as a hydrogen donor. The as-synthesized ZrO₂ exhibited excellent catalytic performance with 98.2% FA conversion and 97.1% FOL selectivity, even comparable with that of a homogeneous Lewis acid catalyst. A series of characterization studies and experimental results revealed that acid sites on the surface of ZrO₂ could adsorb and activate the C[double bond, length as m-dash]O bond in furfural and base sites could facilitate the formation of alkoxide species. The synergistic effect of surface acid-base sites affords a harmonious environment for the reaction, which is crucial for catalytic transfer hydrogenation of furfural with high efficiency. Furthermore, the as-prepared ZrO₂ catalyst also exhibited a potential application for the efficient catalytic transfer hydrogenation of a series of biomass-derived carbonyl compounds.

Ni-Doped ZrO2 nanoparticles decorated MW-CNT nanocomposite for the highly sensitive electrochemical detection of 5-amino salicylic acid

Ni-ZrO₂/MWCNT/GCE for highly sensitive electrochemical detection of 5-ASA in biofluids.

Glucose Oxidase Immobilized on Magnetic Zirconia: Controlling Catalytic Performance and Stability

Here, we report the structures and properties of biocatalysts based on glucose oxidase (GOx) macromolecules immobilized on the mesoporous zirconia surface with or without magnetic iron oxide nanoparticles (IONPs) in zirconia pores. Properties of these biocatalysts were studied in oxidation of d-glucose to d-gluconic acid at a wide range of pH and temperatures. We demonstrate that the calcination temperature (300, 400, or 600 °C) of zirconia determines its structure, with crystalline materials obtained at 400 and 600 °C. This, in turn, influences the catalytic behavior of immobilized GOx, which was tentatively assigned to the preservation of GOx conformation on the crystalline support surface. IONPs significantly enhance the biocatalyst activity due to synergy with the enzyme. At the same time, neither support porosity nor acidity/basicity shows correlations with the properties of this biocatalyst. The highest relative activity of 98% (of native GOx) at a pH 6-7 and temperature of 40-45 °C was achieved for the biocatalyst based on ZrO₂ calcined at 600 °C and containing IONPs. This process is green as it is characterized by a high atom economy due to the formation of a single product with high selectivity and conversion and minimization of waste due to magnetic separation of the catalyst from an aqueous solution. These and an exceptional stability of this catalyst in 10 consecutive reactions (7% relative activity loss) make it favorable for practical applications.

High Selectivity and Stability of Nickel Catalysts for CO2 Methanation: Support Effects

In this work, we present an investigation concerning the evaluation of the catalytic properties of Ni nanoparticles supported on ZrO2, SiO2, and MgAl2O4 for CO2 hydrogenation to methane. The supports were prepared by coprecipitation and sol-gel, while Ni was incorporated by impregnation (10–20 wt %). X-ray diffraction, nitrogen physisorption, temperature-programmed reduction, H2 pulse chemisorption, Raman spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy were the main characterization techniques employed. A laboratory fixed-bed reactor operated at atmospheric pressure, a temperature range of 350–500 °C, and a stoichiometric H2/CO2 molar ratio was used for catalyst evaluation. The most outstanding results were obtained with nickel catalysts supported on ZrO2 with CO2 conversions of close to 60%, and selectivity to methane formation was 100% on a dry basis, with high stability after 250 h of reaction time. The majority presence of tetragonal zirconia, as well as the strong Ni–ZrO2 interaction, were responsible for the high catalytic performance of the Ni/ZrO2 catalysts.

Pt Nanoparticles Supported on Nitrogen-Doped-Carbon-Decorated CeO2 for Base-Free Aerobic Oxidation of 5-Hydroxymethylfurfural

Currently, the base-free aerobic oxidation of biomass-derived 5-hydroxymethylfurfural (HMF) to produce 2,5-furandicarboxylic acid (FDCA) is attracting intense interest due to its prospects for the green, sustainable, and promising production of biomass-based aromatic polymers. Herein, we have developed a new Pt catalyst supported on nitrogen-doped-carbon-decorated CeO₂ (NC-CeO₂ ) for the aerobic oxidation of HMF in water without the addition of any homogeneous base. It was demonstrated that the small-sized Pt particles could be well dispersed on the surface of the hybrid NC-CeO₂ support, and the activity of the supported Pt catalyst depended strongly on the surface structure and properties of the catalysts. The as-fabricated Pt/NC-CeO₂ catalyst, with abundant surface defects, enhanced basicity, and favorable electron-deficient metallic Pt species, enabled an almost 100 % yield of FDCA in water with molecular oxygen (0.4 MPa) at 110 °C for 8 h without the addition of any homogeneous base, which is indicative of exceptional catalytic performance. Furthermore, this Pt/NC-CeO₂ catalyst also showed good stability and reusability owing to strong metal-support interactions. An understanding of the role of surface structural defects and basicity of the hybrid NC-CeO₂ support provides a basis for the rational design of high-performance and stable supported metal catalysts with practical applications in various transformations of biomass-derived compounds.

Controlled Synthesis of ZrO2 Nanoparticles with Tailored Size, Morphology and Crystal Phases via Organic/Inorganic Hybrid Films

In this investigation, well defined mesoporous zirconia nanoparticles (ZrO₂ NPs) with cubic, tetragonal or monoclinic pure phase were synthesized via thermal recovery (in air) from chitosan (CS)- or polyvinyl alcohol (PVA)-ZrO_x hybrid films, prepared using sol–gel processing. This facile preparative method was found to lead to an almost quantitative recovery of the ZrOx content of the film in the form of ZrO₂ NPs. Impacts of the thermal recovery temperature (450, 800 and 1100 °C) and polymer type (natural bio-waste CS or synthetic PVA) used in fabricating the organic/inorganic hybrid films on bulk and surface characteristics of the recovered NPs were probed by means of X-ray diffractometry and photoelectron spectroscopy, FT-IR and Laser Raman spectroscopy, transmission electron and atomic force microscopy, and N₂ sorptiometry. Results obtained showed that the method applied facilates control over the size (6–30 nm) and shape (from loose cubes to agglomerates) of the recovered NPs and, hence, the bulk crystalline phase composition and the surface area (144–52 m²/g) and mesopore size (23–10 nm) and volume (0.31–0.11 cm³/g) of the resulting zirconias.

Nano-zirconia - Evaluation of its antioxidant and anticancer activity

Bioactivity of nanomaterials largely depends on its size, shape and crystalline nature. In this work, the smaller sized spherical shaped nano-zirconia (ZrO₂ NPs) (of ~9 to 11nm) was fabricated and studied its biological activity especially antioxidant and cytotoxicity against human colon carcinoma (HCT-116) and human lung carcinoma (A-549) cell lines. To have its real applications in biological aspects readily available Eucalyptus globulus (E. globulus) leaf extract was used as an effective capping and reducing agent for its synthesis. The prepared ZrO₂ NPs was characterized by using different sophisticated instrumentations such as UV-visible spectrophotometer, XRD, FTIR, TEM, SAED, EDX, DLS and fluorescence spectroscopy. Cellular mitochondrial activity i.e. cell viability was measured by MTT assay and anti-oxidant activity was determined by DPPH assay. The smaller sized ZrO₂ NPs showed strong antioxidant activity as well as cytotoxicity on human cancer cell lines. Comparative cytotoxic studies were conducted on human cancerous cell lines using different techniques. Results confirmed the efficient anti-cancer activities of the fabricated ZrO₂ NPs towards the tested cell lines as well as efficient anti-oxidant activity. This is the first study in which E. globulus leaf extract was used to synthesize smaller spherical shaped ZrO₂ NPs for improved bioactivity i.e. antioxidant and cytotoxicity.