Activity Of Ce Research Articles

Recent Catalysts Used in the Synthesis of 1,4-Disubstituted 1,2,3-Triazoles by Heterogeneous and Homogeneous Methods

1,2,3-triazoles are popular heterocycles employed in material sciences and medicinal chemistry as they show antiviral, antibacterial, anti-HIV, antitubercular, and antifungal activities. Triazoles are appealing due to their stability and interesting click chemistry properties. The Cu(I) catalyzed reaction between azides and alkynes affords the 1,4- disubstituted derivative exclusively becoming a useful synthetic tool. However, one of the main drawbacks of the catalyzed reaction is the need to use Cu(I), which is unstable at standard conditions and rapidly oxidizes to the non-active Cu(II). The most common approach when synthesizing 1,4-disubstituted-1,2,3-triazoles is to reduce Cu in situ employing inorganic Cu salts and a reducing agent. The resulting Cu(I) needs to be further stabilized with organic ligands for the reaction to take place. The aim of homogeneous catalysis is to produce a ligand with a dual function both in reducing and stabilizing Cu(I) without interfering in the overall reaction. Instead, heterogeneous catalysis offers more options when supporting Cu on nanoparticles, complexes, and composites yielding the desired 1,2,3-triazoles in most cases without the need of a reducing agent under green solvents such as ethanol and water. The catalytic activity of Ag, Ru, and Ce is also discussed. This review exemplifies how the use of homogeneous and heterogeneous catalysts offers new and green methodologies for the synthesis of 1,2,3-triazole derivatives. The materials supporting Cu show catalytic properties like high surface area, acid-base sites or phase transfer. Although there is no ideal catalyst, Cu remains the most effective metal since it is economical, abundant and readily available.

Selective Formation of Ce-Ni Hydrogen Storage Alloys By Electrodeposition in LiCl-KCl-CeCl3 Melts Using Ni As Cathode

Cerium-nickel based hydrogen storage alloys are one of the important new rare earth-based hydrogen storage alloys due to their high discharge capacities, easy activation and good hydrogen pressure. Cerium-nickel based alloy compound, CeNi5, is usually used as the hydrogen storage alloy in Ni/MH battery, due to their favorable electrochemical activation, improved discharge and charge kinetic properties. CeNi2 and CeNi3, are also used as hydrogen storage alloys. The electrochemical way in molten salts is more economic for the metallurgical industry, because it has simpler in operation and lower in energy consumption than many existing industrial technologies. However, the electrochemical formation of Ce-Ni hydrogen storage alloys by selective electrodeposition has not been reported on a Ni cathode in LiCl-KCl molten salts. In this study, the electrochemical behavior of Ce(III) ions was explored in molten LiCl-KCl salts using nickel as working electrode to produce the Ce-Ni hydrogen storage alloys. Cyclic voltammetric and square wave voltammetric results indicated that the electrochemical reduction of Ce (III) appeared at a less negative value than that recorded on a W electrode because of the formation of Ce-Ni alloy compounds by the electro-deposition of Ce on a Ni electrode. The nucleation mechanism of Ce deposited on a Ni electrode based on the Scharifker-Hill non-dimensional theoretical model was found to be the progressive nucleation. The change of electrode surface morphology with the deposited time was observed by SEM, which clearly indicated that the nucleation and growth of Ce follows the mechanisms of dendritic growth. Based on the studies of the above electrochemical behavior, Ce-Ni alloys were prepared using potentiostatic electrolysis, five kinds of Ce-Ni intermetallic compounds, CeNi5, Ce2Ni7, CeNi3, CeNi2 and CeNi were formed under our experiment conditions in LiCl-KCl-CeCl3 melts. XRD and SEM-EDS analysis results showed that the hydrogen storage alloys of CeNi5, CeNi3 and CeNi2 could be selectively prepared using potentiostatic electrolysis by controlling applied potential. Furthermore, The thermodynamic properties of Ce-Ni compounds, such as Gibbs free energy(ΔG), enthalpy(ΔH) and entropy(ΔS) of formation for each Ce-Ni alloy compound as well as activity and partial molar Gibbs energy of Ce in Ce-Ni alloy were computed employing open circuit chronopotentiometry measurement. Therefore, this work presents a promising method for the preparation of the Cerium-nickel based hydrogen storage alloys. Keywords: Electrochemical behaviour; Electrochemical formation; Ce-Ni intermetallic compounds; Thermodynamic properties References [1] Y. Zhang, H.Y. Yin, S.D. Zhang, D.Y. Tang, Z.W. Yuan, T.H.Yan, W.F. Zheng, D.H. Wang,Preparation of CeNi2 intermetallic compound by direct electroreduction of solid CeO2-2NiO in molten LiCl,J. Rare Earth.3(9)(2012) 923-927.[2] B.J. Zhao, L. Wang, L. Dai, G.H. Cui, H.Z. Zhou, R.V. Kumar, Direct electrolytic preparation of cerium/nickel hydrogen storage alloy powder in molten salt,J. Alloys Compd. 468 (2009) 379-385.[3] B.J. Zhao, X.G. Lu, Q.D.Zhong, C.H. Li, S.L. Chen, Direct electrochemical preparation of CeNi5 and LaxCe1-xNi5 alloys from mixed oxides by SOM process,Electrochim. Acta 55 (2010) 2996-3001.Fig.1 Square wave voltammogram for Ni electrode in LiCl-KCl-CeCl3 melts at 873 K. Pulse height: 0.1 V; potential step: 0.002 V; frequency: 20 Hz. Figure 1

Synthesis, Characterization, DFT Studies and Biological Activity of Ru(III), La(III) and Ce(III) Triphenylphosphine Complexes Containing 2-Aminothiazole and 2-Aminotriazole

In the present paper a series of triphenylphosphine complexes containing mixed ligands like 2-aminothiazole (Ath) and 2-aminotriazole (Atz) have been prepared. The complexes are of the formula [MCl3((Pph3)(Ath)2] and [MCl3((Pph3)(Atz)2], [M = Ru(III), Ce(III) and La(III)]. These complexes were characterized by different spectral techniques. Additionally, the computational study has been performed using density functional theory (DFT) and the calculation is used to examine the electronic structure of the synthesized complexes. The biological activities of all the synthesized complexes were evaluated and the comparative account in properties between the triphenylphosphine metal complexes containing 2-aminothiazole and 2-aminotriazole ligands has been made. The DNA-binding property of these metal complexes was investigated using electronic absorption spectroscopy and fluorescence spectroscopy. The antibacterial and antifungal activity against bacterial species (Gram −ve bacteria: Escherichia coli, Salmonella typhi) and (Gram +ve bacteria: (Staphylococcus aureus and Bacillus subtilis) and fungi (Aspergillus niger and Candida albicans). The antioxidant study was carried out against the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH·) which showed that the metal complexes are good antioxidant, as compared to BHT. Further, the in-silico molecular docking study was performed to predict the possible binding sites of the metal complexes.

Promoting effect of Ce and Mn addition on Cu-SSZ-39 zeolites for NH3-SCR reaction: Activity, hydrothermal stability, and mechanism study

Abstract In this work, Ce and Mn were added to Cu-SSZ-39 zeolites by ion-exchange process, and their activity performance for selective catalytic reduction of NOx with ammonia (NH3-SCR), especially hydrothermal stability (hydrothermal aging at 750, 800, 850 °C) was investigated systematically. It is found that the addition of Ce and Mn, Mn more evidently, both can greatly improve the activity of Cu-SSZ-39 catalyst. Moreover, MnCu-SSZ-39 catalyst have shown superior hydrothermal stability compared with Cu-SSZ-39 catalyst, and outstandingly its activity is not only not decreased significantly like Cu-SSZ-39 but improved obviously after hydrothermal aging at as high as 850 °C. The high and improved activity of Ce and Mn added Cu-SSZ-39 is ascribed to more active CuO crystallites formation in the inner channel and higher acidity strength. The superior hydrothermal stability of MnCu-SSZ-39 may be due to its well-preserved structure and acid density even after hydrothermal aging at as high as 850 °C. Moreover, during the hydrothermal aging process, not only Cu oxides aggregation is inhibited, but also more Cu2+ ion species are induced to ion exchange sites in MnCu-SSZ-39, which may account for its excellent hydrothermal stability (even higher than the activity of fresh samples). The mechanism analysis has shown NH3-SCR reaction over Cu-SSZ-39 and CeCu-SSZ-39 samples follow the “Langmuir–Hinshelwood” (L-H) mechanism, while on MnCu-SSZ-39, it follows both “L–H” and “Eley–Rideal” (E–R) mechanisms, which may also be another reason for its excellent activity and hydrothermal stability. Moreover, “Fast SCR” mechanisms also occur and contribute over hydrothermal aged A-MnCu-SSZ-39 sample, in addition to “L-H” and “E-R” mechanisms. Thus, the easily prepared MnCu-SSZ-39 catalyst has shown the excellent activity and super hydrothermal stability, with 90% NO conversion at 245 °C and broader temperature window of 245 °C to 550 °C, even after hydrothermal aging at 850 °C, therefore indicate great potential for future application in NOx purifying from diesel engine exhaust.

Synthesis and crystal structure of a novel cyano-bridged Fe2+- Ce4+ supracomplex, designed to produce an effective catalyst for clean fuel production

A new cyano-bridged, FeII–CeIV hetero-binuclear supra-complex formulated as [(FeII)2(CN)6(CeIV)2(CN)6(H2O)3]n.nH2O (1), has been synthesized. Depending on the synthetic conditions, different morphology has been obtained. Using hydrothermal synthesis lead to a micro-structured of complex 1 (MS), while using ultrasonic irradiation resulted a nano-structured of complex 1 (NS). The synthesized complexes were characterized by elemental analysis, Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), differential thermal analysis (DTA) and scanning electron microscopy (SEM). The crystals of complex 1 have been fully characterized by single-crystal X-ray diffraction (SC-XRD), which revealed an orthorhombic system with space group Cmcm of expected composition. Also, the results of SEM show that the synthesized complexes have the different morphology and particle size. In the following, catalysts of Ce–Fe/SiO2-MS and Ce–Fe/SiO2-NS were prepared by thermal decomposition of MS and NS complexes, respectively, and characterized by FT-IR spectroscopy, SEM, powder X-ray diffraction (PXRD), and Brunauer–Emmett–Teller (BET) N2 adsorption-desorption analysis. The catalytic activity of Ce–Fe/SiO2 -MS and Ce–Fe/SiO2 -NS was evaluated in the high-temperature water-gas shift reaction (HT-WGS) for hydrogen production. The high CO conversion (93 and 85.5%) was achieved by Ce–Fe/SiO2 –NS, Ce–Fe/SiO2 –MS, respectively, which can be mainly ascribed to physicochemical features of these catalysts, such as mesoporous nature, particle size, BET surface area and strong synergistic effects between the Ce and Fe in the Ce–Fe mixed oxides.

Zn0.9Ce0.05M0.05O (M = Er, Y, V) nanocrystals: Structural and energy bandgap engineering of ZnO for enhancing photocatalytic and antibacterial activity

Novel photocatalytic and antibacterial material Zn0.9Ce0.05M0.05O (M = Er, Y, V) nanocrystals were synthesized via a facile co-precipitation technique and characterized by different analytical techniques. XRD confirmed the incorporation of Ce, Er, Y, and V, that without modifying the basic ZnO hexagonal wurtzite structure affects strongly structural properties. The Scherrer, W–H, and SSP methods were used to calculate different microstructural parameters using XRD data. The optical energy bandgap was found to be decreased in all co-doped samples (3.14–2.82 eV) calculated from UV–vis spectra by employing different methods. The effect of dopants ions on the optical properties of ZnO was also studied in detail. The FTIR spectrum inveterate the existence of Zn–O, and Zn-M–O (M = Ce, Er, Y, V) vibrational mode that further confirmed the incorporation of dopants ions. The photocatalytic performance of the grown products was evaluated under sunlight illumination against methylene blue (MB) dye. The antibacterial activity was performed against gram-positive Staphylococcus aureus and gram-negative Pseudomonas aeruginosa bacteria. The co-doped nanocrystals have shown enhanced photocatalytic and antibacterial activity as compared to Ce-doped ZnO but the Ce–V co-doped ZnO shown the highest activity. The influence of different operational parameters such as the amount of catalyst, the concentration of dye, and pH of the solution on photocatalytic activity of Ce–V co-doped ZnO nanocrystal was also studied and discussed in detail. The radical trapping experiments were also performed to identify the active species involved in photodegradation reaction. The recyclability test exhibited that Ce–V co-doped ZnO catalyst has high stability and can be reused up to the 6th cycles. Furthermore, a possible photocatalytic mechanism was also proposed for the photodegradation of MB dye.

Leishmanicidal activity of Piper marginatum Jacq. from Santarém-PA against Leishmania amazonensis

Leishmaniasis is an infectious disease that has high endemicity and is among the six parasitic diseases of higher occurrence in the world. The current treatments are limited due to their toxicity, treatment resistance and high cost which have increased the search for new substances of natural origin for its therapy. Based on this, an in vitro biological and chemical investigation was carried out to evaluate the potential of Piper marginatum against Leishmania amazonesis. P. marginatum leaves were collected to obtain the essential oil (EO) and the ethanolic extract (CE). The chemical profile of the CE and fractions was obtained by 1H NMR. The analysis of the EO chemical composition was performed by GC-MS. EO, CE and fractions were submitted to antileishmanial and cytotoxicity assays against macrophages. The chromatographic profiles of EO, CE and fractions showed the presence of phenolic compounds and terpenoids, having 3,4-Methylenedioxypropiophenone as a major compound. All P. marginatum samples showed low toxicity to macrophages. The CE and the methanolic, hexane and ethyl acetate fractions had low cytotoxicity when compared to Pentamidine. All tested samples inhibited growth of L. amazonensis promastigotes. The antileishmanial activity of EO, CE and fractions were evaluated in macrophages infected with L. (L.) amazonensis and treated with the concentrations 1, 10 and 100 μg/mL for 48 h. All samples were active, but EO and CE showed superior activity against amastigote forms when compared to the promastigote forms of L. amazonensis. This work describes for the first time the antileishmanial activity of the species P. marginatum and its cytotoxicity against macrophages, suggesting that it can be an alternative source of natural products in the phytotherapeutic treatment of leishmaniasis.

Cholinergic profile as a target of rational therapy of central nervous system diseases and injuries

A comparative analysis of the clinical efficacy of cholinergic drugs and acetylcholinesterase inhibitors (IHE), as well as their combination, in the treatment of cerebrovascular disease and consequences of intracranial injury according to clinical, instrumental and laboratory dynamic observations. Ninety patients with cerebrovascular pathology, including 45 with chronic brain ischemia stage 2 (ICD-10 I67) and 45 with sequelae of intracranial injury (ICD-10 T90.5), were enrolled in the study. Complex treatment of patients included basic and specific therapy. The groups were divided into 3 subgroups of 15 people: the neuromidin group, the gliatilin group and the neuromidin + gliatilin group. The duration of treatment was 2 months. All patients underwent a comprehensive clinical, neurophysiological and laboratory examination prior to therapy, after 1 month and 2 month from the beginning of therapy: a study of cholinesterase activity in the blood, testing on MMSE and Hamilton scales, transcranial magnetic stimulation with determination of Central motor conduction time and somatosensory evoked potentials with calculation of Central afferent conduction time. Prior to treatment, a significant positive strong correlation was found between the age of patients and the level of CE activity in serum (Rs=0.77; p=0.0001). The treatment resulted in a significant (p<0.05) improvement of all parameters (except for MMSE that showed a trend towards improvement) in the neuromidin and the neuromidin + gliatilin subgroups of each group compared to those in the gliatilin subgroups. In addition, after 2 months from the beginning of treatment, there was a significant decrease in the activity of CE in serum in the neuromidin and the neuromidin + gliatilin subgroups. The study of deviations of the 'cholinergic profile' (the level of CE activity in the blood) in patients with cerebral pathology and the strategy using cholinergic drugs, IHE and their combination for the treatment of neuropsychiatric disorders, is one of the important directions in the optimization of combined therapy of patients of this profile.

Ce掺杂与结构优化策略提高ZnO光催化性能

Ce掺杂与结构优化策略提高ZnO光催化性能

SYNTHESIS, PHOTO- AND ELECTROCATALYTIC PROPERTIES OF NANOSTRUCTURED Ce–TiO2 FILMS

Electrocatalytic films based on nanodispersed titanium dioxide modified by Ce(III) were synthesized by sol-gel method and characterized by X-ray diffraction and ultraviolet-visible photocurrent spectra. The average size of nanoparticles was no more thаn 11 nm. The XRD results indicated that TiO2 and Ce–TiO2 electrodes with Ce concentrations up to 5 % calcined at 500°C consisted of anatase as the unique phase. The photocurrent spectra of the Ce–TiO2 electrodes (0 ≤ Ce concentration ≤ 2% mol.) showed a stronger current in the UV range and a shift in the flat-band potential (Еfb) towards more negative values than that of TiO2 electrodes. Electrocatalytic properties of TiO2 and Ce–TiO2 electrodes were investigated in the process of oxygen electroreduction. It has been found by I–E curves measurements that the potential of oxygen reduction changes with the film composition. Modifying of TiO2 films by Ce(III) improves catalytic activity of Ce–TiO2 electrodes ( Ce concentration up to 2% mol.) in the reaction of oxygen electroreduction, that appears in decreasing of oxygen reduction potential EO2 and increasing of dynamic range of O2 electroreduction potentials. The high electrocatalytic activity of Ce–TiO2 electrodes in the oxygen reduction process may be due to the formation of catalytically active centers which activity may decrease in the presence of an amorphous phase. The correlation between photo- and electrocatalytic properties and structural changes occurring in Ce–TiO2 films on increasing the cerium content is observed. The electrodes investigated were distinguished by a high sensitivity to dissolved oxygen ((4-5)∙10-6 g·l-1) and high reproducibility of characteristics in long-time cycling. These electrodes promise much as reusable electrode materials in electrochemical sensors for the determination of oxygen in liquids.

Synthesis of CenTiOx flakes with hierarchical structure and its enhanced activity for selective catalytic reduction of NOx with NH3

• Synthesis of self-assembly hierarchical structure Ce n TiO x flakes for NH 3 -SCR of NO. • Good activity of Ce 0.21 TiO x due to the increasing surface area, Ce 3+ and O α contents. • Good correlation between the percentage of Brønsted acid sites and NO conversion. • An Eley-Rideal (E-R) mechanism dominates the reaction process. Herein, a series of Ce n TiO x (n = 0.068, 0.15, 0.21 and 0.30) flakes with hierarchical structure was prepared by alcoholysis under solvothermal conditions and explored for the selective catalytic reduction (SCR) of NO x with NH 3 . The morphology of the Ce n TiO x flakes was related to the Ce doping content. Remarkably, the flakes morphology of catalyst greatly promoted the SCR activity derived from the strong interaction between the Ce and Ti oxides. Among these samples, the Ce 0.21 TiO x with rod-like hierarchical structures demonstrated good SCR activity that the NO conversion was still over 90% from 270 °C to 450 °C even under SO 2 and H 2 O. Various characterizations clarified that the good activity over Ce 0.21 TiO x was due to the increase of BET surface area (195 m 2 /g), surface Ce 3+ amount and surface O α species. In-situ DRIFTS was conducted to determine the distribution and reactivity of surface acid sites. The results demonstrated that there was a direct correlation between the coverage of the Brønsted acid sites and the NO conversion. Eley-Rideal (E-R) mechanism is the most likely to represent the reaction mechanism on Ce 0.21 TiO x catalyst.

Catalytic Ozonation of Organics in Reverse Osmosis Concentrate with Catalysts Based on Activated Carbon.

Acid-washed activated carbon (AC-A), nitric acid modified activated carbon (AC-NO2), aminated activated carbon (AC-NH2) and cerium-loaded activated carbon (Ce/AC) were prepared and characterized by BET procedure, Boehm titration and SEM. Their performances were investigated for the ozonation of p-chlorobenzoic acid (p-CBA) in its solution and organic compounds in reverse osmosis concentrate (ROC). Nitration and amination had little effect on the surface area of catalyst, but increased the concentration of surface acid and basic functional group respectively. After loading Ce, the surface area of the catalyst decreased, and amount of Ce particles were agglomerated on the surface of activated carbon. All the four catalysts can improve the removal rate of the organics in water. Among the four catalysts, Ce/AC shows the highest catalytic activity. The removal rates of p-CBA, TOC and three target pollutants (e.g., tetracycline, metoprolol, atrazine) are 99.6%, 70.38%, 97.76%, 96.21% and 96.03%, respectively. Hydroxyl radical (·OH) was proved to be the core of catalytic reaction mechanism for Ce/AC, with the contribution rate to p-CBA removal of 91.4%. The surface groups and the Ce loaded on AC were the initiator for the rapid generation of ·OH. Electron transfer between electron-rich structures and cerium oxide might be a synergistic effect that can increase catalytic activity of Ce loaded on AC. Catalytic ozonation with Ce/AC is a promising ROC treatment technology due to its efficiency and possibilities for improvement.

Aluminium and cerium co-doped ZnO nanoparticles: Facile and inexpensive synthesis and visible light photocatalytic performances

Facile combustion route synthesized Al and Ce co-doped ZnO nanoparticles photocatalysts were characterized using XRD, SEM, BET, EDS, UV-visible DRS, PL, photocurrent and EIS techniques. XRD and SEM analyses identify that crystallite and particle size is reduced from 13.26 to 11.88 nm with introduction of Al and Ce into ZnO which assists inhibiting the recombination of photo generated charge carriers. UV-visible DRS spectra indicate that optical assimilation of ZnO is significantly increased to visible region (∼406 nm) and band gap reduces from 3.18 to 3.06 eV with introduction of Al and Ce co-dopants. Electrochemical impedance spectroscopy analysis under visible light illumination confirms the enhancement in visible light activity of Al and Ce co-doped ZnO nanoparticles as photocatalysts. The enhanced activity of Al and Ce co-doped ZnO photocatalyst can be ascribed to enhanced light assimilation, high surface area and efficient charge transfer process. Our results reveal that by incorporating precise amount of Al (∼2%) and Ce (∼2%) into ZnO, a highly efficient catalyst can be synthesized that have degraded almost 95% methyl orange (MO) dye in just 45 min. Further, the influence of various operational parameters such as solution pH, catalyst dose, dye concentration, airflow rate and light intensity on photodecomposition of MO was evaluated. Furthermore, a possible mechanism for Al and Ce modified ZnO was proposed and designed photocatalysts demonstrates good stability in aqueous medium.

Magnetic and antibacterial studies of sol-gel dip coated Ce doped TiO2 thin films: Influence of Ce contents

Ce-doped TiO2 thin films were synthesized by sol-gel dip coating route to evaluate the effect of Ce doping percentage on properties of TiO2. X-ray diffraction spectra revealed both anatase and brookite phases, and Ce doping favours the anatase–brookite transformation of TiO2 films. The optical constants of the thin films were achieved by evaluating spectroscopic UV-VIS-NIR spectrophotometry data. The band gap of the Ce doped TiO2 was reduced from ~3.93 eV to ~3.79 eV with an increase in Ce doping percentage. All films have shown ferromagnetic behaviors which increase with the increase in Ce content due to enhancement in the bound magnetic polaron. Higher Ce doping increases the oxygen vacancies and saturation magnetization. Boost magnetic properties stem from the generation of the interaction between the Ce ion and an oxygen vacancy. The study showed that the antimicrobial activity of Ce doped TiO2 is ineffective. Hence doping of Ce can modify the properties of TiO2 and are used in LEDs, magneto-optical devices and solar cells.

Surface Functionalization of Metal-Organic Framework Prior to TiO2 Tethering for Oxygen Reduction Catalysis in Alkaline Media

Oxygen reduction reaction (ORR) is one of the most studied reactions for clean energy devices such as fuel cells and metal-air batteries due to its intrinsically sluggish kinetics which often limits device performance. Non-precious transmission metal oxides (TMO) such as Fe3O4, MnOx and Co3O4[1] have been intensively probed as alternatives to platinum-based catalysts. To supplement low electronic conductivity of TMOs, they are often dispersed on a highly conductive carbon nanostructure with a large surface area, maximizing catalytically active sites per volume and mass. We employ a hybrid structure where both cobalt and cerium nitrate salts with a ligand called [1,1’-Biphenyl]-4,4’-dicarboxylic acid create an MOF (MOF-Ce-Co) with extreme surface area and excellent electronic conductivity using the hydrothermal process and pyrolysis. While this structure is conductive, its conductivity can be improved with the functionalization of cerium particles. Specifically, Ce(IV) complexes have been reported to show superior rates of phosphonate ester bond cleavage compared to other metal oxides. The unprecedented activity of Ce(IV) has been attributed to the role of the Ce(IV) 4f orbitals that can mix with the orbitals of the P=O bond to form hybrid orbitals[2]. To functionalize cerium, phosphoric acid is used to bind a phosphate group onto cerium oxide. This gives rise to a penta-coordinate intermediate that is susceptible to a nucleophilic attack[2]. The treated MOF-Ce-Co is then hydrothermally reacted (at 160 ºC for 24 h) with the precursor P25, thus creating MOF-Ce-Co with TiO2 attached. Results have indicated that phosphate groups not only absorb cerium nanoparticles, but TiO2 thus resulting in enhance performance in terms of current density, and onset/half-wave potential as seen in both CV and LSV data. FT-IR results indicate that an absorption of 1040 cm-1 (corresponding to a phosphate group) appeared once MOF-Ce-Co was treated with phosphoric acid. An X-ray analysis showed that both samples (MOF-Ce-Co and MOF-Ce-Co with TiO2) had cerium and cobalt particles, however, MOF-Ce-Co with TiO2 had an additional peak at 56º, indicating that presence of TiO2 (Anatase). Hence, the improved performance of the treated MOF is the result from functionalization. This project was funded by NASA Advanced STEM Training and Research (ASTAR) Fellowship.

Microstructural properties and antibacterial activity of Ce doped NiO through chemical method

The nickel oxide and different concentration of Cerium ions (0.01 M, 0.02 M and 0.03 M) doped NiO nanoparticles (NPs) were synthesized by chemical method. The XRD spectra exhibited the cubic structure of NiO. The average crystalline sizes were observed as 43 nm, 36 nm, 29 nm and 23 nm in NiO and Ce doped NiO NPs, respectively. The Ni (2p), O (1s) and Ce (3d) oxidation states were confirmed by XPS spectra. The FESEM image and TEM image showed the flowers with spherical nanostructure in undoped and doped NiO NPs. The Chemical compositions were identified by EDAX spectra. Metal-oxide (Ni–O) functional groups were found at 439, 435, 445 and 446 cm−1 in undoped and doped samples respectively. The optical studies were carried out using UV–Vis spectra and PL studies. Magnetization values were enhanced in Ce doped NiO NPs as compared to NiO NPs. Antibacterial activities were done by various human pathogens with using NiO and Ce doped NiO NPs.

Intentional hydrolysis to overcome the hydrolysis problem: detection of Ce(iv) by producing oxidase-like nanozymes with F.

Polyvalent metal ions are susceptible to hydrolysis, making their reproducible detection by sensors and biosensors difficult. We herein turned this disadvantage into an advantage to develop a high selectivity colorimetric method for detecting Ce(iv) by intentionally hydrolyzing it through heating, where subsequent addition of F- recovered the activity, allowing a detection limit of 3.8 μM Ce(iv).

CuS/Graphene Nanocomposite as a Transparent Conducting Oxide and Pt-Free Counter Electrode for Dye-Sensitized Solar Cells

We report a simple, low temperature and solution-processable approach to prepare a composite film of copper sulfide/graphene (CuS-G) as a transparent conducting oxide (TCO) and platinum (Pt)-free CE for Dye-Sensitized Solar Cells (DSSCs). We find that CuS with 3.3 vol% of graphene (CuS-3G) yields the highest power conversion efficiency (PCE) of 4.83%, which is about 12% higher than DSSCs based on CEs made of pristine CuS. After optimizing the graphene concentration, the PCE of the DSSC assembled with the optimized CuS-3G is comparable to that based on Pt CE. The similar performance of the CuS-3G CE compared with Pt CE is mainly attributed to the small series resistance and high electrocatalytic activity of the CuS-3G CE; this is confirmed by cyclic voltammetry and electrochemical impedance spectroscopy. These results indicate a straightforward methodology for the low cost and easy synthesis of an alternative CE in DSSCs.

Antioxidant activity and potential of Caesalpinia sappan aqueous extract on synthesis of silver nanoparticles.

The aim of this study was to investigate the antioxidant activity of Caesalpinia sappan aqueous extract (CE) and its potential on synthesis of silver nanoparticles (AgNPs). The antioxidant activity of CE was investigated using ferric reducing antioxidant power (FRAP) assay and two radical scavenging methods using 2,20-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) as free radicals. Silver nitrate (AgNO3) was used as precursor for the synthesis of AgNPs. Effects of AgNO3 concentration, reaction temperature, and duration of reaction were investigated. The obtained AgNPs was characterized using UV-Vis and photon correlation spectrophotometers. The antimicrobial activity of AgNPs was studied by means of diffusion method. The results from FRAP demonstrated that CE had high reducing property of 78.7 ± 2.4 mM Fe2+/mg. The trolox equivalent antioxidant capacity of CE determined by ABTS was 64.8 ± 4.2 µM/mg. The concentration of CE that can inhibit 50% of DPPH radicals (IC50) was 51.2 ± 3.2 µM. These results indicated that CE possesses strong antioxidant and reducing activities. The present study also showed that CE can act as reducing agent to produce AgNPs. The concentration of AgNO3, reaction temperature, and reaction time play an important role on the particles size and zeta potential of the obtained AgNPs. The antimicrobial activity of the AgNPs against Escherichia coli, Candida albicans, and Streptococcus mutants was stronger than against Staphylococcus aureus.

Characterization of Ce-Bi intermetallic compound formations by electrolytic reduction in molten LiCl-KCl eutectic

The intermetallic compound formations of Ce-Bi on an inert W electrode in the molten LiCl-KCl eutectic with CeCl3 and BiCl3 for an electrolytic reduction process was investigated with various electrochemical techniques of cyclic voltammetry, square wave voltammetry, and open circuit chronopotentiometry. The electrochemical reduction of Ce3+ on the inert electrode at 773 K was observed at more positive potential with Bi3+ than that without Bi3+ due to lowering activity of Ce by intermetallic compound formations. Cyclic voltammogram and square wave voltammogram exhibited four reduction peaks with overlapping signals. Application of peak separation technique allow five intermetallic compounds of BiCe1/2, BiCe, BiCe4/3, BiCe5/3, BiCe2 to be determined. Intermetallic compound formations of Ce-Bi were confirmed with open circuit chronopotentiogram which exhibited five plateau corresponding to a state in which two phases of intermetallic compounds coexist on the electrode surface. Analysis of cyclic voltammograms according to molar ratio of Bi to Ce showed that the amount of CeBi2 and CeBi at the reduction potential above −1.5 V were increased at the higher molar ratio of Bi to Ce. The experimental results indicated that intermetallic compounds of Ce-Bi could be formed on the inert electrode in LiCl-KCl-CeCl3-BiCl3 melt by electrolytic reduction and the type and amount of the resulting intermetallic compound on the inert electrode by electrolytic reduction could be varied depending on the applied potential and molar ratio of Bi to Ce, respectively.