Effect of carbon monoxide and sulphur dioxide on the oxidation state of copper in zeolite

A study is made of the reduction and oxidation of Cu²⁺ in CuNaY zeolites by CO and SO₂, using electron spin resonance. It is observed that the Cu⁺ or Cu^o formed by the reduction of Cu²⁺ with CO can be reoxidized to Cu²⁺ by SO₂ at 400°C. SO₂ can also reduce a fraction of the Cu²⁺ sites in the Cu-exchanged zeolites. SO₂ decomposes and forms elemental S under experimental conditions on the zeolite.     

Metal clusters and nanoparticles assembled in zeolites: an example of stable materials with controllable particle size

An ion-exchangeable zeolite (mordenite) is used to control the formation of nanoparticles and clusters within the solid matrix by the hydrogen reduction of metal ions (Ag⁺, Cu²⁺, and Ni²⁺). SiO₂/Al₂O₃ molar ratio in mordenite appears to be an efficient tool to manage the reducibility of the metal ions. Few-atomic silver clusters in line with the larger silver nanoparticles were observed with DRS for the reduced Ag⁺-exchanged mordenites. Cu²⁺-exchanged ones produce the copper nanoparticles with different optical appearance, and Ni²⁺-exchanged mordenites are reduced up to complicated species with no explicit assignment of metal particles under the conditions studied.     

Influence of platinum, antimony and iron ions on coloration of alkali-borosilicate optical glass

We studied influence of platinum, antimony and iron ions on the coloration of alkali-borosilicate glass. The optical transmittances of glass specimens with and without antimony were compared, and the cause of absorption in antimony-free glass was studied. It was found in antimony-free glass that a small amount of dissolved Pt²⁺ on the ppm order causes strong absorption at approximately 360 nm resulting in a yellowish color. This absorption was not observed in the specimens melted at temperatures below 1150 °C, or in the colorless specimens containing antimony or iron. It was indicated, in the colorless specimens that platinum exist as Pt⁴⁺, the absorption of which occurs in the UV region. The oxidation state of platinum ions was strongly affected by melting temperature or coexisting multivalent ions such as antimony or iron ions, which act as an oxidant of platinum ions. Keeping the melting temperature low and employing appropriate oxidant ions are effective means of designing colorless antimony-free optical glass.     

129Xe n.m.r. of Y3+-, La3+-, and Ce3+-exchanged X zeolites

The ¹²⁹Xe n.m.r. spectrum of adsorbed xenon has been used to locate the Y³⁺, Ce³⁺, and La³⁺ ions that are exchanged into NaX zeolite. The chemical shift of xenon adsorbed on yttrium-X zeolite follows a concave plot against the adsorbed xenon concentration, very similar to the previous ¹²⁹Xe n.m.r. study of Mg²⁺, Ca²⁺, and Ni²⁺ in Y zeolites. This result suggests strong adsorption of xenon on the Y³⁺ ion located inside the zeolite supercage. In contrast, the ¹²⁹Xe n.m.r. chemical shift for the CeX and LaX zeolites indicates that the cations are located in hexagonal prisms or sodalite cages inaccessible to the xenon atoms. The example of the Y³⁺ cation proves that not all trivalent cations migrate outside the supercages during thermal treatment of the solid.     

Photoactivated Trifunctional Platinum Nanobiotics for Precise Synergism of Multiple Antibacterial Modes

Integrating multiple strategies of antibacterial mechanisms into one has been proven to have tremendous promise for improving antimicrobial efficiency. Hence, dual‐valent platinum nanoparticles (dvPtNPs) with a zero‐valent platinum core (Pt⁰) and bi‐valent platinum shell (Pt²⁺ ions), combining photothermal and photodynamic therapy, together with “chemotherapy,” emerge as spatiotemporally light‐activatable platinum nano‐antibiotics. Under near‐infrared (NIR) exposure, the multiple antibacterial modes of dvPtNPs are triggered. The Pt⁰ core reveals significant hyperthermia via effective photothermal conversion while an immediate release of chemotherapeutic Pt²⁺ ions occurs through hyperthermia‐initiated destabilization of metallic interactions, together with reactive oxygen species (ROS) level increase, thereby resulting in synergistic antibacterial effects. The precise cooperative effects between photothermal, photodynamic, and Pt²⁺ antibacterial effects are achieved on both Gram‐negative Escherichia coli and Gram‐positive methicillin‐resistant Staphylococcus aureus, where bacterial viability and colony‐forming units are significantly reduced. Moreover, similar results are observed in mice subcutaneous abscess models. Significantly, after NIR treatment, dvPtNP exhibits a more robust bacteria‐killing efficiency than other PtNP groups, owing to its integration of dramatic damage to the bacterial membrane and DNA, and alteration to ATP and ROS metabolism. This study broadens the avenues for designing and synthesizing antibacterial materials with higher efficiency.     

Preparation and characterization of zeolite framework stabilized cuprous oxide nanoparticles

Zeolite framework stabilized copper(I) oxide nanoparticles (4.8 ± 2.6 nm) were prepared for the first time by using a four step procedure: the ion exchange of Cu²⁺ ions with the extra framework Na⁺ ions in Zeolite-Y, the reduction of the Cu²⁺ ions within the cavities of zeolite with sodium borohydride in aqueous solution, the dehydration of Zeolite-Y with the copper(0) nanoclusters, and the oxidation of intrazeolite copper(0) nanoclusters by O₂ at room temperature. Zeolite stabilized copper(I) oxide nanoparticles were thoroughly characterized by ICP-OES, XRD, HR-TEM, Raman, XPS, UV-vis spectroscopy and N₂ adsorption-desorption technique.     

Structural and luminescence study of Ce3+ and Tb3+ doped Ca3Sc2Si3O12 garnets obtained by freeze-drying synthesis method

Ca₃Sc₂Si₃O₁₂ garnets doped with Ce³⁺ and Tb³⁺ ions were synthesized by a freeze-drying precursor method. The structural characterization was performed by X-ray diffraction (XRD) and Raman spectroscopy. Scanning Electron Microscopy (SEM) images of the calcined material were studied. High temperature treatments and doping with RE³⁺ ions resulted in a reduction of the secondary phases (Sc₂O₃) and an increase of the mean size of the nanocrystals, from 75 to 149 nm. These effects were confirmed by means of Raman spectra. Moreover, luminescence features of Ce³⁺ and Tb³⁺ doped samples indicated that these ions are effectively incorporated into the crystalline phase. In addition, the energy transfer processes between Ce³⁺ and Tb³⁺ ions in codoped garnets have been studied.     

Structural and luminescent properties of cerium-ion doped barium borophosphates

The effects of synthesis conditions on the luminescence characteristics of Ce³⁺ in barium borophosphate phosphors are investigated in the present study. Synthesis of cerium-ion doped BaBPO₅ in the oxidizing atmosphere results in partial reduction of Ce⁴⁺ to Ce³⁺. The dominant emission at 320 nm arises due to Ce³⁺ located at Ba²⁺ sites without local charge compensation; while, the relatively weak emission at 380 nm is ascribed to Ce³⁺ substituting at Ba²⁺ sites in association with charge compensatory vacancy. The complete reduction of Ce⁴⁺ to Ce³⁺ occurs for the samples heated in the reducing atmosphere. The increased luminescence of BaBPO₅ codoped with cerium and sodium ions is attributed to the reduction in non-radiative energy transfer.     

Palladium-enhanced reducibility of nickel in NaY

The presence of palladium has been found to strongly enhance the reducibility of nickel in NaY. Pretreatment conditions have a pronounced effect on the temperature-programmed reduction (t.p.r.) profiles of monometallic and bimetallic palladium/nickel catalysts. At high pH, Ni is hydrolyzed in supercages; at low pH, Ni²⁺ ions migrate to smaller cages. Reduced Pd particles in the supercages, in close contact with NiO clusters, enhance their reducibility; the protons formed during Pd reduction, however, redisperse them to form Ni²⁺ ions, thus decreasing their reducibility. Two mechanisms are thought to contribute to the Pd-enhanced reduction of Ni²⁺ ions. One involves the formation of NiPd ion pairs in the small cages; the other requires migration of Ni²⁺ ions out of small cages to interact with reduced Pd particles in supercages.     

Catalyst preparation through ion-exchange of zeolite Cu-, Ni-, Pd-, CuNi- and CuPd-ZSM-5

Ion-exchanged zeolite ZSM-5 is the best known catalyst for direct NO_x decomposition and a viable candidate for NO_x reduction with methane. The preparation is crucial for the efficiency of the conversion and this paper describes the ion-exchange, with Cu²⁺, Ni²⁺ or Pd²⁺, and the dual exchange, with Cu²⁺/Ni²⁺ or Cu²⁺/Pd²⁺, under appropriate pH and ion concentrations for maximum dispersion.     

Down-shifting in Ce3+–Tb3+ co-doped SiO2–LaF3 nano-glass–ceramics for photon conversion in solar cells

95SiO₂–5LaF₃ sol–gel derived nano-glass–ceramics single doped with Ce³⁺ or Tb³⁺ and co-doped with Ce³⁺–Tb³⁺ were synthesized by thermal treatment of precursor glasses. Precipitation of LaF₃ nanocrystals during ceramming process was confirmed by X-ray diffraction with mean size ranging from 12 to 15 nm. An exhaustive spectroscopic analysis has been carried out. As a result, it was found that the green emission of Tb³⁺ ions was greatly enhanced through down shifting process, due to efficient energy transfer from Ce³⁺ to Tb³⁺ ions in the glass–ceramics, which is favored by the reduction of the interionic distances when the dopant ions are partitioned into LaF₃ nanocrystals. These results suggest the use of these materials to improve the efficiency of solar cells.     

Luminescence response and CL degradation of combustion synthesized spherical SiO2:Ce nanophosphor

This study was aimed to systematically investigate the luminescence response of SiO₂:Ce³⁺ nanophosphors with different excitation sources. The powders were synthesized by using an urea assisted combustion method. SiO₂:Ce_1m% samples were also annealed at 1000 °C for 1 h in a charcoal environment to reduce incidental Ce⁴⁺ to partial Ce³⁺ ions. High resolution transmission electron microscopy (HRTEM) images of the as synthesized and annealed powder samples confirmed that the particles were spherical and in the size range of 3-8 nm in diameter. X-ray diffraction (XRD) and electron dispersion spectroscopy (EDS) results showed that the SiO₂ was crystalline and pure. Diffused reflectance, photoluminescence (PL) and cathodoluminescence (CL) results of the SiO₂:Ce³⁺ samples were obtained and compared with each other. The CL degradation and the surface reactions on the surface of the SiO₂:Ce³⁺ were studied with X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). A clear improvement in the chemical stability of the SiO₂:Ce³⁺ annealed at 1000 °C were obtained.     

Ceo2/Cus Nanoplates Electroreduce Co2 to Ethanol with Stabilized Cu+ Species

Copper-based electrocatalysts effectively produce multicarbon (C₂₊) compounds during the electrochemical CO₂ reduction (CO₂RR). However, big challenges still remain because of the chemically unstable active sites. Here, cerium is used as a self-sacrificing agent to stabilize the Cu⁺ of CuS, due to the facile Ce³⁺/Ce⁴⁺ redox. CeO₂-modified CuS nanoplates achieve high ethanol selectivity, with FE up to 54% and FE_C2+ ≈ 75% in a flow cell. Moreover, in situ Raman spectroscopy and in situ Fourier-transform infrared spectroscopy indicate that the stable Cu⁺ species promote C C coupling step under CO₂RR. Density functional theory calculations further reveal that the stronger ^*CO adsorption and lower C C coupling energy, which is conducive to the selective generation of ethanol products. This work provides a facile strategy to convert CO₂ into ethanol by retaining Cu⁺ species.     

Photoluminescence and energy transfer of terbium doped titania film

Strong visible luminescence of Tb³⁺ions due to intra-4f shell transitions are obtained from Tb³⁺-doped titania (TiO₂) films fabricated by sol-gel method. Based on the overlap of excitation band of Tb³⁺-doped TiO₂ and absorption band of undoped TiO₂, we propose an energy transfer mechanism from TiO₂ host to Tb³⁺ions. Photoluminescence (PL) intensity is found to have a well matching relation with the doping concentration of Tb³⁺ ions. Concentration quenching of PL occurs when Tb³⁺ concentration exceeds a certain value (9.5 mol%). Luminescence intensity is improved obviously after co-doped with Ce³⁺ ions because of the sensitization effect of Ce³⁺ ions and the dispersion of Tb³⁺ ions in TiO₂ system.     

Microstructural investigation of Cu2+ doped nanohydroxyapatites

Abstract

Pure and Cu²⁺ doped nanohydroxyapatites were synthesised by a precipitation method to investigate the effect of Cu²⁺ ions on the structure of hydroxyapatite (HA) and its thermal stability after the air sintering at 1100°C. A small amount of CaO was observed in the Cu²⁺ doped HAs after the X-ray diffraction results. The addition of Cu²⁺ changed the hexagonal lattice parameters of the HA and resulted in smaller grain size after sintering at 1100°C. The addition of Cu²⁺ ions into HA resulted in smaller grain sizes (between 282 and 248 nm).     

On the relationship between emission color and Ce3+ concentration in garnet phosphors

It is known that the emission color of Ce³⁺ doped garnets is strongly redshifted at higher Ce³⁺ concentrations. In this report, we study the cause of this redshift in Lu₃Al₅O₁₂:Ce³⁺ (LuAG:Ce) phosphors. These changes in emission color with Ce³⁺ concentration are mainly attributed to a combination of inhomogenous broadening for Ce³⁺ in LuAG and energy transfer from high energy Ce³⁺ ions to low energy Ce³⁺ ions. Evidence for inhomogenous broadening and energy transfer is given through time resolved measurements. Potential reasons for inhomogenous broadening of Ce³⁺ in these phosphors are also discussed.     

Growth and optical properties of (Yb3−xYx)Al5O12:Ce single crystals

To improve the infrared emission of Yb³⁺ ions doped in the garnet host Y₃Al₅O₁₂ (YAG) single crystal through the energy transfer from Ce³⁺ to Yb³⁺ ions, the 〈1 1 1〉-oriented YAG:Ce³⁺, YAG:Yb³⁺, YAG:(Ce³⁺, Yb³⁺) and Yb₃Al₅O₁₂:Ce³⁺ (YbAG:Ce³⁺) single crystals were grown using the Czochralski Method, respectively. The excitation and emission spectra of these garnet single crystals were characterized. In YAG:Ce³⁺ crystal, the yellow emission of Ce³⁺ ions present, but it was completely extinguished in YAG:(Ce³⁺, Yb³⁺) crystal and YbAG:Ce³⁺ crystal. However, the characteristic absorption bands of Ce³⁺ still existed in the excitation spectrum of Yb³⁺ ions, which showed that the energy absorbed by Ce³⁺ ions can be transferred to Yb³⁺ ions for its infrared emission.     

Scintillation and luminescent properties of undoped and Ce3+ doped Y2SiO5 and Lu2SiO5 single crystalline films grown by LPE method

Single crystalline films (SCFs) of undoped and Ce³⁺ doped Y₂SiO₅ (YSO) and Lu₂SiO₅ (LSO) orthosilicates were crystallized for the first time by liquid phase epitaxy method onto undoped YSO substrates from melt-solution based on PbO–B₂O₃ flux. The scintillation and luminescent properties of YSO:Ce and LSO:Ce SCFs were compared with the properties of bulk single crystal counterparts. We show that the peculiarities of luminescent properties of YSO:Ce and LSO:Ce SCFs in comparison with the crystal analogues are caused by the different distribution of Ce³⁺ ions over Y1/Lu1 and Y2/Lu2 positions of YSO and LSO host and strong influence of Pb²⁺ flux-related impurity on luminescent properties of Ce³⁺ ions.     

Comparative and competitive adsorption of cadmium, copper, nickel, and lead ions by Iranian natural zeolite

The competitive adsorption behavior of cadmium (Cd²⁺), copper (Cu²⁺), nickel (Ni²⁺), and lead (Pb²⁺) ions using Iranian natural zeolite has been studied in order to determine its applicability in treating industrial wastewater. Tests to determine both the rate of adsorption and the uptake at equilibrium were performed under batch conditions from single- and multi-component solutions. The optimum conditions for the treatment process were investigated by observing the influence of pH levels, the presence of competing ions, varying the mass of zeolite and different contact time. Adsorption kinetics of the zeolite followed first-order kinetics, showing about 100 % of Pb²⁺ removal within 40 min and reaching an equilibrium state within 24 h for Cd²⁺, Cu²⁺, and Ni²⁺. The results indicated that removal of metals from single- and multi-component solutions is best described by a Freundlich isotherm, in which the distribution coefficient was in the following order: Pb²⁺ > Cu²⁺ > Cd²⁺ > Ni²⁺. In the multi-component solutions, metals exhibit competitive adsorption on the zeolite. The adsorption is reduced to 90, 53, 30, and 22 % of single component of Cu²⁺, Ni²⁺, Cd²⁺, and Pb²⁺, respectively. However, the total adsorption was higher than single component. Finally, soil solution saturation indices and speciation of metals was assessed using Visual MINTEQ 2.6 software, and probability of precipitation of minerals supported by scanning electron microscopy. The research indicates that Cd²⁺ and Ni²⁺ retention by zeolite can be viewed as the result of ion exchange reaction, but Pb²⁺ and Cu²⁺ retention is both due to ion exchange and precipitation. These results show that Iranian natural zeolite particularly effective in removing cationic heavy metal species from industrial wastewater.     

Synthesis of Ce4+ ions doped ZnO electrode as a sensor for hydrogen peroxide

Ce⁴⁺ ions doped ZnO nanoparticles were synthesized by the simple chemical precipitation method with different levels of cerium. The synthesized products were analyzed for X-ray diffraction and photoluminescence measurements. The morphology of the optimum level of Ce⁴⁺ doped ZnO was studied by high resolution transmission electron microscopy analysis. To ascertain the sensor activity of Ce⁴⁺ doped ZnO, the electrocatalytic response to the reduction of H₂O₂ was studied with ZnO and ZnO: Ce⁴⁺ electrodes. Fabricated ZnO: Ce⁴⁺ sensor displays excellent performance towards the detection of H₂O₂ than bare ZnO.