Fabrication and optical features of the sol–gel derived silica glasses doped with copper oxide nanoparticles and europium

Novel sol–gel derived silica glasses doped with copper oxide nanoparticles and europium ions have been fabricated in order to design a multicomponent luminescent material. The photoluminescence studies indicated the significant effect of copper oxide upon the light emission due to europium ions while the emission from copper oxide is similar with that due to Cu⁺. The emission of europium ions in the Cu₂O:Eu³⁺-codoped glasses can be done through excitation of copper oxide.     

Optical and EPR studies on Cu2+-doped sodium borobismuthate glasses

Heavy metal oxide glasses are becoming a good infrared (IR) transmitting windows. The optical, differential scanning calorimeter (DSC), FTIR and EPR studies of Cu²⁺-doped sodium borobismuthate glasses have been investigated. The FTIR studies show that the glassy system contains BO₃ and BO₄ units in the disordered manner. The optical studies confirm the presence of Cu²⁺ ions in the glassy network. The EPR studies show that the Cu²⁺ ions are deposited in the distorted octahedral sites elongated on the z-axis.     

Luminescent properties of Cu+/Sn2+-activated aluminophosphate glass

A robust aluminophosphate glass matrix containing substantial amounts of Cu₂O and SnO has been prepared by the melt-quenching technique, and the luminescent properties have been assessed. The as-prepared material exhibits tunable luminescence by variation of excitation wavelength, in connection with the distinct excitation/emission properties of Cu⁺ ions and twofold-coordinated Sn centers in the host. Under excitation of both Cu⁺ and Sn species at 300 nm, the co-doped material exhibits a bright whitish luminescence, whereas excitation at 360 nm produces an intense orange emission arising merely from Cu⁺ ions. Thus, white light generation is deemed realizable by combination of cool-bluish emission intrinsic to Sn centers with the warm-orange emission from Cu⁺ ions. The optical properties of the material after heat treatment have been also investigated. Results indicate the chemical reduction of ionic copper via Sn²⁺ ultimately producing Cu nanoparticles as evidenced by the surface plasmon resonance. Consequently, the excitation-wavelength dependent photoluminescence bands appear suppressed in relation to Cu⁺ basically and show a dip attributed to light reabsorption by the plasmonic Cu particles.     

A study of interaction between copper and manganese in a soda-borate glass by ESR

The ESR spectra of 30 Na₂O-70 B₂O₃ glasses, containing very low amounts of copper and manganese singly and in mixed proportions, have been studied. The copper glass shows that Cu²⁺ is present in a distorted octahedral environment. The manganese glass shows that Mn²⁺ is also present in an octahedral site possibly with some distortion. The mixed copper-manganese glasses show that both Cu²⁺ and Mn²⁺ are present with Cu⁺ and Mn³⁺, and that there is a considerable interaction between these two ions giving rise to the exchange coupled Cu²⁺-Mn²⁺ pairs. The covalency of Cu²⁺-O bonding decreases in the mixed glasses. The possibility of spin diffusion and nuclear relaxation in the Mn²⁺ site is proposed to account for the absence of the Mn²⁺ hyperfine lines in the spectra of mixed glasses. The possibility of nuclear relaxation of the Cu²⁺ site is not completely ruled out from the broadening of the hyperfine lines in the mixed glasses, as compared to that in the copper glass.     

An electron spin resonance study of copper phosphate glasses containing some rare earth oxides

The electron spin resonance spectra of phosphate glasses containing mixed Cu²⁺-Er³⁺ and Cu²⁺-Lu³⁺ oxides have been examined. A reduction in the copper (II) signal intensity in the glasses as the proportion of rare earth oxide is raised corresponds to an increase in the reduced valency ratio C in the glasses. Differences between the behaviour of glasses containing erbium and those containing lutetium are observed and probably arise from magnetic coupling between copper (II) and erbium (III).     

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).     

Spectral studies on CuO in sodium–calcium borophosphate glasses

Transparent borophosphate glasses doped with CuO were prepared by melt quenching technique. X-ray diffraction (XRD), optical and luminescence properties of sodium–calcium borophosphate glasses doped with CuO have been studied. The XRD results showed the amorphous nature of the sample. The introduction of CuO was favourable for the colour changes from light blue to dark bluish green colour. Direct optical energy bandgaps before and after doping with different percents of copper oxide obtained in the range 4.81–2.99 eV indicated the role of copper in the glassy matrix by ultraviolet (UV) spectra. The glasses have more than 80% transparency for emission wavelength range, and strong absorption bands due to the charge transition of the Cu⁺ and Cu²⁺ ions were observed. The emission bands observed in the UV and blue regions are attributed to 3d⁹4s–3d¹⁰ triplet transition in Cu⁺ ion.     

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.     

ESR of Cu2+and Tl2+ in thallium borate glasses

The electron spin resonance (ESR) and optical absorption spectra of Cu²⁺ were measured in thallium borate glasses in order to investigate the effects of glass transition temperature,T _g, upon the responses of cupric ion in alkali borate glasses. The ESR of Tl²⁺ induced by-ray irradiation was also obtained. An abrupt increase in the covalency of in-plane Cu²⁺-O-bonding was observed in the Tl₂O system as well as in the Na₂O system in a similar B₂O₃ composition range althoughT _g for the Tl₂O glasses has little dependency on the composition compared with the Na₂O glasses. The trend in the variation of the S-character of the Tl²⁺ unpaired electron with composition agreed with that of the covalency of in-plane Cu²⁺-O-bonding. The structure of the anion group present in Tl₂O glasses was also examined by laser reman spectroscopy.     

Electron spin resonance and optical absorption spectra of Cu2+ ions in Na2SO4-ZnSO4 glasses

Electron spin resonance (ESR) and optical absorption spectra of Cu²⁺ ions in Na₂SO₄-ZnSO₄ glasses have been studied. The ESR spectra of Cu²⁺ ion-doped glasses exhibited a pronounced peak atg=2.07 and a shallow quadruplet atg=2.35, the latter arising from the hyperfine splitting of g. ESR spectra of Cu²⁺ ion-doped glasses were also studied by varying the concentration of Cu²⁺ions, temperature and composition of the glasses. The optical absorption spectra exhibited a broad absorption band in the near infrared region, which is attributed to²B_1g²B_2g transition. By correlating the ESR and optical absorption data, the bonding orbital coefficients ² and ₁ ² for Cu²⁺ ions have been evaluated.     

Controlled reduction of Cu to Cu with an N,O-type chelate under hydrothermal conditions to produce Cu2O nanoparticles

N,O-type organic chelates reduced coordinated Cu²⁺ ions under hydrothermal reaction conditions to produce Cu₂O/CuO nanoparticles. Chelates in which the N and O atoms are closely spaced produced smaller amounts of CuO nanoparticles, indicating their higher ability to reduce Cu²⁺ ions to Cu⁺ ions. [Cu(Gly)₂]² with the shortest ligand chain length produced only Cu₂O nanoparticles and, therefore, can be used as a single molecule precursor for the synthesis of Cu₂O nanoparticles.     

Spectral analysis of Cu<Superscript>2+</Superscript> and Mn<Superscript>2+</Superscript> ions doped borofluorophosphate glasses

We report here on the development and spectral analysis of Cu²⁺ (0.5 mol%) and Mn²⁺ (0.5 mol%) ions doped in two new series of glasses. The visible absorption spectra of Cu²⁺ and Mn²⁺ glasses have shown broad absorption bands at 820 nm and 495 nm, respectively. For Cu²⁺ BFP glasses, excitation at 380 nm, a blue emission at 441 nm and also a weak emission at 418 nm ions have been observed. For Mn²⁺ ions doped BFP glasses, excitation at 410 nm and a red shift at 605 nm emission have been observed.     

Study of valence states of copper in copper-phosphate glasses

Phosphate glasses containing CuO with composition, [(CuO) _x (P₂O₅)_1–x ], x=0.10, 0.20, 0.25, 0.30, 0.40 and 0.50, were studied by magnetization, X-ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectrometry (RBS). It was observed that compositional changes take place in going from batch to glass and these changes are more pronounced for low copper concentration. The ratio [Cu²⁺/Cu_total] as a function of x was determined from XPS and magnetization combined with RBS. The magnetization measurements suggest that more than 90% of the copper ions exist in the Cu²⁺ state in the glasses, while the XPS data show that less than 50% of the copper ions may be in the Cu²⁺ state. The low Cu²⁺ states detected by XPS may have resulted form reduction of copper ions upon exposure of the samples to X-ray radiation during measurement.Author to whom all correspondence should be addressed.     

Photo-Induced Construction and Recovery of Cu+ Sites in Metal–Organic Frameworks

The adjustment of the valence state of metal ions is crucial for various applications because peculiar activity originates from metal ions with specific valence. Cu⁺ can interact with molecules possessing unsaturated bonds like CO via π-complexation, while Cu²⁺ doesn't have such ability. Meanwhile, Cu⁺ sites are easily oxidized to Cu²⁺, leading to the loss of activity. Despite great efforts, the development of a facile method to construct and recover Cu⁺ sites remains a pronounced challenge. Here, for the first time a facile photo-induced strategy is reported to fabricate Cu⁺ sites in metal–organic frameworks (MOFs) and recover Cu⁺ after oxidation. The Cu²⁺ precursor was loaded on NH₂-MIL-125, a typical visible-light responsive Ti-based MOF. Visible light irradiation triggers the formation of Ti³⁺ from Ti⁴⁺ in framework, which reduces the supported Cu²⁺ in the absence of any additional reducing agent, thus simplifying the process for Cu⁺ generation significantly. Due to π-complexation interaction, the presence of Cu⁺ results in remarkably enhanced CO capture capacity (1.16 mmol g⁻¹) compared to NH₂-MIL-125 (0.49 mmol g⁻¹). More importantly, Cu⁺ can be recovered conveniently via re-irradiation when it is oxidized to Cu²⁺, and the oxidation-recovery process is reversible.     

Electrochemical polymerization of benzene in the presence of Ag+, Pb2+ and Cu+ ions

Poly(p-phenylene) (PPP) films were synthesized by using benzene and fluorosulphonic acid (FSO₃H) as a strong acid containing Ag⁺, Pb²⁺ and Cu⁺ ions in methylene chloride (CH₂Cl₂) solution. Addition of Ag⁺ or Pb²⁺ ions into the polymerization medium improved the PPP films formation, but Cu⁺ ion did not have an effect on polymerization. PPP films were characterized by cyclic voltammetry, IR and TGA. Dry conductivities were measured by using four probe technique. Received: 18 September 2000 / Reviewed and accepted: 20 September 2000     

Spectroscopic properties of CuO, SnO, and Dy2O3 co-doped phosphate glass: from luminescent material to plasmonic nanocomposite

Prospective applications of noble metal and rare-earth co-doped dielectrics in optical devices demand for a comprehensive understanding of the influence of material composition and processing on resulting properties. In this study, we report on the spectroscopic properties of a 50P₂O₅:50BaO glass matrix containing copper, tin, and dysprosium prepared by melting and subsequently subjected to heat treatment (HT). An achievement in terms of material preparation is that addition of stoichiometric amounts of CuO and SnO dopants along with the source of Dy³⁺ ions (Dy₂O₃) is shown effective for the precipitation of Cu nanoparticles (NPs) during HT. Optical absorption and photoluminescence (PL) spectroscopy including emission decay dynamics are employed in the characterization of the co-doped material as prepared, and as a function of HT. The basic structure of the phosphate host is assessed by ³¹P nuclear magnetic resonance spectroscopy. The optical data suggests the presence of both Cu²⁺ and Cu⁺ ions in the melt-quenched co-doped glass together with the Dy³⁺ ions. Thermal processing is indicated to result in the chemical reduction of ionic copper species via Sn²⁺ and ultimately produces the non-luminescent plasmonic Cu particles. The presence of such NPs is also observed to produce a quenching effect on Dy³⁺ PL, interpreted in terms of an ion-to-particle excitation energy transfer operating via interband transitions in the nanoscale metal. Thus, the glass may act as either a luminescent material or a plasmonic nanocomposite desirable for nonlinear optics dependent upon its thermal history.     

Optical absorption,P NMR,and photoluminescence spectroscopy study of copper and tin co-doped barium–phosphate glasses

The optical and structural properties of 50P₂O₅:50BaO glasses prepared by melting have been investigated for additive concentrations of 10 and 1 mol% of CuO and SnO dopants. Absorption and photoluminescence spectroscopies were employed in the optical characterization, whereas structural properties were assessed by ³¹P nuclear magnetic resonance (NMR) spectroscopy. Residual Cu²⁺ was detectable by absorption spectroscopy for the highest concentration of CuO and SnO. More prominently, the optical data suggests contributions from both twofold-coordinated Sn centers and Cu⁺ ions to light absorption and emission in the glasses. The luminescence depends strongly on excitation wavelength for the highest concentration of dopants where a blue–white emission is observed under short-wavelength excitation (e.g., 260 nm) largely due to tin, while an orange luminescence is exhibited for longer excitation wavelengths (e.g., 360 nm) essentially due to Cu⁺ ions. On the other hand, dissimilar luminescent properties were observed in connection to Cu⁺ ions for the lowest concentration studied, as the copper ions were preferentially excited in a narrower range at shorter wavelengths near tin centers absorption. The structural analyses revealed the glass matrix to be composed essentially of Q² (two bridging oxygens) and Q¹ (one bridging oxygen) phosphate tetrahedra. A slight increase in the Q¹/Q² ratio reflected upon SnO doping alone suggests a major incorporation of tin into the glass network via P–O–Sn bonds, compatible with the 2-coordinated state attributed to the luminescent Sn centers. However, a significant increase in the Q¹/Q² ratio was indicated with the incorporation of copper at the highest concentration, consistent with a key role of the metal ions as network modifiers. Thus, the change in Cu⁺ optical properties concurs with different distributions of local environments around the ions induced by variation in metal ion concentration. Luminescence decay curve analyses were found in agreement with the presence of Cu⁺ ions in the glasses suggesting their existence in tetragonally-distorted octahedral sites.     

Release of Cu2+ from a copper-filled TiO2 coating in a rabbit model for total knee arthroplasty

The aim of this study was the investigation of a copper-filled TiO₂ coating, that in vitro showed good antibacterial properties combined with good tissue tolerance in an animal model. To better understand the antibacterial mechanism of the bioactive coating the release of copper (Cu) ions over time was monitored to be able to detect possible threats as well as possible fields of application. 30 New Zealand White rabbits were divided into two groups with 15 animals per group. In group 1 (control group) Ti6Al4 V bolts were implanted into the distal femur, in group 2 the Ti6Al4 V bolts were coated with four TiO₂-coatings with integrated Cu²⁺-ions (4 × Cu–TiO₂). Blood tests were performed weekly until the animals were sacrificed 4 weeks postoperative. The maximum peak of Cu and ceruloplasmin concentration could be seen in both groups one week postoperative, whereas the Cu values in group II were significantly higher. The Cu concentration in both groups approximated the initial basic values 4 weeks postoperative. The 4 × Cu–TiO₂ coating tested in our rabbit model for total knee arthroplasty is an active coating that releases potentially antibacterial Cu²⁺ for 4 weeks with a peak 1 week postoperative. The bioactive coating could be a promising approach for a use in the field of implant related infection, orthopaedic revision and tumor surgery in the future.     

Highly efficient fluorescence probe for copper (II) ions based on gold nanoclusters supported on wool keratin

A highly efficient fluorescence gold nanoclusters probe for copper (II) (Cu²⁺) ions among various ions has been prepared through wool keratin as chelating and reducing agent. The main features of fluorescent gold nanoclusters supported on wool keratin (AuNCs@WK) probe are the high fluorescence in aqueous solution, the simplicity of synthesis and the hypotoxicity for living cells. The fluorescence probe exhibits high stability of pHs and shows more sensitivity under acidic condition. Upon exposure to various metal irons, only AuNCs@WK system with Cu²⁺ ions shows a fluorescence turnoff response changing from red to blue under UV light, which lead to the dramatically decreased fluorescent intensity of AuNCs@WK at 690 nm. Moreover, the high sensitivity of AuNCs@WK around 1 µM meets the need of detection standards. The slope of Stern–Volmer plot at low concentration of Cu²⁺ ions is greater than it at high concentrations, which indicates the aggregated AuNCs are from small amounts to large numbers with the increasing concentration of Cu²⁺ ions. The design mechanism of AuNCs@WK probe is the coordination of reactive groups to produce the complex (wool keratin-Cu-wool keratin) at 1:2 between Cu²⁺ ions and fluorescence probe. Furthermore, the cytotoxicity in cells indicates that AuNCs@WK system is safe for the selective imaging of copper ions in living cells.     

Electron spin resonance in phosphate glasses containing mixed transition metal ions

Phosphate glasses containing mixed Cu²⁺/Ni²⁺ and Cu²⁺/Co²⁺ oxides have been examined. A pronounced decrease in the optical absorption at 830 nm due to the Cu²⁺ ions is observed as the CuO in the glasses is gradually replaced by NiO or CoO and the decrease is accompanied by a pronounced decrease in the strength of the electron spin resonance (ESR) signal at 9.52 GHz. By combining the ESR and optical absorption data it is concluded that the decrease in concentration of Cu²⁺ ions in phosphate glasses may be due to an oxidation-reduction mechanism between two valency states of the two different transition metals, of the form Cu²⁺+Ni⁺Cu⁺+Ni²⁺ and Cu²⁺+Co⁺Cu⁺+Co²⁺.