Strontium silicate (Sr2SiO4) samples doped with varying Eu3+content were prepared via sol–gel route and characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron ...microscopy (SEM), dynamic light scattering (DLS) and photoluminescence (PL) techniques. The synthesis temperature could be brought down to 600°C for formation of a singe phase sample. The concentration of the dopant ion and the temperature of annealing were optimized for maximum PL intensity. The critical energy-transfer distance for the Eu3+ ions was evaluated based on which the quenching mechanism was verified to be a multipole–multipole interaction. Based on the time-resolved emission data (TRES), it was inferred that, two different types of Eu3+ ions were present in the matrix. The first type was a long lived species (τ=4.7ms) present at 10-coordinated ‘Sr’sites and the other was a short lived species (τ=1.2ms) present at the 9-coordinated ‘Sr’sites which gets selectively excited at 296nm. Judd–Ofelt (J–O) intensity parameters for both the species were evaluated. The trend observed for the two species in the J–O parameters, Ω2 and Ω4 were different confirming their existence in two different environments. The color coordinates of the system were evaluated and plotted on a CIE index diagram. Commercial utility of the phosphor was investigated by comparing it with commercial red phosphor.
► Characterization of Eu3+:Sr2SiO4 samples by XRD, SEM, AFM and PL techniques. ► Optimization of various parameters for maximum luminescence intensity. ► Evidence for the presence of two rare-earth ion sites in the matrix. ► Evaluation of Judd–Ofelt intensity parameters for the two species. ► Evaluation of CIE indices and comparison with commercial phosphor.
•Life time spectroscopy showed the presence of two types of Dy3+.•Effect of concentration and annealing temperature on PL.•Mechanism for TSL is proposed.•Near white light emitting material.
Trivalent ...dysprosium-doped strontium silicate (Sr2SiO4) phosphors were prepared by sol–gel synthesis using tetra ethyl orthosilicate (TEOS) as precursor. The synthesis temperature could be brought down to 600°C for formation of a single phase sample. The material was characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), photoluminescence (PL), and thermally stimulated luminescence (TSL). The luminescence study revealed strong 4F9/2→6H13/2 transition at 577nm (yellow), strong 4F9/2→6H15/2 transition at 482nm (blue) and weak 4F9/2→6H11/2 transition at 677nm (red), when excited by 250nm (Charge transfer band, CTB) or 352nm (f–f band). The concentration of the dopant ion and the temperature of annealing were optimized for maximum PL intensity. The critical energy-transfer distance for the Dy3+ ions was evaluated based on which, the quenching mechanism was verified to be a multipole–multipole interaction. The thermally stimulated luminescence studies of Sr2SiO4:Dy3+ sample showed main TSL glow peak at 413K. The trap parameters namely activation energy (E), order of kinetics (b), and frequency factor (s) for this peak were determined using glow curve shape method.
Synthesis, X-ray diffraction and photoluminescence investigations of Eu3+-doped SrBPO5 phosphor has been carried out in order to characterize the material. PL emission spectrum of air heated ...SrBPO5:Eu3+ phosphor exhibits bands at 590, 614, 651 and 702nm under 238nm excitation, assigned to the 5D0→7FJ (J=1, 2, 3, 4) transitions of Eu3+ ions. Of these transitions, the emission centered at 614nm is the most prominent. Photoluminescence decay time and Time-resolved emission spectrometric (TRES) studies of Eu3+ were carried out with λem=614nm and λex=238nm. It suggested that Eu3+ ions are present at two different sites and predominantly occupying Sr2+ sites in the host lattice. Judd–Ofelt intensity parameters and other radiative properties were evaluated from the emission spectrum by adopting standard procedure. The trend observed in the J–O parameters (Ω2>Ω4) confirms the covalency exiting between the Eu3+ ion and ligands as well as the asymmetry around the metal ion site. The color coordinates of the system were evaluated (x=0.558 and y=0.355) and plotted on a standard CIE index diagram. The observations showed that the SrBPO5:Eu3+ phosphor is very close to the red emission material. Photoluminescence intensity was compared with that of a commercial red phosphor for commercial utility purpose. It is observed that, the photoluminescence intensity of the prepared phosphor was 60% as compared to the commercial phosphor Y2O3: Eu.
Eu3+-doped ZnAl2O4 phosphors were successfully synthesized in air atmosphere at 900°C. The phosphors were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), thermally ...stimulated luminescence (TSL) and photoluminescence (PL) techniques. The average particle size of the system as determined from SEM was found to be 100–150nm (for samples annealed at 900°C). PL spectra of the doped phosphors showed emission peaks corresponding to Eu3+ ions. Lifetime studies revealed Eu3+ ions to be in two different sites. The asymmetric ratio (I616/I592) was observed to be about 3.75. This suggested that Eu3+ ion entered the host mainly substituting Al3+ site distorting the local environment and is partly located on surface of the phosphors. A prominent glow peak at 430K was observed in the TSL of γ-irradiated Eu3+-doped ZnAl2O4 phosphors. Trap parameters for this peak have been determined and the probable mechanism for the glow peak is proposed. CIE chromaticity coordinates for the system were evaluated. It was observed that, the system could be employed as a potential red emitting phosphor. Commercial utility of the phosphor was investigated by comparing it with commercial red phosphor. The PL intensity of the as prepared phosphors was 63% of that of the commercial phosphor. Apart from this, various radiative properties such as the Judd–Ofelt intensity parameters, spontaneous emission probabilities, luminescence branching ratios, radiative lifetimes and quantum efficiency were evaluated for the system.
► Paper deals with synthesis and characterization of Eu3+-doped ZnAl2O4 phosphor. ► Apart from PL and TSL characterizations, CIE coordinates were determined. ► The Judd–Ofelt intensity parameters and quantum efficiency were evaluated. ► The system could be employed as a potential red emitting phosphor.
Breast cancer, the leading cancer type in women worldwide, is affected by reproductive and nonreproductive factors. Estrogen and progesterone influence the incidence and progression of breast cancer. ...The microbiome of the gut, a complex organ that plays a vital role in digestion and homeostasis, enhances availability of estrogen and progesterone in the host. Thus, an altered gut microbiome may influence the hormone-induced breast cancer incidence. This review describes the current understanding of the roles of gut microbiome in influencing the incidence and progression of breast cancer, with an emphasis on the microbiome-induced metabolism of estrogen and progesterone.
Microbiome has been recognized as a promising hallmark of cancer. Next-generation sequencing technologies have aided in rapid identification of components of the gut microbiome that are capable of metabolizing estrogen and progesterone. Moreover, studies have indicated a wider role of the gut microbiome in metabolizing chemotherapeutic and hormonal therapy agents and reducing their efficacy in patients with breast cancer, with a predominant effect in postmenopausal women.
The gut microbiome and variations in its composition significantly alter the incidence and therapy outcomes of patients with breast cancer. Thus, a healthy and diverse microbiome is required for better response to anticancer therapies. Finally, the review emphasizes the requirement of studies to elucidate mechanisms that may aid in improving the gut microbiome composition, and hence, survival outcomes of patients with breast cancer.
Extraction of Am super(3+) from acidic feed solutions was investigated using novel solvent systems containing a tripodal diglycolamide (T-DGA) in three room temperature ionic liquids (RTIL), viz.C ...sub(4)mimNTf sub(2 ), C sub(6)mimNTf sub(2) and C sub(8)mimNTf sub(2). Compared to the results obtained with N,N,N',N'-tetra-n-octyl diglycolamide (TODGA), T-DGA gave significantly higher distribution coefficients in these RTILs. The D sub(Am) values decreased with increasing carbon chain length in the RTILs, which was related to the solubility of the RTIL in the aqueous phase. The distribution studies included the effect of equilibration time, aqueous phase acid concentration variation and T-DGA concentration variation. In general, significantly higher equilibration times were observed for the extraction systems, which was partly due to the viscous RTIL phase and partly due to the slow conformational changes of the T-DGA ligand during complexation. Apart from Am super(3+), extraction of Pu super(4+), UO sub(2) super(2+), Eu super(3+), Sr super(2+) and Cs super(+) was also investigated, since they have significant implications in radioactive waste processing. Stripping studies indicated >99% stripping in three stages using 0.5 M EDTA or DTPA in 1 M guanidine carbonate. Slope analysis indicated the extraction of 1 : 1 complexed species of Am(iii) with T-DGA. Time resolved laser fluorescence spectroscopy (TRLFS) studies showed a strong complexation with no inner-sphere water molecules in the Eu(iii)-T-DGA complexes for C sub(4)mimNTf sub(2) as the diluent. Radiolytic degradation studies of the solvent systems containing T-DGA in the three RTILs were also carried out and while the D sub(Am) values decreased marginally when the solvents were exposed to 500 kGy absorbed dose, a relatively sharp decrease (60%) was seen when the solvents were exposed further to 1000 kGy absorbed dose, suggesting the possibility of recycling. Extraction studies were also carried out at varying temperatures and the thermodynamic parameters were calculated.
SrZrO
3
:Eu
3+
nanoparticles with a size of about 100 nm were synthesized by a simple gel combustion route and characterized by X-ray diffraction, scanning electron microscopy, dynamic light ...scattering, and photoluminescence techniques. Based on the time-resolved emission data, it was inferred that three different types of Eu
3+
ions were present in the matrix. The first type was a long-lived species (~τ = 6.0 ms) present at symmetric “Sr
2+
” sites, observed for excitations at 229 and 393 nm. The second was a short-lived species (τ = 1.0 ms) observed for excitations at 229, 296, and 393 nm, while for 296-nm excitation, a long-lived species (τ = 4.0 ms) was also observed. This suggested that Eu
3+
ions can be present at relatively lower symmetric “Zr
4+
” sites with two different environments, which differ in the presence of charge-compensating defects. The color coordinates of the system were evaluated and plotted on a CIE index diagram.
Context: Infection control is an important concept in the present day practice of dentistry. Disinfection of dental impressions is part of the daily routine in a dental clinics. After disinfection, ...it is important that impressions remain dimensionally stable. Aim: The purpose of this study was to compare the effect of chemical disinfectants and ultraviolet (UV) disinfection on the dimensional stability of the polyvinyl siloxane impressions. Objectives: The objective of the study is (1) To evaluate the effect of chemical disinfectant (2% glutaraldehyde and 1% sodium hypochlorite) and UV disinfectant on the dimensional stability of polyvinyl siloxane impression material. (2) Comparative evaluation of the dimensional discrepancy between the cast poured from the polyvinyl impressions material, that is subjected to chemical disinfectant and UV disinfectant to that of cast poured from impressions that were nondisinfected. Materials and Methods: A customized tray was fabricated to make impressions. Impressions were divided into four groups, 10 samples were disinfected with 2% glutaraldehyde for 20 min, 10 samples were disinfected with 1% sodium hypochlorite for 20 min, 10 samples were disinfected with UV light for 20 min, and 10 samples were not subjected to disinfection which served as control group. All the samples were poured after 30 min in die stone. Measurements were recorded using traveling microscope of 0.001 accuracy. Statistical analysis used in this study was the one-way ANOVA test. Results: The result showed significant dimensional changes in samples disinfected with 2% glutaraldehyde and 1% sodium hypochlorite, whereas samples disinfected with UV disinfectant unit showed no significant dimensional changes when compared with control group samples. Within the chemical groups, impressions disinfected with 1% sodium hypochlorite showed more discrepancy in the dimensions when compared to the 2% glutaraldehyde disinfected group. Conclusions: UV light disinfectant can be safely used to disinfect impressions as compared to chemical disinfectants in clinical prosthodontic procedures.
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