Preparation of bismuth sulfide nanoparticles as targeted biocompatible nano-radiosensitizer and carrier of methotrexate

In this study, Bi₂S₃@BSA–Bio–MTX nanoparticles (NPs) were synthesized for the first time by bovine serum albumin (BSA)-mediated biomineralization (Bi₂S₃@BSA NPs) followed by covalent bonding of biotin (Bio) and methotrexate (MTX) on the surface of the Bi₂S₃@BSA NPs via carbodiimide chemistry. The synthesized NPs were globular and exhibited uniform morphology with a hydrodynamic diameter of 107.6 ± 6.81 nm (mean ± standard deviation) and zeta potential of −20.9 ± 2.18 mV. Drug release from Bi₂S₃@BSA–Bio–MTX NPs indicated an enzyme-dependent release pattern. The in vitro biocompatibility of NPs was confirmed by investigating their cytotoxicity against the HEK-293 cell line and hemolysis assay test, whereas the in vivo biocompatibility of the NPs was evaluated and confirmed by the lethal dose 50 (LD₅₀) test. To evaluate the in vitro anticancer activity of the functionalized NPs and MTX, their cytotoxic effects was assessed against 4T1 cancer cells by 5-dimethylthiazol-z-yl)-2,5-diphenyltetrazolium bromide (MTT) assay with and without X-ray radiation. Results showed that Bi₂S₃@BSA–Bio–MTX NPs have excellent anticancer activity, especially following X-ray radiation.     

Exploring the anticancer effects of tin oxide nanoparticles synthesized by pulsed laser ablation technique against breast cancer cell line through downregulation of PI3K/AKT/mTOR signaling pathway

Tin oxide nanoparticles (SnO₂ NPs) demonstrate potential anti-cancer functions. However, the anti-cancer mechanisms of SnO₂ NPs have not been explored in detail. In the present study, we synthesized SnO₂ NPs through laser ablation technique and examined their anticancer mechanisms and the probable involvement of the PI3K/AKT mediated pathways in human breast cancer cells (MCF-7) in vitro. The synthesized SnO₂ NPs were characterized by transmission electron microcopy (TEM), dynamic light scattering (DLS), and Fourier-transform infrared spectroscopy (FTIR) techniques. Afterwards, the breast cancer cells were incubated with increasing concentrations of SnO₂ NPs, and inhibition of cell proliferation was assessed by the viability assay. Furthermore, the quantification of reactive oxygen species (ROS) and apoptosis were examined by flow cytometry followed by superoxide dismutase (SOD) and catalase (CAT) activity as well as mitochondrial membrane potential assays. The expression levels of phosphoinositide 3-kinase (PI3K), protein kinase B (AKT), mechanistic target of rapamycin (mTOR), B-cell lymphoma 2 (Bcl-2), and Bax were also assessed by western blot and quantitative real time PCR (qRT-PCR). It was shown that SnO₂ NPs, 30 nm, with potential colloidal stability selectively prevented the proliferation of MCF-7 in comparison with MCF-10A cells and triggered ROS production, apoptosis, deactivation of SOD and CAT activity, and mitigation of mitochondrial membrane potential. Moreover, SnO₂ NPs stimulated mitochondrial-mediated apoptosis pathway by overexpression of Bax/Bcl-2 and downregulation of p-PI3K/p-AKT/p-mTOR signaling pathway. This data elucidates the possible mechanisms by which SnO₂ NPs may stimulate their anticancer effects.     

Pectin mediated green synthesis of Fe3O4/Pectin nanoparticles under ultrasound condition as an anti-human colorectal carcinoma bionanocomposite

This work described the one-pot synthesis of apple pectin encapsulated Fe₃O₄ nanoparticles (Fe₃O₄/Pectin NPs) which is prepared by co-precipitation of Fe(II/(III) ions in alkaline solution mediated by pectin under ultrasound condition. This process led to formation of magnetic nanoparticles within the network of pectin. Physicochemical characterization of the as-synthesized Fe₃O₄/Pectin NPs was carried out through electron microscopy (SEM and TEM), energy dispersive X-ray spectroscopy (EDX), vibrating sample magnetometer (VSM) and X-ray diffraction (XRD). The in vitro cytotoxic and anti-colorectal cancer effects of biologically synthesized Fe₃O₄/Pectin NPs against Ramos.2G6.4C10, HCT-8 [HRT-18], HCT 116, and HT-29 cancer cell lines were assessed. The anti-colorectal cancer properties of the Fe₃O₄/Pectin NPs could significantly remove Ramos.2G6.4C10, HCT-8 [HRT-18], HCT 116, and HT-29 cancer cell lines in a time and concentration-dependent manner by MTT assay. The IC₅₀ of the Fe₃O₄/Pectin NPs were 317, 337, 187, and 300 µg/mL against Ramos.2G6.4C10, HCT-8 [HRT-18], HCT 116, and HT-29 cancer cell lines. The antioxidant activity of Fe₃O₄/Pectin NPs was determined by DPPH method. The Fe₃O₄/Pectin NPs showed the high antioxidant activity according to the IC₅₀ value. It seems that the anti-human colorectal cancer effect of recent nanoparticles is due to their antioxidant effects.     

Lime peel extract induced NiFe2O4 NPs: Synthesis to applications and oxidative stress mechanism for anticancer,antibiotic activity

Nanobiotechnology, joined with green science, has incredible potential for the advancement of novel and important products that benefit human health, climate, and industries. Green chemistry of materials from synthesis to diverse biomedical applications is a talk of town in today’s sustainable ideal world. Green synthesized nickel ferrites nanoparticles via biogenic lime peel extract (LPE) are investigated with precision and complete trail has been reported as multiple efficacies. The fcc crystal structure with the crystallite size (31 nm) were accessed by the XRD, magnetic properties using VSM, and FTIR for the functional group analysis of NiFe₂O₄ nanoparticles mediated by Lime peel extract (NiFe₂O₄@LPE NPs). From TEM and SEM analysis the average diameter of the NPs was observed in the range of 31–35 nm. In 3D view, the surface morphology was analyzed by the AFM. NiFe₂O₄@LPE NPs were used to assess cytotoxicity and cellular morphological alterations in In Vitro cervical cancerous cells (HeLa). Nanosized NiFe₂O₄@LPE accompanied the considerable NPs topology induced dose dependent MMP in HeLa cells unlike the previous interpretation of controlled metabolism anticancer activity for HeLa cancerous cells. Therefore, it is referred by oxidative stress and reduction phenomena for anticancer effects and inactivation of carcinogen. Moreover, Antioxidant DPPH radical scavenging method and antibacterial Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus activity were observed in the synthesized nickel ferrites NPs.     

Structural and thermal properties of chemically synthesized Bi2Te3 nanoparticles

Bi₂Te₃ nanoparticles (NPs) have been synthesized at 50?°C by a low-cost wet chemical route. The structural properties of product sample were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy. Thermal properties of product sample were investigated by differential scanning calorimetry (DSC), thermogravimetric (TG), and transient plane source techniques. The XRD and selected area electron diffraction of Bi₂Te₃ NPs result showed the polycrystalline nature with a rhombohedral (R3m) structure of the nanocrystallites. The average grain size of Bi₂Te₃ NPs was found to be about 30?nm by XRD and TEM measurements. DSC result shows one endothermic peak and one exothermic peak. TG result shows that only 48?% mass loss has occurred in Bi₂Te₃ sample. The obtained lower thermal conductivity of Bi₂Te₃ NPs is about 0.3?W m^?1 K^?1 at room temperature, which is caused by considering the crystalline nature of this material.     

Anticancer therapeutic efficacy of biogenic Am-ZnO nanoparticles on 2D and 3D tumor models

The present study fabricates biogenic zinc oxide nanoparticles (ZnO NPs) with the aqueous leaf extract of Annona muricata (Am) plant collected from semi-evergreen forests of Odisha, India. The synthesized Am-ZnO NPs were physicochemically characterized. The ultraviolet/visible spectrum showed the maximum optical absorbance of Am-ZnO NPs at 355 nm. High-resolution transmission electron microscopy analysis presented the nearly spherical shape of Am-ZnO NPs with an average particle size of 80 nm. The net surface charge and hydrodynamic size of Am-ZnO NPs were measured to be ～?2.59 mV and ～417 nm, respectively. Am-ZnO NPs were found to be biocompatible and hemocompatible nature. Furthermore, Am-ZnO NPs displayed strong anticancer effects on both 2D and 3D tumor models. We observed a dose-dependent toxicity on both A549 and MOLT4 cells and observed a size reduction in the A549 tumor spheroids. Subsequently, we observed a depolarization in mitochondrial membrane potential of Am-ZnO NP–treated cancer cells leading to the apoptosis induction in cancer cells.     

The effect of different substrate temperatures on the structure and luminescence properties of Y2O3:Bi3+ thin films

Y₂O₃:Bi³⁺ phosphor thin films were prepared by pulsed laser deposition in the presence of oxygen (O₂) gas. The microstructure and photoluminescence (PL) of these films were found to be highly dependent on the substrate temperature. X-ray diffraction analysis showed that the Y₂O₃:Bi³⁺ films transformed from amorphous to cubic and monoclinic phases when the substrate temperature was increased up to 600 °C. At the higher substrate temperature of 600 °C, the cubic phase became dominant. The crystallinity of the thin films, therefore, increased with increasing substrate temperatures. Surface morphology results obtained by atomic force microscopy showed a decrease in the surface roughness with an increase in substrate temperature. The increase in the PL intensities was attributed to the crystallinity improvement and surface roughness decrease. The main PL emission peak position of the thin films prepared at substrate temperatures of 450 °C and 600 °C showed a shift to shorter wavelengths of 460 and 480 nm respectively, if compared to the main PL peak position of the powder at 495 nm. The shift was attributed to a different Bi³⁺ ion environment in the monoclinic and cubic phases.     

Facile synthesis of multifunctional multiwalled carbon nanotubes/Fe3O4 nanoparticles/polyaniline composite nanotubes

With an average diameter of 100-150 nm, composite nanotubes of polyaniline (PANI)/multiwalled carbon nanotubes (MWNTs) containing Fe₃O₄ nanoparticles (NPs) were synthesized by a two-step method. First, we synthesized monodispersed Fe₃O₄ NPs (d=17.6 nm, σ=1.92 nm) on the surface of MWNTs and then decorated the nanocomposites with a PANI layer via a self-assembly method. SEM and TEM images indicated that the obtained samples had the morphologies of nanotubes. The molecular structure and composition of MWNTs/Fe₃O₄ NPs/PANI nanotubes were characterized by Fourier transform infrared spectra (FTIR), energy dispersive X-ray spectrometry (EDX), X-ray photoelectron spectra (XPS), X-ray diffraction (XRD) and Raman spectra. UV-vis spectra confirmed the existence of PANI and its response to acid and alkali. As a multifunctional material, the conductivity and magnetic properties of MWNTs/Fe₃O₄ NPs/PANI composites nanotubes were also investigated.     

Different [Bi12O14]n Columnar Structural Types in the Bi-Mo-Cr-O System: Synthesis, Structure, and Electrical Properties of the Solid Solution Bi26Mo10−xCrxO69

In order to search for new ionic conductor materials exhibiting a columnar [Bi₁₂O₁₄] structural type, the syntheses of the solid solutions Bi₂Mo_1−xCr_xO₆ and Bi₂₆Mo_10−xCr_xO₆₉ have been undertaken. Single phases were obtained for the last composition with 0≤x≤5 homogeneity range. Moreover, a new oxide with Bi₆Cr₂O₁₅ composition has been obtained from the limit nominal stoichiometries Bi₆CrO₆ and Bi₂₆Cr₁₀O₆₉. X-ray powder diffraction studies have shown that this oxide crystallizes in the orthorhombic system, space group Ccc2 or Cccm, with unit-cell parameters a=19.8986(9) Å, b=12.2756(6) Å, c=5.8868(3) Å, and V=1437.96 ų. Impedance spectroscopy measurements carried out on the representative Bi₂₆Mo₈Cr₂O₆₉ phase, showed that this material is a good oxygen ion conductor, in fact the best one belongs to the columnar structural type, with a conductivity as high as 1.7×10⁻³Scm⁻¹ at 425°C.     

Morphology modulated growth of bismuth tungsten oxide nanocrystals

Two kinds of bismuth tungsten oxide nanocrystals were prepared by microwave hydrothermal method. The morphology modulation of nanocrystals synthesized with precursor suspension's pH varied from 0.25 (strong acid) to 10.05 (base) was studied. The 3D flower like aggregation of Bi₂WO₆ nanoflakes was synthesized in acid precursor suspension and the nanooctahedron crystals of Bi_3.84W_0.16O_6.24 were synthesized in alkalescent precursor. The dominant crystal is changed from Bi₂WO₆ to Bi_3.84W_0.16O_6.24 when the precursor suspension changes from acid to alkalescence. The growth mechanisms of Bi₂WO₆ and Bi_3.84W_0.16O_6.24 were attributed to the different solubility of WO₄²⁻ and [Bi₂O₂]²⁺ in precursor suspensions with various pH. For the decomposition of Rhodamine B (RhB) under visible light irradiation (λ>400 nm), different morphology of Bi₂WO₆ crystal samples obtained by microwavesolvothermal process showed different photocatalytic activity.     

A new bismuth potassium nitrate oxide, Bi1.7K0.9O2(NO3)2: Synthesis, structure, thermal behavior, and photocatalytic properties

We report here the first observation of a bismuth potassium nitrate Bi_1.7K_0.9O₂(NO₃)₂, obtained via thermal decomposition of bismuth and potassium nitrate mixtures. The new compound is orthorhombic, space group Immm (71), Z = 2, with a = 3.8698(7) Å, b = 3.8703(7) Å, and c = 24.1271(4) Å. Its crystal structure was refined from powder X-ray diffraction data by analogy with the mineral beyerite, Bi₂O₂Ca(CO₃)₂. The morphology and elemental composition of Bi_1.7K_0.9O₂(NO₃)₂ were characterized using scanning electron microscopy (SEM) with energy dispersive X-Ray spectroscopy (EDS). Its phase transformations upon heating and products of its thermal decomposition were studied using XRD, TGA and FTIR. At 440 °C, Bi_1.7K_0.9O₂(NO₃)₂ transforms to another basic bismuth potassium nitrate with demonstrates a very similar XRD pattern but slightly larger cell parameters. At 520 °C, the intermediate oxide nitrate decomposes into a mixture of crystalline α-Bi₂O₃ and KNO₃. The as prepared Bi_1.7K_0.9O₂(NO₃)₂ showed lower than TiO₂ (Degussa P25) photocatalytic activity upon decomposition of a widely used model pollutant, Rhodamine B (RhB) and photooxidation of potassium iodide under UV-vis light irradiation. Interaction with potassium iodide in alkaline media resulted in formation of Bi₅O₇I.     

Warm white light from Y4MgSi3O13:Bi, Eu nanophosphor for white light-emitting diodes

Y₄MgSi₃O₁₃:Bi³⁺, Eu³⁺ nanophosphors have been prepared by a facile sol–gel method. The products have been characterized by X-ray diffraction, field-emission scanning electron microscopy and fluorescence measurements. The results show that the nanophosphors are of single phase hexagonal Y₄MgSi₃O₁₃ with size-distribution of 50–90 nm in diameter. White-light emission has been obtained from Bi³⁺ and Eu³⁺ co-doped Y₄MgSi₃O₁₃ nanophosphors upon excitation of 350 nm ultraviolet light. It is noted that Bi³⁺ ions can occupy two different Y³⁺ sites and generate different emissions from the ³p₁ → ¹s₀ transition. Warm white light has been obtained from Y₄MgSi₃O₁₃:Bi³⁺, Eu³⁺ nanophosphors according to Commission International de I’Eclairage (CIE) chromaticity coordinates and color temperature (T_c) with appropriately adjusted contents of Bi³⁺ and Eu³⁺. The results indicate that Y₄MgSi₃O₁₃:0.08Bi³⁺, 0.04Eu³⁺ (x = 0.31, y = 0.31, T_c = 6907 K) are potential nanophosphors for white light-emitting diodes (LEDs) applications.     

Synthesis crystal structure and ionic conductivity of Ca0.5Bi3V2O10 and Sr0.5Bi3V2O10

Two new compounds Ca_0.5Bi₃V₂O₁₀ and Sr_0.5Bi₃V₂O₁₀ have been synthesized in the ternary system: MO-Bi₂O₃-V₂O₅ system (M=M²⁺). The crystal structure of Sr_0.5Bi₃V₂O₁₀ has been determined from single crystal X-ray diffraction data, space group and Z=2, with cell parameters a=7.1453(3) Å, b=7.8921(3) Å, c=9.3297(3) Å, α=106.444(2)°, β=94.088(2)°, γ=112.445(2)°, V=456.72(4) Å³. Ca_0.5Bi₃V₂O₁₀ is isostructural with Sr_0.5Bi₃V₂O₁₀, with, a=7.0810(2) Å, b=7.8447(2) Å, c=9.3607(2) Å, α=106.202(1)°, β=94.572(1)°, γ=112.659(1)°, V=450.38(2) Å³ and its structure has been refined by Rietveld method using powder X-ray data. The crystal structure consists of infinite chains of (Bi₂O₂) along c-axis formed by linkage of BiO₈ and BiO₆ polyhedra interconnected by MO₈ polyhedra forming 2D layers in ac plane. The vanadate tetrahedra are sandwiched between these layers. Conductivity measurements give a maximum conductivity value of 4.54×10⁻⁵ and 3.63×10⁻⁵ S cm⁻¹ for Ca_0.5Bi₃V₂O₁₀ and Sr_0.5Bi₃V₂O₁₀, respectively at 725 °C.     

Assessment of antioxidant and cytotoxic potential of silver nanoparticles synthesized from root extract of Reynoutria japonica Houtt

Free radicals, mostly consist of reactive oxygen species, are generated in human body by several exogenous and endogenous systems. Overproduction of free radicals is known to cause several degenerative disorders including cancer. The aim of this study is to synthesize silver nanoparticles (AgNPs) using root extract of Reynoutria japonica and to investigate its antioxidant and cytotoxic potential. AgNPs were synthesized by green approach and subsequently characterized using UV–vis spectroscopy, SEM, TEM, FTIR, XRD, EDS and DLS. The antioxidant activity was investigated using DPPH, FRAP, H₂O₂, and ABT?⁺ radical scavenging assays while the cytotoxic effect was assessed using different human cancer cell lines including lung (A549), liver (Hep-G2) and breast (MDA-MB-231) by MTS assay. Moreover, the specificity of NPs was assessed against two normal human cell lines e.g. alveolar and renal primary epithelial cells (HPAEpiC and HRPTEpiC). The UV–vis spectra confirmed the synthesis of AgNPs by producing a characteristic peak at 410 nm. Further analysis confirmed that AgNPs were crystalline in nature, predominantly spherical in shape, with an average width and area of 17.34 nm and 164.46 nm², respectively. DLS analysis revealed that NPs possess a high negative zeta potential value (?28.5 mV), thus facilitating its electrostatic stabilization. AgNPs showed dose dependent antioxidant activity against DPPH, FRAP, H₂O₂ and ABTS with IC₅₀ values 19.25, 22.45, 24.20 and 18.88 µg/ml, respectively. The AgNPs depicted significant cytotoxic effects against A549, Hep-G2 and MDA-MB-231 cell lines with IC₅₀ values of 4.5, 5.1 and 3.46 µg/ml, respectively. Moreover, the NPs exhibited highest selectivity index (>2.0) for A549, Hep-G2 and MDA-MB-231, confirming its specificity towards cancer cell lines. In conclusion, AgNPs prepared from root extract of R. japonica possess strong antioxidant and cytotoxic potential which suggests that they should be investigated further in order to develop safe and effective antioxidant and/or cytotoxic formulations.     

Biogenic synthesis of husked rice-shaped iron oxide nanoparticles using coconut pulp (Cocos nucifera L.) extract for photocatalytic degradation of Rhodamine B dye and their in vitro antibacterial and anticancer activity

In this present study, photocatalytic and in-vitro biological properties of biogenic preparation of husked rice-shaped iron oxide nanoparticles (Fe₂O₃ NPs) are investigated. Fe₂O₃ NPs have been prepared by the reduction of iron chloride (FeCl₃) using coconut pulp (Cocos nucifera L.) extract. The Fe₂O₃ NPs were characterized by various analytical techniques such as FE-SEM, TEM, XRD, FT-IR, TGA, VSM, PL, and UV-DRS. Based on the characterization results, the as-prepared Fe₂O₃ NPs are in husked rice shape and exhibit rhombohedral crystal phase and also show an excellent stability. The prepared Fe₂O₃ NPs was investigated as a catalyst for the photocatalytic degradation of Rhodamine B solution. The photocatalytic results indicated that the Fe₂O₃ NPs catalyst possesses good activity with efficiency of 92% after 50 min under visible-light irradiation. In addition, the Fe₂O₃ NPs showed good antibacterial and anticancer properties against Gram-negative Escherichia coli and Gram-positive, Staphylococcus aureus and HepG2 cell lines, resulting in effective antibacterial and anticancer activity. The prepared Fe₂O₃ NPs, thus, proved to be a potential material for environmental remediation and biological applications.     

High sensitivity and multicolor tunable optical thermometry in Bi3+/Eu3+ co-doped Ca2Sb2O7 phosphors

Currently, with increasing demand for non-contact fluorescence intensity ratio-based optical thermometry, a novel phosphor with high-efficiency, dual-emitting centers, and differentiable temperature sensitivity is more and more urgent to develop. In this work, an efficient dual-emitting center optical thermometry with high sensitivity and multicolor tunable in Ca₂Sb₂O₇:Bi³⁺, Eu³⁺ phosphor is firstly designed and successfully prepared. Under 330 nm excitation, the fabricated phosphor presents the featured and distinguishable emissions of Bi³⁺ and Eu³⁺ ions. The high efficiency energy transfer from Bi³⁺ to Eu³⁺ ions is proved and its corresponding mechanism belongs to dipole-dipole interaction. By modulating the ratio of Bi³⁺/Eu³⁺, the multicolor changes from blue to pink are realized. Based on the discriminative thermal quenching behavior between Bi³⁺ and Eu³⁺, the fluorescence intensity ratio of Eu³⁺ to Bi³⁺ in Ca₂Sb₂O₇ samples illustrates excellent optical thermometry performance from 298 to 523 K. The maximum absolute sensitivity (S_a) and relative sensitivity (S_r) reach as high as 0.2773 K^?1 at 523 K and 2.37% K^?1 at 448 K, respectively. Notably, the discriminated surrounding temperature can be directly confirmed by observing the emitting color from purple to orange-red with the temperature increase from 298 to 523 K. Furthermore, the as-prepared phosphor materials also demonstrate outstanding repeatability and excellent reversibility. These results exhibit that the designed Ca₂Sb₂O₇:Bi³⁺, Eu³⁺ phosphors have great promising applications in the field of non-contact optical temperature thermometry and thermochromic.     

Crystal chemistry and crystallography of the Aurivillius phase Bi5AgNb4O18

Bi₅AgNb₄O₁₈ is a new phase, which was discovered during the phase equilibrium study of the Bi₂O₃-Ag₂O-Nb₂O₅ system. Bi₅AgNb₄O₁₈ was prepared at 750°C and is stable in air up to its melting temperature of 1160.1±5.0°C (standard error of estimate). Results of a Rietveld refinement using neutron powder diffraction confirmed that Bi₅AgNb₄O₁₈ is isostructural with Bi₃TiNbO₉, Bi₅NaNb₄O₁₈, and Bi₅KNb₄O₁₈. The structure was refined in the orthorhombic space group A2₁am, Z=2, and the lattice parameters are a=5.4915(2) Å, b=5.4752(2) Å, c=24.9282(8) Å, and V=749.52(4) Å³. The structure can be described as the m=2 member of the Aurivillius family, (Bi₂O₂)²⁺ (A_m−1B_mO_3m+1)²⁻ (where A=Bi and B=Ag, Nb), which is characterized by perovskite-like (A_m−1B_mO_3m+1)²⁻ slabs regularly interleaved with (Bi₂O₂)²⁺ layers. The octahedral [NbO₆] units are distorted with Nb-O distances ranging from 1.856(4) to 2.161(2) Å and the O-Nb-O angles ranging from 82.6(3)° to 98.5(3)°. These octahedra are tilted about the a- and c-axis by about 10.3° and 12.4°, respectively. Ag was found to substitute exclusively into the Bi-site that is located in the layer between the two distorted [NbO₆] units. Although the Ag substitutes into the Bi-site with the Bi:Ag ratio of 1:1, the existence of a superlattice was not detected using electron diffraction. A comparison of (Bi₂O₂)²⁺(A_m−1Nb_mO_3m+1)²⁻ structures (where A=Ag, Na, and K) revealed a relation between the pervoskite tolerance factor, t, and structural distortion. The reference pattern for Bi₅AgNb₄O₁₈ has been submitted to the International Centre for Diffraction Data (ICDD) for inclusion in the Powder Diffraction File.     

Synthesis and characterization of Eu3+/Dy3+ codoped composite phosphors SrAl2Si2O8/SrAlSi1/2O7/2 via a one-pot nitrate-gel process

Composite phosphors SrAl₂Si₂O₈/SrAlSi_1/2O_7/2 codoped with Eu³⁺ and Dy³⁺ were synthesized via a simple one-pot nitrate-gel process. The thermal decomposition process of the precursor is investigated by thermal analysis, X-ray diffraction and infrared spectroscopy, respectively. The as-prepared Eu³⁺/Dy³⁺ codoped SrAl₂Si₂O₈/SrAlSi_1/2O_7/2 phosphors could yield blue (436 nm), bluegreen (486 nm), yellow (583 nm), and red (617 nm) lights under near-UV 380 nm excitation from a composite matrix produced by spontaneous phase separation during heat treatment of the precursor. Moreover, the effects of Dy³⁺ doping concentration on the structures, defect features, and luminescence properties of the composite phosphors were examined in detail.     

Characterization of Bi5Nb3O15 by refinement of neutron diffraction pattern, acid treatment and reaction of the acid-treated product with n-alkylamines

The structure of Bi₅Nb₃O₁₅ was investigated by refinement of the powder neutron diffraction pattern as well as by structural change through acid treatment and subsequent treatments of an acid-treated product with n-alkylamines. Rietveld refinement suggests that Bi₅Nb₃O₁₅ adopts a mixed-layer Aurivillius-related phase structure, [Bi₂O₂]+[NbO₄]+[Bi₂O₂]+[BiNb₂O₇] [Pnc2 (space group No. 30)] with a=2.1011(4), b=0.5473(1) and c=0.5463(1) nm. After the acid treatment of Bi₅Nb₃O₁₅ with 3 mol/L HCl, a new reflection (at 2.25 nm after drying at room temperature or at 1.89 nm after drying at 120 °C) appeared in the X-ray diffraction (XRD) pattern in addition to the reflections due to Bi₅Nb₃O₁₅. Upon acid treatment, a part of the Bi ions were lost and essentially no Nb ions were dissolved during acid treatment to give a Bi/Nb molar ratio of 1.4. The TG curves of the acid-treated product showed mass loss (ca. 4 mass%) in the range of 300-600 °C. It was also demonstrated that the particle shapes did not change upon acid treatment. The reaction of the acid-treated product (after drying at room temperature) with n-alkylamines led to a shift of the newly appearing reflection to a lower angle, and the d-value of the low-angle reflection increased linearly in accordance with the increment of the number of carbon atoms in n-alkylamines. These results indicate that the [Bi₂O₂] sheet in Bi₅Nb₃O₁₅ was partially leached by acid treatment to form a layered compound H₄BiNb₃O₁₁·xH₂O, capable of accommodating n-alkylamines in the interlayer space, and its anhydrous form, H₄BiNb₃O₁₁, upon drying. Based on the variation in the interlayer distance upon intercalation of n-alkylamines into the acid-treated product, the structure of the acid-treated product can be suggested to comprise alternately stacked protonated [BiNb₂O₇] and [NbO₄] sheets, a result consistent with the Rietveld refinement of Bi₅Nb₃O₁₅.     

Structure and Ionic Conductivity of Bi6Cr2O15, a New Structure Type Containing (Bi12O14)n Columns and CrO4 Tetrahedra

Powder samples of the Cr⁶⁺-containing compound Bi₆Cr₂O₁₅ were prepared by solid state reaction of Bi₂O₃ and Cr₂O₃ in air at 650°C. The structure was solved and refined using high-resolution neutron powder diffraction data in space group Ccc2, with anisotropic thermal displacement parameters a=12.30184(5), b=19.87492(7), and c=5.88162(2) Å, V=1438.0 ų, and 126 variables to R_F=1.8%. Bi₆Cr₂O₁₅ exhibits a new structure type that contains (Bi₁₂O₁₄)⁸ⁿ⁺_n columns, of the kind previously found only for phases isotypic with Bi₁₃Mo₄VO₃₄. Each column is surrounded by eight CrO²⁻₄ tetrahedra. The ionic conductivity of Bi₆Cr₂O₁₅ was determined by impedance measurements to be 3.5×10⁻⁵ (Ω cm)⁻¹ at 600°C.