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Iron (Fe3+) is one of the most essential elements in the human body; deficiency or overdose of Fe3+ may have adverse effects on human health and immunity. Hence, it is essential to establish a sensitive and selective method for ion detection. In this study, novel green fluorescent N-doped carbon dots (N-CDs) were prepared with caffeic acid as the carbon source via a simple hydrothermal method. The solution of the as-prepared N-CDs exhibits 21.5% quantum yield, good salt stability, excellent water solubility, low cytotoxicity and good photobleaching resistance. The N-CDs can be used as a fluorescent probe for the detection of Fe3+ ions in aqueous solutions and bioimaging in living cells.

A series of novel Eu3+ activated aluminate Ba2Y1−xEuxAlO5 (x = 0.02–0.40) red-emitting phosphors were synthesized through a high-temperature solid-state route at 1380 °C. The phosphors were well crystallized in the space group P21/c (No. 14). Their photoluminescence emission (PL) and excitation (PLE) spectra were investigated. The results indicate that the Ba2YAlO5:Eu3+ phosphor can be excited effectively under 394 nm irradiation, which is suitable for UV LED chip. The obtained Ba2YAlO5:Eu3+ phosphor shows four peaks, corresponding to the 5D0–7FJ (J = 0, 1, 2, 3 and 4) transitions of Eu3+ upon 394 nm excitation. The optimal doping concentration of Eu3+ in Ba2YAlO5:xEu3+ was determined at 30 mol%. By temperature dependent emission spectra, the quenching temperature for Ba2YAlO5:0.30Eu3+ was found to be over 500 K. And the CIE chromaticity coordinates of Ba2YAlO5:0.30Eu3+ are very close to the National Television System Committee (NTSC) standard red.

A series of novel Eu3+-doped LiSrBiTeO6 red-emitting phosphors were prepared by the solid-state reaction method for the first time. Its crystal structure and luminescence properties are investigated. X-ray powder diffraction patterns in combination with the Rietveld method reveal its single phase structure. The phosphor can be efficiently excited by 394 nm and 465 nm light and emits bright red luminescence at 616 nm corresponding to the electric dipole transition 5D0–7F2. The optimal doping concentration of LiSrBi1-xTeO6:xEu3+ is about 40 mol%. The thermal stability of the phosphor was tested by measuring their temperature-dependent emission intensities. The warm white light LEDs was fabricated based on the InGaN-chip. The chromaticity coordinates of fabricated w-LED are (0.344, 0.381). All results indicated that LiSrBiTeO6:Eu3+ phosphors have potential application as red phosphors in white light emitting diodes.

Eu2+-doped bromophosphateapatite Sr5(PO4)3Br phosphors were synthesized by the conventional high-temperature solid-state reaction. The crystal structure and luminescence properties of the phosphors, as well as their thermal stability and CIE chromaticity coordinates were systematically investigated. Photoluminescence spectra of Sr5(PO4)3Br:Eu2+ exhibit a single blue emission at 450 nm under the excitation of 345 nm, which is ascribed to the 4f–5d transition of Eu2+. The phosphor shows very good thermal stability. The CIE color coordinates are very close to those of BaMgAl10O17:Eu2+ (BAM). All the properties indicate that the blue-emitting Sr5(PO4)3Br:Eu2+ phosphor has potential application in white LEDs.

A new green-emitting phosphor of Ce3+-doped CaGd4F14 (1–15 mol%) was synthesized by a facile solid-phase reaction. The crystal phase was investigated via X-ray polycrystalline powder diffraction (XRD) and Rietveld refinement. The scanning electron microscopy (SEM), photoluminescence (PL), decay lifetime and quantum efficiency (QE) were applied to characterize the phosphor. The phosphor shows the excitable wavelength in the UV region of (220–320 nm). CaGd4F14:Ce3+ has a green-emission band from 400 to 625 nm with maximum wavelength at 525 nm, which is the typical electronic transitions of 4f-5d of Ce3+-ions. The maximum QE was measured to be 67%. And the phosphor presents good thermal luminescence stability on temperature quenching. The thermal quenching energy is 0.503 eV. This phosphor has a potential application in lighting and display.

Eu2+-doped borate fluoride Ba2GaB4O9Cl was synthesized by the conventional high-temperature solid-state reaction. The crystal structure and luminescence properties of the phosphors, as well as their thermal luminescence quenching capabilities and CIE chromaticity coordinates were systematically investigated. Under the excitation at 340 nm, the phosphor exhibited an asymmetric broad-band blue emission with a peak at 445 nm, which is ascribed to the 4f–5d transition of Eu2+. It was further proved that energy transfer among the nearest neighbor ions is the major mechanism for concentration quenching of Eu2+ in Ba2−xGaB4O9Cl:xEu2+ phosphors. The luminescence quenching temperature is 432 K. The CIE color coordinates are very close to those of BaMgAl10O17:Eu2+ (BAM). All the properties indicated that the blue-emitting Ba2GaB4O9Cl:Eu2+ phosphor has potential application in white LEDs.

A new fluoride phosphor of Eu2+-activated Ba2Zn7F18 has been prepared via two-step solid-phase synthesis. Pure crystalline formation was verified by the X-ray diffraction (XRD) Rietveld refinement. The photoluminescence (PL) spectrum, decay curves (lifetimes), time-resolved emission, and internal quantum efficiency (QE) of Ba2Zn7F18:Eu2+ were characterized. The phosphors show sensitive response to near-UV excitation and emit blueish green luminescence with a maximum quantum efficiency of 70%. The excitation band can well match with the commercial near-UV LED chips (360–400 nm). This is favourable for fabricating white LED lighting devices. The scintillating properties were also confirmed under excitation of X-ray irradiation with a lifetime of 850 ns. Eu2+-activated Ba2Zn7F18 has a high thermal stability with activated energy of 0.63 eV. It could be potential for high-performance lighting and scintillator due to desirable luminescence properties.

A series of novel garnet-type tellurate red-emitting phosphors Li 3 Gd 3(1- x ) Te 2 O 12 : x Eu 3+ ( x = 0.01–0.30) were successfully synthesized by a high-temperature solid-state reaction method. The phase structure, photoluminescence properties and thermal stability of the phosphor were investigated in detail. The phosphor shows dominant emission peak at 613 nm belonging to the 5 D 0 → 7 F 2 electric dipole transition under 396 nm excitation. The luminescence intensity keeps increasing with increasing the content of Eu 3+ to 15 mol%, and the critical transfer distance of Eu 3+ was calculated to be 14 A. The quenching temperature for Li 3 Gd 3 Te 2 O 12 :0.15Eu 3+ was estimated to be above 500 K. This spectral feature reveals high color purity and excellent chromaticity coordinate characteristics. Therefore, Eu 3+ -doped Li 3 Gd 3 Te 2 O 12 phosphors are potential red phosphors for near-UV chip-based white light-emitting diode and display devices.

A series of novel bismuthate tellurate SrBi 2(1- x ) Eu 2 x TeO 7 ( x = 0.02–0.40) red-emitting phosphors were successfully prepared through a high-temperature solid-state reaction at 800 °C. The compounds crystallized in the cubic structure with the space group Pa 3 ¯ . Photoluminescence characteristics indicate that the SrBi 2 TeO 7 :Eu 3+ phosphor can be excited effectively under 465 nm irradiation, which matches well with the output wavelength of blue LED chips. The emission spectrum of SrBi 2 TeO 7 :Eu 3+ phosphor shows four peaks assigned to the 5 D 0 – 7 F J ( J = 0–4) transitions of Eu 3+ upon 394 and 465 nm excitation. The maximum photoluminescence intensity was found at 30 mol% in the SrBi 2 TeO 7 : x Eu 3+ phosphors. The quenching temperature for SrBi 2 TeO 7 :0.30Eu 3+ was revealed at 403 K by temperature dependent emission spectra. The CIE chromaticity coordinates of SrBi 2 TeO 7 :0.30Eu 3+ are very close to the National Television System Committee (NTSC) standard red.

A series of novel garnet-type tellurate orange-red emitting phosphors Li3Gd3(1−x)Te2O12:xSm3+(x = 0.003–0.10) were successfully synthesized by a high-temperature solid-state reaction method. The compounds were crystallized in the cubic structure with the space group of Ia $$\bar 3$$ d. The excitation spectrum indicates that the Li3Gd3Te2O12:Sm3+ phosphor can be excited efficiently under 406 nm irradiation, which matches well with the output wavelength of UV LED chips. The photoluminescence spectrum of Li3Gd3Te2O12:Sm3+ phosphor shows four peaks assigned to the 4G5/2–6HJ (J = 5/2, 7/2, 9/2, and 11/2) transitions of Sm3+. The luminescence intensity keeps increasing with increasing the content of Sm3+ to 2 mol%. The quenching temperature for Li3Gd3Te2O12:0.02Sm3+ was estimated to be above 480 K. Therefore, Sm3+-doped Li3Gd3Te2O12 phosphors are potential orange-red emitting phosphors for near-UV chip-based white light-emitting diode and display devices.

This paper describes a numerical model to examine the magnetostriction of bulk high-temperature superconductor (HTS) under non-uniform magnetic field in conjunction with finite element analysis. Through this model, the magnetostriction of homogeneous and nonhomogeneous HTS can be implemented under non-uniform magnetic field. Further, the effects of critical current density, applied field frequency and amplitude are also considered. The computational study can provide a fundamental mechanistic understanding the effects of non-uniform magnetic field on magnetostriction of HTS.

Superconducting multifilamentary N b 3 S n strand and cables have complex microstructure and macrostructure which are used in the International Thermonuclear Experimental Reactor (ITER) superconducting magnet system. In a generic form, the superconducting strand is made of copper, multifilamentary N b 3 S n and bronze which is a composite. The twisted composite strands form the superconducting cables with typical multi-stage structures. Here we propose a numerical model focusing on the problem of characterizing the effective properties of composite superconducting strand and cables at microscopic and macroscopic scales. The effective elastic constants of the composite superconducting strand can be derived by involving the combination of the representative volume element (RVE) and the Mori-Tanaka method. Subsequently, the proposed method is applied to capture the effects of temperature on the effective elastic constants of the superconducting multi-stage cables. Results show the elastic constants predicted by this model agree well with existing theoretical predictions and available experimental data. This numerical model may be utilized to optimize the mechanical properties of the composite superconducting strand by tuning the constituent fractions and to control the tensile stiffness of superconducting cables by tuning the winding laps of the cables.

The synthesis and transformations of a π-conjugated tellurophene-containing polymer are described. A π-conjugated tellurophene-containing polymer was obtained in 56% yield by the Sonogashira-Hagihara cross-coupling polycondensation of 2,5-di(4-bromophenyl)tellurophene and 1,4-bis(2-ethylhexyloxy)-2,5-diethynylbenzene at 80 °C for 24 h using tris(dibenzylideneacetone)dipalladium(0) (Pd2(dba)3)/2-dicyclohexylphosphino-2,4,6-triisopropylbiphenyl (XPhos) as a catalyst and triethylamine as a base. The resulting polymer was transformed to a reactive lithiated polymer by the reaction with n-butyllithium (2.4 equiv) at −78 °C to −60 °C for 3 h, which was further converted into a butadiene-containing and a germole-containing π-conjugated polymers by the reactions with hydrochloric acid and dimethylgermanium dichloride at −60 °C to ambient temperature for 12 h in 83% and 85% yields, respectively, by precipitation into MeOH. The obtained germole-containing polymer reveals the absorption onset (λonset) at 492 nm which is longer than those of the tellurophene-containing polymer and butadiene-containing polymer (λonset = 488 nm and 472 nm, respectively), presumably due to the lowering of the LUMO energy level by the σ*-π* orbital interaction. The germole-containing polymer exhibit a blue photoluminescence with an emission maxima (Emax) at 471 nm.

A simple method was developed to prepare fluorescent nitrogen/boron-doped carbon dots (N,B-CDs) in the gram scale. The results showed that the CDs exhibited blue photoluminescence (PL) under 365 nm ultraviolet radiation and excitation-dependent emission. Heteroatoms entered the CDs to enhance the photochemical properties, and their positive properties can be attributed to the presence of guanidino group and functionalized with boronic acid for realizing their utilization in certain applications. These materials could be applied to monitor Fe3+ via static PL quenching, yielding a limit of detection (LOD) of 0.74 μM. Furthermore, the charged and boronic acid groups on the prepared N,B-CDs enabled their use as recognition elements to bind with the bacteria through electrostatic interaction and allowed covalent interactions to form the corresponding boronate ester with E. coli (E. coli) bacterial membrane. This method could satisfy a linear range of 102–107 with LOD of 165 cfu ml−1 for E. coli. This method was applied for the determination of E. coli in tap water and orange juice samples, and satisfactory results were obtained.

Cohesive-interface-based finite element simulations were conducted to investigate the critical shear stress required for cell de-adhesion from extracellular substrates. The interface ligand–receptor bonds are modeled by a cohesive interface model with initial stiffness, interface strength, and fracture energy as the governing parameters. The ratio of the cell modulus to the interface stiffness defines a length scale. If this length is much less than the contact size, the de-adhesion process can be modeled by the linear elastic fracture mechanics, while the opposite limit leads to the concurrent sliding of the cell or, equivalently, debonding of all the interface ligand–receptor pairs. Since it generates additional shear-stress concentration along the interface, cell contraction generally reduces the critical de-adhesion stress. Cell de-adhesion is more prone to take place for three-dimensional irregular cell shapes because of the much easier failure in the anti-plane Mode III shear, as well as the additional stress concentration in these geometric irregularities.

Single-asperity friction tests have found a critical dependence of friction stress on the nanoscale contact size, as successfully explained by the nucleation of interface dislocations as opposed to concurrent sliding of all the interfacial atoms in contact. Modeling and simulation results, however, vary when the motion and interactions of multiple dislocations dominate at a larger scale regime. A Rice–Peierls framework is employed to investigate the multiplication and storage of interface dislocations, and the critical conditions for dislocation initiation and steady-state gliding are determined numerically. Our findings identify the key parameters that govern various friction mechanisms in the Hurtado–Kim and Deshpande–Needleman–van der Giessen models.