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A selective and sensitive fluorescence biosensor is described for determination of microRNA-167 using fluorescent resonant energy transfer (FRET) strategy. The FRET system comprises carbon dots (CDs, donor) labeled with probe DNA (pDNA) and polydopamine (PDA)-coated Fe3O4 nanoparticles (Fe3O4@PDA NPs, acceptor). The CDs-pDNA can be absorbed onto the surface of Fe3O4@PDA NPs because of the strong π interaction between pDNA and PDA. With the enhanced adsorption ability of Fe3O4@PDA NPs by Ca2+, the fluorescence intensity of CDs at 445 nm (excitation at 360 nm) is quenched. In presence of microRNA-167, the hybridized complex of CDs-pDNA-microRNA-167 will be released from the surface of Fe3O4@PDA NPs due to the weak π interaction of the complex and PDA. This results in the fluorescence recovery of CDs. By application of twice-magnetic separation, the biosensor shows a wide linear range of 0.5–100 nM to microRNA-167 with a 76 pM detection limit. The method was applied to the determination of microRNA-167 in samples of total microRNA extractions from A. thaliana seedlings, and the recoveries ranged from 96.4 to 98.3%. [ABSTRACT FROM AUTHOR]

Tb3+, Eu3+ singly doped and Tb3+-Eu3+ co-doped Ba 2 GdF 7 nanoparticles were obtained by one-step hydrothermal process. Under 273 or 368 nm ultraviolet (UV) excitation, by changing the ratio of Tb3+ and Eu3+, the emission color of Ba 2 GdF 7 : Tb3+, Eu3+ are manipulated from green to yellow, orange and red based on energy transfer (ET) from Gd3+ to Tb3+, Eu3+ and from Tb3+ to Eu3+. The ET mechanism among Tb3+ and Eu3+ was determined as dipole-dipole interaction by the lifetime change of Tb3+. The thermal stability of Ba 2 GdF 7 : 40%Tb3+, 3%Eu3+ phosphor was studied and the activation energy was calculated to be 0.289 eV at 273 nm and 0.297 eV at 368 nm excitation. The multi-color emitting Ba 2 GdF 7 : Tb3+, Eu3+ nanophosphors might have a promising application in phosphors-converted light-emitting diodes. • Tb3+, Eu3+ ions are co-doped into the Ba 2 GdF 7 matrix by a one-step hydrothermal method for the first time. • Color-tunable emission from green to red are obtained by adjusting the concentration of Eu3+ in Ba 2 GdF 7 : Tb3+, Eu3+. • The multi-color emitting Ba 2 GdF 7 : Tb3+, Eu3+ nanophosphors have promising applications in full-color displays and pc-LEDs. [ABSTRACT FROM AUTHOR]

Pr3+ and Mn2+ co-doped CaZnOS phosphors are prepared by high-temperature solid state reaction method and the photoluminescence property is investigated systematically. Under 283 ​nm ultraviolet and 447 ​nm blue light excitations, green emission from CaZnOS, Pr3+ and red emission from Mn2+ are obtained and the emission color is modulated from green to yellow and red by adjusting the ratio of Pr3+ to Mn2+ concentration. The photoluminescence process under 283 ​nm and 447 ​nm excitations are dependent on energy transfer from CaZnOS to Pr3+ and Mn2+, as well as energy transfer from Pr3+ to Mn2+. The energy transfer mechanism between Pr3+ and Mn2+ is confirmed to be dipole-quadrupole interaction. Particularly, under 447 ​nm blue excitation, CaZnOS: 1%Pr3+, 3%Mn2+ exhibits bright yellow emission with chromaticity coordinates of (0.372, 0.428) and quantum yields of 46.37%, implying a potential application in blue-chip excited white light emitting diodes (W-LEDs). [Display omitted] • The photoluminescence property of Pr3+, Mn2+ co-doped CaZnOS phosphor was investigated for the first time. • Under 283 and 447 ​nm excitation, the emission color of CaZnOS: Pr3+, Mn2+ was adjusted from green to red. • The PLQYs of CaZnOS:1%Pr3+, 3%Mn2+ under blue excitation is 46.37%, implying a potential application in white LED. [ABSTRACT FROM AUTHOR]