Supramolecular Copolymerization Strategy for Realizing the Broadband White Light Luminescence Based on N-Deficient Porous Graphitic Carbon Nitride (g-C3N4).

The N-deficient porous g-C3N4 with broadband white light emission was constructed by supramolecular copolymerization design, which combined organic copolymers cyanuric acid and 2,4,6-triaminopyrimidine with melamine upon the mixture gas environment of (95%)N2/(5%)H2. Herein, we achieved great breakthrough in narrowing the band gap of g-C3N4 from 2.64 to 1.39 eV. Furthermore, in contrast to pristine g-C3N4, we demonstrated that the emission wavelengths of N-deficient porous g-C3N4 can be tuned from narrow blue to broadband white range, where the optimal white light coordinate position is (0.297, 0.345). The prepared N-deficient porous g-C3N4 overcomes the limitation of the narrow adjusting range of optical properties while using conventional g-C3N4 and makes it more promising for applications in solid-state displays.

Fe3+-selective and sensitive "on-off" fluorescence probe based on the graphitic carbon nitride nanosheets.

An effective and facile "on-off" fluorescence sensing approach for the determination of Fe3+ ion using a large area and relatively uniform size graphitic carbon nitride nanosheets (GCNS) was developed. The prepared GCNS have blue and stable emission, as well as excellent water dispersion, and were applied as an effective fluorescent probe that based on the quenched fluorescence for selective and sensitive detection of Fe3+ ion. Herein, we explain the ambiguous fluorescence quenching mechanism between the GCNS and Fe3+, which mainly springs from the redox potential and empty d orbital of Fe3+. The redox potential and unfilled d orbit of Fe3+ endow it excellent binding force with GCNS, which generates most obvious fluorescence quenching effect with respect to other metal ions. The limit of detection (LOD) for Fe3+ was found to be about 2.06 µM. Therefore, the prepared GCNS has the potential to be used as a fluorescent probe for detection.

The influence of TeO2 on thermal stability and 1.53 µm spectroscopic properties in Er(3+) doped oxyfluorite glasses.

In this work, the thermal and spectroscopic properties of Er(3+)-doped oxyfluorite glass based on AMCSBYT (AlF3-MgF2-CaF2-SrF2-BaF2-YF3-TeO2) system for different TeO2 concentrations from 6 to 21 mol% is reported. After adding a suitable content of TeO2, the thermal ability of glass improves significantly whose ΔT and S can reach to 118 °C and 4.47, respectively. The stimulated emission cross-section reaches to 7.80×10(-21) cm(2) and the fluorescence lifetime is 12.18 ms. At the same time, the bandwidth characteristics reach to 46.41×10(-21) cm(2) nm and the gain performance is 63.73×10(-21) cm(2) ms. These results show that the optical performances of this oxyfluorite glass are very well. Hence, AMCSBYT glass with superior performances might be a useful material for applications in optical amplifier around 1.53 µm.

Quantitative Analysis of Energy Transfer and Origin of Quenching in Er(3+)/Ho(3+) Codoped Germanosilicate Glasses.

The energy transfer mechanism between Ho(3+) and Er(3+) ions has been investigated in germanosilicate glass excited by 980 nm laser diode. A rate equation model was developed to demonstrate the energy transfer from Er(3+) to Ho(3+) ions, quantitatively. Energy transfer efficiency from the Er(3+):(4)I13/2 to the Ho(3+):(5)I7 level can reach as high as 75%. Such a high efficiency was attributed to the excellent matching of the host phonon energy with the energy gap between Er(3+):(4)I13/2 and Ho(3+):(5)I7 levels. In addition, the energy transfer microparameter (CDA) from Er(3+):(4)I13/2 to Ho(3+):(5)I7 level was estimated to (4.16 ± 0.03) × 10(-40) cm(6)·s(-1) via the host-assisted spectral overlap function, coinciding with the CDA (2,88 ± 0.04) × 10(-40) cm(6)·s(-1) from decay analysis of the Er(3+):(4)I13/2 level which also indicated hopping migration-assisted energy transfer. Furthermore, the concentration quenching of Ho(3+):(5)I7 → (5)I8 transition was the dipole-dipole interaction in the diffusion-limited regime, and the quenching concentration of Ho(3+) reached 4.13 × 10(20) cm(-3).

Tunable mid-infrared luminescence from Er3+ -doped germanate glass.

Er(3+) -doped germanate glasses with superior thermal stability were prepared. Judd-Ofelt intensity parameters and important spectroscopic properties were discussed in detail. Upon 800 nm and 980 nm LD pumping, 2.7 µm fluorescence characteristics were investigated and it was found that the effective 2.7 µm emission bandwidth can reach to 101.79 nm in prepared glasses. The tunability of the 2.7 µm emission band can be realized by adjusting the Er(3+) content. Moreover, a high-emission cross-section (11.09 × 10(-21) cm(2) ), large gain bandwidth (772.30 × 10(-28) cm(3) ) and gain coefficient (6.72 cm(-1) ) were obtained in the prepared sample. Hence, Er(3+) -doped germanate glass might be a promising mid-infrared material for tunable amplifiers or lasers.