Insights on the solvatochromic effects in N-doped yellow-orange emissive carbon dots

We have demonstrated a rapid and facile synthetic method to prepare N-doped Cdots that has excitation independent-emission in yellow-orange region. The Cdots showed solvatochromic behavior in different solvents due to change in solvent polarity illustrating n → π* transition (edge band).

Short communication: Aqueous-acetone extraction improves the drawbacks of using dimethylsulfoxide as solvent for photometric pigment quantification in Quercus ilex leaves

Aim of study: We evaluated the use of dimethylsulfoxide (DMSO) for the photometric determination of chlorophyll (Chla and Chlb) and carotenoids in Quercus ilex L. leaves by comparative analysis using aqueous-acetone extraction.Area of study: a Q. ilex dehesa in Las Majadas del Tietar, Cáceres, SpainMaterial and methods: Q. ilex leaves were sampled during two vegetative periods. Field SPAD-502 Chlorophyll measurements and photometric chlorophyll determinations were performed. Two procedures were used: extraction of intact foliar discs at 65ºC with DMSO and fine foliar powder with cold aqueous-acetone.Main results: DMSO produced Chlb overestimation and different fitting performance for SPAD vs pigment calibrations (R2=0.64, RMSE=0.20, p<0.0001 for Chla (µg/cm2); R2=0.33, RMSE=0.23, p<0.0001 for Chlb (µg/cm2) and R2=0.50, RMSE=0.23, p<0.0001 for carotenoids (µg/cm2)). Aqueous-acetone provided more accurate predictions (R2=0.90, RMSE=0.16, p<0.0001 for Chla and R2=0.91, RMSE=0.16, p<0.0001 for Chlb, R2=0.90, RMSE=0.02, p<0.0001 for carotenoids) and mean ratio Chla/Chlb=3.6 inside the range for sun exposed leaves.Research highlights: Oxidizing conditions and polyphenol concentrations in Q. ilex leaves generated brown coloration in the DMSO extraction procedure, interfering with the photometric measurements in the red-orange region. Aqueous-acetone extraction was free from interference. DMSO should be avoided for pigment determination in Q. ilex leaves or when comparing different tree species.

Photoluminescence and energy transfer of YAG: Ce3+, Gd3+, Bi3+

In this study, Gd[Formula: see text] and Bi[Formula: see text] ions act to redshift the emission band to orange region, and to enhance significantly the maximum emission of YAG: Ce[Formula: see text]. On account that size mismatch between the host and the doped Gd[Formula: see text] ion, the crystal structure turns soft, and the emission spectra are not tuned from 540 to 570[Formula: see text]nm but decreased the emission intensity. Accordingly, an effective way to increase emission intensity is to introduce Bi[Formula: see text] ion into the YAG: Ce[Formula: see text], Gd[Formula: see text] phosphors. Experimental results show partial overlapping between the emission band of Bi[Formula: see text] ion and the excitation band of Ce[Formula: see text] ion, indicating that the energy transfer from Bi[Formula: see text] to Ce[Formula: see text] ions exists in the (Y[Formula: see text]Ce[Formula: see text]Gd)Al5O[Formula: see text]: Bi[Formula: see text] phosphor. Bi[Formula: see text] ion can serve as the activator to provide energy for Ce[Formula: see text] ion via cross relaxation phenomenon. Therefore, the (Y[Formula: see text]Ce[Formula: see text]Gd)Al5O[Formula: see text]: Bi[Formula: see text] phosphor could have potential applications in warm white LEDs.

Spectroscopic Investigation and Optical Properties of Eu3+-Doped Fluorophosphate Glasses

Eu3+-doped fluorophosphate (PKACaLF: P2O5 – K2O – Al2O3 – CaF2 – LiF) glasses have been prepared by melt quenching technique. The structural and optical properties have been characterized through Raman, absorption, photoluminescence and decay time measurements. The Judd-Ofelt parameters have been obtained from the absorption spectrum and are found to be Ω2 = 5.21 x10-20 cm2, Ω4 = 8.11 x10-20 cm2 and Ω6 = 1.03 x10-20 cm2. These parameters have been used to calculate the radiative properties of PKACaLFEu10 glass. The relative luminescence intensity ratio of 5D0 → 7F2 to 5D0 → 7F1 transition (R(2/1)) has been evaluated and is found to be 3.25 which indicates moderate asymmetric nature around Eu3+ ions. The luminescence decay of 5D0 level exhibit single exponential nature and the lifetimes (~ 2.50 ms) are found to be almost constant with increasing Eu3+ ion concentration. The chromaticity color coordinates (x = 0.63, y = 0.31) are in the reddish orange region. From these results, it is confirmed that the present PKACaLF glasses are useful for the development of optical display devices.

Synthesis and luminescence properties of a H2annealed Mn-doped Y3Al5O12:Ce3+single crystal for WLEDs

Compared to the blue LED chip and the as-grown sample, upon increasing the annealing temperature, the emission intensity in the yellow-orange region is enhanced and reaches the highest at 1550 °C.

Colouration mechanism of underglaze copper-red decoration porcelain (AD 13th–14th century), China

Underglaze copper-red decoration,i.e.the copper colourant used to paint diversified patterns on the surface of a body and then covered by transparent glaze and fired at high temperature in a reductive firing environment, is famous all over the world. However, the red colouration mechanism generated by underglaze copper remains unclear. In particular, the fact that the edges of the red patterns are orange has been ignored in previous research. Here, non-destructive analysis has been carried out on a precious fragment of early underglaze red porcelain using synchrotron radiation X-ray fluorescence, X-ray absorption near-edge spectroscopy (XANES) and reflection spectrometry techniques. The results suggest that the copper content in the red region is higher than that in the orange region, and other colour generation elements do not have obvious content difference, indicating that the colour generation effect of the underglaze red product is related to the copper content. XANES analysis shows that the valence states of copper in the red and orange regions are similar and metal copper contributes to their hues. The results of reflection spectrometry demonstrate that tiny orange hues could be attributed to the Mie scatting effect. Therefore, light-scattering effects should be considered when researching the colouration mechanism of underglaze red.