Mn-activated oxide phosphors La(MgTi)O (LMT) with far-red emitting were prepared via a sol-gel route. The structures of samples were determined by X-ray diffraction (XRD) and Reitveld refinement. The occupied sites of Mn (d electronic configuration) in host La(MgTi)O were confirmed by ab initio calculations in which the system has the lower formation energy, stable lattice structure, and strong bonding state as Mn enters into Ti site. The luminescent properties of Mn-doped samples were investigated; the samples emit far-red light centered at 708 nm with ultraviolet light (345 nm) or blue light (487 nm) excitation. According to the photoluminescence (PL) and excitation (PLE) spectra, the crystal field strength of the Mn-occupied environment was estimated. The thermal stability of phosphor was also evaluated through temperature-dependent PL intensity in a heating and cooling cycle process. The emission band is well-matched with the absorption band of phytochrome P under the excitation of light in near-ultraviolet to blue, which suggests that the LMT: Mn phosphor has great potential applications in light-emitting diodes (LEDs) for modulating plant growth.

Eu(2+) activated fluorophosphate Ba3GdNa(PO4)3F (BGNPF) with blue and red double-color emitting samples were prepared via a solid-state method in a reductive atmosphere. Their crystal structure and cationic sites were identified in light of X-ray diffraction pattern Rietveld refinement. Three different Ba(2+) sites, coordinated by six O atoms referred to as Ba1, two F and five O atoms as Ba2, and two F and six O atoms as Ba3, were partially substituted by Eu(2+). Photoluminescence emission (PL) and excitation (PLE) spectra of phosphor BGNPF:Eu(2+) along with the lifetimes were characterized at the liquid helium temperature (LHT), which further confirm the existence of three Eu(2+) emitting centers resulting in 436, 480, and 640 nm emission from the 5d → 4f transitions of Eu(2+) in three different Ba(2+) crystallographic sites. These emissions overlap with the absorption spectra of carotenoids and chlorophylls from plants, which could directly promote the photosynthesis. Temperature-dependent PL spectra were used to investigate the thermal stability of phosphor, which indicates that the PL intensity of BGNPF:0.9% Eu(2+) with optimal composition at 150 °C still keeps 60% of its PL intensity at room temperature, in which blue emission has higher thermal-stability than the red emission. Furthermore, the approaching white LED devices have also been manufactured with a 365 nm n-UV LED chip and present phosphor, which make operators more comfortable than that of the plant growth purple emitting LEDs system composed of blue and red light. Results indicate that this phosphor is an attractive dual-responsive candidate phosphor in the application n-UV light-excited white LEDs for plant growth.

A novel compound Ba3CaK(PO4)3 (BCKP) with new-type structure was synthesized and its structure was determined by X-ray diffraction Rietveld refinement, in which crystal structure consists of Ba1O9, Ba2O12, Ba3O9, CaO8 and KO10 polyhedra, that's five cationic sites. As a phosphor host, Eu2+ doped BCKP emits cold white light with about 90% quantum efficiency (QE) through entering different cationic sites. Based on the results of refinement, three Eu2+ luminescence centers in sites Ca, Ba2 and K were clearly assigned in Eu2+ solely doped BCKP by the time-resolved emission spectra (TRES), Van Uitert equation, but the emissions of Eu2+ at Ba1 and Ba3 sites are not easy to be determined for the same coordination number (CN). According to their different spatial distribution of the coordinated atoms, the first-principles calculation was used to compute the d orbital splitting energy of Eu2+ ions in Ba1 and Ba3 sites to accurately distinguish the ambiguous luminescence centers. In order to meet the requirement of plant growth spectra, Mn2+ was introduced into BCKP: Eu2+ to enhance the red component of spectra, which not only perfectly match with the absorption spectra of carotenoid and chlorophyll-b, but also LEDs fabricated through combining 365 nm near ultraviolet (n-UV) chip with BCKP: Eu2+, Mn2+ phosphor exhibit excellent parameters including high color rendering index (Ra) (92), excellent correlated color temperature (CCT) (4486 K) and outstanding QE up to 65%. Results confirmed that BCKP: Eu2+/Mn2+ phosphor with great potential applications in white LEDs and plant growth. Response to Reviewers: Dear editor, We are pleasure to accept your decision and the reviewers' suggestion. We would like to thank the referees for providing us constructive and valuable queries in bettering our manuscript in the revision. According to the remaining questions of referees, we have answered those questions raised by the referees carefully, and necessary changes have been made in the text. For the received queries, the replies are given below, and the changes in the manuscript have been marked in italic red color letters to show clearly. Reviewers' comments: Reviewer #1: The authors response well to the reviewers' comments and I therefore recommend its publication in Chem. Eng. J. Answer to comments: Thanks for the reviewer's recognition of our answers. Reviewer #3: Compared with the original version, a significant amount of work has gone into the revision of this paper, which has improved it considerably. In my opinion, it is acceptable for publication at its present form. Answer to comments: Thanks for the reviewer's recognition of our answers. Reviewer #9: Question 1: The authors suggested that the results of BCKP structure refinement will convince readers in spite that Biso of cations were over 2 and those for oxygens were over 3. However, as a crystallographer, the suggested crystal structure was less than satisfactory. In addition, the authors discussed the emission properties of BCKP based on the insufficient structure. Answer:...

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Photoluminescence and cathode-luminescence of Eu 3+doped NaLnTiO 4 (Ln = Gd and Y) phosphors3

Yb 3+ -Er 3+ ion co-doped NaLnTiO 4 (Ln ¼ Y, Gd) up-conversion (UC) phosphors were successfully synthesized by a sol-gel method. The phase purity and the structure of the samples were characterized by powder X-ray diffraction (XRD), and the optimal compositions were also determined according to their UC emission intensities. The samples emit orange light and their UC spectra were recorded with excitation by a laser diode with a 980 nm wavelength. The UC luminescence intensity could be enhanced greatly after introducing sensitizer Yb 3+ ions, and the energy transfer (ET) from Yb 3+ to Er 3+ plays a vital role. The UC mechanism and processes responsible for the emissions were investigated and found to involve two-photon absorption. The lifetime of green emission in Er 3+ singly doped and Yb 3+ -Er 3+ co-doped samples were measured to prove the existence of ET. The temperature dependence of the fluorescence intensity ratios (FIR) for the two green UC emission bands peaked at 530 and 550 nm was studied in the range of 300-510 K under excitation by a 980 diode laser with about 4 W cm À2 power density, and the maximum sensitivity was approximately 0.0045 K À1 at 510 K for NaYTiO 4 and 480 K for NaGdTiO 4 . This indicates that Yb 3+ -Er 3+ ion co-doped NaLnTiO 4 (Ln ¼ Y, Gd) phosphors are potential candidates for optical temperature sensors.

Eu3+-activated layered perovskite ionic conductor KGdTiO4 red emitting phosphors to be used for ultraviolet based light emitting diodes (LEDs) and field emission displays (FEDs) were successfully synthesized by a modified sol–gel method.

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