Tremendous Acceleration of Plant Growth by Applying a New Sunlight Converter Sr₄Al_14−xGa_xO₂₅:Mn⁴⁺ Breaking Parity Forbidden Transition

Abstract

Majority of Mn4+ activated oxide phosphors have the wavelength of excitation and emission suitable for acceleration of plant growth as light converter from sunlight to deep red. Here, it is observed that 60% increase of red emission of Sr4Al14O25:0.01Mn4+ is found by substituting 0.1Ga3+. It is clarified that the increase is originated from a unique mechanism of breaking parity forbidden transition under the substitution of cation in d–d transition by using the tool of special aberration corrected transmission electron microscope(AC‐STEM), pre‐edge peak (1s→3d) Mn K‐edge X‐ray absorption near edge structure (XANES), extended X‐ray absorption fine structure (EXAFS), Rietveld analysis of X‐ray diffraction (XRD) patterns, and reflection spectra. Further, a combination of substituted Ga, Mg, and special double flux H3BO3/AlF3 is found to tremendously increase the emission intensity (355% up). Actual growth of chlorella and rose is examined by a combination of the cheap Sr4Al14O25:0.01Mn4+,0.007Mg2+,0.1Ga3+ and a unique reflection typed phosphor‐film system as sunlight converting system. Optical density of chlorella and height of rose grass is increased by 36±14% and 174±80% compared with nonphosphor‐film, respectively.

Blue-light-excitable pure and efficient short-wave infrared luminescenceviaCr3+→ Yb3+energy transfer in a KYbP2O7:Cr3+phosphor

“…The breaking of the parity-forbidden transition of Cr 3+ should also contribute to the increase of the SWIR luminescence intensity of Yb 3+ due to the increase of the excitation transition of Cr 3+ . 46 Then the SWIR luminescence intensity shows a decreasing trend with a further increase in Cr 3+ content owing to the concentration quenching effect. 52,53 It is worth noting that the NIR emission of Cr 3+ that should have appeared theoretically was completely quenched, while the Yb 3+ SWIR luminescence dominates in the emission spectrum.…”

“…The distorted lattice causes an uneven symmetric field, which promotes the deviation from inversion symmetry in the octahedral site occupied by Cr 3+ , helping in breaking the parity-forbidden transition of Cr 3+ . 42–46…”

Recent Advances in Light-Conversion Phosphors for Plant Growth and Strategies for the Modulation of Photoluminescence Properties

“…However, the traditional method of increasing crop yields through fertilizers and pesticides will bring serious long-term pollution, which is no longer suitable for the needs of plant growth development. Therefore, with the development of modern agriculture, indoor plant cultivation has attracted more and more attention [20,21].…”

“…This is mainly because the Ga-O bond is strongly covalent and can significantly alter the overlap of the 2p orbitals in the M-O-Mn bond, distorting the MnO 6 octahedron and disrupting the cosmically forbidden d-d transition in Mn 4+ . They mixed the phosphors with polydimethylsiloxane to prepare the light-conversion film, and the subsequent chlorella growth experiment proved that the light-conversion film has great potential in promoting plant growth (Figure 7c) [21]. Wang et al synthesized a red-luminescent ceramic (Mg 2 TiO 4 :Mn 4+ ) using a high temperature solid-state reaction method.…”

A New Efficient Deep-Red-Emission Phosphor Y3Al4.9Sb0.1O12: Ce3+, Cr3+ with Application Potential in Plant Growth

“…3,4 Therefore, how to regulate the required spectrum of plants during plant growth has been extensively studied. 5,6 In recent years, light conversion materials used in agricultural devices have received more and more attention. Generally, the light conversion materials used for plant growth are divided into several categories according to the PL and PLE bands: (1) Mainly the conversion from green to red, such as CaZnOS: Eu 2+ , (Ca, Sr)S: Eu 2+ , Ba 2 ZnS 3 : Eu 2+ , X − (X = Cl, Br, I), and Sr 2 Si 5 N 8 : Eu 2+ .…”