CRYSTAL FOR SOLAR BLIND TECHNOLOGY

Description

CRYSTAL FOR SOLAR BLIND TECHNOLOGY Field of invention

[001] The present invention relates to obtaining an inorganic crystalline solid with the chemical formula (NH4)2Mn0.47Cu0.53(SO4)2(H2O)6, belonging to the isomorphic class of mixed Tutton salts via an isothermal evaporation method. This product, when excited at a specific wavelength, exhibits light emission in the visible region of the electromagnetic spectrum in the colors green, orange, and red. Furthermore, the crystal exhibits approximately 100% light absorption in the spectral range of 190 to 290 nm, making this system a promising candidate for solar-blind technology. It is also worth noting that the invention produces samples of considerable size, free from surface defects and with good thermal stability. The growth technique used proves advantageous because, in addition to low cost and rapid production, it produces systems with dimensions of commercial interest. Fundamentals of the invention

[002] In recent years, one of the main impacts that has generated great concern for life on Earth is a significant hole in the ozone layer above Antarctica, since the ozonosphere is responsible for protecting around 90% of humans from harmful ultraviolet (UV) radiation from the sun (STOLARSKI, Richard S. et al. Nimbus 7 satellite measurements of the springtime Petition 870250004462, dated 20 / 01 / 2025, page 7 / 23 2 / 11 Antarctic ozone decrease. Nature, v. 322, n. 6082, p. 808-811, 1986.). The UV band can be divided into three regions: UV-A (315 to 400 nm), UV-B (280 to 315 nm) and UV-C (100 to 280 nm). In this context, the UV region between 230 and 290 nm, called the solar blind, has been extensively investigated by scientists because no UV-C photons can reach the Earth's atmosphere; that is, this band can be detected without the influence of solar radiation (CAI, Qing et al. Progress on AlGaN-based solar-blind ultraviolet photodetectors and focal plane arrays).

[003] In this scenario, only some remnants of radiation with wavelengths shorter than 300 nm are present on Earth. In other words, the UV-C range is suppressed, which favors the detection of solar-blind UV photons that do not originate from solar radiation; therefore, it is expected that obtaining a signal in this region will be easier and of high quality. Given this, photodetector materials have been gaining prominence in this field, being used in the development of modern optoelectronic devices, such as: systems for missile approach warnings, ozone layer damage monitoring processes, fire sentinel devices, among others (MANOMENOVA, Vera L.; RUDNEVA, Elena B.; VOLOSHIN, Alexey E. Crystals of the simple and complex nickel and cobalt sulfates as optical filters for Petition 870250004462, dated 20 / 01 / 2025, page 8 / 23 3 / 11 the solar-blind technology. Russian Chemical Reviews, vol. 85, no. 6, p. 585, 2016).

[004] Currently, photodetectors for blind solar purposes are composed of various types of compounds, most notably silicon carbide (SiC), aluminum nitride (AlN), and gallium nitride (GaN). These materials are sensitive to wavelengths below 300 nm and do not respond to infrared, visible, and near-UV radiation (OZDEMIR, Yusuf B.; TEKER, Kasif; YILDIRIM, Mustafa A. High-responsivity flexible ultraviolet photodetector via single aluminum nitride nanowire. Optical Engineering, v. 60, n. 5, p. 057104, 2021). Given this, crystalline sulfated salts, such as Tuttton salts, have emerged as promising systems for this type of technology, due to their structural, optical, and thermal properties.

[005] Tutton salts belong to an isomorphic hexahydrate crystallographic family with the general chemical formula: X2Y(ZO4)2(H2O)6, in which X is occupied by a monovalent cation (Cs+, K+, Rb+, Na+, NH4+); Y is substituted by a divalent positive species (Cd2+, V2+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Ca2+, Mg2+); and Z is an active center due to the introduction of sulfur or selenium atoms (S and Se). These compounds crystallize in a monoclinic system containing space group P 21 / a, two formulas per unit cell (Z= 2), and 3 molecular fragments that interact in the structural unit via intermolecular interactions (PEETS, Darren C. et al. Crystal Growth, Petition 870250004462, dated 20 / 01 / 2025, page 9 / 23 4 / 11 Structure, and Noninteracting Quantum Spins in Cyanochroite, K2Cu(SO4)2-6H2O. ACS omega, v. 7, n. 6, p. 5139-5145, 2022). Furthermore, these materials exhibit varied phases under the effect of extreme temperature, pressure, and magnetic field conditions, and may exhibit new physical properties as a function of these variables.

[006] In the last 5 years, a great diversity of Tutton salts have been synthesized and reported in the state of the art; however, a modification has been introduced compared to past crystals. In the bivalent Y site, there is an occupation of two transition metals, so that they make up one mole according to the chemical equation. This alteration, in addition to causing structural effects in the unit cell of these materials, introduces changes in spectroscopic properties that provide opportunities and broaden their purpose in the area of ​​materials science, and they can be used in the development of devices for solar energy absorption, luminescent systems, electrodes for solid-state batteries, etc. (GHOSH, Santunu et al. Growth and characterization of ammonium nickel-cobalt sulfate Tutton's salt for UV light applications. Journal of Crystal Growth, v. 487, p. 104-115, 2018).

[007] Even with the plurality of Tutton salts previously reported in the literature, no material reports the inclusion of Mn2+ and Cu2+ ions in this class, this combination being of great commercial interest to the optical industry due to its high absorption factor in the UV region. Furthermore Petition 870250004462, dated 20 / 01 / 2025, page 10 / 23 5 / 11 of this, the presence of manganese in the crystal offers new photoluminescence properties to the material, due to electronic deactivation (MANAKA, MC; MOTHUDI, BM; DHLAMINI, MS Photoluminescence and thermoluminescence properties of manganese doped BaAl2O4 phosphor. Materials Science and Engineering: B, v. 278, p. 115604, 2022). Some works similar to these findings are described below.

[008] In the work of A. Souamti et al., single crystals with the chemical composition K2Co(SO4)2(H2O)6 doped with Nd2O3 were obtained by the slow evaporation method and showed light emission properties in the region between 750 and 1100 nm, directing their application to optical devices, however no characteristics of commercial interest were reported in the UV and visible region (SOUAMTI, A. et al. Synthesis, characterization and spectroscopic properties of a new Nd3+-doped Co-picromerite-type Tutton salt. Journal of Luminescence, v. 177, p. 93-98, 2016).

[009] Complementarily, Santunu Ghosh et al. synthesized a series of crystals with the formula (NH4)2NixCo(1x)(SO4)26H2O from stoichiometric proportions in water. These salts were obtained with good optical quality, showed considerable thermal stability, and demonstrated that the introduction of cobalt into the lattice reduces the transmittance of visible light (GHOSH, Santunu et al. Growth and characterization of Tutton's salt of nickel-cobalt ammonium sulfate for Petition 870250004462, dated 20 / 01 / 2025, page 11 / 23 6 / 11 UV light applications. Journal of Crystal Growth, v. 487, p. 104-115, 2018). However, the data did not support a specific purpose for these samples, limiting them to a study characterizing their physical and chemical properties.

[0010] Similarly, in 2018, Santunu Ghosh et al. produced a series of mixed Tutton salts of the type (NH4)2NixCu(1-x)(SO4)26H2O, which exhibited optical properties of great commercial interest due to 98% transmittance in the UV region, making the samples candidates for use in the development of UV sensors and UV filters for solar-blind technology (GHOSH, Santunu et al. Growth and characterization of ammonium nickel-copper sulfate hexahydrate: A new crystal of Tutton's salt family for the application in solar-blind technology. Optical Materials, v. 85, p. 425-437, 2018). However, these materials were limited to this, not exhibiting photoluminescent properties that would broaden their spectroscopic potential.

[0011] Patent registered in US5788755A, titled CRYSTALS FOR ULTRAVIOLET LIGHT FILTERS, is one of the most widely disseminated documents in the world literature on research involving applications of crystalline solids in modern optical devices, in which crystals with the composition Ni(BF4)26H2O are presented, developed to filter UV light and which do not deteriorate at temperatures up to 110 °C. However, the growth method used, besides being complicated, does not always produce crystals with good optical quality. Petition 870250004462, dated 20 / 01 / 2025, p. 12 / 23 7 / 11

[0012] From this scenario, it is observed that even with the varied research related to pure and mixed Tutton salts, there are still adversities in the literature that need to be overcome to make them better candidates for use in optical devices, such as solar blind technology. Examples of these problems are: crystals with very small dimensions, interfacial defects, translucency, opacity, undefined morphology, low interaction between the luminescent centers and the host matrix, passive surface oxidation, inefficient synthesis method, among others. However, all these complications can be resolved by the appropriate choice of synthesis method and starting compounds. This process ensures that the resulting crystalline solids possess desirable physical properties for application in solar blind technology, since, based on the crystallization technique used, crystals with good optical quality can be obtained.

[0013] Given the above, it was analyzed that to date there is no product in the literature compatible with a mixed Tutton salt with chemical composition (NH4)2Mn0.47Cu0.53(SO4)2(H2O)6, obtained with well-defined morphology and facets by the isothermal evaporation method, for application in solar blind technology.

[0014] In contrast to materials already widely discussed in the literature, the mixed Tutton salt (NH4)2Mn0.47Cu0.53(SO4)2(H2O)6 can be used as a photodetector in blind technology. Petition 870250004462, dated 20 / 01 / 2025, page 13 / 23 8 / 11 solar, absorbing around 100% of UV light in the range of 190 to 290 nm. Furthermore, under excitation at 400 nm, this crystal exhibits photoluminescence, emitting light in the green, orange, and red regions of the electromagnetic spectrum. In addition to these properties, it is worth emphasizing the phase transitions that this system exhibits under varying temperature conditions, which also makes it attractive for the development of solar energy storage devices. The synthesis method employed to obtain the material allows for rapid, efficient, and low-cost nucleation of the solid phase. Brief description of the drawings

[0015] The crystal obtained associated with the novel mixed Tutton salt (NH4)2Mn0.47Cu0.53(SO4)2(H2O)6 is presented in Figure 1 shows the crystalline nature, with defined facets and morphology, as well as the blue color resulting from the Cu2+ ions in the crystal lattice.

[0016] Figure 2 shows the structural determination via X-ray diffraction (XRD) method in the single crystal under ambient conditions.

[0017] The inset in Figure 2 shows the structural formula of the new crystal (NH4)2Mn0.47Cu0.53(SO4)2(H2O)6 within the unit cell, in which it is possible to see the 3 molecular fragments (SO42-, NH4+ and Mn0.47Cu0.53(H2O)6) interacting in the unit cell via secondary bonds. Petition 870250004462, dated 20 / 01 / 2025, page 14 / 23 9 / 11

[0018] Figure 3 shows the photoluminescence spectrum in the emission regime under excitation at 400 nm in the spectral range from 540 to 650 nm, where it is possible to verify 4 emission bands associated with the electronic transitions of divalent cationic ions. Description of the invention

[0019] For the synthesis of the mixed Tutton salt (NH4)2Mn0.47Cu0.53(SO4)2(H2O)6, the isothermal evaporation method (25 °C) was used using a saturated solution.

[0020] A 40 mL solution of deionized water was prepared using the precursor compounds (NH4)2SO4 (99% Vetec), MnSO4(H2O) (98% - Vetec) and CuSO4(H2O)5 (99% - Synth), in a molar ratio of 2:1:1, respectively. The metals make up 1 mol at the divalent site (Y), according to the following chemical reaction: (NH4)2SO4 + MnSO4(H2O) + CuSO4(H2O)5 → (NH4)2Mn1 → CuSO4(SO4)2(H2O)6.

[0021] The compounds were homogenized in solution for a period of 300 minutes using a magnetic stirrer at 460 RPM with a stabilized temperature of 75 °C. Subsequently, the precursor solution of the (NH4)2Mn0.47Cu0.53(SO4)2(H2O)6 crystal was stored in a growth chamber at 25 °C for isothermal evaporation of the solvent, and consequently nucleation of the crystalline solid phase. After 15 days, transparent crystals were obtained and removed from the solution by filtration. These materials Petition 870250004462, dated 20 / 01 / 2025, page 15 / 23 Samples 10 / 11 were washed with acetone and left to dry at room temperature for 24 hours before being characterized.

[0022] The (NH4)2Mno.47Cuo.53(SO4)2(H2O)6 crystal had its structural nature determined from XRD applied to a single crystal, as shown in Figure 2, where it was possible to determine all structural parameters. The spectroscopic properties were also confirmed through molecular absorption spectroscopy and photoluminescence. The data obtained favor the application of this system in the development of devices for solar blind technology. Examples of embodiments of the invention

[0023] Several characterization techniques were performed on the (NH4)2Mn0.47Cu0.53(SO4)2(H2O)6 crystal to verify its structural and spectroscopic properties, as well as to confirm its potential for use in optical devices.

[0024] Through the structural determination presented in Figure 2, it was possible to identify that the sample (NH4)2Mn0.47Cu0.53(SO4)2(H2O)6 crystallized in a monoclinic system of space group P21 / c, containing two formulas per unit cell. Furthermore, it was observed that the divalent site Y is occupied by a ratio of 0.47 / 0.53, of Mn and Cu, respectively. The material presented the empirical formula Cu0.53H20Mn0.47N2O14S2 with a molecular weight of 395.84 g / mol. The lattice parameters obtained were: a = 6.2625(4) Â, b= 12.5177(6) Â, c = 9.2839(6) Â, α=β= 90 °, γ= 106, 475(2) ° and V= 697.90(3) Â3. The diffractogram shows the Bragg positions Petition 870250004462, dated 20 / 01 / 2025, page 16 / 23 11 / 11 associated with the crystalline planes: (011), (110), (021), (121), (012), (031), (130), (131), (221), (213), (004), (204) and (053).

[0025] The mixed Tutton salt (NH4)2Mn0.47Cu0.53(SO4)2(H2O)6 showed almost 100% absorbance in the range of 190 to 290 nm and 700 to 1100 nm. Furthermore, in the spectral region of 540 to 650 nm, under excitation at 400 nm, this solid exhibited 4 emission bands associated with photoluminescence in the green, orange, and red regions. These characteristics make the (NH4)2Mn0.47Cu0.53(SO4)2(H2O)6 crystal an excellent candidate to be used as a photodetector for solar blind technology.

Claims

CLAIMS 1. CRYSTAL, characterized by its chemical formula being (NH4) 2Mn0.47CU0.53 (SO4) 2 (H2O) 6.

2. CRYSTAL (NH4)2Mn0.47CuO53(SO4)2(H2O)6, according to claim 1, characterized by the introduction of Mn2+ and Cu species into the (NH4)2(SO4)2(H2O)g matrix, using aqueous solutions of manganese sulfate monohydrate (MnSO4(H2O)) and copper sulfate pentahydrate (CuSO4(H2O)5), such that these make up 1 mol, according to the following chemical reaction: (NH4)23O4 + MnSO4(H2O) + CuSO4(H2O)5 → (NH4)2Mn0.47CuO53(SO4)2(H2O)6 3. PROCESS FOR OBTAINING THE (NH4)2Mn0.47Cu0.53(SO4)2(H2O)6 CRYSTAL, characterized by the synthesis method following these steps: a) preparation of the matrix solution of the mixed Tutton salt (NH4)2Mn0.47Cu0.53(SO4)2(H2O)6 using an aqueous solution of deionized water (40 mL) containing 5.2856 g of (NH4)2SO4; b) insertion of 10 ns Mn and Cu into the crystal lattice, using the starting compounds MnSO4(H2O), 3.3804 g, and CuSO4(H2O)5, 4.9936 g, in a molar ratio of 2 (matrix) : 1 (metal 1) : 1 (metal 2), according to the following chemical equation: (NH4)2SO4 + MnSO4(H2O) + CuSO4 (H2O) 5 - (NH4)2MnixCux(SO4)2(H2O)g; c) solubilization of these reagents by continuous magnetic stirring (460 RPM) for 300 minutes at a fixed temperature of 75 °C, after this process; Petition 870250004462, dated 20 / 01 / 2025, page 20 / 23 2 / 2 d) conditioning of the solution in a crystal growth room with a controlled temperature of 25 °C for isothermal evaporation of the solvent and nucleation of the solid phase.

4. USE OF THE (NH4)2Mn0.47Cu0.53(SO4)2(H2O)6 CRYSTAL, according to claims 1 to 3, characterized by having a transmittance of around 100% in the spectral range of 190 to 290 nm and emitting light in the visible region of the electromagnetic spectrum when excited by a source at 400 nm, being favorable for the development of photodetectors for solar blind technology, for example, due to its characteristic structural and spectroscopic properties.

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