Fast Alkaline Hydrothermal Synthesis of Pyrophosphate BaCr<sub>2</sub>(P<sub>2</sub>O<sub>7</sub>)<sub>2</sub> Nanoparticles and Their NIR Spectral Reflectance
Recently, the development of nanoparticle pigments has attracted interest in chemical preparation due to their potential functional properties, such as phosphate-based pigments. The present research focuses on the feasibility of synthesising the BaCr<sub>2</sub>(P<sub>2</sub>...
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2025-06-01
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| author | Diego Emiliano Carrillo-Ramírez Juan Carlos Rendón-Angeles Zully Matamoros-Veloza Jorge López-Cuevas Isaías Juárez-Ramírez Tadaharu Ueda |
| author_facet | Diego Emiliano Carrillo-Ramírez Juan Carlos Rendón-Angeles Zully Matamoros-Veloza Jorge López-Cuevas Isaías Juárez-Ramírez Tadaharu Ueda |
| author_sort | Diego Emiliano Carrillo-Ramírez |
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| description | Recently, the development of nanoparticle pigments has attracted interest in chemical preparation due to their potential functional properties, such as phosphate-based pigments. The present research focuses on the feasibility of synthesising the BaCr<sub>2</sub>(P<sub>2</sub>O<sub>7</sub>)<sub>2</sub> pigment under hydrothermal conditions. The effect of the microstructural features of ceramic pigments (the crystalline structure, morphology, and particle size) on their optical properties (colour and reflectance) was also studied. The BaCr<sub>2</sub>(P<sub>2</sub>O<sub>7</sub>)<sub>2</sub> compound was prepared in different fluid media, including water and NaOH solutions (0.5–1.0 M), at several reaction temperatures (170–240 °C) and intervals (6–48 h). The single-phase BaCr<sub>2</sub>(P<sub>2</sub>O<sub>7</sub>)<sub>2</sub> did not crystallise without by-products (BaCr<sub>2</sub>O<sub>10</sub>, BaCr<sub>2</sub>(PO<sub>7</sub>)<sub>2</sub>) in water and the alkaline solutions, even at 240 °C for 48 h; in these fluids, the ionic Cr<sup>3+</sup> species oxidised to Cr<sup>6+</sup>. In contrast, the BaCr<sub>2</sub>(P<sub>2</sub>O<sub>7</sub>)<sub>2</sub> single-phase crystallisation was favoured by adding urea as a reductant agent (25.0–300.0 mmol). Monodispersed BaCr<sub>2</sub>(P<sub>2</sub>O<sub>7</sub>)<sub>2</sub> fine particles with a mean size of 44.0 nm were synthesised at a low temperature of 170 °C for 6 h with 0.5 M NaOH solution in the presence of 50.0 mmol urea. The phosphate pigment particle grew to approximately 62.0 nm by increasing the treatment temperature to 240 °C. A secondary dissolution–recrystallisation achieved after 24 h triggered a change in the particle morphology coupled with the incrementation of the concentration of NaOH in the solution. The pyrophosphate BaCr<sub>2</sub>(P<sub>2</sub>O<sub>7</sub>)<sub>2</sub> pigments prepared in this study belong to the green colour spectral space according to the CIELab coordinates measurement, and exhibit 67.5% high near-infrared (NIR) solar reflectance. |
| format | Article |
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| spelling | doaj-art-f1b13c13c58c4b9e9e2d58cc8624c81b2025-07-11T14:41:25ZengMDPI AGNanomaterials2079-49912025-06-01151398210.3390/nano15130982Fast Alkaline Hydrothermal Synthesis of Pyrophosphate BaCr<sub>2</sub>(P<sub>2</sub>O<sub>7</sub>)<sub>2</sub> Nanoparticles and Their NIR Spectral ReflectanceDiego Emiliano Carrillo-Ramírez0Juan Carlos Rendón-Angeles1Zully Matamoros-Veloza2Jorge López-Cuevas3Isaías Juárez-Ramírez4Tadaharu Ueda5Center for Research and Advanced Studies of National Polytechnic Institute, Saltillo-Campus, Ramos Arizpe, Coahuila 25900, MexicoCenter for Research and Advanced Studies of National Polytechnic Institute, Saltillo-Campus, Ramos Arizpe, Coahuila 25900, MexicoGraduate Division, Tecnológico Nacional de México (I.T Saltillo), Technological Institute of Saltillo, Saltillo 25280, MexicoCenter for Research and Advanced Studies of National Polytechnic Institute, Saltillo-Campus, Ramos Arizpe, Coahuila 25900, MexicoEcomaterials and Energy Department, Civil Engineering Faculty, Universidad Autónoma de Nuevo León, San Nicolás de Los Garza, Nuevo León 66455, MexicoDepartment of Marine Resources Science, Faculty of Agriculture and Marine Science, Marine Core Research Institute, MEDi Centre, Kochi University, Nankoku 783-8502, JapanRecently, the development of nanoparticle pigments has attracted interest in chemical preparation due to their potential functional properties, such as phosphate-based pigments. The present research focuses on the feasibility of synthesising the BaCr<sub>2</sub>(P<sub>2</sub>O<sub>7</sub>)<sub>2</sub> pigment under hydrothermal conditions. The effect of the microstructural features of ceramic pigments (the crystalline structure, morphology, and particle size) on their optical properties (colour and reflectance) was also studied. The BaCr<sub>2</sub>(P<sub>2</sub>O<sub>7</sub>)<sub>2</sub> compound was prepared in different fluid media, including water and NaOH solutions (0.5–1.0 M), at several reaction temperatures (170–240 °C) and intervals (6–48 h). The single-phase BaCr<sub>2</sub>(P<sub>2</sub>O<sub>7</sub>)<sub>2</sub> did not crystallise without by-products (BaCr<sub>2</sub>O<sub>10</sub>, BaCr<sub>2</sub>(PO<sub>7</sub>)<sub>2</sub>) in water and the alkaline solutions, even at 240 °C for 48 h; in these fluids, the ionic Cr<sup>3+</sup> species oxidised to Cr<sup>6+</sup>. In contrast, the BaCr<sub>2</sub>(P<sub>2</sub>O<sub>7</sub>)<sub>2</sub> single-phase crystallisation was favoured by adding urea as a reductant agent (25.0–300.0 mmol). Monodispersed BaCr<sub>2</sub>(P<sub>2</sub>O<sub>7</sub>)<sub>2</sub> fine particles with a mean size of 44.0 nm were synthesised at a low temperature of 170 °C for 6 h with 0.5 M NaOH solution in the presence of 50.0 mmol urea. The phosphate pigment particle grew to approximately 62.0 nm by increasing the treatment temperature to 240 °C. A secondary dissolution–recrystallisation achieved after 24 h triggered a change in the particle morphology coupled with the incrementation of the concentration of NaOH in the solution. The pyrophosphate BaCr<sub>2</sub>(P<sub>2</sub>O<sub>7</sub>)<sub>2</sub> pigments prepared in this study belong to the green colour spectral space according to the CIELab coordinates measurement, and exhibit 67.5% high near-infrared (NIR) solar reflectance.https://www.mdpi.com/2079-4991/15/13/982BaCr<sub>2</sub>(P<sub>2</sub>O<sub>7</sub>)<sub>2</sub>hydrothermal synthesisreductant agentnanoparticlesalkaline media |
| spellingShingle | Diego Emiliano Carrillo-Ramírez Juan Carlos Rendón-Angeles Zully Matamoros-Veloza Jorge López-Cuevas Isaías Juárez-Ramírez Tadaharu Ueda Fast Alkaline Hydrothermal Synthesis of Pyrophosphate BaCr<sub>2</sub>(P<sub>2</sub>O<sub>7</sub>)<sub>2</sub> Nanoparticles and Their NIR Spectral Reflectance Nanomaterials BaCr<sub>2</sub>(P<sub>2</sub>O<sub>7</sub>)<sub>2</sub> hydrothermal synthesis reductant agent nanoparticles alkaline media |
| title | Fast Alkaline Hydrothermal Synthesis of Pyrophosphate BaCr<sub>2</sub>(P<sub>2</sub>O<sub>7</sub>)<sub>2</sub> Nanoparticles and Their NIR Spectral Reflectance |
| title_full | Fast Alkaline Hydrothermal Synthesis of Pyrophosphate BaCr<sub>2</sub>(P<sub>2</sub>O<sub>7</sub>)<sub>2</sub> Nanoparticles and Their NIR Spectral Reflectance |
| title_fullStr | Fast Alkaline Hydrothermal Synthesis of Pyrophosphate BaCr<sub>2</sub>(P<sub>2</sub>O<sub>7</sub>)<sub>2</sub> Nanoparticles and Their NIR Spectral Reflectance |
| title_full_unstemmed | Fast Alkaline Hydrothermal Synthesis of Pyrophosphate BaCr<sub>2</sub>(P<sub>2</sub>O<sub>7</sub>)<sub>2</sub> Nanoparticles and Their NIR Spectral Reflectance |
| title_short | Fast Alkaline Hydrothermal Synthesis of Pyrophosphate BaCr<sub>2</sub>(P<sub>2</sub>O<sub>7</sub>)<sub>2</sub> Nanoparticles and Their NIR Spectral Reflectance |
| title_sort | fast alkaline hydrothermal synthesis of pyrophosphate bacr sub 2 sub p sub 2 sub o sub 7 sub sub 2 sub nanoparticles and their nir spectral reflectance |
| topic | BaCr<sub>2</sub>(P<sub>2</sub>O<sub>7</sub>)<sub>2</sub> hydrothermal synthesis reductant agent nanoparticles alkaline media |
| url | https://www.mdpi.com/2079-4991/15/13/982 |
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