Hydrothermal synthesis and properties of pigments Chinese purple BaCuSi2O6 and dark blue BaCu2Si2O7

• In this work, a green chemistry strategy was developed to synthesize two inorganic pigments: Chinese purple BaCuSi2O6 and dark blue BaCu2Si2O7.
• And this soft chemistry method was characterized with good yield and high purity of the products.
• Hydrothermal synthetic BaCuSi2O6 exhibits purple instead of the blue of the reported solid state synthetic sample.
• Our study shows that hydrothermal synthetic BaCuSi2O6 exhibits interesting broad near-infrared luminesce.
• Furthermore, BaCuSi2O6 shows spin gapped antiferromagnetic property and dark blue BaCu2Si2O7 exhibits quasi-one-dimensional antiferromagnetic property.

A green chemistry strategy was developed to prepare two barium copper silicate pigments. Chinese purple BaCuSi2O6 and dark blue BaCu2Si2O7 are synthesized through mild hydrothermal treatment in narrow pH range. The compounds are characterized by powder X-ray diffraction techniques, infrared spectroscopy, X-ray photoelectron spectroscopy, energy dispersive spectroscopy, luminance and magnetic measurements. When excited by a visible laser, hydrothermally synthetic BaCuSi2O6 exhibits a broad emission in the near-infrared region with an excited state lifetime 6.4 μs due to the square-planar Cu2+ ions as the chromophores. Magnetic analysis of BaCuSi2O6 indicates the spin gapped antiferromagnetic property due the presence of the Cu–Cu dimers in the structure. BaCu2Si2O7 shows interesting quasi-one-dimensional antiferromagnetic property.

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