•The doping of Eu3+ ions decreased the size of CaCO3 nanoparticles.•The doping of Eu3+ ions brought about the change of CaCO3's optical bandgap.•Multiple sites of Eu3+ in CaCO3 nanocrystals have been identified.CaCO3:xEu3+ (x = 0, 0.010, 0.015, 0.020, and 0.025) cubic nanoparticles were synthesized by carbonation method. The powder XRD patterns and SEM images of the CaCO3:xEu3+ nanoparticles demonstrate that both the crystalline sizes and average particle sizes of synthesized samples decreased with the increase of Eu3+ content until x = 0.020. Kubelka–Munk plots and bandgap energy estimation indicate that the doping of Eu3+ ions changed optical bandgap of CaCO3. Photoluminescence (PL) spectra show that the PL intensity of the CaCO3:xEu3+ nanoparticles was enhanced with the increase of Eu3+ content in cubic CaCO3:xEu3+, and concentration quenching occurred when Eu3+ concentration exceeded 2.0 mol%. In addition, the doped sites of Eu3+ in CaCO3 crystalline were identified by the site-selective spectroscopy and decay curves.

•The results of FESEM and XRD showed that a coating layer of rutile TiO2 NPs was formed on the surface of calcite CaCO3.•The whiteness of TiO2@CaCO3 is similar to commercial rutile TiO2 particles.•The contrast ratios of the coatings were high and it remained 0.934 when rutile TiO2@CaCO3-15 completely substituted TiO2.•Rutile TiO2@CaCO3 could partly substitute TiO2 applied as pigments in interior emulsion coatings.In this paper, rutile TiO2@CaCO3 composites were in-situ synthesized by disaggregation and deposition of commercial TiO2 in alkaline Ca(OH)2 slurry via a convenient and easy industrialized carbonation method. Field emission scanning electron microscopy and X-ray diffraction were applied to characterize the surface morphology and crystalline phases of the TiO2@CaCO3 composites, and the results showed that a coating layer of rutile TiO2 nanoparticles was formed on the surface of calcite CaCO3. As confirmed by the thermal gravimetric analysis and acid-resistance, the composites had better thermal stability and acid-resistance compared with CaCO3. The UV–vis absorption spectra showed that rutile TiO2@CaCO3 composites possessed similar ultraviolet absorption capacity with TiO2. The contrast ratios of the coatings were high enough, and it remained 0.934 when rutile TiO2@CaCO3-15 completely substituted TiO2. Therefore, rutile TiO2@CaCO3 could partly substitute TiO2 applied as pigments in interior emulsion coatings.

•Monodisperse and uniform Lu2O2S:Eu3+ nanorods were prepared by solvothermal method.•Annealing temperature affects luminescence of the nanorods significantly.•The obtained 1D Lu2O2S:Eu3+ nanorods exhibit excellent red-luminescent properties.Highly crystalline and uniform Lu2O2S:Eu3+ nanorods have been successfully synthesized through a facile solvothermal method followed by a subsequent calcination process for the first time. X-ray diffraction (XRD), energy-dispersive X-ray spectrometry (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), and photoluminescence (PL) spectrum were utilized to characterize the samples. X-ray diffraction results demonstrate that all the diffraction peaks of the samples annealed at 600 °C can be well indexed to the pure hexagonal phase of Lu2O2S. From SEM and TEM it can be seen that Lu2O2S:Eu3+ nanorods are uniform rod-like nanostructures with a mean diameter of 22 nm and length of 500 nm. The effect of annealing temperature on the crystallinity and luminescent properties was investigated in detail. Furthermore, the obtained 1D Lu2O2S:Eu3+ nanorods exhibit strong red (Eu3+, 5D0 → 7F2) luminescence under ultraviolet (UV) excitation.

•This article studied the synthesis of lignin-modified silica nanoparticles from black liquor.•Silicon in black liquor as industrial waste was recovered.•Lignin in black liquor can control the diameter of silica.•CO2 obtained from the waste gas can be used as a precipitating reagent.A novel and green route was developed to prepare lignin-modified silica nanoparticles from black liquor by an integrated utilization strategy of rice straw. The lignin in black liquor was used as a structure directing reagent to control the particles' size, CO2 obtained from the waste gas of pulp mills was used as a precipitating reagent and finally the lignin-modified silica nanoparticles were obtained. The effects of lignin concentration, pH and temperature on the properties of the materials have been investigated in detail, and the synthesis mechanism of the lignin-modified silica nanoparticles was proposed based on a series of experimental results.In a wet colloid, the surface of the silica particles contains silanol groups (Si-O-H). Herein, silica particles and lignin molecules are connected to form hydrogen bonds. The steric hindrance of lignin limits the aggregation of silica.

In this study, in order to improve the dispersion and increase the compatibility between nanoparticles and waterborne polyurethane (WPU) matrix, CaCO3 nanoparticles were firstly modified with oleic acid (OA). A series of WPU/CaCO3 nanocomposites were prepared by further in situ polymerization. SEM examination of the fractured surfaces of nanocomposites showed that OA–CaCO3 achieved well dispersion in WPU matrix. FTIR analysis suggested no major changes in the chemical structure of WPU in the presence of 2 wt% CaCO3. Thermal stability of WPU measured by TGA was greatly improved with the addition of OA–CaCO3. Meanwhile, the mechanical properties of the nanocomposites, examined by tensile tests, showed higher tensile strength than that of the pure WPU, especially incorporation of OA–CaCO3.Graphical abstractThe dispersion and adhesion of 2 wt% nanoparticles in WPU matrix: (a) pure WPU; (b) unmodified CaCO3; (c) OA–CaCO3.Research highlights► Surface modification of CaCO3 nanoparticles by OA. ► Well dispersion of CaCO3 nanoparticles in WPU matrix. ► Preparation of WPU/CaCO3 nanocomposites with higher performance via in situ polymeration.

In this study, a facile solution-based chemical method has been developed to produce ZnO particles in the presence of triethanolamine (TEA) and NaOH. In this novel method, TEA acted as complexing reagents, and NaOH contributed to the transformation of ZnO precursor (Zn–TEA complex) into ZnO particles. The core of this new strategy is to transform Zn–TEA complex into morphological ZnO particles directly by a facile solution method. The results from transmission electron microscope (TEM) and field emission scanning electron microscope (FESEM) analysis revealed that the morphologies of the as-prepared ZnO samples evolved from slices to quasi-spheres by increasing the amount of TEA. X-ray diffraction (XRD), Raman and room-temperature photoluminescence (PL) tests showed that these ZnO samples had wurtzite structures. A reasonable mechanism for the transformation of Zn–TEA complex into morphological ZnO particles was supplied.