These are not the final page numbers! Ü Ü uniform. The low absorption/emission intensity of PNC supernatant is attributed to the low concentration of PNCs. This indicates that the as-formed PNCs can be easily collected by centrifugation (Supporting Information, Figure S5 b), which is desirable for cleaning and postprocessing in various applications.To explain the different capping effects of OA and APTES, we propose the following mechanism based on a dissolution-precipitation model (Figure 4 c). The dissolved precursors precipitate as PNCs at the DMF-toluene interface when the DMF precursor solution is injected into toluene. With OA as the capping ligand, the OA molecules adsorbed on the surface of the formed PNCs and PNSs diffuse from DMF to toluene, along with the products. However, the chain configuration of OA molecules cannot effectively prevent the products from dissolving back into DMF across the DMFtoluene interface and some OA ligands remain in the toluene phase because of their non-polar nature. The loss of OA ligands will result in a lack of ligands in the DMF phase, leading to the formation of large particles in the next round of precipitation. This effect becomes more pronounced when the concentrations of the precursors is high. On the contrary, the strong steric hindrance of APTES and the formation of silica can prohibit the dissolution of the as-formed PNCs back into DMF, which helps to maintain the original structural and optical properties of PNCs. Nevertheless, the PNC APTES-20 sample began to flocculate after standing for a few minutes (Supporting Information, Figure S7) because of hydrolysis of Si-O-C 2 H 5 groups attached to the PNC APTES surface, which generate hydroxy (-OH) groups (as indicated by FTIR spectra), resulting in a change in polarity and hydrogen bonding of the ligands.Water-induced degradation is a major problem for organic metal halide perovskites because protons are captured by methylammonium.[8] Similarly, they are also unstable towards other protic solvents such as alcohols.We hypothesized that PNC APTES may exhibit better stability because of the strong steric hindrance and hydrolysis properties of APTES, which reduces the access of protic solvent molecules to the PNCs surface. To test the stability of PNC APTES in protic solvents, 0.5 mg mL À1 of PNC precipitate capped by different ligands was dispersed in ethanol (Supporting Information, Figure S9 a and b). No emission was observed by the naked eye for PNC OA and PNC OABr dispersed in ethanol, and all XRD peaks (Supporting Information, Figure S9 c) of the decomposed products belong to rhombic PbBr 2 (JCPDS#31-0679). However, the PNC APTES precipitate showed high fluorescence intensity after sonication in ethanol, indicating better stability of PNC APTES in protic solvents.Long term stability tests were also conducted in different protic and polar solvents. As shown in Figure 5 a, the relative PL intensity of the PNC APTES-16 precipitate in isopropanol remained almost 70 % after 2.5 h. However, PNC precipitate showed p...

N-doped TiO(2) nanoparticles modified with carbon (denoted N-TiO(2)/C) were successfully prepared by a facile one-pot hydrothermal treatment in the presence of L-lysine, which acts as a ligand to control the nanocrystal growth and as a source of nitrogen and carbon. As-prepared nanocomposites were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), electron paramagnetic resonance (EPR) spectra, and N(2) adsorption-desorption analysis. The photocatalytic activities of the as-prepared photocatalysts were measured by the degradation of methyl orange (MO) under visible light irradiation at λ≥ 400 nm. The results show that N-TiO(2)/C nanocomposites increase absorption in the visible light region and exhibit a higher photocatalytic activity than pure TiO(2), commercial P25 and previously reported N-doped TiO(2) photocatalysts. We have demonstrated that the nitrogen was doped into the lattice and the carbon species were modified on the surface of the photocatalysts. N-doping narrows the band gap and C-modification enhances the visible light harvesting and accelerates the separation of the photo-generated electrons and holes. As a consequence, the photocatalytic activity is significantly improved. The molar ratio of L-lysine/TiCl(4) and the pH of the hydrothermal reaction solution are important factors affecting the photocatalytic activity of the N-TiO(2)/C; the optimum molar ratio of L-lysine/TiCl(4) is 8 and the optimum pH is ca. 4, at which the catalyst exhibits the highest reactivity. Our findings demonstrate that the as-obtained N-TiO(2)/C photocatalyst is a better and more promising candidate than well studied N-doped TiO(2) alternatives as visible light photocatalysts for potential applications in environmental purification.

Tailored synthesis of well-defined anatase TiO2 nanocrystals with a high percentage of reactive facets has attracted widespread attention due to the scientific and technological importance. Here, high-quality nanosized anatase ultrathin TiO2 nanosheets, mainly dominated by {001} facets, were grown on graphene nanosheets by a simple one-pot solvothermal synthetic route. The obtained samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), ultraviolet–visible (UV–vis) diffuse reflectance spectroscopy, and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of as-prepared TiO2/graphene composites for degradation of methylene blue (MB) under visible-light irradiation at λ ≥ 400 nm was investigated. The results show that TiO2/graphene nanocomposites have a higher photocatalytic activity than pure TiO2 and P25. This enhanced photocatalytic activity suggests that the photoinduced electrons in TiO2 prefer transferring to the graphene efficiently. As a consequence, the electron transfer via Ti–O–C between TiO2 and C interaction greatly retards the recombination of photoinduced charge carriers and prolongs the carrier lifetime, thus contributing to the enhancement of photocatalytic performance. The amount of graphene is an important factor affecting the photocatalytic activity of TiO2/graphene nanocomposites. The optimum amount of graphene is ca. 1 wt %, at which the TiO2/graphene sample displays the highest reactivity. Furthermore, the photodegradation rate does not show an obvious decrease during five successive cycles, indicating that our TiO2/graphene nanocomposites are stable visible-light photocatalysts.