The preparation process of carbon quantum dots and TiO ₂ , and a diagram of the mechanism of the degradation of organic pollutants by composite materials under visible light.

The outstanding photocatalytic activity of Bi₂S₃/BiOCl heterostructures derived from enhanced light-utilization efficiency is demonstrated.

Increasing the electron density on the phthalocyanine (Pc) ring is an effective approach for ensuring an excellent third-order nonlinear optical (NLO) property. Herein, a series of axially substituted indium Pcs (axial substituent: ethyl, n-propyl, n-butyl, n-pentyl) were synthesized on the basis of tetra-[3-(2-ethoxy)ethoxy] indium phthalocyanine chloride (InClPc). The third-order nonlinear optical properties were investigated by the Z-scan technique at 532 nm with 4 ns laser pulses. All the axially alkyl substituted InPcs showed a better nonlinear absorption response than InClPc. The NLO properties of the axially substituted Pcs got better with the increased length of the alkyl chain. The effect of alkyl chain substituents on the nonlinear absorption of indium phthalocyanine was demonstrated through their optical physical parameters (Φ_F, k_ST, Φ_T, and τ_T).

Modulation of surface acid sites (SAS) can effectively enhance the efficiency of reactive oxygen species (ROS) production. However, the role of SAS has been neglected for photoreduction reactions. Here, we report a Lewis acid site (L-acid) rich TiO₂ prepared using the synergistic effect of ethanol and halogen ions. The formation of L-acid improves the adsorption and mobility of O₂, which facilitates its reduction into a superoxide radical (˙O₂ ⁻). L-acid may lift the population of photogenerated electrons (e⁻), which is concluded from the presence of a ˙CH₃ signal in the DMPO–˙O₂ ⁻ ESR spectrum of only L-acid rich TiO₂. In addition, L-acid enhances the migration of photogenerated holes (h⁺) to the surface of the catalyst, which induces a continuous photooxidation reaction of H₂O or –OH. Therefore, L-acid simultaneously enhances the photoredox ROS generation reaction, resulting in higher photocatalytic activity. This work illustrates a dual function of L-acid and provides a useful strategy for improving the photocarrier separation and surface reaction efficiency.