The practical fabrication of quantum dot materials, including their size, shape, form, crystallinity, and chemical composition, is a crucial research area in the field of photocatalysis. Quantum dots can effectively enhance the separation and transfer of carriers and expand the utilization of visible light when used in heterogeneous junctions with wide bandgap semiconductors. Additionally, they exhibit excellent photosensitivity properties that significantly improve the material's capacity for absorbing visible light. This paper systematically presents an overview of the outstanding optical properties exhibited by quantum dots based on both domestic and international research on photocatalytic materials. Furthermore, it summarizes the research content, characteristics, and current challenges associated with common types of quantum dots and photocatalytic materials while highlighting their applications in environmental remediation and energy production. Finally, this paper anticipates future trends in the development of photocatalysis by providing valuable insights into more efficient semiconductor materials that are cost-effective yet environmentally friendly.
A novel hydrophobic and cationic cyclodextrin-based acrylamide flocculant (AM-ß-CD-DMDAAC) was prepared by chemical oxidative polymerization to adsorb water-soluble dyes in dye wastewater. Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscope and thermogravimetric (TG) measurements results demonstrated that the AM-ß-CD-DMDAAC was successfully synthesized. The effects of pH, contact time, initial dye concentration, temperature and adsorbent dose on dye removal efficiency for AM-ß-CD-DMDAAC flocculants were investigated. The kinetic data were found to follow the pseudo-second-order kinetic model. The equilibrium adsorption data were fitted to the Langmuir isotherm model, with the maximum adsorption capacity of 147.1 mg g-1. The adsorbent retained about 60% of the adsorption efficiency after three adsorption/desorption cycles, which implied a promising application as the dye adsorbent.
Air filter paper with a high filtration efficiency that can remove small-size pollutant particles and toxic gases is vital for human health and the environment. We report a nanofiltration paper that is based on wood fiber filter paper with good mechanical properties and a three-dimensional network structure. The filter paper was prepared by impregnation with multi-walled carbon nanotubes (MWCNTs) and phenol-formaldehyde (PF). The results showed that MWCNTs were present on the surfaces of the fibers and between the pores, which increased the specific surface area of the fibers and enhanced the effective interception of the particles. The optimum impregnation concentration of the MWCNT was 0.1%. Compared with the cellulose fibers (CFs), the average pore diameter of the 0.1% MWCNT-CF filter paper was reduced by 8.05%, the filtration efficiency was increased by 0.64%, and the physical properties were slightly enhanced. After impregnation with PF, the mechanical properties of the air filter paper were significantly enhanced. The PF on the fiber surfaces and at the junction of the fibers covered the MWCNTs. Based on the change in the filter paper properties after impregnation, the optimal filter paper strength index and filtration performance were observed at a solid PF content of 8.4%.
Polypyrrole-based (PPy) composite are promising candidates for the treatment of water pollution. Adsorption selectivity as well as a large adsorption capacity are two key factors for treating wastewater containing multiple ions. The structure and morphology of the prepared composites were characterized by the FT-IR, XRD and SEM examinations. The results indicate that the Fe3O4 and PPy nanosphere coats attapulgite (ATP) closely and evenly. Herein, a novel Fe3O4 and ATP doped three-dimensional network structure PPy/Fe3O4/ATP composite was demonstrated as an excellent adsorbent to effectively remove Cr(vi). The as-synthesized PPy/Fe3O4/ATP composite is suitable for Cr(vi) adsorption in a wide pH range (pH 2-6). Up to a 96.44% removal rate was found with 400 mg L-1 Cr(vi) aqueous solution in 30 min for 0.2 g PPy/Fe3O4/ATP adsorbent. Adsorption results showed that Cr(vi) removal efficiency by PPy/Fe3O4/ATP decreased with an increase in pH. The removal rate of Cr(vi) had already reached 93.63% in 15 min contact time. Co-existing ions studies exhibit inorganic oxyacid anion and transition metal cation showed negative effects on Cr(vi) removal rate. A chemical rather than a physical adsorption occurred for these adsorbents as revealed by a pseudo-second-order kinetic study. The results of the adsorption isotherms showed that the adsorption process was similar to the Langmuir isotherm adsorption. Furthermore, the PPy/Fe3O4/ATP composite exhibited a high stability for Cr(vi) adsorption during recycling tests process. This work may provide some useful guidelines for designing adsorbents with selectivity toward specific heavy metal ions.
The polyamidoamine dendrimers, PAMAM-CMAC, was synthesized by decorating PAMAM dendrimer with coumarin-3-methyl acyl chlorine on the periphery. The structures were characterized by FTIR and H-NMR spectra. The fluorescence analysis indicated the PAMAM-CMAC exhibits strong fluorescence emission. The fluorescence intensity of PAMAM-CMAC is much higher than that of PAMAM dendrimer. The fluorescence intensity of PAMAM-CMAC was affected by pH, concentration and solvent. At a considerably big pH value range, the fluorescence emission of PAMAM-CMAC is comparatively stable. Meanwhile, the fluorescence emission of PAMAM-CMAC shifts to longer wavelength with the increase in solvent polarity.
