Two-dimensional (2D) Ti 3 C 2 MXenes have aroused tremendous attention as frontier materials for energy storage, solar energy conversion, and environmental remediation because they exhibit high elemental abundance in the earth, a unique layered microstructure, abundant surface functional groups, and prominent electrical conductivity and optical properties. The present study summarizes and discusses the most recent advancements in the synthesis methods of Ti 3 C 2 MXenes; the routes of intercalation, exfoliation, and cutting for multilayered Ti 3 C 2 to obtain its delaminated compounds and quantum dots; and their photocatalysis applications. Given the differences of applied Ti 3 C 2 on morphology and size, high-efficiency Ti 3 C 2 -based Schottky junction photocatalysts and its derivative photocatalysts are generalized and discussed. The advantages of Ti 3 C 2 MXenes in synthesizing high-efficiency photocatalysts are analyzed, consisting of electronic acceptor, substrate, light harvesting, cocatalyst, and precursor. Lastly, the lingering challenges and directions for the subsequent Ti 3 C 2 -based photocatalyst development are proposed.

In this communication, we fabricated graphene oxide membranes with tunable permeation by embedding carbon nanodots of controllable sizes.

Fluorescent nitrogen-enriched carbon nanodots (C-dots) of 1 to 3 nm were obtained through a one-pot reaction between melamine and glycerol. These C-dots show quantum yields up to 22% and a high two-photon absorption cross-section. The TiO 2 based photoanode sensitized by these C-dots is capable of converting near IR photon energy to photocurrent. The emergence of photoluminescent nanocarbons has attracted significant research interest in recent years, because carbon is cheap, abundant, chemically inert and biocompatible. Carbon nanodots (C-dots) are quasi-spherical particles of finite size, typically less than 5 nm, and comprise either amorphous or graphitic carbon. 1-3 Various works have demonstrated a promising application potential of C-dots in bioimaging, 2,4-7 optoelectronic devices 8 and photocatalysis. 9 A number of methods have been established to synthesize carbon nanodots, from 'top-down' approaches such as arc-discharge, 3 laser ablation, 2 and electrochemical exfoliation 10 to 'bottom-up' syntheses like carrier-supported resol carbonization, 6 dehydration of carbohydrates, 11 thermal oxidation, 12 microwaving 13 and 'hot injection' 14 of carbon precursors. The quantum yields (QYs) of these synthesized C-dots are generally low (typically under 15%). 2,6,13,15-19 While improving synthesis methods towards potential cost-effective mass production is a heated area, various studies have also attempted to unravel the photoluminescence mechanisms of C-dots. The luminescence origin was attributed to a surface trapping effect, 2 and other

The adsorption of reactive blue 4 (RB4) and acid red 183 (AR183) on a multiwall carbon nanotube (MWCNT) was investigated in single and binary dye systems. The MWCNT presented a higher adsorption of RB4 than AR183 in single and binary dye systems, due to stronger interactions. In single dye solutions, adsorption capacities of the MWCNT for RB4 and AR183 at 25 °C are (69 and 45) mg·g–1, respectively. The higher temperature resulted in lower adsorption of the dyes on the MWCNT. In binary dye solutions, RB4 and AR183 showed competitive adsorption, resulting in RB4 adsorption but desorption of AR183 on the MWCNT. RB4 adsorption capacity in binary dye systems was also reduced to 56 mg·g–1 at 25 °C. The interaction of the dyes with MWCNT was found to be dominated by electrostatic attraction.

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h i g h l i g h t s" Adsorption of methylene blue and acid red 183 on a MWCNT in single and binary dye systems was investigated. " MWCNT shows higher adsorption capacity to methylene blue in both systems. " A synergistic effect for basic and acid dyes occurs in a binary dye system. t r a c tA multiwalled carbon nanotube (MWCNT) was used as an adsorbent for removal of a cationic dye (methylene blue, MB) and acid dye (acid red 183, AR183) from aqueous solution in single and binary dye systems. Characterization of the MWCNT and MWCNT-dye systems were performed using several techniques such as Fourier transform infrared spectroscopy (FTIR), thermogravimetric-differential thermal analysis (TG-DTA), zeta potential and elemental analysis. Adsorption tests showed that the MWCNT presented higher adsorption of MB than AR183 in single and binary dye systems, revealing that p-p stacking is the main driving force responsible for the dye-MWCNT interaction. In single dye systems, the MWCNT presented the maximum adsorption capacities of MB and AR183 at 59.7 and 45.2 mg/g, respectively. In a binary dye system, a synergistic effect due to electronic attraction between MB and AR183 was found at low AR183 concentration (10 mg/L), which promotes the adsorption of both dyes on the MWCNT. However, MB adsorption could be reduced at higher AR183 concentration (>20 mg/L) due to a strong electrostatic attraction between MWCNT-AR183.

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