Xiaoping Dong

Facile Construction of g-C3N4 Nanosheets/TiO2 Nanotube Arrays as Z-Scheme Photocatalyst with Enhanced Visible-Light Performance

Semiconductor photocatalysis may be a promising strategy to face energy and environmental issues because it utilizes the solar energy as energy source. The artificially Z‐scheme photocatalytic system has attracted special interests owing to its high efficiency and strong redox ability. Graphitic carbon nitride nanosheets (g‐C3N4 NSs) display prominent performances, which are intensively investigated. Herein, we constructed an all‐solid‐state Z‐scheme photocatalytic system and firstly immobilized g‐C3N4 nanosheets on TiO2 nanotube arrays (TNTAs) by a simple method. The microstructures of prepared g‐C3N4 NSs/TNTAs photocatalyst were characterized by XRD, X‐ray photoelectron spectroscopy, SEM and TEM. The features of light absorption, charge separation, and charge transfer were analyzed by UV/Vis diffuse reflectance techniques, photoluminescence spectroscopy, electrochemical atomic force microscopy, and photocurrent measurement. The synthesized g‐C3N4 NSs/TNTAs samples shows enhanced photocatalytic efficiency for rhodamine B degradation under visible light, which is four times more than that of pure TNTAs. Tetracycline hydrochloride could also be effectively degraded under visible light, which contributes to reducing antibiotic residues in wastewater. Additionally, g‐C3N4 NSs/TNTAs also possess other advantages such as well long‐term stability and easily recyclable properties. A reaction mechanism is also proposed.

Graphene Quantum Dots Decorated Titania Nanosheets Heterojunction: Efficient Charge Separation and Enhanced Visible‐Light Photocatalytic Performance

Titania nanosheets (TNSs) are of importance for photocatalytic application owing to the unique two‐dimensional (2D) morphology, high crystallinity and plentiful surface charge. However, the large band gap prohibited the efficient utilization of sun light. Herein, we employed graphene quantum dots (GQDs) as green photocatalytic promoter to decorate TNSs during the electrostatic flocculation. The obtained GQDs/TNSs heterojunction was systematically characterized, and the results demonstrated that the composite exhibited an intimate coupling of GQDs and TNSs, a markedly visible light absorption and therefore the enhanced separation efficiency of photogenerated charges. This composite photocatalyst shows enhanced photocatalytic performance for the photodegradation of Rhodamine B (RhB) under visible light irradiation in comparison with pure restacked TNSs (rs‐TNSs) and GQDs. Furthermore, this composite exhibited a superior reusability, and a high degradation ratio about 90 % was still achieved in the 5th cycle. Moreover, a possible mechanism was proposed and superoxide radicals, holes and hydroxyl radicals were determined as the active species.

Facile surface modification of textiles with photocatalytic carbon nitride nanosheets and the excellent performance for self-cleaning and degradation of gaseous formaldehyde

Great advances in photocatalysis have been made by developing various efficient photocatalysts, but investigation on practical applications of photocatalysis is relatively backward. Herein we report a facile surface modification approach to functionalize textiles with excellent ability for photocatalytic self-cleaning and degradation of indoor volatile organic pollutants. Graphitic carbon nitride nanosheets (CNNS) in colloidal suspension were directly sprayed onto the surface of cellulose fibers in textiles, and the powerful hydrogen bonding action between surface hydroxyl groups of cellulose and plentiful hydroxyl and amino groups of exfoliated CNNS from alkali-treating realizes high stability of CNNS modified textiles. Due to ultrathin 2D thickness and high visible light transparency, the modification of CNNS would not affect the hand feeling of textiles and shield their original colors. The obtained textiles show superior photocatalytic self-cleaning performance to remove stains from various colored pollutants under solar light irradiation, including industrial organic dyes and juices. Meanwhile, gaseous formaldehyde also can be efficiently decomposed using Xe lamp or commercial LED lamp as light sources. This work realizes photocatalytic performance of textiles using a simple spraying method, and it has great potential application in textile self-cleaning, not only for surface stains but also for volatile organic compounds from textile release.

Facile preparation of N-doped graphene quantum dots as quick-dry fluorescent ink for anti-counterfeiting

Simple anti-counterfeiting printing using biocompatible, non-toxic and highly efficient luminescent materials plays crucial roles in economic and social fields as well as in our daily lives. In this work, new nitrogen doped graphene quantum dots (N-GQDs) are synthesized and applied in the preparation of quick-dry fluorescent ink for both writing and printing. The N-GQDs are synthesized based on a one-step bottom-up molecular fusion between 1,3,6-trinitropyrene and triethylamine by a solvothermal process with a high yield of 84.6%. Triethylamine simultaneously acts as a reaction medium and a nitrogen-doping agent for the formation of fluorescent N-GQDs. The as-prepared N-GQDs exhibit a single-layer graphene structure, high crystallinity, uniform size and excitation-independent fluorescence emission with a narrow half-peak width (66 nm). Successful doping of N atom in GQDs enables bright blue fluorescence with a high absolute photoluminescence quantum yield (17.8%). Owing to their excellent photostability and good solubility in ethanol, N-GQDs are applied to easily prepare quick-dry fluorescent ink for both writing and printing by simply blending GQDs with glycerol in an ethanol medium. Moreover, synthesis of a fluorescent powder and hydrogel is also achieved.

Synergistic effects of phosphorous/sulfur co-doping and morphological regulation for enhanced photocatalytic performance of graphitic carbon nitride nanosheets

Graphitic carbon nitride (g-C3N4) as a metal-free polymer semiconductor has received extensive attentions, but its application was drastically suppressed due to low photocatalytic activity. Herein, non-metal heteroatom co-doping is employed to extend the visible light absorption, and regulating morphology into nanosheets promotes the charge separation and transfer. Elements of P/S were successfully introduced into the carbon nitride framework by thermal condensation of their corresponding precursors with melamine. And, the presence of NH4Cl would produce abundant gas to blow CN layers separately to form thin nanosheets. The obtained P/S co-doped carbon nitride nanosheet (g-PSCNNS) sample presents enhanced absorption in visible light region and efficiencies for separation and transport of photo-generated charges. The synergistic effect of elemental co-doping and nanosheet-like morphology endues g-PSCNNS with superior photocatalytic performance for removal of organic pollutants in comparison with the pristine, P or S individual doped and P/S co-doped g-C3N4 samples. Moreover, this g-PSCNNS sample has excellent photocatalytic stability and reusability. Experiments of radical quenching demonstrate superoxide radical is the main active species in the photocatalytic process.

Highly efficient photo‐reduction of p‐nitrophenol by protonated graphitic carbon nitride nanosheets

Photocatalytic reduction of p‐nitrophenol to p‐aminophenol is important because of the high toxicity of p‐nitrophenol and the wide application of p‐aminophenol. Graphitic carbon nitride (g‐CN) is an excellent photocatalyst for various photo‐reduction reactions, but inefficient for photo‐reduction of p‐nitrophenol due to the electrostatic exclusion. In this work, we control the morphology and surface property of g‐CN and achieve significantly enhanced activity. The obtained protonated g‐CN nanosheet (pg‐CNNS) material has positively charged surface that can adsorb p‐nitrophenolate anions, therefore facilitating the transfer of photo‐generated electrons from catalyst to p‐nitrophenol. Its reaction rate is 1626 times higher than that of the pristine g‐CN. Besides the surface charge, the morphology of photocatalyst also has important effect on activity, which is demonstrated by the relatively low activity of protonated g‐CN in comparison to pg‐CNNS. The pg‐CNNS photocatalyst has an excellent stability and superior catalytic universality for photo‐reduction of various nitroaromatic compounds. This work does not only expand the application of a well‐known material, but also highlights the importance of understanding photocatalytic mechanism for designing photocatalyst.

Advanced nanomaterials for energy and environmental applications

1College of Materials Science and Engineering, China Jiliang University, No. 258 Xueyuan Street, Xiasha Higher Education District, Hangzhou, Zhejiang 310018, China 2Department of Chemistry, School of Sciences, Zhejiang Sci-Tech University, 928 Second Avenue, Xiasha Higher Education Zone, Hangzhou 310018, China 3School of Chemical Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, China 4Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, 610 Taylor Road, Piscataway, NJ 08854, USA 5Dipartimento di Chimica Inorganica, Metallorganica e Analitica, Unita INSTM, Universita degli Studi di Milano, Via Venezian 21, 20133 Milano, Italy