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SCIENCE CHINA Materials, Volume 60, Issue 2: 109-118(2017) https://doi.org/10.1007/s40843-016-5131-9

Reduced-sized monolayer carbon nitride nanosheets for highly improved photoresponse for cell imaging and photocatalysis

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  • ReceivedSep 22, 2016
  • AcceptedOct 31, 2016
  • PublishedDec 13, 2016

Abstract

Two-dimensional graphitic carbon nitride (g-C3N4) nanosheets (GCNNs) have been considered as an attractive metal-free semiconductor because of their superior catalytic, optical, and electronic properties. However, it is still challenging to prepare monolayer GCNNs with a reduced lateral size in nanoscale. Herein, a highly efficient ultrasonic technique was used to prepare nanosized monolayer graphitic carbon nitride nanosheets (NMGCNs) with a thickness of around 0.6 nm and an average lateral size of about 55 nm. With a reduced lateral size yet monolayer thickness, NMGCNs show unique photo-responsive properties as compared to both large-sized GCNNs and GCN quantum dots. A dispersion of NMGCNs in water has good stability and exhibits strong blue fluorescence with a high quantum yield of 32%, showing good biocompatibility for cell imaging. Besides, compared to the multilayer GCNNs, NMGCNs show a highly improved photocatalysis under visible light irradiation. Overall, NMGCNs, characterized with monolayer and nanosized lateral dimension, fill the gap between large size (very high aspect ratio) and quantum dot-like counterparts, and show great potential applications as sensors, photo-related and electronic devices.


Funded by

National Basic Research Program of China(2014CB932400)

National Natural Science Foundation of China(51525204,51302274)

Shenzhen Basic Research Project(ZDSYS20140509172959981)

Key Laboratory of Advanced Materials of Ministry of Education(2016AML02)


Acknowledgment

This work was supported by the National Basic Research Program of China (2014CB932400), the National Natural Science Foundation of China (51525204 and 51302274), Shenzhen Basic Research Project (ZDSYS20140509172959981), and the Key Laboratory of Advanced Materials of Ministry of Education (2016AML02).


Interest statement

The authors declare that they have no conflict of interest.


Contributions statement

All authors contributed to the discussion and preparation of the manuscript. The final version of the manuscript was approved by all authors.


Author information

Qinghua Liang received his Bachelor’s degree from Southwest University in 2009 and Master’s degree from Technical Institute of Physics and Chemistry of Chinese Academy of Sciences in 2012. He obtained his PhD from Tsinghua University under the supervision of Prof. Quan-Hong Yang. His research interest focuses on the synthesis and application of carbon-based and carbon-derived materials for energy storage and environmental protection.


Quan-Hong Yang was born in 1972 and joined Tianjin University as a full professor of nanomaterials in 2006. He is now also leading a graphene lab as a co-PI at Tsinghua-Berkeley Shenzhen Institute (TBSI). His research is totally related to novel carbon materials, from porous carbons, tubular carbons to sheet-like graphenes with their applications in energy storage and environmental protection. See http://nanoyang.tju.edu.cn for more details.


Supplement

Supplementary information

Experimental details and supporting data are available in the online version of the paper.


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  • Figure 1

    Illustration for the preparation of NMGCNs.

  • Figure 2

    (a) Low-magnification AFM image, (b) the corresponding lateral size distribution, (c) high-magnification AFM image, (d) the corresponding height profile, and (e) TEM and (f) HRTEM images of the NMGCNs. The inset in (e) is the corresponding SAED pattern of the NMGCNs.

  • Figure 3

    (a) XRD patterns and (b) FTIR spectra of GCNNs and NMGCNs. (c) C 1s and (d) N 1s XPS spectra of NMGCN.

  • Figure 4

    (a) UV-visible absorption spectra, the Tyndall effect, the fluorescence image under UV light illumination, and (b) mass spectrum of the NMGCNs dispersed in water. (c) UV-visible DRS, and (d) Mott-Schottky plots of GCNNs and NMGCNs. The inset in (b) is the heptazine structure of carbon nitrides.

  • Figure 5

    (a) Bright field image, (b) fluorescence image under UV light, and (c) the corresponding overlay images of A549 cells incubated with NMGCNs for 6 h. (d) Viability of A549 cells incubated with different concentrations of NMGCNs for 48 h.

  • Figure 6

    (a) Photocatalytic degradation curves, (b) EIS plots and photocurrent curves under visible light irradiation, (c) PL emission, and (d) the time-resolved fluorescence decay spectra of the NMGCN powder. The inset in (a) is the UV-Vis absorption spectra of RhB after degradation by NMGCNs for different time.

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