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

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


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)


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.


Supplementary information

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


[1] Zeng Q, Wang H, Fu W, et al. Band engineering for novel two-dimensional atomic layers. Small, 2015, 11: 1868-1884 CrossRef PubMed Google Scholar

[2] Zhang H. Ultrathin two-dimensional nanomaterials. ACS Nano, 2015, 9: 9451-9469 CrossRef Google Scholar

[3] Liu J, Cao H, Jiang B, et al. Newborn 2D materials for flexible energy conversion and storage. Sci China Mater, 2016, 59: 459-474 CrossRef Google Scholar

[4] Liang L, Li K, Xiao C, et al. Vacancy associates-rich ultrathin nanosheets for high performance and flexible nonvolatile memory device. J Am Chem Soc, 2015, 137: 3102-3108 CrossRef PubMed Google Scholar

[5] Yu XY, Hu H, Wang Y, et al. Ultrathin MoS2 nanosheets supported on N-doped carbon nanoboxes with enhanced lithium storage and electrocatalytic properties. Angew Chem Int Ed, 2015, 54: 7395-7398 CrossRef PubMed Google Scholar

[6] Tan C, Yu P, Hu Y, et al. High-yield exfoliation of ultrathin two-dimensional ternary chalcogenide nanosheets for highly sensitive and selective fluorescence DNA sensors. J Am Chem Soc, 2015, 137: 10430-10436 CrossRef PubMed Google Scholar

[7] Ma TY, Tang Y, Dai S, et al. Proton-functionalized two-dimensional graphitic carbon nitride nanosheet: an excellent metal-/label-free biosensing platform. Small, 2014, 10: 2382-2389 CrossRef PubMed Google Scholar

[8] Zheng Y, Dou X, Li H, et al. Bisulfite induced chemiluminescence of g-C3N4 nanosheets and enhanced by metal ions. Nanoscale, 2016, 8: 4933-4937 CrossRef PubMed ADS Google Scholar

[9] Xiang MH, Liu JW, Li N, et al. A fluorescent graphitic carbon nitride nanosheet biosensor for highly sensitive, label-free detection of alkaline phosphatase. Nanoscale, 2016, 8: 4727-4732 CrossRef PubMed ADS Google Scholar

[10] Wang S, Li K, Chen Y, et al. Biocompatible PEGylated MoS2 nanosheets: controllable bottom-up synthesis and highly efficient photothermal regression of tumor. Biomaterials, 2015, 39: 206-217 CrossRef PubMed Google Scholar

[11] Ang H, Tan HT, Luo ZM, et al. Hydrophilic nitrogen and sulfur co-doped molybdenum carbide nanosheets for electrochemical hydrogen evolution. Small, 2015, 11: 6278-6284 CrossRef PubMed Google Scholar

[12] Huang H, Feng X, Du C, et al. High-quality phosphorus-doped MoS2 ultrathin nanosheets with amenable ORR catalytic activity. Chem Commun, 2015, 51: 7903-7906 CrossRef PubMed Google Scholar

[13] Lin Q, Li L, Liang S, et al. Efficient synthesis of monolayer carbon nitride 2D nanosheet with tunable concentration and enhanced visible-light photocatalytic activities. Appl Catal B-Environ, 2015, 163: 135-142 CrossRef Google Scholar

[14] Zhang M, Luo Z, Zhou M, et al. Photocatalytic water oxidation by layered Co/h-BCN hybrids. Sci China Mater, 2015, 58: 867-876 CrossRef Google Scholar

[15] Hu C, Han Q, Zhao F, et al. Graphitic C3N4-Pt nanohybrids supported on a graphene network for highly efficient methanol oxidation. Sci China Mater, 2015, 58: 21-27 CrossRef Google Scholar

[16] Wang X, Maeda K, Thomas A, et al. A metal-free polymeric photocatalyst for hydrogen production from water under visible light. Nat Mater, 2009, 8: 76-80 CrossRef PubMed ADS Google Scholar

[17] Liu J, Liu Y, Liu N, et al. Metal-free efficient photocatalyst for stable visible water splitting via a two-electron pathway. Science, 2015, 347: 970-974 CrossRef PubMed ADS Google Scholar

[18] Zhang J, Chen Y, Wang X. Two-dimensional covalent carbon nitride nanosheets: synthesis, functionalization, and applications. Energ Environ Sci, 2015, 8: 3092-3108 CrossRef Google Scholar

[19] Wang J, Shen Y, Li Y, et al. Crystallinity modulation of layered carbon nitride for enhanced photocatalytic activities. Chem Eur J, 2016, 22: 12449-12454 CrossRef PubMed Google Scholar

[20] Liang Q, Li Z, Huang ZH, et al. Holey graphitic carbon nitride nanosheets with carbon vacancies for highly improved photocatalytic hydrogen production. Adv Funct Mater, 2015, 25: 6885-6892 CrossRef Google Scholar

[21] Rong M, Cai Z, Xie L, et al. Study on the ultrahigh quantum yield of fluorescent P,O-g-C3N4 nanodots and its application in cell imaging. Chem Eur J, 2016, 22: 9387-9395 CrossRef PubMed Google Scholar

[22] Zhang X, Xie X, Wang H, et al. Enhanced photoresponsive ultrathin graphitic-phase C3N4 nanosheets for bioimaging. J Am Chem Soc, 2013, 135: 18-21 CrossRef PubMed Google Scholar

[23] Wang W, Yu JC, Shen Z, et al. g-C3N4 quantum dots: direct synthesis, upconversion properties and photocatalytic application. Chem Commun, 2014, 50: 10148-10150 CrossRef PubMed Google Scholar

[24] Zhu K, Wang W, Meng A, et al. Mechanically exfoliated g-C3N4 thin nanosheets by ball milling as high performance photocatalysts. RSC Adv, 2015, 5: 56239-56243 CrossRef Google Scholar

[25] Han Q, Zhao F, Hu C, et al. Facile production of ultrathin graphitic carbon nitride nanoplatelets for efficient visible-light water splitting. Nano Res, 2015, 8: 1718-1728 CrossRef Google Scholar

[26] Niu P, Zhang L, Liu G, et al. Graphene-like carbon nitride nanosheets for improved photocatalytic activities. Adv Funct Mater, 2012, 22: 4763-4770 CrossRef Google Scholar

[27] Du X, Zou G, Wang Z, et al. A scalable chemical route to soluble acidified graphitic carbon nitride: an ideal precursor for isolated ultrathin g-C3N4 nanosheets. Nanoscale, 2015, 7: 8701-8706 CrossRef PubMed ADS Google Scholar

[28] Xu K, Li X, Chen P, et al. Hydrogen dangling bonds induce ferromagnetism in two-dimensional metal-free graphitic-C3N4 nanosheets. Chem Sci, 2015, 6: 283-287 CrossRef Google Scholar

[29] Yang S, Gong Y, Zhang J, et al. Exfoliated graphitic carbon nitride nanosheets as efficient catalysts for hydrogen evolution under visible light. Adv Mater, 2013, 25: 2452-2456 CrossRef PubMed Google Scholar

[30] Lu Q, Deng J, Hou Y, et al. One-step electrochemical synthesis of ultrathin graphitic carbon nitride nanosheets and their application to the detection of uric acid. Chem Commun, 2015, 51: 12251-12253 CrossRef PubMed Google Scholar

[31] Tian J, Liu Q, Asiri AM, et al. Ultrathin graphitic carbon nitride nanosheets: a novel peroxidase mimetic, Fe doping-mediated catalytic performance enhancement and application to rapid, highly sensitive optical detection of glucose. Nanoscale, 2013, 5: 11604-11609 CrossRef PubMed ADS Google Scholar

[32] Tian J, Liu Q, Asiri AM, et al. Ultrathin graphitic C3N4 nanosheets/graphene composites: efficient organic electrocatalyst for oxygen evolution reaction. ChemSusChem, 2014, 7: 2125-2130 CrossRef PubMed Google Scholar

[33] Tong J, Zhang L, Li F, et al. An efficient top-down approach for the fabrication of large-aspect-ratio g-C3N4 nanosheets with enhanced photocatalytic activities. Phys Chem Chem Phys, 2015, 17: 23532-23537 CrossRef PubMed ADS Google Scholar

[34] Zhao H, Yu H, Quan X, et al. Atomic single layer graphitic-C3N4: fabrication and its high photocatalytic performance under visible light irradiation. RSC Adv, 2014, 4: 624-628 CrossRef Google Scholar

[35] Sun Z, Xie H, Tang S, et al. Ultrasmall black phosphorus quantum dots: synthesis and use as photothermal agents. Angew Chem Int Ed, 2015, 54: 11526-11530 CrossRef PubMed Google Scholar

[36] Liang Q, Ye L, Xu Q, et al. Graphitic carbon nitride nanosheet-assisted preparation of N-enriched mesoporous carbon nanofibers with improved capacitive performance. Carbon, 2015, 94: 342-348 CrossRef Google Scholar

[37] Yuan B, Chu Z, Li G, et al. Water-soluble ribbon-like graphitic carbon nitride (g-C3N4 ): green synthesis, self-assembly and unique optical properties. J Mater Chem C, 2014, 2: 8212-8215 CrossRef Google Scholar

[38] Liang Q, Huang ZH, Kang F, et al. Facile synthesis of crystalline polymeric carbon nitrides with an enhanced photocatalytic performance under visible light. ChemCatChem, 2015, 7: 2897-2902 CrossRef Google Scholar

[39] Cao S, Low J, Yu J, et al. Polymeric photocatalysts based on graphitic carbon nitride. Adv Mater, 2015, 27: 2150-2176 CrossRef PubMed Google Scholar

[40] Rong M, Song X, Zhao T, et al. Synthesis of highly fluorescent P,O-g-C3N4 nanodots for the label-free detection of Cu2+ and acetylcholinesterase activity. J Mater Chem C, 2015, 3: 10916-10924 CrossRef Google Scholar

[41] Lu YC, Chen J, Wang AJ, et al. Facile synthesis of oxygen and sulfur co-doped graphitic carbon nitride fluorescent quantum dots and their application for mercury(II) detection and bioimaging. J Mater Chem C, 2015, 3: 73-78 CrossRef Google Scholar

[42] Liang Q, Li Z, Yu X, et al. Macroscopic 3D porous graphitic carbon nitride monolith for enhanced photocatalytic hydrogen evolution. Adv Mater, 2015, 27: 4634-4639 CrossRef PubMed Google Scholar

[43] Zhang J, Zhang M, Yang C, et al. Nanospherical carbon nitride frameworks with sharp edges accelerating charge collection and separation at a soft photocatalytic interface. Adv Mater, 2014, 26: 4121-4126 CrossRef PubMed Google Scholar

[44] Zhang S, Li J, Zeng M, et al. Polymer nanodots of graphitic carbon nitride as effective fluorescent probes for the detection of Fe3+ and Cu2+ ions. Nanoscale, 2014, 6: 4157-4162 CrossRef PubMed ADS Google Scholar

[45] Liang Q, Ma W, Shi Y, et al. Easy synthesis of highly fluorescent carbon quantum dots from gelatin and their luminescent properties and applications. Carbon, 2013, 60: 421-428 CrossRef Google Scholar

[46] Li X, Wen J, Low J, et al. Design and fabrication of semiconductor photocatalyst for photocatalytic reduction of CO2 to solar fuel. Sci China Mater, 2014, 57: 70-100 CrossRef Google Scholar

[47] Low J, Cheng B, Yu J, et al. Carbon-based two-dimensional layered materials for photocatalytic CO2 reduction to solar fuels. Energ Storage Mater, 2016, 3: 24-35 CrossRef Google Scholar

[48] Gao D, Xu Q, Zhang J, et al. Defect-related ferromagnetism in ultrathin metal-free g-C3N4 nanosheets. Nanoscale, 2014, 6: 2577-2581 CrossRef PubMed ADS Google Scholar

  • 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.

Copyright 2020 Science China Press Co., Ltd. 《中国科学》杂志社有限责任公司 版权所有