A thermally conductive film can be used to laterally conduct heat along the surface of glass windows, toward its edges where a heat sink could be located, thereby reducing temperature differential between the inside and outside surfaces of the window and thus lowering cross-sectional conductive heat transfer. This technique can offer optimized thermal energy management to modern buildings without the weight and cost of double- or triple-glazed window panels. In this work, a thermally conductive film was developed using carbon dots with inherently high thermal conductivity. Nitrogen atoms were then added to the carbon dots structure to intensify high-frequency phonon that would result in higher lateral thermal conductivity. The nitrogen-decorated carbon dots (NCDs) were prepared by a simple hydrothermal synthesis of citric acid with the addition of ethylenediamine as the N source. The NCDs were added to a cellulose-based solution and drop-casted onto FTO glass resulting in a transparent, laterally thermally conductive film, that also blocks ultraviolet (UV) and high-intensity blue light radiation. The visible-light transmission of the NCDs’ film was found to be up to 65%, comparable to the commercial solar films. The lateral thermal conductivity of the NCDs’ film increases with increasing N content up to an optimum level, suggesting the role of N to “concentrate’ the high-frequency phonons responsible for effective lateral thermal conductivity of the films.

    Abstract
    1 Introduction
    2 Experimental
        2.1 Materials and reagents
        2.2 Preparation of nitrogen-decorated carbon dots thermally conductive film
        2.3 Characterization methodology and performance evaluation
    3 Results and discussion
    4 Conclusions
    Acknowledgements 
    References

• Ronn Goei(School of Materials Science and Engineering, Nanyang Technological University, Singapore-HUJ Alliance for Research and Enterprise)
• Frankie Ting Feng Tan(School of Materials Science and Engineering, Nanyang Technological University)
• Amanda Jiamin Ong(School of Materials Science and Engineering, Nanyang Technological University, Singapore-HUJ Alliance for Research and Enterprise)
• Daniel Mandler(Singapore-HUJ Alliance for Research and Enterprise, Institute of Chemistry, The Hebrew University of Jerusalem)
• Alfred Iing Yoong Tok(School of Materials Science and Engineering, Nanyang Technological University, Singapore-HUJ Alliance for Research and Enterprise)