Carbon nanomaterials (CNMs) have been the subject of extensive research for their potential applications in various fields, including photovoltaics and medicine. In recent years, researchers have focused their attention on CNMs as their high electrical conductivity, low cost, and large surface area are promising in replacing traditional platinum-based counter electrodes in dye-sensitized solar cells (DSSC). In addition to their electrical properties, CNMs have also displayed antibacterial activity, making them an attractive option for medical applications. The combination of CNMs with metal oxides to form composite materials represents a promising approach with significant potential in various fields, including energy and biology. Here, we introduce porous carbon nanospheres (PCNS) derived from Cocos nucifera L. and its ZnO composite (PCNS/ZnO) as an alternative material, which opens up new research insights for platinum-free counter electrodes. Bifacial DSSCs produced using PCNS-based counter electrodes achieved power conversion efficiencies (PCE) of 3.98% and 2.02% for front and rear illumination, respectively. However, with PCNS/ZnO composite-based counter electrodes, the efficiency of the device increased significantly, producing approximately 5.18% and 4.26% for front and rear illumination, respectively. Moreover, these CNMs have shown potential as antibacterial agents. Compared to PCNS, PCNS/ZnO composites exhibited slightly superior antibacterial activity against tested bacterial strains, including gram-positive Bacillus cereus (B. cereus) and Staphylococcus aureus (S. aureus), and gram-negative Vibrio harveyi (V. harveyi) and Escherichia coli (E. coli) with MIC values of 125, 250, 125, and 62.5 μg/ml, respectively. It is plausible that the outcomes observed were influenced by the synergistic effects of the composite material.

Cocos nucifera L.-derived porous carbon nanospheresZnO composites for energy harvesting and antibacterial applications
    Abstract
        Graphical abstract
    1 Introduction
    2 Materials and methods
        2.1 Synthesis of porous carbon nanospheres
        2.2 Synthesis of ZnO nanoparticles
        2.3 Synthesis of nanocomposite
        2.4 Preparation of PCNS and PCNSZnO counter electrodes and the fabrication of DSSCs
        2.5 Antibacterial susceptibility test by well-diffusion method
        2.6 Minimum inhibitory and minimum bactericidal concentrations
        2.7 Antibacterial activity of PCNSZnO-coated fabrics
        2.8 Free radical assay
    3 Results and discussion
        3.1 PCNS and PCNSZnO-based DSSC performance
        3.2 Antibacterial performance of PCNS and PCNSZnO composites
    4 Conclusion
    Acknowledgements 
    References

• Meera Varghese(Department of Physics and Electronics, Christ University, Bengaluru, Karnataka 560029, India)
• Gisa Grace Ninan(Department of Physics and Electronics, Christ University, Bengaluru, Karnataka 560029, India)
• Saranya Jayaram(Department of Life Sciences, Christ University, Bengaluru, Karnataka 560029, India)
• Suma Sarojini(Department of Life Sciences, Christ University, Bengaluru, Karnataka 560029, India)
• Manoj Balachandran(Department of Physics and Electronics, Christ University, Bengaluru, Karnataka 560029, India) Corresponding author