Copper, silver, and gold-reduced graphene oxide nanocomposite (Cu-rGO, Ag-rGO, and Au-rGO) were fabricated via the hydrothermal method, which shows unique physiochemical properties. Environment friendly electromagnetic radiation was employed to synthesize rGO from GO. The nonlinear optical phenomenon of noble metal decorated rGO is predominantly due to excited state absorption, which arises from surface plasmon resonance and increases in defects at the surface due to Cu, Ag, and Au incorporation. It is found that the third-order nonlinear absorption coefficient was in the order of 10− 10 m/W, with notable enhancements in the third-order properties of Au-rGO compared to other nanocomposites and their respective counterparts. Functionalizing rGO induces defect states ( sp3), increasing NLO response. Cu, Ag, and Au exhibit higher Surface-Enhanced Raman Scattering (SERS) activity due to rGO-induced structural modifications. SERS signals are influenced by dominant signals from Au nanorods. The electronic structures for pure and doped rGO were investigated through Density Functional Theory (DFT). The computed partial density of states (PDOS) confirms the enhancement of the state in Au-doped rGO is due to the charge transference from Au to C 2p orbital. The optical absorption spectra and PDOS reveal the possibility of free carrier absorption enhancement in Au which validates experimentally observed higher two-photon absorption (β) value of Au-doped rGO. The tuning of nonlinear optical and SERS behaviour with variation in the noble metal upon rGO provides an easy way to attain tuneable properties which are exceedingly required in both optoelectronics and photonics applications.

Noble metals functionalized reduced graphene oxide as an efficient optical limiter: a combined experimental and theoretical investigation
    Abstract
    1 Introduction
    2 Materials preparation and growth mechanism
    3 Experimental section
        3.1 Z-scan experiment
        3.2 Surface-enhanced raman spectroscopy (SERS)
        3.3 Sample characterization
        3.4 Computational details
    4 Results and discussion
        4.1 Morphological studies
        4.2 Crystal and molecular structure analysis
        4.3 Chemical state analysis
        4.4 UV–vis absorption analysis
        4.5 SERS analysis
        4.6 Nonlinear absorption and optical limiting properties
        4.7 Theoretical results and discussion
    5 Conclusions
    Acknowledgements 
    References

• M. Saravanan(Department of Physics, University College of Engineering, BIT Campus, Anna University, Tiruchirapalli 620 024, Tamil Nadu, India) Corresponding author
• Manikandan Kandasamy(Department of Physics, Karpagam Academy of Higher Education, Coimbatore 641021, Tamil Nadu, India, Centre for Computational Physics, Karpagam Academy of Higher Education, Coimbatore 641021, Tamil Nadu, India)
• K. Suresh(Department of Atomic and Molecular Physics, Manipal Academy of Higher Education, Manipal 576104, India)
• Brahmananda Chakraborty(High Pressure and Synchrotron Radiation Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India, Homi Bhabha National Institute, Mumbai 400094, India)
• Sajan D. George(Department of Atomic and Molecular Physics, Manipal Academy of Higher Education, Manipal 576104, India, Centre for Applied Nanosciences (CANs), Manipal Academy of Higher Education, Manipal 576104, India)
• T. C. Sabari Girisun(Nanophotonics Laboratory, Department of Physics, Bharathidasan University, Tiruchirappalli 620024, India)
• I. Vetha Potheher(Department of Physics, University College of Engineering, BIT Campus, Anna University, Tiruchirapalli 620 024, Tamil Nadu, India)
• V. Parthasarathy(Department of Computer Science and Engineering, Karpagam Academy of Higher Education, Coimbatore 641021, Tamil Nadu, India)