Investigating solvent effects on aggregation behaviour, linear and nonlinear optical properties of silver nanoclusters K.B. Bhavitha a, b , Anju K. Nair a, b , Sreekanth Perumbilavil c , Saju Joseph b , M.S. Kala a , Abhijit Saha d , R. Aravinda Narayanan e , Nishar Hameed f , Sabu Thomas b, g , Oluwatobi S. Oluwafemi i, j, * , Nandakumar Kalarikkal b, h, ** a Department of Physics, St Teresa's College, Ernakulam, 682011, Kerala, India b International and Inter University Centre for Nanoscience and Nanotechnology, Mahatma Gandhi University, Kottayam, 686 560, Kerala, India c Optics Laboratory, Tampere University of Technology, FI-33101, Tampere, Finland d UGC DAE CSR, Kolkata Centre, Kolkata, 700098, West Bengal, India e Birla Institute of Technology & Science, Pilani, Hyderabad, 5000078, Telangana, India f Factory of the Future, Swinburne University of Technology, Hawthorn, Australia g School of Chemical Sciences, Mahatma Gandhi University, Kottayam, 686 560, Kerala, India h School of Pure and Applied Physics, Mahatma Gandhi University, Kottayam, 686 560, Kerala, India i Department of Applied Chemistry, University of Johannesburg, P.O. Box 17011, Doornfontein, Johannesburg, 2028, South Africa j Centre for Nanomaterials Sciences Research, University of Johannesburg, Johannesburg, South Africa article info Article history: Received 28 July 2017 Received in revised form 10 September 2017 Accepted 17 September 2017 Keywords: Silver nanoclusters Solvent effects Aggregation behaviour DFT Linear optical properties Non linear optical properties abstract We herein report the solvent effects on the aggregation, linear and nonlinear optical properties of silver nanoclusters synthesised using three solvents namely; ethanol, acetone and isopropanol. The Ag clusters were characterized using UVeVisible (UVevis) and photoluminescence (PL) spectroscopy, Fourier transform-infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), high resolution trans- mission electron microscopy (HRTEM), small angle X-ray scattering (SAXS), dynamic light scattering (DLS), and open aperture Z-Scan measurements. Density functional theory (DFT) calculations at the B3PW91 level of theory, were done to compute the electric dipole, quadrupole, octapole and hex- adecapole moment of mercaptosuccinic acid and mercaptosuccinic acid-Ag 9 cluster in three solvents. Linear optical properties show characteristic absorption profile with quantum confinement at different wavelengths for all the three clusters. The Open aperture Z-scan measurement in Ag clusters establishes the optical limiting properties which arise mostly from excited state absorption (ESA) and relatively weak saturable absorption (SA). The nonlinear optical behaviour varies within the three clusters with maximum optical limiting value obtained for the clusters synthesised using acetone. The theoretically computed hyperpolarizabilities together with z-scan measurements establish the solvent effect on the clusters and their potential applications in optical limiting devices. © 2017 Elsevier B.V. All rights reserved. 1. Introduction Noble metal nanoparticles and quantum clusters (QCs) are of great importance nowadays because of their applications in the field of optoelectronic, nonlinear optical, electrical, magnetic, me- dicinal, catalytic, sensing and environmental applications [1e5]. Nanoclusters or quantum clusters (QCs) are extremely small-sized particles (from sub nanometer scale to < 2 nm) which proceed as a bridge between atoms and nanoparticles. They exhibit unique physicochemical properties because of the enormous changes in size and atomic structure arrangement in this size regime [6]. Metal QCs which are protected by thiolate ligand groups can control the number of metal atoms in the cluster which are stable and exhibit molecular-like properties [7]. When the size of the clusters is comparable to the Fermi wavelength, the properties are governed by quantum confinement effects (HOMO-LUMO bandgap) that * Corresponding author. Department of Applied Chemistry, University of Johan- nesburg, P.O. Box 17011, Doornfontein, Johannesburg, 2028, South Africa. ** Corresponding author. International and Inter University Centre for Nano- science and Nanotechnology, Mahatma Gandhi University, Kottayam, 686 560, Kerala, India. E-mail addresses: oluwafemi.oluwatobi@gmail.com (O.S. Oluwafemi), nkkalarikkal@mgu.ac.in (N. Kalarikkal). Contents lists available at ScienceDirect Optical Materials journal homepage: www.elsevier.com/locate/optmat https://doi.org/10.1016/j.optmat.2017.09.024 0925-3467/© 2017 Elsevier B.V. All rights reserved. Optical Materials 73 (2017) 695e705