Second-Order Nonlinearity of Graphene Quantum Dots Measured by Hyper-Rayleigh Scattering

Manoel L Silva-Neto; Renato Barbosa-Silva; Georges Boudebs; Cid B de Araújo

doi:10.3390/ma16237376

Second-Order Nonlinearity of Graphene Quantum Dots Measured by Hyper-Rayleigh Scattering

Materials (Basel). 2023 Nov 27;16(23):7376. doi: 10.3390/ma16237376.

Authors

Manoel L Silva-Neto¹, Renato Barbosa-Silva², Georges Boudebs³, Cid B de Araújo²

Affiliations

¹ Programa de Pós-Graduação em Ciência de Materiais, Universidade Federal de Pernambuco, Recife 50670-901, PE, Brazil.
² Departamento de Física, Universidade Federal de Pernambuco, Recife 50670-901, PE, Brazil.
³ Univ Angers, LPHIA, SFR MATRIX, F-49000 Angers, France.

Abstract

The first hyperpolarizability of graphene quantum dots (GQDs) suspended in water was determined using the hyper-Rayleigh scattering (HRS) technique. To the best of our knowledge, this is the first application of the HRS technique to characterize GQDs. Two commercial GQDs (Acqua-Cyan and Acqua-Green) with different compositions were studied. The HRS experiments were performed with an excitation laser at 1064 nm. The measured hyperpolarizabilities were (1.0±0.1)×10-27 esu and (0.9±0.1)×10-27 esu for Acqua-Cyan and Acqua-Green, respectively. The results were used to estimate the hyperpolarizability per nanosheet obtained by assuming that each GQD has five nanosheets with 0.3 nm thickness. The two-level model, used to calculate the static hyperpolarizability per nanosheet, provides values of (2.4±0.1)×10-28 esu (Acqua-Cyan) and (0.5±0.1)×10-28 esu (Aqua-Green). The origin of the nonlinearity is discussed on the basis of polarized resolved HRS experiments, and electric quadrupolar behavior with a strong dependence on surface effects. The nontoxic characteristics and order of magnitude indicate that these GQDs may be useful for biological microscopy imaging.

Keywords: graphene quantum dots; hyper-Rayleigh scattering; second-harmonic generation.

Grants and funding

This research was funded by the Brazilian agencies Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Fundação de Amparo à Ciência e Tecnologia do Estado de Pernambuco (FACEPE), Coordenação de Aperfeiçoamento de Pessoal de Ensino Superior (CAPES), and the University of Angers: AAP MIR 2022. This work was performed in the framework of the National Institute of Photonics (INFO) project.