Surface quenching mechanism and optimal coating shell thickness of nanomaterials

The large specific surface area of nanomaterials determines that surface defects significantly affect the properties of nanomaterials. However, the complexity of surface defects makes it difficult to investigate the surface quenching mechanism theoretically, and the small size and highly sensitive growth characteristics of nanomaterials pose a challenge in revealing their regularity through experimental data. In this study, we present a theoretical model that considers various factors to describe the regularity of suppressing surface quenching through shell coating. To validate these theoretical results, nanomaterials with different shell thicknesses were systematically synthesized using an automatic nanomaterial synthesizer. Spectral analysis confirmed the regularity of theoretical prediction and identified the optimal shell thickness, and found that the optimal shell thickness remained consistent over a wider range of particle sizes. The experimental results demonstrated that the surface fluorescence quenching is primarily attributed to the electron exchange interaction. Additionally, the light scattering of particles and ion diffusion within the shells significantly impact the coating effect. Practical applications rely on determining the optimal shell thickness to balance the trade-off between strong fluorescence emission and the small-size nanoparticles.