Size and liquid-substrate interfacial energy effects on melting temperature and band gap in CdSe Nanoparticles: A comparative study of cylindrical and spherical geometries

This paper presents a theoretical comparison examining the effects of nanoparticle size and liquid-substrate interfacial energy on the melting temperature and band gap of cadmium selenide (CdSe) nanoparticles supported on a glass substrate, analyzing both cylindrical and spherical shapes. Using a simple thermodynamic model, this study investigates the influence of nanoparticle size and liquid-substrate interfacial energy on the melting temperature and band gap of supported CdSe nanoparticles with cylindrical and spherical geometries. The model incorporates surface and interfacial energies and wetting parameters to derive analytical expressions for the variations in melting temperature and band gap as functions of nanoparticle size and substrate interaction for both shapes. Results show that the melting temperature decreases with decreasing particle size. In contrast, the band gap increases, but the extent of this dependence varies between cylindrical and spherical geometries, which means nanoparticles with higher surface curvatures (cylindrical shape) exhibit lower melting temperatures than nanoparticles with lower surface curvatures (spherical shape). Furthermore, stronger liquid-substrate interfacial interactions lead to greater melting point depression, while weaker interactions stabilize the nanoparticles, resulting in higher melting temperatures in both geometries. The band gap shows a strong quantum confinement effect in smaller nanoparticles, while their geometry and substrate interactions further influence this trend. The study compares theoretical predictions with existing experimental data and models for unsupported nanoparticles, emphasizing how interfacial energy and shape critically affect the thermal and optical characteristics of CdSe nanomaterials. These findings provide valuable guidance for enhancing the performance and durability of CdSe-based devices in photovoltaic systems, optoelectronic components, and nanosensors.