Optical and luminescence properties of carbon dot-doped sulphamic acid crystals: A potential candidate for LED and display technologies

This study is the first to investigate the influence of carbon dots (CD) on the optical and luminescence properties of sulphamic acid (SA) crystals, with the aim of exploring their potential in optical device applications. High-quality single crystals of pure SA and CD-doped variants (5NCSA and 10NCSA) were synthesized using the slow evaporation solution growth method. The crystalline quality and structural properties were evaluated through powder X-ray diffraction (XRD) analysis. The Williamson–Hall (W–H) method was employed to calculate crystallite size and analyze the anisotropic strain effects introduced by CD doping, with findings compared to those from the Monshi-Scherrer method. Functional group analysis was conducted using FTIR spectroscopy, while SEM coupled with EDAX provided insights into surface morphology and confirmed CD incorporation. Optical transmission studies evaluated transparency in the UV–visible spectrum. The measured band gap values were 5.86 eV for pure SA, 5.77 eV for 5NCSA, and 5.55 eV for 10NCSA. Furthermore, Raman analysis confirmed the presence of CD within the SA lattice. The photoluminescence (PL) spectra were recorded to analyze emissions at specific excitation wavelengths. PL measurements showed emissions at 373 and 425 nm for pure SA, and at 374 and 426 nm for doped variants, with Commission Internationale de l’Eclairage (CIE) coordinates in the intense blue region. Notably, 10NCSA demonstrated enhanced fluorescence under UV light, surpassing that of pure SA. These findings highlight the potential of CD-doped SA crystals for applications in LED technology, display systems, and fluorescent boards. • This is the first study on carbon dots (CD) influencing the optical and luminescence properties of sulphamic acid (SA) crystals. • Pure SA and CD-doped crystals (5NCSA, 10NCSA) were synthesized by slow evaporation. • XRD and Williamson–Hall analysis confirmed crystal quality and strain from CD doping. • Photoluminescence exhibited enhanced emissions at 374 and 426 nm for doped samples. • 10NCSA's strong UV fluorescence suggests its potential for LED, display, and fluorescent applications.