Characterization of pure organic NTI crystals for direct x-ray detection

Accurate detection of x-ray radiation is essential for tissue equivalence detection and safety control during medical radiotherapy. Here, a promising radiation detector based on organic 1,8-naphthalimide (C₁₂H₇NO₂, NTI) single crystals is proposed. NTI single crystals with dimensions of 8 × 2 × 1 mm³ were synthesized by an optimized solvent-cooling method, and the crystal structure was characterized to elucidate the anisotropy mechanism. The coplanar detector made by NTI has a leakage current of less than 0.1 pA at an electric field strength of 1 kV cm⁻¹ and provides excellent detection of 5.49 MeV α-particles (²⁴¹Am) with a full-energy peak resolution of up to 32.3%. The calculated electron mobility ( μ _e) and electron mobility-lifetime product ( μ τ )_e were 7.9 cm² V⁻¹s⁻¹ and 1.56 × 10⁻⁶ cm² V⁻¹, respectively. Additionally, the detection limit of the NTI detector was 0.35 µGy s⁻¹ in the electric field strength range of 0.2-1.0 kV cm⁻¹ under a 20 kV x-ray beam with a high sensitivity of 56.2 μC Gy⁻¹cm⁻². Consequently, the NTI detector achieves an excellent spatial resolution of 0.8-0.9 lp mm⁻¹ in terms of x-ray imaging capability.