Photoluminescence characterization of nitrogen-doped carbon quantum dots using Theremino-based DIY spectrometer

Abstract

Theremino Spectrometer is open-source tool that is mainly used for learning and simple optical measurements. This study adapted Theremino to do photoluminescence analysis of N-CQDs. N-CQDs was synthesized using a microwave method with citric acid and urea resulting a solution with 12.51 mg/ml of N-CQDs and characterized with FESEM analysis. The average N-CQDs size is obtained to be of 2.23 ± 0.043 nm. To enable photoluminescence measurements, the original setup was modified by adding a webcam detector, diffraction grating, and light source for excitation. The measured spectra showed two noticeable emission peaks around 486.83 nm and 708.43 nm, confirming that the material exhibits clear luminescence. The absorption behavior indicated stronger interaction in the ultraviolet and blue regions, while emission occurred in the visible range, which agrees well with an estimated optical band gap of approximately 3.28 eV and 4.63 eV for standard UV spectrum. The quantum yield was 16 %, which is moderate. Rhodamine B is taken as standard solution to compare and test with distilled water. The new setup was able to obtain results with light which shows that the Theremino Spectrometer is a simple and affordable way to study photoluminescent nanomaterials.