Tailored optical properties of graphitic carbon nitride thin films via surface functionalization of growth substrates
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Graphitic carbon nitride has attracted much attention in recent years due to its medium size band gap, mechanical strength, blue fluorescence, and catalysis properties. Mainstream methods to produce carbon nitride thin films rely on multi-step exfoliation processes and atmospheric deposition which is unsuitable for large-scale production of electronic devices and sensors where scaling and defect-free materials are required. Our technique utilizes a low-pressure chemical vapor deposition process that allows for one-step synthesis on many different types of substrates with a removal of unwanted reacting gases during synthesis due to the low-pressure environment. This allows us to deposit highly uniform films with thicknesses on the order of 250 nm. By modifying the growth surface chemistry, the band gap of the graphitic carbon nitride can be tuned from a medium gap of 2.87 eV up to 4.1 eV. The fluorescence emission can also be tuned from 425 nm up to 465 nm through growth substrate surface chemistry engineering. As a sensing material, our graphitic carbon nitride thin films have a limit of detection of 50 nM for metal copper ions which has great potential for applications where metal ion concentration is important to monitor such as in the human body.