Abstract-Graphene Quantum Dot Solid Sheets: Strong blue-light-emitting & photocurrent-producing band-gap-opened nanostructures

• Ganapathi Bharathi, 
• Devaraj Nataraj, 
• Sellan Premkumar, 
• Murugaiyan Sowmiya, 
• Kittusamy Senthilkumar, 
• T. Daniel Thangadurai, 
• Oleg Yu Khyzhun, 
• Mukul Gupta, 
• Deodatta Phase, 
• Nirmalendu Patra, 
• Shambhu Nath Jha & 
• Dibyendu Bhattacharyya

https://www.nature.com/articles/s41598-017-10534-4

Graphene has been studied intensively in opto-electronics, and its transport properties are well established. However, efforts to induce intrinsic optical properties are still in progress. Herein, we report the production of micron-sized sheets by interconnecting graphene quantum dots (GQDs), which are termed ‘GQD solid sheets’, with intrinsic absorption and emission properties. Since a GQD solid sheet is an interconnected QD system, it possesses the optical properties of GQDs. Metal atoms that interconnect the GQDs in the bottom-up hydrothermal growth process, induce the semiconducting behaviour in the GQD solid sheets. X-ray absorption measurements and quantum chemical calculations provide clear evidence for the metal-mediated growth process. The as-grown graphene quantum dot solids undergo a Forster Resonance Energy Transfer (FRET) interaction with GQDs to exhibit an unconventional 36% photoluminescence (PL) quantum yield in the blue region at 440 nm. A high-magnitude photocurrent was also induced in graphene quantum dot solid sheets by the energy transfer process.