Laser assisted self-assembly of diphenylalanine: emergence of robust waveguiding properties and Fano resonances†
Molecular self-assembly is a powerful technique for arranging elementary building blocks and to fabricate functional bio-inspired nanostructures having unique physical properties for various applications in the fields of material science, engineering and medicine. However, the ability to modulate reversible self-assembly based processes with a view towards fabricating tailor-made functional architectures is highly challenging. Significant research has been dedicated to the development of micro-rods and micro-tubes through self-assembly of diphenylalanine (FF) derivatives. But, the reported systems suffer from lack of control, and are based on non-directed self-assembly. Herein, we report new techniques for laser assisted self-assembly of diphenylanaline where we obtain stable annular ring microstructures which exhibit waveguiding properties. In addition, we also obtain self-assembled micro-rod structures in the absence of external stimuli. Interestingly, the self-assembled structures display prominent spectrally asymmetric Fano resonances in the waveguiding response to broadband light. We also demonstrate the potential of such microstructures as sensors from the changes in their Fano resonance profiles and waveguiding response on exposure to the congo red dye. Such intriguing waveguiding systems may have promising applications in biological and chemical sensing, precision diagnostics and in the fabrication of multifarious micro-optical devices, optical fiber communication, photonic integrated circuits, and interferometers.