Bioinspired cyclic dipeptide functionalized nanofibers for thermal sensing and energy harvesting

Abstract

Nanostructured dipeptide self-assemblies exhibiting quantum confinement are of great interest due to their potential applications in the field of materials science as optoelectronic materials for energy harvesting devices. Cyclic dipeptides are an emerging outstanding group of ring-shaped dipeptides, which, because of multiple interactions, self-assemble in supramolecular structures with different morphologies showing quantum confinement and photoluminescence. Chiral cyclic dipeptides may also display piezoelectricity and pyroelectricity properties with potential applications in new sources of nano energy. Among those, aromatic cyclo-dipeptides containing the amino acid tryptophan are wide-band gap semiconductors displaying the high mechanical rigidity, photoluminescence and piezoelectric properties to be used in power generation. In this work, we report the fabrication of hybrid systems based on chiral cyclo-dipeptide L-Tryptophan-L-Tryptophan incorporated into biopolymer electrospun fibers. The micro/nanofibers contain self-assembled nano-spheres embedded into the polymer matrix, are wide-band gap semiconductors with <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>4.0</mn><mo> </mo><mi>eV</mi></mrow></semantics></math></inline-formula> band gap energy, and display blue photoluminescence as well as relevant piezoelectric and pyroelectric properties with coefficients as high as <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>57</mn><msup><mrow><mrow><mtext> </mtext><mi>CN</mi></mrow></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo> </mo><mn>35</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>6</mn></mrow></msup><mo> </mo><msup><mrow><mi>Cm</mi></mrow><mrow><mo>−</mo><mn>2</mn></mrow></msup><msup><mi mathvariant="normal">K</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></semantics></math></inline-formula>, respectively. Therefore, the fabricated hybrid mats are promising systems for future thermal sensing and energy harvesting applications.