Use of betalainic compounds for nanoparticle synthesis and tuning of their characteristics

Author(s)

Arthur Bonfá Fernandes

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ)
• Defense date: 2021-12-20

Examining board members

Erick Leite Bastos; Wilhelm Josef Baader; Carla Cristina Schmitt Cavalheiro

• Advisor: Erick Leite Bastos

Abstract

Betalains are alkaloids found in plants and fungi, with high antioxidant capacity e variety of technological applications, including production and functionalization of nanomaterials. Although extracts and products containing betalains have been used for the synthesis of metallic nanoparticles (NPs), studies about the role of betalains in this process are still limited. This doctoral thesis investigates the use of betalains as starting material to the synthesis and functionalization of different kinds of nanomaterials, establishing structure-properties relationships. Betanin, indicaxanthin and betalamic acid were used as reductants and capping agents to fabricate gold and silver nanoparticles, and these compounds affect size, dispersion e morphology of the NPs. The AgNPs possesses redox and photoredox activity, attributed to the betalains and their degradation products on the surface of the NPs. Then, a betalain covalently bonded to the surface of polymeric microspheres were used to produce supported AuNPs and AgNPs, and the presence of the betalain affected the NPs ´morphology. With this methodology it was also possible to obtain and modulate the morphology of magnetic NPs of iron oxide (III). The adsorption of the NPs on the surface of the polymer allowed its use as reusable and recoverable nanocatalysts in redox processes, comparable to nanoparticles in suspension. Finally, betanin, indicaxanthin, pyrrolidine-betaxanthin, betalamic acid and Beetblue were used as starting material to produce carbon quantum dots, fluorescent and biocompatible carbon nanoparticles. The materials were characterized, and the relationship between the precursors and the photophysical and electron transfer properties were established. The results allow the optimization of choice for natural products used as raw material to produce NPs with interesting properties. (AU)

• FAPESP's process: 15/25629-4 - Synthesis of fluorescent nanoparticles using betalains
• Grantee: Arthur Bonfá Fernandes
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)