Natural biotic polymer bombyx mori silk fibroin for gold nanoparticles: Fabrication, characterisations and application as colorimetric ammonia detection

Gold nanoparticles (AuNPs) were fabricated using a cost-effective and environmentally benign method, using silk fibroin (SF) as a stabilizing and reducing agent. As a natural, renewable protein polymer, silk fibroin can reduce and stabilize material as well as provide shape-tailoring agent. This resulted bio-polymer with gold nanoparticles was biodegradable, biocompatible, and very stable. Au ions are proficiently reduced to neutral Au atoms by silk fibroin, which governs the size, shape, and distribution of the nanoparticles and, consequently, their optical characteristics. The fabricated nanoparticles are very well characterized using a set of advanced analytical techniques that include UV-Vis Spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), and Fluorescence Spectroscopy (FL). The sensing performance of ammonia in aqueous ammonia using the SF-AuNPs is presented herein based on an optical sensing approach utilizing surface plasmon resonance (SPR). It is obvious from the results that the materials synthesized have exhibited some unique plasmonic properties due to the interaction between silk fibroin and gold surfaces, hence enhanced sensitivity in colorimetric detection. The AuNPs acted as an ammonia optical sensor with a detected limit of about 1 parts per billion (ppb), very outstanding performance. Ammonia and AuNPs interact to cause a change in their surface plasmon resonance simple rapid and low-cost to realize, eco-friendly, and can find applications towards environmental monitoring and biomedical research fields for ammonia detection. • Eco-friendly silk fibroin AuNPs synthesis; Ultra-sensitive ammonia detection (1 ppb); Simple, sustainable sensing method. • AuNPs exhibit strong surface plasmon resonance and enable ultra-sensitive colorimetric detection of ammonia (1 ppb limit). • Simple, cost-effective, and sustainable method suitable for environmental and biomedical sensing applications.