Supercritical Carbon Dioxide Impregnation of Gold Nanoparticles Demonstrates a New Route for the Fabrication of Hybrid Silk Materials.

Manish Singh,Estera S Dey,Sunil Bhand,Cedric Dicko

doi:10.3390/insects13010018

Abstract

Simple SummaryThe application of nanotechnology in textiles is limited by the difficulties of loading the fabrics with nanoparticles (NPs) and by their subsequent uncontrolled leakage. More fundamentally, there is a need to answer the question of the “space available” in textile fibers, and generally, other natural polymers for NPs loading. Due to these challenges, there is a risk that uncontrolled leakage of NPs from the textile industry could harm the environment and human health. Here, with a green and straightforward approach, using supercritical carbon dioxide (scCO2) as a carrier fluid, we explored the impregnation in four types of Indian textile silks (Mulberry, Eri, Muga, and Tasar) with five standard sizes of gold NPs (5, 20, 50, 100 and 150 nm). The results suggested that all silks could be permanently impregnated with the gold nanoparticles (Au NPs) up to 150 nm. Knowing the available space in silk or other natural polymers can help us understand how and which natural polymers are suitable for use as catalysts, antimicrobial materials, UV-protective agents, and other valuable properties.How many nanoparticles can we load in a fiber? How much will leak? Underlying is the relatively new question of the “space available” in fibers for nanoparticle loading. Here, using supercritical carbon dioxide (scCO2) as a carrier fluid, we explored the impregnation in four Indian silks (Mulberry, Eri, Muga, and Tasar) with five standard sizes of gold nanoparticles (5, 20, 50, 100 and 150 nm in diameter). All silks could be permanently impregnated with nanoparticles up to 150 nm in size under scCO2 impregnation. Accompanying structural changes indicated that the amorphous silk domains reorganized to accommodate the gold NPs. The mechanism was studied in detail in degummed Mulberry silk fibers (i.e., without the sericin coating) with the 5 nm nanoparticle. The combined effects of concentration, time of impregnation, scCO2 pressure, and temperature showed that only a narrow set of conditions allowed for permanent impregnation without deterioration of the properties of the silk fibers.

Highlights

The primary purpose of impregnating nanoparticles (NPs) in fibers is to increase mechanical strength, improve physical properties, such as electrical conductivity and antistatic behavior, and add functionalities, such as antimicrobial, UV protection, flame retardance, and self-cleaning [1,2,3]
For Mulberry, Muga, and Tasar, we found that the tyrosine ratio was constant and closed to the value from the respective native silks
We found a low percentage of wash leakage (3.0%—Figure 6B) and fastness leakage (2.8%—Figure 6C), a small amount of weakly attached gold NPs to silk fibers

Summary

Introduction

The primary purpose of impregnating nanoparticles (NPs) in fibers is to increase mechanical strength, improve physical properties, such as electrical conductivity and antistatic behavior, and add functionalities, such as antimicrobial, UV protection, flame retardance, and self-cleaning [1,2,3]. There are several ways to impregnate/synthesize nanoparticles, and most importantly, stabilize them on or in fibers. The methods above have drawbacks, a decrease in the tensile strength of the fibers; the process demands harsh chemical pretreatment, and leakage of nanoparticles occurs with time [12,13]. The severe chemical pretreatment step and leakage of NPs from fibers lead to serious environmental and health issues [12,13,14]

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Conclusion