Date of Award

15-4-2024

Document Type

Thesis

School

School of Chemical & Biotechnology

Programme

Ph.D.-Doctoral of Philosophy

First Advisor

Dr. Sakthivel Gandhi

Keywords

Electrochemical sensor, POSS

Abstract

Personal care products (cosmetics) are a diverse group of goods, that includes all the essential routines including the personal hygiene products used in our day-to-day life. It contains a variety of ingredients in its formulation, including preservatives, flavor, UV filters, and other additives. Few of the chemicals utilized are found to impair human health and have serious environmental impacts. The major chemicals include parabens, triclosan, oxybenzone, phthalates, heavy metals, fragrances, etc, Though the Scientific Committee on Consumer Safety (SCCS) has set the usage limits for the chemicals used, exposure to these chemicals from multiple products may exceed the exposure limit. These chemicals are found to act either as endocrine disruptors or endocrine disrupting chemicals (EDC) because they have the tendency to impair the functions of the endocrine system.

The general health impacts arising from this chemical exposure include endocrine disruption, cancer, and developmental and reproductive toxicity. Apart from human health, it causes numerous environmental issues viz., water bodies and groundwater contamination, coral bleaching, and reproductive and developmental toxicity in aquatic species after the wash-off. Immense awareness has been aroused among the public regarding the health and environmental impacts of chemical usage in personal care products which leads to an increased preference for organic (chemical-free) cosmetic products. However, there is a huge lacuna for the evident testing tool in order to evaluate the formulated product. Only a very few works have been reported for EDC detection in chemical-containing (cross-verification of usage limit: quantification), organic (qualitative and quantitative) cosmetic products as a part of QA/QC and water contamination testing.

The ex-situ techniques are generally performed in laboratory environments with low detection limits, high time consumption, and trained personnel requirements for instrumental operation with tedious sample preparation and extraction techniques. This led to the development of a simple in-situ technique to quantify the harmful ingredients known as electrochemical methods, which is considered superior owing to their effortless sample preparation, minimal analysis duration, ease of operation with ideal selectivity, sensitivity, and detection limits.

A clear indication that relatively low research has been carried out , despite the higher exposure to humans and release in water bodies owing to the higher usage of personal care products as a part of the mandatory routine. Based on these reasons and extensive literature surveys, this work has been proposed in such a way that an electrochemical nanosensor was developed for the detection of three predominant chemicals present in personal care products which include paraben, triclosan (TCL) and oxybenzone derivative- 2-hydroxy benzophenone (2-HBP). The preliminary studies were carried out to test the paraben sensing efficiency by utilizing the conducting mesoporous carbon-based material. A reduced electrochemical sensing efficiency was noticed. Meanwhile, our group opted for a different functionalized hybrid class of silica-based material- polyhedral oligomeric silsesquioxane (POSS), which is a completely condensed caged structure with octa arms.

POSS, owing to its hybrid nature showed outstanding properties covering various applications, but with limited exploration in the sensing applications. Hence, three common functionalizations (-OH, -SH, and -vinyl) were tested for driving the electrochemical reaction- paraben and their derivatives followed by optimization. After optimization, it has been used as a lead active material for the formation of composite with the conducting matrix (Carbon allotropes). The optimized material-derived composite has been successfully utilized as the chemical modifier (nano-interfacing element) for detection of the aforementioned EDCs- Paraben, 2-HBP, and TCL using the bulk set-up. Also, the real sample analysis was carried out in spiked water samples, commercially available cosmetic products, and organic products followed by cross-validation with the HPLC-UV technique. Finally, the developed composite-based material has been used for the ink formulation. Then, the electrochemical sensing efficiency of the three EDCs was also tested by casting the formulated ink over the commercially purchased screen-printed electrodes (SPE). We have also successfully fabricated a 3D-printed immobilization device for holding the chemically modified SPEs in order to get rid of noise and to create a well for holding electrolytes.

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