Introduction
Thallium is considered one of the most dangerous heavy metals, and even very small amounts can pose a serious threat to ecosystems and human health. To properly assess the environmental risks associated with its presence, reliable analytical methods are needed. In practice, however, measuring thallium at trace levels is demanding due to its low concentration and the complexity of environmental samples. This has created a need for improved, mercury-free detection tools that can support accurate environmental monitoring.

Methods
In this work, glassy carbon electrodes were modified with starch-stabilized silver nanostructures to increase their sensitivity toward thallium. The nanostructures were obtained through a controlled reduction process to ensure good stability and surface coverage. The modified electrodes were characterized electrochemically and used for anodic stripping voltammetric measurements in both model electrolyte solutions and real environmental samples.

Results
The applied surface modification markedly enhanced the analytical performance of the electrodes. Higher sensitivity, good repeatability, and a clearly improved detection limit enabled the reliable determination of thallium at concentrations relevant to environmental risk evaluation. The electrodes showed stable behavior over repeated measurements and performed well even in more complex sample matrices.

Conclusions
The proposed electrode system offers a practical and environmentally friendly alternative to traditional mercury-based sensors. Its analytical capabilities make it a useful tool for monitoring thallium contamination and supporting environmental impact and risk assessments.