The accumulation of heavy metals in the human body and/or in the environment can be highly deleterious for mankind, and currently, considerable efforts have been made to develop reliable and sensitive techniques for their detection. Among the detection methods, chemical sensors appear as a promising technology, with emphasis on systems employing optically active nanofibers. Such nanofibers can be obtained by the electrospinning technique, and further functionalized with optically active chromophores such as dyes, conjugated polymers, carbon-based nanomaterials and nanoparticles, in order to produce fluorescent and colorimetric nanofibers. In this review we survey recent investigations reporting the use of optically active electrospun nanofibers in sensors aiming at the specific detection of heavy metals using colorimetry and fluorescence methods. The examples given in this review article provide sufficient evidence of the potential of optically electrospun nanofibers as a valid approach to fabricate highly selective and sensitive optical sensors for fast and low-cost detection of heavy metals.

Ohm’s Law is essential for understanding electrical circuits and conductive materials. Formulated by Georg Simon Ohm in the 19th century, it describes the direct proportional relationship between electric voltage and current in ohmic conductors. Despite its apparent simplicity, studies show that students at different educational levels struggle to understand it, mainly due to the abstraction of voltage, current, and resistance concepts. To help overcome these difficulties, this work proposes an experimental activity that applies Ohm’s Law to determine the nanometer-scale thickness of 6B graphite traces deposited on tracing paper. The methodology involves measuring voltage, current, and length, followed by data analysis. The thickness obtained through this approach was compared with results from a Scanning Probe Microscope (SPM). Based on the proposed method, the graphite trace thickness was determined as 456.5(34) nm, while SPM measurements yielded an average thickness of 440(50) nm. The results show good agreement within experimental uncertainties, validating the method’s effectiveness. Therefore, the proposed activity represents a feasible and low-cost alternative for applying Ohm’s Law in undergraduate Electricity courses and, with adaptations, even in high school, helping students connect theoretical concepts with experimental practice.