Metal-free, low-cost, organic photocatalytic graphitic carbon nitride (g-C₃N₄) has become a promising and impressive material in numerous scientific fields due to its unique physical and chemical properties. As a semiconductor with a suitable band gap of ~2.7 eV, g-C₃N₄ is an active photocatalytic material even after irradiation with visible light. However, information regarding the toxicity of g-C₃N₄ is not extensively documented and there is not a comprehensive understanding of its potential adverse effects on human health or the environment. In this context, the term “toxicity” can be perceived in both a positive and a negative light, depending on whether it serves as a benefit or poses a potential risk. This review shows the applications of g-C₃N₄ in sensorics, electrochemistry, photocatalysis, and biomedical approaches while pointing out the potential risks of its toxicity, especially in human and environmental health. Finally, the future perspective of g-C₃N₄ research is addressed, highlighting the need for a comprehensive understanding of the toxicity of this material to provide safe and effective applications in various fields.

Silver nanoparticles (AgNPs) have attracted tremendous attention in recent years due to their unique physicochemical properties, including pronounced surface plasmon resonance, tunable size, and amenability to functionalization. These attributes underpin the growing interest in AgNPs as SMART nanocarriers for targeted drug delivery and as active components in biosensing platforms. In this work, we discuss various synthesis strategies for AgNPs—ranging from conventional chemical methods to green approaches—and highlight their subsequent functionalization with anticancer drugs, notably doxorubicin (DOX). We also examine the potential of AgNPs in biosensor applications, emphasizing electrochemical and optical detection modalities capable of monitoring drug release, oxidative stress, and relevant biomarkers. Our experimental data support the conclusion that AgNPs can effectively improve therapeutic efficacy by exploiting tumor-specific conditions (e.g., lower pH) while also enhancing biosensor sensitivity via surface plasmon resonance and electrochemical signal amplification. We provide a thorough discussion of the results, including mechanistic aspects of reactive oxygen species (ROS) generation, drug release kinetics, and sensor performance metrics. Overall, AgNP-based nanocarriers emerge as a powerful platform to address current challenges in precision oncology and medical diagnostics.

Biochar, a biologically originated carbon-rich material derived from the oxygen-limited pyrolysis of biomass, is usually added to the soil for its enrichment, increasing its water-holding capacity and pH. This revolutionary material thus contributes to a reduction in the overall environmental impact and mitigation of climate change. Due to the beneficial properties of this material, especially for electrochemical applications (large active surface area, conductivity, etc.), biochar demonstrates an extremely high capacity for the adsorption and detection of micropollutants simultaneously. However, finding the optimal conditions for the adsorptive and electrochemical properties of prepared biochar-based sensors is crucial. The adsorption efficiency should be sufficient to remove pollutants, even from complex matrices; on the other hand, the electrochemical properties, such as conductivity and charge transfer resistance, are key factors concerning the sensing ability. Therefore, the balanced design of biochar can ensure both the usability and the effectiveness of sensing. To enhance levels of electroactivity that are already high, the pre- or post-modification of biochar can be performed. Such recycled carbon-based materials could be promising candidates among other electrochemical sensing platforms. In this study, different biochar modifications are presented. Utilizing important biochar properties, it should be possible to create a bifunctional platform for removing micropollutants from water systems and simultaneously confirming purification levels via their detection. We reviewed the use of biochar-based materials for the effective removal of micropollutants and the methods for their detection in water matrices.