Revolutionizing Bioimaging with Carbon Dots: A Single-Step Low-Temperature Approach

Anupam Ghosh
Nov 21
2 min read

Carbon dots (CDs) have emerged as a versatile nanomaterial in recent years, offering unique optical properties, biocompatibility, and cost-effectiveness. Their applications span across biomedical imaging, sensing, catalysis, and even agriculture. However, conventional synthesis methods often require high temperatures and multi-step processes, making industrial-scale production challenging. A recent study published by NanoBio Research Lab, IIT Kharagpur, in ACS Applied Bio Materials introduces a single-step, low-temperature synthesis method that simplifies production while maintaining excellent structural and optical properties.

Diagram showing the synthesis of carbon dots from citric acid, ascorbic acid, and ethylenediamine at 140°C. Applications in zebrafish, microbes, and plants.

Why Carbon Dots Matter

CDs are nanoscale carbon-based particles known for their tunable fluorescence, high water solubility, and compatibility with biological systems. Compared to quantum dots and metal nanoclusters, CDs are safer, cheaper, and easier to fabricate. These advantages make them ideal candidates for applications such as bioimaging, drug delivery, and environmental monitoring.

The Innovation: Single-Step Low-Temperature Synthesis

Traditional hydrothermal methods operate at temperatures between 160 °C and 250 °C, consuming significant energy and complicating scalability. The new approach uses a simple refluxing process at 140 °C for six hours, employing citric acid, ascorbic acid, and their combination as carbon precursors, along with ethylenediamine and hydrochloric acid as catalysts. This method produces CDs with sizes ranging from 3 to 5 nanometers and quantum yields between 3.6% and 16.5%. The process is energy-efficient, environmentally friendly, and suitable for industrial translation.

Structural and Optical Properties

The synthesized CDs were characterized using advanced techniques. FT-IR spectroscopy confirmed the presence of hydroxyl and carboxyl groups, ensuring water solubility. X-ray diffraction revealed their amorphous nature, while transmission electron microscopy showed spherical morphology for citric acid and ascorbic acid CDs, and unique shapes for the composite blend. Optical studies demonstrated strong fluorescence with emission peaks at 465 nm, 510 nm, and 475 nm for the respective CDs, highlighting their suitability for imaging applications.

Applications in Multiparametric Bioimaging

The study explored the potential of CDs in three biological models: zebrafish embryos, bacterial strains, and lettuce plants.

Zebrafish Embryos

Exposure to CDs at concentrations of 0.5 and 1 mg/mL showed significant uptake without causing mortality or physiological changes such as heart rate alterations. A 100% hatching rate was observed, and fluorescence imaging confirmed uptake within 6 to 72 hours post-exposure, demonstrating biocompatibility.

Bacterial Imaging

CDs successfully labeled both Gram-positive Bacillus subtilis and Gram-negative Serratia marcescens without exhibiting bactericidal effects. This positions CDs as promising tools for microbial diagnostics and imaging.

Plant Bioimaging

In lettuce plants, CDs were absorbed through roots and transported to stems and leaves, with fluorescence observed in vascular bundles and mesophyll tissues. This opens new possibilities for agricultural monitoring and enhancing photosynthesis.

Future Prospects

The implications of this research are significant. By simplifying synthesis and reducing environmental impact, CDs can now be produced at scale for diverse applications. In biomedicine, they hold promise for drug delivery and disease diagnostics. In agriculture, they could serve as photosynthesis enhancers and nutrient sensors. Their biocompatibility and fluorescence properties also make them suitable for environmental monitoring and biosensing. This single-step, low-temperature approach represents a major leap toward sustainable nanotechnology, offering multifunctional solutions for healthcare, agriculture, and beyond.

Disclaimer: This article was originally authored by researchers from NanoBio Research Lab, collaborating with other labs and institutes. Original article was published in ACS Applied Bio Materials.

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