Carbon dots (CDs) are a new cluster of carbon atoms with particle size less than 10 nm. CDs also exhibit interesting fluorescence (FL) properties. CDs are attractive because of their fascinating characteristics including low toxicity, good water solubility, and tremendous biocompatibility. Recently, CDs have been investigated as biosensors for numerous target analytes. Meanwhile, the utilization of cheap and renewable natural resources not only fulfills the pressing requirement for the large-scale synthesis of CDs but also encourages the establishment of sustainable applications. The preparation of CDs using natural resources, i.e., plants, offers several advantages as it is inexpensive, eco-friendly, and highly available in the surroundings. Plant parts are readily available natural resources as the starting materials to produce CDs with different characteristics and attractive applications. Several review articles are now available covering the synthesis, properties, and applications of CDs. However, there is no specific and focused review literature discussing plant part-derived CDs for biosensing applications. To handle this gap, we provide a review of the progress of CDs derived from various plant parts with their synthesis methods, optical properties, and biosensing applications in the last five years. We highlight the synthesis methods and then give an overview of their optical properties and applications as biosensors for various biomolecules and molecules in biological samples. Finally, we discuss some future perspectives for plant part-derived CDs for better material development and applications.

Carbon dots (CDs) have generated much interest because of their significant fluorescence (FL) properties, extraordinary photophysical attributes, and long-term colloidal stability. CDs have been regarded as a prospective carbon nanomaterial for various sensing applications because of their low toxicity, strong and broad optical absorption, high chemical stability, rapid transfer properties, and easy modification. To improve their functionality, CD/polymer composites have been developed by integrating polymers into CDs. CD/polymer composites have diversified because of their easy preparation and applications in sensing, optoelectronics, semiconductors, molecular delivery, and various commercial fields. Many review articles are available regarding the preparation and applications of CDs. Some review articles describing the production and multiple applications of the composites are available. However, no such article has focused on the types of precursors, optical properties, coating characteristics, and specific sensing applications of CD/polymer composites. This review aimed to highlight and summarize the current progress of CD/polymer composites in the last five years (2017–2021). First, we overview the precursors used for deriving CDs and CD/polymer composites, synthesis methods for preparing CDs and CD/polymer composites, and the optical properties (absorbance, FL, emission color, and quantum yield) and coating characteristics of the composites. Most carbon and polymer precursors were dominated by synthetic precursors, with citric acid and polyvinyl alcohol widely utilized as carbon and polymer precursors, respectively. Hydrothermal treatment for CDs and interfacial polymerization for CDs/polymers were frequently performed. The optical properties of CDs and CD/polymer composites were almost identical, denoting that the optical characters of CDs were well-maintained in the composites. Then, the chemical, biological, and physical sensing applications of CD/polymer composites are categorized and discussed. The CD/polymer composites showed good performance as chemical, biological, and physical sensors for numerous targets based on FL quenching efficiency. Finally, remaining challenges and future perspectives for CD/polymer composites are provided.

In this study, Volvariella volvacea (VV) mushroom was utilized as a green carbon precursor to synthesize carbon dots (CDs) and applied as a fluorescent (FL) sensor to detect Fe³⁺ and Pb²⁺ ions. The VV-CDs showed a high photostability and FL properties with a quantum yield of about 11.5%. The VV-CDs exhibited an excitation-dependent emission manner, with an optimum emission wavelength at 440 nm excited at 360 nm. The VV-CDs were evaluated and shown to be facile and effective FL sensors for detecting Pb²⁺ and Fe³⁺ ions based on the FL quenching efficiency, demonstrating the special complex chelate between the metal ions and effective surface functional groups of VV-CDs. VV-CDs displayed high responses to Fe³⁺ and Pb²⁺ ions, with the linear relationship of 1-100 μM and limits of detection (LODs) of 12 and 16 nM for Pb²⁺ and Fe³⁺ ions, respectively. Furthermore, the FL sensor was validated with real water samples, showing very good spike recoveries.

• Plant growth-promoting microorganisms (PGPM) as microbial inoculants and biofertilizers. • PGPM mechanisms in enhancing plant growth, nutrient uptake, and soil health. • The interactions between plants and PGPMs, emphasizing their role in crop productivity. • PGPM-mediated stress resistance and soil health improvement.