Utilization of Carbon Dots Derived from Volvariella volvacea Mushroom for a Highly Sensitive Detection of Fe3+ and Pb2+ Ions in Aqueous Solutions

A review on the chemical and biological sensing applications of silver/carbon dots nanocomposites with their interaction mechanisms

The development of new nanocomposites has a significant impact on modern instrumentation and analytical methods for chemical analysis. Due to their unique properties, carbon dots (CDs) and silver nanoparticles (AgNPs), distinguished by their unique physical, electrochemical, and optical properties, have captivated significant attention. Thus, combining AgNPs and CDs may produce Ag/CDs nanocomposites with improved performances than the individual material. This comprehensive review offers an in-depth exploration of the synthesis, formation mechanism, properties, and the recent surge in chemical and biological sensing applications of Ag/CDs with their sensing mechanisms. Detailed insights into synthesis methods to produce Ag/CDs are unveiled, followed by information on their physicochemical and optical properties. The crux of this review lies in its spotlight on the diverse landscape of chemical and biological sensing applications of Ag/CDs, with a particular focus on fluorescence, electrochemical, colorimetric, surface-enhanced Raman spectroscopy, and surface plasmon resonance sensing techniques. The elucidation of sensing mechanisms of the nanocomposites with various target analytes adds depth to the discussion. Finally, this review culminates with a concise summary and a glimpse into future perspectives of Ag/CDs aiming to achieve highly efficient and enduring Ag/CDs for various applications.

Carbon nanoprobe derived from Nyctanthes arbor-tristis flower: Unveiling the surface defect-derived fluorescence

Dual Emissive (green and blue) Carbon dots (C-Dots) aka g-CD and b-CD were synthesized using flowers of Nyctanthes arbortristis as the sole precursor via hydrothermal method without the aid of any external passivating agent. In the present report, the effect of time and temperature on the hydrothermal reaction was evaluated in order to modulate the surface defects that could lead to dual emissions. To gauge the nature, size, morphology, and optoelectronic characteristics, the C-Dots were characterized using high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR), UV-Vis spectroscopy and Fluorescence spectroscopy. The fluorescence studies of both the Carbon Dots revealed their excitation-dependent emission characteristics with the bathochromic shift. Furthermore, both g-CD and b-CD could effectively be utilized as efficient fluorescent probes for the selective and sensitive detection of Fe3+. These fluorescent nanoprobes could selectively detect Fe3+ over a wide range of concentrations (3 µM to 100 µM) with limit of detection (LOD) as low as 0.06 µM and 0.70 µM respectively. These tuneable Carbon Dots having wider solubilities would open a new avenue as Nanosensors for real-time applications.

Constructing hollow ZIF-8/CDs@MIPs fluorescent sensor from Osmanthus leaves to specifically recognize bovine hemoglobin

To develop non-toxic, highly efficient and selective fluorescence sensors was a significance research. In this work, a novel hollow fluorescence sensor was designed with biomass carbon dots (CDs), ZIF-8 and molecularly imprinted polymers (MIPs) via aqueous polymerization. The results demonstrated such unique structure fluorescence sensor exhibited fast response time, excellent stability and highly selectively towards bovine hemoglobin (BHb). Even in a complex environment, the hollow fluorescence sensor (H-ZIF-8/CDs@MIPs) still has a good recognition effect on BHb. Under an optimized condition, the hollow fluorescence sensor was quenched linearly with BHb concentration in the range of 0.058-4.5 μM with the detection limit of 15.6 nM. In addition, a possible quenching mechanism of hollow fluorescence towards BHb was confirmed resonance energy transfer (FRET). In the actual application process, the hollow fluorescence sensor showed a better detection performance towards BHb with the recoveries ranged of 98.6-101.1 %. This work provided a strategy to design green and unique hollow fluorescence sensor for practical application.

Humic Acids Affect the Detection of Metal Ions by Cyanobacteria Carbon Quantum Dots Differently

A "top-down" synthesis of carbon quantum dots (CQDs), novel fluorescent C materials from waste biomass, is both cost-effective and environmentally friendly. N-rich cyanobacteria are promising precursors to produce CQDs with high fluorescence (FL) intensity for the detection of metal ions. Herein, we synthesized cyanobacteria-based CQDs using a hydrothermal process and evidenced their high FL intensity and stability. The cyanobacteria-based CQDs showed powerful sensitivity for the specific detection of Fe³⁺ and Cr⁶⁺, which could be ascribed to (i) static FL quenching as a result of the interaction between -OH, -NH₂, and -COOH groups with the metal ions, (ii) internal filtering effects between the CQDs and Fe³⁺ or Cr⁶⁺, and (iii) fluorescence resonance energy transfer between CQDs and Cr⁶⁺. Humic acids (HAs) coexisting led to an underestimation of Fe³⁺ but an overestimation of Cr⁶⁺ by the CQDs due to the different FL quenching mechanisms of the CQDs. HAs sorbed Fe³⁺ and wrapped the CQDs to form a barrier between them, inhibiting FL quenching of CQDs by Fe³⁺. As for Cr⁶⁺, HAs reduced Cr⁶⁺ and also led to FL quenching; the sorbed HAs on the CQDs acted as a carrier of electrons between Cr⁶⁺ and the CQDs, enhancing FL quenching of the CQDs. This study is the first work to evidence the interference of HAs in the detection of metal ions by CQDs derived from cyanobacteria, which would enlighten the application of CQDs in a natural aqueous environment.

A Review on Carbon Dots: Synthesis, Characterization and Its Application in Optical Sensor for Environmental Monitoring

The development of carbon dots (CDs), either using green or chemical precursors, has inevitably led to their wide range application, from bioimaging to optoelectronic devices. The reported precursors and properties of these CDs have opened new opportunities for the future development of high-quality CDs and applications. Green precursors were classified into fruits, vegetables, flowers, leaves, seeds, stem, crop residues, fungi/bacteria species, and waste products, while the chemical precursors were classified into acid reagents and non-acid reagents. This paper quickly reviews ten years of the synthesis of CDs using green and chemical precursors. The application of CDs as sensing materials in optical sensor techniques for environmental monitoring, including the detection of heavy metal ions, phenol, pesticides, and nitroaromatic explosives, was also discussed in this review. This profound review will offer knowledge for the upcoming community of researchers interested in synthesizing high-quality CDs for various applications.

Folic Acid-Modified Cerium-Doped Carbon Dots as Photoluminescence Sensors for Cancer Cells Identification and Fe(III) Detection

Carbon dots (CDs) are a new class of carbon-based luminescence materials with fascinating properties. They have been given great expectations on superseding traditional semiconductor quantum dots due to their good dispersity and stability, relatively low toxicity, superior resistance to photobleaching, and excellent biocompatibility. The diversified luminescence properties of CDs are largely due to the synthetic strategies and precursors. In view of those described above, this study has explored the possibility to establish a facile one-step hydrothermal method for the one-pot synthesis of folic acid-modified cerium-doped CDs (Ce-CDs-FA), which could be further utilized as a sensitive fluorescent nanoprobe for biosensing. This investigation demonstrates that the Ce-CDs-FA nanocomposites have nice biocompatibility and bright fluorescent properties, which can be readily utilized to detect cancer cells through recognizing overexpressing folate receptors by virtue of folic acid. Meanwhile, it is noted that the Fe3+ ion can actualize a specific and hypersensitive quenching effect for these Ce-CDs-FA nanocomposites, which can be further explored for special ion recognition, including iron ions. It raises the possibility that the as-prepared Ce-CDs-FA nanocomposites could be extended as a dual fluorescence sensor for targeted cell imaging and Fe3+ ion detection.

Amino Appended Coumarin Composites for Pb2+ Capturing in Aqueous Medium

The C1-C3 receptors were synthesized by using coumarin and amines viz., 1-butylpiperazine (1), cis-myrtanylamine (2), and 3-methyldiphenyl amine (3) at room temperature without using harsh conditions. All the probes show beautiful and strong binding with Pb²⁺ ions among all the tested essential elements of human body. The binding is clearly seen and confirmed in UV-visible, NMR and HPLC studies. Also, all the substituted amines (1-3) are well known bioactives viz., piperazine as anthelmintic, cis-myrtanyl use for cannabinoid receptor (CB2) antagonists, 3-methyldiphenyl is used in probes for selective detection of explosive nitroaromatic compounds further increases their sensitivity for use as Pb²⁺ sensor. As they are already well in use for research on human body metabolomics their future introduction as sensors in the human body for lead toxicity is highly favourable.

Carbon Dot/Polymer Composites with Various Precursors and Their Sensing Applications: A Review

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.

Potential Usage of Edible Mushrooms and Their Residues to Retrieve Valuable Supplies for Industrial Applications

Currently, the food and agricultural sectors are concerned about environmental problems caused by raw material waste, and they are looking for strategies to reduce the growing amount of waste disposal. Now, approaches are being explored that could increment and provide value-added products from agricultural waste to contribute to the circular economy and environmental protection. Edible mushrooms have been globally appreciated for their medicinal properties and nutritional value, but during the mushroom production process nearly one-fifth of the mushroom gets wasted. Therefore, improper disposal of mushrooms and untreated residues can cause fungal disease. The residues of edible mushrooms, being rich in sterols, vitamin D2, amino acids, and polysaccharides, among others, makes it underutilized waste. Most of the published literature has primarily focused on the isolation of bioactive components of these edible mushrooms; however, utilization of waste or edible mushrooms themselves, for the production of value-added products, has remained an overlooked area. Waste of edible mushrooms also represents a disposal problem, but they are a rich source of important compounds, owing to their nutritional and functional properties. Researchers have started exploiting edible mushroom by-products/waste for value-added goods with applications in diverse fields. Bioactive compounds obtained from edible mushrooms are being used in media production and skincare formulations. Furthermore, diverse applications from edible mushrooms are also being explored, including the synthesis of biosorbent, biochar, edible films/coating, probiotics, nanoparticles and cosmetic products. The primary intent of this review is to summarize the information related to edible mushrooms and their valorization in developing value-added products with industrial applications.