Fluorescent carbon dots from Indian Bael patra as effective sensing tool to detect perilous food colorant

Recent advancements and prospects in carbon-based nanomaterials derived from biomass for environmental remediation applications

The conversion of waste biomass into a value-added carbonaceous nanomaterial highlights the appealing power of biomass valorization. The advantages of using sustainable and cheap biomass precursors exhibit the tremendous opportunity for boosting energy production and their application in environmental remediation processes. This review emphasis the development and production of carbon-based nanomaterials derived from biomass, which possess favourable characteristics such as biocompatibility and photoluminescence. The advantages and limitations of various nanomaterials synthesised from different precursors were also discussed with insights into their physicochemical properties. The surface morphology of the porous nanomaterials is also explored along with their characteristic properties like regenerative nature, non-toxicity, ecofriendly nature, unique surface area, etc. The incorporation of various functional groups confers superiority of these materials, resulting in unique and advanced functional properties. Further, the use of these biomass derived nanomaterials was also explored in different applications like adsorption, photocatalysis and sensing of hazardous pollutants, etc. The challenges and outcomes obtained from different carbon-based nanomaterials are briefly outlined and discussed in this review.

Carbon Dots: Synthesis, Characterizations, and Recent Advancements in Biomedical, Optoelectronics, Sensing, and Catalysis Applications

Carbon nanodots (CNDs), a fascinating carbon-based nanomaterial (typical size 2-10 nm) owing to their superior optical properties, high biocompatibility, and cell penetrability, have tremendous applications in different interdisciplinary fields. Here, in this Review, we first explore the superiority of CNDs over other nanomaterials in the biomedical, optoelectronics, analytical sensing, and photocatalysis domains. Beginning with synthesis, characterization, and purification techniques, we even address fundamental questions surrounding CNDs such as emission origin and excitation-dependent behavior. Then we explore recent advancements in their applications, focusing on biological/biomedical uses like specific organelle bioimaging, drug/gene delivery, biosensing, and photothermal therapy. In optoelectronics, we cover CND-based solar cells, perovskite solar cells, and their role in LEDs and WLEDs. Analytical sensing applications include the detection of metals, hazardous chemicals, and proteins. In catalysis, we examine roles in photocatalysis, CO2 reduction, water splitting, stereospecific synthesis, and pollutant degradation. With this Review, we intend to further spark interest in CNDs and CND-based composites by highlighting their many benefits across a wide range of applications.

Carbon dots-based fluorescent probe for the detection of imidacloprid residue in leafy vegetables

Consumption of leafy vegetables with excessive imidacloprid (IMI) can cause serious harm to the human body. To achieve rapid IMI detection, a carbon dots (CDs)-based fluorescent (FL) probe was hydrothermally prepared using O-phenylenediamine as the precursor. The morphology, particle size distribution, crystal structure, optics and chemical bond state of the as-prepared CDs were characterized. The mechanism of the CDs in detecting IMI was investigated by Fourier transform infrared spectroscopy, and the CDs' selectivity, stability, sensitivity, and actual sample recovery were tested. The CDs showed good selectivity, stability, and anti-interference ability. Under optimum conditions, there was a strong linear relationship between the FL intensity of the CDs and the IMI concentration in the range of 0.037-0.2 mg/L. The detection limit was 0.00187 mg/kg. The CDs were successfully applied to detect IMI in lettuce, cole, spinach, and pakchoi with spiked recoveries between 81.026% and 106.803% and a relative standard deviation between 0.001 and 0.027%.

Solvothermal synthesis of bifunctional carbon dots for tartrazine and Fe(III) detection from chamomile residue by ternary DES pretreatment

A ternary deep eutectic solvent (DES) consisting of choline chloride, lactic acid, and urea in a molar ratio of 1:2:2 was used to pretreat chamomile residue, followed by carbon dots (CDs) preparation using a one-pot solvothermal method. The CDs prepared under the suitable conditions had a high quantum yield of 47.34% and could be used as a bifunctional fluorescent probe for the detection of tartrazine and Fe(III). The concentration of tartrazine or Fe(III) had a good linear relationship with the fluorescence intensity of CDs that the determination coefficient (R²) was 0.9957 and 0.9943, and the limit of detection (LOD) was 40 nM and 119 nM, respectively. After verifying the different fluorescence quenching mechanisms of CDs by these two substances, a quantitative analysis was performed on real samples with recoveries of 90.70%∼104.29%. Overall, this study provided a promising technology for chemical conversion from low-cost chamomile residue to attractive bifunctional fluorescent probe.

Solvatochromism as a Novel Tool to Enumerate the Optical and Luminescence Properties of Plastic Waste Derived Carbon Nanodots and Their Activated Counterparts

Herein, we have developed a one-pot methodology to synthesise three types of C-dots and their activated counterparts from three different types of waste plastic precursors such as poly-bags, cups and bottles. The optical studies have shown the significant change in the absorption edge in case of C-dots in comparison to their activated counterparts. The respective variation in the sizes is correlated with the change in electronic band gap values of formed particles. The changes in the luminescence behaviour are also correlated with transitions from the edge of the core of formed particles. The obtained variations in the Stokes shift values of C-dots, and their ACs were used to explore the types of surface states and their related transitions in particles. The mode of interaction between C-dots and their ACs was also determined using solvent-dependent fluorescence spectroscopy. This detailed investigation could provide significant insight on the emission behaviour and the potential usage of formed particles as an effective fluorescent probe in sensing applications.

N-doped carbon dots coupled with molecularly imprinted polymers as a fluorescent sensor for ultrasensitive detection of genistein in soya products

Rapid detection of genistein in soya products has remained difficult. Current methods necessitate sample handling and use of costly instruments. Here, using a simple one-pot reverse microemulsion method, a sensor based on N-doped carbon dots conjugated molecularly imprinted polymers (N-CDs@MIPs) was synthesized to analyze genistein. N-doped carbon dots were used as fluorescent component, genistein as the template molecule, and molecularly imprinted polymers as the selective sorbent in this fluorescence sensor. The sensor was then examined and optical studies demonstrated that N-CDs@MIPs not only had strong fluorescence emission and outstanding optical stability, but also had good sensitivity (detection limit 35.7 nM) and selectivity to genistein. Furthermore, the N-CDs@MIPs materials were used to analyze genistein in soya products, and the findings (which ranged from 99.77% to 106.11%) show that the N-CDs@MIPs has high potential for quickly detecting the amount of genistein in complicated food samples.

Nano-Nutraceuticals for Health: Principles and Applications

The use of nanotechnological products is increasing steadily. In this scenario, the application of nanotechnology in food science and as a technological platform is a reality. Among the several applications, the main use of this technology is for the development of foods and nutraceuticals with higher bioavailability, lower toxicity, and better sustainability. In the health field, nano-nutraceuticals are being used as supplementary products to treat an increasing number of diseases. This review summarizes the main concepts and applications of nano-nutraceuticals for health, with special focus on treating cancer and inflammation.

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Supplementary Information

The online version contains supplementary material available at 10.1007/s43450-022-00338-7.

Carbon dots fabricated by solid-phase carbonization using p-toluidine and l-cysteine for sensitive detection of copper

In this study, a label-free "turn off" fluorescent sensor has been resoundingly fabricated using carbon dots (CDs) for ultrasensitive detection of copper ions (Cu²⁺). CDs are prepared by solid phase carbonization method using p-toluidine and l-cysteine as the precursors. The synthesized CDs exhibited the highest fluorescence intensity with excitation and emission wavelengths set at 300 nm and 400 nm, respectively. The CDs were selective and sensitive to Cu²⁺ due to the static quenching mechanism. The concentration of CDs, and solution pH and incubation time were important parameters for the developed sensor. The experimental results showed that 20 mgL^-1 was enough for the analysis. As the solution pH was concerned, it was apparent that the sensor was endowed with an excellent response signal to Cu²⁺ and provided high sensitivity at pH 12. The interaction occurred very quickly, and the incubation time could be set at 1 min. The sensor provided a two-stage calibration curve to Cu²⁺ in the range of 0.05-0.7 and 0.7-4 μM with a limit of detection of 47 nM. The obtained results clearly demonstrated that this facile method was fast, reliable and selective for detecting Cu²⁺, which would explore a prospective strategy for developing effective and low-cost sensors for monitoring metal ions in aqueous environments.

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.