A review on syntheses, properties, characterization and bioanalytical applications of fluorescent carbon dots

Carbon dots: An emerging food analysis nanoprobes for detection of contaminants

Carbon dots are the new class of nanomaterials with a size range of 10 nm or less. These are associate with the important material properties such as good biocompatibility, fluorescent nature, small size and easy to synthesize with low toxicity which make them the first choice over the fluorescent inorganic materials and dyes, to be used as biocompatible nanoprobes for the detection of food adulterations. Herein, we have focused on the methods of synthesis of these tiny zero dimensions, fluorescent nanomaterials (CDs), their properties, mechanism of fluorescence, and lastly their wide applications in food analysis which include the detection of additives, heavy metal ions, organic pollutants, foodborne microbes, antibiotic and pesticides. Further, these nanomaterials open the scope to be used as nanoprobes in the food safety concern. Additionally, we discussed the challenges and future scope of CDs as an auspicious and emerging nanomaterial to be used in the food industries.

Spectrofluorometric determination of Fe3+, Pd2+, and Sn2+ions using carbon nanodots derived from hazelnut shells

Carbon nanodots (CNDs) were synthesized from hazelnut shells using the pyrolysis method in an oven at temperatures ranging from 250 to 400 °C and reaction times between 1 and 3 h. The structural and optical properties of the CNDs, which exhibited strong blue fluorescence under a UV lamp (365 nm), were characterized using UV-vis absorption spectroscopy, fluorescence spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The quantum yield of the CNDs was determined to be between 2.2% and 7.8%. The effect of various cations on the fluorescence spectra of the CNDs was investigated using fluorescence spectrometry. Among the synthesized CNDs, those prepared via pyrolysis for 3 h at 300 °C, 315 °C, and 350 °C (designated as HS300-3, HS315-3, and HS350-3, respectively) exhibited selective fluorescence quenching in the presence of Fe3+, Sn2+, and Pd2+. These CNDs were applied for the determination of Fe3+in tap water and soil samples, while HS315-3 was also employed for the detection of Sn2+and Pd2+in tap water. The limits of detection (LOD) were 4.5 μg l-1for Fe3+and 15.8 μg l-1for both Sn2+and Pd2+. The accuracy of the methods was validated through spiked recovery experiments with tap water samples and by analyzing a certified reference material (CRM-SA-C Sandy Soil C).

Synthesis, Characterization, and Applications of Carbon Dots for Determination of Pharmacological and Biological Samples: A Review

Carbon dots (CDs) are a novel category of carbon-based nanomaterials characterized by their small size, often less than 10 nm. CDs physical, chemical, and optical properties can be tuned using one-pot assembly. Because of their non-toxicity, biocompatibility, chemical and physical responsiveness, photo- and chemical-bleaching resistance, and low cost, nanoparticles have become incredibly versatile. They find various applications in detecting inorganic substances, bio sensing, visualizing cells, studying biological processes in live cells, and aiding in medication delivery. Additionally, CDs exhibit versatility in electronics and energy storage, making them promising candidates for applications in solar cells, light-emitting diodes, and supercapacitors. CDs are more photo stable for hours than typical fluorescent semiconductor quantum dots. Before applying CDs, they must be characterized. Techniques such as UV-VIS spectroscopy, fluorescence spectrophotometry, FT-IR, TEM, XRD, Raman spectroscopy, and NMR are commonly used to assess their photophysical and structural properties. This article review explores the synthesis, characterization applications of CDs in analytical techniques for the determination of various analytes. The article provides a detailed analysis of the different methodologies used to make nanomaterials and devices for the characterization of CDs. It also discusses the challenges that arise when using CDs in analytical techniques for detecting different analytes. The focus of this review is on accurately determining pharmaceutical and biological samples using CDs as sensing probes.

Recent Progress in Folic Acid Detection Based on Fluorescent Carbon Dots as Sensors: A Review

Folic acid (FA) is a water-soluble vitamin found in diverse natural sources and is crucial for preserving human health. The risk of health issues due to FA deficiency underscores the need for a straightforward and sensitive FA detection methodology. Carbon dots (CDs) have gained significant attention owing to their exceptional fluorescence performance, biocompatibility, and easy accessibility. Consequently, numerous research studies have concentrated on developing advanced CD fluorescent probes to enable swift and precise FA detection. Despite these efforts, there is still a requirement for a thorough overview of the efficient synthesis of CDs and their practical applications in FA detection to further promote the widespread use of CDs. This review paper focuses on the practical applications of CD sensors for FA detection. It begins with an in-depth introduction to FA and CDs. Following that, based on various synthetic approaches, the prepared CDs are classified into diverse detection methods, such as single sensing, visual detection, and electrochemical methods. Furthermore, persistent challenges and potential avenues are highlighted for future research to provide valuable insights into crafting effective CDs and detecting FA.

Histidine-derived carbon dots as luminescent probes for detecting apoptosis

Histidine-derived carbon dots (His-CDs) were synthesized to detect staurosporine-induced apoptosis in T lymphoma (Jurkat) cells. The His-CDs were characterized for their physical and chemical properties including size, morphology, fluorescence, and surface functionality. Transmission electron microscopy (TEM) revealed a spherical morphology with an average size of 11.4 ± 3.4 nm. Fluorescence analysis showed maximum excitation at 338 nm and emission at 415 nm, attributed to the carbon dots' quantum confinement effect and surface defects. FTIR and SEM-EDS confirmed the presence of hydroxyl, amine, aromatic rings, and alkyl (C-H) functional groups and carbon, nitrogen, and oxygen elemental composition in ratios of 52%, 24.8%, and 23.3%, respectively. His-CDs were evaluated for cytotoxicity and apoptosis detection in Jurkat cells. Fluorescence microscopy and flow cytometry analysis demonstrated concentration-dependent fluorescence, suggesting effective cellular uptake of His-CDs. The apoptotic-sensing capability of His-CDs was tested using staurosporine, an apoptosis inducer. A concentration-dependent increase in fluorescence was observed with increasing staurosporine concentrations, indicating the His-CDs' sensitivity to apoptosis. The time-dependent fluorescence increases were noted with prolonged staurosporine exposure. Z-DEVD-FMK, a caspase-3 inhibitor, confirmed that the apoptosis detected by His-CDs was caspase-3 dependent, as co-treatment reduced His-CDs' fluorescence in the cell. In conclusion, these results demonstrate that His-CDs are biocompatible, sensitive apoptosis sensors and hold the potential for monitoring apoptotic pathways in cellular systems.

Effect of precursors on carbon dot functionalization and applications: a review

Carbon dots (CDs) are a type of carbon-based nanoparticle (NP) that have risen in popularity due to their unique tuneable physicochemical and optical properties. CDs have received a significant amount of attention in biological based applications due to their low cytotoxicity, stable photoluminescence, and small size. They have demonstrated the ability to retain certain properties from their carbon precursors, enabling NP design via precursor selection. Thus, direct functionalization of a CD can be achieved without the need for post synthesis modification. However, CDs derived from the same class of carbon precursor can also have profoundly variable applications. Indicating that, in conjunction with precursor properties, other functional attributes can be imposed on the CD during the synthesis process to enable cross-cutting applications from a single carbon precursor. Here, we will highlight various CD precursors and the resulting multifunctional CDs, as well as rational design of CDs for specific biological and materials science applications via precursor selection.

Carbon Quantum Dots with Tunable Size and Fluorescence Intensity for Development of a Nano-biosensor

Carbon quantum dots (CQDs) are a class of nanomaterials known for their remarkable photostability, chemical inertness and biocompatibility. Changing their size, structure, and surface chemistry enable the tuning of their luminescence property, which gives them tremendous potential for various applications. CQDs synthesis typically involves long tedious processes, requiring multiple steps and harsh reaction conditions. Here, a new reliable, economical, and ultra-rapid one-step fabrication method is introduced to obtain CQDs with well-defined and reproducible photoluminescence properties via a simple heat treatment. These solid-state CQDs are homogenous in size and are ready to use without the need for further purification. The size of the fabricated CQDs and their corresponding peak fluorescence intensity are confirmed to be tunable by simple adjustment of the heat treatment conditions. Coupled with their selective fluorescence quenching by metal ions, the clinical potential of CQDs is demonstrated for biosensing applications by designing a new nano-biosensor to assess the quality of stored blood units through hemolysis quantification without disrupting storage conditions. This may pave the way for a new standard in blood bank inventory management.

L-tryptophan carbon dots as a fluorescent probe for malachite green detection

Development of a rapid and sensitive detection method for hazardous dyes attracts considerable research interest. In this work, L-Tryptophan-based Carbon dots were developed as a fluorescence sensor for the detection of Malachite green (MG). Green fluorescent L-Trp-C-dots were synthesized by a simple pyrolysis technique using L-Trp as the starting precursor. L-Trp-C-dots exhibited different quenching responses to MG, and other interfering species, consequently offering a selective strategy to detect MG. The proposed sensor shows a limit of detection (LOD) of 0.06 μM and a limit of quantification (LOQ) of 0.22 μM with in the linearity range of 0 to 60 µM concentration. Additionally, the relative standard deviation (RSD) was found to be below 1.7 %. Furthermore, the recovery of MG from the real-time samples (green peas) was investigated.

A DNA-Based Plasmonic Nano-Ruler

DNA is an exceptional building block for the fabrication of dynamic supramolecular systems with switchable geometries. Here, a self-assembled, tunable plasmonic-fluorescent nanostructure was developed. A precise sliding motion mechanism was operated through the control of strand displacement reactions, shifting two single-strand DNA (ssDNA) rails connected by a ssDNA quasi-ring structure. The system was reconfigured as a nano-mechanical structure, generating six discrete configurations, and setting specific distances between a tethered gold nanoparticle (AuNP) and a fluorophore, Sulfo-Cyanine3 (Cy3). Each configuration produced a distinct fluorescence emission intensity via plasmonic quenching/enhancement effects, and therefore the structure behaved as a nano-ruler. To optimize the system, the reversible distance-dependent fluorescence quenching or enhancement phenomena were investigated by testing AuNPs with diameters of 5, 10, and 15 nm, yielding the best performances with 10 nm AuNPs. Furthermore, a geometric model of the system was produced, confirming the observed results. The fluorophore-plasmonic surface positioning, conferred by the DNA ruler, led to a finite state nano-machine with six alternative signal outputs. This mechanism, working as a fluorescent reporter, could find application in a multiple-responsive detection system of single-strand nucleic acids, such as viruses or microRNAs.

A Simple Method for Synthesizing Nitrogen-Doped Carbon Quantum Dots for Fluorescent "Turn off" Mercury (II) Ion Sensing

Here, straightforward and environmentally friendly fluorescent nitrogen doped carbon quantum dots (N-CQDs) with a high blue fluorescence emission at 455 nm are used for ultrasensitive Hg2+ ion detection. Folic acid and urea are used as carbon sources in the carbonization process. Two broad absorption bands at around 280 and 370 nm from UV-Vis spectrum and characteristic absorption peaks from infrared spectrum confirms the successful synthesis of the N-CQDs. Energy dispersive X-Ray analysis confirmed the elemental composition of the N-CQDs. Transmission electron microscopy showed the homogeneous globular morphology of the N-CQDs with an average particle size of 65 nm. Zeta potential measurement established the stability and surface charge of N-CQDs. Dynamic light scattering measurement showed the average size of N-CQDs. With the addition of Hg2+ ion to N-CQDs, the blue fluorescence emission is quenched. Moreover, the N-CQDs can be applied to real water sample such as pond water, river water, and tap water. The detection limit is approximately calculated to be 12 nM and linear range is 0-30 parts per billion.

Adsorption and Corrosion Inhibition Evaluation of Agro-Industrial Waste-Derived Sustainable Carbon Dots for Corrosion Protection of Q235 Steel in 5% HCl

Nitrogen and sulfur codoped carbon dots (SB-CDs) were developed from sugar cane bagasse, an agro-industrial waste, and evaluated as an eco-friendly corrosion inhibitor for Q235B steel in HCl solution. The surface coverage of the adsorbed SB-CDs is strongly influenced by immersion time (6 and 72 h, both in static and dynamic conditions) and inhibitor concentration (20-200 mg/L). Maximum and uniform coverage is achieved with 150 mg/L SB-CDs. At this concentration, SB-CDs demonstrated a high inhibition efficiency of 96% after 6 h of immersion, maintaining effectiveness at 94 and 92% under static and dynamic conditions, respectively, at 72 h of immersion. Electrochemical studies showed that polarization resistance (Rp) increased, and corrosion current density (Icorr) of steel decreased in the presence of SB-CDs compared to uninhibited specimens, confirming SB-CDs' adsorption on metal surfaces. Additionally, surface analysis using scanning electron microscopy and atomic force microscopy confirmed the improved surface morphology and fewer corrosion features, supporting the formation of a protective film. Energy-dispersive X-ray and X-ray photoelectron spectroscopy analyses further confirm the formation of a protective layer by SB-CDs, attributed to the interaction of nitrogen-, oxygen-, and sulfur-containing functional groups with the steel surface. Therefore, a homogeneously adsorbed inhibitor layer entirely blocks the formation of iron chloride/oxide/hydroxide intermediates, ensuring high corrosion inhibition efficiency of Q235B steel in corrosive environments.

Applications of carbon dot-mediated cardiomyocyte maturation in regenerative medicine: a review

The maturation of cardiomyocytes (CMs) plays key roles in regenerative medicine and the treatment of cardiovascular diseases via stem cell-derived CMs. Carbon dots (CDs) have good biocompatibility, optical properties, and electrophysical properties and have been widely applied in bioimaging, biosensors, and biotherapy. In this review, we comprehensively summarize recent advances in promoting the maturation of CMs, mainly human pluripotent stem cell-derived CMs, and related regenerative medicine. Moreover, we explore the innovative application of CDs to enhance the maturation of these CMs. Finally, we look forward to the future design and application of CDs in the maturation of CMs in terms of cell therapies.

Machine Learning-Assisted Biomass-Derived Carbon Dots as Fluorescent Sensor Array for Discrimination of Warfarin and Its Metabolites

Warfarin (WAR), an effective oral anticoagulant, is of utmost importance in treating many diseases. Despite its significance, rapid and precise discrimination of WAR remains a formidable challenge, especially facing its structural analogs of metabolites. Here, three kinds of herb-derived N-doped carbon dots (NCDs) were greenly synthesized via a fast and simple microwave-assisted method. Three NCDs showcased respectable blue fluorescent (FL) properties and sensing capabilities for the discrimination of WAR and its metabolites. To improve accuracy in identifying WAR and its metabolites, a sensor array composed of three unique herb-derived NCDs was meticulously designed. Combined with the machine learning model, the sensor array displayed a strong immunity to interference in the discrimination of the WAR, even in unknown samples. Meanwhile, the FL sensing mechanism is deeply expounded. The methodology proffers broad prospects for biomass-derived nanomaterials and provides an effective and feasible project for pharmaceutical analysis by capitalizing on machine learning.

In vitro evaluation of anthelmintic activity of biocompatibile carbon quantum dot nanocomposite against egg and larval stages of equine strongyles

BACKGROUND

Strongyle nematodes pose a major challenge in veterinary parasitology, causing significant economic losses in livestock due to resistance to conventional treatments. Current anthelmintics, like Ivermectin, often encounter resistance issues. This study aims to address these gaps by synthesizing Carbon Quantum Dots (CQDs) and Copper-Doped CQDs (Cu@CQDs) using glucose extract, and evaluating their nematicidal properties against strongyles in vitro. We assessed the nematicidal effects of CQDs and Cu@CQDs through larval feeding inhibition of first-stage larvae (L1), egg hatch inhibition (EHI), and the mobility and mortality of infectious larvae (L3s). Additionally, we conducted ultrastructural examinations of eggs and larvae and evaluated oxidative/nitrosative stress indicators, including total antioxidant status (TAS), protein carbonylation (PCO), lipid peroxidation (MDA), and oxidative DNA damage in homogenized samples of L3s.

RESULTS

The synthesized CQDs displayed semi-spherical morphology with diameters under 30 nm. Cu@CQDs at 12.5 µg/ml achieved over 90% EHI and larval motility inhibition. Fluorescence microscopy confirmed over 90% larval feeding inhibition at the same concentration. Both CQDs and Cu@CQDs induced oxidative stress, indicated by decreased TAS and increased MDA, PCO, and oxidative DNA damage. Scanning Electron Microscopy showed that CQDs and Cu@CQDs penetrated the larvae cuticle, altered the tegument, caused larval mortality, and resulted in egg deformities.

CONCLUSIONS

Given the potential for resistance to Ivermectin, seeking suitable alternatives is essential. Cu@CQDs exhibit effects similar to Ivermectin, indicating their potential as novel antiparasitic agents against strongyles. These findings emphasize the importance of exploring alternative treatments to address resistance and enhance nematode control efficacy.

Advances in the application of carbon dots-based fluorescent probes in disease biomarker detection

Carbon dots (CDs), as an emerging nanomaterial, have shown tremendous potential in disease biomarker detection. CDs can selectively interact with different target molecules, enabling highly sensitive and specific detection of these biomolecules. Compared to traditional detection methods, CDs sensors offer advantages such as rapid response, high detection sensitivity, and low cost. In this review, we summarize the latest advances in the application of CDs fluorescence probes for the detection of disease biomarkers, including sensing mechanisms, and their applications in the selective detection of metal ions, amino acids, enzymes, proteins, other biomolecules, as well as bacteria and viruses. We discuss the current challenges and issues associated with the practical application of CDs-based fluorescent probes. Furthermore, we propose future directions for the development of CDs. We hope that this review will provide new insights for researchers in the field of disease biomarker detection.

Application of Carbon Quantum Dots Derived from Waste Tea for the Detection of Pesticides in Tea: A Novel Biosensor Approach

Chemical pesticide residues have negative consequences for human health and the environment. Prioritizing a detection method that is both reliable and efficient is essential. Our innovative research explored the application of biosensors based on carbon quantum dots (CQDs) derived from waste tea to detect commonly used pesticides in tea. CQDs have been synthesized using a simple one-pot hydrothermal approach and thoroughly characterized using advanced techniques such as high-resolution transmission electron microscopy, ultraviolet-visible spectroscopy, photoluminescence (PL) spectroscopy, Raman spectroscopy, X-ray diffraction, atomic force microscopy, and X-ray photoelectron spectroscopy. The fluorescence resonance energy transfer-based fluorescence "turn on-off" mechanism has been successfully employed to study the detection of four different pesticides, viz., quinalphos 25 EC, thiamethoxam 25 WG, propargite 57 EC, and hexaconazole 5 EC. The detection limits for quinalphos 25 EC, thiamethoxam 25 WG, and propargite 57 EC were determined to be 0.2, 1, and 10 ng/mL, respectively. Notably, these values are significantly lower than the maximum residue level for each pesticide. We achieved a strong linear correlation (R = -0.96) with a detection limit of 0.2 ng/mL for quinalphos 25 EC. The quantum yield was determined to be 40.05%. Our research demonstrates that the developed nanobiosensor reliably and accurately detects pesticides, including those present in experimental samples containing mixtures of pesticides.

Electroactive Nanomaterials for the Prevention and Treatment of Heart Failure: From Materials and Mechanisms to Applications

Heart failure (HF) represents a cardiovascular disease that significantly threatens global well-being and quality of life. Electroactive nanomaterials, characterized by their distinctive physical and chemical properties, emerge as promising candidates for HF prevention and management. This review comprehensively examines electroactive nanomaterials and their applications in HF intervention. It presents the definition, classification, and intrinsic characteristics of conductive, piezoelectric, and triboelectric nanomaterials, emphasizing their mechanical robustness, electrical conductivity, and piezoelectric coefficients. The review elucidates their applications and mechanisms: 1) early detection and diagnosis, employing nanomaterial-based sensors for real-time cardiac health monitoring; 2) cardiac tissue repair and regeneration, providing mechanical, chemical, and electrical stimuli for tissue restoration; 3) localized administration of bioactive biomolecules, genes, or pharmacotherapeutic agents, using nanomaterials as advanced drug delivery systems; and 4) electrical stimulation therapies, leveraging their properties for innovative pacemaker and neurostimulation technologies. Challenges in clinical translation, such as biocompatibility, stability, and scalability, are discussed, along with future prospects and potential innovations, including multifunctional and stimuli-responsive nanomaterials for precise HF therapies. This review encapsulates current research and future directions concerning the use of electroactive nanomaterials in HF prevention and management, highlighting their potential to innovating in cardiovascular medicine.

N, S-Codoped Carbon Quantum Dots with High Inhibition Efficiency: Implications for Corrosion Mitigation of Carbon Steel in Acidic Environments

The environmental friendliness, economic feasibility, and high efficiency of carbon quantum dots (CQDs) render them as highly promising candidates for corrosion inhibitors. The present study proposed the fabrication of nitrogen- and sulfur-codoped CQDs via an one-step hydrothermal method using l-cysteine and 4-aminosalicylic acid as precursors. The structure, particle size, and surface ligands of the prepared CQDs were determined through spectroscopy and transmission electron microscopy characterization. Subsequently, the inhibition performance of the CQDs on carbon steel in a 0.5 M sulfuric acid solution was evaluated through weight loss measurement, electrochemical methods, and surface analysis. The CQDs exhibited remarkable inhibition efficiencies of 97.9% at 293 K and 98.9% at 313 K, with a concentration of 150 ppm. In addition, the obtained CQDs demonstrated a combined physisorption and chemisorption adsorption behavior, which complied with the Langmuir adsorption isotherm. These findings provide insight into the inhibition mechanism and highlight the potential of codoped CQDs for corrosion mitigation applications in acidic environments.

Highly Blue-fluorescent Carbon Quantum Dots Obtained from Medlar Seed for Hg2+ Determination in Real Water Samples

The carbon quantum dots (CQDs) have been prepared from medlar seeds with pyrolysis method in an oven at 300 °C. UV-vis absorption spectroscopy, fluorescence spectroscopy, Fourier transform infrared spectroscopy (FTIR) spectroscopy, x-ray diffraction (XRD) technique, x-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) were used in the characterization of CQDs. CQDs, give a strong blue fluorescence under UV lamp (at 365 nm), have a quantum yield of 12.2%. The influence of metal ions such as K+, Mg2+, Ca2+, Be2+, Cr3+, Mn2+, Ni2+, Ag+, Hg2+, and Al3+ on the fluorescence properties of the CQDs was investigated by means of emission spectrophotometry. CQDs altering fluorescence characteristics depending on the excitation wavelength show selectivity for Hg2+ ions with outstanding fluorescence quenching among the tested metal ions. Based on these results, a new fluorimetric method has been developed for the determination of Hg2+ in real water samples. The linear range of method is 1.0 to 5.0 mgL- 1. Limit of detection and limit of quantification are 0.26 and 0.79 mgL- 1, respectively. The proposed method has been successfully used in determination of Hg2+ ions in tap, sea, and stream water samples with application of addition-recovery experiments.

Application of Carbon Nanomaterials to Enhancing Tumor Immunotherapy: Current Advances and Prospects

Recent advances in tumor immunotherapy have highlighted the pivotal role of carbon nanomaterials, such as carbon dots, graphene quantum dots, and carbon nanotubes. This review examines the unique benefits of these materials in cancer treatment, focusing on their mechanisms of action within immunotherapy. These include applications in immunoregulation, recognition, and enhancement. We explore how these nanomaterials when combined with specific biomolecules, can form immunosensors. These sensors are engineered for highly sensitive and specific detection of tumor markers, offering crucial support for early diagnosis and timely therapeutic interventions. This review also addresses significant challenges facing carbon nanomaterials in clinical settings, such as issues related to long-term biocompatibility and the hurdles of clinical translation. These challenges require extensive ongoing research and discussion. This review is of both theoretical and practical importance, aiming to promote using carbon nanomaterials in tumor immunotherapy, potentially transforming clinical outcomes and enhancing patient care.

Enhancing interfacial electron transfer and photoelectrochemical kinetics for efficient water-treatment strategy through N-doped carbon dots modified PhC2Cu

To improve the water environment quality, the development of an effective photocatalyst for pollutant removal was considered a promising strategy. The aim of the development of a novel photocatalyst PNC is pursued by modifying copper-phenylacetylide (PhC2Cu) with nitrogen-doped carbon quantum dots (N-CDs). Leading to a remarkable improvement in its light absorption capability, electron transfer efficiency and photoelectrochemical properties. Importantly, PNC possesses the characteristic of straightforward synthesis and demonstrates remarkable performance in the photodegradation of 99.87% sulfamethoxazole (SMX) within just 15 min, with a 3.95-fold increase in the photocatalytic rate. Analysis of the active substances revealed that 1O2, O2·-, and h+ are the generated active species by PNC. Active sites and degradation pathways of SMX were explored through density functional theory (DFT) calculations and intermediate analysis. Key evidence regarding the direction of electron transfer within the system was obtained through in-situ irradiated X-ray (ISI-XPS) techniques. This study deepened our understanding of the electron transfer characteristics of phenylacetylene copper and provided new insights for the modification of photocatalysts.

Biophysical translational posterity of green carbon quantum dots: the unparalleled versatility

Carbon dots (CQDs), zero-dimensional carbon nanostructures, have attracted considerable interest among researchers due to their versatile applications. CQDs exhibit exceptional photoluminescent properties and high quantum yield, making them ideal candidates for bioimaging, drug delivery and environmental sensing. Their biocompatibility and tunable surface chemistry enable targeted therapeutic delivery and real-time imaging with minimal toxicity. Additionally, CQDs are emerging as promising materials in optoelectronics, offering sustainable alternatives in light-emitting diodes and solar cells. This review underscores the unparalleled adaptability of green CQDs in bridging the gap between laboratory research and practical applications, paving the way for innovative solutions in healthcare and environmental monitoring. Through comprehensive analysis, it advances the understanding of CQDs, positioning them at the forefront of next-generation nanomaterials with significant translational impact.

A review on green synthesis, biological applications of carbon dots in the field of drug delivery, biosensors, and bioimaging

Since the beginning of nanoscience and nanotechnology, carbon dots (CDs) have been the foundational idea and have dominated the growth of the nano-field. CDs are an intriguing platform for utilization in biology, technology, catalysis, and other fields thanks to their numerous distinctive structural, physicochemical, and photochemical characteristics. Since several carbon dots have already been created, they have been assessed based on their synthesis process, and luminescence characteristics. Due to their biocompatibility, less toxic effects, and most significantly their fluorescent features in contrast to other carbon nanostructures, CDs have several benefits. This review focuses on the most recent advancements in the characterization, applications, and synthesis techniques used for CDs made from natural sources. It will also direct scientists in the creation of a synthesis technique for adjustable carbon dots that is more practical, effective, and environmentally benign. With low toxicity and low cost, CDs are meeting the new era's requirements for more selectivity and sensitivity in the detection and sensing of various things, such as biomaterial sensing, enzymes, chemical contamination, and temperature sensing. Its variety of properties, such as optical properties, chemiluminescence, and morphological analysis, make it a good option to use in bioimaging, drug delivery, biosensors, and cancer diagnosis.

Surface Passivation of Carbon Dots for Tunable Biological Performance

Recent investigations were shifted this trend toward exploring the biomedical applicability of CDs, relevant to chronic diseases. Herein, a systematic approach is demonstrated for studying the effect of variation in the surface passivation of CDs for tuning its optical character and biological performance. Alginate and pectin were successfully clustered oxygen-surface passivated CDs, while, chitin was used to nucleate nitrogen-surface passivated CDs. Pectin-treated with base (4.1 ± 1.8 nm) and chitin-treated acid (3.5 ± 1.7 nm) were ingrained the smallest O-surface passivated CDs and N-surface passivated CDs, respectively. However, N-surface passivated CDs were shown with the highest optical activity. CDs colloids prepared from alginate, pectin & chitin, resulted in reduction of tumor cell viability percentage to be 80.8%, 74.0% & 69.0% respectively. O-surface passivated CDs nucleated from alginate showed the highest anti-proliferative effects. Moreover, O-surface passivated CDs (from alginate) showed the supremacy in inhibition of inflammation, while, increasing of its concentration ten times resulted in significant increment in inhibition percent to be 28% & 42%, using 1 μg/mL & 10 μg/mL, respectively. In summarization, it could be decided that, compared to N-surface passivated CDs (from chitin), O-surface passivated CDs (from alginate) showed excellency in application as a concurrent anti-inflammatory/antitumor drug, to be applied as a potential therapeutical reagent for treatment of inflammation, in production of vaccines, immune-therapeutics, and immune-suppressive drugs.

An assessment of nanotechnology-based interventions for cleaning up toxic heavy metal/metalloid-contaminated agroecosystems: Potentials and issues

Heavy metals (HMs) are among the most dangerous environmental variables for a variety of life forms, including crops. Accumulation of HMs in consumables and their subsequent transmission to the food web are serious concerns for scientific communities and policy makers. The function of essential plant cellular macromolecules is substantially hampered by HMs, which eventually have a detrimental effect on agricultural yield. Among these HMs, three were considered, i.e., arsenic, cadmium, and chromium, in this review, from agro-ecosystem perspective. Compared with conventional plant growth regulators, the use of nanoparticles (NPs) is a relatively recent, successful, and promising method among the many methods employed to address or alleviate the toxicity of HMs. The ability of NPs to reduce HM mobility in soil, reduce HM availability, enhance the ability of the apoplastic barrier to prevent HM translocation inside the plant, strengthen the plant's antioxidant system by significantly enhancing the activities of many enzymatic and nonenzymatic antioxidants, and increase the generation of specialized metabolites together support the effectiveness of NPs as stress relievers. In this review article, to assess the efficacy of various NP types in ameliorating HM toxicity in plants, we adopted a 'fusion approach', in which a machine learning-based analysis was used to systematically highlight current research trends based on which an extensive literature survey is planned. A holistic assessment of HMs and NMs was subsequently carried out to highlight the future course of action(s).

Carbon dots as versatile nanomaterials in sensing and imaging: Efficiency and beyond

Carbon dots (CDs) have emerged as a versatile and promising carbon-based nanomaterial with exceptional optical properties, including tunable emission wavelengths, high quantum yield, and photostability. CDs are appropriate for various applications with many benefits, such as biocompatibility, low toxicity, and simplicity of surface modification. Thanks to their tunable optical properties and great sensitivity, CDs have been used in sensing as fluorescent probes for detecting pH, heavy metal ions, and other analytes. In addition, CDs have demonstrated potential as luminescence converters for white organic light-emitting diodes and light emitters in optoelectronic devices due to their superior optical qualities and exciton-independent emission. CDs have been used for drug administration and bioimaging in the biomedical field due to their biocompatibility, low cytotoxicity, and ease of functionalization. Additionally, due to their stability, efficient charge separation, and low recombination rate, CDs have shown interesting uses in energy systems, such as photocatalysis and energy conversion. This article highlights the growing possibilities and potential of CDs as adaptable nanomaterials in a variety of interdisciplinary areas related to sensing and imaging, at the same time addressing the major challenges involved in the current research and proposing scientific solutions to apply CDs in the development of a super smart society.

Effect of carbon dots supplementation in Chlorella vulgaris biomass production and its composition

Microalgae cultures have an excellent ability to capture CO2 and produce high, medium, and low valuable biocompounds such as proteins, carbohydrates, lipids, pigments, and polyhydroxyalkanoates; those compounds have shown excellent properties in the pharmaceutical, cosmetic, food, and medical industries. Recently, the supplementation of carbon dots (CDs) in autotrophic microalgae cultures has been explored as a new strategy to increase light capture and improve photoluminescence, which in turn enhances biomass growth and biocompounds production. In this work, we synthesized CDs through a simple carbonization method using orange juice as a natural precursor. The green synthesized CDs were analyzed in detail through characterization techniques such as Fourier-transform infrared spectroscopy (FTIR), UV–visible, fluorescence spectroscopy, and ζ potential analysis. Moreover, CDs were added to Chlorella vulgaris to analyze the response under different photoperiod cycles and CDs dosages. The optimal results were obtained with the addition of 0.5 mg l−1 of CDs under a photoperiod cycle of 16 h:8 h (light:dark). In these conditions, a maximum biomass production of 2.12 g l−1 was observed, which represents an enhancement of 112% and 17% in comparison to the control samples under the photoperiod of 12 h:12 h and 16 h:8 h (light/dark), respectively. Furthermore, the production of lipids, proteins, and carbohydrates was significantly increased to 249 mg g−1, 285 mg g−1, and 217 mg g−1 dry weight, respectively. These results suggest that the addition of CDs enhances cell growth and increases the production of lipids and proteins, being a strategy with great potential for the food and pharmaceutical industries.

Biomass-derived carbon dots as significant biological tools in the medicinal field: A review

Early disease detection is crucial since it raises the likelihood of treatment and considerably lowers the cost of therapy. Therefore, the improvement of human life and health depends on the development of quick, efficient, and credible biosensing methods. For improving the quality of biosensors, distinct nanostructures have been investigated; among these, carbon dots have gained much interest because of their great performance. Carbon dots, the essential component of fluorescence nanoparticles, having outstanding chemical characteristics, superb biocompatibility, chemical inertness, low toxicity and potential optical characteristics have attracted the researchers from every corner of the globe. Several carbon dots applications have been thoroughly investigated in recent decade, from optoelectronics to biomedical investigations. This review study primarily emphasizes the recent advancements in the field of biomass-derived carbon dots-based drug delivery, gene delivery and bioimaging, and highlights achievements in two major areas: in vivo applications that involve carbon dots absorption in zebrafish and mice, tumour therapeutics, and imaging-guided drug delivery. Additionally, the possible advantages, difficulties, and future possibilities of using carbon dots for biological applications are also explored.

Carbon Quantum Dots: Properties, Preparation, and Applications

Carbon quantum dots are a novel form of carbon material. They offer numerous benefits including particle size adjustability, light resistance, ease of functionalization, low toxicity, excellent biocompatibility, and high-water solubility, as well as their easy accessibility of raw materials. Carbon quantum dots have been widely used in various fields. The preparation methods employed are predominantly top-down methods such as arc discharge, laser ablation, electrochemical and chemical oxidation, as well as bottom-up methods such as templates, microwave, and hydrothermal techniques. This article provides an overview of the properties, preparation methods, raw materials for preparation, and the heteroatom doping of carbon quantum dots, and it summarizes the applications in related fields, such as optoelectronics, bioimaging, drug delivery, cancer therapy, sensors, and environmental remediation. Finally, currently encountered issues of carbon quantum dots are presented. The latest research progress in synthesis and application, as well as the challenges outlined in this review, can help and encourage future research on carbon quantum dots.

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 combined with phytosphingosine inhibit acid-induced demineralization of hydroxyapatite in vitro

OBJECTIVES

To study the effects of carbon dots (CDs), in combination with phytosphingosine (PHS), against acid-induced demineralization of hydroxyapatite in vitro.

METHODS

CDs were generated from citric acid and urea by microwave heating. Transmission electron microscope (TEM), FT-IR, and fluorescence intensity were used to characterize the CDs. A hydroxyapatite (HAp) model was used to investigate the protective effects of CDs, PHS, and their combinations with and without a salivary pellicle against acid-induced demineralization in vitro. Ca2+ release as a parameter to evaluate the inhibition of demineralization was measured by capillary electrophoresis. The interactions between CDs, PHS, and HAp discs were investigated using a fluorescence detector.

RESULTS

Uniform-sized CDs were synthesized, showing typical optical characteristics. CDs exhibited no inhibition of acid-induced demineralization in vitro, in contrast to PHS. Notably, a pre-coating of CDs increased the protective effects of PHS against acid-induced demineralization, which was not disturbed by the presence of a salivary pellicle and Tween 20. Scanning electron microscope (SEM) confirmed the binding and layers formed of both CDs and PHS to the HAp surfaces. Based on fluorescence spectra CDs binding to HAp seemed to be dependent on Ca2+ and PO43- interactions.

CONCLUSIONS

CDs combined with PHS showed protective effects against acid-induced demineralization of HAp discs in vitro.

Colloidal Chiral Carbon Dots: An Emerging System for Chiroptical Applications

Chiral CDots (c-CDots) not only inherit those merits from CDots but also exhibit chiral effects in optical, electric, and bio-properties. Therefore, c-CDots have received significant interest from a wide range of research communities including chemistry, physics, biology, and device engineers. They have already made decent progress in terms of synthesis, together with the exploration of their optical properties and applications. In this review, the chiroptical properties and chirality origin in extinction circular dichroism (ECD) and circularly polarized luminescence (CPL) of c-CDots is briefly discussed. Then, the synthetic strategies of c-CDots is summarized, including one-pot synthesis, post-functionalization of CDots with chiral ligands, and assembly of CDots into chiral architectures with soft chiral templates. Afterward, the chiral effects on the applications of c-CDots are elaborated. Research domains such as drug delivery, bio- or chemical sensing, regulation of enzyme-like catalysis, and others are covered. Finally, the perspective on the challenges associated with the synthetic strategies, understanding the origin of chirality, and potential applications is provided. This review not only discusses the latest developments of c-CDots but also helps toward a better understanding of the structure-property relationship along with their respective applications.

Carbon Dots and Their Polymeric Nanocomposites: Insight into Their Synthesis, Photoluminescence Mechanisms, and Recent Trends in Sensing Applications

Carbon dots (CDs), a novel class of carbon-based nanoparticles, have received a lot of interest recently due to their exceptional mechanical, chemical, and fluorescent properties, as well as their excellent photostability and biocompatibility. CDs' emission properties have already found a variety of potential applications, in which bioimaging and sensing are major highlights. It is widely acknowledged that CDs' fluorescence and surface conditions are closely linked. However, due to the structural complexity of CDs, the specific underlying process of their fluorescence is uncertain and yet to be explained. Because of their low toxicity, robust and wide optical absorption, high chemical stability, rapid transfer characteristics, and ease of modification, CDs have been recognized as promising carbon nanomaterials for a variety of sensing applications. Thus, following such outstanding properties of CDs, they have been mixed and imprinted onto different polymeric components to achieve a highly efficient nanocomposite with improved functional groups and properties. Here, in this review, various approaches and techniques for the preparation of polymer/CDs nanocomposites have been elaborated along with the individual characteristics of CDs. CDs/polymer nanocomposites recently have been highly demanded for sensor applications. The insights from this review are detailed sensor applications of polymer/CDs nanocomposites especially for detection of different chemical and biological analytes such as metal ions, small organic molecules, and several contaminants.

Chemical- and green-precursor-derived carbon dots for photocatalytic degradation of dyes

Rapid industrialization and untreated industrial effluents loaded with toxic and carcinogenic contaminants, especially dyes that discharge into environmental waters, have led to a rise in water pollution, with a substantial adverse impact on marine life and humankind. Photocatalytic techniques are one of the most successful methods that help in degradation and/or removal of such contaminants. In recent years, semiconductor quantum dots are being substituted by carbon dots (CDs) as photocatalysts, due to the ease of formation, cost-effectiveness, possible sustainability and scalability, much lower toxicity, and above all its high capacity to harvest sunlight (UV, visible, and near infrared) through electron transfer that enhances the lifetime of the photogenerated charge carriers. A better understanding between the properties of the CDs and their role in photocatalytic degradation of dyes and contaminants is required for the formation of controllable structures and adjustable outcomes. The focus of this review is on CDs and its composites as photocatalysts obtained from different sustainable green as well as chemical precursors. Apart from the synthesis, characterization, and properties of the CDs, the study also highlights the effect of different parameters on the photocatalytic properties of CDs and their composites for catalytic dye degradation mechanisms in detail. Besides the present research development in the field, potential challenges and future perspectives are also presented.

Facile Bond Exchanging Strategy for Engineering Wet Adhesion and Antioxidant/Antibacterial Thin Layer over a Dynamic Hydrogel via the Carbon Dots Derived from Tannic Acid/ε-Polylysine

Adhesive hydrogels, playing an essential role in stretchable electronics, soft robotics, tissue engineering, and so forth, upon functioning often need to adhere to various substrates in wet conditions and simultaneously exhibit antibacterial/antioxidant properties while possessing the intrinsic stretchability and elasticity of the hydrogel network intact. Therefore, simple approaches to conveniently access adhesive hydrogels with multifunctional surfaces are being pursued. Herein, a facile strategy has been proposed to construct multifunctional adhesive hydrogels via surface engineering of a multifunctional carbon dot (CD)-decorated polymeric thin layer by dynamic bond exchange. By this strategy, a double cross-linked network hydrogel of polyacrylamide (PAM) and oxidized dextran (ODA) was engineered with a unique dense layer over the Schiff base hydrogel matrix by aqueous solution immersion of PA-120, versatile CDs derived from tannic acid (TA) and ε-polylysine (PL). Without any additional agents, the PA-120 CDs with residual polyphenolic/catechol and amine moieties were incorporated into the surface structure of the hydrogel network by the combined action of the Schiff base and hydrogen bonds to form a dense surface layer that can exhibit high wet adhesive performance via the amine-polyphenol/catechol pair. The armor-like dense architecture also endowed hydrogels with considerably enhanced tensile/compression properties and excellent antioxidant/antibacterial abilities. Besides, the single-sided modified Janus hydrogel and completely surface-modified hydrogel can be flexibly developed through this approach. This strategy will provide new insights into the preparation and application of surface-modified hydrogels featuring multiple functions and tunable interfacial properties.

Carbon quantum dots derived from polysaccharides: Chemistry and potential applications

Since the beginning of 21th century, nanoscience and nanotechnology become the most promising topics in various fields, attributing to the superior characters of nanoscaled structures. The conventional quantum dots are substituted with new family of luminescent nanostructures, owing to their interchanged optical properties, low-cost of fabrication, biocompatibility, non-toxicity, ecofriendly, hydrophilicity and superior chemical stability. Carbon quantum dots (CQDs) were recently investigated for their simple synthesis, bio-consonance, and different revelation applicability. Obeying the green chemistry aspects, this review demonstrates an overview about CQDs generated from polysaccharides in brief, with a background on CQDs discovery, chemical composition, green synthesis via exploitation of different polysaccharides (cellulose, starch, pectin, chitin, etc) as biocompatible/biodegradable abundant biopolymers. Additionally, applications of CQDs originated from polysaccharides in environmental purposes, textiles industry and medical activities were also presented.

Recent Applications of Quantum Dots in Pharmaceutical Analysis

Nanotechnology has emerged as one of the most potential areas for pharmaceutical analysis. The need for nanomaterials in pharmaceutical analysis is comprehended in terms of economic challenges, health and safety concerns. Quantum dots (QDs)or colloidal semiconductor nanocrystals are new groups of fluorescent nanoparticles that bind nanotechnology to drug analysis. Because of their special physicochemical characteristics and small size, QDs are thought to be promising candidates for the electrical and luminescent probes development. They were originally developed as luminescent biological labels, but are now discovering new analytical chemistry applications, where their photo-luminescent properties are used in pharmaceutical, clinical analysis, food quality control and environmental monitoring. In this review, we discuss QDs regarding properties and advantages, advances in methods of synthesis and their recent applications in drug analysis in the recent last years.

Application of Nanomaterials in the Production of Biomolecules in Microalgae: A Review

Nanomaterials (NMs) are becoming more commonly used in microalgal biotechnology to empower the production of algal biomass and valuable metabolites, such as lipids, proteins, and exopolysaccharides. It provides an effective and promising supplement to the existing algal biotechnology. In this review, the potential for NMs to enhance microalgal growth by improving photosynthetic utilization efficiency and removing reactive oxygen species is first summarized. Then, their positive roles in accumulation, bioactivity modification, and extraction of valuable microalgal metabolites are presented. After the application of NMs in microalgae cultivation, the extracted metabolites, particularly exopolysaccharides, contain trace amounts of NM residues, and thus, the impact of these residues on the functional properties of the metabolites is also evaluated. Finally, the methods for removing NM residues from the extracted metabolites are summarized. This review provides insights into the application of nanotechnology for sustainable production of valuable metabolites in microalgae and will contribute useful information for ongoing and future practice.

Carbon Dots Derived from Traditional Chinese Medicines with Bioactivities: A Rising Star in Clinical Treatment

In the field of carbon nanomaterials, carbon dots (CDs) have become a preferable choice in biomedical applications. Based on the concept of green chemistry, CDs derived from traditional Chinese medicines (TCMs) have attracted extensive attention, including TCM charcoal drugs, TCM extracts, and TCM small molecules. The design and preparation of CDs from TCMs (TCMs-CDs) can improve the inherent characteristics of TCMs, such as solubility, particle size distribution, and so on. Compared with other precursor materials, TCMs-CDs have outstanding intrinsic bioactivities and potential pharmacological effects. However, the research of TCMs-CDs in biomedicine is not comprehensive, and their mechanisms have not been understood deeply either. In this review, we will provide concise insights into the recent development of TCMs-CDs, with a major focus on their preparation, formation, precursors, and bioactivities. Then we will discuss the perfect transformation from TCMs to TCMs-CDs. Finally, we discuss the opportunities and challenges for the application of TCMs-CDs in clinical treatment.

Zero-Dimensional Carbon Nanomaterials for Fluorescent Sensing and Imaging

Advances in nanotechnology and nanomaterials have attracted considerable interest and play key roles in scientific innovations in diverse fields. In particular, increased attention has been focused on carbon-based nanomaterials exhibiting diverse extended structures and unique properties. Among these materials, zero-dimensional structures, including fullerenes, carbon nano-onions, carbon nanodiamonds, and carbon dots, possess excellent bioaffinities and superior fluorescence properties that make these structures suitable for application to environmental and biological sensing, imaging, and therapeutics. This review provides a systematic overview of the classification and structural properties, design principles and preparation methods, and optical properties and sensing applications of zero-dimensional carbon nanomaterials. Recent interesting breakthroughs in the sensitive and selective sensing and imaging of heavy metal pollutants, hazardous substances, and bioactive molecules as well as applications in information encryption, super-resolution and photoacoustic imaging, and phototherapy and nanomedicine delivery are the main focus of this review. Finally, future challenges and prospects of these materials are highlighted and envisaged. This review presents a comprehensive basis and directions for designing, developing, and applying fascinating fluorescent sensors fabricated based on zero-dimensional carbon nanomaterials for specific requirements in numerous research fields.

Live synthesis of selective carbon dots as fluorescent probes for cobalt determination in water with an automatic microanalyzer

A new strategy integrating the straight synthesis of carbon dots (CDs) and their direct use for the determination of heavy metals by means of fluorescence quenching is presented. The proposal consists of a modular analyzer, which includes a low temperature co-fired ceramics (LTCC) microreactor for the synthesis of CDs and a cyclic olefin copolymer (COC) microfluidic platform, which automatically performs a reverse flow injection analysis (rFIA) protocol for the determination of heavy metal ions in water by CD fluorescence quenching. As a proof of concept, nitrogen-doped CDs were synthesized from acrylic acid and ethylenediamine (ED) with quantum yields (QYs) of up to 44%, which are selective to cobalt. With the described system, we synthesized homogeneous CDs without the need for further purification and with the minimum consumption of reagents, and optimized fluorescence measurements can be performed with freshly obtained luminescent nanomaterials that have not undergone decomposition processes. They have an average hydrodynamic diameter of 4.2 ± 0.9 nm and maximum excitation and emission wavelengths at 358 nm and 452 nm, respectively. The system allows the automatic dilution and buffering of the synthesized CDs and the sample prior to the determination of cobalt. The concentration of cobalt was determined with good sensitivity and a limit of detection of 7 μg·L-1 with a linear range of 0.02-1 mg·L-1 of Co2+. Spiked tap water and river water samples were analyzed, obtaining recovery from 98 to 104%. This demonstrates the potential of the equipment as an efficient on-site control system for heavy metal monitoring in water.

Recent Advancements in the Formulation of Nanomaterials-Based Nanozymes, Their Catalytic Activity, and Biomedical Applications

Nanozymes are nanoparticles with intrinsic enzyme-mimicking properties that have become more prevalent because of their ability to outperform conventional enzymes by overcoming their drawbacks related to stability, cost, and storage. Nanozymes have the potential to manipulate active sites of natural enzymes, which is why they are considered promising candidates to function as enzyme mimetics. Several microscopy- and spectroscopy-based techniques have been used for the characterization of nanozymes. To date, a wide range of nanozymes, including catalase, oxidase, peroxidase, and superoxide dismutase, have been designed to effectively mimic natural enzymes. The activity of nanozymes can be controlled by regulating the structural and morphological aspects of the nanozymes. Nanozymes have multifaceted benefits, which is why they are exploited on a large scale for their application in the biomedical sector. The versatility of nanozymes aids in monitoring and treating cancer, other neurodegenerative diseases, and metabolic disorders. Due to the compelling advantages of nanozymes, significant research advancements have been made in this area. Although a wide range of nanozymes act as potent mimetics of natural enzymes, their activity and specificities are suboptimal, and there is still room for their diversification for analytical purposes. Designing diverse nanozyme systems that are sensitive to one or more substrates through specialized techniques has been the subject of an in-depth study. Hence, we believe that stimuli-responsive nanozymes may open avenues for diagnosis and treatment by fusing the catalytic activity and intrinsic nanomaterial properties of nanozyme systems.

Current trends in the detection and removal of heavy metal ions using functional materials

The shortage of freshwater resources caused by heavy metal pollution is an acute global issue, which has a great impact on environmental protection and human health. Therefore, the exploitation of new strategies for designing and synthesizing green, efficient, and economical materials for the detection and removal of heavy metal ions is crucial. Among the various methods for the detection and removal of heavy ions, advanced functional systems including nanomaterials, polymers, porous materials, and biomaterials have attracted considerable attention over the past several years due to their capabilities of real-time detection, excellent removal efficiency, anti-interference, quick response, high selectivity, and low limit of detection. In this tutorial review, we review the general design principles underlying the aforementioned functional materials, and in particular highlight the fundamental mechanisms and specific examples of detecting and removing heavy metal ions. Additionally, the methods which enhance water purification quality using these functional materials have been reviewed, also current challenges and opportunities in this exciting field have been highlighted, including the fabrication, subsequent treatment, and potential future applications of such functional materials. We envision that this tutorial review will provide invaluable guidance for the design of functional materials tailored towards the detection and removal of heavy metals, thereby expediting the development of high-performance materials and fostering the development of more efficient approaches to water pollution remediation.

Recent developments, applications and challenges for carbon quantum dots as a photosynthesis enhancer in agriculture

Since the world's population is expanding, mankind may be faced with a huge dilemma in the future, which is food scarcity. The situation can be mitigated by employing sustainable cutting-edge agricultural methods to maintain the food supply chain. In recent years, carbon quantum dots (CQD), a member of the well-known carbon-based nanomaterials family, have given rise to a new generation of technologies that have the potential to revolutionise horticulture and agriculture research. CQD has drawn much attention from the research community in agriculture owing to their remarkable properties such as good photoluminescence behaviour, high biocompatibility, photo-induced electron transfer, low cost, and low toxicity. These unique properties have led CQD to become a promising material to increase plant growth and yield in the agriculture field. This review paper highlights the recent advances of CQD application in plant growth and photosynthesis rate at different concentrations, with a focus on CQD uptake and translocation, as well as electron transfer mechanism. The toxicity and biocompatibility studies of CQD, as well as industrial scale applications of CQD for agriculture are discussed. Finally, the current challenges of the present and future perspectives in this agriculture research are presented.

Ionic liquid-enhanced lemon biomass carbon dots with sustainable use in bionic antibody microspheres for urea capture and ethyl carbamate inhibition

Herein, we reported the room-temperature fabrication of ionic liquid-modified carbon dots encapsulated in bionic antibodies (IL-modified CDs@BAs) by one-pot green synthesis. In order to enhance the fluorescence intensity of CDs, imidazole ILs and lemon rich in heteroatoms were selected as CDs modifiers and sources. The resulting IL-modified CDs@BAs showed good selectivity and capture toward urea and obviously induced fluorescence quenching by template-binding. The inhibition rate ofIL-modified CDs@BAs on the urea pathway of ethyl carbamate was about 29.07% in the simulated Huangjiu system, indicating a good inhibitory effect. The IL-modified CDs@BAs system was also reproducible after five consecutive uses, thus reducing the economic cost. This research would expand the application fields of BAs-based optical sensing system from the perspectives of energy conservation, environmental protection and resource recovery, focusing on their application in the field of food safety control.

Rational design of a novel acryl-modified CQDs fluorescent probe for highly selective detection and imaging of cysteine in vitro and in vivo

A novel fluorescent nanoprobe CQDs-O-Acryl has been designed and synthesized to directly and accurately identify Cys over other biothiols in PBS (10 mM, pH 7.4) buffer. The carbon quantum dots (CQDs-OH) (λ_ex/em maxima = 495/525 nm) were fabricated by a solvothermal method using resorcinol as the carbon source. The CQDs-O-Acryl was achieved through covalently grafting the acryloyl group on the surface of carbon quantum dots by nuclear reaction based on static quenching. The structure and morphology of CQDs-OH and CQDs-O-Acryl have been characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and UV-vis absorption spectroscopy. Upon the addition of Cys, the ester bond of CQDs-O-Acryl has been broken, and the free CQDs were released by conjugated addition and cyclization reactions successively, emitting strong green fluorescence at 525 nm (λ_ex = 495 nm). Under the optimized conditions, CQDs-O-Acryl exhibited good sensing of Cys within the range 0.095-16 μM (the LOD of 0.095 μM). Due to the high sensitivity, reliability, fast fluorescence response (10 min), and low toxicity of CQDs-O-Acryl, it was successfully applied to fluorescence imaging of Cys in A549 cells and zebrafish.

A Review of Sensing Applications of Molecularly Imprinted Fluorescent Carbon Dots for Food and Biological Sample Analysis

Molecularly imprinted fluorescent carbon dots (MI-FCDs) find numerous applications in analytical chemistry due to their outstanding photoluminescent properties and having specific pockets for the recognition of target molecules. Despite significant advances, practical applications of MI-FCDs-based fluorescent sensors are still in their initial stages. Therefore, the topical developments in the synthesis, working, and application of MI-FCDs for sensing various target species (e.g., pharmaceuticals, biomolecules, pesticides, food additives, and miscellaneous species) in food and biological media have been highlighted. Moreover, a careful evaluation has been made to select the best methods based on their performance in terms of analytical parameters. To expand the horizons of this field, important challenges and future directions for developing MI-FCDs for practical use are also presented. This review will highlight important aspects of MI-FCDs-based fluorescent sensors for their applicability in food science, material science, environmental science, nanoscience, and biotechnology.

Probing Polarity and pH Sensitivity of Carbon Dots in Escherichia coli through Time-Resolved Fluorescence Analyses

Intracellular monitoring of pH and polarity is crucial for understanding cellular processes and functions. This study employed pH- and polarity-sensitive nanomaterials such as carbon dots (CDs) for the intracellular sensing of pH, polarity, and viscosity using integrated time-resolved fluorescence anisotropy (FA) imaging (TR-FAIM) and fluorescence lifetime (FLT) imaging microscopy (FLIM), thereby enabling comprehensive characterization. The functional groups on the surface of CDs exhibit sensitivity to changes in the microenvironment, leading to variations in fluorescence intensity (FI) and FLT according to pH and polarity. The FLT of CDs in aqueous solution changed gradually from 6.38 ± 0.05 ns to 8.03 ± 0.21 ns within a pH range of 2-8. Interestingly, a complex relationship of FI and FLT was observed during measurements of CDs with decreasing polarity. However, the FA and rotational correlation time (θ) increased from 0.062 ± 0.019 to 0.112 ± 0.023 and from 0.49 ± 0.03 ns to 2.01 ± 0.27 ns, respectively. This increase in FA and θ was attributed to the higher viscosity accompanying the decrease in polarity. Furthermore, CDs were found to bind to three locations in Escherichia coli: the cell wall, inner membrane, and cytoplasm, enabling intracellular characterization using FI and FA decay imaging. FLT provided insights into cytoplasmic pH (7.67 ± 0.48), which agreed with previous works, as well as the decrease in polarity in the cell wall and inner membrane. The CD aggregation was suspected in certain areas based on FA, and the θ provided information on cytoplasmic heterogeneity due to the aggregation and/or interactions with biomolecules. The combined TR-FAIM/FLIM system allowed for simultaneous monitoring of pH and polarity changes through FLIM and viscosity variations through TR-FAIM.