Single-atom and subnanocluster platforms are at the cutting edge of translational sensing technologies for future clinical use. Their dispersion at the atomic level ensures optimal metal utilization, clearly defined active sites, and precise control over electronic structures. By combining molecular accuracy with solid-state durability, these materials enhance the adsorption, charge transfer, and catalytic activation of key biomarkers, enabling highly sensitive and selective detection. This review covers recent progress in material design, mechanistic insights, and the integration of these materials into electrochemical and photoelectrochemical diagnostic devices. It also discusses significant challenges related to stability, scalability, and clinical adoption, all of which are crucial for transitioning from laboratory research to real-world medical applications.

ABSTRACT The increasing prevalence of fungal phytopathogens and the widespread emergence of fungicide resistance necessitate the development of alternative antifungal strategies with reduced environmental impact. Here, we report the isolation and characterization of a novel antifungal metabolite, SM06, produced by the rice seed-associated endophytic bacterium Phytobacter sp. RSE02. SM06 exhibited broad-spectrum antifungal activity against plant and human pathogenic fungi, including Curvularia lunata, Fusarium oxysporum, and Candida albicans. In vitro assays and micromorphological analyses revealed that SM06, an indole dimer, disrupts fungal cell membrane integrity, while in planta experiments demonstrated significant suppression of brown leaf spot disease in tomato and rice. Molecular docking suggested that SM06 binds to lanosterol 14α-demethylase (ERG11), a key enzyme in fungal sterol biosynthesis. Consistent with this prediction, LC-MS–based analyses confirmed a significant reduction in ergosterol content in SM06-treated fungal cells. Together, these findings identify SM06 as a biologically active antifungal metabolite produced by a plant-associated bacterium, highlighting its potential application in sustainable fungal disease management.IMPORTANCEFungal diseases cause major losses in crop production and contribute to the growing challenge of antifungal resistance, underscoring the need for sustainable alternatives to chemical fungicides. This study identifies SM06, a novel indole dimer produced by the rice seed endophyte Phytobacter sp. RSE02, with strong antifungal activity against economically important plant pathogens and clinically relevant fungi. Through integrated chemical, cellular, and in planta analyses, we demonstrate that SM06 disrupts fungal membrane integrity by inhibiting ergosterol biosynthesis. The compound is biocompatible, stable, and effective in plant disease suppression, highlighting its translational potential for crop protection. These findings reveal seed endophytes as an important yet underexplored source of antifungal metabolites and provide a mechanistic foundation for developing eco-friendly biocontrol strategies with implications beyond agriculture.

Serotonin, widely recognized as a mammalian pineal hormone, is also present in plants, yet its in vivo dynamics and physiological roles remain poorly understood due to the absence of real-time sensing tools. Herein, we report nitrogen-doped carbon quantum dot (N-CQD) nanosensors (∼5 nm; quantum yield 36%) for the selective detection and visualization of serotonin in plant systems. The sensing mechanism involves static-dominated mixed fluorescence quenching accompanied by a blue shift, corroborated by UV-Vis spectral changes, Stern-Volmer analysis, and fluorescence lifetime decay. The nanosensor exhibits a low detection limit of 0.391 µM and a linear response range of 4.74-75 µM. Using Arachis hypogaea seedlings as a model, stronger and more consistent serotonin-dependent fluorescence responses were observed compared with those in other plant species, enabling reliable in vivo monitoring. Real-time sensing revealed a condition-dependent regulatory role for serotonin, including growth inhibition under non-stress conditions and growth enhancement under stress, indicating a dual function in stress adaptation. Fluorescence microscopy further confirmed the intracellular association of serotonin with N-CQDs, providing direct visual evidence of its localization. This work establishes a nanosensor-based platform for real-time detection of serotonin in plants and advances understanding of serotonin-mediated signalling in plant growth and stress responses.

Quantum dots (QDs), including semiconductor (Cd-based and III-V), carbon/graphene, and emerging halide perovskite QDs, offer size-tunable, bright, and photostable optical signals, making them uniquely suited as nanoreporters for neurotransmitter sensing. This review surveys recent advances in QD chemistry and surface engineering, recognition strategies (aptamers, molecularly imprinted polymers, enzymes, and small-molecule ligands), and signal transduction modalities (photoluminescence quenching/turn-on, FRET, electrochemiluminescence, and photoelectrochemical detection). We emphasise integration at the bio-nano interface for clinically relevant, minimally invasive platforms such as microfluidic sampling, wearable patches, and implantable probes, and analyse the principal barriers to translation (toxicity, stability in aqueous/biofluids, selectivity vs. interferents, and quantitation). Finally, we highlight promising directions: multiplexed spectral coding, ratiometric and lifetime-based readouts, renal-clearable/biodegradable QDs, and hybrid QD-polymer platforms for continuous monitoring of neurochemical signatures in diagnostic settings.

Rapid, portable detection of nerve-agent metabolites and safe mimics is essential for exposure assessment, forensic verification, environmental monitoring, and timely clinical intervention. Recent years have seen significant advances in point-of-use platforms, including colourimetric and paper-based assays, electrochemical sensors, enzyme- and biosensor-based approaches, smartphone-integrated devices, and wearable formats, which target metabolites (e.g., alkyl methylphosphonic acids and dialkyl phosphates), protein adducts, and surrogate markers such as cholinesterase inhibition. Nevertheless, analytical challenges (matrix effects, low concentrations in chronic exposures, selectivity for pesticides/industrial organophosphates, and stability under field conditions) remain. This review summarises detection targets, in-field technologies, analytical and biological challenges, and recommendations for translating laboratory prototypes into robust field-deployable systems.

L-Glutamate is the primary excitatory neurotransmitter in the central nervous system, and its dysregulation is associated with numerous neurological disorders, underscoring the importance of sensitive, real-time detection in living organisms. In this study, we created a biocompatible fluorescent nanosensor using a nitrogen-doped carbon quantum dot aluminium ion composite (N-CQDs/Al) to selectively detect L-glutamate through a straightforward fluorescence "off-on" process. The N-CQDs and the complex were thoroughly analysed with DLS, TEM, FT-IR, EDX, UV-Vis, and fluorescence spectroscopy, confirming their size, surface features, and optical stability. When coordinated with Al3+, fluorescence was quenched, but the addition of L-glutamate revived it via competitive binding. The sensor exhibited high sensitivity, a detection limit of 0.14 µM, a wide linear range, and excellent selectivity toward common amino acids and interfering substances. Its low toxicity and robust photostability allowed for real-time in vivo monitoring of endogenous glutamate and in vitro testing in the optic tectum and retina of live zebrafish. To our knowledge, this is the first report of an N-CQDs/Al3+ based fluorescence "off-on" system for real-time, in vivo glutamate detection, offering a simple and efficient platform for neurotransmitter sensing and neurobiological research.

The extensive use of neonicotinoid pesticides has greatly enhanced crop yields. However, their water solubility, environmental persistence, and toxicity to nontarget species raise ecological and health concerns. In this research, we present nitrogen-doped carbon quantum dots (N-CQDs) approximately 6 nm in size that serve as a multifunctional platform. They can detect neonicotinoid pesticides through a simple fluorescence turn-off method, diminish their effectiveness in water and agricultural settings, and act as nanopesticide repellents. The N-CQDs exhibit strong, stable fluorescence, numerous surface functional groups, and high biocompatibility, enabling selective interactions with compounds such as imidacloprid, thiamethoxam, clothianidin, thiacloprid, and nicotine. Characterization techniques such as TEM, PXRD, FT-IR, XPS, EDX, UV-vis, 1H NMR, and fluorescence spectroscopy were used to analyze the nanosensor's morphology and features. The sensor achieved a detection limit of 23 nM, indicating excellent sensitivity. Spectroscopic analyses indicate that N-CQDs form strong noncovalent associations and stable complexes with neonicotinoid pesticides, accompanied by a noticeable decrease in their biological activity as observed in functional experiments. Practical tests, including cytotoxicity assays, fruit bioassays, and ant-repellence trials, confirm that N-CQDs can effectively neutralize neonicotinoid pesticides in real-world conditions without being toxic or unsafe. This approach offers a sustainable way to address neonicotinoid pesticide pollution, promoting safer farming methods and environmental preservation. Surprisingly, the nanosensor not only detects and mitigates neonicotinoid pesticides but also serves as a nanopest repellent in real-world agricultural use.

Adenine is a vital purine nucleobase that plays essential roles in enzyme regulation, cell signaling, energy metabolism, and the storage of genetic information. As a structural component of key biomolecules such as ATP, NAD+, SAM, and cAMP, its imbalance is associated with immune responses, cardiovascular dysfunction, and cancer. Therefore, accurate and efficient detection of adenine is critical for clinical research and biological diagnostics. In this study, we developed an innovative nitrogen-doped carbon quantum dot complex integrated with silver ions (N-CQDs/Ag composite) of approximate to 25 nm for the selective detection of adenine via a simple fluorescence turn-on mechanism. Techniques including DLS, TEM, FT-IR, EDX, UV-vis, and fluorescence spectroscopy were employed to characterize the morphology and properties of the nanosensor. The probe exhibited a remarkable detection limit of 0.076 mu M, indicating high sensitivity. Importantly, it enabled successful intracellular detection of endogenous adenine in HeLa cells, even under stress conditions. This approach offers a rapid, cost-efficient, and biocompatible platform for real-time monitoring of adenine, with strong potential for applications in bioanalysis and diagnostics, thereby serving as a promising tool for intracellular biomarker monitoring and disease-related diagnostics.

Though CO is a significant environmental pollutant, it serves a pivotal role as a signaling molecule in plants. A novel fluorescent nanodot has been developed for in vivo monitoring of CO inside the plant cells.

The increasing global population threatens food security, necessitating sustainable agricultural practices. Intensive farming has led to the excessive use of pesticides and fertilizers, contaminating soil and water sources and causing the impairment of the environment. Pesticide residues enter the food chain, posing serious health risks like neurotoxicity, genetic mutations, and diseases such as Alzheimer's, Parkinson's, diabetes, etc. Conventional detection methods are costly, complex, time-consuming, unsuitable for onsite detection, and mostly not eco-friendly. Fluorescence-based nano-biosensors, particularly carbon quantum dots (CQDs), offer a promising alternative to detect pesticides and herbicides due to their high sensitivity, biocompatibility, low toxicity, and photostability. In addition to their sensory application, CQDs could be used as an alternative to conventional chemical fertilizers for crop production. CQD-based nanofertilizers improve nutrient absorption, boost plant growth, and increase resistance to environmental stressors. This review will highlight the key advancements in CQDs in terms of various synthetic techniques and their use as nanosensors and nanofertilizers.

Long investigated for its physiological functions, glutamic acid (Glu) is a crucial amino acid implicated in plant development and stress responses. However, there is still limited in vivo monitoring of Glu. Here, we report the design of a "turn-on" fluorescence nanosensor for the selective detection of Glu: a nitrogen-doped carbon quantum dot (N-CQD)/Cu2+ complex. Cu2+ ions quenched the fluorescence of N-CQDs, which was then selectively recovered when Glu was added. This allowed for sensitive detection via a fluorescence recovery mechanism. The sensing technology showed outstanding selectivity, biocompatibility, and quick response. Dynamic quenching was verified as the underlying mechanism by characterization using FT-IR, XPS, DLS, and TCSPC. The uptake of N-CQDs and N-CQDs/Cu2+ complexes in Vigna radiata stem tissues was visualized by confocal laser scanning microscopy (CLSM), with preferential accumulation in the interfascicular, vascular bundle, and epidermal areas. Notably, Glu pretreatment affected the internalization of nanoparticles by modulating fluorescence intensity in a concentration-dependent manner. Remarkably, N-CQDs alone enhanced plant growth under LED light stress, indicating that they may function as regulators of plant development. These results offer a platform that can be used for the biological manipulation of glutamic acid in plants as well as real-time monitoring.

Food contamination is a critical issue that affects consumers worldwide. The contamination is caused by the extensive use of pesticides, insecticides, synthetic food-ripening agents, coloring agents, etc. In recent years, ethephon (2-chloroethylphosphonic acid) has been an active ingredient for artificial ripening in fruits and vegetables and is an essential part of plant growth regulators. Ethephon causes plasma cholinesterase inhibition and a decrease in the metabolic activity of the hepatocytes. In our research, we pioneered a novel method for detecting ethephon in food and agricultural products, utilizing nitrogen-doped carbon quantum dots (N-CQDs) with a simple fluorescence quenching mechanism having a trace amount (LOD 29.6 nM) within fruits or vegetables. The N-CQDs possess high photostability along with sensible quantum yield and are pretty much selective toward ethephon even in the presence of other relevant analytes. The quenching mechanism has been comprehensively illustrated through different spectroscopic methods and analytical tools, including UV-vis spectroscopy, fluorescence titration, Stern-Volmer plot, and fluorescence lifetime decay analysis. Moreover, the structural attributes and size of the N-CQDs have been defined through a broad array of performances, including high-resolution transmission electron microscopy, dynamic light scattering, Fourier-transform infrared spectroscopy, energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy. We used confocal microscopy to validate and visually demonstrate the interaction between ethephon and N-CQDs within the fruit cells. Furthermore, the ethephon toxicity has been successfully established with in vitro analysis using human cell lines (HeLa). This innovative "in-field" technique could provide a significant advancement in monitoring the presence of ethephon as an adulterating agent in food to reduce environmental hazards and risks.

Carbon monoxide (CO), a common environmental contaminant, is responsible for a significant proportion of accidental poisonings and fatalities reported globally each year. Accurate detection and regulation of carbon monoxide in both residential and industrial settings are critical to mitigate the risk of severe health complications in humans due to its hazardous features and widespread sources. CO is odorless, colorless, tasteless, and non-irritating, which makes it particularly challenging to identify without a specialized tool. In this study, we have designed a portable sensing device utilizing N-CQDs for the real-time detection of atmospheric CO with fluorescence quenching and visual detection. In this detection process, we elucidated the fluorescence quenching mechanism of N-CQDs upon binding with CO (binding affinity: 9.2 x 10-4 M-1) with a detection limit of 0.07 mu M (linear range between 4.77 and 41.23 mu M). Several techniques, including HRTEM, DLS, EDX, FT-IR, XPS, UV-vis spectroscopy, fluorescence spectroscopy, and fluorescence lifetime decay, have also been employed to elucidate the quenching mechanism.

A metal-free protocol for oxidative carbotrifluoromethylation of maleimides with imidazopyridines and Langlois' reagent has been developed using (diacetoxyiodo)benzene (PIDA) as an oxidant. This three-component strategy enables one-step construction of 3,4-disubstituted maleimides in good yields with high functional group tolerance. Both experimental and theoretical studies support the proposed radical reaction mechanism.

Aluminium (Al3+) and hypochlorite (ClO- ) have toxic effects on plants, affecting various physiological processes and ultimately impacting plant growth and development. Hence, the preparation of a smart tool for the detection of hypochlorite (ClO- ) and Aluminium (Al3+) in water, a dual-target fluorescent chemosensor APC (anthracenepyridine conjugate) has been synthesized. APC holds a unique diimine character when compared with a few similar diimine and interacts with both Al3+ and ClO- through charge transfer and chemodosimetric mechanisms to display green and blue fluorescence, correspondingly.The detection limits of APC for Al(3+ )and ClO- are 0.68 mu M and 0.25 mu M, respectively. The binding ratio between APC and Al3+ has been determined as 1:1 from Jobs plot analysis. The sensing mechanisms of APC with Al3+ and ClO- have been established by UV-visible, 1H NMR titration, HRMS analysis and theoretical calculations. This method has been successfully employed to examine the consequences of continued exposure to high concentrations of aluminium and hypochlorite on marigold and lettuce plants, respectively.

Dopamine, alongside norepinephrine and epinephrine, belongs to the catecholamine group, widely distributed across both plant and animal kingdoms. In mammals, these compounds serve as neurotransmitters with roles in glycogen mobilization. In plants, their synthesis is modulated in response to stress conditions aiding plant survival by emitting these chemicals, especially dopamine that relieves their resilience against stress caused by both abiotic and biotic factors. In present studies, there is a lack of robust methods to monitor the operations of dopamine under stress conditions or any adverse situations across the plant's developmental stages from cell to cell. In our study, we have introduced a groundbreaking approach to track dopamine generation and activity in various metabolic pathways by using the simple nitrogen and sulfur co-doped carbon quantum dots (N, S-CQDs). These CQDs exhibit dominant biocompatibility, negligible toxicity, and environmentally friendly characteristics using a quenching process for fluorometric dopamine detection. This innovative nanomarker can detect even small amounts of dopamine within plant cells, providing insights into plant responses to strain and anxiety. Confocal microscopy has been used to corroborate this occurrence and to provide visual proof of the process of binding dopamine with these N, S-CQDs inside the cells.

Hydrogen sulfide is a highly toxic gas that can produce extremely rapid CNS and respiratory depression and sometimes becomes fatal at high concentrations. There is no proven antidote for hydrogen sulfide poisoning. Hence, it is important to reduce the production of H2S in several industries, such as oil and gas refining and mining industries. As a consequence, researchers are always inquisitive about inventing different sensing devices or useful tools to detect H2S selectively in a cost-effective manner. Colorimetric and fluorometric detection methods are the most attractive owing to their simplicity, profitability, ease of understanding, and "on-spot" detection convenience. In this research, we developed some colorimetric and fluorometric chemosensors and established an assay for the easy detection of H2S following a specific mechanism. The sensing mechanisms were well established through exhaustive spectroscopic studies and theoretical calculations. We first synthesized a series of chemosensors using 2-hydroxy naphthaldehyde as a primary fluorophore. The chemosensors were developed by incorporating various electron-releasing and donating groups while keeping the binding site unchanged. Subsequently, we compared their efficiency and binding ability towards H2S with a possible mechanism. The chemosensor was employed through a paper strip for demonstration as an "in-field" device by changing the naked-eye and fluorescence color both in liquid and gas phases.

Considering the significant toxicity of arsenite (AsO2-), arsenate (AsO43-), and hydrogen sulphide (H2S), the early detection of these ions and gas using simple methods like naked-eye chemosensing could have substantial implications for environmental and industrial applications. With these factors in mind, we have developed a novel and straightforward colorimetric chemosensor called NADNP (2-hydroxy naphthaldehyde conjugated 2,4-dinitrophenyl hydrazine) for swift paper-based colorimetric detection of arsenite, arsenate, and H2S, based on a deprotonation mechanism. NADNP exhibits strong binding affinity towards sulfide, arsenite, and arsenate, with very lower detection limits (LOD) of 0.17 mu M, 0.15 mu M and 0.15 mu M respectively, and the binding stoichiometry between these detected ions and NADNP is determined to be 1 : 1 through Job's plot analysis. Structural elucidation and electronic properties calculation have been conducted via DFT (Density Functional Theory) studies for correlation with the spectroscopic analyses. The 'three-in-one' paper strip-based chemosensor could be considered a promising colorimetric tool for rapid, cost-effective, selective, and sensitive "on-spot" sensing and monitoring of arsenite, arsenate, and sulfide in environmental samples.

Indirect labelling of the lipopolysaccharide of Gram-negative bacteria by fluorescence turn-on signalling and computational calculations.

Aim This study aimed to isolate, endophytic Streptomyces sp. MSARE05 isolated from root of a peanut (Arachis hypogaea) inhibits the growth of other bacteria. The research focused on characterizing the strain and the antimicrobial compound.Methods and Results The surface-sterilized peanut roots were used to isolate the endophytic bacterium Streptomyces sp. MSARE05. A small-scale fermentation was done to get the antimicrobial compound SM05 produced in highest amount in ISP-2 medium (pH 7) for 7 days at 30 degrees C in shaking (180 rpm) condition. Extraction, purification, and chemical analysis of the antibacterial component revealed a novel class of antibiotics with a 485.54 Dalton molecular weight. The MIC was 0.4-0.8 mu g ml-1 against the tested pathogens. It also inhibits multidrug-resistant (MDR) pathogens and Mycobacterium with 0.8-3.2 mu g ml-1 MIC. SM05 was found to disrupt cell membrane of target pathogen as evident by significant leakage of intracellular proteins and nucleic acids. It showed synergistic activity with ampicillin, chloramphenicol, streptomycin, and kanamycin.Conclusions The new-class antimicrobial SM05 consisting naphthalene core moiety was effective against drug-resistant pathogens but non-cytotoxic to human cells. This study underscores the significance of endophytic Streptomyces as a source of innovative antibiotics, contributing to the ongoing efforts to combat antibiotic resistance.