Fluorescent turn-off sensor based on sulphur-doped graphene quantum dots in colloidal and film forms for the ultrasensitive detection of carbamate pesticides

A microfluidic paper-based fluorescent sensor integrated with a smartphone platform for rapid on-site detection of omethoate pesticide

A novel approach combing a fluorescent microfluidic paper strip with a portable smartphone-based sensing platform is developed for rapid and sensitive detection of omethoate pesticide. The detection mechanism of the microfluidic paper strip is based on the fluorescence quenching of graphene oxide (GO) toward the cyanine 3 (Cy3)-labeled aptamer (Cy3-APT). Upon exposure to omethoate, the Cy3-APT detaches from the surface of GO, resulting in considerable fluorescence recovery, which can be visualized through the smartphone-based sensing platform. The images are analyzed through a self-developed app embedded with a pretrained convolutional neural network model, achieving a high regression coefficient of 0.9964 at an omethoate concentration range of 0-750 nM. The smartphone-based platform enables rapid on-site detection of omethoate pesticide in real samples within 10 min, with results comparable to those obtained using standard methods. In short, the proposed microfluidic paper-based fluorescent sensor combined with the smartphone-based sensing platform enhances the detection performance toward organophosphorus pesticides.

Designed fluorescence "on-off-on" probe based on cobalt, zinc, and nitrogen co-doped graphene quantum dots: A case of quinalphos sensing

In this study, we developed a new fluorescence "on-off-on" sensor utilizing water-soluble cobalt/zinc-nitrogen co-doped graphene quantum dots (Co/Zn-N-GQDs) to recognize quinalphos pesticide in vegetable and fruit samples. Primarily, the synthesis method employed a one-pot hydrothermal approach, using betel leaves as a natural precursor and cobalt ("Co"), zinc ("Zn"), and urea ("N") as dopant sources. The Co/Zn-N-GQDs probes underwent comprehensive analytical characterization. The Co/Zn-N-GQDs were synthesized with a remarkable luminescence yield of 31.49%, exhibiting excitation at 320 nm and emission peak at 393 nm. Interestingly, the luminescence of Co/Zn-N-GQDs was selectively "Turned Off" by Cu2+ via a static quenching setup. Remarkably, quenched fluorescence was surprisingly reactivated upon adding quinalphos to the quench setup, indicating a direct correlation between luminescence reactivation and quinalphos concentration. Briefly, this phenomenon is ascribed to the functional groups in quinalphos, such as quinoxalinyl and phosphorothioate, which chelate with Cu2+ ions, disrupting the nonfluorescent Cu2+-Co/Zn-N-GQDs complex. The design sensor demonstrated a limit of detection (LOD) of 0.11 μM and a broad linear span of 0.5 to 200 μM. In conclusion, Cu2+-Co/Zn-N-GQDs sensor showed immediate applicability, stability, and reproducibility, making it highly effective for quinalphos sensing in various samples.

An Updated Review on Functionalized Graphene as Sensitive Materials in Sensing of Pesticides

Numerous chemical pesticides were employed for a long time to manage pests, but their uncontrolled application harmed the health and the environment. Accurately quantifying pesticide residues is essential for risk evaluation and regulatory purposes. Numerous analytical methods have been developed and utilized to achieve sensitive and specific detection of pesticides in intricate sampl es like water, soil, food, and air. Electrochemical sensors based on amperometry, potentiometry, or impedance spectroscopy offer portable, rapid, and sensitive detection suitable for on-site analysis. This study examines the potential of electrochemical sensors for the accurate evaluation of various effects of pesticides. Emphasizing the use of Graphene (GR), Graphene Oxide (GO), Reduced Graphene Oxide (rGO), and Graphdiyne composites, the study highlights their enhanced performance in pesticide sensing by stating the account of many actual sensors that have been made for specific pesticides. Computational studies provide valuable insights into the adsorption kinetics, binding energies, and electronic properties of pesticide-graphene complexes, guiding the design and optimization of graphene-based sensors with improved performance. Furthermore, the discussion extends to the emerging field of biopesticides. While the GR/GO/rGO based sensors hold immense future prospects, and their existing limitations have also been discussed, which need to be solved with future research.

Construction of coumarin-appended calix[4]arene-based fluorescence sensor for the detection of carbofuran in cabbage

This study presents a novel approach for the detection of carbofuran (CBF) insecticide by systematically exploring a calix[4]arene-derived fluorescence probe, CouC4S, functionalized with two coumarin-labelled cystamine linkages at the narrow edge of the calix[4]arene platform. The proposed method showed a fluorescence "signal - off" effect when CBF binds with CouC4S by quenching the fluorescence intensity of CouC4S. Its limit of detection was as low as 5.55 μM according to the emission study. The working concentration range for this ligand was observed to be up to 5-65 μM. This method could be applied for the on-spot detection of CBF in real samples such as cabbage by spiking CBFvia in situ experiments, which exhibited a limit of detection of 8.823 ppm. For the further confirmation of CouC4S:CBF binding, cyclic voltammetry, differential pulse voltammetry, powder X-ray diffraction, FT-IR spectroscopy, 1H NMR titration, MALDI-TOF and computational investigations were carried out.

Determination of carboxylesterase by fluorescence probe to guide detection of carbamate pesticide

A carboxylesterase fluorescent probe (Probe 1) was developed for determination of carboxylesterase to guide detection of carbamate pesticide. The probe uses benzothiazole as fluorescence group and phenyldimethyl carbamate as recognition group. The solution of the fluorescent probe gradually changes from light blue to dark blue as the concentration of carbamate pesticides increases. The concentration of carbamate pesticides can be quickly calculated according to the colour of the probe solution through Get Color software on a smartphone. It showed that Probe 1 can be used as a rapid detection tool to achieve rapid detection of carbamate pesticides in juice samples without professional personnel and equipment. Furthermore, the probe has been successfully used to detect carbamate pesticides in fruit juice and vegetable juice.

Organophosphorus and carbamate pesticides: Molecular toxicology and laboratory testing

Population and food requirements are increasing daily throughout the world. To fulfil these requirements application of pesticides is also increasing. Organophosphorous (OP) and Organocarbamate (OC) compounds are widely used pesticides. These pesticides are used for suicidal purposes too. Both inhibit Acetylcholinesterase (AChE) and cholinergic symptoms are mainly used for the diagnosis of pesticide poisoning. Although the symptoms of the intoxication of OP and OC are similar, recent research has described different targets for OP and OC pesticides. Researchers believe the distinction of OP/OC poisoning will be beneficial for the management of pesticide exposure. OP compounds produce adducts with several proteins. There is a new generation of OP compounds like glyphosate that do not inhibit AChE. Therefore, it's high time to develop biomarkers that can distinguish OP poisoning from OC poisoning.

An overview of polymer surface coated synthetic quantum dots as therapeutics and sensors applications

Quantum dots (QDs) are a class of remarkable materials that have garnered significant attention since their initial discovery. It is noteworthy to mention that it took approximately a decade for these materials to be successfully implemented in practical applications. While QDs have demonstrated notable optical properties, it is important to note that these attributes alone have not rendered them a feasible substitute for traditional organic dyes. Furthermore, it is worth noting that the substance under investigation exhibited inherent toxicity and instability in its initial state, primarily due to the presence of a heavy metal core. In the initial stages of research, it was observed that the integration of nanocomposites had a positive impact on the properties of QDs. The discovery of these nanocomposites was motivated by the remarkable properties exhibited by biocomposites found in nature. Recent discoveries have shed light on the potential utilization of QDs as a viable strategy for drug delivery, offering a promising avenue to enhance the efficacy of current pharmaceuticals and pave the way for the creation of innovative therapeutic approaches. The primary objective of this review was to elucidate the distinctive characteristics that render QDs highly suitable for utilization as nanocarriers. In this study, we will delve into the multifaceted applications of QDs as sensing nanoprobes and their utilization in diverse drug delivery systems. The focus of our investigation was directed toward the utilization of QD/polymer composites in sensing applications, with particular emphasis on their potential as chemical sensors, biosensors, and physical sensors.

Reusable flexible poly(vinyl alcohol)/chitosan-based polymer carbon dots composite film for acid blue 93 dye adsorption

The design and synthesis of water-insoluble chitosan-based polymer carbon dots [P(CS-g-CA)CDs] are described. A polyvinyl alcohol/chitosan-based polymer carbon dot [PVA/P(CS-g-CA)CDs] composite film was prepared using a simple casting method to be used in dye adsorption. The composite film was characterized using FT-IR, XPS, transparency, contact angle, and mechanical properties tests, which showed the successful incorporation of P(CS-g-CA)CDs into the film and also revealed that hydrogen bonding improved the mechanical properties of the PVA film. Furthermore, the composite film displayed substantially enhanced hydrophobicity, making it suitable for use in aqueous environments. In addition, the composite film exhibited stable adsorption of acid blue 93 (AB93) at pH 2-9, with an enhanced adsorption capacity of 433.24 mg/g. The adsorption obeyed Langmuir law with an efficiency of more than 89% even after five cycles. Therefore, the PVA/P(CS-g-CA)CDs film is a promising material for the treatment of organic dye-polluted wastewater.

Competitive fluorescent immunoassay for the ultrasensitive determination of amyloid beta peptide1-42 based on Ag@SiO2@N, S-GQD nanocomposites

A competitive fluorescent immunoassay is described for the ultrasensitive determination of amyloid beta peptide1-42 (Aβ1-42), a biomarker for early diagnosis of Alzheimer's disease. N, S-doped graphene quantum dots (N, S-GQDs) were freely assembled on the surface of Ag@SiO₂ nanoparticles to obtain a composite (Ag@SiO₂@N, S-GQD nanocomposite), which was successfully prepared and characterized. By theoretical study, the optical properties of nanocomposites are improved compared with GQDs, due to the advantages of combining N, S co-doping and metal-enhanced fluorescence (MEF) effect of Ag NPs. In addition, Aβ1-42 was modified by Ag@SiO₂@N, S-GQDs to prepare a probe with high photoluminescence properties (Ag@SiO₂@N, S-GQDs-Aβ1-42). In the presence of Aβ1-42, a competitive reaction towards anti-Aβ1-42 fixed on the ELISA plate was proceeded between Aβ1-42 and Ag@SiO₂@N, S-GQDs-Aβ1-42 by specific capture of antigen-antibody. The emission peak of Ag@SiO₂@N, S-GQDs-Aβ1-42 (400 nm emission) was used for the quantitative determination of Aβ1-42. Under the optimal conditions, the fluorescent immunoassay exhibited a linear range of 0.32 pg·mL^-1-5 ng·mL^-1 with a detection limit of 0.098 pg·mL^-1. The results show that the immunoassay has good analytical ability and can provide a new method for the clinical determination of Aβ1-42.

Structural and Optical Properties of Graphene Quantum Dots-Polyvinyl Alcohol Composite Thin Film and Its Potential in Plasmonic Sensing of Carbaryl

In this study, graphene quantum dots (GQDs) and polyvinyl alcohol (PVA) composite was prepared and then coated on the surface of gold thin film via the spin coating technique. Subsequently, Fourier transform infrared spectroscopy (FT-IR), atomic force microscopy (AFM), and ultraviolet-visible spectroscopy (UV-Vis) were adopted to understand the structure, surface morphology, and optical properties of the prepared samples. The FT-IR spectral analysis revealed important bands, such as O-H stretching, C=O stretching, C-H stretching, and O=C=O stretching vibrations. The surface roughness of the GQDs-PVA composite thin film was found to be increased after exposure to carbaryl. On the other hand, the optical absorbance of the GQDs-PVA thin film was obtained and further analysis was conducted, revealing a band gap E_g value of 4.090 eV. The sensing potential of the thin film was analyzed using surface plasmon resonance (SPR) spectroscopy. The findings demonstrated that the developed sensor's lowest detection limit for carbaryl was 0.001 ppb, which was lower than that previously reported, i.e., 0.007 ppb. Moreover, other sensing performance parameters, such as full width at half maximum, detection accuracy, and signal-to-noise ratio, were also investigated to evaluate the sensor's efficiency.

Gamma-Ray-Induced Structural Transformation of GQDs towards the Improvement of Their Optical Properties, Monitoring of Selected Toxic Compounds, and Photo-Induced Effects on Bacterial Strains

Structural modification of different carbon-based nanomaterials is often necessary to improve their morphology and optical properties, particularly the incorporation of N-atoms in graphene quantum dots (GQDs). Here, a clean, simple, one-step, and eco-friendly method for N-doping of GQDs using gamma irradiation is reported. GQDs were irradiated in the presence of the different ethylenediamine (EDA) amounts (1 g, 5 g, and 10 g) and the highest % of N was detected in the presence of 10 g. N-doped GQDs emitted strong, blue photoluminescence (PL). Photoluminescence quantum yield was increased from 1.45, as obtained for non-irradiated dots, to 7.24% for those irradiated in the presence of 1 g of EDA. Modified GQDs were investigated as a PL probe for the detection of insecticide Carbofuran (2,2-Dimethyl-2,3-dihydro-1-benzofuran-7-yl methylcarbamate) and herbicide Amitrole (3-amino-1,2,4-triazole). The limit of detection was 5.4 μmol L^-1 for Carbofuran. For the first time, Amitrole was detected by GQDs in a turn-off/turn-on mechanism using Pd(II) ions as a quenching agent. First, Pd(II) ions were quenched (turn-off) PL of GQDs, while after Amitrole addition, PL was recovered linearly with Amitrole concentration (turn-on). LOD was 2.03 μmol L^-1. These results suggest that modified GQDs can be used as an efficient new material for Carbofuran and Amitrole detection. Furthermore, the phototoxicity of dots was investigated on both Gram-positive and Gram-negative bacterial strains. When bacterial cells were exposed to different GQD concentrations and illuminated with light of 470 nm wavelength, the toxic effects were not observed.

Graphene quantum dots: synthesis, properties, and applications to the development of optical and electrochemical sensors for chemical sensing

GQDs exhibits exceptional electrochemical activity owing to their active edge sites that make them very attractive for biosensing applications. However, their use in the design of new biosensing devices for application to the detection and quantification of toxins, pathogens, and clinical biomarkers has so far not investigated in detail. In this regard, herein we provide a detailed review on various methodologies employed for the synthesis of GQDs, including bottom-up and top-down approaches, with a special focus on their applications in biosensing via fluorescence, photoluminescence, chemiluminescence, electrochemiluminescence, fluorescence resonance energy transfer, and electrochemical techniques. We believe that this review will shed light on the critical issues and widen the applications of GQDs for the design of biosensors with improved analytical response for future applications. HIGHLIGHTS: • Properties of GQDs play a critical role in biosensing applications. • Synthesis of GQDs using top-down and bottom-up approaches is discussed comprehensively. • Overview of advancements in GQD-based sensors over the last decade. • Methods for the design of selective and sensitive GQD-based sensors. • Challenges and opportunities for future GQD-based sensors.

Graphene Based Nanohybrid Aptasensors in Environmental Monitoring: Concepts, Design and Future Outlook

In view of ever-increasing environmental pollution, there is an immediate requirement to promote cheap, multiplexed, sensitive and fast biosensing systems to monitor these pollutants or contaminants. Aptamers have shown numerous advantages in being used as molecular recognition elements in various biosensing devices. Graphene and graphene-based materials/nanohybrids combined with several detection methods exhibit great potential owing to their exceptional optical, electronic and physicochemical properties which can be employed extensively to monitor environmental contaminants. For environmental monitoring applications, aptamers have been successfully combined with graphene-based nanohybrids to produce a wide range of innovative methodologies. Aptamers are immobilized at the surface of graphene based nanohybrids via covalent and non-covalent strategies. This review highlights the design, working principle, recent developmental advances and applications of graphene based nanohybrid aptasensors (GNH-Apts) (since January 2014 to September 2021) with a special emphasis on two major signal-transduction methods, i.e., optical and electrochemical for the monitoring of pesticides, heavy metals, bacteria, antibiotics, and organic compounds from different environmental samples (e.g., water, soil and related). Lastly, the challenges confronted by scientists and the possible future outlook have also been addressed. It is expected that high-performance graphene-based nanohybrid aptasensors would find broad applications in the field of environmental monitoring.

Recent advances in synthesis and modification of carbon dots for optical sensing of pesticides

Serious threat from pesticide residues to the ecosystem and human health has become a global concern. Developing reliable methods for monitoring pesticides is a world-wide research hotspot. Carbon dots (CDs) with excellent photostability, low toxicity, and good biocompatibility have been regarded as the potential substitutes in fabricating various optical sensors for pesticide detection. Based on the relevant high-quality publications, this paper first summarizes the current state-of-the-art of the synthetic and modification approaches of CDs. Then, a comprehensive overview is given on the recent advances of CDs-based optical sensors for pesticides over the past five years, with a particular focus on photoluminescent, electrochemiluminescent and colorimetric sensors regarding the sensing mechanisms and design principles by integrating with various recognition elements including antibodies, aptamers, enzymes, molecularly imprinted polymers, and some nanoparticles. Novel functions and extended applications of CDs as signal indicators, catalyst, co-reactants, and electrode surface modifiers, in constructing optical sensors are specially highlighted. Beyond an assessment of the performances of the real-world application of these proposed optical sensors, the existing inadequacies and current challenges, as well as future perspectives for pesticide monitoring are discussed in detail. It is hoped to provide powerful insights for the development of novel CDs-based sensing strategies with their wide application in different fields for pesticide supervision.

Fluorescent sensor based on quantum dots and nano-porphyrin for highly sensitive and specific determination of ethyl carbamate in fermented food

BACKGROUND

Ethyl carbamate (EC) is a potentially toxic carcinogen produced during fermentation and storage of fermented foods, and many countries have set thresholds for its content in food. Therefore, sensitive, rapid and accurate detection of EC is meaningful to ensure the quality of fermented food.

RESULTS

This study introduces a CdTe quantum dots/nano-5,10,15,20-tetrakis (4-methoxyphenyl)-porphyrin (nano TPP-OCH₃ ) fluorescence sensor system detection of EC. The specificity of this sensing mainly relies on a photo-induced electron transfer and electrostatic force interaction between EC and nano TPP-OCH₃ . This sensor presented a linear range of 10 to 1000 μg L^-1 (R²  = 0.9903) with a low detection limit of 7.14 μg L^-1 . Meanwhile, the recovery (91.19-101.09%) and precision [relative standard deviation (RSD) = 0.64-3.05%] of the sensor for the analysis of fermented food (yellow rice wine, soy sauce, Chinese spirits, Pu-erh tea) samples were good and could meet the requirements of practical detection. Moreover, the detection results of fermented food (yellow rice wine, soy sauce, Chinese spirits, Pu-erh tea) samples by this sensor are basically consistent with those of high-performance liquid chromatography with fluorescence detector (HPLC-FLD).

CONCLUSION

This method was expected to provide a potential platform for sensitive and accurate detection of EC in food safety monitoring, which would provide knowledge of the flavor and quality related to fermented food. © 2021 Society of Chemical Industry.

Self-quenching-resistant solid-state carbon dots for mechanism and applications

Solid-state carbon dots (SCDs) have been widely investigated by scholars owing to their stability, environmental friendliness, and their good optical properties. The current studies on carbon dots (CDs) are mainly focused on the solutions of CDs, while the researches on SCDs are relatively few in comparison. Nowadays, the fabrication and design of high-performance SCDs have attracted much interest. However, due to resonance energy transfer and π-π interactions, CDs undergo aggregation-induced quenching (ACQ) phenomena. This poses an obstacle to the acquisition of SCDs and affects their luminescence performance. Publications of the past 5 years are reviewed on how to suppress the ACQ phenomenon and improve the fluorescence and phosphorescence emission of CDs (Ref. 87) and about the mechanism of achieving the luminescence of SCDs. Then, the applications of SCDs in the fields of luminescent devices, anti-counterfeiting, and detection are outlined. The concluding section analyzes the current challenges faced by SCDs and provides an outlook. Mechanism of photoluminescence from solid state carbon dots.

Sulphur-doped graphene quantum dot based fluorescent turn-on aptasensor for selective and ultrasensitive detection of omethoate

Development of selective, ultra-sensitive, rapid and facile methods for the detection of chemical residues of toxic pesticides and hazardous chemicals are quite important in food safety, environmental monitoring and safeguarding public health. Herein, we presented a fluorescent turn-on aptasensor based on sulphur-doped graphene quantum dot (S-GQD) utilizing specific recognition and binding property of aptamer for the ultra-sensitive and selective detection of omethoate (OM) which is a systemic organophosphorus pesticide. The detection method is based on tuning aggregation-disaggregation mechanism of S-GQD by way of conformational alteration of the recognition probe. Fluorescence 'turn-on' process includes aggregation-induced quenching of S-GQD with aptamer via S-GQD-aptamer complex formation and its subsequent fluorescence recovery with the addition of OM by structural switching of S-GQD-aptamer complex to aptamer-omethoate complex. The reported 'switch-on' aptasensor has exhibited a low limit of detection of 0.001 ppm with high selectivity for OM over other pesticides.

Recent progress on graphene quantum dots-based fluorescence sensors for food safety and quality assessment applications

The versatile photophysicalproperties, high surface-to-volume ratio, superior photostability, higher biocompatibility, and availability of active sites make graphene quantum dots (GQDs) an ideal candidate for applications in sensing, bioimaging, photocatalysis, energy storage, and flexible electronics. GQDs-based sensors involve luminescence sensors, electrochemical sensors, optical biosensors, electrochemical biosensors, and photoelectrochemical biosensors. Although plenty of sensing strategies have been developed using GQDs for biosensing and environmental applications, the use of GQDs-based fluorescence techniques remains unexplored or underutilized in the field of food science and technology. To the best of our knowledge, comprehensive review of the GQDs-based fluorescence sensing applications concerning food quality analysis has not yet been done. This review article focuses on the recent progress on the synthesis strategies, electronic properties, and fluorescence mechanisms of GQDs. The various GQDs-based fluorescence detection strategies involving Förster resonance energy transfer- or inner filter effect-driven fluorescence turn-on and turn-off response mechanisms toward trace-level detection of toxic metal ions, toxic adulterants, and banned chemical substances in foodstuffs are summarized. The challenges associated with the pretreatment steps of complex food matrices and prospects and challenges associated with the GQDs-based fluorescent probes are discussed. This review could serve as a precedent for further advancement in interdisciplinary research involving the development of versatile GQDs-based fluorescent probes toward food science and technology applications.

Nano-Enable Materials Promoting Sustainability and Resilience in Modern Agriculture

Intensive conventional agriculture and climate change have induced severe ecological damages and threatened global food security, claiming a reorientation of agricultural management and public policies towards a more sustainable development model. In this context, nanomaterials promise to support this transition by promoting mitigation, enhancing productivity, and reducing contamination. This review gathers recent research innovations on smart nanoformulations and delivery systems improving crop protection and plant nutrition, nanoremediation strategies for contaminated soils, nanosensors for plant health and food quality and safety monitoring, and nanomaterials as smart food-packaging. It also highlights the impact of engineered nanomaterials on soil microbial communities, and potential environmental risks, along with future research directions. Although large-scale production and in-field testing of nano-agrochemicals are still ongoing, the collected information indicates improvements in uptake, use efficiency, targeted delivery of the active ingredients, and reduction of leaching and pollution. Nanoremediation seems to have a low negative impact on microbial communities while promoting biodiversity. Nanosensors enable high-resolution crop monitoring and sustainable management of the resources, while nano-packaging confers catalytic, antimicrobial, and barrier properties, preserving food safety and preventing food waste. Though, the application of nanomaterials to the agri-food sector requires a specific risk assessment supporting proper regulations and public acceptance.

A paper-based chemiluminescence detection device based on S,N-doped carbon quantum dots for the selective and highly sensitive recognition of bendiocarb

Bendiocarb, a type of carbamate pesticide, plays a crucial role in controlling a wide range of pests. Due to its harmful impact on humans and the environment, the need for inexpensive, portable, efficient and easy-to-use analytical devices has become essential. In this study, an environmentally friendly paper-based analytical device (PAD) with a chemiluminescence (CL) sensing platform was investigated and characterized for the facile, reliable and sensitive detection of the bendiocarb pesticide. It is based on the enhancing effect of SO32- on the CL reaction of sulfur, nitrogen-doped carbon quantum dots (S,N-CQDs)-KMnO4 in acidic media. According to the experiments, S,N-CQDs and SO32- both are oxidized by KMnO4 to generate (S,N-CQDs*) and (SO2*) in their excited states, emitting at 510 nm. This indicates that an energy transfer process is taking place from SO2* to S,N-CQDs, resulting in a remarkably intensified CL emission. Interestingly, another emission was also observed around 660 nm contributing to about 20 to 25% of the total CL emission. This emission is related to the Mn2+* species produced by reducing MnO4-. The established multi-emission CL system was tested for analytical applications. Under optimal experimental conditions, a good linear relationship was observed between the bendiocarb concentration and the CL intensity of the established CL system. The linear detection range was 0.1-10 μg mL-1, with a limit of detection (LOD) of 0.02 μg mL-1. Finally, the method was successfully applied for the measurements of bendiocarb in water and juice samples. The obtained recovery values (97.5-105.5) verified the suitable accuracy of the results.

In situ reduction triggers the highly sensitive detection of pesticide by classic gold nanoparticle and quantum dots nanocomposite

Fluorescence "turn on" method is always preferable for target detection under the urgent demand to develop point-of-care portable sensors in practical applications due to its higher selectivity and less false positives. However, there is only few reports of pesticide monitoring based on this strategy so far most probably ascribed to its poor hydrophilicity and reactivity. In this work, triggered by reductant tris (2-carboxyethyl) phosphine hydrochloride (TCEP), initially fluorescence-quenched gold nanoparticles (Au NPs)-decorated quantum dots (QDs)-embedded nanobead shows obvious fluorescence "turn on" signal response to thiram with concentration response range of 0.01-20 μM and limit of detection (LOD) of 7 nM due to the target-induced dissociation of Au NPs from the surface of probe nanobead. Moreover, paper sensor has been successfully developed by immersing commercial drainage membrane in probe solution for visual detection of thiram with the ultrahigh LOD (50 nM) by the naked eye. More importantly, this work, for the first time, reported an in situ reduction strategy to improve the interaction between target and nanoprobe and thus bring obvious signal output for pesticide detection with high sensitivity, demonstrating the potential to expand the detection scope of nanomaterials.

Recent advances in the applications of nano-agrochemicals for sustainable agricultural development

Modern agricultural practices have triggered the process of agricultural pollution. This process can cause the degradation of eco-systems, land, and environment owing to the modern-day by-products of agriculture. The substantial use of chemical fertilizers, pesticides, and, contaminated water for irrigation cause further damage to agriculture. The current scenario of the agriculture and food sector has therefore become unsustainable. Nanotechnology has provided innovative and resourceful frontiers to the agriculture sector by contributing practical applications in conventional agricultural ways and practices. There is a large possibility that agri-nanotechnology can have a significant impact on the sustainable agriculture and crop growth. Recent research has shown the potential of nanotechnology in improving the agriculture sector by enhancing the efficiency of agricultural inputs and providing solutions to agricultural problems for improving food productivity and security. The prospective use of nanoscale agrochemicals such as nanofertilizers, nanopesticides, nanosensors, and nanoformulations in agriculture has transformed traditional agro-practices, making them more sustainable and efficient. However, the application of these nano-products in real field situations raises concern about nanomaterial safety, exposure levels, and toxicological repercussions to the environment and human health. The present review gives an insight into recent advancements in nanotechnology-based agrochemicals that have revolutionized the agriculture sector. Further, the implementation barriers related to the nanomaterial use in agriculture, their commercialization potential, and the need for policy regulations to assess possible nano-agricultural risks are also discussed.

Passivated graphene quantum dots for carbaryl determination in juices

This paper reports a simple method for the preparation of suitable graphene quantum dots after surface passivation, to be used for the determination of carbaryl in juice samples. A comparison of synthetic conditions for the preparation of graphene quantum dots following the top-down approach is described. In the one-step route selected, evaluation of diverse reaction time for cutting and modulating the oxidizing sites in the broken pieces of the initial graphene layer is conducted with a mixture of concentrated acids. Exploring the passivation effect on the purified graphene quantum dots, we demonstrated the suitability of the selected graphene quantum dots for practical application in the detection of carbaryl using fluorometric detection. Higher sensitivity was achieved after 8 min of contact, in which graphene quantum dots promotes the degradation of carbaryl into naphthol, being the latter responsible for the analytical signal. The detection and quantification limits were 0.36 and 1.21 μg/L, respectively, being the response linear up to 26 μg/L with excellent precision (better than 3.2% at the limit of detection). The recovery of the analyte from commercial juice samples (91.4-96.7%) testifies to the applicability of the proposal for the analytical problem selected.

Boron-doped and serine and histidine-functionalized graphene quantum dots with strong yellow fluorescence emissions for highly sensitive detection of carbofuran in cucumber and cabbage

The weak fluorescence of graphene quantum dots upon visible-light excitation limits their applications.