Low Detection Limit Research Articles

An Aptamer-Based Hydrogel Sensing Platform Enabling Low Micromolar Detection of Small Molecules Using Low Sample Volumes.

Poor fluorescence recovery at low analyte dosages and slow ligand binding kinetics are critical challenges currently limiting the use of aptamer-functionalized hydrogels for sensing small molecules. In this paper, we report an adenosine-responsive hydrogel sensor that integrates FRET-signaling aptamer switches into in situ-gelling thin-film hydrogels. The hydrogel sensor is able to entrap a high proportion of the sensing probes (>70% following vigorous washing), delay nucleolytic degradation, stabilize weak aptamer complexes to improve hybridization affinity and suppress fluorescence background, and provide high sensitivity in biological fluids (i.e., undiluted human serum). Furthermore, the developed hydrogel sensors were able to achieve low limits of detection (5.3 μM in buffer and 8.8 μM in serum) within 4 min of exposure to the sample, with signal generation requiring only 20 μL/well of analyte sample. The physical nature of the aptamer encapsulation allows this approach to accommodate virtually any small-molecule aptamer, avoiding the need for covalent anchoring and the complex modification of nucleic acid sequences typically required for effective aptamer-based molecular recognition.

A MOF-Templated Double-Shelled Co3O4/NiCo2O4 Nanocomposite for Electrochemical Detection of Alfuzosin.

We developed a novel electrochemical sensor for the detection of alfuzosin (AFZ), a drug used to treat benign prostatic hyperplasia, using a double-shelled Co3O4/NiCo2O4 nanocomposite-modified electrode. The nanocomposites were synthesized using a template-assisted approach, with zeolitic imidazole framework-67 (ZIF-67) as the sacrificial template, involving the formation of uniform ZIF-67/Ni-Co layered double hydroxide (LDH) hollow structures followed by calcination to achieve the final nanocomposite. The nanocomposite was characterized by various techniques and showed high porosity, large surface area, and good conductivity. The nanocomposite-modified electrode exhibited excellent electrocatalytic activity towards AFZ oxidation, with a wide linear range of 5-180 µM and a low limit of detection of 1.37 µM. The sensor also demonstrated good repeatability, reproducibility, and stability selectivity in the presence of common interfering substances. The sensor was successfully applied to determine the AFZ in pharmaceutical tablets and human serum samples, with satisfactory recoveries. Our results suggest that the double-shelled Co3O4/NiCo2O4 nanocomposite is a promising material for the fabrication of electrochemical sensors for AFZ detection.

Graphene Nanocomposite Ink Coated Laser Transformed Flexible Electrodes for Selective Dopamine Detection and Immunosensing.

Novel and flexible disposable laser-induced graphene (LIG) sensors modified with graphene conductive inks have been developed for dopamine and interleukin-6 (IL-6) detection. The LIG sensors exhibit high reproducibility (relative standard deviation, RSD = 0.76%, N = 5) and stability (RSD = 4.39%, N = 15) after multiple bendings, making the sensors ideal for wearable and stretchable bioelectronics applications. We have developed electrode coatings based on graphene conductive inks, poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (G-PEDOT:PSS) and polyaniline (G-PANI), for working electrode modification to improve the sensitivity and limit of detection (LOD). The selectivity of LIG sensors modified with the G-PANI ink is 41.47 times higher than that of the screen-printed electrode with the G-PANI ink modification. We have compared our fabricated bare laser-engraved Kapton sensor (LIG) with the LIG sensors modified with G-PEDOT (LIG/G-PEDOT) and G-PANI (LIG/G-PANI) conductive inks. We have further compared the performance of the fabricated electrodes with commercially available screen-printed electrodes (SPEs) and screen-printed electrodes modified with G-PEDOT:PSS (SPE/G-PEDOT:PSS) and G-PANI (SPE/G-PANI). SPE/G-PANI has a lower LOD of 0.632 μM compared to SPE/G-PEDOT:PSS (0.867 μM) and SPE/G-PANI (1.974 μM). The lowest LOD of the LIG/G-PANI sensor (0.4084 μM, S/N = 3) suggests that it can be a great alternative to measure dopamine levels in a physiological medium. Additionally, the LIG/G-PANI electrode has excellent LOD (2.6234 pg/mL) to detect IL-6. Also, the sensor is successfully able to detect ascorbic acid (AA), dopamine (DA), and uric acid (UA) in their ternary mixture. The differential pulse voltammetry (DPV) result shows peak potential separation of 229, 294, and 523 mV for AA-DA, DA-UA, and UA-AA, respectively.

Revolutionizing Glucose Monitoring: Enzyme-Free 2D-MoS2 Nanostructures for Ultra-Sensitive Glucose Sensors with Real-Time Health-Monitoring Capabilities.

The growing requirement for real-time monitoring of health factors such as heart rate, temperature, and blood glucose levels has resulted in an increase in demand for electrochemical sensors. This study focuses on enzyme-free glucose sensors based on 2D-MoS2 nanostructures explored by simple hydrothermal route. The 2D-MoS2 nanostructures were characterized by powder X-ray diffraction, energy-dispersive X-ray spectroscopy, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and XPS techniques and were immobilized at GCE to obtain MoS2-GCE interface. The fabricated interface was characterized by electrochemical impedance spectroscopy which shows less charge transfer resistance and demonstrated superior electrocatalytic properties of the modified surface. The sensing interface was applied for the detection of glucose using amperometry. The MoS2-GCE-sensing interface responded effectively as a nonenzymatic glucose sensor (NEGS) over a linearity range of 0.01-0.20 μM with a very low detection limit of 22.08 ng mL-1. This study demonstrates an easy method for developing a MoS2-GCE interface, providing a potential option for the construction of flexible and disposable nonenzymatic glucose sensors (NEGS). Moreover, the fabricated MoS2-GCE electrode precisely detected glucose molecules in real blood serum and urine samples of diabetic and nondiabetic persons. These findings suggest that 2D-MoS2 nanostructured materials show considerable promise as a possible option for hyperglycemia detection and therapy. Furthermore, the development of NEGS might create new prospects in the glucometer industry.

Molecularly Imprinted Electrochemical Sensor Based on α-Cyclodextrin Inclusion Complex and MXene Modification for Highly Sensitive and Selective Detection of Alkylresorcinols in Whole Wheat Foods.

Authenticating whole wheat foods poses a significant challenge for both the grain industry and consumers. Alkylresorcinols (ARs), serving as biomarkers of whole wheat, play a crucial role in assessing the authenticity of whole wheat foods. Herein, we introduce a novel molecularly imprinted electrochemical sensor with modifications involving a molecularly imprinted polymer (MIP) and MXene nanosheets, enabling highly sensitive and selective detection of ARs. Notably, we specifically chose 5-heneicosylresorcinol (AR21), the predominant homologue in whole wheat, as the template molecule. α-Cyclodextrin and acrylamide served as dual functional monomers, establishing a robust multiple interaction between the MIP and AR21. As a result, the sensor exhibited a wide linear range of 0.005 to 100 μg·mL-1 and a low detection limit of 2.52 ng·mL-1, demonstrating exceptional selectivity and stability. When applied to commercial whole wheat foods, the assay achieved satisfactory recoveries and accuracy, strongly validating the practicality and effectiveness of this analytical technique.

Cu2MoS4 Nanocatalyst-based Electrochemical Sensor for Ofloxacin Electro-Oxidation: Delineating the Combined Roles of Crystallinity and Morphology on the Analytical Performance.

In this study, we demonstrate the influence of crystallinity and morphology on the analytical performance of various Cu2MoS4 (CMS) nanocatalysts-based electrochemical sensors for the high-efficiency detection of Ofloxacin (OFX) antibiotic. The electrochemical kinetics parameters including peak current response (ΔIp), peak-to-peak separation (ΔEp), electrochemically active surface area (ECSA), electron-transfer resistance (Rct), were obtained through the electrochemical analyses, which indicate the single-crystalline nature of CMS nanomaterials (NMs) is beneficial for enhanced electron-transfer kinetics. The morphological features and the electrochemical results for OFX detection substantiate that by tuning the tube-like to plate-like structures of the CMS NMs, it might noticeably enhance multiple adsorption sites and more intrinsic active catalytic sites due to the diffusion of analytes into the interstitial spaces between CMS nanoplates. As results, highly single-crystalline and plate-shaped morphology structures of CMS NMs would significantly enhance the electrocatalytic OFX oxidation in terms of onset potential (Eonset), Tafel slope, catalytic rate constant (kcat), and adsorption capacity (Γ). The CMS NMs-based electrochemical sensing platform showed excellent analytical performance toward the OFX detection with two ultra-wide linear detection concentration ranges from 0.25 - 100 and 100 - 1000 μM, a low detection limit of 0.058 μM, and an excellent electrochemical sensitivity (0.743 µA µM-1 cm-2).

Wearable Self‐Powered Smart Sensors Enabled by 2D Flower‐Like Ni–Co Layered Double Hydroxides for Copper Monitoring in Sweat

AbstractThe growing power demands of wearable electronic devices have stimulated the development of self‐powered systems in noninvasive healthcare. Herein, ultrathin homogeneous 2D flower‐like nickel–cobalt layered double hydroxide (Ni–Co LDH) nanocomposites are prepared by a one‐step hydrothermal method to integrate a self‐powered system for wearable sweat copper ions (Cu2+) monitoring. The Ni–Co LDH nanocomposites with a lamellar structure and numerous active sites, exhibit sensitive selectivity and low detection limits for Cu2+. In addition, the optimized Ni–Co LDH provides favorable capacitive characteristics as supercapacitors for self‐powering sensors, ensuring continuous sensing energy sources. By connecting wirelessly to a smart device, a self‐powered system is constructed to achieve wearable sensing of Cu2+ in the practical application of sweat. This simple yet effective strategy provides new opportunities for the development of self‐powering health monitoring sensors, as well as smartsensing more heavy metals.

Evaluation of PVC@Silver Nanocomposite as Sensor for Low Limit Detection of Cadmium Ion By Surface Plasmon Resonance Based Method

AbstractThis study explores the development of a PVC@Silver nanocomposite for enhanced detection of cadmium ions in water samples. Various characterization techniques confirmed the successful incorporation of silver nanoparticles into the polyvinyl chloride (PVC) matrix across different concentrations (1–4%). X-ray diffraction revealed the face-centered cubic crystalline structure of the silver nanoparticles, with the intensities of the (111), (200), (220), and (311) peaks increasing with higher Ag concentrations. The average crystallite sizes ranged from 26.1 nm (3% Ag) to 30.0 nm (2% Ag). Dynamic light scattering showed nanoparticle sizes of 24–43 nm, while zeta potential values of -24 to -40 mV indicated reasonable colloidal stability. Brunauer–Emmett–Teller (BET) surface area analysis demonstrated a decreasing surface area from 30.09 m2/g (1% Ag) to 25.27 m2/g (3% Ag), attributed to pore filling by silver nanostructures. Significantly, the PVC@Silver nanocomposite facilitated sensitive detection of Cd(II) ions using surface plasmon resonance (SPR), exhibiting an SPR angle shift of 26.30° with intensity values ranging from 10.80 (4% Ag) to 12.19 (3% Ag). UV–vis spectra revealed a prominent surface plasmon resonance band at 420–430 nm, indicating the presence of silver nanoparticles. The optical band gap varied from 4.51eV (1% Ag) to 4.12eV (4% Ag).

Enzyme-integrated metal-organic framework platform for cascade detection of α-amylase

As one of the most important industrial enzymes, α-amylase is widely used in food processing, such as starch sugar and fermentation, bringing high added value to industry of more than a trillion dollars. We developed a multi-enzyme system (Glu&Gox@Cu-MOF-74) prepared by embedding α-glucosidase (Glu) and glucose oxidase (Gox) into the biomimetic metal-organic framework Cu-MOF-74 using in situ encapsulation within 15 min at room temperature for efficient and sensitive detection of α-amylase activity. Benefitting from the remarkable peroxidase-mimicking property and rigid skeleton of Cu-MOF-74, the biocatalytic platform exhibited excellent cascade activity and tolerance in various extremely harsh environments compared to natural enzymes. On this basis, a cascade biocatalytic platform was constructed for the detection of α-amylase activity with wide linear range (5–100 U/L) and low limit of detection (1.45 U/L). The colorimetric cascade scheme is important for the sensitive and selective determination of α-amylase in complex fermentation samples, and the detection time is short (∼0.5 h). This work provides new ideas for the detection of α-amylase based on the cascade amplification method.

Development of heat-assisted in-situ solvent formation liquid phase microextraction followed by derivatization for the simultaneous extraction of aliphatic amines from wastewater samples prior to gas chromatography-mass spectrometry

Herein, a cost-effective, rapid, and selective liquid phase microextraction procedure has been developed for the extraction of some aliphatic amines from sewage samples. The method was based on in-situ formation of chloroform as an extraction solvent into the sample solution followed by derivatization by butylchloroformate prior to gas chromatography- mass spectrometry. Chloroform is formed by the reaction of chloral hydrate and sodium hydroxide. The extraction procedure was accelerated by heating. Also heating decreases chloroform solubility in aqueous solution. To improve the analytical signals, derivatization of the analytes is done by butylchloroformate. The effect of major parameters on the extraction efficiency were studied and optimized. Under the optimized conditions, enrichment factor and extraction recovery were in the ranges of 259–296 and 78–89 %, respectively. Low limits of detection (0.08–0.12 ng mL−1) and quantification (0.28–0.41 ng mL−1), wide linear ranges, and relative standard deviations less than 6 % for intra −and inter-day precisions were acceptable. Lastly, the mentioned method was successfully performed to determine aliphatic amines in wastewater samples.

A three-mode biosensor for hypoxanthine assay in aquatic products under various storage conditions

Establishing a rapid and accurate method for monitoring the freshness of aquatic products is of great importance. Hypoxanthine has been considered an essential indicator of aquatic products’ freshness. Here, a novel smartphone colorimetric / inductively coupled plasma mass spectrometry (ICP-MS) / photothermal three-mode sensing strategy was established for monitoring hypoxanthine. Hypoxanthine can be catalyzed by xanthine oxidase to H2O2 and uric acid, which can simultaneously degrade MnO2 nanosheets (NSs) to Mn2+. After filter-assisted separation, the smartphone and ICP-MS were performed by monitoring the color of the membrane and the Mn2+ in the filtrate. Additionally, MnO2 NSs can facilitate the oxidation of dopamine to form polydopamine nanoparticles, which exhibit strong photothermal efficiency. The approach successfully monitored the deterioration of aquatic products under various storage conditions through portable thermometers and smartphones with low limits of detection (LODs), providing a potential application for in-situ evaluation of the freshness of aquatic products.

Uricase conjugated nanostructured NiFe2O4/rGO modified flexible screen-printed carbon electrode based interface for long-range electrochemical determination of uric acid

Uric acid (UA) is a biomarker linked with gout and kidney stones that is harmful to the human body. Thus, this study explores the detection of UA using the differential pulse voltammetry (DPV) method. Initially synthesizing a highly active Nickel ferrite/reduced graphene oxide (NiFe2O4/rGO) nanocomposite ferrite material by simple surfactant-free low-temperature hydrothermal approach. The as-synthesized material was studied using various spectroscopic and microscopic techniques. The bioelectrode was fabricated on a screen-printed carbon electrode (SPCE), and the as-prepared Uricase/NiFe2O4/rGO/SPCE demonstrated improved electrochemical oxidation peak current (Ipa). While its electrochemical biosensing performance towards various UA concentrations shows a wide linear range from 5 to 900 μM, with a lower limit of detection (21·9 μM), high sensitivity (1·05×10−4 mA/μM cm2), good selectivity (RSD < 5·7 %), excellent stability, and repeatability. In addition, the fabricated bioelectrode was also explored to quantify the amount of UA in bovine serum albumin (BSA) real spiked samples. Hence, the proposed biosensor has potential applications in point-of-care-treatment of numerous disorders related to UA metabolism.

Chemiresistive n-butanol gas sensors based on Co3O4@ZnO hollow-sphere-array thin films prepared by template-assisted magnetron sputtering

Rapid and accurate detection of n-butanol in the environment is crucial owing to its negative effects on human health. Herein, gas sensors based on Co3O4@ZnO hollow-sphere-array thin films modified using Au particles are successfully prepared via template-assisted magnetron sputtering for detecting n-butanol. The best sensor performances are achieved when the thicknesses of the sputtered ZnO and Co3O4 films are 60 and 1.2 nm, respectively, and the sputtering time of the Au particles is 10 s. Furthermore, the best sensor exhibits an exceptionally high response to an n-butanol concentration of 100 pm at 275 °C (Ra/Rg = 260), a short response/recovery time (1 s/92 s), a considerably lower limit of detection (Ra/Rg = 5.8 at n-butanol concentration = 100 ppb) as well as high selectivity and repeatability. The remarkable sensing performance of the proposed sensors can be mainly attributed to the charge transfer induced by the Co3O4–ZnO heterojunction formation and the catalytic and spillover effects of the Au particles. This study is important because it provides a simple preparation method for high-performance semiconductor gas sensors using magnetron sputtering, which would enable future large-scale and integrated preparation of high-performance gas sensors.

High-efficient selection of aptamers by magnetic cross-linking precipitation and development of aptasensor for 1-aminohydantoin detection

Accurate and rapid detection of nitrofurantoin metabolite 1-aminohydantoin (AHD), as one of the tissue-bound toxic metabolites in foods, is crucial. In this study, a fluorescent aptasensor was constructed for the detection of AHD, using anti-AHD aptamers firstly obtained by high-efficiency magnetic crosslinking precipitation (MCP)-SELEX. The AHD-specific aptamers were optimized and identified for their binding affinity and specificity using fluorescence-based assays and molecular dynamics simulations. The truncated aptamer AHD50-1, which exhibited highest affinity (Kd = 86 nM) and an excellent specificity, was applied to the construction of fluorescent aptasensor. Under optimized conditions, the aptasensor showed a low limit of detection (0.2 ng/mL) and a wide dynamic linear range (0.25–150 ng/mL). For the five types of samples (pork, beef, shrimp, fish and honey), the recoveries ranged from 89.4% to 110.04%, with coefficients of variation ranging from 1.43% to 14.46%. These results obtained by the proposed aptasensor corroborate very well with the method of HPLC for detection of AHD, indicating that the developed aptasensor provides an efficient and promising sustainable strategy for monitoring AHD in animal derived food.

Reduced graphene oxide electrodes meet lateral flow assays: A promising path to advanced point-of-care diagnostics

Research in electrochemical detection in lateral flow assays (LFAs) has gained significant momentum in recent years. The primary impetus for this surge in interest is the pursuit of achieving lower limits of detection, especially given that LFAs are the most widely employed point-of-care biosensors. Conventionally, the strategy for merging electrochemistry and LFAs has centered on the superposition of screen-printed electrodes onto nitrocellulose substrates during LFA fabrication. Nevertheless, this approach poses substantial limitations regarding scalability. In response, we have developed a novel method for the complete integration of reduced graphene oxide (rGO) electrodes into LFA strips. We employed a CO2 laser to concurrently reduce graphene oxide and pattern nitrocellulose, exposing its backing to create connection sites impervious to sample leakage. Subsequently, rGO and nitrocellulose were juxtaposed and introduced into a roll-to-roll system using a wax printer. The exerted pressure facilitated the transfer of rGO onto the nitrocellulose. We systematically evaluated several electrochemical strategies to harness the synergy between rGO and LFAs. While certain challenges persist, our rGO transfer technology presents compelling potential for setting a new standard in electrochemical LFA fabrication.

Binuclear TbⅢ complex used for the fluorescent detection of 2, 6-pyridindicarboxylic acid, an anthrax biomarker

Anthrax is a potentially highly lethal acute infectious disease caused by the zoonotic bacterium Bacillus anthracis, which poses a threat to human life and health. 2, 6-Pyridinedicarboxylic acid (DPA) is a significant component of bacterial spores as a typical anthrax biomarker. Therefore, it is imperative to develop a simple and efficient detection method for DPA. Here, we successfully synthesized a binuclear terbium complex with formulas [Tb2(DMOMP)2(CH3OH)2(H2O)4Cl2]·2Cl·2CH3OH, which is constructed by 2, 6-dimethoxy-4-methylphenol (DMOMP) and TbⅢ ion. Each TbⅢ ion center is encapsulated by seven O atoms and one Cl− anion. Based on this, the encapsulated coordination environment facilitated efficient ligand energy transfer via the “antenna effect”. Therefore, the complex exhibits interesting luminescence response characteristics, with fast and stable green fluorescence response to DPA, low detection limit Ksv = 1.08 × 10−5 M−1, and fluorescence lifetime τ = 754.93 μs. [Tb2(DMOMP)2(CH3OH)2(H2O)4Cl2]·2Cl·2CH3OH has excellent fluorescence properties and strong immunity to interference and is capable of sensitively detecting the B. anthracis biomarker DPA, allowing it to be potentially used as an effective fluorescent probe and providing a viable strategy for effective anthrax fever prevention.

A nanoDiamond/gold nanoparticle-based electrochemical immunosensor for the detection of HER 2 cancer biomarker

We report a highly sensitive electrochemical immunosensor based on a nanohybrid platform for the detection of the breast cancer biomarker human epidermal growth factor receptor 2 (HER 2). NanoDiamond (nanoD) and gold nanoparticles (AuNPs) immobilised by drop coating and electrodeposition methods, respectively, were employed to fabricate an immunosensor for HER 2 detections on a glassy carbon electrode (GCE). Voltammetry and electrochemical impedance spectroscopy (EIS) techniques were used to characterise each step of the modification process of the immunosensor. In addition, transmission electron microscopy (TEM), X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) techniques were used to characterise the materials used to fabricate the modified electrode. Under optimal conditions of temperature, time, and pH (35 °C, 50 min, and pH 7.2), different concentrations were investigated within a wide range of 1 pg mL−1 to 50 ng mL−1 using differential pulse voltammetry (DPV). With a low detection limit of 0.29 pg mL−1 from the DPV analysis, the immunosensor showed very good sensitivity and had a high specificity for HER 2. Additionally, the immunosensor demonstrated good applicability in the analysis of HER 2 in human serum samples, demonstrating a potential for use in the early identification of breast cancer.

Specific temperature-modulated crab shell-derived porous carbon as a typical recycling material for nitrofurazone electrochemical sensor

Nitrofurazone (NFZ), a nitroimidazole antibiotic, can cause serious toxicity when overused, its quantification is crucial for human health. Herein, crab shell waste is converted into porous biochar at a high temperature, which can be employed for the establishment of an electrochemical sensor for the quantitative detection of NFZ. The morphological and structural properties of the crab shell carbon at different temperatures were characterized by SEM, XRD, FT-IR and N2 adsorption-desorption analyses. The crab shell carbon prepared at 500 °C (C-CS-500) and 700 °C (C-CS-700) is calcite-based and contains micro-fibrillar similar to chitin structure, while the crab shell carbon prepared at 900 °C (C-CS-900) is lime-based and lacks the similar structure. And the synergistic influence of calcite-based composition and micro-fibrillar structure of crab shell carbon offered strong electron-transport properties and a large electrode active at a higher carbonized temperature. The electrochemical signals demonstrated that the crab shell carbon prepared at 700 °C provided enhanced sensing capability for rapid NFZ detection with a wide linear range of 0.40–80 μM, a high sensitivity of 0.55 μA μM−1 and a low detection limit of 0.11 μM (S/N = 3), as compared to the crab shell carbon prepared at 500 °C and 900 °C. In addition, the sensor can also be utilized to quantify nitrofurazone in the real drug (compound cod liver oil ointment) with satisfactory recovery.

Nitrogen-doped carbon dots for 3D printed smartphone-assisted cascade visual detection of morin and aluminium ion, solid fluorescence ink

With the growing emphasis on health management, individuals increasingly focus on monitoring drug molecular residues and harmful ions. Motivated by the concepts of the intelligent system and quantitative detection, we develop a smartphone-assisted cascade visual sensing device based on nitrogen-doped carbon dots (N-CDs) for in-site quantitative detection of morin and aluminium ion (Al3+). Initially, citric acid and o-phenylenediamine are identified as precursors for N-CDs synthesis via the microwave-assisted hydrothermal treatment. Subsequently, systematic studies reveal that the fluorescence of N-CDs is quenched upon the introduction of morin because of the inner filter effect (IFE). Conversely, the fluorescence recovery phenomenon occurs after the cascade addition of Al3+ since the morin binds with Al3+, resulting in the inhibition of IFE. Simultaneously, the fluorescence recovery of N-CDs enhances the cyan fluorescence emission of morin/Al3+. Based on the fluorescence quenching and recovery behavior, morin and Al3+ can be detected in the ranges of 0.070–50 μM and 0.124–40 μM with low detection limits of 0.070 μM and 0.124 μM, respectively. Furtherly, a smartphone-assisted cascade visual sensing device is designed for in-site quantitative detection of morin and Al3+. Moreover, based on the strong fluorescence and concentration-dependent emission behavior of N-CDs, the multi-color fluorescent ink is developed successfully. This work not only offers an excellent solution for simultaneous detection of morin and Al3+ but also shows numerous opportunities for solid lighting, information encryption and flexible optics.

Hydrothermal route upcycling surgical masks into dual-emitting carbon dots as ratiometric fluorescent probe for Cr (VI) and corrosion inhibitor in saline solution

Exploration effective route to convert plastic waste into valuable carbon dots with bifunction of metal fluorescence monitoring and corrosion protection in seawater is promising. Herein, using “white-pollution” polypropylene surgical masks as a single precursor, dual-emitting carbon dots (CDs) with excellent ratiometric fluorescent sensitivity and corrosion inhibitor efficiency were fabricated with high yield (∼100 %) by a one-pot in situ acid oxidation hydrothermal strategy without post-treatment and organic solvents. Chemical, structural, morphological, optical properties and the Cr (VI) detection and Cu inhibition mechanism of the synthesized CDs had been systematically studied. Furthermore, a dual-response-OFF proportional fluorescent probe had been developed for the detection of the analyte Cr (VI) with a low detection limit of 24 nM. Additionally, the corrosion inhibition efficiency of the prepared CDs reached approximately 94.01 % for Cu substrate in 3.5 wt% NaCl electrolyte under a CDs concentration of 200 mg/L, which is higher than that of most previous reports.