On-site Detection Research Articles

Fingerprinting DNAzyme Cross-Reactivity for Pattern-Based Detection of Heavy Metals.

Heavy metal contamination in food and water is a major public health concern because heavy metals are toxic in minute amounts. DNAzyme sensors are emerging as a promising tool for rapid onsite detection of heavy metals, which can aid in minimizing exposure. However, DNAzyme activity toward its target metal is not absolute and has cross-reactivity with similar metals, which is a major challenge in the wide-scale application of DNAzyme sensors for environmental monitoring. To address this, we constructed a four DNAzyme array (17E, GR-5, EtNA, and NaA43) and used a pattern-based readout to improve sensor accuracy. We measured cross-reactivity between three metal cofactors (Pb2+, Ca2+, and Na+) and common interferents (Mg2+, Zn2+, Mn2+, UO22+, Li+, K+, and Ag+) and then used t-SNE analysis to identify and quantify the metal ion. We further showed that this method can be used for distinguishing mixtures of metals and detecting Pb2+ in environmental soil samples at micromolar concentrations.

A three-channel biosensor based on stimuli-responsive catalytic activity of the Fe3O4@Cu for on-site detection of tetrodotoxin in fish

Tetrodotoxin (TTX), a lethal neurotoxin, poses a grave threat to human health. The available spectroscopic methods suffer from limitations such as complex procedures and inadequate on-site capabilities. In this study, we proposed a method using Fe3O4@Cu as a catalytic biosensor combined with SERS, colorimetry and image processing for TTX detection. Integrating the aptamer amplifies the specificity of the system and masks the catalytic activity of Fe3O4@Cu. The catalytic efficiency of Fe3O4@Cu in the H2O2-TMB reaction can quantify the concentration of TTX in the system. Consequently, oxidation of TMB (oxTMB) led to the generation and change of signals for SERS, colorimetry and image processing, enabling a three-channel quantitative detection of TTX. Under the optimal conditions, the detection limit of established SERS, colorimetry and image processing were 0.055, 2.127 and 0.243 ng/mL, respectively. This three-channel biosensor was applied to real samples, providing an accurate, stable and adaptable alternative for on-site TTX detection.

Thermally versatile maleimide-based polymeric thin film for detection and separation of picric acid from polluted areas

2,4,6-Trinitrophenol, commonly known as picric acid, is a powerful explosive that has been used historically in military ammunition. Picric acid is extremely toxic and sensitive to friction and heat; thus, it is prone to accidental detonation at high temperatures. It is critical to detect and separate picric acid from the impacted areas. In the present study, we designed and developed a fluorescent copolymer (P1) for temperature-dependent picric acid detection. The solvatochromic and aggregation-induced emission (AIE) properties of P1 were utilized to detect picric acid at a high temperature of 40 °C (high alert level) by turn-off emission. Additionally, a polymeric thin film (F1) was fabricated by immobilizing P1 onto the surface of quartz slide. Notably, F1 retained its emissive properties across a range of temperatures (both relatively low and high alert levels), facilitated by its AIE characteristics. The portable film, F1, displayed a nanomolar sensitivity toward picric acid, making it suitable for on-site detection in aqueous media (neutral pH). Furthermore, F1 demonstrated efficient separation of picric acid from nitroaromatic explosive mixtures with a separation efficiency of 70 % over four cycles. Importantly, F1 exhibited practical utility in detecting and separating picric acid in real samples, highlighting its potential for environmental monitoring applications.

Pd Nanoclusters-Sensitized MIL-125/TiO2 Nanochannel Arrays for Sensitive and Humidity-Resistant Formaldehyde Detection at Room Temperature.

Among the various hazardous substances, formaldehyde (HCHO), produced worldwide from wood furniture, dyeing auxiliaries, or as a preservative in consumer products, is harmful to human health. In this study, a sensitive room-temperature HCHO sensor, MTiNCs/Pd, has been developed by integrating Pd nanoclusters (PdNCs) into mesoporous MIL-125(Ti)-decorated TiO2 nanochannel arrays (TiNCs). Thanks to the enrichment effect of the mesoporous structure of MIL-125 and the large surface area offered by TiNCs, the resulting gas sensor accesses significantly enhanced HCHO adsorption capacity. The sufficient energetic active defects formed on PdNCs further allow an electron-extracting effect, thus effectively separating the photogenerated electrons and holes at the interface. The resulting HCHO sensor exhibits a short response/recovery time (37 s/12 s) and excellent sensitivity with a low limit of detection (4.51 ppb) under ultraviolet (UV) irradiation. More importantly, the cyclic redox reactions of Pdδ+ in PdNCs facilitated the regeneration of O2-(ads), thus ensuring a stable and excellent gas sensing performance even under a high-humidity environment. As a proof-of-principle of this design, a wearable gas sensing band is developed for the real-time and on-site detection of HCHO in cigarette smoke, with the potential as an independent device for environmental monitoring and other smart sensing systems.

Novel Rhizophus oryzae esterase-immobilized chitosan/carbon nanomaterials as sensing support for enzyme inhibition-based biosensor in the detection of organophosphorus pesticide residues on crops

The use of mobile biosensor would allow for cost-effective and rapid on-site detection of organophosphorus (OP) pesticide. Immobilizing enzyme on electrode would improve the sensitivity of biosensor due to the nature of its specific active site-binding. OP inhibition on esterase enzyme is used as the sensing mechanism of the biosensor. In this study, microbial esterase from Rhizopus oryzae (RoE) was immobilized into modified screen-printed carbon electrode (SPCE) for the fabrication of novel RoE/chitosan/nanomaterial-COOH/SPCE biosensor for the detection of methyl parathion, an OP pesticide. The first phase of this study aims to analyze biochemical characteristics of 1-naphthyl acetate (1-NA) hydrolysis by RoE and enzymatic inhibition of RoE by OP pesticide. RoE kinetic showed the best fit with Langmuir model with the highest linear regression (R2 = 0.996). The inhibition of RoE by OP was shown to be linearly proportional to the enzyme activity (R2 = 0.827). The second phase of this study aims to analyze electrochemical performance of RoE-immobilized biosensor. Various carbon-based sensing support nanomaterials (graphene nanoplatelets (GNP), graphite and multi-walled carbon nanotube (MWCNT)) was functionalised by carboxyl (-COOH) group and screened, where all nanomaterials showed effective sensitivity towards detecting 0.01 ng/L methyl parathion pesticide. GNP-based biosensor exhibited the highest degree of inhibition (9.94 %) and better reproducibility after the first cycle. RoE/chitosan/GNP-COOH/SPCE biosensor is promising to be developed as cost-effective and highly sensitive biosensor for OP pesticide detection.

Magnetic beads-based nanozyme for portable colorimetric biosensing of Helicobacter pylori

Cancer continues to be a significant global health issue with one in six deaths linked to the disease despite advancements in cancer detection and treatment. Recently, Helicobacter pylori (H. pylori) was identified as a risk factor for cancer development. This gram-negative bacterium is associated with gastric conditions, including stomach cancer. Although the exact transmission methods of this bacterium are still unclear, studies suggest that waterborne transmission is possible. This study focuses on the development of a colorimetric nanomaterial-based paper biosensor for specific H. pylori detection using H. pylori extracellular proteases as biomarkers. The biosensor utilizes a unique substrate labeled with magnetic nanobeads and bound to a gold sensing platform. The biosensor's limit of detection (LOD) of 100 CFU/mL, selectivity, stability, and ability to detect H. pylori in clinical specimens were evaluated, demonstrating promising results in terms of sensitivity and specificity. In comparison to traditional methods, this biosensor offers advantages in simplicity and ease of use, making it appropriate for on-site detection in both environmental and clinical settings.

Diffusion-driven height readout analytical device based on gold nanobipyramid-doped supramolecular hydrogel for point-of-care bioanalysis

Point-of-care (POC) diagnostics is crucial for rapid on-site detection in resource-limited settings. However, there are still some challenges in the development of quantitative POC bioassays. Herein, we propose a simple, visual, and instrument-free height readout analytical device injected with target-responsive gold nanobipyramid (AuNBP)-doped guanosine-quartet (G4) supramolecular hydrogel for the quantitative detection of glucose. This sensing platform relies on H2O2 generated by glucose oxidation to induce iodide-mediated etching of AuNBPs, resulting in visualized color-changed hydrogel bar-chart driven by molecular diffusion in a polycarbonate tube. The visual height of the color-changed hydrogel is correlated with the concentration of glucose, and the quantitative determination was achieved simply by using a household ruler or mobile software as a readout. More importantly, this method has been successfully used to detect glucose in human serum samples with high accuracy and reliability. In addition, the AuNBPs are utilized as plasmonic probes to construct two-input logic gates, providing an intelligent strategy to simultaneously detect multiple biomolecules. This height-readout sensing platform demonstrates great promise for applications in POC and intelligent bioanalysis.

A novel SERS method for detecting E. coli based on an aptamer-functionalized Au-Ag@Si triangular pyramid substrate

Escherichia coli contamination in food and pharmaceutical preparations needs to be strictly controlled according to the regulations in many countries. However, rapid and sensitive E. coli detection is still a challenge. In this study, an aptamer-based surface-enhanced Raman spectroscopy (SERS) sandwich method was developed for the rapid and sensitive detection of E. coli using an aptamer-functionalized Au-Ag@Si triangular pyramid (TP) substrate. The Au-Ag@Si TP substrate was functionalized with E. coli aptamer to work as both the capture probe and SERS tag by integrating with Raman reporter (6-carboxy-X-rhodamine). The fabrication of the capture probe, SH-apt@Au-Ag@Si TP, was simple and rapid (20.5 h). This method could selectively and rapidly detect E. coli with a limit of detection of 2.8 CFU/mL within approximately 3 h. It was successfully applied to a traditional Chinese medicine preparation, Xinhuang tablets, with recoveries ranging from 90.19 % to 104.17 %. The results indicated that the developed method was simple and rapid, and it could be a promising alternative for the on-site detection of E. coli in pharmaceutical and food samples.

Gold nanoparticle-based lateral flow immunoassay for the repaid and sensitive detection of pyraclostrobin in wheat, apple, Chinese cabbage, and soil samples

Pyraclostrobin is widely employed for controlling fungal pathogens. Given its potential adverse effects on aquatic organisms, beneficial insects, and mammals, there is an urgent need to develop on-site detection methods for monitoring pyraclostrobin residues. In this study, monoclonal antibodies (mAbs) targeting pyraclostrobin were developed, and a reliable structure of the mAb 4B4C3 was predicted using AlphaFold 3. The structure showed high predicted local distance difference test (pLDDT) values for both the complementarity-determining regions (CDRs) and framework regions (FRs). Molecular docking was employed to investigate its binding pattern with pyraclostrobin. Subsequently, a highly sensitive lateral flow immunoassay (LFIA) based on gold nanoparticles (AuNPs) for detecting pyraclostrobin was established. The AuNP-LFIA method exhibited a visual limit of detection (vLOD) of 1.25 ng/mL and a completely inhibitory concentration of 5 ng/mL, surpassing the sensitivity of previously described methods. The accuracy of the established method was confirmed through spiked-recovery tests, exhibiting a sensitivity of 30 ng/g in wheat, apple, and soil samples, and 60 ng/g in Chinese cabbage samples. The reliability of the method was validated using ultra-high-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). This study presents a sensitive and cost-effective approach for rapidly detecting pyraclostrobin residues, demonstrating the significant potential of AlphaFold 3 in antibody engineering and small molecule on-site detection.

A Visible-Light-Driven Self-Powered Nodularin-R Biosensing Platform Controlled by an Integrated Portable Photoelectrochemical Detection Device.

The presence of nodularin-R (NOD-R) in water has gained considerable attention because of its widespread distribution and high toxicity. In this study, an accurate and rapid visible-light-driven self-powered photoelectrochemical (PEC) biosensor was developed by integrating a portable paper-based electrode with a custom-built miniaturized PEC detection device. The newly designed system successfully achieved on-site detection of NOD-R in real water samples based on PEC technology. First, target recognition triggers the initiation of the hybridization chain reaction to generate double-stranded DNA. The thus-formed double-stranded DNA entrapped methylene blue (MB), and the dye molecules were irradiated with visible light for conversion to leuco-MB in the presence of ascorbic acid. The resulting leuco-MB species significantly amplified the PEC signal output of TiO2-MXene, enabling NOD-R detection. Under optimal conditions, the proposed PEC assay strategy demonstrated NOD-R detection within a concentration range from 20 fg mL-1 to 10 ng mL-1 with a detection limit of 19.6 fg mL-1. In addition, a custom-built miniaturized PEC detection device conveniently integrates the detection component with the light source, enabling the real-time collection of results via a wireless module. This innovative self-powered PEC platform provides significant advancements in smooth and intelligent detection compared to traditional PEC detection devices.

Simple and rapid identification of beef within 30 min using a new food nucleic acid release agent combined with direct-fast qPCR

Simple and rapid molecular detection technologies for authenticating animal species are urgently needed for food safety and authenticity. This study established a new direct-fast quantitative polymerase chain reaction (qPCR) detection technology for beef to achieve rapid and on-site nucleic acid detection in food. This technology can complete nucleic acid extraction in 4 min using a new type of food nucleic acid-releasing agent, followed by direct amplification of the DNA sample by fast qPCR in 25 min. The results indicated that direct-fast qPCR can specifically identify beef and can also identify 0.00001% of beef components in artificially simulated meat mixtures, with a detection precision variation coefficient of <4%. This method can be used to effectively identify beef in different food samples. As a simple, fast, and accurate molecular detection technology for beef, this method may provide a new tool for the on-site detection of beef components in food.

Sensitive and accurate monitoring of urinary albumin and point-of-care testing using a fluorescent probe with anti-interference capacity against exogenous drugs

Fluorescent probes have been reported for monitoring urinary albumin (u-ALB) to enable early diagnosis of kidney diseases and facilitate regular point-of-care testing (POCT) for chronic kidney disease (CKD) patients. However, the albumin can bind hydrophobic drugs through host-guest interactions, which may result in decreased accuracy of probes at regular drug sites and hamper POCT of albuminuria since CKD patients often need to take medications routinely. Herein, we reported a novel fluorescent probe (NC-2) by molecular engineering of a reported AIEgen (NC-1). The introduction of a non-conjugated ring moiety to the molecular rotor granted the NC-2 enhanced sensitivity with a limit of detection in urine of 8.7 mg/L, which is below l the threshold of microalbuminuria (30 mg/L). Moreover, the NC-2 was found to preferentially bind to the FA1 site of ALB, conferring it with excellent anti-interference capacities against exogenous drug molecules and metabolites. Simulation experiments using lab-spiked urine samples containing common drugs taken by CKD patients demonstrated that the probe could provide satisfied detecting accuracy (80–90 %). Furthermore, a paper-based device was constructed and achieved on-site detection of u-ALB in qualitative and semi-quantitative manners. Findings in this work were of great significance to the development of fluorescent probes for accurate detection of ALB in complex urine samples and the further achievement of fluorescence-based POCT for CKD.

Mitigation of urban road collapses based on machine learning via integrating susceptibility assessment and geophysical detection validation

Road collapse is a frequent and damaging disaster in cities. The complexity and uncertainty inherent in urban environments pose significant challenges to mitigating road collapses. This paper presents a novel framework integrating machine learning-based susceptibility assessment and geophysical detection validation for urban road collapse risk reduction. Three oversampling techniques, random oversampling, synthetic minority oversampling technique for nominal and continuous features (SMOTENC), and adaptive synthetic sampling (ADASYN), are first utilized to implement data augmentation on urban road collapse accident samples. Subsequently, three machine learning models, support vector machine (SVM), random forest (RF), and extreme gradient boosting (XGBoost), are developed to evaluate road collapse susceptibility by extracting collapse-inducing patterns from historical accident data. Particularly, on-site geophysical hazard detection is conducted to validate the assessment results. The results demonstrate that XGBoost with SMOTENC achieves satisfactory performance in identifying road collapses with accuracy (0.9608) and AUC (0.9796). The spatial distribution of road collapse susceptibility in Shanghai central area follows a high-moderate-low pattern from northwest to southeast. The geophysical detection reveals a correlation between higher road collapse susceptibility and increased severity of underground diseases, validating the generalization capacity of XGBoost in actual operational environments. Additionally, the structural problems of underground pipelines are identified as the most influential factors for urban road collapse. This research offers valuable insights for urban road collapse mitigation and resilience improvement of transportation infrastructure.

Loop-mediated isothermal amplification (LAMP) assay for early on-site detection of Group B Streptococcus infection in neonatal sepsis blood sample.

Neonatal sepsis, often attributed to Group B Streptococcus (GBS) infection, poses a critical health risk to infants, demanding rapid and accurate diagnostic approaches. Existing diagnostic approaches are dependent on traditional culture methods, a process that requires substantial time and has the potential to delay crucial therapeutic assessments. This study introduces an innovative Loop-Mediated Isothermal Amplification (LAMP) assay for the early on-site detection of GBS infection from neonatal sepsis blood samples. To develop a LAMP assay, the primers are designed for the selective targeting of a highly conserved segment within the cfb gene encoding the CAMP factor in Streptococcus agalactiae ensuring high specificity. Rigorous optimization of reaction conditions, including temperature and incubation time, enhances the efficiency of the LAMP assay, enabling rapid and reliable GBS detection within a short timeframe. The diagnostic efficacy of the LAMP assay was evaluated using spiked blood samples by eliminating the DNA extraction step. The simplified colorimetric LAMP assay has the capability to detect S. agalactiae in a neonatal blood sample containing 2 CFU/mL during sepsis. Additionally, the LAMP assay effectively detected S. agalactiae in both the standard and spiked blood samples, with no detectable interference with blood. This optimised LAMP assay emerges as a promising tool for early GBS detection, offering a rapid and accurate on-site solution that has the potential to inform timely interventions and improve outcomes in neonatal sepsis cases.

An ultrasensitive dual-mode stagey for 17β-estradiol assay: Photoelectrochemical and colorimetric biosensor based on a WSe2/TiO2-modified electrode coupled with nucleic acid amplification

BackgroundThe abuse of 17β-estradiol(E2) has aroused wide concern in environmental and biomedical fields, which severely affects the endocrine function of human and animals. Therefore, an ultrasensitive and accurate assay of E2 is critically important. Traditional chromatography or immunoassay techniques exhibited good sensitivity and selectivity, but expensive instruments and antibodies may pose cost and stability issues, as well as difficulties in meeting on-site detection requirements. Ultrasensitive, reliable, and on-site detection of E2 at trace level remains a challenge. Hence, developing a simple, ultrasensitive assay to simultaneously achieve accurate detection and rapid visual analysis of E2 is extremely crucial. ResultsWe developed a versatile dual-mode photoelectrochemical (PEC) and colorimetric biosensor based on isothermal nucleic acid amplification strategy for the ultrasensitive and accurate detection of E2. The method modified titanium dioxide (TiO2) with tungsten selenide (WSe2) nanoflowers to synthesize WSe2/TiO2 heterostructures as a substrate for signal amplification and nanoprobe modification. Isothermal nucleic acid amplification strategy has been proven to be a powerful tool for strong signal amplification. The presence of a target triggered the nucleic acid amplification reaction, and produced a large amount of tDNA that competed with G-quadruplex immobilized on the electrode surface. The remaining G-quadruplex/hemin catalyzed the 4-chloro-1-naphthol (4-CN) to form biocatalytic precipitation (BCP) and ABTS-H2O2 chromogenic reaction, thus, the dual-mode platform was capable of achieving PEC-colorimetric ultrasensitive detection based on the catalytic activity of G-quadruplex/hemin DNAzyme. Within optimal conditions, the dual-mode biosensor exhibited a remarkable detection limit as low as 0.026 pM. SignificanceBenefiting from the superior performance of WSe2/TiO2 and the power signal amplification of isothermal nucleic acid amplification strategy, this aptasensor achieved the ultrasensitive detection of E2. The independent transmission paths of photoelectrochemical and colorimetric provide mutual support and flexible switching, significantly enhancing the overall sensitivity and accuracy of the detection strategy, which can meet the needs for E2 precise quantification and rapid on-site detection.

A Glycoprotein-Based Surface-Enhanced Raman Spectroscopy-Lateral Flow Assay Method for Abrin and Ricin Detection.

Abrin and ricin, both type II ribosome-inactivating proteins, are toxins of significant concern and are under international restriction by the Chemical Weapons Convention and the Biological and Toxin Weapons Convention. The development of a rapid and sensitive detection method for these toxins is of the utmost importance for the first emergency response. Emerging rapid detection techniques, such as surface-enhanced Raman spectroscopy (SERS) and lateral flow assay (LFA), have garnered attention due to their high sensitivity, good selectivity, ease of operation, low cost, and disposability. In this work, we generated stable and high-affinity nanotags, via an efficient freezing method, to serve as the capture module for SERS-LFA. We then constructed a sandwich-style lateral flow test strip using a pair of glycoproteins, asialofetuin and concanavalin A, as the core affinity recognition molecules, capable of trace measurement for both abrin and ricin. The limit of detection for abrin and ricin was 0.1 and 0.3 ng/mL, respectively. This method was applied to analyze eight spiked white powder samples, one juice sample, and three actual botanic samples, aligning well with cytotoxicity assay outcomes. It demonstrated good inter-batch and intra-batch reproducibility among the test strips, and the detection could be completed within 15 min, indicating the suitability of this SERS-LFA method for the on-site rapid detection of abrin and ricin toxins.

Bottle-in-bottle reaction device: Portable gas pressure meter for rapid and on-site analysis of oxalate in spinach and tea beverages

A gas pressure meter-based portable/miniaturized analytical kit was established for rapid and on-site detection of oxalate. Potassium permanganate (KMnO4) and oxalate solution were mixed together in bottle-in-bottle reaction device, a simple oxidation reaction process occurred within 6 min and carbon dioxide (CO2) was generated, inducing the pressure of the sealed bottle changed, which was measured by a portable gas pressure meter. A detectable range of 0.1–6 μmol mL−1 and a detection limit of 0.064 μmol mL−1 were achieved. The proposed analytical method was further used for the analysis of several real samples (spinach, beverages and water samples), with the recoveries of 89–111%. Considering the interferences from the complicated matrix, calcium chloride (CaCl2) was served as a precipitant, oxalate (C2O42−) was precipitated with Ca2+ to form precipitation (CaC2O4), CaC2O4 was then separated from the matrix by centrifuge/filter, eliminating the interferences. It is a rapid, easy-used and interference-free analytical system/device for oxalate on-site and real time analysis.

A smartphone-assisted portable on-site detection system for organophosphorus pesticides in vegetables and fruits based on all-in-one paper-based sensors: 2,2-Dichlorovinyl dimethyl phosphate as a model

The improper use of organophosphate pesticides (OPs) can lead to residue posing a serious threat to human health and environment. Therefore, the development of a simple, portable, and sensitive detection method is crucial. Herein, a bioenzyme-nanozyme-chromogen all-in-one paper-based sensor was synthesized. Initially, the Ce/Zr-MOF with peroxidase-like activity was grown on filter paper (FP) using in-situ solvent thermal method, resulting in Ce/Zr-MOF@FP. Subsequently, the AChE-ChO-TMB system was immobilized onto Ce/Zr-MOF@FP using biocompatible gelatin, which enhanced cascade catalysis efficiency through the proximity effect. Based on the inhibition principle of OPs on AChE, we integrated this sensor with Python-based image recognition algorithm to achieve detection of OPs. Using 2,2-dichlorovinyl dimethyl phosphate (DDVP) as a model of OPs, it has good detection performance with a detection limit of 0.32 ng mL−1 and a recovery rate range of 95–107%. The potential for on-site detection of DDVP residues in vegetables and fruit samples is highly promising.

Rapid and on-site detection of bisulfite via a NIR fluorescent probe: A case study on the emission wavelength of probes with different quinolinium as electron-withdrawing groups

The emission of venenous sulfur dioxide (SO2) and its derivatives from industrial applications such as coking, transportation and food processing has caused great concern about public health and environmental quality. Probes that enable sensitivity and specificity to detect SO2 derivatives play a crucial role in its regulations and finally mitigating its environmental and health impacts, but fluorescent probes that can accurately, rapidly and on-site detect SO2 derivatives in foodstuffs and environmental systems rarely reported. Herein, a near-infrared (NIR) fluorescent probe (ZTX) for the ratiometric response of bisulfite (HSO3−) was designed and synthesized by regulating the structure of high-performance HSO3− fluorescent probe SL previously reported by us based on structural analyses, theoretical calculations and related literature reports. The Michael addition reaction between the electronic-deficient C=C bond and HSO3− destroys ZTX's π-conjugation system and blocks its intramolecular charge transfer (ICT) process, resulting in a significant fading of the fuchsia solution and the bluish-purple fluorescence turned light blue fluorescence. Fluorescent imaging of HSO3− in live animals utilizing ZTX has been demonstrated. The quantitative analysis of HSO3− in food samples using ZTXvia a smartphone has been also successfully implemented. Simultaneously, the ZTX-based test strips were utilized to quantificationally determine HSO3− in environmental water samples by a smartphone. Consequently, probe ZTX could provide a new method to understand the physiopathological roles of HSO3−, evaluate food safety and monitor environment, and is promising for broad applications.

An investigation of the Excitation Wavelength-Dependent Dynamic Changes in the Mechanism of Detection of Picric Acid using Pyrene-Based Donor-Acceptor Systems.

Picric acid (PA) is an important industrial feedstock and hence the release of industrial effluents without proper remediation results in its buildup in soil and water bodies. The adverse effects of PA accumulation in living beings necessitate the development of efficient methods for its detection and quantification. Herein, we describe pyrene-based fluorescent sensors for PA, where pyrene is appended with electron-withdrawing groups, malononitrile, and 2-(3-cyano-4,5,5-trimethylfuran-2(5H)-ylidene) malononitrile (DCDHF). These molecules displayed the typical emission of pyrene monomers, as well as a broad red-shifted emission resulting from an intramolecular charge transfer (ICT) in the excited state. Both the emissions displayed a turn-off response to PA with high selectivity and sensitivity and the lowest limit of detection was estimated as 27 nM. To prove the feasibility of on-site detection, test paper strips were prepared, which could detect PA up to 4.58 picograms. Using a combination of experimental and theoretical studies the mechanism of the detection was identified as primary/secondary inner filter effect, oxidative photoinduced electron transfer, or a combination of both depending on the excitation wavelength. Interestingly, the contribution of each of these mechanisms to the total quenching process varied with a change in the excitation wavelength.