Linear Range Research Articles

Zn-CD@Eu Ratiometric Fluorescent Probe for the Detection of Dipicolinic Acid, Uric Acid, and Ex Vivo Uric Acid Imaging.

Development of reliable methods for the detection of potential biomarkers is of the utmost importance for an early diagnosis of critical diseases and disorders. In this study, a novel lanthanide-functionalized carbon dot-based fluorescent probe Zn-CD@Eu is reported for the ratiometric detection of dipicolinic acid (DPA) and uric acid (UA). The Zn-CD@Eu nanoprobe was obtained from a simple room-temperature reaction of zinc-doped carbon dots (Zn-CD) and the EDTA-Eu lanthanide complex. Under optimal conditions, a good linear response was obtained for DPA in two concentration ranges of 0-55 and 55-100 μM with a limit of detection of 0.53 and 2.2 μM respectively, which is significantly below the infectious dosage of anthrax (∼55 μM). Furthermore, the Zn-CD@Eu/DPA system was employed for the detection of UA with a detection limit of 0.36 μM in the linear range of 0-100 μM. The fluorescent probe was successfully implemented for determining DPA and UA in human blood serum, sweat, and natural water bodies with considerable recovery rates. In addition, the potential of the nanoprobe for ex vivo visualization of UA was demonstrated in fruit fly (Drosophila melanogaster) as a model organism.

Development of Magnetic Solid Phase Micro-Extraction (MSPE) Method for the Extraction and Preconcentration of the Selected β-Blockers in the Environmental Wastewaters

AbstractEmerging organic pollutants s have always been the greatest environmental concern due to their ubiquity and distinguished adverse effects. These are mostly water-bone pollutants flagged as endocrine disruptors and can greatly inconvenience the ecosystem. Among others, β-blockers have also been detected in the environment at various concentrations that threaten the well-being of humans and animals. In this work, NH2-MIL-101(Cr) doped magnetic nanoparticles nanocomposite was successfully synthesised and characterised using analytical techniques such as X-ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) and transmission electron microscopy (TEM). The Fe3O4@NH2-MIL-101(Cr) was then used as an adsorbent to extract the selected β-blockers in the environmental wastewater. The selected β-blockers were quantified using a high-performance liquid chromatography-diode array detector (HPLC-DAD). Parameters affecting the extraction were screened and optimised using fractional factorial design (FFD) and central composite design (CCD), respectively. Under optimum conditions, the LODs were 0.057 and 0.065 µg L− 1, and LOQs were 0.19 and 0.22 µg L− 1 for acebutolol (ACE) and metoprolol (MET), respectively. The calibration curve exhibited the linearity range of 0.2–1200 µg L− 1 with correlation coefficients of 0.9987 and 0.9968 for ACE and MET, respectively. Repeatability studies demonstrated the %RSD of 0.63 and 0.74% for MET and ACE. At the same time, reproducibility studies displayed the %RSD of 1.057 and 1.178% for MET and ACE, respectively. Spike recovery experiments were carried out to assess the performance of MSPE in real samples, and over 88% of both analytes were recovered. This indicated that the MSPE method could enrich various organic pollutants from different environmental matrices.

Customized carbon dots as a fluorescent sensor for detecting paraquat through enhanced excited state binding energy

A novel fluorescent sensor utilizing customized carbon dots (CDs) has been developed for the rapid and efficient detection of the herbicide paraquat. The 4,4′-diamino-2,2′-stilbenedisulfonic acid (DSD acid) functionalized CDs (DSD-CDs) were synthesized by a hydrothermal method using citric acid and L-cysteine as precursors, followed by amidation with DSD acid. The resultant DSD-CDs exhibited bright blue fluorescence upon UV excitation. The fluorescence of the functionalized carbon dots was effectively quenched by paraquat, following a static quenching mechanism as confirmed by fluorescence lifetime measurements. Interestingly, the mechanism study revealed that the excited-state of the DSD-CDs could interact effectively with paraquat, resulting in stronger fluorescence quenching compared to the ground-state. The sensor showed high sensitivity, selectivity, and stability, with a wide linear range of 0.01 ∼ 2 mg/L (R2 = 0.997) and a low detection limit of 0.003 mg/L. The developed fluorescent sensor demonstrated exceptional potential for paraquat detection in actual samples, encompassing blood, urine, soybean, and river water, with recovery rates exceeding 83 % and relative standard deviations (RSD) below 10 %. This underscores its practical utility in environmental protection and clinical testing applications.

Ti3AlC2 MAX Phase Modified Screen-Printed Electrode for the Fabrication of Hydrazine Sensor.

Hydrazine is considered a powerful reducing agent and catalyst, showing diverse applications in agricultural industries, toxic degradation research, and wastewater management. Additionally, hydrazine can trigger some specific reactions when combined with suitable oxidants. Due to its highly polar nature, hydrazine can easily dissolve in alcohol, water, and various other polar solvents. Therefore, it can be extensively utilized in different areas of application and industries such as rocketry and various chemical applications. Despite its beneficial properties, hydrazine is unstable, posing significant risk due to its highly toxic nature. It is extremely hazardous to both human health and the environment. It can cause various illnesses and symptoms such as dizziness, temporary blindness, damage to the central nervous system, and even death when inhaled in sufficient quantities. Therefore, it is highly important to monitor the level of hydrazine to prevent its toxic and hazardous effects on human beings and the environment. In the present study, we discuss the simple fabrication of a disposable cost-effective and eco-friendly hydrazine sensor. We used a screen-printed carbon electrode, i.e., SPCE, as a base for the construction of a hydrazine sensor. The Ti3AlC2 MAX has been used as a suitable and efficient electrode material for the fabrication of disposable hydrazine sensors. We modified the active surface of the SPCE using a drop-casting approach. The resulting Ti3AlC2 MAX modified SPCE (Ti3AlC2@SPCE) has been utilized as an efficient and low-cost hydrazine sensor. Cyclic voltammetry, i.e., CV, and linear sweep voltammetry, viz., LSV, was employed as a sensing technique in this study. The optimization of pH and electrode material loading was conducted. The Ti3AlC2@SPCE exhibited excellent sensing performance toward hydrazine oxidation. A reasonable detection limit (0.01 µM) was achieved for hydrazine sensing. The fabricated sensor also demonstrated a reasonable linear range of 1-50 µM. This work provides the design and fabrication of simple disposable Ti3AlC2@SPCE as a suitable electrode for the determination of hydrazine using LSV technology.

Nitrogen and Chlorine Co-Doped Carbon Dots with Yellow-Green Emission as a Ratiometric Fluorescent and Colorimetric Dual-Signal Probe for Quercetin Detection and Cell Imaging

Despite the emergence of numerous carbon dots (CDs)-based sensors, most of them are fluorescent probes. To improve the reliability of the results, using ratiometric fluorescence/UV-vis absorption dual-signal probes is an effective method. Herein, nitrogen and chlorine co-doped carbon dots (N, Cl-CDs) with yellow-green fluorescence were prepared and used as a dual-function probe for ratiometric fluorescence/UV-vis. The detection range of the fluorescence method was 0.05–78[Formula: see text][Formula: see text]M, and the limit of detection (LOD) was 1.2[Formula: see text]nM (3[Formula: see text]/s). For the colorimetric method, the linear range was 0.05–186[Formula: see text][Formula: see text]M with LOD of 10.7[Formula: see text]nM. Importantly, the N, Cl-CDs were successfully used to detect Quercetin (QT) in actual water samples. Besides, due to their good biocompatibility, the N, Cl-CDs were applied to in vivo biological imaging of oocysts and shown the potential for environmental survey and biological assay.

Development of a time-resolved immunochromatographic test strip for rapid and quantitative determination of retinol-binding protein 4 in urine.

Urine retinol-binding protein 4 (RBP4) has recently been reported as a novel earlier biomarker of chronic kidney disease (CKD) which is a global public health problem with high morbidity and mortality. Accurate and rapid detection of urine RBP4 is essential for early monitor of impaired kidney function and prevention of CKD progression. In the present study, we developed a time-resolved fluorescence immunochromatographic test strip (TRFIS) for the quantitative and rapid detection of urine RBP4. This TRFIS possessed excellent linearity ranging from 0.024 to 12.50 ng/mL for the detection of urine RBP4, and displayed a good linearity (Y = 239,581 × X + 617,238, R2 = 0.9902), with the lowest visual detection limit of 0.049 ng/mL. This TRFIS allows for quantitative detection of urine RBP4 within 15min and shows high specificity. The intra-batch coefficient of variation (CV) and the inter-batch CV were both < 8%, respectively. Additionally, this TRFIS was applied to detect RBP4 in the urine samples from healthy donors and patients with CKD, and the results of TRFIS could efficiently discern the patients with CKD from the healthy donors. Thedeveloped TRFIS has the characteristics of high sensitivity, high accuracy, and a wide linear range, and is suitable for rapid and quantitative determination of urine RBP4.

Design, fabrication, and evaluation of a novel highly sensitive tuning fork pressure sensor for precise liquid level measurement

This article investigates the under-explored potential of utilizing a thin stainless-steel diaphragm coupled with a quartz tuning fork sensor for liquid depth measurements. The focus is on monitoring molten salt fluid levels in nuclear reactors and concentrated solar power systems. Addressing a literature gap, the research explores cantilever-type configurations of a double-ended quartz tuning fork resonator, with a no-load resonance frequency of 17.37 kHz, on thin stainless-steel diaphragms for fluid depth measurement at room temperature. As the fluid depth increases, hydro-static pressure acting on a 20 μm diaphragm causes deflection, bending a tuning fork. The resulting change in resonance frequency correlates with fluid depth. Experimental setups assess the tuning fork’s sensitivity to strain and bending, revealing strain sensitivity of 7.83 Hz/μ strain (450.78 ppm/μ strain) and bending sensitivity of 0.09 Hz/μm (5.18 ppm/μm). The pressure sensor assembly, tested in a water tank, exhibits a sensitivity of −0.28 Hz/mm (−16.12 ppm/mm) in a single cantilever-type configuration. Despite a limited linear range, it effectively measures water depth changes as small as 0.7 mm. Exploring a double cantilever-type configuration yields a sensitivity of 0.07 Hz/mm (4.03 ppm/mm) with a broader linear range. The article discusses the reasons for opposite sensitivity and highlights the advantages of each configuration. Beyond molten salt level monitoring, the technology’s applications may extend to fluid depth and pressure measurements in industrial and domestic settings.

Synthesis of AgInS2 quantum dots for metronidazole detection in eggs using a fluorescence-quenched probe

Metronidazole (MNZ) is a type of nitroimidazole antibiotic widely used in livestock feed. The extensive use, overuse, and misuse of MNZ have resulted in high levels of MNZ residues in animal products, posing serious health risks to people. Based on the effective fluorescence quenching capability of MNZ, a highly precise technique characterized by low-cost materials, low detection limit, and simple operational procedure was established to detect MNZ in eggs by modulating the fluorescence produced by AgInS2 quantum dots (AIS QDs). The performance of the prepared sample was outstanding as the linear range was 0.25–80.00 μg/mL with a detection limit (LOD) of 0.166 μg/mL and R2 = 0.9996, having an average recovery of MNZ in egg white ranged from 94.88 % to 102.39 %. This detection method has the advantages of a wide detection range, high sensitivity, high accuracy, excellent selectivity, and simple operability, and it can be used to detect MNZ in eggs after further study. The fluorescence quenching mechanism of AIS QDs by MNZ is speculated as a dynamic quenching mechanism of light-induced electron transfer.

Molecularly Imprinted Polymer Biosensor Based on Nitrogen-Doped Electrochemically Exfoliated Graphene/Ti3 CNTX MXene Nanocomposite for Metabolites Detection.

Rapid and accurate quantification of metabolites in different bodily fluids is crucial for a precise health evaluation. However, conventional metabolite sensing methods, confined to centralized laboratory settings, suffer from time-consuming processes, complex procedures, and costly instrumentation. Introducing the MXene/nitrogen-doped electrochemically exfoliated graphene (MXene@N-EEG) nanocomposite as a novel biosensing platform in this work addresses the challenges associated with conventional methods, leveraging the concept of molecularly imprinted polymers (MIP) enables the highly sensitive, specific, and reliable detection of metabolites. To validate our biosensing technology, we utilize agmatine as a significant biologically active metabolite. The MIP biosensor incorporates electrodeposited Prussian blue nanoparticles as a redox probe, facilitating the direct electrical signaling of agmatine binding in the polymeric matrix. The MXene@N-EEG nanocomposite, with excellent metal conductivity and a large electroactive specific surface area, effectively stabilizes the electrodeposited Prussian blue nanoparticles. Furthermore, increasing the content of agmatine-imprinted cavities on the electrode enhances the sensitivity of the MIP biosensor. Evaluation of the designed MIP biosensor in buffer solution and plasma samples reveals a wide linear concentration range of 1.0 nM-100.0 μM (R2 = 0.9934) and a detection limit of 0.1 nM. Notably, the developed microfluidic biosensor offers low cost, rapid response time to the target molecule (10 min of sample incubation), good recovery results for detecting agmatine in plasma samples, and acceptable autonomous performance for on-chip detection. Moreover, its high reliability and sensitivity position this MIP-based biosensor as a promising candidate for miniaturized microfluidic devices with the potential for scalable production for point-of-care applications.

A novel fluorescence sensor based on Al3+-mediated aggregation of gold nanoclusters for determination of citric acid in beverages.

This paper revealed a new strategy for citric acid (CA) detection using aggregation-induced emission (AIE)-based fluorescent gold nanoclusters (AuNCs). AuNCs was synthesized using glutathione (GSH) as the template and reducing agent and used as the fluorescent probe to detect CA under aluminum ion (Al3+) mediation. The fluorescence intensity of AuNCs increased about 4 times with the addition of Al3+, but the enhanced fluorescence was quenched after the addition of CA. Based on this fluorescence phenomenon, an "on-off" fluorescence strategy was designed for the sensitive determination of CA and a linear detection range for CA was achieved within 0-80.0 μM. In addition, the developed probe exhibited high selectivity and accuracy for determination of CA. The mechanism of fluorescence enhancement and quenching of AuNCs was explored in detail. The established probe was used successfully for CA detection in beverages. The spiked recoveries from 97.50% to 103.67% were gratifying, which indicated the probe had potential prospects for detecting CA in food.

Development of a quantification method for arginase inhibitors by LC-MS/MS with benzoyl chloride derivatization

Arginase is an enzyme responsible for converting arginine, a semi-essential amino acid, to ornithine and urea. Arginine depletion suppresses immunity via multiple mechanisms including inhibition of T-cell and NK cell proliferation and activity. Arginase inhibition is therefore an attractive mechanism to potentially reverse immune suppression and thus has been explored as a therapy for oncology and respiratory indications. Small molecules targeting arginase present significant bioanalytical challenges for in vitro and in vivo characterization as inhibitors of arginase are typically hydrophilic in nature. The resulting low or negative LogD characteristics are incompatible with common analytical methods such as RP-ESI-MS/MS. Accordingly, a sensitive, high-throughput bioanalytical method was developed by incorporating benzoyl chloride derivatization to increase the hydrophobic characteristics of these polar analytes. Samples were separated by reversed phase chromatography on a Waters XBridge BEH C18 3.5 μm, 30 × 3 mm column using gradient elution. The mass spec was operated in positive mode using electrospray ionization. The m/z 434.1→176.1, 439.4→181.2, 334.9→150.0 and 339.9→150.0 for AZD0011, AZD0011 IS, AZD0011-PL and AZD0011-PL IS respectively were used for quantitation. The linear calibration range of the assay was 1.00–10,000 ng/mL with QC values of 5, 50 and 500 ng/mL. The qualified method presented herein exhibits a novel, robust analytical performance and was successfully applied to evaluate the in vivo ADME properties of boronic acid-based arginase inhibitor prodrug AZD0011 and its active payload AZD0011-PL.

Green Surfactant Assisted-Solidified Floating Organic Drop Micro-Extraction (SA-SFODME) for the Preconcentration of Trace Lead with Determination by Flame Atomic Absorption Spectrometry (FAAS)

Determination of trace lead from environmental samples was carried out by solidified floating organic drop microextraction for preconcentration before analysis by flame atomic absorption spectrometry. The determination of lead from environmental samples, even at trace levels, was possible with an ordinary flame atomic absorption spectrometer (FAAS). The lead formed a hydrophobic complex with the anionic surfactant sodium dodecyl benzene sulfonate (SDBS), and this hydrophobic complex was extracted into the 1-dodecanol drop. Parameters affecting analytical performance have been studied. The optimum pH value was 3.5. The optimum sample volume, SDBS concentration, and extraction solvent volume were 75 mL, 50 mM in dodecanol, and 75 µL, respectively. The optimum extraction time was determined as 30 min, the optimum extraction temperature was 45 °C, the optimum mixing speed was 650 rpm and the ideal extraction phase volume was 0.50 mL. Methanol has been shown to be effective when used as a diluent. Using the optimum conditions, the enhancement factor was 106, and the limit of detection (3s) and precision were 3.3 ng/mL and 2.3% (n = 9,15 ng/mL), respectively. The limit of quantification (LOQ) (10s) was 10 ng/mL and the linear working range was 15-100 ng/mL. The accuracy was evaluated by certified reference material analysis. The optimized method was applied to the determination of Pb(II) from environmental water samples. This method follows the principles of green analytical chemistry.

A novel potentiometric screen-printed electrode based on crown ethers/nano manganese oxide/Nafion composite for trace level determination of copper ion in biological fluids.

Copper levels in biological fluids are associated with Wilson's, Alzheimer's, Menke's, and Parkinson's diseases, making them good biochemical markers for these diseases. This study introduces a miniaturized screen-printed electrode (SPE) for the potentiometric determination of copper(II) in some biological fluids. Manganese(III) oxide nanoparticles (Mn2O3-NPs), dispersed in Nafion, are drop-casted onto a graphite/PET substrate, serving as the ion-to-electron transducer material. The solid-contact material is then covered by a selective polyvinyl chloride (PVC) membrane incorporated with 18-crown-6 as a neutral ion carrier for the selective determination of copper(II) ions. The proposed electrode exhibits a Nernstian response with a slope of 30.2 ± 0.3mV/decade (R2 = 0.999) over the linear concentration range 5.2 × 10-9 - 6.2 × 10-3mol/l and a detection limit of 1.1 × 10-9mol/l (69.9ng/l). Short-term potential stability is evaluated using constant current chronopotentiometry (CP) and electrochemical impedance spectroscopy (EIS). A significant improvement in the electrode capacitance (91.5 μF) is displayed due to the use of Mn2O3-NPs as a solid contact. The presence of Nafion, with its high hydrophobicity properties, eliminates the formation of the thin water layer, facilitating the ion-to-electron transduction between the sensing membrane and the conducting substrate. Additionally, it enhances the adhesion of the polymeric sensing membrane to the solid-contact material, preventing membrane delamination and increasingthe electrode's lifespan. The high selectivity, sensitivity, and potential stability of the proposed miniaturized electrode suggests its use for the determination of copper(II) ions in human blood serum and milk samples. The results obtained agree fairly well with data obtained by flameless atomic absorption spectrometry.

A novel low oxidation potential hydroxyurea sensor utilizing flower-shaped Zn and N co-doped porous carbon coupled with graphene oxide via one-step electrodeposition

Accurate monitoring of hydroxyurea (HU) dosage is imperative in the administration of anticancer drugs. Existing determination methods face challenges such as operational complexity, low sensitivity, or high oxidation potentials. In this study, a novel HU electrochemical sensor (Zn/N-PC/GO/GCE) was synthesized using flower-shaped Zn/N co-doped porous carbon (Zn/N-PC) with graphene oxide (GO) through a one-step electrodeposition. The sensor features a distinctive three-step oxidation process for HU with a low oxidation potential, attributed to an electrochemical activation electrode strategy and crucial Zn/N co-doping in Zn/N-PC. Three electrons involved oxidation process of HU and Zn/N-PC/GO adsorption energy through transferred electrons and density functional theory (DFT). Under optimized conditions, the sensor demonstrated a broad linear detection range (1–1000 μM) and an impressive limit of detection (LOD) of 0.52 μM. Applicability was confirmed by analyzing HU in tablet formulations, urine and serum samples. This study presents an innovative electrochemical method for accurate HU monitoring, elucidating a potential three-step oxidation mechanism.

RuSe2/CuO nanohybrids coupled with ALP-assisted for MMP-9 photoelectrochemical assay

A photoelectrochemical (PEC) assay strategy for the detection of matrix metalloproteinase-9 (MMP-9) was fabricated. RuSe2/CuO nanohybrids were first prepared by hydrothermal method. As a transition metal element semiconductor, RuSe2 has excellent optical and electrical properties. By combining the excellent conductivity and adjustable bandgap of CuO, a binary heterojunction nanoflower with high photoelectric response was obtained. The combination of RuSe2 and CuO reduces the electron hole recombination rate; the RuSe2/CuO nanohybrids exhibits a higher photocurrent response. In the MMP-9 PEC strategy determination, the magnetic beads (MB)-peptide-alkaline phosphatase (ALP) recognition probe was formed by modifying C-terminal of the peptide chain with biotin and binding to ALP, and the N-terminal was connected to carboxylated MB. When the target MMP-9 exists, the recognition probe, MB-Peptide-ALP, was recognized by MMP-9 to cut the substrate area and coding area and release ALP, catalyzing the hydrolysis of O-phosphonoxyphenol (OPP) to produce benzene-1,2-diol in situ, the photocurrent response was generated. This strategy provides lower background PEC noise for detecting MMP-9, with the advantage of simplicity and the sensitivity than conventional ELISA. The results showed that the recognition peptide probe PEC method achieved ultra-high sensitivity detection of target MMP-9, with a linear detection range of 1 pg/mL–100 ng/mL and a detection limit of 0.3 pg/mL (S/N = 3). The results of PEC assay strategy in human serum sample give the recoveries rate of 94.3 % to 108.1 % and relative standard deviation of 0.45–5.87 %.

A novel electrochemical aptasensor based on AgPdNPs/PEI-GO and hollow nanobox-like Pt@Ni-CoHNBs for procymidone detection

Herein, an aptasensor based on a signal amplification strategy was developed for the sensitive detection of procymidone (PCM). AgPd nanoparticles/Polenimine Graphite oxide (AgPdNPs/PEI-GO) was weaned as electrode modification material to facilitate electron transport and increase the active sites on the electrode surface. Besides, Pt@Ni-Co nanoboxes (Pt@Ni-CoHNBs) were utilized to be carriers for signaling tags, after hollowing ZIF-67 and growing Pt, the resulting Pt@Ni-CoHNBs has a tremendous amounts of folds occurred on the surface, enables it to carry a larger quantity of thionine, thus amplify the detectable electrochemical signal. In the presence of PCM, the binding of PCM to the signal probe would trigger a change in electrical signal. The aptasensor was demonstrated with excellent sensitivity and a low detection limit of 0.98 pg·mL−1, along with a wide linear range of 1 μg·mL−1 to 1 pg·mL−1. Meanwhile, the specificity, stability and reproducibility of the constructed aptasensor were proved to be satisfactory.

A Novel Hollow Graphene/Polydimethylsiloxane Composite for Pressure Sensors with High Sensitivity and Superhydrophobicity.

Flexible pressure sensors have attracted great interest as they play an important role in various fields such as health monitoring and human-machine interactions. The design of the pressure sensors still faces challenges in achieving a high sensitivity for a wide sensing range, and the interference of water restricts the applications of the sensors. Herein, we developed a graphene-polydimethylsiloxane film combining a hierarchical surface with nanowrinkles on it and a hollow structure. The microstructure design of the composite can be facilely controlled to improve the sensing and hydrophobic performance by tailoring the microsphere building units. Attributed to the irregular surface and hollow structure of the sensing layer, the optimized sensor exhibits a superior sensitivity of 1085 kPa-1 in a 50 kPa linear range. For practical applications, the nanowrinkles on the surface of the microspheres and the polymer coating endow the composite with waterproof properties. Inspired by the dual receptors of the skin, two designed microstructured films can simply integrate into one with double-sided microstructures. The sensing performance and the water-repellence property allow the sensor to detect physiological signals under both ambient and underwater conditions. Furthermore, underwater stimuli detection and communication are demonstrated. This method of fabricating a flexible sensor shows great potential in wearable and robotic fields.

Preparation of a Molecularly Imprinted Polymer on Polyethylene Terephthalate Platform Using Reversible Addition-Fragmentation Chain Transfer Polymerization for Tartrazine Analysis via Smartphone.

This work describes the preparation of a molecularly imprinted polymer (MIP) platform on polyethylene terephthalate (MIP-PET) via RAFT polymerization for analyzing tartrazine using a smartphone. The MIP-PET platform was characterized using Fourier transform infrared (FTIR) techniques, Raman Spectroscopy, X-ray photoelectron spectroscopy (XPS), and confocal microscopy. The optimal pH and adsorption time conditions were determined. The adsorption capacity of the MIP-PET plates with RAFT treatment (0.057 mg cm-2) was higher than that of the untreated plates (0.028 mg cm-2). The kinetic study revealed a pseudo-first-order model with intraparticle diffusion, while the isotherm study indicated a fit for the Freundlich model. Additionally, the MIP-PET demonstrated durability by maintaining its adsorption capacity over five cycles of reuse without significant loss. To quantify tartrazine, images were captured using a smartphone, and the RGB values were obtained using the ImageJ® free program. A partial least squares regression (PLS) was performed, obtaining a linear range of 0 to 7 mg L-1 of tartrazine. The accuracy of the method was 99.4% (4.97 ± 0.74 mg L-1) for 10 samples of 5 mg L-1. The concentration of tartrazine was determined in two local soft drinks (14.1 mg L-1 and 16.5 mg L-1), with results comparable to the UV-visible spectrophotometric method.

Gold nanodendrites enriched with gold nanoclusters on carbon-fiber as flexible acetaminophen sensor for clinical diagnostics

In this work, we demonstrate a flexible acetaminophen (APAP) microsensor based on gold dendrites decorated with gold nanoclusters on flexible carbon fiber (AuDS-AuNC|FCF) microelectrodes. The AuDS-AuNC|FCF microelectrodes are fabricated with a facile and single-step electrochemical strategy for electrocatalytic oxidation and sensing acetaminophen in a 0.1 M phosphate buffer (PB) (pH ∼7.4) solution. The as-developed AuDS-AuNC|FCF microsensors demonstrate excellent electrocatalytic oxidation of acetaminophen with a low oxidation potential of ∼0.54 V (vs. Ag/AgCl) and high catalytic current of ∼1.33 μA. This is because they have a lot of active sites, a large quantity of electrochemical active surface area (ECSA), and gold nanoclusters that are spread out homogeneously. The AuDS-AuNC|FCF microsensors exhibit fast sensing response time of ∼5.0 s, low experimental detection limit of ∼5.0 nM, high sensitivity of ∼0.375 ± 0.017 mA μM−1 cm−2 with a broad linear range of 5.0 nm–500.0 mM, good reproducibility, and possessed a robust anti-interference ability against sensing acetaminophen in the presence of potential interferences such as ascorbic acid, uric acid, adenine, guanine, glucose, etc. Notably, the present microsensor platform based on AuDS-AuNC|FCF microelectrodes is successfully tested for sensing acetaminophen in practical human serum samples, demonstrating its practicability in clinical diagnostics.

Hydrazone-linked covalent organic framework functionalized with cysteine as a fluorescence sensor and Exploration of paper chip for p-nitrophenol detection

The large use and emission of p-nitrophenol (p-NP) seriously pollute the environment and endanger human health. In this work, a hydrazone-linked fluorescent covalent organic framework (BATHz-COF) was simply synthesized at room temperature and covalently linked N-acetyl-L-cysteine (NALC) via the "thiol-ene" click reaction, where carboxyl groups were introduced to improve dispersion and fluorescence intensity. As a rapid, good selectivity and reusability fluorescence sensor, the obtained COF-NALC has been used for quantitative analysis of p-NP predicated on the internal filtering effect (IFE). Under optimal conditions, COF-NALC enabled quantitative detection of p-NP with a linear range of 5–50 μM and the detection limit was 1.46 μM. The application of COF-NALC to the detection of p-NP in river water samples was successful, and the satisfactory recoveries were 98.0%–109.3%. Furthermore, the fluorescent COF paper chips constructed by in situ growth were combined with a smartphone to build a visual platform for the quick and real-time detection of p-NP, providing an excellent illustration for the development of intelligent fluorescence sensing in environmental analysis.