Detection In Aqueous Solution Research Articles

Non-invasive paper-based sensors containing rare-earth-doped nanoparticles for the detection of D-glucose

Today, diabetes mellitus is one of the most common diseases that affects the population on a worldwide scale. Patients suffering from this disease are required to control their blood-glucose levels several times a day through invasive methods such as piercing their fingers. Our NaGdF4: 5% Er3+, 3% Nd3+ nanoparticles demonstrate a remarkable ability to detect D-glucose levels by analysing alterations in their red-to-green ratio, since this sensitivity arises from the interaction between the nanoparticles and the OH groups present in the D-glucose molecules, resulting in discernible changes in the emission of the green and red bands. These luminescent sensors were implemented and tested on paper substrates, offering a portable, low-cost and enzyme-free solution for D-glucose detection in aqueous solutions with a limit of detection of 22 mg/dL. With this, our study contributes to the development of non-invasive D-glucose sensors, holding promising implications for managing diabetes and improving overall patient well-being with possible future applications in D-glucose sensing through tear fluid.

Fluorescence ‘Turn-on’ Probe for Chromium Reduction, Adsorption and Detection Based on Cellulosic Nitrogen-Doped Carbon Quantum Dots Hydrogels

This paper proposes a new, highly effective fluorescence test for Cr(VI) detection. This method utilizes a hydrogel composed of hydroxyethyl cellulose (HEC), nitrogen-doped carbon quantum dots (N–CQDs), and poly(co-acrylamido-2-methyl-1-propane sulfonic acid) (AMPS). The N–CQDs were successfully synthesized using a simple microwave method, and then conjugated with HEC and AMPS. The higher adsorption (99.41%) and higher reduction rate in H1 likely stems from both the presence of N–CQDs (absent in HB) and their increased free functional groups (compared to H2/H3, where N–CQDs block them). This facilitates the release (desorption) of Cr(VI) from the hydrogels, making it more available for reduction to the less toxic Cr(III). The fluorescent brightness of the HEC-N–CQDs-g-poly(AMPS) hydrogel increases gradually when Cr(VI) is added in amounts ranging from 15 to 120 mg/L. The fluorescent enhancement of the HEC-N–CQDs-g-poly(AMPS) hydrogel appeared to exhibit a good linear relationship with the 15–120 mg of the Cr(VI) concentration, with a detection limit of 0.0053 mg/L, which is lower than the standard value published by WHO. Our study found that the HEC-N–CQDs-g-poly(AMPS) hydrogel served effectively as a fluorescent probe for Cr(VI) detection in aqueous solutions, demonstrating high sensitivity.

Trace detection of cadmium (II) ions based on an excessively tilted fiber grating

Cadmium (Cd2+) ion is one of the most crucial industrial pollutants that cause serious harm to the human body. We proposed and experimentally demonstrated a highly sensitive Cd2+ sensor based on hydrogel coated excessively tilted fiber grating. The hydrogel with the functional monomer of the allyl thiourea can specifically bind to Cd2+, and hence forming a complex. The grating excites high order cladding modes, and ensures a sufficient interaction between the light and hydrogel binding to Cd2+, providing highly sensitive monitoring. The results show that the sensor can detect 0-160 pM Cd2+ in aqueous solution. The maximum sensitivity is 10600 nm/µM, and the minimum detection concentration is 20 pM (about 0.004 ppb), which is much less than that of the international standard (3 ppb). The proposed sensor exhibits high sensitivity, ultra-low detection limit, specificity, and a compact structure, offering potential as a tool for Cd2+ detection in aqueous solution.

Pyrene-Based "Turn-On" Fluorescent Polymeric Probe with Thioacetal Units in the Main Chain for Mercury(II) Detection in Aqueous Solutions and Living Cells.

A water-soluble polymeric pyrene-based polythioacetal (PTA-Py) with thioacetal units in the main chain is simply synthesized by direct polycondensation of 3, 6-dioxa-1, 8-octanedithiol, 1-pyrene formaldehyde, and mPEG2k-SH. The probe PTA-Py shows a good fluorescence response to Hg2+ ions due to the Hg2+-promoted deprotection reaction of thioacetal groups to regenerate the original 1-pyrene formaldehyde compound. After adding Hg2+ to the PTA-Py solution, the fluorescence intensity (FI) gradually increases with increasing concentrations of Hg2+. Compared with other metal ions, the probe exhibits high sensitivity, good selectivity, and rapid response to Hg2+. The low detection limits are 12.3nm in ethanol-PBS buffer and 13.3nm in water, respectively. The results imply that the simply synthesized water-soluble polymeric probehad potential applications in the rapid detection of Hg2+ ions in aqueous solutions. Moreover, the polymeric PTA-Py shows high sensitivity for CH3Hg+ with detection limits of 26.5nm in ethanol/PBS buffer. In addition, PTA-Py can efficiently detect Hg2+ ions in HeLa cells. The results demonstrate that a valuable method is developed for biocompatible polymeric sensors for Hg2+ ions in biological and environmental samples.

Reticular chemistry guided precise construction of zirconium-pentacarboxylate frameworks with 5-connected Zr6 clusters.

Zirconium-based metal-organic frameworks (Zr-MOFs) have been extensively studied due to their very rich structural chemistry. The combination of nearly unlimited carboxylic acid-based linkers and Zr6 clusters with multiple connectivities has led to diverse structures and specific properties of resultant Zr-MOFs. Herein, we demonstrate the successful use of reticular chemistry to construct two novel Zr-MOFs, HIAM-4040 and HIAM-4040-OH, with zfu topology. Based on a thorough structural analysis of (4,4)-connected lvt-type Zr-tetracarboxylate frameworks and a judicious linker design, we have obtained the first example of a Zr-pentacarboxylate framework featuring unprecedented 5-connected organic linkers and 5-connected Zr6 clusters. Compared with HIAM-4040, a larger Stokes shift is achieved in HIAM-4040-OH via hydroxyl group induced excited-state intramolecular proton transfer (ESIPT). HIAM-4040-OH exhibits high chemical and thermal stability and is used for HClO detection in aqueous solution with excellent sensitivity and selectivity.

Enhancement of integrated nano-sensor performance comprised of electrospun PANI/carbonaceous material fibers for phenolic detection in aqueous solutions

The detection of trace levels of organic residue in water samples is a key health issue. This manuscript describes the fabrication of integrated nano-sensors composed of electrospun microfibers consisting of a nanocomposite of carbonaceous materials (CNMs) containing polyaniline (PANI) and polycaprolactone (PCL) for phenolic detection in aqueous solutions. The morphology of the resulting microfiber composite was characterized by scanning electron microscopy. It revealed elongated fibers with a highly interconnected web-like pattern in the presence of reduced graphene oxide (rGO). Shorter microfibers were observed in the composite filled with multi-walled carbon nanotubes (MWCNTs), whereas large agglomerates were formed upon the incorporation of single-walled CNTs (SWCNTs) and graphene 300 (G300). Comparative analysis showed that the PANI/CNM sensors exhibited the best electrochemical properties, in particular in the presence of rGO and MWCNTs, where greater electrical conductivity was achieved, i.e., 4.33 × 10−3 and 7.22 × 10−4 S/cm, respectively, as compared to the PANI-PCL sensor (3.79 × 10−4 S/cm). All the PANI/CNM sensors exhibited high sensitivity. Notably, PANI/rGO was found to have a detection limit of 8.34 × 10−3 µM for aminophenol. All the sensors exhibited good selectivity in the presence of interference to detecting phenolic compounds in aqueous solutions, thus confirming their value for industrial applications.

Coumarin-hydrazone-based fluorescence sensor for Al(III) detection in aqueous solution: DFT calculation and DNA interaction studies

A new 'turn on' fluorescence chemosensor derived from coumarin-based compounds was successfully synthesised. N'-(2-Oxo-2H-chromene-3-carbonyl)isonicotinohydrazide (H2L) was characterised by different spectroscopic techniques such as IR, UV-vis, and NMR spectroscopy. The electronic structures of H2L and Al@HL were calculated using the density functional theory method using Becke’s three parameter Lee-Yang-Parr (B3LYP) exchange functional with the 6-31G+(d,p) basis set. The detection limit of H2L for the Al (III) ion was found to be 2.6 µM, which is low enough to detect micromolar and is below the World Health Organisation guideline for drinking water.

Highly Sensitive Detection of Formaldehyde by Laser-Induced Graphene-Coated Silver Nanoparticles Electrochemical Sensing Electrodes.

Formaldehyde (HCHO) poses a grave threat to human health because of its toxicity, but its accurate, sensitive, and rapid detection in aqueous solutions remains a major challenge. This study proposes a novel electrochemical sensor composed of a graphene-based electrode that is prepared via laser induction technology. The precursor material, polyimide, is modified via the metal ion exchange method, and the detective electrode is coated with graphene and silver nanoparticles. And the special structure of graphene-coated Ag was demonstrated using scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and X-ray photoelectron spectroscopy (XPS) results show that graphene provides more sites for Ag NRs to be exposed and increases the surface area of contact between the solution and the detection object. In addition, differential pulse voltammetry (DPV) analysis exhibits high linearity over the HCHO concentration range from 0.05 to 5 μg/mL, with a detection limit of 0.011 μg/mL (S/N = 3). The Ag NPs in the electrochemical reaction will adsorb the intermediate •CO and •OH, catalyze their combination, and finally convert to CO2 and H2O, respectively. A microdetection device, specially designed for use with commercial micro-workstations, is employed to fully demonstrate the practical application of the electrode, which paves a way for developing formaldehyde electrochemical sensors.

Reversible and Turn-On Fluorescence Detection of Phosphate in Aqueous Solution and Living Cell Imaging by Supramolecular Metallacycles with AIE-Active Ligands.

Luminescent supramolecular metallacycles have attracted great interest as a new promising class of sensing substrates. In this work, two tetraphenylethene (TPE)-based diimidazole and dipyrazole ligands with the aggregation-induced emission (AIE) feature were designed for the construction of supramolecular tetragonal metallacycles 1-4 with two 90° mononuclear [(bpy)M]2+ or dinuclear [(bpy)2M2]4+ acceptors (bpy = 2,2'-dipyridine; M = Pd, Pt), in which the fluorescence can be quenched to an "off" state due to the ligand-to-metal charge transfer (LMCT). Metallacycle 1 was utilized as a fluorescence sensor for phosphate (PO43-) detection in aqueous solution by means of disassembly, leading to the release of the ligand. Additionally, the metallacycle can be regenerated through self-assembly via the introduction of Pd(II) acceptors. PO43- was detected using TPE-based metallacycles over a wide concentration range, with a detection limit as low as 2.1 × 10-8 M. Furthermore, sensor 1 also presented the semiquantitative visual detection ability for PO43- in the test paper mode via fluorescence changes. The aforementioned studies not only enhance the current research on fluorescent materials but also offer a strategy for the creation of stimuli-responsive supramolecular coordination complexes.

Highly sensitive fiber optic sensor based on chitosan/α-Fe2O3 for trace copper(II) ion detection

Instrument methods are essential for simple and rapid detection of copper(II) (Cu2+) in drinking water and healthcare. However, these methods suffer from complex sample pretreatment and long detection time. This paper proposed a highly sensitive fiber optic sensor for trace Cu2+ detection in aqueous solutions. Based on the principle of modal interference, by surface functionalization, a uniform chitosan (CS)/α-Fe2O3 nanocomposite material was coated on a structure of no-core fiber–multimode fiber–no-core fiber (NCF1-MMF-NCF2). The amino and hydroxyl groups in the material have a specific recognition function for Cu2+, which can chelate with Cu2+ and change the refractive index of the material, leading to the shift of interference spectrum. Trace Cu2+ detection can be achieved by monitoring the displacement of the interference spectrum. The results revealed that within the range of 0–1 μM Cu2+ concentrations, with increasing Cu2+ concentration, the interference spectrum underwent a red shift and the maximum detection sensitivity of Cu2+ ions reached 456.69 nm/μM, with a good linearity of 0.989. Also, the sensor has the advantages of high stability, good repeatability, simple fabrication, and low cost.

Design of DMAP functionalized MoS2-GO hybrid for targeted visual detection of dopamine: a step towards chromogenic substrate free point of care testing

Abnormal release of DA, a crucial neurotransmitter, can cause serious neurological disorders such as Parkinson's and Alzheimer's disease. Thus, sensitive DA detection becomes critical for the investigation of physiological functions and disease diagnosis. Specific DA quantification in real samples is a tedious task due to the presence of analogous neurotransmitters. Therefore, aiming at on-site selective monitoring of DA, a high-performance colorimetric probe has been designed using a DMAP-modified MoS2-GO hybrid for highly selective visual detection of DA, especially for POC testing. The efficient DA recognition can be attributed to the large surface area with potentially active sites for greater electron transport and oxidation ability owing to the synergistic effect of MoS2 and GO. The hybrid has been modified with DMAP, which allows extremely selective and specific DA recognition against potential interferents, especially other neurotransmitters. The proposed mechanism relies on the attachment of DA to the hybrid surface, facilitating the oxidation and complexation processes that induce aggregation causing instant color change. The designed colorimetric method can recognize DA in neutral medium at room temperature without any reagents or supplementary operations. A good linear relationship was observed between the absorbance of the hybrid and DA concentrations in the range 1–100 μM, with a low detection limit of 0.17 μM. Furthermore, the applicability of the present approach was also verified by the analysis of DA in human serum samples and proved to be promising for sequential DA detection in biological samples with good precision and accuracy. From a POC perspective, easy-to-use paper-based test strips were prepared for visual recognition of DA in just 3 min. Results indicate that the designed DA assay provides a powerful, low-cost, convenient, and reagentless colorimetric platform for instant and highly selective DA detection in aqueous solution, strips, and human serum that is predicted to find extended applications in the fields of biosensing, clinical diagnosis, and in-vitro disease monitoring.

Sugar Detection in Aqueous Solution Using an SMS Fiber Device.

We report on the fabrication and testing of a fiber optics sensor based on multimodal interference effects, which aims at the detection of different types of sweeteners dissolved in water. The device, which has a simple structure, commonly known as the SMS configuration, is built by splicing a segment of commercial-grade, coreless multimode fiber (NC-MMF) between two standard single-mode fibers (SMFs). In this configuration, the evanescent field traveling outside the core of the NC-MMF allows the sensing of the refractive index of the surrounding media, making it possible to detect different levels of sugar concentration. The optical sensor was tested with aqueous solutions of glucose, fructose, and sucrose in the concentration range from 0 wt% to 20 wt% at room temperature. The proposed device exhibits a linear response with a sensitivity of 0.1835 nm/wt% for sucrose, 0.1687 nm/wt% for fructose, and 0.1694 nm/wt% for glucose, respectively, with a sensing resolution of around 0.5 wt%. Finally, we show that, despite having similar concentration behavior, some degree of discrimination between the different sugars can be achieved by assessing their thermo-optical response.

Supramolecular fluorescent probe based on a host–guest complex for amino acids recognition and detection in aqueous solution

A supramolecular fluorescent probe based on a host–guest complex has been developed for amino acid recognition and detection in aqueous solution. Cucurbit[7]uril (Q[7]) with 4-(4-dimethylamino-styrene) quinoline (DSQ) formed a fluorescent probe (DSQ@Q[7]). The DSQ@Q[7] fluorescent probe nearly generated changes in fluorescence in response to four amino acids (arginine, histidine, phenylalanine and tryptophan). These changes were attributed to the host–guest interaction between DSQ@Q[7] and amino acids, which occurred as a consequence of the subtle cooperation of ionic dipole and hydrogen bonding. Linear discriminant analysis showed that the fluorescent probe could recognize and distinguish four amino acids, and a mixture with different concentration ratios could be well categorized in ultrapure water and tap water.

A new turn on coumarin-based fluorescence probe for Cr3+ detection in aqueous solution

Isatin-3-(7′-Methoxychromone-3′-methylidene) hydrazone (L) was synthesized based on chromone schiff base, and used to construct a novel sensor to detect Cr3+. Fluorescence detection experiments were carried out for a range of different concentrations of Cr3+ in aqueous solutions. A concentration calculation model was built on the basis of eliminating interference of excitation spectrum in the fluorescence spectra with mathematical method. Results showed that probe L displayed a 70-fold fluorescence enhancement upon the addition of Cr3+ due to the photo-induced electron transfer (PET) effect. On the other hand, metal ions except Cr3+ did not cause significant change in either the absorption or the fluorescence spectrum of L. In addition, L showed a good selectivity to Cr3+ over other metal cations, especially Al3+ and Cu2+. The probe L can detect Cr3+ highly and selectively by the direct chelation enhanced fluorescence with a detection limit of 3.14 × 10−6 M. Furthermore, benefiting from their good water solubility and biocompatibility, cell imaging and real-time monitoring of Cr3+ in living HepG2 cells were successfully achieved.

Versatile sensing capabilities of layer-by-layer deposited polyaniline-reduced graphene oxide composite-based sensors

Precise temperature, humidity, and organic pollutants monitoring are required for industrial, environmental and medical applications. The interesting properties of polyaniline for sensors, such as environmental responsiveness and stability, combined with the large surface area and tunable properties of graphene oxide, offer excellent prospects for the development of sensor materials. In this paper, we show that HCl-doped polyaniline/reduced graphene oxide (PANI/rGO) layer-by-layer deposition and subsequent reduction can be used as resistive sensors for temperature, humidity, acetone, and electrochemical sensors for organophosphate detection in aqueous solutions. Sensors were characterized using atomic force and scanning electron microscopies and energy-dispersive x-ray and Raman spectroscopies, and impedance spectroscopy complemented by semi-empirical quantum chemical calculations. Reduction temperature and bilayer numbers influence PANI/rGO sensor characteristics significantly. The results show that only one PANI/rGO bilayer is needed to provide a temperature coefficient of resistance of − 0.758 °C−1 and 37% sensitivity at 95% relative humidity. PANI/rGO shows potential for electrochemical detection of dimethoate affected by the number of bilayers and reduction temperature. The response to acetone vapor is linear from 1 to 60 ppm and detectable at 1 ppm. The sensors do not respond to methanol and some other volatile organic compounds (VOCs) at the same concentration. Food monitoring with total VOCs detection was successfully demonstrated. PANI/rGO sensors feature versatile sensing capabilities, making them feasible due to their rapid production and low cost.

Spectrophotometric and colorimetric trivalent chromium ions detection in aqueous solution based on citrate-capped gold nanoparticles

Spectrophotometric and colorimetric trivalent chromium ions detection in aqueous solution based on citrate-capped gold nanoparticles

Synthesis of Nanostructured Mixed-Valence Fe(II,III) Metal-Organic Framework and Its Application in Electrochemical Sensing of Amoxicillin

The study reports the development of a nanostructured mixed-valence Fe(II)Fe(III)BTC metal-organic framework (BTC = 1, 3, 5-benzenetricarboxylate) modified carbon paste electrode as a novel sensor for the amoxicillin detection in aqueous solutions using square wave voltammetry. The physicochemical properties of FeBTC were characterized using X-ray diffraction spectroscopy, Fourier-transform infrared spectroscopy, Brunauer–Emmett–Teller analysis, electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy. These techniques revealed that FeBTC has a surface area of 1211 m2 g−1, a total pore volume of 1.46 cm3 g−1, particle sizes ranging from 10 to 20 nm, and a mixed-valence structure. Furthermore, SEM, TEM, and energy-dispersive X-ray spectroscopy exhibited the homogeneous distribution of FeBTC throughout the modified electrode. The electrochemical study showed that the mixed-valence FeBTC improved the electron transfer capabilities of the electrode. Under optimal conditions, the modified electrode exhibited a significant increase in peak height compared to the unmodified electrode (4.6 times higher), with an acceptable reproducibility of 4.88% relative standard deviation. The linear range of the sensor was 1–100 μM with a good coefficient of determination of 0.9985, and a detection limit of 0.107 μM. Additionally, the sensor demonstrated excellent performance with the satisfactory recoveries and a good correlation with LC-MS/MS analysis.

Pyranine Immobilized on Aminopropyl-Modified Mesoporous Silica Film for Paraquat Detection

An optical sensor based on pyranine immobilized on aminopropyl-modified mesoporous silica films was developed for paraquat detection in aqueous solutions. An electrochemically assisted self-assembly method was used to deposit mesoporous silica film on fluorine-doped tin oxide glass. The obtained films were modified with various concentrations of 3-aminopropyl triethoxysilane (APTES) before the immobilization of pyranine. Cyclic voltammetry, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and fluorescence spectroscopy were used to characterize the films. Pyranine-immobilized films gave an emission at 506 nm with an excitation at 450 nm. The fluorescence signal was quenched in the presence of paraquat. The films modified with 3% APTES provided the optimum response to paraquat. The developed films had a linear response to paraquat in the concentration range of 1 to 10 ppm at the optimum conditions, with a detection limit of 0.80 ppm. The developed method was used to quantify paraquat in sugarcane peel and tap water samples with satisfactory results.

Ultra-Low Detection of Perfluorooctanoic Acid Using a Novel Plasmonic Sensing Approach Combined with Molecularly Imprinted Polymers

In this work, a novel optical fiber sensor system for ultra-low perfluorooctanoic acid (PFOA) detection in aqueous solutions is proposed. It is based on the connection, in series, of two different plastic optical fiber (POF) platforms: the first is a chemical chip realized by using a D-shaped POF with microholes filled with a specific molecularly imprinted polymer (MIP); the second is a typical surface plasmon resonance (SPR) sensor based on a D-shaped POF. In particular, the MIP-based chemical chip was used to launch the light inside the SPR–POF chip to change the SPR phenomenon by exploiting the PFOA–MIP interaction in the microholes. At first, experimental results were performed in water to demonstrate the applicability of the proposed sensing approach for measuring PFOA (or C8) in a concentration range of 1 ppt to 750 ppt, obtaining an ultra-low limit of detection (LOD) equal to about 0.81 ppt. Then, experimental results were carried out in simulated seawater to implement a complex matrix. The obtained results denoted a slight matrix effect, paving the way for the applicability of the proposed chemical sensing mechanism in several aqueous solutions.

CsPbBr3 nanocrystals as luminescent probe for in situ detection of chloride and iodide ions in water

All-inorganic cesium lead halide (CsPbX3, X = Cl, Br, I) Perovskite nanocrystals (PNCs) are promising new luminescent nanomaterials. However, PNCs are less stable in ambient environments. The fully encapsulated protective layer greatly improves the stability but limits direct contact with substances in the environment, leading to great challenges for luminescent probe applications. We developed a simple approach that hydrogen-bond cross-linking reinforcement to deal with the challenge. Target ACD-PNCs, which use β-CD (β- cyclodextrin) as the ligand with addition of Arginine, were prepared by adding arginine to an ethanol solution of CsPbBr3 stabilized by β-CD. The ACD-PNCs have a luminescence efficiency of 82% and show good stability in external environments including high temperature, humidity, and ethanol–water mixed solvents. It is worth noting that neither arginine nor cyclodextrin alone could have allowed PNCs to perform so well. More interestingly, the hydrogen-bond network permits the passage of chloride and iodide ions. Through the response of luminescence color upon ion exchange, the ACD-PNCs can detect aqueous Cl− and I− with good selectivity and sensitivity. Under optimum conditions, the LOD and % RSD were determined as 3.2*10−6 M and 5.7% for Cl−, 9.0*10−6 M and 6.7% for I−, respectively. To identify halide ions in samples like sweat, saliva, and kelp, conveniently prepared ACD-PNCs test strips were employed. This work provides insights into the design and development of perovskite probes capable of detection in aqueous solution, and also demonstrates the importance of rapidly forming hydrogen-bonding networks when studying such sensing systems.