Chemosensors

As anionic surfactants are used as cleaning agents, they pose an environmental and health threat. A novel potentiometric sensor for anionic surfactants based on the 1,3-dioctadecyl-1H-imidazol-3-ium tetraphenylborate (DODI–TPB) ionophore is presented. The newly developed approach for DODI–TPB synthesis is faster and simpler than the currently used strategies and follows the green chemistry principles. The DODI–TPB ionophore was characterized by computational and instrumental techniques (NMR, LC–MS, FTIR, elemental analysis) and used to produce a PVC-based DODI–TPB sensor. The sensor showed linear response to dodecylbenzenesulfonate and dodecyl sulfate in concentration ranges of 6.3 × 10⁻⁷–3.2 × 10⁻⁴ M and 5.9 × 10⁻⁷–4.1 × 10⁻³ M, for DBS and SDS, respectively. The sensor exhibits a Nernstian slope (59.3 mV/decade and 58.3 mV/decade for DBS and SDS, respectively) and low detection limits (7.1 × 10⁻⁷ M and 6.8 × 10⁻⁷ M for DBS and SDS, respectively). The DODI–TPB sensor was successfully tested on real samples of commercial detergents and the results are in agreement with the referent methods. A computational analysis underlined the importance of long alkyl chains in DODI⁺ and their C–H∙∙∙π interactions with TPB⁻ for the ionophore formation in solution, thereby providing guidelines for the future design of efficient potentiometric sensors. Full article

Polydopamine (PDA) films were successfully prepared on quartz crystal microbalance (QCM) by in-situ growth method, and the obtained QCM sensor was used for humidity detection. Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) were used to study the chemical composition and microstructure of the in-situ grown PDA sensitive films. The experimental results showed that the PDA-QCM humidity sensor with 2 h polymerization growth times (2-PDA-QCM) owned high sensitivity (20.77 Hz/% RH), good selectivity, short response/recovery time (5 s/11 s) and acceptable long-term stability. In addition, the energy loss of the sensors fabricated under different conditions was investigated by impedance analysis. Based on all the test results, it is concluded that the combination of in-situ growth method and QCM can produce a room temperature humidity sensor with excellent performance. Full article

A small indentation embedded in a microchannel creates a surface energy well (SEW) for a confined droplet due to surface energy release. Inspired by this, we developed a SEW-based microfluidic platform to realize high spatiotemporal-resolved signal profiling at the single-cell level applying droplet stimulus on a single chip. The method allows for controlled droplet replacement within only 3 s with almost 100% exchange efficiency, reliable single-cell patterning of adherent cells and successive treatment of adherent cells with reagent droplets. Furthermore, the PDGFR/Akt pathway served as a model system for evaluating the performance of the SEW-based method in determining the effects of ligand stimulation duration (3 s to 3 min) on receptor phosphorylation. The novel strategy offers a general platform for probing the temporal dynamics of single cells, as well for monitoring rapid chemical reactions in various applications. Full article

In this study, a non-labeled sensor system for direct determining human glycated albumin levels for medical application is proposed. Using machine learning methods applied to surface-enhanced Raman scattering (SERS) spectra of human glycated albumin and serum human albumin enabled the avoidance of complex sample preparation. By implementing linear discriminant analysis and regularized linear regression, classification and regression problems were solved based on the spectra obtained as a result of the experiment. The results show that, coupled with data augmentation and a special cross-validation procedure, the methods we employed yield better results in the corresponding tasks in comparison with popular random forest methods and the support vector method. The results show that SERS, in combination with machine learning methods, can be a powerful and effective tool for the simple and direct assay of protein mixtures. Full article

Science the biological activities of chiral enantiomers are often different or even opposite, their chiral recognition is of great significance. A new assembly structure named TCPP-Zn-(S)-BINOL was obtained based on the interaction between chiral binaphthol (BINOL) and the porphyrin-based MOF structure formed by Meso-Tetra(4-carboxyphenyl)porphine (TCPP) and Zn²⁺, and a new chiral sensor was designed relying on TCPP-Zn-(S)-BINOL. The chiral platform was designed by using binaphthol as a chiral recognizer and the porphyrin MOF as an emitter, which can recognize tyrosine (Tyr) enantiomers via the electrochemiluminescence (ECL) method. According to density functional theory (DFT), TCPP-Zn-(S)-BINOL has a different affinity with L/D-Tyr due to the different strength of the hydrogen bond between chiral ligand BINOL and the tyrosine (Tyr) enantiomer. It will be more suitable for combination with L-Tyr, and the presence of L-Tyr will increase the ECL intensity of the modified electrode via the catalytic reduction of co-reactant reagents, achieving the purpose of the chiral recognition of Tyr enantiomers. These findings show that TCPP-Zn-(S)-BINOL can be used as an advanced ECL chiral recognition platform for biomedical applications. Full article

Cancer antigen 15-3 (CA 15-3) is a biomarker for breast cancer used to monitor response to treatments and disease recurrence. The present work demonstrates the preparation and application of a fluorescent biosensor for ultrasensitive detection of the cancer antigen CA 15-3 protein tumor marker using mercaptopropionic-acid-functionalized cadmium telluride ([email protected]) quantum dots (QDs) conjugated with CA 15-3 antibodies. First, the QDs were synthesized by the hydrothermal route, resulting in spherical nanoparticles up to 3.50 nm in diameter. Subsequently, the QD conjugates were characterized by Fourier transform infrared spectroscopy (FTIR), UV absorption, and fluorescence. The interaction between the conjugates and the protein was studied by fluorescence spectroscopy in buffer and in 10-fold diluted commercial human serum. Calibration in spiked serum samples gave a detection limit of 0.027 U/mL, 1000-fold lower than the clinical limit for CA 15-3 (25 U/mL to 30 U/mL), indicating that this is an ultrasensitive technique. In addition, a rapid response was obtained within 10 min. The biosensor was selective in the presence of the interfering serum proteins BSA, CEA, and CA-125, with a maximum interference of 2% for BSA. The percent recovery was close to 100% with maximum relative standard deviation (RSD%) values of 1.56. Overall, the developed CA 15-3 biosensor provides a simple and sensitive method for ultrasensitive monitoring of breast cancer, as well as the ability to detect other molecules of interest in human serum matrices. Full article

Irbesartan is a drug used to treat hypertension and high blood pressure. Recent studies associated sartans with several forms of cancer, making removing this class of substances from the environment a high priority. The EU has categorized drugs as emerging pollutants, and they can be more potent than other substances because they were designed to operate at low concentrations. Thus, effective and sensitive methods of determining Irbesartan selectively and accurately in environmental samples are necessary. MIPs have already been used to remove pollutants from complex matrixes, so they were also chosen for this work. In particular, a polyacrylate-based MIP was used to functionalize the graphite working electrode of screen-printed cells (SPCs), aiming to develop a voltammetric method for Irbesartan sensing. The MIP composition and the experimental conditions for the electrochemical determination were optimized through a Design of Experiments (DoE) approach. The whole analysis was replicated with different SPCs obtaining similar results, which highlight the good reproducibility potential. MIP-based electrodes were also applied to determine Irbesartan in fortified tap water samples, obtaining high recovery percentages. Given the good results, the electrochemical method based on MIP-modified screen-printed electrodes is promising for quantifying Irbesartan at a trace level. Full article

Supercapacitors have emerged as one of the promising energy storage systems owing to their rapid charge/discharge capability, long-term cycling stability, and high power density. The application of core-shell nanostructures for supercapacitors is one of the effective strategies to achieve a high specific surface area for abundant reaction sites and good electrical conductivity for fast charge transfer, hence improving the performance of supercapacitors. Particularly, the use of NiMoO₄ for the core-shell structure has drawn great attention due to its outstanding advantages, such as its natural abundance, low material cost, superior electrochemical performance, and wide electrochemical potential window in cyclic voltammetry. In this context, this review comprehensively covers the recent progress of the core-shell nanostructures based on the NiMoO₄-composite materials, which find applications in supercapacitors. The composite materials that incorporate metal oxides such as NiMoO₄, metal hydroxides, metal chalcogenides, carbon materials, and conductive polymers are discussed in detail for such core-shell nanostructures with the aim of understanding how the adopted materials and the relevant morphology govern the electrochemical features for supercapacitors. Finally, the existing challenges in current technologies for supercapacitors are discussed, while possible future directions in developing the NiMoO₄-composite-based core-shell nanostructures are proposed for high-performance supercapacitors. Full article

A comparative analysis of the chemiresistive sensor response of thin films of a series of tetrasubstituted phthalocyanines of various metals with F-substituent in peripheral (MPcF₄-p, M = Cu, Co, Zn, Pb, VO) and non-peripheral (MPcF₄-np) positions in macroring to low concentrations of ammonia (1–50 ppm) was carried out. It was found that MPcF₄-p films exhibit a higher sensor response than MPcF₄-np ones. A CoPcF₄-p film demonstrated a calculated LOD of 0.01 ppm with a recovery time of 215 s, while a VOPcF₄-p film had LOD of 0.04 ppm and the recovery time of 270 s. The selectivity test showed that CO₂, ethanol, acetone, benzene, and formaldehyde did not interfere with the determination of ammonia, while H₂S at a concentration of more than 10 ppm could act as an interfering gas. It was shown that, as a result of quantum-chemical calculations, the observed regularities are best described by the interaction of NH₃ with phthalocyanines through the formation of hydrogen bonds between NH₃ and side atoms of the macroring. In the case of MPcF₄-p, the NH₃ molecule approaches the macrocycle more closely and binds more strongly than in the case of MPcF₄-np. The stronger binding leads to a stronger effect of the ammonia molecule on the electronic structure of phthalocyanine and, as a consequence, on the chemiresistive sensor response of the films to ammonia. Full article

Surface-plasmon-based biosensors have become excellent platforms for detecting biomolecular interactions. While there are several methods to exciting surface plasmons, the major challenge is improving their sensitivity. In relation to this, graphene-based nanomaterials have been theoretically and experimentally proven to increase the sensitivity of surface plasmons. Notably, graphene nanoribbons display more versatile electronic and optical properties due to their controllable bandgaps in comparison to those of zero-gap graphene. In this work, we use a semi-analytical approach to investigate the plasmonic character of two-dimensional graphene nanoribbon arrays, considering free-standing models, i.e., models in which contact with the supporting substrate does not affect their electronic properties. Our findings provide evidence that the plasmon frequency and plasmon dispersion are highly sensitive to geometrical factors or the experimental setup within the terahertz regime. More importantly, possible applications in the molecular detection of lactose, α-thrombin, chlorpyrifos-methyl, glucose, and malaria are discussed. These predictions can be used in future experiments, which, according to what is reported here, can be correctly fitted to the input parameters of possible biosensors based on graphene nanoribbon arrays. Full article

We report the synthesis and investigation of Au–Ru composite with highly developed specific surface area exhibiting excellent electrocatalytic performance suitable for detection of such hydrophobic metabolites as epinephrine in the physiological environment. This electrode material was fabricated using two-stage laser-assisted metal deposition technique. The morphological and structural studies of Au–Ru were performed using methods of scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction spectroscopy (XRD). The voltammetric methods, including cyclic voltammetry (CV), differential pulse voltammetry (DPV) and direct amperometry, were used to analyze the composite’s electrochemical properties. The Au–Ru sensor exhibited two linear ranges of the non-enzymatic epinephrine detection: 0.01–10 μM and 10–1000 μM. The calculated sensitivities within these two ranges were 32.8 and 3.3 μA μM${}^{-1}$ cm${}^{-2}$, whereas the corresponding limits of detection were 9 and 20 nM, respectively. The Au–Ru sensor also revealed good stability and reproducibility, as well as high selectivity towards epinephrine detection in the presence of a number of the interfering species. Full article

The present work aims to investigate the feasibility of utilizing Pt and PtCo alloy ultrathin films as hydrogen gas sensors in order to reduce the cost of the hydrogen gas sensors by using low-cost metallic materials. In this study, ultrathin Pt and PtCo alloy thin films are evaluated for hydrogen sensors. The stoichiometry and structural characterization of the thin films are observed from XPS, SEM, and EDX measurements. The 2-nm-thick Pt and PtCo films deposited by sputtering onto Si/SiO₂ covers homogeneously the surface in an fcc crystalline plane (111). The hydrogen gas-sensing properties of the films are assessed from the resistance measurement between 25 °C and 150 °C temperature range, under atmospheres with hydrogen concentration ranging from 10 ppm to 5%. The hydrogen-sensing mechanism of ultrathin Pt_xCo_1-x alloy films can be elucidated with the surface scattering phenomenon. PtCo thin alloy films show better response time than pure Pt thin films, but the alloy films show lower sensor response than pure Pt film’s sensor response. Aside from these experimental investigations, first-principles calculations have also been carried out for bare Pt and Co, and also PtCo alloys. Compared to the theoretical calculations, the sensor response to change decreases with increasing Co content, a result that is compatible with the experimental results. In an attempt to explain the decrease in the sensor response of PtCo alloy films compared to bare Pt film, a variety of different phenomena are discussed, including the shrinking lattice of the structure or dendritic surface structure of PtCo alloy films by the increasing cobalt ratio. Full article

An efficient strategy to develop porous materials with potential for NO₂ sensing was based in the preparation of a metal-organic framework (MOF), UiO-66(Hf), modified with a very small amount of meso-tetrakis(4-carboxyphenyl) N-methylpyrrolidine-fused chlorin (TCPC), [email protected] Chlorin’s incorporation into the UiO-66(Hf) framework was verified by several characterization methods and revealed that the as-synthesized [email protected] brings together the chemical stability of UiO-66(Hf) and the photophysical properties of the pyrrolidine-fused chlorin which is about five times more emissive than the porphyrin counterpart. [email protected] was further incorporated into polydimethylsiloxane (PDMS) and the resulting [email protected]@PDMS film was tested in NO₂ gas sensing. It showed notable sensitivity as well as a fast response in the range between 0.5 and 500 ppm where an emission intensity quenching is observed up to 96% for 500 ppm. This is a rare example of a chlorin-derivative used for gas-sensing applications through emission changes, and an unusual case of this type of optical-sensing composites of NO₂. Full article

The negative effects of environmental estrogens on wildlife and human beings are gaining increasing attention. Research on the highly sensitive detection method for Vitellogenin (Vtg), one of the biomarkers of environmental estrogens (EEs), is expected to detect weak estrogens in complex environments. This study aimed to develop a label-free immunosensor with high specificity and sensitivity for testing Vtg. Carbon quantum dots (CQDs) with high fluorescence and excellent stability were synthesized, and antilipovitellin monoclonal antibody (Anti-Lv-mAb) was prepared. Based on the fluorescence resonance energy transfer (FRET) between CQDs-conjugated Anti-Lv-mAb and reduced graphene oxide (RGO), an ultrasensitive fluorescent “ON-OFF” label-free immunosensor for detection of Vtg of marine medaka was established. By modification of RGO with poly dimethyl diallyl ammonium chloride (PDDA), the Zeta potential of RGO was changed and the FRET efficiency was improved. The immunosensor displayed a wide linear response to Vtg of marine medaka from 0.1 to 3000 ng/mL, a low limit of detection (LOD) of 0.04 ng/mL, and excellent sensitivity (28,833.63 CPS/(ng/mL)), selectivity, and reproducibility. The results demonstrated that the fluorescent “ON-OFF” immunosensor is an easy-to-use, relatively fast, ultrasensitive, and accurate detection method for weak estrogenic activity. Full article

Surface plasmon resonance microscopy (SPRM) is a versatile technique for biosensing and imaging that facilitates high-sensitivity, label-free, real-time characterization. To date, SPR technology has been successfully commercialized and its performance has continued to improve. However, this method is inhibited by low spatial resolution and the inability to achieve single-molecule detection. In this report, we present an overview of SPRM research progress in the field of plasma imaging and sensing. A brief review of the technological advances in SPRM is outlined, as well as research progress in important applications. The combination of various new techniques with SPRM is emphasized. Finally, the current challenges and outlook of this technique are discussed. Full article

Furazolidone (FZD), a typical highly effective nitrofuran antibiotic, has been banned in aquaculture for its carcinogenicity and other adverse health effects, but it is still wildly used for its low cost and significant efficacy. Since FZD will be rapidly metabolized in living organisms, the traditional standard mass spectrometry method can quantitatively analyze trace amount of FZD by detecting its derivative. However, a rapid qualitative analysis method is more consistent with market demand in regular monitoring. In this study, high performance liquid chromatography (HPLC) was used to separate and purify FZD from the sea cucumber culture sediment, and the purified effluent was combined with a substrate of gold nanoparticles (Au NPs) for surface enhanced Raman spectroscopy (SERS) detection. The absolute detection limit of FZD by SERS is 1 ng, and the detection limit of FZD in actual sediment samples is less than 1 μg/kg. The cost and period of FZD analysis by HPLC-SERS are greatly reduced for the omission of derivatization compared with the traditional mass spectrometry method, which can better meet the requirements of practical applications. Full article

Graphene oxide-decorated silver nanoparticles growing on titania nanotube array (GO/Ag/TiO₂ NTA) were designed as active Surface-enhanced Raman scattering (SERS) sensor substrates for sensitive determination of the organic compound bisphenol A. The theoretical simulation calculation and experimental measurements have been adopted to investigate the electronic and sensing properties of GO/Ag/TiO₂ NTA SERS substrate. The molecule adsorption and surface energy are applied to investigate the interfacial interaction between the SERS substrate and the organic molecule. The Raman spectrum response intensity and the electron transfer behavior are applied to investigate sensing activity of GO/Ag/TiO₂ NTA SERS substrate. The specific adsorption amount of BPA is 3.3, 7.1, and 52.4 nmol cm⁻² for TiO₂, Ag/TiO₂, and GO/Ag/TiO₂ NTA, respectively, presenting superior adsorption and aggregation capability. GO/Ag/TiO₂ NTA SERS sensor accordingly achieves the low detection limit of 5 × 10⁻⁷ M for bisphenol A molecule. The density functional theory simulation calculation proves that GO/Ag/TiO₂ reveals a higher density of states, lower HOMO-LUMO gap, stronger electrostatic interaction, and similar band gaps in comparison with Ag/TiO₂. Binary-interfaced GO/Ag/TiO₂ presents a more declined molecule structure surface energy of 5.87 eV rather than 4.12 eV for mono-interfaced Ag/TiO₂. GO/Ag/TiO₂ also exhibits a more declined surface adsorption energy of 7.81 eV rather than 4.32 eV for Ag/TiO₂ in the adsorption of bisphenol A. The simulation calculation verification results well confirm the superior activity of GO/Ag/TiO₂ NTA substrate for sensitive detection and quantitative determination of the organic compound bisphenol A. Full article

Waste incineration is regarded as an ideal method for municipal solid waste disposal (MSW), with the advantages of waste-to-energy, lower secondary pollution, and greenhouse gas emission mitigation. For incineration leachate, the information from the headspace gas that varies at different processing processes and might be useful for chemical analysis, is ignored. The study applied a novel electronic nose (EN) to mine the information from leachate headspace gas. By combining manifold learnings (principal component analysis (PCA) and isometric feature mapping (ISOMAP), and uniform manifold approximation and projection (UMAP) and ensemble techniques (light gradient boosting machine (lightGBM) and extreme gradient boosting (XGBT)), EN based on the UMAP-XGBT model had the best classification performance with a 99.95% accuracy rate in the training set and a 95.83% accuracy rate in the testing set. The UMAP-XGBT model showed the best prediction ability for leachate chemical parameters (pH, chemical oxygen demand, biochemical oxygen demand, ammonia, and total phosphorus), with R² higher than 0.99 both in the training and testing sets. This is the first study of the EN application for leachate monitoring, offering an easier and quicker detection method than traditional instrumental measurements for the enforcement and implementation of effective monitoring programs. Full article

Laser scribing is a technique that converts carbon-rich precursors into 3D-graphene nanomaterial via direct, single-step, and maskless laser writing in environmental conditions and using a scalable approach. It allows simple, fast, and reagentless production of a promising material with outstanding physicochemical features to create novel electrochemical sensors and biosensors. This review addresses different strategies for fabricating laser-scribed graphene (LSG) devices and their association with nanomaterials, polymers, and biological molecules. We provide an overview of their applications in environmental and health monitoring, food safety, and clinical diagnosis. The advantages of their integration with machine learning models to achieve low bias and enhance accuracy for data analysis is also addressed. Finally, in this review our insights into current challenges and perspectives for LSG electrochemical sensors are presented. Full article