•Cellulose nanowhiskers, silver nanoparticles and electrospun nanofibers were combined to produce ternary nanocomposites.•E-tongue sensing units were designed using ternary nanomposites.•Feature ...selection procedure using e-tongue data allowed the discrimination of distinct heavy metal solutions.•Aqueous solutions containing lead could be classified down to nanomolar concentration.
Contamination of water resources with heavy metal ions raises concerns because of their capability to accumulate in living organisms and cause serious health problems. As a consequence, the development of sensitive and reliable sensors capable to provide fast and accessible analysis of water quality regarding heavy metals is highly keen. Nanomaterials advancements have provided considerable improvements in these sensors, enabling efficient detection of different water pollutants even at extremely low concentration. In this work, we evaluated the performance of ternary nanocomposites based on electrospun nanofibers, cellulose nanowhiskers (CNW) and silver nanoparticles as sensing layers used in the electrical detection of heavy metals. These three materials were distinctly combined, resulting in six different sensors, which were arranged to compose an impedimetric electronic tongue. The synergism between the components could be verified by the enhancement of bulk conductance ability when CNW:Ag was combined with electrospun nanofibers. Adjustments of sensors and frequencies enabled efficient discrimination of distinct heavy metal ions. Moreover, the sensor array could distinguish pure water from aqueous solution contaminated with Pb2+ at concentrations as low as of 10 nmol L−1.
Reliable gas sensors operating at room temperature are in demand for monitoring the environment for hazardous pollutants, such as ammonia (NH3) gas that may become toxic to humans and animals above a ...threshold concentration. In this paper we report on the combination of three materials, namely polyaniline (PANI), graphene oxide (GO) and zinc oxide (ZnO), to produce hybrid layer-by-layer (LbL) films used for sensing NH3 with impedance spectroscopy measurements. The deposition of tetralayered PANI/GO/PANI/ZnO LbL films was confirmed with UV–vis. absorption and Raman spectroscopies, while atomic force microscopy (AFM) served to investigate film morphology. Exposure of these LbL films to NH3 caused film roughness to vary, in an effect that depended on the number of tetralayers. Because of synergy in the materials properties, the films with 3 tetralayers were found to be the most adequate for detecting NH3 in the range from 25ppm to 500ppm with a response time of 30s. These figures of merit are adequate for monitoring working environments regarding gas exposure, and highlight the usefulness of the control of film architecture provided by the LbL technique.
•Yolk-shelled ZnCo2O4 structures have been synthesized by a one-step co-precipitation method.•FESEM images revealed that the morphology is based on a yolk-shelled shape.•The yolk-shelled ZnCo2O4 ...exhibits a good sensitivity towards sub-ppb (80-890 ppb) level of ozone.•The sensor worked within a wide range of ozone concentrations,being also selective to ozone compared to CO, NH3 and NO2.
The need to improve the sensitivity, selectivity and stability of ozone gas sensors capable of monitoring the environment to prevent hazard to humans has sparked research on binary metal oxides. Here we report on a novel ozone gas sensor made with ca. 0.5μm yolk-shelled ZnCo2O4 microstructures synthesized via an eco-friendly, co-precipitation method and subsequent annealing. With these ZnCo2O4 microspheres, ozone concentrations down to 80 parts per billion (ppb) could be detected with a.c. and d.c. electrical measurements. The sensor worked within a wide range of ozone concentrations, from 80 to 890ppb, being also selective to ozone compared to CO, NH3 and NO2. The high performance could be attributed to the large surface area to volume ratio inherent in yolk-shell structures. Indeed, ozone molecules adsorbed on the ZnCo2O4 surface create a layer of holes that affect the conductivity, as in a p-type semiconductor. Since this mechanism of detection is generic, ZnCo2O4 microspheres can be further used in other environment monitoring devices.
We report on a bimetallic, bifunctional electrode where a platinum (Pt) surface was patterned with nanostructured gold (Au) fingers with different film thicknesses, which was functionalized with ...glucose oxidase (GOx) to yield a highly sensitive glucose biosensor. This was achieved by using selective adsorption of a self-assembled monolayer (SAM) onto Au fingers, which allowed GOx immobilization only onto the Au-SAM surface. This modified electrode was termed bifunctional because it allowed to simultaneously immobilize the biomolecule (GOx) on gold to catalyze glucose, and detect hydrogen peroxide on Pt sites. Optimized electrocatalytic activity was reached for the architecture Pt/Au-SAM/GOx with 50nm thickness of Au, where synergy between Pt and Au allowed for detection of hydrogen peroxide (H2O2) at a low applied potential (0V vs. Ag/AgCl). Detection was performed for H2O2 in the range between 4.7 and 102.7 nmol L–1, with detection limit of 3.4×10−9 mol L−1 (3.4 nmol L−1) and an apparent Michaelis-Menten rate constant of 3.2×10−6molL−1, which is considerably smaller than similar devices with monometallic electrodes. The methodology was validated by measuring glucose in artificial saliva, including in the presence of interferents. The synergy between Pt and Au was confirmed in electrochemical impedance spectroscopy measurements with an increased electron transfer, compared to bare Pt and Au electrodes. The approach for fabricating the reproducible bimetallic Pt/Au electrodes is entirely generic and may be explored for other types of biosensors and biodevices where advantage can be taken of the combination of the two metals.
•Controlled synthesis of Gold Nanostructures by photolithography on platinum surface•Hybrid surface (bimetallic) with better features compared to their monometallic counterparts•For the first time we propose a methodology for selective immobilization of SAM only on the Au and platinum free•Bifunctional Nanostructured surface for glucose biosensing in artificial saliva.
The growing concern for sustainability and environmental preservation has increased the demand for reliable, fast response, and low-cost devices to monitor the existence of heavy metals and toxins in ...water resources. An electronic tongue (e-tongue) is a multisensory array mostly based on electroanalytical methods and multivariate statistical techniques to facilitate information visualization in a qualitative and/or quantitative way. E-tongues are promising analytical devices having simple operation, fast response, low cost, easy integration with other systems (microfluidic, optical, etc) to enable miniaturization and provide a high sensitivity for measurements in complex liquid media, providing an interesting alternative to address many of the existing environmental monitoring challenges, specifically relevant emerging pollutants such as heavy metals and toxins.
Biomedical applications with emphasis on the design of smart materials, specifically magnetic nanoparticles (MNPs) are considered to have technological benefits because they can be manipulated using ...magnetic fields. Magnetic NPs have been widely used in hyperthermia, target drug delivery system, imaging, and extraction of biomolecules, postulating them also as an important tool in cancer treatment. Morphological structures of magnetic materials have drawn tremendous attention from diverse scientific fields due to their unique surface chemistry, nontoxicity, biocompatibility, and particularly their inducible magnetic moment. This review features recent research accomplishments made in the biomedical field using magnetic nanoparticles. The first part gives a comprehensive overview of magnetic nanoparticles in the treatment of chronic diseases and drug targeting. The second part includes the role of magnetic nanoparticles in electrochemical, optical-based immunoassays. The review also outlines the current challenges and future research perspectives for fostering advanced and high-performance magnetic nanoparticles in technological applications.
Two kinds of flexible ozone (O
3
) sensors were obtained by placing pristine ZnO nanorods and gold-modified ZnO nanorods (NRs) on a bi-axially oriented poly(ethylene terephthalate) substrate. The ...chemiresistive sensor is operated at typically 1 V at room temperature under the UV-light illumination. The ZnO nanorods were prepared via a hydrothermal route and have a highly crystalline wurtzite structure, with diameters ranging between 70 and 300 nm and a length varying from 1 to 3 μm. The ZnO NRs were then coated with a ca. 10 nm gold layer whose presence was confirmed with microscopy analysis. This sensor is found to be superior to detect ozone at a room temperature. Typical figures of merit include (a) a sensor response of 108 at 30 ppb ozone for gold-modified ZnO NRs, and (b) a linear range that extends from 30 to 570 ppb. The sensor is stable, reproducible and selective for O
3
compared to other oxidizing and reducing gases. The enhanced performance induced by the modification of ZnO nanorods with thin layer of gold is attributed to the increased reaction kinetics compared to pristine ZnO NRs. The sensing mechanism is assumed to be based on the formation of a nano-Schottky type barrier junction at the interface between gold and ZnO.
Graphical abstract
Room temperature, flexible UV-enhanced gold modified ZnO nanorods can detect ppb levels of ozone.
"Electronic tongues", "taste sensors", and similar devices (further named as "multisensor systems", or MSS) have been studied and applied mostly for the analysis of edible analytes. This is not ...surprising, since the MSS development was sometimes inspired by the mainstream idea that they could substitute human gustatory tests. However, the basic principle behind multisensor systems-a combination of an array of cross-sensitive chemical sensors for liquid analysis and a machine learning engine for multivariate data processing-does not imply any limitations on the application of such systems for the analysis of inedible media. This review deals with the numerous MSS applications for the analysis of inedible analytes, among other things, for agricultural and medical purposes.
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•Paclitaxel effects on membranes depend on cholesterol concentration.•The paclitaxel effects did not vary monotonically with cholesterol concentration.•The physiological action of ...paclitaxel may depend on membrane elasticity.
The composition of Langmuir monolayers used as cell membrane models is an essential factor for the interaction with biologically-relevant molecules, including pharmaceutical drugs. In this paper, we report the modulation of effects from the antineoplastic drug paclitaxel by the relative concentration of cholesterol in the Langmuir monolayers of ternary mixtures of dipalmitoylphosphatidylcholine, sphingomyelin, and cholesterol. Since the dependence on cholesterol concentration for these monolayers simulating lipid rafts is non-monotonic, we analyzed the surface pressure and compressibility modulus data with the multidimensional projection technique referred to as interactive document mapping (IDMAP). The maximum expansion induced by paclitaxel in surface pressure isotherms was observed for 27% cholesterol, while the compressibility modulus decreased most strongly for the monolayer with 48% cholesterol. Therefore, the physiological action of paclitaxel may vary depending on whether it is associated with penetration in the membrane or with changes in the membrane elasticity.
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High molecular weight Chi modulates the orientation of SF groups (Try and Try).Chi and SF LbL films were successfully used as template for phytase immobilization.The matrix ...improved the performance of phytic acid biosensing.
In this paper, we show that chitosan may induce conformation changes in silk fibroin (SF) in layer-by-layer (LbL) films, which were used as matrix for immobilization of the enzyme phytase to detect phytic acid. Three chitosan (CH) samples possessing distinct molecular weights were used to build CH/SF LbL films, and a larger change in conformation from random coils to β-sheets for SF was observed for high molecular weight chitosan (CHH). The CHH/SF LbL films deposited onto interdigitated gold electrodes were coated with a layer of phytase, with which phytic acid could be detected down to 10⿿9M using impedance spectroscopy as the principle of detection and treating the data with a multidimensional projection technique. This high sensitivity may be ascribed to the suitability of the CHH/SF matrix, thus indicating that the molecular-level interactions between chitosan and SF may be exploited in other biosensors and biodevices.
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