Functionalized polypyrrole nanotube arrays as electrochemical biosensor for the determination of copper ions

Polypyrrole Derivatives: Preparation, Properties and Application

Polypyrrole (PPy) has attracted widespread attention due to its excellent environmental stability, high conductivity, simple synthesis, good biocompatibility, and reversible redox properties. PPy derivatives not only inherit the advantages of polypyrrole, but also have some unique properties. The side and N-site substitution of PPy can not only yield polymers with good solubility, but it also endows polymers with special functionalities by controlling the introduced functional groups. The performance of copolymers can also be adjusted by the type of monomer or polymerization ratio. In this review, an overview of the different types, main preparation methods, and the application prospects of PPy derivatives reported to date are summarized and presented. The current challenges and future opportunities in this research area are also prospected.

N-substituted pyrrole carboxylic acid derivatives from 3,4-dihydroxyketons

Since the chemical industry is largely dependent on petrol-based feedstocks, new sources are required for a sustainable industry. Conversion of biomass to high-value compounds provides an environmentally friendly and sustainable approach, which might be a potential solution to reduce petrol-based starting materials. This also applies for N-heterocycles, which are a common structural motif in natural products, pharmaceuticals and functional polymers. The synthesis of pyrroles is a well-studied and established process. Nevertheless, most routes described are not in line with the principles of green and sustainable chemistry and employ harsh reaction conditions and harmful solvents. In this study, 3,4-dihydroxyketons are used as excellent platform chemicals for the production of N-substituted pyrrole-2-carboxylic- and pyrrole-2,5-dicarboxylic acids, as they can be prepared from glucose through the intermediate d-glucarate and converted into pyrrolic acid derivatives under mild conditions in water. The scope of this so far unknown reaction was examined using a variety of primary amines and aqueous ammonium chloride leading to pyrrolic acid derivatives with N-substituents like alkane-, alkene-, phenyl- and alcohol-groups with yields up to 20 %. The combination of both, enzymatic conversion and chemical reaction opens up new possibilities for further process development. Therefore, a continuous chemo-enzymatic system was set up by first employing an immobilized enzyme to catalyze the conversion of d-glucarate to the 3,4-dihydroxyketone, which is further converted to the pyrrolic acid derivatives by a chemical step in continuous flow.

Green synthesis of silver nanoparticles and its environmental sensor ability to some heavy metals

This study marks a pioneering effort in utilizing Vachellia tortilis subsp. raddiana (Savi) Kyal. & Boatwr., (commonly known as acacia raddiana) leaves as both a reducing and stabilizing agent in the green "eco-friendly" synthesis of silver nanoparticles (AgNPs). The research aimed to optimize the AgNPs synthesis process by investigating the influence of pH, temperature, extract volume, and contact time on both the reaction rate and the resulting AgNPs' morphology as well as discuss the potential of AgNPs in detecting some heavy metals. Various characterization methods, such as UV-vis spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (IR), Zeta sizer, EDAX, and transmitting electron microscopy (TEM), were used to thoroughly analyze the properties of the synthesized AgNPs. The XRD results verified the successful production of AgNPs with a crystallite size between 20 to 30 nm. SEM and TEM analyses revealed that the AgNPs are primarily spherical and rod-shaped, with sizes ranging from 8 to 41 nm. Significantly, the synthesis rate of AgNPs was notably higher in basic conditions (pH 10) at 70 °C. These results underscore the effectiveness of acacia raddiana as a source for sustainable AgNPs synthesis. The study also examined the AgNPs' ability to detect various heavy metal ions colorimetrically, including Hg2+, Cu2+, Pb2+, and Co2+. UV-Vis spectroscopy proved useful for this purpose. The color of AgNPs shifts from brownish-yellow to pale yellow, colorless, pale red, and reddish yellow when detecting Cu2+, Hg2+, Co2+, and Pb2+ ions, respectively. This change results in an alteration of the AgNPs' absorbance band, vanishing with Hg2+ and shifting from 423 to 352 nm, 438 nm, and 429 nm for Cu2+, Co2+, and Pb2+ ions, respectively. The AgNPs showed high sensitivity, with detection limits of 1.322 × 10-5 M, 1.37 × 10-7 M, 1.63 × 10-5 M, and 1.34 × 10-4 M for Hg2+, Cu2+, Pb2+, and Co2+, respectively. This study highlights the potential of using acacia raddiana for the eco-friendly synthesis of AgNPs and their effectiveness as environmental sensors for heavy metals, showcasing strong capabilities in colorimetric detection.

Colorimetric detection of heavy metal ions with various chromogenic materials: Strategies and applications

Detection of heavy metal ions has drawn significant attention in environmental and food area due to their threats to the human health and ecosystem. Colorimetry is one of the most frequently-used methods for the detection of heavy metal ions owing to its simplicity, easy operation and rapid on-site detection. The development of chromogenic materials and their sensing mechanisms are the key research direction in the area of colorimetric method. Since each chromogenic material has their unique optical and chemical properties, they have totally different colorimetric sensing mechanisms. This review focuses on the chromogenic materials and their sensing strategies for the colorimetric detection of heavy metal ions. We divide the chromogenic materials into three types, including organic materials, inorganic materials, and other materials. As for each type of chromogenic material, we discuss their detailed sensing strategies, sensing performance, and real sample applications. Moreover, current challenges and perspectives related to the colorimetry of heavy metal ions are also discussed in this review. The aim of this review is to help readers to better understand the principles of colorimetric methods for heavy metal ions and push the development of rapid detection of heavy metal ions.

Polypyrrole Nanomaterials: Structure, Preparation and Application

In the past decade, nanostructured polypyrrole (PPy) has been widely studied because of its many specific properties, which have obvious advantages over bulk-structured PPy. This review outlines the main structures, preparation methods, physicochemical properties, potential applications, and future prospects of PPy nanomaterials. The preparation approaches include the soft micellar template method, hard physical template method and templateless method. Due to their excellent electrical conductivity, biocompatibility, environmental stability and reversible redox properties, PPy nanomaterials have potential applications in the fields of energy storage, biomedicine, sensors, adsorption and impurity removal, electromagnetic shielding, and corrosion resistant. Finally, the current difficulties and future opportunities in this research area are discussed.

Bio-Derived Fluorescent Carbon Dots: Synthesis, Properties and Applications

The transformation of biowaste into products with added value offers a lucrative role in nation-building. The current work describes the synthesis of highly water-soluble, luminous carbon quantum dots (CQDs) in the size range of 5-10 nm from discarded rice straw. The small spherical CQDs that were formed had outstanding optical and luminescent qualities as well as good photostabilities. By performing quantitative multi-assay tests that included antioxidant activities, in vitro stability and colloidal assay investigations as a function of different CQD concentrations, the biocompatibility of CQDs was evaluated. To clearly visualize the type of surface defects and emissive states in produced CQDs, excitation-dependent fluorescence emission experiments have also been carried out. The "waste-to-wealth" strategy that has been devised is a successful step toward the quick and accurate detection of Cu2+ ion in aqueous conditions. The fluorescence-quenching behavior has specified the concentration dependency of the developed sensor in the range of 50 μM to 10 nM, with detection limit value of 0.31 nM. The main advantage of the current research is that it offers a more environmentally friendly, economically viable and scaled-up synthesis of toxicologically screened CQDs for the quick fluorescence detection of Cu2+ ions and opens up new possibilities in wastewater management.

A Voltammetric Sensor for the Determination of Hydroxylamine Using a Polypyrrole Nanotubes-Modified Electrode

In this work, we develop an electrochemical sensor using a polypyrrole nanotubes-modified graphite screen-printed electrode (PPy NTs/GSPE) for sensing hydroxylamine. The PPy NTs/GSPE-supported sensor has an appreciable electrocatalytic performance and great stability for hydroxylamine oxidation. Compared to a bare graphite screen-printed electrode, we demonstrate that using the PPy NTs/GSPE leads to a significant reduction in the oxidation potential of hydroxylamine. The standard curve shows a linear relationship ranging from 0.005 to 290.0 μM (R2  =  0.9998), with a high sensitivity (0.1349 μA/μM) and a narrow limit of detection (LOD) of 0.001 μM. In addition, the PPy NTs/GSPE has satisfactory outcomes for hydroxylamine detection in real specimens.

Recent Advances and Biomedical Applications of Peptide-Integrated Conducting Polymers

Conducting polymers (CPs) are of great interests to researchers around the world in biomedical applications owing to their unique electrical and mechanical properties. Besides, they are easy to fabricate and have long-term stability. These features make CPs a powerful building block of modern biomaterials. Peptide functionalization has been a versatile tool for the development of CP-based biomaterials. With the aid of peptide modifications, the biocompatibility, target selectivity, and cellular interactions of CPs can be greatly improved. Reflecting these aspects, an increasing number of studies on peptide-integrated conducting polymers have been reported recently. In this review, various kinds of peptide immobilization strategies on CPs are introduced. Moreover, the aims of peptide modification are discussed in three aspects: enhancing the specific selectivity, avoiding nonspecific adhesion, and mimicking the environment of extracellular matrix. We highlighted recent studies in the applications of peptide-integrated CPs in electrochemical sensors, antifouling surfaces, and conductive biointerfaces. These studies have shown great potentials from the integration of peptide and CPs as a versatile platform for advanced biological and clinical applications in the near future.

Adsorptive potential of iron oxide based nanocomposite for the sequestration of Congo red from aqueous solution

The ability of polypyrrole-Iron oxide-seaweed nanocomposite has been tested for the removal of congo red from aqueous solution. The characteristics of nanocomposite after adsorption of Congo red (CR) have been analyzed. FTIR results authorized the involvement of various functional groups in the adsorption of CR. The change in morphology of nanocomposite was analyzed using scanning electron microscope (SEM). TEM and BET analysis were performed to characterize the nanocomposite. The effect of various parameters namely pH, adsorbent dosage, initial dye concentration, adsorption time and temperature are studied. The optimum condition for the effective removal of CR are: pH-3, initial CR concentration- 40 mg/L, nanocomposite dosage- 20 mg, contact time-40 min and temperature-40^οC. Adsorption isotherm studies and kinetic studies were done. Langmuir isotherm fits with the experimental data very well with high coefficient of determination (R² = 0.98) and maximum dye uptake of 500 mg/g is reported. In kinetic studies, pseudo second order model was obeyed (R² = 0.994). Thermodynamic properties were determined and found that the nature of process is spontaneous, endothermic and increased in randomness. The mechanism of sorption was proposed. Desorption studies were carried out and showed that the nanocomposite could be effectively reused up to five cycles. Thus the outcomes proved that the polypyrrole-iron oxide-seaweed nanocomposite to be an operative, recyclable and low-cost adsorbent for the treatment of dye bearing water.

Selective detection of Cu2+ using nitrogen-doped carbon dots derived from humic acid and urea based on specific inner filter effect

A new kind of nitrogen-doped carbon dots (N-CDs) was synthesized via a simple hydrothermal strategy using humic acid as the carbon source and urea as the nitrogen source. The fluorescence intensity of as-prepared N-CDs was quenched significantly in presence of Cu²⁺ based on a specific inner filter effect, which could be utilized to construct a selective sensor for monitoring Cu²⁺ in aqueous samples. The sensor exhibited good linearity over the range of 0.1-2 μM, and high sensitivity with a detection limit of 25 nM. Under the optimal conditions, there was no significant interference by other metal ions such as Cd²⁺, Al³⁺, Cr³⁺, Fe³⁺, Pb²⁺, Na⁺, Ni⁺, Fe²⁺, Ba²⁺, Ca²⁺, Co²⁺, Mg²⁺, As³⁺, K⁺, Zn²⁺ for Cu²⁺ detecting except Hg²⁺.The interference of Hg²⁺ can be masked by addition of sodium chloride. The experimental results demonstrated that the prepared N-CDs owned strong fluorescence, high monodispersity, good stability and good water solubility, and the constructed sensor had many advances and great application prospect in environmental field.

An overview of Structured Biosensors for Metal Ions Determination

The determination of metal ions is important for nutritional and toxicological assessment. Atomic spectrometric techniques are highly efficient for the determination of these species, but the high costs of acquisition and maintenance hinder the application of these techniques. Inexpensive alternatives for metallic element determination are based on dedicated biosensors. These devices mimic biological systems and convert biochemical processes into physical outputs and can be used for the sensitive and selective determination of chemical species such as cations. In this work, an overview of the proposed biosensors for metal ions determination was carried out considering the last 15 years of publications. Statistical data on the applications, response mechanisms, instrumentation designs, applications of nanomaterials, and multielement analysis are herein discussed.

Development strategies of conducting polymer-based electrochemical biosensors for virus biomarkers: Potential for rapid COVID-19 detection

Rapid, accurate, portable, and large-scale diagnostic technologies for the detection of severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) are crucial for controlling the coronavirus disease (COVID-19). The current standard technologies, i.e., reverse-transcription polymerase chain reaction, serological assays, and computed tomography (CT) exhibit practical limitations and challenges in case of massive and rapid testing. Biosensors, particularly electrochemical conducting polymer (CP)-based biosensors, are considered as potential alternatives owing to their large advantages such as high selectivity and sensitivity, rapid detection, low cost, simplicity, flexibility, long self-life, and ease of use. Therefore, CP-based biosensors can serve as multisensors, mobile biosensors, and wearable biosensors, facilitating the development of point-of-care (POC) systems and home-use biosensors for COVID-19 detection. However, the application of these biosensors for COVID-19 entails several challenges related to their degradation, low crystallinity, charge transport properties, and weak interaction with biomarkers. To overcome these problems, this study provides scientific evidence for the potential applications of CP-based electrochemical biosensors in COVID-19 detection based on their applications for the detection of various biomarkers such as DNA/RNA, proteins, whole viruses, and antigens. We then propose promising strategies for the development of CP-based electrochemical biosensors for COVID-19 detection.

Green Route for the Synthesis of Fluorescent Carbon Nanoparticles from Circassian Seeds for Fe(III) Ion Detection

A facile and green strategy was carried out for the preparation of fluorescent carbon nanoparticles (CNp) using non-toxic circassian seeds as carbon precursor (CNp, named ACNp). The surface of amorphous ACNp is latched with different surface moieties such as hydroxyl, carbonyl, ether and amino groups and it is confirmed by FTIR and XPS. These functionalities provide high solubility and stability to ACNp in aqueous medium. The surface of ACNp is highly negatively charged due to the presence of oxygen rich functional groups and it is confirmed by zeta potential. A reasonably good quantum yield (QY) of 5.1% is obtained for ACNp compared to other CNp derived from bioprecursors without any surface passivation. Circassian seeds are self sufficient for the synthesis of N doped CNp. The excitation dependent fluorescence property of ACNp is invariant under ionic and thermal environments. They exhibit good selectivity towards Fe³⁺ ions via static quenching mechanism with detection limit of 32.7 µM.

Electrochemical endotoxin aptasensor based on a metal-organic framework labeled analytical platform

An electrochemical aptasensor for the lipopolysaccharide (LPS) detection was constructed by using copper-based metal-organic framework (Cu-MOF) as a label and the LPS aptamer of specific single-stranded DNA as a probe. The carboxyl-functionalized polypyrrole nanowires (PPy NWs) were synthesized by electrochemical polymerization method, and the amino-terminated aptamer covalently coupling with the carboxyl group of the PPy NWs was immobilized onto the modified electrode. The aptamer can specifically combine with the target LPS molecules, and Cu-MOF was labeled by adsorption based on specific interactions of LPS carbohydrate portions with anionic groups. The fabrication processes of the aptasensor were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). Differential pulse voltammetry (DPV) was used to measure electrochemical performance of the aptasensor, and the electrochemical signal can be directly measured by the electrochemical redox reaction of Cu(II)/Cu(I) existed in the Cu-MOF. The electrochemical aptasensor exhibited a high sensitivity toward LPS ranging from 1.0 pg/mL to 1.0 ng/mL with a detection limit of 0.29 pg/mL. Moreover, the developed sensor was found to have good selectivity, stability and regeneration properties, and the sensor also successfully detected LPS in real tap water samples.

Photoelectrochemical Determination of Cu2+ Using a WO3/CdS Heterojunction Photoanode

Copper ions are not only physiologically essential for life but also hazardous materials causing a series of neurodegenerative diseases. Photoelectrochemical (PEC) detection has attracted a large amount of focus as a potential strategy to develop Cu²⁺ ion sensors. However, relatively low photocurrent signals with poor antidisturbance ability and the limited concentration range have prevented its practical applications. Here, we designed a WO₃/CdS heterojunction photoanode for the PEC determination of Cu²⁺ in aqueous solution through a simple two-step chemical bath deposition method. The obtained WO₃/CdS photoanode had a nanoplate morphology and showed an enhanced photoresponsivity with a photocurrent density of 1.5 mA/cm² at 1.23 V versus RHE under illumination. Naturally, it exhibited a low detection limit (0.06 μM) and wider range (0.5 μM to 1 mM) for Cu²⁺ PEC detection first, suggesting that the WO₃/CdS heterojunction photoanode is a promising tool to monitor copper pollution in natural environments.

Electrochemical fabrication and evaluation of a self-standing carbon nanotube/carbon fiber composite electrode for lithium-ion batteries

A binder-free self-standing carbon nanotube (CNT)/carbon fiber (CF) composite electrode, which has been developed using an electrophoretic deposition approach, was utilized as a lithium-ion battery anode. The morphology of the CNT/CF composite has been examined using scanning electron microscopy, and the results indicated that a CNT layer uniformly deposited on the CFs. The thickness and density of the CNT layer increased as the electrodeposition time increased, while overdeposition caused the CNT layer to exfoliate. Electrochemical evaluation revealed that the specific capacity, cycling stability, and rate capability of the CNT/CF anode were superior to those of the CF anode. The electrochemical impedance analysis results further revealed that the solid/electrolyte interface resistance and interface resistance induced by the oxygen-containing surface functional groups of CFs dominated the impedance of the anode. However, these resistance values could be potentially reduced via CNT surface modification, which could lead to the enhanced electrochemical performance of the CNT/CF anode. Our findings should open new avenues for the potential use of the CNT/CF composite as a self-standing anode for lithium-ion battery applications.

A novel nanocomposite of aminated silica nanotube (MWCNT/Si/NH2) and its potential on adsorption of nitrite

Several parts of the world have been facing the problem of nitrite and nitrate contamination in ground and surface water. The acute toxicity of nitrite has been shown to be 10-fold higher than that of nitrate. In the present study, aminated silica carbon nanotube (ASCNT) was synthesised and tested for nitrite removal. The synergistic effects rendered by both amine and silica in ASCNT have significantly improved the nitrite removal efficiency. The IEP increased from 2.91 for pristine carbon nanotube (CNT) to 8.15 for ASCNT, and the surface area also increased from 178.86 to 548.21 m² g^-1. These properties have promoted ASCNT a novel adsorbent to remove nitrite. At optimum conditions of 700 ppm of nitrite concentration at pH 7 and 5 h of contact with 15 mg of adsorbent, the ASCNT achieved the maximal loading capacity of 396 mg/g (85% nitrite removal). The removal data of nitrite onto ASCNT fitted the Langmuir isotherm model better than the Freundlich isotherm model with the highest regression value of 0.98415, and also, the nonlinear analysis of kinetics data showed that the removal of nitrite followed pseudo-second-order kinetic. The positive values of both ΔS° and ΔH° suggested an endothermic reaction and an increase in randomness at the solid-liquid interface. The negative ΔG° values indicated a spontaneous adsorption process. The ASCNT was characterised using FESEM-EDX and FTIR, and the results obtained confirmed the removal of nitrite. Based on the findings, ASCNT can be considered as a novel and promising candidate for the removal of nitrite ions from wastewater.

An electrochemical sarcosine sensor based on biomimetic recognition

A nonenzymatic electrochemical sensor is described for the prostate cancer biomarker sarcosine (Sar). Riboflavin was employed to mimic the active center of the enzyme sarcosine oxidase for constructing the biomimetic sensor. The use of riboflavon (Rf) avoids the disadvantages of an enzymatic sensor, such as high cost and poor stability. A glassy carbon electrode (GCE) was modified with a graphene-chitosan (GR) composite and further modified with gold-platinum bimetallic nanoparticles in a polypyrrole (PPy) matrix in order to enhance the catalytic activity of the enzyme mimic. Finally, Rf was electrodeposited on the surface of the AuPt-PPy/GR-modified GCE. Under optimized conditions, the GCE provided high sensitivity and selectivity for Sar at around 0.61 V. Response covers the 2.5-600 μM concentration range, and the detection limit is 0.68 μM. The method was successfully applied to the determination of Sar in spiked urine with 98.0%-103.2% recovery. Graphical abstract Schematic presentation of the fabrication of the Rf/AuPt-PPy/GR/GCE surface and the measurement principle by differential pulse voltammetry (DPV).

Ultra-Fast Degradation of p-Aminophenol by a Nanostructured Iron Catalyst

Full degradation of p-aminophenol in aqueous solution at room temperature by using a heterogeneous nanostructured iron hybrid catalyst in the presence of hydrogen peroxide is described. A nanostructured iron catalyst was prepared by in situ formation of iron carbonate nanorods on the protein network using an aqueous solution of an enzyme, lipase B from Candida antarctica (CAL-B). A second kind of iron nanostructured catalyst was obtained by the sunsequent treatment of the hybrid with an aqueous liquid extract of Mentha x piperita. Remarkable differences were observed using TEM imaging. When M. piperita extract was used, nanoparticles appeared instead of nanorods. Catalytic activity of these iron nanocatalysts was studied in the degradation of the environmental pollutant p-aminophenol (pAP) under different operating parameters, such as pH, presence of buffer or hydrogen peroxide concentration. Optimal conditions were pH 4 in acetate buffer 10 mM containing 1% (v/v) H₂O₂ for FeCO₃NRs@CALB, while for FeCO₃NRs@CALB-Mentha, water containing 1% (v/v) H₂O₂, resulted the best. A complete degradation of 100 ppm of pAP was achieved in 2 and 3 min respectively using 1 g Fe/L. This novel nanocatalyst was recycled five times maintaining full catalytic performance.

All-carbon suspended nanowire sensors as a rapid highly-sensitive label-free chemiresistive biosensing platform

Nanowire sensors offer great potential as highly sensitive electrochemical and electronic biosensors because of their small size, high aspect ratios, and electronic properties. Nevertheless, the available methods to fabricate carbon nanowires in a controlled manner remain limited to expensive techniques. This paper presents a simple fabrication technique for sub-100 nm suspended carbon nanowire sensors by integrating electrospinning and photolithography techniques. Carbon Microelectromechanical Systems (C-MEMS) fabrication techniques allow fabrication of high aspect ratio carbon structures by patterning photoresist polymers into desired shapes and subsequent carbonization of resultant structures by pyrolysis. In our sensor platform, suspended nanowires were deposited by electrospinning while photolithography was used to fabricate support structures. We have achieved suspended carbon nanowires with sub-100 nm diameters in this study. The sensor platform was then integrated with a microfluidic chip to form a lab-on-chip device for label-free chemiresistive biosensing. We have investigated this nanoelectronics label-free biosensor's performance towards bacterial sensing by functionalization with Salmonella-specific aptamer probes. The device was tested with varying concentrations of Salmonella Typhimurium to evaluate sensitivity and various other bacteria to investigate specificity. The results showed that the sensor is highly specific and sensitive in detection of Salmonella with a detection limit of 10 CFU mL^-1. Moreover, this proposed chemiresistive assay has a reduced turnaround time of 5 min and sample volume requirement of 5 µL which are much less than reported in the literature.

Multifunctional HA/Cu nano-coatings on titanium using PPy coordination and doping via pulse electrochemical polymerization

An anti-wear and antibacterial hydroxyapatite nanoparticle bioactive coating on a titanium matrix is fabricated through hydroxyapatite/copper nanoparticle co-deposition.

A highly selective electrochemical sensor based on molecularly imprinted polypyrrole-modified gold electrode for the determination of glyphosate in cucumber and tap water

An electrochemical sensor based on molecularly imprinted polypyrrole (MIPPy) was developed for selective and sensitive detection of the herbicide glyphosate (Gly) in cucumber and tap water samples. The sensor was prepared via synthesis of molecularly imprinted polymers on a gold electrode in the presence of Gly as the template molecule and pyrrole as the functional monomer by cyclic voltammetry (CV). The sensor preparation conditions including the ratio of template to functional monomers, number of CV cycles in the electropolymerization process, the method of template removal, incubation time, and pH were optimized. Under the optimal experimental conditions, the DPV peak currents of hexacyanoferrate/hexacyanoferrite changed linearly with Gly concentration in the range from 5 to 800 ng mL-1, with a detection limit of 0.27 ng mL-1 (S/N = 3). The sensor was used to detect the concentration of Gly in cucumber and tap water samples, with recoveries ranging from 72.70 to 98.96%. The proposed sensor showed excellent selectivity, good stability and reversibility, and could detect the Gly in real samples rapidly and sensitively. Graphical abstract Schematic illustration of the experimental procedure to detect Gly using the MIPPy electrode.

Constructed ILs coated porous magnetic nickel cobaltate hexagonal nanoplates sensing materials for the simultaneous detection of cumulative toxic metals

The different morphologies of magnetic nickel cobaltate (NiCo₂O₄) electrocatalysts, consisting of nanoparticles (NiCo₂O₄-N), nanoplates (NiCo₂O₄-P) and microspheres (NiCo₂O₄-S) were fabricated. It was found that the electrocatalytic properties of the sensing materials were strongly dependent on morphology and specific surface area. The porous NiCo₂O₄ hexagonal nanoplates coupled with ILs as modified materials (ILs@NiCo₂O₄-P) for the simultaneous determination of thallium (Tl⁺), lead (Pb²⁺) and copper (Cu²⁺), exhibited high sensitivity, long-time stability and good repeatability. The enhanced electrocatalytic activity was attributed to relatively large specific surface area, excellent electronic conductivity, and unique porous nanostructure. The analytical performance of the constructed electrode on detection of Tl⁺, Pb²⁺ and Cu²⁺ was examined using differential pulse anodic stripping voltammetry (DPASV). Under optimal conditions, the electrode showed a good linear response to Tl⁺, Pb²⁺and Cu²⁺ in the concentration range of 0.1-100.0, 0.1-100.0 and 0.05-100.0μg/L, respectively. The detection limits (S/N=3) were 0.046, 0.034 and 0.029μg/L for Tl⁺, Pb²⁺ and Cu²⁺, respectively. The fabricated sensor was successfully applied to detect trace Tl⁺, Pb²⁺ and Cu²⁺ in various water and soil samples with satisfactory results. Hence, this work provided a promising material for electrochemical determination of cumulative toxic metals individually and simultaneously.

Fabrication of 4-aminophenol sensor based on hydrothermally prepared ZnO/Yb2O3nanosheets

A facile hydrothermal process was used to prepare nanostructures of ZnO/Yb₂O₃in alkaline medium, which were applied for efficient chemical sensor development. The sensor fabricated with ZnO/Yb₂O₃nanostructures may be a promising sensitive chemical sensor for the effective detection of environmental effluents.

Preparation of Highly Dispersed Reduced Graphene Oxide Modified with Carboxymethyl Chitosan for Highly Sensitive Detection of Trace Cu(II) in Water

In this article, reduced graphene oxide (RGO)/carboxymethyl chitosan (CMC) composites (RGO/CMC) were synthesized by a hydrothermal method through in-situ reduction and modification of graphene oxide (GO) in the presence of CMC. An electrochemical sensor for the determination of Cu(II) by differential pulse anodic stripping voltammetry (DPASV) was constructed by an electrode modified with RGO/CMC. The fabricated electrochemical sensor shows a linear range of 0.02⁻1.2 μmol·L^-1, a detection limit of 3.25 nmol·L^-1 (S/N = 3) and a sensitivity of 130.75 μA·μmol·L^-1·cm^-2, indicating the sensor has an excellent detection performance for Cu(II).

A switched catalysis qualified sealers capped one-step synthesis biocompatibility bimetallic scaffold film for Neu5Acα(2-6)Gal β MP Glycoside specific detection

In this work, a novel label-free biosensor was designed for the sensitive and selective determination of Neu5Acα(2-6)Gal β MP Glycoside using AuPt-PPy(polypyrrole) conductive nanocomposite film as the sensor platform. The introduced AuPt-PPy nanocomposite provided a large surface area for the immobilization of Sambucus nigra agglutinis (SNA) through a coupling agent for specifically recognizing analytes and exhibited high electrocatalytic activity toward the reduction of hydrogen peroxide (H2O2) as an analytical signal. Subsequently, to block the non-specific sites of the modified electrode, GOx was employed instead of the usual sealers. Most importantly, in the presence of glucose, these localized GOx further enhanced the electrochemical signal, which was achieved by the efficient catalysis of glucose. This study is the first that demonstrates the specific detection of Neu5Acα(2-6)Gal β MP Glycoside using AuPt-PPy as the electrocatalytic. Under optimal conditions, the electrochemical biosensor exhibited a wide linear range of 0.01 pgmL(-1)-800 ngmL(-1) with a low detection limit of 0.003 pgmL(-1) (S/N=3), due to the affinity between SNA and Neu5Acα(2-6)Gal β MP Glycoside. Therefore, the co-catalysis signal amplification approach has considerable potential in clinical applications and is suitable for the quantification of other biomarkers.

High Sensitive Sensor Fabricated by Reduced Graphene Oxide/Polyvinyl Butyral Nanofibers for Detecting Cu (II) in Water

Graphene oxide (GO)/polyvinyl butyral (PVB) nanofibers were prepared by a simple electrospinning technique with PVB as matrix and GO as a functional nanomaterial. GO/PVB nanofibers on glassy carbon electrode (GCE) were reduced through electrochemical method to form reduced graphene oxide (RGO)/PVB nanofibers. The morphology and structure of GO/PVB nanofiber were studied by scanning election microscopy (SEM), transmission electron microscopy (TEM), and Fourier transform infrared (FTIR). RGO/PVB modified GCE was used for fabricating an electrochemical sensor for detecting Cu (II) in water. The analysis results showed that RGO/PVB modified GCE had good analytical results with the linear range of 0.06–2.2 μM, detection limit of 4.10 nM (S/N = 3), and the sensitivity of 103.51 μA·μM⁻¹·cm⁻².

A porous PdO microrod-based electrochemical sensor for nanomolar-level Cu2+ released from cells

Highly porous PdO microrods (PoPdOMRs) with a well-defined morphology, large surface area and active sites were synthesized via a facile wet chemical method for the first time. A sensitive and selective electrochemical sensor was thus developed by using the PoPdOMRs as a sensing platform. The PoPdOMR modified sensor exhibited a response time of less than 8 s, a linear range between 1.0 × 10^-9 and 8.0 × 10^-5 mM, and a sensitivity up to 112 μA μM^-1 cm^-2 for the determination of Cu²⁺. A sound sensing selectivity towards Cu²⁺ in the presence of interfering ions was also observed. On the basis of this sensor, the trace amount of Cu²⁺ released from Raw 264.7 cells was successfully recorded, which makes the PoPdOMR electrocatalyst promising for the development of effective electrochemical sensors for a wide range of potential applications in bioanalysis and environmental chemistry.

Combining surface topography with polymer chemistry: exploring new interfacial biological phenomena

This review focuses on combining surface topography and surface chemical modification by the grafting of polymers to develop optimal material interfaces with synergistic properties and functions for biological and biomedical applications.

Elaboration of ammonia gas sensors based on electrodeposited polypyrrole--cobalt phthalocyanine hybrid films

The electrochemical incorporation of a sulfonated cobalt phthalocyanine (sCoPc) in conducting polypyrrole (PPy) was done, in the presence or absence of LiClO4, in order to use the resulting hybrid material for the sensing of ammonia. After electrochemical deposition, the morphological features and structural properties of polypyrrole/phthalocyanine hybrid films were investigated and compared to those of polypyrrole films. A gas sensor consisting in platinum microelectrodes arrays was fabricated using silicon microtechnologies, and the polypyrrole and polypyrrole/phthalocyanine films were electrochemically deposited on the platinum microelectrodes arrays of this gas sensor. When exposed to ammonia, polymer-based gas sensors exhibited a decrease in conductance due to the electron exchange between ammonia and sensitive polymer-based layer. The characteristics of the gas sensors (response time, response amplitude, reversibility) were studied for ammonia concentrations varying from 1 ppm to 100 ppm. Polypyrrole/phthalocyanine films exhibited a high sensitivity and low detection limit to ammonia as well as a fast and reproducible response at room temperature. The response to ammonia exposition of polypyrrole films was found to be strongly enhanced thanks to the incorporation of the phthalocyanine in the polypyrrole matrix.