Tailoring MWCNTs and β-Cyclodextrin for Sensitive Detection of Acetaminophen and Estrogen

Fabrication of an innovative electrochemical sensor based on graphene-coated silver nanoparticles decorated over graphitic carbon nitride for efficient determination of estradiol

Monitoring small amount of endocrine disrupting chemical, estradiol (E2) residue in environmental and biological samples is extremely important because of its possible connections to breast and prostate malignancies and gastrointestinal disorders. The newly synthesized graphene-coated silver nanoparticles (GN@Ag) decorated on graphitic carbon nitride (g-C3N4)-based hybrid nanomaterial (GN@Ag/g-C3N4) was used to modify glassy carbon electrode (GCE) for electroanalytical measurement of E2. The GN@Ag/g-C3N4 nanocomposite prepared through ultrasonic-assisted reflux methodology was characterized using various physicochemical methods. The scanning electron microscopy and transmission electron microscopy have shown that GN@Ag nanoparticles were decorated and randomly dispersed over g-C3N4 sheets. The exceptional electrochemical response towards the oxidation of E2 was observed through cyclic voltammetry due to the quick electron transfer ability and superior conductivity of GN@Ag/g-C3N4/GCE. The detection limit was found to be 0.002 μM with wide linear range of E2 concentration (0.005-8.0 μM) along with remarkable stability of the fabricated electrode for 21 days showing 91% retention in initial current. The kinetic parameters such as catalytic rate constant and diffusion coefficient for E2 were estimated to be 1.1 × 105 M-1 s-1 and 1.9 × 10-4 cm2 s-1, respectively, by employing chronoamperometry. The proposed sensor also demonstrated its practical applicability for E2 determination in environmental and biological samples with a recovery range of 95-104%. Furthermore, the developed sensing platform is much better compared to reported methods in terms of simplicity, accuracy, detection limit, linearity range, and usefulness in real sample for E2 sensing.

One-step growth of Cu-doped carbon dots in amino-modified carbon nanotube-modified electrodes for sensitive electrochemical detection of BPA

Copper-doped carbon dots and aminated carbon nanotubes (Cu-CDs/NH2-CNTs) nanocomposites were synthesized by a one-step growth method, and the composites were characterized for their performance. An electrochemical sensor for sensitive detection of bisphenol A (BPA) was developed for using Cu-CDs/NH2-CNTs nanocomposites modified with glassy carbon electrodes (GCE). The sensor exhibited an excellent electrochemical response to BPA in 0.2 M PBS (pH 7.0) under optimally selected conditions. The linear range of the sensor for BPA detection was 0.5-160 μM, and the detection limit (S/N = 3) was 0.13 μM. Moreover, the sensor has good interference immunity, stability and reproducibility. In addition, the feasibility of the practical application of the sensor was demonstrated by the detection of BPA in bottled drinking water and Liu Yang River water.

Photothermal Hydrogel Composites Featuring G4-Carbon Nanomaterial Networks for Staphylococcus aureus Inhibition

Microbial infections represent a significant health risk, often leading to severe complications and, in some cases, even fatalities. As a result, there is an urgent need to explore innovative drug delivery systems and alternative therapeutic techniques. The photothermal therapy has emerged as a promising antibacterial approach and is the focus of this study. Herein, we report the successful synthesis of two distinct supramolecular composite hydrogels by incorporating graphene oxide (GO) and single-walled carbon nanotubes (SWNTs) into guanosine quadruplex (G4) based hydrogels containing covalently bound β-cyclodextrin (β-CD). The G4 matrix was synthesized through a two-step process, establishing a robust network between G4 and β-CDs, followed by the encapsulation of either GO or SWNTs. Comprehensive characterization of these composite hydrogels were conducted using analytical techniques, including circular dichroism, Raman spectroscopy, rheological investigations, X-ray diffraction, and scanning electron microscopy. A notable discovery from the conducted research is the differential photothermal responses exhibited by the hydrogels when exposed to near-infrared laser irradiation. Specifically, SWNT-based hydrogels demonstrated superior photothermal performance, achieving a remarkable temperature increase of up to 52 °C, in contrast to GO-based hydrogels, which reached a maximum of 34 °C. These composite hydrogels showed good cytotoxicity evaluation results and displayed synergistic antibacterial activity against Staphylococcus aureus, positioning them as promising candidates for antibacterial photothermic platforms, particularly in the context of wound treatment. This study offers a valuable contribution to the development of advanced and combined therapeutic strategies for combating microbial infections and highlights the potential of carbon nanomaterial-enhanced supramolecular hydrogels in photothermal therapy applications.

Electrochemical sensor for sensitive detection of bisphenol A based on molecularly imprinted TiO2 with oxygen vacancy

Bisphenol A (BPA) is an endocrine disrupting chemical and broadly used in plastics. The leakage of BPA in food and water cycles poses a significant risk to the environment and human health. Thus, monitoring the concentration of BPA to avoid its potential risk is highly important. In this work, a simple and efficient oxygen deficient molecularly imprinted TiO2 electrochemical sensor was proposed for the detection of BPA. The introduction both oxygen vacancies and molecular imprinting evidently enhanced the electrochemical oxidation signal of BPA. The sensor had a good linear response ranging from 0.01 μM to 20 μM with a limit of detection of 3.6 nM. Additionally, the sensor showed remarkable stability, reproducibility and interference resistant ability. It also exhibits excellent recovery during the detection of real water. These findings suggested that the sensor has the potential to be developed as a simple, efficient and low-cost monitoring system for the monitoring of BPA in water.

Nanostructured N, S, and P-Doped Elaeagnus Angustifolia Gum-Derived Porous Carbon with Electrodeposited Silver for Enhanced Electrochemical Sensing of Acetaminophen

Acetaminophen (N-acetyl-p-aminophenol, APAP) is regularly used for antipyretic and analgesic purposes. Overdose or long-term exposure to APAP could lead to liver damage and hepatotoxicity. In this study, the approach of enhanced electrochemical detection of APAP by nanostructured biomass carbon/silver was developed. Porous biomass carbon derived from Elaeagnus Angustifolia gum was prepared by pyrolysis with co-doping of electron-rich elements of nitrogen, sulfur, and phosphorus. The electrodeposition of silver onto a glassy carbon electrode modified with porous carbon could enhance the sensing signal towards APAP. Two linear ranges from 61 nM to 500 μM were achieved with a limit of detection of 33 nM. The developed GCE sensor has good anti-interference, stability, reproducibility, and human urine sample analysis performance. The silver-enhanced biomass carbon GCE sensor extends the application of biomass carbon, and its facile preparation approach could be used in constructing disposable sensing chips in the future.

Specific Alcohol-Responsive Photonic Crystal Sensors Based on Host-Guest Recognition

A photonic crystal material based on β-cyclodextrin (β-CD) with adsorption capacity is reported. The materials ((A-β-CD)-AM PC) consist of 3D poly (methyl methacrylate) (PMMA) colloidal microsphere arrays and hydrogels supplemented with β-cyclodextrin modified by acryloyl chloride. The prepared materials are then utilized for VOCs gas sensing. The 3D O-(A-β-CD)-AM PC was used to detect toluene, xylene, and acetone and the response was seen as the red-shift of the reflection peak. The 3D I-(A-β-CD)-AM PC was used to detect toluene, xylene, and acetone which occurred redshifted, while methanol, ethanol, and propanol and the peaks' red-shifting was observed. However, among these, methanol gave the largest red-shift response The sensor has broad prospects in the detection of alcohol and the detection of alcohol-loaded drug releases in the future.

Enhanced Acetaminophen Electrochemical Sensing Based on Nitrogen-Doped Graphene

Because of the widespread acetaminophen usage and the danger of harmful overdosing effects, developing appropriate procedures for its quantitative and qualitative assay has always been an intriguing and fascinating problem. A quick, inexpensive, and environmentally friendly approach based on direct voltage anodic graphite rod exfoliation in the presence of inorganic salt aqueous solution ((NH₄)₂SO₄-0.3 M) has been established for the preparation of nitrogen-doped graphene (exf-NGr). The XRD analysis shows that the working material appears as a mixture of few (76.43%) and multi-layers (23.57%) of N-doped graphenes. From XPS, the C/O ratio was calculated to be 0.39, indicating a significant number of structural defects and the existence of multiple oxygen-containing groups at the surface of graphene sheets caused by heteroatom doping. Furthermore, the electrochemical performances of glassy carbon electrodes (GCEs) modified with exf-NGr for acetaminophen (AMP) detection and quantification have been assessed. The exf-NGr/GCE-modified electrode shows excellent reproducibility, stability, and anti-interfering characteristics with improved electrocatalytic activity over a wide detection range (0.1-100 µM), with a low limit for AMP detection (LOD = 3.03 nM). In addition, the developed sensor has been successfully applied in real sample analysis for the AMP quantification from different commercially available pharmaceutical formulations.

Recent Development of Nano-Carbon Material in Pharmaceutical Application: A Review

Carbon nanomaterials have attracted researchers in pharmaceutical applications due to their outstanding properties and flexible dimensional structures. Carbon nanomaterials (CNMs) have electrical properties, high thermal surface area, and high cellular internalization, making them suitable for drug and gene delivery, antioxidants, bioimaging, biosensing, and tissue engineering applications. There are various types of carbon nanomaterials including graphene, carbon nanotubes, fullerenes, nanodiamond, quantum dots and many more that have interesting applications in the future. The functionalization of the carbon nanomaterial surface could modify its chemical and physical properties, as well as improve drug loading capacity, biocompatibility, suppress immune response and have the ability to direct drug delivery to the targeted site. Carbon nanomaterials could also be fabricated into composites with proteins and drugs to reduce toxicity and increase effectiveness in the pharmaceutical field. Thus, carbon nanomaterials are very effective for applications in pharmaceutical or biomedical systems. This review will demonstrate the extraordinary properties of nanocarbon materials that can be used in pharmaceutical applications.

Two Types of Subgroup-Valence Heteroatoms (PIII, TeIV) Synergistically Controlling Octa-CeIII-Encapsulated Heteropolyoxotungstate and Its Electrochemical Recognition Properties

Rapid development of the synthetic chemistry of polyoxometalates (POMs) has greatly driven the generation of structurally variable innovative POM-based materials. Herein, we synthesized a novel P^III and Te^IV synergistically controlling octa-Ce^III-encapsulated heteropolyoxotungstate [H₂N(CH₃)₂]₁₁K₂Na₆H₁₁[Ce₈(CH₃COO)₂(HP^IIIO₃)₂W₈O₂₀(H₂O)₁₂(B-β-TeW₈O₃₀)₂(B-α-TeW₈O₃₁)₄]·64H₂O (1). Its distinctive anion skeleton [Ce₈(CH₃COO)₂(HP^IIIO₃)₂W₈O₂₀(H₂O)₁₂(B-β-TeW₈O₃₀)₂(B-α-TeW₈O₃₁)₄]^30- is built by two tetra-vacancy [B-β-TeW₈O₃₀]^8- and four tetra-vacancy [B-α-TeW₈O₃₁]^10- moieties linked through an inorganic-organic hybrid [Ce₈(CH₃COO)₂(HP^IIIO₃)₂W₈O₂₀(H₂O)₁₂]²⁶⁺ {Ce₈P₂W₈} cluster core. Interestingly, {Ce₈P₂W₈} is assembled from four [W₂O₁₁]^10- groups and two [HP^IIIO₃]^2- anions and eight Ce³⁺ ions. Besides, 1 was further composited with carboxylated multiwalled carbon nanotube (CMCN), resulting in a bi-component 1/CMCN nanocomposite. An electrochemical recognition platform (named as 1/CMCN/GCE) was built by modifying 1/CMCN on a glassy carbon electrode (GCE) for electrochemical detection of dopamine (DPA) at physiological pH (pH = 7.0). The findings have shown that 1/CMCN/GCE exhibits a good detection limit of 4.95 nM for DPA. This work provides considerable inspiration to promote innovative and rational structure designs of POM-based materials and expand their applications to electrochemical and biological detection fields.

β-Cyclodextrin-functionalized graphene and metal–organic framework composites for ultrasensitive electrochemical detection of chloramphenicol

Novel β-CD@functionalized graphene /Cu-BTC composites were in situ prepared using β-CD functionalized graphene and Cu-BTC, and a new electrochemical sensor for sensitive detection of chloramphenicol was developed based on the composites.

Cyclodextrins: Structural, Chemical, and Physical Properties, and Applications

Due to their unique structural, physical and chemical properties, cyclodextrins and their derivatives have been of great interest to scientists and researchers in both academia and industry for over a century. Many of the industrial applications of cyclodextrins have arisen from their ability to encapsulate, either partially or fully, other molecules, especially organic compounds. Cyclodextrins are non-toxic oligopolymers of glucose that help to increase the solubility of organic compounds with poor aqueous solubility, can mask odors from foul-smelling compounds, and have been widely studied in the area of drug delivery. In this review, we explore the structural and chemical properties of cyclodextrins that give rise to this encapsulation (i.e., the formation of inclusion complexes) ability. This review is unique from others written on this subject because it provides powerful insights into factors that affect cyclodextrin encapsulation. It also examines these insights in great detail. Later, we provide an overview of some industrial applications of cyclodextrins, while emphasizing the role of encapsulation in these applications. We strongly believe that cyclodextrins will continue to garner interest from scientists for many years to come, and that novel applications of cyclodextrins have yet to be discovered.

Ferrocene-reduced graphene oxide-polyoxometalates based ternary nanocomposites as electrochemical detection for acetaminophen

Developing a convenient and accurate method for the determination of acetaminophen (APAP) content is very vital, and ferrocene (Fc) based nanocomposites coupled with polyoxometalates (POMs) as electrochemical sensor is a promising approach to address the issues. Herein, a new ternary nanocomposite of Fc based carbon nanomaterials (Fc-rGO) with PMo₁₂ (Fc-rGO/PMo₁₂, rGFP-n) was successfully fabricated, and the electrochemical activities and APAP detection of rGFP-n as electro-active materials were systematically investigated, and results of the differential pulse voltammetry (DPV) and electro-active surface area (0.0332 cm²) show that rGFP-1 is an excellent electrochemical sensor for APAP, and the proportion of Fc in rGFP-n can affect the charge transfer between APAP and rGFP. Under the optimal experimental conditions, rGFP-1 can be used to detect APAP with the limit of detection (LOD) of 13.27 nM (S/N = 3), the sensitivity of 36.81μA⋅μM^-1cm^-2, and the detection range from 1×10^-6 to 1×10^-3M, meeting the lowest plasma concentration of APAP (1.3 mM).

Application of nanomaterials decorated with cyclodextrins as sensing elements for environment analysis

Environmental pollution has brought adverse socio-economic consequences. Organic pollutants and heavy metals are the main culprits of environmental pollution. It is of great importance to develop novel, simple, rapid, sensitive, and low-cost detection approaches for sensing trace pollutants in environmental samples. A lot of detection strategies which are based on varieties of nanomaterials have been developed for environmental analysis in past decades. In this review, we retrospect a variety of nanomaterials decorated with cyclodextrins (CDs), including carbon nanomaterials decorated with CDs, noble metal nanomaterials decorated with CDs and other nanomaterials decorated with CDs, and their application in environmental analysis. CDs is a type of ideal modifying molecules which could recognize targets, improve the solubility and dispersibility of corresponding functionalized materials, and enhance the detecting performance of designed sensors. CDs have been widely immobilized to carbon nanomaterials, noble metal nanomaterials, phosphorene (BP) nanocomposites, metal organic framework (MOF), and magnetic nanomaterials, and these nanocomposites have been utilized as the sensing elements for different target analytes. Immobilizing CDs on different nanomaterials could extremely expand the development of new sensing systems for environmental analysis based on these materials, greatly broaden the species of sensing targets, and apparently improve their sensing performance. Herein, the nanomaterials decorated with CDs, as sensing elements for environmental analysis, were reviewed including the types of nanomaterials decorated with CDs and their applications in various sensing strategies for environmental analysis. Finally, the perspectives of the nanomaterials decorated with CDs used as sensing elements were also discussed.

Harnessing selectivity in chemical sensing via supramolecular interactions: from functionalization of nanomaterials to device applications

Chemical sensing is a strategic field of science and technology ultimately aiming at improving the quality of our lives and the sustainability of our Planet. Sensors bear a direct societal impact on well-being, which includes the quality and composition of the air we breathe, the water we drink, and the food we eat. Pristine low-dimensional materials are widely exploited as highly sensitive elements in chemical sensors, although they suffer from lack of intrinsic selectivity towards specific analytes. Here, we showcase the most recent strategies on the use of (supra)molecular interactions to harness the selectivity of suitably functionalized 0D, 1D, and 2D low-dimensional materials for chemical sensing. We discuss how the design and selection of receptors via machine learning and artificial intelligence hold a disruptive potential in chemical sensing, where selectivity is achieved by the design and high-throughput screening of large libraries of molecules exhibiting a set of affinity parameters that dictates the analyte specificity. We also discuss the importance of achieving selectivity along with other relevant characteristics in chemical sensing, such as high sensitivity, response speed, and reversibility, as milestones for true practical applications. Finally, for each distinct class of low-dimensional material, we present the most suitable functionalization strategies for their incorporation into efficient transducers for chemical sensing.

Electrochemical sensing platform for the simultaneous femtomolar detection of amlodipine and atorvastatin drugs

The development of a proficient and ultra-high sensitive functionalized electrode for accurate analysis of drugs is a long-standing challenge. Herein, we report an electrochemical nanocomposite scaffold, comprising of silver nanoparticles integrated with functionalized carbon nanotubes (COOH-CNTs/Ag/NH₂-CNTs) for the simultaneous quantification of two widely used amlodipine (AM) and atorvastatin (AT) drugs. The sandwiched nanocomposite materials were thoroughly characterized morphologically and structurally. The nanocomposite COOH-CNTs/Ag/NH₂-CNTs immobilized over glassy carbon electrode catalyzed electron transfer reactions at the electrode–electrolyte interface and facilitated detection of targeted drugs, as revealed by the significant decrease in oxidation potentials at 879 mV and 1040 mV and improved current signals. Electrochemical characterization and testing show that the functionalized porous architecture with a large effective surface area is a promising scaffold for the sensing of a binary mixture of AM and AT with limits of detection in the femtomolar range (77.6 fM, and 83.2 fM, respectively). Besides, the specificity, stability, and reliability of the electrochemical sensing platform in simple and complex biological and pharmaceutical samples with high percentage recoveries highlight its scope for practical applications. Computational studies supported the experimental outcomes and offered insights about the role of modifier in facilitating electron transfer between transducer and analytes.

Development of an ultra-sensitive electrochemical platform for the simultaneous detection of two high blood pressure drugs.

A Low-Cost Multi-Parameter Water Quality Monitoring System

Multi-parameter water quality monitoring is crucial in resource-limited areas to provide persistent water safety. Conventional water monitoring techniques are time-consuming, require skilled personnel, are not user-friendly and are incompatible with operating on-site. Here, we develop a multi-parameter water quality monitoring system (MWQMS) that includes an array of low-cost, easy-to-use, high-sensitivity electrochemical sensors, as well as custom-designed sensor readout circuitry and smartphone application with wireless connectivity. The system overcomes the need of costly laboratory-based testing methods and the requirement of skilled workers. The proposed MWQMS system can simultaneously monitor pH, free chlorine, and temperature with sensitivities of 57.5 mV/pH, 186 nA/ppm and 16.9 mV/°C, respectively, as well as sensing of BPA with <10 nM limit of detection. The system also provides seamless interconnection between transduction of the sensors' signal, signal processing, wireless data transfer and smartphone app-based operation. This interconnection was accomplished by fabricating nanomaterial and carbon nanotube-based sensors on a common substrate, integrating these sensors to a readout circuit and transmitting the sensor data to an Android application. The MWQMS system provides a general platform technology where an array of other water monitoring sensors can also be easily integrated and programmed. Such a system can offer tremendous opportunity for a broad range of environmental monitoring applications.

Advanced Li-S Batteries Enabled by a Biomimetic Polysulfide-Engulfing Net

Lithium-sulfur batteries are attractive because of their high specific capacity and energy density, but issues with the polysulfide dissolution and shuttling intrinsically hinder their wide application. Here, hydroxylate multiwalled carbon nanotubes (MWCNT-OH) were grafted with a supramolecular polymer (heptakis(6-amino-6-deoxy)-β-cyclodextrin) to form a polysulfide-engulfing net, which was coated on a separator. Such a molecular microarray structure of a polymer can block the polysulfides and have biomimetic cellular behavior for engulfing polysulfides. The cavity (∼6 Å) and functional groups of the supramolecular polymer can provide a dynamic structure for reversible adsorption of polysulfides while the conductive MWCNT-OH ensure fast electron transfer. The batteries with the modified separator exhibited excellent rate capacities (945.5 and 625.4 mA h g^-1 at 2 C and 4 C rates, respectively). Especially, the high areal capacities of 5.86 and 7.2 mA h cm^-2 achieved at S loadings of 4.5 and 6.0 mg cm^-2 and good cycling stability after 200 cycles at 0.1 C can be obtained. This demonstrates a strategy of supramolecular polymer-grafted carbon for dynamic polysulfide adsorption toward advanced Li-S batteries.

An electrochemical platform based on a hemin-rGO-cMWCNTs modified aptasensor for sensitive detection of kanamycin

Kanamycin (KANA) residue in meat is particularly harmful to public health and there is an urgent need to establish a fast, accurate and low-cost method to determinate KANA in food quality control. In this paper, hemin-reduced graphene oxide-carboxylated multiwalled carbon nanotubes (hemin-rGO-cMWCNTs) were designed and prepared, and the characteristics of hemin-rGO-cMWCNTs are presented. After that, an aptamer/hemin-rGO-cMWCNTs sensor for determination of KANA was developed. The electrochemical characteristics were studied by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). Under optimal conditions, the sensitive response of the aptasensor towards KANA presented a wide concentration range of 10-9 to 10-6 M and a low detection limit of 0.36 nM (S/N = 3). Meanwhile, the aptasensor showed prominent selectivity, high stability and acceptable reproducibility in the application of KANA detection. In addition, the aptasensor detection in real samples correlated well with that obtained by liquid chromatograph mass spectrometer (LCMS).

da Silva Alves D, Okeke C, Breslin CB. Cyclodextrins as Supramolecular Recognition Systems: Applications in the Fabrication of Electrochemical Sensors

Supramolecular chemistry, although focused mainly on noncovalent intermolecular and intramolecular interactions, which are considerably weaker than covalent interactions, can be employed to fabricate sensors with a remarkable affinity for a target analyte. In this review the development of cyclodextrin-based electrochemical sensors is described and discussed. Following a short introduction to the general properties of cyclodextrins and their ability to form inclusion complexes, the cyclodextrin-based sensors are introduced. This includes the combination of cyclodextrins with reduced graphene oxide, carbon nanotubes, conducting polymers, enzymes and aptamers, and electropolymerized cyclodextrin films. The applications of these materials as chiral recognition agents and biosensors and in the electrochemical detection of environmental contaminants, biomolecules and amino acids, drugs and flavonoids are reviewed and compared. Based on the papers reviewed, it is clear that cyclodextrins are promising molecular recognition agents in the creation of electrochemical sensors, chiral sensors, and biosensors. Moreover, they have been combined with a host of materials to enhance the detection of the target analytes. Nevertheless, challenges remain, including the development of more robust methods for the integration of cyclodextrins into the sensing unit.

Detection of pollutants in water bodies: electrochemical detection or photo-electrochemical detection?

The massive discharge of pollutants including endocrine-disrupting chemicals (EDCs), heavy metals, pharmaceuticals and personal care products (PPCPs) into water bodies is endangering the ecological environment and human health, and needs to be accurately detected. Both electrochemical and photo-electrochemical detection methods have been widely used for the detection of these pollutants, however, which one is better for the detection of different environmental pollutants? In this feature article, different electrochemical and photo-electrochemical detection methods are summarized, including the principles, classification, common catalysts, and applications. By summarizing the advantages and disadvantages of different detection methods, this review provides a guide for other researchers to detect pollutants in water bodies by using electrochemical and photo-electrochemical analysis.

Separation of Biological Events from the Photoanode: Toward the Ferricyanide-Mediated Redox Cyclic Photoelectrochemical System of an Integrated Photoanode and Photocathode

Photoanode sensing platforms with remarkable photoelectrochemical (PEC) response and satisfying visible-light absorption have become the most promising detection systems. Nevertheless, their inevitable electrophilic character limits their expansion in the bioassay because of reductive substances in serum or other body fluids that can severely interfere with the photocurrent to be read. To solve it, a PEC platform-assembled dual-active electrode is designed to realize the separation of biological monitoring from the photoanode. The ferricyanide ([Fe(CN)₆]^3-)-mediated redox cycle is first proposed to meet the gain and loss electron requirements of the PEC system. It can avoid the self-reaction in the electrolyte caused by the addition of a traditional electron donor and acceptor, for instance, ascorbic acid and hydrogen peroxide. As a consequence, the traditional counter electrode (Pt wire) is replaced by Fe₂O₃/AgInS₂ heterojunction, which can amplify the PEC response of the cathode to meet the requirement of trace analysis. An aptasensor fabricated by the above strategies exhibits convincing data for 17β-estradiol (E2) detection from which a wide detection range is obtained in 10 fg/mL to 1 μg/mL with a detection limit of 2.74 fg/mL (S/N = 3). These advanced elements show a rosy prospect for environmental monitoring and point-of-care biomarker diagnosis.

Surfactant assisted Cr-metal organic framework for the detection of bisphenol A in dust from E-waste recycling area

Due to their highly porous structures, metal organic framework materials are widely used in analytic areas. In this paper, Cr-metal organic framework (MIL-101(Cr)) modified electrode was prepared and then was used as electrochemical sensor for the detection of bisphenol A (BPA). By using one kind of surfactant of cetyltrimethylammonium bromide (CTAB), the analytic performances of MIL-101 (Cr) towards BPA detection were greatly improved. Compared with pure MIL-101 (Cr), the differential pulse voltammetry (DPV) behavior of CTAB/MIL-101 (Cr) was improved 3.0 times in the presence of BPA. The hydrophobic long chain alkanes of CTAB can improve the enrichment and electrochemical oxidation for BPA. The CTAB/MIL-101 (Cr) sensor exhibited a linear range from 20 to 350 nM and a low detection limit of 9.95 nM (LOD = 3s_b/S) and showed good reproducibility, stability and selectivity. Finally, real samples of dusts from E-waste recycling area in South China were collected and the CTAB/MIL-101 (Cr) sensor demonstrated satisfactory results for BPA detection from these dust samples.

Multi-praseodymium-and-tungsten bridging octameric tellurotungstate and its 2D honeycomb composite film for detecting estrogen

Under coordination driving force of tungsten and rare-earth (RE) bridges, we synthesized a novel giant multi-tungsten-and-RE-bridging octameric tellurotungstate (TT) [H₂N(CH₃)₂]₁₆K₈Na₆H₁₀[Pr₈(H₂O)₂₀W₁₆O₄₈][B-α-TeW₉O₃₃]₈·70H₂O (1) in CH₃CN-H₂O mixed solvent. The cluster anion {[Pr₈(H₂O)₂₀W₁₆O₄₈][B-α-TeW₉O₃₃]₈}^40- features sixteen W^VI bridges, eight Pr^III bridges and eight trivacant Keggin [B-α-TeW₉O₃₃]^8- fragments, which the square {W₄O₁₂} cluster can be imagined as a seed to induce the aggregation of eight [B-α-TeW₉O₃₃]^8- fragments by coordination driving force of additional twelve W^VI bridges and eight Pr^III ions. Furthermore, the 2D 1@DODA (dimethyldioctadecyl ammonium bromide = DODA·Br) honeycomb composite material was prepared. The honeycomb morphology of the 1@DODA composite material provides rich binding sites for electrodepositing Au nanoparticles to make Au/1@DODA electrodes. The aptamer of 17β-estradiol (E2) hormone can be grafted to the Au/1@DODA electrodes via Au-S bonding interaction to construct the Au/1@DODA aptamer biosensors. By virtue of the specific recognition interaction of aptamer and the electrochemical signal amplification function of methylene blue and cDNA, the Au/1@DODA aptamer biosensors can realize the electrochemical detection of E2. This finding not only offers an electrochemical biosensing platform for detecting E2, but also expands POM-based composite materials in the applications of clinical detection and biological analysis.

Fully Integrated, Simple, and Low-Cost Electrochemical Sensor Array for in Situ Water Quality Monitoring

Rapid, accurate and inexpensive monitoring of water quality parameters is indispensable for continued water safety, especially in resource-limited areas. Most conventional sensing systems either can only monitor one parameter at a time or lack user-friendly on-site monitoring capabilities. A fully integrated electrochemical sensor array is an excellent solution to this barrier. Electrochemical sensing methods involve transduction of water quality parameters where chemical interactions are converted to electrical signals. The challenge remains in designing low-cost, easy-to-use, and highly sensitive sensor array that can continuously monitor major water quality parameters such as pH, free chlorine, temperature along with emerging pharmaceutical contaminants, and heavy metal without the use of expensive laboratory-based techniques and trained personnel. Here, we overcame this challenge through realizing a fully integrated electrochemical sensing system that offers simultaneous monitoring of pH (57.5 mV/pH), free chlorine (186 nA/ppm), and temperature (16.9 mV/°C) and on-demand monitoring of acetaminophen and 17β-estradiol (<10 nM) and heavy metal (<10 ppb), bridging the technological gap between signal transduction, processing, wireless transmission, and smartphone interfacing. This was achieved by merging nanomaterials and carbon nanotube-based sensors fabricated on microscopic glass slides controlled by a custom-designed readout circuit, a potentiostat, and an Android app. The sensing system can be easily modified and programmed to integrate other sensors, a capability that can be exploited to monitor a range of water quality parameters. We demonstrate the integrated system for monitoring tap, swimming pool, and lake water. This system opens the possibility for a wide range of low-cost and ubiquitous environmental monitoring applications.

Synthesis of novel ternary heterogeneous anatase-TiO2 (B) biphase nanowires/Bi4O5I2 composite photocatalysts for the highly efficient degradation of acetaminophen under visible light irradiation

Bi₄O₅I₂ loaded anatase-TiO₂ (B) biphase nanowires composite photocatalysts were fabricated by an in situ calcination method and exhibited outstanding photocatalytic activity. The microstructure, optical performance and band structure of the composite photocatalysts were investigated by relevant characterizations. The results demonstrated the successful formation of heterojunction between anatase-TiO₂ (B) biphase nanowires and Bi₄O₅I₂, which integrated the advantages of homojunction and heterojunction. Therefore, it definitely improved separation efficiency of photo-induced electron-holes because of the formation of multi-junctions. In order to test the enhanced photocatalytic activity, acetaminophen was chosen as target pollutant. The sample with 67% Bi₄O₅I₂ (TiO₂-Bi₄O₅I₂-3) presented the highest photocatalytic activity on the degradation of acetaminophen and its reaction apparent rate constant was 10 and 25 times as that of Bi₄O₅I₂ and TiO₂ biphase nanowires, respectively. Through trapping experiments and LC-MS/MS analysis, OH was proved to be the key active specie during the photocatalytic process of acetaminophen degradation. Meanwhile a possible degradation pathway was proposed based on the detected intermediate products.

Copper(I)-Catalyzed Click Chemistry as a Tool for the Functionalization of Nanomaterials and the Preparation of Electrochemical (Bio)Sensors

Proper functionalization of electrode surfaces and/or nanomaterials plays a crucial role in the preparation of electrochemical (bio)sensors and their resulting performance. In this context, copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) has been demonstrated to be a powerful strategy due to the high yields achieved, absence of by-products and moderate conditions required both in aqueous medium and under physiological conditions. This particular chemistry offers great potential to functionalize a wide variety of electrode surfaces, nanomaterials, metallophthalocyanines (MPcs) and polymers, thus providing electrochemical platforms with improved electrocatalytic ability and allowing the stable, reproducible and functional integration of a wide range of nanomaterials and/or different biomolecules (enzymes, antibodies, nucleic acids and peptides). Considering the rapid progress in the field, and the potential of this technology, this review paper outlines the unique features imparted by this particular reaction in the development of electrochemical sensors through the discussion of representative examples of the methods mainly reported over the last five years. Special attention has been paid to electrochemical (bio)sensors prepared using nanomaterials and applied to the determination of relevant analytes at different molecular levels. Current challenges and future directions in this field are also briefly pointed out.

Hierarchically Porous Composite Scaffold Composed of SBA-15 Microrods and Reduced Graphene Oxide Functionalized with Cyclodextrin for Water Purification

Large-scale decontamination of bisphenol A (BPA) from wastewater under field conditions is an urgent need because of the harmful toxic effects of BPA on living organisms. In this study, we report the fabrication of a three-dimensional (3D) hierarchically porous composite scaffold composed of mesoporous SBA-15 silica microrods and reduced graphene oxide (rGO-CD) functionalized with β-cyclodextrin (CD) and its application for BPA separation from contaminated water. The macroporous structure was achieved by sacrificial salt leaching, and the mesoporous structure was derived from the interparticle pores between compressed SBA-15 particles and intrinsic mesopores in SBA-15. The 3D hierarchical macroporous and mesoporous architecture of the scaffold enhances mass transport without any external forces, and the rGO-CD component provides good capture sites for BPA in solution via inclusion complexation between CD and BPA. The inorganic SBA-15 component of the scaffold also allows long-term operation of filters by increasing the mechanical strength of the scaffold. The hierarchically porous SBA-15/rGO-CD composite scaffold could separate BPA from contaminated water significantly better than the scaffold without rGO-CD in both batch and filter systems. Our study indicates that the functional hierarchically porous composite scaffold can be a potential material in wastewater treatment technology.