A new generation of highly sensitive potentiometric sensors based on ion imprinted polymeric nanoparticles/multiwall carbon nanotubes/polyaniline/graphite electrode for sub-nanomolar detection of lead(II) ions

Construction of a fluorescence switch sensor of Mn doped AgInS2 quantum dots for the detection of Fe (III) and ascorbic acid

The convenience and high efficiency of recently developed I-III-VI group AgInS2 (AIS) fluorescence sensors have garnered considerable attention. In this study, glutathione (GSH) was employed as a stabilizer to synthesize Mn doped AgInS2 quantum dots (Mn-AIS QDs) via a one-step hydrothermal method at a lower temperature. The resultant samples displayed favorable photoluminescent characteristics and excellent water dispersibility. The photoluminescence of Mn-AIS QDs is quenched by Fe (III) via a photo-induced electron transfer mechanism (PET), and this quenching can be reversed by ascorbic acid (AA) as a result of the redox reaction between the Mn-AIS-Fe (III) complex and AA. Utilizing the on-off-on fluorescence principle, a fluorescence switch sensor based on Mn-AIS QDs was developed for the detection of Fe (III) and AA. The linear range for the detection of Fe (III) using the Mn-AIS QDs sensor was established to be 0.03-120 µM, with a detection limit (LOD) of 0.16 nM. For the detection of AA within the Mn-AIS-Fe (III) system, the linear range spanned from 0.05 to 180 µM, with a LOD of 0.031 µM. Both Mn-AIS and Mn-AIS-Fe (III) demonstrated robust anti-interference properties, facilitating the accurate detection of Fe (III) in tap water and AA in vitamin C tablets. This approach is notable for its simplicity, cost-effectiveness, and considerable potential for application in the creation of innovative biological and environmental sensors.

Dual-functional DNAzyme powered CRISPR-Cas12a sensor for ultrasensitive and high-throughput detection of Pb2+ in freshwater

Freshwater lead pollution has posed severe threat to the environment and human health, underscoring the urgent necessity for accurate and user-friendly detection methods. Herein, we introduce a novel Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR-Cas) sensor for highly sensitive Pb2+ detection. To accomplish this, we designed a dual-functional deoxyribozyme (df-DNAzyme) probe that functions as an activator for the CRISPR-Cas12a system while also recognizing Pb2+. The df-DNAzyme probe was subsequently combined with gold nanoparticles (AuNPs) to fabricate a DNAzyme/AuNP nanoprobe, facilitating the activation of CRISPR-Cas12a in a one-to-multiple manner. Upon exposure to Pb2+, the df-DNAzyme is cleaved, causing disintegration of the DNAzyme/AuNP nanoprobe from magnetic beads. The degraded DNAzyme/AuNP containing multiple double-stranded DNA activators efficiently triggers CRISPR-Cas12a activity, initiating cleavage of fluorescence-quenched reporter DNA and generating amplified signals accordingly. The amplified fluorescence signal is accurately quantified using a quantitative polymerase chain reaction (qPCR) instrument capable of measuring 96 or 384 samples simultaneously at the microliter scale. This technique demonstrates ultra-sensitive detection capability for Pb2+ at concentrations as low as 1 pg/L within a range from 1 pg/L to 10 μg/L, surpassing limits set by World Health Organization (WHO) and United States Environmental Protection Agency (US EPA) guidelines. This study offers an ultrasensitive and high-throughput method for the detection of Pb2+ in freshwater, thereby advancing a novel approach towards the development of precise and convenient techniques for detecting harmful contaminants.

Poly(vinyl chloride)/Nanocarbon Composites for Advanced Potentiometric Membrane Sensor Design

Polymer nanocomposites filled with carbon nanoparticles (CNPs) are a hot topic in materials science. This article discusses the current research on the use of these materials as interfacial electron transfer films for solid contact potentiometric membrane sensors (SC-PMSs). The results of a comparative study of plasticized poly (vinyl chloride) (pPVC) matrices modified with single-walled carbon nanotubes (SWCNTs), fullerenes-C60, and their hybrid ensemble (SWCNTs-C60) are reported. The morphological characteristics and electrical conductivity of the prepared nanostructured composite films are reported. It was found that the specific electrical conductivity of the pPVC/SWCNTs-C60 polymer film was higher than that of pPVC filled with individual nanocomponents. The effectiveness of this composite material as an electron transfer film in a new potentiometric membrane sensor for detecting phenylpyruvic acid (in anionic form) was demonstrated. Screening for this metabolic product of phenylalanine in body fluids is of significant diagnostic interest in phenylketonuria (dementia), viral hepatitis, and alcoholism. The developed sensor showed a stable and fast Nernstian response for phenylpyruvate ions in aqueous solutions over the wide linear concentration range of 5 × 10-7-1 × 10-3 M, with a detection limit of 10-7.2 M.

Recent advances in the modification of electrodes for trace metal analysis: a review

This review paper summarizes the research published in the last five years on using different compounds and/or materials as modifiers for electrodes employed in trace heavy metal analysis. The main groups of modifiers are identified, and their single or combined application on the surface of the electrodes is discussed. Nanomaterials, film-forming substances, and polymers are among the most used compounds employed mainly in the modification of glassy carbon, screen-printed, and carbon paste electrodes. Composites composed of several compounds and/or materials have also found growing interest in the development of modified electrodes. Environmentally friendly substances and natural products (mainly biopolymers and plant extracts) have continued to be included in the modification of electrodes for trace heavy metal analysis. The main analytical performance parameters of the modified electrodes as well as possible interferences affecting the determination of the target analytes, are discussed. Finally, a critical evaluation of the main findings from these studies and an outlook discussing possible improvements in this area of research are presented.

Highly efficient and simultaneous magnetic solid phase extraction of heavy metal ions from water samples with l-Cysteine modified magnetic polyamidoamine dendrimers prior to high performance liquid chromatography

Due to the strong metal-sulfur interaction between mercapto groups and metal ions, which can be used to functionalize polyamidoamine dendrimer decorated Fe₃O₄ nanoparticles for high enrichment of trace heavy metal ions from waters. Based on this concept, polyamidoamine dendrimer modified Fe₃O₄ nanomaterials were functionalized with l-Cysteine and a new magnetic solid phase extraction for rapid adsorption and separation of Hg²⁺, Pb²⁺, Co²⁺ and Cd²⁺ from waters was established. The factors affecting extraction efficiency have been optimized. Upon the optimal parameters, the established method provided good linear ranges of 0.1-200 μg L^-1 for Hg²⁺ and 0.05-200 μg L^-1 for Pb²⁺, Co²⁺ and Cd²⁺, and high sensitivity with limits of detection (LOD) of 0.018 μg L^-1, 0.014 μg L^-1, 0.013 μg L^-1 and 0.025 μg L^-1 for Cd²⁺, Pb²⁺, Co²⁺ and Hg²⁺, respectively. Real water samples were utilized to validate the proposed method, and achieved results revealed that the proposed method was sensitive, effective, stable and suitable for monitoring Pb²⁺, Cd²⁺, Co²⁺and Hg²⁺ in environmental waters. This work provided a novel strategy for the simultaneous analysis of target cations in waters, and a new direction for developing decoration method of nanomaterials according to specific purpose.

Nanomaterials-Based Ion-Imprinted Electrochemical Sensors for Heavy Metal Ions Detection: A Review

Heavy metal ions (HMIs) pose a serious threat to the environment and human body because they are toxic and non-biodegradable and widely exist in environmental ecosystems. It is necessary to develop a rapid, sensitive and convenient method for HMIs detection to provide a strong guarantee for ecology and human health. Ion-imprinted electrochemical sensors (IIECSs) based on nanomaterials have been regarded as an excellent technology because of the good selectivity, the advantages of fast detection speed, low cost, and portability. Electrode surfaces modified with nanomaterials can obtain excellent nano-effects, such as size effect, macroscopic quantum tunneling effect and surface effect, which greatly improve its surface area and conductivity, so as to improve the detection sensitivity and reduce the detection limit of the sensor. Hence, the present review focused on the fundamentals and the synthetic strategies of ion-imprinted polymers (IIPs) and IIECSs for HMIs detection, as well as the applications of various nanomaterials as modifiers and sensitizers in the construction of HMIIECSs and the influence on the sensing performance of the fabricated sensors. Finally, the potential challenges and outlook on the future development of the HMIIECSs technology were also highlighted. By means of the points presented in this review, we hope to provide some help in further developing the preparation methods of high-performance HMIIECSs and expanding their potential applications.

A Critical Review on the Use of Molecular Imprinting for Trace Heavy Metal and Micropollutant Detection

Molecular recognition has been described as the “ultimate” form of sensing and plays a fundamental role in biological processes. There is a move towards biomimetic recognition elements to overcome inherent problems of natural receptors such as limited stability, high-cost, and variation in response. In recent years, several alternatives have emerged which have found their first commercial applications. In this review, we focus on molecularly imprinted polymers (MIPs) since they present an attractive alternative due to recent breakthroughs in polymer science and nanotechnology. For example, innovative solid-phase synthesis methods can produce MIPs with sometimes greater affinities than natural receptors. Although industry and environmental agencies require sensors for continuous monitoring, the regulatory barrier for employing MIP-based sensors is still low for environmental applications. Despite this, there are currently no sensors in this area, which is likely due to low profitability and the need for new legislation to promote the development of MIP-based sensors for pollutant and heavy metal monitoring. The increased demand for point-of-use devices and home testing kits is driving an exponential growth in biosensor production, leading to an expected market value of over GPB 25 billion by 2023. A key requirement of point-of-use devices is portability, since the test must be conducted at “the time and place” to pinpoint sources of contamination in food and/or water samples. Therefore, this review will focus on MIP-based sensors for monitoring pollutants and heavy metals by critically evaluating relevant literature sources from 1993 to 2022.

Recent Advancement in Disposable Electrode Modified with Nanomaterials for Electrochemical Heavy Metal Sensors

Heavy metal pollution has gained global attention due to its high toxicity and non-biodegradability, even at a low level of exposure. Therefore, the development of a disposable electrode that is sensitive, simple, portable, rapid, and cost-effective as the sensor platform in electrochemical heavy metal detection is vital. Disposable electrodes have been modified with nanomaterials so that excellent electrochemical properties can be obtained. This review highlights the recent progress in the development of numerous types of disposable electrodes modified with nanomaterials for electrochemical heavy metal detection. The disposable electrodes made from carbon-based, glass-based, and paper-based electrodes are reviewed. In particular, the analytical performance, fabrication technique, and integration design of disposable electrodes modified with metal (such as gold, tin and bismuth), carbon (such as carbon nanotube and graphene), and metal oxide (such as iron oxide and zinc oxide) nanomaterials are summarized. In addition, the role of the nanomaterials in improving the electrochemical performance of the modified disposable electrodes is discussed. Finally, the current challenges and future prospect of the disposable electrode modified with nanomaterials are summarized.