Photo-assisted "co-movement catalysis": CoFe2O4/CNS heterojunction based portable electrochemical sensor for simultaneous detection of Pb2+ and Cd2+ in natural water

Machine learning-driven simultaneous quantification of Cd(II) and Cu(II) on Co2P/CoP heterostructure: enhanced electrochemical signals via activated Co-P electron bridge

Simultaneous quantification of multiple heavy metal ions remains a significant challenge in electrochemical methods, as complex high-throughput data from signal interference cannot be accurately analyzed through individual expertise and calibration curves. In this study, machine learning techniques were introduced to co-detect Cd(II) and Cu(II), with their electrochemical interference mechanisms explored on highly active Co2P/CoP heterostructures. The random forest (RF) model initially identified key feature variables in response currents, which were subsequently input into the convolutional neural network (CNN) to uncover the relationship between electrochemical signals and ion concentrations, demonstrating excellent reliability with R2 values of 0.996 for both Cd(II) and Cu(II). The root mean square error (RMSE) values for Cd(II) and Cu(II) were 0.0177 and 0.0206 μM, respectively, indicating high predictive accuracy. The experiments and theory calculations revealed that Cu(II) preferentially bonded with P sites over Cd(II). Enhanced electron transfer from Co to P atoms and weakened Cu-P bonds facilitated Cu(II) reduction and desorption from Co2P/CoP, thereby boosting electrochemical signals, while Cd(II) signals were inhibited due to active site loss. Herein, the integration of machine learning provides robust support for simultaneous detection of multiple analytes, accelerating the practical application of electrochemical methods in environmental monitoring.

C-ZIF-8 modified NiO photocathode and enhanced photosensitizer signal amplification for ultra-sensitive photoelectrochemical detection of lead ions

NiO photocathodes have been developed for photoelectrochemical (PEC) sensing. However, the development of NiO-based photoactive materials with higher performance is still being pursued to further improve the sensitivity of detection. In this article, we prepared a C-ZIF-8/NiO composite material photocathode composed of porous carbon derived from ZIF-8 (C-ZIF-8) and NiO, and utilized its enhanced PEC activity and amplification effect on chlorohemin (hemin) sensitization to achieve ultra-sensitive detection of lead ions (Pb2+). The introduction of C-ZIF-8 improved the charge transfer and light absorption ability of the composite material, and significantly increased the load of hemin on the photocathode, thereby enhancing the photocurrent response by 8 times. Based on the C-ZIF-8/NiO photocathode and in situ generated photosensitizer signal amplification strategy, ultra-sensitive detection of Pb2+ had been attained with a detection linear range of 10 pM to 5 nM and a detection limit of 2.6 pM. This study provides a new platform for high sensitivity detection of Pb2+, and extensive potential applications could be further expected.

MOF Derived Cobalt Ferrite Cubic Rod-Like Materials for Highly Efficient Electrochemical Simultaneous Detection of Multiple Heavy Metal Ions

A series of CoFe2O4 materials derived from metal-organic framework were successfully constructed by the solvent-thermal method. The morphology of a typical sample CoFe2O4-1 was mostly in the form of a cubic rod-like structure with a size distribution of 3.2±0.2 μm, while a small amount of the structure presented hexagonal shape with uniform size dispersion. The XPS characterization results confirmed that the CoFe2O4-1 material contained Co3+ (Co2+/Co3+=0.98), and the redox reaction between Co2+ and Fe3+ produced more Fe2+ (Fe2+/Fe3+=1.63), leading to the production of more OV on the surface of the CoFe2O4-1 material (OV%=0.34), thereby facilitating the efficient adsorption of the efficient adsorption of heavy metal ions (HMIs). CoFe2O4-1/GCE as a typical electrode presented excellent performance for the detection of multiple HMIs. The results should be attributed to the good electrical conductivity and large electrochemically active surface area of CoFe2O4-1/GCE, accelerating the transport of ions and charges in the system. Interestingly, there are interaction mechanisms between the HMIs when performing simultaneous detection, suggesting the detection of target ions can be facilitated by adding additional ions. This study provides new research insights for the development of highly sensitive electrochemical sensors for real-time environmental monitoring.

A portability self-powered sensor facilitates sensitive Cd2+ detection: Dual mechanism and three quantitative mode

As a common heavy metal contaminant, Cd2+ has adverse effects on food safety and consumer health. It is very important for human health to realize highly sensitive Cd2+ detection methods. The self-powered sensing system based on enzyme biofuel cells (EBFCs) does not need an external power supply, which can simplify the experimental equipment and has great application value in portable detection. Thus, the biosensor is innovatively integrated into the screen-printed electrode to construct a new type of portable sensor suitable for on-site and real-time Cd2+ detection. Hybridization chain reaction (HCR) combined with the Cd2+-dependent deoxyribose (DNAzyme) signal amplification strategy is used to enhance the detection sensitivity while specifically recognizing the Cd2+. Moreover, the self-powered sensor combines with smartphones to realize quantitative Cd2+ detection without other instruments and has the characteristic of Effectively improving the hazard detection technology is essential to ensure food safety. Portability, simplicity, and speed are suitable for real-time Cd2+ detection in the field. The dual mechanism and three quantitative modes combining colorimetric and two electrical signals output modes are adopted to realize the visualization and accurate detection. A series of research results confirm that this strategy is of great significance to strengthen the development of intelligent Cd2+ technology, expand the application of self-powered sensing technology, and improve the safety detection system.

Transforming crystal structures of cobalt molybdate to generate electron-rich sites for electrochemical detection of Pb(II)

BACKGROUND

Most of the investigations on distinct crystal structures of catalysts are individually focused on the difference of surface functional groups or adsorption properties, but rarely explore the changes of active sites to affect the electrocatalytic performance. Catalysts with diverse crystal structures had been applied to modified electrodes in different electrocatalytic reactions. However, there is currently a lack of an essential understanding for the role of real active sites in catalysts with crystalline structures in electroanalysis, which is crucial for designing highly sensitive sensing interfaces.

RESULTS

Herein, cobalt molybdate with divergent crystal structures (α-CoMoO4 and β-CoMoO4) were synthesized by adjusting the calcination temperature, indicating that α-CoMoO4 (800 °C) (60.00 μA μM-1) had the highest catalytic ability than β-CoMoO4 (700 °C) (38.68 μA μM-1) and α-CoMoO4 (900 °C) (29.55 μA μM-1) for the catalysis of Pb(II). It was proved that the proportion of Co(II) and Mo(IV) as electron-rich sites in α-CoMoO4 (800 °C) were higher than β-CoMoO4 (700 °C) and α-CoMoO4 (900 °C), possessing more electrons to participate in the valence cycles of Co(II)/Co(III) and Mo(IV)/Mo(VI) to boost the catalytic reduction of Pb(II). Specifically, Co(II) transferred a part of electrons to Mo(VI), promoting the formation of Mo(IV). Co(II) and Mo(IV), as the electron-rich sites, providing electrons to Pb(II), further accelerating the conversion of Pb(II) into Pb(0).

SIGNIFICANCE

In the process of detecting Pb(II), the CoMoO4 structures under different temperatures have distinct content of electron-rich sites Co(II) and Mo(IV). α-CoMoO4 (800 °C), with the highest content are benefited to detect Pb(II). This work is conducive to understanding the effect of the changes of active sites resulting from crystal transformation on the electrocatalytic performance, and provides a way to construct sensitive electrochemical interfaces of distinct active sites.

Development of a novel fluorescent protein-based probe for efficient detection of Pb2+ in serum inspired by the metalloregulatory protein PbrR691

BACKGROUND

The accurate and rapid detection of blood lead concentration is of paramount importance for assessing human lead exposure levels. Fluorescent protein-based probes, known for their high detection capabilities and low toxicity, are extensively used in analytical sciences. However, there is currently a shortage of such probes designed for ultrasensitive detection of Pb2+, and no reported probes exist for the quantitative detection of Pb2+ in blood samples. This study aims to fill this critical void by developing and evaluating a novel fluorescent protein-based probe that promises accurate and rapid lead quantification in blood.

RESULTS

A simple and small-molecule fluorescent protein-based probe was successfully constructed herein using a peptide PbrBD designed for Pb2+ recognition coupled to a single fluorescent protein, sfGFP. The probe retains a three-coordinate configuration to identify Pb2+ and has a high affinity for it with a Kd' of 1.48 ± 0.05 × 10-17 M. It effectively transfers the conformational changes of the peptide to the chromophore upon Pb2+ binding, leading to fast fluorescence quenching and a sensitive response to Pb2+. The probe offers a broad dynamic response range of approximately 37-fold and a linear detection range from 0.25 nM to 3500 nM. More importantly, the probe can resist interference of metal ions in living organisms, enabling quantitative analysis of Pb2+ in the picomolar to millimolar range in serum samples with a recovery percentage of 96.64%-108.74 %.

SIGNIFICANCE

This innovative probe, the first to employ a single fluorescent protein-based probe for ultrasensitive and precise analysis of Pb2+ in animal and human serum, heralds a significant advancement in environmental monitoring and public health surveillance. Furthermore, as a genetically encoded fluorescent probe, this probe also holds potential for the in vivo localization and concentration monitoring of Pb2+.

Application of valence-variable transition-metal-oxide-based nanomaterials in electrochemical analysis: A review

The construction of materials with rapid electron transfer is considered an effective method for enhancing electrochemical activity in electroanalysis. It has been widely demonstrated that valence changes in transition metal ions can promote electron transfer and thus increase electrochemical activity. Recently, valence-variable transition metal oxides (TMOs) have shown popular application in electrochemical analysis by using their abundant valence state changes to accelerate electron transfer during electrochemical detection. In this review, we summarize recent research advances in valence changes of TMOs and their application in electrochemical analysis. This includes the definition and mechanism of valence change, the association of valence changes with electronic structure, and their applications in electrochemical detection, along with the use of density functional theory (DFT) to simulate the process of electron transfer during valence changes. Finally, the challenges and opportunities for developing and applying valence changes in electrochemical analysis are also identified.