ABSTRACT
Achieving accurate detection of different speciations of heavy metal ions (HMIs) in an aqueous solution is an urgent problem due to the different bioavailabilities and physiological toxicity. Herein, we nominated a novel strategy to detect HCrO4- and Cr(OH)2+ at a trace level via the electrochemical sensitive surface constructed by Co3O4-rGO modified with amino and carboxyl groups, which revealed that the interactions between distinct functional groups and different oxygen-containing groups of target ions are conducive to the susceptible and anti-interference detection. The detection sensitivities of 19.46 counts µg-1 L for HCrO4- and 13.44 counts µg-1 L for Cr(OH)2+ were obtained under optimal conditions, while the limits of detection were 0.10 and 0.12 µg L-1, respectively. Satisfactory anti-interference and actual water sample analysis results were obtained. A series of advanced optical techniques like X-ray photoelectron spectroscopy, X-ray absorption near-edge structure technology, and density functional theory calculations under an electric field demonstrated that chemical interactions between groups contribute more to the fixation of target ions than electrical attraction alone. The presence of oxygen-containing groups distinct from simple ionic forms was a critical factor in the selectivity and anti-interference detection. Furthermore, the valence cycle of Co(II)/(III) synergistically boosted the detection performance. This research provides a promising tactic from the microscopic perspective of groups' interactions to accomplish the precise speciation analysis of HMIs in the water environment.
ABSTRACT
Traditional nanomodified electrodes have made great achievements in electrochemical stripping voltammetry of sensing materials for As(III) detection. Moreover, the intermediate states are complicated to probe because of the ultrashort lifetime and complex reaction conditions of the electron transfer process in electroanalysis, which seriously hinder the identification of the actual active site. Herein, the intrinsic interaction of highly sensitive analytical behavior of nanomaterials is elucidated from the perspective of electronic structure through density functional theory (DFT) and gradient boosting regression (GBR). It is revealed that the atomic radius, d-band center (εd), and the largest coordinative TM-N bond length play a crucial role in regulating the arsenic reduction reaction (ARR) performance by the established ARR process for 27 sets of transition-metal single atoms supported on N-doped graphene. Furthermore, the database composed of filtered intrinsic electronic structural properties and the calculated descriptors of the central metal atom in TM-N4-Gra were also successfully extended to oxygen evolution reaction (OER) systems, which effectively verified the reliability of the whole approach. Generally, a multistep workflow is developed through GBR models combined with DFT for valid screening of sensing materials, which will effectively upgrade the traditional trial-and-error mode for electrochemical interface designing.
ABSTRACT
Vacancy and doping engineering are promising pathways to improve the electrocatalytic ability of nanomaterials for detecting heavy metal ions. However, the effects of the electronic structure and the local coordination on the catalytic performance are still ambiguous. Herein, cubic selenium vacancy-rich CoSe2 (c-CoSe2-x) and P-doped orthorhombic CoSe2-x (o-CoSe2-x|P) were designed via vacancy and doping engineering. An o-CoSe2-x|P-modified glass carbon electrode (o-CoSe2-x|P/GCE) acquired a high sensitivity of 1.11 µA ppb-1 toward As(III), which is about 40 times higher than that of c-CoSe2-x, outperforming most of the reported nanomaterial-modified glass carbon electrodes. Besides, o-CoSe2-x|P/GCE displayed good selectivity toward As(III) compared with other divalent heavy metal cations, which also exhibited excellent stability, repeatability, and practicality. X-ray absorption fine structure spectroscopy and density functional theory calculation demonstrate that electrons transferred from Co and Se to P sites through Co-P and Se-P bonds in o-CoSe2-x|P. P sites obtained plentiful electrons to form active centers, which also had a strong orbital coupling with As(III). In the detection process, As(III) was bonded with P and reduced by the electron-rich sites in o-CoSe2-x|P, thus acquiring a reinforced electrochemical sensitivity. This work provides an in-depth understanding of the influence of the intrinsic physicochemical properties of sensitive materials on the behavior of electroanalysis, thus offering a direct guideline for creating active sites on sensing interfaces.
Subject(s)
Electronics , Electrons , Density Functional Theory , X-Ray Absorption Spectroscopy , X-RaysABSTRACT
Interference among multiple heavy metal ions (HMIs) is a significant problem that must be solved in electroanalysis, which extremely restricts the practical popularization of electrochemical sensors. However, due to the limited exploration of the intrinsic mechanism, it is still difficult to confirm the influencing factors. In this work, a series of experimental and theoretical electroanalysis models have been established to investigate the electroanalysis results of Cu(II), Cd(II), As(III), and their mixtures, which were based on the simple structure and stable coordination of nickel single-atom catalysts. X-ray absorption spectroscopy and density functional theory calculations were used to reveal the underlying detection mechanism of the 50-fold boosting effect of Cu(II) on As(III) while Cd(II) inhibits As(III). Combining the application of the thermodynamic model and Fourier transform infrared reflection, the specific interaction of the nanomaterials and HMIs on the interface is considered to be the fundamental source of the interference. This work opens up a new way of thinking about utilizing the unique modes of interplay between nanomaterials and HMIs to achieve anti-interference intelligent electrodes in stripping analysis.
Subject(s)
Metals, Heavy , Smart Materials , Cadmium/chemistry , Ions , Metals, Heavy/chemistry , ThermodynamicsABSTRACT
Constructing high-effective electrode sensing interfaces has been considered an effective method for electrochemical detection toward heavy metal ions (HMIs). However, most research has been devoted to enhancing the stripping currents of HMIs by simply improving the adsorptive capacity and conductivity of the electrode modified materials, while lacking theoretical guidelines in fabricating catalytic sensing interfaces. Besides, the understanding of detection mechanisms is quite unscientific from the perspective of catalysis. This perspective summarizes five general strategies in designing highly efficient sensing interfaces in the recent five years, including modulating crystal phases, orientations and planes, defect engineering, ionic valence state cycle engineering, adsorption in situ catalysis strategy, and construction of atomic level catalytic active sites. What's more, the catalytic mechanisms for improving the signals of HMIs, such as boosting the electron transfer rates and conversion rates, lowering the energy barriers, etc., are introduced and emphasized. This study has a great significance in directionally controlling functionalized electrochemical sensors to achieve excellent sensitivity and selectivity in detecting environmental pollutants from the view of catalysis, and it also brings enlightenments and guidance to develop new electroanalytical methods.
Subject(s)
Environmental Pollutants , Metals, Heavy , Catalysis , Electrodes , Ions/chemistry , Metals, Heavy/chemistryABSTRACT
Designing new catalysts with high activity and stability is crucial for the effective analysis of environmental pollutants under mild conditions. Here, we developed a superior catalyst of Pt single atoms anchored on MoS2 (Pt1/MoS2) to catalyze the determination of As(III). A detection sensitivity of 3.31 µA ppb-1 was obtained in acetate buffer solution at pH 6.0, which is the highest compared with those obtained by other Pt-based nanomaterials currently reported. Pt1/MoS2 exhibited excellent electrochemical stability during the detection process of As(III), even in the coexistence of Cu(II), Pb(II), and Hg(II). X-ray absorption fine structure spectroscopy and theoretical calculations revealed that Pt single atoms were stably fixed by four S atoms and activated the adjacent S atoms. Then, Pt and S atoms synergistically interacted with O and As atoms, respectively, and transferred some electrons to H3AsO3, which change the rate-determining step of H3AsO3 reduction and reduce reaction energy barriers, thereby promoting rapid and efficient accumulation for As(0). Compared with Pt nanoparticles, the weaker interaction between arsenic species and Pt1/MoS2 enabled the effortless regeneration and cyclic utilization of active centers, which is more favorable for the oxidation of As(0). This work provides inspiration for developing highly efficient sensing platforms from the perspective of atomic-level catalysis and affords references to explore the detection mechanism of such contaminants.
Subject(s)
Arsenicals , Nanostructures , Arsenicals/chemistry , Catalysis , Molybdenum , Oxidation-Reduction , PlatinumABSTRACT
An atomic-level Au nanocluster, as an excellent photocatalyst, is generally not considered as an efficient electrocatalyst due to its poor stability. Herein, a method is proposed to stabilize abundant Au25 on Fe2O3 nanoplates (Au25/OV-Fe2O3) successfully with oxygen vacancies (OV) created. Au25/OV-Fe2O3 shows superhigh catalysis in the electrochemical reduction toward As(III). The record-breaking sensitivity (161.42 µA ppb-1) is two orders of magnitude higher than currently reported, where an ultratrace limit of detection (9 ppt) is obtained, suggesting promising applications in the analysis of organic and bioactive substances. The stability of Au25 is attributed to the Au-Fe bond formed after loading Au25 nanoclusters on Fe2O3 nanoplates through "electron compensation" and bond length (Au-S) shortening. Moreover, the ligand S atoms in Au25 nanoclusters significantly contribute to the reduction of As(III). The fantastic stability and superior catalytic ability of Au25/OV-Fe2O3 provide guidelines to stabilize Au nanoclusters on metal oxides, indicating their potential electroanalytical applications.
Subject(s)
Gold , Oxygen , Catalysis , LigandsABSTRACT
Modulating the active sites of oxygen vacancies (OVs) to enhance the catalytic properties of nanomaterials has attracted much research interest in various fields, but its intrinsic catalytic mechanism is always neglected. Herein, we establish an efficient strategy to promote the electrochemical detection of Pb(II) by regulating the concentration of OVs in α-MoO3 nanorods via doping Ce3+/Ce4+ ions. α-MoO3 with the Ce-doped content of 9% (C9M) exhibited the highest detection sensitivity of 106.64 µM µA-1 for Pb(II), which is higher than that achieved by other metal oxides and most precious metal nanomaterials. It is found that C9M possessed the highest concentration of OVs, which trapped some electrons for strong affinity interaction with Pb(II) and provided numerous atomic level interfaces of high surface free energy for catalysis reactions. X-ray absorption fine structure spectra and density functional theory calculation indicate that Pb(II) was bonded with the surface-activated oxygen atoms (Os) around Ce ions and obtained some electrons from Os. Besides, the longer Pb-O bonds on C9M were easier to break, causing a low desorption energy barrier to effectively accelerate Pb(II) desorbing to the electrode surface. This study helps to understand the changes in electronic structure and catalytic performance with heteroatom doping and OVs in chemically inert oxides and provide a reference for designing high-active electrocatalytic interfaces to realize ultrasensitive analysis of environmental contaminants.
ABSTRACT
Heavy metal ions (HMIs) are one of the major environmental pollution problems currently faced. To monitor and control HMIs, rapid and reliable detection is required. Electrochemical analysis is one of the promising methods for on-site detection and monitoring due to high sensitivity, short response time, etc. Recently, nanometal oxides with special surface physicochemical properties have been widely used as electrode modifiers to enhance sensitivity and selectivity for HMIs detection. In this work, recent advances in the electrochemical detection of HMIs using nanometal oxides, which are attributed to specific crystal facets and phases, surficial defects and vacancies, and oxidation state cycle, are comprehensively summarized and discussed in aspects of synthesis, characterization, electroanalysis application, and mechanism. Moreover, the challenges and opportunities for the development and application of nanometal oxides with functional surface physicochemical properties in electrochemical determination of HMIs are presented.
ABSTRACT
Essential tremor (ET) and Parkinson's disease (PD) are common chronic movement disorders that can cause a substantial degree of disability. However, the etiology underlying these two conditions remains poorly understood. In the present study, Whole-exome sequencing of peripheral blood samples from the proband and Sanger sequencing of the other 18 family members, and pedigree analysis of four generations of 29 individuals with both ET and PD in a nonconsanguineous Chinese family were performed. Specifically, family members who had available medical information, including historical documentation and physical examination records, were included. A novel c.1909A>T (p.Ser637Cys) missense mutation was identified in the eukaryotic translation initiation factor 4γ1 (EIF4G1) gene as the candidate likely responsible for both conditions. In total, 9 family members exhibited tremor of the bilateral upper limbs and/or head starting from ages of ≥40 years, 3 of whom began showing evidence of PD in their 70s. Eukaryotic initiation factor 4 (eIF4)G1, a component of the translation initiation complex eIF4F, serves as a scaffold protein that interacts with many initiation factors and then binds to the 40S ribosomal subunit. The EIF4G1 (p.Ser637Cys) might inhibit the recruitment of the mRNA to the ribosome. In conclusion, the results from the present study suggested that EIF4G1 may be responsible for the hereditary PD with 'antecedent ET' reported in the family assessed.
ABSTRACT
Mutual interference issues between heavy metal ions tremendously affect the detection reliability and accuracy in water quality analysis, especially the serious interference of Cu(II) on the detection of As(III) is greatly hard to overcome, which needs to be solved urgently. Herein, iron single-atom catalysts with different coordination structures of FeN2C2 and FeN3P are constructed to selectively catalyze the detection of As(III) in the coexistence of Cu(II). FeN3P achieves a high sensitivity of 3.90 µA ppb-1 toward As(III) in NH4Cl/NH3·H2O electrolyte (pH 8.0), completely avoiding Cu(II)-interference. Moreover, the turnover frequency (TOF) of FeN3P is an order of magnitude higher than that of FeN2C2. X-ray absorption fine structure (XAFS) spectroscopy and density functional theory (DFT) calculations demonstrate that an As-O bond of H3AsO3 is broken by the strong affinities between both P and O atoms and Fe and As atoms, and H3AsO3 are preferentially reduced by FeN3P during adsorptive process. Meanwhile, the low reaction energy barrier of the rate-determined step for As(III) reduction over FeN3P also accelerates the deposition of As(III) and enhances its response signals. The free-Cu(II) are difficult to adsorb on FeN3P and do not compete with As(III) for Fe active sites, which contributes to the excellent anti-Cu(II) interference capability.
ABSTRACT
The mutual interference in the sensing detection of heavy metal ions (HMIs) is considerably serious and complex. Besides, the co-existed ions may change the stripping peak intensity, shape and position of the target ion, which partly makes peak current analysis inaccurate. Herein, a promising approach of partial peak area analysis was proposed firstly to research the mutual interference. The interference between two species on their electrodeposition processes was investigated by simulating different kinetics parameters, including surface coverage, electro-adsorption, -desorption rate constant, etc. It was proved that the partial peak area is sensitive and regular to these interference kinetics parameters, which is favorable for distinctly identifying different interferences. Moreover, the applicability of the partial peak area analysis was verified on the experiments of Cu2+, As(III) interference at four sensing interfaces: glassy carbon electrode, gold electrode, Co3O4, and Fe2O3 nanoparticles modified electrodes. The interference behaviors between Cu2+ and As(III) relying on solid-solution interfaces were revealed and confirmed by physicochemical characterizations and kinetics simulations. This work proposes a new descriptor (partial peak area) to recognize the interference mechanism and provides a meaningful guidance for accurate detection of HMIs in actual water environment.
ABSTRACT
Although the enhanced intrinsic activities of some nano-metal oxides are obtained by manufacturing oxygen vacancies (OVs), the effect of multiple roles of OVs is ambiguous. Herein, an interface catalytic regulation via electron rearrangement and hydroxyl radicals (ËOH) was proposed with the designed ZrO2 hollow sphere rich in OVs (Vo-rich ZrO2). Surprisingly, it was shown that the catalytic ability of Vo-rich ZrO2 was 9.9 times higher than that of ZrO2 with little OVs in electrochemical catalytic reduction of Pb(ii). It was found that the generation of Zr2+ and Zr3+ caused by OVs results in the rearrangement of abundant free electrons to facilitate the catalytic reaction rates. The longer bond length between Vo-rich ZrO2 and reactants, and the lower adsorption energy are beneficial for reactants to desorb, improving the conversion rates. Besides, the produced ËOH were captured which were induced by OVs and trace divalent heavy metal ions in in situ electron paramagnetic resonance (EPR) experiments, contributing to lowering the energy barriers. This study not only revealed the enhanced interface catalytic effect of electron rearrangement and generated ËOH triggered by OVs, but also provided unique insights into interface catalytic regulation on nano-metal oxides simulated by OVs.
ABSTRACT
Single-atom catalysts have been extensively utilized for electrocatalysis, in which electronic metal-support interactions are typically employed to stabilize single atoms. However, this neglects the metal-metal interactions of adjacent atoms, which are essential for the fine-tuning of selective sites. Herein, the high-loading of Ir single atoms (Ir SAs) (8.9 wt%) were adjacently accommodated into oxygen vacancy-rich Co3O4 nanosheets (Ir SAs/Co3O4). Electronic perturbations for both Ir single atoms and Co3O4 supports were observed under electronic metal-support and metal-metal interactions, thus generating Ir-O-Co/Ir units. Electrons were transferred from Co and Ir to O atoms, inducing the depletion of 3d/5d states in Co/Ir and the occupation of 2p states in O atoms to stabilize the Ir SAs. Moreover, the O atoms of Ir-O-Ir functioned as the main active sites for the electrocatalysis of As(iii), which reduced the energy barrier for the rate-determining step. This was due to the stronger electronic affinities for intermediates from reduction of As(iii), which were completely distinct from other coordinated O atoms of Co3O4 or IrO2. Consequently, the resultant Ir SAs/Co3O4 exhibited far more robust electrocatalytic activities than IrO2/Co3O4 and Co3O4 in the electrocatalysis of As(iii). Moreover, there was a strong orbital coupling effect between the coordinated O atoms of Ir SAs and the -OH of H3AsO3, thus exhibiting superior selectivity for As(iii) in contrast to other common heavy metal cations. This work offers useful insights into the rational design of intriguing SACs with high selectivity and stability for the electrocatalysis and electrochemical analysis of pollutants on an electronic level.
ABSTRACT
Constructing catalysts with simple structures, uniform effective sites, and excellent performance is crucial for understanding the reaction mechanism of target pollutants. Herein, the single-atom catalyst of Mn-intercalated graphitic carbon nitride (Mn/g-C3N4) was prepared. It was found that the intercalated Mn atoms acted as strong electron donors to effectively tune the electronic structure distribution of the in-situ N atoms, providing a large number of negative potential atomic-scale sites for catalytic reactions. In the detection, the in-situ N atom established an electron bridge for the transient electrostatic trapping of free Pb(II), which induced Pb-N-Mn coordination bonding. Even in g-C3N4-loaded Mn nanoparticles, the N atom was again confirmed to be the interaction site for coupling with Pb. And the MnII-N4-C/MnIV-N4-C cycle actively participated in the electrocatalysis of Pb(II) was confirmed. Moreover, Mn/g-C3N4 achieved highly stable and accurate detection for Pb(II) with a sensitivity of 2714.47 µA·µM-1·cm-2. And excellent reproducibility and specific detection of real water samples made the electrode practical. This study contributes to understanding the changes in the electronic structure of chemically inert substrates after single-atom intercalation and the interaction between contaminants and the microstructure of sensitive materials, providing a guiding strategy for designing highly active electrocatalytic interfaces for accurate electroanalysis.
ABSTRACT
Combining density functional theory calculation with experiments and kinetics simulation, a multiscale framework describing the influence of reactant-substrate interaction on electrochemical performance was proposed. It was found that the close band center and the rapid adsorption kinetics facilitated the highly selective response of Ni(111) toward Cu(ii), providing a useful tactic to investigate the mechanism of electro-selectivity. This work not only verified that the interaction strength in the ex situ conditions, and kinetics rate could be applied to evaluate the electrochemical selectivity, but also contributed to the options and forecasting of selective electrode materials for heavy metal ions.
ABSTRACT
Fruitful achievements on electrochemical detection toward Pb(II) have been achieved, and their good performance is generally attributed to the adsorption property of nanomaterials. However, the design of sensing interfaces from the electronic structure and electron transfer process is limited. Here, Co@Co3O4 acquired an ultra-high detection sensitivity of 103.11 µA µM-1 toward Pb(II), outperforming the results previously reported. The interfacial oxygen atoms build an electron bridge for Co activating Co3O4. Particularly, new energy levels of oxygen atoms were generated and matched with that of Pb(II). The strong orbital coupling effect between O and Pb makes the Co@Co3O4 sensitive and selective toward Pb(II). Compared with Co metal and Co3O4, Pb(II) got more electrons from Co@Co3O4, and longer Pb-O bonds were formed, allowing more Pb(II) to be catalyzed and reduced. Also, the superior stability and reproducibility of electrochemical detection make electrodes practicably. This work reveals that metals can stimulate intrinsically catalytic activity of their metal oxides, with the generation of orbit energy levels that match to a specific analyte. It provides a promising strategy for constructing sensitive and selective sensing interfaces toward ultra-low concentration analyte in body fluid and other complex samples.
ABSTRACT
An ultrasensitive electrochemical detection of heavy metal ions is achieved via defect- and phase-engineering of Mn-mediated MoS2 nanosheets. We find for the first time that chemical interactions between Pb(ii) and active S atoms in Mn-MoS2 facilitate the electron transfer and in situ catalytic redox reactions.