Detection Of Metal Ions Research Articles

Emerging insights into the application of metal-organic framework (MOF)-based materials for electrochemical heavy metal ion detection

Heavy metal ions are one of the main sources of water pollution, which has become a major global problem. Given the growing need for heavy metal ion detection, electrochemical sensor stands out for its high sensitivity and efficiency. Metal-organic frameworks (MOFs) have garnered much interest as electrode modifiers for electrochemical detection of heavy metal ions owing to their significant specific surface area, tailored pore size, and catalytic activity. This review summarizes the progress of MOF-based materials, including pristine MOFs and MOF composites, in the electrochemical detection of various heavy metal ions. The synthetic methods of pristine MOFs, the detection mechanisms of heavy metal ions and the modification strategies of MOFs are introduced. Besides, the diverse applications of MOF-based materials in detecting both single and multiple heavy metal ions are presented. Furthermore, we present the current challenges and prospects for MOF-based materials in electrochemical heavy metal ion detection.

Fill, Fold, Photo: Preconcentration and Multiplex Detection of Trace Level Heavy Metals in Water.

Heavy metal contamination is an increasing global threat to human and environmental health, particularly in resource-limited areas. Traditional platforms for heavy metal detection are labor intensive and expensive and require lab facilities. While paper-based colorimetric sensors offer a simpler approach, their sensitivity limitations prevent them from meeting legislative requirements for many metals. Existing preconcentration systems, on the other hand, can achieve lower detection limits but typically focus on analyzing only one metal, making comprehensive monitoring difficult. We address these limitations by introducing a low-cost preconcentration system coupled with colorimetric analysis for the simultaneous detection of seven metal ions at low ppb levels without the need for external equipment outside a smartphone. The system achieved detection limits of 15 ppb (Ni(II)), 7 ppb (Cu(II)), 2 ppb (Fe(III)), 20 ppb (Cr(VI)), 13 ppb (Pb(II)), 26 ppb (Hg(II)), and 15 ppb (Mn(II)) with six out of seven limits of detection values falling well below EPA regulatory guidelines for drinking water. The user-friendly Fill, Fold, Photo approach eliminates complex pretreatment steps. Smartphone-based detection offers portable quantification within seconds. Employing masking strategies ensured higher selectivity for each assay on the card, while our packaging protocols enable system stability for over 4 weeks of study, facilitating mass production and deployment within a realistic time frame. To validate the sensor's performance in real-world scenarios, the sensor was tested with environmental water samples. The sensor demonstrated good recovery, ranging from 77% to 94% compared to the standard ICP-MS method. Furthermore, spike recovery analysis confirmed the sensor's accuracy, with a relative standard deviation (RSD) of less than 15%. This technology holds significant promise for future development as a convenient, portable solution for field-based monitoring of a broad spectrum of water contaminants, including pesticides, PFAS, fertilizers, and beyond.

Unsymmetrical ferrocene-based azines: Facile synthesis, investigation of spectral and electrochemical properties, and antibacterial activity

Ferrocenyl azines have been utilized in metal ion detection, as a ligand in the synthesis of metal complexes, in catalysis, in dye-sensitized solar cells, and in studies on antiparasitic, antitumor, and antileishmanial. However, most of the challenging synthesis routes require temperature control, expensive starting materials, and additional steps. In this research, a series of new unsymmetrical ferrocene-based azines (2a-j and 4a-j) were simply synthesized from the reaction of ferrocenecarboxaldehydehydrazone (1) and 1,1′-ferrocenedicarboxaldehydehydrazone (3) with various aryl aldehydes in moderate to good yield (40–80 %). All compounds were characterized using FT-IR, 1H and 13C NMR, and LC-MS. In addition, the molecular structure of 2b and 2h were determined by X-ray structure analysis. UV–Vis spectra of azines revealed weak absorbance in the 460–490 nm region for the d → d transition of Fe(II) and two strong absorbances in the range of 250–350 nm for π → π* and n → π* of aromatic rings and azine bridges. Cyclic voltammetry demonstrated higher half-wave potentials (E1/2) for all ferrocenyl azines in comparison to ferrocene as the internal standard, with a significant decrease of E1/2 for ferrocenyl-rich derivatives. The antibacterial activities of all synthesized ferrocenyl azines were also investigated against Staphylococcus aureus (gram-positive) and Escherichia coli (gram-negative) bacteria. Two ferrocene-rich compounds, 2i and 4j, have shown significant activity against Staphylococcus aureus.

Design of aggregation-induced emission materials for biosensing of molecules and cells

In recent years, aggregation-induced emission (AIE) materials have gained significant attention and have been developed for various applications in different fields including biomedical research, chemical analysis, optoelectronic devices, materials science, and nanotechnology. AIE is a unique luminescence phenomenon, and AIEgens are fluorescent moieties with relatively twisted structures that can overcome the aggregation-caused quenching (ACQ) effect. Additionally, AIEgens offer advantages such as non-washing properties, deep tissue penetration, minimal damage to biological structures, high signal-to-noise ratio, and excellent photostability. Fluorescent probes with AIE characteristics exhibit high sensitivity, short response time, simple operation, real-time detection capability, high selectivity, and excellent biocompatibility. As a result, they have been widely applied in cellular imaging, luminescent sensing, detection of physiological abnormalities in the human body, as well as early diagnosis and treatment of diseases. This review provides a comprehensive summary and discussion of the progress over the past four years regarding the detection of metal ions, small chemical molecules, biomacromolecules, microbes, and cells based on AIE materials, along with discussing their potential applications and future development prospects.

Low-cost signal enhanced colorimetric and SERS dual-mode paper sensor for rapid and ultrasensitive screening of mercury ions in tea

Mercury ions (Hg2+) are highly toxic heavy metals that are commonly found in natural environments. Owning to their non-biodegradability and accumulation in the food chain, the precise detection of trace amounts of Hg2+ is essential for preventing chronic accumulation and ensuring food safety. In this study, we present a dual-mode paper sensor for simultaneous colorimetric and Surface-Enhanced Raman Spectroscopy (SERS) detection of Hg2+ in tea, achieving ultrasensitive, rapid, and on-site screening. 4-Mercaptopyridine (4-MPY) was effectively chemisorbed onto the gold nanoparticles (AuNPs), acting as a signal probe for colorimetric methods. Moreover, it can produce plasmonic hot spots for SERS by interacting with the pyridine ring. To enhance the signal intensity of both colorimetry and SERS, a silver shell is in-situ grown on the surface of AuNPs captured on the paper sensor by reduction of Ag+, achieving signal amplification. The visual limit of detection (LOD) for the colorimetric biosensor is 2.5 pM, while the LOD of SERS is 0.48 pM with this dual-mode paper sensor. The sensitivity of both the colorimetric method and SERS was improved by approximately 200 and 500 times, respectively, with the designed signal amplification strategy. The system allows for multiple parallel screening of the same sample, ensuring accurate results without any false-positive or false-negative. This study provides a valuable platform for the accurate detection of various other heavy metal ions and provides effective strategies for improving the performance of colorimetric methods.

Smartphone-assisted colorimetric sensor arrays based on nanozymes for high throughput identification of heavy metal ions in salmon

The rapid, precise, and high-throughput identification of multiple heavy metals ions holds immense importance in ensuring food safety and promoting public health. This study presents a novel smartphone-assisted colorimetric sensor array for the rapid and precise detection of multiple heavy metals ions. The sensor array is based on three signal recognition elements (AuPt@Fe-N-C, AuPt@N-C, and Fe-N-C) and the presence of different heavy metal ions affects the nanozymes-chromogenic substrate (TMB) catalytic color production, enabling the differentiation and quantification of various heavy metal ions. Combined with a smartphone-based RGB mode, the colorimetric sensor array can successfully identify five different heavy metal ions (Hg2+, Pb2+, Co2+, Cr6+, and Fe3+) as low as 0.5 μM and different ratios of binary and ternary mixed heavy metal ions in just 5 min. The sensor array successfully tested seawater and salmon samples with a total heavy metal content of 10 μM in the South China Sea (Haikou and Wenchang). Overall, this study highlights the potential of smartphone-assisted colorimetric sensor arrays for the rapid and precise detection of multiple heavy metal ions, which could significantly contribute to food safety and public health monitoring.

Impacts of illegal mining activities on water quality for irrigation and implications for public health: A case study of the Oda River in the Ashanti Region of Ghana

ABSTRACT This study evaluated the biological and physicochemical parameters of the Oda River, including the detection of heavy metals. To achieve this purpose, a quantitative experimental research design was employed. Twenty-four water samples were taken along the Oda River from Obeng ne Obeng, Abuakwaa, and Odaso communities. The samples were analysed in a laboratory, and the results were compared to the irrigation water quality standards from the Food and Agricultural Organization (FAO). The study found that the concentration of turbidity and total suspended solids exceeded the recommended standards of FAO, while the river's pH, electrical conductivity, and total dissolved solids concentrations were within permissible boundaries. Lead, cadmium, mercury, arsenic, and fluoride were present at concentrations lower than the recommended guidelines, whereas copper and cyanide were not discovered. However, iron concentrations exceeded the FAO guidelines. Escherichia coli concentrations in the Obeng ne Obeng were lower than the FAO irrigation standards but were higher in the Abuakwaa and Odaso. The Pearson correlation coefficient highlighted significant correlations between the physicochemical parameters. This paper concludes that unregulated mining activities may endanger vital water resources for irrigation, public health, food safety, ecosystems, and livelihoods.

Metabolic engineering-enabled dual-color biosensor for discriminative and sensitive detection of toxic lead and mercury in environmental waters

The ubiquity of toxic heavy metals, particularly lead (Pb) and mercury (Hg), in environmental waters severely threatens ecosystems and human health. We developed a metabolic engineering-based dual-color bacterial biosensor for the sensitive and discriminative detection of Pb(II) and Hg(II) at nanomolar levels. The biosensor leverages the synthetic biology approach to integrate two pigments, prodeoxyviolacein (PDV) and deoxyviolacein (DV), into a single construct that responds distinctly to Pb(II) and Hg(II), respectively. The engineered E. coli biosensor exhibits a detection range of 0.732–3000 nM for Pb(II) and 0.183–750 nM for Hg(II), with low detection limits of 0.732 nM for Pb(II) and 0.183 nM for Hg(II). The biosensor demonstrated high sensitivity, selectivity, and accuracy with a recovery rate close to 1 in freshwater and seawater matrices. Notably, the biosensor's visual readout allows for rapid, equipment-free assessment. It is a practical tool for real-world monitoring of heavy metal pollution, especially in remote or resource-limited settings. This study underscores the potential of whole-cell biosensors as a sustainable and effective alternative to traditional heavy metal detection methods.

Balancing of Resonant Differential Coils for Broadband Inductive Sensor Systems.

Differential coils are frequently implemented in inductive sensing systems. They can be considered as a single coil that is made up of two or more subcoils, wound in series opposition. They can be used on the transmit or receive side of measurement systems, and, if designed correctly, ensure no coupling between coils under background conditions. By cancelling background coupling, the receive electronics only needs to be able to measure the change in coupling produced by a target. This allows for a more efficient use of the dynamic range, and for larger receive-side amplifier gain, thereby improving SNR. When subcoils are not electrically similar, it can be hard to engineer the coil to be perfectly balanced across a wide bandwidth. This paper presents an analytical model of a resonant differential coil pair that is tested and applied on a planar metal detector for the detection of buried objects. The model demonstrates the capability to balance an arbitrary differential coil pair, which has a broad applicability across a range of inductive sensor applications such as metal detection and non-destructive testing. The method is applied to the practical system. The results show that the correction resulting from this method ensures a stable balance across a significantly enhanced bandwidth. In the case studied here, the bandwidth of the experimental system is increased from 20 kHz to 90 kHz.

Synthesis of fluorometric carbon nano dots(CNDs) for selective sensing of biologically important Fe3+ and Cu2+ metal ions and evaluating their antioxidant capacity.

In this research, CNDs were prepared by a green and cost effective method using Cinnamomum Tamala (bay leaf) as carbon sources. TEM, UV, FTIR, ZETA Potential, PL and Fluorescence methods were used to characterize the produced CNDs and the average particle size is 3.42nm. This research was conducted on the development of fluorescent sensors for various metal ions, including Fe3+, Cu2+, Zn2+, Ni2+, Pb2+, Cr3+, Mg2+, Na+ 1 and Cd2+. The CNDs demonstrated selective sensing of biologically important Fe+ 3 and Cu+ 2 metal ions. The CNDs antioxidant assay was tasked with DPPH• radical scavenging properties. CNDs made from Cinnamomum Tamala had the highest DPPH free radical scavenging activity at 100mg/L (42.06%) with the IC50 of 130.68mg/L. The outcome implies that Indian spices are among the best materials for optical metal ion detection and sensing, and they also have therapeutic benefits.

Synergistic photoelectrochemical detection of Cd2+ with carbon-bismuth oxybromide composites: Mechanistic insights from DFT calculations

The existences of hazardous heavy metals like cadmium (Cd) in water bodies necessitates rapid, accurate on-site detection strategies. Herein, a novel photoelectrochemical scheme for sensitive detection of Cd2+ was proposed based on the hybrid carbon-bismuth oxybromide materials (C/Bi4O5Br2 and CNTs/BiOBr). The effects of ultraviolet light (UV-light) illumination during the Cd2+ deposition and desorption stages were analyzed, revealing enhanced photocurrent responses and detection sensitivity compared with those non-illumiantion. The optimal sensitivity of 0.42079 μA/ppb (C/Bi4O5Br2 under both deposition and desorption stages) and 0.15634 μA/ppb (CNTs/BiOBr under desorption stage only) were observed with UV illumination within a Cd2+ range of 10–100 ppb. Density functional theory calculation elucidated that Cd2+ adsorption on the semiconductor surface reduced the badgaps of Bi4O5Br2 and BiOBr, which would benefit electron transfer and redox reactions. Additionally, the interaction between Cd and the semiconductor produced a Schottky barrier, which prolonged the lifetime of the photo-generated electron-hole pairs, where the electrons migrated on the semiconductor surface formed electron capture traps and induced band bending, therefore facilitated the electrons in the conduction band to react with Cd2+ deposited on the electrode surface. The study provides mechanistic insights into the photoelectrochemical processes in enhancng precise and sensitive on-site heavy metal ions detection.

Spectroscopic determination of cobalt(II) ion by using azo dye of triazole derivatives

Highly efficient azo-day triazole derivatives carrying a π bond and OH electron donor groups have been designed, synthesized, and evaluated as colorimetric chemosensors for detecting metal ions in environmental samples, which was further supported by the functional theory studies and UV–Vis spectrophotometric experiment. The 4-amino-5-(2-((2,3-dimethylphenyl)amino)phenyl)-4H-1,2,4-triazole-3-thiol was directed to react with 3-nitrophenol during a diazotization type reaction to form an azo-day 4-((3-(2-((2,3-dimethylphenyl) amino)phenyl)-5-mercapto-4H-1,2,4-triazol-4-yl)diazenyl)-3-nitrophenol (Y), which have been confirmed by FTIR, 1H NMR, and could also be easily used for the detection metal ions. Compound (Y) exhibited a rapid quantitative method for the detection of Co(II) at λmax (532 nm) in an aqueous solution. The current study introduces a facile, low cost, more specific and selective chemosensor for detecting trace amounts of cobalt ions. KEY WORDS: Mefenamic acid, Azo dye, Cobalt(II), Spectroscopy Bull. Chem. Soc. Ethiop. 2024, 38(5), 1557-1567. DOI: https://dx.doi.org/10.4314/bcse.v38i6.5

Anthropological analysis of a padea-panaghiurskii-kolonii incineration grave from letca veche, Giurgiu county, Romania

In March 2023, in a field outside Letca Veche, Giurgiu County, Romania, some metal detector users discovered a cremation burial from the La Tène period (Ist century BC). After the discovery was announced, a team led by Ana Ilie from the Curtea Domnească National Museum Complex in Târgoviște excavated the burial, which had an inventory typical of this type of cremation grave, consisting of a small vessel, a belt buckle, a fibula, two spears and two sicas. The bones were taken to the Francisc I. Rainer Institute of Anthropology in Bucharest, where they were subjected to an anthropological analysis by Costin Șendroiu. The purpose of this article is firstly to present the results of the anthropological analysis of the cremated human bones and secondly to integrate the find into the context of the La Tène cremation burials in this area.

Ultrasensitive Detection of Trace Silver Ions Using MoS42--Intercalated LDH Nanosheets Enhanced SPR Sensor.

The widespread use of silver raises concerns about environmental and health risks, necessitating highly sensitive detection methods for trace silver ions (Ag+). Surface plasmon resonance (SPR) sensors offer benefits like label-free detection and rapid response, but their sensitivity for Ag+ detection is limited due to weak ion adsorption. Here, we developed an SPR sensor with MoS42--intercalated NiAl-layered double hydroxide (LDH) as the adsorption layer of Ag+ to enhance detection sensitivity. Our sensor achieves a sensitivity of 254.75 nm/μg/L and detects Ag+ at a low concentration of 2.8 pM, outperforming various existing sensors. It also shows excellent repeatability, long-term stability, and selectivity, proving effective in real-world environmental samples. This work advances high-performance SPR sensors for heavy metal ion detection.

Effect of carbon dot on preparation of dual-functional Janus particles via photo-initiated seed swelling polymerization

With the development of industry, the detection and removal of heavy metal ions from water has received much attention. Janus particles are distinguished from many other materials by their unique structure and functionalization. We proposed a simple photo-initiated seed swelling polymerization method for preparing carbon dot-coated dual-functional Janus particles (Janus@CD), using glycyl methacrylate (GMA) as monomer and ethylene dimethacrylate (EDMA) as crosslinker. In order to modulate the particle morphology during the phase separation process, carbon dot (CD) was added to the reaction system. The results demonstrated that the presence of CD had a significant effect on the shape of Janus particles. Furthermore, Janus@CD could be directly applied in the adsorption and detection for MnO4−. The limit of detection (LOD) was 6.39 nmol L−1, and the maximum adsorption capacity was 23.9 mg g−1, in line with the Langmuir adsorption model. The adsorption equilibrium reached within 30 min. The results demonstrated that dual-functional Janus@CD would present great potential in the detection and enrichment for metal ions.

The Åker assemblage: Provenance and local workshop-traditions in the North Sea region in the late 6 th and early 7 th centuries

Abstract The so-called Åker assemblage, a collection of stray finds of weapon parts and warrior-related objects dating from c. AD 600, has held a prominent position in Norwegian archaeology since the discovery of the first objects on the estate of Åker in Hedmark in south-eastern Norway in the 19th century. The assemblage comprises high-status objects belonging to a warrior elite whose equipment display close similarities across the European Continent and in Anglo-Saxon England. In early research, many of the objects in the assemblage, e. g., the renowned ‘Åker buckle’ with cloisonné and zoomorphic decoration, were ascribed a Continental provenance. More recent discussions, however, advocate a Scandinavian origin for all the objects in the assemblage. Yet, the question of where the items originally were manufactured was once more actualized when further objects belonging to the assemblage were unearthed by metal detectorists in the 1990s. Among the new finds were some Frankish types of belt mounts that are unique in a Scandinavian perspective and other items with similarities to related equipment found in other regions. The new items may thus potentially shed new light on the question concerning place of origin of the assemblage. The question of provenance, however, is tied up with the phenomenon of local workshop-traditions in Scandinavia and the North Sea region. New insights have been gained on this topic during recent years as several new production sites have been explored. Through a visual assessment of the new items in the assemblage and a discussion of related parallels, it is argued here for a yet unknown western Scandinavian workshop as the most likely source for several of the objects making up the Åker assemblage.

High density nanofluidic channels by self-sealing for metallic nanoparticles detection

High density nanofluidic channels were successfully fabricated by a novel process, nicknamed as self-sealing process, for the detection of metal nanoparticles dispersed in water using color changes excited by polarized electromagnetic waves. The permittivities of aqueous solutions with various concentrations of metal nanoparticles were calculated by a corrected plasma model. Systematic simulations using finite difference time domain method were carried out in investigating the detection capabilities of the nanofluidic channels for silver, beryllium and copper nanoparticles in water. The pronounced color shifts indicates that the channels possess high sensitivity in the metal nanoparticles detection. The designed nanofluidic channels were then fabricated by a direct flood deposition of a silica film on a pre-replicated hydrogen silsesquioxan (HSQ) grating using electron beam lithography (EBL). The self-sealing technique possesses advantages in simplified processing, encapsulation free and potential of multi-layer nanochannels.

AI-Enabled Sensor Fusion of Time-of-Flight Imaging and mmWave for Concealed Metal Detection.

In the field of detection and ranging, multiple complementary sensing modalities may be used to enrich information obtained from a dynamic scene. One application of this sensor fusion is in public security and surveillance, where efficacy and privacy protection measures must be continually evaluated. We present a novel deployment of sensor fusion for the discrete detection of concealed metal objects on persons whilst preserving their privacy. This is achieved by coupling off-the-shelf mmWave radar and depth camera technology with a novel neural network architecture that processes radar signals using convolutional Long Short-Term Memory (LSTM) blocks and depth signals using convolutional operations. The combined latent features are then magnified using deep feature magnification to reveal cross-modality dependencies in the data. We further propose a decoder, based on the feature extraction and embedding block, to learn an efficient upsampling of the latent space to locate the concealed object in the spatial domain through radar feature guidance. We demonstrate the ability to detect the presence and infer the 3D location of concealed metal objects. We achieve accuracies of up to 95% using a technique that is robust to multiple persons. This work provides a demonstration of the potential for cost-effective and portable sensor fusion with strong opportunities for further development.

Micro-droplet printed ion-selective membrane sensors for in situ monitoring of marine heavy metal ions

Fast, accurate, and reliable techniques for marine toxic heavy metal ions (HMI) detection are critical for the ecological environment and human health. One of the fatal drawbacks of traditional ion selective electrochemical sensors is that the modification of electrode cannot be accurately quantified, resulting in poor repeatability of the detection electrode and large error between the multi-electrode detection results. In order to tackle this challenge, this study presents ultra-fine micro-droplet printed electrodes for the in-situ detection of Cd2+, a carcinogenic and toxic HMI commonly found in the ocean. The ion selective membrane casting liquid was dispersed into tiny droplets with a diameter of micron through microfluidic technology, and the microdroplets were precisely arranged on the electrode surface. As a result, the modification error of electrode was reduced to pL level (accurate to 10 pL), which greatly improved the repeatability between electrodes prepared in different batches. The results of experiments with pure electrolyte, interference ions and artificial seawater indicated that the micro-droplet printed sensors possessed excellent properties of accuracy, precision, repeatability, and anti-interference. This novel micro-droplet printed sensor has the potential to capture an accurate picture of nearshore HMI in heterogeneous environments under shock conditions.

Chitosan based fluorescent probe with AIE property for detection of Fe3+ and bacteria

Fluorescent probe with aggregation-induced emission (AIE) property has been widely used because of the advantages of high sensitivity, good selectivity and non-destructive testing. The development of fluorescent probe with good biocompatibility, photostability and biodegradability is of great significance in biomedicine and environmental detection. Herein, a novel type of fluorophore CS-TPE for detection of Fe3+ and bacteria was prepared by the Schiff base reaction of chitosan (CS) and 4-(1,2,2-triphenylethenyl) benzaldehyde (TPE-CHO). The fluorescence response mechanism of CS-TPE system was investigated by various characterization techniques. CS-TPE had an obvious AIE behavior with strong blue-green emissions at 473 nm and reaches the highest photoluminescence (PL) emission in 90 % H2O/ethanol mixtures. CS-TPE fluorescent probe exhibited sensitive quenching response to Fe3+, which can be used as a biosensor for detecting the concentration of Fe3+ with short response time (5 min), low detection limit (0.998 μM) and wide detection range (10–300 μM). Meanwhile, CS-TPE exhibited good antibacterial performance for S. aureus and E. coli. It is expected to realize the real-time fluorescence monitoring of metal ion detection and antibacterial process.