Common Metal Ions Research Articles

The zinc proteome of SARS-CoV-2.

Zinc is an essential element for human health. Among its many functions, zinc(II) modulates the immune response to infections and, at high concentrations or in the presence of ionophores, inhibits the replication of various RNA viruses. Structural biology studies on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) revealed that zinc(II) is the most common metal ion that binds to viral proteins. However, the number of zinc(II)-binding sites identified by experimental methods is far from exhaustive, as metal ions may be lost during protein purification protocols. To better define the zinc(II)-binding proteome of coronavirus, we leveraged the wealth of deposited structural data and state-of-the-art bioinformatics methods. Through this in silico approach, 15 experimental zinc(II) sites were identified and a further 22 were predicted in Spike, open reading frame (ORF)3a/d, ORF8, and several nonstructural proteins, highlighting an essential role of zinc(II) in viral replication. Furthermore, the structural relationships between viral and eukaryotic sites (typically zinc fingers) indicate that SARS-CoV-2 can compete with human proteins for zinc(II) binding. Given the double-edged effect of zinc(II) ions, both essential and toxic to coronavirus, only the complete elucidation of the structural and regulatory zinc(II)-binding sites can guide selective antiviral strategies based on zinc supplementation.

A new fast-responding fluorimetric “turn-on” sensor based on benzothiazole-phenanthridine for the sensitive, selective, and reversible detection of Cu2+ in real water samples and its use in bio-imaging

This article describes a new chemosensor, 2-(benzo[d]thiazol-2-yl)-6-(7,8,13,14-tetrahydrodibenzo [a, i] phenanthridin-5-yl) phenol (BTPP), which is based on the combination of phenanthridine and benzothiazole groups for the sensitive and selective detection of Cu2+. Following the successful synthesis of BTPP in a single step, the molecular structure of BTPP was verified by 1H NMR, 13C NMR, mass spectrometry, and X-ray single-crystal analysis. These sensors exhibit high optical selectivity for the Cu2+ ion across a broad spectrum of other common metal ions in ACN/H2O (1:1) solution, resulting in an extraordinary fluorescence off-on response with a very low Limit of Detection (LOD) value. When Cu2+ was added to the compound BTPP, it displayed outstanding properties such as bright yellow emission, rapid reaction time (10 s), detection over a wide pH range (pH = 6–12), and reversibility with glutathione(GSH). FT-IR analysis, 1H NMR titration experiments, HRMS, and Job's plot analysis were used to determine the mechanism of BTPP's binding to Cu2+. Inspired by these remarkable sensing characteristics, we successfully used BTPP to detect Cu2+ in paper strip-based detection, ambient water samples, and fluorescent bio-imaging in E. coli bacteria with satisfying results.

Highly sensitive electrochemical detection of Hg(II) promoted by oxygen vacancies of plasma-treated ZnO: XPS and DFT calculation analysis

Even though there have been a variety of electrochemical sensors, it is of great importance to search for a nanomaterial with efficient active sites and explain its mechanism in the electrochemical detection of heavy metals. In the present research work, flower-like oxygen vacancy-rich zinc oxide (OV-ZnO) is prepared by processing flower-like ZnO (ZnO) with plasma. The presence of oxygen vacancies is validated using X-ray photoelectron spectroscopy (XPS), electron spin resonance (ESR), and Raman spectroscopy. The prepared OV-ZnO is then used to modify the glassy carbon electrode (GCE) surface to construct an electrochemically sensitive interface for detecting Hg(II). According to the obtained results, oxygen vacancies can significantly improve the sensing performance of the electrode for Hg(II) detection, achieving a detection sensitivity of up to about 1323.91 μA·μM−1·cm−2 and a detection limit of approximately 0.023 μM. In addition, OV-ZnO revealed good anti-interference performance against common heavy metal ions and showed excellent stability and reproducibility. XPS and density-functional theory calculations suggest that its good electrochemical sensing performance could possibly be due to the activation of oxygen vacancies, the low adsorption energy, and the appropriate Hg-Zn bond length. Moreover, the OV-ZnO-modified GCE exhibits high sensitivity to Hg(II) in actual water samples, which offers theoretical guidance for constructing electrochemical sensors for practical applications in the future.

Highly selective fluorescence detection of Pt4+ over Pd2+ and Pt2+ using a polyethyleneimine-based nanosensor prepared via facile three-component reaction

A novel polyethyleneimine (PEI)-based polymeric nanosensor (named PEIMP) was developed for specific fluorescence enhanced sensing of Pt4+ ion in aqueous media. The sensor was fabricated via “one-pot” three-component reaction using ortho-phthalaldehyde (OPA), PEI and mercaptopurine as raw materials, by which the formation of isoindole fluorophore and its chemical grafting onto PEI chain were achieved simultaneously. The morphology, size and structure of PEIMP have been characterized by various techniques. In buffered aqueous solution (pH 7.0), PEIMP had the ability to specifically bind with Pt4+ producing notable increase in fluorescence emission at 463 nm (excited at 395 nm). Based on investigations on the sensing mechanism, the fluorescence turn-on response towards Pt4+ was attributed to the binding of Pt4+ with purine group in PEIMP resulting in the inhibition of photoinduced electron transfer from purine to isoindole fluorophore. Under the optimal conditions (pH 7.0, incubated at 37 ℃ for 20 min) the detection of Pt4+ could be achieved with the linear range of 0.1–10 μM and the detection limit of 80 nM. The sensor had the advantages of low-cost raw materials, simple and environmental-friendly synthesis and analytical detection procedures. What's more, it could selectively and sensitively detect Pt4+ without the effects from common transition metal ions (Pb2+, Fe3+, Cr3+, Al3+, Ag+, Co2+, Hg2+, Cd2+, Cu2+, Mg2+, Ni2+, Mn2+, Zn2+), especially precious metalions of Pt2+ and Pd2+. The proposed method had been successfully applied to quantify Pt4+ in wastewater and urine samples, and also proved to be potential for monitoring Pt4+ in biological systems.

A cationic iridium(III) complex containing a thiosemicarbazide unit: Synthesis and application for turn-on chemiluminescent detection of Hg2+

A novel cationic iridium(III) complex [(ppy)2Ir(bPCPC)]PF6 (ppy: 2-phenylpyridine; bPCPC: 2-([2,2′-bipyridine]-4-carbonyl)-N-phenylhydrazinecarbothioamide) containing a thiosemicarbazide unit was designed and synthesized. The thiosemicarbazide unit was a sensitive functional group to Hg2+, when it reacted with Hg2+, it was desulphurized and thus led to the formation of 1,3,4-oxadiazole, [(ppy)2Ir(bPCPC)]PF6 resultantly was used as a “turn-on” chemodosimeter for luminescent detection of Hg2+ in DMF/PBS buffer solution at pH = 7–11. Except for Ag+, recognition capability of [(ppy)2Ir(bPCPC)]PF6 to Hg2+ was not interfered by other common metal ions (Co2+, Li+, Zn2+, Pb2+, K+, Al3+, Na+, Mn2+, Cu2+, Fe2+, Fe3+, Cr3+, Ba2+, Mg2+, Ni2+ and Ca2+). The detection limit was 1.83 × 10−9 mol∙L−1 (0.37 ppb), which indicated the complex was a highly sensitive chemiluminescent detection reagent of Hg2+.

Triple-Helix Molecular Switch Triggered Cleavage Effect of DNAzyme for Ultrasensitive Electrochemical Detection of Chloramphenicol.

The abuse of chloramphenicol (CAP) in animal-derived products leads to serious food safety problems, so the sensitive and accurate determination of CAP residues has great noteworthiness for public health. Herein, we present a novel electrochemical aptasensor that incorporates a poly(diallyldimethylammonium chloride) functionalized graphene/Ag@Au nanosheets (PDDA-Gr/Ag@Au NSs) composite modified electrode and a DNAzyme signal amplification effect triggered by a triple-helix molecular switch (THMS) for detecting CAP. The PDDA-Gr/Ag@Au NSs composite has the advantages of high surface area, great conductivity, and dispersibility and has successfully improved the electrochemical performance of the electrode. Specific interaction with CAP will cause the signal transduction probe (STP) to be released from the THMS. After that, the DNAzyme will be activated with the help of Pb2+ and remove the immobilized signal probe on the electrode surface. The signal change was recorded by square wave voltammetry (SWV) and led to an accurate quantification of CAP. With all these features, the proposed sensing strategy yielded a satisfactory analytical performance with linearity between 1 pM and 1 μM and a limit of detection of 18.6 fM. Furthermore, the aptasensor shows excellent specificity for CAP in the presence of other antibiotics and resists interference with other common metal ions. Importantly, the performance is not diminished when the constructed aptasensor is applied to measuring CAP in milk powder. This THMS-based method is easy to design, and alteration to different targets can be achieved by simply replacing the aptamer sequence in the THMS. Therefore, this method shows significant prospects as a flexible platform for accurate monitoring of antibiotic residues in foodstuffs.

Novel Layered Double Hydroxides@carboxymethyl Cellulose Composite Aerogel Towards Co(II) Absorption

Cobalt (Co) ion is a common heavy metal ion and the main metal ion in nuclear wastewater. However, the study on the absorption for Co(II) is not sufficient. Herein, a novel ES-layered double hydroxide (LDH) is prepared by intercalated ethylenediaminetetraacetic acid disodium salt (EDTA) and sodium dodecylbenzene sulfonate (SDBS) in a magnesium, iron pristine LDH, which is subsequently used for ES-LDH@carboxymethyl cellulose (CMC) composite aerogel. The results of Fourier transform infrared spectroscopy, X-ray diffraction spectra and thermogravimetric analysis shows successfully preparation of intercalated LDH. The pore morphology, specific surface area and pore size distribution of the composite aerogels are characterized by scanning electron microscope and Nitrogen-BET curves. The significantly improved adsorption capacity, adsorption kinetics and isotherms the absorbents on Co(II) are systematically revealed. This study thus provides an important understanding and path for dealing with the threat of Co(II).

Interaction mechanism of copper ions with the surface of sulfidized malachite and its response to flotation

The copper ion is a common metal ion in the pulp in the beneficiation industry, and it affects the recovery of the target minerals. In this study, we investigated the interaction mechanism of copper ions with the surface of sulfidized malachite and its effect on flotation. The flotation behavior and surface hydrophobicity were studied by microflotation and contact-angle tests. The experimental results showed that the hydrophobicity of sulfidized malachite modified by a suitable concentration of copper ions was enhanced and the recovery increased. However, after high-concentration copper-ion treatment, the surface hydrophobicity and flotation recovery decreased. Adsorption tests of the collector showed that the collector consumption of sulfidized malachite modified by an appropriate amount of copper ions decreased. According to zeta-potential measurement and X-ray photoelectron spectroscopy analysis, after modification with an appropriate copper-ion concentration, the less reactive –OH component was reduced and the Cu–S component was increased, indicating that the reaction activity and sulfidization product activity of the mineral surface improved. After modification with a high copper-ion concentration, a large number of copper hydroxide complexes formed, resulting in a decrease of the mineral surface reaction activity. Finally, the sulfidization layer on the mineral surface modified by an appropriate amount of copper ions was visually characterized by time-of-flight secondary-ion mass spectroscopy.

Fast and facile electrochemical detection and determination of fungicide carbendazim at titanium dioxide designed carbon-based sensor

The current research is focused on developing a sensitive, selective carbon-based sensor modified with nanostructure titanium dioxide (TiO2). The fabricated sensor was suitable for trace level quantification of fungicide, carbendazim (CRZ). The existence of the modifier TiO2 effectively increased the oxidation peak current of CRZ as compared to bare CPE. Voltammetric techniques such as cyclic voltammetry (CV) and square wave voltammetry (SWV) were implemented to ensure the effect of various parameters on CRZ electrochemical activity. Diverse parameters such as immersion interval, pH, scan rate, temperature, and concentration variation were investigated. For electro-oxidation of CRZ, a phosphate-buffer electrolyte solution (PBS) of pH 7.0 and ionic strength of 0.2 M was used. Based on the results, the electrode process involved participation of two electrons and sensor surface reaction was diffusion-controlled. A heterogeneous rate constant (ko) of 2.1 s−1 was obtained. The detection and quantification limits were calculated as 1.71 × 10−8 M and 5.70 × 10−8 M, respectively. Stability, responsiveness, reproducibility, and repeatability are prominent features of the set up procedure. The suggested sensor displayed outstanding detection abilities for CRZ among variety of common metal ions and other pesticide molecules. The analysis of CRZ in environmental samples such as water and soil provided good recovery results.

Chlorination of L-tyrosine and metal complex: degradation kinetics and disinfection by-products generation

The presence of metal ions in drinking water treatment and distribution systems may affect the disinfection process of organic matter, which had aroused people's concern. L-tyrosine can complex with metal ions through carboxyl, carbonyl and amino groups and affected its chemical reactions. In this paper, the complexation of L-tyrosine with common metal ions was studied and the influence of complexation in chlorination with different experimental factors were investigated. It was inferred that L-tyrosine complexed with metal ions by single dentate ligand or double dentate chelation in a ratio of 2:1. The degradation of L-tyrosine-metal complex followed the pseudo-first-order reaction kinetic. TCM, DCAA and TCAA were the main species DBPs in chlorination of L-tyrosine. Compared with L-tyrosine, the reaction rate constants of complex increased by 5.6%, the formation of trihalomethane production decreased by 21.5% and the formation of haloacetic acids production increased by 26.9% at the state of metal complexation. The effect of metal complexation on chlorination was more obvious than that of metal coexistence. For different metal complexation, the order of inhibition on trihalomethane production was Ca2+> Fe3+> Mn2+ and the order of promotion on haloacetic acids production was Mn2+> Fe3+> Ca2+. Moreover, it was found that alkaline conditions were favorable to the formation of DBPs due to the hydroxyl radical. The combination of ultraviolet (UV) and chlorine disinfection promoted L-Tyr degradation and DBPs generation, and the promotion efficiency follow the order: UV/Cl2> UV-Cl2> Cl2.

Green-synthesized, pH-stable and biocompatible carbon nanosensor for Fe3+: An experimental and computational study

Brightly fluorescent Carbon Dots (CDs) were synthesized by green hydrothermal method using commonly available biomass (Aloe vera) as carbon precursor. Their physiochemical and optical characterization was done by standard microscopic and spectroscopic techniques. Photophysical features of their aqueous dispersion were investigated in detail. The influence of wide pH range (2–12), high ionic load (2M) and temperature on their photoluminescence behavior was investigated. Their in-vitro cytotoxicity examination was conducted on Human Cervical Cancer Cells (HeLa) using MTT assay. Testing of their ion-recognition property for common metal ions was done in aqueous medium. These CDs exhibited preferential interaction with Fe3+ over other tested metal ions, without any functionalization. Interaction between CDs and Fe3+ was analyzed in the light of Density Functional Theory (DFT). The work demonstrates that these CDs are acting as nanoprobe for Fe3+ and sensing it at ultra-trace level (5 nM).

Design and Synthesis of Dipeptidomimetic Isocyanonaphthalene as Enhanced-Fluorescent Chemodosimeter for Sensing Mercury Ion and Living Cells.

A novel valine-based isocyanonaphthalene (NpI) was designed and synthesized by using an easy method and enabled the selective fluorescence detection of Hg2+. The chemodosimeter can display an immediate turn-on fluorescence response (500-fold) towards target metal ions upon the Hg2+-mediated conversion of isocyano to amino within NpI. Based on this specific reaction, the fluorescence-enhancement probe revealed a high sensitivity toward Hg2+ over other common metal ions and exhibited excellent aqueous solubility, good antijamming capability, high sensitivity (detection limit: 14.2 nM), and real-time detection. The response mechanism of NpI was supported by NMR spectroscopy, MS analysis and DFT theoretical calculation using various techniques. Moreover, a dipeptidomimetic NpI probe was successfully applied to visualize intracellular Hg2+ in living cells and monitor Hg2+ in real water samples with good recoveries and small relative standard deviations.

New insight into transformation of tetracycline in presence of Mn(II): Oxidation versus photolysis

Tetracycline (TC) and Mn(II) is a common antibiotic and metal ion respectively. Nevertheless, literatures involving in the effects of Mn(II) on TC transformation are still insufficient. In this study, the kinetic experiment, spectral analysis, complexation experiment and electrochemical analysis, theoretical calculation and products detection were carried out to probe into oxidation and photolysis of TC with Mn(II). Mn(II) greatly accelerated TC oxidation, preferably tending to complex with TC at O10 – O12 or O2 – O3 site. There were a TC-Mn(II)/TC-Mn(III) redox couple and electron transfer process. Conversely, Mn(II) inhibited photolysis of TC. The photolysis of excited TC could compete with energy dissipation reactions. The electron transfer and complexation reaction easily made excited TC energy transfer, thus slowing down photolysis process. During the TC transformation, the intensity of functional groups was significantly decreased. Simultaneously, the degradation pathways mainly included eight reactions. It is a very interesting and probably overlooked phenomenon, which identifies new transformation of TC with Mn(II). This study helps to further understand fate and environmental behavior of antibiotics and metal ion.

Fabrication and investigation of novel monochloroacetic acid fortified, tripolyphosphate-crosslinked chitosan for highly efficient adsorption of uranyl ions from radioactive effluents

Chitosan crosslinked with potassium tripolyphosphate (CTPP) and monochloroacetic-acid-modified chitosan crosslinked with potassium tripolyphosphate (MCTPP) were synthesized for removing UO22+ from acidic radioactive effluents. The influential factors, operational requirements, and interactive mechanisms of the adsorption process were systematically investigated. The mesh-structured composites adsorbed UO22+ most effectively at pH 5.0. The maximum adsorption capacities for pure chitosan, CTPP, and MCTPP were 374.93, 780.89, and 1487.72 mg/g, respectively. Batch experiments indicated that the pH and adsorbent dose strongly influenced UO22+ adsorption. MCTPP could adsorb most UO22+ within 15 min, and equilibrium was reached by ~1 h. The adsorption isotherms indicated that UO22+ adsorption by MCTPP may be an endothermic single-layer adsorption process. Moreover, common metal ions in single-metal systems only slightly affected this process. The results of instrumental characterization and natural water application suggested that the highly developed pore structure and abundant tripolyphosphate groups in synthesized composites were dominant adsorption contributors besides amino and hydroxyl groups. Successful development of the novel material for efficiently adsorbing UO22+ and identification of the adsorption mechanism will provide valuable guidance to chitosan modification and further remediation practices of radioactive effluents.

Two Imidazo[1,2‐a]pyridine Congeners Show Aggregation‐Induced Emission (AIE): Exploring AIE Potential for Sensor and Imaging Applications

AbstractDensity functional theoretical calculations predicted non‐coplanar twisted geometry for two new imidazo[1,2‐a]pyridine derivatives, Imp and ImBt. Analysis of single‐crystal of Imp asserted the non‐coplanar twisted geometry, which is implicated in aggregation induced emission (AIE) of small aromatic molecules. Universal quenching by water was observed in aqueous THF solutions of Imp and ImBt, but they showed AIE effect when the water content was more than 80 %. Non‐fluorescent solutions of Imp and ImBt in THF‐water (7 : 3 v/v) mixture turned fluorescent on addition of specific metal ions prompting their potential to be explored for turn‐on sensor applications. While ImBt showed AIE response to Cd2+, Hg2+ and Al3+, Imp displayed AIE effect only to Cd2+ ions, under identical conditions. Absence of interference from common metal ions (including Hg2+ and Al3+) led to selective formation of Imp‐CdCl2 (1 : 1) complex, which offered the limit of detection of Cd2+ to be 19.2 μM. The observed selectivity for Cd2+ permitted the use of Imp in the imaging of live Rhizoctonia oryze contaminated with Cd2+ ions.

Development of novel Schiff base fluorophores for selective detection of Cu2+ ions in seawater using test strips

A novel Schiff bases of 2-((2-aminophenylimino)methyl)-3-phenyl-4(3H)-quinazolinone (3a), 2-((2-aminophenylimino)methyl)-3-(4-tolyl)-4(3H)-quinazolinone (3b), and 2-((2-aminophenylimino)methyl)-3-(4-anisyl)-4(3H)-quinazolinone (3c) were synthesized and characterized by FTIR, NMR, and elemental analysis. In an aqueous solution at pH 8, the quinazolinone derivatives (3a–c) show remarkable selectivity and sensitivity towards Cu2+ ions over other common metal ions. The molar ratio plot confirms a 2:1 stoichiometry complex formation between 3a-c compounds and Cu2+. In addition, the binding constants (Kd) were calculated using Lineweaver-Burk plots and were found to be 2.45×106, 7.80×104 and 4.17×105 M−1 for 3a, 3b, and 3c, respectively. The detection limits were 0.04, 0.16 and 0.10 µmol L−1 for 3a, 3b, and 3c, respectively with a good linearity in the range of 0.2–2.0 µmol L−1. The quenching mechanism of 3a–c toward Cu2+ ions is assigned to the reverse photoinduced electron transfer. The synthesized sensors are applied to detecting Cu2+ions in sea water samples. The developed sensors were successfully used as test strips for fluorescence detection of Cu2+ ions.

Development of tBu-phenyl Acetamide Appended Thiacalix[4]arene as "Turn-ON" Fluorescent Probe for Selective Recognition of Hg(II) Ions.

Herein, a novel N-(4-(tert-butyl)-phenyl)-2-chloroacetamide functionalized thiacalix[4]arene architecture, viz TCAN2PA has been synthesized and the sensing behaviour towards metal ions were explored. The probe, TCAN2PA displayed "turn-on" fluorescence response towards Hg(II) ions in acetonitrile over a series of competing common metal ions. A bathochromic shift in absorption band along with a significant "Turn-On" fluorescence behaviour of TCAN2PA was observed upon interaction with Hg(II) ions. The lower rim modification of thiacalixarene with N-(4-(tert-butyl)-phenyl)-2-chloroacetamide actively contributes toward the fluorescence property due to the presence of strong electron-donating aryl amido substituent. Fluorescence titration experiments were conducted to find out the limit of detection and to understand binding stoichiometry as well. The electron transfer interactions between the electron rich TCAN2PA host with Hg(II) ions have been postulated which is also supported by computational modelling insights.

A low-noise ratiometric fluorescence biosensor for detection of Pb2+ based on DNAzyme and exonuclease III-assisted cascade signal amplification.

As a common heavy metal ion with strong toxicity and wide distribution, lead ions (Pb2+) had great harm to the human body. In this work, a low-noise ratiometric fluorescence biosensor was developed based on Pb2+-dependent DNAzyme and exonuclease III (Exo III)-assisted cascade signal amplification. Firstly, the substrate chain of DNAzyme (S-DNA) was modified on the surface of magnetic beads (MBs) through the combination of biotin and streptavidin, and then the enzyme chain of DNAzyme (E-DNA) was connected to the MBs by forming a double-stranded DNA (dsDNA) with S-DNA. A hairpin DNA (HP) labelled with Cy3 and Cy5 respectively at both ends was used as a fluorescence probe. The emission peaks of Cy3 and Cy5 can appear at 562nm and 665nm respectively, and their fluorescence intensity ratio (F562/F665) was chosen as the acquisition signal. The ratiometric sensor can reduce the interference of detection environment and avoid false positive reactivity. Due to the cleavage of DNAzyme and the release of single-stranded DNA (ssDNA) in the presence of Pb2+, the hairpin structure of HP was opened and the FRET between two fluorophores disappeared, resulting in the strengthened signal of Cy3 and the weakened signal of Cy5. Furthermore, the ratio [Formula: see text] signal increased gradually with the increase of Pb2+ concentration. When the concentration of Pb2+ was in the range of 0.1-1000nM, [Formula: see text] had a good linear relationship with [Formula: see text], the correlation coefficient (R2) was 0.997, and the limit of detection (LOD) was 77pM. The presented ratiometric fluorescence biosensor had lower LOD and wider detection range via comparing with other methods. At the same time, the sensor also obtained the satisfactory results for detection of Pb2+ in tap water, tea, and rice flour samples. The provided ratiometric biosensor has great potential in the monitoring of various targets. A low-noise ratiometric fluorescence biosensor based on the FRET between two fluorophores was developed, and the DNAzyme and exonuclease III-assisted cascade signal amplification was used to improve the sensitivity of the method. The biosensor had a detection limit as low as 77pM.

Relative capability demonstration of luminescent Al-MOFs for ideal detection of nitroaromatic explosives.

Here, we have synthesised three luminescent Al MOFs i.e., Al-NTP, Al-FDA, and Al-TDA, using common metal ions (AlCl3·6H2O) with different carboxylic acid organic linkers (5-nitroisophthalic acid, 2,5-furan dicarboxylic acid, and 2,5-thiophenedicarboxylic acid) in a semi-aqueous medium. The structural analysis of Al-MOFs has been confirmed through powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy and absorption spectroscopy. Afterward, the optical properties of all three Al-MOFs were confirmed using photoluminescence spectroscopy and demonstrated for the detection of nitroaromatic explosives. We have observed host-guest interaction through a quenching mechanism. Among the three synthesised Al-MOFs, Al-NTP MOF exhibit 0.014 ppm lowest limit of detection in chloroform at room temperature. Our comparative study results reveal that the selection of the organic linker and solvent plays a critical role in MOF based sensing applications.

A simple electrochemical aptasensor for saxitoxin detection.

In this study, a simple electrochemical aptasensor for saxitoxin (STX) detection was developed based on a short anti-STX aptamer with a methylene blue (MB) incorporated at the 3′-end. The aptamer was immobilized on the surface of gold electrode and served as the recognition element. The aptasensor was successfully used as a highly selective and sensitive biosensor for STX detection because of the selection of aptamer along with the excellent electrocatalytical properties of MB. With the increase of the dynamic concentration of STX from 1 nM to 1 μM, the aptasensor exhibited a sensitivity with a peak current change of 2.92 μA per decade and a low detection limit of 1 nM. In addition, the aptasensor demonstrated excellent selectivity to STX, which prevented the interferences from neo-STX, okadaic acid and common metal ions. Using the proposed principle, several other aptasensors with improved performance can be constructed via the modification of the electrochemical sensor with appropriate aptamers.