Super rapid removal of copper,cadmium and lead ions from water by NTA-silica gel

Copper (Cu²⁺), cadmium (Cd²⁺) and lead ions (Pb²⁺) are toxic to human beings and other organisms. In this study, a silica gel material modified with nitrilotriacetic acid (NTA-silica gel) was sensibly designed and prepared via a simple amidation procedure for the removal of Cu²⁺, Cd²⁺ and Pb²⁺ from water. The NTA-silica gels showed rapid removal performances for the three metal ions (Pb²⁺ (<2 min), Cu²⁺ and Cd²⁺ (<20 min)) with relatively high adsorption capacities (63.5, 53.14 and 76.22 mg g⁻¹ for Cu²⁺, Cd²⁺ and Pb²⁺, respectively). At the same concentration of 20 mg L⁻¹, the removal efficiencies of the three metals by the adsorbent ranged from 96% to 99%. The Freundlich and Langmuir models were utilized to fit the adsorption isotherms. The adsorption kinetics for the three metal ions was pseudo-second-order kinetics. The removal performance of the NTA-silica gels increased in a wide pH range (2–9) and maintained in the presence of competitive metal ions (Na⁺, Mg²⁺, Ca²⁺ and Al³⁺) with different concentrations. In addition, the NTA-silica gels were easily regenerated (washed with 1% HNO₃) and reused for 5 cycles with high adsorption capacity. This study indicates that the NTA-silica gel is a reusable adsorbent for the rapid, convenient, and efficient removal of Cu²⁺, Cd²⁺, and Pb²⁺ from contaminated aquatic environments.

A silica gel material modified with nitrilotriacetic acid (NTA-silica gel) was sensibly designed and prepared via a simple method for the super rapid removal of Cu²⁺, Cd²⁺ and Pb²⁺ from water.     

Correction: Nano zero valent iron (nZVI) particles for the removal of heavy metals (Cd2+, Cu2+ and Pb2+) from aqueous solutions

Correction for ‘Nano zero valent iron (nZVI) particles for the removal of heavy metals (Cd²⁺, Cu²⁺ and Pb²⁺) from aqueous solutions’ by Mekonnen Maschal Tarekegn et al., RSC Adv., 2021, 11, 18539–18551. DOI: 10.1039/D1RA01427G.

The authors regret that reference 48 was incorrect. The correct reference is given below as reference 1.¹The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.     

An Amberlite IRA-400 Cl− ion-exchange resin modified with Prosopis juliflora seeds as an efficient Pb2+ adsorbent: adsorption,kinetics, thermodynamics,and computational modeling studies by density functional theory

A Prosopis juliflora-seed-modified Amberlite IRA-400 Cl⁻ ion-exchange resin (hereafter denoted as SMA resin) is used for the removal of Pb²⁺ from wastewater. SEM, EDX, FT-IR, BET, XRD, and XPS analyses were used to characterize the SMA resin. Parameters such as Pb²⁺ concentration, pH, temperature, and time are optimized. The obtained results show that the SMA resin has high efficiency for the removal of Pb²⁺ (73.45%) at a concentration of 100 mg L⁻¹ and a dosage of 0.01 g at pH 6. Thermodynamic studies indicate that the adsorption was spontaneous with negative ΔH° and ΔS° values at all temperatures; pseudo-second-order kinetics and the Langmuir adsorption isotherm provided the best fit (q_max = 106 mg g⁻¹ and R² = 0.99) from 298 to 338 K. In addition, a diffusion-controlled mechanism at 298 K was observed from intra-particle studies. A desorption and recovery process has been applied successfully to the SMA adsorbent. The obtained results showed desorption of 90.7% at pH 2.5 with 86.3% recovery over six cycles. Furthermore, the DFT results suggest that all the functional groups of the SMA resin possibly bind with Pb²⁺ and, of these, the –C O group shows the highest binding energy towards Pb²⁺. Moreover, the high-efficiency removal of Pb²⁺ from synthetic wastewater using the proposed SMA resin was demonstrated to show the real-life application potential.

We have demonstrated a high Pb²⁺ removal efficiency (73.45%) from wastewater using a Prosopis juliflora-seed-modified Amberlite IRA-400 Cl⁻ ion-exchange resin (SMA resin).     

Adsorption of Cd2+ by an ion-imprinted thiol-functionalized polymer in competition with heavy metal ions and organic acids

The simultaneous presence of heavy metals and organic acids in nature and wastewaters and their competition for adsorption sites determine the migration, transformation and fate of pollutants in the environment. A Cd²⁺-ion-imprinted polymer (Cd²⁺-IIP) with a thiol-functional group was hydrothermally synthesized by a surface imprinting technique combined with ultrasonic heating for selective adsorption of Cd²⁺ from wastewaters. The adsorbent was characterized by SEM, EDS, XPS, BET and FT-IR measurements. The experimental results concerning Cd²⁺ adsorption from single-, binary-, ternary- and quaternary-metal aqueous solutions containing Cu²⁺, Ni²⁺ and Zn²⁺ revealed high selectivity. In binary-metal solutions, relative selectivity coefficients for Cd²⁺ in respect to Cd²⁺/Cu²⁺, Cd²⁺/Ni²⁺, and Cd²⁺/Zn²⁺ were as high as 3.74, 5.73 and 4.15, respectively. In multi-metal solutions, competing heavy metal ions had little effect on the adsorption of Cd²⁺ attributed to the high selectivity of Cd²⁺-IIP towards Cd²⁺ determined by its coordination geometry. The effect of low-molecular weight organic acids on the Cd²⁺ adsorption was also studied and the results showed that the presence of tartaric, citric and oxalic acids as admixtures in Cd²⁺ aqueous solutions noticeably reduced the cation adsorption in a wide range of concentrations with the minor exception of low contents of citric and tartaric acids slightly improving adsorption.

A Cd²⁺-imprinted thiol-functionalized polymer in competition with heavy metal ions and low molecular weight organic acids was investigated.     

A rapid on-site analysis method for the simultaneous extraction and determination of Pb2+ and Cd2+ in cereals

In order to achieve rapid on-site screening and solve the problem of rapid pretreatment for the determination of lead (Pb²⁺) and cadmium (Cd²⁺) in cereals by a portable electrochemical analyzer with disposable screen-printed electrodes (SPEs), a new reliable and simple extraction method for Pb²⁺ and Cd²⁺ in cereals was developed. The Pb²⁺ and Cd²⁺ in cereals were purified by a mixed solution of 1 mol L⁻¹ potassium iodide (KI)/5% vitamin C (VC)/ethyl acetate after being extracted by 10% HNO₃, which transfers the Pb²⁺ and Cd²⁺ into ethyl acetate after a reaction with KI–VC. Then, the Pb²⁺ and Cd²⁺ were eluted from ethyl acetate with 5% HNO₃ and were determined by an electrochemical analyzer with screen printed electrodes. Under the optimized conditions, the matrix calibration curves of Pb²⁺ and Cd²⁺ in rice and wheat showed good linear relationships with R² > 0.996. The method shows a detection limit (LOD) for Cd²⁺ in rice and wheat of 6.7 μg kg⁻¹ and 11.5 μg kg⁻¹, and the corresponding values for Pb²⁺ were 34.9 and 31.1 μg kg⁻¹, respectively. The relative standard deviation (RSD) was less than 8.7% for Cd²⁺ and Pb²⁺. In addition, the recoveries of the tested reference materials using this method were between 80% and 120%. From sample pretreatment to testing results, the whole process took no more than 25 min, and the operation was simple for operators, green to the environment, cheap in terms of instruments, and above all suitable for on-site detection. The results implied that this portable electrochemical method with new pretreatment may be a good choice for screening Pb²⁺ and Cd²⁺ in cereal samples on-site.

To achieve rapid on-site screening rapid pretreatment for the determination of Pb²⁺ and Cd²⁺ in cereals by a portable electrochemical analyzer with disposable screen-printed electrodes, a new reliable and simple extraction method for Pb²⁺ and Cd²⁺ was developed.     

Nanochannel-based sensor for the detection of lead ions in traditional Chinese medicine

Lead ions (Pb²⁺) are used in the quality control of traditional Chinese medicine (TCM) preparations because they are highly toxic to human health. At present, sophisticated analytical instrumentation and complicated procedures for sample analysis are needed for the determination of Pb²⁺. Herein, a simple, fast, and sensitive peptide-modified nanochannel sensor to detect Pb²⁺ in TCM is reported, which is based on a Pb²⁺-specific peptide modified porous anodized aluminum membrane (PAAM). This peptide-based nanochannel clearly has the highest selectivity for Pb²⁺ when compared to other heavy metal ions, including As²⁺, Cd³⁺, Co²⁺, Cr²⁺, Cu²⁺, Fe³⁺, Hg²⁺, Mg²⁺, Mn²⁺, Ni²⁺, and Zn²⁺. Based on linear ranges from 0.01 to 0.16 μM and 10 to 100 μM, the detection limit was calculated to be 0.005 μM. Moreover, this peptide-based nanochannel sensor was successfully used to detect Pb²⁺ in complex TCM samples. In addition, when compared with the gold standard atomic absorption spectrophotometry (AAS) method, the recovery of the peptide-modified nanochannel sensor was between 87.7% and 116.8%. The experimental results prove that this new sensor is able to achieve accurate detection of Pb²⁺ in TCM samples. Thus, this sensor system could provide a simple assay for sensitive and selective detection of Pb²⁺ in TCM, thereby showing great potential in the practical application for the quality control of heavy metals in TCM.

The nanochannel-based sensor is able to achieve detection of Pb²⁺ in TCM samples.     

Highly efficient heavy-metal extraction from water with carboxylated graphene nanoflakes

Heavy metals such a lead or cadmium have a wide range of detrimental and devastating effects on human health. It is therefore of paramount importance to efficiently remove heavy metals from industrial wastewater streams as well as drinking water. Carbon materials, including graphene and graphene oxide (GO), have recently been advocated as efficient sorption materials for heavy metals. We show that highly carboxylated graphene nanoflakes (cx-GNF) outperform nano-graphene oxide (nGO) as well as traditional GO with respect to extracting Fe²⁺, Cu²⁺, Fe³⁺, Cd²⁺ and Pb²⁺ cations from water. The sorption capacity for Pb²⁺, for example, is more than six times greater for the cx-GNF compared to GO which is attributed to the efficient formation of lead carboxylates as well as strong cation–π interactions. The large numbers of carboxylic acid groups as well as the intact graphenic regions of the cx-GNF are therefore responsible for the strong binding of the heavy metal cations. Remarkably, the performance of the as-made cx-GNF can easily compete with previously reported carbon materials that have undergone additional chemical-functionalisation procedures for the purpose of heavy-metal extraction. Furthermore, the recyclability of the cx-GNF material with respect to Pb²⁺ loading is demonstrated as well as the outstanding performance for Pb²⁺ extraction in the presence of excess Ca²⁺ or Mg²⁺ cations which are often present under environmental conditions. Out of all the graphene materials, the cx-GNF therefore show the greatest potential for future application in heavy-metal extraction processes.

Carboxylated graphene nanoflakes show great potential for heavy-metal extraction from water.     

A bifunctional sensor based on diarylethene for the colorimetric recognition of Cu2+ and fluorescence detection of Cd2+

A novel bifunctional sensor based on diarylethene with a benzyl carbazate unit was synthesized successfully. It not only served as a colorimetric sensor for the recognition of Cu²⁺ by showing changes in absorption spectra and solution color, but also acted as a fluorescent sensor for the detection of Cd²⁺ through obvious emission intensity enhancement and fluorescence color change. The sensor exhibited excellent selectivity and sensitivity towards Cu²⁺ and Cd²⁺, and the limits of detection for Cu²⁺ and Cd²⁺ were 8.36 × 10⁻⁸ mol L⁻¹ and 1.71 × 10⁻⁷ mol L⁻¹, respectively, which were much lower than those reported by the WHO and EPA in drinking water. Furthermore, its application in practical samples demonstrated that the sensor can be effectively applied for the detection of Cu²⁺ and Cd²⁺ in practical water samples.

A bifunctional sensor for colorimetric recognition of Cu²⁺ and fluorescent detection of Cd²⁺ was synthesized. It not only showed high selectivity and sensitivity to Cu²⁺ and Cd²⁺, but also could be used in practical water samples with high accuracy.     

Synthesis,characterization, and comparison of antibacterial effects and elucidating the mechanism of ZnO,CuO and CuZnO nanoparticles supported on mesoporous silica SBA-3

Silanized iminodiacetic acid (GLYMO–IDA) modified mesoporous silica (G-SBA) was prepared following a co-condensation method. G-SBA/Cu²⁺, G–SBA/Zn²⁺ and G-SBA/Cu²⁺–Zn²⁺ were obtained through the impregnation method with coordination by GLYMO–IDA. SBA/CuO, SBA/ZnO, and SBA/CuZnO were generated after calcination of G-SBA/Cu²⁺, G-SBA/Zn²⁺ and G-SBA/Cu²⁺–Zn²⁺. After modification, the amount of metal ion was 6 to 70 times higher than that of the blank mesoporous silica. The diameter of nano-copper oxide particles in mesoporous silica was 4.8 nm. The bacteriostatic rates of SBA/CuO at a copper oxide concentration of 250 ppm against E. coli and S. aureus were 85.87% and 100%, respectively. SBA/CuO and SBA/CuZnO with {111} lattice planes exhibited better antibacterial effects compared to the commercial-grade nano-zinc oxide and nano-copper oxide. When exposed to ultraviolet light, SBA/CuZnO displayed the highest photocatalytic activity and optimal antimicrobial effect. Therefore, SBA/CuZnO can be an alternative to antibiotics because of its non-toxic nature and good antibacterial properties.

Silanized iminodiacetic acid (GLYMO–IDA) modified mesoporous silica (G-SBA) was prepared following a co-condensation method.     

Novel magnetically separable anhydride-functionalized Fe3O4@SiO2@PEI-NTDA nanoparticles as effective adsorbents: synthesis,stability and recyclable adsorption performance for heavy metal ions

In this paper, a novel adsorbent, Fe₃O₄@SiO₂@PEI-NTDA, was first prepared by the immobilization of an amine and anhydride onto magnetic Fe₃O₄@SiO₂ nanoparticles with polyethylenimine (PEI) and 1,4,5,8-naphthalenetetracarboxylic-dianhydride (NTDA) for the removal of heavy metal ions from aqueous solutions. The structure of Fe₃O₄@SiO₂@PEI-NTDA was systematically investigated; the results confirmed that amine and anhydride groups were successfully covalently grafted onto the surface of Fe₃O₄@SiO₂, which showed a homogenous core–shell structure with three layers of about 300 nm diameter (Fe₃O₄ core: 200 nm, nSiO₂ layer: 20 nm, and PEI-NTDA layer: 20 nm). The adsorption performance of Fe₃O₄@SiO₂@PEI-NTDA NPs was evaluated for single Pb²⁺ and coexisting Cd²⁺, Ni²⁺, Cu²⁺, and Zn²⁺ ions in an aqueous solution in a batch system. The amine and anhydride groups may have a synergistic effect on Pb²⁺ removal through electrostatic interactions and chelation; Fe₃O₄@SiO₂@PEI-NTDA NPs exhibited preferable removal of Pb²⁺ with maximum adsorption capacity of 285.3 mg g⁻¹ for Pb²⁺ at a solution pH of 6.0, adsorbent dosage of 0.5 g L⁻¹, initial Pb²⁺ concentration of 200 mg L⁻¹ and contact time of 3 h. The adsorption mechanism conformed well to the Langmuir isotherm model, and the adsorption kinetic data were found to fit the pseudo-second order model. Fe₃O₄@SiO₂@PEI-NTDA NPs could be recovered easily from their dispersion by an external magnetic field and demonstrated good recyclability and reusability for at least 6 cycles with a high adsorption capacity above 204.5 mg g⁻¹. The magnetic adsorbents showed high stability with a weight loss below 0.65% in the acid leaching treatment by 2 M HCl solution for 144 h. This study indicates that Fe₃O₄@SiO₂@PEI-NTDA NPs are new promising adsorbents for the effective removal of Pb²⁺ in wastewater treatment.

A magnetically separable adsorbent, anhydride-functionalized Fe₃O₄@SiO₂@PEI-NTDA, was successfully constructed for removal of heavy metal ions from aqueous solution.     

Functionalization of silver nanoparticles with mPEGylated luteolin for selective visual detection of Hg2+ in water sample

A novel colorimetric sensor based on mPEGylated luteolin-functionalized silver nanoparticles (mPEGylated luteolin-AgNPs) in an aqueous solution was prepared. The mPEGylated luteolin-AgNP solution was utilized to detect Hg²⁺ with high sensitivity and selectivity in the presence of other metal cations including Na⁺, K⁺, Mg²⁺, Zn²⁺, Ni²⁺, Mn²⁺, Ba²⁺, Pb²⁺, Sr²⁺, Ca²⁺, Cd²⁺, Al³⁺ and Cu²⁺. The solution could be induced to aggregate, and a color change from yellow-brown to colorless was observed in the presence of Hg²⁺. Meanwhile, the sensor was successfully used to detect Hg²⁺ in tap water with satisfactory recovery ranges using the standard addition method.

A novel colorimetric sensor for selective detection of Hg²⁺ based on mPEGylated luteolin functionalized silver nanoparticles was prepared.     

Synthesis of Schiff and Mannich bases of new s-triazole derivatives and their potential applications for removal of heavy metals from aqueous solution and as antimicrobial agents

An efficient, simple, and one-pot double Mannich reaction was performed for the synthesis of cyclized 2-methyl-6-substituted-6,7-dihydro-5H-s-triazolo[5,1-b]-1,3,5-thiadiazines via a reaction of 5-methyl-1H-s-triazole-3-thiol (1) with formaldehyde and primary aliphatic amines in ethanol at room temperature, while with primary aromatic amines, uncyclized 3-methyl-1-((substituted-amino)methyl)-1H-s-triazole-5-thiols were produced. Under Mannich reaction conditions, 4-amino-3-methyl-s-triazole-5-thiol (8) reacted with formaldehyde only in boiling ethanol or at room temperature to afford 3-methyl-5,6-dihydro-s-triazolo[3,4-b]-1,3,4-thiadiazole without incorporation of secondary amine. Furthermore, after reaction of compound 8 with aromatic aldehydes under different reaction conditions, uncyclized Schiff''s bases were produced. Therefore, reaction of these Schiff''s bases with primary or secondary amines with formaldehyde in ethanol at room temperature afforded the corresponding Mannich bases 13–14. The structures of all new compounds were confirmed using spectral analysis. Furthermore, most of the synthesized derivatives showed high efficiency for removal of Pb²⁺, Cd²⁺, Ca²⁺, and Mg²⁺ from aqueous solutions, as well as antimicrobial activity.

An efficient synthesis of Schiff and Mannich bases of new s-triazole derivatives under mild conditions has been developed for the removal of Pb²⁺, Cd²⁺, Ca²⁺, and Mg²⁺ from aqueous solutions and as antimicrobial agents.     

Acetylacetone functionalized magnetic carbon microspheres for the highly-efficient adsorption of heavy metal ions from aqueous solutions

Herein, Acac-C@Fe₃O₄, a magnetic carbon (C@Fe₃O₄) modified with acetylacetone (Acac), was first prepared and used as a solid-phase adsorbent for adsorbing some heavy metal ions from aqueous solution. The adsorbent was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometry (VSM) and BET studies. Some parameters affecting the adsorption and desorption processes were studied in Pb²⁺ solution, including sample pH, contact time, initial concentration, type and connection of the desorption solution. Absorption results showed that removal of Pb²⁺ was 100% under optimal conditions at an initial concentration of 10.0 mg L⁻¹. The adsorption mechanism conformed well to a pseudo-second order kinetic model. The adsorption capacity of the sorbent also showed promising results with Hg²⁺, Cr³⁺, Fe²⁺, Cd²⁺, Mn²⁺, Zn²⁺, Cu²⁺ and Pb²⁺, where maximum adsorption capacities reached 98.0, 151.2, 188.9, 202.2, 286.3, 297.2, 305.1 and 345.3 mg g⁻¹, respectively. The Acac-C@Fe₃O₄ microsphere material was successfully applied to the adsorption of heavy metal ions in aqueous solution.

Herein, Acac-C@Fe₃O₄, a magnetic carbon (C@Fe₃O₄) modified with acetylacetone (Acac), was first prepared and used as a solid-phase adsorbent for adsorbing some heavy metal ions from aqueous solution.     

Synthesis of Fe3O4@PVBC–TMT nanoparticles for the efficient removal of heavy metals ions

Core–shell magnetic Fe₃O₄@PVBC–TMT (Fe₃O₄@polyvinylbenzyl chloride–trithiocyanuric acid) nanoparticles containing trithiocyanuric acid groups were fabricated and employed for the fast removal of heavy metals from an aquatic environment. The morphology, structure and properties of Fe₃O₄@PVBC–TMT nanoparticles were characterized by a series of modern analytical tools. The adsorption behavior of the Fe₃O₄@PVBC–TMT nanoparticles for heavy metals ions in aqueous solutions was investigated by batch experiments. The maximum removal capacities of the Fe₃O₄@PVBC–TMT nanoparticles toward Mn²⁺, Ni²⁺, Cu²⁺, Cd²⁺ and Pb²⁺ ions were 127.4, 146.6, 180.5, 311.5, and 528.8 mg g⁻¹, respectively. Importantly, it is found that Pb²⁺ ions can be completely and quickly removed by the Fe₃O₄@PVBC–TMT nanoparticles. The equilibrium was established within 6 min, and the removal efficiencies were found to be 99.9%, 99.8% and 99.5% for Pb²⁺ ions at the initial concentrations of 100 mg L⁻¹, 200 mg L⁻¹ and 300 mg L⁻¹, respectively. It is hoped that the core–shell magnetic Fe₃O₄@PVBC–TMT nanoparticles may find application in wastewater treatment.

Core–shell Fe₃O₄@PVBC–TMT nanoparticles were fabricated and served as a valid magnetic adsorbent for the removal of heavy metals ions.     

Triazole-based novel bis Schiff base colorimetric and fluorescent turn-on dual chemosensor for Cu2+ and Pb2+: application to living cell imaging and molecular logic gates

A triazole-based novel bis Schiff base colorimetric and fluorescent chemosensor (L) has been designed, synthesized and characterized by elemental analysis, ¹H-NMR, ESI-MS, FTIR spectra and DFT studies. The receptor L showed selective and sensitive colorimetric sensing ability for Cu²⁺ and Pb²⁺ ions by changing color from colorless to yellow and light yellow respectively in CH₃OH–tris-buffer (1 : 1, v/v). However, it displayed strong fluorescence enhancement upon the addition of both Cu²⁺ and Pb²⁺ ions, attributed to the blocking of PET. The fluorometric detection limits for Cu²⁺ and Pb²⁺ were found to be 12 × 10⁻⁷ M and 9 × 10⁻⁷ M and the colorimetric detection limits were 3.7 × 10⁻⁶ M and 1.2 × 10⁻⁶ M respectively; which are far below the permissible concentration in drinking water determined by WHO. Moreover, it was found that chemosensor L worked as a reversible fluorescence probe towards Cu²⁺ and Pb²⁺ ions by the accumulation of S²⁻ and EDTA respectively. Based on the physicochemical and analytical methods like ESI-mass spectrometry, Job plot, FT-IR, ¹H-NMR spectra and DFT studies the detection mechanism may be explained as metal coordination, photoinduced electron transfer (PET) as well as an internal charge transfer (ICT) process. The sensor could work in a pH span of 4.0–12.0. The chemosensor L shows its application potential in the detection of Cu²⁺ and Pb²⁺ in real samples, living cells and building of molecular logic gate.

A novel triazole-based bis Schiff base colorimetric and fluorescent chemosensor (L) has been designed, synthesized and characterized. The chemo-sensor L shows its application potential in the detection of Cu²⁺ and Pb²⁺ in living cells and building molecular logic gate.     

A new bio-compatible Cd2+-selective nanostructured fluorescent imprinted polymer for cadmium ion sensing in aqueous media and its application in bio imaging in Vero cells

Cadmium is a very toxic element found in various aqueous samples. The majority of the highly selective fluorescent ligands, designed for cadmium ion sensing, are hydrophobic compounds, thus making them inactive in aqueous media. Fluorescent imprinted polymers, synthesized by the proficient combination of hydrophilic functional monomers and hydrophobic ligands, may give a new and highly selective opportunity for utilizing most fluorescent ligands for toxic metal ion sensing in aqueous media. A novel fluorescent Cd²⁺-imprinted polymer was synthesized based on the co-polymerization of a mixture of acryl amide, vinyl benzene and ethylene glycol dimethacrylate in the presence of a 5-((3-hydroxynaphthalen-2-yl)methylene)pyrimidine-2,4,6(1,3,5)-trione (HMPT)-Cd²⁺ complex. The polymer was characterized by FT-IR spectroscopy, scanning electron microscopy and thermogravimetric analysis. Cadmium ion recognition by IIP created a new emission peak at about 502 nm based on the ICT mechanism, which was different from the emission peak of IIP in the absence of Cd²⁺ (440 nm). The non-imprinted polymer showed a fluorescence emission at about 500 nm, which was not affected by Cd²⁺, highlighting the recognition sites of IIP. The opto-sensor (IIP) exhibited a dynamic linear response range of 10–0.05 μM with the limit of detection (LOD) and quantification (LOQ) of 12.3 and 41 nM, respectively. Also, the relative standard deviation (RSD) of 3 separate determinations was 3.68%. Moreover, the developed chemosensor was highly selective for Cd²⁺ since the IIP fluorescence was not affected by the presence of other metal ions such as Zn²⁺, Cu⁺, Mn²⁺, Co²⁺, Ni²⁺, and Pb²⁺. The synthesized IIP can be used as a fluorescent probe for cadmium detection in live cells because of its minor cytotoxic effect on them.

Schematic representation of Cd²⁺ recognition by the imprinted polymer and fluorescence signal creation as a result of the mentioned recognition process.     

Quick extracellular biosynthesis of low-cadmium ZnxCd1−xS quantum dots with full-visible-region tuneable high fluorescence and its application potential assessment in cell imaging

The biosynthesis of metal nanoparticles/QDs has been universally recognized as environmentally sound and energy-saving, generating less pollution and having good biocompatibility, which is most needed in biological and medical fields. In the arena of chemical routes, however, biosynthesis has long been criticized for its low productivity, time-consuming process, and poor control over size, shape and crystallinity, keeping the much-needed technology away from practical application. In this work, a rapid and extracellular biosynthesis of multi-colour ternary Zn_xCd_1−xS QDs by a mixed sulfate-reducing bacteria (SRB)-derived supernatant was carried out for the first time to solve the problems plaguing this field of biosynthesis. The results showed that about 3.5 g L⁻¹ of Zn_xCd_1−xS QDs with size of 3.50–4.64 nm were achieved within 30 minutes. The PL emission wavelength of Zn_xCd_1−xS QDs increased from 450 to 590 nm to yield multicolor QDs by altering the molar ratio of Cd²⁺ to Zn²⁺. The SRB-biogenic Zn_xCd_1−xS QDs have high stability in gastric acid and at high temperature, as well as excellent biocompatibility and biosafety, successfully entering growing HeLa cells and labelling them without detectable harm to cells. The SRB-secreted peculiar extracellular proteins (EPs) play a decisive function in the time-saving, high-yield biosynthesis of PL-tuned multicolor QDs, which cover an abnormally high concentration of acidic amino acids to provide tremendous negatively charged sites for the absorption of Cd²⁺/Zn²⁺ for rapid nucleation and biosynthesis. The strongly electrostatic connection between the QDs and the EPs and the increasing amount of EPs attached to the QDs in response to the increase of Cd²⁺ concentration account for their high stability and excellent biocompatibility.

The biosynthesis of metal nanoparticles/QDs has been universally recognized as environmentally sound and energy-saving, generating less pollution and having good biocompatibility, which is most needed in biological and medical fields.     

MoS42− intercalated NiFeTi LDH as an efficient and selective adsorbent for elimination of heavy metals

The enormous increase of heavy metal pollution has led to a rise in demand for synthesizing efficient and stable adsorbents for its treatment. Therefore, we have designed a novel adsorbent by introducing (MoS₄)²⁻ moieties within the layers of NiFeTi LDH-NO₃, via an ion exchange mechanism, as a stable and efficient adsorbent to deal with the increasing water pollution due to heavy metals. Characterization techniques such as XRD, FTIR, TGA, SEM, TEM, and Raman spectroscopy were used to confirm the formation of (MoS₄)²⁻ intercalated NiFeTi LDH and structural changes after the adsorption process. The efficiency of the material was tested with six heavy metal ions, among which it was found to be effective for toxic Pb²⁺ and Ag⁺ ions. When selectivity was studied with all six of the metal ions copresent in one solution, the material showed greater selectivity for Pb²⁺ and Ag⁺ ions with the selectivity order of Ni²⁺ < Cu²⁺ < Zn²⁺ < Fe³⁺ < Pb²⁺ < Ag⁺, with great adsorption capacities of 653 mg g⁻¹ for Pb²⁺ and 856 mg g⁻¹ for Ag⁺ metal ions. Further, the kinetics adsorption study for both the metal ions had a great correlation with the pseudo-second-order model and supported the chemisorption process via the formation of M–S bonding. The adsorption process obeyed the Langmuir model. Therefore, the MoS₄-LDH material could be a promising adsorbent for the removal of heavy metals.

Elimination of the heavy metals by using the MoS₄-LDH adsorbent.     

A highly selective multi-responsive fluorescence sensor for Zn2+ based on a diarylethene with a 4,6-dimethylpyrimidine unit

A novel turn-on mode fluorescent diarylethene containing a 4,6-dimethylpyrimidine unit was developed to fluorescently sense Zn²⁺. Its multiple-responsive properties induced by Zn²⁺/EDTA and ultraviolet/visible light have been systematically studied. The fluorescence sensor could efficiently detect Zn²⁺ with a 10 times enhancement of emission intensity and fluorescence color change (dark-green). In addition, the sensor showed clear discrimination from Cd²⁺. The limit of detection of the sensor was measured to be 8.48 × 10⁻⁸ mol L⁻¹ for Zn²⁺. Finally, a molecular logic circuit was fabricated with the emission at 528 nm as the output signal and light and chemical stimuli as input signals.

A novel multi-responsive fluorescence sensor based on a diarylethene derivative with a 4,6-dimethylpyrimidine unit was developed for Zn²⁺ detection.