Fluorescence determination of Fe(iii) in drinking water using a new fluorescence chemosensor

A new fluorescence chemosensor based on (Z)-2-(1-(3-oxo-3H-benzo[f]chromen-2-yl)ethylidene)hydrazine-1-carbothioamide (CEHC) has been developed for the determination of Fe(iii) in drinking water. The optimum conditions were acetate buffer solution with a pH 5.0. In this approach, the determination of Fe(iii) is based on static quenching of the luminescence of the probe upon increasing concentrations of Fe(iii). The CEHC sensor binds Fe(iii) in a 1 : 1 stoichiometry with a binding constant K_a = 1.30 × 10⁴ M⁻¹. CEHC responds to Fe(iii) in a way that is more sensitive, selective, and quick to turn off the fluorescence than to other heavy metal ions. Selectivity was proved against seven other metal ions (Mn(ii), Al(iii), Cu(ii), Ni(ii), Zn(ii), Pb(ii), and Cd(ii)). The calibration curve was constructed based on the Stern–Volmer equation. The linear range was 2.50–150 μM with the correlation coefficient of 0.9994, and the LOD was 0.76 μM. The method was successfully applied to determine Fe(iii) in drinking water samples, and the accuracy of the chemosensor was validated by atomic absorption spectrometry.

A new fluorescence chemosensor based on (Z)-2-(1-(3-oxo-3H-benzo[f]chromen-2-yl)ethylidene)hydrazine-1-carbothioamide (CEHC) has been developed for the determination of the fluorescence probe of Fe(iii) in drinking water.     

Facile transmetallation of [SbIII(DOTA)]− renders it unsuitable for medical applications

The antimony(iii) complex of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate (DOTA) has been prepared and its exceptionally low stability observed. The Sb(iii) ion in Na[Sb(DOTA)]·4H₂O shows an approximately square antiprismatic coordination geometry that is close to superimposable to the Bi(iii) geometry in [Bi(DOTA)]⁻ in two phases containing this anion, Na[Bi(DOTA)]·4H₂O, [H₃O][Bi(DOTA)]·H₂O for which structures are also described. Interestingly, DOTA itself in [(H₆DOTA)]Cl₂·4H₂O·DMSO shows the same orientation of the N₄O₄ metal binding cavity reflecting the limited flexibility of DOTA in an octadentate coordination mode. In 8-coordinate complexes it can however accommodate M(iii) ions with r_ion spanning a relatively wide range from 87 pm (Sc(iii)) to 117 pm (Bi(iii)). The larger Bi³⁺ ion appears to be the best metal–ligand size match since [Bi(DOTA)]⁻ is associated with greater complex stability. In the solution state, [Sb(DOTA)]⁻ is extremely susceptible to transmetallation by trivalent ions (Sc(iii), Y(iii), Bi(iii)) and, significantly, even by biologically important divalent metal ions (Mg(ii), Ca(ii), Zn(ii)). In all cases just one equivalent is enough to displace most of the Sb(iii). [Sb(DOTA)]⁻ is resistant to hydrolysis; however, since biologically more abundant metal ions easily substitute the antimony, DOTA complexes will not be suitable for deployment for the delivery of the, so far unexploited, theranostic isotope pair ¹¹⁹Sb and ¹¹⁷Sb.

The antimony(iii) complex of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate (DOTA) has been prepared and its exceptionally low stability observed.     

Synthesis of Bi2WO6/Na-bentonite composites for photocatalytic oxidation of arsenic(iii) under simulated sunlight

Novel Bi₂WO₆/bentonite (denoted as BWO/BENT) composites were prepared via a typical hydrothermal process and employed for the photocatalytic oxidation of arsenic(iii) (As(iii)). The properties of the prepared samples were characterized through X-ray diffraction, transmission and scanning electron microscopy, UV-visible diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, and photoluminescence spectroscopy. Effects of the BENT ratio on the As(iii) removal were explored under simulated sunlight, and the best photocatalytic effect was observed for the composite with BWO : BENT = 7 : 3 w/w. Compared with the pure BWO, the BWO/BENT composites exhibited an improved photocatalytic ability in the removal of As(iii), which was mainly ascribed to the enlarged specific surface area and the suppressed electron–hole recombination by the incorporated BENT. Furthermore, photo-generated holes (h⁺) and superoxide radicals ·O₂⁻ were confirmed to be the major contributors to the oxidation of As(iii), and an associated mechanism of photocatalytic oxidation of As(iii) over BWO/BENT composites was proposed.

Novel Bi₂WO₆/bentonite (denoted as BWO/BENT) composites were prepared via a typical hydrothermal process and employed for the photocatalytic oxidation of arsenic(iii) (As(iii)).     

Pu(iii) and Cm(iii) in the presence of EDTA: aqueous speciation,redox behavior,and the impact of Ca(ii)

The impact of calcium on the solubility, redox behavior, and speciation of the An(iii)–EDTA (An = Pu or Cm) system under reducing, anoxic conditions was investigated through batch solubility experiments, X-ray absorption spectroscopy (XAS), density functional theory (DFT), and time-resolved laser fluorescence spectroscopy (TRLFS). Batch solubility experiments were conducted from undersaturation using Pu(OH)₃(am) as the solid phase in contact with 0.1 M NaCl–NaOH–HCl–EDTA–CaCl₂ solutions at [EDTA] = 1 mM, pH_m = 7.5–9.5, and [CaCl₂] ≤20 mM. Additional samples targeted brine systems represented by 3.5 M CaCl₂ and WIPP simulated brine. Solubility data in the absence of calcium were well-described by Pu(iii)–EDTA thermodynamic models, thus supporting the stabilization of Pu(iii)–EDTA complexes in solution. Cm(iii)–EDTA TRLFS data suggested the stepwise hydrolysis of An(iii)-EDTA complexes with increasing pH, and current Pu(iii)-EDTA solubility models were reassessed to evaluate the possibility of including Pu(iii)–OH–EDTA complexes and to calculate preliminary formation constants. Solubility data in the presence of calcium exhibited nearly constant log m(Pu)_tot, as limited by total ligand concentration, with increasing [CaCl₂]_tot, which supports the formation of calcium-stabilized Pu(iii)–EDTA complexes in solution. XAS spectra without calcium showed partial oxidation of Pu(iii) to Pu(iv) in the aqueous phase, while calcium-containing experiments exhibited only Pu(iii), suggesting that Ca–Pu(iii)–EDTA complexes may stabilize Pu(iii) over short timeframes (t ≤45 days). DFT calculations on the Ca–Pu(iii)–EDTA system and TRLFS studies on the analogous Ca–Cm(iii)–EDTA system show that calcium likely stabilizes An(iii)–EDTA complexes but can also potentially stabilize An(iii)–OH–EDTA species in solution. This hints towards the possible existence of four major complex types within Ca–An(iii)–EDTA systems: An(iii)–EDTA, An(iii)–OH–EDTA, Ca–An(iii)–EDTA, and Ca–An(iii)–OH–EDTA. While the exact stoichiometry and degree of ligand protonation within these complexes remain undefined, their formation must be accounted for to properly assess the fate and transport of plutonium under conditions relevant to nuclear waste disposal.

Combined advanced spectroscopy and solubility studies provide evidence for the formation of novel calcium-containing and hydrolyzed (Cm,Pu)(iii)–EDTA complex(es).     

Separation of iron(iii), zinc(ii) and lead(ii) from a choline chloride–ethylene glycol deep eutectic solvent by solvent extraction

Deep eutectic solvents (DESs) were used as alternatives to the aqueous phase in solvent extraction of iron(iii), zinc(ii) and lead(ii). The selective extraction of iron(iii) and zinc(ii) was studied from a feed of ethaline (1 : 2 molar ratio of choline chloride : ethylene glycol) and lactiline (1 : 2 molar ratio of choline chloride : lactic acid), with the former DES being more selective. A commercial mixture of trialkylphosphine oxides (Cyanex 923, C923) diluted in an aliphatic diluent selectively extracted iron(iii) from a feed containing also zinc(ii) and lead(ii). The subsequent separation of zinc(ii) from lead(ii) was carried out using the basic extractant Aliquat 336 (A336). The equilibration time and the extractant concentration were optimized for both systems. Iron(iii) and zinc(ii) were stripped using 1.2 mol L⁻¹ oxalic acid and 0.5 mol L⁻¹ aqueous ammonia, respectively. An efficient solvometallurgical flowsheet is proposed for the separation and recovery of iron(iii), lead(ii) and zinc(ii) from ethaline using commercial extractants. Moreover, the process was upscaled in a countercurrent mixer-settler set-up resulting in successful separation and purification.

Deep eutectic solvents (DESs) were used as alternatives to the aqueous phase in solvent extraction of iron(iii), zinc(ii) and lead(ii).     

Experimental and theoretical studies on the extraction behavior of Cf(iii) by NTAamide(C8) ligand and the separation of Cf(iii)/Cm(iii)

In this work we studied the extraction behaviors of Cf(iii) by NTAamide (N,N,N′,N′,N′′,N′′-hexaocactyl-nitrilotriacetamide, C8) in nitric acid medium. Influencing factors such as contact time, concentration of NTAamide(C8), HNO₃ and NO₃⁻ as well as temperature were considered. The slope analysis showed that Cf(iii) should be coordinated in the form of neutral molecules, and the extraction complex should be Cf(NO₃)₃·2L (L = NTAamide(C8)), which can achieve better extraction effect under the low acidity condition. When the concentration of HNO₃ was 0.1 mol L⁻¹, the separation factor (SF_Cf/Cm) was 3.34. The extractant has application prospect to differentiate the trivalent Cf(iii) and Cm(iii) when the concentration of nitric acid is low. On the other hand, density functional theory (DFT) calculations were conducted to explore the coordination mechanism of NTAamide(C8) ligands with Cf/Cm cations. The NTAamide(C8) complexes of Cf(iii)/Cm(iii) have similar geometric structures, and An(iii) is more likely to form a complex with 1 : 2 stoichiometry (metal ion/ligands). In addition, bonding property and thermodynamics analyses showed that NTAamide(C8) ligands had stronger coordination ability with Cf(iii) over Cm(iii). Our work provides meaningful information with regard to the in-group separation of An(iii) in practical systems.

We performed basic chemical studies on Cf using NTAamide extractant. The results of experiments and DFT calculations show that NTAamide has a good coordination ability to Cf/Cm and is expected to be applied to Cf/Cm separation.     

Selective extraction of trivalent actinides using CyMe4BTPhen in the ionic liquid Aliquat-336 nitrate

The extraction of Am(iii), Cm(iii) and Eu(iii) by 2,9-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-1,10-phenanthroline (CyMe₄BTPhen) from nitric acid solution was studied using the ionic liquid Aliquat-336 nitrate ([A336][NO₃]) as diluent. Results show a high selectivity of the solvent for Am(iii) and Cm(iii) over Eu(iii), but rather slow extraction kinetics. The kinetics of CyMe₄BTPhen were largely improved by the addition of 0.005 mol L⁻¹N,N,N′,N′-tetra-n-octyl-diglycolamide (TODGA) as a phase transfer reagent and by the use of 1-octanol as co-diluent. The addition of the phase transfer catalyst and co-diluent did not compromise the selectivity towards the actinide/lanthanide separation and thus this four-component system can be successfully applied to separate Am(iii) and Cm(iii) from the lanthanides.

Improving the kinetics of selective An(iii) extraction from nitric acid feed solutions into an ionic liquid based solvent: combining CyMe₄BTPhen with TODGA in Aliquat-336 nitrate.     

Synthesizing and evaluating the photodynamic efficacy of asymmetric heteroleptic A7B type novel lanthanide bis-phthalocyanine complexes

In this study heteroleptic A₇B type novel Lu(iii) and Eu(iii) lanthanide phthalocyanines (LnPc(Pox)[Pc′(AB₃SH)]) with high extinction coefficients have been synthesized as candidate photosensitizers with reaction yields higher than 33%. The singlet oxygen quantum yields of LuPc(Pox)[Pc′(AB₃SH)] and EuPc(Pox)[Pc′(AB₃SH)], respectively, were measured 17% and 1.4% by the direct method in THF. The singlet oxygen quantum yield of LuPc(Pox)[Pc′(AB₃SH)] in THF is the highest among lutetium(iii) bis-phthalocyanine complexes to date. The photodynamic efficacy of the heteroleptic lanthanide phthalocyanines was evaluated by measuring cell viabilities of A549 and BEAS-2B lung cells, selected to representing in vitro models for testing cancer and normal cells against potential drugs. The cell viabilities demonstrated concentration dependent behavior and were varied by the type of phthalocyanines complexes. Irradiation of the cells for 30 minutes with LED array at 660 nm producing flux of 0.036 J cm⁻² s⁻¹ increased cell death for LuPcPox-OAc, LuPc(Pox)[Pc′(AB₃SH)] and ZnPc. The IC₅₀ concentrations of LuPc(Pox)[Pc′(AB₃SH)] and ZnPc were determined to be below 10 nM for both cell lines, agreeing very well with the singlet oxygen quantum yield measurements. These findings suggest that LuPc(Pox)[Pc′(AB₃SH)] and particularly LuPcPox-OAc are promising drug candidates enabling lowered dose and shorter irradiation time for photodynamic therapy.

Novel bis-lanthanide Lu(iii) and Eu(iii) phthalocyanine complexes have been designed/synthesized and tested their photodynamic efficacy for A549 and BEAS-2B cells in vitro conditions as candidate photosensitizers in PDT.     

Alkaline earth metal ion coordination increases the radical scavenging efficiency of kaempferol

Flavonoids are used as natural additives and antioxidants in foods, and after coordination to metal ions, as drug candidates, depending on the flavonoid structure. The rate of radical scavenging of the ubiquitous plant flavonoid kaempferol (3,5,7,4′-tetrahydroxyflavone, Kaem) was found to be significantly enhanced by coordination of Mg(ii), Ca(ii), Sr(ii), and Ba(ii) ions, whereas the radical scavenging rate of apigenin (5,7,4′-trihydroxyflavone, Api) was almost unaffected by alkaline earth metal (AEM) ions, as studied for short-lived β-carotene radical cations (β-Car˙⁺) formed by laser flash photolysis in chloroform/ethanol (7 : 3) and for the semi-stable 2,2-diphenyl-1-picrylhydrazyl radical, DPPH˙, in ethanol at 25 °C. A 1 : 1 Mg(ii)–Kaem complex was found to be in equilibrium with a 1 : 2 Mg(ii)–Kaem₂ complex, while for Ca(ii), Sr(ii) and Ba(ii), only 1 : 2 AEM(ii)–Kaem complexes were detected, where all complexes showed 3-hydroxyl and 4-carbonyl coordination and stability constants of higher than 10⁹ L² mol⁻². The 1 : 2 Ca(ii)–Kaem₂ complex had the highest second order rate constant for both β-Car˙⁺ (5 × 10⁸ L mol⁻¹ s⁻¹) and DPPH˙ radical (3 × 10⁵ L mol⁻¹ s⁻¹) scavenging, which can be attributed to the optimal combination of the stronger electron withdrawing capability of the (n − 1)d orbital in the heavier AEM ions and their spatially asymmetrical structures in 1 : 2 AEM–Kaem complexes with metal ion coordination of the least steric hindrance of two perpendicular flavone backbones as ligands in the Ca(ii) complex, as shown by density functional theory calculations.

Radical scavenging activity of kaempferol is notably enhanced by Ca(ii) binding.     

Water-soluble lanthanide coordination polymers particles with white-light emission and color tuning

Water-soluble polymer particles (PPs) with strong fluorescence emission were prepared from hyperbranched poly(ethylenimine) (PEI) and terpyridine-bearing aldehyde (TPy) via Schiff base reaction and self-assembly in aqueous phase. TPy/PEI PPs were then used to develop a series of luminescent lanthanide coordination polymers particles (Ln-CPPs). The optical properties of these Ln-CPPs are readily modulated over a wide spectrum in water systems. Finally, water-soluble white-emitting Ln-CPPs were achieved by controlling the lanthanide ion stoichiometry. This Ln-CPPs design approach offers a robust pathway for white-luminescent materials in water systems.

Water-soluble polymer particles (PPs) with strong fluorescence emission were prepared from hyperbranched poly(ethylenimine) (PEI) and terpyridine-bearing aldehyde (TPy) via Schiff base reaction and self-assembly in aqueous phase.

In recent decades, dynamic metal coordination polymers (M-CPs) have attracted great interest in catalysis, drug delivery, chemical sensors and bioanalysis applications.^1–7 M-CPs are constructed from metal ions and organic ligands with a variety of structures and interesting properties for many potential applications. M-CPs acting as chemical sensors are mainly explored by making use of their luminescence properties.^8–10 The luminescent M-CPs can emit a stable and intense luminescent emission, so some substances can be detected by observing changes in luminescence intensity. It is well known that lanthanide ions have high color purity and long lifetime excitation lifetime, and the emission covers the entire visible range of 400 to 700 nm. In particular, Eu(iii) and Tb(iii) ions can emit intense red and green light, respectively. Lanthanide coordination polymers (Ln-CPs) are promising luminescent materials because lanthanide ions have similar chemical properties and two or more lanthanide ions can be randomly distributed in coordination polymers with metal sites, which can modulate the color and brightness of the emission.¹¹ For the above reasons, Ln-CPs have attracted the attention of many scientists and have been effectively used to design multiple color and white light emitting materials. For example, He and co-workers¹² developed a new fluorophore that exhibits white light by combining an Eu(iii) moiety (red emission) with an organic ligand (blue and green emission). Ma et al.¹³ reported a white-light-emitting La(iii)/Tb(iii)/Eu(iii) coordination polymers based on combination of blue-emitting ligand/La(iii), green-emitting Tb(iii) and red-emitting Eu(iii) units. Song et al.¹⁴ developed a white-light-emitting compound by doping a Eu(iii) ion into the Gd(iii) framework.Meanwhile, the selection of suitable ligands plays a crucial role in the synthesis of Ln-CPs with good luminescent properties, since organic ligands can be used not only as building blocks for the construction of new backbones of Ln-CPs, but also as effective sensitizer for Ln(iii) ions.^15,16 However, ligands are generally poorly water soluble, which limits the practical sensing application in environmental and biological systems.¹⁷ An efficient strategy to promote dispersion in water is to prepare Lanthanide coordination polymer particles (Ln-CPPs) by miniemulsion method, reprecipitation method, and so on.¹⁸ Nevertheless, several drawbacks still exist for their preparation and application, such as sophisticated multistep synthetic pathways, use of environmentally unfriendly organic solvents, and the possibility of fluorescence self-quenching in aqueous solution. Therefore, the systematic investigation of water-soluble Ln-CPPs with white-light emission is quite rare. More research studies are urgently needed to accelerate the development of white-light luminescent Ln-CPPs in the water system.Based on the above considerations, we rationally designed water-soluble polymer particles with blue emission and selected Tb(iii)/Eu(iii) to construct white-light-emitting Ln-CPPs (Fig. 1). The water-soluble polymer particles were constructed from hyperbranched poly(ethylenimine) (PEI) and terpyridine-bearing aldehyde (TPy) via Schiff base reaction and self-assembly. Structural characterization and luminescence properties in the water system of Ln-CPPs are studied in detail. An important clue could be obtained from the result that Ln-CPPs constructed by terpyridine ligands can maintain their structural and luminescent properties in the water system. This research also provides a basis for realizing the controllability of water-soluble white-light-emitting Ln-CPPs in the future.Open in a separate windowFig. 1Schematic preparation of TPy/PEI PPs and Ln(III) coordination-based luminescent polymer particles (Ln-CPPs) under UV light (λ_ex = 365 nm).Synthesis of the TPy/PEI PPs is based on facile Schiff base reaction, which refers to the reaction between primary amine on PEI and aldehyde group on TPy, resulting in a product containing C N bonds. Moreover, the diluted TPy/PEI PPs solution emits blue fluorescence under a 365 nm UV lamp. Fig. 2A displays the fluorescence excitation and emission spectra of the TPy/PEI PPs solution, and the maximum excitation and emission wavelengths are 330 and 448 nm, respectively. The UV-vis absorption spectra of TPy/PEI PPs, PEI and TPy were shown in Fig. S4.^† Compared with TPy, the absorption peak at 250 nm in TPy/PEI PPs solution is weakened, which may be due to the decolorization effect caused by the formation of copolymer by TPy and PEI. In addition, the absorption peak at 335 nm in TPy/PEI PPs solution is attributed to n → π* transitions of C N bonds.^18,19 These phenomena indicated TPy/PEI PPs were a newly generated subject.Open in a separate windowFig. 2(A) Fluorescence excitation and emission spectra of TPy/PEI PPs (0.01 g mL⁻¹). (Inset) Photographs of TPy/PEI PPs under visible light and UV light of 365 nm. (B) FT-IR spectra of TPy/PEI, PEI, and TPy.The morphologies of TPy/PEI PPs were characterized by transmission electron microscopy (TEM), Fig. S5A^† is a TEM image and reveals that the TPy/PEI PPs are monodisperse spherical shape with the size distribution in the range of 26–50 nm. Formation of water-soluble nanoparticles is due to the following factors. In TPy/PEI copolymer, ample amine groups and pyridinium groups are hydrophilic, whereas Schiff base bonds are hydrophobic. As a result, the hyperbranched structure of TPy/PEI copolymer tends to fold and collapse, shrinking and self-assembling into uniform polymer nanoparticles in aqueous medium.¹⁸ Many hydrophilic groups on the surface of TPy/PEI PPs make the excellent water dispersity possible. To further explore the chemical composition of TPy/PEI PPs, we performed FT-IR spectra of PEI, TPy, and TPy/PEI PPs (Fig. 2B). Several featured vibration bands at 3284 and 1590 cm⁻¹ in PEI are associated with the stretching vibration of N–H bond, and their intensity is decreased in TPy/PEI PPs, which indicates that some amine groups have reacted with TPy. In addition, another remarkable new peak at 1630 cm⁻¹ was observed in TPy/PEI PPs, which can be assigned to the C N bond.^20–25 Meanwhile, a new peak at 8.37 ppm was observed in the ¹H NMR spectra of TPy/PEI PPs (Fig. S6^†), which can be assigned to N CH protons.²⁶ The monitoring of the aldehyde conversion into imine units can be carried out by measuring the CH̲O/CH̲ N integral ratio, and the conversion rate of the aldehyde into imine units is 69%. The estimation of the conversion rate from the ¹H-NMR spectrum agrees well with the calculation from the weighting measurements with a conversion rate of 73%. These analysis results well demonstrated the formation of Schiff base bonds between TPy and PEI.TPy/PEI PPs possess intrinsic fluorescence, good water solubility, and functional terpyridine structure unit, allowing us to incorporate the Ln(iii)-TPy coordination complexes into polymer networks. With the incremental addition of Tb(NO₃)₃ to the TPy/PEI PPs solution (2% v/v), the TPy : Ln ratio is 2 : 1, which produces green-luminescent Ln-CPPs, GL CPPs (τ = 0.35 ms, Φ = 4.3%, CIE coordinates (0.27, 0.36), Fig. S7, S8 and Table S1^†). In the corresponding emission spectrum, a decrease in the luminescence intensity of the ligand centred emission band at 448 nm with the concomitant emergence of sharp bands at 489 nm, 544 nm, 583 nm, and 622 nm was observed (Fig. S7^†). A decrease in the luminescence intensity of the central emission band of the ligand was observed. These emission bands were assigned to ⁵D₄–⁷F₆, ⁵D₄–⁷F₅, ⁵D₄–⁷F₄, and ⁵D₄–⁷F₃ based transitions, respectively, for Tb(iii).^27–30 A similar procedure was observed upon addition of Eu(NO₃)₃ to the TPy/PEI PPs solution with the occurrence of five characteristic Eu(iii)-based emission bands having maxima at 579 nm (⁵D₀–⁷F₀), 592 nm (⁵D₀–⁷F₁), 617 nm (⁵D₀–⁷F₂), 649 nm (⁵D₀–⁷F₃), and 687 nm (⁵D₀–⁷F₄), resulting in a clear red-luminescent Ln-CPPs, RL CPPs (τ = 0.81 ms, Φ = 11.3%, CIE coordinates (0.52, 0.29)). These emission spectra demonstrate that Ln³⁺ (Eu³⁺ or Tb³⁺) ions were successfully doped to the TPy/PEI PPs. More importantly, strong fluorescence could still be detected even after these Ln-CPPs were stored for over a week, implying that the coordination between the TPy/PEI PPs and Ln³⁺ ions is very stable. The interactions between the TPy/PEI PPs and Ln³⁺ ions were further monitored by FT-IR spectroscopy (Fig. S9^†). Strong absorbent bands at 3256, 1549 and 1398 cm⁻¹ in TPy/PEI PPs are attributed to the stretching vibrations of N–H bond.^18,19 After the formation of RL CPPs, GL CPPs or WL CPPs using Ln³⁺ ions, a dramatically red shift appeared, which indicated the coordination of the TPy/PEI PPs to Ln³⁺ ions. The medium-to-weak bands at 760 cm⁻¹ for RL CPPs, 769 cm⁻¹ for GL CPPs and 765 cm⁻¹ for WL CPPs are observed as additional evidence of the Ln–N formation.³¹Next we investigated how to modulate the emission of polymer particles by adjusting the stoichiometry of the two lanthanide chromophores. Titration of the Tb/Eu molar ratio resulted in a series of Ln-CPPs with a broad spectrum of emission under UV irradiation (Fig. 3A). By testing the emission spectrum (Fig. 3B and C), it was found that the intensity of the green band at 544 nm increased gradually at the expense of the intensity of the red band at 616 nm as a function of Tb/Eu molar ratio. Interestingly, an intense white-luminescent Ln-CPPs, WL CPPs (CIE coordinates (0.33, 0.34)), were observed when the Eu/Tb molar ratio was 1 : 4. The smart illumination control strategy here provides a simple design approach for broad-spectrum color adjustment of luminescent polymer materials.Open in a separate windowFig. 3Luminescence tuning: (A) photographs of Ln-CPPs under UV irradiation, corresponding CIE coordinates are mentioned below; (B) emission spectra (λ_ex = 330 nm) of Ln-CPPs and (C) Job''s plot showing the peak emission intensity of the red band at 544 nm and green band at 616 nm as a function of the Tb/Eu molar ratio (1 : 1, 2 : 1, 3 : 1, 4 : 1, 5 : 1, 6 : 1, 7 : 1, and 8 : 1).In conclusion, we created polymer particles with blue emission from PEI and TPy via Schiff base reaction and self-assembly under mild conditions. The structural characterization and the fundamental properties of the TPy/PEI PPs have been studied. Because of the specific structure, the TPy/PEI PPs exhibit excellent water solubility. Furthermore, we have used the TPy/PEI PPs to develop a series of luminescent Ln-CPPs with Eu(iii), Tb(iii), and mixed Eu(iii)/Tb(iii) in aqueous medium. The individual Ln-CPPs exhibited bright red (Eu-CPPs) and green (Tb-CPPs) fluorescence upon exposure to UV light (λ_ex = 365 nm). Careful tuning of the stoichiometric ratio of Eu(iii) and Tb(iii) helped in achieving water-soluble white-emitting Ln-CPPs, which could offer a suitable pathway for preparing white-luminescent materials in water systems. Due to their stability in water, in our next work efforts will be focused on exploring their potential applications in biological and environmental areas as luminescence sensing and quantitative detection materials.     

The synthesis,characterization, DNA/BSA/HSA interactions,molecular modeling,antibacterial properties,and in vitro cytotoxic activities of novel parent and niosome nano-encapsulated Ho(iii) complexes

Based on the importance of metal-centered complexes that can interact with DNA, this research focused on the synthesis of a new Ho(iii) complex. This complex was isolated and characterized via elemental analysis, and FT-IR, fluorescence, and UV-vis spectroscopy. Additional confirmation of the Ho(iii) complex structure was obtained via single-crystal X-ray diffraction. DNA interaction studies were carried out via circular dichroism (CD) spectroscopy, UV-vis absorption spectroscopy, viscosity measurements and emission spectroscopy; it was proposed that the metal complex acts as an effective DNA binder based on studies in the presence of fish DNA (FS-DNA), showing high binding affinity to DNA in the presence of hydrophobic and electron donating substituents. Also, the interactions of this complex with human (HSA) and bovine serum albumin (BSA) proteins were studied via fluorescence spectroscopy techniques and the obtained results reveal an excellent propensity for binding in both cases. Furthermore, the interactions of the Ho(iii) complex with DNA, BSA and HSA were confirmed via molecular docking analysis. The antimicrobial activities of the Ho(iii) complex were tested against Gram-negative bacteria and Gram-positive bacteria. In addition, a niosome nano-encapsulated Ho(iii) complex was synthesized, and the parent and encapsulated complexes were evaluated as potential antitumor candidates. The main structure of the Ho(iii) complex is maintained after encapsulation using niosome nanoparticles. The MTT method was used to assess the anticancer properties of the Ho(iii) complex and its encapsulated form toward human lung carcinoma and breast cancer cell lines. The anticancer activity in the encapsulated form was more than that of the parent Ho(iii) complex. In conclusion, these compounds could be considered as new antitumor candidates.

A new complex of holmium, [Ho(bpy)(H₂O)₆]Cl₃ has been synthesized, their DNA/BSA/HSA binding, molecular docking, antibacterial activity and MTT assay of niosome nano-encapsulated are investigated.     

Molecular keypad controlled circuit for Ce(iii) and NO3− ions recognition by μw synthesized silicon-embedded organic luminescent sensor

This report demonstrates the mimicking of an electronic circuit diagram towards Ce(iii) ion sensing response supported by molecular keypads. The probe naphthyl based triazole linked silatrane (NTS) was efficiently synthesized using a series of microwave mediated reactions. The luminescent sensor NTS was explored for the ion sensing response towards Ce(iii) ions using DMSO and DMSO : H₂O 4 : 1 (v/v) as solvent media, respectively. The role of water in Ce(iii) ion sensing was detected as ‘turn-off’ response that contradicts the ‘turn-on’ with DMSO. Further, the sensing of NO₃⁻ ions by NTS–Ce(iii) ensemble was associated with blue shift on absorption maxima. These mimicking response studies were sketched as circuit diagrams assisted by molecular keypad behaviour as IMPLICATION output logic gate.

This report demonstrates the mimicking of an electronic circuit diagram towards Ce(iii) ion sensing response supported by molecular keypads.     

A comparative study on the coordination of diglycolamide isomers with Nd(iii): extraction,third phase formation,structure, and computational studies

A novel asymmetric diglycolamide N,N-dimethyl-N′,N′-dioctyl diglycolamide (L^II) was synthesized. The Nd(iii) extraction behavior from HNO₃ and loading capability of the solution of L^II in 40/60 (v/v)% n-octanol/kerosene were studied. Analyses by the slope method, ESI-MS, and FT-IR indicated that, similar to the previously studied isomer ligand N,N′-dimethyl-N,N′-dioctyl diglycolamide (L^I), 1 : 3 Nd(iii)/L^II complexes formed. Under the same experimental conditions, the distribution ratio and limiting organic concentration of L^II towards Nd(iii) were smaller than those of L^I, but the critical aqueous concentration of L^II was larger, which implies that L^II exhibited poorer extraction and loading capabilities towards Nd(iii) than L^I, and L^II has a tendency to be less likely to form the third phase. The quasi-relativistic density functional theory (DFT) calculation was performed to provide some explanations for the differences in their extraction behaviors. The electrostatic potential of the ligands indicated that the electron-donating ability of the amide O atoms in L^II displayed certain differences compared with L^I. This inhomogeneity in L^II affected the interaction between L^II and Nd(iii), as supported by QTAIM and bonding nature analysis, and it seemed to reflect in the extraction performance towards Nd(iii).

The inhomogeneous interactions of M–O_amide in the L^II ligand result in differences between the metal-ion extraction performances of two isomeric ligands.     

Simultaneous removal of Sb(iii) and Cd(ii) in water by adsorption onto a MnFe2O4–biochar nanocomposite

In this study, a jacobsite–biochar nanocomposite (MnFe₂O₄–BC) was fabricated and used to simultaneously remove Sb(iii) and Cd(ii) from water via adsorption. The MnFe₂O₄–BC nanocomposite was prepared via a co-precipitation method and analyzed using various techniques. The results confirm the successful decoration of the biochar surface with MnFe₂O₄ nanoparticles. The maximum Sb(iii) removal efficiency was found to be higher from bi-solute solutions containing Cd(ii) than from single-solute systems, suggesting that the presence of Cd(ii) enhances the removal of Sb(iii). The Langmuir isotherm model describes well Sb(iii) and Cd(ii) removal via adsorption onto the MnFe₂O₄–BC nanocomposite. The maximum adsorption capacities are 237.53 and 181.49 mg g⁻¹ for Sb(iii) and Cd(ii), respectively, in a bi-solute system. Thus, the prepared MnFe₂O₄–BC nanocomposite is demonstrated to be a potential adsorbent for simultaneously removing Sb(iii) and Cd(ii) ions from aqueous solutions.

In this study, a jacobsite–biochar nanocomposite (MnFe₂O₄–BC) was fabricated and used to simultaneously remove Sb(iii) and Cd(ii) from water via adsorption.     

NIR luminescent detection of quercetin based on an octanuclear Zn(ii)–Nd(iii) salen nanocluster

A NIR luminescent octanuclear Zn(ii)–Nd(iii) nanocluster 1 was constructed by the use of a salen-type Schiff base ligand. 1 exhibits a lanthanide luminescent response to Que with high sensitivity. The quenching constant of Que to the lanthanide emission is 2.6 × 10⁴ M⁻¹, and the detection limit of 1 to Que is 2.5 μM. The response behavior of 1 to Que is not affected by the existence of some potential interferents such as biomolecules.

An octanuclear Zn(ii)–Nd(iii) nanocluster was constructed by the use of a salen-type Schiff base ligand, and it shows an interesting NIR lanthanide luminescent response to quercetin with high sensitivity and selectivity.     

Theoretical study of ternary silver fluorides AgMF4 (M = Cu,Ni, Co) formation at pressures up to 20 GPa

Only several compounds bearing the Ag(ii) cation and other paramagnetic transition metal cations are known experimentally. Herein, we predict in silico stability and crystal structures of hypothetical ternary silver(ii) fluorides with copper, nickel and cobalt in 1 : 1 stoichiometry at a pressure range from 0 GPa up to 20 GPa employing the evolutionary algorithm in combination with DFT calculations. The calculations show that AgCoF₄ could be synthesized already at ambient conditions but this compound would host diamagnetic Ag(i) and high-spin Co(iii). Although none of the compounds bearing Ag(ii) could be preferred over binary substrates at ambient conditions, at increased pressure ternary fluorides of Ag(ii) featuring Cu(ii) and Ni(ii) could be synthesized, in the pressure windows of 7–14 and 8–15 GPa, respectively. All title compounds would be semiconducting and demonstrate magnetic ordering. Compounds featuring Ni(ii) and particularly Co(ii) should exhibit fundamental band gaps much reduced with respect to pristine AgF₂. The presence of Cu(ii) and Ni(ii) does not lead to electronic doping to AgF₂ layers, while Co(ii) tends to reduce Ag(ii) entirely to Ag(i).

Only several compounds bearing the Ag(ii) cation and other paramagnetic transition metal cations are known experimentally. Here, we predict as yet unknown AgMF₄ phases and their stability in function of pressure.     

Arsenic(iii) removal from aqueous solution using TiO2-loaded biochar prepared by waste Chinese traditional medicine dregs

Oxidation of As(iii) to As(v) is an effective way to improve the performance of most arsenic removal technologies. In this study, a new alternative biosorbent, TiO₂-loaded biochar prepared by waste Chinese traditional medicine dregs (TBC) was applied in remediation for As(iii) from aqueous solution. Compared with unmodified biochar, the specific surface areas and total pore volumes of TBC increased while the average aperture decreased due to the loading of nano-TiO₂. The X-ray diffraction (XRD) of TBC confirmed that the precipitated titanium oxide was primarily anatase. pH did not have a significant effect on the adsorption capacity at 10 mg L⁻¹ As(iii) in suspension with a pH ranging from 2 to 10. Adsorption kinetics data were best fitted by the pseudo-second-order model (R² > 0.999). The Sips maximum adsorption capacity was 58.456 mg g⁻¹ at 25 °C, which is comparable with other adsorbents reported in previous literature. The Gibbs free energy (ΔG) of As(iii) adsorption was negative, indicating the spontaneous nature of adsorption. The results of free radical scavenging and N₂ purging experiments indicated that O₂ acted as an electron accepter and O₂˙⁻ dominated the oxidation of As(iii). The oxidation of As(iii) obviously affected the adsorption capacity for As(iii) by TBC. X-ray photoelectron spectroscopy (XPS) studies showed that As(iii) and As(v) existed on the surface of TBC, suggesting that the oxidation of As(iii) occurred. TBC played multiple roles for As(iii), including direct adsorption and photocatalytic oxidation adsorption. Regeneration and stability experiments showed that TBC was an environment-friendly and efficient adsorbent for As(iii) removal.

TiO₂-loaded biochar prepared by waste Chinese traditional medicine dregs (TBC) was applied in remediation for As(iii) from aqueous solution.     

Ultrathin quasi-hexagonal gold nanostructures for sensing arsenic in tap water

Monodispersed colloidal gold nanoparticles (AuNPs) were synthesized by an easy, cost-effective, and eco-friendly method. The AuNPs were mostly quasi-hexagonal in shape with sizes ranging from 15 to 18 nm. A screen-printed electrode modified with AuNPs (AuNPs/SPE) was used as an electrochemical sensor for the detection of As(iii) in water samples. The mechanistic details for the detection of As(iii) were investigated and an electrochemical reaction mechanism was proposed. Under the optimal experimental conditions, the sensor was highly sensitive to As(iii), with a limit of detection of 0.11 μg L⁻¹ (1.51 nM), which is well below the regulatory limit of 10 μg L⁻¹ established by the United States Environmental Protection Agency and the World Health Organization. The sensor responses were highly stable, reproducible, and linear over the As(iii) concentration range of 0.075 to 30 μg L⁻¹. The presence of co-existing heavy metal cations such as lead, copper, and mercury did not interfere with the sensor response to As(iii). Furthermore, the voltammogram peaks for As(iii), lead, copper, and mercury were sufficiently separate for their potential simultaneous measurement, and at very harsh acidic pH it may be possible to detect As(v). The AuNPs/SPE could detect As(iii) in tap water samples at near-neutral pH, presenting potential possibilities for real-time, practical applications.

Monodispersed colloidal gold nanoparticles (AuNPs) were synthesized by an easy, cost-effective, and eco-friendly method for electrochemical detection of As(iii).     

Hydrothermal synthesis of a novel nanolayered tin phosphate for removing Cr(iii)

In this work, an outstanding nanolayered tin phosphate with 15.0 Å interlayer spacing, Sn (HPO₄)₂·3H₂O (SnP–H⁺), has been synthesized by conventional hydrothermal method and first used in the adsorptive removal of Cr(iii) from aqueous solution. A number of factors such as contact time, initial concentration of Cr(iii), temperature, pH, and ionic strength on adsorption were investigated by batch tests. Moreover, the isothermal adsorption characteristics and kinetic model of Cr(iii) onto SnP–H⁺ were studied. The results showed that the adsorption of Cr(iii) by SnP–H⁺ was in accordance with the Langmuir adsorption isotherm model and the pseudo-second-order kinetic model. The adsorption capacity of Cr(iii) onto SnP–H⁺ at temperature 40.0 °C and pH 3.0 could reach 81.1 mg g⁻¹. And the distribution coefficient K_d was 23.0 g L⁻¹. Overall, experiments certified that SnP–H⁺ was an excellent adsorbent that can effectively remove Cr(iii) from aqueous solution.

In this work, an outstanding nanolayered tin phosphate with 15.0 Å interlayer spacing, Sn (HPO₄)₂·3H₂O (SnP–H⁺), has been synthesized by conventional hydrothermal method and first used in the adsorptive removal of Cr(iii) from aqueous solution.