Site-recognition boosted the sensing performance of terbium-based organic frameworks for UO22+ detection.

A unique fluorescent sensing probe for UO22+ detection was fabricated with terbium-based metal organic frameworks via introducing specific recognition sites (denoted as Tb-TDPAT). The newly formed Tb-TDPAT presented remarkable detection sensitivity and selectivity towards UO22+, surpassing the need for complex post-modification methods.

Tailoring the Coordination Environment of Fe/Zn-BDC to Boost Peroxidase-like Activity for Highly Selective Detection of PFOS.

Perfluorooctanesulfonic acid potassium salt (PFOS) residues in ecosystems over long periods are of increasing concern and require a selective and stable optical probe for monitoring. Herein, two functional groups (-F and -NH2) with opposite electronic modulation ability were introduced into Fe/Zn-BDC (denoted as Fe/Zn-BDC-F4 and Fe/Zn-BDC-NH2, respectively) to tailor the coordination environment of the Fe metal center, further regulating the nanozyme activity efficiently. Notably, the peroxidase-like activity is related to the coordination environment of the nanozymes and obeys the following order Fe/Zn-BDC-F4 > Fe/Zn-BDC > Fe/Zn-BDC-NH2. Based on the excellent peroxidase-like activity of Fe/Zn-BDC-F4 and the characteristics of being rich in F atoms, a rapid, selective, and visible colorimetric method was developed for detecting PFOS with a detection limit of 100 nM. The detection mechanism was attributed to various interaction forces between Fe/Zn-BDC-F4 and PFOS, including electrostatic interactions, Fe-S interactions, Fe-F bonds, and halogen bonds. This work not only offers new insights into the atomic-scale rational design of highly active nanozymes but also presents a novel approach to detecting PFOS in environmental samples.

On-Site Ratiometric Analysis of UO22+ with High Selectivity.

Uranyl ions (UO22+) are recognized as important indicators for monitoring sudden nuclear accidents. However, the interferences coexisting in the complicated environmental matrices impart serious constraints on the reliability of current on-site monitoring methods. Herein, a novel ratiometric method for the highly sensitive and selective detection of UO22+ is reported based on a [Eu(diaminoterephthalic acid)] (Eu-DATP) metal-organic framework. Benefiting from the unique chemical structure of Eu-DATP, energy transfer from DATP to UO22+ was enabled, resulting in the up-regulated fluorescence of UO22+ and the simultaneous down-regulated fluorescence of Eu3+. The limit of detection reached as low as 2.7 nM, which was almost 2 orders of magnitude below the restricted limit in drinking water set by the United States Environmental Protection Agency (130 nM). The Eu-DATP probe showed excellent specificity to UO22+ over numerous interfering species, as the intrinsic emissions of UO22+ were triggered. This unprecedentedly high selectivity is especially beneficial for monitoring UO22+ in complicated environmental matrices with no need for tedious sample pretreatment, such as filtration and digestion. Then, by facilely equipping a Eu-DATP-based sampler on a drone, remotely controlled sampling and on-site analysis in real water samples were realized. The concentrations of UO22+ were determined to be from 16.5 to 23.5 nM in the river water of the Guangzhou downtown area, which was consistent with the results determined by the gold-standard inductively coupled plasma mass spectrometry. This study presents a reliable and convenient method for the on-site analysis of UO22+.

Rapid analysis of dichlorvos via releasing the phosphate core.

Monitoring the residual dichlorvos (O,O-dimethyl-O-2,2-dichlorovinylphosphate, DDVP) in food has received extensive attention owing to its large consumption in agriculture. However, the previous sensing methods are not time-efficient enough due to the long incubation time for enzyme inhibition (tens of minutes to hours) or bottlenecked by the complicated procedures for senor fabrication. Herein, a novel sensing strategy is proposed based on the hydrolysis of DDVP into PO43-. By using alkaline phosphatase for hydrolysis, a certain portion of DDVP was transformed to PO43- within only 8 min. Then, the released PO43- was detected by a fluorescent terbium metal-organic framework (Tb-MOF). The coordination of the naked P-O groups to the metal nodes of the Tb-MOF disturbed the antenna effects of its ligands. Thus, DDVP was quantified by the decrease of the fluorescence of Tb ions. Based on this method, DDVP residues on plum surfaces were collected by swabs and successfully detected. The recovery of DDVP was determined in the range from 105 % to 115 %, demonstrating the quantification accuracy of this method. The detection limit reached 4.7 µM, which was lower than the restricted amount in fruit set by the National Standard of China. The present method provides an efficient and user-friendly way for the detection of DDVP and many other organophosphorus pesticides in food.

Novel lanthanide nanoparticle frameworks for highly efficient photoluminescence and hypersensitive detection.

Despite the excellent luminescent properties of lanthanide clusters (LnCs), their suprastructures that inherit their characteristic luminescent properties are scarcely reported. Herein, novel and highly luminescent suprastructures are synthesized via a two-step assembly method to incorporate LnCs in covalent organic frameworks (COFs). COFs are pre-synthesized and decorated with rigid anchoring groups on their nanochannel walls, which provide one-dimensional confined spaces for the subsequent in situ assembly of luminescent LnCs. The confined LnCs are termed nanoparticles (NPs) to distinguish them from the pure LnCs. Secondary micropores with predictable sizes are successfully formed between the walls of the nanochannels and the orderly aligned NPs therein. By using a small organic ligand that can efficiently sensitize Ln(iii) cations in the assembly processes, the obtained composites show high quantum yields above 20%. The fluorescence can even be effectively maintained across nine pH units. The secondary micropores further enable the unambiguous discrimination of six methinehalides and ultrasensitive detection of uranyl ions. This study provides a new type of luminescent material that has potential for sensing and light emitting.

Calix[6]arene functionalized lanthanide metal-organic frameworks with boosted performance in identifying an anti-epidemic pharmaceutical.

A novel composite was fabricated by hybridizing terbium 1,3,5-benzenetricarboxylic MOF (TB-MOF) with Cx[6]. The obtained composite TB-Cx[6] possessed long-term stability and dispersion stability and was used for on-site analysis of the anti-COVID-19 disinfection product Prednis via a combing remote sampling technique.

High-quality full-color carbon quantum dots synthesized under an unprecedentedly mild condition.

Carbon quantum dots (CQDs) are highly promising to be applied in light-emitting, chemosensing, and other cutting-edge domains. Herein, we successfully fabricate high-quality full-color CQDs under unprecedentedly low temperature and pressure (85°C, 1.88 bar). Stable and narrow fluorescent emissions ranging from blue to green and red light were realized by simple amine engineering, which were further mixed into white-light CQDs with the absolute photoluminescent quantum yield reaching 19.2%. The average mass yield of the CQDs reached 69.0%. The optical performances demonstrated that the CQDs possessed uniform luminescent centers and dominant radiative decay channels. Component analysis further suggested that dehydrated condensation between carboxyl and amine groups directed the growth of the CQDs. By utilizing the CQDs, full-color light-emitting diodes and logic gate sensors were developed. This study paves an important step for promoting the application of CQDs by providing an energy-efficient, safe, and productive synthetic strategy.

Efficient solid phase microextraction of organic pollutants based on graphene oxide/chitosan aerogel.

The design and synthesis of novel high-performance solid phase microextraction (SPME) coatings towards organic pollutants with diverse chemical properties is still a challenge in sample preparation. Herein, a stable chitosan cross-linked graphene oxide (GOCS) aerogel was reported as a novel coating for solid phase microextraction. The interpenetrated meso- and macropores ensured the large surface area and high accessibility of the functional groups across the aerogel, resulting in high extraction performance towards target hydrophobic pollutants. The extraction capacities of the GOCS-coated SPME fiber towards analytes (e.g. polycyclic aromatic hydrocarbons, organophosphorus pesticides, organochlorine pesticides, pyrethroids, and polychlorinated biphenyls) were about 0.5-13 times as high as those obtained by the commercial fibers (30 µm polydimethylsiloxane (PDMS), 65 µm polydimethylsiloxane/divinylbenzene (PDMS/DVB)), which was attributed to the hydrophobic, π-π, halogen bond and hydrogen bond interactions between the coating and the analytes. Under the optimized extraction conditions, superior analytical performances for PAHs were achieved with a wide linearity (0.5-1000 ng L-1), high enhancement factors (311-3740), and the low limits of detection (0.03-1.28 ng L-1). Finally, the GOCS-coated SPME fiber was successfully applied to the determination of PAHs in real water samples with good recoveries (91.6%-110%).

PDMS-coated γCD-MOF solid-phase microextraction fiber for BTEX analysis with boosted performances.

Owing to the ubiquitous occurrence and chemotoxicity of BTEX (benzene, toluene, ethylbenzene and xylene), the development of stable and accurate analysis methods that can assess environment risks and can generate monitoring data rapidly is urgent. In this work, a new strategy was proposed for efficient detection of BTEX. By creatively utilizing thermal deposition method, a robust SPME fiber was fabricated, where the γCD-MOF acted as the adsorbent, while PDMS functionalized as the adhesive and protective coating. Benefiting from the protection of PDMS, the γCD-MOF fiber presented significantly better extraction performance and exhibited long-term structural stabilities in aqueous or methanol samples up to a week. The stable and improved properties of γCD-MOF demonstrated that the PDMS protected the MOF components from the adverse effects of solvent. The detection limits of PDMS modified γCD-MOF fiber for BTEX was as low as 0.13-0.29 ng L-1 that accompanied with wide linear range of 1-1000 ng L-1, which was significantly superior to commercial PDMS fiber and other MOF-based fibers. Besides, the feasibility of the proposed method was verified by the quantitative determination of BTEX in real water samples. This work presents an effective strategy for creating ultrasensitive and stable SPME fibers based on γCD-MOF for applications in aqueous samples or other poor solvent.

Ratiometric fluorescent probe for the on-site monitoring of coexisted Hg2+ and F- in sequence.

The monitoring of mercury and fluoride ions (Hg2+ and F-) has aroused wide concerns owing to the high toxicity of Hg2+ and the duplicitous nature of F- to human health. As far as we known, more than 100 million people in poverty-stricken areas are still at high risk of being over-exposed to Hg2+ and F- via drinking water. Simple and cost-effective luminescent methods are highly promising for on-site water monitoring in rural areas. However, the development of multipurpose luminescent probes that are accurate and sensitive remains challenging. Herein, a new strategy for rationally designing a multipurpose ratiometric probe is present. The obtained probe is consisted of two emission units with energy transfer between them, which exhibit high coordination affinities to the two coexisted toxic targets (Hg2+ and F-), respectively. Thus, two distinct routes for efficiently modulating the energy transfer in the probe are present to trigger the responses to the two targets in sequence. By detecting the shift of the emission color with a smartphone, an on-site water monitoring method is successfully established with the detection limits as low as 2.7 nM for Hg2+ and 1.9 µM for F-. The present study can expend the toolbox for water monitoring in rural regions.

Polymer Ligand-Sensitized Lanthanide Metal-Organic Frameworks for an On-Site Analysis of a Radionuclide.

Herein, a new strategy to increase the sensitivity of a lanthanide metal-organic framework (Ln-MOF) to UO22+ was proposed by using polymeric ligands. By utilizing [Tb(1,3,5-benzenetrisbenzoate)]n (Tb-TBT) MOF as the host, preloaded 2-vinyl terephthalic acid (VTP) was polymerized in situ, which produced a novel fluorescent composite denoted as PVTP⊂Tb-TBT. Benefiting from the coordination of PVTP to the Tb nodes, the polymeric chains performed both as molecular scaffolds that improved the water stability of the framework and as additional antennae that sensitized the photoluminescence of the Tb nodes. More importantly, the detection sensitivity and selectivity of PVTP⊂Tb-TBT to UO22+ were much improved compared to those of Tb-TBT. Detailed characterizations indicated that the incorporation of PVTP efficiently enriched UO22+ in the probe, which promoted the energy dissipation to UO22+. Besides, UO22+ was also supposed to release PVTP from PVTP⊂Tb-TBT and, thus, exposed the open metal sites to water molecules, which interrupted the sensitization effect of PVTP and induced a nonradiative energy dissipation. A limit of detection (LOD) as low as 0.75 nm was recorded by suspending the PVTP⊂Tb-TBT probe in a water sample, far below the limit in drinking water set by the United States Environmental Protection Agency (130 nm). Furthermore, a remotely controlled sampling and an on-site analysis of real water samples were realized by facilely loading PVTP⊂Tb-TBT on thin films (TFs). The LOD for UO22+ was 2.5 nm by using the TFs. This study reports a new strategy for boosting the sensitivity and selectivity of Ln-MOF to monitor UO22+ and expands the application of the strategy to an on-site analysis.

In vivo tracing of endogenous salicylic acids as the biomarkers for evaluating the toxicity of nano-TiO2 to plants.

Currently, nano-titanium dioxide (nTiO2) is considered an emerging environmental contaminant. Bottlenecked by the traditional destructive and lethal sampling methods, nTiO2's effect in living plants is poorly investigated. Here, in vivo tracing of endogenous salicylic acids at regular intervals was performed by using solid phase microextraction (SPME) technique for evaluating the effects of nTiO2 on plants. By planting aloe in soil containing varying amounts of nTiO2, the titanium (Ti) element accumulated in the leaves to concentrations and then reached the maximum of 1.1 ± 0.4 µg/g after nTiO2 exceeding 0.1 g/kg. The levels of salicylic acid (SA) and acetylsalicylic acid (ASA) were up-regulated upon the exposure to nTiO2, while were positively correlated to the contents of Ti. Moreover, the increased malondialdehyde, decreased total superoxide dismutase and fluctuated glutathione along with the addition of nTiO2 demonstrated the oxidative stress caused by nTiO2. Meanwhile, apparent growth indicators including leaf elongation, plant fresh weight and root development were influenced, which further confirmed the toxicity of nTiO2 imparted on aloe. This study presents the possibility of using salicylic acids as biomarkers for revealing the toxicity of nTiO2 on plants in addition to the other biomarkers and biomass data, and the in vivo SPME technique is powerful for their monitoring.

Graphene Oxide-Supported Lanthanide Metal-Organic Frameworks with Boosted Stabilities and Detection Sensitivities.

The photoluminescent (PL) properties of lanthanide metal-organic frameworks (Ln-MOFs) are intrinsically subtle to water molecules, which remains the major challenge that severely limits their applications as fluorescent probes in aqueous samples. Herein novel composite fluorescent probes were prepared by growing Ln-MOFs (Tb-MOF, Eu-MOF, and Tb/Eu-MOF) on carboxylated porous graphene oxide (PGO-COOH). The 3D thorny composites presented significantly longer fluorescent lifetimes and higher quantum yields than that of the bare Ln-MOFs and exhibited long-term PL stabilities in aqueous samples up to 15 days. The stable and improved PL properties demonstrated that the highly hybrid composite structures protected the MOF components from the adverse effects of water. Furthermore, the unexpected antenna effect of the PGO-COOH substrate on Ln3+ was supposed to be another reason for the improved PL properties. The composites present ultralow detection limits as low as 5.6 nM for 2,4-dinitrotoluene and 2.3 nM for dipicolinic acid as turn-off and ratiometric fluorescent probes, respectively, which was attributed to the incoporation of PGO-COOH that dramatically enahnced inner filter effects and effectively protected the energy transfer process in the MOF components from the interference of the surrounding water. This work presents an effective strategy for creating ultrasensitive and stable fluorescent probes based on Ln-MOFs for applications in aqueous samples.

Electronic synergy between ligands of luminol and isophthalic acid for fluorescence ratiometric detection of Hg2.

Stimulus-responsive double-ligand luminol-Eu-IPA infinite coordination polymer nanoparticles (luminol-Eu-IPA CPNPs) were prepared as a ratiometric fluorescence probe for highly selective detecting Hg2+. The CPNPs were constituted of Eu3+ as the nuclear metal coordinated by isophthalic acid (IPA) together with luminol as an auxiliary ligand. The photoinduced electron transfer (PET) occurring from IPA to luminol prevented the antenna effect between IPA and Eu3+, leading to the quench fluorescence of Eu3+ under light excitation. As Hg2+ has a high affinity to N atom of luminol and the spin-orbit coupling effect, spectroscopically and magnetically silent properties, the fluorescence intensity of luminol was quenched. Meanwhile, the PET effect between luminol and IPA was interrupted under the presence of Hg2+. This process resulted in a significant decrease in the fluorescence intensity of luminol and a significant increase in the fluorescence intensity of Eu3+. Therefore, the fluorescence ratiometric detection of Hg2+ was performed by monitoring the ratio of the fluorescence at 617 nm of Eu3+ to that at 430 nm of luminol. The linear range was from 0.05 to 20 µM with a detection limit as low as 13.2 nM Hg2+ (S/N = 3). Due to the fluorescence of luminol be quenched and the effect of PET be disrupted simultaneously, the probe exhibiting excellent detection selectively can avoid false positive signals, which was demonstrated for monitoring mercury ions in real water samples. Precision in positioning ligands in CPNPs is an advantage to achieve high specificity in comparison to traditional organic dendrimers or precious metal nanomaterials.

Aggregation-induced fluorescence of the luminol-terbium(III) complex in polymer nanoparticles for sensitive determination of thrombin.

A fluorometric method is described for the determination of thrombin. Polymer nanoparticles containing the luminol-terbium(III) complex (luminol-Tb) were prepared where luminol acts as the bridging ligand, and Tb(III) acts as the central metal ion. Thrombin possesses a large number of electrons donating groups that coordinate with luminol-Tb. Following coordination, the rigidity of the linker is increased, and this decreases the non-radiative decay rate and induces an increase in fluorescence intensity at 430 nm. Hence, thrombin can be fluorometrically determined. The detection limit of thrombin is as low as 3.5 pM (at an SNR of 3). This is about 10 times lower than assays using an aptamer. The method was applied in the determination of thrombin in human serum via the standard addition method and gave satisfying results. Graphical abstractSchematic representation of the preparation of the luminol-Tb(III) complex in a nanoparticle host by the self-assembly of luminol and Tb(III) ions. Thrombin readily coordinates with the luminol-Tb(III) system, and this results in particle aggregation. The blue fluorescence of luminol increases strongly, and this effect provides the basis for fluorometric determination of thrombin.

An ultratrace assay of arsenite based on the synergistic quenching effect of Ru(bpy)32+ and arsenite on the electrochemiluminescence of Au-g-C3N4 nanosheets.

A novel ratiometric electrochemiluminescence (ECL) indicator has been constructed for ultratrace As(iii) detection based on the synergistic quenching of ECL emission of Au-g-C3N4 NSs using As(iii) and Ru(bpy)32+, meanwhile generating a new ECL signal of Ru(bpy)32+ with an increased intensity. Due to the dual quenching effect of As(iii) and Ru(bpy)32+ coupled with the generation of the second ECL signal of Ru(bpy)32+, the sensitivity and selectivity for detecting As(iii) are vastly enhanced.

Aggregation-induced emission of luminol: a novel strategy for fluorescence ratiometric detection of ALP and As(v) with high sensitivity and selectivity.

A novel dual-emission fluorescence ratiometric probe of luminol-Tb-GMP CPNPs for highly sensitive and selective detection of ALP and As(v) has been constructed based on the stimulus responsivity of luminol. The introduction of luminol as a ligand for Tb3+, combined with GMP, leads to a sensor which is more robust, sensitive, and efficient.